Constant DIVERGENCE_STREAM_WORD 

pub const DIVERGENCE_STREAM_WORD: u128 = _; // 36_893_488_147_419_103_232u128

Word position (in the 32-bit words of the ChaCha stream) of the segment of a history’s random stream that beam-divergence draws come from: 2^65. The transport draws start at word 0 and never reach it, and it is disjoint from the thermal-displacement segment (2^66) and the crystal-shift segment (2^67) (each is far shorter than the gap to the next), so enabling divergence leaves every other draw of the history unchanged.