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 Science and Technology.
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In our experiments and simulations [1, 2] we discovered a bright source of high-order harmonics and revealed the mechanism of their generation in relativistic plasma driven by multi-terawatt femtosecond lasers focused onto gas jet targets with typical electron densities of ~10^19 cm^-3. The harmonics extended up to the 'water window'; the energy within the 60 to 100 eV bandwidth was up to 100 nJ per shot. Simulations showed that the emission consisted of several attosecond pulses. In our subsequent experiments we confirmed the predictions and observed the soft x-ray emission originated from point-like sources.
\nHere we generalize this mechanism and introduce the concept of BISER, Burst Intensification by Singularity Emitting Radiation. In this concept, we consider an emitting medium with multi-stream flows. Elementary components participating in such flows eventually form structurally stable density singularities explained by catastrophe theory. The wave emission from such singularities can be coherent due to tight localization of elementary emitters. In addition, if the singularities move with relativistic speed towards an observer, the apparent frequency increases and emission becomes more intense and directional. In our previous work the emitting medium was relativistic plasma, the elementary components were electrons, and the emitting waves were high-frequency electromagnetic waves, i.e. soft x-rays. In general, BISER can be applicable to any type of traveling waves, not necessarily electromagnetic.
\n[1] A. S. Pirozhkov, M. Kando, T. Zh. Esirkepov, et al., "Soft-X-Ray Harmonic Comb from Relativistic Electron Spikes," Phys. Rev. Lett. 108, 135004-5 (2012).
[2] A. S. Pirozhkov, M. Kando, T. Zh. Esirkepov, et al., "High order harmonics from relativistic electron spikes," New J. Phys. 16, 093003-30 (2014).
会議概要（会議名, 開催地, 会期, 主催者等）
The Optics & Photonics International Congress OPIC-2017, International Conference on High-Energy Density Sciences HEDS-2017
BISER: Burst Intensification by Singularity Emitting Radiation
