Research Interests:

Studies in experimental gravitational physics use special masses of compensated magnetic material containing >1023 spin aligned electrons in a few cubic cm volume to search for departures from the General Theory of Relativity. The huge intrinsic spin of these "macroscopic electron" masses, without measurable magnetic moment, offers high sensitivity in searches for particle phenomena which would violate the principle of equivalence. Two different experiments with torsion pendulums, have set new limits to the existence of anomalous spin forces. One of these has particle physics implications for the axion existence in the "Turner Window" of astrophysical data. A third experiment uses these masses in a pendulum to scan the sky for anomalous interactions with hypothetical dark matter around the center of our galaxy. In a medical physics program a helmet of six superconducting coils performs "magnetic surgery" by moving a small implant within brain to deliver therapies (drugs, heat, electrical sensors) to otherwise inaccessible regions. The implant is navigated along planned paths under guidance from preoperative Magnetic Resonance Images onto which are fused real time biplanar fluoroscopic images. Physics of the control problem center around methods to deal with the over determination of this inverse problem of electromagnetism, along with dynamic limitations to ramping superconducting coil currents. Recent neural network studies are aimed as improving these solutions.