M.Sc Thesis

M.Sc StudentBen-Itzhak Segev
SubjectInvestigation of Physical Phenomena involved in Nuclear
Spin Gyroscope
DepartmentDepartment of Electrical and Computer Engineering
Supervisors PROFESSOR EMERITUS Gad Eisenstein


Atomic sensors have growing relevance to many aspects of modern science and technology. Atomic sensors based on atomic spins have been ranked as the most sensitive sensors for a wide range of applications. The atomic clock, which utilizes atomic level structure, has become the world's most accurate time standard; the nuclear magnetic resonance (NMR) analyzer, which utilizes NMR phenomena of atomic spin, has become one of the most powerful tools in modern medicine; and the nuclear magnetic resonance gyroscope (NMRG), which measures the shift of the NMR frequency caused by inertial rotation, is believed to be the development trend for high precision and compact gyroscopes in the future. Atomic sensors with ultra high sensitivities are thought to be the key sensors for the development of a self-contained, chip-scale inertial navigation and precision guidance systems that would effectively eliminate the dependence on GPS while enabling uncompromising navigation and guidance capabilities, operable under severe dynamic environments (Micro Position and Navigation (PNT) program - DARPA).

In this research, we investigate two types of ASGs, both based on the physical properties of atomic magnetometers containing two atomic spin species: alkali-metal atoms and noble-gas atoms. The first type studied is the NMR gyroscope which detects rotation by measuring a corresponding shift in the Larmor precession frequency of nuclear spins in an applied magnetic field. The second type is the co-magnetometer gyroscope (CM), with an ASG configuration based on a bias magnetic field tuned to a compensation point, where the two spin species are strongly coupled, to form a hybrid oscillator insensitive to transverse magnetic field and gradients. The CM gyroscope detects the shift of the polarization's orientation of the nuclear spins caused by the inertial rotation. The sensitivity of the CM is dramatically enhanced by using a high density alkali metal vapor in a spin exchange relaxation free (SERF) regime. The ultra sensitive CM suffers from low dynamic range and bandwidth performances, which will make it difficult for its use in navigation applications. We introduce in our research a method to overcome these limitations. An improvement of two orders of magnitude in the dynamic range is presented and an order of magnitude in the sensor bandwidth. Finally, we introduce a novel ASG by coupling two noble-gas isotopes and alkali-metal atoms in a CM-NMR configuration, which utilizes the features of the two types of ASGs to form a 3-axis ASG.