Voltage Droop Compensation for High Power Marx Modulators

The International Linear Collider (ILC) will need more than five hundred modulators to provide pulsed power to 10-MW long-pulse (1.4 ms) klystrons. A Marx modulator controlled by solid state switches promises higher efficiency, longer lifetime, and reduced cost compared with existing hard tube modulator options. However, voltage droop is one of the critical problems that limit the application of Marx modulators. The current solution, which uses vernier cells, is unable to smooth the flat top of the voltage pulse output of the Marx modulator, requiring an additional high voltage charging source and a large number of cells. This project will develop a new compensation scheme that exploits the high speed of the solid-state switches in a modified compensation circuit. Feed-forward control will be used for the timing of the compensation energy release to correct the voltage droop. Simple compensation circuitry based on this scheme can be implemented on the existing Marx main cell structure. Phase I will design the compensation circuit, using circuit simulation codes, and optimize circuit components. The compensation circuitry and the low voltage control circuit will be built in Phase II. Commercial Applications and other Benefits as described by the awardee: Successful demonstration of the compensation circuit would benefit the ILC project directly by meeting its stringent requirement on the pulsed voltage flatness for hundreds of modulators. This method also would complement SLAC¿s program to develop a high-power Marx modulator as an alternative to the ILC baseline klystron modulator. Lastly, the technology should impact other accelerator facilities that require long pulse modulators.