Plasma Diagnostics Overview

You cannot put a thermometer in a 100-million-degree plasma; you measure it with light, waves and particles instead.

A fusion plasma is far too hot for any probe to touch, so its temperature, density, current and impurity content are inferred remotely — from the light it emits, the way it bends waves passed through it, and the particles and neutrons that escape. A modern machine carries dozens of such diagnostics, and Kronos's control and validation both lean on them.