Fall 2016 LHRS optic plans

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)	Raster	θe (deg)	ΔP (%)	Rate [Hz] at 10 μA	minutes at 10 μA	Good Electrons
2.217	2.078	3x3 mm2	17.5	-4	10,000 (2500 Hz with ps = 4)	10	1M events
2.217	2.038	3x3 mm2	17.5	-2	10,000 (2500 Hz with ps = 4)	10	1M events
2.217	1.998	3x3 mm2	17.5	0	10,000 (2500 Hz with ps = 4)	10	1M events
2.217	1.958	3x3 mm2	17.5	+2	10,000 (2500 Hz with ps = 4)	10	1M events
2.217	1.918	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)	Raster	θe (deg)	ΔP (%)	Rate [Hz] at 10 μA	minutes at 10 μA	Good Electrons
2.217	1.998	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.
* For the optics pointing run, decrease the spectrometer momentum to 0.85 GeV/c.  The right dipole will need about 1.5 hours to settle.
* Take one hour on the optics target.
* After the optics run is completed, then increase the spectrometer momentum back to the elastic setting.  
 
  Make sure to cycle the right Q2 and Q3 when increasing the momentum.
* The 15 cm dummy runs need to be taken at the elastic setting.  So keep the momentum as is for this run. 
* A GMp expert will check the data quality.

• 4th Pass (E_beam = 8.5 GeV) Time estimate: 19 days @ 15 μA

Target	Raster	Ebeam [GeV]	P0 [GeV/c]	θe [deg]	Q2 [GeV2]	Electron Rate [Hz] at 15 μA	PAC days at 15 μA
15 cm LH2	2 x 2 mm2	8.517	2.081	48.75	12.08	0.018	19 (for 29k events)
Optics	Off	8.517	0.85	48.75	4.93	6.9	1 hour (for 24k events)
15 cm Dummy	2 x 2 mm2	8.517	2.081	48.75	12.08	----	1 hour