Abstract: The current state of the implementation of the project for building a spin-echo instrument for small-angle neutron scattering at the PIK reactor of the St. Petersburg Nuclear Physics Institute, National Research Center “Kurchatov Institute,” is described. In the course of the project, work is carried out on mathematical modeling, and the design and manufacture of prototypes of the instrument units. Both the optical elements of the instrument and the design of the precession magnets are optimized. The developed model of precession magnets underlies the design submitted for manufacturing. The model of a radio-frequency adiabatic flipper is tested. The test results demonstrate the flipper performance in the range of fields with an induction from 5 to 66 mT.

Abstract: We created software to simulate the Larmor precession in a setup for SESANS with adiabatic/radio frequency flippers in magnets designed to measure the time-of-flight on pulsed or stationary neutron sources. The values and spatial configurations of the magnetic fields of the existing prototype magnets we used as input data. For an empty setup, we calculate the polarization of a “divergent ribbon beam” 2 cm high, depending on the neutron wavelength λ. In the “scattering experiment”, we show how to convert λ to the “spin-echo length” δ. For λ = 10 Å, flippers at a distance of 140 cm and a radio frequency 1 MHz we find δ ≈ 10 μm. Extension to δ = 20 μm is realistic.