Date: 27th February, 2023

Speaker: Dr. Joe Kelleher (ISI Neutron and Muon Source)

Venue: Tycho, ESS

Title: Enhanced analysis beyond macroscopic strain for time-of-flight diffraction experiments

Registration: https://indico.esss.lu.se/event/3192/

Please register in Indico so we have accurate numbers to provide fika after the seminar. Also please share with your networks who might be interested in this event – visitors to ESS will need to register for site access but are welcome to join us. Registration closes at 12:00 on Thursday 23rd February.

Abstract: Time-of-flight neutron diffraction instruments generally employ a significant detector solid angle coverage, subdivided into pixels small enough to give good resolution in 2ϴ angle, but data analysis typically only seeks to reconstruct a single spectrum of diffraction peaks. While different hkl peaks in this spectrum may be analysed separately to study intergranular strains, generally no attempt is made to exploit the per-pixel variation in recorded spectra or the incoherent background. However these signals may offer routes to analysing other parameters of interest to the engineering community, such as hydrogen levels, grain size and crystal orientation relationships. In particular, a route to crystallite size analysis for larger (>10µm) grains is considered, based not on peak broadening but rather on statistical fluctuations in the number of grains aligned for diffraction in a series of different direction. While such fluctuations are normally considered to be unwanted artefacts that result from insufficient number of grains in the diffracting gauge volume, we show that the effect can be deliberately exploited to provide microstructural information. As these techniques are applicable to existing diffraction data that was originally measured for other purposes, they may be useful as the basis of future automated data mining projects at neutron or synchrotron facilities.