Support l'X Ultrashort Lasers for Monitoring the Quality of Industrial Parts
Rodrigo Lopez-Martens (LOA) présente le principe de l'accélération laser-plasma lors du lancement du projet CALYCO à l'École polytechnique le 2 juillet 2026.
Detecting Defects
The presence of defects inside industrial components—such as aircraft wings or landing gear, or nuclear power plant pressure vessels—can be critical. To ensure the quality of parts without having to cut them open for inspection, manufacturers are seeking non-destructive testing methods.
Gamma-ray radiography (using high-energy photons) allows for the acquisition of 3D images of components without damaging them. However, suitable light sources are provided by particle accelerators—large-scale equipment that is impractical for industrial use.
Smaller Accelerators
Laser-plasma acceleration opens the door to the miniaturization of these accelerators. When an ultrashort-pulse laser is focused on a gas, a plasma is created. The electrons are then trapped in the laser’s wake and accelerated to extremely high speeds (close to the speed of light) over a very short distance. When they are subsequently decelerated, these electrons emit gamma radiation.
“The micrometer-scale source size of the laser-plasma accelerator should make it possible to dramatically increase the spatial resolution of gamma-ray imaging techniques compared to what is achievable today,” explains Rodrigo Lopez-Martens, chairholder and researcher at LOA, one of the pioneering laboratories in fundamental research on the phenomenon of laser-plasma acceleration. It is currently the only French institution working on this topic.
Ytterbium Lasers for Scaling Up
The goal now is to make the leap to industrial-scale application of this technology for nondestructive testing. The lasers used in laboratories, which are based on titanium-doped sapphire, do not have the properties required for industrial use. In fact, to achieve particle fluxes intense enough for these applications, lasers are needed that combine high average powers with ultrashort pulse durations, while also being continuously controllable.
As part of the CALYCO project, lasers using the element ytterbium have been identified as the most suitable. Thanks to their kilowatt-level power, ytterbium lasers could enable X-ray penetration depths of up to one meter inside parts. These lasers are already used for industrial machining applications, but their characteristics are not yet compatible with laser-plasma acceleration.
In particular, one of the challenges is to reduce the pulse duration of this type of laser by a factor of 100, in order to reach around ten femtoseconds (i.e., a few millionths of a billionth of a second). To achieve this, LOA has mastered the key technology of “temporal post-compression.” Other areas of focus for the project will include optimizing the human-machine interface and increasing the laser’s average power to rapidly acquire high-resolution images.
*LOA: a joint research unit CNRS, École Polytechnique, ENSTA, Institut Polytechnique de Paris, 91120 Palaiseau, France