Monte Carlo Simulation of TOF Single Crystal Spectroscopy

Article type: Research Article

Authors: Schorr, S. | Mezei, F. | Stride, J. | Guy, C.

Affiliations: Hahn-Meitner-Institut Berlin, Glienicker Str. 100, D-14109 Berlin, Germany

Note: [] Corresponding author. Fax: 03-8062-2535. E-mail: schorr@hmi.de

Abstract: Results of a first Monte Carlo simulation study of constant-q single crystal spectroscopy using a multiwavelength time-of-flight (TOF) technique are presented. We used the time-of-flight wavelength band monochromatization (TOF-monochromator) set-up with an additional fast double chopper just in front of the sample running quasi-asynchronously with the TOF-monochromator and a repetition rate properly chosen for the TOF energy analysis in the secondary spectrometer and independent of the source pulse frequency (repetition rate multiplication). Instead of a single incoming wavelength, we produce a set of short pulses with an array of wavelengths λ1, λ2,  … , λn, with λ(t) and δλ/λ(t) periodically changing in time. Choosing the ratio of the TOF monochromator and the sample end fast chopper speed to be an adequate rational number we measure TOF spectra with a quasi continuous set of incoming wavelengths. The data sets so obtained in two TOF dimensions contain constant Q =q + τ energy spectra with q oriented in any selected direction. The new method inherently ideally adapted for pulsed sources is shown to offer on continuous sources a competetive alternative to triple-axis spectroscopy.

Keywords: long pulsed spallation source, Monte Carlo simulation, time-of-flight constant-q spectroscopy, repetition rate multiplication

DOI: 10.1080/10238169708200101

Journal: Journal of Neutron Research, vol. 6, no. 1-3, pp. 113-123, 1997