From atomic clocks and gyroscopes to human lung imaging: the improbable course of DoD-supported research on optically-polarized spins

Summary form only given. Starting in the 1960\´s, the DoD (mostly AFOSR) began to support work on optical pumping in both academia and industry. The original rationale was to perfect high-quality atomic frequency standards, based on optically pumped Rb or Cs gas cells. This led to the successful development of practical atomic clocks that are widely used today, for example, in GPS satellites. Optically pumped magnetometers were another successful product of this research. A less successful goal of the research was to develop inexpensive nuclear magnetic resonance gyroscopes, based on polarized noble gas nuclei. That line of development was in direct competition with laser gyroscopes, which eventually became the technology of choice. However, the basic research and development involved in studies of spin-exchange polarization of noble-gas nuclei led to the development of magnetic resonance imaging of human lungs with laser polarized He-3 and Xe-129. The research was particularly successful because the AFOSR was willing to permit basic research on seemingly academic topics (for example light shifts, laser snow, and various relaxation phenomena) that turned up as practical goals were pursued. With benefit of hindsight, many of these "academic" topics turned out to have substantial practical relevance.