Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1994. / by Kevin David Rathbun. / B.S.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 57-58). / 21 cm tomography has the potential to become the most powerful cosmological probe yet. The Omniscope is a novel radio telescope being built to take advantage of this signal. This thesis describes my work on integrating, testing, and characterizing all modules of the Omniscope and identifying opportunities for further improving their sensitivity. / by Ashley Nicole Perko. / S.B.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1994. / Includes bibliographical references (p. 165-168). / by Peter J. Rothschild. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, February 2004. / Includes bibliographical references (p. 513-541). / The nucleon elastic electromagnetic form factors are fundamental quantities needed for an understanding of nucleon and nuclear electromagnetic structure. The evolution of the Sachs electric and magnetic form factors with Q2, the square of the four-momentum transfer, is related to the distribution of charge and magnetization within the nucleon. High precision measurements of the nucleon form factors are essential for stringent tests of our current theoretical understanding of confinement within the nucleon. Measurements of the neutron form factors, in particular, those of the neutron electric form factor, have been notoriously difficult due to the lack of a free neutron target and the vanishing integral charge of the neutron. Indeed, a precise measurement of the neutron electric form factor has eluded experimentalists for decades; however, with the advent of high duty-factor polarized electron beam facilities, experiments employing polarization degrees of freedom have finally yielded the first precise measurements of this fundamental quantity. / (cont.) Following a general overview of the experimental and theoretical status of the nucleon form factors, a detailed description of an experiment designed to extract the neutron electric form factor from measurements of the neutron's recoil polarization in quasielastic 2H(e, e')1H scattering is presented. The experiment described here employed the Thomas Jefferson National Accelerator Facility's longitudinally polarized electron beam, a magnetic spectrometer for detection of the scattered electron, and a neutron polarimeter designed specifically for this experiment. Measurements were conducted at three Q2 values of 0.45, 1.13, and 1.45 (GeV/c)2, and the final results extracted from an analysis of the data acquired in this experiment are reported and compared with recent theoretical predictions for the nucleon form factors. / by Bradley Robert Plaster. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2012. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 109-113). / This thesis describes the construction of a versatile apparatus to study ultracold quantum mixtures capable of simultaneously cooling fermionic ⁶Li and ⁴⁰K, as well as the bosonic ⁴¹K. The main features of the experimental setup are presented, in particular the addition of a new species ²³Na, which has enabled the study of the Bose-Fermi mixture ²³Na-⁴⁰K. Three main experimental benchmarks are outlined: first, the production of a Bose-Einstein Condensate of ⁴¹K is discussed and an evaluation of its properties as a coolant are analysed. Secondly, the creation of a triply degenerate Bose-Fermi-Fermi gas of ⁴¹K-⁴⁰K-⁶Li is presented. Simultaneous observation of Pauli Pressure and Bose Condensation in the triply degenerate gas is reported. In addition, interspecies Feshbach resonances between ⁴¹K-⁴⁰K and ⁶Li-⁴¹K are observed, opening the way to the study of a strongly interacting isotopic Bose-Fermi mixture of ⁴¹K-⁴⁰K, which have similar mass. Thirdly, the creation of a quantum degenerate Bose-Fermi mixture of ²³Na-⁴⁰K is discussed and over thirty Feshbach resonances are identified. Finally, a degenerate ²³Na-⁴⁰K Bose-Fermi mixture opens the way to creating fermionic NaK ground state molecules, which are known to be chemically stable and have a larger permanent electric dipole than KRb. This thesis concludes with a review of the molecular properties of NaK and explores the possibilities of bringing Feshbach molecules of NaK into the singlet rovibrational ground state. / by Ibon Santiago González. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2012. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 197-205). / Insights into a distant exoplanet's interior are possible given a synergy between models and observations. Spectral observations of a star's radial velocity wobble induced by an orbiting planet's gravitational pull measure the planet mass. Photometric transit observations of a planet crossing the disk of its star measure the planet radius. This thesis interprets the measured masses and radii of super-Earth and sub-Neptune exoplanets, employing models to constrain the planets' bulk compositions, formation histories, and habitability. We develop a model for the internal structure of low-mass exoplanets consisting of up to four layers: an iron core, silicate mantle, ice layer, and gas layer. We quantify the span of plausible bulk compositions for low-mass transiting planets CoRoT-7b, GJ 436b, and HAT-P-11b, and describe how Bayesian analysis can be applied to rigorously account for observational, model, and inherent uncertainties. We present a detailed case study of GJ 1214b, the first exemplar of a new class of volatile-rich super-Earth exoplanets. At 6.5 Mo and 2.7 Ro, GJ 1214b must have a gas layer to account for its low mean density. We present three possible scenarios for the origin of the gas layer on GJ 1214b: direct accretion of H/He gas from the protoplanetary nebula, sublimation of ices, and outgassing of volatiles from a rocky interior. We next explore the low-density extreme of the mass-radius relations for volatilerich super-Earth exoplanets. Using models of planet formation, structure, and survival, we constrain the minimum plausible planet mass for a measured planet radius and equilibrium temperature. We explore both core-nucleated accretion and outgassing as two separate formation pathways for Neptune-size planets with voluminous atmospheres of light gases. Finally, we present a practical method to assess whether a hydrogen-rich sub-Neptune planet with measured mass and radius could potentially harbor a liquid water ocean. Using a one-dimensional radiative-convective model of energy transport through water-saturated hydrogen-rich envelopes, we constrain the combinations of planet properties (mass, radius, equilibrium temperature, intrinsic luminosity) that are conducive to liquid water oceans. The pace of low-mass exoplanet discoveries is poised to accelerate, and this thesis will contribute to constraining the interior properties of newfound planets. / by Leslie Anne Rogers. / Ph.D.

Thesis (Ph.D.) Massachusetts Institute of Technology. Dept. of Physics, 1954. / Vita. / Bibliography: leaves 97-98. / by Elizabeth Alden Little. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 1984. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by He Sheng Chen. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1993. / Includes bibliographical references (leaves 110-114). / by John Casmir Szczepanski. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2002. / Includes bibliographical references (p. 177-186). / Two experiments are presented which measure atomic properties using an atom interferometer. The interferometer splits the sodium de Broglie wave into two paths, one of which travels through an interaction region. The paths are recombined, and the interference pattern exhibits a phase shift depending on the strength of the interaction. In the first experiment, the interaction involves a gas. De Broglie waves traveling through the gas experience a phase shift represented by an index of refraction. By measuring the index of refraction at various wavelengths, the predicted phenomenon of glory oscillations in the phase shift has been observed for the first time. The index of refraction has been measured for sodium atoms in gases of argon, krypton, xenon, and nitrogen over a wide range of wavelength. These measurements offer detailed insight into the interatomic potential between sodium atoms and the gases. Theoretical predictions of the interatomic potentials are challenged by these results, which should encourage a renewed effort to better understand these potentials. The second experiment measures atomic polarizability with an atom interferometer. Here, the interaction is with an electric field; the atom experiences a phase shift proportional to its energy inside the field. Previously, this method was used to perform the most accurate (< 1%) measurement of sodium polarizability. The precision was limited, however, by the spread of velocities in the atomic beam-the phase shift is different depending on velocity, and the -interference pattern is washed out. / (cont.) This thesis presents a new technique to "rephase" the interference pattern at large applied fields, and demonstrates a measurement that is free of this limitation. In addition, most of the systematic errors that plagued the previous polarizability measurement are eliminated by the new technique, and an order of magnitude improvement in precision now appears quite feasible. The remaining systematic errors can be eliminated by measuring the ratio of polarizabilities between two different atoms, a comparison whose precision is better by another order of magnitude. / by Tony David Roberts. / Ph.D.