t. horn, shms optics update shms optics update tanja horn hall c users meeting 31 january 2009
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T. Horn, SHMS Optics UpdateT. Horn, SHMS Optics Update
SHMS Optics Update
Tanja Horn
Hall C Users Meeting
31 January 2009
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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
HB Q1 Q2 Q3 DIPOLE
Focal Plane
Deflection= 18.4 °Deflection=3 °
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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
Q1
Q2
Q3
D
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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
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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 Q3D
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T. Horn, SHMS Optics Update
SHMS collimator/sieve system
• Design will be octagonal shape• Dimensions depend on location in z
Q1 Q2 Q3HB D
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
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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
HB Q1
SHMS collimator box
• Assume heavymet material for ±5cm at least need 40cm by 25cm per collimator
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T. Horn, SHMS Optics Update
Slit Box Design Limitations: Width
SHMS
HMS
Q1HB
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:
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T. Horn, SHMS Optics Update
Slit Box Design Limitations: Depth
Type Thickness
Box material thickness 0.9 cm
Empty space for motion 0.6 cm
Collimator thickness 6.4 cm
Rod/tooling ball space 4.6 cm
Box/material thickness 0.9 cm
Total depth of slit box 13.4 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
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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
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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=120cm z=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
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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
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T. Horn, SHMS Optics Update
Design Limitation: height of the sieve slit
Type Thickness
Wall thickness 0.9 cm (x2)
Rod/tooling ball thickness 4.6 cm (x2)
Sieve slit height 25.0 cm
Total height of slit box 36.0 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
Q1HB
Q2Special Sieve Slit
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T. Horn, SHMS Optics Update
Design Limitation: depth of the sieve slit
Type Thickness
Thickness of guide before sieve 0.5 cm
Sieve slit thickness (but rod/tooling bar thickness)
3.2 cm5.1 cm
Thickness of guide after sieve 0.5 cm
Back wall material thickness 0.9 cm
Total depth of slit box 6.5 cm
• Analogous to HMS design, assume octagonal sieve slit thickness 3.2 cm
• But cannot forget about additional materials for support
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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
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T. Horn, SHMS Optics Update
Backup material
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T. Horn, SHMS Optics Update
Q1 sieve
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T. Horn, SHMS Optics Update
Special calibration sieve
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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