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

2. With information from action 1, construction of a new FRc experiment will be central
to understanding scaling to high-s conditions. basic plasma parameters impose clear
requirements for achieving s ≥ 10. For low collisionality, a variable separatrix radius up to 1
m and poloidal flux of 20-50 mWb will be required to confine 10-20 kev energetic ions in the
desired thermal-s range. high current (~10-50 amp), medium energy (20-40 kev) neutral
beams will allow a significant fraction of the current to be carried by energetic particles.
Flexibility with respect to shaping is also important for addressing stability. transport
studies will be combined with the high-s studies since cross-field transport in FRcs is
related to the ratio of electron drift velocity to ion thermal velocity (g d ). experiments and
calculations show anomalous resistivity decreasing sharply as g d is reduced below unity.
in FRcs g d ~ 2.3/s, so high-s FRcs will naturally have g d < 1. high-energy axis encircling
ions will also affect transport, so studies of high-s stability and transport are synergistic.
density fluctuation measurements will require laser scattering diagnostics.
3. The outcome of actions 1 and 2 will be used for a proof-of-principle scale experiment that
will integrate high-b operation with boundary plasma control.
integration of Elements
development of the scientific and technological basis for economical fusion power through minimal
applied field unifies the elements of this Thrust. The configurations cover a space of parameters
that extends from large paramagnetism to extreme diamagnetism, over varying degrees of
magnetic shear, and from moderate to large b. While device-specific development paths should be
pursued, the common activities listed earlier will foster greater collaboration. The three configurations
need similar diagnostic developments, and profile and boundary control. collaborations
will increase the versatility of simulation capabilities and the reliability of numerical predictions.
Finally, system studies will help quantify engineering tradeoffs.
Other Scientific benefits
The study of low external field configurations has strong ties to the areas of space, solar, and astrophysical
plasmas. magnetic self-organization in RFPs and spheromaks is related to dynamo,
which is considered important for the generation of interstellar and intergalactic fields. current
collimation and the mhd stability of stellar and astrophysical jets are analogous to basic properties
of the RFP and spheromak. magnetic reconnection and associated ion heating are also important
in these configurations, as they are in solar and space plasmas.
With their robust stability, FRcs with large ion gyro-radii (low-s) have potential application beyond
steady confinement schemes. additional information gained from existing and planned facilities
of this Thrust can be useful for high energy density laboratory plasma (hedlP) programs
such as magneto-inertial fusion. it will also influence the development of plasma thrusters for
space propulsion.
over the last two decades, low external field research in the Us has largely benefitted from and
contributed to fusion science efforts at our major research universities. its exploratory nature fosters
creative thinking and motivates scientific discovery in fusion science. it will continue to have
important educational value throughout the iteR era.
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