SHMS Optics Working Group

Weekly Meetings

• Meetings will be held on Thursdays 11:30-12:30 in F228.
• Next meeting June 2nd.
• Join by Bluejeans by phone and computer +1.888.240.2560 (US Toll Free) Enter Meeting ID: 653182486

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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.
• Looked at cycling procedure for HMS that Dave Gaskell dug up. Need to get what the maximum current for each HMS quad.

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.
  • presentation
• 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

• 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.
• 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

SHMS HB

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.

Mapping

• 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.
  • B/I versus I plot.
• 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

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

HMS and SHMS Dipoles

• Pdf version of the HMS field setting program.

SLITS and COLLIMATORS

• Collimators and Slits for SHMS

SHMS Detector Positions

• Detector_Locations_in_SHMS location

SHMS Characteristics

SHMS Drawings of magnets

• Drawings of SHMS magnets

Study of the SHMS resolution

• Study of the SHMS resolution.

Old HMS information

• HMS Detector survey information,Magnet location surveys
• File with B/I data and plots for dipole and quads.
• Document about dipole field measurements.
• Dipole Transfer Function which compares Tosca and measurements at probe and center.
• Q1 Transfer Function plots and data
• Q2 Transfer Function plots and data
• Q3 Transfer Function plots and data
• Note by Dave Mack on dipole current regulation.
• Plot of Q2 predicted waist versus momentum for effects of zero offset.
• Plots of quads effective field length.
• Plots of quad fringe field.
• Plot X_fp versus momentum.
• Plots Current versus momentum for all Quads.
• 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.

SNAKE

Moved Snake section here.