Spectrometer Optics 2pass 48d

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Procedure without Sieve-slit

  • Time estimate: 2 hours
* Take a run at the following kinematics without the sieve-slit collimator.
* Start with initial right HRS spectrometer tune with the SOS quad in place of right Q1.
* If you need to increase the spectrometer momentum setting, make sure you cycle Q2 and Q3 as per the cycling procedure.
* Electron rates assume 5 carbon foils, 5 mSr acceptance, and 8% delta acceptance.
* A GMp expert will check the data quality and decide, if the right HRS tune needs to be adjusted to change the size of the acceptance.
* This process will be repeated until the spectrometer tune is satisfactory.
Ebeam [GeV] P0 [GeV/c] θe [deg] Q2 [GeV2] W [GeV] Rate [Hz] at 5 μA minutes for 29k events at 5 μA
2.057 0.75 48.0 1.02 1.521 24.7 20

We want to take runs with the following Q1 currents:

  1. 0%: 159.75 A
  2. -6%: 150.165 A
  3. -5%: 151.7625 A
  4. -4%: 153.36 A
  5. -3%: 154.9575 A
  6. +5%: 167.7375 A

Procedure with Sieve-slit

  • Time estimate: 23+ hours
* Trained personnel will be required to install the 1-inch tungsten sieve-slit collimator onto the front face of the HRS.
* Take a sieve slit run with the multi-foil carbon target for the inelastic kinematics in the table.
* If you need to increase the spectrometer momentum setting, make sure you cycle Q2 and Q3 as per the cycling procedure.
* Repeat the above with the beam position shifted so that you see a vertical shift by one row.
* Electron rates assume 5 carbon foils, only 25 out of 63 sieve holes have events (~ 0.265 mSr acceptance), and 8% delta acceptance.
Ebeam [GeV] P0 [GeV/c] θe [deg] Q2 [GeV2] W [GeV] Rate [Hz] at 5 μA hours for 100k events at 5 μA
2.057 0.75 48.74 1.05 1.511 1.2 23+

We want to take a full statistics run at a Q1 current setting -4%(153.36 A).

We want to take short runs with the following Q1 currents:

  1. +5%: 167.7375 A
  2. Off: 0 A

Delta Scan with Proton Elastic

  • Time estimate: 3-4 hours
* Trained personnel will be required to remove the 1-inch lead sieve-slit collimator onto the front face of the HRS.
* Take a run with the 15 cm liquid hydrogen target for the elastic kinematics in the table.
* There will be a time lapse between settings until the right 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 inelastic rate or rate from the target endcaps. 
* The Q2 for these settings is 1.65 GeV2.
Ebeam (GeV) k' (GeV) θe (deg) ΔP (%) Rate [Hz] at 20 μA minutes for 240k events at 20 μA
2.057 1.224 48.74 -4 339 12
2.057 1.201 48.74 -2 339 12
2.057 1.177 48.74 0 339 12
2.057 1.154 48.74 +2 339 12
2.057 1.131 48.74 +4 339 12

For each ΔP (%) setting, we want to take 3 runs with different Q1 currents:

For ΔP = -4%, we want the following Q1 currents:

  1. -5%: 247.6764 A
  2. -4%: 250.2835 A
  3. +5%: 273.7476 A

For ΔP = -2%, we want the following Q1 currents:

  1. -5%: 243.0224 A
  2. -4%: 245.5805 A
  3. +5%: 268.6037 A

For ΔP = 0%, we want the following Q1 currents:

  1. -5%: 238.1660 A
  2. -4%: 240.6730 A
  3. +5%: 263.2361 A

For ΔP = +2%, we want the following Q1 currents:

  1. -5%: 233.5119 A
  2. -4%: 235.9699 A
  3. +5%: 258.0921 A

For ΔP = +4%, we want the following Q1 currents:

  1. -5%: 228.8579 A
  2. -4%: 231.2669 A
  3. +5%: 252.9482 A

Hall A Gmp Luminosity Scan

Set Left HRS to P = 1.0 GeV, θ= 25, 2mmx2mm raster. Take 10 minute runs with the targets and beam currents listed below. Set prescale factor to keep livetimes approximately constant for each current with a given target.

Hydrogen Scan 10μA 15μA 20μA 25μA 30μA 35μA 40μA
Run No.
Carbon Scan 10μA 15μA 20μA 25μA 30μA 35μA 40μA
Run No.
Dummy Scan 20μA 25μA 30μA 35μA 40μA
Run No.


Proton Elastic Run and Dummy Target Runs

  • Go back to the ΔP = 0% elastic setting. Make sure the L-HRS P0 = 1.177 GeV and Q1 current = 240.6730 A (-4%)
  • Take data with this setting for 1 hour


Ebeam (GeV) k' (GeV) θe (deg) ΔP (%) Rate [Hz] at 20 μA minutes for 1M events at 20 μA
2.057 1.177 48.74 0 339 ~ 60 mins


  • Move the target to "Dummy"
  • Take L-HRS run with same setting as previous step. We need at least 200 K events.