While X-ray tubes are well spread and affordable sources for radiography, synchrotrons opened new high resolution imaging techniques taking benefit of the higher brightness of the beam lines, at the cost of a significantly larger size.
Laser-Accelerated Electrons for X-ray Generation
For several decades from now, intense lasers provide the unique ability to accelerate electrons from solid or gas targets, at MeV up to GeV energies in a very compact set-up, together with short pulse durations and small spot sizes. Those electrons can subsequently be converted into high brightness X-ray radiation through various processes : Bremstrahlung, K-alpha emission, Betatron, Inverse Compton Scattering (ICS) or Free Electron Laser (FEL).
The Bremstrahlung involves a solid target that converts the energy of the electron on a broad spectrum, whereas the material exhibits narrowband lines specific to the material used, corresponding to the K-alpha and K-beta transitions. The spot size of the source corresponds to the laser spot size, whereas the emission is wide.
The Free Electron Laser (FEL) process consists in using a magnetic undulator with a cm period to make oscillate the relativistic electrons, producing a directive X-ray emission in the soft X-ray to hard X-ray range, depending on the electron energy.
The Inverse Compton Scattering (ICS) process involves an intense counterpropagative laser pulse acting as an optical undulator to make oscillate the relativistic electrons on a µm scale, producing a directive X-ray emission in the hard X-ray to gamma-ray range, depending on the electron energy. The brightness of the X-ray beam depends on the charge and emittance of the electron beam. The interaction laser can either be coupled with a conventional RF–based accelerator, or a compact Laser Plasma-based Accelerator.
The betatron emission consists in exploiting a self-oscillating process occuring in the laser wakefield accelerator, and produces a directive X-ray emission in the hard-X-ray range, an ultrashort pulse duration and small spot size, with a broadband spectrum with a characteristic synchrotron-like shape.
Amplitude Expertise
Amplitude has a 20 years long experience providing intense ultrafast lasers for X-ray generation. The pionnering work began with TiSa technology, thanks to its ability to reach record breaking peak power and its flexibility.
More recently it has been followed by MIR OPCPA sources, opening unexplored mechanisms. Currently, several X-ray sources are under development using compact high average power Ytterbium lasers, aiming at providing high flux high brightness X-ray sources for industrial or medical applications.
