[Halld] Update on commissioning

[Alexandre Deur]

Dear collaborators,
 
Friday afternoon, accelerator produced a very good initial beam tune for Hall D. So we were hopeful to have a smooth and productive week-end but this had not been the case so far. The beam has been rather unstable, starting later in the afternoon of yesterday. There has been no usable beam since 4am. This was still good enough to enable the initial photon beam setup, allowed Alex Somov to advance the trigger commissioning and Lubomir to start gathering a bit of  straight tracks for the drift chamber alignment. There seems to be several problems but a leading one appears to be that there was no high current beam in the accelerator. A high current beam is necessary for the fast-feedback to maintain the proper orbits in the machine. This current is provided usually by Halls A (or C) but Hall A ran at low current yesterday for its Moller polarimetry and was down several hours today for some detector works. With Hall A now back up, we may hope that we will get back a usable beam. During last Fall when only Hall D was running, with low current, this was not a problem because accelerator was able to set-up a witness beam to enable the fast-feedback. Presently, this cannot be done because there are only 3 lasers available at the source, each one used by one of the 3 halls.
 
Best regards,
 
Alexandre Deur, Hall D Run Coordinator.
 
RC cell: 757-383-5542
Office Phone: 757-269-7526