http://arxiv.org/abs/2003.14248
We measure the liquid argon scintillation response to electronic recoils in the energy range of $2.82$ to $1274.6~{\rm keV}$. The single-phase detector with a large optical coverage used in this measurement yields $12.6 \pm 0.3 ~ (11.1 \pm 0.3)~{\rm photoelectron/keV}$ for $661.7~{\rm keV}$ $\gamma$-ray events based on a photomultiplier tube single photoelectron response modeling with a Gaussian plus an additional exponential terms (with only Gaussian term). It is exposed to a variety of calibration sources such as $^{137}{\rm Cs}$ and $^{241}{\rm Am}$ $\gamma$-ray emitters, and $^{252}{\rm Cf}$ fast neutron emitter that induces quasimonoenergetic $\gamma$-rays through a $(n, n’\gamma)$ reaction with $^{19}{\rm F}$ in polytetrafluoroethylene. In addition, the high light yield enables identification of the $2.82~{\rm keV}$ peak of $^{37}{\rm Ar}$, a cosmogenic isotope in atmospheric argon. The scintillation yield and energy resolution of the detector are obtained by the full-absorption peaks. We find up to approximately $25\%$ shift in the scintillation efficiency across the energy range and less than $3\%$ of the energy resolution for the $661.7~{\rm keV}$ line. The energy dependent scintillation quenching can be attributed by the electron-ion recombination process, and is discussed by an analogy to the dependence of liquid xenon. The Thomas-Imel Box model with its constant parameter $\varsigma=0.07 ^{+0.03} _{-0.02}$ is found to explain the results below $200~{\rm keV}$.
M. M.Kimura, K. K.Aoyama, M. M.Tanaka, et. al.
Wed, 1 Apr 20
11/83
Comments: 10 pages, 13 figures, 2 tables