Chapter 2.8.6 - Neutron Spin Echo—A Technique for High-Resolution Neutron Scattering

Abstract

This chapter provides an introduction to neutron spin echo—a technique for high-resolution neutron scattering. In neutron spin echo, the velocity change of neutrons after scattering by a sample is measured by comparing the Larmor precession in known magnetic fields before and after the scattering. As the comparison is made for each neutron individually, the resolution for measuring the velocity change can be much better than that corresponding to the width of the incident beam. There are two different types of spin-echo techniques in use, one using static magnetic fields and the second using resonant spin flippers called neutron resonance spin echo (NRSE). The chapter finally discusses the application of the NRSE technique with tilted precession field boundaries to the three main fields of elastic scattering—small-angle scattering, reflectometry, and diffraction. The basic idea of all these applications is to overcome the usual coupling between resolution and intensity by marking each neutron trajectory with a Larmor precession angle. Thus, a high resolution can be achieved together with a high intensity of scattered neutrons.