Abstract
The probe is the part of a nuclear magnetic resonance (NMR) spectrometer that delivers RF power to excite the nuclear spins in the sample and receive the emitted signal. Advancing NMR methodologies require state of the art probes which include such features as balanced channels, outstanding efficiencies, and high isolations. This thesis describes the following advances.
With respect to probe elements, we invented three suitable baluns (the clusterable pseudo-Marchand balun, the tunable coaxial balun, and the compound balun), a multi-layer transmission line, a fine impedance and balance adjustment module, a segmented main transmission line, a common null point module and an in-line filter. These innovative elements have been incorporated into three innovative designs of fully transmission line, multi-resonant NMR probes with all the channels balanced.
In addition, we developed instrumentation to measure circuit parameters and facilitate probe construction. These include an active non-invasive voltage probe, a versatile impedance probe, an accurate impedance probe with the reference reactance module, phantom devices, and a null point locator. Using this instrumentation, we introduce novel approaches to accurately determining sample coil balance, impedances, and null point locations.
With respect to systematic design and fabrication methodology, we combine a modular approach with a testing regimen that facilitates design and fabrication.
As a result of these efforts, a 500 MHz 1H13C pseudo-Marchand balun NMR probe was built with peerless performance characteristics. Its design and test results are elaborated in detail. In addition, a 400 MHz 1H13C tunable coaxial balun NMR probe and a 500 MHz 1H13C compound balun NMR probe have been designed. The latter are expected to have promising performance according to simulations. The designs and simulated performance of these two NMR probes are also illustrated in this thesis.