User name paschke
Log entry time 10:02:59 on August 1,2003
Entry number 108433
Followups:
keyword=PITA scan, Charge Asymmetry controlledDuring the night, the charge asymmetry became poor (few hundred ppm).
The IA system was railed ("DAC setpoint" on the runbird GUI was 0 or 10),
meaning we'd run out of dynamic range to control the drifting charge asymmetry.
We had previously decided that when/if this happened, we'd ask for the missing
RHWP to be inserted in the source. This plan we discarded for a much easier and
much better option: using the PITA sensitivity to correct the charge asymmetry.
A PITA scan was done, with IHWP OUT (also RHWP out, which will probably
change during next weeks maintenance). At the start of this study, charge
asymmetry feedback was turned off and the IA cell was set to 5 Volts.
Run 3731
DeltaV HV+ HV- EvLo EvHi
0 7.383 7.518 2 2200
200 7.883 7.018 4800 6800
-200 6.883 8.018 7900 10000
Results of the scan are shown below. Charge asymmetry should be zeroed with
DeltaV = 180V. New setpoints are PC-POS=7.830, PC-NEG=7.071
This scan will need to be repeated when the IHWP is inserted. PC setpoints will be
set for each IHWP state, and noted in a later halog entry. Feedback was turned back
on at the end of the study. Charge asymmetry is well controlled.
FIGURE 1
