Since Tuesday night we did put 40 uA on lh2 target.
First
we measured the ion
chamber det reading at differents beam current and established a trip
point associated with it. The trip point is now set at 8 kRad on
a full scale of 10 kRad. Then we started the gain calibration. A
few channels were found missing, but mst noticeably the TDC associated
with MT octant 4 and 8 gave so confusing results that the calibration was
aborted at that time. The proton
data have confirmed the lost of gain in the pmt observed last month
with cosmics. This is not an issue for this run but would be one if the
phenomenom continues before the backward angle. this night and
morning
the second iteration of gain matching was performed. Adjustement
is completed for octant 1,2,3,5,6,7. The results for octant 4 and 8 are
puzzeling : after the first idata taking, correction factors were
determined
and applied to adjust Hv to the desired amplitude. The data from
the second iteration show that the same factors should be applied to the
same tubes to bring the signal to the target amplitude. something is
fishy...
To be able to progress in the turn on, teh have decided
to wrok temporaly only with the octants we are confident with. At this
precise moment, Herbert is checking that the anode currents with 40 uA
beam are compatible with a stable gain over time. first reports show it
should not be a problem (like last year).
On the afternoon, Jianglai perfomed the check out of the luminosity monitors as well as the calibration of the bcms. Online Jianglai noted that the variation of the width of the lumi asymmetries seems to indicate a local boiling of the target. That does not surprised me because I was asked twice by R. Kazimi if the tiny spot size on target was ok for us. Jianglai swill analyze his data and if he confirm his analysis we will ask MCC to enlarge the spot size. The PD says that should take 2h of tuning.
We have taken parity quality beam data at 40 uA or the maximum beam current that the machine can deliver as part of the feedbacl we will provide to MCC to help them setup our beam. Kaz is going to maintained a summary under this page . The goal is to see how are dispersed the differences in positions when maintaining running conditions equals over time. The conditions are : ask 40 uA, allor a maximum of 0.5 h tuning then take the maximum current available. Run 0.5h of beam data with fast feedback on, position feedback off and PZT voltage =5V for both directions.
The program for the next 24 h :
- finish anode current measurements for 40 uA
beam
- take ~ 5 h of TE data
- maybe increase beam spot and take a new
luminosity
scan in current
- commission fly-swatter
- do luminosity monitor scan on fly-swatter
- if beam spot size increase is succesfull, start
dead-time
measurement
your RC,
Julie Roche
A copy of this log entry has been emailed to: ent,oren