[Primexd] PrimEx RC update

[Justin Stevens]

Dear Collaborators,

On Friday morning we completed the empty target running to be compared with the Be target data collected last week.  In total 2.8 billion triggers were collected with Be and 0.6 billion collected with an empty target for background subtraction. 

Beginning Friday at 6 am the beamline was bled up and LHe target installation proceeded through the rest of the day and completed around 7 pm Friday night.  The target was surveyed, start counter attached and signals checked, and the target and beamline were pumped down.  Thanks to the crews that stayed late to get us ready for beam on Friday.  Unfortunately, late Friday night through Saturday night the accelerator dealt with vacuum issues due to malfunctioning valve.  Thankfully, yesterday evening the valve was successfully bypassed.  We’ve been collecting production data with the empty LHe cell overnight and will continue like this until tomorrow (Monday) morning.

On the target front, the LHe target cell has been cooled, however the vacuum is not at the expected level and there is a concern this could lead to the formation of an iceball.  Yesterday, Chris Kieth checked with the leak detector https://logbooks.jlab.org/entry/3662109 <https://logbooks.jlab.org/entry/3662109>, but couldn’t identify a particular source of the issue.  Investigations of the target are planned to continue with an access on Monday starting at 8:30 am, synchronized with the start of beam studies. 

Justin, Hall D RC
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