Physics: Theses

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A Measurement of the Muon Magnetic Moment Using Cosmic Rays
(Houghton College, 2002-05-08) Kroening, Daniel
The muon magnetic moment was measured via the decay of polarized cosmic-ray muons in a constant magnetic field with a three-scintillator detector system. Cosmic-ray muons stop in the central detector, precess in the magnetic field, and then decay by emitting positrons along the muon spin axis. A quantum-mechanical calculation allows the g-factor to be extracted from a measurement of the number of positrons emitted into one direction as a function of decay time. The results are t = 2.28 ± 0.07 µs (mean decay time) and g = 2.74 ± 0.20. Some possible explanations for the large value of g are discussed.
A Low-Cost Van de Graaff Accelerator
(Houghton College, 2002-05-08) Winey, Brian Andrew
A small, low-cost Van de Graaff electrostatic accelerator capable of accelerating electrons and producing bremsstrahlung x-rays has been constructed using components commonly found in most undergraduate physics laboratories. The electrons originate within the negative high-voltage terminal and are accelerated by a uniform electric field through an evacuated glass tube. Electron currents of up to 6 µA were collected in a Faraday cup. The end-point of the bremsstrahlung x-ray energy spectrum has been measured to be between 300 and 400 keV.
A Tabletop Apparatus to Measure the Magnetic Moment of the Muon
(Houghton College, 2002-05-08) Ely, David Richard
An apparatus was constructed to measure the magnetic moment of cosmic ray muons using their precession in a uniform magnetic field. A 102.0 x 20.6 x 5.4 cm plastic scintillator was sandwiched between two 102.0 x 20.6 x 1.6 cm scintillators inside a uniform, 42 G magnetic field, which was produced by a large solenoid. A small veto scintillator eliminated events occurring in the non-uniform region of the field at the ends of the solenoid. A logic circuit identified muons stopping in the center scintillator and the subsequent decay of these muons. The time difference between the muon stopping and its decay was recorded for about 67,000 events, allowing the decay constant and the magnetic moment to be determined.
A Preliminary Design for a Small Permanent Magnet Cyclotron
(Houghton College, 2003-01-20) King, Barry
A small cyclotron is being constructed using a 0.5 T permanent magnet and a vacuum chamber containing a single brass RF electrode. In this design the magnetic field strength may be modified by adjusting the separation of two iron pole pieces, which will be sealed to the chamber using vacuum grease. The chamber will be filled with low pressure hydrogen gas which will be ionized by electrons from a cathode at the center of the chamber. The required 3.6 to 11.5 MHz RF power will be supplied by a commercial RF amplifier. A diffusion pump backed by a voluntary forepump and a liquid nitrogen cold trap will be used to evacuate the chamber. Expected energies are 37.5 keV and 87.7 keV for protons and 18.7 keV and 43.8 keV for deuterons.
A Wind Driven Power Generating System: Preliminary Modeling of Power Curves
(Houghton College, 2003-05-08) Marthai, Sonya
Most power curves for current wind power systems depend on filed measurements. Relationships between the details of the design and power output are therefore often hidden. The overall goal of this project is to design and build a low cost, mechanically efficient wind driven power-generating system in the 1 to 5 kilowatt range and to predict and improve its performance based on equations derived from fundamental principles. A series of theoretical power curves are presented that successively incorporate greater complexity of blade parameters. The aim is to optimize each individual parameter, then design an efficient blade design based on those specifications.
The (n,2p) Reaction as a Probe for a Nuclear Δ++ Component
(Houghton College, 2003-05-19) De Young, Rachel
An experiment to measure the 3He(n,2p)2n and 4He(n,2p)3n cross-sections was conducted at the Los Alamos Neutron Science Center (LANSCE) as a means to explore the Δ++ contribution to the nuclear wave function. Neutrons incident on gaseous 3He and 4He targets produced outgoing protons which traveled through two magnetic spectrometer arms, each consisting of a thin ΔE plastic scintillator, a permanent bending dipole magnet, two sets of x-y drift chambers, and a final calorimeter of three stacked plastic scintillators. Computer codes are being developed to analyze the delay line readouts from the drift chambers in order to determine particle trajectories through the magnetic field and trace back to the target. This information will be used to identify the outgoing particles and calculate their momenta. Once cross-sections have been determined, comparisons may be made to theoretical predictions that include a Δ component to the nuclear wave function.
A Tabletop Transmission Computed Tomography Scanner
(Houghton College, 2003-11-11) Clifford, Rebekah
A first generation computed tomography (CT) scanner allows for a cross-sectional slice of an object to be analyzed by x-rays passing through the material. These images are created by recording the x-ray energy spectrum at a specified number of translational and rotational steps. Instead of an x-ray tube, 22Na will be used as the radiation source in conjunction with two sodium-iodide scintillation detectors. The source and detectors will remain co-linear and stationary, while the object to be scanned will rotate and translate. During the last two years, the rotation and translation table have been assembled and progress has been made towards a computer code to control the motors that translate and rotate the table on which the object is placed. Once this program has been completed, the source and detectors will be installed and the scanner will be tested.
The Design of a Small Cyclotron
(Houghton College, 2003-12-17) Tuminaro, Sharon
A small cyclotron capable of producing a 45-170 keV proton beam or a 20-85 keV deuteron beam is being designed and constructed at Houghton College. In this design, low pressure hydrogen gas will be ionized by a filament inside the acceleration chamber, which will contain a single RF accelerating electrode. The chamber will be evacuated by a diffusion pump backed with a rotary forepump and a liquid nitrogen cold trap. The magnetic field produced by a permanent magnet (nominal field strength 0.5 T) may be altered using an adjustable pole separation. The motivation, theory, and overall design will be covered in this thesis, with a special emphasis on the design and construction of the vacuum system.
A Novel 1st Generation Computed Tomography Scanner
(Houghton College, 2003-12-19) Kingsley, Nicholas
A preliminary design for a first generation tomography scanner is being designed and constructed. The scanner uses Na-22 as the radiation source, with annihilation photons being counted by shielded NaI detectors. The novel design of the scanner allows a very weak radiation source to be used by taking advantage of the back-to-back 511 keV annihilation photons emitted after Na-22 B+ decay to improve the signal to noise ratio. The object being scanned will be translated and rotated systematically by computerized motor control using two motors attached to a standard rotary table.
The Construction of a 200 KeV Electrostatic Accelerator
(Houghton College, 2004-04-30) Brady, Peter
The original 200 keV electrostatic electron accelerator at Houghton College used a glass acceleration tube with external copper equipotential rings to provide the required uniform electric field along the length of the tube. Unfortunately, in this design stray electrons striking the walls of the tube caused charge to accumulate on the inside wall, eventually deflecting the electron beam. In order to solve this problem, a new design for the acceleration tube is being tested, made up of 51 pairs of alternating aluminum and plastic rings, with inside diameters 3.8 cm and 5.1 cm respectively. The differing inner radii of the rings ensure that the electrons will only strike the aluminum rings, and can therefore be removed as part of the coronal current flowing down the exterior column.
A Wind Driven Power Generating System: Initial Designs and Construction
(Houghton College, 2004-05-01) Merriam, Donald Jr.
The goal of this study is to design and build a low cost, mechanically efficient wind driven powergenerating system in the 1 to 5 kilowatt range and to predict and improve its performance based on equations derived from fundamental principles. Construction and assembly have begun for a directly coupled, low “rpm” (angular frequency) generator consisting of a disk of copper coils sandwiched between two rotating disks of neodymium (NdFeB) magnets to which the blades will be directly coupled.
The Decay Rate of Orthopositronium
(Houghton College, 2005-05-09) Winter, Blake
Until recently, measurements of the orthopositronium decay rate disagreed with the value predicted by quantum electrodynamics. This paper describes a novel attempt to measure this decay rate. Positrons from the decay of 22Na were slowed in a vacuum chamber containing a sample of aerogel. The release of a positron by the 22Na source was signalled by the detection of a 1.27 MeV gamma ray by a plastic scintillation detector. Orthopositronium typically decays into three gamma rays, which were detected by three NaI detectors. By detecting the annihilation gamma rays in coincidence and using energy information from the events, systematic effects due to contamination by parapositronium decay, which plagued previous measurements, may be reduced. Preliminary analysis of data taken over 200 hours has yielded a value for the decay rate of 7.83±0.5 ?s-1. Currently, problems with Compton scattering are preventing the use of the energy information in analysis. Possible solutions to this problem will be discussed.
Examining the d(n,nd) and d(n,np)n Reactions for Evidence of a Three-Nucleon Interaction
(Houghton College, 2005-05-13) Wells, Christopher
A series of experiments has been performed at the Los Alamos Neutron Science Center (LANSCE) by collaborators from the Los Alamos National Laboratory (LANL), the Massachusetts Institute of Technology, the University of Kentucky and Houghton College to examine the possible role of a three nucleon force (3NF) in the strong nuclear interaction. From 1998 to 2002 neutron-deuteron elastic scattering d(n,nd) cross sections were measured in the kinematical region predicted by theory to be most sensitive to contributions from a 3NF. The results of that study motivated measurements of the breakup reaction, d(n,np)n, which theoretical predictions suggested might be even more sensitive to 3NF effects. In each experiment, spallation neutrons were scattered from a liquid deuterium target and outgoing particles were incident on an array of neutron and charged particle detectors. Until 2003, outgoing protons were detected with CsI crystal scintillators and neutrons by either plastic or liquid scintillation detectors. In 2004, several changes were proposed for the detection array, including two permanent magnet charged particle spectrometers and large plastic scintillator bars to detect neutrons. These changes addressed problems discovered in the spring of 2003 with both the experimental setup and the theoretical calculations. Preliminary reaction cross-section results have been obtained for the d(n,nd) reaction, and the d(n,np)n cross-section measurement is planned to begin in August 2005.
The Design and Construction of a Small Cyclotron
(Houghton College, 2006-05-03) Cressman, Mickael
A small cyclotron is under construction at Houghton College. It utilizes a water cooled electromagnet with 15.2 cm pole faces that produces a maximum field of approximately 1.1 T with a 3.8 cm gap. The vacuum pump consists of a rotary forepump, a diffusion pump and a liquid nitrogen cold trap. The chamber consists of a brass ring with eight ports: one for evacuating the chamber, one for introducing gas, two viewports, two feedthroughs, an ion gauge, and the Faraday collector. It is sealed with two aluminum discs with Viton o-ring seals. The ‘dee’ electrodes are constructed from copper, with the dummy dee at ground potential and a true dee supplied with a radiofrequency signal by a function generator and an RF power amplifier. The expected energy for deuterons is 0.15 MeV, and 0.08 MeV for Helium nuclei. The immediate objective is to accelerate Helium nuclei to test the machine, and the ultimate is to accelerate deuterons to produce neutrons for inelastic scattering experiments.
Initial Results from the Houghton College Cyclotron
(Houghton College, 2007-06-22) Loucks, Andrew
Initial performance characteristics for the Houghton College cyclotron have been measured. The cyclotron consists of a cylindrical vacuum chamber with diameter 15.3 cm and height 2.5 cm containing a hollow “dee” electrode and a ground electrode. At resonance, an RF source that can be tuned to frequencies between 2 MHz and 15 MHz creates an oscillating electric potential of several thousand volts between the electrodes. The chamber is placed between the 15.3 cm diameter poles of a 1.1 T electromagnet and is evacuated to a pressure of about 10-6 torr. Hydrogen, helium, and deuterium gas may be introduced and ions created by electron bombardment from a hot cathode. The magnetic and oscillating electric fields cause the ions to spiral outwards, gaining energy as their orbit radius increases. We anticipate maximum kinetic energies for protons, deuterons and helium nuclei to be about 280 keV, 140 keV, and 70 keV respectively.
Considerations in the Design of Electrostatic Accelerator Columns
(Houghton College, 2007-08-10) Troyer, Joshua
Several generations of acceleration columns have been tested for use in the electrostatic electron accelerator at Houghton College. Early designs allowed charge to build up in the column causing the beam to be deflected. The previous design, which used a series of alternating of plastic and aluminum rings held together and sealed with vacuum epoxy, was too fragile and was prone to leak when evacuated. A new design eliminates many of these problems. An alternating series of 50.8 mm OD high-density polyethylene and stainless steel rings are compressed by six pre-stretched, ¼-inch threaded nylon rods. Glands machined into the plastic rings hold Viton o-rings that provide a good vacuum seal. The high voltage is supplied by a Van de Graaff generator mounted in-line with the accelerator column and electron gun. The entire assembly is supported by an insulating acrylic base, with rigid but adjustable joints.
Astrometry from Space: An Overview of the European Space Agency’s Hipparcos Satellite
(Houghton College, 2008-06-14) Runyon, Kirby
The European Space Agency’s Hipparcos satellite was launched in 1989 to provide a high-precision catalogue of stellar astrometric data, including parallaxes and luminosities, from above Earth’s dimming and distorting atmosphere. Despite the satellite failing to reach its intended geosynchronous orbit, its mission successfully measured astrometric characteristics of 120,000 stars and photometric and less accurate astrometric properties of approximately one million stars. Since the mission’s end, the data have been reduced into several catalogues that have proven useful in determining other astrometric and astrophysical properties of stellar phenomena. This report will describe the motivation for and details of the Hipparcos mission, the data reduction, the applications of these data, and the prospects for future space-based astrometry missions.
Design and Construction of a Variable Temperature Atomic Force Microscope
(Houghton College, 2009-05-05) Little, Bethany
A variable temperature atomic force microscope is being constructed at Houghton College. The microscope will operate in a rough vacuum and will utilize spring vibration isolation and eddy current damping to minimize mechanical vibration. A modified “Johnny Walker” beetle is being constructed for the rough approach. The sample will be mounted onto the walker scanning head and scanned across a cantilever tip and laser assembly. When completed, resolution should be on the order of nanometers. Liquid nitrogen and resistive heating will allow operation from ~100 K to 500 K.
Design and Construction of a Deposition Chamber for Thin Metal Films Research
(Houghton College, 2009-05-06) Aikens, Kurt
A high vacuum deposition chamber is being built at Houghton College for the production and study of thin metal films. Up to four electron-beam heated crucibles will be used to evaporate metals whose evaporate is adsorbed onto a substrate, forming a film. Evaporation rates may be monitored via crucible temperatures or direct measurement of the ionized flux. The chamber will feature a computer-controlled shield enabling the deposition of samples with varying thickness gradients and an ion gun for substrate cleaning and ion beam assisted deposition (IBAD). The history and theory of vacuum and deposition technologies are discussed. Future plans and current progress are also presented.
Characterizing The Performance of The Houghton College Cyclotron
(Houghton College, 2009-05-06) Haas, Daniel
The Houghton College Cyclotron briefly accelerated hydrogen ions for the first time in 2007 before a discharge from the dee to the chamber wall damaged the glass insulation and “dee” electrode. To prevent this from happening again, a new vacuum chamber and 15 cm diameter “dee” electrode was designed and constructed. Placed between the poles of a 1.1 T electromagnet, low pressure gas was released into the chamber where a filament, through electron collisions, ionized the gas. The ions were accelerated by an alternating RF electric field and forced to travel in a spiral path by the electromagnet. The new chamber and “dee” has successfully accelerated protons, molecular hydrogen and helium. Eventually, the d(d,n)3He reaction will be used to produce neutrons for use in small-scale nuclear experiments.

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