SHMS Optics Working Group

Weekly Meetings

• Meetings will be held on Thursdays 11:30-12:30 in F228.
• Next meeting April 21st.
• Join by Bluejeans by phone and computer +1.888.240.2560 (US Toll Free) Enter Meeting ID: 653182486

Notes from March 31st meeting

• Tanja discussed initial work going through past run plans. She will present update at next meeting.
• Discussion of beam pipe.

Notes from March 10th meeting

• Need to check whether the beam pipe will allow one to go to 8-9.5 degrees. (Dave Gaskell will look into this.)
  • 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.
• Get the Q1 mapping information from Steve Lassiter.
  • See SHMS Q1 Section
• Need to keep track of detector surveys. Contact Bert Metzger.
  • Not done.
• Put code for setting field on wiki.
  • see HMS and SHMS Dipole section
• Double check to understand why there is a 0.7% difference between field at +3900A and -3900A.
  • The probe readings had not been corrected for non linearity in probe. Plot with correction shows less than 0.2% difference over all currents that drops to .02% at 3900A.
• Change the effective length of HB by 4% to see effects on the optics. Look at sieve.
• Need table for conversion of all magnet currents to momentum.
  • See HB and Q1 sections
• Check with Steve Lassiter about what is exactly thinking of using to mitigate the HB stray fields. Wedges + C-section + iron pipe?
  • See HB fringe field section . C-section has a minimal impact on field.
• Work on run plans. (Rolf and Tanja)

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.

SNAKE

Moved Snake section here.