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

In order to determine absolute scintillation yields due to alpha particles in high pressure rare gases, the number of scintillation photons N_p was measured by using a VUV sensitive photodiode (PD) with a MgF₂ window and a Cs-Te photocathode with spectral quantum efficiency q_e(λ) measured as a function of wavelength λ. The number of photoelectrons from the photocathode N_pe was measured absolutely by using charge-sensitive preamplifier calibrated in numbers of electrons. A collection efficiency F_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_p was determined from N_p=N_pe/(Q_eF_ce), where Q_e is effective quantum efficiency calculated from q_e(λ) and a relative intensity I(λ) of scintillation in rare gases at wavelength λ. 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 λ. 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 1.0×10⁵ Pa to 1.0×10⁶ Pa. The measurements were carried out in gaseous argon, krypton and xenon. In xenon of 1.0×10⁵ Pa, N_p was measured to be 1.6×10⁵.