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

and stability, and mitigation requires systems for rapid delivery of large mass to the plasma core.
model-based control strategies are needed to use these tools for optimal results. These elements
can be developed individually, but ultimately they must be integrated into a unified approach to
disruption avoidance and mitigation for iteR and future burning plasmas.
edge localized mode control, because of its critical importance to the first-wall lifetime, calls for
a broad portfolio of approaches in the near term: active pacing by pellet injection, suppression by
3-d magnetic fields, avoidance by choice of operating regime, etc. development of a theoretical
understanding of the underlying transport and stability physics will provide the basis for assessment
and projection of these approaches. Real-time assessment of plasma stability may ultimately
be useful as input to elm control techniques. eventually these elements must be focused and
integrated into a reliable elm control system for iteR.
Connections to Other Thrusts
This research Thrust on control of transient events has strong connections to several others related
to scientific understanding and control of plasma stability. a principal connection is to Thrust
5, since controlling and sustaining the desired operating state presupposes avoidance of disruptions.
control of equilibrium profiles, feedback control of instabilities, and scenarios for controlled
shutdown of the discharge are dealt with in Thrust 5. improved scientific understanding of
the boundary layer plasma (Thrust 9) will be crucial in developing techniques for control or avoidance
of elms. accurate prediction of disruptions and elms requires accurate real-time diagnostic
measurements and may even drive requirements for some diagnostics (Thrust 1).
The characteristics of the plasma facing components and their interaction with the plasma
(Thrusts 10 and 12) are closely linked to the requirements for avoidance or mitigation of elms
and disruptions. a device to test demo-relevant plasma boundary conditions (Thrust 12) could
also serve to test control of transient events in demo-relevant conditions. liquid walls or other
innovations (Thrust 11) may ease the limits on peak heat flux. on the other hand, a thin-walled
blanket for tritium breeding (Thrust 13) may have less capability to withstand the electromagnetic
loads of a disruption. Use of liquid metal coolants (Thrust 13) may also limit the response time
of magnetic sensors and stabilization coils.
The development of 3-d magnetic configurations such as stellarators (Thrust 17) represents a
possible long-term approach to eliminating the disruption issue.
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