Absolute number of scintillation photons emitted by alpha particles in rare gases

Abstract

In order to determine absolute scintillation yields due to alpha particles in high pressure rare gases, the number of scintillation photons N/sub p/ was measured by using a VUV sensitive photodiode (PD) with a MgF/sub 2/ window and a Cs-Te photocathode with spectral quantum efficiency q/sub e/(/spl lambda/) measured as a function of wavelength /spl lambda/. The number of photoelectrons from the photocathode N/sub pe/ was measured absolutely by using charge-sensitive preamplifier calibrated in numbers of electrons. A collection efficiency F/sub ce/ at the photocathode for scintillation photons can be determined from solid angles subtended by the photocathode at a scintillation point under the condition that there is no photon reflected at surrounding wall. Then, N/sub p/ was determined from N/sub p/=N/sub pe//(Q/sub e/F/sub ce/), where Q/sub e/ is effective quantum efficiency calculated from q/sub e/(/spl lambda/) and a relative intensity I(/spl lambda/) of scintillation in rare gases at wavelength /spl lambda/. Although luminescence spectrums from rare gases emitted by radiation have been measured by many researchers, these spectrums were scarcely corrected by an efficiency of apparatus (e.g. efficiency of monochromator and scintillation detector) for /spl lambda/. In order to exactly determine the luminescence spectrums, these were also measured on our own terms. And, since it was reported that scintillation intensity from rare gases change with a pressure of rare gases, this experiments was carried out in a pressure range from 1.0/spl times/10/sup 5/ Pa to 1.0/spl times/10/sup 6/ Pa. The measurements were carried out in gaseous argon, krypton and xenon. In xenon of 1.0/spl times/10/sup 5/ Pa, N/sub p/ was measured to be 1.6/spl times/10/sup 5/.