GB1061835A - Apparatus for the approximate determination of the levels of contamination of clothing or other articles by counting of alpha and beta particles - Google Patents

Abstract

1,061,835. Determining radiation levels photo-electrically. EUROPEAN ATOMIC ENERGY COMMUNITY (EURATOM). April 10, 1964 [April 11, 1963], No. 14895/64. Heading G1A. [Also In Division H1] Apparatus for the determination of levels of contamination of articles e. g. clothing, by α- and #-particles, comprises a proportional particle detector of the gas flow type, the output pulses, amplified by pre-amplifier PA, from which detector are applied to two amplifier-discriminator channels for the subsequent measurement of the activities of the α and #-particles by counters E α and E#respectively. The apparatus is designed to eliminate pulses in an amplitude range in which both α- and #-particle pulses occur, by use of an anti-coincidence device. The α- and #-pulses can be divided up into three amplitude zones, zone 1, between certain amplitude levels d 0 and d 2 having mainly # pulses and negligible α, zone II between levels d 1 and d 2 (where d 1 > d 2 ) having both α and #pulses and zone III, above level d 1 , having mainly α pulses and negligible p. By eliminating zone II, α-particle pulses can be distinguished from #-particle pulses. Pulses pass from pre-amplifier PA and into two amplifier discriminator channels A 1 , D 1 , and A 0 , D 0 . An α or # pulse in zone II can pass through D 0 but not D 1 , although it can pass through D 2 to cancel the simultaneous pulse coming from the discriminator D 0 , in the anti-coincidence gate AC. The transistorized gate P in the channel prevents overloading of the channel A 0 , D 0 due to very large pulses caused by α-particles. It is found that there are certain counting losses due to the suppression of zone II by the anti-coincidence device, but these are unimportant in view of the self-absorption of the clothing tested. The amplifier A 0 has a high gain with respect to that A 1 since the level d 0 is much smaller than levels d 2 and d 1 . The construction of the detector is described (see Division H1).