A commercial Spectra Diode Laboratories, 1.083 $\mu$m diode laser has been used to efficiently spin polarize an atomic beam of He(2$\sp3$S) metastable atoms by optical pumping on the $\rm 2\sp3S\sb1\rightarrow2\sp3P\sb1$ (D1) transition. The diode laser is an InGaAs/GaAs strained multiquantum well with a distributed Bragg reflector to insure single longitudinal mode operation. The laser has been frequency stabilized to less than 1 MHz/hr drift. The helium metastable atom beam is produced by electron impact and the polarization is measured using a Stern-Gerlach analyzer. Atomic polarizations exceeding 97% have been obtained with $\sim$25 mW of power from the diode laser. A number of experiments currently under construction may also make use of the diode laser. These include the production of a spin polarized helium ion beam by optically pumping the metastable atoms in an rf discharge, and the trapping of helium metastable atoms in a magneto-optical trap (MOT).

The use of ordinary perturbation theory is ubiquitous in modern physics. However, it violates probability conservation, one of the fundamental laws of physics. In this thesis a unitarized perturbation theory is briefly described and its predictions for the behaviour of a number of simple systems are compared with those of ordinary perturbation theory. It is found that the new technique performs just as well as the usual perturbative approach in the regime where the latter is valid and provides improved results where perturbation theory fails. In particular, in the cases studied, the new method is found to reproduce the exact result at resonance.

We use Nonrelativistic Quantum Electrodynamics (NRQED) as an effective field theory to calculate the single photon annihilation contribution to the positronium hyperfine splitting (HFS) in its ground state at order Oa6 . Our analytical result completes the hyperfine splitting calculation to order mea6 . Using NRQED, we derive the Lamb shift of a scalar-scalar bound state and Oa5 hyperfine splitting of positronium for a general excited state. Using the same technique, we also rederive the Lamb shift of Hydrogen atom and Oa5 HFS of positronium in its ground state.

<p> The quality of beam optics is of great importance for the performance of a high energy accelerator like the Relativistic Heavy Ion Collider (RHIC). The turn-by-turn (TBT) beam position monitor (BPM) data can be used to derive beam optics. However, the accuracy of the derived beam optics is often limited by the performance and imperfections of instruments as well as measurement methods and conditions. Therefore, a robust and model-independent data analysis method is highly desired to extract noise-free information from TBT BPM data. As a robust signal-processing technique, an independent component analysis (ICA) algorithm called second order blind identification (SOBI) has been proven to be particularly efficient in extracting physical beam signals from TBT BPM data even in the presence of instrument's noise and error. We applied the SOBI ICA algorithm to RHIC during the 2013 polarized proton operation to extract accurate linear optics from TBT BPM data of AC dipole driven coherent beam oscillation. From the same data, a first systematic estimation of RHIC BPM noise performance was also obtained by the SOBI ICA algorithm, and showed a good agreement with the RHIC BPM configurations. Based on the accurate linear optics measurement, a beta-beat response matrix correction method and a scheme of using horizontal closed orbit bumps at sextupoles for arc beta-beat correction were successfully applied to reach a record-low beam optics error at RHIC. This thesis presents principles of the SOBI ICA algorithm and theory as well as experimental results of optics measurement and correction at RHIC.</p>

<p> The charge distribution associated with an electron has surprising implications for a number of outstanding mysteries in physics. Why is the universe made out of matter versus anti-matter, instead of both equally? What new particles and interactions lie beyond the current reach of accelerators like the LHC? Models which propose answers to these questions, such as Supersymmetry, tend to predict a small, yet potentially measurable, asymmetric interaction between an electron and an electric field, characterized by an electric dipole moment (EDM). Despite over six decades of experimental searching, no EDM of any fundamental particle has ever been measured; however, these experiments continue to provide some of the most stringent limits on new physics. Here, we present the results of a new search for the electron EDM, <i>d</i>_e = (-2.1 &plusmn; 3.7_stat &plusmn; 2.5syst) &times; 10^-29 e cm, which represents an order of magnitude improvement in sensitivity from the previous best limit. Since our measurement is consistent with zero, we present the upper limit of |<i>d</i>_e| &lt; 8.7 &times; 10^-29 e cm with 90 percent confidence.</p>

The need to improve the quality factor of Atomic Force Microscopy cantileversimmersed in fluid has been demonstrated in great length, especially in the caseswhere samples need to be in their natural liquid environment. For that reasona series of low pressure chemical vapor deposited silicon nitride cantilevers werecreated based on a series of defined parameters. Each cantilever had a fixed surfacearea of 5600μm2, comparable with the rectangular cantilever of dimension of 140μmby 40μm used as a reference. A procedure to fabricate these levers in a clean roomenvironment, as well as issues that came up during the fabrication, is explained indetail. Each measurement was done on our in-house setup. The main componentsof this apparatus are a focussed laser, a sample holder and a split photodiode. Theresults obtained were not as impressive as we had hope although some cantileversshowed a significant decrease in the quality factor, helping us direct future workon the subject. One cantilever (#9) did however show equivalent performance withrespect to the reference cantilever and even slightly increasing the quality factor ratioin the second mode. / Le besoin criant d'augmenter le facteur de qualité de micros-levier immergée dans un fluide utilisé en microscopie de force atomique a été démontré a mainte reprise, plus particulièrement dans le cas ou les échantillons devais être dans leur environnent liquide naturelle. C'est pour cette raison qu'une série de micro-levier ont été crée sur une basse de paramètre prédéfini et avec un dépôt de nitrure de silicium chimique en phase vapeur sous pression réduite. Chaque micros-leviers a une aire de surface de 5600μm2, pouvant ainsi être comparé avec le micro-levier de référence ayant pour dimension 140μm par 40μm. Une procédure pour fabriquer c'est micros-leviers dans un environnent de salle blanche, ainsi que les méthodes utiliser pour contrevenir aux problèmes encourus durant la fabrication, sont expliqués en détail. Chaque prise de mesure a été effectué sur notre appareil fait maison ayant comment composante principale un laser focalisé, un porte échantillon et une photodiode divisée. Les résultats obtenu n'ont pas été a la hauteur de nos attentes, néanmoins certain micros-leviers ont démontrés une réduction significative de leur facteur de qualité, nous aidant donc à diriger le travail futur sur le sujet. Un microlevier (#9), a par contre démontré une performance équivalente par rapport au micro-levier de référence augmentant même le ratio de facteur de qualité pour le 2e mode d'opération.

An experimental set-up consisting of an electron-impact induced ionization chamber, a quadrupole mass filter and an ion detector has been constructed. The operating characteristics of the quadrupole mass filter system have been examined and compared to the theoretical predictions. With a moderate mass resolution of 30, an absolute ion transmission efficiency of about 10% has been obtained. This system has been used to investigate the ionization efficiency of noble gases. Charged species up to He$ sp{2+}$, Ne$ sp{4+}$, Ar$ sp{6+}$, Kr$ sp{5+}$ and Xe$ sp{7+}$ have been studied. The behavior of the ionization efficiency curve near threshold is analyzed using a power law fitting approach. For the first and second degree ionization processes, the fitting power law coefficients k are found to be close to the charge number of the ions produced, in agreement with the theoretical predictions. The extracted ionization potentials also agree with the accepted values. For the third and higher degree of ionization, the k-values are generally much lower than the theoretical predictions. However, the extracted ionization potentials are still consistent with the accepted values.

Thesis (Ph.D.)--Tufts University, 2000. / Adviser: Austin Napier. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 139-143). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph.D.)--University of California, Berkeley, 2006. / (UMI)AAI3254097. Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1028. Adviser: Dmitry Budker.

Thesis (Ph. D.)--University of Chicago, 1915. / Includes bibliographical references (p. 27-28).