A high background rejection method in a proportional counter using field-adjusting electrodes as guard cathodes

A single anode single large cell counter, with veto-counters around it, is described. To get uniform response of the pulse height and the energy resolution, the counter has field-adjusting electrodes at the end walls of the anode wire, and these electrodes are also used to reject the background events which are caused by cosmic rays passing through near the end walls of the anode.A rocket flight experiment showed that the combination of rise time discrimination and anti-coincidence method reduced the cosmic ray induced background events to a level of 1.2×10^?4 counts s^?1 cm^?2 keV^?1 in the energy range of 2–40 keV, which represented an overall background reduction of 98% in this energy range.