Erratum to: Measurement of the background activities of a 100Mo-enriched powder sample for an AMoRE crystal material by using a single high-purity germanium detector

The Advanced Molybdenum-based Rare process Experiment (AMoRE) searches for neutrino-less double-beta (0 νββ ) decay of 100 Mo in enriched molybdate crystals. The AMoRE crystals must have low levels of radioactive contamination to achieve low background signals with energies near the Q-value of the 100 Mo 0 νββ decay. To produce low-activity crystals, radioactive contaminants in the raw materials used to form the crystals must be controlled and quantified. 100 EnrMoO 3 powder, which is enriched in the 100 Mo isotope, is of particular interest as it is the source of 100 Mo in the crystals. A high-purity germanium detector having 100% relative efficiency, named CC1, is being operated in the Yangyang underground laboratory. Using CC1, we collected a gamma spectrum from a 1.6-kg 100 EnrMoO 3 powder sample enriched to 96.4% in 100 Mo. Activities were analyzed for the isotopes 228 Ac, 228 Th, 226 Ra, and 40 K. They are long-lived naturally occurring isotopes that can produce background signals in the region of interest for AMoRE. Activities of both 228 Ac and 228 Th were < 1.0 mBq/kg at 90% confidence level (C.L.). The activity of 226 Ra was measured to be 5.1 ± 0.4 (stat) ± 2.2 (syst) mBq/kg. The 40 K activity was found as < 16.4 mBq/kg at 90% C.L.