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 electrons and primary scintillation photons in the noble liquid. Four types of LHM electrodes were investigated: 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. 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. 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.
@article{arxiv.1708.06645,
title = {Recent Advances in Bubble-Assisted Liquid Hole Multipliers in Liquid Xenon},
author = {E. Erdal and L. Arazi and A. Tesi and A. Roy and S. Shchemelinin and D. Vartsky and A. Breskin},
journal= {arXiv preprint arXiv:1708.06645},
year = {2018}
}