Generating plasma using a strong magnetic field directly from solid metal

Plasmas are widely used in many industrial and scientific applications. Typically, a strong electric field is applied to a liquid or gas to generate the plasma. This can be done many ways, but one useful method is microwave excitation, which generates the electric field inside a resonator cavity and enables the generation of radical ions and the use of the luminescence spectra of the elements.

Fujii and Fukushima used this technique to produce a magnetic field, rather than an electric field, producing plasma directly from magnesium and calcium metal solids. They studied the efficient reduction of metal oxides by microwave irradiation and found that metal ions play an important role in lowering the temperature of the reduction reaction.

“The high magnetic field inside the microwave cavity allows efficient generation of metallic plasma without the use of gases or liquids, and its stability is maintained,” said author Satoshi Fujii.

The authors supplied microwave radiation into the resonator cavity, which produced a magnetic field and induced a current in the solid metal. Electrons and ions were emitted due to this induced current and were generated as plasma due to the magnetic field. The authors ensured the stability of the plasma by maintaining the resonant mode and supplying energy by increasing the microwave frequency during the generation process.

Traditional methods of plasma generation are very energy-intensive, and the authors hope their method will reduce electricity requirements and therefore be more environmentally friendly.

“By using this reduction method, it is possible to reduce CO₂ emissions and increase profits,” said Fujii.

Source: “Metal ion plasma generation under strong magnetic field in microwave resonator,” by Satoshi Fujii and Jun Fukushima, AIP Advances (2023). The article can be accessed at https://doi.org/10.1063/5.0134071 .