Difference between revisions of "Mott Run 2 Journal"

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= Prep and HCO w/o beam =
 
# (John) 31 MHz laser -
 
# (Riad) Test laser RF trigger at DAQ
 
# (Joe) Make a photocathode – SL5247-4 (52471-1 was used for Run I, but it's being removed from Gun2 next week)
 
# (Marcy) Check Mott vacuum, configuration (hipot 3D01 again?)
 
# (Joe) Cycle target ladder, test camera, test magnets, test 2D harp
 
# (Riad/Daniel) Check HV, check DAQ, Analysis, Macros ready for 31 MHz
 
  
= Pre-Run Beam Setup and Tests  (2 shifts) =
 
# Recovery to FC2 @ 6.3 MeV by 10/15
 
# Mott beam test - Test 31 MHz synchronization, set L/R/U/D delays, set PMT HV, check PMT response, dump dipole degaussed
 
# Beam diagnostics - Test harp, BCM calibration, quick emittance method
 
  
= Run II Proposed Plan (9 shifts 10/23 DAY - 10/26 OWL) =
+
== Friday, October 23 DAY (Matt, Joe) ==
The goal is to collect final data set for the paper describing the performance and systematics regarding it's ability to measure the absolute polarization at 5.0 MeV.
+
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 [https://logbooks.jlab.org/entry/3355651 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%.
  
== 2.0 shifts - Good knowledge of beam (energy, energy spread, emittance) ==
+
== Friday, October 23 SWING (Tim, Marcy) ==
# Set KE=5.0 MeV
+
Started shift with white board tool-box meeting (Tim, Daniel, Matt, Marcy, Riad, Joe).  The look up [https://logbooks.jlab.org/entry/3355838 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 [https://logbooks.jlab.org/entry/3355853 here.]
# Measure emittance at MQJ0L02
 
# Measure energy spread at IHA2D00
 
# Verify BCM calibration good
 
# Calibrate PITA IHWP=in/out
 
# Setup beam to Mott, check PMT HV, TOF spectra, set thresholds HI, check instrumental asymmetry
 
# Setup spin direction, use Mott for final adjustment
 
  
== 3.5 shifts Target thickness extrapolation at KE=5.0 MeV ==
+
== Saturday, October 24 OWL (Daniel, Riad) ==
# Use the 10 foils with 25mm aperture spanning 8 nominal thicknesses (0.05, 0.05, 0.225, 0.35, 0.35, 0.50, 0.625, 0.750, 0.87, 1.0)
+
Beam was restored after bypass SL klystron.  BCM0L02 cal factors had to be [https://logbooks.jlab.org/entry/3355864 reset] (ioc reboot?). Clean launch [https://logbooks.jlab.org/entry/3355876 set] to Mott, detector timing [https://logbooks.jlab.org/entry/3355886 adjusted] (DAQ or RF trigger drift?), PITA settings to null charge asymmetry [https://logbooks.jlab.org/entry/3355890 corrected] (orbit/transmission change since last calibration?), [https://logbooks.jlab.org/entry/3355938 set vertical polarization] and measured total [https://logbooks.jlab.org/entry/3355942 rate vs. thickness]. Detailed shift summary  [https://logbooks.jlab.org/entry/3355967 here.]
# Interleave 1um gold foils to demonstrate stabiilty
 
  
== 2.0 shifts Sensitivity of analyzing power vs. energy about 5.0 MeV ==
+
== Saturday, October 24 DAY (Marty, Joe) ==
# Imagine 0.5 shift/energy => 4 energies (4.0, 4.5, 5.5, 6.0)
+
 
# In 1 hour: set nominal energy, measure precisely, forego emittance measurement but set spot size at target
 
# In 3 hour: asymmetry measurements at 1.0, 0.75, 0.50, 0.225 um
 
  
== 1.0 shifts Repeat spot size and possibly energy spread systematic at KE=5.0 MeV ==
+
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 [https://logbooks.jlab.org/entry/3355990 0keV setup], [https://logbooks.jlab.org/entry/3356013 -200keV setup], -400keV. At end of shift we are ~halfway done with [https://logbooks.jlab.org/entry/3356104 +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.
# Use emittance measurement to calculate RMS beam size on foil (minimum, 1.0, 1.5, 2.0 mm)
 
# Varying energy spread a bit more tricky since energy and to some extent emittance depends on phase in second cavity : maybe a measurement for another time?
 
  
== 0.5 shifts Asymmetry vs. beam intensity ==
+
== Saturday, October 24 SWING (Tim, Matt) ==
# Test beam and Mott spectra (TOF + discriminators) up to 100 uA to dump in through hole
+
 
# Measure asymmetry 0.35 um foils (1, 5, 10, 25, 50, 75, 100 uA).
+
== Sunday, October 25 OWL (Daniel, Riad) ==
 +
 
 +
== Sunday, October 25 DAY (Marty, Joe) ==
 +
 
 +
== Sunday, October 26 SWING (Tim, Marcy) ==

Latest revision as of 17:20, 24 October 2015


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)

Sunday, October 25 OWL (Daniel, Riad)

Sunday, October 25 DAY (Marty, Joe)

Sunday, October 26 SWING (Tim, Marcy)