Production Rate Measurement of Tritium and Other Cosmogenic Isotopes in Germanium with CDMSlite

Creators: Agnese, R.; Aralis, T.; Chang, Y.-Y.; Cornell, B.; Golwala, S. R.

Abstract

Future direct searches for low-mass dark matter particles with germanium detectors, such as SuperCDMS SNOLAB, are expected to be limited by backgrounds from radioactive isotopes activated by cosmogenic radiation inside the germanium. There are limited experimental data available to constrain production rates and a large spread of theoretical predictions. We examine the calculation of expected production rates, and analyze data from the second run of the CDMS low ionization threshold experiment (CDMSlite) to estimate the rates for several isotopes. We model the measured CDMSlite spectrum and fit for contributions from tritium and other isotopes. Using the knowledge of the detector history, these results are converted to cosmogenic production rates at sea level. The production rates in atoms/(kg · day) are 74  ±  9 for ^3H, 1.5  ±  0.7 for ^(55)Fe, 17  ±  5 for ^(65)Zn, and 30  ±  18 for ^(68)Ge.

Additional Information

© 2018 Published by Elsevier B.V. Received 18 June 2018, Revised 7 August 2018, Accepted 12 August 2018, Available online 14 August 2018. The SuperCDMS collaboration gratefully acknowledges technical assistance from the staff of the Soudan Underground Laboratory and the Minnesota Department of Natural Resources. The iZIP detectors were fabricated in the Stanford Nanofabrication Facility, which is a member of the National Nanofabrication Infrastructure Network, sponsored and supported by the NSF. Funding and support were received from the National Science Foundation, the U.S. Department of Energy, Fermilab URA Visiting Scholar Grant No. 15-S-33, NSERC Canada, the Canada First Research Excellence Fund, and MultiDark (Spanish MINECO). This document was prepared by the SuperCDMS collaboration using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359. Pacific Northwest National Laboratory is operated by Battelle Memorial Institute under Contract No. DE-AC05-76RL01830 for the U.S. Department of Energy. SLAC is operated under Contract No. DEAC02-76SF00515 with the U.S. Department of Energy.

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