First validation experiments of the prototype solid state RF system for IFMIF-DONES

Abstract

Following the current tendency towards solid-state (SS) amplification technology, the IFMIF-DONES (International Fusion Materials Irradiation Facility - DEMO-oriented Neutron Source) Radiofrequency (RF) Power System will be fully based on SS technology. A challenging issue in high power SS amplifiers is focused on the search of an efficient combination technique for a very large number of power signals. A promising RF power combination technique has been proposed for IFMIF-DONES: a resonant cavity combiner. The crucial characteristic of this combining technology is that the high power combination is achieved in just one step, by means of coupling the outputs of a large number of active devices into a resonant circuit. This improves the efficiency compared with traditional corporate topologies, which is a key aspect for SS amplifiers. In addition, it results in a very compact design, although its circular shape may complicate the design of other SSPA components, which are more standardized for rectangular cubicles or rack solutions. In order to demonstrate the feasibility of this combination technology for the IFMIF-DONES RF Power System, a prototype cavity combiner has been designed and fabricated. It has been validated at small-signal and at medium-high power levels: up to 24 kW in continuous wave (CW) and 100 kW in pulsed mode (duty cycle DC = 4%). The design of this prototype combiner and the results of the first validation experiments are presented in this paper.