A high-flux upgrade for the BRISP spectrometer at ILL.

To date, the BRISP spectrometer represents the state-of-the-art for every instrument aiming to perform Brillouin neutron scattering. Exploiting accurate ray-tracing McStas simulations, we investigate an improved configuration of the BRISP primary spectrometer to provide a higher flux at the sample position, while preserving all the present capabilities of the instrument. This configuration is based on a neutron guide system and is designed to fit the instrument platform with no modifications of the secondary spectrometer. These evaluations show that this setup can achieve a flux gain factor ranging from 3 to 6, depending on the wavelength. This can expand the experimental possibilities of BRISP towards smaller samples, possibly using also complex sample environments.