Polarized 3 He Filling Stations. Xin Tong (Tony) Instrument Development Group Neutron Facilities Development Division Oak Ridge National Laboratory Oak Ridge, TN 37831, USA. Polarized 3 He Neutron Analyzer.
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Xin Tong (Tony)
Instrument Development Group
Neutron Facilities Development Division
Oak Ridge National Laboratory
Oak Ridge, TN 37831, USA
Polarized 3He neutron spin filter is based on the spin-dependence of the neutron absorption of 3He. If the 3He nuclear spin and the neutron spin are anti-parallel, the absorption is very strong: sa (↑↓) = 5931 b for l=1 Å neutrons. If the spins are parallel, there is virtually no absorption. sa (↑↑) ~ 0. The absorption cross-section is proportional to the neutron wavelength l.
3He polarization PHe = 73%
Pressure = 1.52bar
ø11.7 cm ID, l = 8.1 cm Pump up time constant = 5 hrs
HYSPEC (Hybrid Spectrometer) Wide-Angle Analyzer
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.
SEOP based polarized 3He filling station
Polarized gas transfer “local filling”
Uniform field coil
Example: Max. 3He polar. =72%, optimized at 90 meV. T1=100 hours, exchange all the gas every 5 hours. (Plot: for 50 meV neutrons)
Laser Power Supplies
Wai Tung Hal Lee
Mark Hagen (HYSPEC)
Tom Gentile (NIST)
Gondon Jones (Hamilton)