Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1942. / MIT copy bound with: The color temperature of white light / Joseph Henry Altman. 1942. / Includes bibliographical references (leaf 33). / by Morton E. Goulder. / B.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 137-145). / In this thesis nanometer scale charge sensors are used to study charge transport in two solid state systems: Lateral GaAs quantum dots and hydrogenated amorphous silicon (a-Si:H). In both of these experiments we use time-resolved charge sensing to study electron transport in regimes that are not accessible to traditional transport measurements. For the lateral GaAs quantum dot experiments, we use a GaAs quantum point contact integrated with the dot as a charge sensor. We use this sensor to observe single electrons hopping on and off the dot in real time. By measuring the time intervals for which the dot contains one and zero electrons, we probe the rate F at which electrons tunnel on and off the dot from the leads. We measure F as a function of the drain source bias V, and gate voltages V applied to the dot. At zero magnetic field, we show that the dependencies of F on Vda and V can be understood in terms of a simple quantum mechanical model which takes into account variations in the electron energy relative to the top of the tunnel barriers separating the dot from the leads. We also show that the tunneling is dominated by elastic processes. At high magnetic fields, we show that tunneling into the excited spin state of the dot can be completely suppressed relative to tunneling into the ground spin state. The extent of the suppression depends on the shape of the electrostatic potential defining the quantum dot. For the a-Si:H experiments, we pattern a nanometer scale strip of a-Si:H adjacent to a narrow silicon MOSFET (metal-oxide-semiconductor field-effect transistor), which serves as an integrated charge sensor. We show that the MOSFET can be used to detect charging of the a-Si:H strip. By performing time-resolved measurements of this charging, we are able to measure extremely high resistances (~ 1017 Q) for the a-Si:H strip at T ~ 100 K. At higher temperatures, where the resistance of the a-Si:H strip is not too large, we show that the resistances obtained from our charge detection method agree with those obtained by measuring current. Our device geometry allows us to probe a variety of electron transport phenomena for the a-Si:H, including the field effect and dispersive transport, using charge detection. We extract the density of localized states at the Fermi level for the a-Si:H and obtain consistent results. We discuss the effect of screening by the substrate on the sensitivity of the MOSFET to charge in the a-Si:H, and show that the MOSFET can detect switching noise in the a-Si:H. / by Kenneth MacLean. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1992. / Title as it appears in the M.I.T. Graduate List, June 1992: Transport properties of NdCeCuO thin films. / Includes bibliographical references (leaves 125-131). / by Andreas Kussmaul. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 163-176). / Experiments using ultracold atomic gases address fundamental problems in many-body physics. This thesis describes experiments on strongly-interacting gases of fermionic atoms, with a focus on non-equilibrium physics and dimensionality. One of the fundamental dissipative processes in two-component gases is the transport of spin due to relative motion between the two spin components. We generate spin transport in strongly-interacting Fermi gases using a spin dipole excitation and measure the transport coefficients describing spin drag and spin diffusion. For resonant interactions, we observe strong suppression of spin transport, with the spin transport coefficients reaching quantum-mechanical limits. Dimensionality plays an important role in the formation of bound states between pairs of particles. We tune the dimensionality of a Fermi gas from three to two dimensions (2D) using an optical lattice potential and observe the evolution of the pair binding energy using radio-frequency spectroscopy. The binding energy increases as the lattice depth increases, approaching the 2D limit. Gases with resonant interactions, which have no two-body bound state in three dimensions, show a large binding energy determined by the confinement energy of the lattice wells. The themes of non-equilibrium dynamics and dimensionality come together in the study of soliton excitations in superfluid Fermi gases. We create a planar defect in the superfluid order parameter of an elongated Fermi gas using detuned laser light. This defect moves through the gas as a solitary wave, or soliton, without dispersing. We measure the oscillation period of the soliton and find it to exceed the predictions of mean-field theory by an order of magnitude. / by Ariel T. Sommer. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1997. / Includes bibliographical references (leaves 169-174). / by David Abusch-Magder. / Ph.D.

Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Physics, 1996. / Includes bibliographical references. / by Jeanne A. Thienprasit. / B.S.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018. / 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 (pages 149-151). / Møller scattering is one of the most fundamental processes in QED. Its knowledge at high precision is necessary for a variety of modern nuclear and particle physics experiments. However, most treatments have neglected the electron mass, which is an approximation that breaks down at relevant low energies. In this thesis, existing soft-photon radiative corrections were combined with new hard-photon bremsstrahlung calculations to take into account the effect of photon emission at any photon energy. The electron mass was included at all steps. The radiative corrections were compiled into a Monte Carlo event generator. To test the results, an experiment was designed, constructed, installed, and executed at the MIT High Voltage Research Laboratory. Measurements are reported, comparing the simulated radiative Møller spectra to data at 2.5 MeV. Good agreement between the measurements and the new calculation is observed in the momentum spectrum at three angles. / by Charles S. Epstein. / Ph. D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 2002. / Includes bibliographical references (leaves 145-149). / In this thesis, we analyze the dynamics and equilibrium of bunched charged particle beams in the presence of perfectly conducting walls using a Green's function technique. Exact self-consistent electric and magnetic fields are obtained for charged particles in the vicinity of a conducting boundary with the use of Green's functions. We present three analytical models of bunched beams in a cylindrical conducting pipe which employ Green's functions, the Non-Relativistic Center-of-Mass (NRCM) model, the Relativistic Center-of-Mass (RCM) model, and the Relativistic Bunched Disk Beam (RBDB) model. The NRCM model assumes that the bunches are periodic and represented as point charges propagating non-relativistically in the presence of a constant magnetic focusing field. We derive a maximum limit on the effective self-field parameter ... necessary for confining the bunched beam, where wp, is the effective plasma frequency and at is the cyclotron frequency. The RCM model extends the analysis of the NRCM model to incorporate relativistic motion of the bunches in the presence of a periodic solenoidal focusing field. We derive a maximum limit on ... for confinement, where ... is the root-mean-square cyclotron frequency. We demonstrate how the self-field parameter limit can be used to predict a current limit in Periodic Permanent Magnet (PPM) klystrons. The 75 MW-XP PPM 11.4 GHz klystron designed by SLAC is found to be operating above this current limit, which may explain the observance of non-negligible beam loss in this experiment. / by Mark H Hess. / (cont.) We model bunches with zero longitudinal thickness and azimuthally symmetric finite transverse distributions in the RBDB model. We derive a limit on ... and apply this limit to bunched annular electron beams. The LANL 1.3 GHz relativistic klystron amplifier (RKA), a high-power microwave source using bunched annular electron beams, is found to be operating slightly above this limit, which may explain the observance of beam loss and anomalous beam halo formation. Finally, we present preliminary results of a Green's function based code called PFB3D, which simulates the dynamics of bunched charged particle beams in a cylindrical conducting pipe. We utilize this code to simulate the dynamics of the LANL 1.3 GHz RKA experiment. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 135-138). / Using the CMS detector at the LHC, a quantitative study of jet energy loss and angular deflection inside the high energy-density medium formed in PbPb collisions is made. Photons are used to measure the initial state of a color-charged probe while jet reconstruction is used to measure the final state. Significant loss of energy to the medium as a function of initial parton momentum is observed, while no significant angular deflection is found. / by Richard Alexander Barbieri. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1994. / Includes bibliographical references. / by Michal J.P. Orkisz. / Ph.D.