A femtosecond plasma imaging modality based on a new development of ultrafast electron microscope is introduced. We investigated the laser-induced formation of high-temperature electron microplasmas and their subsequent non-equilibrium evolution. Based on a straightforward field imaging principle, we directly retrieve detailed information about the plasma dynamics, including plasma wave structures, particle densities, and temperatures. We discover that directly subjected to a strong magnetic field, the photo-generated microplasmas manifest in novel transient cyclotron echoes and form new wave states across a broad range of field strengths and different laser fluences. Intriguingly, the transient cyclotron waves morph into a higher frequency upper-hybrid wave mode with the dephasing of local cyclotron dynamics. The quantitative real-space characterizations of the non-equilibrium plasma systems demonstrate the feasibilities of a new microscope system in studying the plasma dynamics or transient electric fields with high spatiotemporal resolutions.

中文翻译：

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使用超快速电子显微镜对等离子波进行直接成像

介绍了一种基于超快电子显微镜新发展的飞秒等离子体成像技术。我们研究了高温电子微等离子体的激光诱导形成及其随后的非平衡演化。基于简单的场成像原理，我们直接获取有关等离子体动力学的详细信息，包括等离子体波结构，粒子密度和温度。我们发现，直接在强磁场作用下，光生微等离子体在新的瞬时回旋加速器回波中表现出来，并在广泛的场强和不同的激光通量范围内形成新的波态。有趣的是，瞬态回旋加速器波会随着局部回旋加速器动力学的相移而转变为更高频率的上混合波模式。