A new technique for rejection of uv background in soft X-ray proportional counters

Proportional counters used for observations of celestial X-ray sources in the energy range 0.1-1 keV often employ thin plastic films as entrance radiation windows. Ultraviolet background in these counters causes considerable difficulty in obtaining low sensitivities. A new technique for the rejection of ultraviolet background by the use of a wire grid placed a few mm below the window and maintained at a suitable negative potential, is presented. Results of experiments conducted on a laboratory model of a counter employing this technique are presented.