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

• based on these assessments, proceed with either iteR enhancements or a Us d-t facility,
or both.
The integrated core dynamics thrust is focused on the exploration of high-performance fusion
core plasmas relevant to a magnetic fusion demo, in which the alpha power dominates the input
power, the plasma current is dominated by the self-driven bootstrap current, and the strongly
coupled nonlinear physics of the plasma provides a stable combination of plasma transport and
mhd that allows the configuration to be sustained in steady state. The scientific challenges lie
in establishing these configurations and utilizing our physics understanding to sustain and optimize
them. The active control of such a plasma through fueling and pumping, heating, current
drive, and rotation will be challenging and will require coupled controllers on a level not needed
on present tokamaks or even iteR, to be developed in Thrust 5.
The exploration of the high-performance fusion core plasma regime is a fundamental step
to verify the existence of viable plasmas for fusion power production.
1. Thrust activities
The basic parameters of interest for a high-performance fusion core plasma, based on power plant
studies, and motivated by the physics requirements in chapter 2, are shown in table 1, along with
supporting elements. These parameters must be obtained simultaneously. key activities for this
Thrust are described below, and should occur in parallel. The activities identified can benefit from
activities in other thrusts, as described in the summary.
b no wall
n < bn < b with wall
n high normalized plasma pressure
b ped
n ≈ 0.5-1.0 high normalized plasma pressure near the plasma edge
3 < q95 < 5 degree of magnetic field twist near the plasma edge
i non-inductive /i plasma = 1 high fraction of plasma current not provided by an external solenoid
0.65 < (i bootstrap /i plasma ) < 0.90 high fraction of plasma self-generated current
n/nGr ≈ 1
Ratio of plasma particle density relative to an empirical limit approaching
one
Palpha /Pinput ≈ 4-9 high ratio of plasma self-generated power to externally injected power
Prad,core /(Palpha +Pinput ) ≈ 0.35-0.5
significant ratio of power radiated from the plasma core relative to the
total power heating the plasma
zeff < 2.5 Weighted sum of ion charge in the plasma, sufficient plasma purity
t pulse >> t J
supporting elements.
Plasma operation time long compared to the current profile redistribution
time
efficient fueling and pumping, with particle control of the d-t fuel, he ash, and impurities.
efficient coupling of heating and current drive power into the plasma.
consistent pedestal density and temperature to provide high core performance with fueling and divertor compatibility.
multi-level feedback control on parameters ranging from plasma shape to current profile to mhd modes.
Plasma sustainment over many current profile redistribution times (considered the longest time constants for the core plasma)
without disruptions and with acceptable transients.
Table 1. High-performance fusion core targets, and supporting elements.
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