CONFINEMENT NICK ANTONIO DEZ PRINCE M AY 2 , 2 0 1 7 AGENDA Magnetic Confinement Defined Effects on Confinement Plasma Shaping Instabilities Plasma Facing Materials
Magnets ITER Performance Tokamak Symmtery Baseline Tokamaks Scaling Interpretation Shortfalls Impurities Conclusion WHAT IS MAGNETIC CONFINEMENT?
Magnetic confinement fusion is an approach to generating fusion power that uses magnetic fields (which is a magnetic influence of electric currents and magnetic materials) to confine the hot fusion fuel in the form of a plasma Magnetic confinement fusion attempts to create the conditions needed for fusion energy production by using the electrical conductivity of the plasma to contain it with magnetic fields. ITERs Required Confinement Capability Magnetic confinement fusion, Wikipedia ITER Physics, IAEA
CONFINEMENT TIME Initially, in Chapter 3, we explored confinement time The length of time for which particles are confined within the plasma... One of the three critical parameters for fusion plasmas, along with temperature and number density, that form the triple product. a, minor radius (m) 2.0 Ro, major radius (m) 6.2 q95, edge safety factor 3.0 B, toroidal magnetic field (T) 5.3
"Confinement Time, EUROfusion ITER, FusionWiki ENERGY CONFINEMENT TIME Energy confinement time measures the rate at which a system loses energy to its environment. H-mode Correlation (17.18) I, current (MA)
B, toroidal magnetic field (T) n, average electron density M, atomic mass of the ions (amu) R, major plasma radius (m) , plasma elongation (b/a) A, aspect ratio (R/a) P, heating power (MW) Lawson Criterion, Wikipedia Fusion Plasma Physics, Dr. Weston M. Stacey
ENERGY CONFINEMENT TIME The Physics Basis of ITER Confinement, F. Wagner PLASMA SHAPING Geometric factors influencing energy confinement time Aspect ratio, Plasma elongation, , where b is the height of the plasma measured
from the equatorial plane Plasma triangularity, , the horizontal distance between the major radius and the x-point Plasma shaping, Wikipedia Separatrix, FusionWiki PLASMA SHAPING ITER geometry Aspect ratio, A = 3.1
Lower aspect ratios yield increased plasma stability, kink instability suppression, and increased energy confinement time. Elongation, sep = 1.85 Elongation, 95 = 1.70 Allows for increased plasma current, pressure, and confinement time. Triangularity, sep = 0.48 Triangularity, 95 = 0.33 Increased triangularity is associated with an increase in pedestal pressure. Introduction to ITER, Columbia University The Physics of an Ignited Tokamak, F. Troyon
PARTICLE CONFINEMENT For ITER, b = 400 s. a, minor radius (m) D, radial diffusion coefficient (m2/s) ITER, FusionWiki Alpha Particle Confinement in Tokamaks, R. B. White and H. E. Mynick ITER Physics, IAEA
H-MODE CONFINEMENT STATE H-mode is an operating mode possible in toroidal magnetic confinement fusion devices. In this mode, the plasma is more stable and better confined. (15.1) Ai, plasma ion mass (amu) n 20, plasma line-average electron density B, toroidal magnetic field (T) R, major radius (m)
a, minor radius (m) High-confinement mode, Wikipedia Fusion Plasma Physics, Dr. Weston M. Stacey H-MODE CONFINEMENT STATE Figure 15.1. Edge pressure, temperature and density distributions in otherwise similar L-mode and H-mode discharges. (Data are plotted vs. a normalized poloidal flux function which is > 0 for values outside the LCFS and < 0 for values inside the LCFS. Location of the LCFS is indicated by the vertical dashed line) Fusion Plasma Physics, Dr. Weston M. Stacey
INSTABILITIES MICROTEARING MODES Microtearing instabilities are magnetic field fluctuations that cause the formation of small island chains near rational magnetic surfaces. These magnetic islands result when the radial pressure gradient is absent. Simulation of a m = 2, n = 1 magnetic island in an ignited ITER plasma.
Understanding and Predicting Microtearing Instabilities in the ST, K. Tritz, et al. ITER Physics Basis INSTABILITIES MICROTEARING MODES Figure 11.2. The (m = 3, n = 1) magnetic island in a toroidal plasma Fusion Plasma Physics, Dr. Weston M. Stacey INSTABILITIES MICROTEARING MODES [M]icrotearing modes draw free energy from the background
electron temperature gradient. This is significant because [i]n burning ITER plasmas, the fusion processes will predominantly heat the electrons. Unstable microtearing modes have been found in the pedestal region of a simulated ITER plasma. These modes can generate radial electron thermal transport as great as Te 5 keV. 5 keV. Gyrokinetic prediction of microtearing turbulence in standard tokamaks, H. Doerk et al. Microtearing instability in the ITER pedestal, K. L. Wong et al. INSTABILITIES MICROTEARING MODES
If magnetic islands associated with microtearing are allowed to grow large enough, they may limit plasma pressure thereby limiting both E and degrading (6.110) n, density kB, Boltzmann Constant (J/K) T, Temperature (K) B, magnetic field (T) o, permeability of free space (m kg / A kg / A2 kg / A s2) ITER Physics Basis
Fusion Plasma Physics, Dr. Weston M. Stacey INSTABILITIES MICROTEARING MODES Troyon Limit N, normalized I, current (MA) a, minor radius (m) B, toroidal magnetic field (T) Beta (plasma physics), Wikipedia
Beta, FusionWiki INSTABILITIES EDGE-LOCALIZED MODES Edge-localized modes (ELM) are instabilities that occur in the edge region of a tokamak plasma that result from periodic but irregular transport barrier relaxation. These instabilities are particularly damaging to the wall components of a tokamak, especially the divertor plates. Edge-localized mode, Wikipedia Edge Localised Modes, EUROfusion
INSTABILITIES EDGE-LOCALIZED MODES ITER computer models have demonstrated two mechanisms by which the flow of energy from the plasma comes into contact with the wall and divertor plates Perturbed edge magnetic field energy loss Plasma filament expulsion Edge-localized mode, Wikipedia Progress on ELM physics and ELM control, ITER.org
INSTABILITIES EDGE-LOCALIZED MODES ELM Prevention and Control Magnetic energy injection Pellet injection Edge-localized mode, Wikipedia Progress on ELM physics and ELM control, ITER.org PLASMA-FACING MATERIALS AND
COMPONENTS Plasma-facing materials are those materials that are used to construct plasma-facing components, such as the first wall and divertor plates. These components are subjected to high thermal flux, particle flux, and erosion. First wall materials must be carefully selected, as this surface may be a source of impurities which poison and cool the plasma. Plasma Facing Components: Challenges for Nuclear Materials, P. Magaud et al. Proceedings of the Third European Particle Accelerator Conference, Volume 1
PLASMA-FACING MATERIALS AND COMPONENTS Materials currently in use or under consideration for use multilayer, carbon-based tiles Boron carbide Graphite Carbon fiber composite (CFC) Beryllium Tungsten
Molybdenum Lithium Figure 13.7. Energy dependence of the physical sputtering yield of deuterium- and self- sputtering surfaces of beryllium, carbon, and tungsten. Plasma-facing material, Wikipedia Fusion Plasma Physics, Dr. Weston M. Stacey Overview of the JET Results with the ITER-Like Wall, F. Romanelli PLASMA-FACING MATERIALS AND
COMPONENTS New JET results tick all the boxes for ITER, EUROfusion MAGNET SYSTEM Toroidal Field System Poloidal Field System Magnets, ITER.org
MAGNET SYSTEM Central Solenoid In-Vessel Coils Magnets, ITER.org WILL ITER WORK? Examine previous performance objectives of similar tokamaks to determine operational parameters: 1) Confinement time dependency
2) Geometry effects on enhanced confinement 3) Moderating Instabilities Scaling laws, DOE GEOMETRY OF PLASMA AND FIELD LINES Physics vs Empirical Data Grad-Shafranov Equation: 1) Defines axis symmetry equilibrium found in a tokamak 2) Equilibrium parameters determined through field line and
flux surface topology (6.33) 3) Physics of plasma shaping limited to predict certain instabilities Fusion Plasma Physics, Dr. Weston M. Stacey ASDEX CONFINEMENT DISCOVERY 1982 High confinement discovery
Correlation to plasma geometry and temperature Increased confinement time by three folds ~ 1.8s During 50 years of fusion Resarch, Dale Mead, IAEA. LIMITS ON HEATING THE PLASMA ALCATOR-C MODE Alacator-C mode
Produced desire plasma heating without superconductive magnets through auxiliary ICRH source ITER will mirror this approach with the addition of improved ohmic heating and neutral beam injection An Alcator Chronicle, Ron Parker JET
Neoclassical confinement time does not align with observations Confinement time linear coupled to current and inversely power production. Illustrated anomalous transport not governed by physics projection Goldstons scaling first introduced The science of JET, John Wesson.
JET (CONT) Goldstons scaling requires 30MA! Reshaping the plasma and magnetic field creates desired separatrix H mode achieved with 60% improvement in confinement at same power levels
The science of JET, John Wesson. DIII-D Premier plasma shaping tokamak Modeled confinement time in excess of 300s Internal Transport Barrier optimization
DIII-D Development Plan, General Atomics R.D. Stambaugh JT 60 Highest triple point achieved in a tokamak Operates D-D fuel reactions (currently under upgrades for supporting
Tritium fuel) High inductive heating from auxiliary sources JT-60 Plasma Regime Y. Kamada, JAEA. GOLDSTONS SCALING ASDEX, JET, DIII-D and JT-60 and others all demonstrate the key components that derived the current scaling law
Heating Plasma Shaping Plasma Fusion Plasma Physics, Dr. Weston M. Stacey CONFINEMENT TIME SHORTFALL Q < 1! Progress in MFE Science- Tokamak Research, R.D. Stombaugh
INSTABILITIES EFFECTS OF IMPURITIES Main source: Helium Ash kinetic energy depleted First Wall Sputtering Interaction between plasma edge And material surface The Challenge of Plasma Surface Interaction, Dennis Whyte MIT EFFECTS OF IMPURITIES (CONT) Impurities can degrade plasma performance with as little as 10
mm3 of material Diverting material away from core key to sustained confinement ITER will implement additional control mechanism to moderate impurities and MHD instabilities Magnetic confinement fusion, Wikipedia OTHER CONFINEMENT DEVICES Overview of Fusion Research in Japan, Masayohi Sugitmo
WILL IT ITER WORK? YES* * ITER work for its intended purpose. To provide more degree of freedom modeling a testing with higher heating sources, magnetic confinement times. For ITER to achieve more ambitoue goals of ignition and net production Q > 10 will no doubt be a iterative process as new instabilities and analmalous transport is boudn to arise. WILL ITER WORK? PHILOSOPHICAL APPROACH
Kardashev Scale: measuring the advancement of society Extrapolates based on energy production Basis of several NASA missions Fusion alone is the only sourced deemed capable of launching us towards the next level of Advancement Kardashev Scale, Wikipedia
QUESTIONS When we look up at night and view the stars, everything we see is shinning because of distant nuclear fusion. -Carl Sagan
