Broadband spin flippers constructed from thin magnetic films

I describe an optimized design for neutron spin flippers constructed from stacks of permanently magnetized thin films. These devices should provide high flipping efficiency over a broad range of neutron wavelengths, occupy little space in the neutron beam and consume no power. Because they are flat, they are well suited for experiments that use the neutron spin echo technique to code neutron scattering angles. Importantly for this use, π/2 and π flippers have the same orientation with respect to the neutron beam.