TY - JOUR

T1 - Revealing neutral bremsstrahlung in two-phase argon electroluminescence

AU - Buzulutskov, A.

AU - Shemyakina, E.

AU - Bondar, A.

AU - Dolgov, A.

AU - Frolov, E.

AU - Nosov, V.

AU - Oleynikov, V.

AU - Shekhtman, L.

AU - Sokolov, A.

N1 - Publisher Copyright: © 2018 Elsevier B.V.

PY - 2018/12/1

Y1 - 2018/12/1

N2 - Proportional electroluminescence (EL) in noble gases has long been used in two-phase detectors for dark matter search, to record ionization signals induced by particle scattering in the noble-gas liquid (S2 signals). Until recently, it was believed that proportional electroluminescence was fully due to VUV emission of noble gas excimers produced in atomic collisions with excited atoms, the latter being in turn produced by drifting electrons. In this work we consider an additional mechanism of proportional electroluminescence, namely that of bremsstrahlung of drifting electrons scattered on neutral atoms (so-called neutral bremsstrahlung); it is systemically studied here both theoretically and experimentally. In particular, the absolute EL yield has for the first time been measured in pure gaseous argon in the two-phase mode, using a dedicated two-phase detector with EL gap optically read out by cryogenic PMTs and SiPMs. We show that the neutral bremsstrahlung effect can explain two intriguing observations in EL radiation: that of the substantial contribution of the non-VUV spectral component, extending from the UV to NIR, and that of the photon emission at lower electric fields, below the Ar excitation threshold. Possible applications of neutral bremsstrahlung effect in two-phase dark matter detectors are discussed.

AB - Proportional electroluminescence (EL) in noble gases has long been used in two-phase detectors for dark matter search, to record ionization signals induced by particle scattering in the noble-gas liquid (S2 signals). Until recently, it was believed that proportional electroluminescence was fully due to VUV emission of noble gas excimers produced in atomic collisions with excited atoms, the latter being in turn produced by drifting electrons. In this work we consider an additional mechanism of proportional electroluminescence, namely that of bremsstrahlung of drifting electrons scattered on neutral atoms (so-called neutral bremsstrahlung); it is systemically studied here both theoretically and experimentally. In particular, the absolute EL yield has for the first time been measured in pure gaseous argon in the two-phase mode, using a dedicated two-phase detector with EL gap optically read out by cryogenic PMTs and SiPMs. We show that the neutral bremsstrahlung effect can explain two intriguing observations in EL radiation: that of the substantial contribution of the non-VUV spectral component, extending from the UV to NIR, and that of the photon emission at lower electric fields, below the Ar excitation threshold. Possible applications of neutral bremsstrahlung effect in two-phase dark matter detectors are discussed.

KW - Dark matter detectors

KW - Liquid argon

KW - Neutral bremsstrahlung

KW - Proportional electroluminescence

KW - Two-phase detectors

KW - GASES

KW - SLOW ELECTRONS

KW - DARK-MATTER EXPERIMENT

KW - LIQUID ARGON

KW - ELECTRON BREMSSTRAHLUNG

KW - EMISSION DETECTOR

KW - XENON

KW - ATOMS

KW - MONTE-CARLO-SIMULATION

KW - SPECTRA

UR - http://www.scopus.com/inward/record.url?scp=85049511879&partnerID=8YFLogxK

U2 - 10.1016/j.astropartphys.2018.06.005

DO - 10.1016/j.astropartphys.2018.06.005

M3 - Article

AN - SCOPUS:85049511879

VL - 103

SP - 29

EP - 40

JO - Astroparticle Physics

JF - Astroparticle Physics

SN - 0927-6505

ER -