Run2 - October 2015

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Mott Run 2 is scheduled from October 23 - 26. CEBAF_MeV_Mott_Polarimeter

Run II Important Documents

Run II Logistics

Friday, October 23 DAY (Matt, Joe)

Started DAY shift with PSS down until ~1pm due to PSS BCM fault. Hall B beam at 31MHz recovered to FC1 and Vertical Wien filter set to +90 deg. Later INJ/NL locked-up and beam restored to FC2 fine. A "momentum measurement" setup was created, one with quads between IPM0L02-IPM0L03 nulled and minimal correctors; IPM GOF's are here. Central momentum of 5.487MeV/c was set using DL magnet. Crested gradients of 5.27MV/m(146.5deg) and 4.120MV/m(94.2deg) were found to be the best average of 2D line (no survey elements) and 5D line (incomplete survey information), expect both will be consistent at the <1%.

Friday, October 23 SWING (Tim, Marcy)

Started shift with white board tool-box meeting (Tim, Daniel, Matt, Marcy, Riad, Joe). The look up table of R028GSET values has an error - DO NOT use this table. We stepped through energy settings while keeping 0L launch fixed measuring a) 5D BPM's with fixed DL and then b) DL settings with fixed 5D BPM's. We later found the actual range of R028GSET was +/- 40keV, not +/- 400keV. Still the measurement is here.

Saturday, October 24 OWL (Daniel, Riad)

Beam was restored after bypass SL klystron. BCM0L02 cal factors had to be reset (ioc reboot?). Clean launch set to Mott, detector timing adjusted (DAQ or RF trigger drift?), PITA settings to null charge asymmetry corrected (orbit/transmission change since last calibration?), set vertical polarization and measured total rate vs. thickness. Detailed shift summary here.

Saturday, October 24 DAY (Marty, Joe)

During DAY shift we studied asymmetry vs. electron energy using the 1um and 0.35um gold foils about our nominal KE=5.0 MeV. We realized there was a typo in the energy look-up table, it spanned +/-40keV instead of +/-400keV so new gradients are being used and logged. We completed offsets of 0keV setup, -200keV setup, -400keV. At end of shift we are ~halfway done with +200keV setup and will then complete +400keV before completing this study. For most changes today the 0L02-8 auto-tuning was not working so well and converging so Shaun put it in manual mode and operation is fine there. We had two occasions of PSS BCM fault dropping the gun HV - so happening multiple times per shift.

Saturday, October 24 SWING (Tim, Matt)

The +400keV setup was completed on SWING shift and then returned to KE=5.0 MeV setup. Daniel attached a hand-drawn plot for the 1um and 0.35um foils asymmetry vs. energy result.

Sunday, October 25 OWL (Daniel, Riad)

When the 50nm foil was started a pre-TOF peak was observed so the beam was re-steered. Target thickness measurements through foil 14 (350nm) were completed, more details in the run summary .

Sunday, October 25 DAY (Marty, Joe)

Present summary of beam energy and target thickness runs attached here: media:RunII_Summary.xlsx

Sunday, October 25 SWING (Tim, Marcy)

  1. Complete target thickness extrapolation at KE=5MeV

Target thickness extrapolation nearly done - 1.5 more runs required for 350 foil, then final stability run.

File:RunII Summary.xlsx

Monday, October 26 OWL (Daniel, Riad)

Target thickness extrapolation data all taken. Data in File:RunII Summary.xlsx.

  1. Measure spectra of 10 foils without VETO
  2. Explore where the early and late events around elastic peak originate?
  3. Park injector in fixed configuration until DAY shift (gun, magnets, RF, etc constant)

Baseline machine settings for Run II saved in all save 15850.

Raw Data Spreadsheet used to record each run --


Monday, October 26 DAY (Joe)

  1. Measure emittance - IHA0L03 v. MQJ0L02 zig-zag scans in CW and tune mode
  2. Measure energy spread - IHA2D00 harp swipes for 3 different pairs of MQJ0L02/MQJ0L02A lens settings
  3. Measure momentum at gradients used - media:RunII_Summary_Final.xlsx
  4. Measure spectra vs. energy spread - not measured

Preliminary Analysis Results

Relative rates versus thickness measurement:

Ratevthick prelim.gif

Asymmetry vs Target Thickness, Run II: ToF-cut: -2 to +2 sigma. Energy cut: -1 to +3 sigma.

Run2 asymvthick prelim.gif

From Run I, for comparison, Asymmetry vs Target Thickness: ToF-cut: -2 to +2 sigma. Energy cut: -1 to +3 sigma.

Run1 asymvthick.gif