The generation of unexpected super-high energetic electrons at relativistic circularly polarized laser-solid interactions in the presence of large scale pre-plasmas

As an extension of the previous work [arXiv: 1512.02411], we have investigated the role of circularly polarized (CP) laser pulses while keeping other conditions the same. It is found that in the presence of large scale pre-formed plasmas, super-high energetic electrons can be generated at relativistic CP laser-solid interactions. For laser of intensity $10^{20}
$\text{W}$/$\text{cm}$^2$andpre-plasmascale-length$10\ \mu$\text{m}$$, the cut-off energy of electron by CP laser is $120\text{ MeV}$ compared with $100
$\text{MeV}$$ in the case of linearly polarized (LP) laser. The unexpected super-high energetic electron acceleration can also be explained by the two-stage acceleration model, {by taking into account the envelop modulation effects of the reflected CP laser pulse.} The underlying physics of this envelop modulation is figured out, and a modified first-stage electron acceleration scaling law in the presence of the modulated-CP laser is also obtained.