1. Solid Polarized Target Opportunities at JLab Possibilities for Future Experiments

2. 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

3. 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

4. Major Polarized Target Systems

5. UVA/SLAC/JLAB Target

8. DNP

9. TE Polarization P TE = exp [ uB/kT ] Enhanced Polarization P enh = exp [ uB/kT S ]

12. 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

18. 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

19. Table of polarized Target Materials

20. Ammonia Polarization

21. Performance and Experience Target materials Polarization growth, radiation damage, decay of material NH 3

23. Performance and Experience Target materials ND 3

25. 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%

31. Results on trityl doped hydrocarbons The deuteron NMR signal with quadrupole interaction The maximum polarizations at B = 2.5 T !!

32. 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?