Fall 2016 LHRS optic plans

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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 2 x 2 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 2 x 2 mm2 17.5 -4 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 2.038 425.11 2 x 2 mm2 17.5 -2 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 1.998 416.76 2 x 2 mm2 17.5 0 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 1.958 408.42 2 x 2 mm2 17.5 +2 10,000 (2500 Hz with ps = 4) 10 1M events
2.217 1.918 400.08 2 x 2 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 2 x 2 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)



Step L5: LHRS 12C overlap white spectra with optics target

   <td>2.217</td>	
   <td>1.080</td>	
   <td>225.277</td>	
   <td>42.0</td>	
   <td>20 (or > 1M events)</td>	
<tr> <td>Optics foils</td> <td> OFF </sup></td> <td>2.217</td> <td>1.015 </td> <td>211.719</td> <td>42.0</td> <td>20 (or > 1M events)</td> </tr> <tr> <td>Optics foils</td> <td> OFF </sup></td> <td>2.217</td> <td> 0.954</td> <td>198.995 </td> <td>42.0</td> <td>20 (or > 1M events)</td> </tr> <tr> <td>Optics foils</td> <td> OFF </sup></td> <td>2.217</td> <td> 0.897 </td> <td> 187.105 </td> <td>42.0</td> <td>20 (or > 1M events)</td> </tr> <tr> <td>Optics foils</td> <td> OFF </sup></td> <td>2.217</td> <td> 0.843</td> <td> 175.841</td> <td>42.0</td> <td>20 (or > 1M events)</td> </tr> <tr> <td>Optics foils</td> <td> OFF </sup></td> <td>2.217</td> <td> 0.792</td> <td> 165.203</td> <td>42.0</td> <td>20 (or > 1M events)</td> </tr> <tr> <td>Optics foils</td> <td> OFF </sup></td> <td>2.217</td> <td> 0.745 </td> <td> 155.400</td> <td>42.0</td> <td>20 (or > 1M events)</td> </tr> <tr> <td>Optics foils</td> <td> OFF </sup></td> <td>2.217</td> <td> 0.700</td> <td>146.013 </td> <td>42.0</td> <td>20 (or > 1M events)</td> </tr> </table>
Target Raster Ebeam [GeV] P0 [GeV/c] Q1 current [Amps] θe [deg] Minutes at 50 μA
Optics foils OFF </sup>