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

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%), 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 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%), 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 3He 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 StopsDecay starts

Pulse NMR signal vs time

Pulse NMR @ JLab

•Pulse NMR compared with regular NMR•Systematic study continuing

Transversity (350 hours)

A1n with no oven plate

Radiation @ Pumping Chamber vs. Shielding

A1n with regular oven

A1n with oven + 1mm lead

AFP Lost study

AFP lost per sweep Target Chamber (%) Pumping Chamber (%)

AFP Without Convection 0.16% 0.72%

AFP With Convection 0.85% 0.87%

Target ChamberWith convectionSpeed 5.7cm/min25 sweep*2min

Target ChamberWithout convection25 sweep*2min

Pulse NMR Coil

Heater

1st pick up coil 2nd 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

Turnongradientcoil

Turn offgradient coil,remove 1st pick up coil

Disconnect pulse NMRcoil

Connect Pulse NMRcoil

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