Modeling of radiation losses in ultrahigh power laser-matter interaction

Radiation losses of electrons in ultraintense laser fields constitute a process that can be important for electron and ion acceleration and creation of secondary emissions. The importance of this effect for ion acceleration to high energies is studied as a function of the laser intensity and the target thickness and density. For instance, in the piston regime, radiation losses lead to a reduction of the piston velocity and to less-efficient ion acceleration. Radiation losses have been implemented in the relativistic particle-in-cell code by using a renormalized Lorentz-Abraham-Dirac model.

Figure 1

Radiation losses from a laser plasma interaction with (a) and without (b) accounting for the self-force for the laser intensities (from bottom to top) ${10}^{21}$ W/cm${}^2$ (red), ${10}^{22}$ W/cm${}^2$ (green), $8\times {10}^{22}$ W/cm${}^2$ (violet), and $3.3\times {10}^{23}$ W/cm${}^2$ (blue). Other parameters are given in the text.

Figure 2

Ion phase space showing the difference between the models accounting for the radiation effects for the laser intensity $8\times {10}^{22}$  W/cm${}^2$ (a) and $3.3\times {10}^{23}$ W/cm${}^2$ (b). Red (gray) squares denote simulation with the radiation force model described by Eqs. (5). Black circles denote simulation with the radiation force model described by Eqs. (4). The laser and plasma parameters are the same as in Fig. 1.

Figure 3

Distribution of electrons (a, b) and ions (c, d) in the phase space with (a, c) and without (b, d) radiation losses at $t=100T_L$. The parameters of simulation taken from Ref. [7] are given in the text.

Figure 4

Charge separation field with (red [gray] lines) and without (black dashed lines) radiation losses at $t=100T_L$. The simulation parameters are given in the text. The part of the electric field outside the plasma is shown in the dash-dotted frame.

Figure 5

Influence of radiation losses on the electron distribution function in the perpendicular, $p_y$, and parallel, $p_x$, momenta phase space in a thick target with a density of $10n_c$ at $t=100T_L$ for a circular (a) and linear (b) polarization of the laser light with $a_L=192$. Red (gray) circles and black squares represent the electron distribution in the run with and without radiation losses, respectively.

Figure 6

Effects of radiation reaction on the ion phase space at time $t=100T_L$: for a target density of $100n_c$ with the thickness $1/8{\lambda }_L$ (a) and $0.5{\lambda }_L$ (c); and for a target thickness of $100{\lambda }_L$ with the density $10n_c$ (b) and $50n_c$ (d). Different regimes of ion acceleration are presented: a directed Coulomb explosion (a), the induced transparency regime (b), the light sail regime (c), and the piston regime (d). Red (gray) lines and red (gray) circles (black dashed lines and black squares) represent the cases with (without) radiation losses.

Figure 7

Distribution of the electron (black dashed lines) and ion (red [gray] lines) densities and the electrostatic field (green lines with blue triangles up) in the case of a thin target $l=1/8{\lambda }_L$ and $n_e=100n_c$ at time $t=100T_L$ for the laser amplitude $a_L=136$ (a, b) and $a_L=263$ (c, d). The cases with (a, c) and without (b, d) radiation losses are shown. The densities are normalized by the initial density divided by 500; the electric field is normalized by the factor $m_e{\omega }_{L}c/e$.

Figure 8

Effect of radiation losses on the ion and electron energy distribution at time $t=100T_L$: ion (a) and electron (b) energy distribution for the target with $l=100{\lambda }_L$ and $n_e=10n_c$; (c) electron energy distribution for the target with $l=1/8{\lambda }_L$ and $n_e=100n_c$; (d) ion energy distribution for the target with $l=100{\lambda }_L$ and $n_e=50n_c$. Red (black dashed) lines represent the cases with (without) radiation losses.

Figure 9

Time dependence of the effect of radiation losses for thin $l=0.125{\lambda }_L$ (a) and thick $l=100{\lambda }_L$ (b) targets of different densities. The laser amplitude is $a_L=136$. The plasma densities are given in the legend.