Demonstration of the synchrotron-type spectrum of laser-produced Betatron radiation

Betatron X-ray radiation in laser-plasma accelerators is produced when electrons are accelerated and wiggled in the laser-wakefield cavity. This femtosecond source, producing intense X-ray beams in the multi kiloelectronvolt range has been observed at different interaction regime using high power laser from 10 to 100 TW. However, none of the spectral measurement performed were at sufficient resolution, bandwidth and signal to noise ratio to precisely determine the shape of spectra with a single laser shot in order to avoid shot to shot fluctuations. In this letter, the Betatron radiation produced using a 80 TW laser is characterized by using a single photon counting method. We measure in single shot spectra from 8 to 21 keV with a resolution better than 350 eV. The results obtained are in excellent agreement with theoretical predictions and demonstrate the synchrotron type nature of this radiation mechanism. The critical energy is found to be Ec = 5.6 \pm 1 keV for our experimental conditions. In addition, the features of the source at this energy range open novel perspectives for applications in time-resolved X-ray science.Comment: 5 pages, 4 figure

Laser wakefield acceleration: application to Betatron X- ray radiation production and X-ray imaging

International audienceHigh intensity femtosecond laser pulses can be used to generate X-ray radiation. In the laser wakefield process, when a high intensity laser pulse (>10(18) W/cm(2)) is focused onto a gas jet target, it interacts with the instantaneously created under-dense plasma and excites a wakefield wave. In the wakefield electrons are trapped and accelerated to high energies in short distances. The electrons trapped in the wakefield can perform Betatron oscillations across the propagation axis and emit X-ray photons. The Betatron X-ray beam is broadband as the radiation emission has a synchrotron distribution. The X-ray beam is collimated and its pulse duration is femtosecond. For high resolution and phase contrast X-ray imaging applications, the important feature of the X-ray Betatron beam is the mu m source size. Using ALLS 100 TW class laser system we demonstrate that the Betatron X-ray beam is both energetic and bright enough to produce single laser shot phase contrast imaging of complex objects located in air