Calibrations for the XENON1T dark matter search with 83mKr, a high capacity circulating pump, and metallic photocathodes for xenon purification

Abstract

As an extension to XENON1T and beyond, we develop the drive and control system for a clean and sealed magnetic piston pump. Such a pump could provide increased gas circulation rates through purification systems necessary for ton-scale liquid-noble detectors. At the same time all materials in direct contact with the detector medium are minimized, and failure modes directed away from contaminant introducing procedures.

A plethora of experiments have been devised to detect dark matter. The series of XENON experiments have continued to set competitive limits in the direct search for dark matter. Currently XENON1T is the largest operational dual-phase time projection chamber (TPC) in the world, and the first science run results once again set the best limit on the spin-independent weakly interacting massive particle (WIMP)-nucleon interaction cross section, in lieu of a dark matter discovery.

The preponderance of astronomical observations in support of some dark matter requires an explanation. Whether the solution will be the discovery of some particle(s) or an extension or development of theories describing the interaction of matter has yet to be established. However, it has become clear that the particles in the Standard Model and our theories of classical and quantum field theories are insufficient.

Finally, we produce metallic photocathodes to provide clean and stable electron sources for particle physics applications. Photocathodes have been primarily developed as electron sources for particle accelerators or the detection medium in photomultiplier tubes (PMTs), but in both cases these photocathodes operate in vacuum. In this case, we seek a middle ground between these applications, where our primary design goal is a stable photocurrent in a noble gas environment.

83m Kr is an internal calibration source that provides a uniform event distribution and is used to develop an understanding of the XENON1T TPC. The mono-energetic 32 keV decay permits the calculation of position-dependent light collection efficiency (LCE) correction maps. We can also use the XENON1T detector to measure the 83mKr7/2+ half-life.