[Hallb-engineering] Beam line vacuum

Denny Insley dinsley at jlab.org
Fri Nov 20 14:59:07 EST 2009

Hi all,

    Thought I would give everyone a heads up on this just in case you 
have to deal with it. With the beam line configuration that we have now 
there is a possibility that you may have the valves 2H00 and 2H00A close 
without apparent reason. This valve set will not function without a 
coincidence downstream of them. Usually this would come from the Saclay 
targets vacuum gauges.  Since the Saclay target is not installed and the 
valves are I had to provide a signal for these valves.  One of the 
gauges is located on the DVCS vacuum jacket and the other is on the 
transfer line from the buffer dewar.  So far there have been two 
instances where the valves closed.  There is a GFCI outlet mounted to 
the side of the turbo pump unit located next to the buffer dewar which 
has tripped once.  If this is the problem just reset the GFCI and start 
the pump back up.  You should be able to open the valve in just a couple 
of minutes after the pump is restarted.  The other problem occurred 
during a cryo recovery.  Temperature changes in the transfer line cause 
changes in the vacuum jacket therefore the valves close. Once recovery 
is finished you should be able to hit the reset button on the vacuum 
panel and open the valve.  However I would suggest a little caution 
there. I don't know how vacuum tight the downstream beam pipe is and we 
don't have anyway of knowing what kind of vacuum is there.  So if it has 
been an extended recovery we may need to consider bleeding up that 
section of beam line before opening the valve.  If anyone runs into this 
problem and needs a hand feel free to call me and I will come into help.


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