Intense lasers provide the unique ability to generate electrons, protons or neutrons in a compact setup and with reduced radioprotection constraints. The mechanisms involved differ from one particle to another, but all of them rely on a high intensity laser. When focused on a gas or a solid target, the laser pulse first generates a plasma, which electrons experience a strong acceleration induced by the high electric field of the intense laser pulse. The accelerated electrons transfer subsequently their energy to protons, neutrons or alpha particles.
Proton and Neutron Generation
For proton generation, among the numerous processes used, the most common one is the Target Normal Sheat Acceleration (TNSA). This mechanism uses a µm thin metal foil illuminated by a focused intense beam, providing a directional proton emission with multi-MeV energy, short pulse duration and small spot size. The compactness and directivity of the source make such proton source very attractive to selectively target tumors for medical therapy.
For neutron generation, the process relies on the generation of fast electrons or fast protons, followed by a nuclear reaction. Therefore, the process requires in both cases a high intensity laser designed for electron acceleration through laser-wakefield acceleration or proton acceleration through Target Normal Sheat Acceleration.
Temporal Contrast and Amplitude Expertise
The proton generation process is strongly sensitive to temporal contrast and temporal quality, which requires dedicated efforts to minimize the prepulses and the ASE background on one side, and spectral phase on the other side.
Amplitude has more than 20 years of experience in contrast metrology using its dedicated instrument, the Sequoia, which allowed Amplitude to improve the contrast of the Ti:Sa based Petawatt lasers. The techniques were initially based on saturable absorbers, later XPW in double CPA architecture, and more recently OPCPA seeder to meet the contrast requirements for efficient and reliable proton generation. This expertise is of course applicable to any amplification technology, from TiSa to Ytterbium, Neodyme or parametric amplification (OPCPA).
Moreover, Amplitude implements spectral shaping and spectral phase correction to reach the best temporal compression and highest peak power.
