Masaru Yazawa

Development of a Numerical Tool for Foil Acceleration by an Intense Pulsed Ion Beam

When we irradiate a foil with an intense pulsed ion beam, ablation plasma is created, and the foil is accelerated. In this study, we developed a numerical model of this phenomenon. We analyze the temperature and pressure of the ablation plasma, and the velocity of the accelerated foil by numerical simulation. It was possible for us to analyze the behavior and detailed results of the ablation plasma expansion and acceleration of the foil. We could also observe the processes of ablation plasma expansion and foil acceleration by back-lighting high-speed photography. The numerical results of foil velocity agree well with the experimental ones over a wide range of energy density values of an ion beam. We analyzed the time trend of the foil velocity, and we could observe that the foil is rapidly accelerated immediately after a delay.

Foil Acceleration of Double-Layer Target by Intense Pulsed Ion Beam Ablation

High density ablation plasma produced by intense, pulsed, ion beam has been used to accelerate a thin foil target. Pulsed proton beam with energy density of 120 J/cm/sup 2/, which was obtained by a magnetically insulated diode, was irradiated on a double-layer aluminum target coated by a thin film of gold. The foil velocity was measured by a time-of-flight method. The maximum foil velocity of 2.1 km/s was obtained. The acceleration pressure estimated by the target velocity was found to be 0.44 GPa. The target velocity was increased with increasing the thickness of gold. Using a simple MHD model, we considered the behavior of the foil accelerated. From the comparison of the experimental data with that simulated, a considerable agreement was obtained between them. With the velocity data, we obtained the energy transfer efficiency of the flyer to be 17.5%.

Hydrodynamic efficiency of ablation by a pulsed ion beam for propulsion applications

This paper presents the hydrodynamie efficiency of ablation plasma produced by a pulsed ion beam, as obtained on the basis of the ion beam target interaction concept. We used a one-dimensional hydrodynamie model to explain the ablation acceleration behavior. Hydrodynamic variables are evaluated in terms of ablation velocity conversion efficiency and ablation efficiency. We obtained 18% value for the energy conversion efficiency, while an ablation efficiency of about 70% is achieved at an ion-beam energy density of 60 J cm -2 (beam power density of ≈1GWcm -2 ). A thrust producing capability is also investigated.

Intense-Heavy-Ion-Beam Transport through an Insulator Beam Guide

In this study, we investigate an intense-heavy-ion-beam transport through an insulator beam guide by numerical simulation. In our previous papers [Jpn. J. Appl. Phys. 35 (1996) L1127, Jpn. J. Appl. Phys. 37 (1998) L471], we proposed a new system for electron and proton beam transport using an insulator beam guide. We apply this system to a singly charged cesium (Cs+) ion beam transport. An intense Cs+ ion beam generates a plasma on the insulator surface. Electrons are extracted from the plasma, and the beam charge is effectively neutralized by the electrons. Electron extraction is self-regulated by the net space charge of the beam. Consequently, an intense Cs+ ion beam can be efficiently transported by the proposed system.

Inhomogeneity smoothing using density valley formed by ion beam deposition in ICF fuel pellet

We study the beam non-uniformity smoothing effect of the radiation transport in the density valley formed by an ion-beam deposition in an ion-beam inertial confinement fusion pellets by numerical simulation. The simulation results show that the radiation energy is confined in the density valley, and the beam non-uniformity can be smoothed out by the radiation transport along the density valley. The formation of density valley is controlled by changing a beam incident angle. Consequently, the simulation results show that the radiation smoothing can be also controlled by the density valley structure.

Performance and Controllability of Pulsed Ion Beam Ablation Propulsion

We propose novel propulsion driven by ablation plasma pressures produced by the irradiation of pulsed ion beams onto a propellant. The ion beam ablation propulsion demonstrates by a thin foil (50 μmt), and the flyer velocity of 7.7 km/s at the ion beam energy density of 2 kJ/cm2 adopted by using the Time‐of‐flight method is observed numerically and experimentally. We estimate the performance of the ion beam ablation propulsion as specific impulse of 3600 s and impulse bit density of 1700 Ns/m2 obtained from the demonstration results. In the numerical analysis, a one‐dimensional hydrodynamic model with ion beam energy depositions is used. The control of the ion beam kinetic energy is only improvement of the performance but also propellant consumption. The spacecraft driven by the ion beam ablation provides high performance efficiency with short‐pulsed ion beam irradiation. The numerical results of the advanced model explained latent heat and real gas equation of state agreed well with experimental ones ove...

Hydrodynamic Efficiency of Ablation Propulsion with Pulsed Ion Beam

This paper presents the hydrodynamic efficiency of ablation plasma produced by pulsed ion beam on the basis of the ion beam‐target interaction. We used a one‐dimensional hydrodynamic fluid compressible to study the physics involved namely an ablation acceleration behavior and analyzed it as a rocketlike model in order to investigate its hydrodynamic variables for propulsion applications. These variables were estimated by the concept of ablation driven implosion in terms of ablated mass fraction, implosion efficiency, and hydrodynamic energy conversion. Herein, the energy conversion efficiency of 17.5% was achieved. In addition, the results show maximum energy efficiency of the ablation process (ablation efficiency) of 67% meaning the efficiency with which pulsed ion beam energy‐ablation plasma conversion. The effects of ion beam energy deposition depth to hydrodynamic efficiency were briefly discussed. Further, an evaluation of propulsive force with high specific impulse of 4000s, total impulse of 34mN an...

Efficiency of Ablation by Pulsed Ion Beam and Propulsion Performance

This paper presents the hydrodynamic efficiency of ablation plasma produced by pulsed ion beam based on the ion bea m and solid fuel target interaction. We used a one -dimensional hydrodynamic model, which mostly focused on an ion beam energy deposition phenomena and analyze it as a rocketlike model to explain and examine hydrodynamic variables. These variables were esti mated by the concept of ablation driven implosion in terms of ablated mass fraction, ratio of target velocity, and ablation velocity and thrust efficiency. Hydrodynamic efficiency of 17.5% by means of thrust conversion efficiency was achieved. The results show maximum energy efficiency of the ablation process (ablation efficiency) of about 70% meaning the efficiency with which pulsed ion beam energy E ionbeam is converted into exhaust kinetic energy in the solid fuel material. Moreover, propulsion performanc e with specific impulse of 3600 s was briefly reviewed. An effect of an ablation depth to hydrodynamic efficiency was also tested.

Flyer Acceleration by Pulsed Ion Beam Ablation and Application for Space Propulsion

Flyer acceleration by ablation plasma pressure produced by irradiation of intense pulsed ion beam has been studied. Acceleration process including expansion of ablation plasma was simulated based on fluid model. And interaction between incident pulsed ion beam and a flyer target was considered as accounting stopping power of it. In experiments, we used ETIGO‐II intense pulsed ion beam generator with two kinds of diodes; 1) Magnetically Insulated Diode (MID, power densities of <100 J/cm2) and 2) Spherical‐focused Plasma Focus Diode (SPFD, power densities of up to 4.3 kJ/cm2). Numerical results of accelerated flyer velocity agreed well with measured one over wide range of incident ion beam energy density. Flyer velocity of 5.6 km/s and ablation plasma pressure of 15 GPa was demonstrated by the present experiments. Acceleration of double‐layer target consists of gold/aluminum was studied. For adequate layer thickness, such a flyer target could be much more accelerated than a single layer. Effect of waveform ...

Behavior of Ablation Plasma Produced by Pulsed Ion Beam

Thin film production, flyer acceleration, and space propulsion system using ablation plasma produced by an intense pulsed ion beam have been studied. To control the generation of ablation plasma to adequate conditions is a key point for these applications. We studied the behavior of ablation plasma and target by a simple basic numerical hydrodynamic model. This paper discussed the ion beam irradiated angle and target materials effect to behavior of ablation plasma by comparison of numerical results to experimental ones. We could recognize that to change ion beam irradiation angle could affect plasma pressure and mass of ablated plasma without changing temperature significantly. Target materials changed velocity distribution of ablation plasma number density, electron number density, and temperature. Moreover, velocity distribution of ablation plasma number density was almost agreed well with an experimental data at various target materials.