Polarized 3 He Target for A1n-A J. P. Chen, June 11, 2013, Hall A Meeting

1. Polarized 3He Target for A1n-A J. P. Chen, June 11, 2013, Hall A Meeting • Overview • Design Progress • Progress in target lab • Progress from users

2. Overview • Polarized 3He performance for 6 GeV experiments: • luminosity: 1036 with 15 uA on 40 cm cell (average~12 uA) • pol >70% (no beam), ~60% (with beam/flip), ~55% (target) • polarimetry: NMR/water +EPR, total uncertainty ~5% • water (2-3%), diffusion (2-3%), k0 for EPR (2-3%), T/r (2-3%) • A1n-A requirements/plan: • 30 uA on 40 cm convection cell, 60% in beam, 3% polarimetry • use transversity setup with convection cell • uniform polarization between target and pumping chambers •  60% achievable •  eliminate diffusion uncertainty • pulsed NMR, calibrated with EPR and AFP NMR/water , • k0 measurements (users) • Mechanical design • R&D progress: • pulsed NMR setup and systematic study • higher current study: shielding needs? • polarization loss study (field gradient, new material, …) • convection cell tests/transfer heater design • laser system study

3. Overview • Polarized 3He performance for 6 GeV experiments: • luminosity: 1036 with 15 uA on 40 cm cell (average~12 uA) • pol >70% (no beam), ~60% (with beam/flip), ~55% (target) • polarimetry: NMR/water +EPR, total uncertainty ~5% • water (2-3%), diffusion (2-3%), k0 for EPR (2-3%), T/r (2-3%) • A1n-A requirements/plan: • 30 uA on 40 cm convection cell, 60% in beam, 3% polarimetry • use transversity setup with convection cell • uniform polarization between target and pumping chambers •  60% achievable •  eliminate diffusion uncertainty • pulsed NMR, calibrated with EPR and AFP NMR/water , • k0 measurements (users) • Mechanical design • R&D progress: • pulsed NMR setup and systematic study • higher current study: shielding needs? • polarization loss study (field gradient, new material, …) • convection cell tests/transfer heater design • laser system study Jie Liu /Zhiwen Zhao

4. Mechanical Design: Overview

5. Mechanical Design: Down Stream

6. Polarized 3He Progress

7. Diffusion cell to Convection Cell • New convection style cell (single pumping chamber) • “Protovec-I” tested at Uva, transferred to JLab a few months ago • 3D measurement of the cell, CAD model • Made customized mount and oven bottom piece • testing ongoing at JLab now

8. Polarimetry

9. Pulse NMR Send RF pulse Pulse NMR signal vs time RF Stops Decay starts Receive free-induction-decay signal Challenge: to improve signal to noise ratio

10. Pulse NMR @ JLab • Pulse NMR compared with regular NMR • Systematic study continuing

11. Radiation @ Pumping Chamber vs. Shielding A1n with no oven plate Transversity (350 hours) A1n with regular oven A1n with oven + 1mm lead

12. AFP Lost study Target Chamber With convection Speed 5.7cm/min 25 sweep*2min Target Chamber Without convection 25 sweep*2min

13. Convection can be much fast than diffusion (few mins compared to 40 mins) Convection Pulse NMR Coil Heater 2nd pick up coil 1st pick up coil

14. Masing Effect • Masing Effect: non-linear coupling between pick-up coil and spin Turn off gradient coil, remove 1st pick up coil Disconnect pulse NMR coil Connect Pulse NMR coil Reach threshold Turn on gradient coil Spin up test

15. Lasers • New lasers • The Comet laser (25W, 0.2nm width) production was discontinued • Purchased one QPC Laser (Hall C, 25W, 0.27nm width) and doing test now • Possibly upgrade Coherent lasers by Raytum Intensity (counts) vs Wavelength (nm)

16. Summary • Polarized 3He target world-record performance for 6 GeV experiments • Plan for 12 GeV polarized-3He, starting with A1n-A (FOM a factor of 2-3) • R&D progress at JLab • Near term- summer: • Jie Liu and two summer students now • more will be here in July-August • complete convection cell/heating/polarization loss study • pulsed NMR systematic study • Longer term: ~6 month • full polarization test • Goal by 2016: full system ready for A1n-A exepriment