Stephen J. Wukitch

Principal Scientist

617-253-8138

NW21-103

Biography

Education

PhD, Engineering and Engineering Physics, University of Wisconsin (1995)
MS, Engineering and Engineering Physics, University of Wisconsin (1993)
BS, Nuclear Engineering, The Pennsylvania State University (1991)

Expertise

RF  physics (wave propagation, absorption, and coupling); RF-plasma edge interactions, and antenna, transmission; source technology.

Research

Dr. Wukitch research interests include ICRF wave physics (wave propagation, absorption, and coupling), RF-plasma edge interactions, and antenna, transmission, and source technological challenges.

At C-Mod, we have developed a field aligned ICRF antenna that demonstrated, for the first time, an ICRF antenna can be made with reactor relevant materials and be compatible with reactor grade plasmas. This antenna is load tolerant and eliminates RF enhanced heat flux. The emerging physics understanding is that load tolerance derives from elimination of the slow wave coupling between antenna straps and reduction in heat flux and antenna impurity source results from alignment to local convective cells.

An emerging physics area is ICRF antenna and wave penetration/absorption from the high field side of the tokamak. The placement of ICRF antenna on the high field side moves the antenna away from the high heat flux region, reduces the convective cell strength, improves impurity shielding, and improves core wave absorption allowing for possible flow drive.

To improve antenna electrical breakdown limits, we have been evaluating refractory metals. We have shown experimentally that solid tungsten and molybdenum electrodes can provide 40% improvement in breakdown limit compared to copper and potentially would allow for doubling the antenna power density.

Publications

S. J. Wukitch, M. L. Garrett, R. Ochoukov, et al. “Characterization and Performance of a Field Aligned Ion Cyclotron Range of Frequency Antenna in Alcator C-Mod.” Phys. of Plasmas 20, 056117 (2013).

C. Lau, Y. Lin, G. Wallace, S. J. Wukitch, et al., “Effects of ICRF Power on SOL Density Profiles and LH Coupling during Simultaneous LH and ICRF Operation on Alcator C-Mod.” Plasma Phys. Control. Fusion 55, 095003 (2013).

I. Cziegler, J L Terry, S J Wukitch et al., “Ion-cyclotron Range of Frequencies in the Scrape-off-layer: Fine Structure Radial Electric Fields” Plas. Phys. Contr. Fusion 54, 105019 (2012).

M. Garrett and S.J. Wukitch, ‘Mitigation of Radio Frequency Sheaths through Magnetic Field-Aligned ICRF Antenna Design’, Fusion Eng. and Design 87, 1570 (2012).

S.J. Wukitch, B. LaBombard, Y. Lin et al., ‘ICRF Specific Impurity Sources and Plasma Sheaths in Alcator C-Mod’, J. Nucl. Mat. 390-91, 951 (2009).

S.J. Wukitch, B. Lipschultz, E. Marmar et al., ‘RF Plasma Edge Interactions and their Impact on ICRF Antenna Performance in Alcator C-Mod’, J. Nucl. Mat. 363, 491-497 (2007).

P.T. Bonoli, R. Parker, S.J. Wukitch et al., Wave-particle studies in the ion cyclotron and lower hybrid ranges of frequencies in Alcator C-Mod, Fusion Sci. Tech. 51 (3): 401 (2007).

Talks & Media

Towards RF Sustainment of Reactor Relevant Devices – SOFE 2015

Advanced ICRF Antenna for ADX – SOFE 2015

ICRF Actuator Development at Alcator C-Mod IAEA 2014

Field Aligned Antenna Characterization and Performance in Alcator C-Mod APS 2013