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Pump depletion and hot-electron generation in long-density-scale-length plasma with shock-ignition high-intensity laser
摘要： Two-dimensional particle-in-cell simulations for laser plasma interaction with laser intensity of 1016 W/cm2, plasma density range of 0.01–0.28nc, and scale length of 230–330 μm showed signi?cant pump depletion of the laser energy due to stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in the low-density region (ne = 0.01–0.2nc). The simulations identi?ed hot electrons generated by SRS in the low-density region with moderate energy and by two-plasmon-decay near ne = 0.25nc with higher energy. The overall hot electron temperature (46 keV) and conversion ef?ciency (3%) were consistent with the experiment’s measurements. The simulations also showed arti?cially reducing SBS would lead to stronger SRS and a softer hot-electron spectrum.
关键词： pump depletion,two-plasmon-decay,stimulated Raman scattering,stimulated Brillouin scattering,laser plasma interaction,hot-electron generation
更新于2025-09-23 15:19:57
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Hadron Therapy Based on Laser Acceleration in the Plasma Channel Using Oxygen Ionization
摘要： In a cancer radiation treatment, Hadron therapy plays an important role as a technique with a high accuracy providing treatment results better than conventional radiation therapy methods such as chemotherapy. The laser-based Hadron therapy techniques are attractive due to their compactness in producing miniaturized particle accelerators and supporting a more intense electric field compared to other methods. A good-quality laser beam focusing and guiding in a cold plasma channel leads to an accurate and precise laser spot after focus, which is an important necessity in medical aims and occurs in ????-wavelength (ultra-short pulse) laser types. A method used to level up this treatment approach has been emerged by using high-power lasers along with plasma channels as a source for high energy to more effectively perform the Hadron therapy. Additionally, cancer treatment by using ions as the particle transferor is preferred over other methods for Hadron therapy due to some physical properties such as maximum energy deposition to the cancerous targets providing a better dose delivery to the tumor. In this paper, multiple simulations around the dose delivery procedures were presented for efficient dosimetric evaluations. Moreover, the effects of the electric field on the particle energy enhancement were evaluated in the presence of the plasma channel. Finally, it was demonstrated that the use of Oxygen ion in the presence of plasma channel is the appropriate approach due to its minor energy dissipation through matter on the way to the tumor for a better dose delivery which was impressed with radially polarized laser accelerator simultaneously. The proposed research demonstrated that the Hadrons can reach the maximum accelerated energy and convey the maximum path through the body to the cancerous target and finally deliver the sufficient dose to the tumor by using Oxygen ion beam in a cold plasma channel, which is low in density, with appropriate laser power. Consequently, Hadron therapy by using Oxygen ionization in the laser-plasma based accelerator is an impressive and efficient method for precise cancer treatment. Lastly, Laser-Plasma accelerators have three important limitation factors of “Energy Spread”, “Dephasing Length”, and “Pump Depletion”, which can limit the energy increasing. In this paper, facing up to these limitations was a critical challenge in Hadron therapy for better Hadron acceleration and dose delivery.
关键词： Beam Focusing,Hadron Therapy,Oxygen Ionization,Plasma Channel,Laser Acceleration,Cancer Radiation Therapy,Pump Depletion,Dephasing Length,Energy Spread
更新于2025-09-16 10:30:52
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A mixture of vortex terahertz radiation generation in inhomogeneous plasma by considering pump depletion
摘要： An attempt to extend helical terahertz radiation generation based on pump depletion is presented here. By considering an upward plasma density ramp, such a reasonable extension is examined to improve the results. It is claimed that the output terahertz energy is saturated which is attributed to laser pump divergence. The saturation effect is enhanced by considering suitable laser and plasma parameters. The adjustable slope of the density ramp is an important parameter for tuning terahertz generation efficiency, which is restricted to the up and down limit. For the resonant excitation of terahertz radiation, the ripple wave number is suitably chosen to satisfy the phase matching condition. Furthermore, as plasma frequency increases and approaches beat frequency, terahertz generation efficiency increases. Various laser and plasma parameters are employed and we report an efficiency of the order of 5×10?3 for the current scheme.
关键词： Laguerre–Gaussian beam,plasma density ramp,pump depletion,terahertz radiation generation,cross-focusing
更新于2025-09-11 14:15:04