Breakthrough new research shows that ionization-induced self-channeling of a microwave beam can be achieved at a significantly lower power of the microwave beam and gas pressure for radially nonuniform plasma with minimal on-axis density than in the case of plasma formed as the result of gas ionization.
In the journal Physics of Plasmas, Israel Institute of Technology researchers report observing this effect for the first time and studying it in detail in a plasma preliminarily formed by a radiofrequency discharge, in a low-pressure gas (<150 Pa). They were able to do this by using analytical modeling and numerical particle-in-cell simulations, and their work centers on the concept of the nonlinear effect on plasma and magnetic wave interaction.
"Ionization-induced plasma self-channeling is the foundation for microwave plasma wakefield research," said lead author Yang Cao. "A plasma wakefield is a wave generated by particles traveling through a plasma. And a microwave plasma wakefield experiment could give us information about laser wakefield research that's extremely difficult to obtain due to the short time (femtosecond) and geometry scale involved."
This work is significant because microwaves will always diverge, unlike lasers that can be trapped within optical fibers. "In this [way], a self-induced 'microwave fiber' is created that may help the microwave propagate a much longer distance," Cao said.
In the future, the microwave ionization-induced self-channeling effect could be used for further exploring the microwave plasma wakefield or, since it's a form of directed energy, it may also find military applications as a directed-energy weapon.
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Y. Cao et al, Self-channeling of a powerful microwave beam in a preliminarily formed plasma, Physics of Plasmas (2018). DOI: 10.1063/1.5051226