Development Of Solid State Modulating Anode Power Supply For 1 Mw Klystron System

Bhabha Atomic Research Centre (BARC) Mumbai is developing Low Energy High Intensity Proton accelerator (LEHIPA) of energy 20 MeV, 30 mA. LEHIPA comprises of Radio Frequency Quadrupole (RFQ) accelerator (3 MeV), 10 MeV Drift Tube Linac (DTL) and 20 MeV Drift Tube Linac (DTL). As per the accelerator physics design, RFQ and DTLs require about 2.4 MW of total radio frequency (RF) power. Each accelerating cavity will be driven by a 1MW continuous wave (CW) klystron (TH2089F) amplifier at 352.21 MHz. LEHIPA will operate in both, pulsed and CW mode So, the RF system is being designed to operate in the both, CW and pulse mode. The modulating anode of the klystron will be biased with a high voltage DC supply which can operate in both CW and pulse mode. The conventional DC technologies, based on thyratrons, pulse forming networks (PFNs), tetrode etc are inherently limited in scaling to meet the new requirements like tens of micro seconds pulse width (with fast rise and fall time). The output RF power of klystron can be controlled and/or pulsed by modulating anode voltage or cathode voltage. This goal is achieved by using solid state anode power supply which has the capability of operating in both CW and pulse modes. Worldwide, this technology is rapidly becoming the most preferred alternative to conventional vacuum tube modulators, PFNs and thyratrons, The salient features of this supply are output voltage 65 kV (adjustable and floating with respect to cathode voltage, 100kV), output current 10 m Amp, adjustable pulse duration from5 mu sec to CW and (stored) energy less operation. To floating the power supply the dry type isolation transformers are used. To operate the power supply in pulse and CW mode with fast rise and fall time, solid state technology is recently best technology. The IGBT based technology has been selected since it offers very good performances in linear mode operation of the klystron output power. Details of the IGBT drivers, control electronics, IGBT protection and the isolation for the solid state modulator are also presented.This solid state high voltage power supply has been designed and developed. It has completed almost all tests on a high voltage dummy load, simulating as the klystron load. This paper describes the design aspects, test set up, and results achieved so far of this modular and energy less power supply.