Plasma acoustic emission (PLACE)

• Applicants: Dr.-Ing. Mate Gaal; Professor Dr. Holger Kersten
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Acoustics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 507789452

Atmospheric pressure plasma has various industrial applications, for example for activation and cleaning of surfaces, for ionization and surface coating. Nevertheless, plasma acoustic emission is mostly unexplored. Its possibilities of broadband and resonance-free operation make it most interesting for possible applications in plasma diagnostics and as a new type of acoustic source. Within the proposed project, the fundamental knowledge about the acoustic emission of plasma shall be worked out and expanded in view of possible industrial applications. The project partners pursue two goals: The first is the development of a method for acoustically based plasma diagnostics, where acoustical measurements allow conclusions about plasma properties. The second goal is the development of plasma-based acoustic transducers for emitting acoustical signals. Transmitters based on micro hollow cathodes and surface dielectric barrier discharge shall be studied, mostly in the ultrasonic range. These discharge types shall be tested for their application in plasma diagnostics and as acoustic sources. A comprehensive theoretical model of electro-acoustical conversion up to about 1 MHz describing the related experiments shall be worked out. During plasma-based acoustic emission, the changes in the plasma temperature and in the electrohydrodynamic force cause pressure modulations of the surrounding fluid, which initiate an acoustic wave. For applications in plasma diagnostics and in acoustic sensors, it is necessary to investigate various influencing parameters: the geometry, the electrical excitation and the working gas composition. Various prototypes shall be designed and implemented to evaluate the influence of these parameters. The sound pressure distribution of acoustic transmitters shall be measured using ultrasonic microphones and laser vibrometry in the frequency range up to 1 MHz. To enable a systematic comparison between theoretical and experimental results, numerical simulations shall be applied. Various numerical models and methods known from acoustics and plasma physics shall be combined. The project results would contribute to the areas of plasma diagnostics and acoustic sensors. The new knowledge about plasma acoustic emission would enable contact-free and time-resolved plasma diagnostics. Broadband ultrasonic transmitters and receivers would open new possibilities for the application of contact-free ultrasonic testing.

• DFG Programme: Research Grants