Verification of the plasma diffusion-wave propagation in an atmospheric-pressure plasma jet with the solution of a diffusion equation

摘要

The time-dependent solution of diffusion equation by the Fourier integration provides the axial diffusion velocity of a plasma packet, which is a key element of the plasma propagation in a plasma jet operated by the several tens of kHz. The plasma diffusion velocity is higher than the order of u(n) similar to 10 m/s at a high electric-field region of plasma generation and it is about the order of u(n) similar to 10 m/s at the plasma column of a low field region in a jet-nozzle inside. Meanwhile, the diffusion velocity is slower than the order of u(n) similar to 10 m/s in the open-air space where the plasma density flattens due to its radial expansion. Using these diffusion velocity data, the group-velocity of plasma diffusion wave-packet is given by u(g) similar to c(s)(2) /u(n), a combination of the diffusion velocity u(n) and the acoustic velocity c(s). The experimental results of the plasma propagation can be verified with the plasma propagation in a form of the wave-packet whose propagation velocity is 10(4) m/s in a tube inside and is as fast as 10(5) m/s in the open-air space, thereby reconfirming that the theory of a plasma diffusion-wave is the origin of the plasma propagation in a plasma jet. Published by AIP Publishing.