Good news for fusion energy progress and a new world record for the Chinese
Academy of Sciences, as its Experimental Advanced Superconducting Tokamak
(EAST), or "artifical sun," maintains 70 million degrees Celsius (126
million °F) for 1,056 seconds.
High-temperature plasma is a critical part of many large-scale fusion energy
initiatives, which attempt to replicate some of the conditions that make the
Sun a powerful enough fusion reactor to warm our solar system, with the goal
of eventually supplying safe, clean energy for humankind.
Heat can be viewed as an energetic vibration of atoms, and this vibration
becomes so extreme at ultra-high temperatures that atoms begin to randomly
smash into one another with enough speed to jam their nuclei together,
fusing them together and creating a new atomic element.
If you're using lightweight atoms from the lower end of the periodic table –
like the Sun does, fusing hydrogen into helium – the new atom weighs less
than the original two combined, and the difference in mass is ejected as
thermal energy. At the core of the Sun, temperatures around 27 million °C
(48.6 million °F) fuse about 620 million metric tons of hydrogen into about
616 million metric tons of helium every second, converting some 4 million
tons of matter into energy.
A small proportion of this eventually reaches us here on Earth as
electromagnetic radiation, supplying us with visible light, ultraviolet
light, infra-red, radio waves, X-rays and gamma rays, and without this
generous solar gift of energy, life as we know it would never have been
possible.
Tokamak-style fusion reactors like the International Thermonuclear
Experimental Reactor (ITER) obviously don't have the colossal scale and
gravity of the Sun, but they aim to heat up hydrogen atoms – specifically,
deuterium and tritium isotopes – to a point where they begin smashing
together, fusing and releasing energy that can both be harvested, and
sustain the reaction as additional hydrogen atoms are fed in.
ITER's target temperature is 150 million °C (270 million °F). China's EAST
facility, which is a key contributor to the ITER project, has hit this mark
already, reaching 160 million °C (288 million °F) for 20 seconds, and
holding 120 million °C (216 million °F) for 101 seconds in separate
experiments announced last May.
The latest experiment tested the Chinese tokamak's capability to endure
extreme temperatures over longer periods, sustaining a temperature 2.6 times
hotter than the Sun's core for some 1,056 seconds, or 17 minutes and 36
seconds. Nobody's ever sustained a high-temperature plasma for 1,000 seconds
before, so this is an important milestone.
It's natural to wonder how these insane temperatures can possibly exist on
Earth without causing the entire tokamak facility to melt down or burn to a
crisp. Essentially, the donut shape of the tokamak's inner chamber is lined
with the most heat-resistant materials available – tungsten and carbon, for
example. Since even these would be destroyed if exposed to hundreds of
millions of degrees, the superheated plasma is squashed right into the
middle of the chamber, as far from the walls as possible, using powerful
magnetic fields.
Most importantly, though, these extraordinary temperatures are achieved in a
tiny amount of plasma relative to the size of the chamber, so the energy
dissipates rapidly before it reaches the walls.
It's important to clarify: EAST has not created a fusion reaction here, just
a sustained, superheated plasma similar to the kind that will eventually be
used to create fusion. So it's a long way from being energy-positive at this
point. Tokamak-style fusion is still many years from that lofty goal at this
point, and the globe-spanning ITER project has already been described as the
most expensive science experiment of all time and the most complicated
engineering project in human history, since even when it does generate heat
from fusion reactions, it'll vent that heat rather than attempt to capture
and use it.
Indeed, we'll likely have to wait for a "DEMO" class successor to the ITER
facility, like the one planned by EUROfusion, before we see a large tokamak
generating useful amounts of electricity. Where ITER is shooting for a Q
value of 10 – putting in 50 MW of thermal energy and generating 500 MW of
gross thermal output, the EU's DEMO reactor aims to put in 80 MW and
generate some 2 GW for a Q factor of 25.
That's currently planned to begin operation in 2051. Ah well, 29 years away
is better than 30.
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