Abstract
A high power laser was used to accelerate electrons in a laser-driven wakefield accelerator. The high energy electrons were then used to generate an x-ray beam by passing them through a converter target. This bremsstrahlung source was characterised and used to perform penetrative imaging of industrially relevant samples. The photon spectrum had a critical energy in excess of 100 MeV and a source size smaller than the resolution of the diagnostic (150 µm). Simulations indicate a significantly smaller source is achievable. Variations in the x-ray source characteristics were realised through changes to the plasma and converter parameters while simulations confirm the adaptability of the source. Imaging of high areal density objects with 150 µm resolution was performed, demonstrating the unique advantages of this novel source.
Highlights
When the bremsstrahlung converter was in place, this magnet prevented the electrons from irradiating the samples which would have otherwise generated a secondary bremsstrahlung source
Simulating the source generated from an electron beam shows the changes in the x-ray source which may result from changes in converter parameters
Using laser wakefield accelerated electrons and converter targets, a bremsstrahlung x-ray source was produced capable of imaging of high-density, industrially relevant materials with a resolution of ≲150 μm, currently limited by the detector
Summary
ICS, where the highly energetic electrons collide with a second laser pulse, is an effective way to produce MeV-scale, narrow energy spread x-rays [13, 14] Such LWFA light sources have been studied extensively and reviewed by Corde et al [15] and Albert and Thomas [16]. For x-ray NDT requiring photon energies >1 MeV the current industry standard approach is to use a linear accelerator (linac) to produce electrons, which are converted to bremsstrahlung by interacting with a high-Z material. Results are presented of a recent experiment using the Gemini laser system at the Rutherford Appleton Laboratory [28], demonstrating the applicability of a LWFA bremsstrahlung source for high quality imaging of an additively manufactured Inconel (nickel-alloy) industrial test object. It is shown that x-ray emission can be tuned to image a range of objects with different material properties, by changing the electron beam properties or converter thickness and composition
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