Enhancement, analysis and verification of the Gravity Probe B SQUID readout system

This dissertation discusses the analysis, development and testing of key parts of the gyroscope readout system for the Stanford Relativity Gyroscope Experiment, also known as Gravity Probe B (GP-B). The GP-B experiment is designed to measure accurately two physical phenomena that are predicted from the general theory of relativity: the frame-dragging and the geodetic effects. These effects will be estimated by measuring the precession rates of very precise superconducting gyroscopes that are to be placed in a polar earth orbit. The goal of the experiment is to determine the two relativistic precession rates to an accuracy better than 0.5 m-arcseconds/year.; To measure these small precessions a sophisticated detector system is needed to "read-out" the spin axis orientation for each of the four gyroscopes. The superconducting gyroscopes generate a magnetic field (London moment) which provides a convenient indicator of spin axis direction. A DC Superconducting Quantum Interference Device (DC SQUID) is used to measure the magnetic flux coupled from the London moment via a pickup loop. By analyzing the measured SQUID response an estimate of the gyroscope spin axis orientation can be computed.; There are a number of environmental and systemic disturbances that will be present during the mission that can limit the accuracy of the readout system: electromagnetic interference, proton bombardment, temperature induced drifts, noise and nonlinearities. Parts of the readout system were redesigned as part of this research to minimize the effects of these phenomena. Additionally, nonlinear analysis methods were developed to better understand the dynamic behavior of the SQUID flux-locked-loop electronics during various scenarios.; The readout system hardware was then tested under appropriately harsh conditions to show that the subsystems will work as expected. The results of the collective experimental data set provide a promising indicator that the readout concept as presented in this work is sound and should be capable of estimating the general relativistic precession rates to the required accuracy.