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Design and Fabrication of Sensor Probe and Active Noise Reduction Circuit for SQUID MCG System in Magnetically Unshielded Environment

Kalantari, Nafise | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 46919 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Fardmanesh, Mehdi
  7. Abstract:
  8. Characterization of local magnetic activity of the heart muscles is named magnetocardiography (MCG), which measures magnetic field generated by electrical activity around heart. RF SQUID sensors are appropriate choice for measuring magnetic activity of the heart muscles. Because squid detects weak signals as low as fTesla, while heart magnetic field is near 50 pt which is one millionth of earth magnetic field and thousands of time weaker than the environment noise. One of the problems of mcg system is its urgency to shielding of unwanted magnetic field. In this project design of holders and resonators for well coupled input coil with RF SQUID is improved. As a result, at the first stage adequate signal was obtained sensors. Besides that, the appropriate resonators and sensors are selected to get better signal from the system. In the next stage, since the goal of this project is using SQUID MCG in magnetically unshielded environment, noise reduction coils and driver circuits for eliminating noise actively are designed, developed and finally tested.The basic aims of this project are design and fabrication of active noise reduction system for the use in SQUID MCG in magnetically unshielded environment, notably for decreasing noise from power lines at frequency of 50 or 60 Hz and their harmonics. One of the advantages of active shield is its price compared to that of passive one (Magnetically Shielded Rooms). For this purpose, one RF SQUID Sensor measures environment noise, active shield circuit pumping current to the noise reduction coils with opposite phase proportion to the measured signal. Then, the heart signal can be measured with second the RF SQUID
  9. Keywords:
  10. Active Shielding ; Magnetic Shielding ; Magnetic Sensor ; Magnetocardiography ; Radio Frequency Superconducting Quantum Interference Device (SQUID)Sensor

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