Active magnetic field canceller

Abstract

The purpose of the present invention is to provide an active magnetic field canceller capable of suppressing magnetic field variations at a position where a magnetic sensor that is a magnetic field detection means is not disposed. An active magnetic field canceller 1 is provided with: a magnetic field forming means comprising a pair of X-axis loop coils 2 disposed facing each other across a magnetic field control space S, and an X-axis current supply device 3; a magnetic sensor 8 disposed between the pair of X-axis loop coils 2 that is a magnetic field detection means for detecting a magnetic field in the magnetic field control space S; and a controller 9 that is a control means for controlling the X-axis current supply device 3, wherein the controller 9 controls the magnitude of currents flowing through the pair of X-axis loop coils 2 so as to cancel out magnetic field variations detected by the magnetic sensor 8 by making constant a current ratio Kappa x that is the ratio of the magnitude of the current flowing through an X-axis loop coil 2a that is one of the pair of X-axis loop coils 2 to the magnitude of current flowing through the other X-axis loop coil 2b.

Description

Technical field [0001] The invention relates to an active degaussing system. In detail, it relates to an active degaussing system that reduces the fluctuation of the magnetic field generated by an external magnetic field source. Background technique [0002] Conventionally, electronic applications such as electron microscopes and electron beam exposure devices that are susceptible to electromagnetic noise have been installed in a magnetic field control space based on an active degaussing system that suppresses magnetic field fluctuations caused by interference. The active degaussing system is equipped with loop coils with a magnetic field control space interposed therebetween, and controls the current flowing through the opposing loop coils in accordance with magnetic field changes in the magnetic field control space caused by interference. Among such active degaussing systems, there is known an active degaussing system in which a magnetic field detection unit (magnetic sensor) ...

AI Technical Summary

Problems solved by technology

However, the technology described in the patent document is to suppress the fluctuation of the magnetic field at the detection position where the magnetic sensor is arranged.

Therefore, if the magnetic sensor cannot be placed at the position where the magnetic field fluctuation is to be suppressed, the magnetic field fluctuation at the target position where the magnetic field fluctuation is to be suppressed may not be sufficiently suppressed depending on the position and size of the magnetic field generation source.

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