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Today’s high performance electron beam tools are very sensitive to changing ambient magnetic fields. The fields move the beam causing loss of resolution and measurement accuracy. The SC20 system stabilises the ambient field and restores the resolution and accuracy.
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The SC20 system comprises a Magnetic Field Control Unit, one or two AC or DC Magnetic Field Sensors and three multicore cables which are installed in the room where the field is to be cancelled. The Control Unit power amplifiers drive currents through the cables to create a field which is the opposite sign to the changes in the ambient field. The magnetic field sensors measure the resulting field and real time negative feedback reduces the ambient field by the loop gain of the system.
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The system is dynamic, automatically responding to field changes within 100 μs. Line
fields (50/60 Hz) are reduced by 50 x and DC fields by 200 x.