Absolute primary scintillation yield of gaseous xenon under low drift electric fields for 5.9 keV X-rays

Abstract

A standard gas proportional scintillation counter equipped with a photomultiplier tube has been used to measure the primary scintillation yield in Xe at 800 Torr for 5.9 keV x-rays. The value m = 53±8 was measured for the number of primary scintillation photons produced per absorbed 5.9 keV x-ray photon, which gives a value Ws = 111±16 eV for the average energy expended to produce a primary scintillation photon in Xe for this x-ray energy. The experimental method is based on a comparison between the primary and secondary scintillation signals measured with a digital oscilloscope, where the distinction of the small primary signal from the noise is achieved by always triggering the oscilloscope with the secondary scintillation signal, and making a time average over 128 primary/secondary scintillation pulses. No evidence for recombination scintillation was found. A qualitative discussion of Ws in terms of the ratio between excitation and ionization cross sections for electrons in Xe is also presented.