User name LeRose
Log entry time 14:44:32 on May 09, 2008
Entry number 237849
This entry is a followup to: 237848
Followups:
- 237850 05/09/08 17:30 LeRose Left Arm Dipole NMR studies Probe A vs Probe D
- 241951 07/15/08 11:51 LeRose Left NMR Probe A
Finished with left arm NMR studies. Here's a summary:
5/9/08 (left-nmr-tests.txt - JJL)
Tests of Left NMR
Po set = 1 GeV/c (was 0)
Probe A quickly gets lock and settles in.
11:57 switch to probe B (no change- good)
12:02 switch to probe D
Field changes at NMR but P0 remains correct,
magnet current and Hall field stay the same (good!)
12:07 switch to probe E (again good)
current=332.52
12:12 back to A
current=332.47 (1.7e-04 change)
12:16 back to B
current=332.50
Above summarized in plot (probe-switchABDE.JPG)
12:26 back to A
Meter doesn't go into "search mode". Control panel says it is,
but it isn't.
Pushing search OFF then search ON doesn't help.
Changing the DAC# doesn't help.
Going to manual mode, tuning the DAQ# to the correct value,
then going to AUTO doesn't work (positive and negative polarities)
Probe A does go into search mode but gets hung up in the 0.26-0.28 T
range.
13:12 going down to zero
13:21 P0=0.65 Probe A has problems (stuck in the same band)
13:26 switch to probe D. It goes into search mode and finds the lock.
13:31 P0=0.75, controls switch to probe A, same problem
13:33 switch to probe D. Locks in ~one minute.
The AC Power Switch for the Left Arm is hareboot17, port 8. Try this.
No help.
Reboot left arm controls. Still the same.
Probe D works fine.
Switch back and forth between A and D a few times at 0.751 GeV/c.
D works fine. A does not.
Conclusion:
There's something wrong with probe A, possibilities include:
Simply a bad connection easily fixed by unplugging it from the
multiplexor box and plugging it back in. (This is not really
easy. The multiplexor is inside the dipole.)
Could be a bad channel in the mutliplexor. There are two spare channels,
We could use a diffent channel. (Again access is a problem.)
The probe itself could be bad. (We're still inside the magnet)
...
Long term solution: Investigate/repair the above possible problems during
the long summer down.
Short term solution: use probe D in place of probe A. The cross calibration
is OK at better than 2E-04. Will carefully analze the data from the strip
charts to get a better evaluation the 2E-04. D is a better choice than B
because B won't go as low as D (D is identical to A but on the opposite side
of the gap).
Javier will try to have the controls changed to default to D rather than A,
Making the problem transparent to the user. Users must, however, be
aware of the change if they want to interpret B as measured with
the NMR as a value of P0.
A copy of this log entry has been emailed to: gomez@jlab.org
Figure 1
