5-pass production for A1n

Overview

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 5-pass production of A1n, we will do the high x setting (large angle) first, then rotate the target. After target rotation we will take low/medium x data for A1n, followed by the d2n experiment.

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

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

Moller Measurement

 - Will need 8 hours to setup Moller and 8 hours to perform one Moller measurement.
 - Plan: we will perform one Moller measurement every (two?) week or after each beam condition change.

Beam Energy Measurement

 - RC should contact MCC to organize a beam energy measurement during 1-pass running.
 - Time: 1 hour
 - Plan: we will perform one beam energy measurement every (two?) week or after each beam condition change.

Large Angle (30-degree) High Momentum Running (Kine 4,B)

 Overview 
 - We will run 42.5 (40 now?) calendar days with SHMS Kine B/HMS Kine 4;
 - For each kinematic setting, a large fraction of data will be taken with longitudinal target spin, with the rest at transverse target spin;
 - Beam IHWP and Target Spin should be flipped routinely, providing same statistics for ++, +-, -+ and -- configurations;
 - We will take 1 hour of Empty Cell runs. More may be needed.
 - We will take 4 hours of Reference Cell N2 runs at 8 atm;
 - We will take 4 hours of data with SHMS at positive polarity (should be combined with positive polarity kine C below);

Large Angle (30-degree) Low Momentum Running (Kine 3,C)

 Overview 
 - We will run 7.3 (6 now?) days at SHMS Kine C/HMS Kine 3;
 - For each kinematic setting, a large fraction of data will be taken with longitudinal target spin, with the rest at transverse target spin;
 - Beam IHWP and Target Spin should be flipped routinely, providing same statistics for ++, +-, -+ and -- configurations;
 - We will take 1 hour of Empty Cell runs. More may be needed.
 - We will take 4 hours of Reference Cell N2 runs at 8 atm;
 - We will take 4 hours of data with SHMS at positive polarity (should be combined with positive polarity kine B above);
 -  

Small Angle (12.5-degree) Running

3He Reference Cell Runs (N2 and 3He Pressure Curves)

 Goals 
 - 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 5 points at 1, 2, 4, 6 and 8 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: 2 hrs 20min total

 Setup
 - Beam Current: DAQ rate-limited and up to 30uA, raster always ON (5mm diameter)
 - Target:      Reference Cell, Empty, filled with N2, filled with 3He (last)
 - Detectors: We will need to keep only 2 SC bars ON to limit quasi-elastic scattering events. 

 Procedure
 - Set spectrometers at the required settings, target at the Reference Cell position;
 - Make sure the correct 2 SC bars are ON;
 - Pump the reference cell to empty (vacuum);
 
 - Take two 5-minute runs at 5 uA. Ideally this should yield 4.5kHz with PS=1. If rates are too high, lower the current but do not drop below 2uA. If rates are too low, increase current but do not exceed 30uA.

 - Fill Reference Cell with N2 gas to 8.0 atm, take two 5-minute runs at 2 uA. If rates are too high, prescale it down.
 - Pump the cell to 4.0 atm, take two 5-minute runs at 2 uA. If rates are too high, prescale it down.
 - Pump the cell to 2.0 atm, take two 5-minute runs at 2 uA. If rates are too high, prescale it down.
 - Pump the cell (slowly) to 1.0 atm, take two 8-minute runs at 5 uA. If rates are too high, lower the current but do not drop below 2uA. 
 - Pump the cell (slowly) to 0.5 atm, take two 15-minute runs at 5 uA. If rates are too high, lower the current but do not drop below 2uA. 

 - Pump the cell to vacuum
 - Fill the cell to 1 atm with 3He gas, take two 5-minute runs at 5 uA. If rates are too high, lower the current but do not drop below 2uA. 
 - Fill the cell to 2 atm with 3He gas, take two 5-minute runs at 5 uA. If rates are too high, lower the current but do not drop below 2uA. 
 - Fill the cell to 4 atm with 3He gas, take two 5-minute runs at 5 uA. If rates are too high, lower the current but do not drop below 2uA.
 - Fill the cell to 6 atm with 3He gas, take two 5-minute runs at 4 uA. If rates are too high, lower the current but do not drop below 2uA.
 - Fill the cell to 8 atm with 3He gas, take two 5-minute runs at 3 uA. If rates are too high, lower the current but do not drop below 2uA.

 - 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)
 - For each gas pressure setting (except for empty cells), need 10,000 events from gas alone (apply ytar or ztar cuts) for 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: DAQ rate-limited and up to 30uA, raster always ON (5mm diameter)
 - HMS setting: 12.5 deg, -2.1435 GeV/c (electron) 
 - SHMS setting: 12.5 deg, -2.1435 GeV/c (electron) 
 - Target:      Polarized 3He Cell, Reference 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 the Reference Cell position;
 - Pump the reference cell to empty (vacuum in the cell);
 - 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 another short run at 1uA to determine rate and prescale factor. Adjust beam current to reach close to 4.5kHz with PS=1 (but do not exceed 30uA), which means current is probably limited by SHMS rate.
 - Take a five-minute run or until reaching 10,000 events for both HMS and SHMS

 - Move target to Polarized 3He Cell position, spin polarization at either 0 or 180 degrees.
 - Perform one polarimetry measurement before taking data.
 - Make sure the same two SC bars are on as the Reference Cell, 
 - 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, adjust beam current to reach 4.5kHz on HMS with PS=1. For SHMS likely need PS>1 to keep DAQ rate within limit.
 - Take four 30-minute runs, 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 four 30-minute runs, 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 four 30-minute runs, 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 four 30-minute runs, perform one polarimetry measurement after each run. Verify data quality (see below) and verify target is still polarized.

 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 and target spin flip.

 - Expected total rate: (To be updated) 
 - Expected asymmetries (after W and Ytg cuts): Aphys=5.8% Ameas=2.3% if using Pt=50%, Pb=85%, N2 dilution 0.92.
 - Expected uncertainties dA/A=2% (goal) or 3% (minimum).