Closed-Cycle Refrigerators for Hydrogen Targets

Abstract

Hydrogen targets for use in high-energy nuclear experiments are usually filled by bulk hydrogen or hydrogen liquefied by the vaporization of liquid helium. Bulk hydrogen systems are hazardous in that large quantities of liquid for makeup must be maintained. A closed-cycle refrigeration system offers an important safety advantage in that only the quantity of hydrogen actually needed to fill the target would be required; and also it would be less complex. In addition, a reliable refrigerator running remotely without operator attention for long periods of time would reduce exposure of personnel to radiation hazards. A development program was, therefore, started to investigate the interface and operating problems, and the characteristics of hydrogen targets cooled by a closed-cycle helium refrigerator.