[Clas12_rgb] experiment news

[silvia at jlab.org]

Dear all,
as you will soon read officially from the PDL, all RG-B shifts are
canceled from today at 9AM until at least owl shift on Thursday. The
reason for this is the following: the accelerator has been struggling in
the last week to deliver ~10.6 GeV energy. The trip rate is very high, and
down times are extremely frequent. As an example, we basically managed to
take two runs since beam-studies ended yesterday at noon and this morning.
In spite of our effort to fight for the maximum energy (which is crucial
for the J/psi experiment), this morning we were told that the accelerator
will lower the energy down to 10.2 GeV, in order to see if the
performances improve. They will work on this until the end of Thursday day
shift.
This means, in a very optimistic view, 2.5 days lost, and, in a more
realistic view, at least 3 if not more.
I asked the PD this morning, he says that the 2-pass RF seperator test
planned for today will still be carried on. However, there are chances
that the Monday and Tuesday down times for beam studies and RF recovery,
that should have accomodated the energy-change to go to 2-passes for BAND,
may not happen.
Considering the amount of time we have lost until now for beam-related
issues, trip rates, down time, the lost day of this past weekend, two 3
days lost from now to Thursday, and the two days likely lost on March
18-19, I personally feel that fighting to keep up the plan of running at
low beam energy on Monday 11th is not a good idea. If accelerator proposes
us to cancel all interruptions and get normal beam instead, we should go
for it.
The PD will inform me of the outcome of the RF-separator 2-pass test
probably by lunch time today.
I would like to propose to find some time to discuss this afternoon with
the BAND group to understand how crucial this low-energy run is for the
time being, the possibility to postpone it to the fall, etc.
Please let me know if/when you are available. Given the current stop of
the experiment, my own schedule is pretty flexible.
Best regards,
Silvia