Durham E-Theses A new technique for the investigation of high energy cosmic rays Kisdnasamy, S. How to cite: Kisdnasamy, S. (1958) A new technique for the investigation of high energy cosmic rays, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/9180/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk A NE17 TECHNIQUE FOR mE INVir.TIGATION OP HIGH ENERGY COHMIC RATS A thesis Presented "by S. KisdmsanQT For the Degree of Doctor of Ehllosopl^ at The University of Durham. December, 1958. 3 1 JAN 1959 A mi{ TECHNIQUE FOR THE EWESTIGATION OF HIGH ENERGY COSMIC RAYS. Eh.D Thesis sutimitted by S. Kisdnasaniy December, 1958. ABSTRACT A technique has been developed for the precise location of cosmic rays in a magnetic spectrograph. The technique uses the neon flash tube first introduced by Conversi and his co-workers. In this technique ionising particles give rise to visible flashes in a glass tube containing neon. The thesis describes a systematic study of the flash tubes over a wide range of paxameter. Tubes have been constructed having the properties required for operation in a spectrograph and a description is given of the operation of a prototype spectrograph. The accuracy of track location has been found to be at least as great as that in conven• tional cloud chambers. The theoretical aspect of the operation of the tubes is discussed and a new mechanism is postulated for tubes filled at high press;ares. The design and construction of part of the large spectrograph is described. C0RTENT3 Page PEEFACE 1 CHAPTER I latroduetion 2 CHAPTER n Gosmie Ray Speotrograuha 1. Previous Instruments 5 2. 'Bie Haaohester Spectrograph 6 CHAPTER III Bie Design of a High Flux Speptrograph of Resolttt^Qfi. 1* General Design Considerations 2. The Experiments of Conversi et al on the Neon Plash Tube 11 3* The Experiments of Barsanti et al 12 CHAPra IV The Construction of Flash Tubey apd the AsBooiated Ecwipment. 1. The Filling System and Filling Procedure 14 2* The Experimental Arrangement 15 3. The Electronic Circuits 15 CHAPTER V The Characteristics of Low Pressure Flash Tubes 1* The Characteristics under Investigation 18 2. Experiments with I^ex Glass Tubes 19 3* Reproduoibili-t^ of Ttibe Characteristics 20 Bsige 4. The Variation of Efficierwy vdth residual air pressure 21 5. The Variation of Efficiency rdth Eressore of Feon 21 6. The Variation of Efficiency vdth pressfure of Argon 22 7 (a) The Variation of Efficienpy vdth Time Delay 25 (b) Theoretical Analysis 26 8. The Variation of Efficiency vdth Rise Time 31 9. The Variation of Efficiency with Pulse Lenfith 32 10. Af ter^flashing 53 11. General Bemarko and Conclusions 54 CHAPTIE VI The Develoment of the Prototype Speotrograiah 1. The Escpertoental Ararangement and the Results 37 2. Conclusions 41 OHAFTIR VII The Caiaracteristics of Hlfijh Pressure Tubes 1. The Description of the App*aratu3 45 9. The Variation of Efficiency vdth A-plied Field for Various Eressures 44 S. The Variation of Efficiency vi th Time Delay 45 4. The Variation of Ef f iciencgr ^ th the Wall Thickness of the Tube 46 5. The Effect of •tha.O.earing Field on the Variation of Efficiency with Time Delay 46 Bsige 6, Life-time of the Tubes 47 7, Discussion and Conclusions 48 GHAPTIH VIH Theoretical Aspects of the Meohanism of the Flash Tubes. 1. The Elisic Dischaz^e Mechanisms 50 2. The application of the Spark Theoiy to Flash Tubes (a) Low Pressure Tubes 55 (b) High Pressure Tubes 56 5. A Possible Mechanisn for the Operation of High iRressure Tubes 57 4. The Ihteipretation of the Results 61 OHAPTIR IX The Design and Construction of the, Darham Spep-faro^Jira-ph, 1. The Design of the Tube Assmblies 65 2. The Construotion and Aligment of the Tube Assemblies 68 5. General Remarlcs and Future Work 70 ACKNOTJIiEDGEMERTS 71 APPEND jl? 72 REPEREtKJES 74 -1- piaEPACE This thesis describee the development of a new technique for the detection of ionising particles and its use in an instrument for the investigation of high energy cosmic rays. The develpiment and some prellminaxy measurements on the character• istics of the neon flash tubes were made by the author at Manchester. Thie work was continued in Durham by the author and his colleagues under the puperTision of Dr. A. VI. Wolfendale. In viba.t follows earphasis is placed on those aspects of the work which -were the particular oonoena of the author. Acknowledgement is made in the text to any specific contribution made by his colleagues. Scane of the work described has been published by the author and his colleagues, (Gardener et al 1957, Ashton et al 1968). SECTION -2* CHAPTER I The existence of cosnic radiation has been knovm since the early experdments of Hess (1912, 15) and Kblhorster (1914-19). Frcm more recent measuarements made at high altitudes ^dth nuclear amilsions and counter telescopes it has been established that the primary coanic rays entering the earth's atmosphere consist mainly of protons and nuclei of the heavier elements. The priatnaiy nuclei are absorbed by inelastic collisionG with air nuclei. The absorption length for nuoleons Is '^120 g/cm^ and is consider- ^ably shorter for oc particles and heavier nuclei; in consequence most of the primary cosmic rays interact in the irpper layers of the atmosj^iere (above '^50,OCX) ft.). Hiese interactions give rise to the secondary radia• tion consisting of nucleons and nuclear fragments, charged and neut3?al 7t - mesons, a»i heavy mesons and hyperons. The secondary particles produce further mesons and nuoleons by collisions with air nuclei. The positive —8 and negative 7t- mesons have a mean-life of (2.56 ± .05) x 10 sec and either decay in flight into mesons and neutrinos or are absorbed by nuclei in inelastic collicions oacaevAiSLt similar to those of the primary nucleoni. The relative probabilities of these procecses can be evaluated as follows. If Z is the mean life of the meson at rest its apparent mean life when moving with a velocity yg o is The average distance traversed by the meson before it disintegrates is thus where p is the mcmentum of the meson and m Is the rest mses. For a 7l- meson of rest mass 159. 65 + «o6 M.e.v. having an energy of G.e.v. the distance Zd is -^50 ,p^ metres. The probabili-tjr of interaction of the ^ meson cpn be derived under certain slfflfplifyins assumptions. It ban be assxjmed that the ^-mesons are produced at a unique pressure leVel of 100 g/cm2 below the top of the atmos• phere corresponding to 15 kilcmetres above sea level. The interaction length^as dlstijict firom the absorption lengthy has been found to be -^60 g/cm^ at low energies and it is assumed that this result is applicable to all energies^ The nean fVee path before interaction is then —SOOO metres. Sius^since Zd '^50 p^ metres, decay and interaction are equally probable for pig ~20 G. e.v/o. This means that most of the /T-mesons with momentun appreciably below 20 G. e.v/c and a small fraction of those above 20 G.e.v/c decay into yu-^sons. Although the nuclear interaction of the ^i-meson is weak and most of the fast ytt mesons produced by TJ^decay reach sea level MMI the fact that the JA^" meson is unstable and decays Into an electron and two neutrinos results in a loss of low enei^gy JU.- mesons. The neutral TT- mesoas have a short mean life of ~10~-^^ sec and decay into two photons which in turn materialise in the presence of nuclei to foim electron pairs and ultimately electron photon cascades. The heavy mesons and liyperons are produced in relatively small numbers and are unstable, having numerous decay schmes. «4- Of particular relevance to the present discussion is the nature of the cosmic radiation at, or near^sea level. It Is custcmaiy to divide this radiation into two ccctponents, the hard and soft cocgjonents, so named because of their abilUgr or otitierwise to penetrate moderate thicknesses (10 can) of lead. The hard ccniponent consists predoninantly of^- mesons. At low energies ytt- mesons ccme chiefly frqn the 7?"-^ decay process. High energy mesons arise from the decay of 7t~- mesons an^. also frcm the kyt^, ^5 perhaps other heavy mesons. The soft caaponent consists mainly of electrons and photons and ccmes fran the decay of K mesons, the decay of yCx, - mesons and ejection of electrons from oxygen and nitrogen molecules by the energetic Jlju- mesons. The hard component at sea level, has been studied in detail by "aany wprkersi iCn particular the mcmentm spectrm and the ratio of positive to negative ytt- mesons have been extensively investigated. Such investigations are useful in that they throw ligjit on the basic interactions of the primar• ies and v&en ccmbined \7ith underground measurements give infoimation on the energy loss of fast jX^ mesons.