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Latest Technological Trend in High-Energy Capacitor Bank Systems for Equipment that Generates Strong Magnetic Fields



  Since the 1970s, when Nichicon first delivered a capacitor bank system to the Osaka University School of Science, Nichicon has been practically the sole provider of these systems to the strong magnetic field research facilities in Japan, such as the Institute for Solid State Physics at the University of Tokyo and the Institute for Materials Research of Tohoku University. These systems supply high voltage as needed to the strong magnetic field-generating equipment necessary to materials science research, and by providing these capacitor bank systems Nichicon is contributing to the achievement of the world-class results by these Japanese laboratories.
  We would like to introduce the high-energy capacitor bank system for equipment that generates strong magnetic fields that we delivered to the Center for Advanced High Magnetic Field Science (AHMF) at the Graduate School of Science of Osaka University. This system is capable of storing and discharging 10 MJ of energy, which is greater than any other system in Japan.

2.Development Background

  Competition in materials science research involving strong magnetic fields is becoming fierce worldwide, with the European Union, United States and Japan leading the way up to now and China is accelerating its research by building cutting-edge facilities. The Science Council of Japan has stated that in order for Japan, which has led the way in research in this field up to now, to continue to produce world-class results, “the Strong Magnetic Field Research Collaboratory Plan must be included in the master plan for large-scale facilities and research planning in academia.” This means that the four major strong magnetic field research institutions in Japan—the AHMF Center at Osaka University, the Institute for Solid State Physics of the University of Tokyo, the Institute for Materials Research of Tohoku University and the Tsukuba Magnet Laboratory—must coordinate their efforts to make joint use and joint research even easier than before and effectively promote the cultivation and sustainment of human resources and technical foundations, such as measurement and equipment development.
  The decision was made to install strong magnetic field research facilities using a 10 MJ high-energy capacitor bank system at the AHMF Center at Osaka University in accordance with the Strong Magnetic Field Research Collaboratory Plan goal of creating strong magnetic field research establishments throughout Japan for the joint use of researchers. Nichicon designed and built this system and delivered it to the AHMF Center in March 2014.

3.Summary and Characteristics of Capacitor Bank Systems

  The AHMF Center conducts materials research. As seen in Figure 1, we have developed a large, large-bore pulsed magnet capable of producing a maximum 60-Tesla magnetic field with a 100-millisecond generation time for use with a high-pressure diamond anvil cell in a compound extreme (ultrastrong magnetic field, ultrahigh pressure, very low temperature) environment. The goal is to discover and clarify the mechanisms of novel physical phenomena in previously unknown measurement environments.
  Table 1 shows the specifications of the capacitor bank system we delivered in this instance, Figure 2 show system configuration, and Figure 3 is an exterior view of the system.
  This capacitor bank system has 10 separate routes for discharge power, and the capacitor banks and voltage can be freely set up to supply the necessary current to an assortment of electromagnets (load coils), making it possible to used it in a variety of materials research applications.

Capacitance 0.0264F
Max charging voltage 28kV DC
Max charging energy 10MJ
Voltage range 1kV DC to 28kV DC
Maximum discharge current 40 kA/Unit (Coil 1mH, 40 mΩ time)
Discharging frequency Once or less / 30 minutes
Charge time Within 4 minutes

[Table 1] Capacitor bank system specifications

[Figure 1] Large, large-bore pulsed magnet (provided to AHMF Center)

[Figure 1] Large, large-bore pulsed magnet (provided to AHMF Center)

[Figure 2] System configuration

[Figure 2] System configuration

[Figure 3] Capacitor bank

[Figure 3] Capacitor bank

4.Capacitor Characteristics

  A high-energy capacitor bank system has uses other than in strong magnetic field research. An example would be an accelerator power supply. At Nichicon we develop the necessary DC capacitors for capacitor bank systems. An important factor in the DC capacitors used in the capacitor bank system is reduced impedance (ESR). Nevertheless, separation is needed for insulation because of the high voltage used in the capacitor bank system, and the capacitor structure must be large because of the limits of the insulating power of the dielectric film, which makes reduced impedance extremely difficult. Nichicon developed a low-impedance capacitor with high DC high-voltage energy density that can discharge rapidly by using a special procedure to wrap the dielectric film as well as an exclusive vapor deposition pattern for deposition of the electrodes on the surface of the dielectric film to extend its insulating power.


  Nichicon has been developing capacitor bank systems for strong magnetic fields in cooperation with universities and research institutions since the 1970s, and has played a major role in helping Japanese strong magnetic field research gain its world-class reputation. Europe, the United States and Japan have lead the way up to now in strong magnetic field research, while China has recently begun participating in what has become a fiercely competitive field. As part of the Strong Magnetic Field Research Collaboratory Plan, which is in line with the master plan of the Science Council of Japan, Nichicon delivered the largest capacitor bank system in Japan, capable of storing 10 MJ of energy, to the AHMF Center at Osaka University. Our hope is that this system will help bring about even stronger results in Japan’s strong magnetic field research.



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