In the fast ignition of laser fusion, there are two ways of fast heating of imploded high-density plasmas. One is the cone-guiding and the other is the hole boring  to send an intense short pulse laser to the core through long scale corona plasmas. In the hole boring, laser pulse propagation, relativistic electron generation and transport in the plasma channel are critical issues. The hole boring is also the key process in the radiation pressure ion acceleration. In both cases, the laser intensity is higher than 10²⁰ W/cm²  and the normalized laser amplitude a0 is larger than 10.
   The figure shows Ion density profile and the magnetic field profile of the hole-boring with a 1.0 psec laser pulse. The color bar for ion density is shown in t(a) and the qiasi-static magnetic field profile is shown. They are the 2-D PIC simulation results of the hole-boring for a realistic density profile of the ignition scale implosion, in which the hole boring reaches up to 100 times critical density and the strong azimuthal magnetic fields (B-fields) are generated to guide the relativistic electron flow.
  The 3D PIC simulations are also carried out to see the 3D effects on the hole-boring. It is found that a circularly polarized laser pulse burns through a thin foil of the electron density of 1000 nc to generate a helical laser pulse, a spiral electron beam, and strong longitudinal B-fields of Giga Gauss are generated. The longitudinal B-field will guide the relativistic spiral electron beam in the channel to the core. The generation mechanism of helical laser pulses and longitudinal B-fields is related to the laser propagation in the magnetized plasma.
In the presentation, we will discuss that the heating efficiency of dense plasmas is enhanced by the hole boring with the intense circularly polarized laser of a few pico-second and the heating laser energy required for ignition is reduced significantly.

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Fast ignition, Hole-boring, Magnetic field generation, Spiral laser beam,