Relativistic Binary Collisions Research Articles

Lorentz invariant relative velocity and relativistic binary collisions

This paper reviews the concept of Lorentz invariant relative velocity that is often misunderstood or unknown in high energy physics literature. The properties of the relative velocity allow to formulate the invariant flux and cross-section without recurring to nonphysical velocities or any assumption about the reference frame. Applications such as the luminosity of a collider, the use as kinematic variable, and the statistical theory of collisions in a relativistic classical gas are reviewed. It is emphasized how the hyperbolic properties of the velocity space explain the peculiarities of relativistic scattering.

Interaction volume of electron beam in carbon nanomaterials: A molecular dynamics study

ABSTRACTA molecular dynamics (MD) simulation was performed to study the interaction volume of electron beam in carbon nanomaterials. The interaction between incident electron and carbon atom in the target materials during electron irradiation is introduced by the relativistic binary collision theory. The motion of each atom in the material under electron irradiation is calculated with the MD simulation. The primary energy dependence of the interaction volume in the carbon nanotube and the multi-layered graphene are studied. The secondary damages caused by the knock-on atoms are also discussed.

Momentum-energy change in elastic relativistic binary collisions

We consider a relativistic elastic collision between a projectile of momentum p with a target atom of momentum k in a general inertial frame. We employ one space plus one time Minkowski geometry and calculate the momentum transfer vector qμ suffered by the projectile calculated via a Lorentz transformation to the barycentric frame and then eliminate k. The resulting expression for qμ reproduces several known cases, its algebraic behavior can be interpreted physically, and it leads to a simple understanding of the relativistic equipartition law.

Statistical kinetic treatment of relativistic binary collisions

In particle-based algorithms, the effect of binary collisions is commonly described in a statistical way, using Monte Carlo techniques. It is shown that, in the relativistic regime, stringent constraints should be considered on the sampling of particle pairs for collision, which are critical to ensure physically meaningful results, and that nonrelativistic sampling criteria (e.g., uniform random pairing) yield qualitatively wrong results, including equilibrium distributions that differ from the theoretical Jüttner distribution. A general procedure for relativistically consistent algorithms is provided, and verified with three-dimensional Monte Carlo simulations, thus opening the way to the numerical exploration of the statistical properties of collisional relativistic systems.

Full scale explicit PIC simulation of fast ignition experiment

A relativistic binary collision model is implemented in the particle-in-cell simulation code PICLS. Its applicability ranges from the non-relativistic to the ultra-relativistic regime. Using this model we have simulated a recent experiment on cone-guided fast-ignition experiment [Kodama et al., Nature 418, 933 (2002)] and found that there are three important heating process by fast electrons, fast ions and heat conduction from the cone.

Two-dimensional particle-in-cell simulation for magnetized transport of ultra-high relativistic currents in plasma

Nonlinear channel dynamics and magnetized transport of relativistic electron currents in plasma have been investigated, using transverse two-dimensional particle-in-cell simulations allowing for movable ions and fully relativistic binary collisions. Current filaments self-organize in coaxial structures where the relativistic beam in the center is surrounded by magnetized vacuum and a thin return current sheath outside. The current sheath explodes radially. The filament as a whole is current-neutral with almost vanishing magnetic field at the outside. Ion dynamics play an important role, leading to enhanced self-pinching of the filament cores. Collisional effects become significant in the slowly moving return currents. It is shown that electron currents of 100–1000 MA can be transported through dense plasma, but only through a large number of current filaments, each carrying about one Alfvén current. This aspect is essential for relativistic electron transport in fast ignition of targets for inertial confinement fusion (ICF).

Magnetic instability by the relativistic laser pulses in overdense plasmas

The magnetic instability driven by the relativistic electron stream generated by ultra-intense laser is investigated with the help of a two-dimensional particle-in-cell simulation, which includes the relativistic binary collision. The linear growth rate of the instability is also studied using the two-stream fluid model, which consists of a fast electron current and a return current. The growth rate is evaluated numerically from the linearized equations of the electron fluids with the Maxwell equations. The kinetic effects of electrons on the magnetic instability are found to reduce the growth rate. The growth rate is maximum at the wavelength near the plasma skin length because of the plasma kinetic effect. When the initial plasma temperature is high, the growth rates of shorter wavelengths are significantly reduced. In the collisional plasma, the growth rates of modes whose wavelength is shorter than the plasma skin length are suppressed and the spectral peak of the growth rate shifts to long wavelength modes. It is found that the results of the linear analysis agree well with two-dimensional particle simulation results in the early stage.

Particle simulation studies for fast ignitor research — collisional effects on laser–plasma interactions

Relativistic binary collision effects on intense laser–plasma interactions were investigated by the Monte Carlo Coulomb model into a particle simulation code. Our collision model is fully relativistic and collision frequencies are calculated in the framework of quantum electrodynamics (QED). As benchmark tests, we simulated the following two cases. The first one is for the electron heat transport in a steep temperature gradient and the second is for the electron energy distribution function of plasmas heated by the inverse bremsstrahulung. The results of the simulations agree well with previous works. The surface plasma heating and fast ion generation have also been investigated for a solid target interaction with an intense laser beam. The collisional effects are very important even in the intensity range of 10 18–10 19 W/cm 2.

Effects of Relativistic Binary Collisions on PIC Simulation of Laser Plasmas

Relativistic binary collision effects on the intense laser plasma interactions are investigated by introducing the Monte Carlo Coulomb model into a particle simulation code. Our collision model is fully relativistic, where the collision frequency is calculated in the frame work of relativistic electro-dynamics. By the particle simulation, the following two phenomena which are important in laser plasmas are investigated. The first one is for the electron heat transport in a steep temperature gradient and the second is for the electron energy distribution function of plasmas heated by a relativistic intensity laser irradiation. The results of the simulations are compared with the results of numerical analysis of the Fokker-Planck equation.