Student Excellence Award Finalist: Electric field measurements of piezoelectric direct discharge plasmas using electric-field induced second harmonic (E-FISH) generation

Piezoelectric direct discharge (PDD) plasmas are generated by the high voltage output of a piezoelectric transformer (PT). When a PT is actuated at its second harmonic frequency by a low input voltage of ~ 10 V_rms, the generated electric field at the distal end can be sufficient to breakdown the surrounding gas, making it an attractive power source for non-equilibrium plasma generation. Understanding the surface potential and electric field distribution around the distal end is important for effectively using PTs for plasma generation. In this work, the spatiotemporally-resolved characteristics of the electric field generated by a PT operating in open air have been investigated using the electric-field induced second harmonic (E-FISH) generation method. Absolute calibration of the E-FISH signal was obtained by measuring a known uniform electric field generated within the gap of parallel plates. Electric field components were determined by simultaneously conducting E-FISH measurements with the incident laser polarized in two orthogonal directions. Results show the spatial distribution of the electric field around the PT’s output distal end and how it evolves in time. Notably, the strongest electric field appears on the face of the PT’s distal end and when operated just below the breakdown threshold, is 30.4 kV/cm, consistent with the breakdown field of air.

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