Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

in the short term, the Thrust will exploit presently operating devices — diii-d, c-mod, nstX and
other experiments — and increase integration of relevant areas of expertise in diagnostics and
actuators, control model development, control algorithm mathematics, computational simulations,
and scenario physics understanding. in the medium term, new superconducting tokamaks,
both coming on line and being proposed, will be used to develop and demonstrate control solutions
for extended pulse durations. it is expected that the tasks can be achieved either through
collaboration with the new asian superconducting facilities or in a possible domestic long pulse
tokamak experiment. in the longer term, iteR will be used to develop and demonstrate the control
solutions under fusion conditions. Finally, new experiments, in which the pressure and associated
bootstrap current are produced largely from alpha heating, with at least a moderate, but
preferably long or steady-state pulse length, are required to demonstrate the control solutions
needed for a power producing reactor. also required is a high fluence facility for testing survivability
of diagnostics and actuators. approaches for realizing these requirements are described in
Thrust 8 and Thrust 13.
specific issues cover understanding and solutions for:
Active steady-state control: How near optimal can the plasma profiles and bulk parameters be
robustly maintained in sustained steady state?
Startup and shutdown: Does a safe and reliable path exist from low current and low pressure to the
required highly self-regulated, high-performance burning plasma state?
Burn control and thermal stability of the operating point: With what level of dynamic performance
and flexibility can thermal stability be provided in a burning plasma?
Robust active stabilization of instabilities and transient fluctuations: How close to or how far
beyond stability limits can ATs operate with maximum efficiency and negligible probability of control loss
using robust active control?
Regulation of the power flow distribution to material surfaces: What level of power flow regulation
can be achieved in the presence of plasma transients?
Active prediction, avoidance, detection, and response to off-normal and fault events: Can
the probability or occurrence be reduced to levels required for a power plant, and reliable response algorithms
be developed for acceptable device protection?
The goals, challenges, and research plans for each of these are discussed in turn. nevertheless, the
issues are generally interrelated and need to be addressed by an integrated approach. many of the
diagnostics and actuators are used for different control tasks and thus require the same development;
however, the specific goals of what is being optimized vary and these need to be balanced by
an integrated control system. a few key examples are given in the sections following. more comprehensive
research needs are described in the Theme 1 and 2 chapters on measurements and
auxiliary systems.
267