A 45-GHz/20-kW Gyrotron-Based Microwave Setup for the Fourth-Generation ECR Ion Sources

A 45-GHz gyrotron-based microwave oscillator setup has been purposefully developed for powering of a superconducting electron cyclotron resonance (ECR) ion source. The setup provides a smoothly regulated output power in the 0.1-20-kW range (up to 26 kW in manual mode) with an efficiency of up to 50% and collector depression in both continuous wave (CW) and pulse modes. Pulse mode specifications: duration 5-200 ms, leading edge less than {2}~\mu \text{s} , trailing edge less than {1}~\mu \text{s} , repetition rate 1-10 Hz, and triggered operation using an external reference oscillator. The set of high-voltage power supplies (HVPSs) is equipped with a fast electronic protective system to ensure trouble-free operation of the gyrotron. The functional structure of the setup corresponds to the general design method for feedback-controlled microwave sources. The feedback loop consists of a power meter (or a detector unit, to the user's choice), a control system, and an anode HVPS, the regulated voltage of which controls the output power of the gyrotron. The feedback characteristic time is less than 1 s. Feedback control is provided for both CW and pulse modes. The setup includes a unique quasi-optical line that transmits the microwave beam through a 2-m air gap, as well as a synthesized mode converter from the Gaussian beam to the TE 01 or TE 11 mode (to the user's choice) installed on a 300-kV platform. During the tests, the developed setup proved to be a reliable and user-friendly tool applicable for long-term powering of the fourth-generation ECR ion sources.