High-efficiency recovery of ⁸²Se from enriched Zn⁸²Se scintillating bolometer crystals

Abstract

As experiments searching for neutrinoless double beta decay push into the inverted hierarchy, enriched isotope target masses of hundreds of kilograms are required. Due to unavoidable losses throughout the entire production chain, the recovery of expensive enriched material used in crystal-based experiments should be given special attention. The CUPID-0 experiment using Zn82Se scintillating bolomoters provides a unique opportunity at the 10-kg-scale to test a recovery process for enriched 82Se. We present a multi-stage, high-yield method consisting of wet chemistry and vacuum distillation. The chemical purity, isotopic abundance, and radiopurity is demonstrated to be preserved after the 82Se extraction with recovery efficiency no less than 86.4% (that potentially can be higher than 94.7%) and chemical purity of 99.999%.

ZnO-based scintillating bolometers: new prospects to study double beta decay of 64Zn

“…Significantly higher exposures (a factor of 10 3 − 10 4 ) of these leading experiments, as well as their underground location and well-shielded low-background set-ups were the major factors of such enhanced sensitivity, as shown in table 7. It should be also stressed that only a dozen nuclei among potentially 2𝜀, 𝜀𝛽 + , 2𝛽 + active isotopes were investigated at the level of sensitivity around or more than 10 21 yr, such as 36 Ar, 40 Ca, 58 Ni, 64 Zn, 78 Kr, 96 Ru, 106 Cd, 112 Sn, 124 Xe, 130 Ba, 132 Ba, see [94] and references therein. The current limitation of the experimental sensitivity in these studies is a consequence of few reasons: a) lower energy releases in 2𝜀, 𝜀𝛽 + , 2𝛽 + processes in comparison to those in 2𝛽 − decay, that complicates background suppression; b) higher expected 𝑇 1/2 values, as a result of low decay energies and phase space factors; and c) lower natural isotopic abundances of these isotopes (typically less than 1% with only few exceptions).…”

Measurement of the 2νββ Decay Half-Life of Se82 with the Global CUPID-0 Backgroun

“…CUPID-0 detector.-CUPID-0 is composed of 24 ZnSe scintillating crystals [21] enriched at ð95.3 AE 0.3Þ% in 82 Se [22]. The array is completed by two natural ZnSe crystals, for a total ZnSe mass of 10.5 kg.…”

“…The improved precision can be attributed mainly to the integration of Phase I data with Phase II data. Additionally, the analysis threshold has been lowered from 700 keV to 300 keV, while the uncertainty on the isotopic abundance has been reduced by a factor of 3 [22]. Finally, we can convert the half-life in terms of the nuclear matrix element (NME) using the phase space factor G 2ν ¼ ð1.996 AE 0.028Þ × 10 −18 y −1 obtained under the SSD model [37,44].…”