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

Activity 1b: Examine design options for construction of a flexible D-T facility in the US,
to supplement the ITER mission, focused on high P alpha /P input , high pressure, high density,
high self-driven current fraction, D-T plasmas for durations of several current profile
redistribution times.
The demo requirements for a high-performance plasma surpass iteR’s goals, and the Us should
explore a complementary d-t facility with a more focused physics program. The Us could propose
to construct a more flexible d-t tokamak, optimized for the demonstration of high-performance
core plasmas. The highest beta and bootstrap current fraction achieved in d-d experiments
would be sought, while raising the P alpha /P input ratio significantly above 1, the target value
for iteR, toward the Thrust mission target of 4-9. The importance of this mission is to show there
is a sustainable configuration under the influence of the highly nonlinear core plasma processes.
The duration of this plasma would be > 5 t J . The parameters and supporting elements in table 1
would be pursued simultaneously. The Us d-t facility would explore the control of core radiated
power level, particle fueling and pumping, current and safety factor profile, mhd modes, and disruption
avoidance in the presence of a burning plasma in a highly self-organized state. The scrapeoff
layer plasma and its interaction with material surfaces can influence the core through particle
transport, the effects of which can be observed on the multiple current profile redistribution time
scale of these experiments. in addition, issues associated with the handling of demo-level heat
loads can be examined on these plasma durations.
efforts would be made to keep this device smaller than projected power plants (R = 5-7 m) by focusing
on advanced operating regimes with higher beta and plasma energy confinement, higher
bootstrap current fractions, and higher toroidal fields, while minimizing the current redistribution
time. as discussed in chapter 2, it is expected to have gaps remaining between the simultaneous
achievement of demo target parameters listed in table i, and those reachable in such an
experiment, although these would be minimized to the extent possible and would be bridged in
conjunction with predictive simulation development in Thrust 6. This design study should explore
whether the flexible facility needed for this Thrust can be made compatible with the missions of
other fusion energy science thrusts, by phased upgrades and by reusing facility infrastructure
and the tokamak components to the extent possible. in particular, a Fusion nuclear science Facility
(FnsF) would require longer pulses for high fluence testing, perhaps at lower Q. depending on
its design, an FnsF could also contribute to the high-performance steady-state theme.
Activity 1c: Based on the results of the ITER enhancement studies and US D-T facility studies,
proceed with the ITER enhancements or the construction of a US D-T facility, or both.
if the predictive studies carried out in 1a indicate feasibility and significant benefit for steadystate
scenarios, the Us could support on iteR, with international cooperation, 1) the addition of
lower hybrid to the mix of heating and current drive sources, 2) upgrading of existing heating and
current drive sources to higher powers, and 3) upgrading the resistive wall mode coil and plasma
rotation control to access higher plasma betas. increased P alpha /P input above 1, in fully noninductive
modes of operation, would allow exploration toward the more coupled regime of plasma transport,
current and mhd under dominantly self-heated conditions. This research would be carried
out in collaboration with international partners, most likely in the second phase of d-t operation.
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