Thesis (Ph.D.)--North Carolina State University at Raleigh. / Includes index. Bibliography: leaves [108]-112.

Thesis (Ph. D. in Physics)--University of California, Berkeley, Sept. 1960. / TID-4500 (15th ed.). Includes bibliographical references (p. 138).

Thesis (M.S.)--University of Wisconsin, 1960. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 64-65).

The pre-accelerator and the dielectric loaded slow-wave structure are examined in detail. The fields in the pre-accelerator are expressed as an infinite series which converges rapidly. It was found that by considering only the first term of the series, good results were obtained for the stored energy, the power dissipated and the cavity Q. Low power tests on the pre-accelerator gave confirmation of theoretical calculations. The fields in the dielectric loaded slow-wave structure were determined experimentally by means of a perturbation method. The results compare favourably with previous theoretical work. An electron beam was introduced into the pre-accelerator cavity using a 2 KV electron gun and measurements were made of the gain in electron energy. Peak microwave power levels of up to 0.19 MW were used and electron energies up to 340 KEV were obtained. It was concluded that the pre-accelerator can provide adequate initial conditions for the capture of electrons in the main accelerator. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

In part I of this thesis the theory underlying electron beam design is presented. The paraxial ray equation is derived, and is used to determine the focal properties of an aperture and of an Einzel lens, both of which are assumed to be thin lenses. An aperture can exert a positive or a negative focusing action on an electron beam, depending on the potential gradients existing on either side of the aperture. In an Einzel lens the focusing action is always positive, whether the focusing anode potential is greater or smaller than the beam potential. If the focusing anode is made very negative w.r.t. the beam voltage the electrons are reflected. In the above space-charge and thermal velocity effects are ignored. It is well known that in practical guns electron interaction is important and the Pierce method of electron gun design is examined. The effect of thermal velocity on obtainable current density is also considered. In part II of this thesis the theory is applied to the design of an electron source for a resonant linear accelerator. The perveance and cross-over point are calculated for an existing, partly assembled, bombarded cathode, Pierce type, electron gun. Methods are considered for adapting this gun as a 2 kV. electron source for the resonant linear accelerator. Electrostatic focusing methods for this application are inefficient, as less than 5% of the beam current is utilised. If Brillouin type magnetic focusing is used, a current efficiency of up to 75% is possible. A tungsten filament electron gun, capable of producing a 10 ma beam at a gun voltage of 2 kV, is designed and constructed. This gun has a filamentary cathode consisting of seven turns of 0o013" tungsten wire wound on a threaded mandrel (#4-40). Four anodes are used; they are made of Copel, and perform the functions of current control and of focusing the electron beam. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

A precise energy control system has been constructed for the U.B.C. electrostatic accelerator. Over the past six months it has provided analyzed beams of protons as large as 4½ microamperes on a target with an energy homogeneity of 0.1%. In the system adopted, the accelerated positive ions are analyzed by a 90° deflection magnet provided with entrance and exit slits to define the beam path. The magnetic field is stabilized to a few parts in 100,000, and controlled by a nuclear magnetic resonance method. A fraction of the emergent beam falls on two insulated slits, "sniffers", connected to a differential amplifier, the output of which varies as the beam impinges more on one than the other. Thus an error signal is obtained according to the shift in energy and hence position of the beam, which is used to modulate a reverse beam of electrons sent up the differential pumping tube of the generator. This beam loads the generator so as to maintain its voltage, and hence the energy of the ions, constant. The main central part of the beam passes through the slits onto the target mounted beyond. One-dial control over a range of 20 KeV is achieved by simply tuning the oscillator controlling the frequency of the nuclear magnetic resonance fluxmeter head. The energy of the ions can be varied in steps as fine as 0.2 KeV in 1,000 KeV. The generator's voltage scale (the generating volt-meter) and energy scale (the magnetic field of the analyzing magnet) have been calibrated relative to the currently accepted standard value of Herb, Snowdon, and Sala of 0.8735 MeV for the strong F¹⁹(p, α ɤ )O¹⁶ resonance and checked with the 0.3404 MeV resonance occurring in the same reaction. Additional calibration points were obtained using mass 2 and 3 beams. The complete gamma ray excitation curve for the reactions from F¹⁹ bombarded with protons has been taken up to 2 MeV and new resonances found at 1.62 and 1.84 MeV. The 1.355, 1.381 MeV doublet was resolved with a peak to trough value of 9/1 which is excellent confirmation of the homogeneity of the proton beam. The resonances in the N¹⁵¹⁹(p, α ɤ )C¹² reaction have also been investigated and background yields from various target backing materials measured up to 2 MeV. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Natural and commercially available particles of uniform shape and size were used to study the effect of particle shape on hindered settling in creeping flow (Re₀< 0.1), where fluid flow behaviour is independent of particle Reynolds number and the effect of shape is most prominent. Particles of different shapes used were spherical glass beads, cubic salt (NaCl) crystals and ABS plastic pellets, flaky sugar crystals and angular mineral (silicate) crystals. They were carefully sized by sieving and liquid elutriation to avoid other effects like size segregation. Constant settling data were processed in the form of uѵ rather than u to eliminate the effect of temperature variation on viscosity. The effect of the wall on hindered settling rate was found to be small in most cases. The method proposed by Beranek and Klumpar for correlating fluidization data on different shaped particles was found to be only moderately successful in correlating the present settling data for different shapes. Results were plotted as loguѵ versus log €, and the index n of the equation uѵ/(uѵ)ext = €ⁿ was calculated by least squares. It varied from an average value of 4.8 for the smooth spheres to 5.4 for the cubes to 5.8 for the flaky or angular particles. In contrast to the corresponding term proposed by Richardson and Zaki, the term (uѵ)ext was measurably lower than uѵ for free settling of the spherically isotropic particles. More significantly, the index n was graphically found to display a definite trend with the random loose fixed bed porosity, which is shape dependent and easily measured, and may therefore turn out to be a simple and useful parameter for taking account of shape variation. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The multiple Coulomb scattering of negative pions has significant effects on the dose distributions resulting from pion beams incident on thick targets. The use of negative pions in radiotherapy requires a detailed knowledge of the distribution of dose and biological effect. Thus it is important to have an accurate description for the lateral distributions of pions which result from multiple scattering. It has been proposed by Fowler and Perkins that these lateral distributions are of a Gaussian nature for incident pencil beams. In this study an attempt has been made to determine experimentally and theoretically the appropriate value for the standard deviation of the Gaussian in the pencil beam description. The experimental determination involved placing medical x-ray films in a homogeneous water phantom, perpendicular to the beam axis of the M8 biomedical channel at TRIUMF. The distributions recorded on film for circularly collimated beams were measured for optical density and compared to calculated distributions in order to extract the pencil beam information. The presence of contaminating electrons and muons as well as the difficulty in achieving a parallel beam complicated the determination of the standard deviation of the Gaussian for pions. The experimental determination at the end of a 20.1 cm range in water is only 7% greater than the preferred theoretical calculation for pions alone. This calculation is based on the first (Gaussian) term of Moliere’s theory modified for the Fano correction and energy loss and yields results 20% lower than those of the "standard reference" of Fowler and Perkins. The agreement between the theory for pions and the experiment for a real beam in water indicates that the theory presented should be adequate for treatment planning calculations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Several applications of the Heavy Quark Symmetry are studied. They concern the extraction of the quark mixing parameter $V\sb{cb}$, the Standard Model prediction for the branching ratio of $B \to K\sp{*}\gamma$ and the extraction of the quark mixing parameter $V\sb{ub}$ from $B \to \pi e\nu\sb{e}$ decays. An effective theory incorporating both Heavy Quark and Chiral Symmetries is presented and some of its applications are discussed.

Based on a 87 fb−1 dataset, a search for D0-D¯0 mixing is made using the semileptonic decay modes D*+ → π +D0, D0 → [K/K*]eν (+c.c.) at the B-Factory facility at the Stanford Linear Accelerator Center. These modes offer unambiguous initial and final-state charm flavor tags, and allow the combined use of the D0 lifetime and D*+- D0 mass difference (ΔM) in a global likelihood fit. The high-statistics sample of reconstructed unmixed semileptonic D0 decays is used to model both the ΔM distribution and the time-dependence of mixed events directly from the data. Neural networks are used both to select events and to fully reconstruct the D0. A result consistent with no charm mixing has been obtained, Rmix = 0.0023 ± 0.0012(stat) ± 0.0004(sys ). This corresponds to an upper limit of Rmix < 0.0047 (95% C.L.) and Rmix < 0.0043 (90% C.L.). The lowest current published limit on semileptonic charm mixing is 0.005 (90% C.L.) (E791, E.M. Aitala et al., Phys.Rev.Lett. 77 2384 (1996)). The current best published limit using any analysis technique on the total rate of charm mixing is 0.0016 (95% C.L.) (Babar Kπ mixing, B. Aubert et al., Phys.Rev.Lett. 91 171801 (2003)).