Current drive analysis and system design for the ARIES-I tokamak reactor

Fast-wave current drive is selected as the primary scenario for steady-state operation of the Advanced Reactor Innovation and Evaluation Study-I (ARIES-I) tokamak reactor. With a projected efficiency of ≈0.3-0.4, the current drive method uses low-cost, off-the-shelf technology, making it attractive compared to neutral beam current drive. At a frequency of 158 MHz and a wave spectrum centered at 1.6, it is found that as much as 160 MW of power may be required to drive the 4.7-MA seed current on the ARIES-I. To generate the desired current profile, the wave power is launched from above the equatorial plane on the outboard edge of the plasma. A toroidal array of 12 folded waveguides forms the basic launcher module which transmits the desired spectrum with a 95% directivity. Efficiency of coupling to the high-density scrape-off layer is expected to be high (>90%). The overall launcher system consists of four modules delivering 192 MW through 1.6% of the first-wall area. Each waveguide is envisaged to be a closed rectangular box made of SiC/SiC fiber composites, with the conducting surfaces formed by a copper coating on the inside of the structure. With the klystrode as the transmitter, the overall RF system efficiency can be as high as 72%. A viable alternative system based on neutral beam current drive and RFQ (radio frequency quadrupole technology has also been designed