Gamma-Ray Ionization in Several Gases as a Function of Pressure and Collecting Field

Ionization by low intensity $\gamma$-radiation in ${\mathrm{N}}_2$, C${\mathrm{O}}_2$, A and He has been measured with pressures of from 0.98 to 93 atm. of ${\mathrm{N}}_2$, 61 atm. of C${\mathrm{O}}_2$, 25 atm. of A, and 98 atm. of He and with uniform collecting fields from 1.57 to 1065 volts/cm, direct comparison being made with the results of Bowen for air. The marked increase in current with increased collecting gradient and independence of the shape of the current-field curves on intensity of radiation up to the intensity used demands rejection of the wall emission theory of Broxon and adaption of some recombination theory. Junction of Kaye and Laby's results to those of Bowen shows a gradient of 4×${10}^3$ volts/cm as saturation value for air at 10 atm. pressure. A field of only 100 volts/cm is saturation value for argon up to 25 atm., and with this field the current from the inert gases examined is a linear function of the pressure up to 25 atm.