146 / 2023-04-14 20:40:12

Relativistic laser interaction with structured plasmas

极端光下的基础物理学 > 基础物理-I

We  discuss  relativistic  laser  interaction with overdense plasmas, where the laser pulse is incident parallel to the plasma surface, the so-called “peeler” regime [1]. In this scheme, the laser pulse impinges on an edge of a tape or on a sharp edge of a bulk target. The edge allows for an efficient conversion of the laser pulse into a surface plasma wave (SPW). The SPW propagates along the target surface. Its transverse electric field extracts dense buckets of  electrons  into  the  nearby  vacuum  region. The longitudinal electric field of the SPW accelerates the se electrons along the surface. Thus, a large fraction of electrons (tens of nC) from the target skin layer can be “peeled” off and accelerated to high energies. 

These electrons wiggle in the combined quasistatic transverse electric and magnetic fields  at  the  target  surface  and  emit  bright  betatron  radiation.  Using  fully three-dimensional particle-in-cell simulations, we show that a tabletop 100 TW class femtosecond laser can produce an ultrabright hard x-ray pulse with 10 11  photons, flux up  to  10 7  photons/eV  and  brilliance  about  10 23  photons/s/mm 2 /mrad 2 /0.1%BW  by irradiation of an edge of a microtape target [2].

When these  peeled off  energetic electrons arrive at  the  rear  edge  of the  tape,  a longitudinal bunching field is established. Protons are simultaneously accelerated and bunched by this field, leading to a highly monoenergetic proton beam [1]. 

For  a  target  structured  like  nanowires  or  nanograss,  the  laser  pulse  can  be completely  absorbed  deeply  in  the  target  leading  to  volumetric  heating,  nanoscale Z-pinch effects and extreme high energy densities [3].    



References  



[1] X. F. Shen, A. Pukhov, B. Qiao Phys. Rev. X 11 041002 (2021) 

[2] X. F. Shen, A. Pukhov, B. Qiao, arXiv:2212.14329 (2022) 

[3] V Kaymak, A Pukhov, VN Shlyaptsev, JJ Rocca, PRL 117, 035004 (2015)