A 500 GeV pulse as recorded at the CERN SPS on 20 December. This record peak energy was achieved in a machine development run and is not intended to be regularly used in physics runs. (One reason for this is the heavy penalty in electrical power, as can be seen from the shape of the magnet pulse near 500 GeV where field saturation has set in). The SPS will, however, begin regular operating cycles at 450 GeV in the course of 1979.

During the 17 GeV runs PETRA reached a peak luminosity of 1.2 x 1 030 per cm2 per s at each intersec­ tion. This is about a fifth of the value expected at these low' energies. Although beam currents correspond to the design values, the beam cross- sections are wider than expected due to space charge effects. This is being investigated. In February, more high frequency power was installed to enable the machine to move to higher energies.

CERN PS/SPS run of records The CERN PS and SPS accelerators ended 1 978 with a flourish. In their last run of the year, new records of beam intensity, number of protons accelerated and beam energy were clocked up at the SPS — all of great significance for the physics pro­ gramme at the machine. all experimental areas (North, West with the electricity supply were Crucial to the success was the and ) could be operated cleared. On 20 December, the excellent performance of the PS. The simultaneously. The SPS efficiency 450 GeV cycle was repeated, fol­ hew linac injector, which came into moved to 88% compared to 80% lowed by 475 GeV. action at its full energy of 50 MeV in the previous year. The first attempts at 500 GeV September, reaching its design cur­ A major aim in machine operation were thwarted at 491 GeV due to rent of 150 mA a month later, in 1 979 will be to consolidate relia­ radial displacement of the beam enabled higher intensity beams to be ble running at 2 x 1013 protons per because of increased saturation of accelerated through the PS, so that pulse. This is already a significant the magnets causing a distortion of 1.55 x 1 013 protons per pulse at an step towards the longterm aim of the the closed orbit in the region of the energy of 10 GeV were being sent to 'intensity improvement programme' radial r.f. pick up. A minor change the SPS (compared to the previous which is to reach 3 x 1013. However, in radial beam position brought peak of 1.3 x 1013). Using two pulse things get more difficult as the inten­ 500 GeV and the machine ticked injection, this enabled the peak sity climbs, as colleagues at Fermi- over for an hour accelerating protons intensity accelerated to 400 GeV in lab have learned. to this energy. The SPS thus joins the the SPS to reach 2.1 x 1 013 protons After the physics run, a machine accelerator as the highest per pulse. More importantly, the development period was used to test energy proton synchrotron in the intensity could be sustained at 2 x the energy abilities of the machine. world. 1013. Here the aim is to establish reliable It is not, however, intended to During the six week run, 3 x 1 018 operation at 450 GeV which is operate the machine for physics at protons were delivered to the SPS scheduled to begin in June. The 500 GeV. The magnets run heavily experimental targets. This meant installation of a third 90 MVA into saturation, the power require­ that over the year, the number of transformer makes these energies ment is high (e.g. 7.6 kA magnet protons fed to the experiments more possible. On 1 9 December, 450 GeV currents at 500 GeV compared to than doubled compared to 1 977 and was quickly reached when problems 4.9 kA at 400 GeV) and reliable

CERN Courier, March 1979 13 For the proposed scheme to collide protons and antiprotons in the CERN Intersecting

Storage Rings (ISR)r it will take 24 hours of dedicated time on the 28 GeV Proton Synchrotron to produce just one pulse of circulating antiprotons in the /SR. This motivated Phil Bryant of ISR Division to produce his own interpretation of the control room.

operation of the accelerator could not be guaranteed. To complete the story of recent PS/SPS achievements, in the last run of 1 978 a beam storage experi­ ment was carried out in readiness for the collision of proton-antiproton beams in the SPS which is sched­ uled for 1 981. Beam was sent to the SPS at an energy of 15.8 GeV, above the SPS transition energy which was manoeuvred to below 14 GeV for the test. (The proton- antiproton scheme will avoid the complication of going through tran­ sition energy.) This technique proved feasible and will enable stored beams to be studied more easily. Beam was successfully accelerated and stored in single bunches of 8 x 1010 protons. This intensity would actually meet the design require­ ments for the colliding beams but there will then be other different conditions to be met as well. On 19 February, the eight year '300 GeV programme', authorized the development at CERN of sto­ be accelerated to 270 GeV before by the CERN Council in 1971, came chastic beam cooling techniques, being brought into collision in two formally to an end. It was gratifying, and the launching of the project to underground experimental halls (see within time allocated to machine collide beams of protons and anti- page 1 6). This will provide a collisioitL construction, to have comfortably protons in the SPS (see September energy equivalent to that of a exceeded the design energy and 1978 issue, page 291). 1 55 TeV fixed target accelerator, a intensity and to have already The plan is to produce the antipar- considerable increase over the high­ mounted a thriving physics pro­ ticles as a 3.5 GeV secondary beam est collision energies now available, gramme. from the 28 GeV Proton Synchro­ which are those provided by the tron (PS). Each burst of antiprotons 31 GeV beams in the ISR, equiva­ New role for the ISR will be cooled and stored in the Anti- lent to a fixed targed accelerator of proton Accumulator (AA) ring now 2 TeV. The CERN Intersecting Storage under construction. However even after the new Rings (ISR), usually associated with Continuous accumulation of anti- proton-antiproton scheme is imple­ colliding proton beams, is to take on protons over a period of about mented, the SPS will still function for a new role, providing experimenters 24 hours will yield a dense beam of much of the time in its primary role with colliding beams of protons and 6x1011 antiprotons which will be as a fixed target accelerator. During antiprotons. transferred to the PS for subsequent these periods the AA ring will be There is no fundamental reason acceleration to 26 GeV. This beam available to the ISR and other anti- which limits the ISR to proton oper­ will then be sent to the SPS through proton users. ations. Already some physics has a new transfer line, or to the ISR The ISR will be a particularly effi­ been done using deuterons, and the through a second new line. cient user of antiprotons thanks to its storage of alpha particles has been In the SPS, beams of protons and unrivalled storage capabilities. It will studied. The use of antiprotons in the antiprotons will circulate in opposite be able to stack antiproton pulses ISR has become possible following directions in the same ring and will over a period of several days and

14 CERN Courier, March 1979 Proposed configuration of beamlines for the antiproton project at CERN, which will supply beams of antimatter to the SPS proton synchrotron (through tunnel ll/O) and the Intersecting Storage Rings (ISR) (through tunnel TT6).

then continue running with the Another advantage is that equip­ and elastic scattering should be stored beams for several more ment destined for antiproton experi­ available very quickly. Despite an days. ments at the SPS could first be expected rise in the proton-antipro­ At present, ten-day runs are anti­ tested at the ISR, so that maximum ton cross-section over the ISR cipated, with five pulses of 6 x 1 011 use is made of the limited colliding energy range, the difference be­ antiprotons being stacked over four beam time in the SPS. tween proton-proton and proton- days, followed by a six-day run with It is envisaged that the recently antiproton cross-sections should in stable beams. Data taking will be upgraded Split Field Magnet (SFM) fact decrease, but still remain possible throughout the run except at ISR intersection 4 with its very measurable. for brief interruptions when new large solid angle coverage, and the This data, together with results on pulses of antiprotons are stacked. proposed open axial field magnet elastic scattering and on quantum Using this scheme with a 30 A with the superconducting high lumi­ number exchange reactions, should proton beam at 26 GeV, the maxi­ nosity insertion at intersection re­ provide valuable new information to mum luminosity in a standard ISR gion 8 will play a major part in the consolidate our basic understanding intersection would be 1.3 x 1 029 per ISR antiproton physics programme. of hadron interactions. cm2 per s, and 9.2 x 1029 with the Rather than revealing any totally For rarer phenomena, the different superconducting high luminosity in­ new phenomena, the ISR antiproton quark configurations of proton- sertion applied to both beams. This project is expected to open a fresh proton and proton-antiproton inter­ latter figure is not far off the original door on existing physics. Initial actions could make for useful com­ ISR design luminosity (for proton experiments will in many ways parisons (or contrasts) of data to test beams) of 4 x 1 030 ! Operation will be parallel the first ISR proton-proton newer ideas on inner hadron dynam­ possible at standard ISR energies studies, but will benefit from the ics. This could provide us with valu­ and the necessary changes are being superior ISR instrumentation which able insights before results from made to ensure that all existing has been built up over the years. newer accelerator projects become experimental magnets can be used. Results on total cross-sections available.

CERN Courier, March 1 979 15 Model of the proposed detection system for the CERN/Orsay/Pavia/Saclay experiment at the CERN SPS proton-antiproton collider. The search for the intermediate bosons of weak interactions figures high on the list of priorities, although the apparatus will be well suited to a wide range of investigations.

(Photo CERN 211.11.78)

Second intersection region for SPS proton-antiproton collider

1 978's rich crop of physics results in line with gauge theory predictions for electro-weak interactions has given fresh impetus to the search for the long-awaited intermediate bo­ sons of weak interactions, which are an integral part of these theories. If the predictions continue to be right, the bosons could be discovered at the proton-antiproton collider being prepared for the CERN SPS. For this project (described in the September 1978 issue, page 291), a beam intersection has already been booked for an Aachen / Annecy / CERN / London / Paris/ Riverside / Rome / Rutherford / Saclay / Vienna experiment code- named UA1, and work on the under­ ground experimental area is already identification, using lead scintillator directions, which will be equipped under way. sandwich counters, covers a large with magnetic spectrometers and Now a second intersection is to be solid angle with a compact configu­ segmented arrays of lead-scintillator used and a further experimental area ration. shower counters. will be constructed at straight Good rejection of hadronic back­ The spectrometers are designed section LSS4 to house UA2, an grounds is expected, despite the to be as compact as possible, mini­ experiment by a CERN / Orsay / absence of magnetic field in the mizing the solid angle taken up by Pavia/Saclay collaboration. central region, as a result of the the coils, while providing strong Obviously the search for interme­ combined use of hadron calorime­ bending power. diate bosons figures high on the U A2 ters (to veto charged hadrons) and of The inner vertex detector will give agenda, but as well as looking for the multiwire proportional counters pre­ precision information on the position production and decay of these parti­ ceded by a lead converter (to veto of the interaction vertices, and cles the apparatus will be well suited neutral pions subsequently decaying measure the directions of all charged to the study of large angle inclusive into photon pairs). This hadron rejec­ particles. It will be equipped with particle production and of high trans­ tion is essential at the collider ener­ proportional chambers with cathode verse momentum phenomena. It will gies where much hadronic debris strips, interleaved with drift cham­ also be able to search for signs of will be produced. bers. other new particles and for abnormal One particular aim is to look for The central detector will be made behaviour such as that seen in asymmetries in the production of up of 240 independent cells, each cosmic ray studies (see Septem­ and , such as containing hadronic (iron-scintilla- ber 1 977 issue, page 289). would be produced by parity violat­ tor) and electromagnetic (lead-scin­ The experiment will concentrate ing effects in the decays of the weak tillator) detection components. on the decays of the inter­ bosons. These asymmetries are ex­ In the first phase of collider opera­ mediate bosons, rather than those pected to be large in annular regions tion, before the proposed high lumi­ where muons are produced. Electron around the forward and backward nosities are achieved, it is planned to

16 CERN Courier, March 1 979 have a 30° wedge cut out of the paths of decaying particles can only inside bubble chambers (see Octo­ central detector for installation of a be fixed to within a few millimetres. ber 1 978 edition, page 346). magnetic spectrometer. Electron Thus despite the wealth of statistics A 1976 experiment at Fermilab, identification will still be possible in on neutrino interactions gathered in led by Eric Burhop of University this wedge thanks to a large lead bubble chambers at CERN and College London, exposed an emul­ glass wall. This arrangement will Fermilab, no visible tracks of sion target to a neutrino beam, using permit measurements of inclusive charmed particles have been seen, downstream spark chambers to cross-sections and a study of high suggesting that the charmed particle record the secondary products, and transverse momentum phenomena. lifetime is less than 10-12 s and is found one evegt consistent with the The experiment demands the pre­ outside the range measurable in decay of a charmed particle with a paration and commissioning of a bubble chambers. However bubble lifetime of a few times 1 0-13 s. large inventory of equipment, but the chambers can detect the decay In a second experiment at CERN, collaboration hopes that much of products of charmed particles (see an Ankara/Brussels/CERN/Dub- this can proceed in parallel with the for instance the excellent example lin/University College London/ implementation of the antiproton seen in BEBC and published in our Open University/Pisa/Rome/Turin project itself. In this way results November 1978 issue, page 394, collaboration, including many of the should be available as soon as possi­ and the Brookhaven event on participants in the Fermilab experi­ ble. page 1 1 in this issue). ment, has exposed emulsion stacks To record the tracks of the short­ to the wideband neutrino beam. Fixing the charm lived charmed particles, some other These stacks were placed upstream lifetime means has to be used. If the charm of the BEBC bubble chamber. lifetime is as predicted, then they A wire chamber between the There is now considerable agree­ should be directly observable in emulsion stacks and BEBC corre­ ment among theorists that the life­ emulsion targets. Further down­ lated the emulsion and bubble time of charmed particles is some­ stream detectors facilitate identifi­ chamber reference systems to an thing of the order of 10~13 s. At cation of primary interactions and accuracy of 3 mm in the beam direc­ laboratory energies, this means that pick up decay products, enabling tion and 0.3 mm in the other two a charmed particle can only traverse to pinpoint the region of directions. An additional time coinci­ about a millimetre before it decays. the emulsion where the decay dence system correlated informa­ Nevertheless, it is important to pin occurred. Without this, a complete tion from the wire chamber and the down these elusive decays, and a scan of the whole emulsion target BEBC External Muon Identifier new result from a bubble chamber/ would not be feasible. (EMI). emulsion experiment at CERN pro­ One such experiment uses the So far 1 68 000 bubble chamber vides valuable evidence in favour of CERN Omega detector with emul­ pictures have been scanned for signs present theoretical ideas. sion plates exposed to a photon of events where at least three high Such short tracks are almost beam (see June 1978 issue, energy particles enter the bubble impossible to spot in large bubble page 208). Other collaborations chamber and point back to a chamber photographs where the plan to use emulsion targets actually common vertex in the emulsion

Sketch of the charm decay seen in an emulsion/bubble chamber experiment at CERN. The neutrino beam coming in from the left interacts in the emulsion at point A, producing a shower of particles. One minimum ionizing (dotted) track, corresponding to a high energy particle, decays about a millimetre later at the point B, producing three high energy charged hadrons. These are seen in the BEBC bubble chamber downstream. All the evidence points to a charmed particle decay, and the lifetime of a few times 10~13 s is in line with theoretical predictions.

CERN Courier, March 1 979 17 target. From these pictures, some course was Walter R. Nelson of The programs were run on the 350 charged current neutrino inter­ SLAC, presently at CERN as a visit­ CERN computers and the users, actions in the emulsion have been ing scientist. guided by the authors, were able to identified, and so far 60 have been The calculation of the energy solve specific problems. The experi­ located. This sample contains one deposited by accelerator beams, or ment was very successful. Many of event which shows all the character­ particles from nuclear reactors, in the programs presented at the istics of charm decay. targets or machine components is course are now available in the It includes, amongst other parti­ rather a complicated physical CERN computer files. They cover cles, a negative muon identified by problem. Nor is it trivial to calculate hadronic cascades, electromagnetic the EMI and a positively charged the shielding needed for radiation cascades, reactor shielding, unfold­ particle which, after travelling a protection of an accelerator or reac­ ing methods, gamma spectrum ana­ distance of about one millimetre, tor because of the complex geome­ lysis and detector efficiency and produces three charged hadrons tries of the radiation sources and the response. For further details of these which are seen in BEBC. Many inter­ engineering requirements for the programs, contact G.R. Stevenson pretations in terms of charmed parti­ shielding itself. It takes a broad or W.R. Nelson at CERN. cle decays involving at least one knowledge of the physics of particle neutral particle are possible, but the interactions with matter, of the experimental evidence rules out transport of radiation through differ­ ROME known strange particle decays. The ent materials, of dosimetry, etc. But ECFA LEP Meeting possibility that both this event and these calculations are obviously of On 23, 24 November the LEP Work­ the one seen at Fermilab are not vital importance. ing Group of the European Commit­ genuine is now very remote. Some very sophisticated com­ tee for Future Accelerators (ECFA) Like the decay seen in the Fermi­ puter programs have been written, held its first plenary Meeting in lab experiment, this event also and are widely used, for performing Rome. In the superb Biblioteca Valli- corresponds to a lifetime of a few calculations of that type. They can celliana, an important centre of Ital­ -13 times 10 s, well in line with also be applied to many other differ­ ian culture in the baroque era, about current predictions. Meanwhile the ent problems with possible applica­ two hundred scientists from fifteen search continues to consolidate the tions ranging from medical physics European countries met to discuss still scanty information on charmed to high energy research, from radia­ the project to construct a large elec­ particle decays. tion dosimetry to radiobiology. tron- storage ring, LEP. At Erice, experts discussed with AntoninoZichichi, Chairman of the Calculating from more than forty people of different Working Group, emphasized in his Sicily to CERN scientific interests, the physics in­ closing speech that, besides the herent to their programs, the meth­ steady scientific progress toward The Ettore Majorana Centre for ods employed in the calculations and conceiving a wonderful tool for Scientific Culture, founded and di­ their present potential uses. The physics, the Meeting witnessed a rected by Antonino Zichichi, has programs were compared to each strong commitment from the Italian some seventy schools covering all other and related to different fields of Government to build LEP. branches of Science. The schools application either as single programs In their interventions, the two organize courses on different topics or combinations of programs. most important Italian authorities on which are normally held in Erice, a After eight days of lectures and scientific matters — Senator Mario historical village in Sicily. discussions at Erice, almost all the Pedini (Minister of Public Education) One of the schools is the 'Interna­ participants moved to CERN where, and the Hon. Dario Antoniozzi (Min­ tional School of Radiation Damage thanks to the collaboration of G.R. ister of Scientific Research) — and Protection' directed by A. Rindi Stevenson, A. Herz and the Data stated that the Italian Government of INFN, Frascati. From 25 October Handling Division, a Workshop was follows the LEP project very closely to 2 November, this school organ­ organized. Together with interested and hopes that its realization will not ized its second course on The use of people from CERN, the participants be hindered or delayed by extra- computers in health physics: calcu- saw the programs in action for the scientific matters, as has happened lational techniques in shielding and solution of problems in several fields for other European scientific enter­ dosimetry'. The Director of the of interest. prises in the past. For this reason.

18 CERN Courier, March 1 979