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)