A compact solenoid 3He neutron spin filter with a fast spin flip capability

We have designed and demonstrated a compact solenoid 3He neutron spin filter with a fast spin flip capability. The 3He spin is flipped by adiabatic fast passage (AFP) in a short time and with very little polarization loss, which is essential for polarized neuron scattering measurements in cancellation of systematic errors. A solenoid coil and compensation coils provide a uniform magnetic field for the polarized 3He to minimize the longitudinal spin relaxation. This neutron spin filter can be installed rather easily in neutron scattering spectrometers as a neutron polarizer as well as a neutron spin analyzer. We describe the design and the performance of the device tested by AFP-NMR and with a pulsed neutron beam at KEK.