研究目的
Investigating the operation of bubble-assisted Liquid Hole-Multipliers (LHM) in liquid xenon for the detection of radiation-induced ionization electrons and primary scintillation photons.
研究成果
The 125 μm-thick SC-GEM provided the highest electroluminescence (EL) yields, up to ～ 400 photons per electron over 4π, with an RMS pulse-height resolution reaching 5.5% for events comprising ～ 7000 primary electrons. The feasibility of a vertical-mode LHM and the operation of a two-stage LHM configuration were demonstrated for the first time. The study provides valuable insights into the potential of LHM for future applications in noble-liquid time projection chambers (TPCs) for rare-event experiments.
研究不足
The study was limited by the size of the electrodes and the cryostat, which may not fully represent the conditions in larger-scale applications. Additionally, the stability of the bubble and the efficiency of electron transfer from the liquid to the gas phase are areas that require further optimization.
1：Experimental Design and Method Selection:
The study involved the use of four types of LHM electrodes (THGEM, standard double-conical GEM, 50 μm-thick single-conical GEM, and 125 μm-thick SC-GEM) coated with CsI photocathodes. The electrodes were immersed in liquid xenon, and a vapor bubble was confined under or adjacent to them. The setup allowed for the recording of both radiation-induced ionization electrons and primary scintillation photons.
2：Sample Selection and Data Sources:
The experiments were conducted in a dedicated LXe cryostat, the Mini Xenon apparatus (MiniX), comprising a 100 mm-diameter, 100 mm-tall cylindrical LXe volume filled with ～ 250 ml of LXe. A spectroscopic ～ 180 Bq, 6 mm diameter 241Am alpha-particle source was used to provide primary scintillation light and ionization electrons.
3：List of Experimental Equipment and Materials:
The setup included a THGEM, standard double-conical GEM, 50 μm-thick single-conical GEM (SC-GEM), and 125 μm-thick SC-GEM, all coated with CsI photocathodes. Light signals were recorded by two Hamamatsu R8520 photomultiplier tubes (PMTs).
4：Experimental Procedures and Operational Workflow:
The detector assembly comprised the CsI-coated LHM electrode, the alpha-particle source, a field-shaping ring, and a resistive-wire plane underneath. The bubble was formed by ohmic heating and remained stable as long as the system stayed in a thermodynamic steady state. Light signals were recorded and digitized for post-processing.
5：Data Analysis Methods:
Waveforms were digitized and saved using an oscilloscope and were post-processed using dedicated Matlab scripts. The integrated pulse area under S2 and S1' was computed for each waveform, serving to build a histogram of pulse areas for each voltage setting.
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