[Hallc_running] Hall C laser

Jay Benesch benesch at jlab.org
Tue Mar 17 14:50:48 EDT 2020

In the hope of reducing activation in CEBAF, based on Tiefenback's slit 
reduction test and the chopper viewer image, the B Team has decided to 
have CIS swap the B and C laser seeds on Thursday morning. The laser 
seeds are upstairs and fed to the downstairs amps via fiber so this 
should be an easy change.  This will affect A and D beam delivery. 
We'll see what it does to C when CW beam is restored.  We'll learn 
whether it screws up B beam Friday when that hall returns so we can back 
out if necessary.  It is expected that, as with Mike's test, the narrow 
B slit will eliminate consequences  of the long pulse for B.

If it works, A2 interception will remain stable, arc BLMs will be 
quieter, and the X shoulder on the C beam at 3H07 harps will be gone.

After discussion, my proposal to change C beam optics was cancelled.

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