PAIR AND TRIPLET PRODUCTION BY 90 Mev BREMSSTRAHLUNG IN ILFORD G-5 EMULSION
The pair, triplet, and multiplet creation processes produced by 90-Mev bremsstrahlung in Ilford G-5 nuclear emulsion are studied. The photon beam is hardened by introducing 496.43 g/cm/sup 2/ of carbon in the beam path in order to reduce the intensity of compton and photo-electrons and thus increase the signal/ noise ratio for convenient identification and measurement of pair-electron tracks. The nuclear emulsions, of 400 mu thickness, are processed by the temperature- development method, and a Leitz ortholux microscope with 100X objective and 16X eyepiece is used to study the events. The energy determination is accomplished by the multiple scattering technique for high energy electrons and by the range- energy method for low energy ones. The theoretical pair cross sections for G-5 nuclear emulsion are computed from cross section values, taking into account the weighted contributions from the various elements constituting the emulsion. This information is used to calculate the incident bremsstrahlung spectrum from the experimental distribution-in-energy of 5739 electron pairs. This bremsstrahlung spectrum is used to calculate the triplet cross sections from the triplet data, The relative total cross sections for triplet production and pair + triplet production processes are found to be in agreement with theories. The energy partition between the positrons and electrons at various photon energies is compared with the Bethe-Heitler theory for pairs and with differential cross section functions for triplets, In general, the experimental distributions are more peaked for equipartition and have fewer electrons for extremely unequal partition of energy than predicted by the theory. The pair/ triplet ratios are calculated in 8-Mev intervals from 2 to 90 Mev. These ratios are more or less constant within the statistical accuracy. The overall pair/triplet ratio is 11.3 plus or minus 0.2. In all, 106 quartets are identified and their energy distribution is studied, The number of quartets is too small to admit any conclusive results concerning the total cross sections of quartet production, The pair/quartet ratio is found to be 206, which points to the conclusion that the quartet production cannot be considered to be a double pair-creation process. In addition to triplets and quartets, ten quintets and one sextet are also observed. In triplets, as well as in other higher order processes, there are always two high energy tracks, and the rest of the tracks are low energy ones. (Dissertation Abstr., 22: No. 7, 1982.)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-000875
- OSTI ID:
- 4791821
- Resource Relation:
- Other Information: Thesis. Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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