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PREX Main<< HOW TOs << Expert Tools
See also: Harp Scans
- BPM Calibrations (Bullseye Scan, 1-2 hours)
- BPM pedestal run (20 minutes)
- How to use these to calibrate the BPMs.
How to perform a bulls eye scan:
1. You need unrastered, stable beam:
- This must be completed in phase 1! - Target/trigger doesn't matter here. Use clock trigger, adjust PS8 to get high rate - run both arms
2. Ask MCC to steer the tbeam to the nominal center of the target.
3. Wait until beam is stable and have MCC perform a harp scan for the two superharps near the target (1H04A and 1H04B) and take a CODA run for both the left and right spectrometers during the same time. Start the coda run first before asking MCC. Request MCC to make an ELOG entry with the Harp results, you should see all three harp wires. Record ELOG entry numbers and timestamps of both harpscans. Take each run for ~50k events.
You can bring the harp fitter up from JMenu (JMenu > Operations > Harps > Harp Fitter Tool)
Left top corner menu > Harp Selection > HALL A
4. Ask MCC then to steer the beam to positions around the nominal center:
- cover at least the area the raster will cover: (2,2), (2,-2), (-2,-2), (-2,2), and repeat (0,0) - repeat harp and CODA runs for each position
5. Record Harp scan run numbers and corresponding CODA run number for each beam position. As an example, see HALOG # 3324009.
6. Make a record of the harp scans and CODA runs in the HALOG.
How to analyze the bulls eye scan:
- detailed instructions can be found at the Analyzing BPMs website. - the shift crew is not expected to analyze the bulls eye scan.
Bullseye scan 06/21/2019
This scan was taken with position lock on, and was not used for calibration.
|Position||LHRS coda run||RHRS coda run||Harp entry no||Harp A timestamp||Harp B timestamp|
|(0.6,0.4)||1448 (2745 Parity run)||20586||3690856||6/21/2019(3:51:26)||6/21/2019(3:53:08)|
|(2.6,2.4)||1450 (2747 Parity run)||20587||3690869||6/21/2019(4:03:02)||6/21/2019(4:04:01)|
|(2.6,-1.6)||1451 (2748 Parity run)||20588||3690877||6/21/2019(4:13:28)||6/21/2019(4:14:37)|
|(-1.4,-1.6)||1452 (2749 Parity run)||20589||3690885||6/21/2019(4:21:22)||6/21/2019(4:22:28)|
|(-1.4,2.4)||1453 (2750 Parity run)||20590||3690891||6/21/2019(4:29:11)||6/21/2019(4:30:08)|
Bullseye scan 06/22/2019
This scan was used for BPM position calibration. The Harp B scan for (2, 2) was missing, so we just used the results of the fit from (2, -2) for the x position and (-2, 2) for the y position.
|Position||LHRS coda run||RHRS coda run||Harp A entry no||Harp B entry no||Harp A timestamp||Harp B timestamp|
Bullseye scan 08/09/2020
This scan was used for BPM position calibration (Bullseye scan). CREX target nominal center point is (-0.3,-1.5), the scan want to cover at least the area of the raster coverage (2x2). We need two harps(1H04A and 1H04B) scan for each point, which is listed in the bellow table.
- Move target to ops target = carbon 2% target, production target= Home
- Set the Counting DAQ Trigger scale factor to L_PS8=1 (LHRS) and R_PS8=1(RHRS)
- Call MCC to request unrastered beam current I=2uA ( cross check the target to request raster off ). Ask MCC to move the beam to the position listed in the bellow table one by one. E.g. Starting with the first point (X,Y)=(1.7,0.5), and look at the strip chart or HallA tool to make sure that the BPM IPM1H04A and IPM1H04E locked position is right)
- If the position is stable, turn on the CODA for both LHRS and RHRS counting DAQ.
- While the target operator starting the CODA, RC need to Call MCC to request two harps scan (1H04A and 1H04B harps) at the current position (E.g..(X,Y)=(1.7,0.5)) and ask the MCC operator to post the harp scan results on the HALOG too.
- Check the HALOG to make sure that the harp scan results are acceptable, otherwise you need to ask MCC to redo the unacceptable harp scan. Here is the example of the good harpscan https://logbooks.jlab.org/entry/3748443
|Position(X,Y) IPM1H04A, IPM1H04E||LHRS coda run||RHRS coda run||Harp A entry no||Harp B entry no||Harp A timestamp||Harp B timestamp|
BPM pedestal run
The following runs were used to find the pedestals: LHRS Run #1518, RHRS Run #20657
- Ask MCC to set iocse10 to Forced gain = 0.
- Take CODA run for both Right and Left arms.
- Use only clock triggers. T8=100
- Need about 100k events.
- Ask MCC to set iocse10 back to auto gain.
- can be located at /cs/opshome/edm/bpm/diag_see/IPM_E_GainCntrl.edl