Cryogenic technologies of the superconducting NICA accelerator complex.

The international mega project NICA (Nuclotron-based Ion Collider fAcility) is aimed at studying properties of nuclear matter in the region of the maximum baryonic density. This matter existed only at the early stages of the evolution of our Universe and in the interiors of neutron stars. The NICA complex consists of three accelerators with superconducting magnets operating together: booster synchrotron, the Nuclotron and collider. The collisions of Au79+ nuclei in the NICA collider will be performed at the total energy of 4 – 11 GeV at the luminosity up to 1027 cm-2·s-1. Refrigeration capacity needed for the NICA complex will be about 10 kW at 4.5 K. The total “cold” mass of the superconducting magnets is 290 t. A distinguished feature of these magnets is refrigeration by using a twophase liquid and vapour flow of helium. This paper describes in detail the NICA cryogenic system and the facility for magnet testing. Based on the test results of the magnets, the paper presents the estimates of the value of heat leak and heat generation for each accelerator. Information about the plans to complete the work and commission the complex is provided.