Parametrically-enhanced nuclear magnetic resonance spectrometer prototype Wong, Kenneth
This project evaluates the feasibility of using a strong alternating magnetic field, in addition to the Earth’s weaker magnetic field, to improve nuclear magnetic resonance spectroscopy. In this new method of NMR spectroscopy devised by Prof. Michal, an electromagnet, instead of the Earth, is used to generate static magnetic field. A solenoidal coil produces a magnetic field strength of approximately 2.35 mT, over 40 times greater than that of the Earth. The stronger static magnetic field is expected to increase the signal-to-noise ratio of the NMR signal by more than 700 times over traditional Earth’s field NMR. The objective of this project is to produce an engineering prototype demonstrating parametrically enhanced NMR spectroscopy. The prototype consists of a transmitter coil to generate the alternating static magnetic field, a receiver coil to detect the Larmor precession of the test specimen, and an electronic circuit to filter and amplify the NMR signal. By using an alternating static magnetic field, the detrimental spin dephasing caused by field inhomogeneities can be reduced. The prototype necessitates relatively inexpensive components and maintains a portable form factor. In developing the prototype, the transmitter coil and the receiver coil has been fabricated and characterized. After evaluating the two proposed waveforms for driving the transmitter coil, the sinusoidal waveform is selected and a circuit has been designed and breadboarded. The NMR signal processing circuit successfully rejects 37 dB of the offending noise signal to theoretically allow the Larmor precession to be discerned. Due to unforeseen distortion in the output signal of the power amplifier, the specified static magnetic field strength cannot be achieved. As a result, the parametrically enhanced NMR spectrometer prototype has not been realized within the project timeframe. Several recommendations are suggested to correct the identified problems and improve the current design. With additional development, this novel NMR spectroscopy method can be developed into inexpensive and portable NMR spectroscopy applications.
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