Optimisation of multi-petawatt laser-driven proton acceleration in the relativistic transparency regime

Abstract

Laser-driven proton acceleration from ultrathin foils in the relativistic transparency regime is investigated using 2D and 3D particle-in-cell simulations. The optimisation of the maximum proton energy and the overall laser-to-proton energy conversion efficiency with the onset of transparency is investigated for linearly and circularly polarised laser light at intensities up to 2×1023 Wcm-2. The effects of the rising edge of the laser intensity profile and radiation reaction at the most extreme laser intensity are considered. It is found that the time at which transparency occurs relative to the peak of the laser pulse interacting with the plasma is a defining parameter in the optimisation of proton acceleration, over the full range of parameters explored.

Optimization and control of synchrotron emission in ultraintense laser–solid interactions using machine learning

“…Before optimizing the interaction, the influence of a number of input parameters, including each of the chosen optimization parameters, was first explored in 2D parameter space scans. The target thickness was one of the varied parameters in each scan, enabling separation of the effect of RSIT, which can be controlled with target thickness [ 83 ] , from the effect of varying each of the other parameters. Initially, in Figures 2(a)–2(c) a pulse with fs, m and incident at target normal ( ) was considered, and simulated for peak laser intensities – W cm −2 , covering a range for which synchrotron radiation may become measurable, up to where it is expected to dominate.…”

Effect of the rising edge of ultrashort laser pulse on the target normal sheath acceleration of ions

“…Therefore, no increase in ion energies for foils including nanoholes compared with regular foils was observed in the experiment when the foils were irradiated by a real ultrashort laser pulse. Other papers investigate ion acceleration in the relativistic induced transparency regime, which is reached earlier with the slowly rising edge of the laser pulse due to the foil pre-expansion compared with an ideal Gaussian pulse [23,24]. The gradient of intensity increase in time can be even more reduced; thus, asymmetric laser pulse with a slow rise and a sharp fall in time is produced, which can lead to an enhanced ion acceleration as demonstrated in several studies [25][26][27].…”

Synchronized off-harmonic probe laser with highly variable pulse duration for laser–plasma interaction experiments

“…To optimize this control, accurate measurements of the on-shot plasma properties and dynamics are essential. In particular, the preionization of the target and the following expansion of the plasma due to the temporal-contrast imperfections of the laser play a predominant role, especially in laser-ion acceleration [4,5] or the generation of surface high harmonics [6] .…”