Compact Efficient and Frequency Tunable Relativistic Magnetron With Reducing Coaxial Section and Tilted Tuners

Abstract

In this article, we present a compact efficient and frequency tunable relativistic magnetron (RM) with what we have named a reducing coaxial section (RCS) and with tilted tuners. The RCS is a conical-shaped part inserted in front of the output window. The design is adapted to the compact Marx generator of the Concept Léger Aéroporté d'Illuminateur RadioElectrique (CEA)-Gramat demonstrator-Commissariat à l'Energie Atomique et aux Energies Alternatives (CLAIRE)-and meets technical requirements such as input impedance (specifically during frequency shifting), mechanical dimensions, power handling capacity, and electromagnetic (EM) mode. Special care has been taken to lower the EM mode competition, which occurs with specific geometry, extraction waveguide with high dimensions, and/or frequency shifting. To mitigate this effect, the output waveguide diameter was decreased by means of the RCS design. Another challenge was to operate frequency shifting by adding tuners while maintaining high power handling. The premise is that cathode endcap spheres and tilted tuners theoretically reduce the electric field strength from 600 to 280 kV/cm. Particle-in-cell (PIC) simulation exhibits an output power (averaged over the pulse duration) that reaches 680 MW at 1.85 GHz. The corresponding maximum power efficiency is about 50% when the applied voltage is 380 kV, and the current intensity is about 3.8 kA. The frequency operating range is above 19% from 1.85 to 2.25 GHz.