The energy loss of cosmic ray particles in metal plates

Abstract

Measurements have been made of the energy loss of cosmic ray particles in metal plates, making use of a counter controlled cloud chamber in a magnetic field (Blackett 1936). A metal plate was placed across the centre of the chamber and the energy loss of a ray was deduced from the difference of the curvature of a track above and below the plate. Energy loss measurements by this method have been carried out by Anderson and Neddermeyer (1936) up to an energy of about 4 x 10 8 e-volts and recently by Crussard and Leprince-Ringuet (1937) up to an energy of 1·2 x 10 9 e-volts. The curvature measurements were made mainly by means of the optical null method recently described (Blackett 1937 a ) and this proved invaluable. It would have been hard to obtain so high an accuracy by the usual method of measuring coordinates. The curvature corrections to be applied to the measured curvatures were obtained by measurements on tracks in zero magnetic field (Blackett and Brode 1936). Two separate distortion curves were required, one for the top and one for the bottom of the chamber.