Browsing by Author "Fairbank, William M., Jr., advisor"

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Open Access
Barium extraction from liquid xenon on a cryoprobe for the nEXO experiment and a nucleon decay search using EXO-200 data
(Colorado State University. Libraries, 2019) Craycraft, Adam B., author; Fairbank, William M., Jr., advisor; Roberts, Jacob, committee member; Wilson, Robert, committee member; Johnson, Thomas E., committee member
Neutrinoless double beta decay (0νββ) is a theorized decay that is beyond the standard model of particle physics. Observation of this decay would establish the Majorana nature of neutrinos and show violation of lepton number. Nucleon decay is another theorized decay that is beyond the standard model of particle physics that would violate baryon number. Observation of baryon number violation has been pursued for sometime in a wide variety of experiments. EXO-200 is an experiment that utilized a time projection chamber (TPC) filled with liquid xenon (LXe) enriched in the isotope xenon-136 to search for 0νββ. In this thesis, an analysis of EXO-200 data in search of evidence for triple-nucleon decays in ¹³⁶Xe is presented. Decay of ¹³⁶Xe to ¹³³Sb and decay to ¹³³Te were the particular decays searched for in this analysis. No evidence for either decay was found. Limits on the lifetimes of these decays were set that exceed all prior limits. The proposed nEXO experiment will be next generation LXe TPC search for 0νββ. In order to eliminate background events that are not associated with two neutrino double beta decay, a technique to tag the barium-136 decay daughter is under development. In this thesis, continued development is presented of a scheme to freeze the barium daughter in a solid xenon sample on the end of a cryoprobe dipped into LXe and subsequently tag it using its fluorescence in the solid matrix.
Open Access
Investigation of laser cooling and trapping of atomic silicon: towards the development of a deterministic single ion source
(Colorado State University. Libraries, 2023) Ronald, Samuel R., author; Lee, Siu Au, advisor; Fairbank, William M., Jr., advisor; Rocca, Jorge J., committee member; Marconi, Mario C., committee member
The laser cooling and magneto-optical trapping of silicon atoms were investigated experimentally. These are the first steps towards the development of a deterministic single ion source suitable for single ion implantation of a Kane quantum computer. We identified the 3s23p2 3P2 → 3s3p3 3Do3 transition at 221.74nm as a cycling transition suitable for laser cooling. We also identified the 3s23p2 1D2 → 3s3p3 3Do3 at 256.26nm as a repump transition coupling a lower metastable state with the upper cooling state. Two deep ultraviolet (DUV) laser systems were implemented to provide the cooling and repump laser light. Both systems utilized two stage second harmonic generation to quadruple the frequency of a fundamental laser to produce the DUV light. The cooling laser system utilized frequency quadrupling of a tunable cw Ti:Sapphire ring laser to produce up to 90mW at 221.74nm. The repump laser system utilized frequency quadrupling of an external cavity diode laser to produce up to 35mW at 256.26nm. A silicon atomic beam source operating at 1400°C was developed that produced a beam of free silicon atoms for laser studies. The atomic beam characteristics were analyzed, and the velocity distribution was manipulated via laser cooling. Careful spectroscopic studies were performed on the cooling and repump transitions. Frequency references for the DUV lasers were investigated in Te2 and I2 with Doppler free saturated absorption spectroscopy, using the first doubling stage output of the cooling and repump laser, respectively. Specific hyperfine components of the molecular transitions in Te2 and I2, suitable for frequency references, were identified and measured. Locking of the cooling laser on the Te2 reference was demonstrated. A magneto-optic trap (MOT) was implemented in the silicon atomic beam. A CCD optical system to image the fluorescence from atoms in the MOT was developed and achieved single atom ii detection capability. MOT trapping of silicon atoms was attempted. The low flux of atoms in the MOT velocity capture range precluded any observation of trapped atoms. A Zeeman slower, based on a novel design utilizing a variable pitch helical solenoid, was designed, simulated, and constructed to improve the flux of slow atoms. No magneto-optic trap was observed due to insufficient laser power for simultaneous Zeeman slowing and magneto-optic trapping. Investigations were performed for one dimensional laser cooling, via a Zeeman slower, along the atomic beam motion direction. Atomic beam velocity distribution profiles were observed to be modified when the Zeeman slower was on. The parameter space of Zeeman slower currents, laser power and detuning, was explored. A simulation of the atom motion over the 1m long flight path under the influence of the Zeeman slower was carried out and found to agree with the observed results.
Open Access
Measurements of the motions of atoms: flow velocities and diffusion constants
(Colorado State University. Libraries, 1981) Prodan, John V., author; Fairbank, William M., Jr., advisor; She, Chiao-Yao, advisor
Using Fluorescence Correlation Spectroscopy (FCS), the motion of atoms have been measured in real time. Single sodium atoms have been detected with this method and their flow velocity crudely measured. By averaging over many atoms, very clear signals were obtained and velocities up to 85 m/sec were measured. These velocities were determined by measuring the transit time of atoms across two resonantly tuned laser beams. Diffusion constants, D, of sodium in helium, neon and argon buffer gases were also measured using FCS. The products, Dp, where p is the pressure of the buffer gas, for these three cases were determined to be 427 ± 7 Torr cm2/sec, 277 ± 10 Torr cm2/sec and 200 ± 9 Torr cm2/sec, respectively. These numbers were obtained from measuring the average duration of the fluorescence burst from individual sodium atoms diffusing through the laser beam. Also measured was the diffusion constant for the excited sodium atom (2P3/2) in a helium buffer gas at 200 Torr pressure, with a result of 598 ± 84 Torr cm2/sec.