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International audience; Bright femtosecond x-ray beams, with energies up to a few hundreds of keV, have been produced from Betatron oscillations and Compton scattering in a laser-plasma accelerator. The potential of Betatron radiation for phase contrast imaging has been demonstrated. (C) 2011 Optical Society of America

One of the major goals of research for laser-plasma accelerators is the realization of compact sources of femtosecond X-rays. In particular, using the modest electron energies obtained with existing laser systems, Compton scattering a photon beam off a relativistic electron bunch has been proposed as a source of high-energy and high-brightness photons. However, laser-plasma based approaches to Compton scattering have not, to date, produced X-rays above 1 keV. Here, we present a simple and compact scheme for a Compton source based on the combination of a laser-plasma accelerator and a plasma mirror. This approach is used to produce a broadband spectrum of X-rays extending up to hundreds of keV and with a 10,000-fold increase in brightness over Compton X-ray sources based on conventional accelerators. We anticipate that this technique will lead to compact, high-repetition-rate sources of ultrafast (femtosecond), tunable (X- through gamma-ray) and low-divergence (~1 degree) photons from source sizes on the order of a micrometre., 6 pages, 5 figures

International audience; Energetic electron beams accelerated in a laser-produced plasma wakefield cavity can generate collimated beams of X-ray radiation. The oscillation of the electrons in the plasma cavity produces synchrotron-like emission, called betatron radiation. On the basis of state of the art experiments, we discuss the potentiality of this source in terms of spectral brigthness and flux. These characteristics are compared to existing and planned X-ray sources in both laser and accelerator communities.

International audience; This Letter aims to demonstrate the ultrafast nature of laser produced betatron radiation and its potential for application experiments. An upper estimate of the betatron x-ray pulse duration has been obtained by performing a time-resolved x-ray diffraction experiment: The ultrafast nonthermal melting of a semiconductor crystal (InSb) has been used to trigger the betatron x-ray beam diffracted from the surface. An x-ray pulse duration of less than 1 ps at full width half-maximum (FWHM) has been measured with a best fit obtained for 100 fs FWHM.