Lasers as particle accelerators in medicine: From laser-driven protons to imaging with Thomson sources

We report our recent progress using a high‐power, picosecond CO2 laser for Thomson scattering and ion acceleration experiments. These experiments capitalize on certain advantages of long‐wavelength CO2 lasers, such as their high number of photons per energy unit and beneficial wavelength‐ scaling of the electrons’ ponderomotive energy and critical plasma frequency. High X‐ray fluxes produced in the interactions of the counter‐propagating laser‐ and electron‐beams for obtaining single‐shot, high‐contrast images of biological objects. The laser, focused on a hydrogen jet, generated a monoenergetic proton beam via the radiation‐pressure mechanism. The energy of protons produced by this method scales linearly with the laser’s intensity. We present a plan for scaling the process into the range of 100‐MeV proton energy via upgrading the CO2 laser. This development will enable an advance to the laser‐driven proton cancer therapy.