Extending MIEZE spectroscopy towards thermal wavelengths

TL;DR

This paper introduces an advanced MIEZE neutron spectroscopy setup capable of high-resolution measurements at thermal wavelengths, enabling studies of magnetic and spin-incoherent samples with improved flexibility and range.

Contribution

It extends MIEZE spectroscopy to thermal neutrons, allowing high-resolution measurements at larger momentum transfers and energy ranges, bridging classical neutron spin-echo and other spectroscopic techniques.

Findings

Demonstrated feasibility of thermal MIEZE at RESEDA beamline

Achieved energy resolution in the microelectronvolt range

Extended the applicability of neutron spin-echo to more diverse samples

Abstract

We propose a Modulation of intensity with zero effort (MIEZE) set-up for high-resolution neutron spectroscopy at momentum transfers up to 3\r{A}$^{-1}$,energy transfers up to ~ 20 meV, and an energy resolution in the $\mu$eV-range using both thermal and cold neutrons. MIEZE has two prominent advantages compared to classical neutron spin-echo. The first one is the possibility to investigate spin-depolarizing samples or samples in strong magnetic fields without loss of signal amplitude and intensity. This allows for the study of spin fluctuations in ferromagnets, and facilitates the study of samples with strong spin-incoherent scattering. The second advantage is that multi-analyzer setups can be implemented with comparatively small effort. The use of thermal neutrons increases the range of validity of the spin-echo approximation towards shorter spin-echo times. In turn, the thermal MIEZE option for greater ranges (TIGER) closes the gap between classical neutron spin-echo spectroscopy and conventional high-resolution neutron spectroscopy techniques such as triple-axis, time-of-flight, and back-scattering. To illustrate the feasibility of TIGER we present the details of an implementation at the beamline RESEDA at FRM II by means of an additional velocity selector, polarizer and analyzer.