[Requirement] BEER: loader to support 3D detector geometry

[celinedurniak]

Executive summary

Add support for 3D detector geometry in BEER loader

Context and background knowledge

The latest version of the McStas model for BEER simulates 2 detector banks at +/- 90 degrees. Each of these banks contains 12 panels in depth. Each panel is a 2D square of 1 m$^2$.
There is also an added event monitor (same technology of the detector panel)
This requirement is to support this new layout

Inputs

NeXus files from McStas

Methodology

Load NeXus files and storage data from detectors and event monitor in a DataGroup

Outputs

Datagroup split into data arrays; one data array per detector bank and 1 data array for the event monitor

• Add 2 theta coordinates
• Keep positions of pixels

Example of datagroup and dataarray associated to one of the banks

Which interfaces are required?

Integrated into reduction workflow, Python module / function

Test cases

2 NeXus files with Si powder sample for 2d and 3d detector geometries.
Note that the simulations were run with a small count

TestDataBEERLoader.zip

Existing implementations

There is a loader for BEER (supporting the 2D geometry only and with no support for the event monitor)

See https://github.com/scipp/essdiffraction/blob/main/src/ess/beer/io.py

Comments

• The resolutions of the detectors and monitor are not set.
• Banks are names South2 or S2 (x>0) and North2 or N2 (x<0)

[jokasimr]

Should we continue to support McStas files with the old structure (single panel per bank) as well as McStas files with the new structure (multiple panels per bank), or is it okay if future versions of ESSdiffraction only support the new structure?

[jokasimr]

To make sure that this is working properly it would be good to have files with more events, so that the full reduction workflow can be applied to the 3D detector data.

[celinedurniak]

@jokasimr I shared a link to NextCloud on Slack

[jokasimr]

Only for the 3D layout. For the 2D we already have files with enough events.

[celinedurniak]

Yes we have older 2D examples but without the monitor.