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.
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)