Cloud Chamber Study of Cosmic-Ray Particles

Citation

Kuo, I-Cheng (1941) Cloud Chamber Study of Cosmic-Ray Particles. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/A9QD-RA96. https://resolver.caltech.edu/CaltechTHESIS:12052012-163755571

Abstract

In order to study the energy loss of cosmic-ray electrons in light materials where inelastic atomic collisions account for the main part of the loss, 10,000 cloud chamber photographs were taken in which a thin-walled copper counter or a combination of one or two counters with a 1/4 inch carbon plate was placed across the chamber as an absorber. The counter or counters was used at the same time to control the expansion. Only electrons of energy from 10 to 60 Mev are suitable for this purpose. These occur infrequently and only 36 particles in the case of a single counter absorber and 33 in the case of a counter-carbon absorber were found suitable for accurate measurement. The observed average values of energy loss in Mev/cm are compared with the theoretical average value. The result shows that in the energy range considered the theoretical formula for energy loss of electrons (no heavy tracks were included) by direct collisions are in approximate agreement with observation. The importance of an experimental test of these formulae lies in the fact that the mass estimates of the mesotron so far made have been based on the validity of these formulae.

Several heavily ionized tracks were discussed by considering their ionization and range relations. One of these was found to be probably a mesotron of negative charge. Two cases of abnormal energy loss which can not be accounted for by ionization and radiation alone were also discussed.

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