Active Magnetic Field Canceller AMC-331
If magnetic field fluctuations occur, they will adversely affect electron beam application devices such as electron microscopes. The AMC-331 is a system that suppresses magnetic field fluctuations by detecting magnetic field fluctuations with a high-sensitivity magnetic field sensor and using a Helmholtz coil to generate magnetic fields of opposite phases.
Basic Principles
Causes of Fluctuating Magnetic Fields
- Due to the movement of magnetic material (cars, elevators, trains, etc.) ・ Power noise (50 or 60 Hz)
- Influence of peripheral devices
Helmholtz Coil
- A coil connected in a series with the same number of turns in parallel arrangement.
- When a current passes, a magnetic field is generated in the axial direction of the coil.
Magnetic flux density contour map
Parallel magnetic field by Helmholtz coil
Theoretical calculation 1
Theoretical calculation 2
The magnetic flux density in the X-axis direction is obtained by using Pio-Savart's law.
Theoretical calculation 3 Analysis result 1
Theoretical calculation 4 Analysis result 4
Features
- High performance: Excellent attenuation performance up to 40-60 dB
- Low cost: Achieves approximately 1/10 the cost compared to the magnetic field measures of a shield
- Easy installation: Achieves easy installation by fixing the coil around the device
Control method: DC representative value control + independent feedback control for each axis
Control range: ± 15 μT (approvable)
Control frequency: Quasi DC ~ 1kHz
Attenuation rate: 40-60 dB
1) Measured data 200Hz disturbance
2) Measured data Environmental disturbance
Usage
- Scanning electron microscope (SEM)
- Transmission electron microscope (TEM)
- Focused ion beam (FIB)
- Mass spectrometer (MASS)
- Electron beam lithography apparatus (EBL)
- Mask inspection device
- Wafer observation measurement SEM
