Production and transport of conduction electrons in a liquid argon ionization chamber

Free electrons produced by α- and β-particles in a liquid argon ionization chamber have been detected. For minimum ionizing particles the collected charge saturates at a field strength of E < approximately 15 kV/cm.(95+-4)% of the produced electrons were collected. For strongly ionizing α-particles no saturation was observed up to a field strength of 40 kV/cm, where (25 +- 3)% of the produced electrons were detected. The influence of oxygen and nitrogen, solved in the liquid argon, on the charge collection was studied. A nonlinear relationship between the mean free path length for absorption and the applied electric field indicates the existence of hot electrons in liquid argon. The recombination effect in the ionization column produced by α-particles is enhanced by oxygen and nitrogen impurities in liquid argon. (Auth.)