Gas Gain in Air-mixed Argon-Propane (1%)-based Proportional Counters

For the design of a special gas-flow proportional counter intended for a new on-line measurement method of airborne radon (Rn) concentration, the amplification properties of four gas compositions were investigated in air-mixed Argon-propane (1%)-based proportional counters. These four gas compositions are: Ar-C3H8 (1%); Ar-C3H8 (1%) + 2% air; Ar-C3H8 (1%) + 6% air and Ar-C3H8 (1%) + 10% air. The influence of the electron attachment effect due to oxygen on the saturation and gas amplification characteristics was examined in particular. The semi-microscopic gas gain formula was found to describe accurately the gas gain data obtained in each of the gas mixtures analyzed allowing the determination of the gas constants. The use of air-mixed counting gases in a specially designed gas-flow proportional counter for airborne radon concentration measurements appeared quite viable.