Spot++
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Revision as of 16:27, 31 July 2019 by Juliette Mammei (talk | contribs) (→How To Take a spot++ run)
PREX Main<< Information for Shift Takers << Shift Leader << HOW TOs
Description
Performing a spot++ allows us to "image" the target or raster size by plotting the hits as a function of raster x and y current
- CASE 1 If you run with T1 or T2 trigger and target in place, spot gives a view of the target density
- CASE 2 If you run with pulser trigger T8, spot gives a view of the rastered spot size
The steps involved in doing this measurement are:
- Take the spot++ run
- Analyze the run
- Make the plots and post to the logbook
How To Take a spot++ run
Detailed instructions from halog 3711297
- Stop Parity DAQ, turn off beam modulation and Aq feedback.
- Prepare to use low current beam position monitors (4A/4E lock won't work with low current)
- Ask MCC for 1uA current
- Record the x/y positions of BPMs IPM1H04B and IPM1H04D at this current (with target position lock on 4A/4E)
- Ask MCC to disable FFB
- Switch to locking on 4B/4D at the exact positions noted above
- Ask MCC to turn off "slow lock" (=4A/4E lock), and enable "cavity lock" on 4B/4D
- Give them the values found above to be used as setpoints. Note that MCC operators are sometimes unfamiliar with how to establish "cavity lock". (This must be enabled on a special screen called Generic PID Lock)
- Verify that the 4A/4E position readbacks have not changed significantly from where they were before (check white board for current values, x/y 0.2/-0.5 and 0.2/-0.5 as of 7-31).
- If they have moved, you can go ask MCC to undo the cavity lock and to put them to the desired locations and reset the lock
- Ask MCC to send ~20nA beam
- You will have to give them the attenuator and slit settings (look in halog for settings used in last spot and start there)
- The 4A/4E BPM signals will disappear
- Hall current will read 0.00
- Monitor the 4B/4D positions (they will fluctuate more as relative noise levels are higher)
- Set up the detectors for taking the spot data
- Turn S3 scintillator HVs on for both arms. These are connected to channels L0.2 (S0 tab) in the HRS HV control panels.
- Turn on other scintillator paddles and/or VDCs if requested
- Observe the S3 trigger rates in the scaler GUI. Aim for less than 100 kHz.
- If S3 rates are too high, ask for a lower attenuator setting (usually 1 tick is ~50kHz - go slow)
- While the shift leader was performing the above, the target operator should prepare the HRS DAQ
- Take a test run to make sure things are working while the beam is being set up
- Take at least 50k events for a quick spot, but for a target uniformity spot ~1M is better
- End CODA runs
- Back out of the spot run
- Turn S3 HVs off
- Ask MCC to set attenuators back to nominal setting and deliver 1 uA of beam.
- At 1uA, ask MCC to turn off "cavity lock" and re-enable "slow lock" on BPMs 4A/4E using positions on the white board (x/y = 0.2/-0.5 and 0.2/-0.5 currently)
- Log the history of 4A, 4B, 4D and 4E BPM positions during the entire above procedure.
- Unless otherwise instructed, go back to production running
- Go to 70 uA.
- Ask MCC to re-enable FFB. This may require gain searching.
- Once FFB is stable, re-enable beam modulation and Aq feedback.
- Start a parity run
How to analyse the run
- Log into the a-onl account
- ssh –X aonl@aonl2 –l a-onl# Then type either:
- spot_L run# for the LHRS (Recommended)
spot_R run# for the RHRS
- If no run # is given, analyzes last run taken
- Plots should pop up after a few seconds
- The most important plot is on the first page, titled "beam on target y vs x", see, for example RHRS run 21079
- When prompted, type y to upload the plots to the halog or n to skip this step
More information
Making plots for long Runs
Most of the time we just want the normal length of spot++ run, which is 50k events. But occasionally we want to take a higher statistics run, and the spot default is to only analyse 50k events. However, a command like:
spot_L run# firstEvent lastEvent
will analyze the events in the specified range.
This will output the .pdf to the logbook in the same way as above.
raster_check.C
An additional way to make plots is to use the raster_check script.
- go to the /adaqfs/home/a-onl/rastersize/ directory
- open root
.L raster_check.Craster_check(<1 or 0>,run#)(1 for LHRS, 0 for RHRS)- This version of the function creates a single plot of the map of the raster at the target. This plot as well as the rest of the macro uses the Raster2.rawcur
- If this is done on the carbon hole target, you should see the hole on the plot. Make a rough visual estimate of what the bounds of the hole are on both the left and y axis
raster_check(<1 or 0>,run #,xmin,xmax,ymin,ymax)(1 for LHRS, 0 for RHRS)xmin,xmax,ymin,ymaxare the bounds on the carbon hole target from the 2D plot above- This function creates two plots, profile plots of the 2D raster map. Each plot has three different fiducial cuts applied in order to estimate the hole position better.
- By zooming in on the x-axis of each plot and using the Event Statusbar, estimate the point on the x-axis of each plot where all three histograms overlap each other, on both sides of the hole.
- To estimate raster size from the profile plots calculate 2*(max bin - min bin)/(max histogram overlap point - min histogram overlap point). Do this independently for both x and y.
raster_check(<1 or 0>,run#,0,100e3,0,100e3)(1 for LHRS, 0 for RHRS)- This function creates the profile plots like above but applies no fiducial cut to the histograms. This is best when looking at spot runs on the production target.
- Post these plots to the halog if desired
More information about spot++
- Hint: Type "spot help" to learn more options for spot++
- spot++ output files go to:
/chafs1/work1/spot/
- For experts - macros, source codes, DB files are at:
/adaqfs/home/a-onl/rastersize/
- You can get "strange printouts" of errors if you only type spot++ and the last run was for R-HRS because spot++ is aliased to spot_L
What do the plots mean?
Need to put examples of output when we have them
BPMA y vs x: Shows the beam location at BPM A
BPMA x: Shows the number of events at each x value in BPM A
BPMA y: Shows the number of events at each y value in BPM A
BPMB y vs x, BPMB x, BPMB y: Same as above but for BPM B
Beam at target y vs x, …x, …y: Same as above for at the target
BPMA Antenna 1, 2, 3, 4: Signal at the four wires of BPM A, one for X+, X-, Y+, Y-, respectively
BPMB Antenna 1, 2, 3, 4: Same as above but for BPM B
Cavity BCMs
- Low Current running Cavity BCM nominal points
- The cavities are used in <0.5 uA running territory (for commissioning a lead target with spot ++ check)
- Bob's EPICs variable printing to terminal script:
ssh apar@adaq ~/scripts/showCav.C
