Extreme hydrogen plasma fluxes at Pilot-PSI enter the ITER divertor regime

Pilot-PSI produces hydrogen plasma with a cascaded arc. It is demonstrated that the output electron density reaches 4 × 1021 m−3 by pushing the input power to 45 kW. Increasing the diameter of the discharge channel (studied from 4 to 7 mm) does not affect the plasma output but reduces the power input by up to 25%. The plasma was post-heated by feeding the plasma column with a net current. This increased the electron temperature from ∼2 to 4 eV. Calorimetric and voltage measurements on the cascade plates showed that this also influenced the discharge characteristics inside the arc.