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Targets for SoLID Experiments. Jian-ping Chen SoLID Collaboration Meeting Feb 3-4, 2012. Overview of SoLID Target Systems. Cryotarget system for PVDIS

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slide1

Targets for SoLID Experiments

Jian-ping Chen

SoLID Collaboration Meeting

Feb 3-4, 2012

slide2

Overview of SoLID Target Systems

  • Cryotarget system for PVDIS
    • 1kW Cryotarget (LH2/LD2) system with capability of solid targets in a large acceptance strong magnetic field
    • G0 type as starting design.
    • Target polarization due to field
  • Polarized 3He target system for SoLID-SIDIS(n/3He)
    • Standard type with achieved performance
    • SoLID field effect: end cap design
    • Improvements
  • Polarized NH3 target system for SoLID-SIDIS(p) (conditional approved)
    • Transverse Polarization with opening up to +-25 degrees
    • Design underway
    • Effects due to strong field
slide3

Cryotarget: General Requirements/Considerations

  • 50 uA on 40 cm LD2/LH2, ~800 W beam power, ~ 1 KW total power
  • Solid targets: multi-foil 12C (optics), Al (dummy), BeO (viewer), …
  • Large acceptance, 2p azimuthal opening, 20-35 degrees q angle
  • Density fluctuations -- moderate requirement
  • Polarization effect to be < 10-6
slide5

Target polarization in strong magnetic field

  • Small target polarization will introduce large false asymmetry due to
  • double spin asymmetry
  • Ortho-para configurations in LH2
  • 2 protons form I=1 (ortho) and I=0 (para) state
  • at room T, ~75% ortho, 25% para (in equilibrium)
  • at T=20K, ~0.2% ortho, ~99.8% para (in equilibrium)
  • only ortho state can not be polarized
  • Chris Keith: P(ortho) ~ 50 ppm @ 20K, 1T  P(LH2) ~ 0.1 ppm
  • LD2: at 20K, 1T, P ~ 8 ppm (Chris Keith)
  • When hydrogen is cooled down it will have ortho to para conversion, but the spontaneous conversion process is slow
  • A catalyst like ferric oxide, active carbon, … can speed it up significantly
  • It was used at the early stage in Hall A cryotarget for LH2 target
slide6

Polarized 3He Target

  • Existing performance:
    • luminosity: 1036
    • polarization: 60% polarization
    • spin reverse: 10-20 minutes
  • Field gradients from Solenoid:
    • need careful design on endcap to minimize fringe field
    • existing design would require 30-50 mg/cm
    • new convention flow target would significantly reduce requirement
    • new upgrade would increase luminosity by a factor of 4-10, can SoLID take advantage of it?
  • Collimator design
slide7

Polarized Proton (NH3) Target

  • Main issue: large opening angle for transverse polarization
    • +-25 degrees (cone)
    • keep to 5T if possible
    • no requirements on longitudinal
  • Don Crabb Contacting both Oxford and Scientific Magnetics
    • both can have a design satisfying these spec’s
    • Scientific Magnetics, initial quick look, it can be done, cost $600K
    • Oxford, modify from the Hall B design, give a quote to do detailed design
  • Forces between target magnets and Solenoid: need Tosca calculation