Applications Products / Large Magnetic Circuits
Dipole ring magnetic circuits are used to generate uniform strong magnetic fields in a specific direction. The generated magnetic field is uniform to within 3-6% in the inner diameter space in the radial direction on the inner diameter side of the magnetic circuit and the skew angle that expresses the directionality of the magnetic field is a mere 1.0°or less. Dipole ring magnetic circuits are currently used as magnetic field sources in heat treatment processes for hard disk drive heads, MRAM, etc.
6-pole magnets are large magnetic circuits that generate a 6-pole (NS) magnetic field in the inner diameter space.
They are primarily used as ion sources. An ion source is a device for generating multivalent ions from neutral atoms. A typical ion source uses electric cyclotron resonance (ECR). Because multivalent ions have extremely strong electron affinity, if they are irradiated on the target material (focus tumor, semiconductor printed circuit board, or the like), they cause changes in the structure of the material.
The structure of a 6-pole magnet is complex, comprising 24 to 36 flat magnet segments formed into a ring shape, so extremely high levels of technology are required to produce these circuits. 6-pole magnets are generally used in combination with solenoid coil electromagnets called mirror magnetic field generators and high-frequency power sources, but in recent years, for the sake of weight reduction, products that replace the mirror field source with permanent magnets are becoming the mainstream.
Including the mirror magnetic field circuit, the maximum circuit weight reaches over 300 kg. Shinetsu Chemicals led the world in successfully producing 6-pole magnets, which have been used for medicine and basic research and in recent years as magnetic field sources for semiconductors.
An MRI magnetic circuit comprises the huge yoke section, a magnet of 1 ton or more, and magnetic field adjustment plates for making the magnetic field uniform. The magnetic field in the gap space of the magnetic circuit is uniform to within 25 ppm in an elliptical uniform space of φ400 mm by 350 mm. The residual magnetization of the magnetic field generated from the inclined magnetic field is 3 ppm or less and the eddy current observed at the same is extremely minimal.
Shinetsu Chemicals has mass produced more than 500 MRI magnetic circuits and they are contributing to the field of imaging diagnostics at medical sites around the world.