Observation of Persistent Edge Current Driven by Coaxial Helicity Injection (CHI)
Authors: D. Mueller, B.A. Nelson, W.T. Hamp, A.J. Redd, T.R. Jarboe, R.G. O'Neill, and R.J. Smith
Date of PPPL Report: April 2005
Published in: Physics of Plasmas 12: 070702 (2005) (4 pages)
Coaxial Helicity Injection, CHI, has been used on the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 (2000) 557], the Helicity Injected Torus (HIT) [B.A. Nelson et al., Phys. Rev. Lett. 72 (1994) 3666] and HIT-II [T.R. Jarboe et al., Phys. Plasmas 5 (1998) 1807] to initiate plasma and to drive up to 400 kA of toroidal current. On HIT-II, CHI initiated discharges have been successfully coupled to ohmic sustainment [R. Raman et al., Phys. Plasmas 11 (2004) 2565]. This paper presents the first results on the use of CHI to demonstrate the persistence of edge current drive in a preestablished single-null diverted inductive discharge. Edge current drive has the potential to improve plasma stability limits [J.E. Menard et al., Nucl. Fusion 37 (1997) 595]. While most current drive methods drive current in the interior of the plasma, CHI is well suited for driving current in the edge plasma.