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Direct laser acceleration of electrons in high-Z gas target and effect of threshold plasma density on electron beam generation
摘要： An experimental study of laser driven electron acceleration in N2 and N2-He mixed gas-jet target using laser pulses of duration ~60-70 fs is presented. Generation of relativistic electron beam with quasi-thermal spectra was observed at a threshold density of ~1.6×1018 cm-3 in case of the pure N2. At an optimum fraction of 50% of He in N2, generation of quasi-monoenergetic electron beams was observed at a comparatively higher threshold density of ~2×1018 cm-3, with an average peak energy of ~168 MeV, average energy spread of ~21%, and average total beam charge of ~220 pC. Electron acceleration could be attributed to the direct laser acceleration as well as the hybrid mechanism. Observation of an optimum fraction of He in N2 (in turn threshold plasma density) for comparatively better quality electron beam generation could be understood in terms of the plasma density dependent variation in the dephasing rate of electrons with respect to the transverse oscillating laser field. Results are also supported by the 2D PIC simulations performed using the code EPOCH.
关键词： Laser Wakefield Acceleration,Laser Plasma Acceleration,Direct Laser Acceleration,Ionization Induced Injection
更新于2025-09-23 15:19:57
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Laser reflection as a catalyst for direct laser acceleration in multipicosecond laser-plasma interaction
摘要： We demonstrate that laser reflection acts as a catalyst for superponderomotive electron production in the preplasma formed by relativistic multipicosecond lasers incident on solid density targets. In 1D particle-in-cell simulations, high energy electron production proceeds via two stages of direct laser acceleration: an initial stochastic backward stage and a final nonstochastic forward stage. The initial stochastic stage, driven by the reflected laser pulse, provides the preacceleration needed to enable the final stage to be nonstochastic. Energy gain in the electrostatic potential, which has been frequently considered to enhance stochastic heating, is only of secondary importance. The mechanism underlying the production of high energy electrons by laser pulses incident on solid density targets is of direct relevance to applications involving multipicosecond laser-plasma interactions.
关键词： particle-in-cell simulations,superponderomotive electron production,direct laser acceleration,laser reflection,multipicosecond laser-plasma interaction
更新于2025-09-19 17:13:59
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Net energy gain in direct laser acceleration due to enhanced dephasing induced by an applied magnetic field
摘要： Even in the situation where an electron interacts with a single plane wave, the well-known dynamical adiabaticity can be broken when an applied magnetic field is present, which will act to increase the dephasing rate of the electron during the interaction. Here we demonstrate this for the case where there is a uniform static magnetic field which is oriented either parallel or perpendicular to the electric field of the incident plane wave, and perpendicular to the direction of its propagation. The described energy gain phenomenon has direct relevance to laser-plasma interactions that involve external magnetic fields generated by laser-driven capacitor coils.
关键词： net energy gain,direct laser acceleration,magnetic field,laser-plasma interactions,dephasing
更新于2025-09-19 17:13:59