X-ray emission from relativistically moving electron density cusps

Kando, Masaki; Pirozhkov, A. S.; Nakamura, Tatsufumi; Hayashi, Yukio; Kotaki, Hideyuki; Kawase, Keigo*; Esirkepov, T. Z.; Fukuda, Yuji; Kiriyama, Hiromitsu; Okada, Hajime; Daito, Izuru; Kameshima, Takashi*; Mori, Michiaki; Koga, J. K.; Daido, Hiroyuki; Faenov, A. Ya.*; Pikuz, T.; Ma, J.*; Chen, L.-M.*; Ragozin, E. N.*; Kawachi, Tetsuya; Kato, Yoshiaki* ; Tajima, Toshiki*; Bulanov, S. V.

We report on novel method to generate ultra-short coherent X-rays using a laser-plasma interaction. Nonlinear interaction of intense laser pulses with plasma creates stable, specific structures such as electron cusps. For example wake waves excited in an underdense plasma by the laser become dense and propagate along with the laser pulse (Flying Mirror). The flying mirror can reflect a counter-propagating laser pulse and directly convert it into high-frequency radiation and compress the pulse. We have conducted experimental results using 9 TW laser with a He gas target. We observed 10 photons in the extreme ultra-violet region (12.8-22.0 nm).