Measurement of the Specific Ionization of Fast Mesotrons with an Ionization Chamber and a Linear Amplifier

The ionization of single cosmic-ray particles capable of penetrating 12 cm of lead has been measured with an ionization chamber and a linear amplifier. Measurements made at 14.7 atmospheres with argon indicate an average specific ionization of 71 ion pairs per cm at N.T.P. The results apply on the whole to mesotrons with an energy greater than 2×${10}^8$ ev. The specific ionization of maximum frequency of occurrence is approximately 67 ion pairs per cm in argon. The average value for the ionization obtained with the ionization chamber at 14.7 atmospheres appears to be about 10 percent less than the total ionization. The average value obtained corresponds to the value 48 ion pairs per cm in air at N.T.P. as measured by a method that includes only collisions involving ${10}^4$ ev or less. This result is in good agreement with the cloud-chamber results of Corson and Brode and of Hazen.