Speaker
Description
Dual-phase noble-element detectors rely on electron extraction through a liquid-gas interface whose dynamical state is not fully characterized. Accumulated charge on the liquid surface and extraction grid can couple to surface waves, electrode fields, and fluid motion, potentially producing delayed electron emission, nonuniform extraction, and transient changes in S2 amplitude and shape. These effects may become more important as detectors scale: each unit area of the liquid surface collects charge from a taller liquid column, while the characteristic distance and time required to remove residual surface charge to perimeter sinks can also increase with detector size. As rare-event searches become sensitive to increasingly extreme response tails, improved understanding of such time-dependent detector-state effects becomes important for both background modeling and signal classification.
We propose controlled measurements of surface charge, surface motion, extraction efficiency, S2 waveform response, and delayed electron emission. We also discuss two complementary design strategies: active control and removal of charge accumulated on the liquid surface and extraction grid, and alternative extraction geometries that eliminate the conventional immersed extraction grid. These approaches could reduce delayed backgrounds and provide more stable and uniform charge extraction in future dark-matter and CEvNS detectors.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-2024749