| Research Abstract |
Inductive voltage adder is a new type of pulse-power technology where several pulses are superimposed using ferromagnetic cores. In this study, we have successfully developed "VIVA-I", versatile inductive voltage adder, which has the pulse-power output of voltage - 4 MV and pulse width - 60 ns. It has also been characterized by the extremely high average potential gradient of 2.5 MV/m. It consists of Marx generator, Blumlein pulse-forming line (PFL), and voltage adder. The output pulses of 2-MV, 60-ns from PFL are divided into four lines, which are, being connected by two-parallel and two-series, superimposed by two-stages of voltage adder. The adder section is 1-m in diameter, and the axial length is 80 cm long. Three amorphous metallic cores, dimensions of each core are O. D. = 70 cm, I. D. = 30 cm, thickness = 10 cm, are inserted into one cell. In 1989, design, construction, and basic experiment of operation were carried out. In 1990, we modified the machine to optimize the output p
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arameters.
In order to operate "VIVA-I" at the specified voltage, three cores should be inserted in each cell so that the voltage applied on each cell is 2 MV. However, the calculated results of the electric field distribution in the cell have shown that, at this voltage, particularly in the region near the top of the core, the electric field exceeds the breakdown value. To solve this problem, we have improved the core by 1) using a field-relaxing ring and 2) changing the material of the flange. As a result, the safety factor has raised from 1 to - 3. Furthermore, optimization is performed for PFL operation which is based on the results of computer simulation and the experimental results.
With the above improvement, "VIVA-I" is ready to be operated at the specified voltage. Concerning the improvement of the waveform, we have decided to use a saturable inductor in the charging circuit of PFL. It has been confirmed that the waveform can be significantly improved by experiments with 40 % of the full voltage. At present, the detailed experiments with the specified voltage and are being carried out with several diagnostics of the beam properties. Less
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