1-pass calibration for A1n (Jan 2020)

Outline

For polarized 3He running in Fall 2019 and Spring 2020, the nominal raster for production is 5mm diameter circular. The nominal triggers used are 3/4 for both HMS and SHMS. Both HMS and SHMS should be taking data (for example if run plan specify one run, it means one run on HMS and one run on SHMS simultaneously). No coincidence trigger will be used/setup.

For January 2020 run, we will need to do optics calibration (delta scan only, like), 3He elastic cross section on cell Dutch (must), 3He QE longitudinal asymmetry (must), and 3He Delta transverse asymmetry measurements (must). All reference cell (cross section and pressure curves) runs were completed in Dec 2019. Moller and beam energy measurement will also not be required this time if beam conditions remain the same as 1-pass of Dec 2019.

Due to complication in spectrometer rotation, we plan to carry out all 1-pass runs with HMS at 11.7 deg and SHMS at 8.5 deg this time.

Polarized_Helium-3_Experiments#Run_Plan <- click this to return to main run plan page

Beam and raster checkout

 Please refer to Beam and Raster Checkout for A1n/d2n (Short Procedure).

Optics (Momentum) Calibration (6-8 hrs, Like, Not Must)

 Goals 
 - To calibrate momentum reconstruction of spectrometers.
 - Time: estimate 6 hours total including many momentum changes.

 Setup
 - Beam Current:   5-40 uA CW, raster varies, assuming beam energy 2.183 GeV 
 - HMS setting: 11.7 deg, momentum: -2.348 (-8%)
 - SHMS setting: 8.5 deg, momentum: -2.504 (-13%)
 - Target:      Carbon Foil (this should have 2 foils at locations 4 and 6; NOT "Carbon Optics" and not "Carbon Hole")
 - Other: we would like to study charge asymmetry during optics runs. Please see hclog 3756555 and contact Brad S. for how to set this up. (After optics, Qasym feedback must be restored for the remaining of the 1-pass running).

 - In case spectrometer angles are not exactly 11.7 and 8.5 deg, here is a spreadsheet to calculate the proper momentum settings: 

 Procedure
 - Move target to Carbon Foil Target (not Optics, not Carbon Hole) position.
 - start from -8% at HMS and -13% at SHMS, sieve IN;

 - Ask for 40uA raster at 0.5mm, check trigger rates. Adjust the current to reach (3.5-4)kHz on HMS DAQ with PS=1, adjust PS for SHMS to keep DAQ rate within or slightly below (3.5-4)kHz.
 - Take one 20-min runs for HMS and one 20-min run for SHMS at this setting. 
 - Using the same PS factors and beam current, start the delta scan as listed below. Watch the PS and rates.

 - HMS delta scan (Sieve IN for all):
   - -8%: 2.34811 GeV
   - -5%: 2.28289 GeV
   - -2%: 2.21855 GeV
   - 0%: 2.17418 GeV 
    - 0%: 2.17418 GeV 
    - 0%: 2.17418 GeV (set raster to 5mm)
    - 0%: 2.17418 GeV (record PS and beam current. Move sieve out and set raster at 5mm, adjust PS or beam current then take one run for 10 minutes. At the end put sieve IN and raster at 0.5 to continue delta scan. do not forgot to change PS and beam current back to OLD values)
   - 2%: 2.13155 GeV
   - 5%: 2.06547 GeV
   - 8%: 2.00024 GeV
   - at the end of the delta scan, no need to set momentum back to 0%. Check runplan to determine the setting for the next step.

 - SHMS delta scan (Sieve IN for all):
   - -13%: 2.50379 GeV (skip?)
   - -10%: 2.39616 GeV
   - -5%: 2.28724 GeV
    - 0%: 2.17833 GeV 
    - 0%: 2.17833 GeV (set raster to 5mm)
    - 0%: 2.17833 GeV (record PS and beam current. Move sieve out and set raster at 5mm, adjust PS or beam current then take one run for 10 minutes. At the end put sieve IN and raster at 0.5 to continue delta scan. do not forgot to change PS and beam current back to OLD values)
   - 5%: 2.06941 GeV
   - 10%: 1.96049 GeV
   - 15%: 1.85158 GeV
   - 20%: 1.74266 GeV
   - 25%: 1.63375 GeV
   - at the end of the delta scan, no need to set momentum back to 0%. Check runplan to determine the setting for the next step.

 Things to watch for (Expert Analysis)
 - There should be optics expert(s) checking data quality as we go.

reference documents:

https://userweb.jlab.org/~jixie/A1N/optics/result_optics_2.183GeV_8.5deg.txt
https://www.jlab.org/indico/event/330/contribution/5/material/slides/0.pdf
https://userweb.jlab.org/~jixie/A1N/runplan/optics_runplan.pdf

Polarized 3He Delta Transverse Asymmetry (4-8hr)

 Goals 
 - To measure physics transverse asymmetry of Delta resonance to (10)% relative on HMS (larger uncertainty on SHMS), to determine sign of transverse asymmetries.
 - Experts must watch EDTM rate (Brad or Sylvester)

 Setup
 - Beam Current: 5-30uA, raster always ON (5mm diameter)
 - Beam IHWP:    should be switched half-way
 - Target:       Polarized 3He Cell
 - Detectors:    All scintillator bars ON. 
 - Parity check: Inform Hall A prior to taking data to make sure they set the charge asymmetry feedback cutoff at 2uA.
 - 
 Spectrometer Setup (with HMS 11.7, SHMS 8.5 deg)
 - HMS setting:  11.7 deg, -1.75830 GeV/c (electron W=1.232)
 - SHMS setting: 8.5 deg, -1.79736 GeV/c (electron W=1.232) 

 Spectrometer Setup (alternate, with both at 11.7 deg)
 - HMS setting:  11.7 deg, -1.75830 GeV/c (electron W=1.232)
 - SHMS setting: 11.7 deg, -1.75830 GeV/c (electron W=1.232) 

 Pol 3He Target Setup
 - Target spin direction: 90 or 270-deg
 - See Target Field Runplan for coil currents settings.

 Procedure
 - Set spectrometers at the required settings, target at Polarized 3He Cell position, spin polarization at either 90 or 270 degrees.
 - Check and make sure all scintillators are ON;
 - Perform one set of polarimetry (NMR, EPR if possible) measurements before taking data.
 - Ask for 5uA raster ON, check rates and set prescale factors (Save them if changed!). Goal is (3.5-4)kHz DAQ rates on both spectrometers. If rates too low (unlikely), can increase current to reach the desired rates but do not exceed 30uA.

 - The following run time is set for 4 hours of beam time. If time is more/less than 4 hrs, take more/less runs at each beam IHWP setting.

 - Take four 30-minute (beam ON 15 min each) runs; Verify data quality (see below).
 - Perform one NMR measurement. Verify target is still polarized.

 - Switch beam IHWP position. (need to inform other halls in advance, both at 8am meeting and before changing). For example from IN to OUT or from OUT to IN.
 - Take four 30-minute (beam ON 15 min each) runs; Verify data quality (see below).
 - Perform one set of polarimetry (NMR, EPR if possible) measurements.

 Things to watch online
 - Apply y or z cuts to isolate events scattered from 3He gas (We do not want events from the glass windows!)
 - Apply 1.1<W<1.35 GeV cut to isolate the Delta resonance.
 - Run online script to ensure we see physics asymmetry. HMS and SHMS should see opposite asymmetries. 

 - Expected asymmetries (after W and Ytg cuts): Ameas=0.67% at 11.7deg and 0.46% at 8.5 deg if Pt=50%, Pb=85%, N2 dilution 0.92.
 - Expected rate: 5kHz at 1uA, about 40% would be Delta from 3He gas.
 - Counts needed to reach 10% on Ameas relative: N tot of electron, after cutting out glass windows and after applying W cut to select the Delta(1232), is 2.2M on HMS or 4.7M on SHMS. If target polarization is below 50%, scale this number up by (50%/Pt)^2.
 - Expected time to reach 10% on Ameas relativite: ...

Polarized 3He Cell Density Measurement (1 hour including setup)

 - Note: We took some runs on cell Brianna at the elastic setting which can be used to compare with ref cell runs to determine 3He and N2 density in Brianna. However, since we switched to cell Dutch this time, we need to re-take cross section data at the same SC bar settings as December ref cell pressure curve runs to determine 3He and N2 density in Dutch.

 Goals 
 - To determine 3He and N2 density in cell Dutch
 
 Setup
 - Beam Current: 5-10uA, raster always ON (5mm diameter)
 - Target:      Polarized 3He Cell "Dutch"

 Spectrometer Setup
 - HMS setting: 11.7 deg, -2.1483 GeV/c (electron 3He elastic) 
 - SHMS setting: not relevant, so setting at QE peak is fine: 8.5 deg, -2.12860 GeV/c (electron quasi-elastic)
 - Detectors:   Must set SC bars in HMS the same as ref cell pressure curve runs from December 2019. See hclog ...

 Procedure
 - Set spectrometers at the required settings, target at the Polarized 3He Cell position;
 - Check that SC bars in HMS are the same as runs ... 
 - Ask MCC for 10 uA raster ON (5mm dia). Adjust prescale factor to limit the DAQ rate to 3.5-4kHz. Do NOT drop below 10uA. If rates are low, increase beam current but do not exceed 30 uA.
 - Take two 30-min runs at this setting. We need at least 10k events from 3He elastic and N2 elastic peaks (not easy to determine, so take a one-hour run to be sure).

Polarized 3He Runs, 3He QE longitudinal Asymmetries (8-16 hours)

 Goals 
 - To measure physics longitudinal asymmetry of 3He QE scattering. If precision is high this can be used to cross check PbPt from Moller and Target Polarimetry. At the minimum, we should determine the sign of longitudinal asymmetries.

 - Experts must watch EDTM rate (Brad or Sylvester)
 - Note: we will focus on QE asymmetry with a longitudinally polarized target. The spectrometers will be centred at the 3He QE momentum. 

 Setup
 - Beam Current: 10-30uA, raster always ON (5mm diameter)
 - Target:      Polarized 3He Cell
 - Target spin direction: 0 or 180-deg (determined by target experts)
 - See Target Field Runplan for coil currents settings.
 - Parity check: Inform Hall A prior to taking data to make sure they set the charge asymmetry feedback cutoff at 2uA.
 - Time: total 8-16 hours of data taking, flip beam IHWP every 4 hours. Do target NMR every two hours and before and after the full data taking.

 Spectrometer Setup (with HMS 11.7 deg, SHMS 8.5 deg)
 - HMS setting: 11.7 deg, -2.08234 GeV/c (electron quasi-elastic) 
 - SHMS setting: 8.5 deg, -2.12860 GeV/c (electron quasi-elastic)
 - Detectors: Must set SC bars in HMS and SHMS as suggested in hclog 3756736

 Procedure
 - Set spectrometers at the required settings, target at the Polarized 3He Cell position, spin polarization at 0 or 180 deg (we should choose the one that maximize the target polarization).
 - Verify SC bar status the same as hclog 3756736;
 - Perform one full set of polarimetry (NMR, EPR if possible) measurements before taking data.
 - Ask MCC for 10 uA raster ON (5mm dia), check trigger rates. Goal is to reach (3.5-4)kHz DAQ rates. If rates too high, adjust PS factors (save PS file if changed!) and/or drop beam current but do not go below 5uA. If rates too low (unlikely), increase beam current but do not exceed 30uA. 

 - Take 4 60-minute runs (assuming 50% beam efficiency). Perform NMR every 2 hours.

 - Call MCC and ask beam IHWP to be inserted (or taken out). Need to inform other halls prior to the switch.
 - Take 4 60-minute runs (assuming 50% beam efficiency). Perform NMR every 2 hours.

 - Call MCC and ask beam IHWP to be inserted (or taken out). Need to inform other halls prior to the switch.
 - Take 4 60-minute runs (assuming 50% beam efficiency). Perform NMR every 2 hours.

 - Call MCC and ask beam IHWP to be inserted (or taken out). Need to inform other halls prior to the switch.
 - Take 4 60-minute runs (assuming 50% beam efficiency). Perform NMR every 2 hours.

 Things to watch online
 - Ensure the correct SC bars are on (We need QE events from 3He!)
 - Apply z cuts to isolate events scattered from 3He gas (We do not want events from the glass windows!)
 - Apply W or dp cuts to isolate 3He QE events from others.
 - Run online script to ensure we see physics asymmetry. Plot asymmetry as function of nu (=E-E'). QE asymmetry predictions are given in hclog 3755440. HMS and SHMS should see the same asymmetry. Asymmetry should flip sign with beam IHWP switch and target spin flip.