Extraction of high-contrast diffraction patterns of fine-structured electrical sparks from laser shadowgrams

The fine-structured electrical spark is a complex gas discharge phenomenon, which appears as a cluster involving dozens of closely-packed thin plasma filaments that can be revealed by laser shadowgraphy. However, the immense complexity of the spark, together with the features of laser imaging, challenges the spark image processing. Herein, we developed an image processing procedure, providing outstanding shadowgram denoising while preserving the spark image capacity. By employing this procedure, we show that the passage of laser radiation through the spark is accompanied by complicated diffraction, entailing pronounced changes in the radiation intensity distribution in the zones with strong filament overlapping.