Characterization of gas targets relies largely on conventional optical techniques, providing millisecond time resolution, which not only overlooks the fluctuations occurring at shorter time scales but also often challenges the sensitivity limits of optical probing as their refractive index is close to unity. Hence, the ability to resolve these fluctuations needs to be addressed as it is paramount for accurate gas jet characterization for their applications, including laser–matter interaction in laser wakefield electron acceleration or plasma x ray sources. In this Letter, we introduce an advanced gas jet characterization system capable of visualizing fast density fluctuations by Schlieren imaging, combined with density characterization by interferometric tomography, both with increased sensitivity due to the four-pass probing configuration. We demonstrate that combining the two modalities provides a substantial advancement in achieving a comprehensive, both quantitative and qualitative, characterization of gas jets.

中文翻译：

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超音速气流不稳定性的高灵敏度光学层析成像

气体目标的表征很大程度上依赖于传统的光学技术，提供毫秒级的时间分辨率，这不仅忽略了较短时间尺度上发生的波动，而且还经常挑战光学探测的灵敏度极限，因为它们的折射率接近于统一。因此，需要解决解决这些波动的能力，因为这对于准确表征气体射流的应用至关重要，包括激光尾场电子加速或等离子体 X 射线源中的激光与物质相互作用。在这封信中，我们介绍了一种先进的气体喷射表征系统，能够通过纹影成像可视化快速密度波动，并结合干涉断层扫描进行密度表征，由于四通道探测配置，两者都具有更高的灵敏度。我们证明，两种模式的结合在实现气体射流的全面定量和定性表征方面取得了重大进展。