[en] A pulsed-power generator with high current rise based on a pulse-forming-network was studied toward generating intense point-spot X-ray source. To obtain the high rate of current rise, we have designed the compact discharge device with low circuit inductance. The results indicate that the inductance of the compact discharge device was dominated by a gap switch inductance. To reduce the gap switch inductance and operation voltage, the feasible gap switch inductance in the vacuum chamber has been estimated by the circuit simulation. The gap switch inductance can be reduced by the lower pressure operation. It means that the designed discharge device achieves the rate of current rise of 10¹² A/s

[en] To evaluate transport properties of warm dense matter (WDM), we have demonstrated an isochoric foam ablation using pulsed-power discharges. We also determined the density dependence of the electrical conductivity for copper and gold at WDM conditions. The measured electrical conductivity of copper agreed with previous experimental results. However the electrical conductivity for gold at the temperature of 3000 K was 10 times larger than the present measurements at 5000 K. (author)

[en] To evaluate transport properties of warm dense matter (WDM), we have demonstrated an isochoric foam ablation using pulsed-power discharge. In order to confirm the uniform heating of metal foam, the AC skin effect penetration of a magnetic field is observed. The skin effect is observed to be suppressed in foam samples as compared to rod samples. We also determined the density dependence of the electrical conductivity for copper and gold at WDM conditions. The measured electrical conductivity of copper agreed with previous experimental results. However the electrical conductivity for gold at the temperature of 3000 K was 10 times larger than the present measurements at 5000 K

[en] Electron beam behavior in beam diode gap was investigated numerically using electrostatic particle-in-cell model based on the normalized value and experimental results of intense pulsed power discharge device ETIGO-II. Numerical results of the space charge limited electron emission expose the electron beam behavior in diode gap alone with the electrostatic field. Compilation of numerical result shows that due to the space charge limited current, virtual cathode is formed near the cathode surface, which is liable for the low output beam current. Numerically it is also observed that the beam current is significantly change with the change of diode gap distance and the change of emission radius at the cathode surface. Comparison of experimental results with the numerical results revealed the approximate electron emission radius at the cathode surface. Numerical results also qualitatively satisfy the experimental results of pulsed power discharge device ETIGO-II. (author)

[en] To understand particle acceleration mechanisms in non-relativistic collisionless shocks, we have investigated an interaction between a pulsed-power-driven plasma flow and a perpendicular magnetic field. The ion current from the plasma flow in the perpendicular magnetic field was measured by an ion collector. The valuation of the ion current waveform without and with the perpendicular magnetic field was observed. With the magnetic field, the ion current preceding the main current was observed. Results of numerical simulation based on an electromagnetic hybrid particle-in-cell method qualitatively agreed with experimental results. (author)

[en] This paper studies the possibility to generate alternating current (AC) electrical power by using disk MHD generator. Its phenomenon is performed by the finite element method (FEM). The configuration of generator consists of a channel, an insulator and stators. The shape of channel is a flat disk, the liquid metal used as conductor flows inside the channel. As a channel wall, an insulator is used to separate the metal fluid and stator. The stator winding is designed as the coils on top and bottom of a channel. Under this condition, it can produce a magnetic field by means of time harmonics function. The interaction between the metal fluid and the electromagnetic wave can be explained by Maxwell's equations and Ohm’s law. As a result, the distribution of magnetic flux density throughout the channel is evidently shown in two-dimensional space. The active power is limited by slip value and electrical conductivity. The optimized value of active and reactive power is suggested by small slip value as slip s≤-0.1. In addition, mechanical power and power dissipation in the generator are reported in term of 1-s and s respectively. Electrical efficiency is explained in term of 1/(1-s). (author)

[en] Both numerical and experimental approaches are applied to evaluation for warm dense matter. To clear thermal and optical properties of warm dense matter, the numerical simulation of time-dependent one-dimensional thermal diffusion with radiative transfer is carried out in a compact pulsed power discharge device. The numerical model is described to include multi-group approximation for the radiation energy density distribution. Using the numerical model, the radiation energy density depended on the frequency is indicated with the experimental condition. (author)

[en] Using both numerical and experimental approaches are applied to evaluation for low-temperature and dense plasma. To investigate properties of low-temperature and dense plasma, the numerical simulation of time-dependent one-dimensional thermal diffusion with radiative transfer is carried out in a compact pulsed power discharge device. The simulation result is useful to understand the thermodynamic phenomena during the discharge in comparison with the experimental result. (author)

[en] A simulating beam parameter is considered in a compact beam simulator constructed with a Malmberg–Penning trap device for heavy ion inertial fusion. The Malmberg–Penning trap device is expected as an experimental device to simulate longitudinal pulse compression in a driver system for heavy ion inertial fusion. Tune depression is estimated with Brillouin density limit, rigid–rotor Vlasov equilibrium, and a model considering with radial distribution of charge density. As a result, it is considered that these estimations are not suitable for the space charge strength of the condition in the device. (author)

[en] In order to explore high energy density physics, we have performed WDM experiment by using several pulsed-power devices. To generate well-defined warm dense state for evaluating electrical conductivity and its properties, we have proposed an isochoric heating of foamed metal by using pulsed-power discharge. The proposed technique yields the electrical conductivity of warm dense matter with a well-defined temperature. To observe the warm dense matter, a pulsed-power generator based on a pulse-forming-network (PFN) was studied toward generating an intense point-spot-like X-ray source from X-pinch technique. From comparison of the designing and the actual inductances of the X-pinch system, the actual inductance of X-pinch system is 3.5 times higher than the designing inductance. To reduce the total inductance of X-pinch system, we will modify the gap switch system such as multi spake gap