Mott Run 1 Journal

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CEBAF_MeV_Mott_Polarimeter

Shift Summaries

Blank Template - media:MottRun1Database.ods

Wednesday, Jan 14
Thursday, Jan 15
Friday, Jan 16
Saturday, Jan 17
Sunday, Jan 18
Monday, Jan 19

Experiment Goals and Plans

Tasks which have been studied or completed are shown below in bold face.

Prep Work (through Tuesday Jan 13)

  1. Make a photocathode – SL5247-1 made about ~one week ago; QE low at low bias but ~1.8% at 130kV
  2. Test IHA2D00 – the Aurora card was replaced to fix POT sampling and CAMAC wiring fixed for gain
  3. Hi-Pot IP – 3D01 hi-potted, but still bad so moved to Dig#11 holding supply and 3D00 on Dig#12 monitors beam line only
  4. CHL 2K cooldown – 1/13 successful cool down completed
  5. Install laser – first beam test of Hall C laser with division by two rep rate
  6. Test laser RF trigger – Riad is using Hall A laser as reference; appears to be 499/2^N
  7. Verify beam line layout – completed
  8. Build elegant deck – completed and stored at ~grames/elegant/MOTT/
  9. Build qsUtility config file – completed, see below...

Injector Setup and Mott Checkout (Wed Jan 14 - Fri Jan 16)

  1. Restore beam to FC2 @ 6.3 MeV/c - 1/14 task was completed and summarized in link title
  2. Mott test: DAQ FADC/TDC synchronization and event separation with 62MHz; there is a TDC issue that prevents 62MHz so we use 31MHz with 31MHz trigger
  3. Electron bunchlength and transmission from 0-10 uA
  4. Tested harp IHA2D00 and it works
  5. Scale cryounit for p=5.487 MeV/c and minimize energy spread - 1/14 see entry for link initial setup
  6. Tried bunchlength script - didn't coverge, but looks like with more time can work
  7. Calibrate BCM to FC2; Media:BCM-calibration-slope16jan15.ods
  8. John improved the laser polarization and measured the Hall C laser spot size

Mott Setup and Systematics Testing (Sat Jan 17)

  1. Setup good orbit to Mott here
  2. Set PMT HV here
  3. Set PMT energy thresholds are here
  4. Finally we setup the polarization horizontally; initial "rough in" and the final here
  5. Calibrate PITA vs IHWP IN/OUT
  6. Finalize orbit w/ instrumental asymmetry, TOF and spectra
  7. Adjust target offsets per vertical instrumental asymmetry measured, analyzed, and corrected with new offsets media:New_Ladder_Position_Swing16jan15.ods
  8. Measure dump rate fraction to determine run times, Media:Dump_vs_Elastic.ods
  9. Measure asymmetry vs. dead-time and beam current Media:Deadtime_spreadsheet.ods
  10. Measure asymmetry vs. spot size (included emittance measurement and Elegant optimization)
  11. Measure asymmetry vs. energy spread (includes harp scans, see e.g. here
  12. Precisely measure beam momentum (includes BPM quad centering)
  13. Measure asymmetry stability vs. time (by virture of the 1um Au tests interleaved w/ target foil extrapolation)

Target Foil Extrapolation (Sat Jan 17 - Mon Jan 19)

  1. The list of targets and some description is describe in this entry
  2. We are planning to interleave two 1um ~1uA (~15% dead) runs of IN/OUT between each foil
  3. Test each new target foil to determine if energy spectra are good/bad. If not acceptable or don't want to try, move on to next one, make log entry...

Procedures

How to contact people

Joe's cell 
757-344-0188
Riad's cell 
757-254-7895

How to reach the Mott logbook

Mott logbook is here

How to know who's on shift

140112 shifts.png

How to be a shift worker

Beam Driver = Shift Leader
  1. Control delivered beam, especially adjusting PITA with IHWP=IN/OUT
  2. Make sure FSD (BCM, Target) protection is used
  3. Monitor beam loss and vacuum levels
  4. Save and document settings
  5. Write shift summary in logbook
DAQ Driver
  1. Configure/Start/Stop DAQ
  2. Monitor event rates and maintain dead time <5%
  3. Coordinate run start/stop
  4. COPY run information into standard excel sheet
Analysis Driver
  1. Decode, analyze and inspect runs
  2. COPY run information into standard excel sheet
  3. Determine number of events needed for IHWP=IN and OUT

How to measure emittance

Beam Setup
  1. We measure the beam emittance and Twiss at entrance of MQJ0L02 by varying MQJ0L02 and observing response on harp IHA0L03
  2. To simplify matters we turn off the intervening quadrupoles (MQJ0L02A = MQJ0L03A =MQJ0L03 = 0)
  3. Obviously, make sure beam can transports from MQJ0L02 to IHA0L03 w/ those quads off (use BPM's and viewers)
  4. The configuration changes MQJ0L02 B for 21 K1 values (-3.0, -3.2, … , -5.8, -6.0); this takes ~45 minutes, so a smaller data set could be used too
qsUtility
  1. We use program named qsUtility to automatically to make the measurements and analyze the data
  2. The measurement configuration file is here and can also be used as a template /cs/prohome/apps/q/qsUtility/pro/fileio/config/IHA0L03_jmg1.xml
  3. qsUtility is documented here
qsUtility assumes v=c
  1. One must scale the Energy [MeV] entry box as the tool uses this formula B'L [G] = K1[1/m^2] * L[m] * E[MeV] * 10/0.2998

How to measure momentum

Note quads used for centering
  1. MQJ0L02 = IPM0L02
  2. MQJ0L03 = IPM0L03
  3. MQD5D00 = IPM5D00
  4. MQD5D01 = IPM5D01
Center quads
  1. Mike Spata suggests standard dithering, as we do for solenoids
  2. When complete update the BPM .SOF field and log result
Momentum measurement
  1. Excite minimum number of correctors and record values
  2. Set or measure BL using calculation on MDL0L02 control screen
  3. Make note of BL for zeroing IPM0L02-IPM0L03 and IPM5D00-IPM5D01 with (intervening quads OFF, correctors OFF or recorded)
  4. Calculate momentum from KE as p = sqrt [T*(2m+T)], so T = 5.0 MeV => p 5.487 MeV/c
  5. Calculate fraction KE spread as dT/T = (T+2m)/(T+m) * dp/p, so dT/T=1.09 * dp/p @ T=5.0

How to use Elegant files

Elegant files for 2D, 3D, 5D, 0L regions
  1. locate /grames/elegant/MOTT/mott3/
  2. set mott3.ele beamline to be either 0L, 2D, 3D, 5D
  3. set mott3.ele emittance, Twiss and momentum spread
To run
  1. Copy files to local area
  2. Interactively: Start IEE from terminal and then load elegant file: /grames/elegant/MOTT/mott3/mott3.ele
  3. Command: From terminal execute elegant mott3.ele