Direct Inelastic Changes¶

Algorithms¶

Re#13566 New GetAllEi algorithm analyses chopper logs and signals on monitors to identify all possible incident energies used in Direct inelastic experiments in single or multi-rep mode. Internally the algorithm incorporates four sub-algorithms used by instrument scientists on instruments with different background, chopper system and signal quality so it can reliably run on all these instruments. The algorithm is the basis of changes to autoreduction, which allow instrument scientists and users to reduce (convert to SPE) results of an inelastic experiment without any user intervention.

ISIS inelastic instruments descriptions have been modified to contain chopper location and other additional information necessary to calculate time, when chopper lets neutrons trough from appropriate chopper logs.

Re#14071 RenameWorkspace algorithm renames separate monitor workspace, if a monitor workspace is attached to the current workspace. This allows substantial simplification of the Direct Reduction workflow, where the number of operations are performed on a workspace itself and the monitor workspace, which is associated with the main workspace.

Re#13980 On the basis of changes outlined in Re#13566 and Re#14071, ISIS reduction now has the capability to identify incident energies used in direct inelastic experiments and reduce data according to these energies. AUTO key-word allow data reduction without providing a guess for the incident energy. Reduction finishes as normal if no energies were identified, returning the message stating the run is not probably intended for reduction. This feature allows convenient use of the ISIS autoreduction service to process data from direct inelastic experiment without user or instrument scientist intervention.

ISIS Fixes¶

Re#14456. A number of bug-fixes and small modifications were performed in order to enable correct background removal for direct inelastic reduction.

• The CalculateFlatBackground algorithm has a new property NullifyNegativeValues which toggles nullification of negative signals after background subtraction.
• The error calculation procedure used by the RemoveBackground algorithm has been replaced by the procedure used in CalculateFlatBackground algorithm. The previous procedure received many complaints and was therefore deemed to be incorrect.
• RemoveBackground has been modified to allow instrument scientists to nullify negative signals on request.
• New property nullify_negative_signal has been added to ISIS reduction to toggle removal of negative signal according to particular requests. The default behaviour for nullifying negative signals has been defined in instrument definition files according to user preference.
• The negative signal removal, if requested, now occurs after the spectra have been grouped according to the particular maps, which substantially improves statistics and final background in the case when negative signals are nullified.
• Fixed bug causing reduction to fail if monitors are summed and monitor-1 normalisation is requested.

Re#12403 LET IDF has been modified using an embedded IDF correction mechanism which was introduced in Mantid release 3.4. This mechanism allows users to update the Instrument Definition (Files) (IDF) stored within nexus data files. The exclusions based on run numbers, which had to be introduced into ISIS direct inelastic reduction program were removed and this new feature allows Instrument Definition information to be safely embedded into the nexus files (or modified at a later stage).

Other fixes¶

• Fixed problems with the direct geometry planning tool. Re#15182

Full list of changes on github