Difference between revisions of "1-pass calibration for A1n"

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== One-pass calibration/commissioning for Fall 2019 ==
+
== 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 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.
  
−
  We will need to do optics calibration, reference cell (cross section and pressure curves), 3He elastic longitudinal asymmetry, and 3He Delta transverse asymmetry measurements.
+
[[Polarized_Helium-3_Experiments#Run_Plan]] <- click this to return to main run plan page
  
−
=== Beam and raster checkout ===
+
== Beam and raster checkout ==
  
−
   Please refer to [https://hallcweb.jlab.org/wiki/index.php/2-pass_commissioning 2-pass commissioning procedure], follow:
+
   Please refer to [[Beam and Raster Checkout for A1n/d2n (Short Procedure)]].
−
  - Establish beam in the hall
 
−
  - Initial Raster checks
 
−
  - Harp scans
 
−
  - Target/Beam centering, Raster calibration
 
  
−
=== Optics (angle and ytarg) Calibration ===
+
== Moller Measurement (16 hrs) ==
−
   ''' Goals '''
+
  - Will need 8 hours to setup Moller and 8 hours to perform one Moller measurement.
−
   - To calibration spectrometer optics for 40cm long target at 30 deg. Calibrate angle reconstruction.
+
  - Will be carried out by Dave Gaskell.
 +
  - Time: 8+8 hours
 +
 
 +
== Beam Energy Measurement (1hr) ==
 +
  - RC should contact MCC to organize a beam energy measurement during 1-pass running.
 +
  - Time: 1 hour
 +
 
 +
== Optics Calibration ==
 +
 
 +
  - Here is a word doc runsheet file, may be useful to keep track of things: [https://hallcweb.jlab.org/experiments/A1n/meetings/runplan/optics_runplan_runsheets.doc Optics runsheet]
 +
 
 +
=== 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'''
 
   '''Setup'''
−
   - Beam Current:  5 -- 20 uA CW, raster varies
+
   - Beam Current:  5-40 uA CW, raster varies
 
   - HMS setting: 30 degrees, -1.2 GeV/c (electron)
 
   - HMS setting: 30 degrees, -1.2 GeV/c (electron)
 
   - SHMS setting: 30 degrees, -1.68 GeV/c (electron)
 
   - SHMS setting: 30 degrees, -1.68 GeV/c (electron)
−
   - Target:      Multi(7)-foil Carbon Foils
+
   - Target:      "Carbon Optics" Target (this should have 4 foils at locations 1,4,6,7; NOT "Carbon Foil" and NOT "Carbon Hole")
  
 
   '''Procedure'''
 
   '''Procedure'''
−
   - Move target to multi-foil position;
+
   - Move target to "Carbon Optics" Target position;
 
   - Move Sieve Slit IN for both HMS and SHMS;
 
   - Move Sieve Slit IN for both HMS and SHMS;
−
   - Take a short run (2min) at 20uA, verify sieves are both IN;
+
   - Ask 40uA raster at 0.5mm, verify trigger rate and set for ELCLEAN triggers PS3=0 and the rest -1;
−
   - Ask MCC to increase current to 20uA (Max for raster off on this target). Take two runs, 45 minutes each.  
+
   - 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.
−
  - 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;
 
   - Move Sieve Slit OUT for both HMS and SHMS;
−
   - Take one run at 20 uA for 15 minutes.  
+
   - 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 to turn raster OFF, take one run at 20 uA for 15 minutes.  
+
   - 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.
  
−
=== Optics (Momentum) Calibration ===
+
=== Optics (Momentum) Calibration (6 hrs)===
−
   ''' Goals '''
+
   '''Goals '''
−
   - To calibration momentum reconstruction of spectrometers.
+
   - To calibrate momentum reconstruction of spectrometers.
 +
  - Time: estimate 6 hours total including many momentum changes.
  
 
   '''Setup'''
 
   '''Setup'''
−
   - Beam Current:  5--20 uA CW, raster always OFF
+
   - Beam Current:  5-40 uA CW, raster varies, assuming beam energy 2.183 GeV
−
   - HMS setting: 11.7 deg, momentum varies (electron)
+
   - HMS setting: 11.7 deg, momentum: -2.348 (-8%)
−
   - SHMS setting: 8.5 deg, momentum varies (electron)
+
   - SHMS setting: 8.5 deg, momentum: -2.504 (-13%)
−
   - Target:      Double Carbon Foils
+
   - 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 [https://hallcweb.jlab.org/experiments/A1n/meetings/runplan/A1n_commissioning_kine.ods spreadsheet to calculate the proper momentum settings]:
  
 
   '''Procedure'''
 
   '''Procedure'''
−
   - Move target to Double carbon foil position.
+
   - 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.
  
−
   - Ask the target operator to do one target polarimetry measurement.
+
   - HMS delta scan (Sieve IN for all):
−
  - Move target to polarized 3He cell position, take a 2 minute run at 5uA and confirm we see events from both 3He gas and two glass windows at z=+20 and -20cm.
+
    - -8%: 2.34811 GeV
−
  - Stop the beam, ask the target operator to do one target polarimetry measurement.
+
    - -5%: 2.28289 GeV
−
  - take a 10 (what's the time constant for beam depolarization to set in?) minute run at 30uA, watch the beam ramp rate (confirm it is no faster than 1uA/sec), and confirm we see events from both 3He gas and two glass windows at z=+20 and -20cm.
+
    - -2%: 2.21855 GeV
−
  - Stop the beam, ask the target operator to do one target polarimetry measurement.
+
    - 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.
  
−
=== Polarized 3He Delta Transverse Asymmetry ===
+
  '''Things to watch for (Expert Analysis)'''
−
   ''' Goals '''
+
  - There should be optics expert(s) checking data quality as we go.
−
   - To measure/confirm sign of physics transverse asymmetry of Delta resonance
+
 
 +
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 and Reference Cell Runs, Delta resonance setting ==
 +
 
 +
=== Polarized 3He Delta Transverse Asymmetry (2hr minimum, 3-5hr ideal) ===
 +
   '''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'''
 
   '''Setup'''
−
   - Beam Current: up to 5 uA CW, raster always ON (5mm diameter)
+
   - Beam Current: 5-30uA, raster always ON (5mm diameter)
−
   - HMS setting: 11.7 deg, -2.068 GeV/c (electron)
+
  - Beam IHWP:    should be switched half-way
−
   - SHMS setting: 8.5 deg, -2.083 GeV/c (electron)
+
  - Target:      Polarized 3He Cell, Empty Reference Cell
−
   - Target:     Polarized 3He Cell
+
  - Detectors:    All scintillator bars ON.
−
   - Target spin direction: 0-deg, 180-deg
+
  - Parity check: Inform Hall A prior to taking data to make sure they set the charge asymmetry feedback cutoff at 2uA.
−
   - 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.
+
  '''Spectrometer Setup (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)
 +
  -
 +
  '''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)'''
 +
   - HMS setting: 12.5 deg, -1.74695 GeV/c (electron W=1.232)
 +
   - SHMS setting: 12.5 deg, -1.74695 GeV/c (electron W=1.232)
  
 +
  '''Pol 3He Target Setup'''
 +
  - Target spin direction: 90 or 270-deg
 +
  - See [https://docs.google.com/spreadsheets/d/12Vlo3VFXRLx-pcB_TKva8rNHhKBEjzXze3oV1eG_jHA/edit?usp=sharing Target Field Runplan] for coil currents settings.
  
 
   '''Procedure'''
 
   '''Procedure'''
−
   - Set spectrometers at the required settings, target at Polarized 3He Cell position, spin polarization at either 0 or 180 degrees.
+
   - Set spectrometers at the required settings, target at Reference Cell position, pump the reference cell to empty;
−
   - Perform one polarimetry measurement before taking data.
+
  - Check and make sure all scintillators are ON;
−
   - 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).
+
  - 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.
−
   - Once scintillators are set, take one 1-minute run at 2uA, check rates and adjust prescale factor. Adjust current so HMS is at 4.5kHz PS=1. SHMS expected to require PS=15 to limit DAQ rate at 4.5kHz.  
+
  - Take one 20-minute run (beam ON time 10 min) or until reaching 10,000 events for both HMS and SHMS
−
   - 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.
+
 
−
   - Rotate target spin direction from 0 to 180 deg (or from 180 to 0 deg)
+
  - Move target to Polarized 3He Cell position, spin polarization at either 90 or 270 degrees.
−
   - 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.
+
   - Perform one set of NMR, EPR, pNMR 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 3 hours of beam time. If time is less than 3 hrs, take shorter/less runs at each beam IHWP setting.
 +
 
 +
   - Take three 30-minute (beam ON 15 min each) runs; Verify data quality (see below).
 +
  - Perform one pNMR 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 three 30-minute (beam ON 15 min each) runs; Verify data quality (see below).
 +
  - Perform one set of NMR, EPR, pNMR measurements.
  
 
   '''Things to watch online'''
 
   '''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 y or z cuts to isolate events scattered from 3He gas (We do not want events from the glass windows!)
−
   - Apply W or P cuts to isolate elastic events from others.
+
   - Apply 1.1<W<1.35 GeV cut to isolate the Delta resonance.
−
   - Run online script to ensure we see physics asymmetry.  
+
   - Run online script to ensure we see physics asymmetry. HMS and SHMS should see opposite asymmetries.  
  
−
  - Expected total rate: 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): Ameas=2.1% if Pt=50%, Pb=85%, N2 dilution 0.92.
−
   - Expected asymmetries (after W and Ytg cuts): 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 rate: 5kHz at 1uA, about 40% would be Delta from 3He gas.
−
   - Expected uncertainties dA/A=3% on HMS.
+
  - 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 250k. If target polarization is below 50% or beam current is below 30uA, scale this number up by (50%/Pt)^2*(30uA/I).
 +
   - Expected uncertainties better than dA/A=10% on each of HMS and SHMS within 10 minutes of running.
  
 +
== Polarized 3He and Reference Cell Runs, 3He elastic setting (15 hrs ideal, 9 hrs min)==
  
−
=== Polarized 3He Elastic Longitudinal Asymmetry ===
+
  - Experts must watch EDTM rate (Brad or Sylvester)
−
   ''' Goals '''
+
 
−
   - To measure physics longitudinal asymmetry of 3He elastic scattering, cross check PbPt from Moller and Target Polarimetry
+
=== Spectrometer and Pol 3He Targ Setting for All Runs at the 3He Elastic Setting ===
 +
  '''Spectrometer Setup (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)
 +
 
 +
  '''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)'''
 +
  - HMS setting: 12.5 deg, -2.1435 GeV/c (electron 3He elastic)
 +
  - SHMS setting: 12.5 deg, -2.1435 GeV/c (electron 3He elastic)
 +
  -
 +
  '''Pol 3He Target Setup'''
 +
  - Target Spin Direction: 0 and 180 deg
 +
  - See [https://docs.google.com/spreadsheets/d/12Vlo3VFXRLx-pcB_TKva8rNHhKBEjzXze3oV1eG_jHA/edit?usp=sharing Target Field Runplan] for coil currents settings.
 +
 
 +
=== Reference Cell Hydrogen (H2) Cross Section (1hr)===
 +
   '''Goals '''
 +
   - To measure hydrogen elastic cross section as a cross check of data quality
  
 
   '''Setup'''
 
   '''Setup'''
−
   - Beam Current:   up to 5 uA CW, raster always ON (5mm diameter)
+
   - Beam Current: up to 30uA and DAQ rate-limited, raster always ON (5mm diameter)
−
  - HMS setting: 11.7 deg, -2.068 GeV/c (electron)
+
   - Target:       Reference Cell, filled with H2 and Empty.
−
  - SHMS setting: 8.5 deg, -2.083 GeV/c (electron)
+
   - Detectors:   All SC bars on
−
   - Target:     Polarized 3He Cell
 
−
  - Target spin direction: 0-deg, 180-deg
 
−
   - 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 the Reference Cell position;
 +
  - Pump out Reference Cell (to vacuum), record the pressure reading in the Start_Run entries.
 +
  - Ask MCC for 10uA raster ON (5mm dia), check rates and prescale factors (Save PS file if changed). Goal is to reach (3.5-4)kHz DAQ rate on both HMS and SHMS. If rates too low, increase the beam current but do not exceed 30uA. If rates too high, prescale it down and do NOT drop current below 10uA.
 +
  - Take one 20-minute run, make sure there are no less than 10,000 events for each of HMS and SHMS.
 +
  - Record the pressure in End_Run entries.
  
−
   '''Procedure'''
+
   - Fill Reference Cell to 10 atm of hydrogen gas;
−
   - Set spectrometers at the required settings, target at Polarized 3He Cell position, spin polarization at either 0 or 180 degrees.
+
   - Keep beam current the same as the above Empty Cell run, check rates and prescale factors (Save PS file if changed). Goal is to reach (3.5-4)kHz DAQ rate on both HMS and SHMS. If rates too low, increase the beam current but do not exceed 30uA. If rates too high, prescale it down and do NOT drop current below 10uA.
−
  - Perform one polarimetry measurement before taking data.
+
   - Take one 20-minute run, apply ztar and W cut and make sure H2 elastic events from the H2 gas are no less than 10,000 for each of HMS and SHMS.
−
  - 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).
+
   - Record the pressure reading in the Start_Run and End_Run entries.
−
  - Once scintillators are set, take one 1-minute run at 2uA, check rates and adjust prescale factor. Adjust current so HMS is at 4.5kHz PS=1. SHMS expected to require PS=15 to limit DAQ rate at 4.5kHz.  
 
−
   - 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.
 
−
   - 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.
 
  
 
   '''Things to watch online'''
 
   '''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)
+
   - Ensure all SC bars are ON
−
   - Apply y or z cuts to isolate events scattered from 3He gas (We do not want events from the glass windows!)
+
   - For 10atm H2 filled cell, apply ytar or ztar cuts to isolate events scattered from H2 gas (We do not want events from the glass windows!), and apply W cuts to select only H2 elastic. Note the elastic peak is not at dp=0 because the spectrometers are set at 3He elastic.  
−
  - Apply W or P cuts to isolate elastic events from others.
+
   - Run online script to ensure we collect no less than 10,000 H2 elastic (with ytar or ztar and W cuts) for each of HMS and SHMS
−
   - Run online script to ensure we see physics asymmetry.
 
  
−
   - Expected total rate: HMS at 1uA total 1.8KHz 3He gas elastic 240Hz; SHMS at 1uA total 27.7kHz Prescaled by 15 to 3He gas elastic 740Hz
+
=== Setup Scintillator bars for 3He Elastic Scattering (30min max ideally)===
−
   - Expected asymmetries (after W and Ytg cuts): HMS Aphys=4.8% Ameas=2.1% and SHMS Aphys=2.5% Ameas=0.98% if Pt=50%, Pb=85%, N2 dilution 0.92.
+
  '''Goals '''
−
   - Expected uncertainties dA/A=3% on HMS.
+
   - To determine which two SC bars should be turned ON to focus on 3He elastic (suppress quasielastic)
 +
  - Must be done Prior to Polarized 3He Longitudinal Asymmetry and all N2 and 3He reference cell runs at the elastic setting
 +
 
 +
  '''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 two scintillator bars should be kept on to accept the whole 3He elastic peak and to suppress quasielastic and inelastic events. (expert driven).
  
 +
  '''Things to watch for'''
 +
  - Make sure to select the correct peak -- 3He elastic, not quasielastic (not that they can be easily confused);
 +
  - 3He elastic peak should be located at dp=0.
  
−
=== Reference Cell Hydrogen (H2) Cross Section ===
+
=== 3He Reference Cell Runs (N2 and 3He Pressure Curves, False Asymmetries) (5hrs ideal, 3 hrs min) ===
−
   ''' Goals '''
+
   '''Goals '''
−
   - To measure hydrogen elastic cross section, need 10,000 elastic events each for HMS and SHMS
+
   - For empty cell, to determine window background for elastic setting
 +
  - For N2, need 5 points at 0.5, 1.0, 2, 4 and 8 atm, 10,000 N2 elastic events for each pressure setting and each spectrometer.
 +
  - For 3He, need 6 points at 1, 2, 4, 6, 8 and 10 atm, 10,000 3He elastic events for each pressure setting and each spectrometer.
 +
  - Reference cell must be filled with 3He last, and do NOT pump the 3He gas out!
 +
  - time: couple of hours assuming 50% beam efficiency
  
 
   '''Setup'''
 
   '''Setup'''
 +
  - Beam Current: 10-30uA, raster always ON (5mm diameter). Do not drop currents below 10uA.
 +
  - Target:      Reference Cell, Empty, filled with N2, filled with 3He (last)
 +
  - Detectors:    We will need to keep only 2 SC bars ON to take mostly 3He elastic and limit quasi-elastic scattering events.
  
 +
  '''Procedure'''
 +
  - Set spectrometers at the required settings, target at the Reference Cell position;
 +
  - Make sure the correct two SC bars are ON;
 +
  - Pump the reference cell to empty (vacuum);
 +
 
 +
  - Ask for 10 uA raster ON (5mm dia), check trigger rates and PS factors. Ideally we would like to see (3.5-4)kHz DAQ rates. If rates are too high, use Prescaling (save PS file if changed). If rates are too low, increase beam current but do not exceed 30uA.
 +
  - Take one 20-minute run at the optimal current you found.
  
−
   '''Procedure'''
+
   - Fill Reference Cell with N2 gas to 8.0 atm.
 +
  - Keep the same beam current as above, check trigger rate. Ideally we would like to see (3.5-4)kHz DAQ rates. If rates are too high, use Prescaling (save PS file if changed). If rates are too low, increase beam current but do not exceed 30uA.
 +
 
 +
  - Take two 45-minute run. Record the pressure reading in the Start_Run and End_Run entries.
 +
  - Ask MCC to change the beam IHWP plate status, for example from IN to OUT or from OUT to IN.
 +
  - Take two 45-minute run. Record the pressure reading in the Start_Run and End_Run entries.
 +
  - Next proceed to remaining pressure settings. For each setting, follow rate/prescaling criteria above. For each run, record the pressure reading in the Start_Run and End_Run entries.
 +
  - Pump/vent the cell to 4.0 atm, take one 20-minute run.
 +
  - Pump/vent the cell to 2.0 atm, take one 20-minute run.
 +
  - Pump/vent the cell (slowly) to 1.0 atm, take one 20-minute run.
 +
  - Pump/vent the cell (slowly) to 0.5 atm, take one 20-minute run.
 +
 
 +
  - Pump the cell to vacuum.
 +
  - Next proceed to 3He pressure curve measurement. For each setting, follow rate/prescaling criteria above. For each run, record the pressure reading in the Start_Run and End_Run entries.
 +
  - Fill the cell to 1 atm with 3He gas, take one 20-min run at 10uA.
 +
  - Fill the cell to 2 atm with 3He gas, take one 20-min run at 10uA.
 +
  - Fill the cell to 4 atm with 3He gas, take one 20-min run at 10uA.
 +
  - Fill the cell to 6 atm with 3He gas, take one 20-min run at 10uA.
 +
  - Fill the cell to 8 atm with 3He gas, take one 20-min run at 10uA.
 +
  - Fill the cell to 10 atm with 3He gas, take one 20-min run at 10uA.
 +
 
 +
  - Important: After these runs are completed, do NOT pump out the 3He gas!
  
 +
  '''Things to watch for'''
 +
  - These reference cell runs must be taken with exactly the same spectrometer and scintillator settings as polarized 3He elastic asymmetry runs (see next).
 +
  - Beam current should not be below 10uA (BCM accuracy) and should not be above 30uA (glass cell safety).
 +
  - For each gas pressure setting (except for empty cells), need 10,000 events from gas alone (apply ztar cuts) for each of HMS and SHMS.
  
−
=== Reference N2 Pressure Curve ===
+
=== Polarized 3He Elastic Longitudinal Asymmetry (8hrs ideal, 4hrs minimum)===
−
   ''' Goals '''
+
   '''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.
+
   - To measure physics longitudinal asymmetry of 3He elastic scattering to (2-3)% relative, cross check PbPt from Moller and Target Polarimetry
  
 
   '''Setup'''
 
   '''Setup'''
 +
  - Beam Current: 10-30uA, raster always ON (5mm diameter)
 +
  - Target:      Polarized 3He Cell, Reference Cell
 +
  - Target spin direction: 0-deg, 180-deg
 +
  - See [https://docs.google.com/spreadsheets/d/12Vlo3VFXRLx-pcB_TKva8rNHhKBEjzXze3oV1eG_jHA/edit?usp=sharing 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.
  
−
   '''Procedure'''
+
   - 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.
  
−
=== Reference 3He Pressure Curve ===
+
   - Call MCC and ask beam IHWP to be inserted (or taken out). Need to inform other halls prior to the switch.
−
  ''' Goals '''
+
   - Take two 60-minute runs (assuming 50% beam efficiency).
−
   - 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.
+
  - Perform one pNMR polarimetry measurement. Verify target is still polarized.
−
   - 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'''
+
   - 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.
  
−
   '''Procedure'''
+
   - 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).

Latest revision as of 11:06, 17 December 2019

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.

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

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).

Moller Measurement (16 hrs)

 - Will need 8 hours to setup Moller and 8 hours to perform one Moller measurement.
 - Will be carried out by Dave Gaskell.
 - Time: 8+8 hours

Beam Energy Measurement (1hr)

 - RC should contact MCC to organize a beam energy measurement during 1-pass running.
 - Time: 1 hour

Optics Calibration

 - Here is a word doc runsheet file, may be useful to keep track of things: Optics runsheet

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.

Optics (Momentum) Calibration (6 hrs)

 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

Polarized 3He and Reference Cell Runs, Delta resonance setting

Polarized 3He Delta Transverse Asymmetry (2hr minimum, 3-5hr ideal)

 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, Empty Reference 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 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) 
 - 
 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)
 - HMS setting:  12.5 deg, -1.74695 GeV/c (electron W=1.232)
 - SHMS setting: 12.5 deg, -1.74695 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 Reference Cell position, pump the reference cell to empty;
 - Check and make sure all scintillators are ON;
 - 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.
 - Take one 20-minute run (beam ON time 10 min) or until reaching 10,000 events for both HMS and SHMS

 - Move target to Polarized 3He Cell position, spin polarization at either 90 or 270 degrees.
 - Perform one set of NMR, EPR, pNMR 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 3 hours of beam time. If time is less than 3 hrs, take shorter/less runs at each beam IHWP setting.

 - Take three 30-minute (beam ON 15 min each) runs; Verify data quality (see below).
 - Perform one pNMR 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 three 30-minute (beam ON 15 min each) runs; Verify data quality (see below).
 - Perform one set of NMR, EPR, pNMR 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=2.1% 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 250k. If target polarization is below 50% or beam current is below 30uA, scale this number up by (50%/Pt)^2*(30uA/I).
 - Expected uncertainties better than dA/A=10% on each of HMS and SHMS within 10 minutes of running.

Polarized 3He and Reference Cell Runs, 3He elastic setting (15 hrs ideal, 9 hrs min)

 - 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 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)

 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)
 - HMS setting: 12.5 deg, -2.1435 GeV/c (electron 3He elastic) 
 - SHMS setting: 12.5 deg, -2.1435 GeV/c (electron 3He elastic)
 -
 Pol 3He Target Setup
 - Target Spin Direction: 0 and 180 deg
 - See Target Field Runplan for coil currents settings.

Reference Cell Hydrogen (H2) Cross Section (1hr)

 Goals 
 - To measure hydrogen elastic cross section as a cross check of data quality

 Setup
 - Beam Current: up to 30uA and DAQ rate-limited, raster always ON (5mm diameter)
 - Target:       Reference Cell, filled with H2 and Empty.
 - Detectors:    All SC bars on

 Procedure
 - Set spectrometers at the required settings, target at the Reference Cell position;
 - Pump out Reference Cell (to vacuum), record the pressure reading in the Start_Run entries.
 - Ask MCC for 10uA raster ON (5mm dia), check rates and prescale factors (Save PS file if changed). Goal is to reach (3.5-4)kHz DAQ rate on both HMS and SHMS. If rates too low, increase the beam current but do not exceed 30uA. If rates too high, prescale it down and do NOT drop current below 10uA.
 - Take one 20-minute run, make sure there are no less than 10,000 events for each of HMS and SHMS. 
 - Record the pressure in End_Run entries. 

 - Fill Reference Cell to 10 atm of hydrogen gas;
 - Keep beam current the same as the above Empty Cell run, check rates and prescale factors (Save PS file if changed). Goal is to reach (3.5-4)kHz DAQ rate on both HMS and SHMS. If rates too low, increase the beam current but do not exceed 30uA. If rates too high, prescale it down and do NOT drop current below 10uA.
 - Take one 20-minute run, apply ztar and W cut and make sure H2 elastic events from the H2 gas are no less than 10,000 for each of HMS and SHMS.
 - Record the pressure reading in the Start_Run and End_Run entries.

 Things to watch online
 - Ensure all SC bars are ON
 - For 10atm H2 filled cell, apply ytar or ztar cuts to isolate events scattered from H2 gas (We do not want events from the glass windows!), and apply W cuts to select only H2 elastic. Note the elastic peak is not at dp=0 because the spectrometers are set at 3He elastic. 
 - Run online script to ensure we collect no less than 10,000 H2 elastic (with ytar or ztar and W cuts) for each of HMS and SHMS

Setup Scintillator bars for 3He Elastic Scattering (30min max ideally)

 Goals 
 - To determine which two SC bars should be turned ON to focus on 3He elastic (suppress quasielastic)
 - Must be done Prior to Polarized 3He Longitudinal Asymmetry and all N2 and 3He reference cell runs at the elastic setting
 
 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 two scintillator bars should be kept on to accept the whole 3He elastic peak and to suppress quasielastic and inelastic events. (expert driven).

 Things to watch for
 - Make sure to select the correct peak -- 3He elastic, not quasielastic (not that they can be easily confused);
 - 3He elastic peak should be located at dp=0.

3He Reference Cell Runs (N2 and 3He Pressure Curves, False Asymmetries) (5hrs ideal, 3 hrs min)

 Goals 
 - For empty cell, to determine window background for elastic setting
 - For N2, need 5 points at 0.5, 1.0, 2, 4 and 8 atm, 10,000 N2 elastic events for each pressure setting and each spectrometer.
 - For 3He, need 6 points at 1, 2, 4, 6, 8 and 10 atm, 10,000 3He elastic events for each pressure setting and each spectrometer.
 - Reference cell must be filled with 3He last, and do NOT pump the 3He gas out!
 - time: couple of hours assuming 50% beam efficiency

 Setup
 - Beam Current: 10-30uA, raster always ON (5mm diameter). Do not drop currents below 10uA.
 - Target:       Reference Cell, Empty, filled with N2, filled with 3He (last)
 - Detectors:    We will need to keep only 2 SC bars ON to take mostly 3He elastic and limit quasi-elastic scattering events. 

 Procedure
 - Set spectrometers at the required settings, target at the Reference Cell position;
 - Make sure the correct two SC bars are ON;
 - Pump the reference cell to empty (vacuum);
 
 - Ask for 10 uA raster ON (5mm dia), check trigger rates and PS factors. Ideally we would like to see (3.5-4)kHz DAQ rates. If rates are too high, use Prescaling (save PS file if changed). If rates are too low, increase beam current but do not exceed 30uA.
 - Take one 20-minute run at the optimal current you found.

 - Fill Reference Cell with N2 gas to 8.0 atm.
 - Keep the same beam current as above, check trigger rate. Ideally we would like to see (3.5-4)kHz DAQ rates. If rates are too high, use Prescaling (save PS file if changed). If rates are too low, increase beam current but do not exceed 30uA.

 - Take two 45-minute run. Record the pressure reading in the Start_Run and End_Run entries.
 - Ask MCC to change the beam IHWP plate status, for example from IN to OUT or from OUT to IN.
 - Take two 45-minute run. Record the pressure reading in the Start_Run and End_Run entries.
 - Next proceed to remaining pressure settings. For each setting, follow rate/prescaling criteria above. For each run, record the pressure reading in the Start_Run and End_Run entries.
 - Pump/vent the cell to 4.0 atm, take one 20-minute run. 
 - Pump/vent the cell to 2.0 atm, take one 20-minute run. 
 - Pump/vent the cell (slowly) to 1.0 atm, take one 20-minute run. 
 - Pump/vent the cell (slowly) to 0.5 atm, take one 20-minute run. 

 - Pump the cell to vacuum.
 - Next proceed to 3He pressure curve measurement. For each setting, follow rate/prescaling criteria above. For each run, record the pressure reading in the Start_Run and End_Run entries.
 - Fill the cell to 1 atm with 3He gas, take one 20-min run at 10uA. 
 - Fill the cell to 2 atm with 3He gas, take one 20-min run at 10uA.
 - Fill the cell to 4 atm with 3He gas, take one 20-min run at 10uA.
 - Fill the cell to 6 atm with 3He gas, take one 20-min run at 10uA.
 - Fill the cell to 8 atm with 3He gas, take one 20-min run at 10uA.
 - Fill the cell to 10 atm with 3He gas, take one 20-min run at 10uA.

 - Important: After these runs are completed, do NOT pump out the 3He gas!

 Things to watch for
 - These reference cell runs must be taken with exactly the same spectrometer and scintillator settings as polarized 3He elastic asymmetry runs (see next).
 - Beam current should not be below 10uA (BCM accuracy) and should not be above 30uA (glass cell safety).
 - For each gas pressure setting (except for empty cells), need 10,000 events from gas alone (apply ztar cuts) for each of HMS and SHMS.

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).
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