Fellner, K.MLZ*

2022

Abstract: Inelastic neutron scattering (INS) is an important tool for the study of a widespectrum of materials in condensed matter physics. One limitation, however, isthat INS is constrained by a trade-off between energy resolution and the bandwidthof neutron wavelengths. Neutron Spin Echo (NSE) was developed as away to overcome this trade-off. In NSE, the energy resolution is encoded inthe beam polarization instead of the width of wavelength band. More precisely,the velocity of neutrons is encoded via the total precessions of their spins overa fixed distance. Such encoding allows a wider wavelength band to be utilized,thus resulting in a higher usable flux [1]. The precession field in NSE is usuallygenerated by long solenoids. In a sub-type of NSE, neutron resonancespin echo (NRSE), the solenoids are replaced by radio frequency spin flippers[2], which avoids a significant amount of complications from dealing withmagnetic field inhomogeneities [3]. Modulation of Intensity with Zero effort(MIEZE) is a high resolution neutron spectroscopy technique closely related tothe NRSE method but does not use any flippers, polarizers, or magnetic fieldsdownstream of the sample, instead relying on neutron detectors with high timeresolution [3, 4]. This makes it possible to study depolarising (e.g. magnetic)samples with a MIEZE setup [5]. MIEZE enables a relatively large wavelengthbandwidth of 10% [6, 7]. One approach to further increase the usablewavelength bandwidth is to use a pulsed neutron source rather than a continuous(i.e. reactor) source. Here, the specific MIEZE setup of the RESEDAbeamline at the Heinz Maier-Leibnitz Zentrum (MLZ), a reactor source in Germany,is studied using the ray tracing and Monte Carlos simulation softwareMcStas with both a reactor source and a hypothetical pulsed source. This allowsfor a detailed and quantitative comparison of RESEDA’s performance on both types of sources.

Keyword(s): Instrument and Method Development (1st) ; Instrument and Method Development (2nd)

1. RESEDA (RESEDA)

1. RESEDA: Resonance spin echo spectrometer (NL5S)