[Hallb-engineering] [Revised Logentry] Saclay Target

[kashy at jlab.org]

Logentry Text:
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Bob called in and asked me to change the set point of the Target from 20.65 to 19K. I did so but it the control for JT_2K did not react. I called him back and we agreed to set it to 20K. The valve still was not working well.  It appears that JT_2K, ( the liquid helium vavle to the condensor) is getting stuck. To free it up I just make a manual change and it jumps open. It may be that the air pressure is low or maybe the valve needs servicing.

An additional issues appears to be that there is a plug in the piping between the target and the gas tanks. This is keeping from loading up the condensor with lots of gas to liquify. The oberservation is that PT_T drops fast when LHe flows to the condensor and way below the tank pressure, and then goes above tank pressure when the condensor warms. This could be dangereous to the cell as I saw the temperature drop to 14. 3K breifly (very near the freezing point of H2 and this is coborated by the PT_T dropping to ~100mBar

Dave

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