No abstract

In order to generate high quality ion beams through the stable radiation pressure acceleration (RPA) of the near critical density (NCD) target, we propose a new type of target where an ultra-thin high density (HD) layer is attached to the front surface of an NCD target, which has a preferable self-supporting property in the RPA experiments than the ultra-thin foil target. It is found that in one-dimensional particle-in-cell (PIC) simulation, by the block of the HD layer in the new target, there emerges the hole-boring process rather than propagation in the NCD layer when the intense laser pulse impinges on this target. As a result, a typical RPA structure that the compressed electron layer overlaps the ion layer as a whole is formed and a high quality ion beam is obtained, e.g., a circularly polarized laser pulse with normalized amplitude a 0 = 120 impinges on this new target and a 1.2 GeV monoenergetic ion beam is generated through the RPA of the NCD layer. Similar results are also found in the two-dimensional PIC simulation.

In order to generate high quality ion beams through a relatively uniform radiation pressure acceleration (RPA) of a common flat foil, a new scheme is proposed to overcome the curve of the target while being radiated by a single transversely Gaussian laser. In this scheme, two matched counterpropagating transversely Gaussian laser pulses, a main pulse and an auxiliary pulse, impinge on the foil target at the meantime. It is found that in the two-dimensional (2D) particle-in-cell (PIC) simulation, by the restraint of the auxiliary laser, the curve of the foil can be effectively suppressed. As a result, a high quality monoenergetic ion beam is generated through an efficient RPA of the foil target. For example, two counterpropagating transversely circularly polarized Gaussian lasers with normalized amplitudes a 1 ¼ 120 and a 2 ¼ 30, respectively, impinge on the foil target at the meantime, a 1.3 GeV monoenergetic proton beam with high collimation is obtained finally. Furthermore, the effects on the ions acceleration with different parameters of the auxiliary laser are also investigated.

The propagation of an intense laser beam in a corrugated plasma channel is investigated. By using the source-dependent expansion technique, an evolution equation of the laser spot size is derived. The behaviors including aperiodic oscillation, resonance, beat-like wave, and periodic oscillation with multipeak are found and analyzed. The formula for the instantaneous wave numbers of these oscillations is obtained. These theoretical findings are confirmed by the final numerical simulation.

We investigate the impacts of the laser contrast on ion acceleration when an ultra-intense laser pulse irradiates on a sub-micron foil target. In high-intensity laser driven ion acceleration experiments, the rising edge of the pulse could significantly preheat the target, which is likely to cause premature relativistic induced transparency of the target before the pulse peak. In this case, our particle-in-cell simulations show that the breakout afterburner (BOA) mechanism has obvious advantages over the radiation pressure acceleration (RPA). With the ATLAS laser contrast of 10 −8.8 in 2 ps and 2.8 × 10 21 W cm −2 peak intensity, the optimized target thickness is increased to 0.27 µm, where BOA works well and the maximum proton energy can reach 250 MeV. The proton energy is higher than that generated via RPA in a nanometer thin target either with and without the rising edge. Besides, the BOA appears robust against the laser contrast.