Electron cyclotron heating power supplies on DIII-D

Abstract

The electron cyclotron heating system on DIII-D has been supporting experiments with six gyrotrons. The gyrotrons are connected to three power supplies: two have single modulators, each energizing two gyrotrons, while the third has three modulators that can energize three gyrotrons asynchronously. However, only two gyrotrons can be run synchronously due to the limitation of the high voltage dc power supply providing the input voltage to the modulators. These two configurations mimic proposed architectures of power systems for multiple gyrotron systems and demonstrate their advantages or disadvantages, which will be discussed in more detail. A fourth power system is being built as part of an upgrade to eight gyrotrons. The two future gyrotrons will have depressed collectors. A 1.2 MW gyrotron will be delivered in mid-2011 and the design of a 1.5 MW gyrotron has been initiated. This fourth power supply will have two modulators to independently energize the cathode of each gyrotron. Commercially available high voltage amplifiers will provide the body voltage. It will also have a solid-state crowbar instead of an ignitron crowbar. This power supply is described in more detail, as well as the testing performed on the solid-state crowbar to prove its performance.