Development of liquid helium-3 target for experimental studies of antikaon-nucleon interaction at J-PARC

TL;DR

This paper reports the development of a liquid helium-3 target system for studying antikaon-nucleon interactions at J-PARC, featuring efficient heat transport, minimal material use, and high x-ray transmission.

Contribution

A novel liquid helium-3 target system was designed and constructed for kaonic atom experiments, optimizing heat management and material transparency.

Findings

Target cell maintained at 1.3 K during cooling test

Heat load estimated at 0.21 W, helium-4 consumption 50 L/day

Efficient helium-3 circulation achieved for large acceptance

Abstract

A liquid helium-3 target system was developed for experimental studies of kaonic atoms and kaonic nuclei at J-PARC. helium-3 gas is liquefied in a heat exchanger cooled below 3.2 K by decompression of liquid helium-4. To maintain a large acceptance of the cylindrical detector system for decay particles of kaonic nuclei, efficient heat transport between the separate target cell and the main unit is realized using circulation of liquid helium-3. To minimize the amount of material, a vacuum vessel containing a carbon fiber reinforced plastic cylinder having an inside diameter of 150 mm and a thickness of 1 mm was produced. A target cell made of pure beryllium and beryllium-aluminum alloy was developed not only to minimize the amount of material but to obtain also high x-ray transmission. During a cooling test, the target cell was kept at 1.3 K at a pressure of 33 mbar. The total estimated heat load to the components including the target cell and heat exchanger cooled by liquid helium-4 decompression, was 0.21 W, and the liquid helium-4 consumption rate was 50 L/day.