Novel Photosensors for Direct Dark Matter Detection

by Torben Flehmke (Stockholm University)

Thursday 19 Mar 2026, 10:00 → 12:00 Europe/Stockholm

Albano 3: 5230 - Xenon (12 seats) (Albano Building 3)

Abstract
This thesis presents some of the work I have done during the first three
years of my Ph.D. studies at Stockholm university and as a member of the
XENON collaboration. A full photomultiplier tube (PMT) testing run of
14 PMTs for potential replacement in the XENONnT electrode upgrade is
presented. Out of the 14 PMTs one PMT could not be tested properly due to
problems with the testing facility. For the other PMTs the gain and dark count
measurements were within specifications. One PMT showed medium argon
afterpulse, however these were not strong enough to completely disqualify it.
In total, all but one PMTs passed the test and the PMT that did not pass
was not due to issues with the PMT itself.
Furthermore, results of the study of the novel ABALONE photosensor are
presented. The gain, dark count, and afterpulse measurements all met expectations.
However, serious problems with the stability of the supply voltage
make it an unlikely candidate for future dark matter detectors.
In the last part my work of monitoring the afterpulse rates in the PMTs in
XENONnT is presented. While there were 4 PMTs that showed a significant
increase in afterpulse rates, these were still within the safe margin and no
PMTs had to be excluded from the analysis due to high rates.