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تسجيل مستخدم جديدBubble-assisted Liquid Hole Multipliers in LXe and LAr: towards local dual-phase TPCs
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The bubble-assisted Liquid Hole Multiplier (LHM) is a novel concept for the combined detection of ionization electrons and scintillation photons in noble-liquid time projection chambers. It consists of a perforated electrode immersed in the noble liquid, with heating wires generating a stable bubble underneath. Radiation-inducted ionization electrons in the liquid drift into the electrodes holes and cross the liquid-vapor interface into the bubble where they induce electroluminescence (EL). The top surface of the electrode is optionally coated with a CsI photocathode; radiation-induced UV-scintillation photons extract photoelectrons that induce EL in a similar way. EL-photons recorded with an array of photosensors, e.g. SiPMs, provide event localization. We present the basic principles of the LHM and summarize the results obtained in LXe and LAr.
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We report on recent advances in the operation of bubble-assisted Liquid Hole Multipliers (LHM). By confining a vapor bubble under or adjacent to a perforated electrode immersed in liquid xenon, we could record both radiation-induced ionization electr
ons and primary scintillation photons in the noble liquid. Four types of LHM electrodes were investigated: a THGEM, standard double-conical GEM, 50 $mu$m-thick single-conical GEM (SC-GEM) and 125 $mu$m-thick SC-GEM - all coated with CsI photocathodes. The 125 $mu$m-thick SC-GEM provided the highest electroluminescence (EL) yields, up to ~400 photons per electron over 4$pi$ with an RMS pulse-height resolution reaching 5.5% for events comprising ~7000 primary electrons. Applying a high transfer field across the bubble, the EL yield was further increased by a factor of ~5. The feasibility of a vertical-mode LHM, with the bubble confined between two vertical electrodes, and the operation of a two-stage LHM configuration were demonstrated for the first time. We combine electrostatic simulations with observed signals to draw conclusions regarding the location of the liquid-gas interface and suggest an explanation for the observed differences in EL yield between the investigated electrodes.
In bubble-assisted Liquid HoleMultipliers(LHM), developed for noble-liquid radiation detectors, the stability of the bubble and the electro-mechanical properties of the liquid-to-gas interface play a dominant role in the detector performance. A model
is proposed to evaluate the static equilibrium configurations of a bubble sustained underneath a perforated electrode immersed in a liquid. For the first time bubbles were optically observed in LAr; their properties were studied in contact with different material surfaces. This permitted investigating the bubble-electrodynamics via numerical simulations; it was shown that the electric field acts as an additional pressure term on the bubble meniscus. The predictions for the liquid-to-gas interface were successfully validated using X-ray micro-CT in water and in silicone oil at STP. The proposed model and the results of this study are an important milestone towards understanding and optimizing the parameters of LHM-based noble-liquid detectors.
We report on the recent development of a versatile analog front-end compatible with a negative-ion $mu$-TPC for a directional dark matter search as well as a dual-phase, next-generation $mathcal{O}$(10~kt) liquid argon TPC to study neutrino oscillati
ons, nucleon decay, and astrophysical neutrinos. Although the operating conditions for negative-ion and liquid argon TPCs are quite different (room temperature textit{vs.} $sim$88~K operation, respectively), the readout electronics requirements are similar. Both require a wide-dynamic range up to 1600 fC, and less than 2000--5000 e$^-$ noise for a typical signal of 80 fC with a detector capacitance of $C_{rm det} approx 300$~pF. In order to fulfill such challenging requirements, a prototype ASIC was newly designed using 180-nm CMOS technology. Here, we report on the performance of this ASIC, including measurements of shaping time, dynamic range, and equivalent noise charge (ENC). We also demonstrate the first operation of this ASIC on a low-pressure negative-ion $mu$-TPC.
First imaging results in liquid xenon of a Liquid Hole Multiplier (LHM) coupled to a Quad-Silicon Photomultiplier (SiPM) array are presented. Ionization electrons deposited in the noble liquid by 5.5 MeV alpha particles, are collected into the holes
of a Thick Gas Electron Multiplier (THGEM) electrode having a xenon gas bubble trapped underneath. They drift through the liquid-gas interface, inducing electroluminescence within the bubble. The resulting photons are detected with a Hamamatsu VUV4 quad-SiPM array - providing the deposited energy with a charge-only RMS resolution of 6.6%. The image reconstruction resolution was estimated to be ~200 um (RMS).
Bubble formation in liquid xenon underneath a Thick Gaseous Electron Multiplier (THGEM) electrode immersed in liquid xenon was observed with a CCD camera. With voltage across the THGEM, the appearance of bubbles was correlated with that of electrolum
inescence signals induced by ionization electrons from alpha-particle tracks. This confirms recent indirect evidence that the observed photons are due to electroluminescence within a xenon vapor layer trapped under the electrode. The bubbles seem to emerge spontaneously due to heat flow from 300K into the liquid, or in a controlled manner, by locally boiling the liquid with resistive wires. Controlled bubble formation resulted in energy resolution of {sigma}/E~7.5% for ~6,000 ionization electrons. The phenomenon could pave ways towards the conception of large-volume local dual-phase noble-liquid TPCs.
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