Growth and characterization of isotopically enriched 40Ca100MoO4 single crystals for rare event search experiments

Calcium molybdate is considered as a very promising scintillator material for experimental studies of rare processes. This paper reports on the production and characterization of a 40Ca100MoO4 scintillator. Using the Czochralski technique, a crystal of high optical quality with total mass 0.55 kg, 42 mm diameter (minimum) and 53 mm 1ength of the cylindrical section was produced from isotopically enriched raw materials, containing 96.1% of 100Mo and 99.964% of 40Ca. To satisfy the requirement of low intrinsic radioactivity the purity of the materials was monitored at different stages of the production process and it is shown that the concentration of 238U and 232Th in the final crystal does not exceed 0.05 ppb. The scintillation properties of 40Ca 100MoO4 were measured over the 8 - 300 K temperature range and it is found that the light yield of the 40Ca 100MoO4 crystal is very similar to that of the CaMoO 4 reference scintillator. © 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim

First results from the AMoRE-Pilot neutrinoless double beta decay experiment

The advanced molybdenum-based rare process experiment (AMoRE) aims to search for neutrinoless double beta decay (0νββ) of100Mo with ∼ 100kg of 100Moenrichedmolybdenumembeddedincryogenicdetectorswith adualheatandlightreadout.Atthecurrent,pilotstageofthe AMoRE project we employ six calcium molybdate crystals withatotalmassof1.9kg,producedfrom48Ca-depletedcalcium and 100Mo-enriched molybdenum (48deplCa100MoO4). The simultaneous detection of heat (phonon) and scintillation (photon) signals is realized with high resolution metallic magnetic calorimeter sensors that operate at milli-Kelvin temperatures. This stage of the project is carried out in the Yangyang underground laboratory at a depth of 700 m. We report first results from the AMoRE-Pilot 0νββ search with a 111 kg day live exposure of 48deplCa100MoO4 crystals. No evidence for 0νββ decay of 100Mo is found, and a upper limit is set for the half-life of 0νββ of 100Mo of T0ν 1/2 > 9.5×1022 years at 90% C.L. This limit corresponds to an effective Majorana neutrino mass limit in the range mββ≤(1.2−2.1)eV. © The Author(s) 201911sciescopu