Abstract
The measurement of the internal 222Rn activity in the NEXT-White detector during the so-called Run-II period with 136Xe-depleted xenon is discussed in detail, together with its implications for double beta decay searches in NEXT. The activity is measured through the alpha production rate induced in the fiducial volume by 222Rn and its alpha-emitting progeny. The specific activity is measured to be (38.1 ± 2.2 (stat.) ± 5.9 (syst.)) mBq/m3. Radon-induced electrons have also been characterized from the decay of the 214Bi daughter ions plating out on the cathode of the time projection chamber. From our studies, we conclude that radon-induced backgrounds are sufficiently low to enable a successful NEXT-100 physics program, as the projected rate contribution should not exceed 0.1 counts/yr in the neutrinoless double beta decay sample.
Highlights
Qα = 6114.7 keV of radon-induced backgrounds, and plate-out of radon daughters on detector surfaces is common
The measurement of the internal 222Rn activity in the Neutrino Experiment with a Xenon TPC (NEXT)-White detector during the so-called Run-II period with 136Xe-depleted xenon is discussed in detail, together with its implications for double beta decay searches in
A high-pressure xenon gas time projection chamber (TPC) is the detector technology chosen by the Neutrino Experiment with a Xenon TPC () to search for 0νββ in 136Xe [8]
Summary
The detection concept [8] is based on a high-pressure gaseous xenon TPC. uses electroluminescence (EL) as a nearly noiseless amplification stage for ionization produced in the xenon gas. While none of the radon-induced data discussed in this work used decays from these sources, some of the runs were taken concurrently with sources near/inside the detector. In this case, trigger and offline event selection were used to effectively reject calibration source events. The measured activity of airborne radon (222Rn) at the Laboratorio Subterraneo de Canfranc (Hall A) varies between 60 and 80 Bq m−3 [26] Left at this level, airborne radon would represent an intolerably high source of gamma-rays from 214Bi, at the level of 10−3 counts/(keV·kg· yr), see [17]. While the radon activity in the air surrounding the pressure vessel still needs to be measured, we expect air-borne radon contributions to the background budget to be completely negligible in
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