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Interpretation of f({epsilon}) measurements by T. Kimura, K. Akatsuka and K. Ohe

Description: This note describes my analysis of the measurement of the electron energy distribution function in a DC glow discharge reported by T. Kimura, K. Akatsuka, and K. Ohe, in `Experimental and theoretical investigations of DC glow discharges in argon-nitrogen mixtures,`J. Phys. D: Appl. Phys. 27 (1994) 1664-1671. T. Kimura of the Department of Systems Engineering at the Nagoya Institute of Technology sent me this paper in 1994, as well as `Electron Energy Distribution Function in Neon-Nitrogen Mixture Positive Column,` T. Kimura, and K. Ohe, Jpn. J. Appl. Phys. Vol. 3 1, Part 1, No. 12A, December 1992, pp. 4051- 4052. I base my analysis on the data for a pure N{sub 2} discharge at p=1 torr in the 1994 paper. Figures 2 and 3 in that paper show a discrepancy between f({epsilon}) as measured by Langmuir probing and f({epsilon}) as calculated from E/N based on the measured axial field. Kimura et. al. explain their observation of hotter than expected electrons on superelastic collisions with vibrationally excited nitrogen. My fundamental point is that the radial field generated by ambipolar diffusion significantly augments E/N above the contribution from the axial field in this experiment, and creates a higher than expected radially averaged electron energy.
Date: November 26, 1996
Creator: Garcia, M.
Partner: UNT Libraries Government Documents Department

Radio-loud high-redshift protogalaxy canidates in Bootes

Description: We used the Near Infrared Camera (NIRC) on Keck I to obtain K{sub s}-band images of four candidate high-redshift radio galaxies selected using optical and radio data in the NOAO Deep Wide-Field Survey in Bootes. Our targets have 1.4 GHz radio flux densities greater than 1 mJy, but are undetected in the optical. Spectral energy distribution fitting suggests that three of these objects are at z > 3, with radio luminosities near the FR-I/FR-II break. The other has photometric redshift z{sub phot} = 1.2, but may in fact be at higher redshift. Two of the four objects exhibit diffuse morphologies in K{sub s}-band, suggesting that they are still in the process of forming.
Date: July 20, 2007
Creator: Croft, S; van Breugel, W; Brown, M J; de Vries, W; Dey, A; Eisenhardt, P et al.
Partner: UNT Libraries Government Documents Department

Two-electron time-delay interference in atomic double ionization by attosecond pulses

Description: A two-color two-photon atomic double ionization experiment using subfemtosecond UV pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.
Date: October 4, 2009
Creator: Rescigno, Thomas N
Partner: UNT Libraries Government Documents Department


Description: There are two different types of investigation of interest in high energy nuclear phenomena. One can observe gross effects such as the production of large numbers of heavy particles of different types, or one can study the elementary particles themselves which result from these collisions, for example, the kappa mesons, to determine modes of decay and the energy spectra of the resulting particles. This discussion will deal with the gross aspects of high energy interactions and will review the work of Fermi: High Energy Nuclear Interactions, Progress in Theoretical Physics, 5, No. 4, July-August, 1950.
Date: November 3, 1953
Creator: Lepore, Joseph
Partner: UNT Libraries Government Documents Department

Differential spectral synthesis with a library of elliptical galaxies

Description: Spectrophotometry of elliptical galaxies spanning a large rang in luminosity is analyzed for cosmic variations in color and line strength. The results are used to construct a base sequence spectral energy distribution as a function line strength, color, and velocity dispersion, representing old, red, uniform elliptical galaxy stellar populations. The sequence can be used as the starting point for investigating and modeling the stellar populations of other systems such as dwarf ellipticals, merger remnants, and, eventually, high redshift ellipticals.
Date: December 7, 1995
Creator: Gregg, M.
Partner: UNT Libraries Government Documents Department


Description: Three and four center unimolecular elimination reactions of HCl have been investigated for CHF{sub 2}Cl, CHFCL{sub 2}, CH{sub 3}CCl{sub 3}, CH{sub 3}CF{sub 2}Cl and in a molecular beam experiment using infrared multiphoton absorption to energize the molecule. The translational energy distributions obtained in this work show that the average translational energy released to the fragments is around 8-12 kcal/mole, except for the three center elimination reaction from CHClCF{sub 2}, which gives a value of 1 kcal/mole. In four center eliminations, the translational energy released is less than 20% of the potential energy barrier of the back reaction. This is somewhat less than previous indications that approximately 30% of the potential energy barrier of the exit channel in four center reactions should be released into translation.
Date: April 1, 1978
Creator: Sudbo, Aa. S.; Schulz, P.A.; Shen, Y.R. & Lee, Y.T.
Partner: UNT Libraries Government Documents Department

Two-photon double ionization of the helium atom by ultrashort pulses

Description: Two-photon double ionization of the helium atom was the subject of early experiments at FLASH and will be the subject of future benchmark measurements of the associated electron angular and energy distributions. As the photon energy of a single femtosecond pulse is raised from the threshold for two-photon double ionization at 39.5 eV to beyond the sequential ionization threshold at 54.4 eV, the electron ejection dynamics change from the highly correlated motion associated with nonsequential absorption to the much less correlated sequential ionization process. The signatures of both processes have been predicted in accurate \textit{ab initio} calculations of the joint angular and energy distributions of the electrons, and those predictions contain some surprises. The dominant terms that contribute to sequential ionization make their presence apparent several eV below that threshold. In two-color pump probe experiments with short pulses whose central frequencies require that the sequential ionization process necessarily dominates, a two-electron interference pattern emerges that depends on the pulse delay and the spin state of the atom.
Date: May 14, 2010
Creator: Palacios, Alicia; Horner, Daniel A; Rescigno, Thomas N & McCurdy, C William
Partner: UNT Libraries Government Documents Department


Description: Angle-resolved photoemission energy distributions (PED's) were obtained from valence bands of MnF{sub 2} single crystals using AlK{alpha} radiation. A pronounced variation in the PED's was observed as the electron take-off angle was varied relative to the crystalline axes, for the (111) crystal face. The observed variation is attributed to the t{sub 2g} and e{sub g} symmetry properties of the manganese 3d initial state wave functions and is well described by an angle-dependent transition-matrix model. The results are in good agreement with the multi-configurational Hartree-Fock calculations of Viinikka and Bagus.
Date: September 1, 1977
Creator: Sherwood, P.M.A.; McFeely, F.R.; Kowalczyk, S.P. & Shirley, D.A.
Partner: UNT Libraries Government Documents Department

Absolute Measurement of Electron Cloud Density in aPositively-Charged Particle Beam

Description: Clouds of stray electrons are ubiquitous in particle accelerators and frequently limit the performance of storage rings. Earlier measurements of electron energy distribution and flux to the walls provided only a relative electron cloud density. We have measured electron accumulation using ions expelled by the beam. The ion energy distribution maps the depressed beam potential and gives the dynamic cloud density. Clearing electrode current reveals the static background cloud density, allowing the first absolute measurement of the time-dependent electron cloud density during the beam pulse.
Date: April 27, 2006
Creator: Kireeff Covo, Michel; Molvik, Arthur W.; Friedman, Alex; Vay,Jean-Luc; Seidl, Peter A.; Logan, Grant et al.
Partner: UNT Libraries Government Documents Department

Monochromatic Cosmic Ray Deuterion Source

Description: The reaction pp {yields} {pi}{sup +}d resulting from the high energy cosmic rays incident on the interstellar hydrogen gas gives rise to secondary deuterons. Since the total cross section for this reaction is appreciable only at proton kinetic energies of 600 MeV, the deuterons have a very small spread in energy. It is estimated that the flux of deuterons from this mechanism should be easily discernible from deuterons produced by other reactions and copious enough to be detected at the earth. The narrow deuteron energy distribution could provide an energy calibration for the study of the existence of a postinjection acceleration.
Date: August 6, 1968
Creator: Anderson, Jared A.
Partner: UNT Libraries Government Documents Department

K-corrections and spectral templates of Type Ia supernovae

Description: With the advent of large dedicated Type Ia supernova (SN Ia) surveys, K-corrections of SNe Ia and their uncertainties have become especially important in the determination of cosmological parameters. While K-corrections are largely driven by SN Ia broadband colors, it is shown here that the diversity in spectral features of SNe Ia can also be important. For an individual observation, the statistical errors from the inhomogeneity in spectral features range from 0.01 (where the observed and rest-frame filters are aligned) to 0.04 (where the observed and rest-frame filters are misaligned). To minimize the systematic errors caused by an assumed SN Ia spectral energy distribution (SED), we outline a prescription for deriving a mean spectral template time series that incorporates a large and heterogeneous sample of observed spectra. We then remove the effects of broadband colors and measure the remaining uncertainties in the K-corrections associated with the diversity in spectral features. Finally, we present a template spectroscopic sequence near maximum light for further improvement on the K-correction estimate. A library of ~;;600 observed spectra of ~;;100 SNe Ia from heterogeneous sources is used for the analysis.
Date: March 20, 2007
Creator: Nugent, Peter E.; Hsiao, E.Y.; Conley, A.; Howell, D.A.; Sullivan, M.; Pritchet, C.J. et al.
Partner: UNT Libraries Government Documents Department

Supersymmetry, Naturalness, and Signatures at the LHC

Description: Weak scale supersymmetry is often said to be fine-tuned, especially if the matter content is minimal. This is not true if there is a large A term for the top squarks. We present a systematic study on fine-tuning in minimal supersymmetric theories and identify low energy spectra that do not lead to severe fine-tuning. Characteristic features of these spectra are: a large A term for the top squarks, small top squark masses, moderately large tan {beta}, and a small {mu} parameter. There are classes of theories leading to these features, which are discussed. In one class, which allows a complete elimination of fine-tuning, the Higgsinos are the lightest among all the superpartners of the standard model particles, leading to three nearly degenerate neutralino/chargino states. This gives interesting signals at the LHC--the dilepton invariant mass distribution has a very small endpoint and shows a particular shape determined by the Higgsino nature of the two lightest neutralinos. We demonstrate that these signals are indeed useful in realistic analyses by performing Monte Carlo simulations, including detector simulations and background estimations. We also present a method that allows the determination of all the relevant superparticle masses without using input from particular models, despite the limited kinematical information due to short cascades. This allows us to test various possible models, which is demonstrated in the case of a model with mixed moduli-anomaly mediation. We also give a simple derivation of special renormalization group properties associated with moduli mediated supersymmetry breaking, which are relevant in a model without fine-tuning.
Date: February 10, 2006
Creator: Kitano, Ryuichiro & Nomura, Yasunori
Partner: UNT Libraries Government Documents Department

CRADA Final Report CRADA No. LB05-001820"Ion Beam Drift Compression Technology for NDCX"

Description: Summary of the specific research and project accomplishments: Through this collaboration, LBNL and FPSI determined the specific energy manipulations that apply to the Neutralized Drift Compression Experiment (NDCX) ion beam and developed the preliminary design of a Fast Induction Energy Corrector (FIEC). This effort was successfully completed, firmly establishing the technical feasibility of the proposed approach for regulating the longitudinal energy distribution of the NDCX ion beam. This is a critical step in achieving the NDCX goal of axial compression of the beam by a factor of 100 during neutralized drift.
Date: October 5, 2009
Creator: First point Scientific, Inc.; Laboratory, E.O. Lawrence Berkeley National & Waldron, William L.
Partner: UNT Libraries Government Documents Department

Applications of Laser and Synchrotron Based ARPES to Photocathode Research

Description: Laser angle resolved photoelectron spectroscopy (ARPES) provides unique information about angle and energy distribution of photoelectrons. Laser ARPES gives unique insight into how NEA materials work. ARPES combined with some ancillary measurements gives a very complete picture of system electronic physics. For H:C[100] there is now a clear program for engineering as well as development analogous systems. ARPES well suited for identifying 'ideal' photocathodes with intrinsically low emittance and high QE.
Date: October 12, 2010
Creator: J., Rameau; J., Smedley; Muller, E.; Kidd, T.; Johnson, P.; Allen, P. et al.
Partner: UNT Libraries Government Documents Department

The Extended X-ray Nebula of PSR J1420-6048

Description: The vicinity of the unidentified EGRET source 3EG J1420-6038 has undergone extensive study in the search for counterparts, revealing the energetic young pulsar PSR J1420-6048 and its surrounding wind nebula as a likely candidate for at least part of the emission from this bright and extended gamma-ray source. We report on new Suzaku observations of PSR J1420-6048, along with analysis of archival XMM Newton data. The low background of Suzaku permits mapping of the extended X-ray nebula, indicating a tail stretching {approx} 8 minutes north of the pulsar. The X-ray data, along with archival radio and VHE data, hint at a pulsar birthsite to the North, and yield insights into its evolution and the properties of the ambient medium. We further explore such properties by modeling the spectral energy distribution (SED) of the extended nebula.
Date: August 19, 2011
Creator: Van Etten, Adam; Romani, Roger W. & /Stanford U., Phys. Dept.
Partner: UNT Libraries Government Documents Department

Characterizing high energy spectra of NIF ignition hohlraums using a differentially filtered high energy multi-pinhole X-ray imager

Description: Understanding hot electron distributions generated inside hohlraums is important to the ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with the target materials. We used an array of 18 pinholes, with four independent filter combinations, to image entire hohlraums with a magnification of 0.87x during the hohlraum energetics campaign on NIF. Comparing our results with hohlraum simulations indicates that the characteristic 30 keV hot electrons are mainly generated from backscattered laser plasma interactions rather than from hohlraum hydrodynamics.
Date: May 11, 2010
Creator: Park, H; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J et al.
Partner: UNT Libraries Government Documents Department

Particle Simulations of a Linear Dielectric Wall Proton Accelerator

Description: The dielectric wall accelerator (DWA) is a compact induction accelerator structure that incorporates the accelerating mechanism, pulse forming structure, and switch structure into an integrated module. The DWA consists of stacked stripline Blumlein assemblies, which can provide accelerating gradients in excess of 100 MeV/meter. Blumleins are switched sequentially according to a prescribed acceleration schedule to maintain synchronism with the proton bunch as it accelerates. A finite difference time domain code (FDTD) is used to determine the applied acceleration field to the proton bunch. Particle simulations are used to model the injector as well as the accelerator stack to determine the proton bunch energy distribution, both longitudinal and transverse dynamic focusing, and emittance growth associated with various DWA configurations.
Date: June 12, 2007
Creator: Poole, B R; Blackfield, D T & Nelson, S D
Partner: UNT Libraries Government Documents Department


Description: We present experimental data of electron energy distributions from ultra-intense (>10{sup 19} W/cm{sup 2}) laser-solid interactions using the Rutherford Appleton Laboratory Vulcan petawatt laser. These measurements were made using a CCD-based magnetic spectrometer. We present details on the distinct effective temperatures that were obtained for a wide variety of targets as a function of laser intensity. It is found that as the intensity increases from 10{sup 17} W/cm{sup 2} to 10{sup 19} W/cm{sup 2}, a 0.4 dependence on the laser intensity is found. Between 10{sup 19} W/cm{sup 2} and 10{sup 20} W/cm{sup 2}, a gradual rolling off of temperature with intensity is observed.
Date: December 8, 2005
Creator: Chen, H; Wilks, S C; Kruer, W L; Moon, S; Patel, N; Patel, P K et al.
Partner: UNT Libraries Government Documents Department

Extra dimensions vs. supersymmetric interpretation of missing energy events at a linear collider

Description: The photon plus missing energy signature is a primary handle on two important classes of theories. Theories with large extra dimensions predict the production of photons in association with Kaluza-Klein excitations of the graviton. In supersymmetric theories with superlight gravitinos, photons can be produced in association with gravitino pairs. The signatures for these two theories are compared, and it is found that they can be distinguished by studying the photon energy distributions and scaling of the cross section with center-of-mass energy. Both these methods fail, however, if there are six extra dimensions. In that case, additional phenomena predicted by the theories would be required to narrow down the underlying causes of the photon plus missing energy signal. We also study the ability of these measurements to determine the number of extra dimensions.
Date: October 25, 2001
Creator: Gopalakrishna, Shrihari; Perelstein, Maxim & Wells, James D.
Partner: UNT Libraries Government Documents Department

Neutron Production by Muon Spallation I: Theory

Description: We describe the physics and codes developed in the Muon Physics Package. This package is a self-contained Fortran90 module that is intended to be used with the Monte Carlo package MCNPX. We calculate simulated energy spectra, multiplicities, and angular distributions of direct neutrons and pions from muon spallation.
Date: November 13, 2006
Creator: Luu, T & Hagmann, C
Partner: UNT Libraries Government Documents Department

Intensity distributions of gamma-ray bursts

Description: Observations of individual bursts chosen by the vagaries of telescope availability demonstrated that bursts are not standard candles and that their apparent energy can be as great as 10{sup 54} erg. However, determining the distribution of their apparent energy (and of other burst properties) requires the statistical analysis of a well-defined burst sample; the sample definition includes the threshold for including a burst in the sample. Thus optical groups need to the criteria behind the decision to search for a spectroscopic redshift. Currently the burst samples are insufficient to choose between lognormal and power law functional forms of the distribution, and the parameter values for these functional forms differ between burst samples. Similarly, the actual intensity distribution may be broader than observed, with a low energy tail extending below the detection threshold.
Date: January 1, 2001
Creator: Band, D. L. (David L.)
Partner: UNT Libraries Government Documents Department