[ESSSPECTROSCOPY] Drop the position offsets from the BIFROST providers - #703
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[ESSSPECTROSCOPY] Drop the position offsets from the BIFROST providers#703SimonHeybrock wants to merge 1 commit into
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DetectorPositionOffset and MonitorPositionOffset are dead knobs here: they default to a zero vector and nothing in essspectroscopy or esslivedata ever sets one. They are also the wrong shape for BIFROST. Both are added after the transform, so they are lab-frame constants, while every component they apply to rides the rotating detector tank. A correction one would actually want -- "this sits a few mm off along its own axis" -- is local-frame and belongs in the transformation chain, which is already the handle used for the tank angle. A fixed lab vector instead translates the whole swept arc rigidly. essreduce says as much at the definition of compute_detector_position: the offset is "mainly used for handling files from other facilities and it is not clear if it is needed for ESS data and should be kept at all". compute_detector_position still requires the argument, so it is pinned to no_offset at that one call. The monitor provider drops the term outright. Positions are unchanged. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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DetectorPositionOffsetandMonitorPositionOffsetare dead knobs in the BIFROST providers: both default to a zero vector, and nothing in essspectroscopy or esslivedata ever sets one.They are also the wrong shape for this instrument. Both are added after the transform, so they are lab-frame constants, while every component they apply to rides the rotating detector tank. The correction one would actually want — "this sits a few mm off along its own axis" — is local-frame and belongs in the transformation chain, which is already the handle used for the tank angle. A fixed lab vector instead translates the whole swept arc rigidly.
essreduce says much the same where
compute_detector_positionis defined: the offset is "mainly used for handling files from other facilities and it is not clear if it is needed for ESS data and should be kept at all".compute_detector_positionstill requires the argument, so it is pinned tono_offsetat that one call rather than threaded through four signatures. The monitor provider drops the term outright.Stacked on #698.
Testing
Positions are unchanged: the BIFROST Bragg peak Q-map in scipp/esslivedata#1236 produces a bit-identical map over a multi-angle rotation scan.