INSTR'20

A Facility for mass production of ultra-pure NaI powder for the COSINE-200 experiment

Not scheduled

15m

Budker Institute of Nuclear Physics

Board: 57

Poster Instrumentation for Astroparticle and Neutrino physics

Speaker

Ms Keonah Shin (CUP, IBS)

Description

The COSINE experiment aims to reproduce DAMA/LIBRA’s observation of an annual modulation signal that can be interpreted as interactions of WIMPs (Weakly Interacting Massive Particles) dark matter. Ultra-low background NaI(Tl) crystal detectors are being developed for the next-phase experiment, COSINE-200. For the COSINE-200 experiment, all steps in the low-background detector production process, including the purification of ultra-pure powder, the growing of crystal, and the detector assembly, are being carefully developed. In this presentation, we discuss the purification of the ultra-pure powder, including the development of an instrument based on recrystallization for its mass production in our laboratory at the Center for Underground Physics, Daejeon, Korea. The COSINE-200 experiment’s goals require in total at least 500 kgs of NaI powder with contaminations from potassium (K) below 20 ppb and Pb-210 below 0.1 mBq/kg for the production of a 200 kg detector. To satisfy these requirements, a special clean facility that purifies NaI powder by means of fractional recrystallization from a water solution has been constructed. This facility consists of a dissolving tank, a recrystallization tank, a filter housing and a vacuum biconical dryer. The Maximum initial powder charge capacity is 70 kg and its recovery rate is typically ~45%. In normal operation, a single batch produces 30 kg of purified NaI powder in five days. To validate the purity of the produced product, the concentrations of K, Pb, Sr, Ba, Th and U were measured by ICP-MS method and these confirmed sufficient reduction of K concentration to below 20 ppb and those of all other radio-impurities as well. Details of the mass-production of purified NaI powder for the COSINE-200 experiment will be presented.