Cryogenic targets of the lightest gases (hydrogen, deuterium and helium-4) with GM cryocooler for experiments of high energy physics.

Researches of collision processes of elementary nuclei on the extracted beams of the NICA accelerator complex by the BM@N physics installation need cryogenic targets with unique ratios between the amounts of working substance (liquid hydrogen, deuterium or helium) and the mass of the target's housing, which may have the interaction with an ion beam, result the secondary particles, and initiate the background events. In this research authors provided the results of experimental cold down testing of liquid hydrogen target. A maximum cooling capacity of the used GM cryocooler is 1.5 watts at 4.2 Kelvin, which looks acceptable for
such application. The using of GM cryocooler allows creating a fully autonomous and mobile cryogenic target, which not depends from outside cold source. Authors put attention on a serious problem of heat losses, including heat gain from radiation at a maximum beam intensity of 10 11 particles/s, and propose using cryocooler's refrigeration power to prevent it. During the experimental testing of the new liquid hydrogen target with cooled shield it was successfully proofed. The cold down time was 90 minutes and GM cryocooler worked well. However, a lot of problems were recognized when liquid helium target was running. Authors assumed that additional research of heat leaks and radiation losses is necessary.