Magnetic Reconnection in plasma; a Celestrial Phenomenon in the Laboratory
Jan Egedal
April 17, 2018
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• Fusion - Why do we care?
•What is a Plasma?
•Definition
•Examples
•The fuel for fusion power is a plasma
•Applications of plasma physics
•What are we working on?
• Projects around the world
Outline (first Fusion)
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mii.org
Some familiar forms of fuel
U235
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mii.org
15 kJ/g
40 kJ/g
20 kJ/g
3 kJ/g
Energy density of non-nuclear fuels
U235
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Hydroelectric
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Wind
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Solar
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Nuclear
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Coal
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The scale of industrial power production is immense
Global Energy Production per Year
~ 400 QBtu = 1 quadrillion Btu = 1015 Btu
~ 4 x 1020 J
~ 3 x 1012 Watts
The US contributes 25% of this total
~ 1020 J/year per person in the US
~ 10 kW per person per year
Where does our 10 kW per person per year come from?
People use a lot of energy.
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Only about 15% of US energy is supplied by
Nuclear and Renewable Sources
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New nuclear energy sources
U235
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• The nucleus contains
protons (+) and neutrons (no charge)
• Protons (+) in nucleus want to repel each other due to electromagnetic forces
• Nucleus is held together by the strong force (nuclear force)
• Powerful enough at atomic
scale to overcome repulsion of protons (+)
Oxygen Atom
Oxygen Nucleus
Nuclear forces we do not experience directly in our daily lives
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The binding energy curve shows the nuclear
energy available from fusion and fission
U235
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U235
Nuclear Reactions of Interest for Energy Production
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mii.org
15 kJ/g
40 kJ/g
20 kJ/g
3 kJ/g
Nuclear fuel has much higher energy density
than wood or coal or gas
U235
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mii.org
15 kJ/g
40 kJ/g
20 kJ/g
3 kJ/g
Nuclear fuel has much higher energy density
than wood or coal or gas
U235
50 Million
kJ/g
350 Million
kJ/g
Nuclear fuel has much higher energy density
than wood or coal or gas
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U235
Like charges repel each other
Issue 1:
Particles must have enough energy to
overcome the coulomb barrier.
Therefore: fuel must be very hot (100 Million Degrees)
The Problem: Coulomb Barrier
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Plasma
U235
Plasma is the so-called “4th state of matter”
States of matter are organized by average energy per particle.
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Definition of Plasma
U235
Matter becomes a plasma when the electrons have enough energy to “detach” from their nuclei (ions). Temperature is a measurement of average (random) energy per particle. In plasma physics we measure temperature in electron-volts (eV) 1 eV = 11,600 K = 20,400° F
States of Matter - Plasmas
• Molecules no longer exist, Hydrogen and Oxygen disassociate: 2H2O 2H2 + O2 and ionize: H2 2H+ + 2e-
• Ions and electrons are free to move, but feel a force from each other. Coulomb collisions dominate.
• Temperatures are extremely high: T > 11,000 °C • Plasmas are good conductors of electricity and heat
Forces of Fields on Plasma
•The plasma now feels
a force from the
magnetic field
•Ions and electrons
follow the field lines
•Plasma is confined
•More organization
ion electron
Magnetic Field Lines
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Plasma Examples
U235
Lightning
Sun / Stars
Interstellar “Gas” / Nebulae
Ionosphere / Northern Lights
Neon Lights / Florescent Lights
Plasma TV
Plasma deposition for semiconductors
Fusion
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The Horsehead Nebula
U235
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Sun
U235
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Sun
U235
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Simple Fusion Power System Concept
U235
Generator Turbine
Deuterium
Tritium
Fusion
Plasma
Heat Exchanger
Lithium
n
Magnet
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Inertial Confinement
Image: National Ignition Facility
A tiny chamber made of gold contains a frozen pellet of heavy hydrogen fuel
Laser beams enter through the two open ends of the hohlraum. The beams bombard the inside walls of the hohlraum generating x-rays that are reflected in toward the fuel capsule, heating it, causing it to implode to produce the fusion reaction.
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Inertial Confinement, National Ignition Facility (NIF)
U235
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Magnetic Confinement
U235
From Basic physics – cyclotron orbits a. Good confinement perpendicular to B b. No confinement parallel to B
Uniform Field Incomplete confinement!
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Tokamak Magnetic Geometry
U235
Combined toriodal and poloidal fields
How much magnetic field?
5 Tesla: 100,000 times the earth’s field
The Tokamak Device
Solenoid
Shaping and Control Coils
Plasma Toroidal
Field Coils
JET TOKAMAK, UK (biggest in the world)
Inside JET
Fusion Just Around the Corner
MST
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Current Status of Global Fusion Research
U235
•We are ready for ignition.
•ITER is begining construction in
Cadarache, France
•Following ITER comes DEMO
tentatively in Japan.
•There is still a long road ahead:
Optimistic forecasts still predict it
will be 30 years before DEMO
•DEMO would be a
demonstration tokamak reactor
n (m^-3)
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ITER
U235
Plasma Parameters: Major Radius: 6.2m Minor Radius: 2m Volume: 837m3 B: 5.3T Ip: 15MA Gain: 10 Net Power Out: 410MW Alpha Power: 82MW External Heating Power: 40MW (from beams and ICRF) Energy Confinement time: ~3.7s Equipped with Superconducting Coils
Tore Supra
ITER
ITER has a site… Cadarache, France
Magnetic Reconnection in Fusion Devices
Reconnection in ITER could destroy the device:
International Thermonuclear
Experimental Reactor
Magnetic Reconnection in Fusion Devices
Reconnection in ITER could destroy the device:
International Thermonuclear
Experimental Reactor
Magnetic Reconnection in Fusion Devices
Fusion: Internal relaxations (strong guide field)
Magnetic reconnection is observed together with loss of core energy
during “sawtooth crash” (Yamada, Phys. Plasmas, 1994)
Dens. Vs. time
Example of model for Sawtooth
Crash: Kolesnichenko, PRL 1992.
• More Pretty Pictures
• Models for Reconnection
• Spacecraft Observations
• TREX, the Terrestrial Reconnection EXperiment
(“The” Reconnection EXperiment)
• Conclusions
Second Outline
Jan Egedal Les Houches, March, 2015
Magnetic Reconnection • A change in magnetic topology
in the presence of a plasma
Plasma carrying a current
Magnetic fields
j
Consider a small perturbation
Jan Egedal
Magnetic Reconnection • A change in magnetic topology
in the presence of a plasma
Consider a small perturbation
Jan Egedal
• A change in magnetic topology
in the presence of a plasma
Magnetic Reconnection
Consider a small perturbation
Jan Egedal
• A change in magnetic topology
in the presence of a plasma
Consider a small perturbation
Jan Egedal
Magnetic Reconnection
• A change in magnetic topology
in the presence of a plasma
Magnetic Reconnection
Nearly all the initial magnetic energy is converted into:
1. thermal energy
2. kinetic energy on fast electrons and ions
3. kinetic energy of large scale flows
Consider a small perturbation
Jan Egedal
Coronal Mass Ejections
The most powerful explosions in our solar system
Can power the US
consumption of
electricity for 10
million years
Jan Egedal Les Houches, March, 2015
Coronal Mass Ejections
Movie from NASA’s Solar Dynamics Observatory (SDO)
Jan Egedal Les Houches, March, 2015
The Solar Wind affects the Earth’s environment
Space Weather
Jan Egedal
Magnetic Storms
Jan Egedal
Aurora Borealis
October 26th, 2011, Kola Peninsula, Russia
Jan Egedal
Carrington Flare (1859, Sep 1, am 11:18)
• Richard Carrington (England) first observed a solar flare in 1859.
• White flare for 5 minutes.
• Very bright aura appeared next day in many places on Earth including Cuba, the Bahamas, Jamaica, El Salvador and Hawaii.
• Largest magnetic storm in recent 200 years (> 1000 nT). Telegraph systems all over Europe and
North America failed, in some cases even shocking telegraph operators. Telegraph pylons threw sparks and telegraph paper spontaneously caught Fire. (Loomis 1861)
http://en.wikipedia.org/wiki/Solar_storm_of_1859 Jan Egedal
Magnetic storm and aurora on March 13, that lead to Quebeck blackout (for 6 million people)
Magnetic storm ~ 540 nT, Solar flare X4.6. A Carrington Flare today 30 – 70 billion dollars of damage
Jan Egedal
Electromagnetism 101
• Faraday’s law:
• Faraday’s law for a conducting ring: EMF=0.
dt
dBAreaEMF
• The magnetic flux through the ring is trapped • This also holds if the ring is made of plasma plasma frozen in condition
Jan Egedal
Reconnection: A Long Standing Problem
Jan Egedal
Simplest model for reconnection:
E + v×B = j [Sweet-Parker (1957)]
XjE
tX
X
Reconnection: A Long Standing Problem
Jan Egedal
59 Jan Egedal
Standard two-fluid equations
Anisotropic pressure model
• Moments over kinetic model yields fluid closure with anisotropic pressure, EoS, [Le et al., PRL 2009]
• EoS implemented by O Ohia using the HiFi framework developed in part by VS Lukin
EoS Implemented in Two-Fluid Code
Large Scale Fluid Simulation
p||/p
Jy
0
2
0
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Kinetic Simulations for Fine and Medium Scale Dynamics
Jan Egedal
Use the biggest super-computers to simulation the plasma one particle at the time
NASA’s Pleiades
Particle-In-Cell (PIC) codes scales well to architectures with millions of CPUs
Kinetic Simulations for Fine and Medium Scale Dynamics
e|| / Te
E||
E||
E||
E||
Jan Egedal
MMS Successfully Launched!
Jan Egedal
March, 12, 2015 Magnetospheric Multiscale Missing
The Magnetosphere as a Laboratory
Jan Egedal
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MMS October 16, 2015 event (Burch et al., 2016)
[Fig 3, Burch et al., Science, 2016]
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MMS October 16, 2015 event (Burch et al., 2016)
[Fig 3, Burch et al., Science, 2016]
B out-of-plane
B Normal B out-of-plane
Diffusion Region Electron Beams
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MMS4
[Egedal et al., PRL, 2018]
Zoom-in from Kinetic simulation
Diffusion Region Electron Beams
[Egedal et al., PRL, 2018]
The Madison Plasma Dynamo Experiment
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Vacuum pumps
Helmholtz coil(s)
20kW magnetron
LaB6 cathodes
2D sweep probe
Water cooling
Interferometer
Insulated Al vacuum vessel
Madison Plasma Dynamo eXperiment
TREX Upgrades, 2015
• New internal coils • Redesigned heating and
reconnection drives • Better/more diagnostics
Flux array measures in-plane fields in a single shot
Area covered by 160 channel magnetic flux array.
Cross-section of TREX implemented in the MPDX facility
Plasmoids observed!
Plasmoids observed!
Plasmoid
J along separators
Olson et al., PRL, 2016
• The new TREX experiment is now online. It provides huge flexibility in available configurations.
Conclusion
• Reconnection is fascinating a process which is still purely understood.
• It powers the production of energetic particle is celestial objects and is being investigated by a fleet of NASA spacecraft
Jan Egedal
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Advantages of Fusion as an Energy Source
U235
Unlike nuclear fission (the current means of producing nuclear power),
fusion does not produce long-lived nuclear waste.
•Also unlike fission, fusion fuel is not a proliferation threat (you can’t build nuclear bombs out of it).
• Again unlike fission, fusion plants do not pose any danger of
meltdown or any catastrophic failure.
• Unlike fossil fuels, fusion does not cause climate change, acid rain,
smog or have any emissions whatsoever, and will never* run out.
• Unlike most renewables (wind, solar, hydroelectric, etc) fusion is 24/7
and does not occupy vast amounts of land or coastline.
* Terrestrial Lithium Reserves for D-T fusion: 30,000 years.
Ocean Deuterium reserves for D-D fusion: ~1 Billion years (of order predicted lifetime of the planet)
Magnetic Topology Constant in Ideal Plasma
– Ideal Plasma
B B
0' BvEE 0'E Plasma and B frozen together
Ideal MHD: E·B=0,
Excellent for 99.9% of all plasmas, 99.9% of the time.
Jan Egedal
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