量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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We have discovered a new regime of bright coherent x-ray generation by relativistic plasma singularities driven by a multi-terawatt femtosecond laser focused onto a gas jet target [1]-[2]. The laser pulse propagates through the plasma, pushes electrons producing an electron-free cavity, and generates a bow wave [3]; singularities are produced at the joining of the cavity wall and the bow wave and represent point-like coherent x-ray emitters, which is a realization of Burst Intensification by Singularity Emitting Radiation (BISER) proposed in [4].
\nIn previous experiments, BISER occurred spontaneously, after the relativistic self-focusing, resulting in relatively large fluctuations of the x-ray source position and low overall stability. Based on simulations with the Particle-In-Cell (PIC) REMP code [5], we propose to control the BISER with a tailored plasma density profile. We demonstrate the BISER control employing a sharp plasma density jump generated by a shock in supersonic gas flow in experiments with the J-KAREN-P laser [6]-[7]. The induced BISER resulted in controllable x-ray source with low-jitter position and higher x-ray yield. Our results, on the one hand, represent an important step towards implementation of a next-generation bright compact coherent x-ray source, and on the other hand, demonstrate the new technique of relativistic self-focusing control and its diagnostics.
\nWe thank the J-KAREN-P laser operation group and I. Daito for technical support. We acknowledge the financial support from JSPS Kakenhi JP 25390135 and JP 26707031.
\n[1]A. S. Pirozhkov, et al., Phys. Rev. Lett. 108, 135004-5, (2012).
[2]A. S. Pirozhkov et al., New J. Phys. 16, 093003-30 (2014).
[3]T. Zh. Esirkepov, Y. Kato, and S. V. Bulanov, Phys. Rev. Lett. 101, 265001-4 (2008).
[4]A. S. Pirozhkov, T. Zh. Esirkepov, et al., Scientific Reports 7, 17968 (2017).
[5]T. Zh. Esirkepov, Comput. Phys. Comm. 135, 144-153 (2001).
[6]H. Kiriyama, et al., IEEE J.S.T.Quantum Electron. 21, 1601118-18 (2015).
[7]A. S. Pirozhkov, et al., Opt. Express 25, 20486-20501 (2017).
Relativistic plasma singularity and its coherent x-ray emission control using density jump
