Speaker
Description
Optical probing provides a fundamental tool for research and development and for exploring the mysteries of nature. However, when dealing with objects made of transparent materials with a refractive index near unity, such as low-density gas jets, these samples frequently challenge the limits of sensitivity in optical probing techniques.
To address this challenge, we introduce an advanced optical probing method utilizing multiple probe passes through the object [1], thereby enhancing phase sensitivity. The effectiveness of this approach was validated through the tomographic characterization of low-density supersonic gas jets. The results demonstrate a significant increase in sensitivity, enabling precise quantification of intricate features such as shocks formed by obstacles to the gas flow or barrel shocks formed by ambient pressure [1,2,3].
Gas target characterization traditionally relies on optical methods with millisecond time resolution. However, these techniques often overlook fluctuations occurring at shorter timescales, presenting sensitivity challenges. These rapid fluctuations may originate from manufacturing defects in nozzles or interactions between the gas flow and static ambient gas, particularly common in high repetition rate operations [4].
The accurate characterization of gas jets demands the resolution of rapid fluctuations, particularly for applications like laser-matter interaction in laser wakefield electron acceleration or plasma X-ray sources [5,6]. To address this, we employ Schlieren imaging, enabling the visualization of rapid density fluctuations with a temporal resolution of hundreds of microseconds [3]. This integration of time-averaged density measurements on a millisecond timescale and visualization of shorter instabilities represents a significant advancement in achieving a comprehensive and accurate portrayal of gas jet dynamics.
References
- Karatodorov, S. et al. Multi-pass probing for high-sensitivity tomographic interferometry. Sci Rep 11, 15072 (2021).
- Chaulagain, U. et al. Tomographic characterization of gas jets for laser-plasma acceleration with increased sensitivity, Proc. SPIE 11886, International Conference on X-Ray Lasers 2020
- Raclavský, M. et al. High-sensitivity optical tomography of instabilities in supersonic gas flow, Optics Express 2024
- F. Brandi, F. Giammanco, F. Conti, et al., Rev. Sci. Instruments 87257 (2016)
- Chaulagain, U. et al. ELI Gammatron Beamline: A Dawn of Ultrafast Hard X-ray Science. Photonics 2022
- J. Nejdl et al. "Update on Laser-driven X-ray Sources at ELI Beamlines," in Optica High-brightness Sources and Light-driven Interactions Congress 2022, (Optica Publishing Group, 2022)
