Studies on liquid argon S1 and S2 properties for low mass WIMP search experiments

Abstract

Liquid argon is known as an excellent target material for WIMP dark matter direct search experiment. Relatively small atomic mass (A=40) gives high nuclear recoil energy for WIMP-Ar nuclear scattering, thus it potentially has high sensitivity for low mass WIMP (<10 GeV/c2) . There are two crucial R&D topics for the liquid argon detector to explore such low mass WIMP signal, namely, deep understanding the liquid argon scintillation and ionization process for low energy deposition (<10 keV), and increasing the signal light yield by improving the argon scintillation light collection efficiency. In this paper, we report recent results from Waseda university liquid argon test facility.

Neutral bremsstrahlung and excimer electroluminescence in noble gases and its relevance to two-phase dark matter detectors

“…This is seen when comparing the experimental and theoretical EL yields in Fig. 2 and when comparing the experimental and theoretical photon emission spectra [4,20,24].…”

“…In the most elaborated way, NBrS EL was introduced in [4] applying both theoretical and experimental approach to explain two observations: the photon emission below the Ar excitation threshold and the contribution of the non-VUV spectral component in proportional EL (extending from the UV to NIR). It was further experimentally studied in [6,[20][21][22][23][24].…”

Electroluminescence and Electron Avalanching in Two-Phase Detectors

“…From Figures 4 and 9 one can see that NBrS EL, albeit being significantly weaker than ordinary EL above the Ar excitation threshold, has no threshold in electric field, in contrast to ordinary EL, and thus dominates below the threshold. Accordingly, the NBrS effect can explain two remarkable properties of proportional EL observed in experiment [9,13,19]: that of the photon emission below the Ar excitation threshold and that of the substantial contribution of the non-VUV spectral component above the threshold. ) and ionization ( ) (from [9], with permission from Elsevier).…”

“…Instruments 2020, 4, x FOR PEER REVIEW 9 of 31 Figure 10. Photon emission spectra of proportional EL in Ar in the UV and visible range [19], measured at room temperature in [19] (data points) in comparison with those of the NBrS EL theory [9] (lines), at reduced electric field of 4.6 and 8.3 Td.…”

“…Figure19. Left: gain characteristic of double-THGEM multipliers in a two-phase Ar detector for a THGEM active area of 10 × 10 cm 2 (maximum gain was limited by discharges) compared to that of 2.5 × 2.5 cm 2 (maximum gain was not reached)[72]; a comparison to that of a single-THGEM multiplier (maximum gain was limited by discharges) is also shown.…”