@misc{oai:repo.qst.go.jp:00066713,
 author = {ピロジコフ, アレキサンダー and エシロケポフ, ティムル and 匂坂, 明人 and 小倉, 浩一 and 中新, 信彦 and 黄, 開 and A., Pikuz T. and Ya., Faenov A. and Namba, S. and 福田, 祐仁 and コーガ, ジェームズ and 桐山, 博光 and 近藤, 公伯 and 河内, 哲哉 and 神門, 正城 and ピロジコフ アレキサンダー and エシロケポフ ティムル and 匂坂 明人 and 小倉 浩一 and 中新 信彦 and 黄 開 and 福田 祐仁 and コーガ ジェームズ and 桐山 博光 and 近藤 公伯 and 河内 哲哉 and 神門 正城},
 month = {Mar},
 note = {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)., JPS Spring Meeting},
 title = {Relativistic plasma singularity and its coherent x-ray emission control using density jump},
 year = {2018}
}