A spark in the dark Scintillation time dependence and neutron-induced signals in dual-phase xenon TPCs

Dual-phase (liquid and gas) xenon time projection chambers (TPCs) are currently the world's leading detector technology in the search for dark matter by direct detection. The XENON1T experiment, which contains an instrumented mass of 2 tons of liquid xenon, measured for a year and found no indication for any dark matter interaction, thus further constraining dark matter models. TPCs require excellent background rejection, part of which is achieved by making a distinction between a nuclear and an electronic interaction. This in turn requires a calibration with a neutron source, which in the case of XENON1T is a plasma fusion neutron generator. In this manuscript, a complete characterization of the neutron generator is presented. The calibration using the neutron generator is also shown. In addition to large xenon TPCs looking for dark matter, there are several smaller R&D setups worldwide. One of such setups is the XAMS experiment in Amsterdam. This manuscript elaborates on details on the setup and its data taking. There have been extensive measurements with various radiation sources and at several electric fields. Based on this data, the conclusion can be drawn that pulse shape discrimination, once believed to aid background rejection, does not meaningfully contribute to this. The data at various fields shows that the parameters of interest to TPC operation change significantly at low fields, which could present challenges to future large-scale TPCs looking for dark matter.