Managed by UT-Battelle for the Department of Energy Polarized 3 He Filling Stations Xin Tong (Tony) Instrument Development Group Neutron Facilities Development Division Oak Ridge National Laboratory Oak Ridge, TN 37831, USA

Managed by UT-Battelle for the Department of Energy Cell Barbara 3 He polarization P He = 73% Pressure = 1.52bar ø11.7 cm ID, l = 8.1 cm Pump up time constant = 5 hrs Laser optics Neutrons 3He NSF Polarized 3 He neutron spin filter is based on the spin-dependence of the neutron absorption of 3 He. If the 3 He nuclear spin and the neutron spin are anti-parallel, the absorption is very strong:  a (↑↓) = 5931 b for =1 Å neutrons. If the spins are parallel, there is virtually no absorption.  a (↑↑) ~ 0. The absorption cross-section is proportional to the neutron wavelength. Polarized 3 He Neutron Analyzer

Managed by UT-Battelle for the Department of Energy Why 3 He Filling Station The need to change 3 He pressure throughout an experiment –For neutron scattering experiments off different neutron wavelengths, the optimized 3 He pressure is different. –The two conventional way of using 3 He in polarized neutron scattering does not involve changing of 3 He pressure / 3 He cell. Polarized 3 He for instruments with limited space which can not accommodate an in-situ SEOP pumping system –Space for laser, optics, solenoids, etc. Solution for cells with difficult shape (HYSPEC wide angle analyzer) –Conventional cylindrical 3 He cell is easily pumped and preserves a long 3 He relaxation time –With current optical pumping technology, it is not easy to pump an irregular cell.

Managed by UT-Battelle for the Department of Energy 3 He Filling Stations at Oak Ridge Instrument based 3 He filling station with Spin- exchange optical pumping –Compact system which will be installed onto an SNS beamline – Hybrid Spectrometer (HYSPEC) –Its subsystems include a 3 He gas filling station, a 3 He polarizing system a gas transfer system and a gas recycle system Lab based 3 He filling station –A sophisticated system with three gas lines –Ability to fill up to three different 3 He cells at the same time –Able to create sealed 3 He cells for in-situ 3 He pumping based on experiment requirements

Managed by UT-Battelle for the Department of Energy  Should cover the 60 degree horizontal range of the detector bank  Should cover as much as is possible of the ± 7.5 degree vertical range of the detector bank  Should allow an exclusion zone at the sample position of diameter 150mm HYSPEC (Hybrid Spectrometer) Wide-Angle Analyzer No stress point seen under polarized light Optical pumping is difficult due to the limited space in the instrument and the shape of the cell. Refilling in-situ with a on-site compact filling station is the solution we are going for.

Managed by UT-Battelle for the Department of Energy Gas return Polarize Gas supply SEOP based polarized 3 He filling station Example: Max. 3 He polar. =72%, optimized at 90 meV. T 1 =100 hours, exchange all the gas every 5 hours. (Plot: for 50 meV neutrons) 3 He cell Polarized gas transfer “local filling” Sample Uniform field coil HYSPEC 3 He Filling Station Design

Managed by UT-Battelle for the Department of Energy Laser Power Supplies Function Generator Amplifier Power Supply Rough PumpTurbo Pump Laser Optics Shielding Gas Supply Getter Breadboard Pressure Gauge

Managed by UT-Battelle for the Department of Energy HYSPEC 3 He Filling Station Features  Three-level compact station  Gas filling level  Optical pumping level  Pumps / Electronics level  Potassium instead of Rubidium for fast pumping process  Fully electronically control

Managed by UT-Battelle for the Department of Energy Compact Filling Station Schemes – Next Steps Customize magnetic shielding and oven Test polarized gas transfer components Test valved Potassium-based cell for high temperature operation Instrument Development Test beam lines available beginning in June for testing.

Managed by UT-Battelle for the Department of Energy Lab-based 3 He Filling Station Gas-supply system 15-bar gas pressure Supply gas to polarizing system while preparing 2 sealed cells. Status: Baking the system. Ready to fill a cell.

Managed by UT-Battelle for the Department of Energy Lab-based 3 He Filling Station – Optical Pumping Cell 4 bar-liter optical-pumping cell Material: GE180 ID 84 mm x 130 mm (nominal) 6 mm thick wall = 12 bar limit T=300ºC, maximum 6 bar at RT Production rate for this cell Assume a relaxed 8-hour cycle Prod. rate = 15 bar-liter/day Status: 2 cells made. Install gas- polarizing system for polarized gas production soon.

Managed by UT-Battelle for the Department of Energy Summary Compact filling station –In progress –HYSPEC beam commission 2010 Lab-based filling station –Cells made, prepare to fill –Test and commission soon

Managed by UT-Battelle for the Department of Energy Wai Tung Hal Lee Dennis Rich Mike Fleenor Akbar Ismaili Lee Robertson Mark Hagen (HYSPEC) Bill Leonhardt David Anderson Acknowledgement Tom Gentile (NIST) Wangchun Chen Changbo Fu Gondon Jones (Hamilton)