Generations of spiral laser beam, spiral electron beam and longitudinal magnetic fields in hole-boring

The hole-boring by intense laser is one of the key issues for fast ignition laser fusion, laser radiation pressure ion acceleration, generation of high energy radiations, and so on. In the hole-boring, laser pulse propagation and generation of relativistic electrons and magnetic fields are critical phenomena. When the laser intensity is higher than ${10}^{20}W/c{m}^2$ and $a_0$ is larger than 10, the self-generated quasi-static magnetic fields reaches Giga Gauss to play important roles in the electron dynamics and the laser propagation. We explore the hole-boring by a linearly and a circularly polarized laser-pulses with the 3 dimensional (3D) PIC simulations. It is found that strong longitudinal magnetic fields are generated in front of the hole-boring driven by a circular polarization laser. The circularly polarized laser is converted into spiral electromagnetic waves which include both radially polarized wave and azimuthally polarized wave in the hole. The radially polarized spiral wave generates a spiral electron beam which induces the longitudinal magnetic field. Those spiral structure-formations are essentially 3D-phenomena which are investigated in details in the first time. The spiral structure-formations may play important roles in fast ignition, radiation pressure ion acceleration, and so on.