Characterisation of a laser plasma betatron source for high resolution x-ray imaging

Abstract

We report on the characterisation of an x-ray source, generated by a laser-driven plasma wakefield accelerator. The spectrum of the optimised source was consistent with an on-axis synchrotron spectrum with a critical energy of 13.8 +2.2 −1.9 keV and the number of photons per pulse generated above 1 keV was calculated to be 6 +1.2 −0.9 × 10 9 . The x-ray beam was used to image a resolution grid placed 37 cm from the source, which gave a measured spatial resolution of 4 µm × 5 µm. The inferred emission region had a radius and length of 0.5 ± 0.2 µm and 3.2 ± 0.9 mm respectively. It was also observed that laser damage to the exit aperture of the gas cell led to a reduction in the accelerated electron beam charge and a corresponding reduction in x-ray flux due to the change in the plasma density profile.

Light-to-Plasma Momentum Transfer

“…For example, the electron density profile of plasma material expanding from laser-irradiated solid targets has been modified due to light pressure [1][2][3], and there have been proposals to use direct light momentum to compress plasma material for inertial fusion studies [4][5][6]. Light pressure can accelerate electrons in laser-plasmas to high energies that are useful for many applications [7][8][9][10][11]. Electrons accelerated by light pressure may be used as a heating source for fusion ignition when the electrons or co-moving ions are injected into laser-compressed deuterium/tritium [12][13][14].…”