Abstract
Abstract
The radiation emitted from radon is a critical background in
rare event search experiments conducted at the Yemi Underground
Laboratory (Yemilab) in Jeongseon, Korea. A Radon Reduction System
(RRS) has been developed and installed in Yemilab to reduce radon
concentration in the air. The RRS primarily provides a purified air
of 50 m3/h to the cleanroom used to assemble crystal
detectors in the AMoRE, a neutrinoless double beta decay search
experiment. RRS can reduce the radon level by a factor of 300, so a
high-sensitivity radon detector was required. A highly sensitive
radon detector was constructed using a 70 L chamber with a large
PIN photodiode to measure radon concentration in the purified air.
The radon detector shows an excellent resolution of 72 keV (FWHM)
for 6.003 MeV alphas from 218Po decay and a sensitivity down
to 23.8 ± 2.1 mBq/m3 with a boil-off N2 gas sample.
The radon concentration level from the RRS measured by the radon
detector was below 0.29 Bq/m3 with a reduction factor of
about 300.