The Elimination of the End Effects in Counters

Abstract

The operation of cylindrical proportional and Geiger counters near the ends of the wire is examined closely by means of thin sheets of soft homogeneous X‐radiation. It is found that small field‐adjusting tubes, fitted over the usual grounded guard tubes (where these are required) and maintained at the potential appropriate to their diameter, reduce the end effects to negligible proportions. The computed field distribution is thus confirmed experimentally. Both theory and practice show that the concentric field‐adjusting and guard tubes need not be longer than a radius of the counter. The method can be used in designing counters of very short operating length. In practice the technique is simple and it can be applied to the construction of ionization chambers (pulse or steady current type), proportional counters with constant gas gain along the whole wire, and Geiger counters. It insures in each case a precisely defined counting volume.