Preparation of low-radioactive high-purity enriched 100MoO3 powder for AMoRE-II experiment

Abstract

This paper describes preparing radiopure molybdenum trioxide powder enriched with Mo-100 isotope for the AMoRE-II experiment. AMoRE-II, the second phase of the AMoRE experiments, will search for the neutrinoless double-beta decay (0νDBD) of the 100Mo isotope using over 100 kg of 100Mo embedded in 200 kg of ultra-pure Li2100MoO4 bolometric crystals. Efficient purification technology was developed and adapted to purify 100MoO3 powder with a 5 kg per month production capacity. Based on the ICP-MS analysis of purified powder, the 232Th and 238U were reduced to <9.4 μBq/kg and <50 μBq/kg, respectively. The concentrations of potassium, transition metals, and heavy metals were lower than 1 ppm. HPGe counting confirmed the reduction of progenies from the 232Th and 238U decay chains, reporting upper limits of <27 μBq/kg for 228Ac and <16 μBq/kg for 228Th. The 226Ra activity was acceptable at 110 ± 30 μBq/kg. In the last 3 years, 100 kg of pure 100MoO3 powder was produced. The production yield for the final purified product was above 90%, while irrecoverable losses were under 1.5%, and all by-products could be recycled further.

Selection and purification of Li2CO3 precursor for bolometric double beta decay experiments

“…These crystals had a yellowish color and were unsuitable for use in the experiment. The coloration of the crystals could not be caused by impurities from molybdenum since the molybdenum oxide was purified at CUP, and its purity was confirmed [27]. With extensive ICP-MS and HPGe analysis of Li 2 CO 3, we did not find any contaminants at the levels over a few ppm, which may explain the yellowish color of the crystals.…”

“…About 180 kg of molybdenum trioxide ( 100 MoO 3 ), enriched in the 100 Mo isotope, and 150 kg of lithium carbonate are used as precursors for the crystal synthesis. The procedure for the purification of enriched 100 MoO 3 for AMoRE-II was finalized and carried out at the CUP facility [27]. This study was focused on understanding the initial Li 2 CO 3 purity required for AMoRE-II crystal synthesis with both techniques and what purity levels are commercially available in the market.…”

AMoRE-II preparation status

“…All the crystals needed for the second stage of AMoRE-II are expected to be ready by mid 2025. The raw materials for the crystal growing, MoO 3 and Li 2 CO 3 powder, have been being purified at CUP/IBS for reducing radioactivity [5].…”

Purification of Lithium Carbonate from Radioactive Contaminants Using a MnO2-Based Inorganic Sorbent

“…Calcium-based and carbonate-based carriers were selected for Ra removal. Our previous studies demonstrated that the CMO-based carrier [14,18] efficiently separates thorium and radium. After the co-precipitate was filtered out using the PTFE membrane filter, the lithium nitrate solution was analyzed with ICP-MS at the CUP (Table 2).…”

“…Bolometers for AMoRE-II have been produced with conventional [12] and low-temperature gradient Czochralski [13] techniques. To ensure the radiopurity and uniformity of the synthesized crystals despite the crystallization technique used, high-purity and low-radioactive initial materials, namely, 100 MoO 3 [14] and Li 2 CO 3 powders, are required. The current study mainly focuses on Li 2 CO 3 preparation for the AMoRE project.…”