Development of a helicon current drive system for installation in the DIII-D tokamak

Abstract

A new mechanism for driving current off-axis in high beta tokamaks using fast electromagnetic waves, called Helicons, will be experimentally tested for the first time in the DIII-D tokamak. This method is calculated to be more efficient than current drive using electron cyclotron waves or neutral beam injection, and it may be well suited to reactor-like configurations [1]. DIII-D can provide the conditions and measurement capabilities for a quantitative evaluation. At around 500 MHz, the optimum for DIII-D, an injected power of 1 MW would be adequate for these measurements and provide the equivalent current drive of a 2.5 MW neutral beam source. A “combline” antenna, which consists of many inductively coupled, electrostatically shielded, modular resonators, will be used to couple to the fast wave.