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

• increase sustained noninductive current drive capability to 100% with 50-70% bootstrap
fraction. The current drive systems and profile control techniques should enable tests
of sustained q above 2 and control the magnetic shear to optimize the stability and
confinement.
• increase plasma pulse length by at least one to three orders of magnitude to demonstrate
sustained control of fully noninductive st plasmas for many current relaxation times.
Links to other thrusts: Thrusts 2, 3, 5, 6, 9, 10, 11, 12, 15
6. Develop normally conducting radiation-tolerant magnets for low-A applications.
The inability to shield the central toroidal field (tF) coil in an st from neutron bombardment motivates
the development of neutron tolerant, insulator-free, low impedance, tF centerpost magnets.
The simplest approach is to employ a single-turn, resistive, intensely cooled copper centerpost,
driven by a low impedance current source such as a homopolar generator. tight coupling of
the generator output to the tF is required to minimize resistive losses. Presently envisioned applications
for the st emphasize neutron production, and since fusion power scales as b t 4 , systems
with higher toroidal fields than available in present devices should be developed.
actions:
• conduct engineering studies for single-turn centerpost tF magnets. evaluate insulatorfree,
multiple-turn tF systems, using air-gapped conductors, resistive shims, or other
approaches.
• conduct engineering studies of integrated, low impedance current sources for the tF
system.
• design and construct a candidate test tF magnet set. Perform electrical, mechanical,
and thermal testing of the system, including generator(s), bus work, joints, and the coil
proper.
• conduct design and engineering studies for radiation-tolerant compact ohmic heating
(oh) systems to determine if inductive startup is practical for a nuclear st.
• design and construct candidate oh system, and test electrical, mechanical, and thermal
properties.
• test radiation tolerance, displacement per atom limits, tritium migration into coolant
channels, etc., for tF and oh systems. employ fission neutron sources, international
Fusion materials irradiation Facility (as available), and tritium facilities.
Links to other thrusts: Thrust 16 (element 1), Thrust 7.
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