Diagnostic of ultrafast temporal plasma evolution in high-power microwave discharge

• Published in: Journal of applied physics 2017-06, Vol.121 (21)
• Main Authors: Chang, C., Wu, C., Pu, Y. K., Zhu, M., Zhang, X., Verboncoeur, J.
• Format: Article
• Language: English
• Subjects: Cameras; Diagnostic systems; Electron density; Evolution; Frames; High power microwaves; Microwave discharge; Optical fibers; Plasma dynamics; Plasma jets; Response time
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4984014

For the most advanced multi-frame camera in the world, the shortest response time between two frames is no shorter than 1.5 ns. Thus, there is no effective way to diagnose the ultrafast sub-nanosecond dynamic of a microwave-driven plasma discharge in a single pulse. Different-length multi-sub-beam optical fibers, together with a spectrometer and an EMICCD camera, are proposed and designed to detect the nanosecond discharge spectra in a single pulse, like a real-time multi-frame spectral camera. This novel method could realize a time interval between two consecutive frames shorter than 0.1 ns by a length difference of 2 cm for sub-fibers, achieving the measurement of ultrafast plasma dynamics. Temporal evolution of electron density as well as energy of electrons and ions during nanosecond microwave discharge is further studied by de-convolving the Stark broadening and thermal Doppler broadening and by calculating the ratio of emission coefficients.