When intense and ultra short laser pulses (10¹⁸-10¹⁹W/cm²), like the ones available today, are focused in a plasma, relativistic electron beams can be generated with remarkable properties: short-term, low divergence, high energy. In the "bubble" regime (very nonlinear), the accelerated electrons are quasi-monoenergetic, up to several hundreds of MeV or even GeV on centimetric accelerating lengths. For comparison, conventional accelerators achieve these energies but on kilometric distances!

Laser-plasma accelerators have been extensively studied. The research aims to both understand more finely the processes involved in the coupling of the laser and the plasma, and optimize, through the control of all laser-plasma parameters, the source itself for potential applications. Previous experiments with the UHI10 laser facility (10TW, 60FS) in collaboration with INFN and LULI teams helped accelerate electrons to few tens of MeV [Giulietti 2008]. The characteristics of the electron beam products have allowed to consider using this laser-plasma accelerator for intraoperative radiotherapy research [ La recherche 2008].

The last years, encouraged by these results, we develop a new theme on the laser-plasma acceleration. The laser system has evolved into UHI100 (100TW-25fs) now offering the opportunity to work in two radioprotected rooms, whose one is especially dedicated to electron acceleration. We are interested in this topic of laser-plasma accelerator, mainly through: