A Rn-220 source for the calibration of low-background experiments

作者：Lang R F; Brown A; Brown E; Cervantes M; Macmullin S; Masson D^*; Schreiner J; Simgen H

来源：Journal of Instrumentation, 2016, 11(04): P04004.

DOI：10.1088/1748-0221/11/04/P04004

• Detector alignment and calibration methods (lasers, sources, particle-beams)
• Noble liquid detectors (scintillation, ionization, double-phase)
• Dark Matter detectors (WIMPs, axions, etc.)
• Double-beta decay detectors

We characterize two 40 kBq sources of electrodeposited Th-228 for use in low-background experiments. The sources efficiently emanate Rn-220, a noble gas that can diffuse in a detector volume. Rn-220 and its daughter isotopes produce alpha-, beta-, and gamma-radiation, which may used to calibrate a variety of detector responses and features, before decaying completely in only a few days. We perform various tests to place limits on the release of other long-lived isotopes. In particular, we find an emanation of < 0.008 atoms/min/kBq (90% CL) for Th-228 and (1.53 +/- 0.04) atoms/min/kBq for Ra-224. The sources lend themselves in particular to the calibration of detectors employing liquid noble elements such as argon and xenon. With the source mounted in a noble gas system, we demonstrate that filters are highly efficient in reducing the activity of these longer-lived isotopes further. We thus confirm the suitability of these sources even for use in next-generation experiments, such as XENON1T/XENONnT, LZ, and nEXO.

• 出版日期2016-4