Fast component re-emission in Xe-doped liquid argon

Abstract

A: We present the first direct experimental confirmation of the fast component re-emission in liquid argon (LAr) doped with xenon (Xe). This effect was studied at various Xe concentrations up to ∼3000 ppm. The rate constant of energy transfer for the fast component was quantified. It was shown that LAr doped with a high concentration of Xe without TPB has a better PSD efficiency than pure LAr or Xe-doped LAr with TPB. The stability of LAr+Xe mixture was tested for the first time at high Xe concentration for long continuous runtimes. K: Ionization and excitation processes; Noble liquid detectors (scintillation, ionization, double-phase); Particle identification methods; Scintillators, scintillation and light emission processes (solid, gas and liquid scintillators) 1Corresponding author.The most commonly used WLS for LAr is tetraphenyl butadiene (TPB). It is used for coating PMTs, detector walls and other elements of optical systems [10,11]. The main disadvantage of any WLS film is low geometrical efficiency, since the light is re-emitted in 4π solid angle, sensitivity to mechanical stress, long term stability [12], scattering and re-absorption of the re-emitted light inside the WLS layer [11,13] and also dependence of the WLS efficiency on the coating method.An elegant idea is to use volume-distributed WLS, which can provide a higher efficiency of re-emission and better collection of the scintillation light. This improves position reconstruction since the re-emission occurs in the point of interaction.It was shown that gaseous xenon doped in LAr works as a volume-distributed WLS shifting the wave length from 128 nm to around 175 nm [14][15][16]. Currently several groups are studying its wavelength shifting parameters and the properties of the LAr+Xe mixture [17][18][19][20]. As shown previously [21], Xe doped in small concentrations (up to 260 ppm by mass) re-emits only the slow component of LAr scintillation. Thus, at small concentrations it is impossible to use Xe as a single stage WLS and to keep PSD capability of the LAr+Xe mixture at the same time.In previous studies with a broad concentration range (up to 1000 ppm by mass) [19,20], it was shown that Xe-doping slightly improves the light yield and the energy resolution. Also they demonstrated that the PSD capability degrades with decreasing of Xe concentration in LAr. Both experiments [19,20] have shown that at the concentrations of Xe > 300 ppm the PSD capability of the LAr+Xe mixture is higher than that of pure LAr.One experimental study [20] indicated evidence of fast component re-emission at high Xe concentrations. However, the measurement scheme was very complicated, statistics were quite low, and the effect of the re-emission by Xe was obscured by the use of TPB. In our study, we confirm the clear observation of the fast component re-emission in LAr doped at high Xe concentration (∼1100 ppm by mass). We show the dependence of this effect on the increase of Xe concentration and its relation to PSD efficiency. We also present the first experimental measur...

Using $^{22}$Na and $^{83{\rm m}}$Kr to calibrate and study the properties of scintillation in xenon-doped liquid argon

“…5. The waveform distortion is consistent with results in the literatures [17,18,20]. The first hump is caused by the scintillation of argon and the second hump is the consequence of argon excimers transferring to xenon excimers.…”

Wavelength Shifters for Applications in Liquid Argon Detectors

“…This wavelength is significantly more accessible to conventional photosensors than 128 nm. Akimov et al [83] showed that LAr doped with even higher concentrations of Xe, and without TPB, has a better PSD efficiency than pure LAr or Xe-doped LAr with TPB. This implied that the singlet (short-lived) Ar excitation is transferred to Xe as well, and a mechanism assuming an emission of 128 nm photon, subsequently absorbed by Xe, was proposed.…”

Scintillation and optical properties of xenon-doped liquid argon

“…Adding small amounts of xenon to LAr overcomes these limitations. Xenon-doped liquid argon (XeDLAr) features a longer emission wavelength, higher photoelectron yield 𝑌 , shorter effective triplet lifetime 𝜏 3 and longer effective attenuation length 𝜆 att than pure LAr [8,18,[21][22][23]. The increase in photoelectron yield is partly due to the increase in photodetection efficiency with increasing wavelength.…”