Design of a quadrupole resonance probe using high-temperature superconducting resonators

Quadrupole resonance detection systems are an emerging technology for non-invasive detection of concealed contraband. Yet, despite many advances in instrumentation, signal processing and pulse sequence design, the use of quadrupole resonance in contraband detection systems is still hampered by the low signal-to-noise ratio of the quadrupole resonance measurements. In contraband detection, measurement signal-to-noise ratio can be improved by lowering the probe's temperature and raising its quality-factor.;This thesis outlines the development of a cryogenically cooled quadrupole resonance probe with a quality-factor on the on the order of 20,000 during detection. The probe's high Quality-factor improves the signal-to-noise ratio by more than an order of magnitude compared to conventional probes. This improvement is achieved using self-resonant circuits fabricated from a high-temperature superconductor on a low-polarization loss substrate. However, a high-temperature superconducting resonator alone is a poor quadrupole resonance probe. This thesis presents techniques for resolving the challenges involved in integrated a high-temperature superconductor resonator into a quadrupole resonance probe. These challenges include measuring the resonator's behavior under various conditions typical to quadrupole resonance detection, tuning the probe over a wide frequency range and dissipating the probe's natural response to the excitation pulse. The resulting quadrupole resonance probe has a quality-factor on the order of 20,000 during detection.;Experimental validation of the probe was conducted to demonstrate the probe's functionality using both a high impedance input receiver and the more conventional 50 O duplexed configuration. For the high impedance receiver configuration, detection of both the free induction decay and spin echo are shown for the probe using sodium nitrite as the sample. The response of the sodium nitrite sample is also found using the multi-pulse spin-lock spin-echo sequence. For the duplexed probe, the multi-pulse Carr-Purcell-Meiboom-Gill sequence was used to detect the QR response from the explosive RDX.