Difference between revisions of "Run1 - January 2015"

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= Shift Schedule =
+
;[[CEBAF_MeV_Mott_Polarimeter]]
[[File:140112_shifts.png|thumb|center|300px]]
 
  
= Shift Worker Duties =
+
Mott Run 1 was performed January 13-19 with physics energy KE=5.0 MeV
; Beam Driver
 
Beam setup: gun + laser + spin + beam to Mott
 
BCM & target motion FSDs enabled
 
Vacuum levels reasonable
 
Magnet and RF setup saved
 
PITA adjusted for IHWP IN/OUT
 
; DAQ Driver
 
Start/Stop DAQ entering correct run information
 
Monitor event rates and maintain dead time <5%
 
Coordinate run start/stop with Beam and Analysis Drivers
 
; Analysis Driver
 
Runs decoded, analyzed and promptly inspected
 
Run # and information logged onto run sheets
 
Elastic events counted for IHWP=IN/OUT
 
  
= Prep Work (through Tuesday Jan 13) =
+
== [[Mott Run 1 Journal]] - Our online summary of the experiment with many useful links ==
#Make a photocathode – SL5247-1 made
 
#Test IHA2D00 – wires & stroke good, but data file odd vs. others
 
#Hi-Pot IP – FE’r potted, but high again, vac readback not good
 
#CHL 2K cooldown – maybe early, Monday Jan 12th
 
#Install laser – Tue or Wed
 
#Test laser RF trigger – after laser installed (1V, 10ns @ RF)
 
#Verify beam line layout –documented below
 
#Build elegant deck – working
 
#Build qsUtility config file –documented below
 
  
= Injector Setup and Mott Checkout (Wed Jan 14 - Fri Jan 16) =
+
== [[Mott Run1 Target Thickness Study]] ==
#Restore beam to FC2 @ 6.3 MeV/c
+
* elastic rates summary tables from January and May [[media:rates_summarytable.ods]]
#Mott test: DAQ FADC/TDC synchronization
 
#Mott test: event separation and transmission at 62MHz acceptable
 
#Quad center BPMs for momentum measurement
 
#Test harp IHA2D00 if ready for energy spread measurement
 
#Scale cryounit for p=5.487 MeV/c and minimize energy spread
 
#Precisely measure beam momentum
 
#Measure beam emittance
 
#Measure energy spread
 
#Calibrate BCM to FC2
 
  
= Mott Setup and Systematics Testing (Sat Jan 17) =
+
== Run1 January Analysis Documents ==  
#Setup good orbit to Mott
+
* element locations [[media:Run1_Beamlines.pdf]]
#Set PMT HV
+
* MBH3D00H/V are in reality MAD3D00H/V and use MAD field maps [[media:MAD_FMAP.pdf]]
#Set PMT energy thresholds
+
* chronology in different formats [[media:run1summary.txt]], [[media:run1summary.docx]], [[media:run1summary.pdf]]
#Set polarization vertically
+
* on-line summary spreadsheets [[media:run1database.ods]], [[media:run1database.xlsx]]
#Calibrate PITA vs IHWP IN/OUT
 
#Finalize orbit w/ instrumental asymmetry, TOF and spectra
 
#Adjust target offsets per vertical instrumental asymmetry
 
#Measure dump rate fraction to determine run times
 
#Measure dead-time vs. rate
 
#Measure asymmetry vs. beam current
 
#Measure asymmetry vs. time (stability)
 
#Measure asymmetry vs. spot size
 
#Measure asymmetry vs. energy spread
 
  
= Target Foil Extrapolation (Sat Jan 17 - Mon Jan 19) =
+
== Matt's Campaign Strategy Notes from 5/1/2015 meeting ==
; 14 foils to study + 1 thru hole
 
spectra – with typical low ~2 MeV energy threshold
 
statistics – possibly higher ~3 MeV threshold to reduce dump events
 
; Deadtime
 
Semi-int mode we use w/ FADC/TDC/scalar is ~5% @ 1500 Hz
 
; Inelastic fraction
 
Worst case ~200 Hz/det  (best case ~25 Hz/det)
 
Energy threshold will be defined to set this value
 
Time veto is tricky and too risky at 62 MHz
 
; Assuming I=5uA, R<1500Hz, 200Hz/det background
 
28 hours * 1.2 / 8 = 4-5 shifts
 
dP/P sets N_elastic (using 1σ analysis cut of all 4 det)
 
Measurement of of inelastic (dump) events figures into run time
 
; [[File:140112_runtimes.png|center]]
 
  
= How to measure emittance =
 
; Beam Setup
 
We measure the beam emittance and Twiss at entrance of MQJ0L02 by varying MQJ0L02 and observing response on harp IHA0L03
 
To simplify matters we turn off the intervening quadrupoles (MQJ0L02A = MQJ0L03A =MQJ0L03 = 0)
 
Obviously, make sure beam can transports from MQJ0L02 to IHA0L03 w/ those quads off (use BPM's and viewers)
 
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
 
We use program named qsUtility to automatically to make the measurements and analyze the data
 
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
 
qsUtility is documented [http://opweb.acc.jlab.org/CSUEDocs/q/qsUtility/pro/doc/dataCollector_user_guide/dataCollector_user_guide.html here]
 
; qsUtility assumes v=c
 
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 ==
+
'''''Measure Asymmetry vs Target Thickness'''''
; Before using absolute BPM's perform centering procedure to adjacent quadrupoles:
+
* Take data at 5 MeV/c (done)
  MQJ0L02 = IPM0L02
+
* Measure the thickness of companion foils, our x-axis error bar (Mamun finished with measurements, Marcy completing analysis)
MQJ0L03 = IPM0L03
+
* Assess mott spectra and assign sensible cuts, energy and time (Joe working on this now)
MQD5D00 = IPM5D00
+
* Using the cut guidance from above, analyze our runs and create the Asym vs Target Thickness plot, with statistical error bars in Y and error bars in foil thickness from step 1b (Daniel to work on this soon, with Joe's helpBatch runs favored)
MQD5D01 = IPM5D01
 
Mike Spata suggests standard dithering, as we do for solenoids
 
When complete update the BPM .SOF field and log result
 
; Beam steering
 
Earth’s field is likely too strong to turn zero intervening correctors
 
Excite minimum number of correctors and record values
 
  p = sqrt [T*(2m+T)] so T = 5.0 MeV =>  p 5.487 MeV/c
 
  Check me: dT/T = (T+2m)/(T+m) * dp/p so dT/T=1.09 * dp/p @ T=5.0
 
  Use the BL calculation on the control screen of MDL0L02
 
  
= How to use Elegant files =
+
 
 +
'''''How to assign Systematic Error?'''''
 +
* Review our results, hopefully we find Asymmetry was relatively insensitive to the things we varied.  Still a bit vague to me, how to assign a systematic error.  (Daniel will analyze and summarize results from systematic studies, group should brainstorm to assign the value)
 +
 
 +
 
 +
'''''Extrapolate asymmetry to Zero Thickness, determine single atom Mott Asymmetry'''''
 +
* What is a sensible functional form to fit data?  GEANT model will tell us this.  (Marty working on this now). Assign a systematic error to the extrapolation.
 +
* Use our fit result of Mott Asymmetry at zero thickness and Xavier’s theoretical prediction of Sherman function to calculate beam polarization, what is the error on the theoretical prediction? (Charlie working on this now, Joe mentions this might already be on wiki)
 +
 
 +
 
 +
'''''Assign a polarization value to our beam: Pol = P ± Stat ± Syst ± Theory'''''
 +
* Joe makes the point, Asym vs Thickness at different energies can provide more confidence (in Syst uncertainty) that our functional form fit is credible.
 +
* A good fit obtained for all tested beam energies, with each fit indicating the same beam polarization, like Michael did, would be a powerful validation of our "model" (could take more data in summer, Riad cautions, better to assess Run1 first)
 +
 
 +
''Riad favors asymmetry measurements using low-Z target material, as providing more impact for Theory''

Latest revision as of 20:00, 13 August 2015

CEBAF_MeV_Mott_Polarimeter

Mott Run 1 was performed January 13-19 with physics energy KE=5.0 MeV

Mott Run 1 Journal - Our online summary of the experiment with many useful links

Mott Run1 Target Thickness Study

Run1 January Analysis Documents

Matt's Campaign Strategy Notes from 5/1/2015 meeting

Measure Asymmetry vs Target Thickness

  • Take data at 5 MeV/c (done)
  • Measure the thickness of companion foils, our x-axis error bar (Mamun finished with measurements, Marcy completing analysis)
  • Assess mott spectra and assign sensible cuts, energy and time (Joe working on this now)
  • Using the cut guidance from above, analyze our runs and create the Asym vs Target Thickness plot, with statistical error bars in Y and error bars in foil thickness from step 1b (Daniel to work on this soon, with Joe's help. Batch runs favored)


How to assign Systematic Error?

  • Review our results, hopefully we find Asymmetry was relatively insensitive to the things we varied. Still a bit vague to me, how to assign a systematic error. (Daniel will analyze and summarize results from systematic studies, group should brainstorm to assign the value)


Extrapolate asymmetry to Zero Thickness, determine single atom Mott Asymmetry

  • What is a sensible functional form to fit data? GEANT model will tell us this. (Marty working on this now). Assign a systematic error to the extrapolation.
  • Use our fit result of Mott Asymmetry at zero thickness and Xavier’s theoretical prediction of Sherman function to calculate beam polarization, what is the error on the theoretical prediction? (Charlie working on this now, Joe mentions this might already be on wiki)


Assign a polarization value to our beam: Pol = P ± Stat ± Syst ± Theory

  • Joe makes the point, Asym vs Thickness at different energies can provide more confidence (in Syst uncertainty) that our functional form fit is credible.
  • A good fit obtained for all tested beam energies, with each fit indicating the same beam polarization, like Michael did, would be a powerful validation of our "model" (could take more data in summer, Riad cautions, better to assess Run1 first)

Riad favors asymmetry measurements using low-Z target material, as providing more impact for Theory