In-situ polarized ³He systems at ORNL and their applications

Xin Tong (Neutron Sciences Directory, Oak Ridge National Laboratory)

Polarized 3He based neutron spin filters can act both as neutron polarizers and analyzers in polarized neutron experiments, they are especially suitable for divergent neutron beam and polychromatic beam profiles. Typical usage of polarized ³He involves polarization build-up, ³He container transfer followed by installation to neutron instruments. However, ³He polarization suffers from decay once detached from its polarization build-up process, leading to complicated neutron polarization degradation throughout polarized neutron experiments. Although this problem can be circumvented using sophisticated signal monitoring and data reduction process, we, at the Oak Ridge National Lab, have been focusing on an alternative approach, namely developing in-situ polarized ³He systems which can be installed to a neutron beamline preserving ³He polarization hence keeping a constant neutron polarization.
In this talk I’ll introduce to you several generations of in-situ polarized ³He systems developed at ORNL, including a high performance 84 % ³He polarization system, a compact 70 % + ³He polarization system and other even more compact systems currently under development. I’ll also present several applications from these systems include polarized neutron reflectometry, polarized neutron imaging and Larmor labelling techniques.

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