Thermalization times of positrons in molecular gases

Abstract

The time that a particle takes to reach thermal equilibrium in gas is a gross measure of the efficiency with which such particle can exchange its kinetic energy with the medium. The time taken for positrons to reach thermal equilibrium in H2, CO, CO2, N2O, CH4, and SF6 molecular gases were estimated using the gas mixture technique developed by D.A.L. Paul and C.Y. Leung. Times below 100 ps Amagat was found for several species. Gases other than molecular oxygen were found to have prospective use as efficient coolers for rapid-cycle positron traps and accumulators.