Yuri P. Zakharov

Collisionless laboratory astrophysics with lasers

Possibilities of laboratory simulation of various explosive phenomena in space and cosmic plasmas with magnetic fields are analyzed on the bases of similarity criteria, properties of collisionless interactions, and parameters of laser-produced plasmas. It is shown how the physics of such widely different phenomena as barium releases in Earths magnetosphere, collisionless deceleration of supernova remnants, and related shock-wave generation in interstellar medium or possible near-Earth anti-asteroid explosions could be reproduced in the laboratory. This review of worldwide efforts tries to reveal the problems and perspectives of modern collisionless laboratory astrophysics with high-power lasers.

Laboratory experiments simulating solar wind driven magnetospheres

Magnetosphere-solar wind interactions are simulated in a laboratory setting with a small permanent magnet driven by two types of supersonic plasma wind sources. The first higher speed, shorter duration plasma wind is from a laser blow-off plasma while the second longer duration, lower speed plasma wind is produced with a capacitor discharge driven coaxial electrode creating plasma jets. The stand off distance of the solar wind from the magnetosphere was measured to be 1.7±0.3 cm for the laser-produced plasma experiment and 0.87±0.03 cm for the coaxial electrode plasma experiment. The stand off distance of the plasma was calculated using data from HYADES [J. T. Larsen and S. M. Lane, J. Quant. Spectrosc. Radiat. Transf. 51, 179 (1994)] as 1.46±0.02 cm for the laser-produced plasma, and estimated for the coaxial plasma jet as rmp=0.72±0.07 cm. Plasma build up on the poles of the magnets, consistent with magnetosphere systems, was also observed.

Laser-Produced Plasma Experiments and Particle in Cell Simulation to Study Thrust Conversion Processes in a Laser Fusion Rocket

An experiment is conducted to study the thrust conversion process of a laser fusion rocket (LFR) in a scaled-down manner. The temporal evolution of laser-produced plasma clouds (LPC) expanding in a dipole magnetic field is examined and the thrust conversion efficiency is estimated. For comparative purposes, numerical analyses of plasma behaviour in a dipole magnetic field are also performed using a three-dimensional (3D) hybrid particle-in-cell (PIC) code. An overall good agreement between the experimental and simulation data is found. It is also found that a thrust conversion efficiency as high as 60% is possible in the scaled-down model considered here. The experiments will be very useful in developing LFR designs and testing the basic features of the large-scale simulative LFR experiments proposed for the National Ignition Facility (NIF).

Laser Plasma Experiments to Simulate Coronal Mass Ejections During Giant Solar Flare and Their Strong Impact on Magnetospheres

Giant solar flares are the most powerful phenomenon in the solar system, which can strongly affect various geospheres and technical systems in the near Earths space or its surface. During the space era, only few events with a total energy of more than 1034 erg happened, and probably, only one of these ldquowas directedrdquo to the Earth (August 4, 1972). In this paper, we report on the first attempts to simulate in a laboratory both the initial (at the Sun) and final (near the Earth) stages of relevant interaction processes between the plasma flows and magnetic fields. By using laser-produced plasmas and intense magnetic dipole, we performed two types of simulation experiments: 1) on the interaction of ejected solar plasma flows with/in dipole magnetic field and 2) on the extreme (three fold) compression of the Earths magnetopause by giant coronal mass ejections from the Sun. General physical conditions of these phenomena are briefly described, and the developed methods of laboratory simulation and numerical modeling of various explosive processes in collisionless space plasmas are discussed on the basis of relevant dimensionless criteria of the problems.

Analysis of Exploding Plasma Behavior in a Dipole Magnetic Field.

Numerical analyses on plasma behaviors in a dipole magnetic field are performed using a three-dimensional (3D) hybrid code. Results are compared with the experimental data and magnetohydrodynamics (MHD) analysis. Dependence of plasma expansion on initial plasma energy and location are discussed by temporal evolutions of plasma position and magnetic field strength. An overall good agreement in the expansion behavior of plasmas among these results is found. The asymmetrical shape of the expanding plasma in the cross-field direction is also noticed, and the reason for this is discussed. For future engineering applications, these results will be useful in designing an optimal configuration of the magnetic thrust chamber for laser fusion rockets, and for studying the effective explosive methods for protecting the earth from collisions by asteroids or comets.

Numerical simulation of plasma detachment from a magnetic nozzle by using fully Particle-In-Cell code

A numerical simulation is performed by using a fully 2D3V electromagnetic Particle-In-Cell (TRISTAN) code in order to clarify the plasma behavior and the possibility of the plasma detachment from the magnetic nozzle. As a result of calculation, the plasma detachment was found.

Influence of Non-MHD Flutes on the Efficiency of Energy Transfer from the Laser-Produced, ICF and Space Exploding Plasmas to Magnetic Field

The results of <<MHD>> experiment with quasispherical Laser-produced Plasma Clouds (LPC) expanding into strong (B0 ~10 kG) and uniform magnetic field at KI-1 facility of ILP are presented. Main characteristics and the influence of non-MHD flute instability onto effectiveness of plasma-field interaction were studied especially for the purpose of plasma confinement and the direct conversion of its kinetic energy into magnetic and electric ones (of pick-up coils). A new model of enhanced field penetration into plasma due to Hall-effect in its flutes and under conditions of finite ion Larmor radius is discussed. The data obtained on the current generation by LPC in short-circuited surrounding coils (with total conversion efficiency up to ~10%) are compared with the models of ILP and last results of relevant 3D/PIC calculations done at KU. All these results show the opportunities of LPC-experiments to simulate both space exploding plasmas (AMPTE) and MHD-effects of ICF micro-explosions in planned NIF experiments for study Laser Fusion Rocket like a VISTA.

Particle‐In‐Cell Simulations of Laser‐Produced Plasma Experiments to Study Thrust Conversion Processes in a Laser Fusion Rocket

Here we present the comparison analysis of Laser‐produced Plasma Cloud (LPC) expansion in a dipole field between experimental data and simulation results obtained by a three‐dimensional (3D) hybrid code. The thrust conversion process in a laser fusion rocket (LFR) and the plasma behaviour are examined. We found a real thrust efficiency as high as 60% can be achieved in a future LFR. It was also found that the experiments with a “usual” LPC will be very useful to develop LFR design and test the basic features of large ‐ scale simulative LFR experiment proposed for National Ignition Facility (NIF).

Use of an ignition facility for fusion propulsion experiments

The utilization of an ignition facility for a fusion propulsion experiment is proposed. An experimental setup in the facility chamber is presented along with plasma behaviors calculated by a three-dimensional hybrid code. The plasma instability in a magnetic nozzle is examined and the effect on thrust efficiency is discussed. Implications of this experiment to fields other than propulsion are also discussed.

Analysis of Exploding Plasma Behavior in Various Magnetic Fields

Plasma behaviors in various magnetic fields were discussed by using the result from a 3D hybrid code. First, an instability of expanding plasma in a uniform magnetic field was discussed by comparing experimental data with numerical result. The effect of magnetic field diffusion on the plasma instability was studied. Second, the plasma behaviors in a dipole field were examined and comparison was made among the experimental data, MHD analysis and the result from the 3D hybrid code. So far, an overall good agreement among these result was found.