Generation of quasi-monoenergetic protons from a double-species target driven by the radiation pressure of an ultraintense laser pulse

In laser-driven proton acceleration, generation of quasi-monoenergetic proton beams has been considered a crucial feature of the radiation pressure acceleration (RPA) scheme, but the required difficult physical conditions have hampered its experimental realization. As a method to generate quasi-monoenergetic protons under experimentally viable conditions, we investigated using double-species targets of controlled composition ratio in order to make protons bunched in the phase space in the RPA scheme. From a modified optimum condition and three-dimensional particle-in-cell simulations, we showed by varying the ion composition ratio of proton and carbon that quasi-monoenergetic protons could be generated from ultrathin plane targets irradiated with a circularly polarized Gaussian laser pulse. The proposed scheme should facilitate the experimental realization of ultrashort quasi-monoenergetic proton beams for unique applications in high field science. © 2016 AIP Publishing LLC1441sciescopu

Low-divergence relativistic proton jet from a thin solid target driven by an ultra-intense circularly polarized Laguerre-Gaussian laser pulse

© 2020 IOP Publishing Ltd.We propose a new ion acceleration scheme of irradiating a thin solid target with an ultraintense circularly polarized Laguerre-Gaussian (LG) laser pulse. Three-dimensional particle-in-cell simulations are performed to demonstrate that this scheme can generate a low-divergence high-density relativistic proton jet. By this scheme, the number of protons emitted with a small angle (<1°) from the laser axis can be more than tens of times as high as that of the protons accelerated by a circularly polarized Gaussian pulse. The inward ponderomotive force of the LG pulse drives such a proton beam along the laser axis11Nsciescopu

Direct laser acceleration of electrons from a plasma mirror by an intense few-cycle Laguerre-Gaussian laser and its dependence on the carrier-envelope phase

© 2022 IOP Publishing Ltd.A direct acceleration scheme to generate high-energy, high-charge electron beams with an intense few-cycle Laguerre-Gaussian (LG) laser pulse was investigated using three-dimensional particle-in-cell simulations. In this scheme, an intense LG laser pulse was irradiated onto a solid density plasma slab. When the laser pulse is reflected, electrons on the target front surface are injected into the longitudinal electric field of the laser and accelerated further. We found that the carrier-envelope phase (CEP) of the few-cycle laser pulse plays a key role in the electron injection and acceleration process. Using a three-cycle LG laser pulse with a0=2 and an appropriate CEP, an about 60 pC electron beam could be obtained at a maximum energy of 16 MeV. In comparison, when a laser pulse with mismatched CEP was used, a total of 4 pC electron beam with a maximum energy of 3.5 MeV was obtained. Linear scaling of electron energy to the laser strength was shown up to a0=100 at which a quasi-monoenergetic electron beam of 850 MeV energy with a charge equal to 600 pC could be obtained. These results demonstrate that high-energy electron beams can be stably generated through direct laser acceleration using a CEP-controlled intense few-cycle LG laser pulse.11Nsciescopu

Strong field physics pursued with petawatt lasers

Recent ultra-short high-power lasers can provide ultra-high laser intensity over 1022 W/cm2 . Laser fields of such extreme strengths instantaneously turn matter into plasma, which exhibits relativistic collective dynamics, thereby leading to unprecedented physical systems with potential breakthrough applications. In this article, we introduce the basic concepts and trace the progress in ultra-high intensity laser development and relativistic laser-plasma interactions, including laser-driven charged particle acceleration.11Yscopu

Characteristics of electron beams accelerated by parallel and antiparallel circularly polarized Laguerre–Gaussian laser pulses

A direct comparison of the properties of electron beam generated by antiparallel circularly polarized Laguerre–Gaussian (CPLG) laser pulse and parallel CPLG laser pulse has been performed with three-dimensional particle-in-cell simulations. It is known that the longitudinal field of an antiparallel CPLG laser pulse with opposite signs of spin and orbital quantum number preferentially accelerates electrons to high energy. However, a direct comparison of electron beam between the other combination of spin and orbital angular momentum, the parallel CPLG laser pulse with the same sign of spin and orbital angular quantum number, has not been conducted. While the two pulses have an identical transverse field envelope, the generated electron beam properties are different. Although the magnitude of the longitudinal field is about one order of magnitude less than that of the transverse field, it has a significant effect on beam divergence. For antiparallel CPLG laser pulse, collimated electron bunches are formed with small divergence ( 100 mrad) electron beam is formed. This difference in beam quality can indicate a field-induced acceleration in actual experiments. A few-cycle laser pulse and low-density plasma are used to rule out the effect of laser–plasma interaction. It is also shown that for antiparallel CPLG laser pulse, the maximum kinetic energy increases with the square root of incident laser power, consistent with the scaling law for field-induced acceleration. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.11Nsciescopu

Multi-GeV Laser Wakefield Electron Acceleration with PW Lasers

Featured Application Compact electron accelerators, Compact synchrotron source, Radiography. Laser wakefield electron acceleration (LWFA) is an emerging technology for the next generation of electron accelerators. As intense laser technology has rapidly developed, LWFA has overcome its limitations and has proven its possibilities to facilitate compact high-energy electron beams. Since high-power lasers reach peak power beyond petawatts (PW), LWFA has a new chance to explore the multi-GeV energy regime. In this article, we review the recent development of multi-GeV electron acceleration with PW lasers and discuss the limitations and perspectives of the LWFA with high-power lasers.11Nsciescopu

Neuroprotective Effects of Ethanol Extract of <i>Polyscias fruticosa</i> (EEPF) against Glutamate-Mediated Neuronal Toxicity in HT22 Cells

In traditional herbal medicine, the Polyscias fruticosa has been frequently used for the treatment of ischemia and inflammation. Oxidative stress mediated by elevated glutamate levels cause neuronal cell death in ischemia and various neurodegenerative diseases. However, so far, the neuroprotective effects of this plant extract against glutamate-mediated cell death have not been investigated in cell models. The current study investigates the neuroprotective effects of ethanol extracts of Polyscias fruticosa (EEPF) and elucidates the underlying molecular mechanisms of EEPFs relevant to neuroprotection against glutamate-mediated cell death. The oxidative stress-mediated cell death was induced by 5 mM glutamate treatment in HT22 cells. The cell viability was measured by a tetrazolium-based EZ-Cytox reagent and Calcein-AM fluorescent dye. Intracellular Ca2+ and ROS levels were measured by fluorescent dyes, fluo-3 AM and 2′,7′-dichlorodihydrofluorescein diacetate (DCF-DA), respectively. Protein expressions of p-AKT, BDNF, p-CREB, Bax, Bcl-2, and apoptosis-inducing factor (AIF) were determined by western blot analysis. The apoptotic cell death was measured by flow cytometry. The in vivo efficacy of EEPF was evaluated using the Mongolian gerbil mouse by surgery-induced brain ischemia. EEPF treatment showed a neuroprotective effect against glutamate-induced cell death. The EEPF co-treatment reduced the intracellular Ca2+ and ROS and apoptotic cell death. Furthermore, it recovered the p-AKT, p-CREB, BDNF, and Bcl-2 levels decreased by glutamate. The EEPF co-treatment suppressed the activation of apoptotic Bax, the nuclear translocation of AIF, and mitogen-activated protein kinase (MAPK) pathway proteins (ERK1/2, p38, JNK). Further, EEPF treatment significantly rescued the degenerative neurons in the ischemia-induced Mongolian gerbil in vivo model. EEPF exhibited neuroprotective properties that suppress glutamate-mediated neurotoxicity. The underlying mechanism of EEPF is increasing the level of p-AKT, p-CREB, BDNF, and Bcl-2 associated with cell survival. It has therapeutic potential for the treatment of glutamate-mediated neuropathology