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

Research Plan:
Short-term: Develop and test improved actuators. Examples include high-efficiency, steady-state, highpower,
flexible (frequency variable) gyrotrons for effective electron cyclotron heating (ECH) and current
drive (ECCD), with extension to higher density operation, and rotation control through lower hybrid
(LH) and ion cyclotron range of frequency (ICRF) waves. Demonstrate full closed loop equilibrium
control on existing experiments.
Medium-term: Develop new diagnostics and radiofrequency actuator systems scalable to high-fluence
environments, for example, ICRF and LH systems that minimize interaction with the scrape-off layer
plasma, and innovative ECCD steering methods. Demonstrate integrated control methods in steadystate
D-D plasmas and test new actuators.
Long-term: Demonstrate fully functioning integrated control methods, and develop and test new
actuators and diagnostics in ITER D-T plasmas. Extend to strongly alpha dominated, DEMOprototypical
environment.
Develop and demonstrate reliable procedures for robust startup to a largely self-heated and
self-driven steady-state configuration and reliable shutdown protocols: Does a safe and reliable
path exist from low current and low beta to the required highly self-regulated, high-performance
state envisaged in a burning plasma?
startup and shutdown of tokamak plasmas is prone to heightened possibility of disruption if
not done carefully. Generally, the pressure, current, and plasma shape need to be ramped up to a
largely self-sustaining bootstrap current and alpha heated state, and terminated when necessary
by a careful ramp-down.
Specific Challenges:
While existing experiments routinely reach bootstrap dominated plasma current states using
auxiliary heating methods, the alpha-heated state will provide unique challenges. achieving the
desired current profile with large bootstrap fraction will require optimization of the current drive
tools (whether radiofrequency or neutral beam injection) to meet the current drive magnitude
and location requirements within the available power constraints.
Research Plan:
Short-term: Explore more fully from current experimental databases and additional experiments
the dependence of disruptivity on startup rates across multiple machines for developing control-level
models. Continue bootstrap current startup experiments and other novel ohmic-free startup scenarios
in existing experiments.
Medium-term: Test new control methods for startup to full noninductive current and high pressure in
D-D plasmas.
Long-term: Test startup scenarios to full steady state in ITER D-T advanced scenarios with significant
alpha heating and corresponding bootstrap current. Extend to alpha-dominated heating and bootstrap
current.
269