Fast Degaussing Procedure for a Magnetically Shielded Room

Area of Science:

• Physics
• Materials Science
• Biomedical Engineering

Background:

• Magnetically shielded rooms (MSRs) are crucial for sensitive magnetic measurements.
• Optically pumped magnetometers (OPMs) require extremely low residual magnetic fields (< 5 nT) for optimal performance.
• MSRs often utilize mu-metal composites for effective magnetic field shielding.

Purpose of the Study:

• To investigate the demagnetization process of a novel MSR.
• To achieve a residual magnetic field below 5 nT within the MSR.
• To assess the effectiveness of the demagnetization procedure for magnetoencephalography (MEG) and material testing applications.

Main Methods:

• A demagnetization study was performed on an MSR constructed with mu-metal and aluminum layers.
• Six individual coils were used to actively degauss the MSR.
• The residual magnetic field was measured within the central 1 m³ volume.

Main Results:

• The degaussing process successfully reduced the residual magnetic field to the target level (< 5 nT) within four minutes.
• The MSR demonstrated a low-frequency shielding factor of 100.
• Environmental magnetic field fluctuations after degaussing were identified as the limiting factor for the residual field.

Conclusions:

• The implemented demagnetization procedure is effective for achieving ultra-low magnetic fields required for OPMs and MEG.
• The MSR design and degaussing technique meet the stringent requirements for advanced magnetic sensing applications.
• Future efforts should focus on mitigating environmental magnetic field variations to further enhance measurement stability.