“…But these sources have in common that they rely on plasma generation in a cylindrical discharge vessel via inductive coupling with a helical antenna (due to the large size the ITER sources is going to be equipped with 8 discharge vessels, the so-called drivers). However, in order to achieve the required H − currents very high RF powers are needed: for the ITER source a maximum RF power of up to 100 kW per driver is foreseen (operating pressure 0.3 Pa, working gas hydrogen and deuterium, RF frequency 1 MHz, driver volume ≈ 7.5 l) [1,2]; for the Linac4 source up to 100 kW are used (IS-02, operating pressure several Pa, working gas hydrogen, RF frequency 2 MHz, discharge vessel volume ≈ 0.25 l) [3]. These high RF powers pose strong demands on the RF circuit and generators which makes a reduction of the required powers very desirable.…”