Ionization Yield of Protons in Nitrogen and Argon

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Abstract
The total ionization yield of protons in nitrogen and argon gases was studied for energies in the range of a few to 250 kev. A large cylindrical ionization chamber was used for this study. The chamber was alternately operated as a proportional counter and an ionization chamber to measure the rate with which the protons entered the chamber and the total ionization produced by them, respectively. The results indicated a straight-line relation between the ionization yield and proton energy for energies above 75 kev in nitrogen and above 25 kev in argon. Straight-line plots of the data had slopes corresponding to 36.6±0.7 ev per ion pair for nitrogen and 26.5±0.5 ev per ion pair for argon. For argon the straight-line plot intercepted the energy axis at 1.4±0.9 kev, indicating a slight ionization defect.