Skip to main content

urr_cross_sections

nereids_physics::urr

Function urr_cross_sections 

Source 
pub fn urr_cross_sections(
    urr: &UrrData,
    e_ev: f64,
    ap_fm: f64,
) -> (f64, f64, f64, f64)
Expand description

Compute energy-averaged Hauser-Feshbach cross-sections in the Unresolved Resonance Region (width-fluctuation correction not yet applied; see the module docs).

Returns (total, elastic, capture, fission) in barns. All four are zero when e_ev falls outside the URR energy band [urr.e_low, urr.e_high].

elastic = compound-nuclear elastic + smooth potential scattering. total = elastic + capture + fission + competitive (GX). Potential scattering σ_pot = 4π·AP²/100 (AP in fm, result in barns) is folded in here rather than at the call site, so the URR band yields a physically complete elastic cross-section.

§SAMMY Reference

SAMMY manual Section VIII.A — energy-averaged cross-section equations.

§Arguments

  • urr — Parsed URR parameters (LRF=1 or LRF=2).
  • e_ev — Neutron lab-frame energy in eV.
  • ap_fm — Scattering radius in fm at this energy. The caller is responsible for evaluating any AP(E) table (NRO≠0) or falling back to the constant urr.ap.

§Panics

Panics if e_ev is not finite or is non-positive. This is a defensive guard at the public boundary; the Python wrapper and the SAMMY-style dispatcher already validate the energy grid via validate_energy_grid, so this assertion only fires for direct callers (other Rust crates, tests) that bypass the grid check.