HRS Optics
From APEXwiki
Group: Vincent Sulkosky (leader), Jin Huang, Doug Higinbotham, John LeRose, Tim Holmstrom
Priority Tasks
- Provide final conceptual design for calibration target to the Target Group
- Provide procedures and schedule for optics calibration to be included in the June Run Plan (see below)
- Analysis tools for optics calibration
Status_of_HRS_Optics
Summary
Updated on July 02, 2010 by Jin Huang
| HRS | Variable | Available Data | Planned Data | Further Data Needed | Matrix Status |
|---|---|---|---|---|---|
| LHRS w/ PREX septum | theta | June 26 Sieve data | None | None | Yi matrix for Online |
| phi | June 26 Sieve data | None | None | Yi matrix for Online | |
| vertex z | Run 1345-1346 | None | None | Online matrix Calibrated | |
| dp | June 26 Sieve data for 0% to +4% | None | calibrate -5% to 0% | Yi matrix for Online | |
| LHRS w/ APEX septum | theta | Could use calibration with PREX septum | None | None | Yi matrix for Online |
| phi | Could use calibration with PREX septum, But there will be offsets | None | 1 pass sieve run with APEX septum configuration | Yi matrix for Online | |
| vertex z | None | 2 pass data during R-HRS optics run | None | Yi matrix for Online | |
| dp | Could use calibration with PREX septum (0% to 4%) But there will be offsets | None | 1 pass elastic scan from -4% to 4%? | Yi matrix for Online | |
| LHRS w/ APEX septum | theta | none | positron sieved run | None | Yi matrix for Online |
| phi | none | positron sieved run | None | Yi matrix for Online | |
| vertex z | none | 2 pass run w/o sieve | None | Yi matrix for Online | |
| dp | none | None | search for edge of LHRS coincidence phase space limit? | Yi matrix for Online |
Miss data and discussion
- LHRS ph with APEX momentum setting
- Require a sieved run with APEX septum configuration
- Any model of septum to correct?
- Size of offset could be demonstrated comparing un-sieved run with APEX and PREX septum
- LHRS dp (-4% to 0%)
- go to lower beam energy than 1.1155GeV?
- increase septum current to 830A?
- other low sharp peak with p<1.16GeV @ 5degree.
- RHRS dp
- search for edge of LHRS RHRS coincidence data and calibrate with edge of e+ phase space limit? (suggested by Phillips)
Septum Magnet Settings
Septum magnet is set the same as PREX, i.e. 729 Amps for 1.063 GeV/c or 685.7949 Amps/GeV/c.
(n.b. Imax = 800 Amps).
How to change septum magnet setting.
Quadrupole Cycling
Affects due to not cycling Q2 and Q3.
Cycling Procedure
- Note that Q2 and Q3 can and should be cycled simultaneously.
- The left and right HRS Q2 is presently limited to 1000 A.
- The left and right HRS Q3 limit is 1400 A.
1) Turn off the regulators (click GeV/c button on Hall A Tools screen right of the "P0 SET" field).
2) Set the "P0 SET" field to the desired momentum.
3) Here is how to cycle (HALOG 312896):
a) Ramp up to 1000 A and back to zero. b) Repeat this a 2nd time. c) Go back to the max and then to the desired setting by turning on the Q2 regulator.
4) For the Q3 magnets the cycling procedure is normal:
Ramp to 1400 A, then go to the desired setting by turning on the Q3 regulator.
5) Don't cycle Q1!
Optics Commissioning Plan (using PREX target)
Goal: Establish that the beam quality is acceptable by checking the size of an elastic peak from a single sieve hole on the focal-plane.
Next take high quality optics data to establish the initial APEX septum optics database.
Intial Conditions
Beam Energy: 1.162 GeV (Assuming first pass beam is available) Septum angle: 5 Degrees HRS and septum polarity: negative Sieve-slit: IN Raster: Off Target: No Target Left HRS Momentum: 1.16 GeV/c Right HRS Magnets: Off (except septum)
(This plan assumes that the raster size and nominal beam position have already been previously established.)
Negative Polarity Procedure
1) Once beam has been sent back to the Hall, request 5 uA and do a harp scan to make sure the beam size at both harps 1H04A and 1H04B is
approximately 50-100 um in width. Fast feedbacks MUST be on and working.
2) Verify that the OTR's are out (both target and arc!) before taking optics data.
3) Before beginning a measurement in any kinematics, the shift workers must log the Hall A Tools screen and the magnet strip tool! Waiting for
the dipole magnets to settle is one of the key parts in taking good optics data.
4) Start with delta=0% with the left spectrometer at 1.16 GeV/c. More than likely the right spectrometer will not be ready.
For all data runs optimize the rate such that the DAQ collects data at or below the maximum rate (4 kHz) by adjusting * beam current (> 2 μA if possible) * keep prescale factors as low as possible with deadtime < 20%. Take about 5 minutes of data for each run or about 500k events. Raster should be OFF at this point.
5) Take two 500k data runs with this setup using the single carbon foil target labeled as "Carbon" on the target GUI.
6) Perform elastic delta scan with two runs at each point for both optics and Ta targets. Each file should have AT LEAST 500k.
Remember to cycle the quadrupoles Q2 and Q3 when increasing momentum! Quality of this test is very important. Please check all runs with the analyzer. (central momenta are for 12C elastic)
(a) 0% Momentum = 1.16 GeV/c (one run with raster on and off) (b) -1% Momentum = 1.150 GeV/c (c) -2% Momentum = 1.1383 GeV/c (one run with raster on and off) (d) -3% Momentum = 1.1266 GeV/c (e) -4% Momentum = 1.1150 GeV/c (one run with raster on and off) (f) -10% Momentum = 1.0454 GeV/c (one run with raster on and off)
7) To check for the effects of cross talk between the HRS's and while the sieve is in, we should also:
(This step assumes that the right HRS Q1 is operational. If it is not, then skip to step 8.)
(a) return left HRS to delta = 0 and take a run (b) turn RHRS Q1 on (Momentum = 1.16 GeV/c) and take a run (c) turn RHRS Q1 off and flip polarity to positive (d) set RHRS Q1 50% of delta = 0 and take a run (e) set RHRS Q1 100% of delta = 0 and take a run (f) return Q1 polarity to negative, set to delta = 0 and take a run
8) Leaving the spectrometers in negative polarity, take an access and rotate the sieve slits to the OUT position.
9) Repeat delta scan. Take data with the optics target and possibly with the Ta foil. The beam current might have to be limited to 20-30 nA.
(The current limitation depends on the VDC performance at high rate).
Again take two runs with 500k each:
(a) 0% Momentum = 1.16 GeV/c (one run with raster on and off) (b) -2% Momentum = 1.1383 GeV/c (c) -4% Momentum = 1.1150 GeV/c (one run with raster on and off) (d) -10% Momentum = 1.0454 GeV/c (one run with raster on and off)
If we are short on time, the (*)'ed points could be left out, but we should really try to get the data if we can.
HRS Polarity Reversal Study
1) With an agreed upon time, have the Hall A technicians reverse the polarity of the left HRS dipole and septum magnet to positive.
2) Reverse the left HRS quadrupoles Q1, Q2 and Q3 polarities to positive.
3) Rotate the sieve slits to the IN position.
4) Ramp the magnets up either to maximum current or to the desired momentum set point. Follow the Q2 and Q3 cycling procedure discussed above.
5) Depending on the beam energy either the 1-pass or 2-pass momentum settings should be chosen below.
Option 1 for 1-pass beam (1.162 GeV):
Perform delta scan around 581 MeV/c. Take data with the optics target and with the Ta foil. Raster should be OFF.
Again take two runs with 500k each:
(a) +4% Momentum = 0.6042 GeV/c (b) +2% Momentum = 0.5926 GeV/c (c) 0% Momentum = 0.581 GeV/c (d) -2% Momentum = 0.5694 GeV/c (e) -4% Momentum = 0.5578 GeV/c (f) -10% Momentum = 0.5229 GeV/c
Option 2 for 2-pass beam (2.262 GeV):
Perform delta scan around 1131 MeV/c. Take data with the optics target and with the Ta foil. Raster should be OFF.
Again take two runs with 500k each:
(a) +2.6% Momentum = 1.160 GeV/c (b) +2% Momentum = 1.1536 GeV/c (c) 0% Momentum = 1.131 GeV/c (d) -2% Momentum = 1.1084 GeV/c (e) -4% Momentum = 1.0858 GeV/c (f) -10% Momentum = 1.0179 GeV/c
6) With an agreed upon time, have the Hall A technicians reverse the polarity of the left HRS dipole and septum magnet back to negative.
Ramp all magnets down to zero Amperes prior to the techs entering Hall A.
7) Reverse the left HRS quadrupoles polarities to negative.
8) Start with delta=0% with the left spectrometer at 1.16 GeV/c.
9) Perform elastic delta scan with two runs at each point for both optics and Ta targets. Each file should have AT LEAST 500k. Raster should be OFF.
Remember to cycle the quadrupoles Q2 and Q3 when increasing momentum! Quality of this test is very important. Please check all runs with the analyzer. (central momenta are for 12C elastic)
(a) 0% Momentum = 1.160 GeV/c (b) -2% Momentum = 1.1383 GeV/c (c) -4% Momentum = 1.1150 GeV/c (d) -10% Momentum = 1.0454 GeV/c
10) Take an access and rotate the sieve slits to the OUT position.
11) At the -10% Momentum = 1.0454 GeV/c setting, take two runs, each file should have AT LEAST 500k for both optics and Ta targets.
12) Offline analysis will verify to what level optics before and after the polarity flip are the same.
Initial online analysis can check the differences in the focal plane quantities before and after the polarity change.
R-HRS Optics Calibration Procedure with Positive Polarity and PREX Target Only
Version 2.0. Initiated by Jin Huang; Commented by Yi Qiang, Vincent Sulkosky, Natalia Toro
General
This is preliminary procedure for R-HRS initial optics commisioning for following conditions:
- No one pass beam provided. Have to commision with 2 pass beam
- No APEX optics target. Have to use preinstalled PREX target, which misses 1~2 carbon foils.
- PID detector in R-HRS is commissioned
Within these limits, there will be no calibration on R-HRS for dp. ph th calibration is probable, depending on clear position sieve parttern. Vz calibration is straight forward with pi+
With correction magnet, beam position/direction on target will pose a serious problem to optics calibration. At calibration, we will need to know good beam x, y at each foil. Therefore both position and slope is important to know. Therefore I suggest, if possible, keep correction magnet at constant current within this study. Once calibration is done, change in beam direction will not affect quality of optics reconstruction (leading correction is 2nd order for th, ph, dp; 1st order for vz). New ideas are welcome.
Time Cost
- Approximate beam time is 4-5 hour, with in which, 2~3 hour is optional
- Approximate configuration change time is 5 hour
- 1 control access to remove sieve
Assumed initial condition
Beam Energy: 2.262 GeV Septum angle: 5 Degrees HRS and septum polarity: APEX configuration, correction magnets working. Sieve-slit: any (prefer IN) Raster: any (prefer OFF) Target: any (prefer Empty) Left HRS Momentum: any (prefer 1.131GeV/c) Right HRS Magnets: any (prefer 1.131GeV/c) R-HRS in positive polarity L-HRS in Negative polarity Yi's Hypernuclear 6 degree super conducting optics database for both arms as start software point. PID detectors in R-HRS commissioned!!
Run plan
0) General Procedure:
a) Q2/Q3 need cycling. How to Cycle Quads Q2 and Q3:
* Turn off the regulator (click GeV/c button on magnets screen to the things to click)
* Q2 is presently limited to 1000A. Here is how to cycle (halog 312896): Ramp up to 1000A and back to zero. Repeat this a 2nd time, then go to the desired setting.
* For Q3 the cycling procedure is normal: ramp to 1400A, then go back to the desired setting.
* Don't cycle Q1.
* Turn on regulator
b) We take this batch of optics data by pre-scaling to 500kHz LHRS s2m trigger (T1?) and 1500kHz RHRS s2m trigger (T??) + all coincidence trigger(T??). DAQ dead time is not important.
c) Beam current on optics target is 2uA (Call MCC and ask for max current on optics. If 2uA is above their limit, use max they can provide.), Ta target is 2uA.
d) Replay each run to demonstrate
* high VDC efficiency.
* Check s2m, gac Cer, pion rejector is working and calibrated.
* Check Trigger type distribution is as described (b)
e) call MCC before change momentum on septum (or PREX P0 SET on hall A tools)
1) Rotate the both sieve slits to the IN position.
2) p->1.1310GeV/c for both HRS. Follow the Q2 and Q3 cycling procedure discussed above, (suggested to do so event HRSs are already 1.1310GeV/c. This prevent missing cycling occurred before).
- Notice : change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS! Please also Halog Hall A tool for each change. Wait for all magnets stable before taking data
3) Tune beam through correction magnets and septum to beam dump with HRS momentum = 1.1310
4) Must: Perform delta scan around 1131 MeV/c with Sieve IN. Take data with the optics target and with the Ta foil.
- Main purpose for this study is for this study is to identify Sieve with positron on R-RHS. Also trying test angular reconstruction on L-HRS with new septrum polarity (probably not working due to elastic electron punch through). Momentum scan is to search for better kinematics region for position samples. Since there is no elastic peak to show clear sieve, more data are needed to perform regional cuts on VDC. Raster-ON-runs are for raster correction check.
(a) 0% Momentum = 1.131 GeV/c Raster OFF; Take 4 runs with 1000k each (b) 0% Momentum = 1.131 GeV/c Raster ON; Take 2 runs with 500k each (d) -10% Momentum = 1.0179 GeV/c Raster OFF; Take 4 runs with 1000k each (Optional, Call RC to know) (e) -10% Momentum = 1.0179 GeV/c Raster ON; Take 2 runs with 500k each (Optional, Call RC to know) (d) -20% Momentum = 0.9048 GeV/c Raster OFF; Take 4 runs with 1000k each (Optional, Call RC to know) (e) -20% Momentum = 0.9048 GeV/c Raster ON; Take 2 runs with 500k each (Optional, Call RC to know)
- Notice : Change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS! Please also Halog Hall A tool for each change. Wait for all magnets stable before taking data
- Raster ON = no less than 2x2mm on spot++; Raster OFF = ask MCC to turn off raster and verify on raster oscilloscope.
5) Take an access and rotate the sieve slits to the OUT position.
6) p->1.131GeV/c for both HRS. Follow the Q2 and Q3 cycling procedure discussed above.
- Notice : change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS! Please also Halog Hall A tool for each change. Wait for all magnets stable before taking data
7) Must: p0=1.131GeV/c Sieve out runs. Take data with the optics target and with the Ta foil.
- Main purpose for this study is for establishing vertex reconstruction for both arm with pions. It will be main vertex data for R-HRS, also test for vz shift on L-HRS at new septum configuration. Since there is no elastic peak to show clear sieve, more data are needed to perform regional cuts on VDC. Raster on runs are for raster correction check.
(a) 0% Momentum = 1.131 GeV/c ; Take 4 runs with 1000k each (b) 0% Momentum = 1.131 GeV/c ; Raster ON; Take 2 runs with 500k each
- Raster ON = no less than 2x2mm on spot++; Raster OFF = ask MCC to turn off raster and verify on raster oscilloscope.
8) Optional: Repeatability test. Recycle Q2 and Q3 and set back to same momentum. Take data with the optics target and with the Ta foil.
- Main purpose for this study is for demonstrate vertex reconstruction stability as a demonstration of optics stability for magnet cycling, scaling and rate
(a) 0% Momentum = 1.131 GeV/c ; Raster OFF; Take 2 runs with 500k each (a.1)0% Momentum = 1.131 GeV/c ; 50uA on Ta target, 2min limit. Raster OFF; Take 2 runs with 500k each (b) -10% Momentum = 1.0179 GeV/c ; Raster OFF; Take 2 runs with 500k each
- Notice : change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS! Please also Halog Hall A tool for each change. Wait for all magnets stable before taking data
R-HRS Optics Calibration Procedure with Negative Polarity and PREX Target Only
Time Cost
- Approximate beam time is 4-5 hour, with in which, 2 hour is optional
- Approximate configuration change time is 5 hours with the R-HRS dipole changes dominating the time.
- 1 control access to remove sieve 20-30 minutes.
- L-HRS optics data should be taken concurrently with the R-HRS data.
Intial Conditions
Beam Energy: 1.162 GeV (Assuming first pass beam is available) Septum angle: 5 Degrees HRS and septum polarity: APEX hybrid configuration, corrector and permanent magnets working. Sieve-slit: any (prefer IN) Raster: any (prefer OFF) Target: any (prefer Empty) Left HRS Momentum: any (prefer 1.16 GeV/c) Right HRS Magnets: any (prefer 1.16 GeV/c) L-HRS/R-HRS in Negative polarity Yi's Hypernuclear 6 degree super conducting optics database for both arms as software starting point.
- This plan assumes that the raster size and nominal beam position have already been previously established.
- Also assumes that the 2-pass and 1-pass beamline commissioning has been completed with both permanent magnets.
Run plan
0) General Procedure:
a) Q2/Q3 need cycling. How to Cycle Quads Q2 and Q3:
* Turn off the regulator (click GeV/c button on magnets screen to the things to click)
* Q2 left and right are presently limited to 1000A. Here is how to cycle (HALOG 312896):
ramp up to 1000 A and back to zero. Repeat this a 2nd time, then go back to 1000 A
and then to the desired setting by turning on the Q2 regulator
* The right Q3 should follow the same procedure above to cycle left/right Q2 only to 1000 A.
* For left Q3 the cycling procedure is normal:
ramp to 1400 A, then go to the desired setting.
* Don't cycle Q1 or dipole.
* Turn on regulator
b) We take this set of optics data by pre-scaling to 1.5 kHz LHRS PID trigger (T5?)
and 1.5 kHz RHRS PID trigger (T6?).
DAQ dead time is preferred to be less than 20%.
c) Beam current on optics target is 2uA (Call MCC and ask for max current on optics.
If 2uA is above their limit, use max they can provide.), Ta target is 2uA.
d) Replay each run to demonstrate
* high VDC efficiency.
* Check s2m, gac Cer, pion rejector is working and calibrated.
* Check that Trigger type distribution is as described in step (b)
e) Call MCC before change momentum on septum (or PREX P0 SET on hall A tools)[?]
1) Rotate the both sieve slits to the IN position, if not already done.
2) p->1.160GeV/c for both HRS. Follow the Q2 and Q3 cycling procedure discussed above, (suggested to do so even if HRSs are already at 1.160GeV/c.
This will help avoid taking data with incorrect cycling, which has occurred before).
- Notice : change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS!
- Please also Halog Hall A tool for each change. Wait for all magnets to be stable before taking data.
3) Tune beam through correction magnets and septum to beam dump with HRS momentum = 1.160[?]
For all data runs optimize the rate such that the DAQ collects data at or below the maximum rate (3 kHz) by adjusting * beam current (> 2 μA if possible) * keep prescale factors as low as possible with deadtime < 20%. Take about 5 minutes of data for each run or about 900k events. Raster should be OFF at this point.
4) Take two 900k data runs with this setup using the optics foil and Ta targets.
5) Must: Perform delta scan around 1160 MeV/c with Sieve IN. Take data with the optics target and with the Ta foil.
- Main purpose for this study is to acquire optics data with Sieve IN and OUT with elastic electrons on R-HRS and repeatability study on L-HRS. Raster-ON runs are for raster correction check.
(a) 0% Momentum = 1.160 GeV/c Raster OFF; Take 2 runs with 900k each (b) 0% Momentum = 1.160 GeV/c Raster ON; Take 2 runs with 900k each (c) -2% Momentum = 1.1383 GeV/c Raster OFF; Take 2 runs with 900k each (d) -2% Momentum = 1.1383 GeV/c Raster ON; Take 2 runs with 900k each (Optional, Call RC to know) (e) -4% Momentum = 1.1150 GeV/c Raster OFF; Take 2 runs with 900k each (f) -4% Momentum = 1.1150 GeV/c Raster ON; Take 2 runs with 900k each (Optional, Call RC to know) (g) -10% Momentum = 1.0454 GeV/c Raster OFF; Take 2 runs with 900k each (h) -10% Momentum = 1.0454 GeV/c Raster ON; Take 2 runs with 900k each
- Notice : Change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS!
- Please also Halog Hall A tool for each change. Wait for all magnets to be stable before taking data.
- Raster ON = no less than 2x2mm on spot++; Raster OFF = ask MCC to turn off raster and verify on raster oscilloscope.
6) Take an access and rotate the sieve slits to the OUT position.
7) p->1.160GeV/c for both HRS's. Follow the Q2 and Q3 cycling procedure discussed above.
- Notice : change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS!
- Please also Halog Hall A tool for each change. Wait for all magnets to be stable before taking data.
8) Must: p0=1.160 GeV/c Sieve out runs. Take data with the optics target and with the Ta foil.
- Main purpose for this study is for establishing vertex reconstruction for both arm with pions. It will be main vertex data for R-HRS, also test for vz shift on L-HRS at new septum configuration. Since there is no elastic peak to show clear sieve, more data are needed to perform regional cuts on VDC. Raster on runs are for raster correction check.
- This section is split into left and right HRS sections, since the R-HRS dipole takes several minutes to stabilize after a momentum change.
Right HRS only:
(a) 0% Momentum = 1.160 GeV/c ; Raster OFF; Take 2 runs with 900k each (b) 0% Momentum = 1.160 GeV/c ; Raster ON; Take 2 runs with 900k each (Optional, Call RC to know) (c) -10% Momentum = 1.0454 GeV/c ; Raster OFF; Take 2 runs with 900k each (d) -10% Momentum = 1.0454 GeV/c ; Raster ON; Take 2 runs with 900k each
- Raster ON = no less than 2x2mm on spot++; Raster OFF = ask MCC to turn off raster and verify on raster oscilloscope.
Left HRS only:
(a) 0% Momentum = 1.160 GeV/c Raster OFF; Take 2 runs with 900k each (b) 0% Momentum = 1.160 GeV/c Raster ON; Take 2 runs with 900k each (Optional, Call RC to know) (c) -2% Momentum = 1.1383 GeV/c Raster OFF; Take 2 runs with 900k each (d) -2% Momentum = 1.1383 GeV/c Raster ON; Take 2 runs with 900k each (Optional, Call RC to know) (e) -4% Momentum = 1.1150 GeV/c Raster OFF; Take 2 runs with 900k each (f) -4% Momentum = 1.1150 GeV/c Raster ON; Take 2 runs with 900k each (Optional, Call RC to know) (g) -10% Momentum = 1.0454 GeV/c Raster OFF; Take 2 runs with 900k each (h) -10% Momentum = 1.0454 GeV/c Raster ON; Take 2 runs with 900k each
9) Optional: Repeatability test. Recycle Q2 and Q3 and set back to same momentum. Take data with the optics target and with the Ta foil.
- Main purpose for this study is for demonstrate vertex reconstruction stability as a demonstration of optics stability for magnet cycling, scaling and rate
(a) 0% Momentum = 1.160 GeV/c ; Raster OFF; Take 2 runs with 900k each
(b) -10% Momentum = 1.0454 GeV/c ; 50uA on Ta target, 2min limit. Raster OFF; Take 2 runs with 900k each
(c) -10% Momentum = 1.0454 GeV/c ; Raster OFF; Take 2 runs with 900k each
- Notice : change momentum through PREX P0 setting on Hall A tool. NOT momentum setting for each HRS!
- Please also Halog Hall A tool for each change. Wait for all magnets to be stable before taking data.
Beam Steering Procedure
A full test plan will need to be developed and carried out with MCC.
Here is a preliminary plan:
- Establish beam on target with septa and steering magnet off
- Ramp septa current up and determine beam steering effect
- Turn on corrector magnet to compensate for septa steering (beam into dump)
Raster and Beam Position Monitor (BPM) Scan Procedure
This is required for beam position calibration. Once the beam position is established by doing a raster scan on the wire alignment target, do the Bull's eye scan.
This also does not take into account the effect of the steering magnet upstream of the target chamber yet.
Wire Alignment Target Locations
1. Vertical alignment wires: Z = -20 cm, Y = -2.5 mm Z = 0 cm, Y = 0 mm Z = 20 cm, Y = 2.5 mm
2. Horizontal alignment wires: Z = -25 cm, Y = -7.5 mm Z = -10 cm, Y = -2.5 mm Z = 10 cm, Y = 2.5 mm Z = 25 cm, Y = 7.5 mm
General info, applies to both raster and bull's eye scans
1. Target: wire alignment target <- Do this first! 2. Beam current: <5 uA. Beam raster: ON. [Raster ON might be required to see the wire. To see a better wire, use a clock trigger (T8), prescale away all physics triggers.] 3. Take both HRS CODA runs. Establish the center of the target by doing raster scan and seeing the wire at Z = 0 and centering it.
Preliminary Raster scan procedure
1. Start from raster size 2x2 mm2. 2. Run spot++ and try to find the alignment wire at Z = 0 (at center of target). 3. if cannot see the wire, increase raster size by 1 mm in each direction, goto step 2. 4. if raster size has reached the maximum (perhaps 6x6 mm2) and you still cannot see the wire at Z = 0, call RC. 5. if at a particular raster size you can see the wire at Z =0, check if it is at the center of the raster pattern: If not, ask the MCC to change the beam position at both BPMA and BPMB (the 2 BPMs must have the same changes to ensure a straight beam) and repeat, until the wire is seen at the center of the raster pattern. 6. Write down the beam position. This will be the one to use for all productions runs.
Bull's eye scan procedure
Starting Configuration:
- Unrastered beam
- You should not do this with a target requiring rastered beam, use carbon or in the worst case empty instead.
- Ask MCC to steer the beam to the nominal center of the target, then follow the procedure below.
- Wait until beam is stable and perform a harp scan and a HRS run right next to each other for each step.
- Cover at least the area the raster will cover, and repeat harp and HRS runs
1. One run at the nominal beam center as established above. 2. One run at (x,y) of both BPM A and B at (+3.0, +3.0). (if it takes more than 5-10 minutes for MCC to set it up, settle with (+2.5, +2.5) or lower values) 3. One run at (x,y) of both BPM A and B at (+3.0, -3.0). 4. One run at (x,y) of both BPM A and B at (-3.0, -3.0). 5. One run at (x,y) of both BPM A and B at (-3.0, +3.0). 6. Make a halog entry saying which runs correspond to which conditions. 7. End of Bull's eye scan
Preliminary Optics Run Plan (using APEX optics target)
(This plan assumes that the raster size and nominal beam position have already been previously established.)
For all data runs optimize the rate such that the DAQ collects data at or below the maximum rate (4 kHz) by adjusting
- beam current (> 2 μA if possible)
- keep prescale factors as low as possible with deadtime < 20%.
Take about 5 minutes of data for each run about 1 million events.
Starting Configuration:
Beam Energy: 1.162 GeV (Assuming first pass beam is available) Septum angle: 5 Degrees HRS and septum polarity: negative Sieve-slit: IN Raster: Off Target: Optics section 1 or 2 Left HRS Momentum: 1.2080 GeV/c Right HRS Momentum: 1.2080 GeV/c
Procedure:
1) Perform a momentum scan of the carbon elastic peak on both of the optics target sections and both spectrometers:
(One run should be taken at each momentum setting for both carbon foil sections.)
a) +4% Momentum = 1.2080 GeV/c b) +2% Momentum = 1.1847 GeV/c c) 0% Momentum = 1.1615 GeV/c d) -2% Momentum = 1.1383 GeV/c e) -4% Momentum = 1.1150 GeV/c f) -10% Momentum = 1.0454 GeV/c
For settings c and f, take a run with the raster off and on.
2) Make an access to remove the sieve slit.
3) Repeat the momentum scan with the sieve slit removed with the raster off and on. The beam current will probably have to be limited to 20-30 nA.
Online Optics Check
Reference
- Study by J. LeRose (PDF): effect of reversing right septum polarity on optics quality.
- From 11/17/2008: Forward Transfer functions for the right HRS at 5 degrees using the PREX room temperature septum.
