Spot++

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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:

1. Take the spot++ run
2. Analyze the run
3. Make the plots and post to the logbook

How To Take a spot++ run

Detailed instructions from halog 3711297

1. Stop Parity DAQ, turn off beam modulation and Aq feedback.
2. 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
     1. Ask MCC to turn off "slow lock" (=4A/4E lock), and enable "cavity lock" on 4B/4D
     2. 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)
     3. 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).
     4. 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
3. 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)
4. 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)
5. 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
6. 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.
7. 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

1. 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
2. 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
3. When prompted, type y to upload the plots to the halog or n to skip this step

More Info

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.C
  • raster_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, ymax are 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