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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
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