@misc{oai:repo.qst.go.jp:00086567,
 author = {Shatokhin, A. and Kotov, A. and M. Jeong, T. and M. Grittani, G. and Dzelzainis, T. and Hull, G. and Dann, S. and Akito, Sagisaka and Vishnyakov, E. and Kolesnikov, A. and Masato, Koike and Timur, Esirkepov and Masaki, Kando and Koichi, Ogura and A. Pikuz, T. and Kevin Koga, James and Hiromitsu, Kiriyama and Soloviev, A. and Ragozin, E. and Bulanov, Sergey and Kiminori, Kondo and Tetsuya, Kawachi and Symes, D. and Neely, D. and Pirozhkov, Alexander and Akito, Sagisaka and Masato, Koike and Timur, Esirkepov and Masaki, Kando and Koichi, Ogura and Kevin Koga, James and Hiromitsu, Kiriyama and Bulanov, Sergey and Kiminori, Kondo and Tetsuya, Kawachi and Pirozhkov, Alexander},
 month = {Apr},
 note = {1. Introduction
Burst Intensification by Singularity Emitting Radiation (BISER) [1] is the emission of coherent traveling waves by multi-stream flow singularities. Such singularities can be produced in relativistic plasma by high-power lasers, resulting in very bright coherent x-ray emission [2],[3].
2. Experimental
We have recently performed an experiment on BISER coherent x-ray generation with the Astra Laser at the CLF RAL, UK. We extensively optimized the experimental conditions, namely the plasma density and profile, and laser spot [4] and pulse, making use of substantial beam time. This resulted in a ~2 orders of magnitude higher BISER brightness compared to earlier experiments with 10 TW lasers.
3. Results
In this presentation we discuss results from two soft x-ray spectrographs: a three-channel flat field spectrograph [5] in the forward direction (channels at −0.6, 0, and 0.8°) operating in the 17-34 nm range and a normal-incidence imaging spectrograph [6] in a 10° off-axis direction operating in the 12.4-20 nm range. Under optimum conditions, both spectrographs showed μJ and higher BISER pulse energies per shot in the corresponding spectral ranges and within their acceptance angles. This implies multi-100 μJ BISER pulses in the entire spectral range and within the full angular width.
Acknowledgement
We acknowledge support from the Astra Laser Group and the CLF Target Fab, Mechanical, and Electrical. Financial support: JSPS Kakenhi JP 19KK0355 and 19H00669, CLF, Russian Science Foundation (20-62-46050), IAP RAS, ELI-Beamlines, MŠMT by the project "Advanced Research Using High Intensity Laser Produced Photons and Particles" (CZ.02.1.01/0.0/0.0/16_019/0000789), High Field Initiative (CZ.02.1.01/0.0/0.0/15_003/0000449) from the European Regional Development Fund, and the QST Director Fund 創成的研究 #20.
References
[1]A. S. Pirozhkov, T. Zh. Esirkepov et al., "Burst intensification by singularity emitting radiation in multi-stream flows," Sci. Rep. 7, 17968 (2017).
[2]A. S. Pirozhkov, et al. "Soft-X-Ray Harmonic Comb from Relativistic Electron Spikes" PRL 108, 135004 (2012).
[3]A. S. Pirozhkov, et al., "High order harmonics from relativistic electron spikes" NJP 16, 093003 (2014).
[4]A. S. Pirozhkov, et al. "Laser Requirements for High-Order Harmonic Generation by Relativistic Plasma Singularities," Quantum Beam Sci. 2, 7 (2018).
[5]D. Neely, et al., "A multi-channel soft X-ray flat-field spectrometer," AIP Conf. Proc. 426, 479 (1998).
[6]A. N. Shatokhin, et al., "High-resolution stigmatic spectrograph for a wavelength range of 12.5-30 nm," Opt. Express 26, 19009 (2018)., OPIC-2022 (ALPS-2022)},
 title = {Optimization of BISER via Laser and Plasma Tuning},
 year = {2022}
}