Study of the Multiple Scattering of Fast Charged Particles in a Gas and Its Role in the Interpretation of Cloud-Chamber Tracks

Abstract

The curvature of the track of a fast charged particle in a magnetic cloud chamber varies along the track because of the multiple scattering of the particle by the gas in the chamber. By measurement of the mean and the fluctuations of the curvature, it is possible (1) to determine the multiple scattering in a gas of a particle of known mass, and (2) to estimate, on the basis of a verified multiple scattering law, the mass and energy of a particle. The statistical uncertainty inherent in such estimates is discussed. The multiple scattering of 132 beta-particles, ranging in energy from 50 to 1700 kev, with a total path length of 1800 cm in one atmosphere of argon, was measured and compared with the predictions of the theories of Bothe, Williams, Goudsmit and Saunderson, Molière, and Snyder and Scott. The theories of Molière, and Snyder and Scott, as well as that of Williams, if an available parameter is suitably adjusted, agree fairly well with our results.