`filewriter`: Neutron histogram data (`raw_data_1/detector_1`)

[Tom-Willemsen]

The file-writing infrastructure must be able to write out histogram-mode data (.nxs files without an NXevent_data group).

This refers to the NeXuS groups under raw_data_1/detector_1.

The issue is intentionally phrased as

file-writing infrastructure

because this does not necessarily have to be done in the same process as the event-mode filewriter.

Questions

• Support streamed histograms (hs00) at some point in future? i.e. a scheme where a monitor emits a histogram every N frames, where N could be 1 in the extreme case. This then lets a run be sliced a bit like event mode, but only on N-frame boundaries.
  • This might be needed for SANDALS2 if monitor event-rates are too high for pure-event mode.
  • Need to define how we would write this kind of data to .nxs.

Approaches

• This could be an option in the filewriter process itself. It would then need various options to cope with:
  • event files only
  • combined histogram+event files
  • separate histogram and event files
• This could be implemented as a separate process which reads in an event-mode .nxs file and outputs a histogram-mode .nxs file

Potential differences from existing files

None known at this time.

[Tom-Willemsen]

If we want to do this as a separate process, the following may be relevant:

• https://github.com/ISISMuon/MNeuEventLib (being implemented for SuperMusr, but "should work for neutrons")
• https://github.com/disorderedmaterials/np (used by disordered materials to pre-process event mode files, then produces histograms for GudRun)