Experimental Townsend Ionization Coefficients for Isopentane

Abstract

Townsend α and γ values have been measured over the range 60≤E/p₀≤3000 for isopentane using the dc method of measuring the ionization current. The experimental apparatus and procedure are described. It is shown that Townsend's law α/p₀=A exp (—Bp₀/E) is obeyed within 80≤E/p₀≤500. Positive ion action at the cathode sets in at E/p₀≥500. The results agree with previous breakdown measurements. It was found possible to follow the current growth due to ionization of the gas over a multiplication range exceeding eight orders of magnitude. The influence of space‐charge distortion within single avalanches and that due to neighboring ones has been examined. No space‐charge reduction of the avalanche multiplication was observed until e^αd≥10⁷.