Advanced Tokamak Plasmas and the Fusion Ignition Research

Experiment

Charles KesselPrinceton Plasma Physics Laboratory

Spring APS, Philadelphia, 4/5/2003

What is an Advanced Tokamak?• The advanced tokamak plasma simultaneously

obtains– Stationary state– High plasma kinetic pressure ----> MHD stability– High self-driven current ----> Bootstrap current– Sufficiently good particle and energy confinement ---->

Plasma transport– Plasma edge that allows particle and power handling ---->

Boundary condition between hot core plasma and vacuum/solid walls

• The advanced tokamak is a recognition that the tokamak is an integrated system and requires control to succeed

• The advanced tokamak is a tough nut to crack

TransportSafety factor

Pressure profileCurrent profile (bootstrap)

LHCD, FWCD, NBCD, ECCD, HHFW

NBI rotationPellet injection

Plasma shapingImpurity injection

RWM feedback

NTMfeedback

Divertorpumping

plasma

Ion/electron heating

Alpha heating

Appreciating the plasma’s integrated behavior is helping us learn to control it

Next Step Devices Must Provide the Basis for Advanced Tokamak Reactor Regime

FIRE

Inductive

AT

KSTAR

FIRE AT is approaching the reactor AT regime

Present tokamak experiments are pushing the envelope

Local Reduction of Energy, Particle, and Momentum Transport in Plasmas

By Manipulating:Magnetic field distributionMomentum injectionElectron/ion heatingCurrent distributionImpurity injectionD Pellet injection

we are learning to control the location and width of the transport reduction

thermal conductivity

temperatures density&velocity

magnetic field twist

center edge ASDEX-U

Theory and Experiments Show That Powerful MHD Instabilities Can Be Controlled

HBT-EP, Columbia Univ.

DIII-D, General Atomics

Impurities Can Control Where Power from the Plasma is Deposited

Power radiated onto high heat flux surfaces

Power radiated more uniformly throughout vessel

Large Plasma Self-Driven Current Fractions are Being Attained

60-90% of the plasma current is driven by the plasma itself, from its pressure gradient

ASDEX-U, Germany

DIII-D,USA

Japan

FIRE Has Adopted the AT Features

Identified by ARIES Reactor Studies • High toroidal field

• Double null

• Strong shaping

• Internal vertical position control coils

• Wall stabilizers for vertical and kink instabilities

• Very low toroidal field ripple

• ICRF/FW on-axis CD

• LH off-axis CD

• NTM stabilization from LHCD, ECCD, q>2

• Tungsten divertor targets

• Feedback coil stabilization of RWMs

• Burn times exceeding current diffusion times

• Pumped divertor/pellet fueling/impurity control to optimize plasma edge

FIRE is Aggressively Pursuing AT Control Tools

AT Physics Control Capability on FIRE

Strong plasma shaping and control

Pellet injectionDivertor pumpingImpurity injection

ICRF/FW (electron heating/CD) on-axis ICRF ion heating on/off-axis

LHCD (electron heating/CD) off-axis

ECCD off-axis (Ohkawa current drive)

RWM MHD feedback control

t(flattop)/t(curr diff) = 1-5

Diagnostics

MHD

J-Profile

P-profile

Flow-profile

FIRE Pushes to Self-Consistently Simulate Advanced Tokamak Modes

0-D Systems Analysis:Determine viable operating point global parameters that satisfy constraints

Plasma Equilibrium and Ideal MHD Stability: (JSOLVER, BALMSC, PEST2, VALEN), Determine self-consistent stable plasma configurations to serve as targets

Heating/Current Drive: (LSC, ACCOME, PICES, SPRUCE, CURRAY), Determine current drive efficiencies and deposition profiles

Transport:(GLF23 and pellet fueling models to be used in TSC) Determine plasma density and temperature profiles consistent with heating/fueling and plasma confinement

Integrated Dynamic Evolution Simulations: (Tokamak Simulation Code, WHIST, Baldur) Demonstrate self-consistent startup/formation and control including transport, current drive, fueling and equilibrium

Edge/SOL/Divertor:(UEDGE) Find self-consistent solutions connecting the core plasma with the divertor

FIRE AT Integrated Simulations Show Attractive Features

Q ≈ 5

Advanced Tokamaks --- We Want to Have It Our Way

• The advanced tokamak is characterized by the features we need for a viable fusion power plant

• Access to this regime requires control of the plasma and we are learning how by penetrating its coupled physics

• FIRE is a next step burning plasma device– Utilizing experimental advanced tokamak accomplishments

– Adopting design features of advanced tokamak reactor designs

– Applying integrated simulation tools to project the advanced tokamak performance

• FIRE can bridge the AT physics gap from present experiments to the reactor regime