Ionization defect for alpha particles in various gases
The ionization produced by the Li7* and beta-particles from the reaction B10(n, beta)Li7* as they were stopped in argon, argon-nitrogen, and argon-carbon dioxide gas mixtures was measured. A gridded parallel-plate ionization chamber employing electron collection was used. Plutonium alpha particles were used for calibration and the ionization electron pulses were amplified and sorted with an electronic pulse height analyzer. The neutron source was a 300 kev linear positive ion accelerator utilizing the D-D reaction. The neutrons were thermalized by blocks of paraffin stacked around the chamber. The thin boron film was made by evaporating boron enriched to 95 percent with B10 onto an aluminum backing. The gas mixtures were purified by continuous circulation over hot calcium-magnesium alloy.