Large probes in Tokamak scrape-off plasmas. The collisionless scrape-off layer: operation in the shadow of limiters or divertor plates

With the exception of simple Langmuir probes, all other probes used to diagnose the scrape-off plasma behind the limiter radius of separatrix in Tokamaks are usually sufficiently large that they disturb the plasma they are measuring. An analysis procedure is outlined for recovering the undisturbed plasma parameters from those measured by a large probe in a collisionless scrape-off layer. The analysis is applied to experimental data recorded by large probes inserted into the scrape-off layer of the DITE Tokamak.