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The Burning Plasma Experiment in Magnetic Fusion:
What it is and how to do it
S. C. PragerUniversity of Wisconsin
February, 2004
What is a burning plasma?
A self-sustaining, self-heated plasma;
High temperature maintained by heat from fusion;
Analogous to a burning star
• Magnetic confinement
•Two approaches to fusion energy inertial confinement, magnetic confinement
international effort since 1958,development of plasma physics as a new field,now ready for frontier of burning plasmas,new challenge for international collaboration
Burning Plasmas
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
Fusion power density in sun ~ 300 Watt/m3,
in burning plasmas experiment ~10 MWatt/m3
plasma physics challenge to
•Understand a burning plasma
•Create a burning plasma
A burning plasma requires a large experiment
• Large, but “domestic-scale” (~$1B)FIRE
or
• Larger, “international-scale” (~$5B)ITER
either
Choices: domestic vs international, large vs larger
International agreement to build ITER is almost complete
ITER partners: ChinaEuropean UnionJapanRussian FederationSouth KoreaUnited States
Outline
• Burning plasmas - physics challenges
• Experimental options - ITER, FIRE
• US perspective
The fusion reaction
D + T n + 10 keV 14 MeV 3.5 MeV
The Fusion Challenge
Confine plasma that is
hot (100 million Kelvin)
dense (~1014 cm-3)
well-insulated (~1 sec energy loss time)
€
} several atmospheres
Status of Fusion Research
More than half way there, judging from
• Plasma parameters
• Physics understanding
• Timetable
Huge advance in plasma parameters
year
fusion power
The burning plasma regime is a reasonable extrapolation from current
experiments
Establishing the physics basis
Fusion plasma physics developed
for example,control of turbulence and energy lossunderstanding of pressure limits
We are ready for a burning plasma experiment
A burning plasma is self-heated by alpha particles
D + T n +
particles trapped in plasma, particles heat plasma
Generates large amount of fusion power
prior plasma experiments
• Mostly operated without fusion fuel - no tritium
• Plasmas heated by external means
• Exceptions - JET (EU) and TFTR (Princeton) generated 16 MW for 1 sec alpha particle heating, but weak
ITER will produce 500 MW for 300 sec
350 MW for 3000 sec
Why burning plasmas?
• New physics
• New technology
• Demonstration of fusion power
Burning Plasma Physics
New physics from alpha particles
• Effects on stability and turbulence
• Alpha heating and burn control
Effect of alpha particles on plasma stability
Kinetic energy of alpha particles
Plasma waves
Loss of alpha particles
Plasma cools
The Alfven Wave
in an infinite, uniform plasma
vphase = vAlfven where vAlfven ~
€
Bρ
vphase
B
Phase velocity spectrum
in a torus
vphase
waves driven by wave-particle resonance
Alpha particles excite wave,
Wave scatters alpha particles out of plasma
€
VAlfvenwave
=Valphaparticle
Alpha Heating and Burn Control
temperature
reaction rate
thermal stability
add a little alpha physics,
temperature
reaction rate
Alfven waves
loss of alphas
heating by alphas
temperature reaction rate
Alfven waves
loss of alphas
heating by alphas
turbulence
transport
etc
add some more physics
A burning plasma is a strongly coupled system
Alpha ash accumulation
resonance
Burning Plasma Technology
• Plasma technologyMaterials for high heat fluxesHigh field magnetsPlasma control tools
• Nuclear technologyBlankets for breeding tritiumMaterials for high neutron fluxes
Experimental Approaches to Burning Plasmas
FIREFusion Ignition Research Experiment
Burning, but integration later
US based (~ $1B)
ITER International Thermonuclear Experimental Reactor
Integrates burning and steady state
International partnership (~ $5B)
ITER Characteristics
strongly burning: 500 MegaWatts fusion power gain ~ 10, ~ 70 % heating by alphas
Near steady state: 300 to > 3000 seconds, many characteristic physics time scales.
technology testing, power plant scale
Strongly burning plasmas in near steady-state conditions
plasma current ~15 Meg Amps, magnetic field ~5 Tesla/SC,
temperature ~ 100 million Kelvin, density ~ 1014 m -3
The History of ITER85 discussions begin (Reagan/Gorbachev summit)
88 - 91 Conceptual Design Activities(European Union, Japan, Soviet Union, US)
92 - 98 Engineering Design Activities
99 US withdraws
98 - 01 Design of reduced cost ITER (50%)
02 Four sites proposed (Canada, France, Japan, Spain)
03 US, China, S. Korea join negotiations
03 Sites in Canada, Spain eliminated
Current Status
Stalemate on siteEU, Russia, China favor French siteJapan, S. Korea, U.S. favor Japanese
site
Hopefully resolved in upcoming months
Ready to build, negotiations underway on the site
Proposed ITER Sites
Cadarache, France
Rokkasho, Japan
Approximate ITER schedule
• Select site 2004
• Authorize construction 2004 - 5
• Construction to first plasma ~ 8 years
• Begin operation ~2015
• End operation ~2035
FIRE Characteristics
strongly burning: 150 MegaWatts
fusion power gain ~ 10, ~ 70 % heating by alphas
quasi-stationary: ~ 20 - 40 seconds,
several characteristic physics time scales
Strongly burning plasmas in quasi-stationary conditions
FIRE is comparable in size to existing tokamaks
FIRE
plasma current ~8 Meg Amps, magnetic field ~10 Tesla (Cu),
temperature ~ 100 million Kelvin, density ~ 5 x 1014 m -3
FIRE and the International Program
Envisioned as part of multi-machine strategy
• Burning plasmas in FIRE
• Steady state in non-burning plasma(e.g., KSTAR in S. Korea, JT-60 SC in Japan)
Integrate at later stage, employing new knowledge and innovation from full fusion research
FIRE Status
• Design scoping studies underway
• National effort > 15 participating institutions
• Preparing to start design in 2005
• Can be sited at one of the existing US labls
The US strategy for a burning plasma experiment
recommended by US fusion community, not necessarily the government strategy
• Join ITER
• If ITER does not go forward, proceed with FIRE
Summary
• A burning plasma experiment would be a huge step forward in plasma science, and establish the scientific feasibility of fusion energy
• ITER is a unique international science project, international from conception to execution
• FIRE is an attractive option if ITER should not move forward
Extra Slides
The Role of International Collaboration( in executing a large project)
The good• Cost sharing: essential beyond some cost
• Sharing of ideas, even in project conception
• International political support: provides stability
• International management and execution: a useful experiment, facilitates additional joint activities
The challenges
• Joint international management and decision-making(site selection, cost-sharing, procurement,…….)
• Need for international political support(need approval and sustainment from multiple governments)
International partnership to build a multi-billion dollar science facility may be without precedent
Fusion community perspective
• Ready/anxious to study burning plasmas
• Neutral to whether international or domestic in management
• The net result of the political pluses and minuses in unknown
• Any burning plasma experiment will have strong int’l collaboration
• Any burning plasma experiment will have huge scientific benefit for all nations; and establish the scientific feasibility of fusion energy.
Why Fusion Energy Research?
For fundamental plasma physics
For fusion energy• Clean - no greenhouse gases, no air pollution• Safe - no catastrophic accidents• Inexhaustible - fuel for thousands of years• Available to all nations
The US Strategy for Burning Plasmas
based on
• Three community workshops
• A 2 week community technical assessment
• Recommendations of 40 person FESAC panel
Recommended by the Fusion Energy Sciences Advisory Committee (Sept, 02)
The strategy is the strong consensus of the fusion community
Basis for the strategy
• ITER and FIRE are each attractive options for the study of burning plasma science.
• Each could serve as the primary burning plasma facility, although they lead to different fusion energy development paths
• Because additional steps are needed for the approval of construction of either FIRE or ITER, a strategy that allows for the possibility of either burning plasma option is appropriate
Recommended Strategy for US
Join ITER negotiations
ITER will be constructed?
Join ITER project; if no go, then build FIRE
US Participates in ITER
Terminate FIRE project
Build FIRE,
yes
No
Notes: advance FIRE design until US ITER decision
recommended conditions for US participation,
set time deadline for US ITER decision (~ 7/04)