Fall 2016 LHRS optic plans

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Revision as of 18:51, 15 October 2016 by Vasulk (Talk | contribs) (Step L4: Proton Elastic Kinematics)

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Step L1: Procedure with Sieve-slit

  • Time estimate: 1 hour
* Trained personnel will be required to install the 1-inch tungsten sieve-slit collimator onto the front face of the HRS.
* If you need to increase the spectrometer momentum setting, make sure you cycle Q2 and Q3 as per the cycling procedure.
* Take sieve-slit runs with the multi-foil carbon target (optics) for the inelastic kinematics in the table.
* Electron rates assume 9 carbon foils, only 37 out of 155 sieve holes per foil have events (~ 0.41 mSr acceptance), and 8% delta acceptance.
* Electron rates assume 15 cm LH2 target, only 45 out of 155 sieve holes have events (~ 0.49 mSr acceptance), and 8% delta acceptance.
* Adjust the prescale factors to keep the DAQ deadtime below 10%.
* Before moving on to the next target, a GMp expert will determine online how many good electron events have been collected. 
Target Ebeam [GeV] P0 [GeV/c] Raster θe [deg] Q2 [GeV2] W [GeV] Rate [Hz] at 60 μA minutes at 60 μA Good Electrons
Optics 2.217 1.0 Off 17.5 0.20 1.72 540 32 1M events
15 cm LH2 2.217 1.0 3x3 mm2 17.5 0.20 1.72 4600 10.0 2.7M events


Step L2: Delta Scan with Proton Elastic (with sieve slit)

  • Time estimate: 1.5 hours
* Keep the 1-inch tungsten sieve-slit collimator on the front face of the left HRS.
* Take runs with the 15 cm liquid hydrogen target for the elastic kinematics in the table.
* Wait until the left dipole reaches the desired momentum and is stable.
* If you need to increase the spectrometer momentum setting, make sure you cycle Q2 and Q3 as per the cycling procedure.
* Rate estimates only include elastic electrons and does not include rate from inelastic events or from the target endcaps.
* Adjust the prescale factors to keep the DAQ deadtime below 10%.
* The Q2 for these settings is 0.41 GeV2.
Ebeam (GeV) k' (GeV) LQ1 (A) Raster θe (deg) ΔP (%) Rate [Hz] at 10 μA minutes at 10 μA Good Electrons
2.217 2.078 433.45 3x3 mm2 17.5 -4 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 2.038 425.11 3x3 mm2 17.5 -2 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 1.998 416.76 3x3 mm2 17.5 0 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 1.958 408.42 3x3 mm2 17.5 +2 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 1.918 400.08 3x3 mm2 17.5 +4 10,000 (2500 Hz with ps = 4) 10 1M events


Step L3: Dummy Target Runs

  • Go back to the ΔP = 0% elastic setting. Make sure the L-HRS P0 = 1.998 GeV.
  • Move the target to "15 cm Dummy"
  • Take L-HRS run with same setting as previous step.
  • Take data with this setting for 10 minutes


Ebeam (GeV) k' (GeV) LQ1 (A) Raster θe (deg) ΔP (%) Rate [Hz] at 10 μA minutes at 10 μA Good Electrons
2.217 1.998 416.76 3x3 mm2 17.5 0 460 10 270k events


Step L4: Proton Elastic Kinematics

  • Time estimate: 1 hour
* Trained personnel will be required to remove the 1-inch tungsten sieve-slit collimator from the front face of the HRS.
* Hall A Technical staff will need to move the left HRS from 17.5 degrees to 42 degrees.
* If you need to increase the spectrometer momentum setting, make sure you cycle Q2 and Q3 as per the cycling procedure.
* Elastic electron rates assume 15 μA on 15 cm LH2 target, 5 mSr acceptance.
* Use the following prescale factors: ps1=1, ps2=1, ps3=1, ps8=100. All other triggers should have zero prescale factor.
* The 15 cm dummy and carbon pointing runs need to be taken at the elastic setting.  So keep the momentum as is. 
* A GMp expert will check the data quality.
Target Raster Ebeam [GeV] P0 [GeV/c] θe [deg] Q2 [GeV2] Electron Rate [Hz] at 60 μA Minutes at 60 μA
15 cm LH2 2 x 2 mm2 2.217 1.366 42.0 1.57 1700 10 (for 1M events)
15 cm Dummy 2 x 2 mm2 2.217 1.366 42.0 1.57 55 at 40 μA 35 (115k events)
Single Carbon Off 2.217 1.366 42.0 1.57 200 10 (for 120k events)