Simulation and experimental studies of a 2.45GHz magnetron source for an SRF cavity with field amplitude and phase controls

Abstract

As a drop-in replacement for the CEBAF 8kW CW klystron system, A 1497 MHz, CW type high- efficiency magnetron using injection phase lock with amplitude variation is attractive. Amplitude control using magnetic field trimming and anode voltage modulation has been studied using MatLab/Simulink simulations [1]. Along with a magnetron we are planning to use an FPGA based digital LLRF system, which allows to apply various types of control algorithms in order to achieve the required accelerating field stability. Since the 1497 MHz magnetron has not yet been built, the proof of principle measurements of a typical 2450MHz commercial magnetron are made to characterize the anode I-V curve, output power (the tube electronic efficiency), frequency dependence on the anode current (frequency pushing) and the Rieke diagram (frequency pulling by the reactive load). In the Simulink simulation, extension of the Adler equation governing injection phase stability by Chen's model is included. The results of the linear response to the amplitude and phase control of an SRF cavity, and the specification of the new LLRF control chassis for both 2450 and 1497MHz systems will be presented in this paper.