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Published byAlisha Johnson Modified over 9 years ago
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Solid Polarized Target Opportunities at JLab Possibilities for Future Experiments
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Introduction 4 He, 3 He and 3 He/ 4 He dilution refrigerators used over ~ 40 years. Divergence to using either 4 He or dilution fridges At same time – improvement in magnets DNP process used over range of 2 T to 7 T and 100 mK to ~1 K. Modern Systems High power in high intensity beams Moderate power in low intensity or neutral beams Most recent progress in materials
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Requirements for DNP Target material doped with paramagnetic centers Cryogenic system to reach temperatures of < 1K Magnetic field > ~ 2 Tesla Microwave system – 140 GHz at 5 T NMR to measure polarization
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Major Polarized Target Systems
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UVA/SLAC/JLAB Target
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DNP
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TE Polarization P TE = exp [ uB/kT ] Enhanced Polarization P enh = exp [ uB/kT S ]
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The Conventional Hall B Polarized Target Protons (and deuterons) in 15 NH 3 ( 15 ND 3 ) are continuously polarized by 140 GHz microwaves at 5 Tesla, 1 Kelvin Used for several experiments (beam current ~ 2 nA – 7 nA) Currently running eg1 dvcs Proton polarization: ~75 – 90% Deuteron polarization: ~25 - >45% 1.5 cm
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Materials Standard at JLab: Radiation doped NH 3 and ND 3 Butanol doped with TEMPO Investigate: Radiation doped alcohols and other materials with high proton or deuteron content. Have looked at CH 2, CD 2, BH 3 NH 3, butanol, d-butanol,d-pentanol etc. Future: Ethane and Methane
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Table of polarized Target Materials
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Ammonia Polarization
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Performance and Experience Target materials Polarization growth, radiation damage, decay of material NH 3
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Performance and Experience Target materials ND 3
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6 LiD 6 Li ~ d + alpha 50% Dilution Factor Actual Dilution factor ~ 40% P Li ~ P d Irradiation: at 180 K for ~2. 10 17 e - cm -2 Used in SLAC experiments E155 and E155X (g 1 and g 2 for proton and neutron). E143 used 15 ND 3 Agreement at ~ 5% to 10% level JLab experiment 6 LiD/ND 3 to ~1%
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Results on trityl doped hydrocarbons The deuteron NMR signal with quadrupole interaction The maximum polarizations at B = 2.5 T !!
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CONCLUSIONS Repair 5 T magnet depending on cost. Construct new 1 K refrigerator New magnet for g2p experiment in Hall A Design to accommodate existing and new refrigerators Existing magnet a spare for experiment For 12 GeV more complicated transverse magnet. Horizontal 1 K fridge for Hall B Frozen Spin Refrigerator – internal polarizing magnet? Material Development. - DNP of HD?
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