@misc{oai:repo.qst.go.jp:00073348,
 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 難波, 愼一 and 大東, 出 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 難波 愼一 and 大東 出 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 = {Apr},
 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 particular case of Burst Intensification by Singularity Emitting Radiation (BISER) [4].
In previous experiments, BISER occurred spontaneously, after the relativistic self-focusing, resulting in a relatively large fluctuations of the x-ray source position and low overall stability. Basing on simulations with the 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, low-jitter x-ray source 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.
We thank the J-KAREN-P laser operation group. We acknowledge the financial support from JSPS Kakenhi JP 25390135 and JP 26707031.
\n[1]A. S. Pirozhkov, M. Kando, T. Zh. Esirkepov, P. Gallegos, H. Ahmed, E. N. Ragozin, A. Ya. Faenov, et al., "Soft-X-Ray Harmonic Comb from Relativistic Electron Spikes," Phys. Rev. Lett. 108, 135004-5, (2012).
[2]A. Pirozhkov et al., "High order harmonics from relativistic electron spikes," New J. Phys. 16, 093003-30 (2014).
[3]T. Zh. Esirkepov, Y. Kato, and S. V. Bulanov, "Bow Wave from Ultraintense Electromagnetic Pulses in Plasmas," Phys. Rev. Lett. 101, 265001-4 (2008).
[4]A. S. Pirozhkov, T. Zh. Esirkepov, T. A. Pikuz, A. Ya. Faenov, K. Ogura, Y. Hayashi, H. Kotaki, et al., "Burst intensification by singularity emitting radiation in multi-stream flows," Scientific Reports (accepted).
[5]T. Zh. Esirkepov, "Exact charge conservation scheme for Particle-in-Cell simulation with an arbitrary form-factor," Comput. Phys. Comm. 135, 144-153 (2001).
[6]H. Kiriyama, M. Mori, A. S. Pirozhkov, K. Ogura, A. Sagisaka, A. Kon., et al., "High-Contrast, High-Intensity Petawatt-Class Laser and Applications," IEEE J.S.T.Quantum Electron. 21, 1601118-18 (2015).
[7]A. S. Pirozhkov, Y. Fukuda, M. Nishiuchi, H. Kiriyama, A. Sagisaka, K. Ogura, M. Mori, M. Kishimoto, et al., "Approaching the diffraction-limited, bandwidth-limited Petawatt," Opt. Express 25, 20486-20501 (2017)., OPIC-2018 (HEDS-2018)},
 title = {Control of Burst Intensification by Singularity Emitting Radiation (BISER) with density jump},
 year = {2018}
}