Research Interests
I am currently working in a collaboration between the quantum optics lab at William & Mary and the accelerator division of Thomas Jefferson National Accelerator Facility to build a quantum-based atomic sensor for magnetic fields generated by an electron beam. My work primarily consists of designing a tabletop electron beamline to detect using our proposed atom-based electromagnetic field sensor, and applying quantum enhancement to improve the sensitivity of magnetic field measurements.
Magnetic Field Electron Beam Tracker
My PhD work involves using atomic sensors to spatially map the magnetic field of a charged particle beam and reconstructing the current density of said beam through it's magnetic field. By measuring the electromagnetic fields generated by the particle beam, we don't rely on the direct interaction or scattering of electrons, as is the case with wire scanners and scattering-based fluorescence methods, respectively. Further, using atomic vapors as our detection medium, we also reduce the chances of electrons interacting with our medium, while still using spectroscopy to get information about electromagnetic fields.
The electron beam generates an axial magnetic field as it propagates through our atomic detection vapor, and the atoms will sense this magnetic field through a perturbation in their magnetically-sensitive quantum states. To monitor this perturbation, we use a liearly polarized laser tuned to the transition between the magnetically-sensitive quantum states. Upon experiencing the magnetic field, the atoms will alter the probability of absorbing and emitting one polarization component of the laser over the other, which results in a physical rotation of the linear polarization angle of the laser after the detection medium. This polarization rotation angle will therefore be directly proportional to the magnetic field experienced by the atoms.
To map out the magnetic field of the electron beam spatially, we use each atom in our detectio vapor as a local probe for magnetif field. By imaging the total polarization rotation angle, instead of reading out on a photodiode, we can extrapolate the magnetic field around the electron beam. Further, using some assumptions about the current distribution of the electron beam, we can determine the current density distribution of the electron beam from the magnetic field it generates. This assumption about the distribution can be relaxed if we could easily measure the direction of the magnetic field using Maxwell's equations, and our group has substantial work in this vector magnetometry through the VAMPIRE project.
The strength of using atoms as the detection medium is that we can derive all vital beam characteristics (position, width, total current) in a single detector, without relying on the interaction with the electron beam. Of course, if the method is too invasive with an atomic vapor, the use of cold atom clouds can be used to localize our detection medium and significantly reduce the chance of electron beam interaction, while also providing some sensitivity boosts at the cost of detector complexity.
Biography
Nicolas DeStefano is a PhD student in physics at William & Mary in Williamsburg, VA and holds a BSc in physics from Old Dominion University. He conducts research under the Novikova quantum sensing group to develop sensitive electromagnetic field detectors through coherent interactions between atoms and light. His work on quantum-based detectors earned recognition through fellowships from the DoE Office of Science Graduate Student Research and Virginia Space Grant Consortium, as well as presentation awards from various conferences. His work connects multiple disciplines of physics -- including nuclear and plasma physics -- to provide sensitive and non-interacting detectors for highly-constrained experiments. Nicolas's future work utilizes quantum light to improve detector sensitivity beyond the classical limit.