No Arabic abstract
The use of xenon-doped liquid argon is a promising alternative for large pure liquid-argon TPCs. Not only xenon-doped liquid argon enhances the light production, mitigating the possible suppression due to impurities, but also it increases the wavelength of the scintillation light, enlarging the effective Rayleigh scattering length and improving the detection uniformity. ProtoDUNE Dual-Phase is a 300-ton active volume LAr TPC, a prototype for the Deep Underground Neutrino Experiment (DUNE), a dual-site experiment for long-baseline neutrino oscillation studies, neutrino astrophysics and nucleon decay searches. ProtoDUNE Dual-Phase took cosmic muon data at CERN with pure liquid argon and with xenon-doped liquid argon for over a year. The impact of the presence of xenon in the scintillation light and its comparison with the pure liquid argon data will be presented. These results are of interest to any future large LAr TPCs.
Scintillation from noble gases is an important technique in particle physics including neutrino beam experiments, neutrino-less double beta-decay and dark matter searches. In liquid argon, the possibility of enhancing the light yield by the addition of a small quantity of xenon (doping at 10-1000 ppm) has been of particular interest. While the pathway for energy transfer between argon and xenon excimers is well known, the time-dependence of the process has not been fully studied in the context of a physics-based model. In this paper we present a model of the energy transfer process together with a fit to xenon-doped argon data. We have measured the diffusion limited rate constant as a function of xenon dopant. We find that the time dependence of the energy transfer is consistent with diffusion-limited reactions. Additionally, we find that commercially obtained argon can have a small xenon component (4 ppm). Our result will facilitate the use of xenon-doped liquid argon in future experiments.
The detection of scintillation light from liquid argon is an experimental technique key to a number of current and future nuclear/particle physics experiments, such as neutrino physics, neutrinoless double beta decay and dark matter searches. Although the idea of adding small quantities of xenon (doping) to enhance the light yield has attracted considerable interest, this technique has never been demonstrated at the necessary scale or precision. Here we report on xenon doping in a 100 l cryogenic vessel. Xenon doping was performed in four concentrations of 1.00$pm$0.06 ppm, 2.0$pm$0.1 ppm, 5.0$pm$0.3 ppm, and 10.0$pm$0.5 ppm. These measurements represent the most precise xenon doping measurements as of publishing. We observed an increase in average light yield by a factor of 1.92$pm$0.12(syst)$pm$0.02(stat) at a dopant concentration of 10 ppm.
Liquid argon is used as active medium in a variety of neutrino and Dark Matter experiments thanks to its excellent properties of charge yield and transport and as a scintillator. Liquid argon scintillation photons are emitted in a narrow band of 10~nm centered around 127 nm and with a characteristic time profile made by two components originated by the decay of the lowest lying singlet and triplet state of the excimer Ar$_2^*$ to the dissociative ground state. A model is proposed which takes into account the quenching of the long lived triplet states through the self-interaction with other triplet states or through the interaction with molecular Ar$_2^+$ ions. The model predicts the time profile of the scintillation signals and its dependence on the intensity of an external electric field and on the density of deposited energy, if the relative abundance of the unquenched fast and slow components is know. The model successfully explains the experimentally observed dependence of the characteristic time of the slow component on the intensity of the applied electric field and the increase of photon yield of liquid argon when doped with small quantities of xenon (at the ppm level). The model also predicts the dependence of the pulse shape parameter, F$_{prompt}$, for electron and nuclear recoils on the recoil energy and the behavior of the relative light yield of nuclear recoils in liquid argon, $mathcal{L}_{eff}$
The propagation velocity of scintillation light in liquid argon $v_{g}$ at $lambda sim 128$~nm wavelength, has been measured for the first time in a dedicated experimental setup at CERN. The obtained result $frac{1}{v_{g}} = 7.46 pm 0.08$~ns/m , is then used to derive the value of the refractive index (n) and the Rayleigh scattering length ($mathcal{L}$) for liquid argon in the VUV region. For $lambda = 128$~nm we found $n= 1.358 pm 0.003$ and $mathcal{L}= 99.1 pm 2.3$~cm. The measured values are of interest for a variety of experiments searching for rare events like neutrino and dark matter interactions. The derived quantities also represent key information for theoretical models describing the propagation of scintillation light in liquid argon.
Xenon-doped liquid argon has been proposed as a good alternative to pure liquid argon in scintillation detectors. In this study, we report on the measurement of the time profile of scintillation light emitted from xenon-doped liquid argon with molar concentrations up to 1600 ppm. A compact setup has been developed for this study, with silicon photomultiplier (SiPM) as the photosensor and $^{210}mathrm{Po}$ and $^{90}mathrm{Sr}$ as scintillation sources. An effective model based on the de-excitation processes has been developed to describe the data. The results show that xenon-doped liquid argon is a good fast scintillator and can be used in lieu of tetraphenyl butadiene (TPB) in a way that preserves its capability for particle identification via pulse shape discrimination (PSD).