POLANO: Wide angle spin analysis using polarizing supermirrors m = 5.5

Abstract

We report on a wide angle neutron spin analyzer for neutron energies up to 40 meV (λ = 1.4 Å) that was recently realized in collaboration with Tohoku University and KEK, Japan (Ohoyama et al., 2014; Yokoo et al., 2014). Curved polarizing Fe/Si supermirrors with m = 5.5/1.5 (Schanzer et al., 2016) are arranged radially around the sample covering an angular range of 40° if all channels are equipped with supermirrors. The mirrors are saturated by a vertical permanent magnetic field B≃40 mT generated by NdFeB magnets. It was optimized using finite element analysis. The polarization and transmission of the spin filter have been determined at the beamline BOA at the Swiss spallation neutron source (SINQ) to be P=(0.975±0.01) and Tup=T=(0.55±0.017) for spin-up neutrons at λ=3 Å (E=9 meV), respectively. The transmission is excellent considering that approximately one third of the neutrons hit the front faces of the polarizing blades. The experimental results are in good agreement with Monte Carlo simulations using the software package McStas.