PHYSICISTS Radiation Physics

X " iNIS-mf —11396 ^>v S.A. INSTITUTE OF PHYSICS S.A. INSTITUUT VIR FiSIKA

32nd Annual Conference 32ste Jaarlikse Konferensie

Durban

1987

UNIVERSITY of NATAL

DURBAN

Pittwir«rilzburg SOUTH AFRICAN INSTITUTE OF PHYSICS SUID-AFRIKAANSE INSTITUUT VIR FISIKA

32nd 32ste Annual Conference Jaarlikse Konferensie 22nd 22ste Annual Theoretical Jaarlikse Teoretiese Seminar Seminaar 5th Winter School 5de Winterskool

DURBAN 13-17.7.1987

Organisation - Reelings Physics Departments Flslks Departemente University of Natal Unlversiteft Natal Durban & Pletermaritzburg ATC combjnaa M-tach South African innovation with tba bast that overseas technology can offar. This has lad ATC to bacoma tha only manu- facturar of optical fibre in South Africa.

1. A chemical deposition process, producing optical fibre preforms. 2. Preform inspection. 3. The drop at the start of optical fibre drawing.

;abling the fibre ...

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1. Stranding the fibre. 2. Buffering the fibre. 3. Quality control of optical fibre.

nd putting the fibre to work...

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a Unks for process control and pfotaction. a Connectors, taHa, fly-leads and

e InataWatlon. and maintenance. 1. Bbn» optics connectors an) tails. I kwMng ton optics. & Fix* optic termin»t*quiptJmt. Contents Inhoud

Welcome from the Principal and Vice-Chancellor 7 Boodskap van die President van die SAIF 9 Keynote Speaker: Dr H.B. Dyer 11 Genooide Sprekers 15 General Information 23 Algemene Inligting 25 Student Sessions 29 Vergaderings 33 Winter School Programme and Abstracts 37 Konferensieprogram 45 Abstracts of Papers 67

Acknowledgements Dankbetuigings

The Organizing Committee would like to thank the many advertisers, exhibitors and sponsors whose financial support has made a vital contribution to the success of this Conference. In addition to firms appearing in this Programme, a particular word of thanks goes to Shell SA (Pty) Ltd for providing the attractive Conference bags and to the Coca-Cola Bottling Co. for a donation. Ondersteun asseblief ons adverteerders. uitstallers en borge — sonder hul guile ondersteuning sou dit onmoontlik gewees het om die Konferensie in sy huidige vorm te reel. We acknowledge with gratitude the unstinting assistance given by various service bodies within the University of Natal in the preparation of this Conference, in particular Multicopy Centre (Durban).

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MUTUAL MAKING THE MOST OF LIFE VerweBkoming Welcome

On behalf of the University of Natal. I should like to extend a warm welcome to all delegates attending the 32nd Annual Conference of the South African Institute of Physics, and to participants in the associated 22nd Theoretical Seminar and 5th Winter School. We trust that this Indaba of physicists from within the Republic and from overseas will prove most fruitful. From the programme it is clear that the papers presented at the Conference will cover a broad spectrum of disciplines within the field of Physics and include much research at the very frontiers of mankind's understanding of the fundamentals of Nature. On the other hand, such areas as the teaching of Physics and industrial applications have not been neglected. The discussion of the Chernobyl disaster and its aftermath will. I am sure, be of interest to a wide audience of South Africans concerned with the impact of nuclear technology on the environment. Dit is verblydend om te sien dat die Instituut vir Fisika besondere aandag aan die volgende geelag van natuur- wetensteplikes skenk. Ek verwys natuurlik na die Win- terskool oor Aspekte van die Moderne Optika. wat op Honneursstudente gemik is. en die verskeie Studente- sessies. Dit is 'n prysenswaardige manier om die jonger geslag na die Konferensie te lok. Buitendien sal dit bydra om die kennis van fisici van alle ouderdomsgroepe in die huidige era van toenemende spesialisering te verbreed. Dit is nou twaalf jaar sedert die Universitiet van Natal laas as gasheer van u Konferensie opgetree het. en ons is bly dat u besluit het om weer Durban te besoek. Ons vertrou dat u verrigtinge vrugbaar sal wees en dat u almal u verblyf in die Tuinprovinsie sal geniet. Hartlik welkom!

P. de V. Booysen Principal and Vice-Chancellor University of Natal

This page'sponsored by the De Beers Diamond Research Laboratory

7 The National Accelerator Centre It's really smashing!

Yes, we're smashing protons into things ...... at 170 000 kilometres per second! Fast enough to go around the earth in j of a second. Or to reach the moon in l\ seconds.

Our new separated-sector cyclotron has delivered its first beams of protons with an energy of 200 MeV for the first nuclear physics experiments.

We also use this cyclotron to produce carrier-free radioisotopes for medical and industrial use.

And 66 Mev proton beams are being used to produce neutrons for radiotherapy with one of the largest isocentric neutron therapy units in the world, now being commissioned.

We also operate: • a 6 MV Van de Graaff accelerator at Faure • a 16 MeV deuteron cyclotron in Pretoria, and • an 8 Mev injector cyclotron at Faure.

Soon we'll start installing a second injector cyclotron, this time with the most modern external ion-sources for heavy ions and polarized ions.

And we're now busily assembling a very large magnetic spectrometer for nuclear physics.

Prospective users in the physical or biophysical fields are invi:ed to register themselves as such, and to submit research proposals during January or July each year, for evaluation and allocation of beam time.

Information regarding facilities, procedures and employment opportunities may be obtained from The Chief Director National Accelerator Centre PO Box 72 FAURE 7131 Tel.: (024) 4-3820 CSIFW Message from the President of the SAIP Boodskap van die President van die SAIF

Someone once said: "Nobody has ever had a brilliant idea in a dress-suit". The annual conference of the South African Institute of Physics is the opportunity provided by its Council for physicists to get together, take off their jackets and roll up their sleeves tc do some hard thinking. We all do this at our home institutions but because we are few in number and spread out geograph- ically, cur contact with colleagues is limited, apart from this annual event at which more than fifty percent of our community get together. It affords us the opportunity to work together, not only with those of us that share our own field of specialization, but also with others in different fields. That is the environment in which new ideas are generated. A great social responsibility rests on us as physicists to generate new ideas. Doing more of the same thing does not contribute much to the development of our people: it is new ideas that create new opportunities and new jobs. Often such new ideas have had their beginnings at the SAIP conference.

Die reelingskomitee sien elke jaar die konferensie as 'n uitdaging om beter te organiseer. beter sprekers te nooi en 'n beter en meer omvattende program daar te stel. Elke jaar wen hulle deur in hul doelwit te slaag. Die enigste verloorders is die mense wat nie die konferensie bywoon nie. Vanjaar is die mense wat die uitdaging aanvaar het ons kollegas by Universiteit van Na- tal — beide te Durban en Pietermaritzburg. Aan hulle wat al die werk gedoen het byvoorbaat my en die Raad se hartlike dank en goeie wen&e vir 'n baie suksesvolle byeenkoms. Dankie ook aan al die ander persone en organisasies wat bydraes lewer deur advertensies. uit- stallings of borgskappe. Die konferensie sou onmoontlik kon pl&asvind sonder die geriewe wat die Universiteit van Natal aan ons beskikbaar stel. Ons het al vanievore daarvan gebruik gemaak en ons weet hoe goed hulle aan ons beantwoord. Ons hartlike dank daarvoor.

Dr G. Heymann President, SAIF

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1200 Opening Address Openingsrede DRHB DYER Henry Brooke Dyer was born Ut Durban in 1927. After obtaining an MSc in Physics at the University of Na- tal, he proceeded to Cambridge University where he was awarded his PhD in 1951. The same year. Dr Dyer joined the staff of the De Beers Diamond Research Laboratory and, after three years sec- ondment at Reading University studying irradiation damage in diamond, was recalled to join the team of scientists who successfully succeeded in synthesising diamond in 1959. In 1962 Dr Dyer became Director of Research at the Diamond Research Laboratory and was appointed Tech- nical and Research Director of De Beers four years later. He was Managing Director of the Ultra High Pressure Unit diamond synthesis plant at Springs from 1968 until his appointment as Managing Director of the De Beers Industrial Diamond Division in 1971.

Dr Dyer became Manager of the Anglo American Cor- poration in 1967. a Director of De Beers Consolidated Mines in 1975. and a Director of the Diamond Trading Company in 1981.

In addition to the above. Dr Dyer is on the Boards of numerous other companies throughout the world. In 1982 Dr Dyer was awarded the degree Doctor of Sci- ence Honoris Causa by the University of the Witwaters- rand. Dr Dyer is married to Joan Gwendoline and has a son and a daughter. He is a keen sportsman and. being too old for rugby, enjoys waterskiing. squash, deep sea fishing and various other sporting activities.

Tuesday 14 July Dinsdag 14 Julie

•CEIIINOSSSTTUV't Robert Hooke. 1676

Robert Hooke stated in 1576 that solid bodies perform in a predictable way when acted upon by external forces. So it is with human institutions; the body of physics in South Africa is increasingly likely to be subjected to powerful forces for change. The nature of these forces and the way physicists react to them will determine the shape of physical science in this country for many decades to come.

t Hooke's anagram of his law: "UT TENSIO SIC VIS".

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HUNT LASCARtStBWA 8705023 The Fabric of Society Clay. The stuff of life first mentioned in Genesis. And recognised since then as the ideal material to help shelter the family of man. Yet mankind's inventiveness has discovered uses for clay other than making brick. The sculpting and moulding of clay into immaculate ceramics is an example of the versatility of this raw material. Thus Corobrik strives alongside society to enhance the quality of life in our country. More than producing a variety of quality face bricks which beautify our towns and cities. Also supporting a wide spectrum of cultural and artistic endeavours. So extending our rich heritage for the benefit of generations to come. And helping today to keep the fabric of society intact.

COROBRIK

SUMOUND VOUHSELF WimlHE STUENCTH OF COKOIHK

Vw*mCTD 240680 PHYSICAL METALLURGY AT MINTEK The Physical Metallurgy Division of Mintek carries out R&D work on

• selected alloys, so that the use of locally produced metals can be promoted; • the wear and corrosion of the materials used in the mining and metallurgical industries, since the replacement of these materials costs the industry several hundred million rands annually. There are openings in this Division for graduates and technicians with a background in physics, chemistry, and materials science, and in metallurgical, chemical, and mechanical engineering. Bursaries are also awarded for university and technikon sludy.

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YESTERDAY FICTION TODAY FACT

_ Satellite images ol the courts j expected as warm sea currents Qlbng o> ancient ~natera thai sheds • q*> or the history c' the wf1 \ : patterns Measurements wlfi an accwacy o' \ Clean ai' and clear 'am •• •"• "•- •-

Manipulation and Tieasu^.,,^,, u- ,u» .* -u. *y. .-. ^»^. >., „ Electric currents show the hidden st't/cL'e o' t*e W'/^ s :rJSl and cont\ Fifty years ago many of these examples wv^rp sr iprt f» f.(.tion Physics above a]1 s the disc p'np th,it prjvrfps .itswvs t ) th TODAY FICTION TOMORROW FACT

1 but . for. NPRL CS'H POBJI V)'> Pr.-l .' invited Speakers Genocide Sprekers

DR J B CLARK

James Brian Clark, who is now Group Executive of the Research, Development and Implementation Group of the CSIR. started his career at the National Physical Research Laboratory of the CSIR in 1965 and at the same time commenced his undergraduate studies at the University of Pretoria, obtaining a DSc in Physics in 1973 for research on phase studies at high pressures and temperatures. Dr Clark has received several awards. He has worked in Germany and the USA.

Brian Clark has travelled extensively representing the CSIR in an official capacity overseas. He is the author/co-author of 85 publications for scientific journals and 2 book chapters, was co-editor of a book entitled " Speciality Steel it Hard Metals' and is co-inventor of four patents. He also serves on a number of advisory boards. His current responsibilities include corporate management for eleven institutes in- corporated into the Research. Development and Implementation (RDI) group of the revised CSIR structure. The major function of this group is to service the research, development and implementation demands from a diverse range of identified priority market areas.

TRENDS IN SOLID STATE PHYSICS

The presentation will review highlights from the past and identify current trends in the field of Solid State Physics, internationally and nationally. The major current demands and unanswered questions in the field of Solid State Physics will also be highlighted.

PROFESSOR C GOODMAN

Charles Goodman is an eminent nuclear physicist from the Physics Department. Indiana University, USA. who has a long fist of publications in the following anas: nuclear structure, nuclear reactions, neutron time-of-dight spectroscopy. nuclear in- strumentation, and computer-driven data acquisition systems. His PhD is from the' University of Rochester (1955). He has worked at the Oak Ridge National Labora- tories, and has held visiting posts at the Weitzmann Institute and the University of Colorado. Professor Goodman is a fellow of the American Institute of Physics, and in 1983 received the Bonner prize in Nuclear Physics from the A.P.S. for his work in the study of(p.n) reactions. Professor Goodman is married and has two children.

PROBING THE NUCLEUS WITH NUCLEON CHARGE EXCHANGE REACTIONS

Quantitative relationships for transition rates have been established between the weak interaction nuclear probe, beta decay and the strong interaction nuclear probe, nucleon charge exchange. These relationships are used to study the role of the intrinsic properties of nucleons. i.e.. spin and isospin. in the structure of nuclei. These relationships are also used in the measurement of certain characteristics of the nucleon-nucleus force. Some of the findings remain as unsolved puzzles. The possible relevance of these discoveries to underlying nucleon structure, perhaps quarks, will be discussed.

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PNI Scientific A division ot Protea Technology Ltd. PROFESSOR R H LEMMER

Richard Lmmer obtained his undergraduate degrees at the University of the Orange Free State and his PhD in Physics from Florida State University in I960. After spending the period 1960-68 on the Physics Faculty of the Massachusetts Institute of Technology, he returned to South Africa as Professor of Theoretical Physics at UNISA. He is now a Professor in the Physics Department at the University of the Witwatersrand. His current research interests lie in many-body nuclear and quark physics. In 1986 he was awarded the De Beers Gold Medal of the South African Institute of Physics.

THE STRUCTURE OF MATTER AT HIGH ENERGIES

An overview of our current understanding of aspects of the structure of matter at high energies is presented together with the various theoretical models that appear to be successful for describing this structure.

DR G NICOLSON

After receiving the degree BSc(Eng) (Witwatersrand). George Nicolson joined the National Institute for Telecommunication Research in 1960. After a year at the NASA Minitrack Satellite Tracking station, he transferred to the new NASA Deep Space Station at Hartebeesthoek. with a brief to develop a local research programme in radio astronomy using the facilities there. This work led to an MSc(Eng) and he was subsequently appointed as a full time astronomer in 1965. During the period 1970 — 1974 he collaborated in the first southern hemisphere experiments between Australia and South Africa using the new technique of very-long-baseline interferometry (VLBI) and used the results to study the nuclear regions of quasars. He was awarded a PhD in 1975 by the University of the Witwatersrand.

When NASA closed the Deep Space Station in 1975, George Nicolson was appointed Head of the newly-formed Hartebeesthoek Radio Astronomy Observatory and led the development of the 26m antenna and associated equipment into a national facility, which is accessible to South African astronomers and which regi'lariy cooperates in global VLBI networks spread over five continents. His research interests are concerned with radio emissions from X-ray binaries, quasars and active galaxies and the application of VLBI in astronomy and geophysics.

RECENT ADVANCES IN THE TECHNIQUES OF VERY LONG BASELINE INTERFEROMETRY AND ITS APPLICATIONS IN ASTRONOMY AND GEOPHYSICS

The technique of VLBI utilises global networks of radio telescopes to map nuclei of quasars with an angular resolution of 0.001 arc seconds. By then using quasars as a precise reference frame, the baselines connecting the telescopes can be determined with accuracies of 2 to 5 cm. VLBI thus finds applications in both astronomy and geophysics, and has led to discovery of "superiuminai motions" in quasars on the one hand, and to the direct measurement of current motions of tectonic plates on the other. This paper reviews the basic techniques of VLBI and then discusses the implications of recent work on theories of the central energy source in quasars and active galaxies. The results of recent geodetic and geodynamic studies and their impact on the measurement of tectonic motions, variations in the rotation of the earth, and the measurement of polar motion are also discussed.

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17 Challenging and rewarding career opportunities await PHYSICISTS who wish to apply their knowledge of physics and are interested in the dynamic and advanced research, design Radiation and technological development at the 11 Atomic Energy corporation of SA Ltd Physics kU I, in one of the following fields: studies oo the enaracteriratlon of radiation sources, radiation fields and radiation effects as determined by the source properties, interaction of the radiation with materials and geometric conditions. Application to scientific, technological and economic uses of radiation m various disciplines. Health Physics Monitoring of man and environment, dose assessment, radiation protection, evaluation and control, radiation safety, and aerosol physics.

Safety Safety evaluation, guidance and supervision. safety control measures, hazards analysis. emergency planning and preparedness

Nuclear Technology Development and application of radiation and radioisotope technology In mining. Plasma industry and agriculture, study ana control of Industrial processes through nuclear Nuclear Piiysics methodology. Development of analytical nuclear techniques. Doing of Trie achievement of controHeo supportive research. Physics tnermonudear fusion is the ultimate goal of Research into Nuclear and Atomic Physics research on hot piasmss. At PeilndaDa work using neutron and accelerated km Beams. centres around Tokotoshe. a tokama* with study of reaction mechanisms. interesting features A muKKlisciplinary spectroscopy, charge exchange, electron team aims to understand and comrot plasma emission... Application of nuclear disruptions in an effort to con tribute techniques for material analysis. to international knowledge, A variety Development of computer data of sophisticated and challenging accumulation and analysis diagnostic techniques are being systems. used. Reactor Physics Research and develop cafcmational techniques Cased on sound physical Solid-state principles for modelling the behaviour of nuclear reactors under a variety of Physics operating conditions. use of neutron and ion-beam prones to study the sow state. Neutron diffranion studies of magnetic prose transitions. Physics Associated x-ray, ultrasonic and resistivity measurements Cryogenic studies. Small-angle neutron scattering of Materials analysis of materials, A study of the physical and chemical lon-oeam probe analyses of surfaces properties and behaviour of alloys, ceramics and other materials with special reference to their application and utilization m the nigh-radiation environment of me nuclear-energy industry. use is made of sophisticated instruments and tecrmioues such as electron microscopy Auger and photo-eiectron spectroscopv. ATOMIC x-ray and neutron diffraction. optical metaNograpnv. fractograpny ENERGY and many more CORPORATION PO BOX 4587 PRETORIA OOC1 OR E NIELSEN

Erilng Nielsen Is » Danish citizen working In West Germany. Born in Copenhagen in 1940. he obtained an MSe In electro-physics engineering at the Technical University of Denmark. The year 1969-1970 was spent north of the Arctic Circle when he was employed as a scientific observer at the Air Force Cambridge Research Lab- oratory Geopole Station at Thule. Gnentind. This was followed by several years at the Band Research foundation of the Franklin Institute, at that time located in Philadelphia. This culminated in a PhD in Space Physics in 1974. Since then he has Lien employed as a physicist at the Max-Planck-lnstitut fur Aeronomie at Lindau-Han, near Gottingen in West Germany. He has been Principal Investigator of the narrow beam riometer project since 197S and Principal Investigator of the STARE/SABRE* project since 1979. These projects have been highly successful in elucidating the highly dynamic behaviour of the aurora/ionosphere. Dr Nielsen is married with four children. * Scandinavian Twin Auroral Radar Experiment/Sweden and Britain Radar Experi- ment.

CURRENTS AND ELECTRIC FIELDS IN THE EARTHS MAGNETOSPHERE AND IONOSPHERE

The concept of magnetospheric convection is introduced and the overall time-independent (or average) pattern of plasma flow and electric field in the Earth's magnetosphere. and the associated flow and field in the ionosphere is outlined. Dynamic time-independent processes are then considered. It is outlined how ground-based experimental techniques offer possibilities to make contributions to the observation of ionospheric and magnetospheric processes.

DR D VAN AS

Dannie van As studied at the Universities of Stellenbosch and Pennsylvania (USA) and has been with the Atomic Energy Board for 22 years. He is closely involved in the environmental impact of the nuclear industry, which was also the subject of his PhD study at SteHenbosch. From 1977 to 1979 he was with the international Atomic Energy Agency in Vienna, where he was responsible for coordinating international research and findings on questions of radioactive waste disposal for the purpose of establishing international guidelines on safety standards and practices. Dr van As is now manager of the Department of Isotopes and Radiation of the Atomic Energy Corporation of South Africa Ltd (formeriy the Atomic Energy Board). His responsibilities cover the promotion of the use of radioisotopes as welt as protection against radiation, which includes the protection of workers, the public and the environment.

CHERNOBYL—A CRISIS IN THE NUCLEAR INDUSTRY

The nuclear accident at Chernobyl in the USSR is a "worst case" in terms of of the risks of nuclear energy. The accident took place during an elementary test carried out on a turbogenerator, and resulted in a third of the core being destroyed, releasing the total gaseous inventory of the reactor and 10% of the other radionuclides. This relates to the concept of a maximum credible accident as understood by the nuclear industry. The presence of radioactive contamination was detected over thousands of kilometres. In close proximity to the reactor the effects were catastrophic. Further away, it varied in severity from evacuation sf the population to a ban on foodstuffs, and on a global basis intense human concern and anxiety. Now one year later, after an exhaustive study by different international bodies, the sequence of events that resulted in the accident has been established, the causes of the mishap have been determined, and the health effects have been quantified. Valuable lessons have been learned which would hopefully prevent such a catastrophe from ever happening again. This page sponsored by Addison- Wesley Publishing Group 19 Heout-i hfawhe

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Our Speciality? Special gases are not just a sideline for Air Products, they are our speciality. For years we have maintained high standards of gas purity, mixing accuracy and quality control. We're dedicated and are expanding our facilities to meet your every requirement. But for all our technical achievements we still operate like a grand hotel of Europe and take pride in our old-fashioned service and reliability. Whether you are in a laboratory, research, or a demanding manufacturing environment, Air Product's speciality is special gas. AIR^ ~^^^ PRODUCTS Mr Products South Africa (Pty) Ltd (Reg No. 89/03571/07} Call Wessels Els of Special Products Department for technical advice or the Air Products branch nearest you (011) 763-5290 General Information Conference VMHM Apart from the Opening Ceremony and Reception, all conference proceedings take place in the Science Lecture Theatre Complex. i Desk The Reception Desk is situated in the foyer of the Complex. It will be staffed daily from 07h45 to 17h00. Name Tag* Delegates wear WHITE name tags; The Organizing Committee RED name tags; Assistants, e.g. projectionists, wear BLUE name tags. Slides Room 251 is available for checking slides and for speakers to load cassettes at least 10 minutes before their session starts. Materials for producing overhead transparencies may also be loaned there. Exhibition The exhibition of scientific equipment is located in a second floor laboratory in the Desmond Clarence Buildina. The following firms are exhibiting: Computer Wholesalers, Hewlett Packard S.A., Labotec Natai, Logan's University Bookshop, Philquip Scientific, PNI Electronics, Wiliiston Bin. Science Library This is located on the fourth floor of the Desmond Clarence Building. Announcements Important announcements and messages will be displayed on notice boards. Essential changes in the programme must be directed to the Organizing Committee and the Chairman of the session must be consulted. Telephone Numbers Conference Reception Desk (031) 816-3179 Conference Organizers (031) 816-2775/6 Mabel Palmer - Women (031) 81 -1297/8 Mabel Palmer - Men (031) 81 -3118; 81 -4116 Ansell May (031) 81 -5802/7 Bank First National, Nedbank and Standard Bank have agencies located in the Shepstone Building. Travel Agency Braby-Ross Travel will be manning a desk in the foyer at certain times. Post Letters for posting may be handed in at the Reception Desk. A mobile post office is available outside Howard College daily (08h30 to 09h30). Lunch and Beverages Those delegates not staying in University Residences will be served lunch in Charles Smith Dining Hall on production of a lunch ticket. These may be purchased at the Reception Desk before 10h00. Meals are available in the Students' Union. Tea and coffee will be served in the foyer area of the Science Lecture Theatre Complex during the morning and afternoon breaks. University Club Delegates may become temporary members of the University Club at a fee of R3. The Club has a bar and offers lunches as well as snacks in the evening. Transport There is a regular municipal bus service (Numbers 70 to 73) from the Campus (bus stop outside Administration Building) into the City (Pine Street Terminal B5, near the Post Office). DepartCity : 08h45;10h25;11h30;12h45;13h10;13h50;15h05;15h35;16h20. Depart Campus : 07h55; 08h30; 09h10; 10h15; 11h15; 12h30; 13h25; 14h10; 15h30

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Now every laboratory involved in solutions elemental ARLABS (PTY) LTD. analysis can afford to employ the fast, sensitive ICP Mars Street technique. The new affordable ARL 3410 ICP with P.O. Box 557, Rhodesfield KEMPTON PARK 1620 Minitorch™ and IBM-PC-XT makes it all possible, Tel. (011) 394 14 10 and offer these advantages over other systems: ARL Headquarters: • lower instrument cost, with ARL's Minitorch™; ARL Applied Research Laboratories SA En Vallaire • lower operating costs - lower power usage, CH-1024 ECUBLENS / Switzerland lower argon flow give savings of up to 40% over conventional instruments; • easier to operate - ARL's ICP software is spe- cially written for the powerful IBM-PC-XT. The ARL 3410 offers the high performance and flexibility of ICP in the most cost-effective package. Am. •IIIHHMIH Can you afford to be without it? APPLIED RESEARCH LABORATORIES Algemene Inligting Konfw«n*l«tokMi Afgesien van die Openingsptegtigheid en Onthaal vind alle konferensieverrigtinge in die Lesing- saalkompteks van die Fakulteit Natuurwetenskappe plaas. Ontvangstilt«! Oie Ontvangstafe! is in die portaal van die Kompleks. Dit sal daagliks vanaf 07h45 tot 17hOC oop wees. Naametikotte Afgevaardigdes dra WIT naametikette. Lede van die Reëlingskomitee drs ROOI naametikette. Assistente, bv. projektor-assistente, dra BLOU naametikette. Skyfies Kamer 251 is beskikbaar waar skyfies getoets kan word en waar sprekers hulle kasseïie kan laai. Dit moet minstens 10 minute voor die aanvang van die betrokke sessie gespied. Materiaal vir die maak van transparante kan hier geleen word. Uitstalling Die uitstalling van wetenskaplike apparate vind plaas in 'n laboratorium op die tweede vloer van die Desmond Clarence-Gebou. Die volgende firmas stal uit: Computer Wholesalers, Hewlett Packard S.A., Labotec Natal, Logan's University Bookshop, Philquip Scientific, PNI Electronics, Williston Elin. Natuurwetenskapllke BiMioteek Die biblioteek is op die vierde verdieping van die Desmond Clarence-Gebou gelee. Kennisgewings Belangrike aankondigings en boodskappe sal op kennisgewingsborde aangedui word. Die Reëlingskomitee moet in kennis gestel word van enige noodsaaklike wysigings aan die program, en die Voorsitter van die betrokke sessie moet geraadpleeg word. Telefoonnommers Ontvangstafel (031 ) 816-3179 Reëlingskomitee (031 ) 816-2775/6 Mabel Palmer - Dames (031 ) 81 -1297/8 Mabel Palmer - Mans (031 ) 81 -3118; 81 -4116 Ansel! May (031 ) 81 -5802/7 Bank Eerste Nasionale Bank, Nedbank en Standardbank het agentskappe in die Shepstone Gebou. Reisagentskap Braby-Ross is gedurende sekere tye in die portaal op diens. Pos As u briewe wil pos, kan u huile by die Ontvangstafel inlewer. 'n Mobiele poskantoor is daagliks tussen 08h30 en 09h30 voor die Howard Coilege-Gebou gestasioneer. Middagete, Tee en Koffie Kongresgangers wat nie in die Universiteitskoshuis gehuisves is nie, word in die Charles Smith Eetsaal met middagete bedien. Kaartjies vir middagetes moet vooruit by die ontvangstafel gekoop word voor 10h00. Maaltye kan ook in die Studente Sentrum genuttig word. Tee en koffie sal gedurende die oggend- en middagpouses in die portaal van die Lesingsaalkom- pleks bedien word. Universiteitsklub Kongresgangers kan tydelik by die Universiteitsklub aansluit teen 'n fooi van R3. Die Klub het 'n kroeg en bedien middagetes, sowel as snoeperye in die aartd. Vervoer Daar is 'n gereelde munisipale busdiens (Nommers 70 tot 73) vanaf die Kampus (bushalte buite die Administrasiegebou) na die binnestad (Pinestraat Terminus B5, naby die Hoofposkantoor). Vertrek vanaf Stad : 08h45; 10h25; 11h30; 12h45:13h10:13h50:15hO5; 15h35; 16h20. Vertrek vanaf Kampus : 07h55; 08h30; 09h10:10h15:11h15:12h30; I3h25; 14h10; i5h30

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E.V.J. Krisch Engineering Co. (PTY) CTD. P.O. Box 50206, Randburg 2125, 287 Samantha Street, Stydom Park Ext. 18, Randburg 2194 Tel.: 793-8831/2/3/4/5 IS THIS YOU? MEET JACK When Jack joined the National Institute for Materials Research in 1985 we asked him to make semiconductor epitaxial layers equal in quality to those made at the best labs overseas. He said he needed one million rand and a small team of people.

The OMVPE reactor designed and constructed at the NIMR forms the basis of We got Jack his million rand and a team of the South African drive in Solid State capable people. He started building his Microwave technology and Optical Communications. Organometallic Vapour Phase reactor in 1985. He grew his first layer in August 1986 and by March 1987 he couid grow material to match the best in the world. He now grows GaAs layers in which electrons move 60 times faster than in Si and to a purity of a couple of parts per billion. If you are, like Jack, the kind of person who can handle a challenge ... CSIR

or phone Harry Booyens 869211 x 362 Stewart Hart 869211 x 27£ THEN CONTACT US! or Neville Comins 869211 x 28£ Student Sessions Studentesessies These reviews are aimed at students and non-specialists Hierdie oorslgte is gemik op studente en nie-spesialiste

Ptasma Physics C1 Plasmafisika Wednesday 09h00-09h30S1 Woensdag Professor RJ. Barrett (UND) PLASMA WAVES IN LABORATORY AND SPACE

Solar-Terrestrial Physics E1 Son-aardfisika Wednesday 09h30-10h00 S1 Woensdag Professor J.A. Gledhill (RU) SOLAR-TERRESTRIAL PHYSICS: THE IONOSPHERE AND THE MIDDLE ATMOSPHERE

Astrophysics and Astronomy F1 AstrofisikaenSterrekunde Wednesday 10h00-l0h30 S1 Woensdag Dr. M.W. Feast (SAAO) SUPERNOVAE

Solid State Physics AS Vastetoestandfisika Wednesday 12hOO-12h30 S9 Woensdag Dr. H. Booyens (NIMR) SOLID STATE PHYSICS AND MICROELECTRONICS

Optics and Spectroscopy D7 Optika en Spektroskopie Thursday 09h00-09h30 S2 Donderdag Dr. D.J. Brink (NPRL) NON-LINEAR OPTICS: SOME PRINCIPLES AND APPLICATIONS

Nuclear and Particle Physics B15 Kern- en Deeltjiefisika Thursday 11h0O-11h3OS4 Donderdag Professor J.P.F. Sellschop (WITS) SOME CURRENT CHALLENGES IN NUCLEAR PHYSICS AND ITS FIELDS OF APPLICATION

Physics Education G3' Fisika Opleiding Thursday 12h00-12h30 S1 Oonderdag Dr. G.E. Oberem (RU) WILL COMPUTERS REPLACE PHYSICS PROFESSORS?

Applied and Industrial Physics H29 Toegepaste- en Nywerheidsfisika Friday 09h00-09h30 S6 Vrydag Dr. G. Gafner (Intergold) SOME RESULTS OF INTERGOLD'S RESEARCH PROGRAMME

Theoretical Seminar 126 Teoretiese Seminaar Friday 11h0O12h00S5 vrydag Professor R. VlolUar (UCT) ON THE CREATION OF MATTER IN THE UNIVERSE

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Pica Centra, Cotawold Road, Florida Hllia Box 5283, Wertevreden Park -171B South Africa ANAVAC Tel.: (011) 674-1190/1 Talax: 4-24980 The Chamber of Mines of South Africa RESEARCH ORGANIZATION

Functionally, the Chamber's research organization is split into a number of laboratories and branches which cover the multi-disciplinary fields of research. The Coal Mining Laboratory conducts research into mining, strata control and environmental problems in coal mines. Coal mining methods and equipment are adapted to suit the particular geological, economic and labour conditions found in South Africa. The Engineering Services Branch essentially performs a support role to other activities by providing a service which covers design, manufacture, inspection repair and assistance in conducting experiments. The Engineering Systems Laboratory provides specialist R & D in the fields of mechanical, hydraulic, electrical and electronic engineering. Much of (he effort of the branch is related to leading slope mechanization. The Environmental Engineering Laboratory devises methods for reducing heat flow into mines and develops improved methods of dust suppression, pollutant control, refrigeration and ventilation. The Gold Exploitation Laboratory is involved in developing methods for predicting gold distribution and improving gold valuation. Techniques which enable a lower grade ore to be mined are also being examined, as are methods of backfilling to improve stoping conditions and gold extraction. The Human Resources Laboratory is engaged in manpower planning for the gold mining industry, improving the work performance of miners and assessing their attitudes and behaviour for the maintenance of peace, harmony and the quality of life. The Industrial Hygiene Laboratory is concerned with air pollution and its measurement, control and effects on the worker. Detailed research into work stress is conducted and much effort is given to the improvement of acclimatization procedures. Research and services are provided to outside organizations on a contractual basis. The Mining Branch is responsible for conducting trials and financial evaluations of new mining methods and associated equipment. The human engineering aspects of mechanical mining are also investigated. The Rock Mechanics Laboratory is engaged in designing mine layouts, developing new rock support systems and research aimed at improving the understanding of rock behaviour in deep level mines. The Stoping Technology Laboratory develops improved method* and machinery for gold mines. Mechanized systems for use both with and without explosives are being developed. Opportunities The South African mining industry is working at the forefront of mining technology, whose traditional methods and equipment are not always practical or efficient. Currently, the deepest mines are at some 3.8 km below ground level and this creates substantial additional problems in terms of working conditions. The Chamber therefore offers opportunities to a wide range of graduates to become involved in a variety of problems and projects. Long-term career prospects are excellent, as are the opportunities to undertake work leading to higher degrees. Salaries and other conditions of employment are highly attractive.

Application forms can be obtained from: The Personnel Manager, Chamber of Mines Research Organization, P.O. Box 91230. Auckland Park 2006. CA/I Meetings Vergaderings MONDAY 13 JULY: 1 (a) SCOPS WORKSHOP ON MAGNETIC STORMS, 14h00- 17hOO, S4. DINSDAG14 JULIE: 1 (b) SCOPS WORKSHOP ON MAGNETIC STORMS, 09h00 - 13h00, S4. 2. F1SIKAWOORDELYSKOMITEE, 15h15, Kamer 253. 3. RESEARCH PROGRAMME IN HIGH-TEMPERATURE SUPERCONDUCTORS, 14h30 Romatex Room 4. SSPMS EXECUTIVE MEETING, 16h00, Room 052. WEDNESDAY 15 JULY: 5. REDAKSIONELE ADVIESKOMITEE MESON, 08h00 - 09h00, Kamer 253. 6. PHYSICS - THEOLOGY GROUP: "Present Physics-Theology concerns", 13hOO, Principal's Dining Room, Students' Union. 7. SAIF RAADSVERGADERING (saam met Voorsitters van Spesiialisgroepe), 13h00, Universiteitsklub. 8. SOUTH AFRICAN JOURNAL OF PHYSICS EDITORIAL BOARD, 17h00, Room 253. 9. FISIKAHANDBOEKVERGADERING,17h15, Kamer 052. DONDERDAG16 JULIE: 10. SAIF RAADSVERGADERING, 13hO0, Universiteitsklub (Barend's). 11. PHYSICS - THEOLOGY GROUP: "The Anthropic Cosmologioal Principle", 13h00, Principal's Dining Room, Students' Union. 12. SAIF ALGEMENE JAARVERGADERSNG, 15h30, S8. FRIDAY 17 JULY: 13. PHYSICS - THEOLOGY GROUP: "Ethical Issues - Faith, Science and the Future)113h00, Principal's Dining Room, Students' Union. 14. HOOFDE/VOORSITTERS VAN FISIKA DEPARTEMENTE, 13h00 - 13h50, Universiteitsklub. Voortsetting: 15h15 - 16h30, Kamer 253. 15. SCOPS MEETING ON POLICY AND OBJECTIVES, 15h15 - 18hOO, Romatex Room. Continuation: SATURDAY 18 JULY, 08h3O- 18h00.

Institutional Institusioneie lede Members of the SAIP van die SAIF Institutional Members of the SAIP are a group of com- Institusioneie lede van die SAIF vorm 'n groep van mercial and scientific organisations who believe it is kommersiele en wetenskaplike organisasies wat gto valuable to them and to South Africa to maintain a dat dit vir hulle en vir Suid-Afrika waardevol is om 'n vigorous growth in the physical sciences. By their par- kragtige groei in die fisiese wetenskappe te handhaaf. ticipation and membership dues they give significant Deur hul deelname en lidmaatskapgelde word beteke- support to the South African Institute of Physics in the nisvolle steun aan die SAIF verleen in sy strewe na die pursuit of its objectives - the advancement of the prac- bevordering van die beoefening van fisika en sy toe- tice, and the diffusion of knowledge, of the science of passings en die verspreiding van kennis daarvoor tot physics and its applications for the benefit of the com- voordeel van die gemeenskap. Vir hul ondersteuning is munity. The SAIP is grateful for their assistance. die SAIF dankbaar.

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"Wip^|ffi:;;6iiiSSfliaii Winter School S8 Winterskool ASPECTS OF MODERN OPTICS ASPEKTE VAN DIE MODERNE OPTIKA

Monday Maandag 08h45 Dr. G. Heymann (CSIR) 08h45 OPENING

09h00 Dr.GRitter(NPRL) 09h00 PHOTONICS - HIGH TECHNOLOGY OF THE 21ST CENTURY

10h30 Dr. H.M. von Bergmann (NPRL) 10h30 HIGH-AVERAGE-POWER EXCIMER LASERS

11h30 Dr. E. Ronander (AEC) 11h30 HIGH-RESOLUTION LASER SPECTROSCOPY

14h00 Dr. P.F. Cunningham (UND) 14h00 LASERS IN INERTIAL CONFINEMENT FUSION RESEARCH

15h30 Mr. C.J. van der Hoeven (NPRL) 15h30 SOME ASPECTS OF MODERN HOLOGRAPHY

Tuesday Dinsdag 08h30 Professor R.E. Raab (UNP) 08h30 THE INTERACTION OF RADIATION WSTH MATTER

09h30 Dr. H.S.T. Driver (UCT) 09h30 COHERENT ANTI-STOKES RAMAN SPECTROSCOPY OF GASES

11h00 Dr. C Graham (UNP) 11h00 POLARIZATION THEORY

12h00 Professor E. van Rooyen (UP) 12h00 OPTIESE SEINPROSESSERING

14h00 Mr. R.N. Phillips (Aberdare) 14h00 OPTICAL FIBRE COMMUNICATION SYSTEMS IN SOUTH AFRICA TODAY

15h00 Dr.G.Ritter(NPRL) 15h00 CLOSING

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WINTER SCHOOL WINTERSKOOL

WOTONICS - HIGH TECHNOLOGY OP LASERS IN INSRTIAL CONFINEMENT W1 THE 21ST CENTURY W4 FUSION RESEARCH a Ritter, NPRL, CSIR P.F. Cunningham, U.Natal, Durban The Held of Optic* hat frown and matuttd to such an Fusion may be expected if D-T fuel is simultaneously com- extent duting the pjtft 2$ • 26 ytan sine* the advent of pressed and heated tc many times solid density and fceV the iMtr, chat it necessitated the creation of a mm t«rm- temperature* respectively. Spherical implosions caused by inology in order to properly dMciibt the diran* and trow- taut-driven ablation may produce the necessary parameter ing activitiat in t!» field. Just M tbt ttim •Electronics* The pertinent processes of absorption, scattering and gen- was invented for describing tha host of dosaly related erated usabilities will be reviewed. The use of secondary technologies based on the control of electrons, so the tetn. lasers for probing and diagnosing these and other plasmas •Photonics' has bean coined to daacriba tho technologies directly and indirectly will be discussed. Up-to-date of generating light and hamtssing it in a vast number of trends in the field will be reported. diffetant applications. A discussion of racant highlights in modern optics provides tha background against which the state of photonics in the RSA will be seviewed. W5 SOME ASPECTS Of MODERN HOLOGRAPHY HICH-AVEMCE-POWBH. EXCIMER LASERS W2 C.J. van der Hoeven, NPRL , CSIR The general principles and some applications of modem H.M. von Btrgaaoa, NEM./CSU holography will be discussed. During the last few years exciaer lasars have been developed into reliable powerful laser systeas that are eoaDereially available and have found a large THE INTERACTION OP RADIATION WITH nuaber of applications in ell areas of science, tech- MATTER nology and aedicinc. W6 R.B. Raab, U.Natal, Pietermaritxburg Ihe lecture will esplain the physics of Che exciaer laser, it will discus* and suaaarixe present day ex- Optical effect* result from the interaction of an electro- ciaer laser technology and give an overview of the magnetic wave witb matter. Theoretically this is conveniently aost iaportant applications in aatarial processing, described by the energy of interaction of the electric and photocheaistry and nedicina. magnetic field* and field gradients of the wave with the electric «nd magnetic multipot* moments induced in matter by the radiation. A semi-classical Hamiltonian (i.e. fields not quantized) of this interaction is presented, and a particular choice of gauge is shown to describe the multi- pole interaction in a natural way. This Hamiltonian is used to obtain quantum-mechanical expressions of molecular W3 HIGH-RESOLUTION LASER SPECTROSCOPY properties responsible for certain optical effects. E. Ronander, AEC COHERENT ANTI-STOKES RAMAN The laser as a source of coherent optical radiation has W7 SPECTROSCOPY OF GASES made it possible to investigate nonlinear interaction of optical radiation with atoms and molecules. Its availability has given rise to new research fields, such as nonlinear H.S.T. Driver, UCT optics, laser spectroscopy, laser photochemistry, that lie at the boundary between quantum electronics and physical In the non-linear optical process of coherent anti-Stokes optics, optical spectroscopy and photochemistry, respectively. Raman scattering (CARS), a pump beam at frequency^ The use of coherent optical radiation in each of these fields is mixed in a medium with a Stokes beam at frequency «* has led to the discovery of qualitatively new effects and (w, < «,) to produce a new coherent beam at the anti- possibilities; in particular, some rather subtle effects of Stokes frequency wa • 2Mt -«,. Maxwell's equations interaction between highly monochromatic light and atoms will be used to derive the amplitude of the anti-Stokes and molecules, in optical spectroscopy, have formed the wave in terms of the third order susceptibility {"of bases for certain methods of so-called nonlinear, laser the medium and the amplitudes of the two incident waves. Doppler-fret spectroscopy. These methods' have made it The relation of if to the molecular properties of the possible to increase resolution of spectroscopic studies from medium will be discussed. With this theoretical background, between 10 and 10 limited by Doppler linear broadening the practical implementation of CARS can be delineated. up to about 10*! Various applications of laser and diode- After a d ;ription of the CARS facility a: present in use lasers for the study of high-resolution features which have at UCT, tne diagnostic capabilities of the system wtil be contributed significantly to a better knowledge of atoms surveyed. and molecules will be discussed.

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C Grahamt U. Natal, Pietetmaritrbutg afferent models of polarised light are reviewed and syn- thesized to reveal a rationale behind the Poincare sphere at the Mueller calculus. The usefulness of the Poincare spher as a mental aid in simple polarization problems at the optii workbench is demonstrated; and areas of application of th Mueller calculus are discussed. The Junes calculus is briefly introduced and the Jones and Mueller calculi are compared and contrasted.

W9 OPTIESE SEINPROSESSERING E,vtn Rooyen, U. Pretoria

Die gebruik van 'n akoesto-optiese Bragg-sel, as inset (component, vir 'n optiese prosesseerder bied die moontlik - heidom byvoorbeeld die spektrale aard van RF seine praktu intyds te kan bepaal. Die aanwending van optiese operatoi nl Fourier-cransforme, konvolusie en korrelasie bied die geleentheid vir vele ander toepassings soos optiese teiken- herkenning, rekenkundige berekenings en nog veel meet. Alhoewel die tegniek van optiese prosesseerers en die AO- There are smarter interaksie reeds lank bekend is, het dit in die afgelope paar jaar moontlik geword om met nuwe AO materiale en ways to spend money koherente ligbronne die nuwe generasie toerusting te ont- than on leaks. werpen realistter. In die lesing sal die fisiese eienskappe van die komponente wat vir die opbou van die stelsel vereis word beskryf en If you deal with high-vacuum pro- ontleed word. Die teorie van die AO interaksie, optiese cesses, you know that a leak can argitekture en holografiese filters wat vir die stelsels be a nightmare. Leaks always cost gebruik word sal toegelig en behandel word. money, be it in terms of ruined pro- Optika is 'n analoogtegnologie en vir die verkryging van duction batches, process crashes, groter noukeurigheid kan die aanwending daarvan uitgebrei substrate replacement costs or word sodat dit moontlik is om syferverwerkings te Joea. just plain system downtime. Daar sal aangctoon word hoe optiese prosesseerders gebruik kan word om sistoliese berekenings deur te voer vir die Now, there's a sensible way to oplossing van onder andere linere stelsels. curb the risk of a costly leak: the Balzers HLT100 helium leak tes- ter. It gives you real, no-nonsense quality control. It eliminates the nuisance and expense of liquid nitrogen. It is remarkably easy to OPTICAL FIBRE COMMUNICATION SYSTEMS operate. And it is a precise and W10 IN SOUTH AFRICA TODAY dependable system for repairs or R.N. Phillips, Aberdare Group maintenance, too.

Optical fibre provides an alternative digital communication medium to digital microwave and coaxial cable system both for long distance broad band systems as well as intra-office local area networks. This paper will discuss the relatively new technology of optical fibre communications, its advantages over conventional systems, the basics of system design, and will describe the systems currently being installed in South Africa and internationally.

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EPICON 87 CONFERENCE ON EPITAXY KRUGER GAME RESERVE 18-20 November 1987

The intention of the conference is For further information contact: to bring together scientists and engineers in the general field of epi- The Secretary - EPICON 87 taxy. This includes theory, growth, c/o EM Unit characterization and device design University of the North and fabrication associated with epi- Private Bag XI106, SOVENGA taxial structures. 0727 South Africa

Tel: 01522-4310 X 2804 or 2264; Telex: 3 22798 SA

42 Social Programme Sosiale Program

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Dinsdag 14 Julie 19h00 Elizabeth Sneddon-Teater Openingsrede en Onthaal

Wednesday 15 July 17h30 Foyer Sherry 19h30 for 20H00 Elangeni Hotel Conference Banquet

Donderdag 16 Julie 18h00 Durbanse Stadsaal Skemeronthaal

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CONFERENCE ENTRANCE WEDNESDAY 15 JULY MORNING

- 9HS0 REGISTRATION Foyer

S7 S9 S4 SI SOLID STATE PHYSICS 1 SOLID STATE PHYSICS Z H'^LEAR AND PARTICLE PHYSICS PLASMA/ SOLAR-TEHRESTRIhU Chairman: Dr S Bart Chairman: Dr T E Derry Chaiman: Dr U R Holttrray '•oTROPHYSICS Chairman: Dr I H A OUdhill

9hOO - $hlS AI ShOO - ShlS A2 9h00 - 9hlS Bl 9h00 - 9HS0 a THE STABILITY OF CERTAIN USING ACRT FOR THE GROWTH STATUS VAN DIE NASIONALE STUDENT SESSION INSTRUMENTS WHICH ARE OF CdHjTt VER5NELLERSENTRUM, FAURE "PLTiSHA PHYSICS' ESSENTIAL IN THE FUNCTIONING OF AN OHVPE REACTOR J R S Roodt, M A fkzrais and D Rtitmann en A H Botha (SVS) PLASMA HAVES IN LABORATORY B J duller (SINR) 0 J Lombard (MMR) AND SPACE P J Barrett (USD)

9hlS - 9h30 Ai ShlS - 9hZ0 Ai 9hlS - 3h30 BS THE DESIGN OF AN OVERALL CORRELATION BETWEEN CARRIER OPWEKKING VAN REUSE HULTI- SAFETY SYSTEM FOR THE SAFE CONCENTRATION IN HgCdT. AND POOL RESONANSIES OPERATION OF AN OMVPE CHLORINE DENSITY AS DETER- V J SatuM (US), D J Suanepoel, REACTOR MINED BT SINS AND FAB W da X Loubaer, J A Stander A P Vya, A P 3&tha, B J Strydan, M A Haraie, en J V Koen DEC Rogers and J B Basaon J C Q Fletaher (SIM) (SIHR)

9h30 - 9h4S AS 9hlO - AS 9hS0 - 9h4S S3 9h30 - lOhOO El A SIMPLE FAT-FET GROWN ANOMALOUS HALL EFFECT ON INTRODUCTION TO THE KNOCKOUT STUDENT SESSION BY OMVPE a-TYPE g aQ Te GROWN AND CONTINUUM DECAY STUDIES "PHYSICS BY THE SOL&3 ST WITH THE NAC SEPARATED Jaak C Q Fletoher (NZMIt) RECRTSTALLIZATION TECHNIQUE SECTOR CYCLOTRON SOLAR-TERRESTRIAL PHYSICS: J B Baeaon and B. Booyene A A Cowley (SAC) THE IONOSPHERE AND THE MIDDLE ATMOSPHERE J A Gledhill (RU)

9h4S - WhOO A? 9h4S - lOhOO AS 9htS - lOhOO Bt THE GROWTH OF AlGaAs BY SURFACE LASERS ON F« FORMED 12C(p,2p) "B AT 66 M.V: MOVPE DURING PLASMA NITRIDING EXPERIMENTAL METHOD AND DATA STUDIED BY XPS AND EELS ANALYSIS D Faubenheimev, A W R Leitoh and -I S Vemaak 'UPE) I le R Strydom IHIMP.) J J Laurie, A .', Coaley, D U Uhittal, J Hlahtr (SAC) f/

lOhOC - 2OhlS A9 lOhOO - lOhlS A10 lOhOO - lOhlS BS lOhOO - lOhZO Fl THE GROWTH OF AlCaAs-GaAs THE ROLE OF AN INTERFACIAL MODEL CALCULATIONS FOR THE STUDENT SESSION l2 QUANTUM WELL LAYERS BY MOVPE LAYER OF Ni IN AuGc OHMIC C(p,2p) REACTION AT 66 HtV ASTROPHYSICS AND ASTRONOMY CONTACTS TO G*Aj A U R Leitah and J S Vevnaak D M Uhittal, A A Cowley, (UPE) A P Botha (nntl), E Relling J J Laurie and J Pitcher SUFERtnVAE and R 0 Copperthwaite M W Feast (SAAO)

lOhlS - lOhlO All lOhlS - 10M0 Alt EFFECT OF ANNEALING ON THE METALLURGICAL AND ELECTRI- COINCIDENCE STUDY OF 1.49 eV BAND IN SEMI- CAL INVESTIGATIONS OF Au-Ce CONTINUUM DECAY INDUCED BY INSULATING LEC G«A9 BASED OHMIC CONTACTS TO PROTONS OF 200 HeV ON 12C n-TYPE GaAs H I Ehlers, J S Ver-mak and J Pilaher, A A Cowley, A V R Leitah (UPE) W 0 Barnard (SIHR), J J Laurie, D.H. 'Jhittal and ' J 3 Malherbe and A J Uillia SJIHIU (SAC) d

10h30 - lOhSO (Ct/vWfWlT- W'3EJ7/™r TEA ' ?oy,r

UhOO - IZhOQ OR 0 VAN AS S8 Chairman: Or D Reitmam WOENSDAG 15 JULIE OGGEND

7*1« - «MO REGISTRAS IE Portaal

THEORETICAL SEMINAR S5 S2 S6 Chaînon: Dr F J Kok 3H30 - »hOO I. OPTICS AHO SPECTROSCOPV APPLIED AND INDUSTRIAL PHYSICS FORMELE UIÎDRUKXINCS V« D Chairman; Dr D J Brink Chairman; Dr A S H d» Jttu» TOESTATOVEKÏLYXINCS VAN CASSE J J Binning (AEK) 9hOO ' 3MS Dl 3hÛO - 9hlS B: 9M0 - QhSO I- SISTEMATIESE HEIGINGS IN DIE BEVOLKIKGSBLOOTSTZLLING AAN STUDIES VAN DIE EMC-EFFEK LBEFTYE VAN VUKXE IN DIE RADON: BRONNE EN METINGS S C Haraiê en C A Engel- KOOLSTOF EK STIKSTOF ISOELEK- g Strydom an A B Lmscfmer breaht tué) TKIESE SEKWENSIES lAEki f J Coetzer (US), FJ Mo3t*rt en F van dar Weatkuisen

9hl5 - 9h30 D2 9hlS - 9h30 BS LEEFTïD-ANALISE VAN DIE CHARACTERISATION OF THE NAC 3J, 'B' ENERGIEVLAKKE IN 0 III NEUTRON THERAPT BEAM T C Kotzê tStralingsbaheerl, g T ù Jonas (SAC), M Tudalev F J Zoatzer an P van dar and V L J Bandrikae Ueathuïzen

9hîO - 10h30 9h30 - 9h*S Bî 9hîO - 9h4S SPECIALIST GROUP MEETING STRALINGSTRANSPORTBEREKENINGS ELECTRGKAGNETIC NEUTRON VIR DIE ONTWERP VAN 'N GANMAr STRUCTURE FUNCTION OPTICS AND SPECTROSCOPY BESTRALIHGSFASILITEIT ******* Kouiohi Sakano (UCT) G P da Baar »n D E Sartori SPESIALISGROEPVERGAOERING IMKi OPTIKA EN SPEKTROSKOPIE

3h4S - lOhÛO m 9h4S - lOhOO II A ONE-DIMENSIONAL LIGHT EMC EFFECT AT SHALL X REGIC WATER REACTOR SHIELDING Kauiahi Sakano (VCT) BENCBURIC STUDT D S Sartari, S Tavio, O P de Baar (AEC) and C De Luca

10M0 - lOhlS «S lOhOO - lOhlS DIE OPTDŒRDfG VAN 'N TEL- PECULIARITIES ASSOCIATED GEOMETRIE BY 'N INDIREKTE WITH THE WIGNER ROTATION STRALINGSMETING VANAF 'N GAMCABRON C 3 van Wyk (UOFS! J B Venter (AEK)

lOhlS - 20h30 36 lOhlS - 10h30 II THE SHALL ANGLE NEUTRON SYMŒTRY VECTOR FIELDS AND SCATTERING FACILITY AT SIMILARITY SOLUTIONS OF A PELINDABA NON-LINEAR FIELD EQUATION DESCRIBING THE RELAXATION 1 C B Pranklyn (AEC) A MAXWELL DISTRIBUTION g SuUr and W-R Steeb (SAU,

10H30 - ÎOhîO T E E Portaal

CHERNOBYL - A CRISIS IN THE NUCLEAR INDUSTRY

49 WEDNESDAY 15 JULY HORNING

12H00 - 12hlO STUDENT SESSION : SOLID STATE PHYSICS AS NUCLEAR so SI Chairman; Or £ Albert* Chairman! f'DrCPARTJCLEPHYi B Frmklynl

SOLO) STATE PHYSICS AND MICROELECTRONICS 12H0O - sIZhlS 87 12HO0 - IShOO M S9 S Booyn* IHIHR) (p.Y) izACTioNS AT nrroi- SPECIALIST GROUP MEETING HEDIAR ENEKGIES AND GIANT SOLAR-TERRESTRIAL PHYSICS DIFOU EXCITATIONS **»•*•• David A$ohnm (VCT) SPESIALISGROEPVERGADERING SON-AARDHSIKA

12H1S - 12h3O BS TESTS OF NEUTROH DETECTORS FOR NEUTRON TIME-OF-FLIGHT S7 S9 SPECTRCHETER FOR (p,n) STUDIES AT NAC CYCLOTRON SOLID STATE PHYSICS 1 SOLID STATE PHYSICS 2 David Atahnm (UCT) Chairman: Dr S Luyckx Chairman: Prof S Kritzingtr

12hlO - 12MS A13 WHO - 12htS AH 12h20 - 12h4S B9 HALL MEASUREMENTS ON UNDOPED THE GROWTH OF PURIFIED 'BE • llC ELASTIC SCATTBRIKG OMVPE-GROWN GaAs POLYOtYSTALLINE SILICON IN REACTION GRAPHITE CRUCIBLES R Thavaf INIMRl E Sidtrae-Baddad, Bit Ftariak MEL** (UXT), A M Letaoalo, and J P F Stlltehop (WITS) J a Janteky and S Bart

12h.4S -13h00 A1S 12MS - IZhOO A1S SKUIFSLYTASIE EIENSKAPPE VAN DETERMINATION OF IMPURITY VERSTUIWINGSIOONPLATEERDE CONCENTRATIONS IN POLY- PLATINUM LAGIES CRYSTALLINE SILICON BY MASS SPECTROMETRY 0 •/ de Wez en A Wella (NIMH) D E Rogers (RIMR), U E Let and J A A EngeIbraoht

IZhOO - 13hS0 LUNCH Charles Smith Dining Sail

SO W0ENSDA6 IS JULIE OGGEND S2 S3 S6 S5

IShOO - IShOO IZhOO - IZhOO 12h00 - IShOO IShOO - 13hO0 SPECIALIST GROUP MEETING SPECIALIST GROUP MEETING SPECIALIST GROUP MEETING SPECIALIST GROUP NEETIfl PLASMA PHYSICS ASTROPHYSICS AND ASTRONOMY APPLIED AND INDUSTRIAL PHYSICS THEORETICAL PHYSICS ******* ******* ******* ******* SPESIALISGROEPVERGADERING SPCSIALISGROEPVERGAOERING SPESIALISGROEPVERGADERING SPESIALISGROEPVERGADERII PLASMAFISIKA ASTROFISIKA EN ASTRONOMIC TOEGEPASTE EN NYWERHEIDSFISiKA TEORETIESE FISIM

IShOO - 13hS0 MIDDAGETE Charles 9nith Seteaal

SI WEDNESDAY 15 JULY AFTERNOON

HMO • lihOO ! f PROFESSOR CHARLES D GOODMAN S8 /i 1 VooTjitttn Proftnor D AioHnm li. 00 - IShZO ' TEA S7 S9 S4 SI

VASTET0ESTWDF1SIKA 1 VA5TET0ESTANDF1S1KA 2 KERH- EN DEELTJIEFISIM SOfl-AARUWSIKA Voortitter: Df A 0 Every Voorritter: Prof E Friedland Voortitttv: I ftp D V Mingay j 7oortxtUr; Or P R Sutoliff*

ishio - ish4S A:? IShSO - ISMS IShZO - t$hO\Q0 SBIOi I IShiO - IShlS El

ELECTRICAL ASSESSMENT OF SiN THE THERMAL CONDUCHVITIES AURORACEBEURTEHIS VAN LAYERS ON G*As OF SOLD) PRESSJJRF-TRANSHIT- 27 JUNIZ 1982 c B Mils imm) TING AND GAS&T MATERIALS P S Stoker and A 0 Cottttr AS A FUNCTION OF PRESSURE AND; Qumoa and 1 Sigalae (NIMH)

IShiS - IShOO A19 7Sh4S - lehOO A20 1SH4S - lBhOO E3 THE PASSIVATION OF (HgCd)Te ELASTIC CONSTANTS OF ONE DATAVERUERKINGSMETODES VIR SURFACES GLASS AND ONE GLASS CERAMIC KLEIN ABSORPSIES IN RIOMETERDATA MET NIE-NORMAAL- C J Botha, M A Marais and 5 Graoatt, I Sigalas and VERDEELDE STEDRIHGS R ,' Mullet- P R Clayton (NIMBI D g Serfontvin en P B Stoker 1W)

IShCO - 17hO0 lShOO - IShlS Bll 16H00 - IShlS E4 S8 SPECIALIST GROUP MEETING ON THE PHENOMENOLOGY OF ELECTRON PRECIPITATION DECONFINEMENT AND CHIRAL EFFECTS IN THE DAYTIME SOLID STATE PHYSICS SYMMETRY RESTORATION E-REGION IN THE SOUTH ATLANTIC ANOMALY SPESIALISGROEPVERGADERING J CUymane (UCT), K Ridlieh, S SatM *n E Suhcmen R Saggard and J A Glcdhill VASTETQESTANDFISIKA

IShlS - lBhZO B12 lBhlS - lShiO BS EMPIRICAL EFFECTIVE INTER- AN EVALUATION OF COM- ACTIONS FOR SHELL-MODEL PUTERIZED METHODS FOR CALCULATIONS AROUND MASS 40 HF MUF PREDICTION B J' CoU (Wits) and W.I. S Lambert (Him) Gadinabokao

IShSO - 1SH4S BIS lShSO - 16h4S E6 DINAMIESE SIMMETRIE - fa NUWE OBSERVATIONS OF GRAVITY GESIGSPUNT VAN DIE SRILMODEL HAVES AT DURBAN I. AGTERGROND EN STRUTTOUR H D Barker (USD) 8 B (layer (US)

16h4B - 17hO0 B14 1SH4S - l?hO0 E7 DINAMIESE SIMKETRIE - fa NUWE INCLUSION OF A WAVY NEUTRAL GESIGSPUNT VAN DIE SKILMODEL SHEET IN A TWO-DIMENSIONAL II. TOEPASSINGS EN RESULTATE DRIFT MODEL R A Burger, H S Potgieter andBHoraal (PU) •.•"rOO - 2?h3J n POSTER SESSION : ALL GROUPSEXCEPT SOLID STATE (Pl-PW i/ppar Foyer IThlO - IBhOO SHERRY Poy&r

19hS0 for ZOhCO CONFERENCE 8ANQUET 'Great tlanga' Elangeni Hotel

52 W0ENSDA6 IS JULIE MIDDAS

PROBING THE NUCLEUS WITH NUCLEON CHARGE EXCHANGE REACTIONS

15M0 - IShBO TEE Portaal

S2 S3 .S6 S5 PLASWnSIKA ASTROFISIKA EN ASTROKOHIE TOEGEPASTE ENNYHERHEIDSFISIKA TSORETIESE SEHINAAR Vooraittar: Dr D Shtruall Voorsitfr: Dr M W F*att Voortitttr: Dr A S M da Jamt* Voovti tfr: Prof C 3 van tj IShZO - 2Sh4S CS - moo re IShiO - 1SM5 H? lihiO - IShOO • I

COLLISIONS EFFECTS ON THE PRESENTATION AND DISCUSSION NEUTRON ACTIVATION OF LARGE QUANTIZATION IN AN ANGULAR CURRENT-DRIVEN ION-ION OF DATA OBTAINED FOR THE SAMPLES USING A ONE MILLI- MOMENTUM BASIS : ALGEBRAIC HYBRID AND ION CYCLOTRON SUPERNOVA 1987. AT THE SOUTH GRAM CALIFORNIUM 2S2 SOURCE FORMULATION INSTABILITIES AFRICAN ASTRONOMICAL OBSER- M Lyccudi and J I W Watter- C L de Umg* (UNP) VATORY D Johnston* and J£ JSnWJS) !J5T R H Catoknole (SAAOi

15h4S - 16W0 CS IShiS - lthOO H8 THE ION ACOUSTIC INSTABILITY REPORT ON PROMPT GAMMA IN A MAGNETIZED TWO-ION NEUTRON ACTIVATION ANALYSIS PLASMA AT SAFARI-1 J Govender and S Bharuthram C Boflntyr (AEC) )

tehoo - iskis a 2ShOO - lShlS F3 IShOO - lShli B9 IShOO - ieh30 II ELECTROSTATIC WAVES IN AN 13 CM VERY LONG BASELINE DIE GEBRUIK VAN OUTOREGRES- FACTORIZATIONS OF TWO VECTO ION-BEAM MAGNETIZED PLASMA INTERFEROMETRIC OBSERVATIONS SIEWE METODES BY DIE RUIS- OPERATORS FOR THE COULOMB SYSTEM OF THE SUPERNOVA SN I987A ANALISE VAN 'N NAVORSINGS- PROBLEM KERNREAKTOR K Saidu and J P MaKenzis A Kenball (HRAO) at al. Old* hang* and R E Raab Itino) J ff Conradi* en F van (VHP) !tiek*rk(AEKI

18hlS - lSh3O CS - 17HCO F« ISMS - IShiO BIO ANISOTROPIC ION BEAM-PLASMA DWARF NOVAE, NOVAE, BUT NOT STAND VAN DIE NVS SE EtADIO- INSTABILITIES SUPERNOVAS ISOTOOPPRODUKSIEPROGRAH TE FAURE P Sinah and R Bharuthram S Warner (UCT) s j mil*

ishzo - ishis ce IShiO - IShiS Bll 16h30 - l?teC II. NUMERICAL CONSTRUCTION OF FRODUKIE VAN lI3I BY DIE HOE OM FERMI ENERGIES UIT THE SAGDEEV POTENTIAL AND NVS - EERSTE ERVARINGS THOMAS-FERMI TEORIE TE VOOR- ASSOCIATED SOLITONS AND SPEL P H SortUr (SVS1, 0 F Steyn DOUBLE LAYERS IS A WARM «n V L Rauttnbaah MULTI-FLUID PLASMA J H Brink an F i Kok (UP) S Baboolal (UDW), R Bharuth- ram and M A Bellberg

ieh4S - C? IShiS - IThOO H12 MODULATIONAL INSTABILITY OF PRODUKSIE VAN 52F« UIT Mn STRONG ELECTROMAGNETIC WAVES MET 66 MtV PROTONS IN A MAGNETIZED PLASMA GFSUyn,G F Steyn, F M Nortier en S Sharuthram (WU), P Singh S J Mitla mvs) and P K Shukla

17H00 - VhlO PLAKKAATSESSIE: ALL£ SROEPE BEHALWE VASTETOESTAfOFISIKA (Pi-pie) Soportaal

17h30 - lBhOC SJERRIE Portaal 19K30 vir 20hC0 KONFERENSIEOINEE 'Great TLanga' ilangeni Hotel

53 THURSDAY 16 JULY HORNING

S7 S9 SI SOIID STATE PHYSICS 1 SOLID STATE PHYSICS 2 NUCLEAR AND PARTICLE PHYSICS SOUR-TERRESTRIAL PHYSICS Chairman; 5r C I Chv: •"» Chaiman: Prof H I Albtrta Chairman: Mi 5 Lcmbtrt

ShOO - $h00 - ShlS All ehoo - skis n LASER EPITAXY OF DEPOSITED BEHAVIOUR OP THE TURNANCLB A UNIFIED TRIMT OF OIF SILICON THIN • FILMS : OF DYSPROSIUM NEAR THE PUUAnOHS CHANNELING AND ELECTRON IC •* C PHASE TRANSITION A DH Ualktr and JF MICROSCOPY MEASUREMENTS f P"de tHAV) and (UNO) J Adam (UHC), 0 Knoesan F Brit$ and H ?r*toriue

ShlS - 3h33 AS3 8hlS - 8h30 Ait ShlS ' ShJO E» DOPING OF SILICON BY LASER- CRITICAL BEHAVIOUR OF THE THE STXUCTUU OF COUPLED INDUCED DIFFUSION SINUSOIDAL — PARAMAGNETIC MACKETOSONIC A» ALFVEN PHASE TRANSITION TN HAVES AT PCS FREQUENCIES T K Maraia MC), » S Allis and S ppetoriue \CB F Brita (AEC) and B p*!a~:d*i and ADM VaVtmv I Pd»V_ du ~ 7MT)

3h3C - 8h4S ASS 8h30 - 8h4S AZ6 ShiO - 9h30 8h30 - 3h4S BIO BURIED ANTIMONY PROFILES IN ELECTRICAL RESISTIVITY OF SPECIALIST GROUP MEETING DAMN PeS PULSATIONS SILICON FORMED SY LASER DILUTE (Cr^AI^gjHOj NUCLEAR AND PARTICLE PHYSICS H S Barter (USD) DOPING ALLOYS ******* .? Caroliaaen (SAC), P Smit and S I Alberta (RAU) SPESIALISGROEPVERGADERING 0 Knotaen, H J "4cGttrick and H PretoriuB KERN- EN OEELTJ1EFISIKA

3k4S - ShOO A2? 8h4S - 9hOO AS8 BhiS - ShOO Ell EVIDENCE OF MULTILAYER STUDIES OF ELASTIC CONSTANTS IONOSPHERIC PULSATION FIELDS STRUCTURE IN AMORPHOUS OF LaF3 AT HIGH TEMPERATURES AND MECHANISMS FOR OBSERVED SILICON P S Bgovx (VST), J D Comina DOPPLER VELOCITY OSCTIXA- TIONS •/ Auc

3hCC - ihlS A29 ShOO - 9hlS A30 9h00 - 9hlS BIZ EFFECTS OF RE-SPUTTESISC THERMOLUKINESCENCE

ShlS - 9h30 A31 9hlS - 3h30 432 ihlS - 9h30 £13 ELERTRIESE GELEIDING EN FOTO- THE THERMAL STABILITY OF RESOLUTION OP TEMPORAL AMD GETEIDINr VAN AHORFE SILIKON SOME LANTHANIDE NITRATES SPATIAL AMBIGUITIES III J J ? Priralco en R Suane- C Strudom and C P J van PULSATSIC AURORA noel i'MV) Vuuren TV?) H J Koaah and M W J Seour- IUHU)

9H3C - 10h30 OR E NIELSEN S8 Chairman: Profeaaor J A CltdkCll

:Ch30 - lOhSO TEA Poyir

54 DONDERDAG 16 JULIE 06GEND

S2 S3 S6 S5 OPTICS AND SPECT8O3COPY EDUCATION APPLIED HMD INOUSTK1AI PHYSICS THEORETICAL SEMWH Chairmani Be 8 H van Btrgmtm Chairman; M* H Stanven Chairman: Dr S tuyokx Chairman! Or I I Sty*.

ShOO - MS P thOO - this HIS ShOO - thOO FOCUSING OF LASER IEAKS WITH AEROSOL ADVKJROMS - UCENT OOHIFMK TAN OIK OIHI A CAS UNS RESULTS FROM FIXE ANALYSIS QF AIRBORNE PAKTICOLAnS w i K Itotautt, » H Ntohatli* and ? F tunniisghan (UHB) B J Annsgem (WITS), A Zuoh- wsomoon ohiatti and J P F Stlliohop S B Otyr «n £ A it tot (US)

3hlS - 8k30 24 Shli - BhSO 81 C.A.R.S. TECHNIQUES FOR COM- FOB ANALYSIS OF MINERAL BUSTION AND CHEMtCAl REACTOR HATTER IN THIN SECTIONS OF DIAGNOSTICS BIHAR LUNG D Ball. 8 S T OrCvtr, R, J A S Pillay, B J Anntgarn Hutehton and G H Robertson (HITS), D Faurt and J C A CJCT) Davit*

ehio - iha ss BhlO - SH4S BIS a- MINIATURE CO2 WAVEGUIDE A VERSATILE UHV APPARATUS A- LASER FOl SU1FAC I PHTSICS AND CHEMISTRY 0 Sahneder (NPSl), C 8 Diakerton md D Preuei- TEDjnm, R G Copptrth- Ur uaitt, P H Loggtnbti\ . V S Brook* and J P F S*lliehap (WITS)

3h4S - 9h00 Pe 8hiS - ShlS a: Sh4S - ShOO BIS THE USE Of A WAVEGUIDE AS THE TASK OF THE UNIVERSITY THE REDUCTION AND SUBSEQUENT^ CARJURIZATTON OF AN INDUS^^ RAKAN CELL FOR CEMERATION OF U de Baa* (VSO) IR LASER LIGHT TRIAL CO-HYDROGENATHUKtATA- LYST : AH XPS AHg^rffS STUDY .f Budtinaki and D «T Brink p H U>qg*nbf#Q. R J Copptrth- (NPBL) xxtitt cnt'J P F Selliohop (WIIST

3HC0 - ah3O 2' ShOO - 9hlS 81? ShOC - 9h3: STUDENT SESSION k STODT OF THE FORMATION OF CAVITY QUANTM CKROHOOT!! OPTICS AHD SPeCTHOSCOPY ZIRCONIUM SUICIDE ON MICS TO ORDER oj SILICON (100) SUBSTRATES A J Stoddart md r i MOK-LUEAR OPTICS : SOME US 3rvo_k* (VIIS), t XutM- Viollitr ;VCT! PRINCIPLES AND APPLICATIONS lan, ASK lAtteh, T E Dtrry 0 J Brink tSFPX) and fl G Copptrthxritt

9hlS - 9h30 02 9hlS - 9hZ0 ?78 HUMirOIE OR DISCOMTORI INDEX, RAPID COMPUTER-CONTROLLED D.I. CAPACITAIICE TRAHSIENT CRARAC- TERIZATIOir OF DEEP-LEVEL X D 9ark*r (UNO) CENTERS B a Haguir* (7>*nt Poly ttehnie, ilk), A Horthall and J P F Stlltohop

ShSO - lOhZO CURRENTS AND ELECTRIC FIELDS IN THE EARTH'S MAGNETOSPHERE AND IONOSPHERE lOHZO - lOhSO TEE Portaal

SS THURSDAY 16 JULY MORNING

$7 S9 SI SOLID STATE PHYSICS 1 SOLID STATE PHYSICS Z NUCLEAR AW) PARTICLE PHYSICS EDUCATION Chairman; DP S Bart Chairman; DP R Pratcriu* ChaiiTnan; DP W R HoHavay Chairman: Prof P B Stoktr llhOO - UhlS A3! UhOO - :iMS AH UhOQ - llhiO BIS UhOO ' IShOO GRONTH OP G*Al EPITAXIAL MAGHETIC EFFECTS IN DILUTE STUDENT SESSION SPECIALIST GROUP MEETING LAYERS USING CURRENT CON- Cr-Si ALLOYS NUCLEAR AND PARTICLE PHYSICS EOUCATION TROLLED LIQUID PHASE EPITAXY B L Albarta and J AJ Zourant SOME CORHNT CHALLENGES IN V J Wtrtt*ra, J S Vemaak (RAO) and A W S Uitah (VPE) NUCLEAR PHYSICS t ITS FIELDS SPESIALISGR0EPVERQADERIN6 OF APPLICATION OPLEIDING J P P Stlltahop (WITS)

llhlS - Uh30 A3S JIMS - IIMO Ale AN INVESTIGATION INTO THE THE EFFECTS OF PLASTIC DEFOR- MECHANISM OF FORMATION OF KATION ON THE ANNEALING OF INTERSTITIALS PRODUCED BY RT IRRADIATION C >i Coirrit fVCT), J C Uu and J 'it Mayer P M M,TOara (WITS), JR Sexvtlo and AM Hdebuka

Zlh33 - Uh4S A3? WHO - Hh4S A3S HMO - llhii B16 HIGH TEMPERATURE APPLICATION KKCDIUESS FRACTION STUDIES NUCLEAR PHYSICS DATA ACQUISI- OF SCHOTTKY CONTACTS TO GaAl OF SUPERCONDUCTING NIOBIIM- TION WITH A PERSONAL COMPUTER TIN ALLOTS S Felling IHIMR), A P Botha fi U Ptarisk (WITS) and 3 Pretorius G R Baame and B Xolk (WITS)

Hh4S - 12HO0 A39 Uh4S - IShOO A40 11H4S 12hOO B17 Co- AND Ni-SILICIDE FORMA- PHONON FOCUSING IN PIEZO- POSITRON PRODUCTION IN TION IN THE PRESENCE OF GOLD ELECTRIC CYSTALS NUCLEAR COLLISIONS 3 A Has rsfflffj, J J Cruy- A a Every (WITS) and B Spoalstra (HZ), J P P Stll- *jagen and H Pretorius eahop and U Von Wirmersperg

ZZWO ~ IShlS A41 12h00 - 12hlS AiZ IZhQO - lthli BIS IZhOO - 12h30 G3 THE EFFECT OF OXYGEN IMPURI- RAMAN STUDIES OF IRRADIATED OBSERVATION OP A DEVIATION STUDEHT SESSION TIES ON THE SOLID STATE tl AND KI(Sr) FROM BHABBA SCATTERING HI INTERACTION BETVEEN THIN ?t- THE ELECTRON-POSITRON SYSTEM EDUCATION A M T Allen, C E AllenspaoH FILMS AND SILICON WILL COMPUTERS REPLACE and J D Camins (WITS) !) Don Wirntrsptrg, S B Con- PHYSICS PROFESSORS? .V A i/andt and R Pretoriua ntll, R P A Hoernle and E Sidtraa-Baddad (WITS) G E ObtPtm (RV)

IShlS - 1BH30 A43 mis - zzhzo PDl - 12h30 B19 Ni-Si SOLID-STATE REACTION : SYNTHESIS AND CHARACTERIZA- TDPAD MEASUREMENTS OF IMPLAN- FORMATION OF SILICON-RICH TION OF SOME HIGH-TEMPERA- TATION TEMPERATURE DEPENDENCE 1? LAYER WITHIN NiSi2 IN THE TURE SUPERCONDUCTORS IK F UFLANTED DIAMOND PRESENCE OF EXCESS AMORPHOUS ? R Clayton, A van Zyl, S Connall (WITS), IP? Stll- SILICON X Sioalaa and S Janteky aahop, H S Stvmtt, B Apptl J I toslesd (SAC), 3 A ROB (tiMR), D S MaCachlan and K Bharuth-Ram •md ?. Prezoriua

12H3C - 13hOC POSTER SESSION : SOLID STATE PHYSICS (P17-P30) upper Foyer

a: - :3Hso LUNCH Charl*B Smith Dining Sail THURSDAY 16 JULY AFTERNOON

ZihCC - lihOC j DR G D NICOLSON ^- S3 i '/ooreitter: Dr H W Feaat C^* :s-.oc - :s TEA Foyer :sh33 S8 ANNUAL GENERAL MEETING S A I P

MAYORAL COCKTAIL PARTY Durban City Sail OONDERDAG 16 JULIE OGGEND S2 S3 S6 ss ASTROPHYSICS AMD ASTRONOMY APPLIED AND INDUSTRIAL PHYSICS PLASM* PHYSICS THEORETICAL SEMINAR Chairman; Prof B Warmr Chairman: Dr B J Annagam Chairman: Hr P H Krwm Chairman! Dr R Ttgtn UhOO - Uh30 Fi UhOO " UhlS HIS UhOO - UhlS C3 UhOO - UhSO ZZZ DESIGN OF HELICAL MAGNETIC THE AGING OF OLD DEGENERATES: AANWENDING VAN TITAANNITRIED LEE-YANG TEORIE VM FASE- COILS FOR THE AEC TOKAMAK ASTEROSEISMDLOGY OF WHITE

UhlS - llk30 C9 llhlS - UhiO 320 MAGNETIC FIELD MEASUREMENTS DIE VERSICYNSEL VAN RESSPAN- OF RESONANT HELICAL WINDINGS NING EN DIE METING DAARVAN ON THE AEC TOKAMAK MET BEHULP VAN X-STRAAL- DIFFRAXSIE D P Coater, J A M de Villiara, J D Pletoher, y B du Pree* en G Ifieuuoudt 0 Sothnagal, D E Roberta and (AEK) D Shenxll

Uh30 - 11H4S CIO Un30 - Uh4S F6 UhSO - IMS H21 UhiO - 12hZO I2S REPAIR AND BE-ASSEMBLY OF IMPLICATIONS OF RAPID STELLAR DIE METING VAN RESSFANNINGS NON-O(6) RELATED DYNAMICAL TOKOLOSHE ROTATION FOR NONRADUL PULSA- IN HETAALKOHPONENTE MET BE- SYMMETRIES OF THE INTERACT- TION HOD'S IDENTIFICATION HULP VAN X-STRAALDIFFRAKSIE J R O'Hahcny (AEC) ING BOSON MODEL C A Engalbreeht (UNISA) g Sieuuoudt an U B du Preez B g Gayer, F J U Safma and TASK) F G Seholta (US)

Uh4S - IZhCO CU Uh4S - IZhOO F? Uh4S - IZhOO RZZ RESONANCE STREAMING IN OBSERVATIONS OF SHORT PERIOD WEAR MECHANISMS MODIFICATION TOKAMAKS Be STARS IN THE YOUNG GALAC- INDUCED BT ION IMPLANTATION TIC CLUSTER NGC3766 IN WC-Co. D Sherwell (AEC) S a Cuyakx. 1 Caaeuto and J P F Sallsahop (WITS) WITHDRAWN

IZhOO - 12hlS CIZ IZhOO - IZhlS F8 IZhOO - IZhlS SS3 ENERGY TRANSPORT IN AN SOME QUESTIONS ABOUT THE EFFECT OF VARYING SHEET ERGODIC MAGNETIC LIMITER HYDRODYNAMICS OF'ACCRETION THICKNESS ON THE FRACTURE DISKS TOUGHNESS OF HIGH STRENGTH •V A Hellberg (UND) and STEEL W Feneberg C Kotn (imiBO) g Protopappat, J Nieuumeijer and W B du Praez (AEC)

12hlS - IZhZO C13 IZhlS - IZhZO F3 IZhlS - 12h3O HZ 4 PROBE MEASUREMENTS IN A PROPERTIES OF ALFV& WAVE ELECTRON PROBE MICRO-ANALYSIS STEADY-STATE TOKAMAK DIS- DRIVEN STELLAR WINDS (EPMA) OF IRON IN GALVANIZED CHARGE PLASMA COATINGS PRODUCED ON LOW 11 K Dougherty and J F Ha- SILICON STEELS P J Barrett (UND), M Ono, Xenzie (USD) V Darrou and G J Greene A It Kirkbrid* and A Wells (Sim)

IZhiO - IZhOO PLAKKAATSESSIE : VASTETOESTANDFISIKA (P17-P30) 3oportaal llhOO - IZhSO HIODAGETE Charles Smith Eetsaal DONDERDAG 16 JULIE MIDDAG

RECENT ADVANCES IN THE TECHNIQUES OF VERY LONG BASELINE INTERFEROHETRY (VI.BI) AND ITS APPLICATIONS IN ASTRONOMY ANO GEOPHYSICS

IShOO - IShiO TEE Portaal UhSO ss JAARVERGADERING S A I F lBhOO SKEHERONTHAAL OEUR BURGEMEESTER Durbante Stadeaal

57 FRIDAY 17 JULY MORNING

S7 S9 SI SOLID STATE PHYSICS 1 SOLID STATE PHYSICS 2 NUCLEAR AWD PARTICLE PHYSICS SOLAR-TERRESTRIAL PHYSICS Chairman: Prof P dt 7 du Chairman: Dr 3 Sooytnt Chairman: Prof W J RauM Chaiman: Dr A W V PooU Pl**til

ShOO - ShlS A1S ShOO - this AM ShOO - ShlS I "N STUDIE VAN DIE Pt/Si ATOMIC SITE LOCATION OF A SOURCE r« 3 Hx AURORAL DONLAGIE SISTEEM TUSSEN DOPANTS IK CaAa BY ELECTRON PULSATIONS 7SO*C «D lOOO'C CHANNELING g J Banitn. E Hravlag and G I P Btrnina tn t W Loxai E H Ghtnn*, R C Snymxn, HV J SoemrfUld (USD) WOVS) CAB Ball and B Smith (UPE)

BUS - BhSO A4? BhlS - 8h30 A4S BhlS - BhSO BIS DIE EPITAKSIALE GROB1 VAN Cr A TEM STUDY OF THE STRUCTURE AURORAL PULSATIONS AND OP Ag(ni) SUBSTRATE OF ANNEALED NITROGEN - ASSOCIATED CHORUS H 0 van dmr B»ra «n IMPLANTED SILICON g J Ban$en and M W J Soour- g I Oaiqher (UP) B C Snuaan, B P Zetlie and fUld (USD) J S Itttthlina (UPE)

Sh30 - 3H4S A49 8h30 - SMS A4B BhSO - Sh4S BIO BhSO - ShiS IDENTIFICATION OF DEFECTS BT DEEP RADIATION DAMAGE IN SOEXXOG VAN DIE WAARNEMUIG AN INTERPRETATION OF SO- MEASURING THE IN-PHASE (I) METALS AFTER ION IMPLANTA- VAN SONVLAMIEDTRONE IN DIE CALLED 'DRIFTING DARK AND QUADRATURE (0) DLTS TION VTFMOIUTEDATA VAN DIE AURORA' SPECTRA DURING A SINGLE NEUTRONMOHITOR IE TSUMEB TEMPERATURE SCAN (IQ-DLTS) E Friedland and B V Albert* g SehouU-yanntek, H W J (UP) P 8 Stoltar (PI/) Scour field and £ Hravlag f D Ata-et and H Hal (UPE) (»

Bh4S - ShOO AS1 8h4S - 9h00 ASO Bh4S - ihOO BS1 ShiS - ShOO Zl? IMPROVEMENT OF SEMICONDUCTOR I0ONINPLANTERING IN Al:Si- KARAKTERISTIEKE VAN SEKOND- THE RELATIONSHIP BETWEEN THE MATERIALS BY MEANS OF DEFECT KONTAKTE SRE-EIEKTRON ENERGIESPEKTRA' PLASMASPHERE AND AURORAL ENGINEERING S A Carr, J B Malherbe «n C Dtdnan, 1 van Waart »n OVAL L W Snurm (UPE) B Fi-iedlmd (UP) W Hingay Oiffl J Stepfwnem and M U J Scour- Jd L fitla (Cimi

9k00 - ShlS ASS ShOO - 9hlS AS2 3h00 - ShlS B22 ShOO - this SIB PROBLEMS EXPERIENCED WITH DIE MODIFTKASIE VAN Ni-Si STROamiGTHEtD EFFERTE IN EXIT-POINTS OF WHISTLERS HI OPTICAL FTIR CHARACTERIZA- SCROTTKYKONTAKTE MET BERULP SEKONDtRE ELEKTRON ENSRGIE- THE REGION OF SANAE - TION OF C«A» VAN IOONBUNDELVERMENGING ANTARCTICA J A A Engelbrveht, I J lee C Muburg, J B Malhtrb* tn C Dtdnam tn J van Vaart J HLa&tig and A R U Ought* and A Botha (UPS) E Fntdland (UP) 7 (HUD)

9hlS - 9h30 AS4 9MS - 9h30 823 ShlS - 9H30 E19 IMPLANTED FLUORINE PROFILES LEEFTTD VAN DIE Oj TOE STAND RAY-TRACING STUDIES OF THE IN DIAMOND PROPAGATION PATHS OF VLF SIGNALS ORIGINATING NEAR THE J F Print, T S D»ny. C C P V H Pro*»skf4 *n D W Mingay Madiba and IP? Salltehop tAEK) EQUATOR (WITS) Praveth Ranlall and A D !4 Walker (UNO)

9hS0 - JOhlO PROFESSOR R K LEfflER S8 Chairman: Profttsor C A Sngtlbrtaht lOhZC - lOhSO TEA Foyer

& ^ VRYDAG 17 JULIE OGGEND

S2 S3 S6 S5

OPTICS AMO SPECTROSCOPY EDUCATION APPLIED AHD INDUSTRIAL PHYSICS THEORETICAL SEMINAR Chairman: Dr F J Co*t*»r Chairman: Prof B SpotUtra Chairman: Dr T E Dtrry Chairman Prof R D ViollUr

ShOO - BhlS B2S ShOO - ShiO 124 PASSIVE SINGLE-PASS SOLAR ACOUSTIC CHERENKOV RADIATION WATER BEATERS BT SUPERSONIC HEUTROHS T B Sah»: and J C van 0 Tmxr (UCT) Stadin ffir

ShlS - ShSO SB 8hlS - 8h30 04 BhlS - BhSO B28 OPTICAL FIBRE COMMUNICATION SIMPLE ELECTRICAL CIRCUITS OPTIMAL FLOW IN A SOLAR A PRACTICAL TUTORIAL APPROACH WATER HEATER S Gunn (AbarSare Group) M S Alii* and J E King (VCD T B SaheffUr (UP)

8hS0 - 8MB D9 Sh30 - 9h00 GS 8h30 - 8h4S B27 8hSO - 9h30 12 S COUPLED-MODE THEORY FOR THE CONCEPTUAL PROBLEMS IN DEVELOPMENT OF HIGHLY EFFICI- SUPERNOVA MODELS ACOUSTC-ELECTRO-OPTIC SIMPLE DC CIRCUITS: INSIGHTS ENT, LOW COST THERMAL INSULA- C A Engelbreoht (US) EFFECT IS SAW DEVICES GAINED FROM STUDENT RESPONSES TIONS FOR USE IR THE IN EXAMINATIONS 100-400'C RANGE A V Soholtz (UP) H Stanton WITS) B Potgitttr, P R Clayton, I Sigalas and R J Gumow (MM)

- 9h00 D10 ShtS - 3h00 B28 DIE CEBRUIK VAN APODISASIE C.A.R.S. TEMPERATURE MEASURE- IN DIE ONTWERP VAN b AKOESTO- MENTS IN A RUNNING INTERNAL OPTIESE SPEKTRUMANALISEERDER COMBUSTION ENGINE £ de Koker (UP) D Ball, B S T Driver, R J But- ohecn, G 8 Robtrtacm (UCT), K P Btnnttt, R K Dutkitoicz, R Sattt and A rates

9h00 - 9hlS Dll 9hOO - 9hS0 Gt 9h00 - 9h30 829 AKALISE VAN NIE-LINEARITEITE THE SIMPLE ELECTRIC CIRCUIT STUDENT SESSION IN AKOESTO-OPTIESE INTER- AS AM ENERGY SYSTEM: SOME APPLIED AND INDUSTRIAL AKSIES CDNCE»TDAL DIFFICULTIES PHYSICS WHICH CONFRONT STUDENTS IN A J Boffman (UP) SIMPLE CIRCUIT TEEORY SOME RESULTS OF UITERGOLD'S RESEARCH PROGRAM Z Jiya (UPB) G Gafner (ISTERGOLD)

9hlS - 9h30 D12 EVALOASIE VAN KODERIKGS- TEGNIEKE VIS REKENAAR- GEGENEREERDE-HOLOGRAHME PSRoux (UP)

THE STRUCTURE OF MATTER AT HIGH ENERGIES lOhSO - lOhSO TEE Portaal

59 FRIDAY 17 JULY HORNING

$7 S9 SO SI SOLID STATE PHYSICS 1 SOLID STATE PHtSICS 2 NUCLEAR AND PARTiaE PHYSICS SOLAR-TERRESTRIAL PHYSICS Chairman: Nt'at J Auoam? Chaimm: Dr 1/ 8 du Prvc« Chairman; Prof J P I Chairmn: He 8 Haggard Rtimokt

llhOO - UhlS ASS UhOO - UhlS ASt UhOO ' UhlS B24 UhOO - UhlS IZO THE APPLICATION OF REAL TIME GEPDLSEERDE EL3RW>NBUNDEL- ANOMALOUS RESPONSE OF THIN tflHD PATTERNS IN THE METEOR FAST FOURIER TRANSFORMATIONS vatRiTnxc (PEV), LASER EH FILM PLASTIC SCWTTLLATOI TO REGION IN EDS ELECTRON MICROSCOPY HEAVY IONS TEMPERATUURUITGLOeiWC VAN L H G PooU (W> D R Scalding and £ ttaiatzy CEfHPLANTEEW)!! InSb B Fronklyn (ABcTl (USD) "" S WAlUrti «n R CillUn 7BP7

UhlS - Uh30 AS? llhlS - UhlO ASS UhlS - Uh30 B2S UhlS - Uh30 CORE-EXCITATION EDGE AND EX- STRALINGSKADE VANWE LIGTE PROMPT GAMMA-RAYS FROM THER- GEOMAGNETIC INDUCTION TENDED ELECTRON LOSS SPECTRA IONE IN InSb MAL NEUTRON CAPTURE IN EFFECTS FROM VARIOUS CARBON SURFACES NATORAL Oi AND Ct 5 J E van Sonder tn E Fritd- 0 I H Sohfptrt (HOB) USING LOU ENERGY REFLECTED land (UP) C B Fmnklyn (ABC) ELECTRONS B G Maguire (Trent Polyteeh- nio, UK) and J P F Sellaehop llhSO - Uh4S A5S llhiO - 11H4S UhiO - Uh4S BBS UhlO - Hh4S E22

LINEAR AND PARABOLIC REAC- DIE GEStfJIK VAN LAE ENERGIE Kg/K EMISSION RATES FOR PLASMA SIMULATION ON A TION KINETICS IN BINARY IOONVERSTROOIING VIR DIB X-RAY PRODUCTION BY PROTONS, MASSIVELY PARALLEL PROCESSOR COUPLES ONDER5O1EX VAN DEUTERONS, AND ALPHA PARTI- I HA OUdhill, 0 Buntman KANGSKIOCINGS CLES S C Zingu (MEDUNSA) and t R0 Stormy (STARLab, C H van (UOVS) P B Kottt and 0 V Hingay Stanford Vnivrtity, USA) JAEC)

Uh4S - IZhOO A61 JZhiS - IZhOO Uh4S - IZhOO 827 CORRUGATED GLIDE SURFACES 'N STODIE VAN DIE ADSORPSIE K X-RAY SPECTRA PRODUCED BY AND THE ORIGIN OF EARTH- VAN l;20 OP POLIKRISTALLYNE NITROGEN IONS HI Ti AND V QUAKES VLET/RK STAAL MET BEHOIP VAN P B Kotzt and D V Mingay EDELGAS IOONVERSTROOLN3 P J Jaakaon (UffP) 7SEC1 G n van Wyk (UOVS), U Sng- lert «n E Taglauer

12hO0 - 12hlS AB2 WiOO - 12hlS A64 12HO0 - 12hlS B28 'M KOHSISTENTE HERANALISE DIE ONDERSOEK VAN VERIIKIL- MICRODOSTMEnSY - CONCEPTS VAN DIE TEORIE VAN OPPERVLAK- LENDE TIPES AMORFE KOOLSTOF AND QDAHTOIES SEGREGASIE IN MJLTI1COMPONENT- H.B.V. X-STRAALDIFFRJUCSIE J B Hough and P J Sinna ALLOOIE : EWEWKSEGREGASIE M P/ifk (AEK)

12hlS - IZhZO ASS 12hlS - IZhSO ASS i2his - nhio m 'N KONSISTENTE HERANALISE TRANSMISSION ELECTRO* DIF- MEASUREMENT OF SINGLE EVERT VAN D?E TEORIE VAN OPPERVLAK- FRACTION PATTEBK ANALYSIS SPECTRA IN A HIGH LET RADIA- SEGREGASIE IN MULTIKOMPONENT- USING mCRODENSITOMETRY TION FIELD ALLOOIE : KRITIEK OP ANDER C I Churns (UHC) and S Xrit- P J Binnt and J B Bough TEORIE zinger J du Pleasis en 0 H -Jan ifyk (UOVS) 12h30 - 13hOO At? 12hS0 - 12h4S A68 APPLICATION OF SPACE GROUP SEGREGASIE VAN TITANIUM IN THEORY TO SECOND ORDER PHASE GOUD TRANSITION IN CRYSTALS P g 7iljom, J P 3 W Xunert I UP) 0 Holtzhauaen (UOVS)

12H4S - 13hOO A?0 DTE ROL VAN KLEIN PERSENTA- SIES Pt-METAALTOEVOEGINGS IN Fe40Cr STAAL J ? Roux, D J Holtzhaueen tn H 'J •Jcni Stadtn (UOVS)

- :3hs: LUNCH Chart** Smith Dining Ball

60 VRYDAS JULIE 0G6END S2 S3 S6 PLASHA PHYSICS ASTROPHYSICS AND ASTROHOHY APPLIED AND INDUSTRIAL PHYSICS THEORETICAL SEMINAR Chaimms Mr J 0 Ft*tah*r Chairman: Prof P H Stoktr Chairman: Dr D T I Jon** Chairman: Prof C A Engtl- brtoht

llhOO -IMS CU llhOO - UhlS P10 llhOO - llhlS B30 llhOO - IZhOO Ite OBSERVATIONS Of THE ION-ION A T«V TRIPLE PEAK FROM THE APPLICATION OF THE RADIAL STUDENT SESSION IWO-STIEAM INSTABILITY PSR 1509-587 DiFFusmrr EQUATION TO THE THEORETICAL PHYSICS 0 C da Jqgtr, B C Rauban- PETROLEUM INDUSTRY, El PARTI- p J Barrett and R 0 Grtav** ON THE CREATION OF MATTER VI h*inar, A R north, a I da CULAR WITH RESPECT TO WELL THE UNIVERSE and G van Urk (PU) TEST ANALYSIS P Stligmann (SOEKOR) R 0 VioUier (VCT)

UhlS - Hh30 CIS UhlS - llh30 F2 IMS - Uh4S B31 SPATIAL CHARACTERISTICS OF THE EA¥El"m> TcV GAMMA-RAY SIKLOONSKEIERNAVORSING aOSSFTELD ION ACOUSTIC FLUX FROM ISOLATED PULSARS P A KareUn (AEK) TURBULENCE 0 C de Jager, Bid* Jagtr R 0 Greaves and P J Barrett and B C Raubenhrimtr (PU) (tm>

UhiO - 21h4S CIS Uh30 - Hh4S P12 CURRENT RESULTS FROM THE A SEARCH FOR SOURCES OF LASER SECTION OF THE PLASMA ULTRA HIGH ENERGY GAHKA-RATS PHYSICS RESEARCH INSTITUTE, WITH THE POTCHEFSTROOM EXTEN- UNIVERSITY OF NATAL SIVE AIR SHOWER KRRAT J A Waltham, P F Cunningham 0 C de Jagtr, A R north *t et at. (USD) al. (PU)

Uh4S - IShOO Cl? 22*45 - IZhOO F13 - moo pi4 DRIFT IN A MAGNETIC FIELD FURTHER RESULTS FROM THE COKING COAL CONTROL BY WITH UNLIMITED GRADIENTS RHODES 2.3 GHz SURVEY AUTOMATED IMAGE ANALYSIS ' and B Moraal (PU) 3 Woermann and J Jonas (RU1 L E Konrin-Kottakouski (NICR) and a Roux

i2hoo - izhis as IZhOO - IShlS F14 IZhOO - 13h00 12? PLASMA ROSSBY WAVES OB MASERS IN SOUTHERN IRAS NUCLEOH-ANTINUCLEON ANNIHILA- M K Dougherty and J F UaKen- SOURCES TION IN RELATIVISTIC QUARK zie (USD) M S Dollery (BSAO), H J Gay- MODELS lard, P n f/hitelock and R J R Tegen (VCT) Cohen

IZhlS - 12k3C C19 22*25 - 12h30 F1S PHASE MEASUREMENTS OF THE OH MASERS IN OBJECTS SHOWING ION CYCLOTRON INSTABILITY 10 MICRON ABSORPTION W J Alvort and E 0 van M J aavlaed (IBUO), M E Dol- Si»T

12h30 - 12H4S C20 MAPPING THE FREQUENCY DETER- MINING REGIONS OF THE ELEC- TROSTATIC ION CYCLOTRON INSTABILITY P Krurni and R Sehrittuieaer turn) 12h4S - IZhOO CZl A SIMPLE METHOD TO DETERMINE ABSOLOTE VALUES OF SPACE POTENTIAI. g Hraulaa and P Knmm (USD)

IShOO - 13hS0 HIDDAGETE Charles Snith Eattaal POSTERS FOYER/BOPORTAAL PLAKKATE

ON TIHE-DBFBNDENT POTENTIALS pie H VKfcmOld (ABC)

VOORXEURVBRSTUIWING VAN VERBINDINGS PI? J B Halherbe {Uf->

DIFFUSIESTUDIES VAN Si IN F«-CEBASEERDE AMORFE ALLOOIE PIS W D Roos en 0 X van Vyk (UOVS)

HAGNETIC PROPERTIES OF AMORPHOUS (METALLIC GLASS)Fe.n Ni,0 B PIS m * • M D Rang. T B Doyle and D R Spalding (UND)

A M5SSBAUER STUDY OF THE MAGNETIC HYPERFINE FIELD DISTRIBUTION IN AMORPHOUS Fe,^ Ni4Q B2Q A Maekenjee, H Sdxirds and K Sharutk-Ram (VW)

NEUTRON DIFFRACTION EXPERIMENTS OF SOME RARE-EARTH INDIUM COMPOUNDS P21 )fl G Booysen (RAH), P de V du Pleaeis and GBP Brits

ELASTIC BEHAVIOUR OF MOLYBDENUM PHOSPHATE GLASSES PSS J D Comins (WITS), J E Maadonald, F F lambeon and G A Sounders

ON SURFACE DAMAGE TO (100) CdTe P23 M E Lee, E 0 de Neijs (VST), A H Leteoalo and R J Muller

BROMINE-METHANOL ETCHING OF (100) CADMIUM TELLURIDE SURFACES PZ4 M E lee, A M letaoalo (UNT) and il 0 Barnard

!| THE OXYGEN COVERAGE ON DIAMOND SURFACES P25 T E Perry (WITS), J 0 Sanaen, P E Harris, R G Copperthjaite and J P F Sellachop

INFLUENCE OF TEM GRIDS ON AMORPHOUS SILICON DURING IN SITU SILICIOE FORMATION P26 S Kritzinger, C J Bedehsr and J C Lombaard (US)

OPTICAL BIREFRINCENCE STUDIES OF DEFECTS IN GaAs P27 E E van 3yk, J S Ver->aak -2nd A V R Zeitah !VPE>

HALL PROFILING OF CaAs EPITAXIAL LAYERS

J A Goodman, A U P teitah and «.' 5 Vermaak 'VPS)

EFFECTS OF PEBA ON GaAs P2$ H W Alberts (UP), ? D Auret (UPE), H Wei and H le Roux

DETECTION OF ELECTRON AND HOLE TRAPS BY DLTS IN PROTON IMPLANTED VPE GROWN n-GaAs USING SBD'S P30 M Sel and F D Auret (VPE)

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WILLISTON ELIN Box 39481 Bramlay 2018 South Africa T»l. (011) 702-2227/8/9 T«lm 4-24206 SA Abstracts Opsommings

SOLID STATE PHYSICS VASTETOESTANDFISIKA

THE STABILITY OF CERTAIN INSTRUMENTS USING ACRT FOR THE GROWTH OF CdHgTe A1 WHICH ARE ESSENTIAL IN THE FUNCTIONING A2 OF AN OMVPE REACTOR J H S Roodt. M A Marais and R J Muller National Institute for Materials Research, CSIR 0 j Lombard National Institute for Materials Research Buules of cad«*lum mercury telluride produced by the Bridgman method suffer from radial and axial lnhomo- Stability of certain instruments in m OMVPE reactor, geneity due to the orcnounced segregation of HgTe and /or- example the mass flow controllers, pressure CdTe during such equilibrium type growth techniques. controllers, etc., are essential to obtain reproduce- The Accelerated Crucible Rotation Technique (ACRT) able results. This Mill be discussed along with applied to Bridgraan growth will be discussed as a results wnich were obtained from calibrations done on method to improve the radial homogeneity and to in- these instruments which are used to control the OMVPE crease yield. Recent results obtained at the NIMR, CSIR reactor in operation at the N1MR. using this technique will be presented.

THE DESIGN OF AN OVERALL SAFETY SYSTEM CORRELATION BETWEEN CARRIER CONCENTRATION M FOR THE SAFE OPERATION OF AN OHVPE REACTOR A4 IN HgCdTe AND CHLORINE DENSITY AS DETER- A P Uys, A P Botha, 0 J Lombard and J C Q Fletcher MINEO BY SIMS AND FAB National Institute for Materials Research, CSIR H J Strydom, M A Marais, DEC Rogers and J H Basson Organometallic Vapour Phase Epitaxy (OMVPE) is a key National Institute for Materials Research, CSIR materials technology for advanced high-frequency optical and microwave devices. The purpose of this In order to produce (HgCd)Te for photoconductive presentation is to profile the hazardous properties detector applications, near-intrinsic material with of gasses being used on a research reactor, and few residual impurities is required. Material with describes an OMVPE-reactor safety interlock and high carrier concentration has been found to contain automatic shutdown system now being used at the NIMR. large amounts of chlorine using SIMS. A direct cor- Some specific features employed are reactor over- relation between the Cl concentration and the carrier pressure detection, susceptor overheating detection concentration were found. The sources of Cl contamina- and toxic gas exposure control. This presentation tion have been found to be the Cd starting material will also deal with the technique used to remove As (as determined by FAB). Chemicals used to clean the and AsH from the reactor exhaust. starting Materials as well as the silica ampoules used during growth. The powerful combination of magnetic sector SIMS, quadruple SIMS and FAB mass spectrometry is unequalled in the field of ppm to ppb concentration levels.

ANOMALOUS HALL EFFECT ON n-TYPE A SIMPLE FAT-FET GROWN BY OMVPE A6 AS H30 gCdfl 2Te GROWN BY THE SOLID STATE Jack C Q Fletcher RECRYSTALLIZATION TECHNIQUE National Institute for Materials Research. CSIR J H Basson and H Booyens A simple, large gate length (FAT) FET nas been grown National Institute for Materials Research, CSIR by Organometallic Vapour Phase Epitaxy. Conditions governing the growth of both buffer and active layers Anomalous Hall curves have been obtained for thick will be presented as will various aspects of materials low-doped n-type Hg o.sCd 0.2 Te samples grown by the consistency over large deposition areas. Device solid state recrystallization technique. These curves processing and performance charactaristies will be are of such a shape that the 77 K value of Hall discussed briefly. coefficient is significantly lower than that at very low temperature, contrary to theoretical predictions. These results are explained in terms of a p-type core sandwiched between two n-type surface regions.

67 AT TH« GROWTH OF AlGaAa BY MOVPE A8 SURFACE LAYERS OH ft FORMED DURING PLASMA D Raubanhaimer. A W R I*itch and J S Vtnutk W1TRIDIHG STUDIED BY XPS ANO EELS. Mill Strydon - NINR, CSIR. Physic* Department University of Port Elizabeth AnoMlous compound surface 1ay*r growth Is observed during plasma nitriding of ferrous materials undtr Th« presentation reports on the MOVPE growth certain operating conditions. The formation of an Iron of AlGaAs from trimethyl gallium (TMG), oxy-nitride laytr by the redeposition of sputttrtd triaethyl aluminium (TMA). and AsH,. The most cathode material was found to Influence the growth critical growth parameters appear to be kinetics of the ?'-Fe,,N layer which forms during the substrate temperature, and the ratio of input plasma nitriding of a-Fe to the extent where the v'-Ft.N partial pressures of AsH, to TMG plus TMA, surface layer Initially increases and subsequently i.e. the V/III ratio. Doping techniques decreases in thickness after deposition of the Iron oxy- utilizing dimethyl zinc (DM!) and H.Se will nitride layer. The nature of these layers were studied also be discussed. The properties of the by XPS and reflection EELS to elucidate the electron epitaxial layers were characterized by Hall structure of the valence bands of these compounds. measurements, photoluminescence and optical Results are shown which explain the thermodynamic microscopy. The variation of these properties stability of the iron oxy-nitride layer and the apparent as function of growth parameters will be de-nitriding effect that this layer formation has on the discussed. underlying Y'-FeHN layer.

THE ROLE OF AH INTERFACIAL LAYER OF Ni IN A10 AuGe OHMIC CONTACTS TO GaAs A P Botha*. E Relling*. and R G Capperthwaite* "National Institute for Materials Research, CSJR THE GROWTH OF AlGaAs-GaAs QUANTUM •Schonland Centre, University of the Hltwctersrand A9 WELL LAYERS BY MOVPE The quality and electrical behaviour of AuGe olatic contacts to GaAs depend critically on the role Ni plays A W R Leitch and J S Vermaak as a wetting agent. The atomic ratio of Ni to Ge In- fluences the distribution of the Ga in the alloyed Physics Department, University of Port contact layers. It is well accepted that the Ge plays a Elizabeth major role in the lowering of the contact resistance. Not only does the relative amount of ¥.1 that is present Metal-organic vapour phase epitaxy (MOVPE) has in the metallization, determine the ohmicit.y, but also in recent years proved to be a technique the initial position of the Ni layer is critical to tne capable of the growth of layers having final state in which the Ge is available. In soae cases thicknesses of atomic dimensions. The growth a nickel germanide forms in such a way that Ge is being by MOVPE and the characterization of such trapped away from the interface where it is needed to quantum well layers, using the AlGaAs-GaAs initiate one of the possible mechanisms in lowering the system, will be discussed. contact resistance. In this investigation the Ni/AuGe/Ni/GaAs system was studied as a function of interfacial Ni layer thickness and the contact resistance was correlated with the atomic distribution of the Ge.

EFFECT OF ANNEALING ON THE All 1.49 eV BAND IN SEMI-INSULATING LEC GaAs METALLURGICAL AND ELECTRICAL INVESTI- A12 GATIONS OF Au-Ge 8ASED OHHIC CONTACTS H L Ehlers, J S Vermaak and A W R Leitch TO n-TYPE GaAs Physics Department, University of Port Elizabeth W 0 Barnard J B Malherbe* and A J Willis* •National Institute for Materials Research, CSIR In this paper the influence of rapid thermal •Department of Physics, University of Pretoria annealing on the dominant residual acceptor, carbon (1,49 ev) in undoped semi-insulating Metallization systems based on Au-Ge have been used liquid encapsulated Czochralski (LEC) GaAs is extensively to form ohmic contacts to n-type GaAs. reported. Different fabrication techniques are being used in present day contact formation such as furnace alloy- 50 mm Diameter undoped 1100) GaAs wafers from ing, sintering, ion beam mixing etc. fn this investi- two different vendors were examined and gation furnace alloying and ion beam mixing were used compared. Annealing was carried out at 650#C to form Au-Ge based ohmic contacts to n-type GaAs. for 2 sec in an argon ambient. The radial The contacts faoricated in this way were both studied distribution of the 1.49 eV band was determin- by means of Auger electron spectroscopy and ion beam ed using a 10 K scanning photoluminence etching, while current voltage measurements were also system. performed on these contacts. The results obtained from the above measurements will be given and discussed.

68 SOLID STATE PHYSICS ANO MICROELECTRONICS H Booytns, NIMR/CSIR Tht phrast "high technology" has become practically synonamous with tht fitid of microelectronics. While It 1s popular to vitw microelectronics as tht domain of tht electronics tflg1nt«r. Solid Statt Physics Is tht crucial undariying science that makes It all possible. Tht history of microelectronics-related solid statt physics will bt nrtstnttd. SOM of tht exciting developments art discussed and some views vtnturad on the futurt.

HALL MEASUREMENTS ON UNOOPED 0MVPE-6R0WN THE GROWTH OF PORXFIBD POLYCRYSTAL- A13 LINE SILICON IN GRAPHITE GaAs CRUCIBLES MELee*, A M Letsoalo*. J G Jantsky1 and S Hart* R Thavar •Electron Microscope Unit, University of the North National Institute for Materials Research, CSIR + Physics Department, University of the North • NIMR, CSIR Fro* the Hall analysis of a semiconductor Material, The use of polycrystalline silicon as a photovoltaic the carrier concentration and mobility may be deter- material is well known. Firstly, in the growth of mined at various temperatures. For this purpose a silicon the choice of crucible material is critical staple and efficient Hall system is used to charac- with respect to tht chemical reactivity and the terize OMVPE grown GaAs at the NIMR. Tht system is relative thermal expansion coefficient. Secondly, capable of both 30UK and 77K measurements of the GaAs it is essential to characterize this material in terms sample on which annealed tin dots »rt used for onmic of it's crystalline structure, optical and electronic contacts. Results show that high purity OMVPE layers properties and Impurity concentration. grown under identical conditions have differing mobilities and carrier concentrations for different In this paper the recasting of purified metallurgical epilayer thicknesses. The accuracy of results for grade silicon in graphite crucibles will bt described. thicknesses below S microns is also questionable, This will bt followed by the presentation of results however, the system shows excellent reproducibility for the characterization of this material. of results. These characteristics and limitations will be discussed.

A4C DETERMINATION OF IMPURITY CONCENTRATIONS SKUIFSLYTASIE EIEHSKAPPE VAN VERSTUIWINGS- Mill IN POLYCRYSTALLINE SILICON BY MASS A15 1OONPLATEERDE PLATINUM LA6IES SPECTROMETRY O.E. Rogers*. M.E. Lee*, O.A.A. Engelbrecht0 D J dt wet tn A Hells, NIMN, VMNR * NIMR. CSIR Tydens vtrstuiwingsioonpiatering word 1> eenvoudige ge- * Electron Microscope Unit, University of the North lykstroom gloei-ontladina In argon-gas gtbrulk om platinum vanaf "n katode (skyf) deur d1t prosts van loon 0 Physics Department, University of Port Elizabeth bombardtment (verstuiwing) oor te dra na "n substraat The major difficulty encountered during the purification 1n D sagte vakuuM kamer. Ioonplatering word gewoonlik gebrulk om goele adhesie tussen die lagie en die sub- and growth of polycrystalline silicon is the determina- straat te verkry. tion of the impurity concentrations in the ppma range. ti Klein verstuiwingsioonplatering-sisteem Is ontwerp en In this paper the technique of nass spectrometry using self vervaardig om dun platinum lagits teen it lae koste a glow discharge source for the analysis of impurity en relatiewe lae tegnoiogie te vervaardig. Die wry- concentrations in polycrystalline silicon will be wings- en slytas1e-e1enskappe van hierdie platinum ge- discussed. This will be followed by the presentation plateerde opperviakke Is bestudeer tydens skuifsiyt- of results for the analysis of metallurgical grade toetse met keramiek-, metail- en Pt-geplateerde balle silicon, purified silicon and recast polycrystalline onder droe en gesmeerde toestande. Die slytasie-groewe silicon in various crucible materials. 1s gekarakteriseer met behuip van SEM- en AES-tegnicke. A17 ELECTRICAL ASSESSHEHT OF SIN LAYERS OH A18 c » mils R J Gu—ow and I Sigaias National Institute for Materials Research, CSIR National Institute for Materials Research, CSIR SIN is used extensively In the GaAs Industry as an PyrophylHte and t»lc are widely used as pressure encapsulant and dielectric overcoat. It Is Important transmitting and gasket materials In high pressure to know what the electrical properties of a deposited synthesis and related techniques. For the thermal SIN layer art in order to model the fabricated modelling of such processes, the high pressure, high device/circuit properly. The work done here was done temperature thermal conductivity 1s an Important Input with this aim in mind. Capacitance - voltage (C-V) parameter. Results arc presented for both pyrophylHtc VM) thermally stimulated capacitance (TSCAP) measure- and talc e. a function of temperature and pressure In ments were made in order to characterize the SIN the ranges 0-2.5 GPa and 300-850 K, which .were obtained layer and the GaAs/SIN interface. by using the hot-wire technique. The trends observed arc discussed In the light of the current understanding of the structure and chemistry of tftse materials.

THE PASSIVATION OF (HgCd)Te SURFACES ELASTIC CONSTANTS OF ONE GLASS AND ON| A19 A20 GLASS CERAMIC C J Botha. M A Marais. R J Muller S Gravett, I Sigaias and P R Clayton National Institute for Materials Research, CSIR National institute for Materials Research, CSIR The semiconductor material (HgCd)Te is widely used The elastic moduli of one glass, Photogrcy, and one for the production of infrared detectors operating in glass ceramic, Zerodur, have been measured as a function either the photoconductive or photovoltaic mode. of pressure. An ultrasonic pulse echo overlap technique However, as a result of the reactive nature of-its was used up to 2 GPa. The glass shows an unusual surface, the cerformance and long-term stability of behaviour due to Its chemical composition. The such devices are severely limited by surface related longitudinal modulus and the shear modulus decrease with phenoaency. The development of a suitable passivant pressure, but the bulk modulus increases. The glass for the (HgCd)Te surface is thus of great technologi- ceramic shows a phase transition at l.S GPa. cal importance to device performance. Preliminary work as regards the passivation of 'HgC<)Te material produced at the NIMR has been done and will be discussed briefly.

BEHAVIOUK OF THE TUIUIAHCLE OT PTSHOSIPH A22 NEAR M IC**C PHASE niAWSlTl0s7 LASER EPITAXY OF DEPOSITED SILICON f de ? du rlassis. «AO, GIT Brits, AK A21 THIN - FILMS ; CHANNELING AMD ELECTRON MICROSCOPY MEASUREMENTS The lubject of iacoasMnsurata (IC) «-> cosBMnsurace (C) phase transitions has, sines the pioneering work of D. A

70 DOPING OF SIUCON BY LASER-INDUCED A23 DIFFUSION A24 frfr Marata, M.S. AUI«« and R. Pmtoriua a H F Hrlta. AtC, t d ¥ du rlaaat*, UU to»>totld Int«racttoB Division, Van de Gruff Croup, NAC. Paw*, The critical behaviour of the alowoldal — •Dtpt. of PayaJlci, Univeriity of Cape Town. paramagnetic phaae tranaltloa aa eihlbltrt by tx at TH - W.OR baa until now attracted only Unite* Very ahafl> "•* *»»Uow dopant profUit can be obtained by theoretical and experimental acttntloa. Hlgo utilising 1*MT doping of semiconductor*. Such profile* are raaolutlon peak atutxoa Maaurewata takes abas desirable fcr producing solar cells and special typei of cycling up and down In temperature through IV microelectronic device* such aa IMPATT diode*. Thin antimoay Indicate a contlnoua tranaltlov without any layers fc 50A thick) were evaporated onto single crystal silicon nyatereala. Integrated neutron a«s«u;«a«ot« pertenwd sample* aad irradiated with a pulled ruby laaar (wavelength between 90.9K and 8».5K give a critical eipoamt v • • 6940A, pulMwidtb « 30M). During melting of toe Mrfaca l.a aad a 9-espoaent that cshlbtta a crossover ttom • i-egion interdiffwion tftkai place with the Sb being trapped value of 0.37 when only •eaaureaenta near TJJ ase in Uw silicon (attic* upon solidification. B«cauM of the Included In the analyala to a value of 0.4& for Che non-equilibrium nature of the proc«M, dopant conccntratiou coaplet* teaperature range studied. The lnveatlgatlon Z to 3 orden of magnitude greater ;han the normal value of the critical behaviour waa further auppleawnted by can be obtained. Channeling of charged nuclear particle*, ultrasonic velocity and attenuation Maaurcacats. show that nearly all the dopantt occupy subatituiional sites. Tncs* result* are compared with theoretical modelling of laaer doping.

BURIED ANTIMONY PROFILES IN SILICON A2S FORMED BY LASER DOPING a. Carollasen. D. Knoesen*, M.J. McG«trick* and R. Pretorius ELECTRICAL RESISTIVITY OF DILUTE (Cr,-xAtx)95Mos ALLOYS ~ Ion-solid Interaction Division, Van de Graaff Grctm, NAC, A26 Faure. P. Sait and H.L. Alberts •Physica Department, University of the Western Cape, Bellville. Department of Physic*, Rand Afrikaans University To obtain buried dopant layers in semiconductors, it U usually The temperature dependence of the electrical resistivity necessary to grow an epitaxial layer of the semiconductor (0) of (Cr.__A«x)9cHoe alloys with x • 0.113, 0.441, material after doping. By irradiating a Si < 100> /Sb (50A/S1- O.77Z, 1.492, 2.07Z, 3.111, 4.841, 7.312 and 1O.63Z, amorphous (2000A) structure with a pulsed ruby later, it is wa* measured in the temperature range (4-500) K. A envisaged to carry out the doping and epitaxy process in a remarkable phenomenon wa* observed, namely that the single step. Theoretical heat-flow calculations have been addition of SZ Mo to Cr-A< completely supresses anti- carried out far this structure, in order to determine the ferromagnctism for ZZ < x •€ 62. The non-magnetic temperature profiles in the sample during pulsed laser behaviour of o of the antiferromagnetic alloys (x«0.11Z, annealing. ThU information enabled us to determine the 0.44Z, O.77Z, 1.492, 7.312 and 10.632) wa* determined melt-depths a* a function of laser energy and the, solidification by using the temperature dependence of the alloys with velocity. The dopant profiles were measured by Rutherford x • 2.O7Z, 3.112 and 4.842 that remain paramagnetic at Backscattering Spectrometry of charged nuclear particles, all temperatures, as a model. This allowed ui to while the quality of the epitaxial layer has been determined analyses the data in terms of existing theories. Rela- by using the channeling effect as well as electron microscopy. tive good fits were obtained with theories for both the low and high temperature behaviour as well as for the magnetic contribution to o.

EVIDENCE OF MULTILAYER STRUCTURE IN AMORPHOUS SILICON A27 J.Aucaap and R. "Swantpoel, RAU. In the literature it is generally itsuocd that a-Si:H STUDIES OF ELASTIC CONSTANTS Of i* a homogeneous material. Very tittle research has A28 been done on the effect that variation in thickness of AT HIGH TEMPERATURES the thin films has on the optical and electrical pro- P.E. Sgoepe••o J.D. Comins0 and A.G. Every0 perties. By investigating the electrical conductivity + department of Physics, University of the (north and other physical characteristics, especially at the substrate-fila interface, it is reported in the litera- o Department of Physics, University of the WitwatersrarW ture that the possibility of an intermediate layer at Brillouin scattering studies of the fast-ion conductor substrate-fila interface does exist. LaF, have been carried out in the temperature range The effect of film thickness has been studied by growing 300-1400 K. The frequency shifts associated with a-Si:H thin films of various thicknesses and characteri- modes in the various phonon propagation directions sing them by scans of ellipsometry. It was found that show a linear decrease below 1100 K, followed by a the results could only be satisfactorily explained narked reduction above this temperature. Significant using a two layer model for the a-Si:H film. Approxima- changes in the frequencies related to separate tely the first 1000A of the fila was found to consist elastic constants are also noted around the same of one type of material while the bulk of the film temperature. The results are discussed in terms of consists of a second type of material. These results anharmonic effects and the cooperative generation will be discussed for Corning 70S9 as well as c-Si of disorder. substrates.

71 EFFECTS OF RF-SgyTTERHIC PROCESS PARA- METERS ON tiiE OPTICAL CONSTANTS OF J.Aucaap and K. Swanepoel, RAU soon IC i* wall known from tha literature chat Cha optical A30 >RTt iKRADIATEU KC<: Na CRYSTALS and alactrical characteristics of a-Si:H thin filae ara affected by a change in eh* praparacion condition*. To A.M. Mdnbuka and J. I. Seratlo, Departaetit of Phvslcs optically charactaria* a-Si;H thin filat a* a function UNIVERSITY Of FORT HARE. of thickness and rf-sputt«ring power, tha following preparation condition! wara leapt constant: Growth pro- n In 8T A- *na JF> irradiated iCi: Na O25U f>wn> ha* cess (rf-sputtering), chamber geometry, Ar-Hj ga< ratio, sten examine J. Tha orocaxsas involved durini. lu roilot. gas flow rate and substrata temperature. :irst-oruer kinetics. It is suggested that the Through calibration of tha system, it was found that

THE THERMAL STABILITY OF SOME IANTHANIDE A32 NITRATES ELEKTRIESE GELEIDING EN FOTQGELEIDXNG C. Strydom, C.P.J.van Vuureo, A31 VAN AMORFE SILIKON Department of Chemistry, University of Pretoria. J.J.R. Prinsloo en R. Swanepoel, RAU The temperature where decomposition starts when using Die elektriese eienskappe van a-Si:H is iterk afhank- a heating rate of 5'C.min"1 is used as a relative lik van die bereidingaparameters. Verder verander die measure of the thermal stability of tore lanthanide eienskappe mec uitgloeiing na bereiding, hoofsaaklik nitrates.. The reaction enthalpy values at atmospheric as gevolg van verli.es aan H, en to mate van kristal- pressure and a pressure of 5 x 10' kPa showed lisering. remarkable differences, due to reversible processes, occurring during the decomposition reactions. The Die elektriese geleiding sowel as foto-geleiding van number of temperature dependent reversible processes rf-verstuifde silikon is as funksie van temperatuur are determined using the kinetic rate constants for gtaeet. Die effek van uitgloeiing en lagiedikte is the isothermal reactions in Arrhenius plots. An ook ondersoek. Die verandering in elektriese gelei- increase in the number of temperature dependent dingsvermoe en bandgaping sal bespreek word. Eksperi™ reversible processes, as well as the increasing aentele bepalir.g van die werklike temperatuur van die instability, when moving down the lanthanide series, lagie op die verhitte substraat sal ook toegelig word. could be due to the lanthanide contraction.

GROWTH OF GaAs EPITAXIAL LAYERS MAGNETIC EFFECTS IN DILUTE Cr-Si ALLOYS A33 USING CURRENT CONTROLLED LIQUID A34 PHASE EPITAXY H.L. Alberts and J.A.J. Lourens V J Watters, J S Vermaak and A W R Leitch Department of Physics, Rand Afrikaans University

Physics Department, University of Port Measurements have been made of the thermal expansion Elizabeth and elastic constants of seven Cr-Si alloys in the concentration range from 0 to 3.A2 at.X Si. The results Control of the growth rate for submicron point to the absence of a re-entrant feature in the layers using conventional liquid phase epitaxy vicinity of the triple point where the paramagnetic (P), (LPE) has been a persistent problem in the commensurate (C) spin density wave and incommensurate past. This paper reports on liquid phase (1) spin density wave states coexist, favouring the electro epitaxy (LPEE] where an electric sequence of phase changes from P to C to I. The first current across the solid-liquid interface order C-P transitions are marked by discontinuities in induces Peltier cooling (or heating) at the Che thermal expansion and by large ultrasonic attenua- interface. Because c; the localised nature of tion near TN. Calculated latent heats associated with this coding (heating) effert at the the first order transitions compare uel} with direct interface, much more accurate control of the measurements. Application of existing itinerant elec- growth rate to produce submicron layers can be tron theories to the magnetoelastic iaca does not give achieved. The design and construction of such the correct concentration dependence of the magnetic a system and the initial results obtained with mo&ent and Nee I temperatures. the LPEE reactor will be discussed.

72 ;*««:r

r pwMTIGATIOH INTO TW MICHAWiaw Of TION A35 gnwftflOM OF IPITAXIAL Pd,Sl A36 J.C. Liut and J.M. Hayart t. M. Miwarat. J. R. Saretlo and a. H. Mdabuka* t Now in tha DspartMnt of Physics, University of tha Vltvatararasd •J ii which has t haxagonal cloaa packed structura, * University of Fort Rara 1 1 on Si ul •MOT*"' ' ^ * > substratas bat not on tlM Tha annealing of intaratltlala In XC2 cryatala doped with 5hM Sew •* tilicon. Thtn Ta and Ti fllaa hava been divalent and aonovalent iapurlty atoas (Ca and Na re- •*TM inert aarker» to aonitor tha growth process of spectively) has baas invastlgatad by various worker*. itaxial Pd»Si. It «u found that SI Is tha dominant Froa tha activation anargy spactra obtained by Hdabuka, 2.UK •pad" d«ln» «Pit*xlal »iUeid« growth. It two additional paaks aaaoeiatad with lntriaslc traps 2, i3«o found that polycrystalline Pd,Sl will re-order aawrgad. In this papar an attaapt is Mda to undarstand ITbacoae epitaxial during slllcida growth. Thi» which of tha two paaka ia affactad by plastic datama- M-ordaring is due to th« growth process alona and ia tion, and why. This was aehlavad by calculating acti- not dwa to tharaal effects, indicating that Si ia vary vation anariy spactra on plastically daforswd undopad KC1 •nfcila during alllcida growth. Sinca only Si vacancy crystals. Tha rasults ara axplainad in tana of a pref- diffusion would result In high Si aobility it is arguad arantial trapping aodal. that the findinga atrongly auggaat that Si dlffusaa by » vacancy machanlia during epitaxial Pd,Sl formation.

HIGH TEMPERATURE APPUCATION OF ACTION STUDIES OF SCHOTTKY CONTACTS TO GaAa MDUCT1N£11 G KIOHUM-TIN ALliiVS A37 A38 Hearne and 1. Kolk »• ReUing, A.P. Botha and R. Pretoriua* Oapartasnt of Physics and Condensed Mattar Physics Research Group, University of tha Vitwatararand National Institute for Materials Research, CSIR, PRETORIA *Ion-aolid Interaction Division, Van de Graaff Group, NAC, HSssbauer-affact (HE) aeaaureaents ware carried out on HbtSn and NbSn, at taaparaturas between 300 K and 4 K to FAURE exaalae anharaonlc effects in theaa interaatallic alloys. The aaaauraaeats were perforaed on superconducting tape To integrate G»A» MESFETi on a very Urge scale, a containing both Nb-Sn alloys as well as pure tin. This Mlf-alignment fabrication technology has been developed allows us to coapare recoilleis fractions of tha "*Sn ahica involves a high dosage implantation through a gate atoas ia tha various Nb-Sn phases with those of "*Sn metallisation. Annealing temperatures >800*C are required atoas in Sn which are accurately known. In our previous to activate implanted dopanta. Since GaAs degradation occur* analysis of thlt data, tha recoilless fractions of the above 600* C, annealing muit occur using a suitable encapaulant Sn atoas In tha various tin phaaas were detcrained •- to prevent arsenic evaporation. The excellent stability as Is often done •- froa the absorption areas of the HE exhibited by metal filicide* at high temperatures makes them spectra. Mere we report on an iaproved aethod of ana- auitable to form Scaottky contacts on GaAs. In this study, lysing HE spectra which takes Into account saaple thickness affects. These effects, if Ignored, asy lead to an ire used cobalt filicide for the gate metallisation with Si Incorrect estiaation of the recoilleas fractions. Our as an encapiulant. Rutherford Backacattering Spectroacopy new analy*is provides us with sore reliable values of the was used to study the chemical atability of this system. Some anharaonic Constanta of the lnteratoaic potentials in the of the problems encountered as well as the electrical various phase*. characteristics of the contact will be discussed.

*«A Co; AMD Ni-SILICIDE FORMATION IN A"a?9 THE PRESENCE OF GOLD H.A. Ras*. J.J. Crufwagen* and R. Pretorius 4 PHONON FOCUSING IN PIEZOELECTRIC CRYSTALS •National Institute for Materials Research, CSIR, Pretoria A40 A.G.Every* and A.K.McCurdy* '''Chemistry Department, University of Stellenboich *Physics Department, Witwatersrand University 4Ion-*olid Interaction Division, Van de Graaff Group, NAC, *E.E. Department, WPI, Worcester, Mass. U.S.A. Faure Striking changes are predicted in acoustic vave Although relatively inert in metal silicide matrices, gold propagation and the phonon focusing properties of can be treated as a special type of impurity that affects piezoelectric crystals as a result of piezoelectric silicide formation through the very low Au-Si eutectic stiffening of the elastic constants. Monte Carlo at 3?2*C. At temperatures close to and above this value,, phonon focusing patterns are preserved for a number of the Si atoms are dislodged from the covaient Si-lattice strongly piezoelectric crystals. It is shown that the to become "free" and highly mobile in the solid state degree of the equation of the slowness surface is structure. Because of this increase of the effective Si raised from 6 to 12, and that as a result, fast phonon concentration, f'.e mechanism of Co-silicide formation branch focusing caustics are permitted. changes to operate in a lower temperature range and to produce a different phase sequence, relative to the no-gold case. No such drastic effects could be measured for the presence of gold during Ni-silicide formation. An explanation for this different behaviour, exhibited by the Co-Si and Ni-Si systems, ia given in terms of the intrinsic diffusivities of the two systems.

73 THE EFFECT OF OXYGEN IMPURITIES A41 ON THE SOUP STATE INTERACTION BETWEEN THIN Pt-FILMS AND SILICON RAMAN STUDIES OF IRRADIATED KI AND KI(Sr> M.A. Wandt and R. Prttorius A42 ton-tolid Interaction Division, Van de Graaff Group, National A.M.T. Allen, C. E Allenspach and J.D. Comlns Accelerator Centre, FAURE. Department of Physics, University of the Platinum lllicidet formed during the solid-state interaction Witwatersrand, Johannesburg between thin Pt-fllm* and silicon are important ai contact* in micro-electronic devices. The silicide phase which forms Annealing experiment* have been carried out on KI and first is PtjSI, while PtSi forms at higher temperatures. In KKSr) after gamma-irradiation at room temperature. this study we have investigated the effect of oxygen impurities Studies of defect concentrations were made using both on platinum silicide phase formation. Oxygen doping of the Raman and optical absorption methods. The Raman Pt or Si films was carried out by introducing oxygen into results show that the trapped halogen interstitial* the ultra-high vacuum system during evaporation. The kinetics are in the form of large iodine aggregates. The and sequence of phase formation upon subsequent heating kinetics of the defect annealing behaviour is studied was investigated by using Rutherford backscattering of charged in detail using various annealing routines and nuclear particles. The observations were evaluated in terms including a Primak-type analysis. of the effective heat of formation theory (1). (1) R. P^itoriui, Material Research Society Proceedings, Vol. 25 page 15-20 (1984).

L S_IT_E_L._QCATION..QF DOPANTS A44 1_N .GAAS_ BY~ ELECTRON CHANNELING. Ni-Si SOLID-STATE REACTION : FORMATION i---1-_Shenne, H.C Snyman, C.A.B.Ball, and H. A43 OF SILICON-RICH LAYER WITHIN NiSi; Smith. IN THE PRESENCE OF EXCESS AMORPHOUS Department of Physics. University of Port SILICON Elisabeth. J.E. McLeod. H.A. Ras* and R. Pretorius The electrical activation of dopants in semi- Ion-solid Interaction Division, Van de Graaff Group, NAC, conductors is determined Oy their incorpora- Faure. tion into substitutional and/or interstitial 'Electronic Materials Division, NIMR, CSIR, Pretoria. lattice sites. In principle, measurements of the ratios of the matrix and impurity X-Ray Thin film structures with the configuration Si<100>/Ni/Si(a) electron-induced yield at various crystal were prepared and heated in a vacuum furnace at temperatures orientations lead to the determination of the ranging up to 800* C. This enabled us to compare silicide impurity concentration and its atomic site. formation with single crystal and amorphous silicon in the This paper reports on the influence of the same sample. It was found that if the amorphous silicon electron beam, imaging and spectrometer para- is present in excess amounts, the remaining surface silicon meters on the sensitivity of the technique. diffuse* through the nickel silicide to regrow on the Si <100 > Theoretical calculations of the transmitted substrate, as well aa forming a Si-rich layer within the silicide. electron wave intensity with depth in the Experiments, to account for this behaviour are described. crystal are also used to optimise the experimental conditions as far as specimen orienta- tion and thickness parameters are concerned.

\ •N STUDIE VW DIE Pt/Si DUNLAGIE SISTEEM A45 TUSSEN 750"C EN 1000'C. A TEM STUDY OF THE STRUCTURE OF A46 ANNEALED NITROGEN - IMPLANTED GLP Berning en CW Louw SILICON Departement Fisika, UOVS pt/poli-Si/SiO2/Si(100) monsters is gebruiJc net die Pt H C Snyman, B P Zeelie and J H Neethling lagie ICC run en die poli-Si lagie 400 randik . Onder :000*C diffundeer nie Pt of Si deur die SiO2 lagie nie. Department of Physics, University of Port Elizabeth Monsters is by vaste temperature tussen 750*C en 1000°C jehcu vir 10 ram in 'n N2 atmosfeer. Auger dieptepro« Nitrogen implantation of silicon is a prcmisir.g riele is gemeet. 'n ?t/Si lagie groei by 7SC°C en is technique of forming bu'ied insulating layers. In this stabiel tot omtrent SSO'c die laagste eutektiese tem« + oeratuur van die Pt-Si bine're sisteem. Na verhitting paper we report on the structure of 150 keV, 10 N by temperature tassen 33C°C en ongeveer 9508C verhoog an' implanted layers as a function of laser, rapid iie Si kcr.sentrasie op die opperviak terwyl die Pt thermal and conventional annealing paraneters. TEM kor.ser.trasie hoer is naby iie SiOj lagie. sokant shows that, depending on the annealing paraneters, the 950°C is iie kor.sentrasie van die Si en die Pt (constant recrystallised zone may consist, frcm the surtace met diepte tot by die SiO2 lagie. .Va verhifung by inwards, of a single crystalline surface layer, a large 1300°C in Nj vir 5 ain is 'n 150 A0 SiO; lagie op iie polycrystaliine, a macrocrystalline and an amorphous oppervlak gevorm. 3y veraere c

74 DIE EPITAKSIALE CROEI VAM Cr OP Ati111 ) DEEP RAMATÏON DAMAGE IN META1.S AFTER ION A47 SUBSTRATE. A48 IMPLANTATION K.G. vao dar Barg «o H.L. Gaigher E. Friadland and H.H. Albert! Di« oriantatia an norfologia van opgcdaapta Dapt. of Physics, University of Pretoria Cr(gaaiddtlda dikta 11.5 tot 20 na), gevora op Ag{lll} substrate in ultrahoë vakuua (~10"' torr), ii daur The depth of radiation damage in copper and platinua •iddal van daurstraalalaktronmikroikopit tn elektron- has bean analyzed after implantation of different ions diffrakaic ondersoek. Substraattanparatura waa in die with energies ranging bctwtep 50 keV and 150 keV at beraik 25 tot 290°C. Orientasie varwantikappa sal in rooa 'emperaturc. Th* damage range entends ouch deeper taraa van suiwtr gaomttriesc modelie, an van dar Karue than the projected ion range and depend* primarily on I« ccoric, wat alastisiteit van dia oproeisel in ag the ion energy. Possible reasons for deep radiation oaaa» baapraak word. damage will be discussed. '

IDENTIFICATION OF DEFECTS BY MEASUR- A49 ING THE IN-PHASE (I) AND QUADRATURE (Q) DLTS SPECTRA DURING A SINGLE TEMPERATURE SCAN (IQ-DLTS). f.D AURET and M. Nel, Physics Dept. UPE. A50 IOONINPLANTERISC IN At:Si-KONTAKTE A simple method of analysing the transient signal observed during deep level transient B.A. Carr, J.3. Malherbe, E, Friedland spectroscopy (DLTS) is presented. In this Departement Fisika, Universiteit van Pretoria Mthod, IQ-DLTS, the transient is analysed by recording its in-phase (I) and quadrature (Q) OpgedampCe /iluminiumkoncakce op n-Si is met verski Uende DLTS spectra by using the corresponding out- ione (Ar*, Xe*, Si*) geînplanteer. Elektriese (I-V) put of a two-phase lock-in amplifier with a metings voor en na inplantering is gedoen. sine wave mixing function. Measurement of the peak positions on the I- and Q-spectra, which are simultaneously recorded during a single temperature scan, facilitates the calculation of the defect activation energy and capture cross-section,which are required! for its identification.

IMPROVEMENT OF SEMICONDUCTOR DIE MODIFIKASIE VAN Si-Si SCHOTTKV- A51 MATERIALS BY MEANS OF DEFECT A52 KONTAKTE MET BEHULP VAN IOONBUNDEL- ENGINEERING VERMENGING

L W Snytnan G. Myburg, J.B. Malherbe, E. Friedland Departement Fisika, Universiteit van Pretoria fhysics Départaient, University of Port Elizabeth Metaal-silikon tussenvlakke speel 'n belangrike rol in The thermo-dynamicai behaviour of defects during device die elektroniese nywerheid en gevolglik is die processing has important implications In various fields ontwikkeling van metodes vir die vervaardiging van of the semiconductor technology. sulke kontakte met bepaalde elektriese eienskappe van tegnologiese belang. Iocnbundelvermenging, deur middel In the presentation the interaction mechanisms between van die inplantering van ione deur opgedampte Si- extended detects (eg dislocations) and point defects kontakte op enkelkristal silikon, is ondersoek. Die will be discussed. Experimental results obtained from a effek van inplanteringsdosis op die eienskappe van recent electron beam induced current (EBIC) genoemde kontakte sal met dié van ongeïnplanteerde investigation (which enables the high resolution kontakte vergelyk word. inaging of the electrical activity ir. a semiconductor crystal) will be presented. Existing detect engineering techniques will be evaluated and new defect engineering techniques will be proposed to improve the electrical activity in a semiconductor crystal.

75 PROBLEMS EXPERIENCED WITH OPTICAL • Pi IMPUKTEP nvonm worms m DIAHOHP A53 FTIR CHARACTERIZATION OF GaAs ~ A9MV J.P.Print. T.E.Parry. CC.P.Hadiba, J.P.r.Scllachop. J A A gngelbrecht, I G Lee and A Botha Witi-CSIR Schonland Research Centra for Nuclear Sciences, University of Ch« Wicvatartrand, Johannesburg, Physics Department, University of Port South Africa. Elizabeth StudU» of th« volume axpantion of diaaond ("mesa The determination of varioua electrical and growth") resulting from fluorin* ion irradiation ha* physical properties of semiconductor materials been reported previously by ui and explained in uni by optical techniques has many advantages. of tha generation and notion of point defects. The Many methods are well established for silicon, mechanics of this notion will affect tha (hape and but when some of these techniques are employed position of the implanted fluorine profile*. These profiles have now been measured directly, using the for GaAs and related compounds in the infrared 1 region, problems are experienced. These resonant "FCP.OY) '*) nuclear reaction for different ion include effects due to sample surfaces and dosas. The results were used to analyse tha possible carrier concentrations. Results obtained for mechanisms responsible for the broadening of the MOCVD grown samples will be discussed. inputted fluorine profile and to obtain information on the vacancy density distribution.

THE APPLICATION OF BEJU. TIME FAST FOURIER CSPULSEERDE ELEKTRONBUNDELVERHITTING(PEV), TRANSFORMATIONS IN EDS ELECTRON MICROSCOPY LASER EH TEMPERATUURUITGLOEIISC VAN D.R. SpaIding and L. Haiatry GEfOTLANTEERDE InSb ' Dept. of Physics, University of Natal, Durban. H W Alberts en R Cilliers A problea that often arises in energy dispersive spec- Universiteit van Pretoria trometry (EDS) is the correlation of electron image InSb-enkelkristalle is by 'n verskeidenheid energiee variations with fine structure of the image generated en temperature gelnplanteer met Be-ione. Die by means of an X-ray energy window. This paper dis- inplanteringsdosis was cussen 5 * 10" tot 2 * 10" cusses the problem and shows how a personal computer ione/cm2. Die anaiise is oet die RBS en kanaliserings- can be hard wired to an EDS system to help facilitate tegniek uitgevoer wiarin daar van 0,5 tot 2,5 HeV data interpretation. a-deeltjics gebruik gemaak ia. Die restourasieproses van die geinplanteerde enkelkristalle is ondersoek aan die hand van gepulseerde elektronbundelverhitcing (PEV), LASER en teoperatuurbehandelings daarvan.

CORE-EXCITATION EDGE AND EXTENDED ELECTRON A57 LOSS SPECTRA FROM VARIOUS CARBON SURFACES STRAL1NGSKADE VANWEE LIGTE IONE IM InSb USING LOW ENERGY REFLECTED ELECTRONS. A58 B.G.Maguire*, J.P.F.Sellschop* •Trent Polytechnic, Nottingham, United Kingdom. B J E van Tonder, E Friedland, Universiteit van Pretoria *Schonland Research Centre, University of the Witwater- srand, Johannesburg, South Africa. Stralingskade veroorsaak deur alfadeeltjies in InSb is veral act behulp van kanalisering ondersoek. The energy loss spectrum (ELS) obtained with low energy electrons, <2 keV, reflected off clean atomically Die invloed van die volgende fakcore op die omvang van ordered Diamond surfaces in Che near-elastic. It-edge die stralingskade is bepaal: dosis, dosis tempo, and extended K-edge energy regions reveals greater inplantcemperacuur, isochroniese en elekcronbundel- structural detail than that observed with high energy uitgloeiing. electrons-80-100 keV-in transmission. These differing techniques are compared and contrasted and possible Die vervagce stralingskade is ook bereken deur die causes for che dramatic differences observed are TRIM- en MARLOWE-programoe Co gebruik. discussed. Of particular significance in the lowered K-edge region are the possible diffraction effeccs 'n Model vac die hoofcrekke van die resultace verklaar encountered by these emerging secondaries. Similar word aangebied. results are also presented for graphite and variously prepared amorphous carbon films.

76 LI WEAR ANO PARA80UC REACTION KINETICS IN Oil OEBBUHt VAH IMt POOCH IQOWVtMTKOOI- AS9 BINARY COUPLES A60 IMG VI» O« OWOKMOeX VMI OPPEHVLAKATOOH- EC 2IM6U. M6DUNSA GM van Wyk, Mputaitnt Plalka, UOVS, eloeBfontein Solid state reactions such «s thermal oxidation of sill- Di* verstrooling van la* energle (1 keV) edelgas- an con and Mtais, or mtal silicida formtion, involvt alkalie-ione word gebrulk am die lokal* rangwkiJtking Interfacial reactions at tht phast boundaries and van atom* op dla oppervlak te btpaal. Die uk»perlaen> diffusion of at least ont of tha rtactants through tht tala op«tailing bastMn basic* ult 'n ioonbron, matta- compound layer. •D enetgle-analiseardar an detektor in UHV, >«t dla First order differential aquations ware usad to model faallitelt am nagatlawa terugslagiona waar ta new. tht Inttrfadal reactions whareas tha diffusion process Kwantlflaerlng word bapazk daur nautrallaanle van ver« Mas modeled by a parabolic differential equation. The ttrooide lona. Dla toepasting van dia aetode It dla finite-difference approximation Mthod Mas used to ondartoek van segregasia, vcork*urv*r*tuiwlng, gas* obtain a solution to this moving boundary problem. adaorbata an spreidlng In katallaatora. Gaordanda The results suggest linear kinetics (compound layer oppervlakstruktura kan kwantitatief waaxgeneaa word, thickness • reaction time t) In the Initial stage, ay laa atrooihoaka 1* dlt nodlg ca ta vargalyk net followed by parabolic kinetics (thickness « t1). rekenaarsiaulaslas «oo» ARGUS an MARLOWE. Th«$« predictions will be compared with those of similar models and with experimental results.

COWUGATCT GLIPe SUM ACES AM) THE ORICIW A61 OF EARTHQUAKES T.J. Jackson, Physic* Department, University of Natal, 'N STUDIE VAN DIE ADSOBPSIE VAN HaO OP Pieteraari tsburg A62 POLIKBISTALLYNE VLEKVOT STAAL MET BEHULP It haa baan known for many yaari that cryttal* tkaar on VAN EDELGAS IOONVERSTROOI ING. •lida iurfaca* that art corrugated parallel to tha GM van Wyk*, W Englart* an B Taglauar* direction of shaar. Tha corrugation* do not run right through tha Material, but and on itep* where tamila •Dapartaaant Fiaika, UOVS, Blowfontcin and eoaprattiva atraatea davalop parallel to the thaar- •Max Planck znstltuut vlr Plaaaafiaika, Garchlng ing direction. In cryitela, glide occur* whan disloca- tion* tprted on cryatallographic planet. Corrugation* Ola adaorpala van vatar op poli*ristallyn« vlekvry and ftapt for* at a reault of the crott-tlip of terew ataal It ondaraock mat bahulp van 1 kaV ioonvarstrooi> di*location*. The propentity that glide ha* to deviate Ing by varsklllanda tamparatura tusaan 140 K an 500 K. conaervativaly froa a plane it howavar not peculiar to Ola a* rujjicjttin an dia itrooistlr.e vanaf Fa tn 0 crystalline tolida. Tha boundaritt of fault* can, «nd i' • By laa taoparatura (<180 K) la sonolaagba> heva been, modelled with Voltarra ditlocetiona, and the & ...... jrkry na ISO L. Hat vardar* blootatalling hat largfiol* analogue of ditlocation croae>elip ihould <-. H" cit.n toaganatn tot 'n naksimuB by 550 L waarna produce corrugation* and (tap* on fault turfact*. tt. •- .- ->r hat. Laaaganoaada word varklaax daur Tha foratation by croaa-alip of *t*p* on corrugation* •u: zqii iia. Bokant ISO K was vclladige bedak- may explain tha origin of dil tional and antidilational king nla aoontllk n;i« an 'n toanaaa in die O/B-v«r» Jogt on ttrika-alip fault*. Such jog* are thought to houding la gaaavt »«t to«namandc tanperatuur. Ioon- exert major control* on aarthquaka rupture in region* ga/tndussaarda dasorpala is gaoact an rasultata vir tuch a* Che San Aadrta* fault in California, dasorpaiadaursnitta word aangabiad an baspreck.

•N KOM«I8T»MCT OTIvWAWSt VAH TtOBI" A63 VAN OmXVXAXaSGMtGASIl IN DIE OHPERSOEX VAN VCTSKILLPCE TIPES HMOXt i IMMIGHGM6A9X1. AHOKTE KDOLSTOF M.B.V. X-STRAALPirFBAKSIE 3 4u Haasls an ON van wyk Department Fiaika, uova, aioamfontein N P FICX» «n r R L SCH6NIMG* * Oapartaoant Matariaalwatanskap, AEX van SA Bpk 'n Kon*ist*nt* en voUediga heranaiiaa va.n dia baskry • Fiaika Dapartaoant, Univarsitait van dia Witwat;arsrand winq van oppervUksegregasie in aiUtikooponent sistaae In term* van makroakopiaaa temodinaaiesa aianakappe Varskillanda vorms van grafiat soot glasagtiqa koolstof. word be«pre«k, Dlt word aangatoon dat 'n analitiea* dun opgaaanc>ca laglas grafiat, ana., i« m.b.v. X-straal> uitdrukking in 44-e appervl*ksp*nning varkry kan word diffrakaia ondarsoak. t)ia spaktra wat varkry is, het en det die awewigaapparvlakkonaantraeias geldentiflsaer dia tipiasa alanskappa van anorfa natcriala vartoon. ken word mat minima in hierdio funksia. oia Langauir- , Rr^gg-'WilliM)*" en Guttman aegragaai* v«rge> Siardia spaktra is gabruik on radiala distributee funk- wQr4 uit 4ic appervlakapanningsfunkala be- siaa a.b.v. vinniga Fourier transforraasies te vertcry. reken d*W *e*iiit*te van dia gawona oploasingisoodel te Ult die funksies was dit duidelik dat daar wel kort af> aebrulk. T*Qretieaa en eksporiaentele reaultata, stand «1 no) orda bestaan tussan die atome van die too* hl*«»r*al« effekt* an diakontlnus oorgang* in die grafiate wat ondersoak is. Nia alltan kon die afstande atfreeani* i»ot«m, wcrd varduidelik aan dia hand van tussen naaste bura betaken word nie, saar ook kon dia ilt fedrae; van die oppervlakapanningafunktl*. aantal atone op daardie afstand varkry word an varvol* (jen« dla struktuur van die oaterical bepaal word.

77 'N KOHSISTEMTC H8WWM.ISE VAH 018 TBOHIE TKAMSHISMOH EUCTMH nimACTIOW A65 VAM OPPERVLAKSBJRIGASIE IB HULTIKOHPOWENT- UtkLYSI* AIXOOIB •- KKITIEK OP ANDEK TEOME. A66 J du Plessi» en GN van Wyk C.L. Ghana** «nd S. Krl winger* Department Fisika, uovs, Bloemfontein "University of the Beseem Cape University o£ Stellenbosch Transalssion Electron Diffraction (TED) can be used Die Guttman en under makroskoplese ternodineaiese effectively In the characterisation of -rystalllne analiaea van oppervlaksegregasie word bespreek in speclaens. However, the process can be tedioua especially when only a ssull area of poly-crystalline tern* van die neranalise van du Plessis en van Wyk. specloan Is available for analysis, and/or two or aore Verskcie gebreke en ernstiga foute in die ontwikke* coaplex diffraction patterns are superlitposed. This ling van hierdie teorit word uitgevys. is especially trua In the ease of tnatnaenta on which •icro-dlffraction is noc possible.

A facility to simplify the analysis of TED alcrocraphs using computer-controlled •icrodensicoaeery has been developed, and la described alone with the general principles on which the software is based. The applicability of the aystea in eh* handling of non- continuous diffraction rings and diffraction peak deconvolutlon is also discussed. Exaaples Illustrate that the systea, though relatively siaple in design and operation, can obtain data froa otherwise unuseable TED micrographs.

APPLICATION OF SPACE GROUP THEORY TO SE • A67 COOT ORDER PHASE TRANSITIOW IK CRYSTALS Herbert Willi Kunert SEGREGASIE VAN TITmiUH IN GOUD Department of Physics.University of Pretoria. PE Viljoen, JP Roux en 0 Holtzhausen 0002 Pretoria Departement Flsika, oovs. In the Landau theory the symmetry change which takes Die seqregasie van titaniua na die oppervlak van 'n place at a continuous transition is related to the sy- goucteonster vat 4 at. % Ti bevat, is ondersoek. Die mmetries of a certain active,physically irreducible re segregasieprose* vir Ti begin eers aeetbaar word bo- representation of the high symwtry apace group. The kant ongeveer 300*C. Koolstof wat aa 'n onsuiwcrheld selection of Che appropriate active irreducible repre - in die allooi vecrkoa, segregeer self* by laer tenpera* sentations of a space group is discussed.In particular ture sterk na die oppcrvlak waar dit in die voia van the Reality Test and the Landau-Lifshier** criterion grafiet verskyn. By ho«r temperature is dit in 'n are analysed. chenies-gebonde of karbiedvorm op die oppervlak. By 'n bepaalde temperatuur is die Ti, C en 0 in 'n vastc v«r- houding ten opsigt* van mekaar teenwoordig in die oppep vlaklaag en word die afleiding gemaak dat die drie ele« mente <5f teen dieselfde tempo ko-segregeer na die oppep vlak iSf dat vast* chemiese verbindings tussen huile vora in die oppervlakgebied wat gemonitor word. Op hierdie stadiun is die proses of prosessc wat die segregasietempo beheer nog nie bo alle twyfel vasgestel nie. Die segregasiegedrag van die allooi in 'n suur" stofaemoafeer word intussen ondersoek cm lig te werp op die korrosieg«dr«g van di< komiersie

P.R. Clayton, A. van Zyl, I. Slgalaa, G. Jantsky and O.S. .JfcLaehlan*. ~ DIE ROL VAN KLEIN PERSEKTASIES Pt- National Institute Tor Materials Research, CSIR A70 METAALTOEVOEGINGS IN Fe40Cr STAAL. •University of the Witviatersrand J.P. Roux O.J. Holtzhausen en M.J. v Staden Chemical synthesis techniques were employed to produce intimately mixed oxide precursor powders from which Dept. Fisika, UOVS, Sloemfonteia dense ceramic superconductors were prepared. Die invloed van Pd en Ru in klein This paper deals with the synthesis and process- persencasies aanwesig(o,5 - 3 %) in Fe 40Cr ing of the oxiae precursors, as weii as the subsequent vlekvry staal «ord bespreek. Die segregasie characterization of tfte materials with respect to en oksidasiegedrag in UHV-toestande is onder- resistivity. Xeissner effect, crystal structure and soek met behulp van AES en ESCA-tegnieke. microstructures. Die oppervlak van die monsters'is ook vertyk met Pd deur opdamping van • 600 A laag Pd. ay verhitting blyk dit dat die Pd-laag Cr selektief deurlaat wat 'n belangrike eien- skap is in die bevordering van korrosiebe- standheid. Die gedrag van Ru word vergelyk met die van Pd.

78 KERN-ENDEELTJIEFISIKA B NUCLEAR AND PARTICLE PHYS.

STATUS VAN DIE NASIONALE VERSNELLER- 12ÇU 11 AT 66 HaVi EXPERIMENTAL BI SENTRUM, .FAURE B4 METC "DATA ANALYSIS n ».if arm en A H Both« 3.3. Lawrle, A.A. Cowley, D.M. Whittal, 3. Pllcher Rationale Veranelleraentrum National Accelerator Centre Vordering »et die versnellers en ander fasiliteite van Coincidence data for the 12C(p,2p) knock-out reaction dl« NVS te Faure gedurende die afgelope jear aal at a quaoi-free angle pair was obtained using a 66 MeV beapceek word met die klem op die inbedryfstelling van proton beam fro* the NAC cyclotron. The experimental die oopaektorsiklotron en toerusting vir die gebruik method and the method or data analysis, leading to the daarvan. Vooruitsigte vir die voltooiing van determination of a binding-energy spectrum in which oorblywende take en die prosedure wat voornemende the ground-' and first excited states of B are gebruikers moet volg aal ook toegelig word. resolved and an energy-sharing distribution for knock-out to the ground state, will be discussed. Results compare well with previous experimental data at SO and 100 MeV. V

B2 OPWEKKING VAN REUSE MULTIPOOL RESONANSIES MODEL CALCULATIONS FOR THE l2C(p,2p) W J Naudé*. D J Swanepoel*. W de K Loubser*. J A Stan- B5 REACTION AT 66 MeV der*, J W Koen* »Universiteit van Stellenbosch P.M. Whittal, A.A. Cowley, 3.3. Lawrie and 3. Pilcher •EVKOM National Accelerator Centre

Die resultate van die nie-elastiese verstrooiing van The experimental data are represented in the form of protone vanaf atoomkerne in die massagebied an energy-sharing distribution (see preceeding A « 58 - 197 en vir laboratoriumhoeke e. = 8° - 35°, presentations). As is usual for this type of knock sal bespreek word. out experiment, model calculations are based on the Distorted Wave Impulse Approximation, but are in surprisingly poor agreement with the data. Attempts to understand the discrepancies will be discussed, with particular reference to Optical Model parameters, the bound state wave function and off-shell effects.

INTRODUCTION TO THE KNOCKOUT AND B3 CONTINUUM DECAY STUDIES WITH IHE NAC SEPARATED SECTOR CYCLOTRON COINCIDENCE STUOY OF CONTINUUM DECAY A.A. Cowley U National Accelerator Centre INDUCED BY PROTONS OF 200 MeV ON C An introduction to knockout reactions pursued at the 3. Pilcher. A.A. Cowley, 3.3. Lawrie, D.M. Whittal, new separated sector cyclotron will be presented, with S.3. Mills a brief review of present knowledge regarding the National Accelerator Centre reaction mechanism at 66 to ZOO MeV. The experimental technique will be described, as well as the method to An experimental study of coincident protons emitted in relate the measured quantities to physical properties the reaction p + C at 200 MeV has been carried out. of the scattering system. Previous experiments on a single oiedium-mass nucleus have indicated that the reaction mechanism is I shall describe our research programme to evaluate dominated by an initial intranuclear nucleon-nucleon the role of an intra-nuclear nucleon-nucleon interaction in the formation of continuum yields. The interaction. current experiment examines whether the target mass dependence of the reaction follows the expectation. Results will be presented.

79 V THE 2HICU0M AS A COLOK HACSETIC SOLITOH BIO J M Crsbsn. Thsorscieal Physics Division, EQJATE NMMS, csm

B7 EXCITATIONS Th« QCD equations of notion for tha nucleon are solved aiiag * seai-classical aneats for Ch« (luon fi«ld. The Oevid A»crwMn. ansstz ii suggested by th« perturbacive solution of th« University of Cape Town. aquations of notion, uicb th« nucUon bains described In tanu of thraa valanca quarks. Tha f.luon sslf coupling, A Wlts-UCT experiment to study (p.?) tens do not affact tha tiae component of tha gluon fiai< reactions oo light nuclei at Intermediate but hava a profound affact on tha space component* of thi« energies has begun taking data at the fitld. A non-trivial color-aaenetic vacuum solution is cyclotron at the National Accelerator found which can ba eonnactad to tha parturbativa vacuun Centre. Giant dloole excitations of the by virtu* of tha quark-gluon intaraction, so that ths ground and excited states can be studied. baryon emerge* at a color-najnetic quantum soliton. Th* as can the higher harmonics of the giant icala of tha solutions is fixad by tha nuclaon sass. u« dloole states. Gassse rays mrm detected In •tudy tolutions for two valuas of tha strong coupling cocv> a large volume sodium. Iodide scintillation stant and give tha composition of tha nuclaon «ast in tars counter with ant3-coincidence shield. Data of gluonic, quark sad spurious eantsr of tun components. taken with carbon-I2 and boron-tI targets Wa also give results for tha static properties of tha will be ©resented. nuclaon, and discuss various properties of ths quarks (percentage saall component, asymptotic behaviour ate.) and the gluon fields.

OT OF MCOWaXWT MH> B11 CTOAfr f TESTS Of NEUTRON DETECTORS J. Clsyaaaa, Mraltft ftr Miyslk, (Ntlvarat- FOR NEUTRON TlME-Of-f^IGHT tit, 0-4*00 atelefsU, IMcral Xssvelle of Oenwy aiMI SPECTROMETER FOR (o.n) STUDIES Inatituta of Thaovstieal fkysies vU Astrealqrsless Omi- AT NAC CYCLOTRON Texsity at Case tm. Keaesseaek 7700, Ope, MA. Oavld Aschman. K. ladliok, Dalvardtit, MeleCeM, fsd. Mpok. Oetassy. University of Cape Town. I. Cats, Delfwsisik, Slslsfsld, 9*4. Xepua. Oacaany. I. lahosee, Ofeivenitr, ir-tOHO Oaio, nalaad. Large elastic scintillation counters for tmtUGIi Ms eoswicsr S tHrse-sMse aodel of stroafly neutron detection have been tested In a iatwaotiaf aattor, tnstlaf esefc snsse as am ideal «aa zero-degree neutron beam at the NAC modtClea ky s slaele pliswaaeiioloeioal intaractiom faatnr*. cyclotron. These will be used In a long For aoelxac matter, wa take lute aooowt tke baryoaie ftight oath time of flight spectrometer for rapolstear far tke ejsackf IUM plasaa, vm laoioda th» studying (p.n) reactions at Intermediate bmf pcassurai tke ssMtitnsat «jo*rk phase has a BOO-IMTO energies, where Gamow-Teller nuclear •ffaetlve sjssrk eass ss w»Xl es aa Udepamoast baf pew! excitations have been observed. •ore. ay statyiaf wklek stasasoainatM tketaa«ysaalcally ia unat reeiaa ef taaasratare awe keiyoa moaber aeaslty, urn eetela a passe dlafTsa far stxoaflr intuaetiaa matter aa< taia seas lastfkt oa the ralatiea batmaa deeeaCtaaasat sat eklrsl syaastry restoration.

EMPIHICAL EFnCTIVt INTERACTIONS FOR SHELL B12 -MODEL CALCULATIONS ABOUND MASS 40

'BE *C ELASTIC 3CATTERIMG REACTION. B.J. COLE* and W.L. Oadinabokao*1 *Univereity of the Witwaterarand, Johannesburg E Sldaraa-Haddad. RU Fearlck and JPF Sellschop. '''University of Bophuthatewana WltJ-CSIR Schonland Research Centre for Nuclear To perform nuclear structure calculations in the Science*, University of the Wltwatersrand, f, - d|. model space the effective Hainiltonian, com- Johannesburg. prising two single-particle energies and 1<1 two-body We have used a 4E-E detector telescope to measure the matrix elements, must be specified. tn the absence of *Be • lJC elastic scattering excitation function in any reliable theoretical calculation of the two-body the Cab energy range 11.5 MeV to 19 MeV, at two angles. interaction, these matrix elements must be extracted in Siallar structure to that seen by De Rosa et al (ref.l) some way from experimental spectra. h*s been observed. The data are presented here and we are proceeding with the theoretical analysis. We have investigated several methods of obtaining information on matrix elements by computing configur- 1. A De Rosa, G. Inglioa and H Sandoli, II Nuovo ation averages for the energies of states based on one Cieento 65A (3) 1985. and two single-particle orbitals. Thia procedure provides constraints on the values of two-body matrix elements.

60 DINAHIESE SlHCTRie - n HUWE 6ES16SPUNT VAW POSITRON PROOUCTION IN NUCISAK COLLISIONS B13 DIE SKIlHQOg B17 1. A6TERCMM0 EM STRUKTUUR 8. Spoalatra*. J.P.F. Sellschop* end U Von Mi«ewraperg+ •University"of Zululcnd. H I S«ytr groepttorttiest struktuur ult t« voer. terpreted satisfactorily [1]. The latest indications Oft agtergrond en struktuur van hicrdit model word are that such peaks are also preser In the positron kortUks geskcts. spectra for Zu « ISO. This paper is a report of our investigation of the positron spectra generated in >2C bombardment of nuclei. Cl] U NUller U at. Z. Phys. A323 (1986) 261 ^ OINAHIESE SIWETRIE - Yi NUWE GSSIGSPUNT VAW B14 PIE SKILHODEL II. TOEPASSINGS EN RESULTATE BHABHA H-8 Gcyer Instituut vir Teoretiese Kemfisika, Un1vers1teit 0 von Wimmersperg, 5H ConneU. REAJfoeralff 'and Stellenbosch E Sideras-Haddad. Spesifieke toepassings van die fermion-dinamiese* Wits-CSIR Schonland Research Centre (or Nuclear stmmetriemodel en vergelyking met eksperimentele Sciences, University of Hitwatersrand, Johannesburg. resultate word toegelig. Positrons froa a source .of "Si. obtained through the reaction >rAl(p,n)27Si, were scattered off electrons in a target of polyethylene, and e*o" coincidences were "Some current challenges in nuclear detected in a pair of plastic scintlllators. The BIS physics a its fields of detector apertures were restricted to accept only application" events corresponding to aaxiauB aosentua transfer at J.P.F. Sellschop centre of aass angle 90*. The variation with energy of the corresponding lab angle was utilized to obtair the Wits-CSIR Schonland Research Centre for scattering excitation function from the continuous Nuclear Sciences.University of the Witwatersraad positron spectrua. Centre of aass kinetic energies in Johannesburg. ______^_____^_^_____ Che e*e~ system covered the range 342 to 845 keV. A deviation froe Bhabha scattering of order 10* was A (small) selection is presented of recent observed at 720 keV. The possibility is considered that developments in the field of low energy nuclear this phenomenon eight correspond to a scalar aagnetic physics r heavy ion physics at low, medium and higher energies, and from nuclear astrophysics («*«') resonance of sass 1740 keV. to illustrate the ongoing excitement and open questions in the overall field. In similar vein a survey of a few of the> current applications is explored to reveal TDPAfl MEASUREMENTS OF IMPLANTATION the increasing extent and value thereof in B19 TCEMPE1ATUM DEPEMDAHCE IM '^F UgUWTED an ever-widening variety of fields. S. Conncll*. T.r.T.T?*!lichop*, H.S.Stt H. App«l*, K. Bharuth-Ram*. *Wit*-CSIK Schooland Research Centre {or Nuclear Sciences University of the Witwatersrand, Johannesburg, S.Africa NUCLEAR PHYSICS DATA ACQUISITION WITH A •Univertitat Karlsruhe, FR Germany. 'University of Durban-Hestville, South Africa. PERSONAL COMPUTER 9 B16 ' F has been used to probe the structure of the diamond S U Fearlck lattice. The oeasurenents were performed via the time differential perturbed angular distribution (TDPAD) Vlts-C3IR Schonland Research Centre for Nuclear I9 Sciences, University of Wltwatersrand, Johannesburg. technique applied to the 197 keV scsce of F. The pre- inplanced probe nuclei were excited using a(p,p'.gamnu) Tha PC offers several capabilities which can usefully reaction initiated by a pulsed 6 HeV proton bean. be exploited for data acquisition in nuclear physics. Two applications will be discussed: using a PC to The one plane face of a type IIB Diaaond slab was control and display data froo a Nuclear Data HlcroMCA, implanted at 700*C and the other (opposite face) at near LN temperatures. The residence sices for Che probe ions and using a PC In a CAMAC-baaed aultiparameter were determined. The hot implanted tide had almost acquisition systen. The performance of the latter twice the fraction of probe ions at s unique sice as the system is enhanced by distributing part of the cold implanted side, *M expected in accordance with the processing load to an ln-erate computer, thus allowing mobility of defects above 600*C. The results are canpared buffering of data and the use of efficient block to Measurements made at similar temperatures by the transfers. recoil implantation TDPAD technique.

81 TP.N:

SOEKTOG VAN DIE WAAKHEHISG VA» SONVLAH- BAA LEEFTYD VAM Pit 0* TOISTAm TAW B20 NEUTRONS IN DIE VYfMINUTEDATA VAN DIE KEUTRONMONITOR TE TSUMEB. V M Proieaky. 0 V Mlngays Atoo*esergl«- P.H. Stoker, PU vlr CHO korporaala van Sold Airlka Bpk Die 18NM64 neutronaonltor te Tsuaeb (10*12'S, 17*35'E. 'n GeraanluadttekCor vat as akjrf as dataktor gtbrulk hoogte (240 •) reglatreer kosaieae ttrale vlr 5 alnuca la, It ate oeutrone van 'o -2*lA«(ia5-aroii vanaf Januarit 1978. Sonvlaaae gepubllaeer ulc dit gaboabardtar, co 41* 0J 691 kaV toaataad In 1*0* waarneainga van SUM (Solar Maxlaua Million) an In dl« la daur oaclaatiaaa oaucroDvaratroollag opgawak. Dta lictratuur la gebrulk oa gclyktydige raglatraala van laaftyd van dla totatand la bapaal daus dla sonnautront deur dla neutronaonltor ee Tauaab ca tydavarakll ta aaat tuaaan dia tamgakopatln van dla ondersoek. Gaan atatlatlts-duldende gabaurcanla kon '*G«-k«ra an dla vaa dla volltdlga lnttrna sastctlng gevlnd word nit. Ntutront la vanaf dla ionvlaa van van dla vlak. Dlt aaclnga It op twee dataktote 3 Junla 1982 daur neutronmonitora op Aarda gcrcgl- (G«-Ll, ko-aka, dleptat 51 aa> dlaaatar: 4S,6 m) «& atraar. Ook vlr hlardla gtbcurtenla waa dla eoenaoe IG, vlak, dlapta: 5 aa dlaaatar: 10 aa) gtdoea as o.». in ttlteapo van dl« neutronoonitor ca Tauaab nit varakllla In ladlngavaraaaallngatyd ta tdandflaaac. atatistits duidtnd nit. Ola gaaaca leeftydvaarde van 634 + 20 aa la vcxgelyk •at vorlga aetlnga. ~

J vaa Waart ta D.W. Mingty, AEX C B Franktyn. AEC The intensity of scintillation light due to the passage Sckoadcrt-tlcktrootaiaaic vanaf C- an Mylar*akyvc of fission fragments through ME102A thin fila plastic a.g.v. invallanda awaarioonbundtla aec tnarglaa tuaaaa 1 en 3.5 MtV, ia btatudacr. Met bahulp van 'n scintillator has bean measured for fila thicknesses from parallel plaat-anallieerdcr, la karakterlatleke ven 0.5 to 10 |ia>. As film thickness is increased up to 3 um aekondcrt-elektros tnergittpektra waargeneea. Oaar la o.a. gekyk aa eindpunt tncrgiea konvool- en anci from S urn upwards the luminescence increases Augtr^tltkerouc. Die ladlogatoeacand afhanklikhcid, gradually, however, from 3 to 5 um there is a rapid aowcl aa vergtlyklnga tusitn aolckultrt (Hj+) «o acoacra (U*) bundtla, la getraf. increase in luminescence. A similar transition is observed for 2.3 MeV He ions. Possible causes for this effect are discussed.

BAB PROMPT GAMMA-RAYS FROM THERMAL MEUTROS STKOOMDICTHEIP EFFEKTE IN SEKOSPeRE ^ CAPTURE IN NATURAL Os AND Ce B22 ELEKTROS ESERCIESPEKTRA ' ~ C B Franklyn. AEC C Dednaw en J van Uaart, AEK Discrepancies have been found between standard tables

Die stroomdigtheid afhanklilcheid van sekondere-e lektron of prompt V-ray energies from

82 •ttftaS *«*' IC- EMISSION MJES FOR X-fAY HICKODOSIMETRV - CONCEPTS AND QUANTITIES BZO HHiBPHflbH IT PROTONS. DEUTaOMS. wm AMD ALPHA PARTICLES J.H. Houth and P.J. Biunf, Nationrl Accelerator Centre, CSIR, Pretoria » • Kotaa aannd 0 W Hlngay lc Phyaica, AEC, PrtcorU jjuclaar aod la contrast to conventional dosiaetry where the absorbed m* rtlatlvt transition probabilities of dose D*dT/dm is clearly a macroscopic quantity, aicro- eharacttristlc K X-raya were measured in thin dosimatric data reflects the pattern or distribution of targets of X, Ca, Sc, Tl. V, Cr. to. Ft. Co. Ml. energy depositions along track lengths of the order of ,a CJ, Ga. and Sr rttultlng froa bombardment by M micron. These dimension* are relevant to radiation •roton, dtuttron, and alpha particle beams. The action at a cellular level and a tissue-equivelcnt pro- experimental valuta art compared with Hartrce-Fock portional counter can be used to evaluate lineal energy calculation* aa well at the theoretical valuta of spectra for simulated track lengths in the range 0,25 - Scofield. The proton - and alpha particle Induced 10um. Probability distribution function* and mean calsalon ratta compart favourably with photon values for aicrodosimatric quantities will be discussed, loductd data, with minor anomalies at Cr, and Cu, in particular single event spectra which are ocacured but the anomaloua behaviour of tha deuteron data experimentally and are usually displayed as a function cannot be explained. The Influence of projectile of lineal energy. energy on the KA I K, ratio* waa alao Investigated between 0.6 Mev and 2.* Hev. No direct velocity dependence could be obaerved In the present data.

MiASUKtrtENT"Ut SINGLE" tVLfli irtHKA in A B29 HIGH LET RADIATION FIELD P.J. Binns and J.H. Hough, NAC, CSIR, Pta The quality of a fast neutron bean intended for medical K X-RAY SPECTRA PRODUCED BY or biological application can be determined vith varying B27 NITROGEN IONS IN Tl AND V degrees of exactness. In routine dosimetry the total absorbed dose is stated with acceptable accuracy in terms P B Katie and D V Klngay of the constituent neutron and photon components. This Nuclear and Atomic Physic*, AEC, Pretoria accuracy is improved if the spectral distribution of the incident neutron flux is known. Of more fundamental in- K X-ray spectra aa produced by nitrogen Ion impact terest is microdosimetry which provides a fuller discri- on Tl and V are compared with proton-Induced ption of beam quality as related to the event size spectra at 2.4 (lev. The K^ and K« lines from spectra of recoil electrons, protons, a-particles and nitrogen bombardment are found to be shifted heavy nuclei, as measured M a microscopic level (ie approximately 45 and 90 eV, respectively, relative 1-2 urn). Track lengths of these dimensions are simulated to the proton-induced spec.tra. Hartrtt-Fock in a tissue-equivalent proportional counter filled with calculations show that the obaerved ahifta are m* tissue-equivalent gas at the appropriate pressure. The expected from atoms with two or more additional detector pulses are processed using NIM electronics and lneer-shell vacancies. Double K-shell lonlzatlon pulse height spectra accumulated in a oulti channel can be ruled out in these cases. analyser. From this data, single event spectra are calculated and probability distributions expressed as a function of lineal energy. Spectra obtained under varying physical conditions in a d(16) + Be fast neutron m!ffo&Hme1r?J*plS?a£eltel?s.discus»ed in teras of various

PLASMA PHYSICS PLASMAFISIKA

A A COLLISIONAL EFFECTS OH THE CURREMT-DRIVEN C2 ION-ION HYBRID AND ION CYCL0T3CN INSTABILITIES

A. PLASMA WAVES IN LABORATORY AND SPACE D. Johnstone and M.A. Hellbcrg, University of Natal, V I P.J. Barrett Durban. Plasma Physics Research Institute, Numerical and analytic analyses of the growth rate of university of Natal, Durban. tne ion-ion hybrid mode (IIH) as a function of w A description of the wide variety of plasma waves will electron-ion collision frequency ( ) are presented. be given in terms of two-fluid theory. Laboratory Linearity is lost Tor ^fl > hR - K^l. A parameter experiments on some of these will be described and related to observatior.s in the Magnetosphere and survey of the IIH mode ha3 been carried out. as well as ionosphere. The significance of wave studies for the s study of the effects or M?h «gl on the lignt ion fusion programme will be discussed briefly. and heavy ion cyclotron modes. The transition diagram of Sharuthram and Hellberg is found to be Inappropriate for high vel.

83 THE ION ACOUSTIC INSTABILITY IN A Modulatlona! Instability of Strong C3 MAGNETIZED TWO-ION PLASMA ^ Electromagnetic Haves In a Hagnetned Plasms J. Govender and R. Bharuthran ». Bharuthran*. P. Singh* and P.K. Shukla* University of Durban-WestviUe and Plasm* Physics •University of Durban-Westville, Durban Research Institutt, Univarsity of Natal, Durban. Ruhr-Universltat Bochum, Fed. Rep. of Germany Accounting for the relatlvistlc electron quiver velocity The behaviour of the crossfield current-driven ion and the relativiatic pondcronotlve force, the acoustic instability in a magnetized plasma containing nodulational instability of an arbitrarily large two ion species is theoretically examined. The amplitude electromagnetic wave in a magnetized plasma is dependence of the critical drift speed for C Investigated for three type* of plasma slow responses. instability (VQ ) on several plasma parameters is A parameter study of the instability growth rates is studied. These include the heavy to light ion mass presented. ratio, fraction of light ions, magnetic field strength and the propagation angle. 'Also at Plasma Physics Research Institute, University of Natal, Durban.

ELECTROSTATIC WAVgS IK AN ION-BEAM C4 MAGNETIZED PLASMA SYSTEM K. Naidu and J.F. McKenzie Department of Mathematics and DESIGN OF HELICAL MAGNETIC COILS FOR Applied Mathematics C8 THE AEC IOKAMAK Univarsity of Natal, Durban. D P Coster, J A M de ViUiers, J B Fletcher, £ In this papar, a multi-fluid approach is used to Nothnagel, D E Roberta, 0 Shervell ~ obtain the electrostatic ion-cyclotron acoustic wave in a plasma syst«a consisting of hot, massless elec- Fusion Studies Division trons and cold ions. The properties of the dispersion Atomic Energy Corporation of South Africa relation in different frequency regime* is investigated using the wave number surfaces. Three sets of helical colls (I - 1,2 and 3) have been Installed on Tokoloshe for the purpose of The generalized wave aquation for a plasma consisting studying their effects on disruptions. A particular of a stationary magnetized background plasma goal of the coll design has been the achievement of relative to which an ion bean drifts with velocity u D as pure a magnetic island structure as possible. perpendicular to the magnetic field is also obtained. The properties of the dispersion relation for this ion The design philosophy la outlined while computed bean systea are investigated in the V.L.F. regime Island alzes and their Importance for future for instabilities. studies arc discussed.

MACNCTIC FIELD MEASUREMENTS ANISOTROPIC ION BEAM - PLASMA INSTABILITIES C9 RESONANT HELICAL WIMP DIGS ON THE AEC C5 P. Singh and R. Bharuthram TOKAMAK University of Durban-Westville and Plasma Physics D P Coster, J A M de ViUi«r«, J 0 Fletcher. C Research Institute, University of Natal, Durban. Nothnagcl, D E Roberts, D Sherwell Fusion Studies Division Using kinetic theory, the dispersion relation for Atoaic Energy Corporation of South Africa electrostatic instabilities arising from the interaction of an anisotropic ion beam and a background Observation ports and engineering constraints re*ult plasma is established. Solutions of the dispersion in deviations of tha helical vladlage from their relation are presented for varying plasma parameters. theoretical path on Che surface of the vacuum chamber. These deviations must be such' that the perturbation of the resultant field la small.

Sj«6flIC

ana * 3eoa*t«en; of Applied «itne»ati •• D«3*-;»en: of 'hysics jnwesity of 3ur&an-eiest*i] le C10 REPAIR AND Jt£-ASSEM6LV OF TOKOLSSHE

entei for canst'jct;rtq :*)f for «n J R O'Mahony Atomic Energy corporation :onsisting of :«o iotzifi An arc which developed between the ohalc heatiag iad toroidal field colls of TaKoloshe necessitated a *«p*it-fle ion-»c3ustic loliton iia :ouble-'.a««r potential complete disassembly of tne tokamak. This paper at 33£a.*c4 without the usual cold *on or \aail aiplitude details the damage caused, Its repair and the re-asseably of Tokoloshe unlch Is now In progress.

84 or m IOH.IOM nsramci STtmmw 01 tomwa en and K.c. Graavaa r«y Corporatloa yaios Raaaarch Xnatltute, 'Jntvaralty of Xatal, OurMn. nin atnuiai don aoa-lUaar Itlaad coctowa *arlou» typo* et bawgantrcced inatabUltlaa hav* •" - tltlaplp a wyy of rlauallsia^ uaufotf t Mchaaleaa baan studied In tha Dovbla FUana davlce. Moat or *" t0>ir>ir-fc-fc«« - IItt aakaak a elaarl , CCo r *Maa4a4 , to* thess ara kinetic Instabilities, drlvan by raaonant * r1...

SPATIAL CHARACTERISTICS OF CBOS5FIELO CIS ION ACOUSTIC TUBFUIEKCE. C12 EHERGY TRANSPORT IH AH EHGODIC MAGNETIC R.G. Crtivti mi P.J. Bimtt LIHITER Dtftfim4nt of Pkfiiei, Uttiurtilf oj Nttst, Dnin. and W. P*n*b*rg , University of Haul, Duroan. TM cnMslfeM to* tcouttii iniMbJIity occurs whtn there Is rditiv* drift be- tweui unm»|fHt?iMd IM* and ftiifnttlied titttiont tent* » mignctic Md A 3-dioansional numarieal aodtl for tnargy tranaport In (w^ « w « vn). Cbsarv«tlon* of the twbutane* Mwcitted wli* this initibtHty ai.> tr«o! far Plaaaaphyalk, Garching, U. Germany. A. Chaaberlain, H.M. Mlchaalla and H. Hoteutt, Plaaaa Phyaica Research Institute, University of Hatal. Durban Up to 300 MM of Ruby laser light la focuaeed on solid planar targets under vacuua. Tha plaaaa la diagnosed with an N2*laaar proba beta, X-i-ay diagnostics and charga collecting Paraday cupa. Lataat raaulta regard- PROBE MEASUMCHTS IH A STEADY-STATE ing ion-flows and X-ray characterisation will be TOKAMAK DISCHARGE PLASHA praaantad. P.J.Barpatf. M. Coo, 0. Darrow and G.J. Graana, Princaton Plaaaa Phyaica Laboratory, PrJr.caton, «J 0«5M, U.S.A. IH A, MACHETIC FIELD WITH UNLIHITEP Tha Cjrrant Drlva Exparlaant (CDX) at' Princaton in- Ct7 GKADIEHTS volvaa "Hallelty injaction" In tha fora of a lov-anargy Mgh«currant alactron b«aa which antara tha plaaaa R.A. Burter and H. Mortal along dlvartar fiald linaa. This eonatitutaa a jurfact currant which gats transferred acro«s tha aagnatle fiald PU/CSIR Cosalc Kay Research Unit, Potchefstrooa to fora toroidal current throughout tha plaaaa voXuaa, The slaplc drift cxprcsalon thertby ionizing th* (heliua) g*M and aalntalning a tokaaak fi«ld configuration. Typical paraaatara are xv^j, - (p v/3

85 C18 tlASHA KQSSWt VkVtS U.K. fotthatty and J.F. McKensU C20 Department of t.r>O)ea»atics and Applied Natheaatica, Dtsarfcatai •/ Mfmi, (M««rnrf t/Xelef, Oerlaa. University of Natal. Durban. Electrostatic tea CydMroa Waits an netiatly dettabfliaed by drawiai a Th« latitudinal variation of th« vertical component carnal to a dak f battoa*) isuatrttd ia a •Mfutiiea' plasm colmau. Tat of the aarth's rotational frequency gives rl«a to fraqaeacy dttarmiaiai ttfioa of tkt iattabilky caa bt Mapped by awnac. tkt large-scale incompressible ahoar waves in tha earth's battoa aloM tkt axa of a Q-meekiae ia a tpallaUy varyisi aarattic ttld ataoephere/ocean • known aa Rosaby wavea. In a aad aoaitoriag tkt frtqatacy at a faactioa of battoa positioa. Uadar ctrlaia magnetized pUsaa a slallar type of vava (electroata- coaditioat two ptakt an obttnrtd ia tkt aoiat tptctraa ef tke battoa camat. tie in nature) arises whan tha background Mfnetlc Wt tetablitk tkai tktat an die to iattabilitke wkick an excited ia diftrtal fiald varlaa In a direction perpendicular to It. For •patial rtfioa* ia Eroat of tkt battoa. simplicity, in thia paper, we assume that tha plaaaa consists of cold ion* and hot ttasslass electron*. Tiwifil tiilraM Tmill.K fm Tk«ei«tictl Pbgnia, tfalmnlir tt UMtrak, loa*. Tha low frequency llalt (i.e. u « Q.) yield* "RoMby" type shear vavaa M wall as acoustic waves Modified by thla "0" affect. The properties of these vtvea are discussed in detail in teras of the geoaetry of their wave normal iurfaces. A SIMPLE METHOD TO C21 ABSOLUTE VALUES Ot SPACE POTENTIAL PHASE MEASUREMENTS OF THE ION CYCLOTSOH E.Mrarlai aad P. Xnmn C19 INSTABILITY Dtttrttiuni net, Vttiwiitf af NtUt, Dwivi * M.J. Alport and E.G. van Nlekerk Pmbwd tnuanvt probtt, at sppottd to cold Ltafmmir probtt, «llow for tkt Plaaaa Physics Research Institute, University of Natal, dinet, aaarabi(aomf dtttnniastioe ot tfc* tpta poUalial ia a planaa. Uafor- Durban. tnaattly, tkk nctthod nqairtt a fairly complex electronic circaitry, aad ktact Phase measurements of the lor cyclotron instability it aot oaly itiiau but alto proa* to dutarbiaf ialatactt. driven by an electron drift are presented. Tha experi- CoatUaoaaly optrated tmiattrt probtt, oa tkt otktr kaad, providt aa tqaallj aent waa perforaed in a Q-aachine (n "*• 1010 eaT^ accaratt aad mmca aiapkr way to dtttmiat tat ebtcfat* valw of tkt (pact T, = T s 0.2 eV, B "* 0.27} and the measurements oade poUatUL previdad tat tltctroa tatoratioa cunat b tqaal to C< maraud tketraa aniorioa emmat. Tkt potaatial ia tkta tma by tkt mtanrtd vala< using signal processing techniques. The propagation ot tkt loatiaf pottatiil akifttd by kalf tbt poUatial drop acroat tkt probe tip characteristics of the ion cyclotron waves were For a Q-mackiat platma tkt ralata of tkt «p#- pottatisl dtttrmistd in tkir determined by making measurements in the radial, axial way utiaf aa «mi»«v« probe operated ia tke coatinaooa moJe an compute and azimuthal directions. The effect of plasaa density, with tkt Ttlaat determined ia the palted modi. Wt Sad txcelkat airtamta! aagnetic field and electron drift velocity on the phase witkia tkt experimeatal actor of tkt emutehw probt mttkod. of the waves was Investigated. We analyze the data in the light of the Druaaond-Rosenbluth theory and sake TUt wttt ••• «ip«u(t«lbr t]» Autrlaa KaMank Find umhr Onsa N*. Ptiri. The eewparisons with an alternative "2-0 potential driven l o« the Q-««calm a/ U» toUltuM farT)ao»««ki i ftriici tf aodel".

OPTICS ANDSPECTROSCOPYDOPTIKA EN SPEKTROSKOPIE

S15TEMAT1ESE NEIGIWgS IN DIE LEEFTYE VAW D1 VLAKkE 13 DIE KOOLSTOF EH STIKSTQF IS0- ELEKTR1E5E kEI LEEFTYO-ANALISE VAH DIE 3p 'D" ENERRIE- D2 VIAKKE IN 0 III F J Coetzer , F 0 Mostert* en P van der Westhuiren T C Kotz< , F J Coetzer* en P van der Westhuizen* *Universiteit Steilenbosch, 7600 Somchem, Somerset-West 7130 Straiingsbeheer •Universiteit van Steilenbosch Die bepaling van die vtrloop van leeftye in isogiektro- niese raeksekan bydra tot die afskatting van die Leeftye van die 3p 50° energievlakke in 0 111 soos qe- kaskadebydrae as gevoig van repopuiasie van energie- meet in bundeifoelie-eksperimente is onderhewig aan vlakke. tn hierdie ondersoek word Yi peg ing aangewend foute as gevolg van kaskade-repopulasie vanaf hoe"r- om die verloop van die viatcleeftye yan die kooistof- en liggende vlakke, YI Uitvoeriqe studie van die verval- Stikstof-isoe*lektroniese reekse te verkry dear r. ver- wyse en kaskade-bydraes van die 3p 5D° tenne is met geiyking van eStsperimentele en teoretiese viakieeftye behuip van statistiese metodes op die leeftyddata uitge- van C, N, 0, F en Ne. Besondere aandag word gegee aan voer. Die gekorrigeerde waardes toon goeie ooreenstem- afwykings vanaf die algemene leeftydverlcop as gevolg ming met teoretiese en arder eksperimentele waardes. van Qie inaqneming van kaskade-effekte.

86 focuamc of LASER BEAMS WITH A GAS LEWS BOH-LIMEA* OPTICS: SOME PRINCIPLES AMP M. Wotoutt. H.H. MchaeUs and P.F. D3 Cunnlnchaa Plato* Phrslee Reeearch D7 institute, University of Natal, Durban. D. J. Irink. C3» . Ma itM it ua«d to rocua the focal length and spot (ton-linear interactions of light waves aaong themselves •lfe are investigated for different gases and varying and with the aediua they pats through encompass a vide flow rates. A hole la drilled in a iheet of alualniuB rang* of interesting and often useful phenomena. These, which cannot be done by a coaparable glass convex lena however, usually only occur at such high intentitiet that powerful later beau are a prerequisite for practical utilization. Consequently the field of non-linear optics it still relatively new with large scope for future developments. The lecture will outline tli* main principles at well as some applications and future trends in this field. C.A.R.S. TECHNIQUES FOR COMBUSTION AND D4 CHH1ICAll

We present preliminary results on flame temperature measurements and on the diagnostics of a tubular catalytic chemical reactor (CO • H • huH«w*rhnnO. D9 /».¥. SCHCLT2 Carl Md Billy Fuchs Institute for Micro Electronics, University of Pretoria. Aco ito-opt1c (AD) and electro-optic (E0) Interaction can be levieMnttd siauUtneously 1n a surface- •kB MINIATURE CO? WAVEGUIDE LASER acoustic-nave (SAM) device. The resulting acousto- electro-optic (AEO) Interaction can be used to give the designer of optical signal processing devices aore D. Schaieder. C.B. Dickerson and 0 Preussler flexibility than the cut «h«re to or CO Interaction 1i ased jeperately. This paptr will discuss the Optical Science! Division, NPBL/CSIE coup1ed-e»rfe theory that has been developed to describe this Interaction, as Mil as practical results obtained wUh Raun-Nath diffraction. CO, waveguide later* can be exciterd in the DC and BF •ode. They find applications at later radar transmitter and in laser eoaaunication systeas. Mt report here about our effort to build « CO^ DC excited waveguide laser and give aore details about electrode construc- D10 on ciinom VM Afoonxan IM tion, cooling and stabilization problems. In a first Oil OHTWiKP V3MI '» aKOMTO- attempt ve achieved an output power of 4 Watt in a 450 •a long device. OrTllSt

In die ontworp van 'n akoeste-optiea* •p«ktruaanalla««rd paraaetera nl reeoluale en dlnealeae THE USE OF A WAVEGUIDE AS RAMAN CELL FOR becaik balangrlka rolle. In hlecdla D6 GENERATION OF IR LASER LIGHT rafaraat sal aangetoon word hoadat M Budzinski and D J Brink apodlaaalm "jmbrulk kan word oa bei.de Generation of far infrared laser light by Raman scatter- hlerdle paraaatare ta opttmaar. Raaultate ing can be substantially enhanced by confining the van *n alaulaala eal beapreek an eovar interacting beams in a low-loss waveguide. The paper will discuss che construction and characteristics of aoontllk a«t praktleae raaultate vergelyk such a waveguide cell. word*

87 IHEAMTEITE IN AKKST9- D11 KlU 012 u:u;r.\i.uuu;'i.UJC~Kxr;- <•• i v A.J.HOFFHMI F. $. RONS Carl tn Gaily Fucnsinstituut v1r Mkrolitktronika, Carl a* brily Fwh» InatUutit vir HUrMiaktrmiUa Univtrsittit van Pretoria. Univtrsittit van Pretoria 'n Fundwtnttit btptrking wort op dta dinwitti btrtik Vtrsktit kodtringsttgnttk* Is voorgutti v1r dit van 'n tkotsto-opttm prostssttrdtr gaplaas dtur dit kodtring van rtktnaar-gtgtntrttdt-ho1ograt»t ( MH opwtkiring van inttmodutuitproduktt. Oit twtt bt- ). 'n itiangrika totpasiirtg van MHi Is waar dit lanarikstt ananisats vir dit opwtkfcing van Inttrwdu- gtbruik word as tangtpasdt nilnU'lkt filters in lasitproduktt Is akotsto-optitst ftstmdulasit tn nit- optitM korrtiasit tttistTs. '» StHdit Is gtdotn M Iinttrt akotstitst voortpianting. 'n Viskundigt lodti dit vtrskilitndt kodtringstwnitkt In hitrdit wat hitrdit tfftktt btskryf, word aangabitd. Oit totpassing tt tvaiuttr. 01t tvaluasit is s»t bthulp ttndiatnsiontlt anal lit vir dit voortpianting van van 'n rt«ks »lau)as1ts uttgtvotr. Ott btvtntftnfs akotstitst goiwt In n1t«11nttrt Md1a, wat rttds voor- van hitrdit studit tn d1t siswlasits wat ultgtvotr hatn dturgtvotr Is, word ultgtbrti na twtt of drit Is sal btspratk word. diuwnsits. D1t twtt MgaMsnts word vtrgtiyk In tera* van dit dcgradering In wtrkvtrrigting van dit Sragg- Oit tfftktitwa gtbruik van optitst drywing 1s 'n stl. Voorwaardts wat dit don1nans1t van ttn van dit baUngrikt asptk In dit ontwtrp van aangtpasdt twtt meganisMs sal bapaal, word btsprttk. ru1itt?

SOLAR-TERRESTRIAL PHYSICS E SON-AARDFISIKA

DATAVERWERKINGliMETODES VIR KLEIN E3 ABSORPSlES N RIOMETERDATA MET NIE NORMAALVE

AURORAGEBEURTENIS VAN 27 JUNIE 1982 EJ^CTRONPRECIPn^ONEFfECTSINTHE E2 P.H. Stoker en A.G. CoeC2er, PU vir CHO E4 DAYTIME E-RE6I0N IN THE SOUTH ATLANTIC SNDMALT HoogteproJleLe vlr energleverlies van elektrone en R Haggard and J A Gledhi11 hulle X-scrale Is met behulp van Mono Carlo-meCodes Hermann onlthaver Institute for Aeronomy, Rhodes deur Berger et al. (J.A.T.P. 35, 591, 1974) b«rek*n. University, Grahamstown, 6140, South Africa Hierdle berekenlnge is gebruik on die absorpsie van Analysis of the diurnal variation of foE during the kosmiese radioruis van 20, 30 en 31.4 MHz vir eksponen.- International South Atlantic Anomaly Campaign siSle elektronspektra met vouenergie 10, SO en 200 keV (ISAAC), an a cruise from Cape Town via Gough Island C* bereken. Hierdie berekeninge is gebruik om die to 30°S 45°w and back, shows that an extra source of absorpsiegebeurtenls wat gedurende die vroei oggendure ionization in addition to solar photoionization is van 27 Junie 1982 ce Sanae waargeneem is, te oneleed. present. The magnitude and variation of this extra Aanduldlngs is verkry dac golflengteverstrooiing vanaf source in the South Atlantic Anomaly agree remarkably die helderder dele van die radlo-hemelruim volgens die well with the ionization that would be produced by Bragg-voorwaarde voorgekom het. precipitating electrons measured by Atmosphere Explorer C. AW tVALUATIOM Of COWPOCTRIUP UL OF COUPLED MITHODS FOR HF MUF PWEDICTIOW SMrrOSOMC AKO ALFVtH WAVE3 AT 3. Lambert. KITH, Johannesburg B*. ttkddu and-S§S"gg« Department of Phyaica, computer programs are available for Univeraity of Natal, -Tedlctlng Haxiaua Oaeable Frequencies for Durban, 4001 E* coaaiunlcations. Agreement between the A sat of coupled aquations describing Predictions and experimental Kaxiaua Observed hydroaagnetic wavas with short asiauthal frequanciaa ia oftan disappointing, even wavelength has bean developed. This ia when vertical-incidence critical frequenclea expected, to be useful in the atudy of PcS match closely. pulsations near geostationary orbit. Computations have bean carried out to find tfte Syt arrora axpactad froa coaaonly characteristic pariods and polarisation ua«d pradictlon programs axa outllnad. Ray structure of such waves. The results are tracing through aora raalistic ionoapharic compared with obeervatione. Some features of •odeIs makas quantitaciva arror estiaatee the calculations are that tha coapraasional possible. Results are presented and eoapantd and Meridional coapononts of tha acgnetic with experimental data where possible. field perturbation are of opposite ayaoMtriea about the equator. Tha oscillation for higher karaonics can be confinad to a region quite OBSEBVATIOHS OP GRAVIT* WAVES AT DURBAN cloae to tha equator. M.B. Barker. Physic* Dept. Univarsity of E6 Natal, Durban. DAWK Pc5 PULSATIOHS E10 H.D. Barker. Physics Dept. University of Observations of cloud patterns provide evidence for iatal, Durban. tha presence of gravity waves In the high altitude Clear PcS pulsations of period approximately 300 westerly wind* prevailing over Durban. The aeconds are observed infrequently at SANAZ over a characteristics of these gravity wave* will be nuaber of daya. Coaparison of results of spectral discussed. analysis of dawn pulsations observed during 12th-27th Doceaber 1970 and 8th-l«th Moveaber 1972 are presented.

1KCLPSIOH OP A WAVT BEOTIAL SHEET IH A IONOSPHERIC PUISATIOH flElDS AMD E7 TWO-DIMENSIONAL DRIFT MODEL Ell TKClUATlOHSUR UB5fcCTH> WUPKLtK VELOCITY •..A. Burger. M.S.* Potglater and B. Moraal A H V Pooltf, P R Sutclifft* «nd A 0 M Milker* PU/CSIR Coiaic Ray Research Unit, Poechefstrooa » H*n*m cnlthaver Institute for Aarooosy, Rhodes University Two existing aechods for the Incorporation of neutral * Magnetic Observatory, Herainus sheet drift In tm-dlaensloiial drift aodels are evalua- > Oepartatftt of •ftyilci. University of Natal. Durban ted and coopered to a aodel which uses the actual Grovxi basad Mgrwtlc pulsation •NSunaants ftavt neutral sheet drift velocity field. We show "^*t the i*jA sham to be «ccosp*nisd by oscillations In the cornea denominator between physically correct t«tbods Dappler velocity of ionospheric echoes recorded by • Is a-spatially averaged neutral sheet drift of •agnltudc co-located digital lonosonde. By calculating the v/6> end that It Is possible to elaulate the (fleet of cosplex amplitude of the electric and Magnetic fields e vavy neutral aheet by decreasing this quantity. In the ionosphere. It Is possible to quantify the relative contriiHitlons of the various sscfcanlsss Hhlch give rise to the Ooppler pulsations. Indications are that the sost isportant are: (i) bodily vertical aoveaent of the Ionosphere under A IfNIFTEl? 1TL9 PtTLflA. the action of the eastward directed electric field and (11) Increases of plasaa density along the ray path proportional to tha field aligned component of A. P. M. WaJfcet* and J. F. McKeniie*. the pulsation sjgnetic field. Vnivtrntif of Natal, Dvrlan. A unified theory of standing hydromagnctie oscillations in a re- alistic magnetic field geometry is developed. The theory allows VO. IP^TIOMSHIP BETMIEM LATITUDE for two plasma ipeciss, one hot and one cold and can thus be E12 AMD THE EISEH?ESIOD OF Pc3 UKd for modelling pulsations in a region of ring current.' While POXSATIOHS cylindrical symmetry is assumed the theory is otherwise applica- S K P Hattlnah and P B Sutdlff*. Hagnetlc ble to an arbitrary geometry. An important feature of the theory Obaervatory, BerBanua is that cut-off frequencies are displayed explicitly. These cut-off frcqnencks arise from the geometry and the inhomogeneitiai in A distinct latitude dependence is evident In the the medium. Furthermore, in appropriate circumstances, some of elgeaperlod of Pc3 pulsations recorded during 1982 at a nuaber of altea lying along a coeBon geoaagnetlc these cut-off frequencies may be imaginary, allowing the possibil- aerldlan la Southern Africa. Hodel calculations ity of instabilities. In this paper some examples of the application based oa the assumption that pulsations recorded on of the theory are given. the ground arise froa standing Alfvln waves on geoaagnetlc field lines support these obsarvatlona. *D«p*rtm«*t of T jwics Data collected during subsequeae »utvy» (19S6 sad *D«p*rtmmt of Miiatmatks aad Applitd MatfctnUka 19S7), however, show no latitude dependence In the doalaanc period. lesults froa the varloua aurveys are presented and possible ressons for tha differences discussed.

89 RESOLUTION Of TEMPORAL ANP gPATIAL THE RELATIONSHIP BETVllM THE PLASHA3PHES» E13 AMBIGUITIES IN PULSATING AURORA E17 AND AURORAL OVAL n.J. Koict, and M.W.J. Scourfleld J. Stephenaon and M.W.J. Scourfield pnyaiea Dept., Uni varsity of Natal, Durban. Th* poaition of auroral torn», observed at SAJIAE by a Th« detailed «volution or an auroral fora In apaea and light level TV ay«tea, la uaed to define th« poaition tin« has an Important Input to understanding th« of th« auroral oval. Simultaneous whiatler associated electron precipitation Mchanlaa. TV iaagaa observations *p» ua«d to demarcate th« position of of aurora racorded at SANAE, Antarctica, ara analytad th« plasaaaphcr«. A eooparlaon of th« spatial re- using advanced digital laag« processing tachniquaa. lationship between th« plasaasphere and oval can be w« show that such techniques »vav« r«v«al«d that it is used to gain an insight Into th« relativ« raapons« of essential to unravel any spatial-teaporal aabilgultlea. these two région« to changing magnetic conditions. Indirectly it is also possible to answer th« question of whether auroral precipitation occurs on closed magnetic field Unas. A SOURCE FOB 3 Hi AURORAL PULSATIONS El 4 H.J. Hansen, E. Hravlag and M.H.J. Scourfieli, Dept. of Physics, University of Natal, Durban.

Correlated auroral and VLF taissiona hav« been Identi- OF WHISTLERS IN THE fied at L : 1 during simultaneous recordings of 'TV E18 KEG ION OF SANAE -ANTARCTICA auroral images as>ä broadband VLF. Coaaon periodicities of 1.5 * 0.3 Hz and 3.0 ± 0.1 Hz occur in the power spectra of both the VLF and the optical intensity vari- J.M. Ludwig ud A.K.W. Huf hw. ations. These are shown to be consistent with an DtpêttmtiU of Pkfrict, Ihnwtnitf of S*t*i, Dtrttn. external oscillator source driving at a frequency of aoout 3 Hz with varying amplitude. The external Ova 1300 Wkiitlen *n toUywd from VLF d>U »corded durinf 1985. Exit* source induces wave growth and strong pitch angle point« «r» dcttnnintd vine tkt L-vtlne ud (he uimutb of tm'vtL Tkt scattering via the cyclotron resonance interaction dutibation of tket* poiai* à duciund. whan the electron pitch angle distribution function is such that the flux levels exceed the flux trapping liait.

AURORAL PULSATIONS AND ASSOCIATED CHORUS E15 H.J. Hansen and M.W.J. Scourfield. RAY-TRACING STUDIES OF THE Oept. of Physics, University of Natal, El 9 PROPAGATION PATHS OF VLF SIGNALS Durban. ORIGINATING HEAR THE EQUATOR Images of pulsating aurorae and correlated chorus ele- Pravsh RamlalJ and A. D.M. Walker •ents have been observed in television and broad-band Department of Phymics, VLP recordings' at Sanaa (L : 4). University of Natal, Durban, 4001 Peaks in auroral-light intensity are displaced In time A ray tracing program ha» b««n developed to by -400 to 4-400 as from the associated chrous ale- study the propagation of radio waves in r. •ents. On frequency versus tlae spectrograms the magneto-ionic aediua. In this paper we use it slopes of successive chorus groups change in s random to study the patlis of vl? »ignäls originating manner. in various parts of the aagnetosphere, These results are compatible with a gyroresonance particularly near the equatorial plane in the interaction between VLF waves and 50 to 200 keV presence and absence of ducts. The results electrons. The source Is randomly located within are applied to aid the understanding of the a region extending from the equatorial plane to a propagation path of waves which arise froa position 8000 km beyond it. A relaxation oscillator cyclotron resonance with energetic particles. BOdel (G.T. Davidson, J. Geophys. Res., 81, 6517- 6523, 1979) is suggested as the modulation source.

AH INTERPRETATION OF SO-CALLED 'DRIFTING E16 DARK AURORA' H. Schoute-Vanneck M.W.J. Scourfield and WINO PATTERNS IN THE METEOR REGION E. Mravlag, Physics Dept., University of E20 Natal, Durban. A comprehensive data set has been assembled on the L.M.G. POOtE Rhodes University phenomena of 'dark aurora' from observations made at Skibotn, Noruay (L : 6,6). The set consists of low A coherent wave ireteor radar system has been in light level TV observations, electric fields from operation near Grahamstown for the past year. STARE and particle data from GEOS. Ooppier shifts in radio echoes from ionized meteor trains enable drifts due to motion of the neutral We will show that the 'drifting dark aurora' could atmosphere at meteor heights (winds) to be determined. occur as the result of luminous regions moving through Some results obtained to date will be presented stable dark channels embedded in the background aurora. and discussed with particular reference to diurnal The auroral precipitation is of limited vertical and other periodicities found cy spectral analysis extent and the movement of luminous regions is an of the data. apparent effect resulting from the localized field aligned extension of the auroral precipitation.

90 SIMULATION ON A HASSIVEIY PARALLEL CEOHACMTIC IWWCTIO1I tTPICTS E21 C I M 3dWMt>. KiWtlC Obaarratory l.M.A. fiUdhlll. o. Bunwun and L.R.O. Storey curreata flowlag la tb« lemoaphara aaa SIMLM, Stanford University laduca eurrwca la tha eoaductlag Parallel computers Kith large nuaiMrs of proc«»ing lay*** •*• Earca. Tha aatura of Che Induced tl«wnts art toslymd for highly rtpttltiv* sets of earr t dependa on tha ccadacdvlty la tha calculations, such is tho*t for ttcii partlcl« and Mi(ltbouraood of tha obatrraeloa polat. Lateral grid point In • PUSM sisuUtion. W* dtscribt a Hacoaclaaldaa la tha conducting layera will produce siMlation for NASA's MPP (Sassivtly Parallel laoar*— varlttloaa la tha vartlcal coapoaaac of Che Processor), Mtiich consists of 16384 proctssing geoaataeclc field. Tha affact la lUuaeratad by tha elajMitts, each with local maory. conntctsd In a behaviour of tha Z variation* recorded to tha tMo-dlwnstonal atsh, and operating in locksttp. riclaity of Baraaaua. A battar understanding of Tht mdtl Is fully electromagnetic and relativlstlc, Induction aooaallaa la Important for various and eaploy? 2k diaensions (two spatial and three («caagnatlc application*. velocity). The sipping of particle and field data and corresponding choice of algorithm depend on both hardware architecture and the problwi in hand, and new algorithms have been developed accordingly. TlRing results show that under optiMl conditions the MPP competes with conventional supercomputers.

ASTROPHYSICS AND ASTROFISIKA EN ASTRONOMY STERREKUNOE

13 CM VERY LONC BASELINE INTERFER- F1 SDPERHOVAE W OMETRIC OBSERVATIONS OF THE SUPER- H.V. F«««t. SAAO . HOVA SN 1987A. A. Cuba.:1", at al. Our currant understanding of suparaova tiplosions will 'Hartebees"hoek Radio Aatronoay Observatory ba outlinad. Tha iaportanca of thata avants in astrophysics and co«nology will ba strassad. Sooe coaoants During tha period Fab 28 to Mar 2 1987 inter- on tha 1987 suparnova in tha Large Hagallanic Cloud feroaetric obaarvatlona at 13 ca wavelength will ba aada as a background to papara in saction F. were carried out of the supernova SN 1987A in chs Large Megellanlc Cloud using tha long btaallna between the Hartebecsthoak Radio Aatronoay Obaarvatory (Johannesburg) and DSS42 , a radio telescope at Tldblnbllla, Australia. Tha ala of tha experiment waa the determination of tha angular siza of the supernova shall during tha early stages of expansion. Prallaloary result* ara reported. PRESENTATION AND DISCUSSION OF DATA OBTAINED FOR THE SUPERNOVA 1987a AT THE SOUTH AFRICAN ASTRONOMICAL OBSERVATORY DWARF NOVAE, NOVAE, BUT NOT SUPER- R.M. CATCHPOLE SAAO M NOVAE Brian Warner, Department of Astronomy, The brightest supernovc observed in 300 years occurred Umutpaity of Cave Town on February 23 1937 in the Large Magellanic Cloud. A review of some of the research on cataclysmic The South African Astronomical Observatory, ideally variable stars being undertaken at the Univer- placed to observe this event, has obtained excellent sity of Cape Town. photometric and spectrosc.opic data coverage. These data, obtained by many members of staff, will be presented and discussed. THE AGING OF OLD DEGENERATES : ASTERO- The supernova is of type II but is atypical in that F5 after the initial decline in brightness over the first SEISH0L06Y OF WHITE DWARF STARS 5 days the supernova started to brighten exceeding its D. O'Danoqhue. Department of Astronomy initial luminosity within 30 days. University of Cape Town The use of pulsations as seismic probes of the structure of white dwarf stars is reviewed and a description of work in this area being carried out at the "niversity of Cape Town given.

91 IKrUCATIOHS OF»»» A TeV TRIPLE PEAK FROM P$ftt9Ot>Mr P6 NOtfRn.DIAL PULSAIIOH MODE F10 0* Jaqar.O.C., Raubenhahner,6.C., Nerth.A.R., 0* C A Bngalbrecht jager, H.I. and van Urk.C. Departaent of Physic*. University of South Africa Rapid stellar rotation and ii.j concoadtant distortion PU/CSIR Cosmic Ray Research Unit, Potchefstroom of th* spherical gtoaatry of a star My have a University ataeurable effect on th« shapes of the radial velocity curve and th<> light curve. An investigation of this effect ic discussed and implications for pulsation Vary high energy I-ray (VHE) observations of •ode identification are considered. PSR1509-S8 with the Potchafftroom Carankov telescope produced positive results which indicate that the light curve hat a tripla p«ak with phase conservation for at least eievan days, whilst the I-ray output was steady from night to night. Tha significance of tha third OBSERVATIONS OF SHORT PERIOD Be STABS IN harmonic alone ia 6*10 . A naw tast was developed to F7 THE YOUNG GALACTIC CLUSTER HGC3T66 identify this pulsar at a final confidence level of 99.92%. Tha VHE luminosity of this pulsar is 3«HT* erg s"1 at an energy threshold Ej>2 TaV. This luminosity is in accordance with calculations from existing outar gap T-ray production models.

WITHDRAWN

THE EXPECTED TaV GAMMA-RAY FLUX F11 FROM ISOLATED PULSARS., O.C. da Jager, H.I. da Jager and B.C. Raubanhaimar.

PU/CSIR Cosmic Ray Research Unit, Potchefstroom University

SOME QUESTIONS ABOUT THE W HYDRODYNAMICS OF ACCRSTION DISKS Evaluating existing models for isolated pulsars, we Chris Koen, University of Bophuthatswana. found that both tha polar cap and outer gap models can produce TeV gamma-ray emission, but from different Two alternatives to the standard -model populations of pulsars. The outer gap modal explains of disk accretion, namely semi-radial and the radiation from all five known TeV gamma-ray pressure driven accretion, are discussed. A pulsars successfully and identifies a number of candi- number of questions regarding the possibility date sources. and nature of turbulence and turbulent stresses in disks are raised.

PROPERTIES OF AL^VEM WAVE DRIVEN STELLAR FS WINDS

U.K. Dougherty and J.F. McKenzie A SEARCH FOR SOURCES OF UL7 ^ Department of Mathematics and F12 HIGH ENERGY GAMMA-RAYS WITH THE Applied Mathematics, POTCHEFSTROOM EXTENSIVE AIR University of Natal, Durban. SHOWER ARRAY.

The equations of conservation of mass, momentum and D.J.Van Oar Walt, B.C.Raubenheimer, 0.0.De Jager, energy in a one-fluid theory vhich describe the A.R.North, C.Van Urk and E.J.De Villiers. steady, spherically synnetric outflow of a plasma from a gravitating point mass, Ms, art generalized to PU/CSIR Cosmic Ray Research Unit. Potchefstroom include the effects of Alfven waves propagating University radially outward. The critical point requirements which ensure a snooth subsonic - supersonic flow together with the Bernoulli - fom oi Che energy Results are presented which confirm that Vela X-1 is equation are used to determine tha mass flux and a PcV gamma-ray emitter. As in the case of Cyg X-3 ultimate speed of the wind. The results for various this effect was only found for showers with large age values of adiabatic index, r and wave pressure are parameters. The light curve may indicate that PeV discussed. In particular, it is shown that Alfven gamma-rays are emitted by a particle beam interacting waves can have a dramatic effect on the properties of with the limb of tha companion star. the wind.

92 OH MASSES IN OBJECTS SHOWISC 10 MICRON FURTHER RESULTS FROM THE RHODES j.3 GHz F15 ABSORPTION SURVEY. "" F13 M J Caylard . H E Dolltry , P A Whltslock S. * Hartebeesthoek Radio Astrouoay Obsirvatory University + South African Astronomical Observatory During March and Apri1 1986 we observed an area of The infra-rtd spectra of OH/IR stars, which posses* the southern sky, S hrs to 12 hrs dense, cool, oxygen-rich dust shells, often exhibit M -24s to -63s Dec, at 2.3 GHz using the a strong absorption feature attributed to silicates, mrtrteesthoek radio telescope. This paper at a wavelength of 10 microns. Ten southern infra-red reports on a number of interesting features visible sources showing such a feature were selected froa the in the data. IRAS Atlas of Low Resolution Spcctr*. They were observti at 18 ca wavelength using the Hartebeesthoek antenna. The characteristic double-peaked OH maser emission at 1612 MHz was detected in eight of the ten. None showed detectable main line emission at 1665 or 1657 MHz.

F14 OH MASERS IN SODTHERN IRAS SOURCES

M E Dollery •. fH J Gaylard P A Whitelock •ad ft J Cohen •Hartebeesthoek Radio Astronomy Observatory •South African Astronomical Observatory fjoarell Bank, UK

A set of UU southern IRAS sources were •elected as being possible OH/IR stars on the bads of their infrared colours. Ten of these were already known OH/IR stars. Of the 34 unknown sources about one third showed 1612 MHs OH maser emission with the characteristic double-peaked spectrum. Some of them also showed 166S and 1667 MHz OH user emission. JHKL photometry has been done on most of the sources and the infrared spectra of the maser and non-maser sources are compared. The low resolution spectra of the sources are also compared, where available.

EDUCATION OPLEIDING

HUMITURE OR DISCOMFORT INDEX, D.I. G2 M.D. Barker. Physics Dept. University of THE TASK OF THE UNIVERSITY G1 Natal, Durban. During the months December to March, the high air temp- W. de Haas - University of the North, Qwaqva Branch erature and high humidity conditions along the Natal With the independence of the Qwaqwa Branch of the coast result in discomfort for humans and animals. University of the North just around the corner, it Oiinatoiugical records for the period January to March 1987 will be presented, illustrating the unusually seems an opportunity to reflect upon the task of a high occurrence of days and nights of extreme discom- university arl to attempt an answer to the question: fort during these months. The physiological effects what is a university? of conditions of high Discomfort Index will be discussed.

93 GS CONCEPTUAL PROBLEMS IX SIMPLE PC CIRCUIT*. th WtarUnafcS HILL COMPUTERS REPLACE PHYSICS H. Stanton University of the Mittatersrand G3 PROFESSORS? An In-depth study has bc«n Mde of the responses 6 E Oberew, Rhodes University offered by students to two questions on series and parallel resistors In 1986 exMinations at the Uni- Computer-assisted instruction (CA1) is being used to versity of the Witwatersrand. The students concerned * limited extent by several Physics Departments in CUM mainly from academically disedvantaged back- South Africa. In this paper, SOM of the questions grounds. frequently asked about CAI by persons new to this area of Physics Education will be addressed, for It Is clear that a number of misconceptions concerning example ."can computers really teach Physics and if so electric current and PO are very prevalent and persis- what do they do best?" A brief review of some of the tent; these will be described and discussed. The programs available will be presented together with an study also attempts to show the timilarttii* and indication of where the future emphasis Bight lit. diffcvnot* that exist between the Alternative conceptual frameworks exhibited by these students tn4 comparative studies made In Israel and the USA.

THE SIMPLE ELECTMC CIRCUIT AS AW ENEKCY SIMPLE ELECTSICM. CIRCUITS G6 SYSTEM: SOME CONCEPTUAL DimCULTIES G4 A PRACTICAL TUTORIAL WHICH CONFRONT STUDENTS IB SIMPLE CIRCUIT THEORY U.S. AlIle and J.E. King University of Cape Town Z JIYA: UNIVERSITY OP FORT HARE First year students often experience problems Conceptions of students about tl» electric circuit as in trying to reconcile the symbolic an energy systesi 4T« established and discus tad. Than representation of electrical circuits with the inappropriata conceptions ara justified in tana of practical realisations thereof. The result of th« atomistic approach to reaaonln| about natural this is that many baste circuit laws are not phanoaana, which accepts that a physical problaat is really understood In practice and curious understood, at least in principle, If it ts explained misconceptions arise. In the case of Physics in aechanical tenac. An argument ia put forward students on our Academic Support Programme against accepting that an energy system may be satis- Science Foundation Year the problem Is more factorily understood without using the approach to acute owIng to genera11y dIsadvantaged energy genarallv used in thers»dvna*ics and quantum backgrounds. A simple laboratory practical on theory. electrical circuits was developed with the aim The difficulties with conceptualization in tens of of addressing the problems described. Basic the frjaevork of eaf, potential, potential!energy) concepts such as res I si tors In series and In difference are highlighted and the influence of noe»n parallel are covered. clature on the understanding of the theory is analysed. Certain guidelines towards resolution of these problem* ara proposed.

APPLIED AND TOEGEPASTE- EN INDUSTRIAL PHYSICS H NYWERHEIDSFISIKA

CHARACTERISATION OF THE WAC NEUTRON H2 THERAPY g HI O.T.L. Jones*, H. Yudelev* end W.L.J. Hendrikse* \ Strtdcat. A H Lauacbnar •National Accelerator Centre •Faure Hospital Atoo««Q«riUROrpora«l« vao SA apk Dla tocaU bavolklat oaxvaaa. 'a srotar doala loasaaraada atrallng wmi The neutron therapy facility at the National ndM»sl|srodiikta aa imf alia «ait«r aroaoa taaaa*. ItdH ta '• adalfaa vac me radluadraaada ucarult aatanaa. jUnoival dla frakalooala Accelerator Centre has been operational since February radltiakoaairacrislaa la utuurllka iioad aal< ' laa| la, la dlt ill 1987. A baas» of 66 MeV protons is used to produce radloloilea nalaacbaar on. !laaallka aitlvltalc* aaea waou Ui ' lu>od>rda H/s3. ladon la 'a b«»«««H«« taa an ay ±185° rotation. Neutron fields fro* 5 ct > J d to radlolojUM •Ifat «otd Wpaai daur a; »ol|»toduktt. Ola aatlag van radoe roduata. 30 c« * 30 c" are defined by a rotatable continuously Da*r baatua 'a varakfldaoftald vao aaattagalata vtr radoa aa ay variable "book-end" collimator. A manually activated ra|raa oat dla oct«l«k«Llm >u Mtlaw aa paaalam moving floor has been constructed to permit full radoo«acca(t>ltk> loslult. Hlardla casiuia It oorxlkul oa rotation of the gantry. Preliminary measurements of radoakooaaat?aalaa al&aaaahvla io«*l «a 1ft dla aaiaavlat ca aaaaal. the beam characteristics hsve been wade. A full description of the Facility will be given and S detailed analysis of the neutron bees properties will be presented. HEUTMM ACTIVAT1OH OF LA«CE SAWLES U8IHC H7 A OWE HUXICHAH CALironwiuti T51 souicE M. lycoudi **& J.I-W.tfaccanon H3 Witi-CSH School and Kaitarch Cantr* for Nuclaar Sci«nc«», Univariicy of th« Uicvatarirand, Johannaaburc> S. Africa. *. a al«tttaaatrall*| w< niaietkd »|r laaaaralfla qi ***Trf.i.i««aUalt tttallaetataaattatio* (UnU. Me nKHlfiwr* A n«w oachod for analysing oras and ainaralf ia iotro- J* £T» »MtlllM«H »aa aadltaa atatakta Ml aalu katualart ti ducad uaing iiotopt-tourca nautron accivacioiuNautront **"* anaatl«ta< iwtri. M* *rlt ilpa* •»•)!•* Mi tJt takan and (atjau-raya ara highly panacracing radiationa and tha aachod ia uaad ee analyta taaplas in bulk. This ovarcoaat _• banal t "•» «taaaaattattakaala»t It 'a Mafia »aa rawalJIaaaa inhoaoganaity and saapling preblaaa and iaprovaa tha aan- ZH^m .an -a laaaJt-aO taalltialt aaawt. •araklJlaaaa •itivUy of eha aathod. laotop* aourea nautron activation faftacadlM la* tana «aa akaaaala at daalaaalfataitait ia aaa aat .a* aarakaaiaaa vlr 41a gakaaa aacwara gadaaa. Oltalaaa)ik la haa baan vidaly appliad to avail aaaplaadaa* than 50 g) [jajattla ratal uta tackri vac ta«radtf*ad eat aarakatet caaultaia and thia, togathar with tha low intanaity of tha aourca* haa providad inadaquata aanaicivity. Containing tha larga nautron fluxaa available with an intanta Cf-2S2 nautron tourca and a aaopla aiza of tha ordar of a tbouaand eiaaa tha sita practieabla for raactor irradiation, tha graat aanaitivitiaa characteriatic of raactor nautron activation analysis ara approached. The aethod ii non-destruct- ive but it doea require a detailed study of the effects H4 of aeutren abd gaaaa-ray absorption. a I lulKl*! * TtvlW, CIH laar*. G Da Lacaf Initial results comparing this aethod and conventional reactor activation will be presented ud discussed in skialdlis •' aaciaar >SMC raaccota ia aa iaaattaat aaaact af cba the context of thil aooroach.

*t ti, laartctt ' Miclaaf Sociaty Staadataa Caaaictaa 4.1.1. taaat t< ctlltasrttora fton tha lattmtioaal aclaatlftc •It. aalTa tba atokUaa tialat Uffaraac eoaauutlaaat tacaai«uat aad ,ru«4actlaa data kaaaa. Tka ratalta tktalaad ia tall "»T aca coaparad lITcaaclytlaaa CM U «raaa aa tka Uiamcj af tka cnta-aactloa teta Zta aaad aad caaa»tatlaaal tacbkl«uaa. laaattaat itaat paraaatart caa REPORT ON PROMPT GAMMA NEUTXDS JT-. M avalaHad la tana af accuracy aad acaaiaj »t caaaatat kacdmre naviraaaata. Ika tatulu «1U alae aa coaaawa «ltk aiparlantal data H8 ACTIVATION ANALYSIS AT SAFAU-1 if tatf aaceaa avallaUa. ... * . na anMaat da*cj akatoa daaa ratat aad tka cattaapaadlas aaataj aatctta at oartowa -. dlataacaiat tka eota r'--1 — In-bcaa proatpt gaauu analysis utlllctag thenal- aautroo capture foraa a part of neutron b«aa utilization at the SAFARI-1 reactor. Progreaa will jlMO VAX 'N TtLClOMtTKIt H5 SSMT1WC VAN»f -II 5AMMA1KO be reported and dlacueaed. Reference will b* aade to eleaental differentiation aa a function of [ Cr..ff an J a Vantar, AIK van SA specific gravity In carboniferous eedlaeotary 'a Studia batraffanda dia ultstraling van Co«ptonalaktrona uit 'a fotonba-atraalda 7at*rakjf« >a fadoan. *n Kobalt-SO-»untbron dian aa bron van deposits froa three locallty-apeciflc atrata. The Itt osiiaua dikta van dia akrf t«t opai(t* van di« occurrence of coapound-deptndent variation In .laktroauitatraling it «kss«ria«nta*l ta tooratlaa bapaal. y.rakllland. diktaa van *n yatarakjf it ia dia aktpariaant •leaeatal aenaltlvity In aaall aaaplea will be takrulk. an di* oatisua dikta it bapaal dtur di* aantal cl.ilrona nt uit dia akyf vrrlaata) "ord, ta lat. substantiated. Dia iaeraticaa to«rakanlng b*hala di* nabootainc van dia proaaa aat 'n Horn. Carlo-aetod*.

THE SMALL ANGLE NEUTRON SCATTERIWC FACILITY AT PELISDABA DIE GEBRlTK VAK OITOR£GRESSIE»E METOPES »Y DIE USt VA*» '.< SAVORS 1-SCSKERSREAKTOR C B franklvn. AEC H9 It has become increasingly recognized chat neutron J N Conradi« *n f van Nickcrk. AEK van SA. scattering and especially small angle neutron scattering PJ# a>nBliai* v»n n»ut.ronrui» by ti«rnr>*litorc OB b»si«ac r*aktorhin«ii««« par«actcr» t» b»p»«1, it r»eds 'n bekende (SANS) is * powerful and in some cases unique cool in tcrrcin van r*»htorf.aikt. "n Rftdvl.lt onl»ngie ont**tklt«ling ia OB outor#^r#«*i*?™ t*on• ta? t#bruik v t r di * b#r*k*ftiB# van aaterials science studies. A review of the capabilities outoMorr*lasi«t «n ipektra. Oi* b*>»i«a* t«ori« v*n outor«ar*>«t««>e actod** Sftl bcaprttfc of the SANS facility at Pelindaba, in che basic and •ord, asook vo^rlop.ge resultat* van di* locpasunl nivrvan op applied research field, will be given. b*ak*kbarw nvutronruiidata.

95 RADIOISOTOOPPROOUK- H14 PIXB ANALYSIS OP.HINntAL MATTfB JN SIEPROGHAH TE FAURE TU. J0J.^_y_W!!g H10 Al Pillar, HJ Annegarn. D Fayra* & JCA 0»viaa* S.3. Hllla Wits-CSIR Sohonland Raaaaroh Centra for Naelonaie""Veranellaraentrua Nuclaar 3oianc«a, Univeralty of Witwatararand, and 'National Centra for Occupational Health, •n Ooralg Ml gsgee word van die vordering wet geaaek Dapartaant of National Haalth and Population la Mt die beplanda aanvanklike radioisotoopprodukaie- Developaent, Johannaaburg. pcogrtM by did NVS a* oopaektoralklotronfaailiteit ta The NCOH, aa a aatter of routine, receivea the Faura. Baplartde an andar aoontlika to«ko«atlga heart and lunga froa all daceeaed, ainara. ultbraiding tot hlerdie prograa aal ook kortlika Saaplea of tissue fro* each autopay, oeapreek word. "1000 aia>, are preaerved in wax for archival purpoaea. The NCOH now haa aeveral thouaand auch aaaples. Aa part of a propoaed api- deaiological survey of duat-induced lung diseaaea, a rapid, inatruaental technique ia required to aeaaure the aineral content of 123 PRODUKSIE VAN I BY DIE NVS - EERSTE these aaaplea. Particle Induced X-ray Eaisaion H11 ERVARINGS (PIXE) haa been Investigated aa a auitable method. Methoda of thin aection preparation F.H. Nortier*. G.F. Steyn*, S.O. Hills* en have been evaluated. Suitable irradiation W.I. Rautenbaeh* conditions have been developed, including the *Naaionale Versnellersentrun irradiation of samples in a He ataoaphere. •Universiteit van Stellenbosch Preliainary results show that PIXE ia auitable for thia application. 123I ia een van die eerate radiolsotope vir aediese toepasaings wat by die NVS, Faure se isotoopprodukaie- raailiteit geproduseer gaan word. Mat die beaklkbaar- heid van 66 MeV protonbundels vanaf die oopaektorsiklotron, is voorlopige U3I-produksielopiea by lae A VERSATILE UHV APPARATUS FOR SURFACE bundelatroae gedoen. Die aerate ervaringa met die PHYSICS AMD CHEMISTRY. aanvanklike produksieproaea word beapreek. T.E.Parry*. R.G.Copp«rtbvi»it«+, P.M.Logg«nb«rgr, W.S.Brooks*, J.P.F.ScUschop*. * Schonland Research Centre for Nuclear Sciences, + Deportment of Cheaiscry, University of the Uitvaterarand, Johannesburg. South Africa. 52 PRODOKSIE VAN Fe PIT Mn HET 66 MeV Surface physics and cheaiitry experiaenta are performed H12 PROTONE at the Schonliod Research Centre on a modified conaercial UHV system containing the following G.F. Steyn. F.M. Nortier, S.J. Milla facilities: XPS, icanning Auger, LEED, Ar* sputtering, Nasionale Veranelleraentrue MBE, pure gas admisiion and quadrupola analysis. Connection Co two accelerators via differentially Opwekkingakraaaes is geaeet aet die foelieatapel- S2 punped baaaliaaa enables RBS or implantation to be aetode oa dla Fe-opbrenga sowel aa die opbrengate carried out *t 1O~" abar. Saaplea can be transported van die gelyktydig-geproduaeerde kontaainante ta into UHV without breaking vacuum, if desired via a bapaal. Hlerdia infornaale kan gebruik word OM die high-pretiurc reaction chamber operating to IS bar. geakikata produksieparaMtera te verfcry. Ander Once ia UHV they are transferred to a universal aani- aapekta van Fe-produkaia sal ook beaproak word. pulator where they can be heated to 1200*C or cooled to U>2 teapcratura before or during analysis. Exaaplaa of the uae of this unique apparatus are presented in subsequent papers.

AEROSOL ADVENTURES -__RBC8NT RBSULTS FROM PI IB ANALYSES OP II4 C THE REDUCTION AMD SUBSEQUENT CARBURIZATION AIRBORNB PARTICULATBS.* II IW OF AS INDUSTRIAL CO-HYDROGENAIION CATALYST: HJ Annecarn, A Zuchchiatti• and JPF Sellschop AM XPS AND AES STUDY. Wita-CStR Schonland Research Centre for P.M.Loggenbera*. R.G.Copperthwtice*. J.P.F.Sellschop* Nuclear Sciences, University of Witwatersrand, * Oept of Chemistry, University of the Witwatersrand. Johannesburg and *Isr.ituto Sazionale di * Schonland Research Centre, University of the 'Jitwaters- Fisici Sue 1 eare, Cenova, Italy. rand, Johannesburg, South Africa. A number of environaental and industrial hygiene related studies of airborne particles The reduction of an industrial CO-hydrogenation catalyst are in progress at the SCRNS. The coaaon theme at 400*C changes the surface composition drastically. linking these projects is the use of Particle As che differenc structural and chemical promoters play Induced X-ray Emission for saaple analysis. a vital role during synthesis, eha surface composition Results will be reported froa studies in is important for an active CO-hydrogenation catalyst. underground gold nines, where ioie unexpected The build up of surtace-carbon during carburization with elemental components were encountered, in the carbon monoxide sheds some light on the active phases for vicinity of surface gold mining and of coal- ^O-hydrogenation. We have found evidence which strongly fired power stations. The well matched suggests chat carbon is deposited on potassium rich protocol of tine-sequence saapling, PIXE sites. These carbon species are removed by H^O creac- analysis and statistical interpretations will aent at 320*C enriching potassium ac che surface. be emphasised.

96 A STUOY Or ftC FOKHATIOH Of 2IRCOWIUM DIB VEKSKVNSEL VAN RESSPAHNING EH DIE SUICIDE ON SILICON (100) SUBSTRATES HI 7 H20 METING DAARVAH MET BEBULP VAN X-STKAAL* U.S. Brook* , I. Kusttelan A.C.K. Lutch , T.E. D«rvy Dinrmnsie R.G. Copp«rthv«itt * Chemistry Department, University of the W B du Pro i en G Nisuwoudt Witwatersrand Departeaont Materiaalwetanskap, AEK van SA> Bpk ** Schonland Research Centre, University of the Witwtterarand Met die geveldige tegnologiese voorultgang van die af» + NEERt, CSIR "•lope dekades, hat dlt noodsaaklik geword on betrou* bare kwantltatiewe metings van resspannings in metaal* Zirconium Silicide contacts have been produced on komponente te kan doen. Waar hoe-graadse tegnologie Silicon (100) surfaces by deposition of Zr metal and ter sprake is en komponente aan uitcrste bedryfstot- subsequent annealing in vacuum. The lilicidation stande onderwerp word, kan dlt ultcrs riskant wee* om process was monitored, in situ, by Rutherford Back- die moontllk* teenwoordlgheid van resspannings te ig» scattering and X-Ray Photoclectron Spectroscopy. The norcer. Indien resspannings van h spesiflckc aard en current/voltage characteristics of the annealed con- grootte beheerd gctnduseer kan word, kan dit egter ook tacts w«r* determined. cot voordeel in 'n komponent aangewend word. Die aard en oorsprong van resspannings, die invloed daarvan op materiaalclenskappc en die beskikbare oeet> tegnleke sal bespreek word. Hierna word die beginsels RAPID COMPUTER-CONTROLLED CAPACITANCE waarop die X-straaldiffraksiemeetcegniek berus, behan* H18 TRANSIENT CHARACTERIZATION OF DEEP-LEVEL del en die voordele van die tegniek uitgelig. H-CMaguire*. A.Marshall*. J.P.F.SeXlschop* * Trent Polytechnic, Nottingham, United Kingdom. * Texas Instruments Ltd., United Kingdom. DIE METING VAN RESSPANNINGS IN METAAL* * Schonland Research Centre, University of the Witwaters- KOMPONENTE MET BEHULP VAN X-STRAALDIFFRAK' rand, Johannesburg, South Africa. SIE A computer-basad deep-level capacitance transient spectrometer is described which was designed and constructed G Nieuwoudt en W B du Preez as a result of the inadequacy of present commercially Departement Materiaalwetenskap, AEK van SA Bpk available deep-level transient spectroaetcrs. Deep-level activation energies and trap concentrations arc here Die sin1 ijMnetoda word hoofsaaklik aangewend vir die me* obtained in a single-temperature scan. Unlike conventiont ting van makro-resspannings m.b.v. ta X-straaldiffrakto- al systems, which "contour" predetermined emission rates meter. X-straaldiffraksie is tans ook een van die by viewing a rate window, giving only one point per level;, enigste eksperimentele tegnieke wat aangewend kan word thermal emission rates are here directly determined.This vir die meting van mikrovervormings in metale. retains more information and reduces the redundancy of conventional methods by obtaining all information neces- Na ~n kort vcrduideliking van die meettegniek, sal fakto- sary to construct an Arrhenlus plot in a single-temper- re soos die monstergrootte wat hanteer kan word en die ature ramp. The method requires fewer coaputer calcul- diepte van resspanningneting onder die oppervlak van "n ations compared with systems using Fast Fourier Analysis, metaalkooponent, bespreek word. and displays improved signal-to-noise ratios. Die eksperimentele gemete spanningstoestand in ioonpla« teerde TIN-deklagies, asook die invloed van voorkeur* oriintasie op hicrdie tipe resspanningmetings, sal be< spreek word.

AANWENDINC VAN TITAANNITRIED (TIN) -DEKLA- H19 GIES DEOR IPONPLATERIHG EM DIE INVLOEP VAN PROSESVERANDERLIKES OP DIE EIENSKAPPE VAN

DIE Df AGIES WEAR MECHANISMS MODIFICATION ISPUCEP BY H22 ION IMPLANTATION IN UC-Co. D Pietersen. I A Kotztf en P H de Lange Oepartenent Materiaalwetenskap, AEK van 5A Bpk Y. Cassuto, J.P.F.SeUschop Wits-CSIR Schonland Research Centre, Universitv of the TiN-deiclagi.es word in die nywerheid veral op mas?ir.eer» Uitvatersrand, Johannesburg, South Africa. gereedskap qebruik. Dlt verskaf ft baie harde, slyt.asie> Scratching and rubbing tests were carried jut on S* werende en chemies stabiele lagie, wat die leeftyd van implanted and non-implanted HC-6Z Co samples. The die gereedskap aansienlik verleng. scratching tests were carried out bv applying a 100 e load to a diamond microindenter. These revealed chat TiN-deklagies is op sagte- en ho*spoedstaal aangebring ior. implantation inhibits the extrusion of cobalt, deur "n ioonp later ing stegniek wat gebruik maak van hol« which is the first step in the abrasive wear process of katode-ontlading in "n scikstof-argon ataosfeer. Met UC-Co. die oog op die optioering van die lagies se eienskappe is verskeie eienskappe van die lagies as Vt funksie van The rubbing cescs were carried out by rubbinz a brass stikscofdeeldruk, substraattesiperatuur en negatiewe ball on th« surface of the sample under controlled voorspanning op die substraat gemeet. Die resultata conditions. By means of scanning electron microscopy van hicrdie ondersoek sal bespreek word en daar sal it was established that less brass adhered to the aangetoon word wat die optimum eienskappe is wat nage* implanted surface than to the non-implanted one. word.

97 ?TT«CT OP VAKYIHC ««CTT CTIOOIt OM W H26 H23 Towamm or •ic» inuuwrn ITCTL I I Icktditr, rvtut Mat, Prttsrlt tuganla frotopappaa. J HleuwNljer and w • du Preec Ftr tttt iHttn It ••• |Htrill* tallt*** tktl te sttlsli* tfct Materials Science Department, «K«(M Ltd kttt ctlltcttt I* i ulir atttr ktattr, MI kis la aaiitlit tkt Maarata • t» HWI UrkcliMt MM m* Milslia ta*a-»t»»attr hwttwn (and oftan costly) component failure My In kilt tratt'tr »» krittlns Im Ut ittMMt tMiftrr t«»ar. ew a«ar, tlMlt calcalitlwf tkM tktt ft tkt IM kcit traatftr ratt Mny Instances be avoided by th« appropriate use of atr MM craa at « lltt Plata Kite ctlltttw, tkik Ik lk»lkkifi- fracture Mchanlca analyiwa. The application of frac- cMt< liitrisMt tk«*» that iktratwikMlkt iftttt* iMlck ture aachtnlcs In engineering design of critical coapo- M«r«tt M tkl IIH ^iMiflk •• CMITKtlM (t«t I* • (IM IM*>< nant* for fractura control and fatlgua Ufa prediction in* aklck »ir» r§rr IM flmrttM) cMtlttMtlf mAfmim* klak la vail aatabllahad. Flana-straln (Ktc) fracture tough* • Itirtti t*»t»t •«•(••• - k» *H«t U • in. naaa tasting uaually antftlle tha uaa of thick enough Ir ipplrl"! Ik* I»l»r-».«ir««|t rtrUHMil cilc*la* It tk* tlM- specluans to yield representative reaulte. aovever, itrt •<«>tit« 4tr tkt kttt 4tll«trM kr i (kl«r ctll«tw, M different tasting techniques, tuch aa J-lntagral Mic) l*rl 4cfMM*ct t< tkt and crack growth raalatanca curve* (R-curvas) are ra» U«r«tt t« UttlatlM. H O1IM tkt Itttar is « stMtr tkit quired for tasting of thin coaponents, or whera plana laclalti it lit prlMfy CIHHHI Ikt c«l*f lrra

DEVELOPMENT OF HIGHLY EFP1CIEMT. LOW ELECTRON PROBE MICRO-ANALYSIS (EPHA) Of H27 THERMARMAL INSULATIONS FOR USE IN H24 tON IN GALVANIZED COATINGS PRODUCED 100-400*C RANGE ON LOW SILiCOH STEELS EHze Potaieter, P R Clayton. I Sigalas and R J Gusnw Rational Institute for Materials Research, CSIR A H Kirkbride. A Wells - Nation*} Institute for Effective thermal mnagenent of temperature- Materials Research - CSIR sensitive systems or equipment Is highly Important, and t'.«e thermel Insulations employed should have the Hot-dip galvanizing of certain low silicon content following characteristics: possess very low total steels (semi-killed steels) is known to result In thermal conductivities (a few nW/n.K) with small excessively thick and brittle corrosion resistant temperature dependences, be easily fabricated from cheap coatings (termed the Sandelin effect). and re«v'n,w available materials, be Inert and stable for A series of galvanized layers produced on a range extended periods. of binary Fe-SI alloys were examined using electron Various materials combinations are suggested which probe «icro~ana1ysis. Studies have shown the Sandelin nay satisfy the above requirements, showing how their effect to be associated with the absence of the specifications are derived from the necessity of 6i Fe-Zn intermetallic phase. The analytical sethod minimizing the Joint contributions of solid-phase, developed &nd the results obtained will be presented gas-phase and radiative thermal conductivities. and discussed. Our guarded hot-plate apparatus capable of measuring the performance of Insulations at different gas pressures Is described, together with results obtained for some thermal Insulators which were designed 1n accordance with the relevant physical criteria. PASSIVE »iweLc-»>Ae» SOCAW W>TM HSATITO H25 T 1 lcka««lar mi l C »«• Haifa, (aft a« Uatvertlt? al Prataria C.A.R.S. TEMPSRATU RUNWIN6 Itvtrtl Kwikara kavt racntlr iktm, k« aaaaaraaatti aa« ataaU- H28 tiaat *t-» tkaraal ktatlitt a< »M flaa". AccardUf ta Haitaaa'a D.Ball*,H.S.T.Driver*.R.J.Hutcheon*. G.W.Robertson*, [ItIS] "•*•» a talar kat aatar tr«tt* .. liat kaaa ra-*nf!aatratf ttr + f T la> Ut», it it aiicft flaplar ta inttali •** caataiaa ttrit, laaa K.F.Bennett , R.K. Dutkiewicz . R.N«tes , and A.Yates tiptnilirt caapanant* than th> carrtttanaini ki|k Han tritaa*. Lt« Brtiaurt (ariai-ianiiictar lnen-rtclrcgl»tli>|) tyttaas tllar Ivrtkar * Department of Physics, University of Cape Town Htntiitti hifkar ateraia tMleitucy tn« «iapiilla< |UaklR|. * Energy Research Institute, University of Cape Town

Far a %\»%\t-ntt <*ltr wtir lisstar It la latartaat ta aptiaally The onset of "knock" in a spark-ignition engine Units ithat it, m • aaanar that aili aaiiaiia eallactaf haat) aatcki the usable compression ratio and hence the thermodynamic Hi iK-ctantanaaua Haxrttt to iniaUtiam tut efficiency. The synthetic fuels in use in South (kl tally callacter Moa (I.a. Itilv praluctua a» hat aattrl Africa differ chemically from the natural petroleum tt faily caatuaptian • ta altki* iktvt JOJ. fuels for which the engines were designed. Fundamental studies of the chmical kineties of autoignition of T« titffy li>, tkt llurili autt an i |)'t« 4tr ftllam ana •» tka the engines in synthetically-fuelled engines are aptiatl Mo* curvat. Tha cnaica e< Maacurva it ta •• tuch at ta •atlKy ill. Sanaltlvtty afialytn mtlcataa titat nalthar nttt at need. tatttlltt ta Hl|h accuracy ta tttna in aJHciaacv sail ikavi a ctfl'tntlenal puapat lyttta. Coherent Anti-Stokes Raman Scattering (CARS) is the most advanced optical technique for temperature measure- (a fatcriit t tiaplt furitit tyttia tha( tchltytt tkttt ikjtc- ments in an engine. The experiments being set up at tl>«t 4*4 proaiaaa ta tiaultanatutly lacraaaa parf;raaact taf ttcrtasa inatallat coit. UCT are described. The results will be used as input data for chemical kinetic modelling of engine knock.