Hybrid Modulator Upgrade

72073-The Next Generation Linear Collider (NLC) will require approximately 2200 high voltage pulse modulators to drive 4400 NLC klystrons at 500 kV, 265 A each. The cost and efficiency of these modulators represents a substantial portion of the cost of building and operating the NLC. As part of the ongoing effort to reduce these costs, a prototype Hybrid Modulator was developed and delivered, which is currently operating at the Stanford Linear Accelerator Center (SLAC). However, its performance is less than expected, due to impedance added to the system to handle arc faults in the klystron without damaging the modulator itself. This project will develop methods to simultaneously improve the modulator performance and reliably handle klystron fault currents. In particular, very fast and efficient pulse waveforms will be provided, while safely and reliably handling klystron fault (arc) currents. Phase I investigated two different approaches to removing the inserted impedance in the Hybrid Modulator. In the first, improved gate drivers were designed and tested to speed the response of the modulator to klystron faults, reducing the peak currents seen within the modulator and allowing much faster pulse risetimes (and efficiency) during normal operation. In the second, intrinsic current-limiting techniques were designed and demonstrated within the solid state switch of the modulator itself, to prevent fault currents from reaching levels that could damage the modulator or klystron. Phase II will build, test, and install these upgraded gate drives within the Hybrid Modulator, and assess the performance improvement of the Hybrid Modulator itself. Commercial Applications and Other Benefits as described by awardee: In addition to the NLC application, the development of active current-limiting technology should have commercial benefits by reducing the overal number (and cost) of the switches required in a solid state modulator. This cost reduction should significantly speed the adoption of solid state modulators in a variety of applications, including cancer treatment, container inspection, and semiconductor manufacturing.