Reconstruction of lateral coherence and 2D emittance in plasma betatron X-ray sources.

X-ray sources have a strong social impact, being implemented for biomedical research, material and environmental sciences. Nowadays, compact and accessible sources are made using lasers. We report evidence of nontrivial spectral-angular correlations in a laser-driven betatron X-ray source. Furthermore, by angularly-resolved spectral measurements, we detect the signature of spatial phase modulations by the electron trajectories. This allows the lateral coherence function to be retrieved, leading to the evaluation of the coherence area of the source, determining its brightness. Finally, the proposed methodology allows the unprecedented reconstruction of the size of the X-ray source and the electron beam emittance in the two main emission planes in a single shot. This information will be of fundamental interest for user applications of new radiation sources.

Direct refractive index retrieval from interferometry measurements.

We present an alternative numerical method to the Abel inversion technique, which can be applied to complex non-symmetrical systems. A comparison with the Abel inversion algorithm was conducted. For benchmarking, the method was applied to a synthetic trace representing a plasma waveguide characterized by a constant parabolic density profile. Furthermore, the temperature and refractive index of a plume of hot air surrounding a non-cylindrical soldering iron were retrieved. Temperatures between 50 °C and 200 °C were successfully retrieved within the instrument precision. The proposed method allows robust and fast data retrieval while maintaining the accuracy and resolution of well-known methods, as Abel inversion.

Pulse front tilt control using non-collimated beams in a single pass grating compressor.

High power laser systems based on the chirped pulse amplification (CPA) technique make use of grating pairs to compress the pulse to a short duration. When designing the pulse compressor, it is normally assumed that good beam collimation is a strong requirement in order to avoid spatio-temporal couplings. We analyze the propagation through a single pass compressor without the good collimation approximation and show that this results in a compressed pulse exhibiting pulse front tilt, whose magnitude is proportional to the normalized distance to the beam waist, providing a simple mechanism for controlling the tilt angle. We perform experimental measurements in a large-scale CPA laser for a range of beam curvatures that confirm these results.