No abstract

We established Q spectroscopy, a novel method for the study of alpha decay, by combining 4π detection scheme with a low-temperature microcalorimeter. A 4π metal absorber guarantees absolute measurement of radioactivity without energy loss in the source and absorber. As a clear demonstration of Q spectroscopy, the 241Am alpha source enclosed by a thin gold foil was measured below 100 mK. Its resulting energy spectrum has two dominant peaks with 10 keV FWHM. The more dominant one corresponds to the complete absorption of the Q value, the total decay energy, and the less dominant one to γ-ray escapes. Consequential one-to-one correspondence with high-energy resolution appears between mixed radioisotopes and peaks in Q spectroscopy, which will simplify procedures of nuclear material analysis.

Dark matter interpretations of the DAMA signals are excluded by COSINE-100 with the same NaI(Tl) target for various models.

The level of radioactivity from 222 Rn in the air has to be monitored to control systematic effects on the background level at the KIMS (Korea Invisible Mass Search) dark matter search experiment. We designed and constructed a radon detector using a silicon photodiode that collects 218 Po and 214 Po daughter ions electrically and detects their α decays. Results for the detector calibration with a standard radon source, as well as the dependence of the α-particle detection efficiency on the humidity, are presented. The radioactivity of radon at the YangYang underground laboratory is measured and continuously monitored.

No abstract