Spin-analyzed diffuse scattering measurements of magnetic thin films with a 3He analyzer and a position sensitive detector

Polarized 3He gas, produced by optical pumping, can be used to polarize or analyze neutron beams because of the strong spin dependence of the neutron absorption cross section for 3He. 3He spin filters have been identified as important polarizing elements in the development of polarized neutron scattering instruments for the upcoming spallation neutron source (SNS) because they are broadband and suitable for divergent scattered beams. In this talk, I will discuss efficient polarization analysis of diffusely reflected neutrons in a reflectometry geometry using a polarized 3He spin filter in conjunction with a position-sensitive detector (PSD). Spin-analyzed two-dimensional Qx-Qz reciprocal space maps for a patterned array of Co antidots in the saturated and the demagnetized states have been obtained. Data obtained from a 3He analyzer and a PSD are compared with those obtained from a conventional supermirror analyzer, and they are in good agreement. For this experiment, 3He gas is polarized by the spin-exchange optical pumping (SEOP) method and stored in a uniform magnetic field provided by a shielded solenoid. I will also address two important issues for significantly improving the overall performance of the 3He spin-filter device: high 3He polarization and long relaxation time of the 3He cell.

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