1-pass calibration for A1n

One-pass calibration/commissioning for Fall 2019

 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.

Outline

 We will need to do optics calibration, reference cell (cross section and pressure curves), 3He elastic longitudinal asymmetry, and 3He Delta transverse asymmetry measurements. 

Beam and raster checkout

 Please refer to 2-pass commissioning procedure, follow:
 - Establish beam in the hall
 - Initial Raster checks
 - Harp scans
 - Target/Beam centering, Raster calibration

Optics (angle and ytarg) Calibration

  Goals 
 - To calibration spectrometer optics for 40cm long target at 30 deg. Calibrate angle reconstruction.

 Setup
 - Beam Current:   5-20 uA CW, raster varies
 - HMS setting: 30 degrees, -1.2 GeV/c (electron)
 - SHMS setting: 30 degrees, -1.68 GeV/c (electron)
 - Target:       Multi(7)-foil Carbon Foils

 Procedure
 - Move target to multi-foil position;
 - Move Sieve Slit IN for both HMS and SHMS;
 - Take a short run (2min) at 20uA, verify sieves are both IN;
 - Ask MCC to increase current to 20uA (Max for raster off on this target). Take two runs, 45 minutes each. 
 - Ask MCC to turn raster ON to 5mm diameter, take one run at 20 uA for 45 minutes.
 - Move Sieve Slit OUT for both HMS and SHMS;
 - Take one run at 20 uA for 15 minutes. 
 - Ask MCC to turn raster OFF, take one run at 20 uA for 15 minutes.

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

Optics (Momentum) Calibration

  Goals 
 - To calibration momentum reconstruction of spectrometers.

 Setup
 - Beam Current:   5--20 uA CW, raster always OFF
 - HMS setting: 11.7 deg, momentum varies (electron)
 - SHMS setting: 8.5 deg, momentum varies (electron)
 - Target:      Double Carbon Foils

 Procedure
 - Move target to Double carbon foil position.

 - To be filled

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

Polarized 3He Delta Transverse Asymmetry

  Goals 
 - To measure physics transverse asymmetry of Delta resonance to 10% relative on each spectrometer.

 Setup
 - Beam Current:  up to 5 uA CW, raster always ON (5mm diameter)
 - Beam IHWP: should be switched half-way
 - HMS setting: 11.7 deg, -2.068 GeV/c (electron) <- note: need to change this to 12.5 deg
 - SHMS setting: 8.5 deg, -2.083 GeV/c (electron) <- note: need to change this to 12.5 deg
 - Target:      Polarized 3He Cell, Empty Reference Cell
 - Target spin direction: 90 or 270-deg
 - Target coil setting: TBD
 - 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 0.5uA.

 Procedure
 - Set spectrometers at the required settings, target at Polarized 3He Cell position, spin polarization at either 90 or 270 degrees.
 - Perform one polarimetry measurement before taking data.
 - Check and make sure all scintillators are ON, take one 1-minute run at 2uA, check rates and adjust beam current and prescale factors. In principle we should take 4.5kHz with PS=1 if possible.
 - Take three 30-minute (TBD) runs at the optimal current set above, perform one polarimetry measurement after each run. Verify data quality (see below) and verify target is still polarized.
 - Switch beam IHWP position. (may need to inform other halls in advance). For example from IN to OUT or from OUT to IN.
 - Take three 30-minute runs at the optimal current set above, perform one polarimetry measurement after each run. Verify data quality (see below) and verify target is still polarized.

 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 total rate: To be filled
 - Expected asymmetries (after W and Ytg cuts): To be filled HMS Aphys=4.8% Ameas=2.1% and SHMS Aphys=2.5% Ameas=0.98% if Pt=50%, Pb=85%, N2 dilution 0.92.
 - Expected uncertainties dA/A=10% on each of HMS and SHMS.

Polarized 3He Elastic Longitudinal Asymmetry

  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: up to 5 uA CW, raster always ON (5mm diameter)
 - HMS setting: 11.7 deg, -2.068 GeV/c (electron) <- need to change to 12.5 deg
 - SHMS setting: 8.5 deg, -2.083 GeV/c (electron) <- need to change to 12.5 deg
 - Target:      Polarized 3He Cell
 - Target spin direction: 0-deg, 180-deg
 - Target coil settings: TBD
 - Detectors: We will need to keep only 2 SC bars ON to 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 0.5uA.

 Procedure
 - Set spectrometers at the required settings, target at Polarized 3He Cell position, spin polarization at either 0 or 180 degrees.
 - Perform one polarimetry measurement before taking data.
 - Take one 1-minute run at 1 uA, check focal plane event distribution and determine which two scintillator bars should be kept on. (expert driven).
 - Once scintillators are set, take one 1-minute run at 2uA, check rates and adjust prescale factor. Ideally we want 4.5kHz on each of HMS/SHMS with PS=1.
 - Take three 30-minute (TBD) runs at the optimal current set above, perform one polarimetry measurement after each run. Verify data quality (see below) and verify target is still polarized.
 - Rotate target spin direction from 0 to 180 deg (or from 180 to 0 deg)
 - Take three 30-minute runs at the optimal current set above, perform one polarimetry measurement after each run. Verify data quality (see below) and 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 xxx runs ... (repeat above)

 Things to watch online
 - Ensure the correct SC bars are on (We need elastic events! One SC bar is in principle enough but we keep TWO on)
 - Apply y or z cuts to isolate events scattered from 3He gas (We do not want events from the glass windows!)
 - Apply W cuts to isolate 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.

 - Expected total rate: (To be updated) HMS at 1uA total 1.8KHz 3He gas elastic 240Hz; SHMS at 1uA total 27.7kHz Prescaled by 15 to 3He gas elastic 740Hz
 - Expected asymmetries (after W and Ytg cuts): (To be updated) HMS Aphys=4.8% Ameas=2.1% and SHMS Aphys=2.5% Ameas=0.98% if Pt=50%, Pb=85%, N2 dilution 0.92.
 - Expected uncertainties dA/A=2% (goal) or 3% (minimum) on each of HMS and SHMS.

Reference Cell Hydrogen (H2) Cross Section

  Goals 
 - To measure hydrogen elastic cross section, need 10,000 elastic events each for HMS and SHMS

 Setup

 Procedure

Reference N2 Pressure Curve

  Goals 
 - To measure yield and cross section for varying N2 pressure. This will be used to determine amount of N2 in the polarized 3He cell in the offline analysis.

 Setup

 Procedure

Reference 3He Pressure Curve

  Goals 
 - To measure yield and cross section for varying N2 pressure. This will be used to determine amount of 3He in the polarized 3He cell in the offline analysis.
 - Important: Among all reference cell runs (N2, H2 and 3He), run 3He last, and do NOT vent 3He gas after completing the run plan.

 Setup

 Procedure