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To improve the purity of ion beams produced in a plasma focus (PF), the dependence of the characteristics of the nitrogen ion beams on the shape of the anode was investigated. Two types of anodes, i.e. rod type (type A) and hollow type (type B) were used with a PF pre-filled with nitrogen gas. Thomson parabola spectrometer measurements showed the existence of a large amount of impurity ions, O 1-2+ , C + , and Cu 1-2+ , with nitrogen ions (N 1-3+ ) and the percentage of nitrogen ions is only 25% in type A. In contrast, in type B the impurity is extremely reduced and the percentage of nitrogen ions is enhanced to 91%. The maximum energies and power brightnesses of the nitrogen beams were evaluated to be 0.5 MeV and 0.23 GW cm −2 sr in type A and 1 MeV and 1.6 GW cm −2 sr in type B; hence, energy and brightness are also enhanced in type B. From x-ray pinhole images we see that strong electron irradiation occurs on the top of the anode in type A, whereas in type B, electron irradiation is weak and irradiation area is far from the pinch plasma. Hence, the impurity ions observed in type A are considered to be produced in the following process. Due to the strong irradiation of electrons on the anode top, the electrode and the absorbed gas on the electrode are vaporized, mixed with pinch plasma and accelerated with nitrogen ions.

The characteristics of the ion beams produced in a plasma focus device were studied. In the experiment, a Mather-type plasma focus device was used which was prefilled with H 2 at 2.3 Torr. Ion species and their energy spectra were evaluated with a Thomson parabola spectrometer. The particle pinhole image was obtained with an aluminum filtered particle pinhole camera. The ion current density was measured with a biased ion collector. From the measurement, the proton beam energy was found to be distributed from 0.15 MeV to 2 MeV. The particle pinhole image of the proton beam with an energy of more than 1 MeV has spotlike patterns. The ion current density of 2400 A/cm 2 with a pulse width of 50 ns was observed on the axis at z = 260 mm from the top of the anode. The peak power brightness of the proton beams was evaluated to be 18 GW/cm 2 /sr/keV, and the total power brightness was evaluated to be 20 TW/cm 2 /sr.

In high-power density power converter designs, power losses of power devices are essential design parameters because they determines the volume of cooling systems. The power loss of a SiC power module using a SiC Implantation and Epitaxial MOSFET (SiC-IEMOSFET) has been evaluated in the junction temperature range from 150 °C to 250 °C and the current density range from 100 A/cm 2 to 250 A/cm 2 . By using the power loss data, design criteria of the junction temperature and current density of the SiC-IEMOSFET to realize the power density of 50W/cm 3 have been extracted.Index Terms--Power density, Power loss, Silicon carbide.

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