Refrigerated Liquid Hydrogen Targets at the Zero Gradient Synchrotron

Commercially available helium gas refrigerators with capacities of 5 and 10 W at 20?? K are being used at the Argonne National Laboratory´s (A N L) Zero Gradient Synchrotron (Z G S) to condense hydrogen gas for liquid hydrogen targets. Excellent reliability of operation has been obtained. A standard, universal system has been designed and duplicate systems have been constructed to meet the increasing demand for additional targets. Increased safety has been achieved by reducing the amount of hydrogen at the experiment site. Decreased cost of operation has also been realized. The system design discussed in this paper has been used on small (2 liters maximum) liquid hydrogen targets only. A system design using a remotely located cryogenic helium gas generating refrigerator has been proposed. Such a system would have larger capacity and should be applicable to almost any size liquid hydrogen target.