Luminescence Response and Quenching Models for Heavy Ions of 0.5 keV to 1 GeV/n in Liquid Argon and Xenon

Abstract

Biexcitonic collision kinetics with prescribed diffusion in the ion track core have been applied for scintillation response due to heavy ions in liquid argon. The quenching factors q = EL/E, where E is the ion energy and EL is the energy expended for luminescence, for 33.5 MeV/n 18O and 31.9 MeV/n 36Ar ions in liquid Ar at zero field are found to be 0.73 and 0.46, compared with measured values of 0.59 and 0.46, respectively. The quenching model is also applied for 80–200 keV Pb recoils in α-decay, background candidates in direct dark matter searches, in liquid argon. Values obtained are ~0.09. A particular feature of Birks’ law has been found and exploited in evaluating the electronic quenching factor qel in liquid Xe. The total quenching factors qT for 0.5–20 keV Xe recoils needed for weakly interacting massive particle (WIMP) searches are estimated to be ~0.12–0.14, and those for Pb recoils of 103 and 169 keV are 0.08 and 0.09, respectively. In the calculation, the nuclear quenching factor qnc = Eη/E, where Eη is the energy available for the electronic excitation, is obtained by Lindhard theory and a semi-empirical theory by Ling and Knipp. The electronic linear energy transfer plays a key role.

Snowmass2021 Cosmic Frontier White Paper: Calibrations and backgrounds for dark matter direct detection

“…[316] found that recoiling 210 Pb nuclei in LAr are quenched more strongly than predicted by SRIM. Similar challenges are reported more broadly in [317] for LAr and LXe, which identifies a need for more quenching factor measurements of low-energy heavy ions, particular for Pb. Improving models of backgrounds involving such slow nuclei, such as backgrounds arising from (possibly attenuated) α-decays on detector surfaces or in particulates, requires improving these low-energy stopping power calculations and additional measurements of these ions' scintillation and slowing-down behaviors.…”

The liquid-argon scintillation pulseshape in DEAP-3600

“…A number of experimental studies have been performed to measure the scintillation yield due to neutron-induced NRs in LAr in the low-energy region [9][10][11][12]. The scintillation quenching at low energies cannot completely be explained by the Lindhard et al theory [13] and various models have been proposed to understand the light yield for low-energy NRs in LAr [11,12,14,15]. In contrast to NRs, few measurements are available for studying scintillation light due to α-particles in LAr at high energies using a 210 Po source [16][17][18].…”

Attenuated Alpha Backgrounds in the DEAP-3600 Dark Matter Search Experiment

“…As the incoming particle passes through, a number of free excitons are created in the target material. Exciton-exciton collisions can occur [55], in the form of:…”

“…This results in a lost exciton without scintillation light. These excitons can also undergo Penning ionization, where the exciton interacts with a ground state argon nucleus, but creates an ionized atom and an emitted electron [55]. Again, energy lost to this electron is not converted to scintillation, and is another form of quenching.…”

“…The recommended new model for alpha quenching combines some of the improvements found in this appendix. For the luminescent quenching, this means using the Hitachi version of Birk's Law [55] with the fitted parameters kB = 1.70×10 −4 g/MeV/cm 2 and A = 0.86. For nuclear quenching, this means using the SRIM calculated values from Figure A.1 instead of the analytical model.…”