Magnetics Business & Technology - July/August 2022 - 16

FEATURE ARTICLE
Engineers and scientists from CFS and MIT's PSFC lower the superconducting magnet into the test stand in which the magnet was gradually
powered up to produce a magnetic field of 20 tesla. (Photos by Gretchen Ertl, CFS/MIT-PSFC, 2021)
Continued from page 15...
Developing the new magnet is seen as the greatest technological
hurdle to making that happen; its successful operation
now opens the door to demonstrating fusion in a lab, which
has been pursued for decades with limited progress. " The
challenges of making fusion happen are both technical and
scientific, " says Whyte, but once the technology is proven, " it's
an inexhaustible, carbon-free source of energy that you can
deploy anywhere and at any time. It's really a fundamentally
new energy source. " The recent demonstration represents a
major milestone, addressing the biggest questions remaining
about the feasibility of the SPARC design. " It's really a watershed
moment, I believe, in fusion science and technology. "
Most tokamaks use conventional electromagnets made of
copper, but the latest and largest version, under construction
in France in a multinational scientific collaboration called
ITER, uses low-temperature superconductors. For that project,
General Atomics of San Diego, California completed last year
the first module of the central solenoid, capable of reaching a
magnetic field strength
of 13 tesla, at the time
considered the world's
most powerful magnet.
The major innovation
in the MIT-CFS fusion
design is the use of
high-temperature superconductors
which
enable a much stronger
magnetic field in
a smaller space. This
design was made possible
by a new kind of
superconducting material that became commercially available
a few years ago. Until now, the only way to achieve the colossally
powerful magnetic fields needed to create a magnetic
" bottle " capable of containing plasma heated up to hundreds
of millions of degrees was to make them larger and larger.
But the new HTS material, made in the form of a flat, ribbonlike
tape, makes it possible to achieve a higher magnetic field
in a smaller device, equaling the performance that would be
achieved in an apparatus many times larger using conventional
low-temperature superconducting magnets.
Bringing that new magnet concept to reality required three
years of intensive work on design, establishing supply chains,
and working out manufacturing methods for magnets that may
eventually need to be produced by the thousands.
" We built a first-of-a-kind, superconducting magnet. It required
a lot of work to create unique manufacturing processes and
equipment. As a result, we are now well-prepared to ramp-up
for SPARC production, " says Joy Dunn, head of operations
for CFS. " We started with a physics model and a CAD design,
and worked through lots of development and prototypes to
turn a design on paper into this actual physical magnet. "
Spools of high-temperature superconducting
tape used in the new
class of fusion magnet. The magnet
built and tested by CFS and MIT
contains 267 km (166 mi) of tape.
16 Magnetics Business & Technology * July/August 2022
That entailed building manufacturing capabilities and testing
facilities, including an iterative process with multiple suppliers
of the superconducting tape, to help them reach the ability to
produce material that met the needed specifications - and for
which CFS is now overwhelmingly the world's biggest user.
They worked with two possible magnet designs in parallel,
both of which ended up meeting the design requirements, she
says. " It really came down to which one would revolutionize
the way that we make superconducting magnets, and which
one was easier to build. "
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