“…Notably, the spatial distribution of the mean electron kinetic energy partially overlaps with the spatial distribution of E x , as seen by comparing figure 3 with figure 2. This effect is mentioned as 'electron capture' by the laser field (Wang et al 1998;Wang et al 2001;Braenzel et al 2017), where similar electron patterns are observed in Bulanov et al ( , 2010a. Therefore, those captured electrons are continuously accelerated for as long as they are kept in phase with the pulse (Wang et al 2001;.…”
Section: Energy Transfer Electron Evolution and Charge Separationsupporting
Although the interaction of a flat foil with currently available laser intensities is now considered a routine process, during the last decade, emphasis has been given to targets with complex geometries aiming at increasing the ion energy. This work presents a target geometry where two symmetric side holes and a central hole are drilled into the foil. A study of the various side-hole and central-hole length combinations is performed with two-dimensional particle-in-cell simulations for polyethylene targets and a laser intensity of
$5.2\times 10^{21}~\text{W}~\text{cm}^{-2}$
. The holed targets show a remarkable increase of the conversion efficiency, which corresponds to a different target configuration for electrons, protons and carbon ions. Furthermore, diffraction of the laser pulse leads to a directional high energy electron beam, with a temperature of
${\sim}40~\text{MeV}$
, or seven times higher than in the case of a flat foil. The higher conversion efficiency consequently leads to a significant enhancement of the maximum proton energy from holed targets.
“…Notably, the spatial distribution of the mean electron kinetic energy partially overlaps with the spatial distribution of E x , as seen by comparing figure 3 with figure 2. This effect is mentioned as 'electron capture' by the laser field (Wang et al 1998;Wang et al 2001;Braenzel et al 2017), where similar electron patterns are observed in Bulanov et al ( , 2010a. Therefore, those captured electrons are continuously accelerated for as long as they are kept in phase with the pulse (Wang et al 2001;.…”
Section: Energy Transfer Electron Evolution and Charge Separationsupporting
Although the interaction of a flat foil with currently available laser intensities is now considered a routine process, during the last decade, emphasis has been given to targets with complex geometries aiming at increasing the ion energy. This work presents a target geometry where two symmetric side holes and a central hole are drilled into the foil. A study of the various side-hole and central-hole length combinations is performed with two-dimensional particle-in-cell simulations for polyethylene targets and a laser intensity of
$5.2\times 10^{21}~\text{W}~\text{cm}^{-2}$
. The holed targets show a remarkable increase of the conversion efficiency, which corresponds to a different target configuration for electrons, protons and carbon ions. Furthermore, diffraction of the laser pulse leads to a directional high energy electron beam, with a temperature of
${\sim}40~\text{MeV}$
, or seven times higher than in the case of a flat foil. The higher conversion efficiency consequently leads to a significant enhancement of the maximum proton energy from holed targets.
“…While the scheme of ionizing highly-charged ions predicted GeV acceleration numerically 34 , preliminary experiments only showed ~1 MeV photoelectrons generated from this process 36 . The scheme exploiting partially transmitted laser for acceleration between two foils showed no amplification in the energy but only an increase of electron number around 1 MeV energy 37 . Recently, a breakthrough was made in VLA using a plasma mirror injector accelerating electrons to relativistic energies around 10 MeV 25 .…”
Section: Introductionmentioning
confidence: 89%
“…Several schemes have been proposed to facilitate electron injection in VLA, for example, by tailoring the laser profile, ionizing highly-charged ions, or using nanocluster targets 33 – 35 . Nevertheless, clear experimental demonstration of VLA has been difficult 19 , 36 , 37 . Despite using relativistically intense lasers, many experiments demonstrated only 100 s keV acceleration 19 .…”
Intense lasers can accelerate electrons to very high energy over a short distance. Such compact accelerators have several potential applications including fast ignition, high energy physics, and radiography. Among the various schemes of laser-based electron acceleration, vacuum laser acceleration has the merits of super-high acceleration gradient and great simplicity. Yet its realization has been difficult because injecting free electrons into the fast-oscillating laser field is not trivial. Here we demonstrate free-electron injection and subsequent vacuum laser acceleration of electrons up to 20 MeV using the relativistic transparency effect. When a high-contrast intense laser drives a thin solid foil, electrons from the dense opaque plasma are first accelerated to near-light speed by the standing laser wave in front of the solid foil and subsequently injected into the transmitted laser field as the opaque plasma becomes relativistically transparent. It is possible to further optimize the electron injection/acceleration by manipulating the laser polarization, incident angle, and temporal pulse shaping. Our result also sheds light on the fundamental relativistic transparency process, crucial for producing secondary particle and light sources.
“…The T2 target is located at a certain position, and is induced by the action of the target-back electric field E to generate an additional electric field E ’, which in turn may induce a re-acceleration effect. This configuration was first proposed by Braenzel et al [ 59 ] based on the relativistic transparency mechanism, and the possibility of a double-film structure to enhance the quality of proton beams was theoretically illustrated. Figure 6 Two different double target structures. (a) Double-layer target for a plasma mirror.…”
Section: Studies Of Laser-driven Proton Acceleration Based On Target ...mentioning
The target backsheath field acceleration mechanism is one of the main mechanisms of laser-driven proton acceleration (LDPA) and strongly depends on the comprehensive performance of the ultrashort ultra-intense lasers used as the driving sources. The successful use of the SG-II Peta-watt (SG-II PW) laser facility for LDPA and its applications in radiographic diagnoses have been manifested by the good performance of the SG-II PW facility. Recently, the SG-II PW laser facility has undergone extensive maintenance and a comprehensive technical upgrade in terms of the seed source, laser contrast and terminal focus. LDPA experiments were performed using the maintained SG-II PW laser beam, and the highest cutoff energy of the proton beam was obviously increased. Accordingly, a double-film target structure was used, and the maximum cutoff energy of the proton beam was up to 70 MeV. These results demonstrate that the comprehensive performance of the SG-II PW laser facility was improved significantly.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
