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Enhancement of proton collimation and acceleration by an ultra-intense laser interacting with a cone target followed by a beam collimator

A special method is proposed of a laser-induced cavity pressure acceleration scheme for collimating, accelerating and guiding protons, using a single-cone target with a beam collimator through a target normal sheath acceleration mechanism. In addition, the problems involved are studied by using two-dimensional particle-in-cell simulations. The results show that the proton beam can be collimated, accelerated and guided effectively through this type of target. Theoretically, a formula is derived for the combined electric field of accelerating protons. Compared with a proton beam without a beam collimator, the proton beam density and cut-off energy of protons in the type II are increased by 3.3 times and 10% respectively. Detailed analysis shows that the enhancement is mainly due to the compact and strong sheath electrostatic field, and that the beam collimator plays a role in focusing energy. In addition, the simulation results show that the divergence angle of the proton beam in type II is less than 1.67 times that of type I. The more prominent point is that the proton number of type II is 2.2 times higher than that of type I. This kind of target has important applications in many fields, such as fast ion ignition in inertial fusion, high energy physics and proton therapy.