Two-dimensional particle-in-cell (PIC) simulations have been used to investigate the interaction between a laser pulse and a foil exposed to an external strong longitudinal magnetic field. Compared with that in the absence of the external magnetic field, the divergence of proton with the magnetic field in radiation pressure acceleration (RPA) regimes has improved remarkably due to the restriction of the electron transverse expansion. During the RPA process, the foil develops into a typical bubble-like shape resulting from the combined action of transversal ponderomotive force and instabilities. However, the foil prefers to be in a cone-like shape by using the magnetic field. The dependence of proton divergence on the strength of magnetic field has been studied, and an optimal magnetic field of nearly 60 kT is achieved in these simulations.

中文翻译：

---

通过使用外部强磁场改善辐射压力加速方式中的离子加速

二维单元格内粒子（PIC）模拟已用于研究激光脉冲与暴露于外部强纵向磁场的金属箔之间的相互作用。与不存在外部磁场的情况相比，由于电子横向膨胀的限制，质子在辐射压力加速（RPA）状态下随磁场的发散性得到了显着改善。在RPA过程中，铝箔由于横向质动力和不稳定性的共同作用而发展成典型的气泡状形状。然而，箔片优选通过使用磁场而呈圆锥形。研究了质子散度对磁场强度的依赖性，并在这些模拟中获得了接近60 kT的最佳磁场。