Laser driven proton beam for the applications: toward ultra‐high intensity & short pulse proton beam

As a benchmark experiment to realize a novel and compact laser driven proton accelerator whose significant features are high number density in a short pulse width (∼ns), 2.4 MeV laser driven proton beam is stably focused at 1 Hz repetition rate by using a pair of permanent quadrupole magnets (PMQs) with large apertures whose diameters and field strengths are 3.5 cm and 55 T/m for the first and 2.3 cm and 60 T/m for the second magnets, respectively. The proton beam has been focused to a focal spot of 3×8 mm2 in horizontal and vertical direction (full width at half maximum) at 650∼mm from the source, which is well reproduced by the simulation. The further optimization of the focusing system will sure to pave a way to the novel proton accelerator with which we can investigate the physics appeared in the short time scale as well as that in a high energy density matter, oncology, astrophysics, and so on.