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In this paper, a power supply which can generate pulsed high voltage with high repetition rate is proposed. It can generate pulsed high voltage up to several kilovolts even from several volts dc. This circuit is the Marx-generator which consists of multi-staged magnetic energy recovering switches. A magnetic energy recovering switch is made of four IGBTs and one capacitor. Two IGBTs in reverse-series are connected in anti-parallel. Their terminals are connected to the capacitor. It generates high voltage by absorbing the magnetic energy of an inductor to the capacitor. In order to generate high voltage, this Marx-generator utilizes the inductor. While all the switches are turned on, current flows through the switches and the inductor. When the switches are turned off, the magnetic energy which stored in the inductor is charged in the capacitors in parallel. Next, by turning on the switches, the capacitors discharge in series and high voltage is applied to the inductor. Experiments were carried out. A pulsed voltage of 1.5 kV with a repetition rate of 5 kHz was generated from 36 V dc. It was confirmed that this circuit can be applied to a power supply for high repetition plasma discharge.

Although high field is very favorable for magnetically confined fusion devices such as Tokamaks, electromagnetic forces derived from the field become serious. In particular, the large in-plane centering force hinders toroidal field coils from operating at higher fields. Instead of toroidal field coils, force-balanced coils (FBCs), by which this force is drastically reduced, are proposed for the coil system of a Tokamak. FBC can also provide enough poloidal flux for plasma breakdown and current induction during the ramp-up phase of the coil current. In this paper, how to design the FBC for Tokamaks is discussed. FBCs of ITER-EDA size were designed and compared with conventional toroidal field coil systems in terms of the electromagnetic force and the poloidal field in the vacuum vessel. The construction of a small Tokamak with FBCs, for the demonstration of Tokamak plasma confinement, was completed and plasmas have been generated in it.

Background and purpose Angioplasty of the dural sinus has rarely been performed for the treatment of cavernous sinus dural arteriovenous fistulas. We evaluated the efficacy of selective transvenous embolization (TVE) combined with balloon angioplasty of the occluded inferior petrosal sinus (IPS) for the treatment of cavernous sinus dural arteriovenous fistulas (CSDAVFs).Materials and methods A total of 8 consecutive patients with CSDAVFs with occlusion of the IPS treated by selective TVE with balloon angioplasty of the IPS from July 2018 to January 2019 were retrospectively reviewed. There were 6 females and 2 males with an average age of 77.6 years. All patients showed ocular symptoms. Angiography showed cortical venous reflux in 7 cases and localized shunted pouches at the medial portion of the cavernous sinus, intercavernous sinus, or laterocavernous sinus. Selective TVE was performed via the occluded IPS with bilateral femoral venous approaches, and the occluded IPS was reconstructed by angioplasty with a 2- to 3-mm diameter balloon during or after selective TVE.Results CSDAVFs disappeared immediately after treatment, and the occluded IPSs were successfully reconstructed with re-establishment of normal antegrade venous flow in all cases. No complications were observed, and symptoms resolved within 2 weeks after treatment. During the 7-month mean follow-up period (range 1-12 months), no cases showed recurrence of CSDAVFs.Conclusion Selective TVE combined with balloon angioplasty of the occluded IPS is safe and effective for the treatment of CSDAVFs and re-establishes normal venous circulation in selected cases with localized shunted pouches.

Coumarin 4, a pH indicator, was entrapped in a silica matrix coated as a thin film onto a silica substrate by the sol-gel technique. The absorbance and fluorescence changes of the immobilized indicator were examined in the pH sensing range. The increase in absorption and fluorescence intensities as the acid form of the immobilized coumarin 4 is converted to its basic form, is dependent on pH. The dynamic range and the response time of this probe were pH 3-9 and less than 10 s, respectively.