Physics Commons^™

Emergent Spectra Of Young X-Ray Emitting Populations Across Environments, Alex Siebenmorgen

Physics Undergraduate Honors Theses

We construct reasonably accurate models of the X-Ray spectra of a multitude of sources in M51. We construct both average and individual models for the sources, which are split into 16 groups as the counts per source increases. Then, we create a plot to show how the model-predicted values of column density (nH) and photon index (gamma) change with luminosity. These models will be used to create an accurate X-Ray stellar energy distribution (SED) for M51, and to better understand how the SED changes with environmental factors like metallicity and star formation rate (SFR).

Therapy And Medical Imaging Applications Of Focusing Polycapillary X-Ray Optics, Weiyuan Sun

Legacy Theses & Dissertations (2009 - 2024)

Focusing polycapillary optics yield high gains in intensity and increased spatial resolution for a variety of clinical, lab-based, synchrotron, or in situ analysis applications. In this dissertation we investigate the extension of two applications of focusing polycapillary optics. The first is the application of polycapillary optics in radiation therapy. This discussion includes measurements and calculation of dose for focused beam orthovoltage therapy. A system has been designed to investigate whether the polycapillary optics can produce an X-ray beam which can give more accurate dose painting due to the higher dose concentration at the focal spot. X-ray exposures were measured with …

Modeling The Obscuring Features In Active Galactic Nuclei: An X-Ray Analysis Of Ngc 1052, Samantha E. Cabral

Graduate Masters Theses

We present a multi-epoch analysis of the X-ray spectrum of NGC 1052, a nearby galaxy notorious for its well-studied spectral variability. We utilize observations from NuSTAR, XMM-Newton, Chandra, Swift, Suzaku, BeppoSAX, and ASCA to create a comprehensive set of data that spans roughly 20 years. Organizing our data by observation date and grouping into specific epochs allows us to explore a model allowed to flex and accommodate any spectral changes that occur over time in the X-ray spectrum of NGC 1052. We find that the spectrum takes on a relatively flat nature and is best modeled with two neutral absorption …

The Crystal Structure Of (Cuxzn1-X)0:456in1:084ge0:46o3 (Cuzigo) Using Neutron And X-Ray Diffraction, Boluwatife A. Adekoya

College of Science and Health Theses and Dissertations

The solid solution (CuxZn(1-x))0.456In1.084Ge0.46O3 (CuZIGO) has a complex structure where zinc and copper partially occupy a site shared by indium and germanium. ZIGO, the x = 0 endpoint, is a potential transparent conducting oxide (TCO) with similar conductivity and transparency to cubic In2O3, which, when doped with Sn4+, is the most prevalent TCO. ZIGO structure possesses a tetragonal structure and has the ability to produce multiple new phases with an array of properties that are beneficial to identify and understand. Analyzing this structure is best done through chemical substitution to identify the newly produced phases. Copper is a suitable choice …

Characterizing Decaying Dark Matter: X-Ray Emission From Sterile Neutrinos, Murat Hüdaverdi̇

Turkish Journal of Physics

Recently, an unknown emission line at E $\sim$3.5 keV from several astrophysical objects has been detected. The line is suggested to be originating from decaying dark matter particles. The results have drawn great attention from the astrophysics and particle physics community. Since the detected line is significantly weak there has also been a long debate over the origin of this mysterious signal. The most accepted scenario is a radiatively decaying sterile neutrino of 7.1 keV in mass producing a monochromatic 3.5 keV line, which is observable in X-ray energy ranges. The problem has not been settled and further observations from …

On The Contribution Of The 6.7 Kev Line Emission Of The Algol Binary System To The 6.7 Kev Line Emission From The Galactic Ridge, Ambrose Chukwudi Eze, Romanus Nwachukwu Chijioke Eze, Sudum Esaenwi

Turkish Journal of Physics

We carried out spectroscopic analysis of the extracted stellar flare of the Algol binary system observed using the Suzaku satellite (OBSID: 401093010), and resolved a strong 6.7 keV line emission. The 6.7 keV line emission of the Algol binary system is similar to the 6.7 keV line of the galactic ridge X-ray emission (GRXE). The equivalent width (EW) compared favorably with the EW of the 6.7 keV emission line obtained from different galactic ridge regions. In the galaxy, we have a reasonable number of Algol binary systems and many other stars as strong coronal X-ray emitters characterized by frequent quiescent …

Manipulation Of Beams Of Ultra-Relativistic Electrons To Create Femtosecond X-Ray Pulses, Jordan T. O'Neal, Austin Schulte, Rafal Rakowski, Matthias Fuchs

UCARE Research Products

The research proposed here is expected to result in a crucial component used in a next-generation X-ray source. Typical conventional high-brightness X-ray sources (so-called synchrotron lightsources) are up to 30 football fields in size. Our group uses a novel technique based on ultrahigh-power lasers to develop a similar source that can readily fit into a single, university-scale laboratory. More specifically, the research conducted within this proposal will be concerned with the manipulation of beams of ultra-relativistic electrons, (electrons that move with almost the speed of light) with the goal to focus the particles into an area that is smaller than …

The Role Of Cold Gas In Low-Level Supermassive Black Hole Activity, Erik D. Alfvin

Macalester Journal of Physics and Astronomy

The nature of the relationship between low-level supermassive black hole activity and galactic cold gas, if any, is currently unclear. It has been hypothesized that feedback may heat or expel gas and quench star formation; alternatively, central black holes may feed at higher rates (either directly or as a secondary effect from stellar winds) in gas-rich galaxies. We use a combination of radio data from the on-going ALFALFA survey and from the literature, along with archival X-ray flux measurements from the Chandra X-ray observatory, to investigate this potential relationship. We construct a sample of 136 late-type galaxies, with MB < −18 out to 50 Mpc, that have both HI masses and sensitive X-ray coverage. Of these, 76 host a nuclear X-ray source, a 56% detection fraction. There is a highly significant correlation between LX and Mstar with a slope of 1.5±0.2, and a tentative correlation (significant at the 2.5σ level) between LX and MHI. However, a joint fit to LX as a function of both Mstar and MHI finds no significant dependence on MHI, and similarly the residuals of LX − LX(Mstar) show no trend with MHI. We conclude that the galaxy-wide cold gas content in these spirals does not strongly influence their low-level supermassive black hole activity.

Control Of Radiation Exposure To Paediatric Patients At Conventional Radiology And Cardiac Centers At Dubai Hospital, Najlaa Khalfan Saeed Almazrouei

Theses

In view of increasing the number of x-ray examinations over the years, paediatric radiation safety is considered as one of the critical subjects in the modern medical imaging. Paediatric patients are at higher risk from ionizing radiation than adults if they receive same amount of dose. This project was conducted to evaluate paediatric patient radiation dose levels in digital radiology (both fixed and mobile x-ray units) and interventional cardiology at Dubai Hospital. The results of this study are expected to contribute in establishing local and national diagnostic reference levels in United Arab Emirates (UAE). A combination of phantom studies and …

X-Ray Polarimetry With X-Calibur, Qingzhen Guo

Arts & Sciences Electronic Theses and Dissertations

ABSTRACT

X-Ray Polarimetry with X-Calibur

by

Qingzhen Guo

Doctor of Philosophy in Physics, Washington University in St. Louis,

September, 2014. Professor Henric Krawczynski, Chair

X-ray polarimetry is a prime tool to investigate the unexplored compact sources and to provide crucial information that other techniques can not produce. By measuring the degree and orientation of the polarization of radiation from a cosmic source, unique inferences about the morphology and the magnetic field structure can be made.

Krawczysnki's group at Washington University is working on a uniquely sensitive scattering polarimeter, X-Calibur, to be used in the focal plane of a focusing X-ray …

A Prototype Microwave Cavity Control Circuit For Use In Next Generation Free Electron Laser, Josh Thompson, Peter Neal Barrina, Jiayi Jiang, Joe Frisch, Steve Smith, Daniel Van Winkle

STAR Program Research Presentations

One of the current programs at SLAC National Accelerator Laboratory is the Linac Coherent Light Source, or LCLS. Using the existing hardware of the last third of their linear accelerator (or “linac”), SLAC has created one of the most energetic X-ray free electron lasers (or “FEL”). Since 2009, LCLS has used this FEL to perform a wide range of experiments across all sciences, most notably ultrafast filming at the molecular scale. As requests for beam-time with this laser increases, SLAC is purposing a linac upgrade to better match this demand. This upgrade, named LCLS-II, will replace existing copper radio frequency …

Radiation-Induced Radicals In Polyurea-Crosslinked Silica Aerogel, Benjamin Michael Walters

Masters Theses

Free radicals are atoms or molecules with an odd number of electrons in an outer shell. Since electrons typically occur in pairs, this leaves one electron that is unpaired. In seek of another electron to pair with, free radicals react with and steal electrons from neighboring molecules, which then become free radicals themselves. This can start a chain reaction, cascading into large scale damage.

Ionizing radiation can tear through molecules, just as bullets can tear through things that we see. If free radicals can be detected, and seen to increase in a material upon radiation exposure, this can indicate molecular …

Analysis Of Atmospheric Aerosols Collected In An Urban Area In Upstate Ny Using Proton Induced X-Ray Emission (Pixe) Spectroscopy, Jeremy Smith

Honors Theses

We have performed a PIXE analysis of atmospheric aerosol samples collected in Schenectady, NY, to study airborne pollution in an urban environment. The samples were collected using a PIXE International, 9-stage, cascade impactor that separates the airborne particles according to aerodynamic diameter and deposits them on thin Kapton foils. The impacted foils were bombarded with 2.2-MeV proton beams from the Union College 1.1-MV Pelletron accelerator and the emitted X-rays were detected with an Amptek silicon drift detector. The X-ray energy spectra were analyzed using GUPIX software to determine the elemental concentrations in the samples. A broad range of elements from …

Coherent Scatter Imaging For Mammography, Katie Kern

Legacy Theses & Dissertations (2009 - 2024)

Traditional x-ray images are good at distinguishing between materials with different absorption coefficients. The problem with mammography stems from the fact that there is very low contrast between cancerous and normal tissue types. Since cancerous and normal tissue have similar absorption coefficients, using conventional x-ray imaging to distinguish between the two is difficult. Coherent scatter is an alternative method to detect cancerous material within human breast tissue. Coherent scatter can distinguish between tissue types, if the intermolecular spacing of the tissues differ.

Structure And Dynamics Of Model Systems: From Ferrofluids To Brain Membranes, Matthew A. Barrett

Matthew J. Barrett

Soft condensed matter systems are a very diverse and challenging subject to study. To understand the complex macro-properties of such systems one approach is to characterize the microscopic structure and dynamics. A powerful technique for determining micro and nanoscale properties is scattering of radiation sources. Light, electron and neutron scattering techniques provide insight into the complicated molecular structures and the processes happening on these small scales. We have used neutron and x-ray scattering techniques to determine structural and dynamical information from two different types of soft condensed matter systems. The microscopic nature of a cobalt magnetic fluid was studied using …

Optical Studies Of The Liquid Crystal B2 Phase Formed By Banana-Shaped Molecules, D. A. Olson, M. Veum, A. Cady, M. V. D'Agostino, P. M. Johnson, H. T. Nguyen, Liang-Chy Chien, C. C. Huang

Liang-Chy Chien

Null-transmission ellipsometry and depolarized light microscopy have been performed on free-standing films of three achiral banana-shaped compounds in the B2 phase. Our results support a two-layer unit cell previously proposed to explain the observed antiferroelectricity in thin films and bulk samples. We have studied thicker films than previously reported and have found no deviations in the film structure from the earlier findings. Moreover, we can determine the layer spacing, the molecular tilt from the layer normal, and the three principal indices of refraction in the molecular reference frame.

Unmasking The Mysteries Of High-Mass X-Ray Binaries (Hmxbs): The Role Of The Electron Beam Ion Trap (Ebit), Carey L. Baxter, Greg Brown, Natalie Hell

Carey L Baxter

The Electron Beam Ion Trap (EBIT) uses a very narrow electron beam (~60μm) to excite and trap ions. X-ray emissions of the excited ions are then diffracted and analyzed. I studied specific spectral emission lines of ionized silicon. This data can be used as a point of reference for similar spectra measured by the satellite Chandra so that the Doppler shift due to wind around the accretion disks of High Mass X-ray Binaries (HMXBs) can be calculated. HMXBs are pairs of stars that are luminous in X-rays. They are composed of a donor star that gives up mass to an …

Commissioning Of The Asta Laser Lab With Uv Pulse Length Characterization, Daniel Kelley, Jeff Corbett

STAR Program Research Presentations

The Linac Coherent Light Source (LCLS) at SLAC depends on a photocathode electron gun to provide the linear accelerator with the raw material – electrons – used for making X-ray laser pulses. The photocathode used in the LCLS Injector is a clean copper plate in high vacuum. When the cathode is struck with high energy UV light, electrons are liberated from its surface and then accelerated down the linac with radio-frequency electric fields. These fast-moving bunches of electrons are directed through an undulator magnet to radiate X-ray light.

Although scientists have been using photocathode techniques at SLAC for 25 years, …

K-Shell X-Ray Spectroscopy Of Atomic Nitrogen, M. M. Sant'anna, Gunnar Ohrwall, Wayne C. Stolte, Alfred S. Schlachter, Dennis W. Lindle, B. M. Mclaughlin

Chemistry and Biochemistry Faculty Research

Absolute K-shell photoionization cross sections for atomic nitrogen have been obtained from both experiment and state-of-the-art theoretical techniques. Because of the difficulty of creating a target of neutral atomic nitrogen, no high-resolution K-edge spectroscopy measurements have been reported for this important atom. Interplay between theory and experiment enabled identification and characterization of the strong 1s → np resonance features throughout the threshold region. An experimental value of 409.64 ± 0.02 eV was determined for the K-shell binding energy.

The Role Of Llnl's Fast Calibration Facility In Diagnosing Nif Fusion Plasmas, Joshua G. Thompson, Carey Scott, Greg V. Brown

STAR Program Research Presentations

The Fusion and Astrophysics (FAST) Calibration and Diagnostic Facility uses the original Electron Beam Ion Trap (EBIT-I) to profile x-ray filters that are used in the Dante Soft X-Ray Diagnostic at the National Ignition Facility (NIF). FAST has an advantage over any other facility not only for its high accuracy, but also for its proximity to NIF in the Lawrence Livermore National Laboratory (LLNL). This makes for highly accurate and near-instantaneous filter calibration turnover.

EBIT-I was first constructed to create, trap, and observe static highly charged ions (HCIs) and conduct experimental astrophysics (creating an x-ray spectroscopy catalogue of ions). To …

Measurements Of K-Shell Fluorescence Yields For Ti, V, Cr, Fe, Co, Ni And Cu Elements And Their Halogen Compounds, Eli̇f Baydaş, Eli̇f Orhan Öz, Mehmet Büyükyildiz

Turkish Journal of Physics

K-shell fluorescence yields \omega_K were measured for the elements Ti, V, Cr, Fe, Co, Ni, Cu and F and Cl compounds of these elements. Measurements were carried out at 10 keV excitation energy using secondary excitation method. K x-rays emitted by samples were counted by a Si(Li) detector with 160 eV resolution at 5.9 keV. Measurement of K-shell fluorescence yields \omega_K for these elements are compared with earlier experimental results obtained by other methods.

New Phases Of Ybacugeo Superconductors Identified From X-Ray Diffraction And Infra-Red Absorption Measurements, Ahmed Abo-Arais, Mohamad Ahmad Taher Dawoud

Turkish Journal of Physics

X-ray powder diffraction patterns and infra-red absorption spectra have been evaluated and analysed for the Y_1 Ba_2 Cu_3 O_{7-\delta} - Ge_x compound samples prepared by the solid state reaction with x values ranging from 0.0 to 1.13. All samples show bulk superconductivity above liquid nitrogen temperature using the levitation test (Meissner effect). Samples with Ge content up to x = 0.2 have offset T_c between 83K and 92K while the sample with x = 1.13 shows semiconducting behavior above 100K. As a result of the solid state interaction between YBCO and Ge, new phases are observed and determined, mainly three …

Structural, Electrical And Spectral Studies On Double Rare-Earth Orthoferrites La_{1-X}Nd_Xfeo_3, O.M. Hemeda, Mohsen Mohamed Barakat, D. M. Hemeda

Turkish Journal of Physics

Samples of double rare-earth ferrite La_{1-x}Nd_xFeO_3 are synthesized by a high-temperature double sintering ceramic technique. X-ray diffraction shows that all compounds have an orthorhombic structure. The values of lattice parameter and the volume of the unit cell, changes with increasing Nd^{3+} content. The Goldschmidt tolerance factor decreases and goes far from unity with increasing Nd content. The samples containing Nd ions with x = 0.1, 0.2 and 0.3 have higher resistivity than that of LaFeO_{3}, but for x \ge 0.4 the resistivity decreases. The results indicate the presence of extrinsic semiconducting properties up to 100 °C above which the hopping …

Femtosecond Laser-Produced Plasma X-Rays From Periodically Modulated Surface Targets, J. C. Gautheir, S. Bastiani, P. Audebert, J. P. Geindre, K. Neuman, Thomas D. Donnelly, M. Hoffer, R. W. Falcone, R. Shepherd, D. Price, B. White

All HMC Faculty Publications and Research

We have studied theoretically and experimentally the x-ray production above 1 keV from femtosecond laser plasmas generated on periodically modulated surface targets. Laser energy coupling to plasma surface waves has been modeled using a numerical differential method. Almost total absorption of incident laser radiation is predicted for optimized interaction conditions. Silicon gratings have been irradiated by a 120fs Ti:sapphire laser at irradiances in excess of 10¹⁶ W/cm². X-ray intensities above 1.5 keV (K-shell lines) have been measured as a function of the incidence angle. Results show a distinct x-ray emission maximum for the first order diffraction …

X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve Ii. Sodium, Keith H. Brown, J. Dean Barnett

Faculty Publications

Coherent x-ray diffraction patterns for liquid Na have been extracted from measured patterns at 0.5, 7.5, 17, and 43 kbar along the melting curve. The experimentally determined liquid structure factor and resulting radial distribution function are given at each pressure. The position of the principal x-ray intensity peak is reproducible to within 0.5% and shows shifts of the order of 12%. The resulting nearest neighbor distance in the radial distribution function also shifts 12% but is reproducible only to approximately 2%. The distribution functions obtained at points along the melting curve suggest a simple dimensional compression or scaling; however, a …

X-Ray Diffraction Studies On Liquids At Very High Pressures Along The Melting Curve. I. Methods And Techniques, Keith H. Brown, J. Dean Barnett

Faculty Publications

A technique using the tetrahedral anvil high-pressure x-ray system has been developed to extract coherent x-ray intensity patterns of liquids near melting from measured scattering curves in the presence of high-background counts. Radial distribution functions for liquids along the melting curve to pressures of at least 50 kbar can be obtained. At each pressure scattering curves are recorded for the liquid and solid on opposite sides of the melting curve and a subtraction is made to eliminate background and incoherent scattering. Theoretical estimates of the thermal diffuse scattering from the solid are added to the appropriately corrected difference patterns to …