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