Abstract

We have measured the energy dependence of the liquid xenon (LXe) scintillation yield of electrons with energies between 2.1 and 120.2 keV, using the Compton coincidence technique. A LXe scintillation detector with a very high light detection efficiency was irradiated with $^{137}\mathrm{Cs}$ $\ensuremath{\gamma}$ rays, and the energy of the Compton-scattered $\ensuremath{\gamma}$ rays was measured with a high-purity germanium detector placed at different scattering angles. The excellent energy resolution of the high-purity germanium detector allows the selection of events with Compton electrons of known energy in the LXe detector. We find that the scintillation yield initially increases as the electron energy decreases from 120 to about 60 keV but then decreases by about 30% from 60 to 2 keV. The scintillation yield was also measured with conversion electrons from the 32.1 and 9.4 keV transitions of the $^{83m}\mathrm{Kr}$ isomer, used as an internal calibration source. We find that the scintillation yield of the 32.1 keV transition is compatible with that obtained from the Compton coincidence measurement. On the other hand, the yield for the 9.4 keV transition is much higher than that measured for a Compton electron of the same energy. We interpret the enhancement in the scintillation yield as due to the enhanced recombination rate in the presence of Xe ions left from the 32.1 keV transition, which precedes the 9.4 keV one by 220 ns, on average.

Highlights

  • The experimental work presented in this paper is part of an ongoing effort to understand the ionization and scintillation response of liquid xenon (LXe) to low energy (

  • Values of Re, which were calculated at 1 keV high-purity germanium (HPGe) energy intervals, were averaged over ranges of electronic recoil energies where Re did not vary appreciably. These results are the first measurements of the scintillation response of LXe to nearly monoenergetic low-energy electrons over a wide range of energies

  • The Compton coincidence technique allows the production of electronic recoils which most closely resemble the background of large LXe dark matter detectors, without the need to deconvolve the response for any atomic shell effects present in the case of the response to low-energy photo-absorbed γ rays

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Summary

Introduction

The experimental work presented in this paper is part of an ongoing effort to understand the ionization and scintillation response of liquid xenon (LXe) to low energy (

Methods
Results
Conclusion

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