title: Ultrafast high-power microwave window breakdown: nonlinear and postpulse effects.
abstract: The time- and space-dependent optical emissions of nanosecond high-power microwave discharges near a dielectric-air interface have been observed by nanosecond-response four-framing intensified-charged-coupled device cameras. The experimental observations indicate that plasma developed more intensely at the dielectric-air interface than at the free-space region with a higher electric-field amplitude. A thin layer of intense light emission above the dielectric was observed after the microwave pulse. The mechanisms of the breakdown phenomena are analyzed by a three-dimensional electromagnetic-field modeling and a two-dimensional electromagnetic particle-in-cell simulation, revealing the formation of a space-charge microwave sheath near the dielectric surface, accelerated by the normal components of the microwave field, significantly enhancing the local-field amplitude and hence ionization near the dielectric surface. The nonlinear positive feedback of ionization, higher electron mobility, and ultraviolet-driven photoemission due to the elevated electron temperature are crucial for achieving the ultrafast discharge. Following the high-power microwave pulse, the sheath sustains a glow discharge until the sheath collapses.
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China and Key Laboratory of Physical Electronics and Devices of the Ministry of Education, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China and Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
authors.forename: C
authors.initials: C
authors.lastname: Chang
authors.affiliation: Department of Electrical and Computer Engineering, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: J
authors.initials: J
authors.lastname: Verboncoeur
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China.
authors.forename: M N
authors.initials: MN
authors.lastname: Guo
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China.
authors.forename: M
authors.initials: M
authors.lastname: Zhu
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China.
authors.forename: W
authors.initials: W
authors.lastname: Song
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China.
authors.forename: S
authors.initials: S
authors.lastname: Li
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China.
authors.forename: C H
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China.
authors.forename: X C
authors.initials: XC
authors.lastname: Bai
authors.affiliation: Laboratory on Science and Technology of High Power Microwave, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China.
authors.forename: J L
authors.initials: JL
authors.lastname: Xie