place – the electrical charge on the particles to
be fused – comes to the rescue.
Ever since Victorian times we’ve known that
electrically charged particles can be steered by
magnets. It’s how the old cathode ray tube TVs
worked. So these ultra-high temperature machines
keep their fuel away from the machine itself by using
a kind of magnetic bottle, an intensely powerful
magnetic field that pushes the stream of charged
particles away from the wall of the generator.
Historically there were a whole range of
configurations for this ‘magnetic confinement’, but
in recent years one approach has dominated – the
tokamak. This Russian acronym roughly means
‘toroidal chamber with magnetic coils’ (there is some
argument over exactly what the original phrase was).
The ‘toroidal’ part tells us that the fuel is contained in
a chamber the shape of a ring doughnut, though mostmodern tokamaks have a roughly D-shaped cross-
section.
Surprisingly, getting up to those intense
temperatures has not proved the biggest problem in
taking tokamaks towards a workable fusion generator.
The heat is generally produced by a combination
of friction, caused by the resistance of the charged
particles to a high electrical current, an energy boost“The next big step, ITER will
still not be a usable power
plant, but it should crack
the break-even barrier”
The foundations for the ITER
experiment, in Cadarache, France take
shape in a picture taken last February10
is the energy factor
expected from ITER,
ie 10 times as much
energy out as
you put in.FUSION