1-pass calibration for A1n
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Revision as of 14:06, 1 December 2019 by Xiaochao (talk | contribs) (→Setup Scintillator bars for 3He Elastic Scattering)
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
- 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
- RC should contact MCC to organize a beam energy measurement during 1-pass running. - Time: 1 hour
Optics Calibration
Optics (angle and ytarg) Calibration
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: Multi(7)-foil Carbon Foils
Procedure - Move target to multi-carbon foil position; - Move Sieve Slit IN for both HMS and SHMS; - Ask 40uA raster OFF, verify trigger rate and set prescale factors; - Take a short run to verify sieves are both IN; - Take two 30-minute runs (assuming 50% beam quality i.e 15 min "beam ON" time) at this setting. - Ask MCC to turn raster ON to 5mm diameter, take one run at 40 uA for 30 minutes (15 min "beam ON" time). - Move Sieve Slit OUT for both HMS and SHMS; - Take one run at 40 uA (raster OFF) for 10 minutes (5 min "beam ON" time). Check trigger rate and prescale if necessary. - Ask MCC to turn raster ON to 5mm diameter, take one run for 10 minutes (5 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
Goals - To calibrate momentum reconstruction of spectrometers. - Time: estimate 6 hours total including many momentum changes.
Setup - Beam Current: 5-40 uA CW, raster always OFF - HMS setting: 11.7 deg, momentum: nominal(0%) setting for carbon elastic scattering is 2.17418 GeV, also need 5%, 8% -> cycle to -8%, -5%, 0%. - SHMS setting: 8.5 deg, momentum: nominal(0%) setting for carbon elastic scattering is 2.17833 GeV, also need 5%, 10% -> cycle to -25%, -20%, -15%, -10%, -5%, 0%. - Target: Double Carbon Foils (not Double Carbon Hole)
Procedure - Move target to Double Hole Carbon position. - start from 0%, sieve OUT; - Ask for 5uA raster OFF; Check trigger rates and adjust PS to reach (3.5-4)kHz on each DAQ. - Take two 20-minutes runs for each spectrometer. - Move Sieve slits IN for both spectrometers. - Ask for 20uA raster OFF, check trigger rates. Adjust the current up to 40uA to reach (3.5-4)kHz on HMS DAQ with PS=1, adjust PS for SHMS to reach (3.5-4)kHz on SHMS DAQ. - Take two 20-min runs for HMS and one 20-min run for SHMS at this setting (0%). If SHMS ends early, can proceed to delta scan below. - Using the same PS factors and beam current, start the delta scan as listed below. For each delta setting, take two 20-min run for HMS and one 20-min run for SHMS.
- In case spectrometer angles are not exactly 11.7 and 8.5 deg, here is a spreadsheet to calculate the proper momentum settings:
- HMS delta scan (Sieve IN for all): - 0%: 2.17418 GeV (already done two steps up) - 5%: 2.06547 GeV - 8%: 2.00024 GeV - -8%: 2.34811 GeV - -5%: 2.28289 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): - 0%: 2.17833 GeV (already done two steps up) - 5%: 2.06941 GeV - 10%: 1.96049 GeV - 15%: 1.85158 GeV - 20%: 1.74266 GeV - 25%: 1.63375 GeV - -10%: 2.39616 GeV - -5%: 2.28724 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.
Polarized 3He and Reference Cell Runs, Delta resonance setting
Polarized 3He Delta Transverse Asymmetry
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 - HMS setting: 12.5 deg, -1.799 GeV/c (electron) - SHMS setting: 12.5 deg, -1.799 GeV/c (electron) - Target: Polarized 3He Cell, Empty Reference Cell - Target spin direction: 90 or 270-deg - Target coil settings for 90 deg (beam left): BZ(HL)=-5.23057A, BX(HS)=5.16315A, VL=1.0A, VS=1.5A, HS=0.0A, HL=0.0A (HB current 594.4A) - Target coil settings for 270 deg (beam right): BZ(HL)=5.23057A, BX(HS)=-5.16315A, VL=2.6A, VS=1.5A, HS=1.0A, HL=1.0A (HB current 594.4A) - 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.
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. - Take two 30-minute (beam ON 15 min each) runs; Verify data quality (see below). - Perform one pNMR measurement. Verify target is still polarized. - 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. (may need to inform other halls in advance). For example from IN to OUT or from OUT to IN. - Take two 30-minute (beam ON 15 min each) runs; Verify data quality (see below). - Perform one pNMR measurement. Verify target is still polarized. - 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 uncertainties better than dA/A=10% on each of HMS and SHMS.
Polarized 3He and Reference Cell Runs, 3He elastic setting
- Experts must watch EDTM rate (Brad or Sylvester)
Spectrometer Setting for All Runs at the 3He Elastic Setting
- HMS setting: 12.5 deg, -2.1435 GeV/c (electron) - SHMS setting: 12.5 deg, -2.1435 GeV/c (electron) - Target Spin Direction: 0 and 180 deg - Target coil settings for 0 deg (pointing downstream along beamline): BZ(HL)=-5.23057A, BX(HS)=-5.16315A, VL=2.5A, VS=2.3A, HS=0.0A, HL=0.0A (HB current 708.7A) - Target coil settings for 180 deg (pointing upstream along beamline): BZ(HL)=5.23057A, BX(HS)=5.16315A, VL=2.0A, VS=1.5A, HS=0.0A, HL=0.0A (HB current 708.7A)
Reference Cell Hydrogen (H2) Cross Section
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); - 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.
- Fill Reference Cell to 10 atm of hydrogen gas; - Keep beam current the same as 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.
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
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 (2-5 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 (H2 elastic); - H2 elastic peak will NOT be at dp=0 because the spectrometer momenta are set at 3He elastic.
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 we would like to see (3.5-4)kHz 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 (3.5-4)kHz 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 (3.5-4)kHz 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).
