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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• 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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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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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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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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• 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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Historically, magnetic field technology has limited accessible space
!"#+ ∼ ./01⋆3
45.7*7Inaccessible magnetic fields with traditional
superconductors
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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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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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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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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• 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”
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