29th Symposium on Fusion Technology (SOFT 2016)

O2C.3 Development of a high power helicon system for DIII-D

6 Sep 2016, 11:40

20m

Meeting Hall V 2nd floor (Prague Congress Centre)

Board: 3

Oral B. Plasma Heating and Current Drive O2C

Speaker

Joseph Tooker (General Atomics)

Description

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]. A low power (100 W) 476 MHz “combline” antenna, consisting of 12 inductively coupled, electrostatically shielded, modular resonators [2], was recently installed in DIII-D. Initial operation showed that the plasma operating conditions were achieved under which helicon waves can be launched. Plasma operations also showed that the location of the antenna has not reduced the performance of, or introduce excessive impurities into, the discharges produced in DIII-D. The development of a high power (1 MW) Helicon system is underway. This antenna consists of 35 modules mounted on the inside of the outer wall of the vacuum vessel slightly above the midplane. Carbon tiles around the antenna protect the antenna from thermal plasma streaming along field lines. A 1.2 MW, 476 MHz klystron system will be transferred from the Stanford Linear Accelerator to DIII-D to provide the RF input power to the antenna. A description of the design and fabrication of high power antenna and the RF feeds, the klystron and RF distribution systems, and their installation will be presented. This work is supported by the US DOE under DE-FC02-04ER54698¹1 and DE-AC02-0H11466²2. [1]  J. Tooker, P. Huynh., J. Fusion Eng. Des., 88 (2013), 521 [2]  J. Tooker, et al., Proceedings of the 26th IEEE Symposium on Fusion Engineering (SOFE), May 31 – June 4, 2015, Austin, TX