An Improved High-Sensitivity Airborne Transient Electromagnetic Sensor for Deep Penetration.

Area of Science:

• Geophysics
• Electromagnetism
• Sensor Technology

Background:

• Transient electromagnetic (TEM) sensors are vital for subsurface investigation.
• System noise, including sensor internal noise and electromagnetic interference (EMI), limits investigation depth.
• High-sensitivity airborne transient electromagnetic (AEM) sensors with low noise and effective shielding are crucial for deep penetration.

Purpose of the Study:

• To design and optimize a high-sensitivity AEM sensor for increased investigation depth.
• To reduce sensor internal noise through modeling and analysis.
• To enhance electromagnetic compatibility (EMC) via improved shielding.

Main Methods:

• Established a noise model for sensor internal noise, considering damping resistors and preamplifiers.
• Analyzed factors influencing internal noise, such as sensor diameter, resonant frequency, and sampling rate.
• Developed and applied an electromagnetic shielding model for a central-tapped coil to suppress EMI and eddy currents.

Main Results:

• Optimized AEM sensor features a diameter of 1.1 m, effective area of 114 m², and resonant frequency of 35.6 kHz.
• Achieved a normalized equivalent input noise of 13.3 nV/m², demonstrating significant reduction in sensor internal noise.
• Verified experimental results show good agreement with the noise model and confirmed over 20 dB shielding effectiveness in complex electromagnetic environments.

Conclusions:

• The developed noise and shielding models accurately predict sensor performance.
• The optimized AEM sensor design significantly improves internal noise and shielding effectiveness.
• This advancement enables deeper and more accurate subsurface investigations using airborne electromagnetic methods.