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

• ability to handle liquid metals, e.g., gallium or tin, as well as more reactive liquids, e.g.,
lithium.
• variable magnetic field, with maximum |b| > 1 tesla, to study Psi effects in the divertor
region.
• Progressively longer plasma durations, starting from 10 2 s, and eventually to 10 6 s,
respectively corresponding to the anticipated time constants of the physical processes
of high-z impurity migration, to hydrogenic species permeation in ferritic steel under
relevant operating conditions.
• Full suite of diagnostics for Psi measurements, including in-situ optical and mass
spectroscopy, laser-induced fluorescence, thermal desorption spectroscopy, quartz-crystal
microbalances, as well ex-situ analysis of the target by Uv and visible Raman spectroscopy,
scanning and auger electron microscopy, X-ray photoelectron spectroscopy, direct-recoil
spectroscopy and atomic force microscopy. measurements of plasma density, total ion flux,
neutral density, and electron and ion energies will also be required using interferometers,
langmuir probes, retarding potential analyzers, spectroscopic diagnostics, etc.
• These experimental measurements would be invaluable for the validation of the
computational simulations of the plasma-surface interactions using a multi-scale
approach, which will be key for the successful prediction of demo Psi.
as indicated, to evaluate the performance of surface materials and designs from the impact of
transients, long pulses, and elevated temperature, dedicated new and upgraded facilities will be
required. many of the required assessments do not need the full complexity of a tokamak. dedicated
laboratory experiments can provide a cost-effective, well-diagnosed, long-pulse, and wellcontrolled
environment for performing Psi research. These facilities should be operable in pulsed
mode to simulate disruptions and elms to understand the effects of these phenomena on target
materials over longer times than are achieved in today’s confinement devices. similarly, the effect
of extended pulse lengths and elevated wall temperature on many Psi processes can be addressed
in simplified linear plasma devices on a shorter time scale.
although reliable Psi performance will need to be ultimately demonstrated in a long-pulse, highpower
density, high wall temperature, toroidal confinement device, the knowledge basis developed
in this research program should establish confidence in the success of these integrated demonstrations.
moreover, the knowledge gained here will guide the design of such future facilities.
The fundamental science advances from this Thrust will be key in the design of plasma facing
components and internal components for long pulse, hot wall devices, e.g., as envisioned to fulfill
the goals of Thrusts 12 and 13.
Predictive Modeling, Validation, and Experiment
a strong theoretical basis is required to further the understanding and prediction of the Psi process
in magnetically confined fusion plasmas. Therefore, an integral part of this Thrust is for enhanced
modeling combined with measurements from both existing and new, dedicated Psi facili-
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