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

extended operation phase. The optimal result from the research on iteR will be to obtain a sufficient
scientific and technical basis for operation at reactor-relevant engineering parameters and
in burning plasma conditions and thus enable confidence in designing a next-step fusion device
(e.g., demo).
many of the scientific issues in burning plasmas — such as confinement, macro-stability, power
and particle handling, long-pulse operation, diagnostics, and plasma control — are similar to
those already being addressed in existing experimental facilities. What makes them more challenging
are the scale-up to large reactor size and strong magnetic field; the need to operate near
performance limits, with high heat flux on plasma facing components; and the thermonuclear environment,
with harsh radiation and neutron fluxes, along with nuclear science issues such as tritium
dust, tritium retention in the vessel walls, and the need to breed tritium fuel. in addition, as
already mentioned, the distinguishing feature of a burning plasma is self-heating by a large population
of alpha particles. The self-heating property means that the pressure, current, and rotation
profiles in the plasma will be “autonomous” (i.e., self-organized), rather than controlled externally.
The presence of the supra-thermal alpha particles, approximately 300 times more energetic
than plasma ions and electrons, leads to new instabilities, anomalous transport, profile modification,
perturbation of burn dynamics, and other impacts on the plasma behavior.
The topic of Theme 1 in this Research needs Workshop was divided among the following six panels:
1. Understanding alpha particle effects.
2. extending confinement to reactor conditions.
3. creating a self-heated plasma.
4. controlling and sustaining a self-heated plasma.
5. mitigating transient events in a self-heated plasma.
6. diagnosing a self-heated plasma.
each of these panels contributed a section in this chapter, in which the current status, research
requirements, and scientific opportunities for the respective panel are described. The members of
the panels, who represent a broad range of expertise in fusion physics and engineering science,
are listed at the end of the chapter.
The scientific issues for achieving and understanding the burning plasma state in iteR, which is
the overall topic of Theme 1, have a significant overlap with those for creating predictable, highperformance,
steady-state plasmas, which is the topic of Theme 2. Thus, it was natural, in organizing
the efforts of Themes 1 and 2, to set up some of the panels — viz., on plasma control (#4 in
the list above), off-normal transient events (#5), and plasma diagnostics (#6) — as joint panels of
Themes 1 and 2. however, the descriptions of the research issues and requirements in this chapter,
even those for the joint panels, are focused on the research work needed to ensure that iteR
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