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Abstract. A radio frequency (rf) system has been installed on the National
Spherical Torus Experiment (NSTX) with the aim of heating the plasma and
driving plasma current. The system consists of six rf transmitters, a twelve
element antenna and associated transmission line components to distribute
and couple the power from the transmitters to the antenna elements in a
fashion to allow control of the antenna toroidal wavenumber spectrum. To
date, power levels up to 3.85 MW have been applied to the NSTX plasmas. The
frequency and spectrum of the rf waves has been selected to heat electrons
via Landau damping and transit time magnetic pumping. The electron
temperature has been observed to increase from 400 to 900 eV with little
change in plasma density resulting in a plasma stored energy of 59 kJ , a
toroidal beta,
= 10% and a normalized beta,
= 2.7.
IAEA 2001