Fusion neutron sources

Sample a tokamak ring fusion-neutron source, histogram its birth energies, and emit MCNP SDEF and Serpent source cards.

A burning deuterium–tritium (or deuterium–deuterium) plasma is a neutron source with a thermal spectrum: the birth energy of each neutron follows a Gaussian whose width grows with the square root of the ion temperature — the Brysk scaling, refined by the closed-form fits of Ballabio et al., Nucl. Fusion 38 (1998) 1723. At the 14.1 MeV D-T line the broadening is small at reactor temperatures but never exactly zero.

The demo below samples a tokamak midplane ring source (fixed major radius and height, uniform azimuth, isotropic directions) with a seeded generator, histograms the sampled birth energies, and renders the same configuration as MCNP SDEF and Serpent src cards that transport codes can read directly. Identical inputs always reproduce the identical particle stream. The 3D lattice tab samples a five-node base-sector cloud replicated by field-period symmetry instead — the stellarator-style spelling with the same spectrum. The parametric tab samples a synthetic H-mode plasma volume with an editable D/T fuel mixture and an optional deuterium hot-tail fraction. Blank both mixture fractions for the single-fuel kernel at the selected reaction, with an optional per-species temperature pair: single-fuel D-T then reacts at the mass-weighted pair temperature while single-fuel D-D reacts at the deuterium temperature, and an equal pair reproduces the shared-temperature kernel exactly.

ECRH accessibility

Electron-cyclotron heating reaches the plasma only where the wave meets its resonance before a cut-off stops it. The demo below evaluates the closed-form accessibility scalars — cold resonance, relativistic shift, and O1/X1 cut-off densities — for an editable wave and plasma point.

Further reading

• Theory: Fusion neutron sources
• Tutorial: Fusion sources with Python
• Crate docs: crates/plasma-source/src/lib.rs