The Advanced Tokamak: Goals, prospects and research opportunities Amanda Hubbard MIT Plasma Science and Fusion Center with thanks to many contributors, including A. Garafolo, C. Greenfield, C. Kessel, D. Meade, M. Murakami, F. Najmabadi, T. Taylor Opinions are my own…
GCEP Fusion Energy Workshop on Opportunities for Fundamental Research and Breakthrough in Nuclear Fusion Princeton, NJ May 1-2 2006 The Advanced Tokamak
• Introduction: What is an ‘advanced tokamak’?
• The AT vision for fusion energy – Drawing heavily on ARIES studies. • Current results and near-term prospects – Focusing here on US program.
• AT on ITER: What we will (and won’t) learn.
• Research Opportunities: ideas to advance and accelerate fusion energy prospects. To start the discussion…. An “advanced tokamak” device is, in terms of magnetic configuration, simply a TOKAMAK
Pure toroidal field does not confine charged particles
Tokamak needs a toroidal current for stability. Adding poloidal field does Current conventionally driven by tranformer; confine charged particles. - Current is driven around central solenoid. Produced by toroidal current. Inherently NOT steady-state. Tokamaks lead other configurations in fusion performance, are approaching ‘breakeven’
ITER
D. Meade, ARIES workshop 4/24/05 “Conventional” tokamak operation will be primary mode of operation on ITER
• Heating applied mainly on-axis, inductive current drive, profiles relax to ‘natural’ state. • Much experience worldwide, good confidence in extrapolation to burning plasma conditions. – This will allow critical exploration of burning plasma physics.
• Could probably be used to make a fusion power plant. – Advantages of relative simplicity, staying away from performance limits. – BUT projected power plant not seen as economically attractive (at least in prior assessments with low cost oil!) Tokamak current does not have to be driven by a transformer!
• Alternative means of current drive: – External current drive, by neutral beams, or microwaves (various ranges from ion cyclotron (~100 MHz), Lower Hybrid (~ 5 GHz), electron cyclotron (~100 GHz))
–“Bootstrap current”: Self-generated current due to temperature, density, pressure gradients in the plasma.
• All of these are fairly well understood, and have been demonstrated to work on many experiments. – Gives potential for steady-state operation. • “The crucial distinguishing feature of an Advanced Tokamak over a conventional tokamak is …the use of active control of the current or shear profile, and of the pressure profile or transport characteristics” (AT Workshop, GA, 1999) – Same tokamaks can (and do) operate in both conventional and advanced regimes. OPTIMIZATION OF THE TOKAMAK CONCEPT LEADS TO AN ATTRACTIVE FUSION POWER PLANT