Data Sources

PyEPICS processes evaluated nuclear data from the LLNL EPICS 2025 database. This page documents the authoritative sources for each data type.

ENDF Libraries

All cross-section, relaxation, and transition data are parsed from ENDF-6 format files provided by LLNL:

Library	Description	Source
EEDL	Evaluated Electron Data Library	LLNL EPICS 2025
EPDL	Evaluated Photon Data Library	LLNL EPICS 2025
EADL	Evaluated Atomic Data Library	LLNL EPICS 2025

Binding Energies

Binding energies are sourced from the EADL (Evaluated Atomic Data Library), parsed from the ENDF-6 format files. They are not sourced from the NIST X-Ray Transition Energies database.

The reference validation data in tests/fixtures/reference_binding_energies.csv contains binding energies extracted from the EEDL ENDF files themselves. These values are used for round-trip validation: the report generator compares PyEPICS-parsed values against the ENDF source values to verify parsing correctness.

The analysis covers all available subshells (K, L1, L2, L3, M1, …) for elements Z=1 through Z=100, not only the K-shell.

Physical Constants

Physical constants are sourced from NIST CODATA 2018:

Constant	Value	Source
Fine-structure constant (α)	7.2973525693 × 10⁻³	NIST CODATA 2018
Electron rest-mass energy (m_e c²)	0.51099895069 MeV	NIST CODATA 2018
Barn to cm² conversion	1 × 10⁻²⁴	Definition
Planck constant (h)	6.62607015 × 10⁻³⁴ J·s	SI definition (exact)
Speed of light (c)	299 792 458 m/s	SI definition (exact)
Elementary charge (e)	1.602176634 × 10⁻¹⁹ C	SI definition (exact)

MF/MT Mapping Tables

Every section in an ENDF file is identified by a pair of integers (MF, MT) — MF selects the data type (cross sections, distributions, form factors, …) and MT selects the reaction or subshell. PyEPICS keeps three mapping dictionaries in pyepics/utils/constants.py:

Dictionary	Library	Purpose
ELECTRON_MF_MT / ELECTRON_SECTIONS_ABBREVS	EEDL	Electron cross-section & distribution sections
PHOTON_MF_MT / PHOTON_SECTIONS_ABBREVS	EPDL	Photon cross-section & form-factor sections
ATOMIC_MF_MT / ATOMIC_SECTIONS_ABBREVS	EADL	Atomic relaxation sections

Each *_MF_MT dict maps (MF, MT) → human-readable description; each *_SECTIONS_ABBREVS dict maps the same keys → short mnemonic used as HDF5 group names.

Adding a new (MF, MT) pair — If a new evaluation introduces a previously unseen section:

1. Add the (MF, MT) key and its description to the appropriate *_MF_MT dictionary, following the ENDF-6 Formats Manual [1] for the correct meaning.

2. Add the same key with a short mnemonic to the matching *_SECTIONS_ABBREVS dictionary.

3. Run pytest tests/test_mapping_completeness.py — it will flag any ENDF (MF, MT) pair that lacks a mapping.

[1]

A. Trkov et al., “ENDF-6 Formats Manual”, BNL-90365-2009 Rev. 2, https://www.nndc.bnl.gov/endfdocs/ENDF-102-2023.pdf

Reference

NIST CODATA 2018 — Wallet Card (PDF)