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

techniques for integrated data analysis, and 3) turbulence and fast ion diagnostics.
accurate magnetic field and temperature profile measurements need new techniques.
turbulence and fast ion diagnostics are required in all magnetically confined plasmas,
particularly for micro-turbulent transport studies. integrated data analysis maximizes
extraction of reliable information from sets of related and complementary diagnostics. it
also facilitates model validation. Resources will be required for engineering and hardware,
and for student training that incorporates both computational and instrumentation
aspects.
• development and application of plasma control tools — neutral beam injection and
radiofrequency will greatly contribute to current drive, current and flow profile control,
b-limit studies, stabilization techniques, and ion charge-exchange diagnostics. With
relatively modest magnetic field and size, the well-developed and efficient positive-ionbased
beam technology that operates at high power (mW) and tens of kev/nucleon energy
level will be well suited for all of the Thrust’s configurations. because the RFP, spheromak,
and FRc configurations have high-b, radiofrequency techniques for high density and b
must be developed.
• development for liquid walls — low particle recycling through the use of a liquid
lithium limiter is a new, potentially breakthrough strategy for influencing edge plasma
conditions. The sensitivity of confinement and current drive scaling to edge plasma
conditions provide strong motivation for this effort. collaboration with the ltX program
at PPPl will contribute important data on low recycling physics, providing opportunities
to improve next-step experiments and accelerating development of the RFP and ct
concepts. also, liquid metal walls may be particularly well suited for low external field
configurations, because poloidal flows at the surface are not impeded, and smaller RFP
and ct experiments can provide direct tests.
• system studies — early reactor studies for FRcs, spheromaks, and RFPs indicate that
many of their engineering features would be attractive if physics challenges can be met.
since then, the evolution of ct and RFP physics, and of fusion engineering as a whole, has
altered the development terrain. a critical issue is how ct and RFP reactor technology
development needs differ from those of the tokamak; addressing such needs typically
requires long lead times. These considerations motivate two tasks: 1) quantify the
engineering, economic, and safety characteristics of ct and RFP reactors by performing
modern systems studies, and 2) assess whether divertors, blankets, and shields designed
for ct and RFP reactors can benefit from low external fields and relatively uniform heat
and neutron fluxes.
Scale of Effort and Readiness
Research over the past decade produced significant advances in each of the three minimal external-field
configurations. however, their programmatic development levels are sufficiently different
as to require separate discussions regarding readiness and scale.
Reversed field pinch accomplishments include transient control of magnetic fluctuations, yielding
a ten-fold improvement in global energy confinement and simultaneous kev electron and ion
382