International MegaGauss Science Laboratory, the Institute for Solid State Physics

Destructive-type maget

ElectroMagneric Flux Compression system (5MJ, 2MJ)

  The ultra-high magnetic field up to 730 T can be generated by the ElectroMagneric Flux Compression (EMFC) system [1]. There, a metallic cylinder called the "liner" is subjected to the inductive electromagnetic force from a main(primary) coil, and the initial(seed) magnetic field of around 4 T is compressed by an imploding liner within a few microseconds before the magnet coil destruction. The energy injected to the main coil is stored in the fast main condenser bank. Several types of magneto-optical measurements (Faraday rotation, streak spectroscopy) can be performed under the low temperature of 5 K. The sample are also destroyed by the explosion just after the magnetic field generation. In 2014, 5MJ system (left) and 2MJ system (right) was installed for the higher peak magnetic field generation and theapplication for solid state physics measurements above 300 T.

[1] S. Takeyama, and E. Kojima, J. Phys. D: Appl. Phys. 44, 425003 (2011).
Main condenser bank of the EMFC system

  The fast condenser bank used for the EMFC system. 5MJ system has 10 modules of 0.5 MJ condenser bank unit, which connects to the load coil in parallel. 2MJ system has 4 modules of the same unit to the 5 MJ system. The maximum charging voltage is 50 kV, and the rated current is 7 MA (5 MJ system). For discharging the condenser banks, one air-gap switch is used per 0.5 MJ condenser bank unit.

Seed condenser bank of the EMFC system

  The condenser bank unit for the seed field coil. The maximum stored energy is 2.0 MJ and the maximum charging voltage is 20 kV. For the switch to discharge the condenser, the two ignitrons are used per 0.5 MJ unit.

Primary coil of the EMFC method

  The currently being used primary coil is called as "Cu-lined primary coil", which is provided with two-layer structures [1]. On the inner wall of the Fe coil, Cu coil of 2 mm thickness is hardly glued by stycast1266 (epoxy). The liner made by the tough-pitch copper is placed inside the primary coil. The typical dimension of liner is 119 mm of outer diameter, 50 mm of lingth, and 1.5 mm of thickness. By modifying the dimension of the primary coil and the liner, we control the magnetic field curve for the many kinds of experiment.

[1] S. Takeyama, and E. Kojima, J. Phys. D: Appl. Phys. 44, 425003 (2011).

Seed field coil of the EMFC system

  The seed field coil of the EMFC system (upper) is a Hermhortz coil of around 26 mH, in between which the primary coil is settled. The typical bore diameter is 155 mm and the distance between the two split coils is 180 mm. The magnetic field of 4 T within 50 ms can be generated by injecting the current from the seed condenser bank. In experiments, a dummy coil of 1 mH (below) is connected in series for the accidental destruction of seed field coil.

Horizontal single-turn coil system

  The single-turn coil (STC) system can generate the magnetic fields of up to 300 T with the duration time of 6-8 microseconds by a fast-capacitor bank of 200 kJ. We have two STC systems, one is a horizontal type (H-STC) and the other is a vertical type (V-STC). Various kinds of laser spectroscopy experiments such as the cyclotron resonance and the Faraday rotation using the H-STC system are available. Although the magnet coil destracts in every shot, the sample and the cryostat settled inside the magnet coil are not damaged by the magnetic field generation. Therefore, we can perform the reproducible experiments using the same sample by using the STC system.

Vertical single-turn coil system

  For very low-temperature experiments, a combination of the V-STC system with a liquid helium bath cryostat is very useful and the magnetization measurements at temperature as low as 2 K can be performed up to 120 T with high precision.

Condenser bank of single-turn coil system

  The energy of 200 kJ fast condenser bank is used. For V-STC system, the we can choose the unit number of the condenser bank system (100 kJ/ 200 kJ). The air-gap switch is used for the discharge of each condenser.

Single-turn coil

  The magnet coil used in the single-turn coil system is made by wounded copper plate with thickness of 2 mm. The several types of bore diameter of coil can be selected between 6-18 mm, in accordance with the type of experiments.