Open, calibrated predictions of neutron reaction cross sections across the chart of nuclides, with a public blind benchmark and a registry of predictions made before the data.
- Website: www.incognitanuclear.org. Inside a Nuclear Reaction is a teaching walkthrough of what the engine computes; Every nuclide shows the predicted curves for 6,168 nuclides beside every curated measurement; the Scoreboard compares the engine with other reaction codes, losses first.
- Scoreboard result (development comparisons against existing measurements, not a blind test): against the TALYS-2.24 program, 10 wins, 9 ties, 0 losses; against all rivals together, 47 wins, 19 ties, 0 losses in 66 decided comparisons (14 more are not applicable).
- Data package:
docs/walkthrough/data/board/holds the per-nucleus rows behind every scoreboard cell, andrecompute.pyrecomputes the verdicts from them. - Prediction registry:
predictions/2026-10-23/holds predictions registered on 2026-10-23 for measurements not yet published, with a fixed scoring rule; 16 of the targets are blind and decide the headline verdict. - Engine: release tag
engine-2026-10-22. - Library:
library/v0.2.3/is the latest version: v0.2, built with the scored engine, with its Maxwellian averages and rates in the centre-of-mass definition, the engine's own capture below 1 keV and the correct reduced mass. v0.2.3 is an errata release of v0.2.2 with the same values: exact ANCHORED factors, per-kT MACS resonance flags and fuller tier definitions (what changed:CHANGELOG.md);library/v0.2.2/,library/v0.2.1/,library/v0.2/andlibrary/v0.1/stay available unchanged. - Citing:
CITATION.cff(see Citing).
Most nuclei have never had a neutron cross section measured, yet reactors, nucleosynthesis networks, fusion shielding and isotope production all need values for them. Incognita gives each nuclide a value, an uncertainty interval whose coverage has been tested on nuclei held out of the fit, and a regime label (measured, anchored, interpolated or extrapolated). The code, the predictions, the exam they were graded on and timestamped predictions for nuclei not yet measured are all public, so every claim can be checked.
| Coverage | 6,168 nuclides (Z = 8–110), 1 keV – 20 MeV: capture, MACS, stellar rates, (n,p), (n,2n), (n,α) |
| Held-out capture | with measured D0, beats the default TALYS recipe on the sealed vault: 0.1519 vs 0.1712 dex |
| Tested intervals | 95 % interval covers 95.3 % of 674 sealed capture bins published after 2012 |
| Engine | a Python/C port of TALYS-2 physics; matches stock TALYS to four decimals on total, elastic, (n,p), (n,α) scores; 11.7x faster per target (no cache) |
Ties and losses are reported too: see the full benchmark.
Needs Linux or macOS, Python 3.12 and uv.
git clone https://github.com/seth-michael-weaver/incognita.git incognita && cd incognita
uv sync --extra dev
uv run python -m incognita.library show Au-197 # capture curve with 68 / 95 % bands, MACS at 30 keV
bash scripts/reproduce.sh # regenerate the benchmark tables and compare with the shipped onesRunning the engine itself needs the TALYS structure database: see Running the engine.
| path | content |
|---|---|
library/v0.2.3/, library/v0.2.2/, library/v0.2.1/, library/v0.2/, library/v0.1/ |
the predictions (CC-BY-4.0): v0.2.3 latest, v0.2.2, v0.2.1, v0.2 and v0.1 kept unchanged |
incognita/ |
library reader, benchmark scorer and tracks, calibration and curation tools |
physics/ |
the Hauser–Feshbach engine |
scripts/ |
reproduce.sh, scorers, engine driver, native-kernel builds |
docs/release/, docs/registry/ |
frozen exam inputs and expected tables; pre-registered predictions |
predictions/ |
dated prediction registries (blind targets, fixed scoring rule) |
emu/ |
fast emulators of the engine |
docs/walkthrough/ |
the explainer website |
The full layout is in the guide.
This is a v0.1 preview: research output, not an evaluation. Held-out tests are retrospective; the pre-registered predictions have not yet been scored against new measurements. There is no claim of better accuracy than evaluated libraries for measured nuclei; where good data exist, use the data or an evaluation. The library and its benchmark numbers come from the v0.1 engine; the scoreboard uses the current engine (22 October 2026). Details: Status and limitations.
- Using the library: format, regime tiers
- Running the engine and engine versions
- Method: physics, global rules, independence from evaluated libraries, curation
- Benchmark, performance and reproducing the numbers
- Prospective registry
- Acknowledgements
Millisecond emulators of the engine, with Jacobians and sampling: emu/README.md.
Use CITATION.cff, and also cite EXFOR (N. Otuka et al., Nucl. Data Sheets 120 (2014) 272) and
TALYS (A. Koning, S. Hilaire, S. Goriely, Eur. Phys. J. A 59 (2023) 131) when you use the engine or the EXFOR-derived
tables.
Code: Apache-2.0 (LICENSE, NOTICE); predictions and data: CC-BY-4.0
(LICENSE-DATA, including third-party terms); ported TALYS routines keep their MIT notice
(physics/hf/NOTICE-TALYS.md).
See CONTRIBUTING.md and the Code of Conduct. If a number here is wrong,
please open an issue with the measurement.