Coulomb explosion effect and the maximum energy of protons accelerated by high-power lasers

Abstract

The acceleration of light ions (protons) through the interaction of a high-power laser pulse with a double-layer target is theoretically studied by means of two-dimensional particle-in-cell simulations and a one-dimensional analytical model. It is shown that the maximum energy acquired by the accelerated light ions (protons) depends on the physical characteristics of a heavy-ion layer (electron-ion mass ratio and effective charge state of the ions). In our theoretical model, the hydrodynamic equations for both electron and heavy-ion species are solved and the test-particle approximation for the light ions (protons) is applied. The heavy-ion motion is found to modify the longitudinal electric field distribution, thus changing the acceleration conditions for the protons.

Accelerating protons to therapeutic energies with ultraintense, ultraclean, and ultrashort laser pulses

“…However, after a time interval equal to or longer than the inverse of the heavy ion Langmuir frequency, the heavy ion layer explodes because of the repulsive Coulomb force. Moreover, if the laser field is much stronger than the Coulomb attraction field, the ions cannot retain electrons near the backside of the target, which leads to ion acceleration in the so-called Coulomb explosion regime [9,33,36].…”

“…While the energy increase with the decrease of target thickness was shown, the results can be explained in the framework of TNSA. Several other regimes of ion acceleration from thin foils were theoretically considered: Coulomb Explosion [33], the Laser Piston regime [34], enhanced TNSA [35], and Coulomb mirror [36].…”

Achieving Stable Radiation Pressure Acceleration of Heavy Ions via Successive Electron Replenishment from Ionization of a High- Z Material Coating

“…Assuming the CE develops mainly in 1D, the foil thickness evolving with time can be estimated [18] as…”

TH‐C‐350‐06: Laser‐To‐Proton Energy Transfer Efficiency in Laser‐Plasma Interactions

“…A strong electrostatic field (∼ TV/m) is set up between the expanding electrons and the target that field ionizes the thin hydrogen-rich layer present at its back surface. Subsequently, the protons are accelerated in this electrostatic field [10,11]. For thicker targets (≥ 2 µm) a shock wave acceleration mechanism has also been proposed [12] in which a laser acts as a piston driving a flow of ions into the target and launching an electrostatic shock at the front of the target with high Mach number M=v shock /c≃ 0.2-0.3.…”