1. T. Horn, SHMS Optics Update SHMS Optics Update Tanja Horn Hall C Users Meeting 31 January 2009

2. T. Horn, SHMS Optics Update SHMS Optics Configuration Need charged particle detection with momenta up to the beam energy (11 GeV) at forward angles down to 5.5° even with HMS at small angles Most reasonable configuration: HBQQQD HBQ1Q2Q3DIPOLE Focal Plane Deflection= 18.4 ° Deflection=3 °

3. T. Horn, SHMS Optics Update Collimator reduces uncertainties due to optics Event loss at Q1 due to geometric effects Acceptance at dipole entrance depends on aperture and δ –Events at negative δ are focused more +10% < δ < +15% Collimator can eliminate events that would be lost inside the dipole –Reduces model dependent systematic uncertainty Q1Q1 Q2Q2 Q3Q3 D

4. T. Horn, SHMS Optics Update Sieve Slit for Spectrometer Optics Sieve slit is used to understand the optics properties the spectrometer Figures show HMS sieve slit reconstruction data H. Blok, T. Horn, G. Huber et al., Phys. Rev. C78 (2008) X’ (individual holes)1.8 mr X’ (columns)1.8-2.1 mr Y’ (individual holes)0.3-0.7 mr Y’ (rows)0.8-1.0 mr Y (mean)2 mm HMS

5. T. Horn, SHMS Optics Update HMS collimator/slit system Sieve slit –0.508 cm holes in 7 (9) columns at 1.524 cm (2.540 cm) intervals in the horizontal (vertical) direction –Center of sieve slit at 168 cm from target center –No holes at +1.524/+2.540 cm and -1.524 cm/- 5.080cm for orientation checks –Outermost holes are at ±10.160 cm (±60.5 mr) Octagonal collimators –6.35 cm thick heavymet (90% W, 10% CuNi) HMS Collimator box Q1 Q2 Q3 D

6. T. Horn, SHMS Optics Update SHMS collimator/sieve system Design will be octagonal shape Dimensions depend on location in z Q1Q2Q3HBD Possible sieve collimator locations y x Sieve collimator in front of HB: standard optics calibration may be complicated –Aperture defining slits: best location in front of HB Sieve collimator in front of Q1: optics modeling straightforward, but have to assume that perturbations due to HB are small

7. T. Horn, SHMS Optics Update Place SHMS collimator after HB No room before HB for collimator box with collimator(s) and sieve slit Assume front of collimator is at 82 cm after the HB center or at 2.58 m from the pivot –Collimator is then ±0.055*258=±14.2 cm high and ±0.030*258=±7.7 cm wide HBQ1 SHMS collimator box Assume heavymet material for ±5cm at least need 40cm by 25cm per collimator

8. T. Horn, SHMS Optics Update Slit Box Design Limitations: Width SHMS HMS Q1 HB Q2 35-cm wide slit box is possible –Move horizontally from SHMS left to beam axis –Mechanical (surveyed) stop at SHMS right Guiding rods (w/ tooling balls) on top and bottom –Two options: guiding rods in the back or to sides Slit box Guiding rod options:

9. T. Horn, SHMS Optics Update Slit Box Design Limitations: Depth TypeThickness Box material thickness0.9 cm Empty space for motion0.6 cm Collimator thickness6.4 cm Rod/tooling ball space4.6 cm Box/material thickness0.9 cm Total depth of slit box13.4 cm Analogous to HMS design, assume octagonal collimator thickness 6.4 cm –Sieve slit is thinner (e.g., HMS: 3.175 cm thick) Also take into account additional material for support etc. Sieve slit Two octagonal collimators

10. T. Horn, SHMS Optics Update SHMS Slit Box in Hall C Front of slit box is 80 cm after the HB center, or at 2.56 m from target center –Sufficiently far away from HB to have minimum stray field Slit box fits between HB and Q1

11. T. Horn, SHMS Optics Update SHMS sieve slit design Size of sieve holes: 3 mrad –For comparison: HMS sieve holes diameter is 0.504cm (3 mrad) Further studies of the focal plane patterns will determine the optimal design for optics reconstruction z=120cmz=258cm Standard calibrations of SHMS with the sieve before Q1 possible –Preliminary simulations show small distortions of mid-plane symmetry FP pattern of sieve before HB shows strong delta dependence of the bending

12. T. Horn, SHMS Optics Update Additional Sieve Slit before HB Assume front of sieve slit is 56 cm in front of HB center or at 1.20 m from the pivot –Need to cover at least ±0.055*120cm=±6.6 cm high and ±0.030*120cm=±3.6cm wide for a point target Assume heavymet material for ± 5 cm at least at the edges –Assume 30 cm wide by 25 cm high sieve (note: HB gap is 35cm by 36 cm) –Weighs about 40 kg, so movable by hand Q1HB Special calibration sieve slit 120 cm from target center

13. T. Horn, SHMS Optics Update Design Limitation: height of the sieve slit TypeThickness Wall thickness0.9 cm (x2) Rod/tooling ball thickness4.6 cm (x2) Sieve slit height25.0 cm Total height of slit box36.0 cm Additional sieve slit (simple hand motion) before HB –Move horizontally from SHMS left to beam axis –Only inserted for special calibration runs SHMS HMS Q1 HB Q2 Special Sieve Slit

14. T. Horn, SHMS Optics Update Design Limitation: depth of the sieve slit TypeThickness Thickness of guide before sieve0.5 cm Sieve slit thickness (but rod/tooling bar thickness) 3.2 cm 5.1 cm Thickness of guide after sieve0.5 cm Back wall material thickness0.9 cm Total depth of slit box6.5 cm Analogous to HMS design, assume octagonal sieve slit thickness 3.2 cm But cannot forget about additional materials for support

15. T. Horn, SHMS Optics Update Bender Q1’ Target HMS Q1 HMS Q2 Beamline Additional studies for understanding the optical properties of the SHMS including HB –Look how HB distorts the “image” of a collimator or sieve slit in front of it. –How does an entrance octogonal look like in position and angle space at the planned location at the entrance of Q1 – can easily be done using HB TOSCA Next Steps Short report on simulation results Additional techniques for calibration techniques –Possibilities of H(e,e’p) for calibrations especially the HB part Optimization of the distance between and the size of the Q1 sieve holes and the special calibration sieve slit before HB

16. T. Horn, SHMS Optics Update Backup material

17. T. Horn, SHMS Optics Update Q1 sieve

18. T. Horn, SHMS Optics Update Special calibration sieve

19. T. Horn, SHMS Optics Update Target Region Slot in HB for Beamline Vertical Slot in HB for HMS Q1 at 12° Slot in Q1’ for Beamline Slot in Q2 for Beamline