Transcript Document

Profile Control/Heating and
Current Drive Issues
Presented by
T. C. Luce
(H & CD for R. Prater)
General Atomics
Presented at
FESAC sub-committee meeting
San Diego, CA
June 25, 2007
Profile Control Issues for DEMO
•
Operation of DEMO in advanced scenarios will require
model-based control for access to and maintenance of the
desired operating scenario
• Current and rotation profile control are the only clear
DEMO-relevant methods known at present
• Model-based control is needed because:
– Resistive times in DEMO are too long for simple PID
control
– Actuators will be relatively weak (by definition) at high
fusion gain and are typically uni-directional
– Authorization of a fast-track DEMO will require a wellcharacterized, robust operating scenario
Bridging the Gap to DEMO
• Three elements are required for profile control
– Control domain map
• Includes landscape and boundaries
• Can be first-principles, empirical, or mixed
– Control method
• Beyond the state of the art at present
– DEMO-compatible current and rotation profile diagnostics
• Development of both can be carried out to a large extent the
present generation of tokamaks, but only with a substantial
increase in dedicated resources (people, experimental time,
hardware)
– Next generation superconducting machines allow validation
and optimization
– ITER is the only device to add the essential missing ingredient-self-heating
• A dedicated DEMO-similar low-fluence companion tokamak
may be needed for software testing and personnel training
Heating and current drive physics issues for DEMO
• Physics models of ICRF, LHCD, NBI, and ECH/ECCD need to be
tested under reactor conditions
-- first-principles models are in development and validation
-- careful experiments can extrapolate to reactor conditions
-- support of SciDAC, SWIM, and FSP are critical to generating
the ability to understand and predict H&CD inputs and their
effects on the plasma
• ARIES AT DEMO calls for FWCD/ICRF and LHCD, but ECCD may
be useful for off-axis CD and for NTM control and NBI for off-axis
CD and introducing momentum for rotation
• ECCD has the best-developed physics and technology of
these H&CD methods, and the extrapolation to DEMO from ITER is
small
• NBI needs resolution of off-axis CD physics and FP interactions
-- NB technology for ITER satisfactory for DEMO
-- 120 keV beams for edge rotation should be tested
LHCD and ICRF have major technology issues
regarding the antennas
• LHCD and ICRF have evanescent barriers between the
antenna and the plasma, but in a DEMO the antenna may not
be placed near the plasma
• For LHCD there are some potential solutions which should be
aggressively tested:
-- injection of gas near the antenna (JET, JT-60U)
-- PAM launcher (Tore Supra, FTU; revalidation on C-Mod,
EAST, and KSTAR should follow)
• For ICRF new antenna concepts appear to be required, but
no plan is in place
-- e.g., ITER design calls for unrealistically high voltage
-- possible alternates: segmented straps or combline should
be developed on present tokamaks