Method and system for cryogenic refrigeration

A method for producing refrigeration in a closed cycle for application to a heat load comprising the steps of:

• compressing a warmed return cryogenic fluid stream to form a compressed refrigerant stream;
• passing said compressed refrigerant stream into a heat exchanger for cooling by heat exchange with returning refrigerant;
• dividing said refrigerant stream into a major stream and a minor stream as it passes through said heat exchanger;
• taking said major stream from said heat exchanger and expanding said major stream to further cool said major stream prior to using said major stream as a heat exchange fluid for cooling said compressed refrigerant stream,
• taking said minor stream and expanding it to further cool said minor stream and using said minor stream to provide refrigeration to said heat load;
• and
• thereafter compressing said minor stream;
• and
• combining said compressed minor stream and said major stream at one of, before, during or after using said major stream and said minor stream in said heat exchanger to cool said compressed refrigerant stream, said combined major and minor streams after heat exchange forming said warmed return cryogenic fluid stream.