Plasma cooking using microwave ovens

Lead author Yuriy Viktorovich Kovtun, despite being forced to evacuate the Kharkiv Institute of Physics and Technology amid the current Russian-Ukrainian war, has continued to work with Kyoto University to produce stable plasma using microwaves.

Getting the plasma right is one of the hurdles to harnessing the massive amounts of energy that nuclear fusion promises.

The plasma—the soup of ions and electrons—must be kept at the right density, temperature, and duration for the atomic nuclei to fuse together to achieve the required release of energy.

One recipe involves the use of large donut-shaped devices with powerful magnets containing plasma while carefully aligned microwave generators heat the atomic mixture.

Now, Kyoto University’s Institute for Advanced Energy, has collaborated with the Kharkiv Institute and the Max Planck Institute for Plasma Physics, to produce plasma with a density suitable for melting, using low-frequency microwave energy.

The research team identified three important steps in plasma production: the lightning-like collapse of the gas, the initial production of the plasma, and the stable plasma. The study is being conducted using the Heliotron J, the latest iteration of experimental fusion plasma devices at the Institute for Advanced Energy, located on Kyoto’s Uji campus in southern Kyoto.

“At first, we did not expect these phenomena in Heliotron J but were surprised that the plasma forms without cyclotron resonance,” explains Kazunobu Nagasaki, group leader.

Building on decades of experience, the Nagasaki team explores fusion plasma discharges on Heliotron J.

The team injected intense bursts of 2.45GHz microwave energy into the feed gas. Microwaves in the home operate at the same frequency but the J heliotron is about 10 times more powerful and is concentrated to a few gas atoms.

“Unexpectedly, we found that microwave detonation without alignment of the magnetic field of the J heliotron created a discharge that rips electrons from their atoms and produces a particularly dense plasma,” Nagasaki said.

“We are very grateful that our colleague can continue to support the study, despite the war in Ukraine. Our findings on this method of generating plasma using microwave discharges may simplify future fusion research.”

Publication of the research in the journal Problems of atomic science and technology.