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Description:
A liquid hydrogen/deuterium target is used at COSY of the FZ-Rilich in the external experiments TOF, GEM and MOMO. The combination of Imm diameter beam from COSY with the small target provides the necessary very well defined interaction vertex within few mm$^{3}$. The target liquid is made on a cooled condenser and guided through a central tube assisted by gravitation into the target cell. There the liquid is kept below boiling temperature by evaporation cooling. The vapor rises up to the condenser through a very well isolated concentric center tube. This circulation provides a stable dynamic equilibrium . The target container should have as small as possible material between the reaction volume and the detectors in order to minimize secondary interactions of reaction products. In order to reduce unnecessary material, a very thin target cell is fabricated by galvanization technique. An aluminum condenser is now used instead of copper. This decreased the material from 100 g to 20g. It provides better thermal properties and performance . The cool down time from 300K to LH$_{2}$/LD$_{2}$ is improved to 38 minutes instead of 52 minutes for copper. A 7mm-diameter HP (heat pipe) has been developed instead of the previously used 16mm-diameter one. The diameter of the condenser part stayed 16 mm to keep enough condensation area. The HP material was decreased to 70%. The cool down time of the 7mm HP is reduced to 8 minutes instead of 18 minutes for 16mm HP. The 7mm system has lower heat capacity, higher heat transfer rate, lower heat radiation from the surroundings due to the smaller surface and higher vapor speed that makes the HP response to the thermal load changes in the evaporator area faster and more sensitive. For the TOF and WASA applications at COSY, a 200cm long-7mm diameter HP is developed and tested under the maximal filling condition (9.45 liter at 228 mbar) with our 4 working gases. The cool down times are 107, 200, 54 and 38 minutes for H$_{2}$, D$_{2}$, N$_{2}$ and CH$_{4}$ respectively from 300K until ...