A travelling acoustic wave enters a perfect crystal. Its steady-state X-ray satellites are textbook material. This repository resolves how the satellites form while the wavefront crosses the crystal, using two-beam Takagi–Taupin theory, and records every step in a lab notebook.
KPS 2026 Fall Meeting, poster P2.17 (Jeju, 22 October 2026). Isaac Yong, Ouyoung Kwon, Hyunjung Kim — Center for Ultrafast Phase Transformation, Sogang University.
| result | notebook | |
|---|---|---|
| Clock | Satellite n diffracts from the filled depth vst with coupling α|Jn(S)|. Laue reads sin²(παnt̃) and Bragg reads tanh²(παnt̃), with no fit parameter. Each order has its own clock, τn = ΛP/(vs|Jn(S)|). | Entries 1, 9, 24 |
| Memory | A satellite reads the last transit time of the drive, Θn = ∫Jn(S A(t−ζ)) dζ. An order that is forbidden at the final amplitude can be the brightest line during formation. | Entries 28, 30 |
| Validity | The independent-satellite picture is accurate to 5 % for R = Λac/ΛP ≲ 0.3. Past that, the channels couple through sidebands of the forward beam. | Entries 52–54 |
| Outlook | The Fourier weight of R(t) is the strain spectrum times a crystal transfer function H(ω), in closed form at first order. It holds inside the Darwin width, where the plane-wave perturbation of Sondhauss & Wark (2003) is off by ×3–8. | Entries 59, 64 |
pip install tratt
Requires Python 3.12+; the package is the solver (src/tratt, numpy and scipy only). Notebooks, figure scripts and the poster build need a
clone of this repository.
uv sync --extra dev
uv run pytest -q # 54 tests: analytic limits, Floquet cross-check, formation law
uv run python explore/make_poster_figs.py # poster figures -> figures/poster/
uv run python poster/build.py # poster/poster.md -> poster/out/poster.pdf
src/tratt/ solver package
core.py Laue IVP and Bragg Riccati (RK4, vectorised over eta and time; Bragg absorption kappa)
drive.py travelling acoustic drive phi(zeta; t): front, rise, amplitude profile
floquet.py exact Floquet solver for a uniformly filled crystal (independent cross-check)
observe.py channel windows, formation time, peak width
cube.py rocking curve over time (I(eta, t) cubes)
sweep.py parameter grids
tests/ analytic ground truth as asserts
notes/ lab_notebook.md: every result, with its script and its caveats (numbered entries)
explore/nb/ one script per notebook entry (eNN_*.py), with small cached results
explore/ figure scripts; make_poster_figs.py draws the poster figures
poster/ poster.md (the only source of poster text), build.py (layout + checks), fonts
figures/ figures referenced by the notebook and the poster
DESIGN.md physics conventions, analytic limits, assumptions
Every item on the poster carries a tag pointing to a notebook entry. poster/build.py refuses to
pass if a tag points to an entry that does not exist.
explore/*.ipynb are tracked with nbstripout as a git filter (.gitattributes). Outputs are
removed at commit time and stay in your working copy. If you move the repository or rebuild the
venv, re-register the filter:
uv run nbstripout --install --attributes .gitattributes
This work was supported by the National Research Foundation of Korea, grant RS-2021-NR059920.
See CITATION.cff.
MIT, see LICENSE.