[21a-221B-1~7] 4.3 Ultrafast Optics and Photonics

▲ [21a-221B-3] Experimental results on BISER control

〇Alexander S. Pirozhkov¹、Timur Zh. Esirkepov¹、Bruno Gonzalez-Izquierdo¹、Akito Sagisaka¹、Koichi Ogura¹、Nobuhiko Nakanii¹、Kai Huang¹、Tatiana A. Pikuz²、Anatoly Ya. Faenov²、Shinichi Namba³、Yuji Fukuda¹、James K. Koga¹、Hiromitsu Kiriyama¹、Kiminori Kondo¹、Tetsuya Kawachi¹、Masaki Kando¹ (1.KPSI, QST、2.Osaka University、3.Hiroshima University)

キーワード：Burst Intensification by Singularity Emitting Radiation (BISER), Relativistic plasma singularities, Coherent x-ray sources

Burst Intensification by Singularity Emitting Radiation (BISER) is a universal phenomenon, which occurs in media emitting travelling waves. If a singularity appears in such medium, e.g., due to multi-stream flow, it produces strongly intensified emission due to constructive interference of waves from elementary emitters. In particular, BISER results in bright coherent x-ray generation by relativistic plasma singularities driven by multi-terawatt femtosecond lasers focused onto gas jet targets. In plasma, density singularities are produced by the laser pulse which pushes electrons aside, creating a multi-stream flow, typically seen as a bow wave. These singularities manifest themselves as point-like coherent x-ray emitters. In previous experiments, BISER resulted from relativistic self-focusing, which is the laser beam instability. This spontaneous regime exhibited relatively large shot-to-shot fluctuations of the x-ray source position and low overall stability. However, stability is desirable for prospective applications of the new coherent x-ray source.

A tailored plasma density profile can help to control the BISER, as shown by our simulations with the Particle-In-Cell code REMP. We have recently demonstrated this control for the first time in experiment with the J-KAREN-P laser using a sharp density jump created by a blade in the supersonic gas flow.

Here we present new experimental results on the BISER control. In particular, we discuss the results obtained at different plasma densities and the dependence of the BISER x-ray source position stability on the laser power.

We thank the J-KAREN-P laser operation group. We acknowledge the financial support from JSPS Kakenhi JP 25390135, JP 26707031, and QST Director Fund.