Laser induced ionisation in proportional counters seeded with low ionisation potential vapours

Abstract

Four vapours with low ionisation potentials: triethylamine (TEA), N,N-dimethylaniline (DMA), N,N-diethylaniline (DEA) and tetrakis (dimethylamino) ethylene (TMAEO) have been studied to produce controlled amounts of laser induced ionisation in proportional counters. DMA, DEA, and TMAE produce large amounts of ionisation at the nitrogen lase wavelength (337 nm) but TMAE has proved difficult to control. At 337 nm TEA does not ionise significantly but initial tests show that it also becomes suitable as a seeding agent at shorter wavelengths.