NOV 17, 2017 5:06 PM PST

L to H mode transition: the key mechanism to fusion success

WRITTEN BY: Daniel Duan

Fusion experiment: MAST Plasma. Credit: CulhamFusionEnergy

Francois Ryter from Germany’s Max Planck Institute for Plasma Physics has won the IAEA’s 2017 Nuclear Fusion Journal Prize for experimental work elucidating a mechanism that can trigger a fusion plasma to a state that allows the fusion device to operate under high performance.

To produce energy from fusion, scientists must control the temperature, density and lifespan of the plasma fuel. Since all deuterium/tritium fuelled fusion takes place at 150 million degrees Celsius, the two variables that can be controlled to produce fusion are plasma density and lifespan.

At one end of the spectrum is low density, long lifespan fusion, in which the low density produces a relatively small number of energy producing collisions, but the plasma is long lived enough to achieve sufficient interactions to generate energy. Because the plasma is held stable (confined) for these long periods using magnetic fields, this technique is referred to as magnetic confinement fusion. The International Thermonuclear Experimental Reactor (ITER) uses this approach in its tokamak to generate fusion.

At the other end of the spectrum is very high-density plasma with very short lifespans, referred to as inertial confinement fusion. Using extremely rapid compression to heat a capsule of fuel to fusion temperatures, inertial confinement fusion takes place in a matter of nanoseconds and produces a short-lived burst of energy. The National Ignition Facility is the world’s largest inertial confinement fusion research facility.

Initiating and sustaining fusion takes a lot of energy and a key issue is being able to achieve the condition in which the fusion output power exceeds the auxiliary input power supplied from outside to sustain the reaction. The operation of ITER in so called high (H)-mode is critical to achieving this condition.

The award-winning paper has shown that, of the several factors that had been considered as potential triggers for the transition from the low (L)-mode confinement state of the device to H-mode, ion heat flux is key. This video shows the transition of the plasma from L-mode to H-mode inside a tokamak. The transition occurs at around 0:22.

The findings can improve the capability to predict the amount of input power required to operate the device in H-mode. Filling this kind of gap in the understanding of magnetic confinement plasma physics can facilitate the preparation for the operation of future fusion reactors for energy production.

Source: IAEA

About the Author
  • Graduated with a bachelor degree in Pharmaceutical Science and a master degree in neuropharmacology, Daniel is a radiopharmaceutical and radiobiology expert based in Ottawa, Canada. With years of experience in biomedical R&D, Daniel is very into writing. He is constantly fascinated by what's happening in the world of science. He hopes to capture the public's interest and promote scientific literacy with his trending news articles. The recurring topics in his Chemistry & Physics trending news section include alternative energy, material science, theoretical physics, medical imaging, and green chemistry.
You May Also Like
MAR 21, 2020
Chemistry & Physics
MAR 21, 2020
Ergodic Theory Earned Retired Duos the Top Prize in Maths
The Abel Prize, organized by the Norwegian Academy of Science and Letters, is the world's highest honor in mathemati ...
MAR 29, 2020
Space & Astronomy
MAR 29, 2020
NASA is Sending This Golden Box to Mars to Make Oxygen
NASA’s Perseverance rover, formerly known as just the Mars 2020 rover, will do quite a bit more than merely drive ...
APR 19, 2020
Chemistry & Physics
APR 19, 2020
This polymer degrades faster in the ocean
New research supported by the National Science Foundation's Center for Sustainable Polymers showcases a novel kind o ...
MAY 08, 2020
Chemistry & Physics
MAY 08, 2020
Scientists to Spiders: How Do You Handle Sticky (Nanofiber) Situation?
The term "biomimicry" describes the models and methods harnessed by scientists to imitate natural element ...
MAY 07, 2020
Chemistry & Physics
MAY 07, 2020
What can we learn from catnip?
Findings from a recent study published in Science Advances report new insights on the evolution of a commonly enjoyed pl ...
MAY 21, 2020
Chemistry & Physics
MAY 21, 2020
The Nature of Glass Still Dumbfounds Scientists
There are many things we humans have come to perfect, but don't yet fully understand. Take glass for example, scientists ...
Loading Comments...