The pre-scan's plane test read per-pixel sector medians of the mean projection. On a large
photon-counting detector with a background of a fraction of a count per pixel over the 60
frames read, those medians were zero and the test returned no harmonic at all: on 21 of 255
battery sweeps (EIGER2 16M and JUNGFRAU 4M sweeps, the laboratory EIGER sweeps, the
small-molecule sweeps at 20-25 keV) the correlation was NaN or within 0.01 of zero, so the
plane could not be decided there. The background is now pooled over 9 x 9 pixels first, as the
mask itself already is; 216 of 244 synchrotron sweeps then show their (horizontal) plane past
both gates, against 159 of 229 before.
Pooling also lifted one long-distance sweep (500 mm, 2theta under 21 deg, polarization can
move its background by at most 4 %) over the correlation gate: its background carries a 10 %
cos 2phi harmonic along image y, 2.9 times what a fully polarized source would give, on a
horizontally polarized beamline. No polarized source exceeds a scale of 1, so a harmonic of
twice that or more now decides nothing (PLANE_MODULATION_MAX).
The pre-scan logs the correlation and the scale on every run that detects the beam stop
(GetPlaneEvidence). A turned plane is kept on the run and re-applied where a pass starts again
from an experiment taken before the decision while the shadow is already in the mask (the
rotation measured-centre arm, the no-lattice pass), which previously went on with the stated
plane.
No battery sweep turns; where the plane is not turned the applied coefficient is unchanged.
The degree is still never fitted.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015CeEGgpKdfkCTJb3YNMJcu
(cherry picked from commit 50a145a4f1ddf6d58332a8ab745627dc36a2dc3d)
leonarski_f
c62a67975e