Detection of dark matter particles using liquified noble elements
Current Research
Our current group of research scientists, postdoctoral associates, and graduate students work hands-on with experiments in the Department of Physics at University of California Berkeley (UCB), the Lawrence Berkeley National Lab (LBNL) and the Sanford Underground Research Facility (SURF) in Lead, South Dakota. Our group collaborates with other liquid noble research groups throughout the United States and Europe. We contribute to detector R&D as well as experimental simulations, analysis, and operations.
LUX
The McKinsey group is heavily involved in the Large Underground Xenon (LUX) experiment. LUX is used to search for the leading particle dark matter candidate, WIMPs, with a two-phase xenon detector. The 350-kg detector was installed 4850 feet underground in the Davis Campus at SURF and was the most sensitive dark matter detector between 2012 and 2017. Professor McKinsey serves as co-spokesperson of this 120-member collaboration.
LZ
Immediately following LUX, the McKinsey group continues to work on the LUX-ZEPLIN (LZ) experiment, adding the expertise of the scientists from UK's ZEPLIN dark matter experiment to the current LUX collaboration. LZ will be a whopping 7-ton two-phase xenon detector and is being installed in the Davis Campus at SURF after the LUX detector had run its course. Work for LZ is underway here at Berkeley in the form of background simulations, calibration source research, and the high voltage subsystem design, research, and development. Notably, our high voltage tests at Berkeley has demonstrated an ability to deliver hundreds of kilovolts into a cryogenic liquid noble detector.
PIXeY and CoDeX
The Particle Identification in Xenon at Yale (PIXeY) experiment was a two-phase liquid/gas xenon time projection chamber, used to study recoils in liquid xenon and detector physics. Some results from the experiment include calibration of light and charge yields with an Argon-37 source and measurement of extraction effiency as a function of field. Continued work includes calibration of a Kr83m source to study its yields and energy resolution. PIXeY was upgraded to the Compton Detection in Xenon (CoDeX) experiment by adding wire readout grids to measure charge as it is drifted through the detector, in order to do Compton imaging.
XeBrA
The Xenon Breakdown Apparatus (XeBrA) is being used to characterize the high voltage behavior of liquid xenon and liquid argon. With large noble liquid detectors planned for the future, or already in construction phase, this research will shed light on how to achieve a stable high voltage.
IBEX
IBEX is an experiment designed to measure the angular distribution of light reflected off of polytetrafluoroethylene (PTFE) submerged in liquid xenon, in order to investigate microphysical models of reflection in this context. This is valuable information for experiments employing PTFE in liquid xenon time projection chambers, such as LZ. Such detectors rely on the poorly understood high total reflectance of PTFE to xenon scintillation light to achieve excellent light collection efficiency. Since the energy thresholds of such experiments are strongly dependent on the light collection efficiency, a model of the reflectance behavior is desired. Furthermore, IBEX can be used to inform a more accurate simulation of the distribution of light in such detectors. IBEX is investigating the dependence of reflectivity on xenon temperature and pressure, the wavelength of light, the type of PTFE, and the surface finish of the sample.
HeRALD
Helium Roton Apparatus for Light Dark Matter (HeRALD) will use quantum evaporation of helium-4 atoms to amplify the phonon/roton signal from a dark matter recoil. Coupled with transition-edge sensor readout and the low He-4 nucleus mass, HeRALD will try to detect light dark matter, with mass less than that of the proton. The project is done in collaboration with the Hertel Group at UMass Amherst and the Pyle group at UC Berkeley.