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

mum of nuclear activation and preserve manned access to the facility, a number of issues would
benefit from deuterium operation. These issues include degraded core plasma confinement and
less robust pedestal performance at given heating power with hydrogen, as well as isotopic scaling
of scrape-off layer transport, sputtering and other plasma-material phenomena. direct effects
of neutron irradiation on plasma-material interactions, which are not anticipated to be strong,
can nonetheless be examined in this facility by installing samples and/or components that have
been previously irradiated. The balance and sequencing of hydrogen versus deuterium operation
should be examined with respect to the trade-offs in flexibility, and requirements for shielding
and remote maintenance, to maximize the scientific output of this facility.
Research activities of the Facility Required for this Thrust
The large array of scientific issues to address in Thrust 12, as listed earlier, assures a rich and diverse
scientific program. The Thrust provides a dedicated, enabling facility that will investigate the
integration of an extremely wide-ranging set of core and edge scientific issues, while simultaneously
implementing required technologies. extensive diagnostics will be deployed to provide critical
science information on the core and edge plasma, and on the evolution of PFc material surfaces.
a variety of steady-state heat flux solutions would be tested, which may include a radiative divertor
and/or mantle, precision PFc alignment in conjunction with large flux expansion (e.g., vertical
target, X-divertor, snowflake) and expanded flux-tube divertors (e.g., super-X). solid and liquid
PFc surfaces will be tested in accommodating demo-like heat flux, material temperatures and
cooling technology. in both cases the solutions to be tested will be dependent on positive results
in other thrusts. The ambient PFc temperature will be a particularly important parameter to vary
in the effort to limit fuel retention, control the fuel cycle and potentially improve core plasma performance.
Furthermore, the facility’s long-pulse and diagnostic capabilities will for the first time
allow a credible examination of the mechanisms controlling long-term material migration and
PFc surface evolution in a demo-like environment.
critically, these scientific and technological solutions to edge problems must be shown to be consistent
with plasma sustainment and sufficient core plasma performance, such that steady-state
operation is feasible within the window of allowable core plasma parameters. a controlled pedestal
is central to this task since it the intermediary between the edge and core. a sufficient range
of pedestal scenarios must be available and examined to enable the long-pulse plasma surface interaction
science mission. Pedestal parameters, in particular particle density, will be varied to examine
tradeoffs in confinement, bootstrap fraction and current drive efficiency toward simultaneously
meeting the steady-state and edge missions. core and edge integration will also require
control of elms and perturbing disruptions, suggesting exploration of 3-d fields and innovative
core confinement regimes. a battery of actuators will be used to drive current and modify the
core profiles. all this must be demonstrated to have long-term reliability and be compatible with
steady-state heat flux control while maintaining a robust pedestal.
successful operation of this facility should demonstrate solutions for demo-like boundary conditions
that are compatible with optimized core plasma operations. The timely development of
these core-edge solutions should accelerate the successful operation of a Fusion nuclear science
Facility and a demo power plant.
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