Investigation of high-precision {Lambda} hypernuclear spectroscopy via the (e,e'K{sup +}) reaction (open access)

Investigation of high-precision {Lambda} hypernuclear spectroscopy via the (e,e'K{sup +}) reaction

The study of {Lambda} hypernuclear structure is very interesting in point of the understanding of the interaction between {Lambda} and nucleon ({Lambda}-N interaction) and its ”strange” structure itself due to the containment of a {Lambda} hyperon which has a strangeness as a new degree of freedom. In the several way to study the Lamda hypernuclei, the (e,e'K{sup +}) reaction spectroscopy is a powerful tool for the precise investigation of {Lamda} hypernuclear structure. The purpose of the preset thesis is the establishment of the experimental design with the efficient data analysis method for the (e,e'K{sup +}) hypernuclear spectroscopic experiment in the wide mass region (from A=7 to A=52). It is very challenging to perform the (e,e'K{sup +}) spectroscopic experiment with such a heavy target, because of the huge electron background due to the bremsstrahlung process. In the experiment, it is required to obtain the necessary hypernuclear yield, suppressing the background event ratio. We achieved these requirements by newly constructing the high resolution electron spectrometer (HES) and splitter magnet (SPL) dedicated to the (e,e'K{sup +}) spectroscopic experiment. The HES consists of two quadrupole magnets and a dipole magnets (Q-Q-D) with a momentum resolution of dp/p = 3x10^-4 at p = 0.84 GeV/c. …
Date: March 31, 2012
Creator: Kawama, Daisuke
System: The UNT Digital Library
Probing Novel Properties of Nucleons and Nuclei via Parity Violating Electron Scattering (open access)

Probing Novel Properties of Nucleons and Nuclei via Parity Violating Electron Scattering

This thesis reports on two experiments conducted by the HAPPEx (Hall A Proton Parity Experiment) collaboration at the Thomas Je#11;erson National Accelerator Facil- ity. For both, the weak neutral current interaction (WNC, mediated by the Z{sup 0} boson) is used to probe novel properties of hadronic targets. The WNC interaction amplitude is extracted by measuring the parity-violating asymmetry in the elastic scattering of longitudinally polarized electrons o#11; unpolarized target hadrons. HAPPEx-III, con- ducted in the Fall of 2009, used a liquid hydrogen target at a momentum transfer of Q{sup 2} = 0.62 GeV{sup 2}. The measured asymmetry was used to set new constraints on the contribution of strange quark form factors (G{sup s}{sub E,M} ) to the nucleon electromagnetic form factors. A value of A{sub PV} = -23.803{+-}#6; 0.778 (stat){+-}#6; 0.359 (syst) ppm resulted in G{sup s}{sub E} + 0:517G{sup s}{sub M} = 0.003{+-} 0.010 (stat){+-} #6;0.004 (syst){+-}#6; #6;0.009 (FF). PREx, conducted in the Spring of 2010, used a polarized electron beam on a 208Pb target at a momentum transfer of Q{sup 2} = 0.009 GeV{sup 2}. This parity-violating asymmetry can be used to obtain a clean measurement of the root-mean-square radius of the neutrons in the {sup 208}Pb nucleus. …
Date: May 31, 2012
Creator: Mercado, Luis
System: The UNT Digital Library
Towards a Precision Measurement of Parity-Violating e-p Elastic Scattering at Low Momentum Transfer (open access)

Towards a Precision Measurement of Parity-Violating e-p Elastic Scattering at Low Momentum Transfer

The goal of the Q-weak experiment is to make a measurement of the proton's weak charge Q{sub W}{sup p} = 1 - 4 sin{sup 2}({theta}{sub W}) to an accuracy of {approx} 4%. This would represent a {approx} 0.3% determination of the weak mixing angle sin{sup 2}({theta}{sub W}) at low energy. The measurement may be used for a precision test of the Standard Model (SM) prediction on the running of sin{sup 2}({theta}{sub W}) with energy scale. The Q-weak experiment operates at Thomas Jefferson National Accelerator Facility (Jefferson Lab). The experiment determines Q{sub W}{sup p} by measuring the parity violating asymmetry in elastic electron-proton scattering at low momentum transfer Q{sup 2} = 0.026 (GeV/c){sup 2} and forward angles (?8 degrees). The anticipated size of the asymmetry, based on the SM, is about 230 parts per billion (ppb). With the proposed accuracy, the experiment may probe new physics beyond Standard Model at the TeV scale. This thesis focuses on my contributions to the experiment, including track reconstruction for momentum transfer determination of the scattering process, and the focal plane scanner, a detector I designed and built to measure the flux profile of scattered electrons on the focal plane of the Q-weak spectrometer to …
Date: May 31, 2012
Creator: Pan, Jie
System: The UNT Digital Library
Meausrement of the Neutron Radius of {sup 208}Pb Through Parity Violation in Electron Scattering (open access)

Meausrement of the Neutron Radius of {sup 208}Pb Through Parity Violation in Electron Scattering

In contrast to the nuclear charge densities, which have been accurately measured with electron scattering, the knowledge of neutron densities still lack precision. Previous model-dependent hadron experiments suggest the difference between the neutron radius, R{sub n}, of a heavy nucleus and the proton radius, R{sub p}, to be in the order of several percent. To accurately obtain the difference, R{sub n}-R{sub p}, which is essentially a neutron skin, the Jefferson Lab Lead ({sup 208}Pb) Radius Experiment (PREX) measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 208}Pb at an energy of 1.06 GeV and a scattering angle of 5{degrees}#14;. Since Z{sup 0} boson couples mainly to neutrons, this asymmetry provides a clean measurement of R{sub n} with respect to R{sub p}. PREX was conducted at the Jefferson lab experimental Hall A, from March to June 2010. The experiment collected a final data sample of 2x#2;10{sup 7} helicity-window quadruplets. The measured parity-violating electroweak asymmetry A{sub PV} = 0.656 {+-}#6; 0.060 (stat) {+-}#6; 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions, R{sub n}-R{sub p} = 0.33{sup +0.16}{sub -0.18} fm and provides the #12;first electroweak observation of the neutron skin …
Date: May 31, 2013
Creator: Saenboonruang, Kiadtisak
System: The UNT Digital Library
Compensation Techniques in Accelerator Physics (open access)

Compensation Techniques in Accelerator Physics

Accelerator physics is one of the most diverse multidisciplinary fields of physics, wherein the dynamics of particle beams is studied. It takes more than the understanding of basic electromagnetic interactions to be able to predict the beam dynamics, and to be able to develop new techniques to produce, maintain, and deliver high quality beams for different applications. In this work, some basic theory regarding particle beam dynamics in accelerators will be presented. This basic theory, along with applying state of the art techniques in beam dynamics will be used in this dissertation to study and solve accelerator physics problems. Two problems involving compensation are studied in the context of the MEIC (Medium Energy Electron Ion Collider) project at Jefferson Laboratory. Several chromaticity (the energy dependence of the particle tune) compensation methods are evaluated numerically and deployed in a figure eight ring designed for the electrons in the collider. Furthermore, transverse coupling optics have been developed to compensate the coupling introduced by the spin rotators in the MEIC electron ring design.
Date: May 31, 2011
Creator: Sayed, Hisham Kamal
System: The UNT Digital Library
Laser Processing of Metals and Polymers (open access)

Laser Processing of Metals and Polymers

A laser offers a unique set of opportunities for precise delivery of high quality coherent energy. This energy can be tailored to alter the properties of material allowing a very flexible adjustment of the interaction that can lead to melting, vaporization, or just surface modification. Nowadays laser systems can be found in nearly all branches of research and industry for numerous applications. Sufficient evidence exists in the literature to suggest that further advancements in the field of laser material processing will rely significantly on the development of new process schemes. As a result they can be applied in various applications starting from fundamental research on systems, materials and processes performed on a scientific and technical basis for the industrial needs. The interaction of intense laser radiation with solid surfaces has extensively been studied for many years, in part, for development of possible applications. In this thesis, I present several applications of laser processing of metals and polymers including polishing niobium surface, producing a superconducting phase niobium nitride and depositing thin films of niobium nitride and organic material (cyclic olefin copolymer). The treated materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), atomic force microscopy (AFM), high resolution …
Date: May 31, 2012
Creator: Singaravelu, Senthilraja
System: The UNT Digital Library
Beam Line Design and Beam Physics Study of Energy Recovery Linac Free Electron Laser at Peking University (open access)

Beam Line Design and Beam Physics Study of Energy Recovery Linac Free Electron Laser at Peking University

Energy recovering linac (ERL) offers an attractive alternative for generating intense beams of charged particles by approaching the operational efficiency of a storage ring while maintaining the superior beam quality typical of a linear accelerator. In ERLs, the decelerated beam cancels the beam loading effects of the accelerated beam with high repetition rate. Therefore, ERLs can, in principle, accelerate very high average currents with only modest amounts of RF power. So the efficiency of RF power to beam is much higher. Furthermore, the energy of beam to dump is lower, so it will reduce dump radiation. With the successful experiments in large maximum-to-injection energy ratio up to 51:1 and high power FEL up to 14kW, the use of ERL, especially combining with superconducting RF technology, provides a potentially powerful new paradigm for generation of the charged particle beams used in MW FEL, synchrotron radiation sources, high-energy electron cooling devices and so on. The 3+1/2 DC-SC photo injector and two 9cell TESLA superconducting cavity for IR SASE FEL in PKU provides a good platform to achieve high average FEL with Energy Recovery. The work of this thesis is on Beam line design and Beam dynamics study of Energy Recovery Linac Free …
Date: December 31, 2011
Creator: Wang, Guimei
System: The UNT Digital Library