29th Symposium on Fusion Technology (SOFT 2016)

P4.034 Design of high power RF amplifier for 3 MW/CW transmission line test rig

8 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 34

Poster B. Plasma Heating and Current Drive P4 Poster session

Speaker

Raghuraj Singh (IC H&CD)

Description

India is developing 2.5 MW RF source at VSWR 2:1 in the frequency range 35-65 MHz for ITER project. Eight such RF sources will generate total 20MW of RF power for plasma heating and current drive. A large number of high power transmission line components are required for connecting various stages of RF source. To test these passive transmission line components at high power, a 3MW test facility based on the concept of Traveling Wave Resonator (TWR) is underway. For feeding power to the TWR using 10dB coupler, a high power (around 150 kW) CW RF amplifier is required.   A tetrode based amplifier is designed to operate in class B operation, considering the optimized efficiency, gain and harmonics level. Grounded grid configuration is chosen for the stable operation and simplicity in mechanical assembly. The expected gain is around 14-15dB, therefore, 10kW Solid State Power Amplifier (SSPA) is chosen to drive this amplifier. The amplifier consists of input and output tunable coaxial cavities to cover the required frequency range along with support structure, tuning mechanism, transmission lines, high voltage and auxiliary power supplies and active cooling arrangements. High frequency electromagnetic simulation software Microwave Studio (MWS) is used for simulation and analysis of coaxial input and output cavities. Thermal analysis is conducted to check the adequacy of the amplifier design for continuous mode operation. The paper describes the detail design aspects, operational parameters derived from the data sheet of selected tetrode, simulation results, power supply requirements and thermal management for CW operation.