Events at Physics |
Events on Friday, September 8th, 2023
- Graduate Program Event
- Advances in All-Optical Magnetometry for Femto-Tesla Sensitivity in Earth-Field-Scale Magnetic Fields
- Time: 9:00 am - 10:30 am
- Place: 5280 Chamberlin
- Speaker: Michael Bulatowicz, Department of Physics Graduate Student
- Abstract: The ability to detect femto-Tesla ($10^{-15}$) magnetic fluctuations in the presence of large background magnetic fields encountered in unshielded environments on Earth is a capability which can enable a wide array of applications presently requiring magnetically shielded environments. This has been possible for many years through the use of superconducting quantum interference devices (SQUIDs); however, SQUIDs are expensive to purchase, operate, and maintain. In contrast to SQUIDS, optically pumped magnetometers based on warm alkali vapor are relatively inexpensive to purchase, operate, and maintain while promising similar sensitivity capabilities.
In the present work, I have demonstrated an optically pumped scalar magnetometer using a 1 cm diameter by 1 cm length internal dimension cylindrical vapor cell with a photon shot noise limit of 3.5 $fT/\sqrt{Hz}$ and a demonstrated single-channel noise of 10 $fT/\sqrt{Hz}$ as limited by the electrical current source generating a 29 $\mu T$ bias field. I have further demonstrated a differential pair of these magnetometers, separated by a distance of 9 cm, with measured differential noise of 1 $fT cm^{-1}/\sqrt{Hz}$, consistent with a single-channel noise of 6 $fT/\sqrt{Hz}$. I present a straightforward procedure for optimization of the sensitivity of this magnetometer to achieve fundamental sensitivity limits in the low single digit $fT/\sqrt{Hz}$ and guidelines for detection electronics supporting total noise from the magnetometer dominated by the fundamental sensitivity limit. I demonstrate, analyze, and characterise the basis of a method for detection of the vector components of the incident magnetic field through the use of an applied oscillating field along each vector axis to be measured, and I present initial results with single-axis vector component detection. Included in the relevant chapter are algorithms and feedback methods for achieving high performance, along with a demonstration of each, and measurements of performance including relative accuracy and uncertainty. I further present a demonstration and theory of detection of RF magnetic fields near the natural Larmor precession frequency of the spins, taking advantage of the AC Stark shift of the optical pump beam to generate a linear sensitivity to the RF signal, measured at the difference between the RF frequency and Larmor frequency. Finally, I look toward future work, proposing a method for measurement of the vector direction of the incident magnetic field by real-time observation of the spin precession. - Physics Department Colloquium
- NO COLLOQUIUM THIS WEEK
- Time: 3:30 pm - 5:00 pm
- Abstract: You should plan to attend the Department Picnic, tomorrow, Saturday, September 9!