SHMS Optics Working Group

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Weekly Meetings

  • Meetings will be held on Thursdays 11:30-12:30 in F228.
  • Next meeting time (TBD). Presently having Hall C detectors/software meetings for near future.
  • Join by Bluejeans by phone and computer +1.888.240.2560 (US Toll Free) Enter Meeting ID: 653182486

Notes from the Jan 5th 2017 meeting

  • commissioning plan needs to be streamlined with configurations and goals more clearly visible
    • Jure agreed to convert the Word document into wiki page to ease the collaborative editing: commissioning wiki
    • Rolf thinks it not needed to write a detailed procedures for the shift crew, since this would take too much time and the plan will probably be shifted around depending on the situation during the commissioning
    • the commissioning plan cannot be merged with the KPP run plan since that needs to contain only the KPP procedures
  • Gaskell will talk to Jay Benesch about ATLis 16570
  • we need better mapping data in order to plan the setting of the SHMS magnets (Mark ?)
  • there might be an opportunistic beam in hall for beamline and HMS prior to the KPP if no more work is needed on SHMS dipole and it is being cooled down
  • Jure and Eric Pooser need to setup the analysis software on the online machines prior to data taking
  • current plan is to start with CO2 in both HMS Cerenkov and SHMS heavy gas Cerenkov detectors

Notes from the Dec 22nd meeting

Notes from the Dec 1st meeting

  • The HMS dipole probe was not able to lock at the highest field region. The plan is to use a hall probe.
  • Thia will check into the precise restrictions of beam dump and interlocks needed for SHMS magnet operation.

Notes from Oct 20th meeting

  • Dipangkar did carbon elastic rate calculations posted plots under the Carbon elastics section.
  • Tanja found that the Hydrogen elastics scan at Q^2=5 GeV^2 is doable and as well as rates other elastic settings. Will update the run plan.
  • Mark has to follow up about the HMS dipole NMR probe position.
  • John Arrington agree to lead effort for the detector checkout plan. Eric Christy emailed the plans for Sprint03 and Rosen07 given in section.
  • Steve Lassiter did calculations for SHMS Q2 fringe field and found that 1/8" thick pipe would reduce field by factor of 4.
  • No update about the precise restrictions of beam dump and interlocks needed for SHMS magnet operation.

Notes from Sept 22nd meeting

From last time:

  • Dave Gaskell will check the procedure, however, he thinks it won't work.
  • Dipangkar posted plots under the Carbon elastics section
    • 8 - 9.5 deg should be doable
    • minima would be good to have in acceptance
    • will do exact rates calculations, however, it looks like minutes should do
  • Tanja will determine the optimal Q2 for hydrogen elastic
  • Mark will look into the HMS dipole NMR probe position
    • engineers currently cannot get a lock at higher momenta
    • HMS has a non-linear behavior at high momenta due to saturation. This means we would need a mapping if Hall probe is to be used. This mapping should be done soon. Thia will check with engineers about this.
  • We have enough gas for the HMS Cerenkov.
  • Thia will talk to John Arrington about detector checkout plan.

New business:

  • Jure gave a presentation about Geant4 simulation of the beam profile at the dump
    • the beam center positions agree with previous Python raytracer
    • beam shape is mainly due to the multiple scattering in the target; almost no distortion due to the magnetic field
    • plots of beam position for HB v9.3 and Q2 unshielded and half shielded
  • Thia will check the precise restrictions in the beam dump
    • size and shape of sweet spot, how is with wide beams of low energy electrons
  • someone needs to talk to Mike about how the big downstream BPMs will be used
    • (0, 0) problem, relative position, sweet spot monitoring
  • Thia will talk to Mike about the interlocks in case of magnet failure
    • ion chambers are probably too slow to stop the beam
    • downstream BPMs should be fast enough, but software interlock might not be. Hardware interlock on BPMs?
    • proximity switching with power supply interlocks
    • main question: how fast do we need to respond
  • shielding of the Q2 fringe fields is not high priority for now
    • Steve Lassiter should be notified to avoid overshielding

Notes from Sept 1st meeting

  • Need to check setting procedure works to highest momentum. Volunteered Dave Gaskell to check.
  • Went through plots by Jure of the fringe fields along beam line. Looks ok for first 7 experiments, but feel free to check yourself.
  • Dipangkar will finalize the carbon elastic angle for optics.
  • For hydrogen elastic data in runplan need to pick the Q2.
  • The HMS dipole NMR was moved to be inside a aluminum enclosure after being found to be outside the enclosure. Rolf and Dipangkar remember that it was left outside the enclosure on purpose but not sure of the reason. Mark will look into old report to find the reason.
  • Simona reported that for HMS cerenkov need to use C4F10 or C4F8O. She will double check on supply of gas that is available.
  • (Spoiler alert) John Arrington will be asked by Thia to develop detector checkout plan.

Notes from Aug 4th meeting

  • Presented the plan for the cryotargets.
    • Present plan is to build cryo stack with 3 cell blocks.
    • One cell block would have a 4cm and 10cm long "6GeV era" targets with the smaller diameter cylinder target and the other two cell blocks would each have one 10cm long of the newer style large diameter cylinder targets.
    • File describing the Hall A DVCS/GMP target with photos.
    • Swapping between cell blocks would take between 8-12 hours
    • With the large swapping time to go between cell blocks, the question was raised about what was the plan for using the 4cm cell? At the meeting the justification was to check the understanding of the HMS acceptance with the 10cm cell by having the 4cm to compare. It would be a good idea to have a volunteer to develop the plan for using the 4cm cell.
  • Discussed Garth's report on the SHMS Heavy gas PID. This raised the question about who is in charge of implementing the decision for 1) the gas/pressure for the heavy has cerenkovs in the HMS and SHMS, 2) the aerogel configuration in HMS and SHMS 3) whether the SHMS Argon/Neon gas cerenkov is IN or OUT. Also how this information is agreed upon and transmitted. It seems that for the ERR it would be good to have a table that list what the HMS and SHMS detector configuration will be. The SHMS front Argon/Neon gas cerenkov needs to be IN at the beginning for the 12 GeV KPP, but needs to be removed for the optics. Does it need to be put back in for any of the 7 experiments?
  • Jure presented his work on the beamline deflections due to the spectrometer magnets from the TOSCA calculations by Steve Lassiter. His presentation is here. The plots of the deflection versus SHMS angle are for the the beam momentum equal to the SHMS momentum. For the first seven experiments it looks like one can use shielding config V9.3 of extended yoke and front clamp with maybe shielding of the Q2 field. Jure is going to make plots of deflection versus SHMS momentum for fixed beam energy and SHMS angle and show where the 7 experiments would be. Another point raised at the meeting was that for the ERR , a plan for FSDs linked to the SHMS magnets and angles needs to be made. Need to determine at which SHMS angle having the magnets trip would not move the beam beyond its limits. Also need to confirm the +/-4cm at the beam dump.
  • Jure will present a poster at next week's Gordon conference on his plan for an automatic pattern matching of carbon elastic data at the focal plane to get the actual setting of the quads so that the quads can be fine tuned to the desired setting.

Notes from July 21st meeting

  • Discussed whether having carbon foils at -7.5 and +7.5 cm or at carbon foils at -5 and 5 cm. Decided to go with +/-5cm. If need to have intermediate ytgt then change the HMS angle. Discussed cryo targets but need more info from target group. Mark will contact Dave Meekins.
  • Jay sent email to Dave about intrinsic beam size. Expect 300um for 5 pass after one round of beam optics. Details below.
  • Garth and his group produced a report on PID using the SHMS Heavy Gas Cerenkov.
  • Jure reported that he has made progress on automatic pattern matching to get the offset of quadrupole tune from optimal tune. Presently he is using a grid of settings. He is working on interpolating between grid points. Looks promising.
  • Discussed HB stray field and the need to have field for different magnets settings with the just the shims/field clamps. Jure and Mark will discuss with Thia and Steve Lassiter.

Notes from June 30th meeting

  • Talked about the new target drawings.
    • Triple optics target has carbon foils at -10, 0 and +10 cm.
    • Double optics target has carbon foils at -7.5 and +7.5 cm.
      • Question was raised, whether it would be better to to have it at -5 and +5 cm instead.
    • Talked about the 10 cm target cell. It seems that Meekins' version is preferable to Silviu's.
  • Discussed Jure's talk on the Hall A/C collaboration meeting.
    • Garth Huber requested to join the optics group.
    • Questions were raised after the presentation about the details of PID and surrounding calibration.
  • Tanja presented updates to the commissioning plan.
    • Detailed angles are now included for the elastic checkout.
      • Rates need to be checked, since the Q^2 is about 5 (GeV/c)^2.
    • Need to put in details about the PID.
  • Rolf raised a question if we can go below 10 deg during the commissioning. Rolf will talk to Thia about this.
  • Jure presented the plan he is working on to have an automatic pattern matching to get the offset of quadrupole tune from optimal tune.
  • Dave Gaskell did not get response for the intrinsic beam size. Will retry.
  • Still need to get a parametrization of the HB field integral.

Notes from June 2nd meeting

  • Tanja and Rolf went through an updated commissioning plan.
    • Question about expect intrinsic beam size. Dave Gaskell will contact Jay B.
    • Question on what range of delta for the carbon delta scan. Looking at delta plot maybe -15 to 25.
    • Need to incorporate KPP plan. List of Key Performance Parameters.
    • During carbon elastics study effect of tuning Q1, Q2 and Q3 in focal plane plots.
      • plots
      • theta = 9.5 deg; p_cent = 2.2 GeV/c; delta = 0; point target, multiple scattering, vacuum pipe
      • Please note: the quad strength is changed by 1%; the plot scale is different than usually.
      • The second page shows the standard "spider plot".
    • To get both carbon elastic ground state and 4.4 state need SHMS angle down to 7.5 degrees.
  • Ask Dave Meekins for latest target list. Target section has drawing of target ladder. A reminder that to have SHMS y_tgt optics for 10cm target at 40deg need to do optics study with 20cm carbon at around 20deg.
  • Jure presented a rough overview of a Hall C optics commissioning talk for the Hall A/C collaboration meeting.
  • General issue with effect of HB on beam. Need to have simple parametrization of HB field integral along beam line as a function of SHMS angle for a few HB settings. Will ask Steve Lassiter.

Notes from May 12th meeting

  • Tanja and Rolf went through an updated commissioning plan.
    • Look into adding beam check out with harps and bpm integrated into initial beam centering using the HMS and sieve slit.
    • After beam centering , use "hole" target to check target ladder position
  • Jure presented slides
    • Showed the delta resolution improved by factor of 2-3 when replacing Cerenkov with exit vacuum pipe. Angle resolution improved by 50%. Need exit vacuum pipe for carbon elastics.
    • Showed patterns in the focal plane with sieve, single carbon target and 6 GeV electrons. In focal plane can separate xsieve columns using xfp versus xpfp and separate ysieve rows using yfp versus ypfp
    • Tuning the SHMS quads
      • xfp versus yfp and xpfp vs ypfp are sensitive to changes in Q2.
      • Showed that xfp versus yfp is sensitive to Q3. Less than Q2. Jure argued that it was not possible to disentangle Q1,Q2 and Q3.
      • Showed xpfp versus xfp and xfp vs yfp are sensitive to Q1 with Q2,Q3 off.
      • Showed xfp vs yfp is sensitive to Q2 with Q1, Q3 off.
      • Showed xfp vs yfp is sensitive to Q3 with Q1, Q2 off.
      • Asked Jure to put plots for different permutations of Q1,Q2 and Q3 settings for the various focal plane correlations in one pdf , for all to peruse at their leisure.
        • File1 : two spectrometers at nominal power.
        • File2 : two spectrometers turned off.
  • Looked at cycling procedure for HMS that Dave Gaskell dug up. Need to get what the maximum current for each HMS quad.
  • Jure about the effective field lengths of SHMS magnets. Need to get the latest TOSCA calculations and put them in COSY file. COSY fox is outdated.

Notes from April 21st meeting

  • Rolf and Tanja presented a beta version of the commissioning plan.
    • Need to contact John Arrington to see if he has an old detector checkout plan.
  • For carbon elastic, need to know if the front cerenkov can be replaced by a vacuum pipe and what is the time for the change out.
    • Talked with Howard. Vacuum pipe is the plan. Mike's quick response was one day to change out.
  • Next meeting present plots of sieve for different steps in Q1, Q2 and Q3 to determine how to do the determination of the SHMS magnet settings.
  • For beam pipe, need to determine what minimum SHMS angles the experiments need in first 2-3 years.
    • For the A(e,e'p) color transparency experiment: angle down to 10 degrees while P_SHMS = 9.6 and E = 11 GeV
    • For E12-09-017 - SIDIS/PT: angle down to 5.5 degrees while P_SHMS < 4.1 and E = 11
    • For E12-09-002 - SIDIS/CSV: angle down to 10.7 degrees while P_SHMS < 3.8 and E = 11
    • For E12-09-011 - Kaon DES: angle down to 5.6 degrees while P_SHMS = 5.2 and E = 7.4 and angle down to 6 degrees while P_SHMS = 7.1 and E = 9.3
  • Look at HMS quads data to determine what cycling procedure is needed in future.
    • Dave Gaskell added documents to Old HMS section
      • One document was the cycling procedure used during one of the later "standard equipment" experiments.
      • Plots of HMS quad field measurements that Steve Avery and I made way back in 1998. I think based on those plots, when we go to "high" currents (say above 500 A) aspecial "overshoot" procedure is probably not needed. It does seem to be important for lower currents though.

Preparation plans

Previous detector checkout plans

Target info

  • Drawing of Hall C 2016 target. 3D model of target.
  • Talked with Dave Meekins about cryotargets for first 7 experiments at end of July 2016.
    • Present plan is to build cryo stack with 3 cell blocks.
    • One cell block would have a 4cm and 10cm long "older style" with the smaller diameter cylinder target and the other two cell blocks would each have one 10cm long of the newer style large diameter cylinder targets.
    • File describing the Hall A DVCS/GMP target with photos.
    • Swapping between cell blocks would take between 8-12 hours.

Beam info

  • Jay Benesch sent a note about the intrinsic beam size. "Using measured E01 emittances from Feb 2016, sigmas, all round spots, with at least two rounds of matching at 3C07 and one using either quads before or after Compton, depending on whether that has planned use. In other words, about two shifts of Hall C matching. With one round of 3C07 matching before the hall is locked up, 50-100% increase. The focus is at pivot, beam spots are a few percent larger at last harp 2m upstream. Wearing my Ops hat, I'd say pass diagnostic girder harp measurements under 200 microns sigma for passes 1-4 and 300 microns for pass 5 through FY18 and revisit thereafter."
Pass Sigma
1 70 microns
2 100 microns
3 100 microns
4 110 microns
5 160 microns


  • Magnets.
    • Determination of B versus I curve. Develop new code for setting SHMS. Revise HMS field setting codes.
    • Cycling procedure especially for HB. Look what is done for the HMS.
    • Double check that the magnet field between magnets are superpositions.
    • Survey of the positioning of magnets.
  • Carbon elastics at 2 pass.
  • Survey of collimators, detectors and beamline components.
  • Survey of HMS/SHMS pointing at different angles. Look into what was done in the past for HMS commissioning. Determine a list of angles for survey.
  • Need to come up with the sieve pattern as a function of quad settings.
  • Need to look at use of ideal dipole versus TOSCA field map for HB in COSY.
  • Checked with Howard about the quad field centering. The idea that Howard had didn't work. Need to rely on mapping data.
  • Integration of detector checkout and optics.

Carbon elastics

  • Results from Dipangkar for 1 pass- 2.2 GeV, and 2 pass -4.4 GeV). Measurements at 8-9.5 are doable and the rates are also reasonable.
  • Using the 2nd plan configuration of the initial beam pipe ( SHMS to about 10, HMS to 10.5) it was checked by Dan Young that SHMS could go to 9 degrees drawing of beam pipe region.
  • Beam energies available for Fall 2016 and all of 2017.
Pass Beam Energy (MeV)
1 2217
2 4317
3 6417
4 8517
5 10617
5.5 11667


Sensitivity of scattering angle to HB central field setting

  • The distance, d1, from the targe center to the magnetic entrance of the HB is 138.4cm.
  • The effective length, d2, of the HB is nominally 75cm. This is presently used in COSY . Need to update using mapping data.
  • The distance, d3, from the magnetic exit of the HB to he sieve is 40cm.
  • The horizontal angle and position relative to the central ray are y and yp. Delta = 100*(p-pcentral)/pcentral .
  • At HB magentic entrance, yp_ent=yp_tar and y_ent(cm) =y_tar(cm) + d1*yp_tar(radians)
  • For the HB, the transport of yp and y only depends on delta and delta^2 terms.
    • yp_exit (mr) = -0.52*delta + 0.0052*delta^2 + yp_ent(mr)
    • y_exit (cm) = -0.019*delta + 0.00019*delta^2 + (d1+d2)*yp_tar(radians) + y_tar(cm)
    • y_sieve (cm) = y_exit + d3*yp_exit(radians)
    • To make it through y_sieve = 0 with y_tar = 0
      • y_exit = -d3*(-0.52*delta + 0.0052*delta^2 + yp_tar(mr))
      • (d1+d2+d3)*yp_tar(mr) = (0.019+0.52*d3)*delta - (0.00019+0.0052*d3)*delta^2
      • yp_tar (mr) = 0.153*delta - 0.00153*delta^2 .
    • So delta = 6.5% gives yp_tar = 1 mr.


  • A Lakeshore Hall probe was used for the mapping measurements. The probe has a linearity error as a function of magnetic field which was measured by the company ( Table of data). This linearity error is different for positive and negative field directions. In the data table, the Error = abs(Measured Field)-abs(True Field). So for positive fields True Field = Measured Field - Error. For negative fields True Field = Measured filed + Error.
  • Document and plots about mapping of B versus I at center of HB bore and the fringe fields in the beam region.
  • Measurements of B at bore center versus I when ramping magnet from 0 to +3900 and back to 0. Then switch polarity and ramp from 0 to -3900 and back to zero.
    • plot of absolute difference between B when ramping magnet up and down versus I when going to +3900 and -3900.
    • plot of relative difference between B when ramping magnet up and down versus I when going to +3900 and -3900.
    • Plot of difference in B between ramping up to +3900 and ramping up to -3900 versus current.
    • When ramping to negative currents there was a trip at I= -3139A. Plot of difference between first ramp to -3139A and the second.
  • Document and plots about mapping Of B versus z for five different x,y locations (center,top,bottomleft and right) for I = 2000, 3000, 3500 and 3900A.
  • Presentation on the harmonic analysis of the HB using field measurements at radius of 5.9cm at center of magnet at currents of -1200,-2000,-3000,-3500,-3900 and +3900.
  • Table of momentum versus current:
Momentum (GeV) Current (A)
3.687 1200
6.110 2000
8.967 3000
10.283 3500
11.277 3900

Fringe fields

  • NIM article on the TOSCA calculations of SHMS fringe fields effects on the beam and mitigation.
  • For SHMS at 5.5 degrees, Drawing.
    • 2.065 inch diameter pipe fills HB cut-out.
    • Transition to 2.875 inch diameter pipe at 98 inches (250cm). Mechanical exit of HB is around 230cm. Pipe diamter set by the Q1 cut-out.
    • Transition to 5.5 inch diameter pipe at 165 inches (419cm). So smallest opening is 2.875/165/2 = +/-8.7mr .
  • For HMS at 10.5 degrees, Drawing of beam pipe region.
    • Notch in Q1 determines pipe diameter of 1.9 inches.
    • Transition to 2.875 diameter pipe is where the support is possible.
  • Presentation with more drawings of beam pipe configurations.
  • The integral Bdl along the beam line for different angles of SHMS set at 3900A with and without wedges.
SHMS angle HB Bdl (As built) HB Bdl ( with wedges)
5.5 0.117 Tm 0.070
10 0.035 0.0109
  • At 10 deg the fringe field from Q1 and Q2 is very small. theta_b = .299*.0109/11. = 0.0003 and displacement at the beam dump (50m upstream) is .0003*5000 = 1.5cm
  • New calculations of beam displacement at the dump, based on raytracing through July 2016 Tosca field maps.

SHMS Q1 mapping

  • Report on the analysis of the Q1 mapping data.
  • Plot of B versus I compared to OPERA.
  • Table of momentum versus current:
Momentum (GeV) Current (A)
6 1228
8 1672
10 2169
11 2454


SHMS Detector Positions

SHMS Characteristics

SHMS Drawings of magnets

Study of the SHMS resolution

  • Study of the SHMS resolution.

HMS information

Quad Max Current Tested (A) Current at 7.3 GeV
Q1 1100 1045
Q2 1023 -839
Q3 1023 389
  • HMS quad cycling procedure from 2007 (pdf).
  • Plot of difference in HMS quad fields when decreasing or increasing current (from 1998). In this plot, the quads were ramped as follows: 500 A -> 0 A, polarity change, 0 A -> -500 A -> 0 A, polarity change, 0 A -> 500 A. This plot follows the same cycle, but up to 1000 A instead of 500. No Q2 data because it was tripping off at higher currents.


Moved Snake section here.