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has difficulties with the stability of the plasma. This
has been an issue in tokamaks for many years, with
many modifications to the design made to counter it,
but has not really been addressed until recently with
inertial confinement, where the main thrust has been
to get as much energy out of a single shot as possible.
Late last year, though, Sandia announced that a change
to the Z-machine, adding secondary electrical coils
in a formation known as a Helmholtz pair, restrained
the plasma in a way that had never been seen before.
This kind of incremental development is essential, but
painfully slow.

A work in progress
Looking at the plan for tokamaks to reach working
generators shows how far we still have to go.
Though ITER will be twice the size of JET in every
dimension, it still won’t be a working generator. The
aim is to get considerably more power out than is put
in, but ITER is still a study machine. It is the next
device after ITER that is hoped will be the first true
generator, and even that will still be an experiment,
requiring one further stage to get to the production
machines that could pump out energy. For inertial
fusion devices, the path is less clear. There really isn’t
yet a route from the NIF or the Z-machine to reliable
generating capability.
There can be no doubt that achieving a working
fusion-based power station has been far more difficult
than was first envisaged. The basic physics is well
understood. We have clear examples in the stars of
fusion reactors acting as huge producers of energy that
stand the test of time. And there has never been more
need for a large scale, clean, green source of energy
that doesn’t consume scarce resources and doesn’t
leave a legacy of radioactive waste. Nuclear fusion has
everything to play for.
It is unlikely that we will ever reach the vision of
“energy too cheap to meter”. This quote from Lewis
L Strauss, an early chairman of the Atomic Energy

Commission hangs like a spectre over those trying to

defend the cost of nuclear power plants. It has often

been assumed that Strauss was talking about nuclear

fission, but the chances are that he had fusion in mind.

Given the difficulties involved, it seems unlikely even

fusion will ever be so cheap.

“We haven’t proved that it is economically viable,”

says Prof Cowley. “We are still focussed on whether

or not it is feasible. I know that we can do fusion, but

no one is certain if we can do it at the required scale

within reasonable costs.” But with all its advantages

over current power sources, it would be a waste

if all the work on nuclear fusion did not result in

a transformation of our energy production in the

future. It might take another 40 years – but there are

people alive today who will benefit from the change

in energy generation that fusion will bring.

BRIAN CLEGG is a science writer and the author of Dice World:

Science And Life In A Random Universe (Icon Books)

Looking like the Eye of

Sauron from The Lord Of

The Rings, plasma is held

steady in the MAST facility

FUSION DESIGN #5

TECHNOLOGY - MAST is an

experimental machine to test the

physics of tokamak technology

with a different configuration. The

spherical shape makes it possible

to produce a smaller, cheaper

device. Though it can’t be directly

scaled up to production size, the

technology will help shape the

design of fusion-based generators

in the future.

ODDS OF WINNING RACE Evens

DATE STARTED 1995

METHOD Spherical magnetic

confinement plasma tokamak

SIZE 4m in diameter

LOCATION Culham, Oxfordshire

COMPLETED 1999

MAST

(MEGA AMP SPHERICAL

TOKAMAK)

2050

is when the first fusion

power station will

enter service.