Physics
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Item Experiments with Ultracold Strontium in Compact Grating Magneto-Optical Trap Geometries(2022) Sitaram, Ananya; Campbell, Gretchen K; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this thesis, we present the construction of a new apparatus for conducting experiments withultracold strontium. The new apparatus is designed with a high-flux atomic source, a custom science chamber optimized for optical access, high-current Bitter electromagnets, and an updated computer control system. We discuss in-depth the implementation of an insulated-gate bipolar transistor (IGBT) for fast current control of the magnetic field coils. We also present the design of JQI AutomatioN for Experiments (JANE): a programmable system on chip (PSoC)-based pseudoclock device that we use as the main clocking device for our experiments. Next, we report the realization of the first magneto-optical trap (MOT) of an alkaline-earth atom with a tetrahedral trap geometry produced by a nanofabricated diffraction grating. We have demonstrated a broad-line MOT in bosonic 88Sr and fermionic 87Sr. We trap approximately 4x10^7 atoms of 88Sr and achieve temperatures of around 6 mK, with a trap lifetime of around 1 s. Finally, we demonstrate sawtooth wave adiabatic passage (SWAP) in a narrow-line MOT of 88Sr atoms. In the narrow-line MOT, we trap approximately 3x10^6 atoms, with an average temperature of 3.4 µK and a trap lifetime of 0.77 s. We also discuss the possibility for a narrow- line grating MOT of the fermionic isotope. Our work with strontium grating MOTs is a step in the direction of compact quantum devices with alkaline-earth atoms.Item Experiments with laser cooling and cold spinor gases(2022) Anderson, Madison J.; Campbell, Gretchen K.; Lobb, Christopher D.; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis is the result of work on two separate Bose-Einstein condensate (BEC) experiments. First, I describe several projects in the construction of an ultracold Er and Na mixture experiment (Er:Na experiment). These include the design and characterization of a high temperature induction oven for Er as well as the capture of Er atoms into a 2D magneto-optical trap (2D MOT). Together, the induction oven and 2D MOT constitute a novel, compact source of cold Er atoms. Additionally, the construction and characterization of high current magnetic field coils for a magnetic quadrupole trap (MQT) and Helmholtz coils for future Feshbach spectroscopy are detailed.Second, I describe a series of experiments with spinor gases carried out on the JQI Na spinor apparatus. In the first experiment, I demonstrate the freezing of nonlinear spin mixing dynamics in a 23Na BEC using a microwave dressing. This technique can be used to preserve squeezing of a probe state in future metrological applications. The spinor phase of a frozen state evolves at an enhanced rate proportional an effective quadratic Zeeman shift, q, of the |F = 1, mF = 0⟩ energy level. In the second experiment, I demonstrate a radio frequency (rf) atomic spin-1 Ramsey interferometer which can measure the effective q, and thereby the spinor phase precession rate of a frozen probe state. The interferometer can simultaneously measure the rf detuning and q, and I demonstrate that it can be operated in both resonant and off-resonant regimes, using differential phase modulation between the two Ramsey pulses. The spin-1 Ramsey interferometer therefore has distinct advan- tages over both rf and microwave Rabi spectroscopy which are alternative methods to measure the effective q. Finally, I demonstrate theoretical grounds for spin squeezing in a cold spin-1 thermal gas. In particular, I derive a spin-1 Boltzmann transport equation for the Wigner phase space density operator without recourse to Hartree-Fock theory. I then apply three different theoretical paradigms to model an experimental observation of classical relative number squeezing in a cold spin-1 thermal gas of Na: a simplified undepleted pump model which I solved analytically, a semiclassical quasiprobability distribution (QPD) numerical method, and numerical solution of the Schro ̈dinger equation using Fock states.Item Studies of Ultracold Strontium Gases(2017) Reschovsky, Benjamin; Campbell, Gretchen K.; Rolston, Steven L.; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We describe the operation and performance of an ultracold strontium apparatus that is capable of generating quantum degenerate gases. The experiment has produced Bose-Einstein condensates (BECs) of 84Sr and 86Sr as well as degenerate Fermi gases (DFGs) of 87Sr with a reduced temperature of T/TF = 0.2 at a Fermi temperature of TF = 55 nK. Straightforward modifications could be made to allow for isotopic mixtures and BECs of the fourth stable isotope, 88Sr. We also report on a technique to improve the continuous loading of a magnetic trap by adding a laser tuned to the 3P1 - 3S1 transition. The method increases atom number in the magnetic trap and subsequent cooling stages by up to 65% for the bosonic isotopes and up to 30% for the fermionic isotope of strontium. We optimize this trap loading strategy with respect to laser detuning, intensity, and beam size. To understand the results, we develop a one-dimensional rate equation model of the system, which is in good agreement with the data. We discuss the use of other transitions in strontium for accelerated trap loading and the application of the technique to other alkaline-earth-like atoms. Finally, we also report on an updated investigation of photoassociation resonances relative to the 1S0 + 3P1 dissassociation limit in bosonic strontium. Multiple new resonances for 84Sr and 86Sr were measured out to binding energies of -5 GHz and several discrepancies in earlier measurements were resolved. These measurements will allow for the development of a more accurate mass-scaled model and a better theoretical understanding of the molecular potentials near the 3P1 state. We also measure the strength of the 84Sr 0u transitions in order to characterize their use as optical Feshbach resonances.