A new diagnostic method to measure transport properties of negative Hydrogen ions has been devised. It uses multi‐point, multi‐time laser pulse photodetachment of H−, inducing changes in the electron and ion densities, whose space and time evolution are traced in detail by laser pulses and probes. A kinetic analysis of plasma an self‐consistent field evolution in space‐time, following localized photodetachment of H−, is presented. The fit of measurements to analysis is used to infer H−temperatures.