pub fn ic_cdf(alpha: f64, beta: f64, r: f64, tau: f64) -> f64Expand description
Cumulative probability of the Ikeda–Carpenter moderator pulse.
Returns P(U <= tau) for moderator delay U. tau is in µs and rates
are in 1/µs. The prompt term is the Gamma(3, α) cumulative distribution;
the storage term is the cumulative distribution of Gamma(3, α) plus an
independent exponential delay with rate β.
The expression is evaluated without subtracting nearly equal exponentials
when α ≈ β. This is the bin-integral companion to ic_pulse.
Domain contract: non-finite alpha, beta, or r returns NaN so garbage
in stays visible; finite non-positive rates are floored to MIN_RATE
(1e-9 µs⁻¹) and r <= 0 disables the storage term, matching
ic_pulse. A NaN tau
returns 0 — tau is the integration coordinate, not a parameter, and a
non-arriving coordinate contributes no mass.