Amplification of the Ionisation Produced by Radioactive Sources

Abstract

VARIOUS devices have been described for employing thermionic valves to measure small current. In most of these, the necessary sensitivity is only obtained by using very sensitive galvanometers in the anode circuit of the amplifying valve, which magnify all irregularities due to faulty filament and anode batteries, as well as zero creep effects due to leakage or accumulation of wall charges. Compensation for anode battery fluctuations can be eliminated by the valve bridge method, but such an arrangement, whilst considerably complicating the circuits, only partly removes the causes of unsteadiness, so that a comparatively low limit of sensitivity is attainable, under steady conditions.