3D plots of ion density, temperature and polytropic coefficient for a fixed potential ϕ = 0.5. Fig. 10 of the paper by Majid Khan et al. https://doi.org/10.1002/ctpp.70010
3D plots of ion density, temperature and polytropic coefficient for a fixed potential ϕ = 0.5. Fig. 10 of the paper by Majid Khan et al. https://doi.org/10.1002/ctpp.70010
This paper presents a detailed study of the stopping power of a homogeneous electron gas in moderate and strong coupling regimes using the self-consistent version of the method of moments as the key theoretical approach capable of expressing the dynamic characteristics of the system in terms of the static ones, which are the moments. We develop a robust framework that relies on nine sum rules and other exact relationships to analyze electron–electron interactions and their impact on energy loss processes. We derive an expression for the stopping power that takes into account both quantum statistical effects and electron correlation phenomena. Our results demonstrate significant deviations from classical stopping power predictions, especially under the strong coupling conditions, where electron dynamics are highly dependent on the collective behavior. This work not only advances the theoretical understanding of the homogeneous electron gas but also has implications for practical applications in fields such as plasma physics and materials science.
The Coulomb logarithm often enters various plasma models and simulation methods for computing the transport and relaxation properties of plasmas. Traditionally, a classical pair collision picture was used to calculate the Coulomb logarithm for different plasma parameters. With the recent emergence of the high interest in dense plasmas with partially degenerate electrons, new approaches have been developed to treat electron-ion collisions in a quantum-mechanical way. In this context, gaining a deeper physical understanding of the criteria for the applicability of classical plasma models is crucial. We have analyzed the Coulomb logarithm describing the electron-ion collisions in hydrogen plasmas in a wide range of temperatures and densities relevant to inertial confinement fusion experiments. The electron-ion collision cross-sections were computed using both quantum and classical scattering theories. We found that the classical description of the electron-ion scattering in plasmas and related plasma models is applicable if the de Broglie wavelength of electrons is smaller than the ion charge screening length in plasmas. Additionally, we show that the quantum first-order Born approximation for describing the electron-ion collision is accurate only in the regime where classical scattering theory is accurate.
Spatial distribution of particles hitting the collector probes based on different simulations for the DIII-Dcase: (a) 40 million, (b) 80 million, (c) 160 million. Fig.18 of the paper by Dhyanjyoti D. Nath et al. https://doi.org/10.1002/ctpp.202400073
We discuss charged particle transport in a turbulent magnetic field. The pitch angle diffusion is essential to the transport processes of energetic particles in real and momentum spaces. We integrate particle trajectories in time under the influence of the turbulent magnetic field given as a superposition of parallel-propagating magnetohydrodynamic waves (“slab-turbulence”). As in the standard theory for cosmic ray transports, the small wave amplitude and the random phase approximation are the fundamental assumptions of the quasi-linear theory. In the presence of large amplitude waves, our numerical study shows the anomalous pitch angle diffusion of the energetic particles. In the presence of waves with strong phase correlation, where the MHD turbulence is represented as intermittent wave packets, the particles are transported in the momentum space due to the mirror reflections rather than the pitch angle diffusion. The particle motions are mostly ballistic and occasionally reflected by the intermittent wave packets; thus, the spatial transport of the energetic particles can be super-diffusive in the presence of large amplitude MHD waves with strong phase correlation.
Experiments of isochoric heating by protons of solid material were recently performed at LULI laser facilities. In these experiments, protons, produced from target normal sheath acceleration (TNSA) of Au foil with the PICO2000 laser, deposit their energy into an aluminum or copper foil initially at room temperature and solid density. The heated material reaches the warm dense matter regime with temperature in the rear face of the material between 1 and 5 eV. The temperature is inferred by streaked optical pyrometry and the proton beam is characterized by Thomson parabola. The high-energy protons produced by TNSA are modeled to deduce the initial proton distribution before the slowing down in the target. Hydrodynamic radiative simulations were next performed using the Troll code in multidimensional geometry. In the Troll code, the heating of protons is modeled with a Monte Carlo transport module of charged particles and the calculation of the energy deposited by the protons in the matter is performed using stopping power formulas like Srim functions. The results of simulations with the Troll code are compared with the experimental results. An acceptable agreement between experiment and simulation is found for the temperature at the rear of the material using Sesame equation of state and Srim stopping power for protons in aluminum.
By irradiating an ultra-thin graphene target, large-area suspended graphene (LSG) with a picosecond and moderate-intensity laser, protons with energies exceeding 100 MeV have been achieved. However, the optimal conditions for ion acceleration in such an atomic-thin target regime using a picosecond intense laser remain unclear. By performing particle-in-cell (PIC) simulations, we discuss optimum conditions to realize energy frontier of laser-driven ion acceleration. Parameter scans over LSG thickness and laser -number reveals the optimal conditions under which proton energies exceed 500 MeV. This can be realized with the upgraded laser focus of the LFEX in the future.
Short-pulse intense lasers have the potential to model extreme astrophysical environments in laboratories. Although there are diagnostics for energetic electrons and ions resulting from laser-plasma interactions, the diagnostics to measure velocity distribution functions at the interaction region of the laser and plasma are limited. We have been developing the diagnostics of the interaction between the intense laser and plasma using scattered intense laser. We performed experiments to measure electron density by observing the spatial distributions and the ratio of horizontal to vertical polarization components of the scattered laser beam using optical imaging. The observed ratio of polarization components is consistent with the drive laser beam, indicating the observed light originates from the drive laser. Imaging of the scattered light shows the structure of electron density, the zero moment of the electron velocity distribution function, interacting with the intense laser. We observed the change of structure due to the laser pre-pulse that destroys the target before the arrival of the main pulse.
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