Charles Karney: Publication 49/85, Jobes(1986)

F. C. Jobes, S. Bernabei, T.-K. Chu, N. J. Fisch, W. M. Hooke, C. F. F. Karney, E. B. Meservey, R. W. Motley, J. E. Stevens, and S. E. von Goeler.
Start-up and ramp-up of the PLT tokamak by lower hybrid waves.
In H. Knoepfel, editor, Tokamak Start-up, volume 26 of Ettore Majorana International Science Series, Physical Sciences, pages 203–216, Plenum Press, New York (EUR 10114 EN), 1986.
Princeton Univ. Rept. PPPL-2241 (Aug. 1985) 31 pp.
Proc. Seventh Course of the International School of Fusion Reactor Technology, Erice, Sicily, July 14–20, 1985.
BibTeX Entry

Lower hybrid waves have been used on the PLT tokamak both to start the plasma current and to ramp it up from pre-existing levels. The waves, at 800 MHz, were launched from a 6-waveguide grill. The phasing between adjacent guides could be selected electronically, and thus the launched spectrum could be set and changed at will. For start-up, the waveguide phase difference was initially set at 0° in order to create a plasma, then switched to 90° to drive the current. Over 100 kA of plasma current, at a density of 0.5–1 × 10¹² cm⁻³, was generated in this manner. Ramp-up experiments were performed under a wide variety of conditions. The most efficient ramp-up was found at the lowest plasma densities and with the fastest launched spectrum (n_e ∼ 2 × 10¹² cm⁻³, N_|| ∼ 1.6 peak); ∼ 20% of the launched RF power was converted to (increased) poloidal field energy. All of the ramp-up results are in excellent agreement with a theory which determines the efficiency of ramp-up from the consideration of the relative energy losses of the superthermal current-carrying electrons to collisions and to the opposing inductive E-field.