Abstract
The neutron spin-echo spectroscopy technique involving pulsed beams can be used to effectively access a wide range of space-time correlations of condensed matter. In this study, the features of this technique, in particular, the modulation of the intensity with zero effort (MIEZE) by using pulsed beams, which is based on the quantum-state manipulation of the neutron spin and energy, are comprehensively examined. A formulation of the MIEZE combined with the time of flight method (TOF MIEZE) is established by considering the characteristics of the pulsed neutron beams. Moreover, a parameter, namely, the detuning parameter, is introduced as a measure of the magnitude of detuning from the optimized instrumental state, known as the spin-echo condition. The phase and frequency shifts of the neutron intensity signals resulting from the TOF MIEZE under various configurations are investigated systematically. It is found that the detuning parameter equals the derivative of phase with respect to the TOF, whose zero-point corresponds to the spin-echo condition. The theoretical predictions on phase and frequency shifts by the established formulation are well validated by the experiments using an intense pulsed neutron source. The detuning parameter helps clarify the principle of the TOF MIEZE technique and can provide practical guidance regarding the implementation and optimization of spectrometers.
Highlights
Neutron spin echo (NSE) [1] represents a type of quasielastic neutron-scattering spectroscopy with a high resolution in energy
We further developed a formulation of TOF modulation of the intensity with zero effort (MIEZE) technique considering its specific features that arise from the characteristics of pulsed neutron beams
Td is likely a significant factor in most scattering experiments, in the present study we focus on the dephasing effect associated with t0, which is known as the pulse width and is a fundamental parameter characterizing a neutron pulse beam, to investigate the characteristics of TOF MIEZE signals
Summary
Neutron spin echo (NSE) [1] represents a type of quasielastic neutron-scattering spectroscopy with a high resolution in energy. The inherent fine wavelength resolution of the TOF approach permits the measurements of I(Q, t) in precisely divided regions of interest in the reciprocal space This feature plays an important role in identifying whether the characteristic scattering pattern arising near phase boundary is derived from the static disorder or dynamical one, which pertains to the order stability and formation process. Accelerator-based spallation neutron sources such as ISIS, SNS, J-PARC, CSNS, and ESS have been established as alternatives to research reactors Under such circumstances, NSE spectroscopy using the TOF method at the pulsed source has been studied [15,16,17,18] and applied [19] to cover a wide space-time range with the broadband wavelength. The characteristics of the TOF MIEZE signals are discussed in detail, which are essential to perform NSE experiments with high precision
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