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Targets for SoLID Experiments

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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Targets for SoLID Experiments

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  1. Targets for SoLID Experiments Jian-ping Chen SoLID Collaboration Meeting Feb 3-4, 2012

  2. 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

  3. 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

  4. G0 Style Target for SoLID

  5. 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

  6. 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

  7. 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

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