PACE - Proper Analysis of Coherent Excitations
25 Oct 2018
- Toby Perring





What is PACE?

PACE will be a software application that enables a step change in the rapidity and quality of analysis of neutron experiments on the ISIS spectrometers in the Excitations Group 

The goal is to provide an integrated visualisation, simulation and fitting environment on massively parallel and distributed computing, and which interfaces to third party modelling codes. It will:

  • Allow virtual experiments to be performed before and during the beam time to make the most effective use of neutron beam.
  • Enable quantitative analysis of the full set of data collected during the experiment, with proper account of instrument resolution.
  • Lower the barrier for users to analyse their data, so increasing the number of publications and reducing the time between experiment and publication.
The Data Analysis bottleneck

The latest spectrometers at ISIS – LET, MAPS and MERLIN – create four dimensional maps of the scattering intensity S(Q,w)  as a function of momentum, Q, and frequency, w, at the rate of 1 – 2 TB per day.

  • Most functions of Horace, the current 'gold standard' application for visualisation and analysis of such data, are not parallelised and cannot operate on the latest data volumes.
  • Computer codes that quantitatively model the data are not implemented for high performance computing (HPC), or their output is not integrated into the analysis framework.
  • Proper account of resolution – whether for powder or single crystal data – is mostly not performed, as current codes are not parallelised and require HPC to be feasible.

Goals of PACE

PACE will be a one-stop environment for visualising, analysing, and simulating or fitting to models with resolution convolution on high performance computing – 'Rietveld for Inelastic'. The project has several components:​

  • Parallelisation of the established Horace data analysis and visualisation framework for multiple core computers and distributed computing, operating on HPC services at STFC.
  • Production of a parallel version of the current Tobyfit resolution convolution application, using the framework developed above. The formalism will be extended to include a hybrid of the Tobyfit​ method and Monte Carlo instrument simulations from McStas.
  • Integration with SpinW for spin wave modelling and scattering cross-section computation.
  • Computation of scattering functions for single crystals and powders from ab initio determination of phonons using CASTEP and other codes that provide force constant matrices.
  • Development of an Application Programming Interface (API) to third party modelling to interface them to the Horace framework and the Tobyfit resolution convolution application. Integration of SpinW and CASTEP into the framework using the API.
  • Construction of GUI based 'workbenches' for managing analysis of data with refinement of parameters in resolution broadened models for scattering, that is, GUI interfaces to Tobyfit​.

To return to Excitations Software, click here.
Contact: Tabbett, Justin (STFC,RAL,ISIS)