Heat exchanger material and heat exchanger for cryogenic cooling systems, and a system

A cryogenic cooling system, comprising:

• a flow path for a liquid cryogen, and
• along said flow path at least one heat exchanger for transferring thermal energy to or from a liquid cryogen flowing through said flow path;
• wherein said cryogenic cooling system is configured to make liquid cryogen of temperature below 77 K flow through said flow path,
• wherein said at least one heat exchanger comprises solid material rendered into its final form in an additive manufacturing process, at least a surface layer of said final form of the solid material having a surface-to-volume ratio of at least 105 1/m,
• wherein said surface layer comprises a plurality of extended thermal conduction paths in the form of regularly shaped portions of said solid material that extend through a majority of a thickness of the surface layer and occur in a repetitive pattern throughout the surface layer, and
• wherein said surface layer is exposed to liquid cryogen on said flow path.