Challenge on Ca-48 enrichment for CANDLES double beta decay experiment

TL;DR

This paper investigates chemical isotope effects of calcium using liquid-liquid extraction with crown ethers to develop a cost-effective method for enriching Ca-48, crucial for neutrinoless double beta decay research.

Contribution

It evaluates the contributions of field shift and hyperfine splitting effects on calcium isotope separation, providing preliminary insights for chemical enrichment of Ca-48.

Findings

Field shift effect contribution is small for Ca-48.

Enrichment factors are less affected by field shifts compared to chromium.

Preliminary results are promising for chemical Ca-48 enrichment methods.

Abstract

Chemical isotope effects of calcium were studied by liquid-liquid extraction using a crown ether of dicyclohexano-18-crown-6 for the purpose of finding a cost-effective and efficient way of enrichment of Ca-48 towards the study of the neutrinoless double beta decay of Ca-48. We evaluated each contribution ratio of the field shift effect and the hyperfine splitting shift effect to the mass effect of the calcium isotopes for the first time. The present preliminary result suggests the contribution of the field shift effect is small, especially for Ca-40-Ca-48 case, compared with the case of Chromium trichloride-crown in which the isotope enrichment factors are strongly affected by the field shifts. These indications are promising towards the mass producion of enriched Ca-48 by the chemical separation method.