DC Power Supplies for LHD Superconducting Magnets and Their Enhancement for Dynamic Control of the Magnetic Field

The Large Helical Device (LHD) has six superconducting coil pairs that form a magnetic field, and plasma experiments of LHD require high accuracy and stability to control the coil current, which must be controlled in a wide range to change the magnetic field. This paper introduces the power system for the LHD superconducting magnets and the enhancement of the power supplies.

When designing the power supplies, it is difficult to satisfy the requirements for the current control with a simple controller installed in each power supply because of the tight magnetic coupling between the superconducting coils. In addition, synchronized operation of these power supplies is important for LHD operation. To satisfy the current control requirements and to synchronize operation of the power supplies, six dc power supplies controlled by a computer system were constructed and are operating. The fundamental operation of the LHD is performed under the dc magnetic field, and a power system suitable for steady-state operation was designed and constructed. With the progress in fusion plasma research, more dynamic experiments are planned, and they require dynamic control of the magnetic field. For this purpose, the output voltages of power supplies were enhanced using additional pulse power supplies.