Detecting contamination of a cryogenic refrigerant in a cryogenic refrigeration system

A sensor system for refrigeration system, said sensor system comprising:

• an inlet for coupling to a refrigerant flow path in said refrigeration system;
• a thermal conductivity detector in fluid communication with said inlet, said thermal conductivity detector being configured to generate a thermal conductivity signal indicative of a detected thermal conductivity of said refrigerant received from said refrigeration system when said sensor is coupled thereto;
• circuitry configured to convert said thermal conductivity signal to an indication of contamination of said refrigerant based on the thermal conductivity signal being produced after warming of the refrigeration system caused the refrigeration system to release contaminants and while the contaminants are in the thermal conductivity detector;
• and
• an output configured to output said indication of contamination of said refrigerant.