Abstract
We study the optimization of collisionless shock acceleration of ions based on hydrodynamic modelling and simulations of collisional shock waves in gaseous targets. The models correspond to the specifications required for experiments with the $\text{CO}_{2}$ laser at the Accelerator Test Facility at Brookhaven National Laboratory and the Vulcan Petawatt system at Rutherford Appleton Laboratory. In both cases, a laser prepulse is simulated to interact with hydrogen gas jet targets. It is demonstrated that by controlling the pulse energy, the deposition position and the backing pressure, a blast wave suitable for generating nearly monoenergetic ion beams can be formed. Depending on the energy absorbed and the deposition position, an optimal temporal window can be determined for the acceleration considering both the necessary overdense state of plasma and the required short scale lengths for monoenergetic ion beam production.
Highlights
Over the past 15 years, the generation of multi-MeV proton and ion beams with unique properties has attracted intense interest due to the numerous fundamental and applicative prospects these beams offer[1,2,3,4,5]
At higher energies and deposition positions close to the throat of the jet, the density decreased very fast because it is possible to move below the critical density since the shock wave moves towards the descending side of the density’s ramp, resulting in undercritical density gradients even in the blast wave’s walls (Figure 8)
It is thought that the sharper the density gradient the more monochromatic the accelerated ion beam
Summary
Over the past 15 years, the generation of multi-MeV proton and ion beams with unique properties has attracted intense interest due to the numerous fundamental and applicative prospects these beams offer[1,2,3,4,5]. The mechanism proposed here constitutes a novel laser driven ion acceleration scheme[2] that offers greater control on the energy of the ions. In this mechanism, ions are accelerated by being pushed by the potential barrier located at a collisionless shock front generated by the laser source[2, 6,7,8,9]. In experiments performed using intense CO2 lasers, it is surmised that the profile is modified by a pulse train inherent to the laser system[15, 16], Downloaded from https://www.cambridge.org/core. 02 Nov 2021 at 12:37:14, subject to the Cambridge Core terms of use
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