Abstract: A modulator for regulating high voltage pulsed plasma-immersion ion implantation (PIII) acting as a substantial component in a PIII installation is provided. The modulator enables low-cost, easy connection and disconnection of a flow of large high voltage pulsed currents during PIII. In the modulator, pulse regulation occurs by means of an additional electrode which is controlled by a shielding grid as opposed to a high voltage switch mounted as a technically autonomous unit. The electrode and shielding grid are integrated into the implantation chamber and connected to a capacitor to provide high voltage. The shielding grid is triggered by a pulse generator with voltage pulses of 1-2000 V. The shielding grid surrounding the electrode is immersed in plasma and ensures that the additional electrode is either insulated from the plasma or in electric contact therewith by applying controllable grid voltages.