Transcript Tokamaks and Spheromaks .

Tokamaks and Spheromaks
Kevin Blondino
5 November 2012
“We say that we will put the sun into a
box. The idea is pretty. The problem is,
we don’t know how to make the box.”
-- Pierre-Gilles de Gennes
Summary of Fusion
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Fusion of light nuclei into heavier ones
releases energy.
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Most popular candidate for reaction is the D-T
cycle. Others include D-D and D-3He.
Overwhelming majority hypothesize that
magnetic confinement is the way to go.
Lawson criterion is to be met for fusion to be
a viable energy source.
What is a Tokamak?
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The confinement of plasma as a torus using
external magnetic fields.
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Field lines are required to move around the torus
in a helical shape, generated by a toroidal and
poloidal field.
Most popular candidate for thermonuclear
fusion.
Russian acronym for “toroidal chamber with
magnetic coils.”
The overall goal is to produce a
magnetic field that follows around the
torus while also wraping around it.
History of the Tokamak
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Invented in the 1950’s by Igor Tamm and
Andrei Sakharov in the Kurchatov Institute.
Introduced to the public in 1968, with results
that demolished competition from every other
design.
Still the most developed for fusion: ITER,
NSTX, Pegasus Toroidal Experiment, and
many more.
What is a Spheromak?
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Confinement of plasma through self-induced
magnetic field
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The current due to the flow of plasma creates a
magnetic field, which in turn, confines it.
Less popular candidate for fusion
Considered a compact toroid
Name is the arrangement of plasma, not the
device that generates it
History of the Spheromak
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Initially developed to study magnetohydrodynamical
waves in astrophysical plasma in 1959 by Hannes
Alfvén (Alfvén waves).
ZETA machine provided boom in design ideas,
including the spheromak.
By the 1980’s, tokamaks surpassed confinement
times by orders of magnitude.
SSX and SSPX in 1994
Pros
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Tokamak:
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Highly scalable
Relatively simple to control and model
Spheromak:
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Much less upkeep power required
Generally smaller
No complicated magnets required
Cons
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Tokamak:
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Large power requirement due to “brute force”
method
Cryogenics required for superconducting magnets
Spheromak:
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Hard to scale up
Plasma behavior is complex and hard(er) to
predict and control
General Problems with Fusion
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High energy neutrons could be damaging
Turbulence! – something not quite understood
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Some hypothesize that there is some underlying quantum
mechanical effect that has not been taken into account or
not yet discovered that causes it.
Sputtering – when higher mass particles are mixed into the
fuel, lowering its temperature.
“…squeezing a balloon – the air will always attempt
to pop out somewhere else.”
KSTAR
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Korea Superconducting Tokamak Advanced
Research at the National Fusion Research
Institute in Daejon, South Korea.
Completed in 2007; first plasma in July 2008
Features fully superconducting magnets
Uses hydrogen and deuterium fuels (D-D
cycle), but not deuterium-tritium
ITER
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International Thermonuclear Experimental Reactor
being built in southern France; will be the largest and
most powerful tokamak
EU, India, Japan, China, Russia, South Korea, and
the US is funding and running
Designed to produce 500 MW output for 50 MW
input
First plasma production scheduled for 2020
DEMO, the successor to ITER, will be the first power
plant scheduled to make fusion energy in 2033.
SSPX
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Sustained Spheromak Physics Experiment at
Lawrence Livermore National Lab
Completed in 1999
One of the only spheromaks actively
researching fusion
References
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http://plasma.physics.swarthmore.edu/ssx/
http://en.wikipedia.org/wiki/Tokomak
http://en.wikipedia.org/wiki/Spheromak
http://www.iter.org/
https://www.llnl.gov/str/Hill.html