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 required, angle/ytg calibration optional), 3He elastic longitudinal asymmetry, and 3He Delta transverse asymmetry measurements. 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 Calibration

Optics (Momentum) Calibration (6-8 hrs) - Must/Required

 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")

 - 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

Optics (angle and ytarg) Calibration (2-2.5hrs -- LIKE -- can also be done at 5-pass)

 Goals 
 - To calibrate spectrometer optics for 40cm long target at 30 deg. Calibrate angle reconstruction. Note: existing Hall C optics data is not sufficient to cover the 40-cm long extended target of A1n/d2n
 - Time: 2 hour data taking plus short runs to check rate or setup.

 Setup
 - Beam Current:   5-40 uA CW, raster varies
 - HMS setting: 30 degrees, -1.2 GeV/c (electron)
 - SHMS setting: 30 degrees, -1.68 GeV/c (electron)
 - Target:       "Carbon Optics" Target (this should have 4 foils at locations 1,4,6,7; NOT "Carbon Foil" and NOT "Carbon Hole")

 Procedure
 - Move target to "Carbon Optics" Target position;
 - Move Sieve Slit IN for both HMS and SHMS;
 - Ask 40uA raster at 0.5mm, verify trigger rate and set for ELCLEAN triggers PS3=0 and the rest -1;
 - Take two 30-minute runs (assuming 50% beam quality i.e 15 min "beam ON" time) at this setting. Or until expert decide that there is enough data.
 - Move Sieve Slit OUT for both HMS and SHMS;
 - Take one run at 40 uA (raster OFF) for 20 minutes (10 min "beam ON" time). Check trigger rate and prescale if necessary.
 - Ask MCC set raster to 5mm diameter, take one run for 20 minutes (10 min "beam ON" time) at the same condition. 

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

Polarized 3He and Reference Cell Runs, Delta resonance setting

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

 Goals 
 - To measure physics transverse asymmetry of Delta resonance to (5-10)% relative on each spectrometer.
 - 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 relativit: ...

Polarized 3He and Reference Cell Runs, 3He elastic setting (8-16 hours)

 - Experts must watch EDTM rate (Brad or Sylvester)

Spectrometer and Pol 3He Targ Setting for All Runs at the 3He Elastic Setting

 Spectrometer Setup (with HMS 11.7 deg, SHMS 8.5 deg)
 - HMS setting: 11.7 deg, -2.1483 GeV/c (electron 3He elastic) 
 - SHMS setting: 8.5 deg, -2.164516 GeV/c (electron 3He elastic)

 Spectrometer Setup (alternate with both at 11.7 deg)
 - HMS setting: 11.7 deg, -2.1483 GeV/c (electron 3He elastic) 
 - SHMS setting: 11.7 deg, -2.1483 GeV/c (electron 3He elastic)
 -
 Pol 3He Target Setup
 - Target Spin Direction: 0 or 180 deg
 - See Target Field Runplan for coil currents settings.

Setup Scintillator bars for 3He Elastic Scattering (30min data taking, 1-2 hours to analyze data and determine setting)

 Goals 
 - To determine which SC bars should be turned ON to focus on 3He quasi-elastic or QE events (suppress nuclear elastic from windows)
 - Must be done Prior to Polarized 3He Longitudinal Asymmetry data taking
 
 Setup
 - Beam Current: 5-10uA, raster always ON (5mm diameter)
 - Target:      Polarized 3He Cell
 - Detectors:   All SC on to start with 

 Procedure
 - Set spectrometers at the required settings, target at the Polarized 3He Cell position;
 - Ask MCC for 5 uA raster ON (5mm dia).
 - Take a short run (5-10 minutes is enough), check focal plane event distribution and determine which scintillator bars should be kept on to focus on 3He quasielastic and suppress nuclear elastic and inelastic events. (expert driven).

 Things to watch for
 - Make sure to select the correct peak;
 - 3He elastic peak should be located at dp=0 for the proposed momentum setting.

Polarized 3He Elastic Longitudinal Asymmetry (8hrs ideal, 4hrs minimum)

 Goals 
 - To measure physics longitudinal asymmetry of 3He elastic scattering to (2-3)% relative, cross check PbPt from Moller and Target Polarimetry

 Setup
 - Beam Current: 10-30uA, raster always ON (5mm diameter)
 - Target:      Polarized 3He Cell, Reference Cell
 - Target spin direction: 0-deg, 180-deg
 - See Target Field Runplan for coil currents settings.
 - Detectors:    We will need to keep only 2 SC bars ON to accept 3He elastic and limit quasi-elastic scattering events. 
 - Parity check: Inform Hall A prior to taking data to make sure they set the charge asymmetry feedback cutoff at 2uA.
 - Time: total 8 hours of data taking, 2 hours each at target spin/beam IHWP =0/IN,0/OUT,180/IN,180/OUT. If beam time is less than 8 hours, reduce time at each spin/IHWP setting. Full target polarimetry measurements at the start and the end, plus pNMR (pulsed NMR) only every two hours or after each target spin flip.

 Procedure
 - Verify the correct two SC bars are ON.
 - Move target to Polarized 3He Cell position, spin polarization at 0 deg.
 - Perform one full set of NMR, EPR, pNMR polarimetry measurements before taking data.
 - Ask MCC for 10uA 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!). If rates too low (unlikely), increase beam current but do not exceed 30uA. 

 - Take two 60-minute runs (assuming 50% beam efficiency).
 - Perform one pNMR polarimetry measurement. Verify target is still polarized.

 - Rotate target spin direction from 0 to 180 deg.
 - Perform one pNMR polarimetry measurement. Verify target is still polarized.
 - Take two 60-minute runs (assuming 50% beam efficiency).
 - Perform one pNMR polarimetry measurement. Verify target is still polarized.

 - Call MCC and ask beam IHWP to be inserted (or taken out). Need to inform other halls prior to the switch.
 - Take two 60-minute runs (assuming 50% beam efficiency).
 - Perform one pNMR polarimetry measurement. Verify target is still polarized.

 - Rotate target spin direction from 180 to 0 deg.
 - Perform one pNMR polarimetry measurement. Verify target is still polarized.
 - Take two 60-minute runs (assuming 50% beam efficiency).
 - Perform one full set of NMR, EPR, pNMR polarimetry measurements.

 Things to watch online
 - Ensure the correct SC bars are on (We need 3He elastic events!)
 - 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 elastic events from others.
 - Run online script to ensure we see physics asymmetry. HMS and SHMS should see the same asymmetry. Asymmetry should flip sign with beam IHWP switch and target spin flip.

 - Expected asymmetries (3He elastic only): Aphys=5.0% Ameas~2% at 11.7 deg, or Aphys=5.8% Ameas=2.3% at 12.5 deg, if using Pt=50%, Pb=85%, N2 dilution 0.92.
 - Expected uncertainties dA/A=2% (goal) or 3% (minimum).