Theoretical Model of Laser-Driven Proton Acceleration via Hybrid Scheme Based on KPSI J-KAREN-P 1-PW Laser

The laser-driven proton acceleration has been extensively studied via simulations and experiments, such as target normal sheath acceleration (TNSA)<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</sup> and radiation pressure acceleration (RPA)<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</sup>. Recently, pioneers have explored the use of laser wakefield acceleration (LWFA)<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[3]</sup> to accelerate protons. However, achieving higher proton energies with this method requires significantly more laser energy. In 2021, Isayama et al. introduced a three-stage hybrid acceleration scheme (RPA-LWFA-TNSA)<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[4]</sup> achieving high proton energy efficiently. The configuration of this scheme is shown in Fig. 1(a). Two circularly-polarized pulses are used. The targets consist of a solid-density (SD) target and a near-critical density (NCD) target separated by a vacuum gap. The first pulse interacts with the SD target and causes the RPA acceleration. The second pulse interacts with the NCD target and induces the LWFA and TNSA acceleration mechanism.