Abstract:Structured solid targets are widely investigated to increase the energy absorption of high-power laser pulses so as to achieve efficient ion acceleration. Here we report the first experimental study of the maximum energy of proton beams accelerated from sub-micrometric foils perforated with holes of nanometric size. By showing the lack of energy enhancement in comparison to standard flat foils, our results suggest that the high contrast routinely achieved with a double plasma mirror does not prevent damaging o… Show more
“…Figure 1 a shows the contrast ratio measured by a third-order cross-correlator, which reaches on the 100s-of-ps timescale and at 1 ps before the main pulse. Although the intensity rapidly increases in the region of the coherent pedestal (later than ps), the scale length of the produced pre-plasma is short enough to still allow for TNSA in the BWD direction 31 . Figure 1 ( a ) Temporal contrast measured by a third-order cross-correlator, with and without DPM.…”
Section: Resultsmentioning
confidence: 99%
“…Comparable energies in both directions support that the temporal contrast is high enough even for the 10 nm-thick foil to remain essentially unperturbed until the arrival of the main laser pulse (panel (a)). If a pre-plasma is formed at the front surface, its extent is negligible since the acceleration mechanism is similar on both sides of the target 4 , 31 . The energies obtained from the 10 nm foil are higher than those from the 100 nm one (panel (b)), compatible with the reduced thickness that favours electron recirculation and heating in the laser field 36 .…”
Optimisation and reproducibility of beams of protons accelerated from laser-solid interactions require accurate control of a wide set of variables, concerning both the laser pulse and the target. Among the former ones, the chirp and temporal shape of the pulse reaching the experimental area may vary because of spectral phase modulations acquired along the laser system and beam transport. Here, we present an experimental study where we investigate the influence of the laser pulse chirp on proton acceleration from ultrathin flat foils (10 and 100 nm thickness), while minimising any asymmetry in the pulse temporal shape. The results show a $$\pm 10\%$$
±
10
%
change in the maximum proton energy depending on the sign of the chirp. This effect is most noticeable from 10 nm-thick target foils, suggesting a chirp-dependent influence of relativistic transparency.
“…Figure 1 a shows the contrast ratio measured by a third-order cross-correlator, which reaches on the 100s-of-ps timescale and at 1 ps before the main pulse. Although the intensity rapidly increases in the region of the coherent pedestal (later than ps), the scale length of the produced pre-plasma is short enough to still allow for TNSA in the BWD direction 31 . Figure 1 ( a ) Temporal contrast measured by a third-order cross-correlator, with and without DPM.…”
Section: Resultsmentioning
confidence: 99%
“…Comparable energies in both directions support that the temporal contrast is high enough even for the 10 nm-thick foil to remain essentially unperturbed until the arrival of the main laser pulse (panel (a)). If a pre-plasma is formed at the front surface, its extent is negligible since the acceleration mechanism is similar on both sides of the target 4 , 31 . The energies obtained from the 10 nm foil are higher than those from the 100 nm one (panel (b)), compatible with the reduced thickness that favours electron recirculation and heating in the laser field 36 .…”
Optimisation and reproducibility of beams of protons accelerated from laser-solid interactions require accurate control of a wide set of variables, concerning both the laser pulse and the target. Among the former ones, the chirp and temporal shape of the pulse reaching the experimental area may vary because of spectral phase modulations acquired along the laser system and beam transport. Here, we present an experimental study where we investigate the influence of the laser pulse chirp on proton acceleration from ultrathin flat foils (10 and 100 nm thickness), while minimising any asymmetry in the pulse temporal shape. The results show a $$\pm 10\%$$
±
10
%
change in the maximum proton energy depending on the sign of the chirp. This effect is most noticeable from 10 nm-thick target foils, suggesting a chirp-dependent influence of relativistic transparency.
“…2011; Fischer & Wegener 2013; Cantono et al. 2021). In particular, it has been shown experimentally that by adjusting the spatial profile of the laser prepulse and introducing a variable delay with the main laser pulse, one can create transient plasma gratings on the surface of the thin-foil target with controllable precision (Monchocé et al.…”
The process of radiation pressure acceleration (RPA) of ions is investigated with the aim of suppressing the Rayleigh–Taylor-like transverse instabilities in laser–foil interaction. This is achieved by imposing surface and density modulations on the target surface. We also study the efficacy of RPA of ions from density modulated and structured targets in the radiation dominated regime where the radiation reaction effects are important. We show that the use of density modulated and structured targets and the radiation reaction effects can help in achieving the twin goals of high ion energy (in GeV range) and lower energy spread.
“…A paradigm shift has been seen in the last years in the target morphology, from simple flat foils to micro-and nano-structured targets presented in several reports, in order to highlight the benefit of the latests. Targets consisting of nanowires [88], micropillars and microtubes [51,72,89], nanochannels [59], nanoholes [90], flat foils embedded with nanoparticles [91] or with nanospheres [66,69,92], double layers made of different materials [38,93], a combination of double-layer and embedded nanospheres [67], foams [94][95][96] and flat foil with grooves or micro-gratings [28,69,97,98] have already been tested. The results reported with these types of targets are presented also in Figure 4.…”
The target normal sheath acceleration is a robust mechanism for proton and ion acceleration from solid targets when irradiated by a high power laser. Since its discovery extensive studies have been carried out to enhance the acceleration process either by optimizing the laser pulse delivered onto the target or by utilizing targets with particular features. Targets with different morphologies such as the geometrical shape (thin foil, cone, spherical, foam-like, etc.), with different structures (multi-layer, nano- or micro-structured with periodic striations, rods, pillars, holes, etc.) and made of different materials (metals, plastics, etc.) have been proposed and utilized. Here we review some recent experiments and characterize from the target point of view the generation of protons with the highest energy.
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