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Abstract. We present a brief synopsis of the phenomenology associated with
Neutral Beam heating (NBI) of the MAST Spherical Tokamak. Results, although
at an early stage of analysis, are highly encouraging for the future
auxiliary heating capabilities of the device. In particular, only 500-800kW
of NBI power (30keV H injection, 10% of design total) is sufficient
to significantly increase
Te and to double the thermal electron
pressure. Further, preliminary results indicate that the ion temperature
increases by a factor of
3, qualitatively consistent within systematic
errors with that expected, given tolerable fast ion loss and ITER
confinement scaling IPB98(y,1). NBI data recorded so far exhibit
suprathermal ion tail formation and ohmic discharges a phenomenologically
similar tail following Internal Reconnection Events. The injected fast ions,
corresponding to 10-50% of the total stored energy, are responsible for
driving a wide variety of sporadic, high frequency MHD modes, the low
magnetic fields (and hence low Alfvén speeds) inherent to the Spherical
Tokamak geometry providing an ideal testing ground for fast-particle MHD
theory.
IAEA 2001