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Spectral catalogue of the intermediate ionization states of iron in the extreme ultraviolet

Description: Using precisely controlled laboratory conditions we have begun to establish a spectral catalogue of the intermediate ionization states of iron, Fe IX - Fe XXIV, in the extreme ultraviolet. The measurements are being performed in support of the development of reliable modeling codes for the analysis of data from the Extreme Ultraviolet Explorer and future space astrophysics missions sensitive to extreme ultraviolet radiation. They aim to resolve the controversies surrounding the short-wavelength spectra of stellar coronae. Preliminary measurements showing the wealth of iron lines in the 50-120 {Angstrom} region are presented.
Date: May 13, 1998
Creator: Beiersdorfer, P.; Utter, S. B. & Brown, G. V.
Partner: UNT Libraries Government Documents Department

Constraining Cosmic Evolution of Type Ia Supernovae

Description: We present the first large-scale effort of creating composite spectra of high-redshift type Ia supernovae (SNe Ia) and comparing them to low-redshift counterparts. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with excellent light-curve information. In addition, we have obtained 397 spectra of low-redshift SNe through a multiple-decade effort at Lick and Keck Observatories, and we have used 45 ultraviolet spectra obtained by HST/IUE. The low-redshift spectra act as a control sample when comparing to the ESSENCE spectra. In all instances, the ESSENCE and Lick composite spectra appear very similar. The addition of galaxy light to the Lick composite spectra allows a nearly perfect match of the overall spectral-energy distribution with the ESSENCE composite spectra, indicating that the high-redshift SNe are more contaminated with host-galaxy light than their low-redshift counterparts. This is caused by observing objects at all redshifts with similar slit widths, which corresponds to different projected distances. After correcting for the galaxy-light contamination, subtle differences in the spectra remain. We have estimated the systematic errors when using current spectral templates for K-corrections to be {approx}0.02 mag. The variance in the composite spectra give an estimate of the intrinsic variance in low-redshift maximum-light SN spectra of {approx}3% in the optical and growing toward the ultraviolet. The difference between the maximum-light low and high-redshift spectra constrain SN evolution between our samples to be < 10% in the rest-frame optical.
Date: February 13, 2008
Creator: Foley, Ryan J.; Filippenko, Alexei V.; Aguilera, C.; Becker, A.C.; Blondin, S.; Challis, P. et al.
Partner: UNT Libraries Government Documents Department

ORFEUS and EUVE observations of AM herculis

Description: Far-UV spectra of AM Her in a high optical state were obtained in 1993 September with the University of California, Berkeley (UCB) spectrometer aboard the ORFEUS telescope. The UCB spectrometer has a spectral resolution {lambda}/{Delta}{lambda} 3000 and covers the 390-1170 {Angstrom} bandpass, but interstellar absorption leaves no detectable -flux below the Lyman limit. Spectra of AM Her were acquired during the intervals 04:19:40-04:36:26 UT on September 16 and 08:34:03-09:09:06 UT on September 17 of 1993. The corresponding magnetic phases are 0.75-0.84 and 0.88-1.07 according to the linear polarization ephemeris of S. Tapia. The main spectral features are the 0 VI doublet, C III {lambda}977, and He II {lambda}1085 (Balmer {gamma}). The bright C III {lambda}1176 multiplet, which is detected by IUE, is at the very end of the spectrum. At the full spectral resolution of the instrument, the 0 VI doublet shows broad and narrow components similar to that of the optical emission lines. The intensity ratio of the narrow component of the 0 VI doublet is {approximately} 1.3:1, much closer to the optically thick limit of 1:1 than the optically thin ratio of 2:1.
Date: April 6, 1995
Creator: Mauche, C.W.; Paerels, F.B.S. & Raymond, J.C.
Partner: UNT Libraries Government Documents Department

A Physico-Chemical Study of Some Areas of Fundamental Significance to Biophysics

Description: This report covers: Radiation Signatures; Electronic Structure of Steroids, Vitamins, and others; Laser Optogalvanic Effect; Vacuum Ultraviolet Spectroscopy, including Electron Scattering, Photochemistry, and Magnetic Circular Dichroism; and Ozone.
Date: April 1, 1999
Creator: Kumar, Devendra & McGlynn, S. P.
Partner: UNT Libraries Government Documents Department

X-ray and EUV observations of the boundary layer emission of nonmagnetic cataclysmic variables

Description: EUVE, ROSAT, and ASCA observations of the boundary layer emission of nonmagnetic cataclysmic variables (CVs) are reviewed. EUVE spectra reveal that the effective temperature of the soft component of high-M nonmagnetic CVs is kT {approx}10-20 eV and that its luminosity is {approx} 0.1-0.5 times the accretion disk luminosity. Although the EUV spectra are very complex and belie simple interpretation, the physical conditions of the boundary layer gas are constrained by emission lines of highly ionized Ne, Mg, Si, and Fe. ROSAT and ASCA spectra of the hard component of nonmagnetic CVs are satisfactorily but only phenomenologically described by multi-temperature thermal plasmas, and the constraints imposed on the physical conditions of this gas are limited by the relatively weak and blended fines. It is argued that significant progress in our understanding of the X-ray spectra of nonmagnetic CVs will come with future observations with XMM, AXAF, and Astro-E.
Date: March 9, 1996
Creator: Mauche, C.W.
Partner: UNT Libraries Government Documents Department

Absolute intensities of the vacuum ultraviolet spectra in oxide etch plasma processing discharges

Description: In this paper, the authors report the absolute intensities of ultraviolet light between 4.9 eV and 24 eV ( 250 nm to 50 mn ) striking a silicon wafer in a number of oxide-etch processing discharges. The emphasis is on photons with energies greater than 8.8 eV, which have enough energy to damage SiO{sub 2}. These discharges were in an inductively-driven Gaseous Electronics Conference reference cell which had been modified to more closely resemble commercial etching tools. Comparisons of measurements made through a side port in the cell and through a hole in the wafer indicate that the VUV light in these discharges is strongly trapped. For the pure halocarbon gases examined in these experiments (C{sub 2}F{sub 6}, CHF{sub 3}, C{sub 4}F{sub 8}), the fluxes of VUV photons to the wafer varied from 1 x 10{sup 15} to 3 x 10{sup 15} photons/cm{sup 2} sec or equivalently from 1.5 to 5 mW/cm{sup 2}. These measurements imply that 0.1% to 0.3% of the rf source power to these discharges ends up hitting the wafer as VUV photons for the typical 20 mT, 200 W rf discharges. For typical ashing discharges containing pure oxygen, the VUV intensities are slightly higher--about 8 mW/cm{sup 2} . As argon or hydrogen diluents are added to the fluorocarbon gases, the VUV intensities increase dramatically, with a 10/10/10 mixture of Ar/C{sub 2}F{sub 6}/H{sub 2} yielding VUV fluxes on the wafer 26 mW/cm{sup 2} and pure argon discharges yielding 52 mW/cm{sup 2} . Adding an rf bias to the wafer had only a small effect on the VUV observed through a side-port of the GEC cell.
Date: May 1, 2000
Partner: UNT Libraries Government Documents Department

Ti:sapphire based ultrafast pump-probe laser source in the violet and ultraviolet

Description: Frequency conversion of an ultrafast 810 nm Ti:sapphire laser has produced 15 mJ, 165-fs pulses at 405 nm with an energy conversion efficiency of 35%. Upon tripling the fundamental to 270 nm, an energy of 0.8 mJ is obtained. Unconverted to 405-nm light is used to generate an ultrafast supercontinuum in water that extends from 200 nm to 600 nm. The system operates at a 5 Hz repetition rate, and is useful for applications in deep ultraviolet pump-probe ultrafast spectroscopy.
Date: March 1, 1994
Creator: Rodriguez, G.; Roberts, J. P. & Taylor, A. J.
Partner: UNT Libraries Government Documents Department

Verifying the Cosmological Utility of Type Ia Supernovae:Implications of a Dispersion in the Ultraviolet Spectra

Description: We analyze the mean rest-frame ultraviolet (UV) spectrum ofType Ia Supernovae(SNe) and its dispersion using high signal-to-noiseKeck-I/LRIS-B spectroscopyfor a sample of 36 events at intermediateredshift (z=0.5) discoveredby the Canada-France-Hawaii TelescopeSupernova Legacy Survey (SNLS). Weintroduce a new method for removinghost galaxy contamination in our spectra,exploiting the comprehensivephotometric coverage of the SNLS SNe and theirhost galaxies, therebyproviding the first quantitative view of the UV spectralproperties of alarge sample of distant SNe Ia. Although the mean SN Ia spectrumhas notevolved significantly over the past 40 percent of cosmic history,preciseevolutionary constraints are limited by the absence of acomparable sample ofhigh quality local spectra. The mean UV spectrum ofour z 0.5 SNe Ia and itsdispersion is tabulated for use in futureapplications. Within the high-redshiftsample, we discover significant UVspectral variations and exclude dust extinctionas the primary cause byexamining trends with the optical SN color. Although progenitormetallicity may drive some of these trends, the variations we see aremuchlarger than predicted in recent models and do not follow expectedpatterns.An interesting new result is a variation seen in the wavelengthof selected UVfeatures with phase. We also demonstrate systematicdifferences in the SN Iaspectral features with SN lightcurve width inboth the UV and the optical. Weshow that these intrinsic variations couldrepresent a statistical limitation in thefuture use of high-redshift SNeIa for precision cosmology. We conclude thatfurther detailed studies areneeded, both locally and at moderate redshift wherethe rest-frame UV canbe studied precisely, in order that future missions canconfidently beplanned to fully exploit SNe Ia as cosmological probes.
Date: November 2, 2007
Creator: Ellis, R.S.; Sullivan, M.; Nugent, P.E.; Howell, D.A.; Gal-Yam,A.; Astier, P. et al.
Partner: UNT Libraries Government Documents Department

Early-time measurements of laser-plasma conditions in OMEGA-upgrade ICF targets. Final report, April 1, 1998--January 31, 1999

Description: All of the experimental results from OMEGA shots described here are from CY-1998 experiments under an (extended) FY-98 grant. This research involves fielding at LLE their two flat-field euv spectrographs in the 30--250 {angstrom} range, mainly utilizing on one o them a gated stripline microchannel plate as a time-resolved detector, with photographic recording. The experimental layout for the 1998 experiments is shown. During the week beginning May 3, 1998, the authors obtained 24 data shots over 4 days, and fielded both the time-gated extreme ultraviolet (euv) spectrograph mounted external to the target chamber, as well as their newly-constructed TIM-mounted euv spectrograph mounted closer to the target with time-integrated photographic recording on a trial basis. They also had available the LLE/LLNL streak x-ray spectrograph and x-ray imaging cameras. In this series, the first two shots appeared from the x-ray streak spectra to be normal in the sense that the spectral line emissions from the two coatings sequenced beginning with magnesium followed by aluminum as the coatings were vaporized. Unfortunately, on the following shots in this campaign it became increasingly apparent that conditions had changed radically, and later analyses showed that x-ray spectra lines from the deep aluminum undercoating appeared initially along with weak magnesium lines, indicating a premature vaporization of the magnesium heavier top layer. The second campaign in 1998 occurred during the week beginning October 18, 1998 and consisted of 21 data shots over two extended (12-hour) days following setup. For this series the authors again used their externally-mounted euv spectrography with time resolution and the x-ray streak spectrograph and imaging cameras. Much to their relief, it was immediately evident from the x-ray streak spectra obtained that significant ablation of the magnesium coatings by a (presumed) prepulse was not present, as it had been in the May campaign.
Date: February 8, 1998
Creator: Griem, H.R. & Elton, R.C.
Partner: UNT Libraries Government Documents Department

Action spectrum for melanoma induction in hybrid fish of the genus Xiphophorus

Description: Cutaneous malignant melanoma (CMM) is a complicated disease that is dependent on a number of factors that influence its incidence in ways that are quantitatively uncertain. The incidence of CMM increases with proximity to the Equator -- an observation in line with the conclusion that sun exposure is the most important etiologic agent. However, the latitude effect does not implicate UVB because the intensities of all spectral regions increase toward the Equator. An understanding of the useful public health measures to lower the incidence of CMM would benefit greatly if the spectral region of sunlight implicated in melanoma incidence were known. Such knowledge requires animal models to evaluate the incidence as a function of wavelength. There are marsupial models, a transgenic mouse model, and a fish model. To date, only the fish model has been employed to obtain an action spectrum. The paper describes a fish model, implications of the fish spectrum, and epidemiological data.
Date: March 1, 1997
Creator: Setlow, R. B.
Partner: UNT Libraries Government Documents Department

XUV and X-ray spectra from Texas Experimental Tokamak plasmas

Description: The first XUV and x-ray spectra were recorded from TEXT with a grazing-incidence grating spectrograph and new crystal spectrographs. Time- and space-integrated data yielded a qualitative description of the plasma. Line radiation from O, Cr, Fe, and Ni ions was recorded and identified with the aid of ab initio atomic structure calculations. Approximate values of plasma characteristics were obtained from the spectra. A derived electron temperature of 800 eV and electron density of 2 {times} 10{sup 13} cm{sup {minus}3} are consistent with results from other diagnostics. Spectrometers which will provide time- and space-resolved data are being designed for quantitative rate and transport studies.
Date: May 28, 1982
Creator: Bleach, R.D.; Burkhalter, P.G.; Nagel, D.J. & Rowan, W.
Partner: UNT Libraries Government Documents Department

Calculation of Hamaker constants in non-aqueous fluid media

Description: Calculations of the Hamaker constants representing the van der Waals interactions between conductor, resistor and dielectric materials are performed using Lifshitz theory. The calculation of the parameters for the Ninham-Parsegian relationship for several non-aqueous liquids has been derived based on literature dielectric data. Discussion of the role of van der Waals forces in the dispersion of particles is given for understanding paste formulation. Experimental measurements of viscosity are presented to show the role of dispersant truncation of attractive van der Waals forces.
Date: May 9, 2000
Partner: UNT Libraries Government Documents Department

1994 Activity Report, National Synchrotron Light Source. Annual report, October 1, 1993-September 30, 1994

Description: This report is a summary of activities carried out at the National Synchrotron Light Source during 1994. It consists of sections which summarize the work carried out in differing scientific disciplines, meetings and workshops, operations experience of the facility, projects undertaken for upgrades, administrative reports, and collections of abstracts and publications generated from work done at the facility.
Date: May 1995
Creator: Rothman, E. Z.
Partner: UNT Libraries Government Documents Department

Techniques for the reconstruction of two-dimensional images from projections

Description: Several plasma diagnostics techniques measure the line integrals of quantities such as densities and optical, ultraviolet, and X-ray emission. Some approaches for reconstructing the local quantities from their line integrals, based on methods utilized in computerized tomography, electron microscopy, holographic interferometry, and radio astromony, are derived and presented. Results for the special cases with source functions posessing helical symmetry--ranging from DNA to MHD--are emphasized.
Date: August 1, 1978
Creator: Sauthoff, N.R. & Von Goeler, S.
Partner: UNT Libraries Government Documents Department

WZ Sge: An accretion test case

Description: WZ Sge provides us with an excellent test for numerical codes trying to reproduce the heating and cooling of a white dwarf due to accreted material. This is because of both the many observed quantities of this binary and its long quiescent state. However, a large discrepancy appears between the observed white dwarf`s cooling curve and calculated cooling curve from the deduced accreted mass. Possible causes for this discrepancy are discussed.
Date: December 31, 1991
Creator: Sparks, W. M.; Sion, E. M.; Starrfield, S. G. & Austin, S.
Partner: UNT Libraries Government Documents Department

Novel target configurations for selective ionization state studies in molybdenum

Description: Details of experiments aimed at achieving low ionization state selectivity in molybdenum are presented. Targets are excited with a 10 J CO{sub 2} laser and the resultant VUV spectrum (300--700 {Angstrom}) has been studied. Combinations of focal spot size, target depth, and target geometries are compared. Simple attenuation of energy is shown not to vary ionization stage composition significantly. Experiments conducted with grazing incidence targets result only in a hot plasma. Modular targets with cooling cylinders of various radii demonstrated good selectivity of the ionization states, but with low absolute signals. Finally, results from combinations of focal spot adjustment and radiative cooling illustrate increased control over desired plasma temperature and density for spectroscopic studies of molybdenum. 7 refs., 14 figs.
Date: March 1, 1990
Creator: Ilcisin, K.J.; Feldman, U.; Schwob, J.L.; Wouters, A. (Princeton Univ., NJ (USA). Plasma Physics Lab.) & Suckewer, S. (Princeton Univ., NJ (USA). Plasma Physics Lab. Princeton Univ., NJ (USA). Dept. of Mechanical and Aerospace Engineering)
Partner: UNT Libraries Government Documents Department

Verifying the Cosmological Utility of Type Ia Supernovae: Implications of a Dispersion in the Ultraviolet Spectra

Description: We analyze the mean rest-frame ultraviolet (UV) spectrum of Type Ia Supernovae (SNe) and its dispersion using high signal-to-noise ratio Keck-I/LRIS-B spectroscopy for a sample of 36 events at intermediate redshift (z=0.5) discovered by the Canada-France-Hawaii Telescope Supernova Legacy Survey (SNLS). We introduce a new method for removing host galaxy contamination in our spectra, exploiting the comprehensive photometric coverage of the SNLS SNe and their host galaxies, thereby providing the first quantitative view of the UV spectral properties of a large sample of distant SNe Ia. Although the mean SN Ia spectrum has not evolved significantly over the past 40percent of cosmic history, precise evolutionary constraints are limited by the absence of a comparable sample of high-quality local spectra. The mean UV spectrum of our z~;;=0.5 SNe Ia and its dispersion is tabulated for use in future applications. Within the high-redshift sample, we discover significant UV spectral variations and exclude dust extinction as the primary cause by examining trends with the optical SN color. Although progenitor metallicity may drive some of these trends, the variations we see are much larger than predicted in recent models and do not follow expected patterns. An interesting new result is a variation seen in the wavelength of selected UV features with phase. We also demonstrate systematic differences in the SN Ia spectral features with SN light curve width in both the UV and the optical. We show that these intrinsic variations could represent a statistical limitation in the future use of high-redshift SNe Ia for precision cosmology. We conclude that further detailed studies are needed, both locally and at moderate redshift where the rest-frame UV can be studied precisely, in order that future missions can confidently be planned to fully exploit SNe Ia as cosmological probes.
Date: February 28, 2008
Creator: Nugent, Peter E; Ellis, R.S.; Sullivan, M.; Nugent, P.E.; Howell, D.A.; Gal-Yam, A. et al.
Partner: UNT Libraries Government Documents Department

Development and Quantification of UV-Visible and Laser Spectroscopic Techniques for Materials Accountability and Process Control

Description: Ultraviolet-Visible Spectroscopy (UV-Visible) and Time Resolved Laser Fluorescence Spectroscopy (TRLFS) optical techniques can permit on-line, real-time analysis of the actinide elements in a solvent extraction process. UV-Visible and TRLFS techniques have been used for measuring the speciation and concentration of the actinides under laboratory conditions. These methods are easily adaptable to multiple sampling geometries, such as dip probes, fiber-optic sample cells, and flow-through cell geometries. To fully exploit these techniques for GNEP applications, the fundamental speciation of the target actinides and the resulting influence on 3 spectroscopic properties must be determined. Through this effort detection limits, process conditions, and speciation of key actinide components can be establish and utilized in a range of areas of interest to GNEP, especially in areas related to materials accountability and process control.
Date: December 29, 2010
Creator: Czerwinski, Ken; Weck, Phil & Poineau, Frederic
Partner: UNT Libraries Government Documents Department

Search for promethium-like gold lines and other transitions of interest to fusion research

Description: EUV spectra in the range lambda = 13 to 40 rm were measured for foil-excited gold ions at 31 to 238 MeV. Data was recorded at the higher energies to extend and to complement previous measurements and at the lowest energy to see if the recently predicted 5s - 5p resonance lines in the Pm-like ion, Au XIX, could be seen in beam-foil excitation. The experimental results are presented, previous beam-foil measurements are reviewed, and the contributions and relations to fusion research are discussed.
Date: January 1, 1981
Creator: Johnson, B.M.; Jones, K.W.; Kruse, T.H.; Curtis, L.J. & Ellis, D.G.
Partner: UNT Libraries Government Documents Department

Initial development of efficient, low-debris laser targets for the Sandia soft x-ray projection lithography effort

Description: During the fiscal years 92-94 a joint group from Sandia/New Mexico and Sandia/California studied the development of new laser-plasma targets for projection x-ray or EUV (extreme ultraviolet) lithography. Our experimental and theoretical analyses incorporated target design as an integral part of the lithographic optical system. Targets studied included thick solid targets, thin-foil metal-coated targets, and cryogenic targets. Our complete measurement suite consisted of x-ray conversion efficiency measurements, source size imaging, source x-ray angular distribution measurements, debris collection, and source EUV spectrum. Target evaluation also included the variation of laser characteristics, such as, laser intensity, spot size, wavelength, pulselength, and pulseshape. Over the course of these experiments we examined targets using KrF (248nm), XeCl (308nm), and CO{sub 2} (10.6 {mu}m) lasers. While debris issues now dominate research in this area, final details were concluded on our understanding of material spectra and radiation transport of 13 run light in laser-plasmas. Additionally, conclusive results were obtained with 308 rim light, showing the pulselength threshold below which plumes no longer limited the transmission of (and thus the conversion efficiency to) 13 nm radiation.
Date: March 1, 1997
Creator: Rockett, P.D.; Hunter, J.A. & Kubiak, G.D.
Partner: UNT Libraries Government Documents Department