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

Overview Polarized 3 He performance for 6 GeV experiments: luminosity: 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%), 0 for EPR (2-3%), T/ (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, 0 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

Overview Polarized 3 He performance for 6 GeV experiments: luminosity: 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%), 0 for EPR (2-3%), T/ (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, 0 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

Mechanical Design: Overview

Mechanical Design: Down Stream

Polarized 3 He Progress

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

Polarimetry

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

Pulse JLab Pulse NMR compared with regular NMR Systematic study continuing

Transversity (350 hours) A 1 n with no oven plate Pumping Chamber vs. Shielding A 1 n with regular oven A 1 n with oven + 1mm lead

AFP Lost study AFP lost per sweepTarget Chamber (%)Pumping Chamber (%) AFP Without Convection0.16%0.72% AFP With Convection0.85%0.87% Target Chamber With convection Speed 5.7cm/min 25 sweep*2min Target Chamber Without convection 25 sweep*2min

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

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

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)

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