Excursion to North Wales

n/

Perceptual Display Strategies of Hyperspectral Imagery Based on PCA and ICA

This study investigated appropriate methodologies for displaying hyperspectral imagery based on knowledge of human color vision as applied to Hyperion and AVIRIS data. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) were used to reduce the data dimensionality in order to make the data more amenable to visualization in three-dimensional color space. In addition, these two methods were chosen because of their underlying relationships to the opponent color model of human color perception. PCA and ICA-based visualization strategies were then explored by mapping the first three PCs or ICs to several opponent color spaces including CIELAB, HSV, YCrCb, and YUV. The gray world assumption, which states that given an image with sufficient amount of color variations, the average color should be gray, was used to set the mapping origins. The rendered images are well color balanced and can offer a first look capability or initial classification for a wide variety of spectral scenes

Applications of Small Satellites for Defense Space Communication Systems and Technology Development: Pegasus Flight-2 and the Launch of Microsat

DARPA\u27s seven Microsats were placed into orbit on the second flight of the Pegasus. The Microsat program objective is to assess the tactical utility of small, low-cost communications satellites. This paper describes the changes made to the Pegasus since its first flight, provides an overview of the Microsat demonstration program, and outlines the preliminary results of the Pegasus launch. Finally, the near-term Army and Navy demonstration plans for Microsat are discussed

Lithiated ternary compounds for neutron detectors: material production and device characterization of lithium zinc phosphide and lithium zinc arsenide

Doctor of PhilosophyMechanical and Nuclear EngineeringDouglas S. McGregorThere is a need for compact, rugged neutron detectors for a variety of applications including national security and oil well logging. A solid form neutron detector would have a higher efficiency than present day gas filled ³He and ¹⁰BF ₃ detectors, which are standards currently used in the industry today. A sub-branch of the III-V semiconductors is the filled tetrahedral compounds, known as Nowotny-Juza compounds (A[superscript I]B[superscript II]C[superscript V]). These materials are desirable for their cubic crystal structure and semiconducting electrical properties. Originally studied for photonic applications, Nowotny-Juza compounds have not been fully developed and characterized. Nowotny-Juza compounds are being studied as neutron detection materials here, and the following work is a study of LiZnP and LiZnAs material development and device characterization. Precursor binaries and ternary materials of LiZnAs and LiZnP were synthesized in-house in vacuum sealed quartz ampoules with a crucible lining. Synthesized powders were characterized by x-ray diffraction, where lattice constants of 5.751 ± .001 Å and 5.939 ± .002 Å for LiZnP and LiZnAs, respectively, were determined. A static vacuum sublimation in quartz was performed to help purify the synthesized ternary material. The resulting material from the sublimation process showed characteristics of a higher purity ternary compound. Bulk crystalline samples were grown from the purified material. Ingots up to 9.0 mm in diameter and 13.0 mm in length were harvested. Individual samples were characterized for crystallinity on a Bruker AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS D8 DISCOVER, high-resolution x-ray diffractometer with a 0.004° beam divergence. High-resolution XRD measurements indicated reasonable out-of-plane and in-plane ordering of LiZnP and LiZnAs crystals. Devices were fabricated from the LiZnP and LiZnAs crystals. Resistivity of devices were determined within the range of 10⁶ – 10¹¹ Ω cm. Charge carrier mobility and mean free drift time products were characterized for electrons at 8.0 x 10⁻⁴ cm² V⁻¹ ± 4.8% and 9.1 x 10⁻⁴ cm² V⁻¹ ± 4.4% for LiZnP and LiZnAs respectively. Sensitivity to 337 nm laser light (3.68 eV photons) was observed, where an absorption coefficient of 0.147 mm⁻¹ was determined for LiZnAs devices. Thermal neutron sensitivity was evaluated with unpurified and purified LiZnP and LiZnAs devices. Sensitivity was observed, however material quality and crystalline quality significantly hindered device performance

Facilities for the Energy Frontier of Nuclear Physics

The Relativistic Heavy Ion Collider at BNL has been exploring the energy frontier of nuclear physics since 2001. Its performance, flexibility and continued innovative upgrading can sustain its physics output for years to come. Now, the Large Hadron Collider at CERN is about to extend the frontier energy of laboratory nuclear collisions by more than an order of magnitude. In the coming years, its physics reach will evolve towards still higher energy, luminosity and varying collision species, within performance bounds set by accelerator technology and by nuclear physics itself. Complementary high-energy facilities will include fixed-target collisions at the CERN SPS, the FAIR complex at GSI and possible electron-ion colliders based on CEBAF at JLAB, RHIC at BNL or the LHC at CERN.Comment: Invited talk at the International Nuclear Physics Conference, Vancouver, Canada, 4-9 July 2010, to be published in Journal of Physics: Conference Series. http://inpc2010.triumf.ca

On the Evolution of Ion Bunch Profile in the Presence of Longitudinal Coherent Electron Cooling

In the presence of longitudinal coherent electron cooling, the evolution of the line-density profile of a circulating ion bunch can be described by the 1-D Fokker-Planck equation. We show that, in the absence of diffusion, the 1-D equation can be solved analytically for certain dependence of cooling force on the synchrotron amplitude. For more general cases with arbitrary diffusion, we solved the 1-D Fokker-Planck equation numerically and the numerical solutions have been compared with results from macro-particle tracking

Electric multipole plasmons in deformed sodium clusters

The random-phase-approximation (RPA) method with separable residual forces (SRPA) is proposed for the description of multipole electric oscillations of valence electrons in deformed alkali metal clusters. Both the deformed mean field and residual interaction are derived self-consistently from the Kohn-Sham functional. SRPA drastically simplifies the computational effort which is urgent if not decisive for deformed systems. The method is applied to the description of dipole, quadrupole and octupole plasmons in deformed sodium clusters of a moderate size. We demonstrate that, in clusters with the size N>50, Landau damping successfully competes with deformation splitting and even becomes decisive in forming the width and gross structure of the dipole plasmon. Besides, the plasmon is generated by excitations from both ground state and shape isomers. In such clusters familiar experimental estimates for deformation splitting of dipole plasmon are useless.Comment: 27 pages, 10 figure

High energy Coulomb-scattered electrons for relativistic particle beam diagnostics

A new system used for monitoring energetic Coulomb-scattered electrons as the main diagnostic for accurately aligning the electron and ion beams in the new Relativistic Heavy Ion Collider (RHIC) electron lenses is described in detail. The theory of electron scattering from relativistic ions is developed and applied to the design and implementation of the system used to achieve and maintain the alignment. Commissioning with gold and 3He beams is then described as well as the successful utilization of the new system during the 2015 RHIC polarized proton run. Systematic errors of the new method are then estimated. Finally, some possible future applications of Coulomb-scattered electrons for beam diagnostics are briefly discussed.Comment: 16 pages, 23 figure

Analysis of intensity instability threshold at transition in RHIC.

The beam intensity of ion beams in RHIC is limited by a fast transverse instability at transition, driven by the machine impedance and electron clouds. For gold and deuteron beams we analyze the dependence of the instability threshold on beam and machine parameters from recent operational data and dedicated experiments. We fit the machine impedance to the experimental data