34 November/December 2021
Machines
7Moving the Massive Magnet
Transporting even one of the
magnet’s modules requires ingenuity
at every turn. The main mechanism
is an enormous crane—but that’s
complicated, too. “You have to have a
crane to build the crane,” Smith says.
“The body of the crane fits on one
nine-axle truck. They have 40 to 60
semi-trucks of parts, components,
deadweights, and counterweights
that are required to come on site
for this.”
That’s all just to move the magnet
onto the truck. “I’m awed by the truck
that takes this thing out of here,”
Smith says. “There’s a gasoline enginepowering a hydraulic system, and
there’s a guy steering the back set
of wheels. I was surprised how easily
they can actually maneuver. They had
one puller unit and two pusher units.
There’s two big semi-truck diesels
behind it pushing it the whole time.”
From there, the module is loaded
onto a train, where multiple engines
help to pull the massive payload. It
eventually reaches the Caribbean Sea,
where it’s loaded onto a ship designed
to carry easy-to-load shipping
containers. With the module secured
using extreme care, it’s ready for its
journey to France.of proving that fusion is a feasible, carbon-free
energy solution. So far, no existing fusion reac-
tor has even come close to producing more energy
than it uses. This is a huge sticking point, because
the reactors use an enormous amount of electric-
ity. But armed with the Central Solenoid as its
powerhouse, ITER just may become the blueprint
for sustainable energy.
So how do you actually build a magnet of this
caliber? It’s fundamentally the same process
you’d use to create any coil-wound electromag-
net in your garage: simply twist conductive wire
around a sturdy core. Of course, this magnet is
almost unfathomably huge and is made of super-
conducting niobium and tin, making matters a bit
more complicated.
First, General Atomics sources the cables from
a manufacturing plant in Japan. Then, the mate-
rials are carefully wound together and subjected
to five weeks’ worth of heat treatment, topping
out at 1,200 degrees Fahrenheit. By “cooking”
niobium and tin into the chemical compound
Nb3Sn, the scientists transform the simple con-
ductor into a superconductor. Temperatures are
increased very progressively, maintained, and
then decreased gradually again. Finally, the
company gently loosens the springy coils so that
a special machine can wrap all 3.5 miles of cable
in insulation, inch by inch.
Afterward, engineers use 180 miles’ worth of
tape to cover all of the superconducting cable.
Meanwhile, the air inside the magnet module is
replaced with about 1,000 gallons of resin, cured
at 260 degrees Fahrenheit until solid. This satu-
rates and sets the insulation material, preventing
unwanted bubbles. Then, the entire unit must be
supercooled to just 4 Kelvin (about –450 degrees
Fahrenheit) for testing.
So far, the first module passed with f lying col-
ors. General Atomics will manufacture the other
five modules on a staggered basis, rotating among
the different construction stations for steps like
heat-treating the coils, and then taping them. “It
takes two years to make a coil from start to fin-
ish,” Smith says.
The difficulties don’t end with the manufac-
turing process, though. General Atomics is based
in California, but each module needs to make it
all the way to Saint-Paul-lez-Durance, France,
making the transport process a bit tricky (see
sidebar). After loading each module into special-
ized heavy transport vehicles, General Atomics
will ship the pieces to Houston, where a trans-
port ship will then pick them up. The company
sent Module 1 to sea in late July, and it arrived
in France by mid-August. ITER estimates that
ground transit to the reactor site will take place
sometime this fall.
Luckily, this isn’t ITER’s first rodeo—the team
is used to finagling huge pieces of equipment. For
instance, engineers have already constructed a
specially prepared, heav y-dut y road to the facilit y
in the south of France, allowing workers to bring
immensely heavy items overland—not dissimilar
to the special roads that move space vehicles from
preparation spaces to the launchpad.THE SUPERCONDUCTING
ELECTROMAGNET IS THE
“BEATING HEART” OF THE ITER
TOKAMAK—A MAGNETIC CONFINEMENT
DEVICE THAT PRODUCES CONTROLLED
THERMONUCLEAR FUSION POWER.