1 - Nuclear Sciences and Applications - IAEA

IAEA-CN-50/E-IV-7
NON-INDUCTIVE STARTUP AND
CURRENT RAMP-UP SCENARIO OPTIMIZATION
FOR A TOKAMAK REACTOR
G.V.PEREVERZEV
I.V. Kurchatov Institute of Atomic Energy,
Moscow,
Union of Soviet Socialist Republics
Abstract
NON-INDUCTIVE STARTUP AND CURRENT RAMP-UP SCENARIO OPTIMIZATION FOR A
TOKAMAK REACTOR.
The stages of gas ionization and current ramp-up in a non-inductive tokamak are considered. The
main feature of this consideration of the ionization stage is the use of the recently developed theory of
plasma equilibrium in a toroidal system without rotational transform. The transport model based on this
theory is used for selecting the optimal conditions for power input into a tokamak. The dependences
of plasma density and temperature on the input power for auxiliary heating are found. Current ramp-up
with lower hybrid waves and neutral beam injection is considered. It is shown that the current ramp-up
rate, as a function of input power and plasma density, has a maximum. This allows either the current
rise time or the energy consumption to be minimized at this stage. However, even in this optimized case
the stage of current ramp-up in a tokamak of the reactor type turns out to be rather long.
1. INTRODUCTION
Gas ionization and current ramp-up are necessary elements in the discharge
scenario. However, while there exists a great body of experience with the traditional
inductive technique for discharge production, there are few experiments on the noninductive
technique [1-5]. In inductive discharges the stages of gas ionization and
current ramp-up coincide in time and, as a rule, by the end of gas ionization there
are closed magnetic surfaces in the tokamak chamber. The situation is different in
the non-inductive tokamak. Gas ionization (hot plasma production) and current rampup
can be performed by different methods and not necessarily at the same time. In
this case, at the ionization stage closed magnetic surfaces can be absent from the
plasma and the mechanisms of particle and energy confinement can be different, in
principle, from the well studied case of inductive discharges.
In this paper the stages of gas ionization and current ramp-up in the noninductive
tokamak are considered. Our approach differs from that of all previous
papers mainly in the use of the recently developed theory of plasma equilibrium in
a toroidal magnetic system without rotational transform [6, 7]. As- shown in
Refs [6, 7], toroidal drift, which has been considered as the main loss channel, being
non-ambipolar, results in the emergence of a vertical electric field and in a toroidal
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