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User name folts
Log entry time 20:23:27 on April 9,2000
Entry number 38463
keyword=cryo problems
what it appears to me to have happened at approx. 1530, is that during the change from 15K to 4 K in the cryo target, the LHe system was over presurized causing the relief valve on the Hadron Q1 magnet to vent. This valve vented long enough for ice to form blocking the closure of the valve. This in turn cooled the ball valve O rings to freese causing a larger leak. This leak sprayed LHe onto the other valves in the same proximity causing other leaks. This is what we found on arrival. I requested that cryo close the supply valves for the LHe and LN2 to the Hadron arm. Once this was done we were able to warm up the valves and stop the leak. In stopping the He flow to the Hall we caused a heat load to ESR and created an instability in the cryo system. At this time the system is now as stable as is was prior to the event.