User name R. Michaels
Log entry time 12:03:24 on November21,2005
Entry number 160878
keyword=Q2 ETC at low-ISwitched to spectr DAQ run 3116. Purpose is to study Qsq,
low current monitors, and background and very low current.
I = 0.5 uA
Rates
T1 = 330 kHz
T2 = 250 kHz
T3 = 300 kHz
T4 = 250 kHz
T5 = T6 = 0
T7 = 286 kHz
T8 = 400 kHz
11:32 End run 3116. Ask for 0.1 uA. Rates:
T1 = 73 kHz
T2 = 55 kHz
T3 = 58 kHz
T4 = 56 kHz
T7 = 76 kHz
T8 = 93 kHz
Run 3117 at 0.1 uA
Observed that some R-arm S2 voltages were off. Turned them
on during run 3117.
Next, a position scan at 0.1 uA
Run 3118: Starting at event 250K, MCC will make deliberate
beam movements. Relative to our present X,Y = (0,0) although
it does not read (0,0), MCC will go to (-2,+2), (-2,-2), (+2,-2)
and (+2,+2) and wait 2+ minutes at each one during the run.
Note, the first 250K events of run 3118 are a good Q2
measurement. See fig 1 for 200K events.
11:55. End of run 3118. Turn things over to Dave Meekins who
will bleed up the target, etc.
My tentative conclusions about low-I mode of BPMs
1. Low-I mode work as well as normal mode at I >= 0.5 uA.
2. For 0.1 < I < 0.5 uA, the low-I mode is better than nothing but
the readings have large offsets. They might be good enough for
a relative position (need to check).
3. For I < 0.1 uA, I would not trust beam position measurements.
Note, the script "getbeam" mentioned in halog 160864 has been
running continuously, logging EPICS BPM data. File saved as
"~apar/epics/bpm_21nov05_save.out".
FIGURE 1
