Ultrafast Imaging of Laser Driven Shock Waves using Betatron X-rays from a Laser Wakefield Accelerator

Abstract

Betatron radiation from laser wakefield accelerators is an ultrashort pulsed source of hard, synchrotron-like x-ray radiation. It emanates from a centimetre scale plasma accelerator producing GeV level electron beams. In recent years betatron radiation has been developed as a unique source capable of producing high resolution x-ray images in compact geometries. However, until now, the short pulse nature of this radiation has not been exploited. This report details the first experiment to utilize betatron radiation to image a rapidly evolving phenomenon by using it to radiograph a laser driven shock wave in a silicon target. The spatial resolution of the image is comparable to what has been achieved in similar experiments at conventional synchrotron light sources. The intrinsic temporal resolution of betatron radiation is below 100 fs, indicating that significantly faster processes could be probed in future without compromising spatial resolution. Quantitative measurements of the shock velocity and material density were made from the radiographs recorded during shock compression and were consistent with the established shock response of silicon, as determined with traditional velocimetry approaches. This suggests that future compact betatron imaging beamlines could be useful in the imaging and diagnosis of high-energy-density physics experiments.

Quantitative phase contrast imaging of a shock-wave with a laser-plasma based X-ray source

“…The use of XPCI for shock-wave imaging and characterisation has been reported in several previous works 16,18–21 , which demonstrated how XPCI is superior to X-ray absorption imaging in shock detection. However, only recently has XPCI was demonstrated to work also with for broadband laser-plasma X-ray source 18,19 , in a configuration similar to the one employed in ICF facilities.…”

Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures

“…To address this confounding issue, a few investigators have recently employed synchrotron-based X-ray microtomography to track the microstructural evolution as a function of time 27,62 . High-speed synchrotron hard X-ray imaging on the nanosecond timescale has recently been demonstrated 20 , however LWFA sources offer temporal resolution on the order of femtoseconds 16,63,64 . The realization of high-repetition rate laser drivers for LWFA 65–67 could enable dynamic measurements on an ultra-short timescale.…”

“…1(c), contained 1.94 ± 1.24 × 10 8 photons above 5 keV, and is estimated to have a source size smaller than 3 μ m, as discussed in Results . The LWFA X-ray beam has been found in similar experiments to have divergence on the order of a few millirads 15,17,18 and femtosecond duration 16,19 . The electron and X-ray measurements shown in Fig.…”

“…And although compact synchotron sources have recently been developed 30 , laser-driven sources also have the unique capability to be co-timed to other laser-initiated events. In this way, LWFA sources can be used for so called pump - probe experiments of laser-irradiated targets 16,19 . Additionally, while the source size of newest generation conventional beamlines has been reduced to the order of 10–20 μ m, the resolution limit for X-ray imaging in a parallel beam geometry on these systems is dependent on the pixel size of the detector and the brightness of the source.…”

Self-Referencing Spectral Interferometric Probing of the Onset Time of Relativistic Transparency in Intense Laser-Foil Interactions

“…Ultrabright sources of high energy particles and radiation driven by intense laser pulses are opening up scientific applications (e.g. ultrafast imaging [1][2][3], highflux neutron generation [4,5] and material damage studies [6]), and have wide-ranging potential applications in medicine, security and industry [7,8]. Much of the research into the development of these sources focuses on interactions in which the target plasma is either wholly transparent (gaseous) or opaque (solid) to the laser pulse over the full interaction.…”