Generating Monoenergetic Heavy-Ion Bunches with Laser-Induced Electrostatic Shocks

A method for efficient laser acceleration of heavy ions by electrostatic shock is investigated using particle-in-cell (PIC) simulation and analytical modeling. When a small number of heavy ions are mixed with light ions, the heavy ions can be accelerated to the same velocity as the light ions so that they gain much higher energy because of their large mass. Accordingly, a sandwich target design with a thin compound ion layer between two light-ion layers and a micro-structured target design are proposed for obtaining monoenergetic heavy-ion beams.

Figure 1

(a) Phase space of the light and heavy ions and the electric field distribution of the collisionless electrostatic shock at $t=150T_0$ for $a_L=2$, $n_e=5n_c$, and $d=2{\lambda }_0$. (b) The energy spectrum of the light and heavy ions. Here, ${\epsilon }_l$ and ${\epsilon }_h$ are the longitudinal kinetic energies of the light and heavy ions, and $N_{\mathrm{ion}}$ is the species ion number normalized by the total ion number.

Figure 2

Reflected heavy-ion momentum vs (a) $\alpha$ and (b) $\beta$ from simulations (circles) and Eq. (4) (solid line) at $t=150T_0$. The other parameters are the same as in Fig. (1).

Figure 3

Sandwich target scheme (a) and energy spectrum of normal compound target (red solid) and sandwich target (blue solid) (b) at $t=240T_0$ for a Gaussian laser pulse with peak amplitude $a_L=4$ and FWHM of $22T_0$.

Figure 4

Space distribution of hydrogen (black dots) and carbon ions (red dots) at $t=30T_0$ (a), phase space of heavy ions at different time (b), energy spectrum of heavy ions at different time (c) and transverse distribution of $p_L/p_T$ (d), where $p_L=\gamma m_i{v}_{ix}$ and $p_T=\gamma m_i(v_{iy}^2+v_{iz}^2{)}^{1/2}$ are heavy ions’ longitudinal and transverse momentum and $\rho =(y^2+z^2{)}^{1/2}$ is the distance from the target center.