THC accessible diffraction angles¶

For a given reflection's required detector angles (gamma, delta) (see the diffraction reflections app), this checks whether Bernina's optional THC sample-chamber hardware can actually reach them. Each of the three detector-arm options physically limits the accessible (gamma, delta) range:

• In-vacuum detector — a rectangular in-vacuum detector on a manually rotated flange.
• Be window — scattering out through a circular beryllium window on the rotatable top flange (dashed grey = the CF250 flange opening itself, the hard outer limit).
• Otti — the motorized in-vacuum arm with a JUNGFRAU module. Its envelope (orange) comes from the original tool (data/otti.npy); the panel below computes where the module actually looks for given arm rotations otti_nu and otti_del (eco's calc_otti geometry): a sky map coloured by 2θ, a top view and the footprint in the grid above, with the detector's turn about its normal either twist-free (eco's "auto"), from a cardan mount, or as read from the encoder.

Move a rotation slider to see the corresponding aperture position (top row) and how the accessible angle envelope (bottom row, solid curve) sits within the widest envelope reachable over all rotations (dashed curve).

Ported from the original thc_angles Binder app (thc_angles_2.ipynb). The annotated hardware photos from that version are not reproduced here — they hot-link an external, personally hosted image store, which doesn't fit a fast, offline-friendly Binder build — but the geometry math and interactive sliders are otherwise unchanged.