New developments in cryo-targets for the external COSY experiments

Abstract

For cooling the liquid hydrogen/deuterium target from room temperature to the operating temperature (15 K/19 K) until recently a long solid copper heat conductor and a short heat pipe was used between cooling machine and the target cell. Recently, a new target version with metallic heat conductor of minimal length and a long gravity-assisted heat pipe section was constructed. The target material is used as a heat transport medium and high heat transfer is achieved by liquid-gas circulation. This design drastically reduces the weight of the system to less than 10 g in the 32 cm long standard geometry as compared with the previous copper heat conductors of 600 g. Uncontrollable secondary interactions are thus avoided. The cycle time of cooling down or heating up is reduced. The characteristics at steady-state operating conditions of the new 32 cm heat pipe–target system have been measured for hydrogen, deuterium, nitrogen and methane as the working fluids. Also successful was the development of a 2 m long heat pipe–target system (diameter 1.6 cm) needed for future experiments. It has less than 60 g weight and a cooling down time of 5 h.