Simulations of a convergent bender as neutron polariser for NSE spectrometers

Abstract

Soller-type collimators with supermirror coating may be used for polarisation of neutron beams. The disadvantage of such devices is a high level of gamma background and fast neutrons in the case of pulsed neutron sources. In order to increase the neutron flux, the collimator was made convergent. Generally, benders make it possible to suppress the fast neutron and gamma background completely. The combination of a bender and a convergent Soller collimator (convergent or focusing bender) is proposed for polarisation of the neutron beam for future NSE spectrometers at the cold source of ESS. Simulations and optimisation of convergent benders as neutron polarisers for NSE spectrometers are presented. The VITESS software package proved to be a powerful tool for the optimisation of polarising devices.