[clas_members] RC summary for Tuesday February 28

silvia at jlab.org silvia at jlab.org
Tue Feb 28 10:34:32 EST 2023

Day shift (Monday):
Production data taking on ND3 at 4 nA, 35M events collected.
Beam goes off at 10:30AM when the South Linac drops to Restricted Access.
We exploit this by anticipating the change of target to CD2.
Beam back at 13:30, beam tuning, started Moeller run, aborted half way
through as SL drops again to RA.

Swing shift (Monday):
Beam comes back at 19:30, we start taking Moeller runs, at 4 nA as
suggested by Stepan in the Hall-B meeting of Monday morning. The results
we obtain for different configurations are not compatible:
- Negative Helmoltz polarity, left target: (-84.2 +/- 1.5) %
- Positive Helmoltz polarity, left target: (71.5 +/- 2.1) % (we stopped
the run before it reached 1.5 of uncertainty as the result was clearly
differing a lot from the previous one).
- Positive Helomltz polarity, right target: (81.172 +/- 1.733) %
(These tests were done under the guidance of Eugene and Nathan via zoom)
We did not fully understand what the problem was. At MCC meeting today it
was said that Hall A Moeller measurement gave ~84% of polarization, so it
seems like our first measurement could be the good one. These
discrepancies in our measurements need to be understood.
Beam was lost during further Moeller tests, and it was decided to resume
data taking once it would come back.
Started production data taking at 10:30.
19.5 M events on CD2 collected.
Minor alarm on LTCC gas, experts were informed.

Night shift (Tuesday):
Beam was unstable all night.
DC trips, LTCC gas problem clears.
65 M events collected on CD2.

Day shift:
Taking data on CD2 at 4 nA, 55M events collected by now.

The plan is to continue this way until tomorrow at 8:30AM, when the beam
will go off (until 3PM). The target group will come in at 8:30AM to change
to ND3 and repolarize (positive).

We'll have our RC meeting at 2PM.
RC Meeting Coordinates:
Meeting ID: 160 867 4253
Passcode: 786506

More information about the clas_members mailing list