Soft X-ray generation by the light reflection from the relativistic mirror in plasma

Pirozhkov, A. S.; Bulanov, S. V.; Daido, Hiroyuki; Daito, Izuru; Esirkepov, T. Z.; Kando, Masaki; Kato, Yoshiaki ; Kimura, Toyoaki; Koga, J. K.; Kotaki, Hideyuki; Ma, J.-L.; Mori, Michiaki; Ogura, Koichi; Sagisaka, Akito; Tajima, Toshiki; Fukuda, Yuji; Hayashi, Yukio; Homma, Takayuki; Chen, L.-M.

Electromagnetic wave frequency upshifting upon the reflection from a mirror moving with relativistic velocity can be used for the generation of coherent high-frequency radiation. We present the results of experimental and theoretical study of the novel soft X-ray source based on the reflection of a laser pulse from a nonlinear plasma wave (relativistic flying mirror). In the experiment, the breaking wake wave is created by a Ti:S laser pulse (2 TW, 76 fs) in helium plasma with the electron density of cm. The reflection of a second laser pulse is measured with a grazing-incidence spectrograph. The measured wavelength of reflected radiation is 14.3 nm, which corresponds to the frequency upshifting factor of 56. The new source promises the generation of coherent ultrashort X-ray pulses with tunable wavelength and duration. In the presentation we also discuss requirements to X-ray optical elements for effective use of the new radiation source.