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A: The Beam Dump Facility (BDF) is a proposed general-purpose facility at CERN, dedicated to fixed target and beam dump experiments, currently being developed in the context of the Physics Beyond Colliders program. The design of the facility will allow to host different types of experiments, of which SHiP is planned to be the initial one. The core of the facility is a high-density target/dump absorbing the full intensity of the SPS beam and generating a cascade of particles that are detected downstream the target complex. The target and its shielding blocks are positioned inside a vessel, which is planned to be passivized with helium, in order to reduce the activation of the gas surrounding the target and to extend the operational life of materials and equipment. The passivation system that will be in charge of purifying and circulating the helium is a critical component for the operation of the facility. Fluid dynamics simulations have been performed to study the circulation of the helium through the vessel. A detailed design of the helium passivation system and its main components has been developed. K: Gas systems and purification A X P : 1910.00333

Recently with the increasing demand for isotopic materials, the development of customized refrigeration units which allows temperature stabilization, or cryostatting in the temperature range of 30…50 K became necessary. The required temperature stabilization depends on the isotope and process type and need to be performed at different temperatures. Thus, it is obvious that the development of a reliable and efficient refrigeration unit operating in the temperature range of 30…50 K is a relevant objective. This paper presents the result of a preliminary study of the cryogenic system designed for the cold production in the temperature range of 20...50 K. Structurally, the system is designed as a cascade of two refrigeration machines using a mixed refrigerant media as coolant. The Linde-Hampson refrigeration unit, which generates cold at a temperature level of about 90...100 K, is the upper high-temperature stage of the refrigeration cascade. The working fluid of the upper stage is a multicomponent zeotropic mixture of hydrocarbons. The working mixture is compressed in a hermetic lubricated compressor with a moderate compression ratio and a maximum discharge pressure of up to 30 bar. The lower "cryogenic" stage of the system implements the Bell-Coleman cycle. A three-component zeotropic mixture 2H-Ne-He is used as the working fluid of the low-temperature stage, which ensures the operability of the "cryogenic" stage of the system in the temperature range of 20...90 K. The current paper presents the design diagrams and thermodynamic cycles of the system and its elements. The rationale for selection of the refrigerant mixture and a preliminary analysis of the system components are reported.

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