Libby TolmanIAP @ PSFCJanuary 15th, 2019Acknowledgments: Jerry Hughes, Catherine Fiore, Jeff Freidberg, Martin Greenwald, Zach Hartwig, Alberto Loarte, Bob Mumgaard, Geoff Olynyk, Brian LaBombard, Dennis Whyte

Introduction to magnetic fusion and the SPARC project

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• What is fusion?

• Advantages of fusion as an energy source

• How we get fusion on earth

• Progress of the tokamak to date

• The SPARC project

• Profiles of students at PSFC involved in fusion development

Please raise your hand at any point with questions!

Outline of talk

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What is fusion?

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• Fusion happens when isotopes lighter than iron combine to form heavier nuclei, with less final mass

• The extra mass is released as energy

2mcE =

Fusion is a basic physical process that produces energy

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Fusion is the energy source of the sun

• The sun is powered by the fusion of hydrogen

• Over its 4.5 billion year lifetime thus far, the Sun has lost approximately the mass of Saturn through this process

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Advantages of fusion as an energy source

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Global warming, economic development present energy challenges

Smog in New Delhi, India (source: Vox)

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As an energy source on earth, fusion would have advantages

• No emissions

• Nearly inexhaustible fuel supply (deuterium and lithium, which is used to breed tritium)

• High power density land use

• On when needed

• Can be sited anywhere

• No chain reaction = no possibility of meltdown

• No long-lived nuclear waste for deep storage (lower level activation of components)

• Low proliferation risk

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How we get fusion on earth

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Fusion is hard because nuclei tend to repel

• Like charges repel (Coulomb force)

• Throw them at each other and they tend to scatter

• To obtain fusion, nuclei must be confined over numerous scattering times

• High temperature is necessary for significant fusion probability

confinement mechanism

(107 K)

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At high temperatures necessary for fusion, materials become plasma

• When energy is added to matter, phase changes can occur à new physical properties

• When sufficient heat energy is added to matter, bound electrons strip from the nuclei

• Plasma = “soup” of negatively charged electrons and positively charged nuclei

Add heat

Solid / liquid / gas Plasma

Neutron

Proton

e–e–

e–

e–

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The sun confines and heats its plasma fuel through gravity

Pressure from

gravity

Proton-proton fusion

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Fusion bombs use x-rays from fission primary to compress fusion fuel

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Magnetic fusion energy uses magnetic fields to confine plasma

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Tokamaks confine plasma by wrapping field lines in a donut shape

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A twist is necessary to confine plasma in toroidal geometry

• Field is weaker on the outside

• Plasma wants to expand

• Hole gets bigger

• Need to wrap the field lines around the plasma like on a barber pole

• Can do this by passing a current around the plasma

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Tokamak power plant uses fusion reaction to provide power

D+T plasma: makes

neutrons and alpha particles

magnet

blanket: breeds tritium, captures energy

heat exchanger

turbine generator

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Plasma conditions determine tokamak energy production

Plasma density Plasma temperature Energy confinement

n × T × τE“fusion triple product”

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!"#E is related to relationship between rion and device size

Wall

Plasma

Low B

High B

$%&'Plasma temperature, set by fusion cross-section

Magnetic field, set by device magnets

Make many of these fit inside the device

$%&'~"�*

• Basic understanding of triple product can be obtained by considering how many times the ion gyroradius fits inside device

• More gyroradii in device = better energy confinement, higher temperature, better able to hold plasma

• Higher magnetic field and larger device size are both good for triple product

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Rigorous analysis says:

!"#+ ∼ ./01⋆3

45.7*7How good your tokamak is at

producing energy

Devicesize

Plasma physicsDevice magnetic

field strength

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Progress of the tokamak to date

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• The ratio of fusion power producedto plasma heating power suppliedis defined as capital Q:

• Q=1 à BreakevenQ=∞ à Ignition (no external heating)

• Q increases as triple product increases

8 = :;<=>?@:ABCD>@E

Progress has been made towards net energy with tokamaks

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Roughly 170 tokamaks have been built worldwideAlcator C-Mod, Cambridge, MA, USA

DIII-D, San Diego, CA, USA

ASDEX Upgrade, Garching, Germany

EAST (HT-7), Hefei, Anhui, China

Joint European Torus (JET), Oxfordshire, UK

JT-60SA, Naka, Japan

KSTAR, Daejeon, Republic of Korea

SST-1, Gandhinagar, Gujarat, India

Tore Supra, Cadarache, France

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• C-Mod is a compact device with some pretty hefty parameters

• Operated until 2016

• Magnetic field at the plasma center up to 8 T (>100,000 x Earth’s surface magnetic field)

• Plasma densities span the range expected for reactors

• Volume averaged plasma pressure of 2 atmospheres (world record)

Alcator C-Mod

Next door is a tokamak—tour follows lunch

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Q for next-generation tokamak designs depends on size, field

!"#+ ∼ ./01⋆3

45.7*7

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Historically, magnetic field technology has limited accessible space

!"#+ ∼ ./01⋆3

45.7*7Inaccessible magnetic fields with traditional

superconductors

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ITER, a tokamak under construction with Q∼10, is a large device

Human

2820

Cadarache

• Joint effort among China, EU, India, Japan, Korea, Russia, US

• Political origin: 1985 Geneva summit

• ITER agreement reached in 2006

• Construction began in 2010 in France

• Construction cost > €10B

• First plasma: 2025

• D-T operations: 2035

ITER aims to demonstrate scientific, technological feasibility of fusion

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The SPARC project

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Recent developments enable smaller and faster fusion development

• Large size and resulting slow development has traditionally been a major drawback of fusion

• Recent technological developments present faster, smaller pathways

• High temperature, high field superconductors (HTS) have been developed

• HTS tapes have recently become an industrially produced product

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HTS expands accessible parameter space

!"#+ ∼ ./01⋆3

45.7*7Now accessible!

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ARC study (2015) outlined the size reductions allowed by HTS

• Design study led by MIT students

• Conceptual design of demonstration fusion pilot power plant that obtains ITER-level performance in much smaller size

ITER

Torus Radius [m] 6.2Magnet Technology LTS

Magnetic Field Strength [T]

5.3

Pfusion [MW] 500Pelectric [MW] 0

ARCTorus Radius [m] 3.2

Magnet Technology HTSMagnetic Field

Strength [T]9.2

Pfusion [MW] 500Pelectric [MW] 200

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Intermediate steps needed to reach ARC

• ARC requires too big of an investment and is too big of a step in technology, plasma physics to build immediately

• After ARC design study, MIT PSFC leadership started discussing the most important elements of ARC to develop and demonstrate and how they could be packaged in an achievable project

• Desire to attract private capital as funding

• Result of this deliberation is the SPARC project (soonest [or smallest] possible ARC)

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SPARC

~ 12 T, 100 MW, Q=2-5

In spring, PSFC started the SPARC project as first step towards a reactor

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SPARC funded with novel private financing strategy

• MIT PSFC remains an independent research establishment

• Providing scientific R&D to the joint project

• Bringing the best of both worlds together: the scientific underpinnings from tokamak research and the speed, capital, and drive of the private sector

• CFS is a private company

• Investor-backed with the aim of commercializing the high-field path

• Investors are in it for the long haul with capital to see it through

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Commonwealth Fusion Systems (CFS) announced in March 2018

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SPARC has attracted significant investment capital

• CFS has attracted significant capital from a range of investors

• Leading investor is Italian oil company ENI ($50 million)

• Other investors include billionaire-led Breakthrough Energy Ventures and The Engine

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First step of SPARC is magnet development: ongoing presently

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Profiles of students at PSFC involved in fusion development

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PSFC attracts devoted scientists, engineers, and technical staff

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• Received A.B. (2015) in Physics from Princeton

• Loves challenging physics problems

• Explored many areas of physics in undergrad (black holes etc.), but was drawn to the practical applications of plasma physics and fusion

• At MIT, focuses on plasma instabilities relevant to the confinement of energetic fusion products in high magnetic field tokamaks

• Computational and analytical work, in close collaboration with experimentalists

Libby Tolman, Ph.D. student in Physics (Me)

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Erica Salazar, Ph.D. student in Nuclear Science and Engineering

Erica, the only female engineer in the General Atomics magnet development program and the leader of her team

• Received B.S. (2010) and M.S. (2012) in Mechanical Engineering from Stanford

• Deeply passionate about technological challenges

• Worked for 5 years at General Atomics manufacturing magnets for ITER

• Wanted to move more into research and heard about the SPARC project

• Came to PSFC as a PhD student to work on SPARC magnet development

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Lucio Milanese, Ph.D. student in Nuclear Science and Engineering

• Grew up in Italy, and learned basics of fusion at a young age

• Was fascinated by Fusion Power Plant in SimCity 4

• While interviewing to get into undergrad at Imperial College, plasma physics professor asked him how to confine a plasma

• Realized fusion research was actually happening!

• At PSFC, uses analytical and computational methods to study how different types of turbulence interact to determine how heat is confined in a plasma

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Leigh Ann Kesler, Postdoc

• Grew up in Illinois on a corn and soybean farm

• Learned about fusion through writing assignment in high school

• For undergrad, studied Nuclear, Plasma, and Radiological Engineering and worked in a lab that focused on plasma-material interactions

• Came to MIT for PhD in Nuclear Science and Engineering

• Currently uses experiments to study the effects of neutron damage on HTS

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• Fusion is a fundamental energy source that powers the sun

• Fusion has many attractive features as an energy source on earth

• One device for obtaining fusion is the tokamak

• The tokamak has made significant progress to date, but has not yet achieved break even

• The SPARC project aims to accelerate fusion development using high temperature superconductors

• PSFC’s path to fusion has attracted a diverse and passionate set of scientists and engineers

Summary

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Recommended resources for additional learning

• More info about what we discussed today and discussion of alternative fusion concepts: IAP 2017 talk “MIT’s Pathway to Fusion Energy” : https://www.youtube.com/watch?v=L0KuAx1COEk

• C-Mod tour at 1:00 pm

• Future IAP events:

Jan. 16th, 10 am, here: “Design your own fusion plant with Excel”

Jan. 18th, 11 am, here: “Inertial confinement fusion and high energy density physics at the NIF, OMEGA, and Z” (tour follows)

Jan. 22nd, 1 pm, 34-101: “The MIT Fusion Landscape”

Jan. 23rd, 11 am, here: “Overview of the Divertor Tokamak Test Facility project”

Jan. 26-27th, starting at 10 am, here: “Hack for Fusion: A Machine Learning Hackathon at MIT’s Plasma Science and Fusion Center”