SBIR-STTR Award

Optically pumped magnetic detectors are currently used in military applications to detect buried ordnance and underwater mines, but existing instruments have limited sensitivity. Dr william mapper has suggested that optically pumped sensors can be dramatically improved and might ultimately provide a sensitivity comparable to that of superconducting gradiometers. In this proposal we outline preliminary experiments which should demonstrate the feasibility of constructing a free precession, optically pumped magnetic detector such as mapper describes. Phase I will address the critical problems of absorption cell wall coatings, the dephasing of the coherent larmor precession, and the detection of the larmor frequency in a free precession system. The final part of phase I will briefly examine the engineering problems of producing a high intensity optical pumpng beam, a common-source detecting beam, and the electronic signal processing system. The final report will combine these data into a preliminary conceptual design for a prototype instrument.

Although optically pumped magnetic detectors are now used tn a variety of both military and commercial applications, there has been little interest in recent years in developing more sensitive instruments based on the optical pumping technique. However, dr. William rapper of princeton university has recently described the techniques for obtaining a dramatic increase in sensitivity from these devices, and during phase i, we performed experiments which have demonstrated the fundamental concept. In this proposal we present a program for developing an optically pumped l,%gnettc sensor based on happer's analyses. The first part of the program addresses the critical issues of spin relaxation of the alkali metal vapor in the absorption cell, and the generation of a reliable high intensity pumping beam to establish the initial polarization. The last half of the program ts devoted to constructing and testing an initial evaluation unit, then refining the design to produce a second generation instrument which can be used to perform some initial evaluation tests in a field environment. The proposal presents a detailed description of the problems to be solved tn the development program, and discusses our approach to each.