Sample records for 10sup minus11 cmsup

  1. Physics at 10/sup 34/ cm/sup -2/ s/sup -1/

    SciTech Connect

    Diebold, R.; Wagner, R.


    Most of the detector studies at Snowmass-84 have rightfully concentrated on detailed studies of individual interactions - their rates, signatures, and backgrounds. Depending on the physics and the detector components, there seems to be agreement that general-purpose detectors will likely be able to accept luminosities up to 10/sup 32 -33/ cm/sup -2/ s/sup -1/. The purpose of this paper is to show how the physics reach of the SSC is extended by going to a luminosity of 10/sup 34/ cm/sup -2/ s/sup -1/, to take a first look at what sort of detector could be used at this luminosity, and to discuss how one might trigger on interesting events in the presence of many overlapping minimum bias events. We will assume that the SSC turns on at 10/sup 31/ or 10/sup 32/ cm/sup -2/ s/sup -1/, with an increase of luminosity to 10/sup 33/ over a period of a few years as the machine and detectors become better understood. Thus, the lower mass scale will have been explored and we can set our thresholds high when running 10/sup 34/.

  2. Pattern recognition in the GEM central tracker at luminosity of 10{sup 33} cm{sup {minus}2}s{sup {minus}1}

    SciTech Connect

    Brooks, M.L.; Kinnison, W.W.


    A GEANT based pattern recognition algorithm has been developed for simulations of the GEM central tracker. We describe the pattern recognition algorithm and present the results of studies of the track finding efficiency for single isolated tracks and for all tracks present in a Higgs event with minimum bias background at luminosity 10{sup 33} cm{sup {minus}2}s{sup {minus}l}.

  3. Ultrahigh B doping ({<=}10{sup 22} cm{sup -3}) during Si(001) gas-source molecular-beam epitaxy: B incorporation, electrical activation, and hole transport

    SciTech Connect

    Glass, G.; Kim, H.; Desjardins, P.; Taylor, N.; Spila, T.; Lu, Q.; Greene, J. E.


    Si(001) layers doped with B concentrations C{sub B} between 1x10{sup 17} and 1.2x10{sup 22} cm{sup -3} (24 at %) were grown on Si(001)2x1 at temperatures T{sub s}=500-850 degree sign C by gas-source molecular-beam epitaxy from Si{sub 2}H{sub 6} and B{sub 2}H{sub 6}. C{sub B} increases linearly with the incident precursor flux ratio J{sub B{sub 2}}{sub H{sub 6}}/J{sub Si{sub 2}}{sub H{sub 6}} and B is incorporated into substitutional electrically active sites at concentrations up to C{sub B}{sup *}(T{sub s}) which, for T{sub s}=600 degree sign C, is 2.5x10{sup 20} cm{sup -3}. At higher B concentrations, C{sub B} increases faster than J{sub B{sub 2}}{sub H{sub 6}}/J{sub Si{sub 2}}{sub H{sub 6}} and there is a large and discontinuous decrease in the activated fraction of incorporated B. However, the total activated B concentration continues to increase and reaches a value of N{sub B}=1.3x10{sup 21} cm{sup -3} with C{sub B}=1.2x10{sup 22} cm{sup -3}. High-resolution x-ray diffraction (HR-XRD) and reciprocal space mapping measurements show that all films, irrespective of C{sub B} and T{sub s}, are fully strained. No B precipitates or misfit dislocations were detected by HR-XRD or transmission electron microscopy. The lattice constant in the film growth direction a{sub (perpendicular} {sub sign)} decreases linearly with increasing C{sub B} up to the limit of full electrical activation and continues to decrease, but nonlinearly, with C{sub B}>C{sub B}{sup *}. Room-temperature resistivity and conductivity mobility values are in good agreement with theoretical values for B concentrations up to C{sub B}=2.5x10{sup 20} and 2x10{sup 21} cm{sup -3}, respectively. All results can be explained on the basis of a model which accounts for strong B surface segregation to the second-layer with a saturation coverage {theta}{sub B,sat} of 0.5 ML (corresponding to C{sub B}=C{sub B}{sup *}). At higher C{sub B} (i.e., {theta}{sub B}>{theta}{sub B,sat}), B accumulates in the upper layer as

  4. Composite fermions in 2 x 10{sup 6} cm{sup 2}/Vs mobility A1GaAs/GaAs heterostructures grown by MOCVD

    SciTech Connect

    Simmons, J.A., Chui, H.C., Harff, N.E., Hammons, B.E.; Du, R.R., Zudov, M.A.


    Recent growth by MOCVD (metalorganic chemical vapor deposition) of 2.0x10{sup 6} cm{sup 2}/Vs mobility heterostructures are reported. These mobilities, the highest reported to date, are attributed to use of tertiarybutylarsine as the arsenic precursor. Measurements in tilted magnetic fields of the fractional quantum Hall effect states near filling factor 3/2 are consistent with a spin-split composite fermion (CF) model proposed earlier. Extracted values of the product of the CF g-factor and CF effective mass agree with values previously obtained for MBE samples.

  5. Pattern recognition and tracker resolutions for the GEM central tracker at luminosity of 10{sup 34} cm{sup {minus}2}s{sup {minus}1}

    SciTech Connect

    Brooks, M.L.


    A GEANT based pattern recognition algorithm has been used to study the track finding capabilities of the GEM central tracker at high luminosity (10{sup 34} cm{sup {minus}2}s{sup {minus}1}). The efficiency for finding tracks has been studied as a function of the number of silicon layers present in the tracker, as a function of the resolution of the pad chambers, as a function of the efficiency of the pad chambers, and as a function of eta and p{sub T} for each of the above studies. The number of {open_quotes}fake{close_quotes} tracks that are found with the pattern recognition has also been calculated for each pattern recognition study.

  6. Measurements of Energy Transport Patterns in Solid Density Laser Plasma Interactions at Intensities of 5x10{sup 20} W cm{sup -2}

    SciTech Connect

    Lancaster, K. L.; Clarke, R. J.; Green, J. S.; Murphy, C. D.; Norreys, P. A.; Hey, D. S.; Akli, K. U.; Davies, J. R.; Habara, H.; Nakatsutsumi, M.; Yabuuchi, T.; Key, M. H.; Kodama, R.; Krushelnick, K.; Simpson, P.; Zepf, M.; Stephens, R.; Stoeckl, C.


    K{sub {alpha}} x-ray emission, extreme ultraviolet emission, and plasma imaging techniques have been used to diagnose energy transport patterns in copper foils ranging in thickness from 5 to 75 {mu}m for intensities up to 5x10{sup 20} W cm{sup -2}. The K{sub {alpha}} emission and shadowgrams both indicate a larger divergence angle than that reported in the literature at lower intensities [R. Stephens et al., Phys. Rev. E 69, 066414 (2004)]. Foils 5 {mu}m thick show triple-humped plasma expansion patterns at the back and front surfaces. Hybrid code modeling shows that this can be attributed to an increase in the mean energy of the fast electrons emitted at large radii, which only have sufficient energy to form a plasma in such thin targets.

  7. Quantum Coherence between Two Atoms beyond Q=10{sup 15}

    SciTech Connect

    Chou, C. W.; Hume, D. B.; Thorpe, M. J.; Wineland, D. J.; Rosenband, T.


    We place two atoms in quantum superposition states and observe coherent phase evolution for 3.4x10{sup 15} cycles. Correlation signals from the two atoms yield information about their relative phase even after the probe radiation has decohered. This technique allowed a frequency comparison of two {sup 27}Al{sup +} ions with fractional uncertainty 3.7{sub -0.8}{sup +1.0}x10{sup -16}/{radical}({tau}/s). Two measures of the Q factor are reported: The Q factor derived from quantum coherence is 3.4{sub -1.1}{sup +2.4}x10{sup 16}, and the spectroscopic Q factor for a Ramsey time of 3 s is 6.7x10{sup 15}. We demonstrate a method to detect the individual quantum states of two Al{sup +} ions in a Mg{sup +}-Al{sup +}-Al{sup +} linear ion chain without spatially resolving the ions.

  8. PROCESS OF PRODUCING Cm$sup 244$ AND Cm$sup 24$$sup 5$


    Manning, W.M.; Studier, M.H.; Diamond, H.; Fields, P.R.


    A process is presented for producing Cm and Cm/sup 245/. The first step of the process consists in subjecting Pu/sup 2339/ to a high neutron flux and subsequently dissolving the irradiated material in HCl. The plutonium is then oxidized to at least the tetravalent state and the solution is contacted with an anion exchange resin, causing the plutonium values to be absorbed while the fission products and transplutonium elements remain in the effluent solution. The effluent solution is then contacted with a cation exchange resin causing the transplutonium, values to be absorbed while the fission products remain in solution. The cation exchange resin is then contacted with an aqueous citrate solution and tbe transplutonium elements are thereby differentially eluted in order of decreasing atomic weight, allowing collection of the desired fractions.

  9. Composite fermions in 2 {times} 10{sup 6} cm{sup 2}/Vs mobility AlGaAs/GaAs heterostructures grown by MOCVD

    SciTech Connect

    Simmons, J.A.; Chui, H.C.; Harff, N.E.; Hammons, B.E.; Du, R.R.; Zudov, M.A.


    The authors report on the recent growth by MOCVD of 2.0 {times} 106 cm2/Vs mobility heterostructures. These mobilities, the highest reported to date, are attributed to the use of tertiarybutylarsine as the arsenic precursor. Measurements in tilted magnetic fields of the fractional quantum Hall effect (FQHE) states near filling factor 3/2 are consistent with a spin-split composite fermion (CF) model proposed earlier. The extracted values of the product of the CF g-factor and CF effective mass agree with values previously obtained for MBE samples.

  10. Primordial black holes with mass 10{sup 16}−10{sup 17} g and reionization of the Universe

    SciTech Connect

    Belotsky, K.M.; Kirillov, A.A. E-mail:


    Primordial black holes (PBHs) with mass 10{sup 16}−10{sup 17} g almost escape constraints from observations so could essentially contribute to dark matter density. Hawking evaporation of such PBHs produces with a steady rate γ- and e{sup ±}-radiations in MeV energy range, which can be absorbed by ordinary matter. Simplified estimates show that a small fraction of evaporated energy had to be absorbed by baryonic matter what can turn out to be enough to heat the matter so it is fully ionized at the redshift z∼ 5... 10. The result is found to be close to a borderline case where the effect appears, what makes it sensitive to the approximation used. In our approximation, degree of gas ionization reaches 50-100% by z∼ 5 for PBH mass (3...7)× 10{sup 16} g with their abundance corresponding to the upper limit.

  11. Electron mobility exceeding 160 000 cm{sup 2}/V s in AlGaN/GaN heterostructures grown by molecular-beam epitaxy

    SciTech Connect

    Manfra, M.J.; Baldwin, K.W.; Sergent, A.M.; West, K.W.; Molnar, R.J.; Caissie, J.


    We report on the transport properties of a two-dimensional electron gas (2DEG) confined in an AlGaN/GaN heterostructure grown by plasma-assisted molecular-beam epitaxy on a semi-insulating GaN template prepared by hydride vapor phase epitaxy with a threading dislocation density of {approx}5x10{sup 7} cm{sup -2}. Using a gated Hall bar structure, the electron density (n{sub e}) is varied from 4.1 to 9.1x10{sup 11} cm{sup -2}. At T=300 mK, the 2DEG displays a maximum mobility of 167 000 cm{sup 2}/V s at a sheet density of 9.1x10{sup 11} cm{sup -2}, corresponding to a mean-free-path of {approx}3 {mu}m. Shubnikov-de Haas oscillations, typically not observed at magnetic fields below 2 T in GaN, commence at B=0.6 T.


    SciTech Connect

    Cheng, K.-S.; Chernyshov, D. O.; Dogiel, V. A.; Ko, C.-M.; Wang, Y.; Ip, W.-H.


    The Fermi Large Area Telescope has recently discovered two giant gamma-ray bubbles that extend north and south of the Galactic center with diameters and heights of the order of H {approx} 10 kpc. We suggest that the periodic star capture processes by the Galactic supermassive black hole Sgr A*, with a capture rate of {tau}{sup -1}{sub cap} {approx} 3 Multiplication-Sign 10{sup -5} yr{sup -1} and an energy release of W {approx} 3 Multiplication-Sign 10{sup 52} erg per capture, can result in hot plasma injecting into the Galactic halo at a wind velocity of u {approx} 10{sup 8} cm s{sup -1}. The periodic injection of hot plasma can produce a series of shocks. Energetic protons in the bubble are re-accelerated when they interact with these shocks. We show that for energy larger than E > 10{sup 15} eV, the acceleration process can be better described by the stochastic second-order Fermi acceleration. We propose that hadronic cosmic rays (CRs) within the 'knee' of the observed CR spectrum are produced by Galactic supernova remnants distributed in the Galactic disk. Re-acceleration of these particles in the Fermi Bubble produces CRs beyond the knee. With a mean CR diffusion coefficient in this energy range in the bubble D{sub B} {approx} 3 Multiplication-Sign 10{sup 30} cm{sup 2} s{sup -1}, we can reproduce the spectral index of the spectrum beyond the knee and within it. The conversion efficiency from shock energy of the bubble into CR energy is about 10%. This model provides a natural explanation of the observed CR flux, spectral indices, and matching of spectra at the knee.

  13. A technique for extending by ∼10{sup 3} the dynamic range of compact proton spectrometers for diagnosing ICF implosions on the National Ignition Facility and OMEGA

    SciTech Connect

    Sio, H. Séguin, F. H.; Frenje, J. A.; Gatu Johnson, M.; Zylstra, A. B.; Rinderknecht, H. G.; Rosenberg, M. J.; Li, C. K.; Petrasso, R. D.


    Wedge Range Filter (WRF) proton spectrometers are routinely used on OMEGA and the NIF for diagnosing ρR and ρR asymmetries in direct- and indirect-drive implosions of D{sup 3}He-, D{sub 2}-, and DT-gas-filled capsules. By measuring the optical opacity distribution in CR-39 due to proton tracks in high-yield applications, as opposed to counting individual tracks, WRF dynamic range can be extended by 10{sup 2} for obtaining the spectral shape, and by 10{sup 3} for mean energy (ρR) measurement, corresponding to proton fluences of 10{sup 8} and 10{sup 9} cm{sup −2}, respectively. Using this new technique, ρR asymmetries can be measured during both shock and compression burn (proton yield ∼10{sup 8} and ∼10{sup 12}, respectively) in 2-shock National Ignition Facility implosions with the standard WRF accuracy of ±∼10 mg/cm{sup 2}.

  14. The All-Particle Spectrum of Primary Cosmic Rays in the Wide Energy Range from 10{sup 14} to 10{sup 17} eV Observed with the Tibet-III Air-Shower Array

    SciTech Connect

    Amenomori, M.; Bi, X. J.; Ding, L. K.; Feng, Zhaoyang; He, H. H.; Hu, H. B.; Chen, D.; Cui, S. W.; Danzengluobu; Ding, X. H.; Guo, H. W.; Hu, Haibing; Fan, C.; Feng, C. F.; He, M.; Feng, Z. Y.; Gao, X. Y.; Geng, Q. X.; Hibino, K.; Hotta, N.


    We present an updated all-particle energy spectrum of primary cosmic rays in a wide range from 10{sup 14} to 10{sup 17} eV using 5.5 x 10{sup 7} events collected from 2000 November through 2004 October by the Tibet-III air-shower array located 4300 m above sea level (an atmospheric depth of 606 g cm{sup -2}). The size spectrum exhibits a sharp knee at a corresponding primary energy around 4 PeV. This work uses increased statistics and new simulation calculations for the analysis. We discuss our extensive Monte Carlo calculations and the model dependencies involved in the final result, assuming interaction models QGSJET01c and SIBYLL2.1, and heavy dominant (HD) and proton dominant (PD) primary composition models. Pure proton and pure iron primary models are also examined as extreme cases. A detector simulation was also performed to improve our accuracy in determining the size of the air showers and the energy of the primary particle. We confirmed that the all-particle energy spectra obtained under various plausible model parameters are not significantly different from each other, which was the expected result given the characteristics of the experiment at high altitude, where the air showers of the primary energy around the knee reach near-maximum development, with their features dominated by electromagnetic components, leading to a weak dependence on the interaction model or the primary mass. This is the highest statistical and the best systematics-controlled measurement covering the widest energy range around the knee energy region.

  15. Acceptances for space-based and ground-based fluorescence detectors, and inference of the neutrino-nucleon cross-section above 10{sup 19} eV

    SciTech Connect

    Palomares-Ruiz, Sergio; Irimia, Andrei; Weiler, Thomas J.


    Detection of ultrahigh energy neutrinos will be useful for unraveling the dynamics of the most violent sources in the cosmos and for revealing the neutrino cross-section at extreme energy. If there exists a Greisen-Zatsepin-Kuz'min (GZK) suppression of cosmic-ray events above E{sub GZK}{approx}5x10{sup 19} eV, as predicted by theory, then the only messengers of energies beyond E{sub GZK} are neutrinos. Cosmic neutrino fluxes can initiate air-showers through interaction in the atmosphere, or in the Earth. Neutrino trajectories will be downgoing to nearly horizontal in the former case, and 'Earth-skimming' in the latter case. Thus it is important to know the acceptances (event rate/flux) of proposed air-shower experiments for detecting both types of neutrino-initiated events. We calculate these acceptances for fluorescence detectors, both space-based as with the EUSO and OWL proposals, and ground-based, as with Auger, HiRes and Telescope Array. The neutrino cross-section {sigma}{sub {nu}}{sub N}{sup CC} is unknown at energies above 5.2x10{sup 13} eV. Although the popular QCD extrapolation of lower-energy physics offers the cross-section value of 0.54x10{sup -31}(E{sub {nu}}/10{sup 20} eV){sup 0.36} cm{sup 2}, new physics could raise or lower this value. Therefore, we present the acceptances of horizontal (HAS) and upgoing (UAS) air-showers as a function of {sigma}{sub {nu}}{sub N}{sup CC} over the range 10{sup -34} to 10{sup -30} cm{sup 2}. The dependences of acceptances on neutrino energy, shower-threshold energy, shower length, and shower column density are also studied. We introduce a cloud layer, and study its effect on rates as viewed from space and from the ground. For UAS, we present acceptances for events over land (rock), and over the ocean (water). Acceptances over water are larger by about an order of magnitude, thus favoring space-based detectors. We revisit the idea of Kusenko and Weiler [Phys. Rev. Lett. 88, 161101 (2002)] to infer {sigma}{sub {nu

  16. CO/H{sub 2} abundance ratio ≈ 10{sup –4} in a protoplanetary disk

    SciTech Connect

    France, Kevin; McJunkin, Matthew; Herczeg, Gregory J.; Penton, Steven V.


    The relative abundances of atomic and molecular species in planet-forming disks around young stars provide important constraints on photochemical disk models and provide a baseline for calculating disk masses from measurements of trace species. A knowledge of absolute abundances, those relative to molecular hydrogen (H{sub 2}), are challenging because of the weak rovibrational transition ladder of H{sub 2} and the inability to spatially resolve different emission components within the circumstellar environment. To address both of these issues, we present new contemporaneous measurements of CO and H{sub 2} absorption through the 'warm molecular layer' of the protoplanetary disk around the Classical T Tauri Star RW Aurigae A. We use a newly commissioned observing mode of the Hubble Space Telescope Cosmic Origins Spectrograph to detect warm H{sub 2} absorption in this region for the first time. An analysis of the emission and absorption spectrum of RW Aur shows components from the accretion region near the stellar photosphere, the molecular disk, and several outflow components. The warm H{sub 2} and CO absorption lines are consistent with a disk origin. We model the 1092-1117 Å spectrum of RW Aur to derive log{sub 10} N(H{sub 2}) = 19.90{sub −0.22}{sup +0.33} cm{sup –2} at T {sub rot}(H{sub 2}) = 440 ± 39 K. The CO A - X bands observed from 1410 to 1520 Å are best fit by log{sub 10} N(CO) = 16.1 {sub −0.5}{sup +0.3} cm{sup –2} at T {sub rot}(CO) = 200{sub −125}{sup +650} K. Combining direct measurements of the H I, H{sub 2}, and CO column densities, we find a molecular fraction in the warm disk surface of f {sub H2} ≥ 0.47 and derive a molecular abundance ratio of CO/H{sub 2} = 1.6{sub −1.3}{sup +4.7} × 10{sup –4}, both consistent with canonical interstellar dense cloud values.

  17. A technique for extending by ~10<sup>3 the dynamic range of compact proton spectrometers for diagnosing ICF implosions on the National Ignition Facility and OMEGAa)

    SciTech Connect

    Sio, H.; Séguin, F. H.; Frenje, J. A.; Gatu Johnson, M.; Zylstra, A. B.; Rinderknecht, H. G.; Rosenberg, M. J.; Li, C. K.; Petrasso, R. D.


    Wedge Range Filter (WRF) proton spectrometers are routinely used on OMEGA and the NIF for diagnosing ρR and ρR asymmetries in direct- and indirect-drive implosions of D3He-, D2-, and DT-gas-filled capsules. By measuring the optical opacity distribution in CR-39 due to proton tracks in high-yield applications, as opposed to counting individual tracks, WRF dynamic range can be extended by 10<sup>2 for obtaining the spectral shape, and by 10<sup>3 for mean energy (ρR) measurement, corresponding to proton fluences of 10<sup>8 and 10<sup>9 cm>-2, respectively. Finally, using this new technique, ρR asymmetries can be measured during both shock and compression burn (proton yield ~10<sup>8 and ~10<sup>12, respectively) in 2-shock National Ignition Facility implosions with the standard WRF accuracy of ±~10 mg/cm2.

  18. Thermonuclear flashes in the envelopes of accreting hot neutron stars. II. M = 10/sup 16/, 10/sup 18/ g/sec

    SciTech Connect

    Kudryashov, A.D.; Ergma, V.


    The results of calculations of the accretion of matter and the subsequent flash at the surface of a hot neutron star for accretion rates of 10/sup 16/< or =M< or =10/sup 18/ g/sec are presented. It is found that a helium layer is formed for M< or approx. =M/sub c//sub r/approx. =4x10/sup 16/ g/sec. Hydrogen--helium flashes occur for M>M/sub c//sub r/. The connection between the different types of flashes and the observed properties of bursters and fast transients is discussed. The results are compared with observations of the burster XB 1608-522.

  19. Subpicosecond KrF{asterisk}-laser plasma interaction at intensities between 10{sup 14} and 10{sup 17} W/cm{sup 2}

    SciTech Connect

    Teubner, U.; Gibbon, P.; Foerster, E.; Fallies, F.; Audebert, P.; Geindre, J.P.; Gauthier, J.C.


    The interaction of high-intensity subpicosecond KrF{asterisk}-laser pulses with aluminium plasmas is investigated at intensities between 10{sup 14} and 10{sup 17} W/cm{sup 2}. Using a one-dimensional hydrocode, the laser energy absorption and time evolution of plasma parameters have been studied as a function of laser intensity, incidence angle, and polarization. Complementary particle-in-cell simulations have also been performed to check the collisionless absorption component carried by hot electrons and ions. These simulations are compared to previous experiments on laser pulse absorption and x-ray generation. {copyright} {ital 1996 American Institute of Physics.}

  20. Time distribution of EAS with E>10/sup 14/ eV

    SciTech Connect

    CHEN Ying-xuan; HE Chang-xiao; XIAO Qian-yi; WANG Li-xiang


    We have observed the arrival times of EAS initiated by cosmic rays of E>10/sup 14/ eV using the EAS array in Beijing. The distribution of arrival time intervals of EAS with E>2.6 x 10/sup 14/ eV is considerably higher than the exponential distribution in the region of time intervals t<21 second. It is suggested that a time correlation component is probably present in the EAS events.


    SciTech Connect

    Narayanan, Anand; Wakker, Bart P.; Savage, Blair D.; Keeney, Brian A.; Shull, J. Michael; Stocke, John T.; Sembach, Kenneth R. E-mail: wakker@astro.wisc.ed


    We present a clear detection of a broad Ly{alpha} absorber (BLA) with a matching O VI line in the nearby universe. The BLA is detected at z(Ly{alpha})=0.01028 in the high signal-to-noise ratio spectrum of Mrk 290 obtained using the Cosmic Origins Spectrograph. The Ly{alpha} absorption has two components, with b(H i) = 55{+-}1 km s{sup -1} and b(H i) = 33{+-}1 km s{sup -1}, separated in velocity by v {approx} 115 km s{sup -1}. The O VI, detected by the Far-Ultraviolet Spectroscopic Explorer at z(O vi) = 0.01027, has a b(O vi) = 29{+-}3 km s{sup -1} and is kinematically well aligned with the broader H I component. The non-detection of other ions such as C II, Si II, Fe II, C III, Si III, C IV, Si IV, and N V at the same velocity as the BLA and the O VI implies that the absorber is tracing highly ionized gas. The different line widths of the BLA and O VI suggest a temperature of T = 1.4 x 10{sup 5} K in the absorber. Photoionization, collisional ionization equilibrium as well as non-equilibrium collisional ionization models do not explain the ion ratios at this temperature. The observed line strength ratios and line widths favor an ionization scenario in which both ion-electron collisions and UV photons contribute to the ionization in the gas. Such a model requires a low metallicity of {approx}-1.7 dex, ionization parameter of log U {approx} -1.4, a large total hydrogen column density of N(H) {approx} 4 x 10{sup 19} cm{sup -2}, and a path length of {approx}400 kpc. The line of sight to Mrk 290 intercepts at the redshift of the absorber, a megaparsec scale filamentary structure extending over {approx}20{sup 0} in the sky, with several luminous galaxies distributed within {approx}1.5 h {sup -1} Mpc projected distance from the absorber. The collisionally ionized gas phase of this absorber is most likely tracing a shock-heated gaseous structure, consistent with a few different scenarios for the origin including an overdense region of the warm-hot intergalactic medium in

  2. Charmed meson physics accessible to an L = 10/sup 33/ cm/sup /minus/2/ sec/sup /minus/1/ e/sup +/e/sup /minus// collider operating near charm threshold

    SciTech Connect

    Schindler, R.H.


    In this report, the potential for dedicated charmed D/sup 0/, D/sup +/ and D/sub s/ meson physics in a high-luminosity e/sup +/e/sup /minus// collider operated near charm threshold is explored. The construction of such a high-luminosity collider or Tau-Charm Factory in conjunction with a new detector whose design draws heavily on the extensive operational experience of previous detectors at SPEAR, could achieve three orders-of-magnitude improvement in sensitivity in most areas of charmed meson studies. 27 refs., 10 figs., 9 tabs.

  3. An optical beam frequency reference with 10{sup -14} range frequency instability

    SciTech Connect

    McFerran, J. J.; Hartnett, J. G.; Luiten, A. N.


    The authors report on a thermal beam optical frequency reference with a fractional frequency instability of 9.2x10{sup -14} at 1 s reducing to 2.0x10{sup -14} at 64 s before slowly rising. The {sup 1}S{sub 0}{r_reversible}{sup 3}P{sub 1} intercombination line in neutral {sup 40}Ca is used as a frequency discriminator. A diode laser at 423 nm probes the ground state population after a Ramsey-Borde sequence of 657 nm light-field interactions on the atoms. The measured fractional frequency instability is an order of magnitude improvement on previously reported thermal beam optical clocks. The photon shot-noise of the read-out produces a limiting square root {lambda}-variance of 7x10{sup -14}/{radical}({tau})

  4. Single-qubit-gate error below 10{sup -4} in a trapped ion

    SciTech Connect

    Brown, K. R.; Wilson, A. C.; Colombe, Y.; Ospelkaus, C.; Meier, A. M.; Knill, E.; Leibfried, D.; Wineland, D. J.


    With a {sup 9}Be{sup +} trapped-ion hyperfine-state qubit, we demonstrate an error probability per randomized single-qubit gate of 2.0(2)x10{sup -5}, below the threshold estimate of 10{sup -4} commonly considered sufficient for fault-tolerant quantum computing. The {sup 9}Be{sup +} ion is trapped above a microfabricated surface-electrode ion trap and is manipulated with microwaves applied to a trap electrode. The achievement of low single-qubit-gate errors is an essential step toward the construction of a scalable quantum computer.

  5. Absorption-line detections of 10{sup 5}-10{sup 6} K gas in spiral-rich groups of galaxies

    SciTech Connect

    Stocke, John T.; Keeney, Brian A.; Danforth, Charles W.; Syphers, David; Yamamoto, H.; Shull, J. Michael; Green, James C.; Froning, Cynthia; Savage, Blair D.; Wakker, Bart; Kim, Tae-Sun; Ryan-Weber, Emma V.; Kacprzak, Glenn G.


    Using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, the COS Science Team has conducted a high signal-to-noise survey of 14 bright QSOs. In a previous paper, these far-UV spectra were used to discover 14 'warm' (T ≥ 10{sup 5} K) absorbers using a combination of broad Lyα and broad O VI absorptions. A reanalysis of a few of this new class of absorbers using slightly relaxed fitting criteria finds as many as 20 warm absorbers could be present in this sample. A shallow, wide spectroscopic galaxy redshift survey has been conducted around these sight lines to investigate the warm absorber environment, which is found to be spiral-rich groups or cluster outskirts with radial velocity dispersions σ = 250-750 km s{sup –1}. While 2σ evidence is presented favoring the hypothesis that these absorptions are associated with the galaxy groups and not with the individual, nearest galaxies, this evidence has considerable systematic uncertainties and is based on a small sample size so it is not entirely conclusive. If the associations are with galaxy groups, the observed frequency of warm absorbers (dN/dz = 3.5-5 per unit redshift) requires them to be very extended as an ensemble on the sky (∼1 Mpc in radius at high covering factor). Most likely these warm absorbers are interface gas clouds whose presence implies the existence of a hotter (T ∼ 10{sup 6.5} K), diffuse, and probably very massive (>10{sup 11} M {sub ☉}) intra-group medium which has yet to be detected directly.

  6. Fractional frequency instability in the 10{sup -14} range with a thermal beam optical frequency reference

    SciTech Connect

    McFerran, John J.; Luiten, Andre N.


    We demonstrate a means of increasing the signal-to-noise ratio in a Ramsey-Borde interferometer with spatially separated oscillatory fields on a thermal atomic beam. The {sup 1}S{sub 0}{r_reversible}{sup 3}P{sub 1} intercombination line in neutral {sup 40}Ca is used as a frequency discriminator, with an extended cavity diode laser at 423 nm probing the ground state population after a Ramsey-Borde sequence of 657 nm light-field interactions with the atoms. Evaluation of the instability of the Ca frequency reference is carried out by comparison with (i) a hydrogen-maser and (ii) a cryogenic sapphire oscillator. In the latter case the Ca reference exhibits a square-root {Lambda} variance of 9.2x10{sup -14} at 1 s and 2.0x10{sup -14} at 64 s. This is an order-of-magnitude improvement for optical beam frequency references, to our knowledge. The shot noise of the readout fluorescence produces a limiting square-root {Lambda} variance of 7x10{sup -14}/{radical}({tau}), highlighting the potential for improvement. This work demonstrates the feasibility of a portable frequency reference in the optical domain with 10{sup -14} range frequency instability.

  7. Mg dopant in Cu{sub 2}SnSe{sub 3}: An n-type former and a promoter of electrical mobility up to 387 cm{sup 2} V{sup −1} s{sup −1}

    SciTech Connect

    Kuo, Dong-Hau Wubet, Walelign


    Mg-doped Cu{sub 2}SnSe{sub 3} bulk materials with the (Cu{sub 2−x}Mg{sub x})SnSe{sub 3} (Mg-x-CTSe) formula at x=0, 0.05, 0.1, 0.15, and 0.2 were prepared at 550 °C for 2 h with soluble sintering aids of Sb{sub 2}S{sub 3} and Te. Defect chemistry was studied by measuring structural and electrical properties of Mg-doped Cu{sub 2}SnSe{sub 3} as a function of dopant concentration. Mg-x-CTSe pellets show p-type at x=0, 0.05 and 0.1 and n-type at x=0.15 and 0.2. The low hole concentration of 3.2×10{sup 17} cm{sup −3} and high mobility of 387 cm{sup 2} V{sup −1} s{sup −1} were obtained for (Cu{sub 2−x}Mg{sub x})SnSe{sub 3} bulks at x=0.1 (5% Mg) as compared to 2.2×10{sup 18} cm{sup −3} and 91 cm{sup 2} V{sup −1} s{sup −1} for the undoped one. The explanation based upon the Mg-to-Cu antisite donor defect for the changes in electrical property was declared. A high Mg content for Mg-x-CTSe at x≥0.1 can lead to the formation of second phases. The study in bulk Mg-x-CTSe has been based upon defect states and is consistent and supported by the data of structural and electrical properties. - Graphical abstract: The effects of extrinsic doping of Mg{sup 2+} on the electrical properties of Cu{sub 2}SnSe{sub 3} bulks. - Highlights: • p-Type Mg-CTSe with n{sub p} of 3.2×10{sup 17} cm{sup −3} and μ{sub p} of 387 cm{sup 2} V{sup −1} s{sup −1} was obtained. • This p-type occurred for 5%Mg-doped CTSe with the (Cu{sub 1.9}Mg{sub 0.1})SnSe{sub 3} formula. • Mg dopant acts as a donor to lower n{sub p} and an accelerator to increase mobility. • High Mg content leads to the p-to-n transitions. • Defect was explored by measuring electrical property and lattice parameter.


    SciTech Connect

    Jennings, Donald E.; Anderson, C. M.; Samuelson, R. E.; Flasar, F. M.; Nixon, C. A.; Bjoraker, G. L.; Romani, P. N.; Achterberg, R. K.; Cottini, V.; Hesman, B. E.; Kunde, V. G.; Carlson, R. C.; De Kok, R.; Coustenis, A.; Vinatier, S.; Bampasidis, G.; Teanby, N. A.; Calcutt, S. B.


    An emission feature at 220 cm{sup -1} which has been attributed to a cloud of condensed material in Titan's winter stratosphere has been seen for the first time in the south. This feature had previously been found only at high northern latitudes during northern winter and spring. The material emitting at 220 cm{sup -1}, as yet unidentified, may be volatiles associated with nitrile gases that accumulate in the absence of ultraviolet sunlight. Not detected as recently as 2012 February, the 220 cm{sup -1} feature clearly appeared at the south pole in Cassini spectra recorded on 2012 July 24, indicating a rapid onset of the emission. This is the first indication of the winter buildup of condensation in the southern stratosphere that has been expected as the south pole moves deeper into shadow. In the north the 220 cm{sup -1} feature continued to decrease in intensity with a half-life of 3 years.

  9. Lattice-Induced Frequency Shifts in Sr Optical Lattice Clocks at the 10{sup -17} Level

    SciTech Connect

    Westergaard, P. G.; Lodewyck, J.; Lecallier, A.; Millo, J.; Lemonde, P.; Lorini, L.; Burt, E. A.; Zawada, M.


    We present a comprehensive study of the frequency shifts associated with the lattice potential in a Sr lattice clock by comparing two such clocks with a frequency stability reaching 5x10{sup -17} after a 1 h integration time. We put the first experimental upper bound on the multipolar M1 and E2 interactions, significantly smaller than the recently predicted theoretical upper limit, and give a 30-fold improved upper limit on the effect of hyperpolarizability. Finally, we report on the first observation of the vector and tensor shifts in a Sr lattice clock. Combining these measurements, we show that all known lattice related perturbations will not affect the clock accuracy down to the 10{sup -17} level, even for lattices as deep as 150 recoil energies.

  10. {sup 87}Sr Lattice Clock with Inaccuracy below 10{sup -15}

    SciTech Connect

    Boyd, Martin M.; Ludlow, Andrew D.; Blatt, Sebastian; Foreman, Seth M.; Ido, Tetsuya; Zelevinsky, Tanya; Ye Jun


    Aided by ultrahigh resolution spectroscopy, the overall systematic uncertainty of the {sup 1}S{sub 0}-{sup 3}P{sub 0} clock resonance for lattice-confined {sup 87}Sr has been characterized to 9x10{sup -16}. This uncertainty is at a level similar to the Cs-fountain primary standard, while the potential stability for the lattice clocks exceeds that of Cs. The absolute frequency of the clock transition has been measured to be 429 228 004 229 874.0(1.1) Hz, where the 2.5x10{sup -15} fractional uncertainty represents the most accurate measurement of a neutral-atom-based optical transition frequency to date.

  11. Communication: Global minimum search of Ag{sub 10}{sup +} with molecular beam optical spectroscopy

    SciTech Connect

    Shayeghi, A. Schäfer, R.; Johnston, R. L.


    The present study is focused on the optical properties of the Ag{sub 10}{sup +} cluster in the photon energy range ℏω = 1.9–4.4 eV. Absorption spectra are recorded by longitudinal molecular beam depletion spectroscopy and compared to optical response calculations using time-dependent density functional theory. Several cluster isomers obtained by the new pool-based parallel implementation of the Birmingham Cluster Genetic Algorithm, coupled with density functional theory, are used in excited state calculations. The experimental observations, together with additional simulations of ion mobilities for the several geometries found within this work using different models, clearly identify the ground state isomer of Ag{sub 10}{sup +} to be composed of two orthogonal interpenetrating pentagonal bipyramids, having overall D{sub 2d} symmetry.

  12. Measurement of the magnetic moment of the 10{sup +} isomer in {sup 132}Ba

    SciTech Connect

    Harissopulos, S.; Gelberg, A.; Dewald, A.; Hass, M.; Weissman, L.; Broude, C.


    The magnetic moment of the 10{sup +} isomeric state of {sup 132}Ba at 3115 keV was measured as {ital g}={minus}0.156(11). A 60 MeV {sup 12}C beam from the Koffler Pelletron accelerator at the Weizmann Institute was used in the reaction {sup 124}Sn({sup 12}C,4{ital n}){sup 132}Ba. The measured {ital g} factor confirms the ({nu}{ital h}{sub 11/2}){sup {minus}2} configuration of the level. The result is compared with other {ital g} factors in neighboring {ital N}=76 isotones.

  13. The measurement of elemental abundances above 10 sup 15 eV at a lunar base

    SciTech Connect

    Swordy, S.P. )


    At {approx}10{sup 15} eV the slope of the energy spectrum of cosmic rays becomes significantly steeper than at lower energies. The measurement of relative elemental abundances at these energies is expected to provide a means to resolve the origin of this feature and greatly contribute to the understanding of the sources of cosmic rays. We describe a moon based detector for making well resolved elemental measurements at these energies using hadronic calorimetry. This detector is particularly well suited for a site on the lunar surface because there is no overlying layer of atmosphere and the large mass required can be provided by the lunar regolith.

  14. A large-scale magnetic shield with 10{sup 6} damping at millihertz frequencies

    SciTech Connect

    Altarev, I.; Bales, M.; Fierlinger, K.; Fierlinger, P.; Kuchler, F.; Marino, M. G.; Niessen, B.; Petzoldt, G.; Singh, J. T.; Stoepler, R.; Stuiber, S.; Sturm, M.; Taubenheim, B.; Beck, D. H.; Chupp, T.; Lins, T.; Schläpfer, U.; Schnabel, A.; Voigt, J.


    We present a magnetically shielded environment with a damping factor larger than 1 × 10{sup 6} at the mHz frequency regime and an extremely low field and gradient over an extended volume. This extraordinary shielding performance represents an improvement of the state-of-the-art in the difficult regime of damping very low-frequency distortions by more than an order of magnitude. This technology enables a new generation of high-precision measurements in fundamental physics and metrology, including searches for new physics far beyond the reach of accelerator-based experiments. We discuss the technical realization of the shield with its improvements in design.

  15. Calcium optical frequency standard with ultracold atoms: Approaching 10{sup -15} relative uncertainty

    SciTech Connect

    Degenhardt, Carsten; Stoehr, Hardo; Lisdat, Christian; Wilpers, Guido; Schnatz, Harald; Lipphardt, Burghard; Nazarova, Tatiana; Pottie, Paul-Eric; Sterr, Uwe; Helmcke, Juergen; Riehle, Fritz


    An optical frequency standard based on an ensemble of neutral calcium atoms laser-cooled to 12 {mu}K has been realized. By using ultracold atoms, one major previous source of uncertainty, the residual Doppler effect, was reduced. We show that cold collisions contribute a negligible amount to the uncertainty. The influence of a temporal evolution of the phase of the laser pulses used to interrogate the clock transition was measured and corrected for. The frequency of the clock transition at 657 nm was referenced to the caesium fountain clock of PTB utilizing a femtosecond comb generator with a fractional uncertainty of 1.2x10{sup -14}. The transition frequency was determined to be (455 986 240 494 144{+-}5.3) Hz, making the calcium clock transition one of the most accurately known optical transitions. A frequency stability of 3x10{sup -15} at 100 s averaging time was achieved and the noise contributions that limit to the observed stability were analyzed in detail. Additionally, the natural linewidth of the clock transition has been determined.

  16. Measurement of the composition and energy spectrum of cosmic rays above 10 sup 15 eV

    SciTech Connect

    Berley, D. ); Ellsworth, R.W. )


    The availability of a launch vehicle with the capability of carrying a heavy payload, would make possible several definitive experiments including: (1) the determination of the composition and energy spectrum of cosmic rays up to 10{sup 12} electron volts (eV) (2) the observation of gamma rays from compact sources, up to energies of 10{sup 12} eV. The instrument proposed, weighing about 30 tons, is designed to address these fundamental questions.

  17. High contrast ion acceleration at intensities exceeding 10{sup 21} Wcm{sup −2}

    SciTech Connect

    Dollar, F.; Zulick, C.; Matsuoka, T.; McGuffey, C.; Bulanov, S. S.; Chvykov, V.; Kalinchenko, G.; Willingale, L.; Yanovsky, V.; Maksimchuk, A.; Thomas, A. G. R.; Krushelnick, K.; Davis, J.; Petrov, G. M.


    Ion acceleration from short pulse laser interactions at intensities of 2×10{sup 21}Wcm{sup −2} was studied experimentally under a wide variety of parameters, including laser contrast, incidence angle, and target thickness. Trends in maximum proton energy were observed, as well as evidence of improvement in the acceleration gradients by using dual plasma mirrors over traditional pulse cleaning techniques. Extremely high efficiency acceleration gradients were produced, accelerating both the contaminant layer and high charge state ions from the bulk of the target. Two dimensional particle-in-cell simulations enabled the study of the influence of scale length on submicron targets, where hydrodynamic expansion affects the rear surface as well as the front. Experimental evidence of larger electric fields for sharp density plasmas is observed in simulation results as well for such targets, where target ions are accelerated without the need for contaminant removal.

  18. The success story at Birchwood: Operation below 0.10 lb/10{sup 6} Btu

    SciTech Connect

    Cohen, M.B.


    The Southern Energy, Inc. (SEI) Birchwood Power Facility is successfully operating on coal maintaining stack NO{sub x} emissions below 0.10 lb/10{sup 6} Btu (73 ppmvd at 3% O{sub 2}, 43 ng/J) on a 30-day rolling average. The cogeneration plant uses an integrated approach for controlling NO{sub x} including in-furnace reduction from a TFS 2000{trademark} firing system and post-combustion control from selective catalytic reduction (SCR). The plant began operation in November 1996, and continues to meet the State of Virginia's stringent environmental requirements under all operating conditions. This paper focuses upon recent performance and operation of the NO{sub x} control technologies. Operational data of the NO{sub x} emissions from the steam generator as well as those exiting the SCR are presented. In addition, the latest information from the Spring '99 outage is discussed.

  19. A search for. mu. yields e. gamma. at the level of 10 sup minus 13

    SciTech Connect

    Amann, J.F.; Black, K.; Bolton, R.D.; Carius, S.; Cooper, M.D.; Foreman, W.; Hansen, C.; Harrison, R.; Hart, G.; Hart, V.; Hoffman, C.M.; Hoffman, N.; Hunter, T.; Hogan, G.E.; June, N.; Kercher, D.; Little, J.; Kozlowski, T.; Mischke, R.E.; Naivar, F.J.; Novak, J.; Oothoudt, M.A.; Pillai, C.; Schilling, S.; Smith, W.; Stanislaus, S.; Sturrock, J.; Szymanski, J.; Van Dyke, J.; Werbeck, R.D.; Whitehouse, D.; Wilkinson, C. (Los A


    The status of the MEGA experiment is described. It is a search for the decay {mu} {r arrow} e{gamma} with a branching ratio sensitivity of approximately 10{sup {minus}13}. The observation of this decay would indicate the existence of physics outside the standard model of electroweak interactions. The experiment employs highly modular, fast detectors, state-of-the-art electronics, and a staged trigger with on-line filters. The detectors are contained in a 1.5 T solenoidal field produced by a superconducting magnet. Positrons are confined to the central region and are measured by a set of thin MWPCs. Photons are measured by one of four layers of pair spectrometers in the outer region. Most aspects of the detector design have been validated in engineering runs; data taking will begin in 1990 with most of the electron arm and one pair spectrometer layer installed. 5 refs., 4 figs.

  20. Beyond y and μ: the shape of the CMB spectral distortions in the intermediate epoch, 1.5 × 10{sup 4}∼10{sup 5}

    SciTech Connect

    Khatri, Rishi; Sunyaev, Rashid A. E-mail:


    We calculate numerical solutions and analytic approximations for the intermediate-type spectral distortions. Detection of a μ-type distortion (saturated comptonization) in the CMB will constrain the time of energy injection to be at a redshift 2 × 10{sup 6}∼>z∼>2 × 10{sup 5}, while a detection of a y-type distortion (minimal comptonization) will mean that there was heating of CMB at redshift z∼<1.5 × 10{sup 4}. We point out that the partially comptonized spectral distortions, generated in the redshift range 1.5 × 10{sup 4}∼10{sup 5}, are much richer in information than the pure y and μ-type distortions. The spectrum created during this period is intermediate between y and μ-type distortions and depends sensitively on the redshift of energy injection. These intermediate-type distortions cannot be mimicked by a mixture of y and μ-type distortions at all frequencies and vice versa. The measurement of these intermediate-type CMB spectral distortions has the possibility to constrain precisely not only the amount of energy release in the early Universe but also the mechanism, for example, particle annihilation and Silk damping can be distinguished from particle decay. The intermediate-type distortion templates and software code using these templates to calculate the CMB spectral distortions for user-defined energy injection rate is made publicly available.

  1. Frequency Stability of 1X10(sup -13) in a compensated Saphirre Oscillator Operating Above 77K

    NASA Technical Reports Server (NTRS)

    Dick, G. John; Santiago, David G.; Wang, Rabi T.


    We report on tests of a compensated saphirre oscillator (CS) which shows frequency-stable operation at temperatures above 77k.The frequency stability for this oscillator shows an apparent flicker floor of 7.5X10(sup -14) for measuring times between 3 and 10 seconds, and stability is better than 2X10(sup -13) for all measuring times between 10 and 100 seconds... Frequency sensitivities os the microwave sapphire resonator to temperature and temperature rate have been characterized, and a careful analysis of several aspects of the ac frequency-lock.

  2. Ultra-high brightness (10 sup 21 W/cm sup 2 ) laser facility

    SciTech Connect

    Perry, M.D.; Campbell, E.M.; Hunt, J.T.; Keane, C.; Szoke, A. ); Mourou, G.; Bado, P.; Maine, P. )


    New short-pulse laser technology has made possible the production of extremely bright laser sources. The use of these new techniques on large scale Nd:Glass based laser systems would make it possible to produce 1000 TW (Petawatt) pulses. Such pulses would yield focused intensities exceeding 10{sup 21}W/cm{sup 2} corresponding to an electric field in excess of 100 e/a{sub 0}{sup 2} and an energy density equivalent to that of a 10 keV blackbody. Such a source would have important applications in x-ray laser research and lead to a fundamentally new class of experiments in atomic, nuclear, solid state, plasma and high-energy density physics. Such a facility could be constructed with existing chirped-pulse'' technology. A one-year period of research addressing outstanding technical questions can extend the technology resulting in a more compact and cost effective design. For this reason, we are seeking a Director's Initiative grant in the amount of $590,000 for FY89 to investigate these issues. An equivalent amount in personnel and facilities would be provided by Y-Division. The study will include development of a chirped-pulse'' front-end capable of producing laser pulses of 2 J at 1.053 {mu}m with a 1 psec pulsewidth laser. Upon completion, this front-end will be installed on the Nova laser system in order to investigate propagation and compression issues associated with amplification of a chirped-pulse. Our goal is to demonstrate the production of 100 TW pulses using a portion of a Nova beamline.

  3. Systematic study of Rayleigh-Taylor growth in directly driven plastic targets in a laser-intensity range from {approx}2x10{sup 14} to {approx}1.5x10{sup 15} W/cm{sup 2}

    SciTech Connect

    Smalyuk, V. A.; Hu, S. X.; Goncharov, V. N.; Meyerhofer, D. D.; Sangster, T. C.; Stoeckl, C.; Yaakobi, B.


    Direct-drive, Rayleigh-Taylor (RT) growth experiments were performed using planar plastic targets on the OMEGA Laser Facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] at laser intensities between {approx}2x10{sup 14} and {approx}1.5x10{sup 15} W/cm{sup 2}. The primary purpose of the experiments was to test fundamental physics in hydrocodes at the range of drive intensities relevant to ignition designs. The target acceleration was measured with a streak camera using side-on, x-ray radiography, while RT growth was measured with a framing camera using face-on radiography. In a laser-intensity range from 2 to 5x10{sup 14} W/cm{sup 2}, the measured RT growth agrees well with two-dimensional simulations, based on a local model of thermal-electron transport. The RT growth at drive intensities above {approx}1.0x10{sup 15} W/cm{sup 2} was strongly stabilized compared to the local model predictions. The experiments demonstrate that standard simulations, based on a local model of electron thermal transport, break down at peak intensities of ignition designs, although they work well at lower intensities. These results also imply that direct-drive ignition targets are significantly more stable than previously calculated using local electron-transport models at peak intensities of ignition designs. The preheating effects by nonlocal electron transport and hot electrons were identified as some of the stabilizing mechanisms.

  4. Search for discrete gamma-ray sources emitting at energies greater than 10/sup 15/ eV

    SciTech Connect

    Samorski, M.; Stamm, W.


    The data of the extensive air shower experiment at Kiel have been scanned systematically for possible discrete ..gamma..-ray sources in the energy range E>10/sup 15/ eV and in the declination band delta = 25/sup 0/-75/sup 0/. Photon fluxes for celestial positions with the statistically most significant excesses of showers and 3 sigma upper limit photon fluxes for COS B ..gamma..-ray sources visible to the extensive air shower experiment at Kiel are presented.

  5. A technique for the measurement of electron attachment to short-lived excited species

    SciTech Connect

    Christophorou, L.G.; Pinnaduwage, L.A. ); Bitouni, A.P. . Dept. of Physics)


    A technique is described for the measurement of electron attachment to short-lived ({approx lt}10{sup {minus}9} s) excited species. Preliminary results are presented for photoenhanced electron attachment to short-lived electronically-excited states of triethylamine molecules produced by laser two-photon excitation. The attachment cross sections for these excited states are estimated to be >10{sup {minus}11} cm{sup 2} and are {approximately}10{sup 7} larger compared to those for the unexcited (ground-state) molecules. 8 refs., 4 figs.

  6. Searching for a correlation between cosmic-ray sources above 10{sup 19} eV and large scale structure

    SciTech Connect

    Kashti, Tamar; Waxman, Eli E-mail:


    We study the anisotropy signature which is expected if the sources of ultrahigh energy, >10{sup 19} eV, cosmic rays (UHECRs) are extra-galactic and trace the large scale distribution of luminous matter. Using the PSCz galaxy catalog as a tracer of the large scale structure (LSS), we derive the expected all sky angular distribution of the UHECR intensity. We define a statistic that measures the correlation between the predicted and observed UHECR arrival direction distributions, and show that it is more sensitive to the expected anisotropy signature than the power spectrum and the two-point correlation function. The distribution of the correlation statistic is not sensitive to the unknown redshift evolution of UHECR source density and to the unknown strength and structure of inter-galactic magnetic fields. We show, using this statistic, that recently published >5.7 Multiplication-Sign 10{sup 19} eV Auger data are inconsistent with isotropy at Asymptotically-Equal-To 98% CL, and consistent with a source distribution that traces LSS, with some preference for a source distribution that is biased with respect to the galaxy distribution. The anisotropy signature should be detectable also at lower energy, >4 Multiplication-Sign 10{sup 19} eV. A few-fold increase of the Auger exposure is likely to increase the significance to >99% CL, but not to>99.9% CL (unless the UHECR source density is comparable to or larger than that of galaxies). In order to distinguish between different bias models, the systematic uncertainty in the absolute energy calibration of the experiments should be reduced to well below the current Asymptotically-Equal-To 25%.

  7. Reducing SS 304/316 hydrogen outgassing to 2x10{sup -15} torr l/cm{sup 2} s

    SciTech Connect

    Sasaki, Y. Tito


    Significant reduction in the outgassing rate of 300-series stainless steel is routinely attained through combination of electropolishing and vacuum baking. Preferential removal of Ni, Fe, and Mn from the surface of stainless steel by electropolishing creates a chromium-enriched surface. It also reduces the atomic surface area of the work piece closer to its geometric surface area. When the material is vacuum fired to remove interstitial hydrogen, the resultant stainless steel exhibits an outgassing rate of about 2x10{sup -15} torr l/cm{sup 2} s, as well as drastically reduced adsorption, absorption, and catalytic behaviors.

  8. {sup 39}Ar Detection at the 10{sup -16} Isotopic Abundance Level with Atom Trap Trace Analysis

    SciTech Connect

    Jiang, W.; Williams, W.; Bailey, K.; O'Connor, T. P.; Mueller, P.; Davis, A. M.; Hu, S.-M.; Sun, Y. R.; Lu, Z.-T.; Purtschert, R.; Sturchio, N. C.


    Atom trap trace analysis, a laser-based atom counting method, has been applied to analyze atmospheric {sup 39}Ar (half-life=269 yr), a cosmogenic isotope with an isotopic abundance of 8x10{sup -16}. In addition to the superior selectivity demonstrated in this work, the counting rate and efficiency of atom trap trace analysis have been improved by 2 orders of magnitude over prior results. The significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.

  9. A review of the use of Al-alloy vacuum components for operation at 10 sup minus 13 Torr

    SciTech Connect

    Ishimaru, H. )


    An extremely high vacuum (XHV) chamber was fabricated and tested. The vacuum chamber was made of special surface finished (EX-process) aluminum alloy in oxygen and argon atmosphere. The chamber was assembled using TIG welding in an argon atmosphere and by electron beam welding. The system was evacuated with a turbo-backed 300 l/s turbomolecular pump separated from the main chamber using a right angle valve. The liquid nitrogen shroud is installed inside the main vacuum chamber. The XHV is maintained by two 300 l/s sputter ion pumps and a titanium sublimation pump with a liquid nitrogen shroud. These pumps are also made of aluminum alloys. An ultimate pressure of 3{times}10{sup {minus}13} Torr was measured with a point collector gauge with a spherical anode mounted on an Al-flange. Residual gas analysis in the order 10{sup {minus}13} Torr was performed by a newly developed Q-mass filter. To suppress outgassing from the quadrupole electrode, the ion source is mounted on an Al-flange separated from the quadrupole electrode.

  10. Comparison of aperture determinations on RHIC for single particles tracked 10{sup 6} turns and 100 particles, having randomly generated initial coordinates, tracked for 1000 turns

    SciTech Connect

    Dell, G.F.


    Aperture determinations from 100 particles tracked for 1000 turns using randomly selected initial coordinates are compared with results from 10{sup 6} turn runs when initial coordinates are defined by {epsilon}{sub x} = {epsilon}{sub y} and X{sub i}{prime} = Y{sub i}{prime} = 0. Measurements were made with ten distributions of magnetic field errors. The results from tracking 100 particles for 10{sup 3} turns are equivalent to those from 10{sup 6} turn runs, have a distribution of considerably less width, and require only one tenth the computer time.

  11. Comparison of aperture determinations on RHIC for single particles tracked 10[sup 6] turns and 100 particles, having randomly generated initial coordinates, tracked for 1000 turns

    SciTech Connect

    Dell, G.F.


    Aperture determinations from 100 particles tracked for 1000 turns using randomly selected initial coordinates are compared with results from 10[sup 6] turn runs when initial coordinates are defined by [epsilon][sub x] = [epsilon][sub y] and X[sub i][prime] = Y[sub i][prime] = 0. Measurements were made with ten distributions of magnetic field errors. The results from tracking 100 particles for 10[sup 3] turns are equivalent to those from 10[sup 6] turn runs, have a distribution of considerably less width, and require only one tenth the computer time.

  12. Astrophysical and structural peculiarities of extensive air showers with energy E{sub 0} {>=} 10{sup 17} eV from Yakutsk EAS array data

    SciTech Connect

    Glushkov, A. V. Pravdin, M. I.


    The astrophysical characteristics of primary cosmic rays (PCRs) and the structure of extensive air showers (EASs) with energy E{sub 0} {>=} 10{sup 17} eV are simultaneously analyzed using the Yakutsk EAS array data acquired in the period 1974-2005. Enhanced and reduced particle fluxes are shown to come from the disk of the Supergalaxy (the Local Supercluster of galaxies) at E{sub 0} {>=} 5 x 10{sup 18} eV and E{sub 0} {<=} (2-3) x 10{sup 18}, respectively. The development of air showers with E{sub 0} {>=} (3-5) x 10{sup 18} eV differs significantly from that at lower energies. This is interpreted as a manifestation of the possible interaction between extragalactic PCRs and the matter of this spatial structure.

  13. Biological effectiveness on live cells of laser driven protons at dose rates exceeding 10{sup 9} Gy/s

    SciTech Connect

    Doria, D.; Kakolee, K. F.; Kar, S.; Litt, S. K.; Ahmed, H.; Lewis, C. L.; Nersisyan, G.; Prasad, R.; Zepf, M.; Borghesi, M.; Fiorini, F.; Kirby, D.; Green, S.; Jeynes, J. C. G.; Kirkby, K. J.; Merchant, M. J.; Kavanagh, J.; Prise, K. M.; Schettino, G.


    The ultrashort duration of laser-driven multi-MeV ion bursts offers the possibility of radiobiological studies at extremely high dose rates. Employing the TARANIS Terawatt laser at Queen's University, the effect of proton irradiation at MeV-range energies on live cells has been investigated at dose rates exceeding 10{sup 9} Gy/s as a single exposure. A clonogenic assay showed consistent lethal effects on V-79 live cells, which, even at these dose rates, appear to be in line with previously published results employing conventional sources. A Relative Biological Effectiveness (RBE) of 1.4{+-}0.2 at 10% survival is estimated from a comparison with a 225 kVp X-ray source.

  14. HEAP---An instrument to measure the elemental abundances above 10 sup 15 eV at a lunar base

    SciTech Connect

    Swordy, S.P. )


    At {approx}10{sup 15} eV the slope of the energy spectrum of cosmic rays becomes significantly steeper than at lower energies. The measurement of relative elemental abundances at these energies is expected to provide a means to resolve the origin of this feature and greatly contribute to the understanding of the sources of cosmic rays at high energies. We describe a moon based detector, HEAP, for making well-resolved elemental measurements at these energies using hadronic calorimetry. This detector is particularly well suited for a site on the lunar surface because there is no overlying layer of atmosphere and the large mass required can be provided by the lunar regolith.

  15. Large transverse momenta in nuclear interaction at E{sub 0} > 10{sup 16} eV detected in stratosphere

    SciTech Connect

    Managadze, A. K. Osedlo, V. I.; Roganova, T. M.; Sveshnikova, L. G.; Galkin, V. I.; Rakobolskaya, I. V.; Goncharova, L. A.; Kotelnikov, K. A.; Polukhina, N. G.


    A gamma-hadron superfamily of cosmic-rays created by a primary cosmic-ray particle with energy above 10{sup 16} eV was detected at an altitude of 30 km by a stratospheric balloon-borne emulsion chamber. Being of superhigh energy, this event is the unique example in the world statistics of practically pure nuclear interactions in the energy range unattainable for modern accelerators. The present analysis allowed one to estimate the interaction height above the chamber and transverse momenta of the secondaries produced in the interaction. The mean value of transverse momenta appears to be very large ( > 2.5 GeV/c)

  16. Spectral content of buried Ag foils at 10{sup 16} W/cm{sup 2} laser illumination

    SciTech Connect

    Huntington, C. M. Maddox, B. R.; Park, H.-S.; Prisbrey, S.; Remington, B. A.


    Sources of 5–12 keV thermal Heα x-rays are readily generated by laser irradiation of mid-Z foils at intensities >10{sup 14} W/cm{sup 2}, and are widely used as probes for inertial confinement fusion and high-energy-density experiments. Higher energy 17–50 keV x-ray sources are efficiently produced from “cold” Kα emission using short pulse, petawatt lasers at intensities >10{sup 18} W/cm{sup 2} [H.-S. Park, B. R. Maddox et al., “High-resolution 17–75 keV backlighters for high energy density experiments,” Phys. Plasmas 15(7), 072705 (2008); B. R. Maddox, H. S. Park, B. A. Remington et al., “Absolute measurements of x-ray backlighter sources at energies above 10 keV,” Phys. Plasmas 18(5), 056709 (2011)]. However, when long pulse (>1 ns) lasers are used with Z > 30 elements, the spectrum contains contributions from both K shell transitions and from ionized atomic states. Here we show that by sandwiching a silver foil between layers of high-density carbon, the ratio of Kα:Heα in the x-ray spectrum is significant increased over directly illuminated Ag foils, with narrower lines from K-shell transitions. Additionally, the emission volume is more localized for the sandwiched target, producing a more planar x-ray sheet. This technique may be useful for generating probes requiring spectral purity and a limited spatial extent, for example, in incoherent x-ray Thomson scattering experiments.

  17. High accuracy {sup 18}O(p,{alpha}){sup 15}N reaction rate in the 8{center_dot}10{sup 6}-5{center_dot}10{sup 9} K temperature range

    SciTech Connect

    La Cognata, M.; Spitaleri, C.; Cherubini, S.; Crucilla, V.; Gulino, M.; Kiss, G. G.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Rapisarda, G. G.; Romano, S.; Sergi, M. L.; Mukhamedzhanov, A.; Banu, A.; Goldberg, V.; Tabacaru, G.; Trache, L.; Tribble, R. E.; Coc, A.


    The {sup 18}O(p,{alpha}){sup 15}N reaction is of great importance in several astrophysical scenarios, as it influences the production of key isotopes such as {sup 19}F, {sup 18}O and {sup 15}N. In this work, a high accuracy {sup 18}O(p,{alpha}){sup 15}N reaction rate is proposed, based on the simultaneous fit of direct measurements and of the results of a new Trojan Horse experiment. In particular, we have focused on the study of the broad 660 keV 1/2{sup +} resonance. Since {Gamma}{approx}100-300 keV, it strongly influences the nearly-zero-energy region of the cross section by means of the low-energy tail of the resonant contribution and dominates the cross section at higher energies. Here we provide a factor of 2 larger reaction rate above T{approx}0.5 10{sup 9} K based over our new improved determination of its resonance parameters.

  18. A 10{sup 10} solar mass flow of molecular gas in the A1835 brightest cluster galaxy

    SciTech Connect

    McNamara, B. R.; Russell, H. R.; Main, R. A.; Vantyghem, A. N.; Kirkpatrick, C. C.; Nulsen, P. E. J.; Edge, A. C.; Murray, N. W.; Hamer, S.; Combes, F.; Salome, P.; Fabian, A. C.; Baum, S. A.; O'Dea, C. P.; Bregman, J. N.; Donahue, M.; Voit, G. M.; Egami, E.; Oonk, J. B. R.; Tremblay, G.


    We report ALMA Early Science observations of the A1835 brightest cluster galaxy (BCG) in the CO (3-2) and CO (1-0) emission lines. We detect 5 × 10{sup 10} M {sub ☉} of molecular gas within 10 kpc of the BCG. Its ensemble velocity profile width of ∼130 km s{sup –1} FWHM is too narrow for the molecular clouds to be supported in the galaxy by dynamic pressure. The gas may instead be supported in a rotating, turbulent disk oriented nearly face-on. Roughly 10{sup 10} M {sub ☉} of molecular gas is projected 3-10 kpc to the northwest and to the east of the nucleus with line-of-sight velocities lying between –250 km s{sup –1} and +480 km s{sup –1} with respect to the systemic velocity. The high-velocity gas may be either inflowing or outflowing. However, the absence of high-velocity gas toward the nucleus that would be expected in a steady inflow, and its bipolar distribution on either side of the nucleus, are more naturally explained as outflow. Star formation and radiation from the active galactic nucleus (AGN) are both incapable of driving an outflow of this magnitude. The location of the high-velocity gas projected behind buoyantly rising X-ray cavities and favorable energetics suggest an outflow driven by the radio AGN. If so, the molecular outflow may be associated with a hot outflow on larger scales reported by Kirkpatrick and colleagues. The molecular gas flow rate of approximately 200 M {sub ☉} yr{sup –1} is comparable to the star formation rate of 100-180 M {sub ☉} yr{sup –1} in the central disk. How radio bubbles would lift dense molecular gas in their updrafts, how much gas will be lost to the BCG, and how much will return to fuel future star formation and AGN activity are poorly understood. Our results imply that radio-mechanical (radio-mode) feedback not only heats hot atmospheres surrounding elliptical galaxies and BCGs, but it is able to sweep higher density molecular gas away from their centers.

  19. A compact, robust, and transportable ultra-stable laser with a fractional frequency instability of 1 × 10{sup −15}

    SciTech Connect

    Chen, Qun-Feng; Nevsky, Alexander; Cardace, Marco; Schiller, Stephan; Legero, Thomas; Häfner, Sebastian; Uhde, Andre; Sterr, Uwe


    We present a compact and robust transportable ultra-stable laser system with minimum fractional frequency instability of 1 × 10{sup −15} at integration times between 1 and 10 s. The system was conceived as a prototype of a subsystem of a microwave-optical local oscillator to be used on the satellite mission Space-Time Explorer and QUantum Equivalence Principle Space Test (STE-QUEST) ( ). It was therefore designed to be compact, to sustain accelerations occurring during rocket launch, to exhibit low vibration sensitivity, and to reach a low frequency instability. Overall dimensions of the optical system are 40 cm × 20 cm × 30 cm. The acceleration sensitivities of the optical frequency in the three directions were measured to be 1.7 × 10{sup −11}/g, 8.0 × 10{sup −11}/g, and 3.9 × 10{sup −10}/g, and the absolute frequency instability was determined via a three-cornered hat measurement. Two additional cavity-stabilized lasers were used for this purpose, one of which had an instability σ{sub y} < 4 × 10{sup −16} at 1 s integration time. The design is also appropriate and useful for terrestrial applications.

  20. Scaling Time Warp-based Discrete Event Execution to 10<sup>4 Processors on Blue Gene Supercomputer

    SciTech Connect

    Perumalla, Kalyan S


    Lately, important large-scale simulation applications, such as emergency/event planning and response, are emerging that are based on discrete event models. The applications are characterized by their scale (several millions of simulated entities), their fine-grained nature of computation (microseconds per event), and their highly dynamic inter-entity event interactions. The desired scale and speed together call for highly scalable parallel discrete event simulation (PDES) engines. However, few such parallel engines have been designed or tested on platforms with thousands of processors. Here an overview is given of a unique PDES engine that has been designed to support Time Warp-style optimistic parallel execution as well as a more generalized mixed, optimistic-conservative synchronization. The engine is designed to run on massively parallel architectures with minimal overheads. A performance study of the engine is presented, including the first results to date of PDES benchmarks demonstrating scalability to as many as 16,384 processors, on an IBM Blue Gene supercomputer. The results show, for the first time, the promise of effectively sustaining very large scale discrete event execution on up to 10<sup>4 processors.

  1. Proton emission from thin hydrogenated targets irradiated by laser pulses at 10{sup 16} W/cm{sup 2}

    SciTech Connect

    Torrisi, L.; Giuffrida, L.; Cirrone, P.; Cutroneo, M.; Picciotto, A.; Krasa, J.; Margarone, D.; Velyhan, A.; Laska, L.; Ullschmied, J.; Wolowski, J.; Badziak, J.; Rosinski, M.


    The iodine laser at PALS Laboratory in Prague, operating at 1315 nm fundamental harmonics and at 300 ps FWHM pulse length, is employed to irradiate thin hydrogenated targets placed in vacuum at intensities on the order of 10{sup 16} W/cm{sup 2}. The laser-generated plasma is investigated in terms of proton and ion emission in the forward and backward directions. The time-of-flight technique, using ion collectors and semiconductor detectors, is used to measure the ion currents and the corresponding velocities and energies. Thomson parabola spectrometer is employed to separate the contribution of the ion emission from single laser shots. A particular attention is given to the proton production in terms of the maximum energy, emission yield, and angular distribution as a function of the laser energy, focal position, target thickness, and composition. Metallic and polymeric targets allow to generate protons with large energy range and different yield, depending on the laser, target composition, and target geometry properties.


    SciTech Connect

    Abreu, P.; Andringa, S.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muniz, J.; Alves Batista, R.; Ambrosio, M.; Aramo, C.; Aminaei, A.; Anchordoqui, L.; Antici'c, T.; Arganda, E.; Collaboration: Pierre Auger Collaboration; and others


    A thorough search for large-scale anisotropies in the distribution of arrival directions of cosmic rays detected above 10{sup 18} eV at the Pierre Auger Observatory is presented. This search is performed as a function of both declination and right ascension in several energy ranges above 10{sup 18} eV, and reported in terms of dipolar and quadrupolar coefficients. Within the systematic uncertainties, no significant deviation from isotropy is revealed. Assuming that any cosmic-ray anisotropy is dominated by dipole and quadrupole moments in this energy range, upper limits on their amplitudes are derived. These upper limits allow us to test the origin of cosmic rays above 10{sup 18} eV from stationary Galactic sources densely distributed in the Galactic disk and predominantly emitting light particles in all directions.

  3. Energy Spectrum and Anisotropy of Cosmic Rays with E{sub 0} {>=} 10{sup 17} eV from Yakutsk EAS Array Data

    SciTech Connect

    Glushkov, A.V.; Pravdin, M.I.


    Data from the Yakutsk extensive air shower array for the period 1974-2004 are used to analyze the energy spectrum and anisotropy of primary cosmic rays (PCRs) with energy E{sub 0} {>=} 10{sup 17} eV. The spectra from different regions of the sky are shown to differ in shape. Enhanced and reduced particle fluxes come from the disks of the Galaxy and the Supergalaxy (the Local Supercluster of galaxies) at E{sub 0} {>=} 5 x 10{sup 18} eV and E{sub 0} {<=} (2-3) x 10{sup 18} eV, respectively. This is interpreted as a manifestation of the possible interaction between extragalactic PCRs and the matter of these spatial structures.

  4. TRAC-PF1/MOD1 calculations and data comparisons for MIST (Multi-Loop Integral System Test) small-break loss-of-coolant accidents with scaled 10 cm/sup 2/ and 50 cm/sup 2/ breaks

    SciTech Connect

    Steiner, J.L.; Siebe, D.A.; Boyack, B.E.


    Los Alamos National Laboratory is a participant in the Integral System Test (IST) program initiated in June 1983 for the purpose of providing integral system test data on specific issues/phenomena relevant to post-small-break loss-of-coolant accidents (SBLOCAs), loss of feedwater and other transients in Babcock and Wilcox (B and W) plant designs. The Multi-Loop Integral System Test (MIST) facility is the largest single component in the IST program. MIST is a 2 x 4 (2 hot legs and steam generators, 4 cold legs and reactor-coolant pumps) representation of lowered-loop reactor systems of the B and W design. It is a full-height, full-pressure facility with 1/817 power and volume scaling. Two other experimental facilities are included in the IST program: test loops at the University of Maryland, College Park, and at Stanford Research Institute. The objective of the IST tests is to generate high-quality experimental data to be used for assessing thermal-hydraulic safety computer codes. Efforts are underway at Los Alamos to assess TRAC-PF1/MOD1 against data from each of the IST facilities. Calculations and data comparisons for TRAC-PF1/MOD1 assessment have been completed for two transients run in the MIST facility. These are the MIST nominal test. Test 3109AA, a scaled 10 cm/sup 2/ SBLOCA and Test 320201, a scaled 50 cm/sup 2/ SBLOCA. Only MIST assessment results are presented in this paper.

  5. Peculiarities of the anisotropy of cosmic rays with E{sub 0} {>=} 10{sup 19} eV from Yakutsk EAS array data

    SciTech Connect

    Glushkov, A. V.


    The arrival directions of primary cosmic ray particles with energies E{sub 0} {>=} 10{sup 19} eV and zenith angles {theta} {<=} 60{sup o} recorded on the Yakutsk array over the period 1974-2009 are analyzed. These events separated by different time intervals are shown to have different global anisotropies.

  6. Local anisotropy of cosmic rays with E{sub 0} {>=} 10{sup 17} eV from Yakutsk EAS array data

    SciTech Connect

    Glushkov, A. V.


    The arrival directions of primary cosmic ray particles with energies E{sub 0} {>=} 10{sup 17} eV and zenith angles {theta} {<=} 60{sup o} recorded on the Yakutsk array over the period 1974-2009 are analyzed. These events are shown to have different anisotropies in different energy ranges.

  7. Measurement of the cosmic ray spectrum above 4×10<sup>18 eV using inclined events detected with the Pierre Auger Observatory

    SciTech Connect

    Aab, Alexander


    A measurement of the cosmic-ray spectrum for energies exceeding 4×10<sup>18 eV is presented, which is based on the analysis of showers with zenith angles greater than 60° detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above 5.3×10<sup>18 eV, the ``ankle'', the flux can be described by a power law E–γ with index γ=2.70 ± 0.02 (stat) ± 0.1 (sys) followed by a smooth suppression region. For the energy (Es) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find Es=(5.12±0.25 (stat)+1.0–1.2 (sys))×10<sup>19 eV.

  8. Spectroscopic line parameters of water vapor for rotation-vibration transitions near 7180 cm{sup -1}

    SciTech Connect

    Lisak, D.; Havey, D. K.; Hodges, J. T.


    We present low uncertainty measurements of line parameters for 15 rotation-vibration transitions of water vapor in the wave number range of 7170.27-7183.02 cm{sup -1}. These experiments incorporated frequency-stabilized cavity ring-down spectroscopy and a primary standard humidity generator which produced a stable and accurately known amount of water vapor in a nitrogen carrier gas stream. Intensities and line shape factors were derived by fitting high-resolution spectra to spectral models that account for collisional narrowing and speed-dependent broadening and shifting effects. For most transitions reported here, we estimate the relative combined standard uncertainty of the line intensities to be <0.4%, of which approximately one half this value we ascribe to limited knowledge of the line shape. Our measured intensities and broadening parameters are compared to experimental and theoretical literature values. Agreement between our experimental intensity measurements and those derived by recent ab initio calculations of the dipole moment surface of water vapor is within 1.5%.

  9. Time-resolved photoluminescence of undoped InP

    SciTech Connect

    Keyes, B.M.; Dunlavy, D.J.; Ahrenkiel, R.K. ); Shaw, G.; Summers, G.P. ); Tzafaras, N.; Lentz, C. )


    Energy and time-resolved photoluminescence data have been obtained for nominally undoped ([ital n] 4.5[times]10[sup 15] cm[sup [minus]3]) bulk InP grown by the vertical-gradient freeze method. The data were taken as a function of temperature, from 80 to 290 K, and analyzed using a solution to the continuity equation. The resulting lifetime values range from 300 ns to 3.2 [mu]s, and surface recombination velocities were fund to be on the order of 10[sup 3] cm/s. The temperature dependence can be explained by assuming a radiatively limited recombination with a resulting [ital B] coefficient [ge]5.9[times]10[sup [minus]11] cm[sup 3]/s at 300 K.


    SciTech Connect

    Abreu, P.; Andringa, S.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Castillo, J. Alvarez; Alvarez-Muniz, J.; Alves Batista, R.; Ambrosio, M.; Aramo, C.; Aminaei, A.; Anchordoqui, L.; Antici'c, T.; Arganda, E.; Collaboration: Pierre Auger Collaboration; and others


    A thorough search for large-scale anisotropies in the distribution of arrival directions of cosmic rays detected above 10{sup 18} eV at the Pierre Auger Observatory is reported. For the first time, these large-scale anisotropy searches are performed as a function of both the right ascension and the declination and expressed in terms of dipole and quadrupole moments. Within the systematic uncertainties, no significant deviation from isotropy is revealed. Upper limits on dipole and quadrupole amplitudes are derived under the hypothesis that any cosmic ray anisotropy is dominated by such moments in this energy range. These upper limits provide constraints on the production of cosmic rays above 10{sup 18} eV, since they allow us to challenge an origin from stationary galactic sources densely distributed in the galactic disk and emitting predominantly light particles in all directions.

  11. Gamma-ray emission in near critical density plasmas at laser intensities of 10{sup 21 }W/cm{sup 2}

    SciTech Connect

    Wang, H. Y.; Liu, B.; Yan, X. Q.; Zepf, M.


    We study synchrotron radiation emission from laser interaction with near critical density (NCD) plasmas at intensities of 10{sup 21 }W∕cm{sup 2} using three-dimensional particle-in-cell simulations. It is found that the electron dynamics depend on the laser shaping process in NCD plasmas, and thus the angular distribution of the emitted photons changes as the laser pulse evolves in space and time. The final properties of the resulting synchrotron radiation, such as its overall energy, the critical photon energy, and the radiation angular distribution, are strongly affected by the laser polarization and plasma density. By using a 420 TW∕50 fs laser pulse at the optimal plasma density (∼1n{sub c}), about 10{sup 8} photons/0.1% bandwidth are produced at multi-MeV photon energies, providing a route to ultraintense, femtosecond gamma ray pulses.

  12. Resonantly-enhanced, four-photon ionization of krypton at laser intensities exceeding 10/sup 13/ W/cm/sup 2/

    SciTech Connect

    Perry, M.D.; Landen, O.L.; Campbell, E.M.


    The yield of singly- and multiply- charged ions of krypton and xenon is presented as a function of laser intensity and frequency. The measurements were performed using the second harmonic output of a well-characterized, tunable picosecond dye laser in the range 285 to 310 nm at laser intensities from 1 x 10/sup 12/ to 10/sup 14/ W/cm/sup 2/. Enhancement of the Kr/sup +/ yield by two orders of magnitude by three-photon resonant, four-photon ionization is observed in the vicinity of the 4d'(5/2)/sub 3/ and the 4d(3/2)/sub 1/ intermediate states. A model incorporating line shifts and widths scaling linearly with intensity is in good agreement with the experimental results.

  13. Modulation of over 10{sup 14} cm{sup −2} electrons in SrTiO{sub 3}/GdTiO{sub 3} heterostructures

    SciTech Connect

    Boucherit, M.; Shoron, O.; Polchinski, C.; Jackson, C. A.; Cain, T. A.; Buffon, M. L. C.; Stemmer, S.; Rajan, S.


    We demonstrate charge modulation of over 10{sup 14} cm{sup −2} electrons in a two-dimensional electron gas formed in SrTiO{sub 3}/GdTiO{sub 3} inverted heterostructure field-effect transistors. Increased charge modulation was achieved by reducing the effect of interfacial region capacitances through thick SrTiO{sub 3} cap layers. Transport and device characteristics of the heterostructure field-effect transistors were found to match a long channel field effect transistor model. SrTiO{sub 3} impurity doped metal–semiconductor field effect transistors were also demonstrated with excellent pinch-off and current density exceeding prior reports. The work reported here provides a path towards oxide-based electronics with extreme charge modulation exceeding 10{sup 14} cm{sup −2}.

  14. Design considerations and initial performance of a 1.2 cm{sup 2} beta imaging intra-operative probe

    SciTech Connect

    Tornai, M.P.; MacDonald, L.R.; Levin, C.S.; Siegel, S.; Hoffman, E.J.


    A novel small area beta ({beta}{sup {+-}}) detector is under development for nuclear emission imaging of surgically exposed, radiolabeled tumor beds. The imaging device front-end consists of a 0.5 mm thick by 1.25 cm diameter CaF{sub 2}(Eu) scintillator disk coupled to a rapid bundle of 2 mm diameter double clad optical fibers through a polystyrene light diffuser. The detector area (1.2 cm{sup 2}) was determined by the requirement of introducing the probe into small cavities, e.g. during neuro-surgical lesion resection, but large enough to produce images of clinical significance. Flexible back-end optical fibers (1.9 m long) were coupled to the front-end components allowing {approximately} 75 photoelectrons to e detected for mean beta energies of 250 keV, indicating that sufficient signal can be obtained with clinical beta emitters (e.g. {sup 18}F, {sup 131}I). The long flexible fibers guide the scintillation light to a Philips XP1700 series, fiber optical faceplate, Multi-Channel PMT. The parallel MC-PMT outputs re fed into a variable gain, charge divider network and an i-V pre-amplifier/line driver network, whose resulting four outputs are digitized and histogrammed with standard Anger positioning logic. The various components in the imaging chain were evaluated and optimized by both simulations and measurements. Line spread functions measured in the 10.8 mm FOV were 0.50 mm {+-} 0.038 mm and 0.55 mm {+-} 0.065 mm FWHM in X and Y, respectively. A 20% variation in pulse height and minimal variation in spatial resolution was observed. The differential image uniformity was measured to be {+-}15.6% with {approximately} 150 cts/pixel. Preliminary images show excellent reproduction of phantom activity distributions.

  15. Investigation of broadening and shift of vapour absorption lines of H{sub 2}{sup 16}O in the frequency range 7184 – 7186 cm{sup -1}

    SciTech Connect

    Nadezhdinskii, A I; Pereslavtseva, A A; Ponurovskii, Ya Ya


    We present the results of investigation of water vapour absorption spectra in the 7184 – 7186 cm{sup -1} range that is of particular interest from the viewpoint of possible application of the data obtained for monitoring water vapour in the Earth's stratosphere. The doublet of H{sub 2}{sup 16}O near ν = 7185.596 cm{sup -1} is analysed. The coefficients of broadening and shift of water vapour lines are found in the selected range in mixtures with buffer gases and compared to those obtained by other authors. (laser spectroscopy)

  16. L-shell emission from high-Z solid targets by intense 10{sup 19}W/cm{sup 2} irradiation with a 248nm laser

    SciTech Connect

    Nelson, T.R.; Borisov, A.B.; Boyer, K.


    Efficient (1.2% yield) multikilovolt x-ray emission from Ba(L) (2.4--2.8{angstrom}) and Gd(L) (1.7--2.1{angstrom}) is produced by ultraviolet (248nm) laser-excited BaF{sub 2} and Gd solids. The high efficiency is attributed to an inner shell-selective collisional electron ejection. Much effort has been expended recently in attempts to develop an efficient coherent x-ray source suitable for high-resolution biological imaging. To this end, many experiments have been performed studying the x-ray emissions from high-Z materials under intense (>10{sup 18}W/cm{sup 2}) irradiation, with the most promising results coming from the irradiation of Xe clusters with a UV (248nm) laser at intensities of 10{sup 18}--10{sup 19}W/cm{sup 2}. In this paper the authors report the production of prompt x-rays with energies in excess of 5keV with efficiencies on the order of 1% as a result of intense irradiation of BaF{sub 2} and Gd targets with a terawatt 248nm laser. The efficiency is attributed to an inner shell-selective collisional electron ejection mechanism in which the previously photoionized electrons are ponderomotively driven into an ion while retaining a portion of their atomic phase and symmetry. This partial coherence of the laser-driven electrons has a pronounced effect on the collisional cross-section for the electron ion interaction.

  17. On the temperature dependence of collisional linewidths of the 10{sup 0}0 - 00{sup 0}1 laser transition in the CO{sub 2} molecule

    SciTech Connect

    Arshinov, Konstantin I; Arshinov, M K; Nevdakh, Vladimir V


    Unsaturated absorption coefficients in pure carbon dioxide and CO{sub 2} - N{sub 2} and CO{sub 2} - He binary mixtures are measured at a pressure of 100 Torr in the temperature range of 300-700 K using a frequency-stabilised tunable CO{sub 2} laser. The relative coefficients of collisional broadening caused by N{sub 2} and He buffer gases and their temperature dependence are determined for the R(22) absorption line (10{sup 0}0 - 00{sup 0}1 transition) of the CO{sub 2} molecule. (active media)


    SciTech Connect

    Krolik, Julian H.; Piran, Tsvi E-mail:


    We propose that the remarkable object Swift J1644+57, in which multiple recurring hard X-ray flares were seen over a span of several days, is a system in which a white dwarf was tidally disrupted by an intermediate-mass black hole. Disruption of a white dwarf rather than a main-sequence star offers a number of advantages in understanding the multiple, and short, timescales seen in the light curve of this system. In particular, the short internal dynamical timescale of a white dwarf offers a more natural way of understanding the short rise times ({approx}100 s) observed. The relatively long intervals between flares ({approx}5 Multiplication-Sign 10{sup 4} s) may also be readily understood as the period between successive pericenter passages of the remnant white dwarf. In addition, the expected jet power is larger when a white dwarf is disrupted. If this model is correct, the black hole responsible must have a mass {approx}< 10{sup 5} M{sub Sun }.

  19. Effect of strain rates from 10/sup -2/ to 10 sec/sup -1/ in triaxial compression tests on three rocks

    SciTech Connect

    Blanton, T.L.


    Room-temperature, compression tests at strain rates from 10/sup -2/ to 10 sec/sup -1/ have been run on Charcoal Granodiorite to 0.45 GPa confining pressure and on Berea Sandstone and Indiana Limestone to 0.25 GPa confining pressure. For each rock at each confining pressure, the differential stress at failure is relatively constant up to a strain rate of 1 sec/sup -1/ and apparently increases abruptly above this strain rate. Dynamic analysis of the testing apparatus indicates that the apparent sudden increase in strength is due to machine inertia and does not reflect a real increase in the strength of the rocks. Taking inertia into account, the actual failure stresses of the three rocks are relatively independent of strain rate betweeen 10/sup -2/ and 10 sec/sup -1/. In the same interval, the strains at which the unconfined rocks begin to fragment tend to be lower at higher strain rates. The combination of decreasing strains and relatively constant stresses with increasing strain rate suggests that the energy necessary to fragment the unconfined rocks is lower at higher strain rates.

  20. Investigation of gamma-ray families originating from nucleus-nucleus interactions at ultrahigh energies E{sub 0} in excess of 10{sup 16} eV

    SciTech Connect

    Yuldashbaev, T. S.; Nuritdinov, Kh.


    Various spatial and energy features of gamma-ray families originating from the interactions of primary nuclei of galactic cosmic rays with nuclei of atmospheric atoms (AA interactions) are studied. The mass composition of galactic cosmic rays is analyzed on the basis of data from x-ray emulsion chambers of the Pamir experiment with the aid of a criterion for selecting gamma-ray families originating from AA interactions (A families) at energies E{sub 0} of primary galactic cosmic rays in excess of 10{sup 16} eV. According to the results obtained in this way only the experimental spatial parameters R{sub 1E} and ρ differ from their counterparts in the MC0 model.

  1. 10sup>B(n, Z) measurements in the energy range 0.7 to 5.0 MeV

    SciTech Connect

    Massey, T. N.; Ralston, J.; Grimes, S. M.; Haight, R. C.


    Four ΔE E telescopes were used at the WNR (n,Z) station to investigate the production of charged particles from 10sup>B. The telescope consisted of a gas proportional detector and a silicon surface barrier detector. The flux was determined using a 238U fission chamber. A clear separation of the ground state alpha group and first excited state a was not achieved due to the target thickness. Proton emission was also observed. Furthermore, the proton branch was up to an order of magnitude larger than predicted in ENDF/B-VII A simple R-matrix analysis has been performed on the available data

  2. Cantilever stress measurements for pulsed laser deposition of perovskite oxides at 1000 K in an oxygen partial pressure of 10{sup −4} millibars

    SciTech Connect

    Premper, J.; Sander, D.; Kirschner, J.


    An in situ stress measurement setup using an optical 2-beam curvature technique is described which is compatible with the stringent growth conditions of pulsed laser deposition (PLD) of perovskite oxides, which involves high substrate temperatures of 1000 K and oxygen partial pressures of up to 1 × 10{sup −4} millibars. The stress measurements are complemented by medium energy electron diffraction (MEED), Auger electron spectroscopy, and additional growth rate monitoring by a quartz microbalance. A shielded filament is used to allow for simultaneous stress and MEED measurements at high substrate temperatures. A computer-controlled mirror scans an excimer laser beam over a stationary PLD target. This avoids mechanical noise originating from rotating PLD targets, and the setup does not suffer from limited lifetime issues of ultra high vacuum (UHV) rotary feedthroughs.

  3. Self-Organizing GeV, Nanocoulomb, Collimated Proton Beam from Laser Foil Interaction at 7x10{sup 21} W/cm{sup 2}

    SciTech Connect

    Yan, X. Q.; Wu, H. C.; Meyer-ter-Vehn, J.; Sheng, Z. M.; Chen, J. E.


    We report on a self-organizing, quasistable regime of laser proton acceleration, producing 1 GeV nanocoulomb proton bunches from laser foil interaction at an intensity of 7x10{sup 21} W/cm{sup 2}. The results are obtained from 2D particle-in-cell simulations, using a circular polarized laser pulse with Gaussian transverse profile, normally incident on a planar, 500 nm thick hydrogen foil. While foil plasma driven in the wings of the driving pulse is dispersed, a stable central clump with 1-2lambda diameter is forming on the axis. The stabilization is related to laser light having passed the transparent parts of the foil in the wing region and enfolding the central clump that is still opaque. Varying laser parameters, it is shown that the results are stable within certain margins and can be obtained both for protons and heavier ions such as He{sup 2+}.

  4. Effect of a 100-MGy (10/sup 10/ RADS) gamma-ray dose at 5 K on the strength of polyimide insulators

    SciTech Connect

    Coltman, R.R. Jr.; Klabunde, C.E.; Long, C.J.


    This study seeks to determine the strength of polyimide materials as a function gamma-ray irradiation dose at 5 K. It compares new results with those from previous studies of epoxies made under the same conditions. The most recent efforts in this program have examined the strength and other properties of pure and glass-fiber-filled polyimide materials irradiated to a dose of 100 MGy (10/sup 10/ rads). At this dose the losses in strength measured at 78 K were less than 40%, and at 300 K slight increases were observed. Overall, the glass-fiber-filled polyimide materials are 5 to 10 times more radiation resistant than glass-fiber-filled epoxy materials.

  5. MHD waves detected by ice at distances > 28 x 10/sup 6/ km from Comet Halley: Cometary or solar wind origin

    SciTech Connect

    Tsurutani, B.T.; Brinca, A.L.; Smith, E.J.; Thorne, R.M.; Scarf, F.L.; Gosling, J.T.; Ipavich, F.M.


    Spectral analyses of the high resolution magnetic field data are employed to determine if there is evidence of cometary heavy ion pickup when ICE was closest to Halley, approx.28 x 10/sup 6/ km. No evidence is found for the presence of heavy ion cyclotron waves. However, from this search, two new wave modes are discovered in the solar wind: electromagnetic ion cyclotron waves and drift mirror mode waves. Both modes have scales of 10 to 60 s (1 to 6 T/sub p/) in the spacecraft frame. The possibility of wave generation by cometary hydrogen pickup is explored. Theoretical arguments and further experimental evidence indicates that cometary origin is improbable. The most likely source is plasma instabilities associated with solar wind stream-stream interactions. VLF electrostatic emissions are found to occur in field minima or at gradients of the drift mirror structures. Possible generation mechanisms of drift mirror mode waves, cyclotron waves and electrostatic waves are discussed.

  6. Evaluation of cross sections for neutron-induced reactions in sodium. [10/sup -5/ eV to 20 MeV

    SciTech Connect

    Larson, D.C.


    An evaluation of the neutron-induced cross sections of /sup 23/Na has been done for the energy range from 10/sup -5/ eV to 20 MeV. All significant cross sections are given, including differential cross sections for production of gamma rays. The recommended values are based on experimental data where available, and use results of a consistent model code analysis of available data to predict cross sections where there are no experimental data. This report describes the evaluation that was submitted to the Cross Section Evaluation Working Group (CSEWG) for consideration as a part of the Evaluated Nuclear Data File, Version V, and subsequently issued as MAT 1311. 126 references, 130 figures, 14 tables.

  7. {sup 248}Cm({sup 22}Ne,xn){sup 270-x}Sg reaction and the decay properties of {sup 265}Sg reexamined

    SciTech Connect

    Duellmann, Ch. E.; Tuerler, A.


    Recent studies of the hot fusion reaction {sup 248}Cm({sup 26}Mg,xn){sup 274-x}Hs have provided new nuclear decay data on {sup 265,266}Sg and confirmed the existence of an isomeric state in {sup 261}Rf. The results reported in [J. Dvorak et al., Phys. Rev. Lett. 100, 132503 (2008)] suggest that all decay chains observed in previous studies of the reaction {sup 248}Cm({sup 22}Ne,xn){sup 270-x}Sg, which were originally attributed to {sup 266}Sg, originated from {sup 265}Sg. Here, the decay properties of {sup 265}Sg are reevaluated. Indications for the existence of an isomeric state in {sup 265}Sg are found. The half-lives and main {alpha} particle energies of the two {sup 265}Sg states are 8.9 s/8.85 MeV and 16.2 s/8.70 MeV, respectively. Direct production of this isotope as an evaporation residue of a nuclear fusion reaction populates both states with similar intensity while {alpha} decay of {sup 269}Hs into {sup 265}Sg preferentially populates the longer-lived state, which in turn decays almost exclusively into the short-lived state in {sup 261}Rf. The cross section of the reaction {sup 248}Cm({sup 22}Ne,5n){sup 265}Sg is reanalyzed and found to be of the order of a few hundred pb, assuming that {alpha} decay is the only decay mode of {sup 265}Sg. A decay scheme that is consistent with the published data on {sup 265}Sg and {sup 261}Rf is proposed, which can serve as a working hypothesis in the design of new experiments dedicated to study the production and decay of these two isotopes.

  8. Cannabinoid receptor-2 (CB2) agonist ameliorates colitis in IL-10{sup −/−} mice by attenuating the activation of T cells and promoting their apoptosis

    SciTech Connect

    Singh, Udai P.; Singh, Narendra P.; Singh, Balwan; Price, Robert L.; Nagarkatti, Mitzi; Nagarkatti, Prakash S.


    Inflammatory bowel disease (IBD) is a chronic intestinal inflammation caused by hyperactivated effector immune cells that produce pro-inflammatory cytokines. Recent studies have shown that the cannabinoid system may play a critical role in mediating protection against intestinal inflammation. However, the effect of cannabinoid receptor induction after chronic colitis progression has not been investigated. Here, we investigate the effect of cannabinoid receptor-2 (CB2) agonist, JWH-133, after chronic colitis in IL-10{sup −/−} mice. JWH-133 effectively attenuated the overall clinical score, and reversed colitis-associated pathogenesis and decrease in body weight in IL-10{sup −/−} mice. After JWH-133 treatment, the percentage of CD4{sup +} T cells, neutrophils, mast cells, natural killer (NK1.1) cells, and activated T cells declined in the intestinal lamina propria (LP) and mesenteric lymph nodes (MLN) of mice with chronic colitis. JWH-133 was also effective in ameliorating dextran sodium sulfate (DSS)-induced colitis. In this model, JWH-133 reduced the number and percentage of macrophages and IFN-γ expressing cells that were induced during colitis progression. Treatment with aminoalkylindole 6-iodo-pravadoline (AM630), a CB2 receptor antagonist, reversed the colitis protection provided by JWH-133 treatment. Also, activated T cells were found to undergo apoptosis following JWH-133 treatment both in-vivo and in-vitro. These findings suggest that JWH-133 mediates its effect through CB2 receptors, and ameliorates chronic colitis by inducing apoptosis in activated T cells, reducing the numbers of activated T cells, and suppressing induction of mast cells, NK cells, and neutrophils at sites of inflammation in the LP. These results support the idea that the CB2 receptor agonists may serve as a therapeutic modality against IBD. -- Highlights: ► JWH-133, a cannnabinoid receptor-2 agonist ameliorates experimental colitis. ► JWH-133 suppressed inflammation and

  9. Forecasts for CMB μ and i-type spectral distortion constraints on the primordial power spectrum on scales 8∼10{sup 4} Mpc{sup −1} with the future Pixie-like experiments

    SciTech Connect

    Khatri, Rishi; Sunyaev, Rashid A. E-mail:


    Silk damping at redshifts 1.5 × 10{sup 4}∼10{sup 6} erases CMB anisotropies on scales corresponding to the comoving wavenumbers 8∼10{sup 4} Mpc{sup −1} (10{sup 5}∼10{sup 8}). This dissipated energy is gained by the CMB monopole, creating distortions from a blackbody in the CMB spectrum of the μ-type and the i-type. We study, using Fisher matrices, the constraints we can get from measurements of these spectral distortions on the primordial power spectrum from future experiments such as Pixie, and how these constraints change as we change the frequency resolution and the sensitivity of the experiment. We show that the additional information in the shape of the i-type distortions, in combination with the μ-type distortions, allows us to break the degeneracy between the amplitude and the spectral index of the power spectrum on these scales and leads to much tighter constraints. We quantify the information contained in both the μ-type distortions and the i-type distortions taking into account the partial degeneracy with the y-type distortions and the temperature of the blackbody part of the CMB. We also calculate the constraints possible on the primordial power spectrum when the spectral distortion information is combined with the CMB anisotropies measured by the WMAP, SPT, ACT and Planck experiments.

  10. The reaction of glass during gamma irradiation in a saturated tuff environment: Part 3, long-term experiments at 1 x 10{sup 4}rad/hour

    SciTech Connect

    Abrajano, T.A. Jr.; Bates, J.K.; Gerding, T.J.; Ebert, W.L.


    Savannah River Laboratory 165 type glass was leached with equilibrated J-13 groundwater at 90{degree}C for times up to 182 days. These experiments were performed as part of an effort by the Nevada Nuclear Waste Storage Investigations Project to assess the importance of radiation effects on repository performance and waste glass corrosion. The gamma radiation field used in this work was 1. 0 +- 0.2 x 10{sup 4} rad/h. Glass dissolution is notably incongruent throughout the entire experimental periods and normalized releases follow the sequence Li {ge} Na {ge} B {approx_equal} U {ge} Si. The normalized leach rates of these elements, as well as the measured growth rates of the reaction layers, decreased with time. The only significant variation observed in the abundance of anions is the systematic decrease in NO{sub 3}/sup {minus}//NO{sub 2}/sup {minus}/ ratio from the starting EJ-13 groundwater to the EJ-13 blank experiments to the tuff- and glass-containing experiments. A leaching model that is consistent with the observed solution data and depth profiles is presented. The applicability and limitation of the present results in predicting the actual interactions that may occur in the NNWSI repository are discussed. 35 refs., 30 figs., 12 tabs.

  11. Conditions for efficient and stable ion acceleration by moderate circularly polarized laser pulses at intensities of 10{sup 20} W/cm{sup 2}

    SciTech Connect

    Qiao, B.; Zepf, M.; Borghesi, M.; Dromey, B.; Kar, S.; Geissler, M.; Gibbon, P.; Schreiber, J.


    Conditions for efficient and stable ion radiation pressure acceleration (RPA) from thin foils by circularly polarized laser pulses at moderate intensities are theoretically and numerically investigated. It is found that the unavoidable decompression of the co-moving electron layer in Light-Sail RPA leads to a change of the local electrostatic field from a ''bunching'' to a ''debunching'' profile, ultimately resulting in premature termination of ion acceleration. One way to overcome this instability is the use of a multispecies foil where the high-Z ions act as a sacrificial species to supply excess co-moving electrons for preserving stable acceleration of the lower-Z ion species. It is shown by 2D particle-in-cell simulations that 100 MeV/u monoenergetic C{sup 6+} ion beams are produced by irradiation of a Cu-C-mixed foil with laser pulses at intensities 5 x 10{sup 20} W/cm{sup 2}, which can be easily achieved by current day lasers.

  12. Backward-propagating MeV electrons from 10{sup 18} W/cm{sup 2} laser interactions with water

    SciTech Connect

    Morrison, J. T.; Chowdhury, E. A.; Frische, K. D.; Ovchinnikov, V. M.; Feister, S. Orban, C.; Nees, J. A.; Freeman, R. R.; Roquemore, W. M.


    We present an experimental study of the generation of ∼MeV electrons opposite to the direction of laser propagation following the relativistic interaction at normal incidence of a ∼3 mJ, 10{sup 18} W/cm{sup 2} short pulse laser with a flowing 30 μm diameter water column target. Faraday cup measurements record hundreds of pC charge accelerated to energies exceeding 120 keV, and energy-resolved measurements of secondary x-ray emissions reveal an x-ray spectrum peaking above 800 keV, which is significantly higher energy than previous studies with similar experimental conditions and more than five times the ∼110 keV ponderomotive energy scale for the laser. We show that the energetic x-rays generated in the experiment result from backward-going, high-energy electrons interacting with the focusing optic, and vacuum chamber walls with only a small component of x-ray emission emerging from the target itself. We also demonstrate that the high energy radiation can be suppressed through the attenuation of the nanosecond-scale pre-pulse. These results are supported by 2D particle-in-cell simulations of the laser-plasma interaction, which exhibit beam-like backward-propagating MeV electrons.

  13. Intramolecular energy transfer in actinide complexes of 6-methyl-2-(2-pyridyl)-benzimidazole (biz): comparison between Cm{sup 3+} and Tb{sup 3+} systems

    SciTech Connect

    Assefa, Zerihun . E-mail:; Yaita, T.; Haire, R.G.; Tachimori, S.


    Coordination of the 6-methyl-2-(2-pyridyl)-benzimidazole ligand with actinide and lanthanide species can produce enhanced emission due to increased efficiency of intramolecular energy transfer to metal centers. A comparison between the curium and terbium systems indicates that the position of the ligand's triplet state is critical for the enhanced emission. The energy gap between the ligand's triplet state and the acceptor level in curium is about 1000cm{sup -1}, as compared to a {approx}600cm{sup -1} gap in the terbium system. Due to the larger gap, the back transfer with curium is reduced and the radiative yield is significantly higher. The quantum yield for this 'sensitized' emission increases to 6.2%, compared to the 0.26% value attained for the metal centered excitation prior to ligand addition. In the terbium case, the smaller donor/acceptor gap enhances back transfer and the energy transfer is less efficient than with the curium system.

  14. Cross section limits for the {sup 248}Cm({sup 25}Mg,4n-5n){sup 268,269}Hs reactions

    SciTech Connect

    Dvorak, J.; Dvorakova, Z.; Schuber, R.; Tuerler, A.; Yakushev, A.; Bruechle, W.; Duellmann, Ch. E.; Jaeger, E.; Schaedel, M.; Schausten, B.; Schimpf, E.; Eberhardt, K.; Thoerle, P.; Eichler, R.; Nagame, Y.; Qin, Z.; Semchenkov, A.; Wegrzecki, M.


    We report on an attempt to produce and detect {sup 268}Hs and {sup 269}Hs in the nuclear fusion reaction {sup 25}Mg+{sup 248}Cm using the gas phase chemistry apparatus COMPACT. No decay chains attributable to the decay of hassium isotopes were observed during the course of this experiment. From the nonobservation of {sup 269}Hs we derive a cross section limit of 0.4 pb (63% confidence limit) for the reaction {sup 248}Cm({sup 25}Mg,4n){sup 269}Hs at a center-of-target beam energy of 140 MeV. The evaluated cross section limit for the {sup 248}Cm({sup 25}Mg,5n){sup 268}Hs reaction depends on the assumed half-life of unknown {sup 268}Hs. Current systematics of the half-lives for even-even Hs isotopes suggests a value of 0.5 s, resulting in a cross section limit of 1.3 pb.


    SciTech Connect

    Willott, Chris J.; Omont, Alain; Bergeron, Jacqueline


    We present Atacama Large Millimeter Array observations of rest-frame far-infrared continuum and [C II] line emission in two z = 6.4 quasars with black hole masses of Almost-Equal-To 10{sup 8} M{sub Sun }. CFHQS J0210-0456 is detected in the continuum with a 1.2 mm flux of 120 {+-} 35 {mu}Jy, whereas CFHQS J2329-0301 is undetected at a similar noise level. J2329-0301 has a star formation rate limit of <40 M{sub Sun} yr{sup -1}, considerably below the typical value at all redshifts for this bolometric luminosity. Through comparison with hydro simulations, we speculate that this quasar is observed at a relatively rare phase where quasar feedback has effectively shut down star formation in the host galaxy. [C II] emission is also detected only in J0210-0456. The ratio of [C II] to far-infrared luminosity is similar to that of low-redshift galaxies of comparable luminosity, suggesting that the previous finding of an offset in the relationships between this ratio and far-infrared luminosity at low and high redshifts may be partially due to a selection effect due to the limited sensitivity of previous continuum data. The [C II] line of J0210-0456 is relatively narrow (FWHM = 189 {+-} 18 km s{sup -1}), indicating a dynamical mass substantially lower than expected from the local black hole-velocity dispersion correlation. The [C II] line is marginally resolved at 0.''7 resolution with the blue and red wings spatially offset by 0.''5 (3 kpc) and a smooth velocity gradient of 100 km s{sup -1} across a scale of 6 kpc, possibly due to the rotation of a galaxy-wide disk. These observations are consistent with the idea that stellar mass growth lags black hole accretion for quasars at this epoch with respect to more recent times.

  16. Single pulse laser induced reactions of hexafluorobenzene/silane mixtures at 1027 and 944 cm/sup -1 1,2/

    SciTech Connect

    Koga, Y.; Serino, R.M.; Chen, R.; Keehn, P.M.


    C/sub 6/F/sub 6//SiH/sub 4/ mixtures were irradiated with a single pulse of a megawatt CO/sub 2/ infrared laser at 1027 and 944 cm/sup -1/, using fluences which ranged from 0.26 to 2.0 J/cm/sup 2/. Neat C/sub 6/F/sub 6/ (7.5 Torr, 1027 cm/sup -1/) underwent decomposition to C/sub 2/F/sub 4/ at a fluence of 0.7 J/cm/sup 2/ with a conversion per flash (CPF) of 4.5%. At 0.3 J/cm/sup 2/ no reaction was observed, setting a fluence threshold for the laser-induced decomposition of C/sub 6/F/sub 6/ between 0.3 and 0.7 J/cm/sup 2/. In the presence of SiH/sub 4/ explosive reactions occurred with conversion of C/sub 2/F/sub 2/ as high as 70%exclamation Different decomposition products were observed depending upon the amount of SiH/sub 2/ present. The observed results are discussed in terms of (a) the low fluence threshold observed for the laser-induced decomposition of C/sub 6/F/sub 6/, (b) the effects that added gases have on the decomposition of C/sub 6/F/sub 6/, (c) the use of C/sub 6/F/sub 6/ as a sensitizer for laser-induced reactions, and (d) the potential for using SiH/sub 4/ for the laser-induced reduction of C-F bonds (C-F + Si-H ..-->.. C-H + Si-F).

  17. Long-term phase-locking technique for locking the repetition rate of an optical frequency comb laser with 1.67 × 10<sup>-19 precision.


    Ci, Cheng; Zhang, Xuesong; Li, Xinran; Chen, Xing; Cui, Yifan; Zhao, Yingxin; Liu, Bo; Wu, Hong


    An ultrahigh stable phase-locked loop system for synchronization of an optical frequency comb to a hydrogen maser has been proposed and experimentally demonstrated. A mathematical model has been set up to investigate the feasibility and steady state of the phase-locking system. The fractional frequency instability is evaluated by measuring the mixed-phase signal of an improved experimental system. Experimental results show that the fractional frequency instability of the phase-locked loop system lies from 8.83×10<sup>-16 at 1 s to 1.67×10<sup>-19 at 1000 s, which indicates our proposed phase-locking system possesses ultrahigh measurement precision with good long-term stabilization performance. PMID:27556998

  18. Stimulated-emission cross sections of the /sup 5/F/sub 1/--/sup 5/I/sub 5/ and /sup 5/F/sub 1/--/sup 5/I/sub 6/ transitions of Pm/sup 3+/ in a phosphate glass

    SciTech Connect

    Beach, R.; Weinzapfel, S.; Staver, R.; Solarz, R.; Shinn, M.; Krupke, W.


    We report a laser cavity measurement of stimulated-emission cross sections for both the /sup 5//ital F//sub 1/--/sup 5//ital I//sub 5/ (0.93-/mu/m) and /sup 5//ital F//sub 1/--/sup 5//ital I//sub 6/ (1.1-/mu/m) laser transitions of Pm/sup 3+/ ions in a lead--indium--phosphate glass host. The measured cross sections for these two transitions are 1.8/times/10/sup /minus/20/ (/plus minus/11%) and 2.8/times/10/sup /minus/20/ cm/sup 2/ (/plus minus/22%), respectively. These values agree with previously reported values based on a Judd--Ofelt-type analysis of spectroscopic data.

  19. Molecular eigenstate spectroscopy: Application to the intramolecular dynamics of some polyatomic molecules in the 3000 to 7000 cm{sup {minus}1} region

    SciTech Connect

    Perry, D.S.


    Intramolecular vibrational redistribution (IVR) appears to be a universal property of polyatomic molecules in energy regions where the vibrational density of states is greater than about 5 to 30 states per cm{sup {minus}1}. Interest in IVR stems from its central importance to the spectroscopy, photochemistry, and reaction kinetics of these molecules. A bright state, {var_phi}{sub s}, which may be a C-H stretching vibration, carries the oscillator strength from the ground state. This bright state may mix with bath rotational-vibrational levels to form a clump of molecular eigenstates, each of which carries a portion of the oscillator strength from the ground state. In this work the authors explicitly resolve transitions to each of these molecular eigenstates. Detailed information about the nature of IVR is contained in the frequencies and intensities of the observed discrete transitions. The primary goal of this research is to probe the coupling mechanisms by which IVR takes place. The most fundamental distinction to be made is between anharmonic coupling which is independent of molecular rotation and rotationally-mediated coupling. The authors are also interested in the rate at which IVR takes place. Measurements are strictly in the frequency domain but information is obtained about the decay of the zero order state, {var_phi}{sub s}, which could be prepared in a hypothetical experiment as a coherent excitation of the clump of molecular eigenstates. As the coherent superposition dephases, the energy would flow from the initially prepared mode into nearby overtones and combinations of lower frequency vibrational modes. The decay of the initially prepared mode is related to a pure sequence infrared absorption spectrum by a Fourier transform.

  20. Origin of the 900 cm{sup −1} broad double-hump OH vibrational feature of strongly hydrogen-bonded carboxylic acids

    SciTech Connect

    Van Hoozen, Brian L.; Petersen, Poul B.


    Medium and strong hydrogen bonds are common in biological systems. Here, they provide structural support and can act as proton transfer relays to drive electron and/or energy transfer. Infrared spectroscopy is a sensitive probe of molecular structure and hydrogen bond strength but strongly hydrogen-bonded structures often exhibit very broad and complex vibrational bands. As an example, strong hydrogen bonds between carboxylic acids and nitrogen-containing aromatic bases commonly display a 900 cm{sup −1} broad feature with a remarkable double-hump structure. Although previous studies have assigned this feature to the OH, the exact origin of the shape and width of this unusual feature is not well understood. In this study, we present ab initio calculations of the contributions of the OH stretch and bend vibrational modes to the vibrational spectrum of strongly hydrogen-bonded heterodimers of carboxylic acids and nitrogen-containing aromatic bases, taking the 7-azaindole—acetic acid and pyridine—acetic acid dimers as examples. Our calculations take into account coupling between the OH stretch and bend modes as well as how both of these modes are affected by lower frequency dimer stretch modes, which modulate the distance between the monomers. Our calculations reproduce the broadness and the double-hump structure of the OH vibrational feature. Where the spectral broadness is primarily caused by the dimer stretch modes strongly modulating the frequency of the OH stretch mode, the double-hump structure results from a Fermi resonance between the out of the plane OH bend and the OH stretch modes.

  1. Confinement of nonequilibrium plasmas in microcavities with diamond or circular cross sections: Sealed arrays of Al/Al{sub 2}O{sub 3}/glass microplasma devices with radiating areas above 20 cm{sup 2}

    SciTech Connect

    Park, S.-J.; Kim, K. S.; Chang, A. Y.; Hua, L. Z.; Asinugo, J. C.; Mehrotra, T.; Spinka, T. M.; Eden, J. G.


    Arrays of Al/Al{sub 2}O{sub 3}/glass microplasma devices with microcavities having diamond or circular cross-sectional geometries and radiating (active) areas >20 cm{sup 2} have been operated sealed-off in Ne, Ar, and Ar/D{sub 2} gas mixtures. Microcavities are fabricated in only one of the two electrodes, and the thickness of the completed package is {approx}170 {mu}m (excluding the quartz output window). Excited by a sinusoidal 20 kHz voltage wave form, arrays with active areas of 4.5x3 cm{sup 2} exhibit ignition voltages as low as 110{+-}5 V rms for Ne pressures of 400-700 Torr. Mixtures of 1% D{sub 2} in Ar at a total pressure of 300 Torr produce wavelength-integrated ({lambda}{approx}250-400 nm) intensities of {approx}1 mW cm{sup -2} over a 25 cm{sup 2} area. Optical micrographs show the operation of the microplasmas in two well-defined modes. For current densities below a threshold value ({approx}53 mA cm{sup -2} for 250 {mu}m dia. cavities and p{sub Ne}=400 Torr), diffuse uniform plasma is produced in each cavity but, with higher currents, a positive column having near-cylindrical geometry appears, as evidenced by the generation of intense emission localized in the region of weak electric field gradient near the axis of symmetry.

  2. High Resolution Far-Infrared Spectra of Thiophosgene with a Synchrotron Source: The nu{sub 2} and nu{sub 4} Bands Near 500 cm{sup -1}

    SciTech Connect

    McKellar, A. R. W.; Billinghurst, B. E.


    Thiophosgene (Cl{sub 2}CS) is a favorite model system for studies of vibrational dynamics. But there are no previous rotationally-resolved infrared studies because the spectra are very congested due to its (relatively) large mass and multiple isotopic species. Here we report a detailed gas-phase study of the nu{sub 2} (approx504 cm{sup -1}) and nu{sub 4} (approx471 cm{sup -1}) fundamental bands, based on spectra obtained at the Canadian Light Source far-infrared beamline using synchrotron radiation and a Bruker IFS125 FT spectrometer.

  3. Infrared spectrum of the simplest Criegee intermediate CH{sub 2}OO at resolution 0.25 cm{sup −1} and new assignments of bands 2ν{sub 9} and ν{sub 5}

    SciTech Connect

    Huang, Yu-Hsuan; Li, Jun E-mail:; Guo, Hua; Lee, Yuan-Pern E-mail:


    The simplest Criegee intermediate CH{sub 2}OO is important in atmospheric chemistry. It has been detected in the reaction of CH{sub 2}I + O{sub 2} with various spectral methods, including infrared spectroscopy; infrared absorption of CH{sub 2}OO was recorded at resolution 1.0 cm{sup −1} in our laboratory. We have improved our system and recorded the infrared spectrum of CH{sub 2}OO at resolution 0.25 cm{sup −1} with rotational structures partially resolved. Observed vibrational wavenumbers and relative intensities are improved from those of the previous report and agree well with those predicted with quantum-mechanical calculations using the MULTIMODE method on an accurate potential energy surface. Observed rotational structures also agree with the simulated spectra according to theoretical predictions. In addition to derivation of critical vibrational and rotational parameters of the vibrationally excited states to confirm the assignments, the spectrum with improved resolution provides new assignments for bands 2ν{sub 9} at 1234.2 cm{sup −1} and ν{sub 5} at 1213.3 cm{sup −1}; some hot bands and combination bands are also tentatively assigned.

  4. Electrocatalytic H2 production with a turnover frequency >10<sup>7 s-1: the medium provides an increase in rate but not overpotential

    SciTech Connect

    Hou, Jianbo; Fang, Ming; Cardenas, Allan Jay P.; Shaw, Wendy J.; Helm, Monte L.; Bullock, R. Morris; Roberts, John A. S.; O'Hagan, Molly


    In this paper, rapid proton movement results in exceptionally fast electrocatalytic H2 production (up to 3 × 10<sup>7 s-1) at overpotentials of ~400 mV when catalysed by [Ni(PPh2NC6H4x2)2]2+ complexes in an acidic ionic liquid–water medium ([(DMF)H]NTf2–H2O, χH2O = 0.71).

  5. Probing of the neutrino magnetic moment at the level of 10{sup -22} μ{sub B} with an intense tritium source of (anti)neutrino and helium target (project)

    SciTech Connect

    Martemyanov, V.P.; Aleshin, V.I.; Tarasenko, V.G.; Tsinoev, V.G.; Sabelnikov, A.A.; Yukhimchuk, A.A.; Popov, V.V.; Baluev, V.V.; Golubkov, A.N.; Klevtsov, V.G.; Kuryakin, A.V.; Sitdikov, D.T.; Bogdanova, L.N.


    We present research results of the preparation project for the experimental measurement of the (anti)neutrino magnetic moment at the level of 10{sup -12} μ{sub B} using an intense tritium source of antineutrinos and a liquid helium scintillation detector. The neutrino detection in the scintillation detector is based on the scattering of neutrinos by the electrons of the helium atoms that produces fast electrons able to ionize and exciting helium atoms. The detection of the atomic radiation emitted during the relaxation process of the helium atoms and the knowledge of its parameters will allow us to conclude on the neutrino properties.

  6. Unconfined compression experiments on Topopah Spring Member tuff at 22{degrees}C and a strain rate of 10{sup {minus}9} s{sup {minus}1}: Data report; Yucca Mountain Site Characterization Project

    SciTech Connect

    Martin, R.J. III; Boyd, P.J.; Noel, J.S.; Price, R.H.


    Experiment results are presented for unconfined compressive strength and elastic moduli of tuffaceous rocks from Busted Butte near Yucca Mountain, Nevada. The data have been compiled for the Yucca Mountain Site Characterization Project Site and Engineering Properties Data Base. Experiments were conducted on water-saturated specimens of the potential nuclear waste repository horizon Topopah Spring Member tuff (thermal/mechanical unit TSw2). The influence of strain rate on mechanical properties of the tuff was examined by loading six specimens in uniaxial compression at a strain rate of 10{sup {minus}9} s{sup {minus}1}. The experiments performed under ambient pressure and temperature conditions and conformed to Technical Procedure 91, titled ``Unconfined Compression Experiments at 22{degrees}C and a Strain Rate of 10{sup {minus}9} s{sup {minus}1}.`` The mean and standard deviation values of ultimate strength, Young`s modulus and Poisson`s ratio determined from these experiments are 85.4{plus_minus}21.7 MPa, 33.9{plus_minus}4.6 GPa, and 0.09{plus_minus}0.07, respectively.

  7. Searches for large-scale anisotropy in the arrival directions of cosmic rays detected above energy of 10{sup 19} eV at the Pierre Auger observatory and the telescope array

    SciTech Connect

    Aab, A.; Abreu, P.; Andringa, S.; Aglietta, M.; Ahn, E. J.; Al Samarai, I.; Albuquerque, I. F. M.; Allekotte, I.; Asorey, H.; Allen, J.; Allison, P.; Almela, A.; Castillo, J. Alvarez; Alvarez-Muñiz, J.; Batista, R. Alves; Ambrosio, M.; Aramo, C.; Aminaei, A.; Anchordoqui, L.; Arqueros, F.; Collaboration: Pierre Auger Collaboration; Telescope Array Collaboration; and others


    Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 10{sup 19} eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above 10{sup 19} eV. No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits on the amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varying between 7% and 13% for the dipole and between 7% and 10% for a symmetric quadrupole.

  8. A correlated K-distribution model of the heating rates for H[sub 2]O and a molecular mixture in the 0-2500 cm[sup [minus]1] wavelength region in the atmosphere between 0 and 60 km

    SciTech Connect

    Grossman, A S; Grant, K E


    For this report a prototype infrared radiative transfer model using a correlated k-distribution technique to calculate the transmission between atmospheric levels has been used to calculate the radiative fluxes and heating rates for H[sub 2]O and a mixture of the major molecular absorbers in the atmosphere between 0 and 60 km. The mixture consists of H[sub 2]O, CO[sub 2], O[sub 3], CH[sub 4], and N[sub 2]O. The wave number range considered is 0-2500 cm[sup [minus]1]. The use of the k-distribution method allows 25 cm[sup [minus]1] wave number bins to produce fluxes and heating rates which are within ten percent of the results of detailed line by line calculations.

  9. Highly accurate potential energy surface, dipole moment surface, rovibrational energy levels, and infrared line list for {sup 32}S{sup 16}O{sub 2} up to 8000 cm{sup −1}

    SciTech Connect

    Huang, Xinchuan E-mail:; Schwenke, David W.; Lee, Timothy J. E-mail:


    A purely ab initio potential energy surface (PES) was refined with selected {sup 32}S{sup 16}O{sub 2} HITRAN data. Compared to HITRAN, the root-mean-squares error (σ{sub RMS}) for all J = 0–80 rovibrational energy levels computed on the refined PES (denoted Ames-1) is 0.013 cm{sup −1}. Combined with a CCSD(T)/aug-cc-pV(Q+d)Z dipole moment surface (DMS), an infrared (IR) line list (denoted Ames-296K) has been computed at 296 K and covers up to 8000 cm{sup −1}. Compared to the HITRAN and CDMS databases, the intensity agreement for most vibrational bands is better than 85%–90%. Our predictions for {sup 34}S{sup 16}O{sub 2} band origins, higher energy {sup 32}S{sup 16}O{sub 2} band origins and missing {sup 32}S{sup 16}O{sub 2} IR bands have been verified by most recent experiments and available HITRAN data. We conclude that the Ames-1 PES is able to predict {sup 32/34}S{sup 16}O{sub 2} band origins below 5500 cm{sup −1} with 0.01–0.03 cm{sup −1} uncertainties, and the Ames-296K line list provides continuous, reliable and accurate IR simulations. The K{sub a}-dependence of both line position and line intensity errors is discussed. The line list will greatly facilitate SO{sub 2} IR spectral experimental analysis, as well as elimination of SO{sub 2} lines in high-resolution astronomical observations.

  10. Electron velocity of 6 × 10{sup 7 }cm/s at 300 K in stress engineered InAlN/GaN nano-channel high-electron-mobility transistors

    SciTech Connect

    Arulkumaran, S. Manoj Kumar, C. M.; Ranjan, K.; Teo, K. L.; Ng, G. I.; Shoron, O. F.; Rajan, S.; Bin Dolmanan, S.; Tripathy, S.


    A stress engineered three dimensional (3D) Triple T-gate (TT-gate) on lattice matched In{sub 0.17}Al{sub 0.83}N/GaN nano-channel (NC) Fin-High-Electron-Mobility Transistor (Fin-HEMT) with significantly enhanced device performance was achieved that is promising for high-speed device applications. The Fin-HEMT with 200-nm effective fin-width (W{sub eff}) exhibited a very high I{sub Dmax} of 3940 mA/mm and a highest g{sub m} of 1417 mS/mm. This dramatic increase of I{sub D} and g{sub m} in the 3D TT-gate In{sub 0.17}Al{sub 0.83}N/GaN NC Fin-HEMT translated to an extracted highest electron velocity (v{sub e}) of 6.0 × 10{sup 7 }cm/s, which is ∼1.89× higher than that of the conventional In{sub 0.17}Al{sub 0.83}N/GaN HEMT (3.17 × 10{sup 7 }cm/s). The v{sub e} in the conventional III-nitride transistors are typically limited by highly efficient optical-phonon emission. However, the unusually high v{sub e} at 300 K in the 3D TT-gate In{sub 0.17}Al{sub 0.83}N/GaN NC Fin-HEMT is attributed to the increase of in-plane tensile stress component by SiN passivation in the formed NC which is also verified by micro-photoluminescence (0.47 ± 0.02 GPa) and micro-Raman spectroscopy (0.39 ± 0.12 GPa) measurements. The ability to reach the v{sub e} = 6 × 10{sup 7 }cm/s at 300 K by a stress engineered 3D TT-gate lattice-matched In{sub 0.17}Al{sub 0.83}N/GaN NC Fin-HEMTs shows they are promising for next-generation ultra-scaled high-speed device applications.

  11. On the anisotropy of E{sub 0} Greater-Than-Or-Slanted-Equal-To 5.5 Multiplication-Sign 10{sup 19} eV cosmic rays according to data of the Pierre Auger Collaboration

    SciTech Connect

    Glushkov, A. V.


    The Pierre Auger Collaboration discovered, in a solid angle of radius about 18 Degree-Sign , a local group of cosmic rays having energies in the region E{sub 0} {>=} 5.5 Multiplication-Sign 10{sup 19} eV and coming from the region of the Gen A radio galaxy, whose galactic coordinates are l{sub G} 309.5 Degree-Sign and b{sub G} = 19.4 Degree-Sign . Near it, there is the Centaur supercluster of galaxies, its galactic coordinates being l{sub G} = 302.4 Degree-Sign and b{sub G} = 21.6 Degree-Sign . It is noteworthy that the Great Attractor, which may have a direct bearing on the observed picture, is also there.

  12. Electronic state spectroscopy of diiodomethane (CH{sub 2}I{sub 2}): Experimental and computational studies in the 30 000–95 000 cm{sup −1} region

    SciTech Connect

    Mandal, Anuvab; Jagatap, B. N.; Singh, Param Jeet; Shastri, Aparna


    The electronic absorption spectrum of diiodomethane in the 30 000–95 000 cm{sup −1} region is investigated using synchrotron radiation; the spectrum in the 50 000–66 500 cm{sup −1} region is reported for the first time. The absorption bands in the 30 000–50 000 cm{sup −1} region are attributed to valence transitions, while the vacuum ultraviolet (VUV) spectrum (50 000–95 000 cm{sup −1}) is dominated by several Rydberg series converging to the first four ionization potentials of CH{sub 2}I{sub 2} at 9.46, 9.76, 10.21, and 10.56 eV corresponding to the removal of an electron from the outermost 3b{sub 2}, 2b{sub 1}, 1a{sub 2}, and 4a{sub 1} non-bonding orbitals, respectively. Rydberg series of ns, np, and nd type converging to each of the four ionization potentials are assigned based on a quantum defect analysis. Time dependent density functional theory calculations of excited states support the analysis and help in interpretation of the Rydberg and valence nature of observed transitions. Density functional theory calculations of the neutral and ionic ground state geometries and vibrational frequencies are used to assign the observed vibronic structure. Vibronic features accompanying the Rydberg series are mainly due to excitation of the C-I symmetric stretch (ν{sub 3}) and CH{sub 2} wag (ν{sub 8}) modes, with smaller contributions from the C-H symmetric stretch (ν{sub 1}). UV absorption bands are assigned to low lying valence states 1{sup 1}B{sub 2}, 1{sup 1}B{sub 1}, 2{sup 1}A{sub 1}, 3{sup 1}A{sub 1}, 2{sup 1}B{sub 1}, and 2{sup 1}B{sub 2} and the unusually high underlying intensity in parts of the VUV spectrum is attributed to valence states with high oscillator strength. This is the first report of a comprehensive Rydberg series and vibronic analysis of the VUV absorption spectrum of CH{sub 2}I{sub 2} in the 50 000–85 000 cm{sup −1} region. The VUV absorption spectrum of CD{sub 2}I{sub 2} which serves to verify and


    SciTech Connect



    SGR 1900+14 had a brief episode of exceedingly rapid spindown immediately following its 1998 Aug. 27 superburst. On a timescale of hours, it increased its period by a part in 10{sup 4}. The corresponding P {approximately} 10{sup {minus}8} is orders of magnitude higher than the typical quiescent rate of P {approximately} 6 x 10{sup {minus}11}.

  14. Neutrino magnetic moment

    SciTech Connect

    Chang, D. . Dept. of Physics and Astronomy Fermi National Accelerator Lab., Batavia, IL ); Senjanovic, G. . Dept. of Theoretical Physics)


    We review attempts to achieve a large neutrino magnetic moment ({mu}{sub {nu}} {le} 10{sup {minus}11}{mu}{sub B}), while keeping neutrino light or massless. The application to the solar neutrino puzzle is discussed. 24 refs.

  15. Decay Properties of {sup 266}Bh and {sup 262}Db Produced in the {sup 248}Cm+{sup 23}Na Reaction - Further Confirmation of the {sup 278}113 Decay Chain

    SciTech Connect

    Morita, K.; Morimoto, K.; Kaji, D.; Haba, H.; Ozeki, K.; Kudou, Y.; Yoneda, A.; Ichikawa, T.; Katori, K.; Yoshida, A.; Sato, N.; Sumita, T.; Fujimori, Y.; Tokanai, F.; Goto, S.; Ideguchi, E.; Kasamatsu, Y.; Koura, H.; Tsukada, K.; Komori, Y.


    Decay properties of an isotope {sup 266}Bh and its daughter nucleus {sup 262}Db produced by the {sup 248}Cm({sup 23}Na,5n) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. {sup 266}Bh was clearly identified from the correlation of the known nuclide, {sup 262}Db. The obtained decay properties of {sup 266}Bh and {sup 262}Db are consistent with those observed in the {sup 278}113 chain by RIKEN collaboration, which provided further confirmation of the discovery of {sup 278}113.

  16. Survey of the high resolution infrared spectrum of methane ({sup 12}CH{sub 4} and {sup 13}CH{sub 4}): Partial vibrational assignment extended towards 12 000 cm{sup −1}

    SciTech Connect

    Ulenikov, O. N.; Bekhtereva, E. S.; Albert, S.; Bauerecker, S.; Niederer, H. M.; Quack, M.


    We have recorded the complete infrared spectrum of methane {sup 12}CH{sub 4} and its second most abundant isotopomer {sup 13}CH{sub 4} extending from the fundamental range starting at 1000 cm{sup −1} up to the overtone region near 12 000 cm{sup −1} in the near infrared at the limit towards the visible range, at temperatures of about 80 K and also at 298 K with Doppler limited resolution in the gas phase by means of interferometric Fourier transform spectroscopy using the Bruker IFS 125 HR prototype (ZP 2001) of the ETH Zürich laboratory. This provides the so far most complete data set on methane spectra in this range at high resolution. In the present work we report in particular those results, where the partial rovibrational analysis allows for the direct assignment of pure (J = 0) vibrational levels including high excitation. These results substantially extend the accurate knowledge of vibrational band centers to higher energies and provide a benchmark for both the comparison with theoretical results on the one hand and atmospheric spectroscopy on the other hand. We also present a simple effective Hamiltonian analysis, which is discussed in terms of vibrational level assignments and {sup 13}C isotope effects.

  17. The rare crystallographic structure of d(CGCGCG){sub 2}: The natural spermidine molecule bound to the minor groove of left-handed Z-DNA d(CGCGCG){sub 2} at 10 {sup o}C

    SciTech Connect

    Ohishi, Hirofumi . E-mail:; Tozuka, Yoshitaka; Da-Yang, Zhou; Ishida, Toshimasa; Nakatani, Kazuhiko


    Several crystal structure analyses of complexes of synthetic polyamine compounds, including N {sup 1}-(2-(2-aminoethylamino))ethyl)ethane-1,2-diamine PA(222) and N {sup 1}-(2-(2-(2-aminoethylamino)ethylamino)ethyl)ethane-1,2-diamine PA(2222), and left-handed Z-DNA d(CGCGCG){sub 2} have been reported. However, until now, there have been no examples of naturally occurring polyamines bound to the minor groove of the left-handed Z-DNA of d(CGCGCG){sub 2} molecule. We have found that spermidine, a natural polyamine, is connected to the minor groove of left-handed Z-DNA of d(CGCGCG){sub 2} molecule in a crystalline complex grown at 10 {sup o}C. The electron density of the DNA molecule was clear enough to determine that the spermidine was connected in the minor groove of two symmetry related molecules of left-handed Z-DNA d(CGCGCG){sub 2}. This is the first example that a spermidine molecule can form a bridge conformation between two symmetry related molecules of left-handed Z-DNA d(CGCGCG){sub 2} in the minor groove.

  18. Kinetics and products of the BrO + ClO reaction

    SciTech Connect

    Poulet, G.; Lancar, I.T.; Laverdet, G.; Le Bras, G. )


    The overall rate constant of the BrO + ClO reaction has been measured by the discharge flow mass spectrometry method. The value found at 298 K is k{sub 1} = (1.13 {plus minus} 0.15) {times} 10{sup {minus}11} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. Branching ratios for two of the three reaction channels were determined from the direct measurements of OClO and BrCl and were found to be (0.43 {plus minus} 0.10) and (0.12 {plus minus} 0.05), respectively. These results are compared with recent literature data and their implication for the polar ozone stratospheric chemistry is discussed.

  19. Results of charpy V-notch impact testing of structural steel specimens irradiated at {approximately}30{degrees}C to 1 x 10{sup 16} neutrons/cm{sup 2} in a commercial reactor cavity

    SciTech Connect

    Iskander, S.K.; Stoller, R.E.


    A capsule containing Charpy V-notch (CVN) and mini-tensile specimens was irradiated at {approximately} 30{degrees}C ({approximately} 85{degrees}F) in the cavity of a commercial nuclear power plant to a fluence of 1 x 10{sup 16} neutrons/cm{sup 2} (> 1MeV). The capsule included six CVN impact specimens of archival High Flux Isotope Reactor A212 grade B ferritic steel and five CVN impact specimens of a well-studied A36 structural steel. This irradiation was part of the ongoing study of neutron-induced damage effects at the low temperature and flux experienced by reactor supports. The plant operators shut down the plant before the planned exposure was reached. The exposure of these specimens produced no significant irradiation-induced embrittlement. Of interest were the data on unirradiated specimens in the L-T orientation machined from a single plate of A36 structural steel, which is the same specification for the structural steel used in some reactor supports. The average CVN energy of five unirradiated specimens obtained from one region of the plate and tested at room temperature was {approximately} 99 J, while the energy of 11 unirradiated specimens from other locations of the same plate was 45 J, a difference of {approximately} 220%. The CVN impact energies for all 18 specimens ranged from a low of 32 J to a high of 111 J. Moreover, it appears that the University of Kansas CVN impact energy data of the unirradiated specimens at the 100-J level are shifted toward higher temperatures by about 20 K. The results were an example of the extent of scatter possible in CVN impact testing. Generic values for the CVN impact energy of A36 should be used with caution in critical applications.

  20. Measurements of production cross sections of 10sup>Be and 26Al by 120 GeV and 392 MeV proton bombardment of 89Y, 159Tb, and natCu targets

    SciTech Connect

    Sekimoto, S.; Okumura, S.; Yashima, H.; Matsushi, Y.; Matsuzaki, H.; Matsumura, H.; Toyoda, A.; Oishi, K.; Matsuda, N.; Kasugai, Y.; Sakamoto, Y.; Nakashima, H.; Boehnlein, D.; Coleman, R.; Lauten, G.; Leveling, A.; Mokhov, N.; Ramberg, E.; Soha, A.; Vaziri, K.; Ninomiya, K.; Omoto, T.; Shima, T.; Takahashi, N.; Shinohara, A.; Caffee, M. W.; Welten, K. C.; Nishiizumi, K.; Shibata, S.; Ohtsuki, T.


    The production cross sections of 10sup>Be and 26Al were measured by accelerator mass spectrometry using 89Y, 159Tb, and natCu targets bombarded by protons with energies Ep of 120 GeV and 392 MeV. The production cross sections obtained for 10sup>Be and 26Al were compared with those previously reported using Ep = 50 MeV–24 GeV and various targets. It was found that the production cross sections of 10sup>Be monotonically increased with increasing target mass number when the proton energy was greater than a few GeV. On the other hand, it was also found that the production cross sections of 10sup>Be decreased as the target mass number increased from that of carbon to those near the mass numbers of nickel and zinc when the proton energy was below approximately 1 GeV. They also increased as the target mass number increased from near those of nickel and zinc to that of bismuth, in the same proton energy range. Similar results were observed in the production cross sections of 26Al, though the absolute values were quite different between 10sup>Be and 26Al. As a result, the difference between these production cross sections may depend on the impact parameter (nuclear radius) and/or the target nucleus stiffness.

  1. Infrared absorption spectroscopy and chemical kinetics of free radicals. Progress report, February 1, 1991--March 1, 1994

    SciTech Connect

    Curl, R.F.; Glass, G.P.


    Rate of reaction of ketenyl radical with O{sub 2} at room temperature was determined as 6.5(6) {times} 10-{sup {minus}13} CM{sup 3} molecules{sup {minus}1} s{sup {minus}1} and an upper bound of 1 {times} 10{sup {minus}13} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} was estimated for the reaction rate of acetylene with ketenyl. The high resolution spectrum of the {nu}1 acetylenic CH stretch of propargy1 radical (HCCCH{sub 2}) near 3322 cm{sup {minus}1} has obtained and analyzed. Nuclear spin weights demonstrate that the CH{sub 2} hydrogen atoms are in the carbon atom plane. We have attempted to measure the propargy1 recombination rate constant at 296 K; however, the observed rate constant of (1.2{times}0.2) x 10{sup {minus}10} cc-molecule{sup {minus}1}-s{sup {minus}1} may be affected by other reactions. The CH stretch fundamental, {nu}1, of HCCN has been observed, assigned, and analyzed. Analysis of the hot bands associated with bending shows that HCCN is a quasilinear molecule with a very floppy potential function for the HCC bending angle. The barrier to linearity is estimated to be about 100 cm{sup {minus}1}. Rate of the reaction between C{sub 2}H and H{sub 2} has been measured at 295--855 K. The rate constant exhibited a non-Arrhenius form well represented by k = (9.44{plus_minus}0.50) {times} 10{sup {minus}14}T{sup 0.9}exp(-1003{plus_minus}40/T)cm{sup 3}molecule{sup {minus}1}s{sup {minus}1}. The reaction between atomic oxygen and the amidogen radical, NH{sub 2} has been studied at 295 K; the room temperature rate constant was measured as (6.5 {plus_minus} 1.3) {times} 10{sup {minus}1} s{sup {minus}1}. The minor channel leading to NH + OH was observed but accounted for at most about 8% of the NH{sub 2} reacting. The rate constant for the reaction NH+O was determined from fitting the NH time profile to be 6.6{plus_minus}10{sub {minus}11} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}.

  2. Properties of H, O and C in GaN

    SciTech Connect

    Pearton, S.J.; Abernathy, C.R.; Lee, J.W.


    The electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at {ge} 450 C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until > 800 C, and its diffusivity is relatively high ({approximately} 10{sup {minus}11} cm{sup 2}/s) even at low temperatures (< 200 C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30--40 meV. It is essentially immobile up to 1,100 C. Carbon can produce low p-type levels (3 {times} 10{sup 17} cm{sup {minus}3}) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.

  3. Mass transport phenomena in thin films of poly(2-vinylpyridine) studied via optical guided wave techniques

    SciTech Connect

    Fell, N.F. Jr.; Bohn, P.W. )


    The unique ability of optical waveguide techniques to determine simultaneously film thicknesses and mass transport behavior in swollen polymer films is utilized in these experiments to make accurate determinations of diffusion coefficients of fluorescein into H[sub 2]O-swollen poly(2-vinylpyridine) films from aqueous solution. The diffusion behavior is determined from fitting the fluorescence-time curves to an intensity expression derived from Fick's second law and the appropriate boundary conditions to obtain the diffusion coefficient of the fluorophore in the film. Two techniques for characterizing the fluorescence behavior spatially and temporally are critically compared. Fiber optic-based detection schemes suffer from inaccuracies relative to the use of an imaging camera based on a charge-coupled device (CCD) array. The diffusion coefficients obtained show no significant dependence on the bulk solution concentration in the range 1 nM [le] [fluorescein] [le] 10 [mu]M of the fluorophore. The value of the diffusion coefficient was found to be in the range 1 x 10[sup [minus]12] cm[sup 2]/s [le] D [le] 3 x 10[sup [minus]11] cm[sup 2]/s and was found to vary widely with small changes in sample preparation conditions. 25 refs., 5 figs., 1 tab.


    SciTech Connect

    Mastrapa, R. M.; Dalle Ore, C. M.; Sandford, S. A.; Cruikshank, D. P.; Roush, T. L.


    Using new laboratory spectra, we have calculated the real and imaginary parts of the index of refraction of amorphous and crystalline H{sub 2}O-ice from 20-150 K in the wavelength range 2.5-22 {mu}m (4000-455 cm{sup -1}) and joined these results with previous measurement from 1.25 to 2.5 {mu}m. These optical constants improve on previous measurements by having better temperature and spectral resolution and can be used to create model spectra for comparison to spectra of solar system objects and interstellar materials. In this wavelength range, the infrared band shapes and positions of amorphous H{sub 2}O-ice are strongly dependent on deposition temperature. Amorphous and crystalline H{sub 2}O-ice have distinctive spectral bands at all wavelengths in this region with bands weakening and shifting to shorter wavelength in amorphous H{sub 2}O-ice compared to crystalline H{sub 2}O-ice. Some notable exceptions are the band near 6 {mu}m, which is stronger in amorphous H{sub 2}O-ice, and the bands near 4.5 {mu}m and 12.5 {mu}m, which shift to longer wavelength in amorphous H{sub 2}O-ice.


    SciTech Connect

    Kim, D.-C.; Evans, A. S.; Privon, G. C. E-mail:; and others


    A Hubble Space Telescope/Advanced Camera for Surveys study of the structural properties of 85 luminous and ultraluminous (L{sub IR} > 10{sup 11.4} L{sub Sun }) infrared galaxies (LIRGs and ULIRGs) in the Great Observatories All-sky LIRG Survey (GOALS) sample is presented. Two-dimensional GALFIT analysis has been performed on F814W ''I-band'' images to decompose each galaxy, as appropriate, into bulge, disk, central point-spread function (PSF) and stellar bar components. The fraction of bulge-less disk systems is observed to be higher in LIRGs (35%) than in ULIRGs (20%), with the disk+bulge systems making up the dominant fraction of both LIRGs (55%) and ULIRGs (45%). Further, bulge+disk systems are the dominant late-stage merger galaxy type and are the dominant type for LIRGs and ULIRGs at almost every stage of galaxy-galaxy nuclear separation. The mean I-band host absolute magnitude of the GOALS galaxies is -22.64 {+-} 0.62 mag (1.8{sup +1.4}{sub -0.4} L{sup *}{sub I}), and the mean bulge absolute magnitude in GOALS galaxies is about 1.1 mag fainter than the mean host magnitude. Almost all ULIRGs have bulge magnitudes at the high end (-20.6 to -23.5 mag) of the GOALS bulge magnitude range. Mass ratios in the GOALS binary systems are consistent with most of the galaxies being the result of major mergers, and an examination of the residual-to-host intensity ratios in GOALS binary systems suggests that smaller companions suffer more tidal distortion than the larger companions. We find approximately twice as many bars in GOALS disk+bulge systems (32.8%) than in pure-disk mergers (15.9%) but most of the disk+bulge systems that contain bars are disk-dominated with small bulges. The bar-to-host intensity ratio, bar half-light radius, and bar ellipticity in GOALS galaxies are similar to those found in nearby spiral galaxies. The fraction of stellar bars decreases toward later merger stages and smaller nuclear separations, indicating that bars are destroyed as the merger

  6. A novel waste form for disposal of spent-nuclear-fuel reprocessing waste: A vitrifiable cement

    SciTech Connect

    Gougar, M.L.D.; Scheetz, B.E.; Siemer, D.D.


    A cement capable of being hot isostatically pressed into a glass ceramic has been proposed as the waste form for spent-nuclear-fuel reprocessing wastes at the Idaho National Engineering and Environmental Laboratory (INEEL). This intermediate cement, with a composition based on that of common glasses, has been designed and tested. The cement formulations included mixed INEEL wastes, blast furnace slag, reactive silica, and INEEL soil or vermiculite, which were activated with potassium or sodium hydroxide. Following autoclave processing, the cements were characterized. X-ray diffraction analysis revealed three notable crystalline phases: quartz, calcite, and fluorite. Results of compressive strength testing ranged from 1452 and 4163 psi, exceeding the US Nuclear Regulatory Commission (NRC)-suggested standard of >500 psi. From American National Standards Institute/American Nuclear Society 16.1-1986 leach testing, effective diffusivities for Cs were determined to be on the order of 10{sup {minus}11} to 10{sup {minus}10} cm{sup 2}/s and for Sr were 10{sup {minus}12} cm{sup 2}/s, which are four orders of magnitude less than diffusivities in some other radwaste materials. Average leach indices (LI) were 9.6 and 11.9 for Cs and Sr, respectively, meeting the NRC Standard of LI > 6. The 28-day Materials Characterization Center-1 leach testing resulted in normalized elemental mass losses between 0.63 and 28 g/(m{sup 2}{center_dot}day) for Cs and between 0.34 and 0.70 g/(m{sup 2}{center_dot}day) industry-accepted standard while Cs losses indicate a process sensitive parameter.

  7. Kinetics and mechanisms of reactions involving small aromatic reactive intermediates. Annual report

    SciTech Connect

    Lin, M.C.


    Phenyl (C{sub 6}H{sub 5}), phenoxy (C{sub 6}H{sub 5}O) and benzyne (C{sub 6}H{sub 4}) are fundamentally important prototype molecules. C{sub 6}H{sub 5} and C{sub 6}H{sub 5}O are also very important reactive intermediates in hydrocarbon combustion systems, particularly with regard to soot formation chemistry, as well as to the combustion chemistry of aromatic additives in gasoline. The authors proposed to study the kinetics and mechanisms of these three benchmark reactive intermediates using two complementary laser diagnostic techniques -- laser resonance absorption (LRA) and resonance enhanced multiphoton ionization mass spectrometry (REMPI/MS). In the first year of this contractual work, they have employed a new type of LRA, i.e. the intra-cavity resonance absorption technique, to measure the rate constants for C{sub 6}H{sub 5} reactions, extending the limit of rate constant measurement down to 10{sup {minus}18} cm{sup 3}/s. They have tested this method for the following reactions: C{sub 6}H{sub 5} + HBr, CH{sub 2}O, O{sub 2}, C{sub 2}H{sub 2} and C{sub 2}H{sub 4} at 297 K and obtained their rate constants to be 3.0 {times} 10{sup {minus}11}, 1.2 {times} 10{sup {minus}14}, 1.0 {times} 10{sup {minus}16}, 7.0 {times} 10{sup {minus}18} and 6.7 {times} 10{sup {minus}18} cm{sup 3}/s, respectively. In the second study, the REMPI spectroscopy of C{sub 6}H{sub 5} is being investigated with the two laser pump-probe surface photolysis method. The desorbed C{sub 6}H{sub 5} photofragment is ionized by (1+1) MPI in the spectral range 200--260 nm. Similarly, the NO photofragment is also detected by (1+1) MPI in the same spectral region. The detailed photofragmentation of the absorbed C{sub 6}H{sub 5}NO at 193 and 248 nm is being analyzed presently and a new experiment with acetophenone on a quartz surface is under way.

  8. The 700-1500 cm{sup −1} region of the S{sub 1} (A{sup ~1}B{sub 2}) state of toluene studied with resonance-enhanced multiphoton ionization (REMPI), zero-kinetic-energy (ZEKE) spectroscopy, and time-resolved slow-electron velocity-map imaging (tr-SEVI) spectroscopy

    SciTech Connect

    Gardner, Adrian M.; Green, Alistair M.; Tamé-Reyes, Victor M.; Reid, Katharine L.; Davies, Julia A.; Parkes, Victoria H. K.; Wright, Timothy G.


    We report (nanosecond) resonance-enhanced multiphoton ionization (REMPI), (nanosecond) zero-kinetic-energy (ZEKE) and (picosecond) time-resolved slow-electron velocity map imaging (tr-SEVI) spectra of fully hydrogenated toluene (Tol-h{sub 8}) and the deuterated-methyl group isotopologue (α{sub 3}-Tol-d{sub 3}). Vibrational assignments are made making use of the activity observed in the ZEKE and tr-SEVI spectra, together with the results from quantum chemical and previous experimental results. Here, we examine the 700–1500 cm{sup −1} region of the REMPI spectrum, extending our previous work on the region ≤700 cm{sup −1}. We provide assignments for the majority of the S{sub 1} and cation bands observed, and in particular we gain insight regarding a number of regions where vibrations are coupled via Fermi resonance. We also gain insight into intramolecular vibrational redistribution in this molecule.

  9. Mg dopant in Cu{sub 2}ZnSnSe{sub 4}: An n-type former and a promoter of electrical mobility up to 120 cm{sup 2} V{sup −1} s{sup −1}

    SciTech Connect

    Kuo, Dong-Hau Wubet, Walelign


    Mg-doped Cu{sub 2}ZnSnSe{sub 4} (CZTSe) bulk materials with the (Cu{sub 2−x}Mg{sub x})ZnSnSe{sub 4} formula at x=0, 0.1, 0.2, 0.3, and 0.4 were prepared at 600 °C for 2 h with soluble sintering aids of Sb{sub 2}S{sub 3} and Te. Defect chemistry was studied by measuring structural and electrical properties of Mg-doped CZTSe as a function of dopant concentration. Except at x=0, all Mg-doped CZTSe pellets showed an n-type behavior. The Mg-doped CZTSe pellets showed an n-type behavior. n-Type Mg-CZTSe pellets at x=0.1 showed the highest electrical conductivity of 24.6 S cm{sup −1} and the net hole mobility of 120 cm{sup 2} V{sup −1} s{sup −1}, while they were 11.8 S cm{sup −1} and 36.5 cm{sup 2} V{sup −1} s{sup −1} for the undoped p-type CZTSe. Mg dopant is a strong promoter of electrical mobility. Mg dopant behaves as a donor defect in CZTSe at a 5% doping content, but is also used as an acceptor at a high content above 5%. Mg doping has further developed CZTSe into a promising semiconductor. - Graphical abstract: The effects of extrinsic doping of Mg{sup 2+} on the electrical properties of Cu{sub 2}ZnSnSe{sub 4} bulks. - Highlights: • (Cu{sub 2−x}Mg{sub x})ZnSnSe{sub 4} bulks were fabricated by liquid-phase sintering at 600 °C. • All Mg-x-CZTSe pellets except at x=0 exhibited n-type conductivity. • Electrical properties of CZTSe pellets changed with the Cu and Mg ratios. • Mg{sup 2+} goes to the Cu{sup 1+} site to form the Mg{sub Cu}{sup 1+} donor defect for the n-type CZTSe. • n-Type Mg-0.1-CZTSe bulk with 5% Mg showed the highest mobility of 120 cm{sup 2} V{sup −1} s{sup −1}.


    SciTech Connect

    Vikas, Shailendra; Wood-Vasey, W. Michael; Lundgren, Britt; Ross, Nicholas P.; Myers, Adam D.; AlSayyad, Yusra; York, Donald G.; Schneider, Donald P.; Brinkmann, J.; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Pan, Kaike; Snedden, Stephanie; Ge, Jian; Muna, Demitri; Paris, Isabelle; Petitjean, Patrick; and others


    We measure the two-point cross-correlation function of C IV absorber systems and quasars, using spectroscopic data from the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey (BOSS; Data Release 9). The 19,701 quasars and 6149 C IV ''moderate'' absorbers, 0.28 A < rest-frame equivalent width (EW) < 5 A, in our study cover a redshift range of 2.1 < z < 2.5 over 3300 deg{sup 2} and represent a factor of two increase in sample size over previous investigations. We find a correlation scale length and slope of the redshift-space cross-correlation function of s{sub 0} = 8.46 {+-} 1.24 Mpc, {gamma} = 1.68 {+-} 0.19, in the redshift-space range 10 < s < 100 Mpc. We find a projected cross-correlation function of C IV absorption systems and quasars of r{sub 0} = 7.76 {+-} 2.80 Mpc, {gamma} = 1.74 {+-} 0.21. We measure the combined quasar and C IV bias to be b{sub QSO} b{sub C{sub IV}} = 8.81 {+-} 2.28. Using an estimate of b{sub QSO} from the quasar auto-correlation function we find b{sub CIV} = 2.38 {+-} 0.62. This b{sub CIV} implies that EW > 0.28 A C IV absorbers at z {approx} 2.3 are typically found in dark matter halos that have masses {>=}10{sup 11.3}-10{sup 13.4} M{sub Sun} at that redshift. The complete BOSS sample will triple the number of both quasars and absorption systems and increase the power of this cross-correlation measurement by a factor of two.

  11. Laser flash photolysis studies of radical-radical reaction kinetics: The HO{sub 2} + IO reaction

    SciTech Connect

    Cronkhite, J.M.; Stickel, R.E.; Nicovich, J.M.; Wine, P.H.


    Reactive iodine as a potential tropospheric O{sub 3} sink has received considerable attention recently. Laser flash photolysis of Cl{sub 2}/CH{sub 3}OH/O{sub 2}/I{sub 2}/NO{sub 2}/SF{sub 6}N{sub 2} mixtures at 308 nm has been coupled with simultaneous time-resolved detection of HO{sub 2} (by infrared tunable diode laser absorption spectroscopy) and IO (by visible absorption spectroscopy) to investigate the kinetics of the atmospherically important reaction HO{sub 2} + IO {r_arrow} products over the temperature range 274--373 K in N{sub 2} buffer gas at pressures of 12 and 25 Torr. All experiments were performed under near pseudo-first-order conditions with HO{sub 2} in excess over IO. At 298 K, the rate coefficient was determined to be (9.7 {+-} 2.9) {times} 10{sup {minus}11} cm{sup 3} molecule{sup {minus}1}s{sup {minus}1}, with the primary source of uncertainty being knowledge of the infrared line strength(s) required to convert measured HO{sub 2} absorbances to absolute concentrations. The temperature dependence of the HO{sub 2} + IO rate coefficient was found to be adequately described by the Arrhenius expression k = 9.3 {times} 10{sup {minus}12} exp(680/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. The results reported in this study are compared with other recent studies of HO{sub 2} + IO kinetics, and the potential roles of this reaction in atmospheric chemistry are discussed.

  12. The thermal reactions of CH{sub 3}

    SciTech Connect

    Lim, K.P.; Michael, J.V.


    The thermal reactions of CH{sub 3}-radicals have been investigated in reflected shock waves experiments at temperatures between 1224--2520 K. The fast dissociation of CH{sub 3}I served as the source of CH{sub 3}. Experiments were performed at three loading pressures with variations in [CH{sub 3}I]{sub 0}. H-atoms formed in the reaction, 2CH{sub 3} {yields} C{sub 2}H{sub 5} + H, were measured by the atomic resonance absorption spectrometric (ARAS) technique. The product ethyl radicals subsequently decompose to give a second H-atom and ethylene. A reaction mechanism was used to fit the data, and the resulting value for the rate constant was 5.25 {times} 10{sup {minus}11} exp({minus}7384 K/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. This value is compared to earlier determinations. At higher temperatures, 2150--2520 K, the H-atom formation rate was dominated by CH{sub 3} thermal dissociation. With simulations, the rate constant for CH{sub 3} + Kr {yields} CH{sub 2} + H + Kr could be determined. The rate constant for this process is: k = 4.68 {times} 10{sup {minus}9} exp({minus}42506 K/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. This result is compared to earlier experimental determinations and also to theoretical calculations using the semi-empirical Troe formalism.

  13. Analysis of the crystal-field spectra of the actinide tetrafluorides. II. AmF[sub 4], CmF[sub 4], Cm[sup 4+]:CeF[sub 4], and Bk[sup 4+]:CeF[sub 4

    SciTech Connect

    Liu, G.K.; Carnall, W.T.; Jursich, G.; Williams, C.W. )


    We report a systematic analysis of the crystal-field spectra of four fluoride compounds containing tetravalent actinide ions. The first part of this work [J. Chem. Phys. [bold 95], 7194 (1991)] provided interpretation of the absorption spectra of UF[sub 4], NpF[sub 4], and PuF[sub 4]. To extend our analysis to heavier elements of the series, low-temperature absorption spectra of AmF[sub 4] and CmF[sub 4], and site selective laser-induced emission and excitation spectra of Cm[sup 4+]:CeF[sub 4] and Bk[sup 4+]:CeF[sub 4] were obtained. A model energy level calculation was found to be in good agreement with the experimental results. It is shown that the crystal-field interaction in combination with spin--orbital coupling results in significant [ital J] mixing in the excited states, but ground state wave functions are still relatively pure in [ital J] character for the tetravalent actinide ions Am[sup 4+], Cm[sup 4+], and Bk[sup 4+]. Trends in the parameters of the effective operator Hamiltonian are compared with those of a Hartree--Fock free-ion model. Interpretation of the ground-state splitting of the nominal [ital S]-state ion Bk[sup 4+] in CeF[sub 4] and color center formation in AmF[sub 4] are also discussed.

  14. APS storage ring vacuum chamber: Section 1, Evaluation

    SciTech Connect

    Benaroya, R.; Roop, B.


    The vacuum characteristics of the APS storage ring vacuum chamber prototype, Section One (S1), is presented. The base pressure achieved was 4 {times} 10{sup {minus}11}, the welds contained no virtual or real leaks, the NeG strip mounting design and activation procedures have been determined, and S1 was found contaminated with hydrocarbons.

  15. Photon burst mass spectrometry for the measurement of {sup 85}Kr at ambient levels

    SciTech Connect

    Fairbank, W.M. Jr.; LaBelle, R.D.; Hansen, C.S.


    Photon Burst Mass Spectrometry has been used to measure {sup 85}Kr in a sample with an abundance of 6 x 10{sup {minus}9}. Improvements in detection efficiency by the use of avalanche photodiodes cooled to liquid nitrogen temperature are reported, which should make possible measurement of {sup 85}Kr at the ambient atmospheric abundance of 10{sup {minus}11}. Potential applications include nuclear monitoring, atmospheric transport, and dating young ground water up to 40 years.

  16. Evidence for transition from polaron to bipolaron conduction in electroactive Li{sub x}Cr{sub 0.11}V{sub 2}O{sub 5.16} powders: A dynamic study from 10 to 10{sup 10} Hz

    SciTech Connect

    Badot, J.C.; Dubrunfaut, O.


    This paper presents a study on the electrical transport properties of lithiated Cr{sub 0.11}V{sub 2}O{sub 5.16}, which can be used as a rechargeable cathodic material in lithium batteries. Dielectric and conductivity spectra of Li{sub x}Cr{sub 0.11}V{sub 2}O{sub 5.16} powders (x=0, 0.05, 0.40 and 1.20) were recorded in a broad frequency range of 10-10{sup 10} Hz at temperature varying between 300 and 400 K. Complex resistivity diagrams have enabled to obtain thermal behaviors of bulk dc-conductivity. Dielectric relaxations were found, attributed to small polarons and (intersite) bipolarons hopping. The transport properties are shown to be consistent with small polaron and bipolaron conduction models. The change from polaronic to bipolaronic conduction has been evidenced with the increase of the lithium content x from 0.40 to 1.20. This work opens up new prospects for a more fundamental understanding of the electronic transport in relation with the electrochemical properties of Cr{sub 0.11}V{sub 2}O{sub 5.16}. - Graphical Abstract: Schematic structure of Cr{sub 0.11}V{sub 2}O{sub 5.16}. Highlights: Black-Right-Pointing-Pointer Chromium-vanadium mixed oxide as cathodic material. Black-Right-Pointing-Pointer Broadband dielectric spectroscopy from low frequencies to microwaves. Black-Right-Pointing-Pointer Transition from polaron to bipolaron conduction as lithium content increases.

  17. Flow-tube kinetics study of the reaction between ground-state hydrogen atoms and nitromethane

    SciTech Connect

    Ko, Taeho; Flaherty, W.F.; Fontijn, A. )


    The kinetics of the H + CH{sub 3}NO{sub 2} reaction have been studied by using a discharge-flow resonance-fluorescence technique. H atoms are produced from microwave discharges through NH{sub 3}Ar mixtures. The data in the 360-570 K range are well fitted by the empirical expression k(T) = 7.8 {times} 10{sup {minus}12} exp(-1878K/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. Precision of the data varies from {plus minus} 6 to {plus minus} 11%, and the resulting accuracy is estimated to be better than {+-} 20%, where both figures represent 2{sigma} statistical confidence intervals. Results of some experiments where h{sub 2} was discharged indicate that the channel leading to OH and CH{sub 3}NO is significant for the reaction. A comparison of the kinetics of several reactions where a methyl-group hydrogen is abstracted by H atoms indicates that such a channel is not important in the present work but could become significant at elevated temperatures. To confirm the accuracy achieved with the present apparatus, measurements on the H + C{sub 6}H{sub 6} reaction have been made in the 410-530 K range and are compared to results from other studies.

  18. Characteristics of the high-rate discharge capability of a nickel/metal hydride battery electrode

    SciTech Connect

    Geng, M.; Han, J.; Feng, F.; Northwood, D.O.


    The high rate discharge capability of the negative electrode in a Ni/MH battery is mainly determined by the charge transfer process at the interface between the metal hydride (MH) alloy powder and the electrolyte, and the mass transfer process in the bulk MH alloy powder. In this study, the anodic polarization curves of a MH electrode were measured and analyzed. An alloy of nominal composition Mm{sub 0.95}Ti{sub 0.05}Ni{sub 3.85}Co{sub 0.45}Mn{sub 0.35}Al{sub 0.35} was used as the negative electrode material. With increasing number of charge/discharge cycles, the MH alloy powders microcrack into particles several micrometers in diameter. The decrease in the MH alloy particle size results in an increase in both the activation surface area and the exchange current density of the MH alloy electrode. The electrode overpotentials of the MH electrode decreases with increasing number of cycles at a large value of anodic polarization current. The decrease in electrode overpotential leads to an increase in the high rate discharge capability of the MH electrode. By using the limiting current, the hydrogen diffusion coefficient in the MH alloy was estimated to be 1.2 x 10{sup {minus}11}cm{sup 2}s{sup {minus}1} assuming an average particle radius of 5 {micro}m.

  19. Atom trap trace analysis of krypton isotopes

    SciTech Connect

    Bailey, K.; Chen, C. Y.; Du, X.; Li, Y. M.; Lu, Z.-T.; O'Connor, T. P.; Young, L.


    A new method of ultrasensitive isotope trace analysis has been developed. This method, based on the technique of laser manipulation of neutral atoms, has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton gas sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. This method is free of contamination from other isotopes and elements and can be applied to several different isotope tracers for a wide range of applications. The demonstrated detection efficiency is 1 x 10{sup {minus}7}. System improvements could increase the efficiency by many orders of magnitude.

  20. Controlled in situ boron doping of short silicon nanowires grown by molecular beam epitaxy

    SciTech Connect

    Das Kanungo, Pratyush; Zakharov, Nikolai; Bauer, Jan; Breitenstein, Otwin; Werner, Peter; Goesele, Ulrich


    Epitaxial silicon nanowires (NWs) of short heights ({approx}280 nm) on Si <111> substrate were grown and doped in situ with boron on a concentration range of 10{sup 15}-10{sup 19} cm{sup -3} by coevaporation of atomic Si and B by molecular beam epitaxy. Transmission electron microscopy revealed a single-crystalline structure of the NWs. Electrical measurements of the individual NWs confirmed the doping. However, the low doped (10{sup 15} cm{sup -3}) and medium doped (3x10{sup 16} and 1x10{sup 17} cm{sup -3}) NWs were heavily depleted by the surface states while the high doped (10{sup 18} and 10{sup 19} cm{sup -3}) ones showed volume conductivities expected for the corresponding intended doping levels.

  1. Spectroscopy and reaction kinetics of HCO

    SciTech Connect

    Guo, Yili


    The high-resolution infrared spectrum of the C-H stretching fundamental of HCO has been studied by means of infrared flash kinetic spectroscopy. HCO was generated by flash photolysis of acetaldehyde or formaldehyde using a 308 nm (XeCl) excimer laser. The transient absorption was probed with an infrared difference frequency laser system. The high resolution spectra obtained were assigned and fitted with rotational, spin-rotational, and centrifugal distortion constants. The 1/ band origin is 2434.48 cm/sup /minus/1/. New ground state constants have been derived from a least-squares fit combining the 1/ data with previous microwave and FIR LMR measurements. A new set of spectroscopic constants for the (1, 0, 0) state, the equilibrium rotational constants, and the orientation of the transition dipole moment are also reported. The kinetics and product branching ratios of the HCO + NO/sub 2/ reaction have been studied using visible and infrared laser flash kinetic spectroscopy. The rate constant for the disappearance of HCO radical at 296 K is (5.7 +- 0.9) /times/ 10/sup /minus/11/ cm/sup 3/ molec/sup /minus/1/ sec/sup /minus/1/, and it is independent of the pressure of SF/sub 6/ buffer gas up to 700 torr. Less than 10% of the reaction goes through the most exothermic product channel, HNO + CO/sub 2/. The product channel, H + CO/sub 2/ + NO, is responsible for 52% of the reaction. HONO has been observed, though not quantitatively, as a reaction product corresponding to the HONO + CO channel. 51 refs., 21 figs., 8 tabs.

  2. Identification of third-order (approx. 10{sup 6} yrs) and fourth-order (approx. 10{sup 5}/10{sup 4} yrs) stratigraphic cycles in the South Addition, West Cameron Lease Area, Louisiana offshore

    SciTech Connect

    Lowrie, A.; Meeks, P.; Hoffman, K.


    In the highly explored South Addition of the West Cameron Lease Area, Louisiana offshore, interpretation of a six-mile ({approx}10 km) seismic section across a single intraslope basin yielded 20 sediment packages. Several interpretive tools were necessary. Seismic stratigraphy indicated that the shallower zone was an outer shelf marked by 8 major sea level oscillations. In the portion between 1 and 3 seconds, seismic stratigraphy and paleontology led to the interpretation of depositional environments such as upper slope, and paleobathymetrically deeper intervals with descent through the section. The intraslope basin, while small, may be viewed as a micro-continental margin. Each sea level oscillation cycle apparently made a distinct progradational unit, decipherable in the seismic data. Fourth order cycles have been provisionally interpreted, throughout most of the entire 3.7 second section. Such precision is possible only in explored basins with excellent seismic data. The sequence thickness showed a seven-fold variability, from 0.08 to 0.58 seconds. The shallower section, deposited along an outer shelf, has an average individual sequence thickness of 0.13 seconds. Individual seismic sequences in the deeper section, interpreted to have been deposited on an upper slope, have average thicknesses of 0.25 seconds. The thinner sequences of the shallower section are compatible with the notion that the outer shelf was a bypass zone during a glacial epoch. The thicker sequences of the deeper section are the result of deposition onto an aggrading upper slope within an intraslope basin during a highstand.

  3. Concentration dependence and interfacial instabilities during ion beam annealing of arsenic-doped silicon

    SciTech Connect

    Priolo, F.; Rimini, E. ); Spinella, C. ); Ferla, G. )


    Ion beam induced epitaxy of amorphous Si layers onto {l angle}100{r angle} substrates has been investigated by varying the As concentration. At As concentrations below 4{times}10{sup 18}/cm{sup 3} no rate effect is observed. In the intermediate regime, between 4{times}10{sup 18}/cm{sup 3} and 2{times}10{sup 21}/cm{sup 3}, the growth rate increases linearly with the logarithm of As concentration and reaches a value about a factor of 2 higher than that of intrinsic Si. At concentrations above 2{times}10{sup 21}/cm{sup 3}, the epitaxy experiences a sudden, severe retardation. Finally, at a concentration of {similar to}6{times}10{sup 21}/cm{sup 3}, twins are observed to form.

  4. Polarity control and transport properties of Mg-doped (0001) InN by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Choi, Soojeong; Wu Feng; Bierwagen, Oliver; Speck, James S.


    The authors report on the plasma-assisted molecular beam epitaxy growth and carrier transport of Mg-doped In-face (0001) InN. The 1.2 {mu}m thick InN films were grown on GaN:Fe templates under metal rich conditions with Mg concentration from 1 Multiplication-Sign 10{sup 17}/cm{sup 3} to 3 Multiplication-Sign 10{sup 20}/cm{sup 3}. A morphological transition, associated with the formation of V-shape polarity inversion domains, was observed at Mg concentration over 7 Multiplication-Sign 10{sup 19}/cm{sup 3} by atomic force microscopy and transmission electron microscopy. Seebeck measurements indicated p-type conductivity for Mg-concentrations from 9 Multiplication-Sign 10{sup 17}/cm{sup 3} to 7 Multiplication-Sign 10{sup 19}/cm{sup 3}, i.e., as it exceeded the compensating (unintentional) donor concentration.

  5. Blood lead concentrations in marine mammals validate estimates of 10{sup 2}- to 10{sup 3}-fold increase in human blood lead concentrations

    SciTech Connect

    Owen, B.D.; Flegal, A.R.


    Measurements of ultra-low ambient blood lead (PbB) concentrations (mean {+-} SD = 0.13 {+-} 0.06 {micro}g/dL) in Northern elephant seals (Mirounga angustirostris) validate previous estimates of ultra-low PbB levels in preindustrial humans. These estimates had been unsubstituted, since PbB levels in this range had never been measured in any organisms prior to this study. Similarities in PbB levels among these contemporary and preindustrial mammals are consistent with similarities in their measured and estimated lead exposures, respectively. The marginally higher PbB levels and rates of lead exposure in contemporary marine mammals are, also, consistent with lead isotopic composition analyses that indicate their PbB levels have been elevated from exposure to industrial lead. Consequently, these analyses substantiate concerns that current baseline PbB levels in humans, which are estimated to be two to three orders of magnitude above natural levels, may still constitute public health risks.

  6. Laser Plasma Interactions at Intensities from 10{sup 12}W/cm{sup 2} to 10{sup 21} W/cm{sup 2}

    SciTech Connect

    Kruer, W L


    A tutorial introduction is given to some important physics and current challenges in laser plasma interactions. The topics are chosen to illustrate a few of John Dawson's many pioneering contributions to the physics and modeling of plasmas. In each case, a current frontier is also briefly discussed, including the .53{micro}m option for laser fusion, kinetic inflation of instability levels, and new regimes accessed with ultra-high power lasers.

  7. Interaction of oppositely directed plasma streams in a longitudinal magnetic field

    SciTech Connect

    Zhitlukhin, A.M.; Ilyushin, I.V.; Safronov, V.M.; Skvortsov, Y.V.


    Streams of a deuterium plasma with a density 10/sup 15/ cm/sup -3/ and directed velocities from 3 x 10/sup 7/ to 8 x 10/sup 7/ cm/s were made to collide in a uniform longitudinal magnetic field. Complete randomization of the directed energy of the stream was observed, and a hot ''steady-state'' plasma with a density n = 10/sup 15/ cm/sup -3/ and T/sub i/ = 2--3 keV was formed. The neutron yield reached 4 x 10/sup 9/ neutrons per shot. The stopping of the colliding streams is ascribed to a firehose instability.

  8. Atom trap trace analysis

    SciTech Connect

    Lu, Z.-T.; Bailey, K.; Chen, C.-Y.; Du, X.; Li, Y.-M.; O'Connor, T. P.; Young, L.


    A new method of ultrasensitive trace-isotope analysis has been developed based upon the technique of laser manipulation of neutral atoms. It has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. The atom counts are free of contamination from other isotopes, elements,or molecules. The method is applicable to other trace-isotopes that can be efficiently captured with a magneto-optical trap, and has a broad range of potential applications.

  9. The RAP unit: A remote autoranging picoammeter

    SciTech Connect

    Martin, E.R. ); Bennion, K.M. . Dept. of Mathematics and Statistics); Jones, D.F. )


    A digital instrument for remote acquisition of low-level current measurements is described. Primarily designed for operation with ionization chambers, this instrument provides the capability of local or remote operation over the current range from 10{sup {minus}11} to 10{sup {minus}4} A. It is capable of autoranging operation, or it can be placed in a hold'' mode where the range is specified. The digital communication link is an optically-isolated 60-mA current loop for noise-free operation, and the unit can be daisy-chained for multiple-unit communication. 10 figs.

  10. Production of ozone and nitrogen oxides by laser filamentation

    SciTech Connect

    Petit, Yannick; Henin, Stefano; Kasparian, Jerome; Wolf, Jean-Pierre


    We have experimentally measured that laser filaments in air generate up to 10{sup 14}, 3x10{sup 12}, and 3x10{sup 13} molecules of O{sub 3}, NO, and NO{sub 2}, respectively. The corresponding local concentrations in the filament active volume are 10{sup 16}, 3x10{sup 14}, and 3x10{sup 15} cm{sup -3}, and allows efficient oxidative chemistry of nitrogen, resulting in concentrations of HNO{sub 3} in the parts per million range. The latter forming binary clusters with water, our results provide a plausible pathway for the efficient nucleation recently observed in laser filaments.

  11. Growth mechanism of hydrogen clusters

    SciTech Connect

    Nickel, N.H.; Anderson, G.B.; Johnson, N.M.; Walker, J.


    It is demonstrated that the exposure of polycrystalline silicon (poly-Si) to monatomic hydrogen results in the formation of H clusters. These H stabilized platelets appear in the near-surface region (100 nm) and are predominantly oriented along {l_brace}111{r_brace} crystallographic planes. Platelet concentrations of {approx}5 x 10{sup 15}, 1.5 x 10{sup 16} -cm{sup {minus}3}, and 2.4 x 10{sup 17} cm{sup {minus}3} were observed in nominally undoped poly-Si, phosphorous doped poly-Si (P = 10{sup 17} cm{sup {minus}3}), and phosphorous doped single crystal silicon (P > 3 x 10{sup 18} cm{sup {minus}3}), respectively. Results obtained on doped c-Si demonstrate that platelet generation occurs only at Fermi-level positions of E{sub C} - E{sub F} < 0.4 eV.

  12. A kinetics study of the O( sup 3 P) + CH sub 3 Cl reaction over the 556-1485 K range by the HTP and LP-ST techniques

    SciTech Connect

    Ko, Taeho; Fontijn, A. . High-Temperature Reaction Kinetics Lab.); Lim, K.P.; Michael, J.V. )


    The high-temperature photochemistry (HTP) and laser photolysis-shock tube (LP-ST) techniques have been combined to study the kinetics of the reaction between ground-state oxygen atoms with CH{sub 3}Cl over the temperature range, 556--1485 K. In the HTP reactor, used for the 556--1291 K range, O atoms were generated by flash photolysis of O{sub 2}, CO{sub 2} or SO{sub 2}, and the atom concentrations were monitored by resonance fluorescence, while with the LP-ST technique, used for the 916--1485 K range, O atoms were generated by the photolysis of either SO{sub 2} or NO with the 193 nm light from a pulsed ArF excimer laser, and atomic resonance absorption spectroscopy (ARAS) was used to monitor (O){sub t}. In both studies, rate coefficients were derived from the (O) profiles under the pseudo-first-order condition, (O){much lt}(CH{sub 3}Cl). The data obtained by the two techniques are in excellent agreement and are best represented by the expression, k(T) = 2.57 {times} 10{sup {minus}11} (T/K){sup 0.31} exp({minus}5633 K/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} with a 2{sigma} precision varying from {plus minus}6 {plus minus}22% and an estimated 2{sigma} accuracy of {plus minus}21% to {plus minus}30%, depending on temperature. The rate coefficients for the title reaction are essentially identical to those for the O + CH{sub 4} reaction over the observed temperature range, the reasons for which are discussed.

  13. A kinetics study of the O({sup 3}P) + CH{sub 3}Cl reaction over the 556-1485 K range by the HTP and LP-ST techniques

    SciTech Connect

    Ko, Taeho; Fontijn, A.; Lim, K.P.; Michael, J.V.


    The high-temperature photochemistry (HTP) and laser photolysis-shock tube (LP-ST) techniques have been combined to study the kinetics of the reaction between ground-state oxygen atoms with CH{sub 3}Cl over the temperature range, 556--1485 K. In the HTP reactor, used for the 556--1291 K range, O atoms were generated by flash photolysis of O{sub 2}, CO{sub 2} or SO{sub 2}, and the atom concentrations were monitored by resonance fluorescence, while with the LP-ST technique, used for the 916--1485 K range, O atoms were generated by the photolysis of either SO{sub 2} or NO with the 193 nm light from a pulsed ArF excimer laser, and atomic resonance absorption spectroscopy (ARAS) was used to monitor [O]{sub t}. In both studies, rate coefficients were derived from the [O] profiles under the pseudo-first-order condition, [O]{much_lt}[CH{sub 3}Cl]. The data obtained by the two techniques are in excellent agreement and are best represented by the expression, k(T) = 2.57 {times} 10{sup {minus}11} (T/K){sup 0.31} exp({minus}5633 K/T) cm{sup 3} molecule{sup {minus}1} s{sup {minus}1} with a 2{sigma} precision varying from {plus_minus}6 {plus_minus}22% and an estimated 2{sigma} accuracy of {plus_minus}21% to {plus_minus}30%, depending on temperature. The rate coefficients for the title reaction are essentially identical to those for the O + CH{sub 4} reaction over the observed temperature range, the reasons for which are discussed.

  14. Possibility of applying a hydrodynamic model to describe the laser erosion of metals irradiated by high-intensity nanosecond pulses

    SciTech Connect

    Kozadaev, K V


    We report the results of experimental investigations of the production and development of plasma-vapour plumes upon irradiation of metal targets by nanosecond (10–100 ns) pulses with a high (10{sup 8}–10{sup 10} W cm{sup -2}) power density under atmospheric conditions. The transition from a quasi-stationary thermal mechanism of metal erosion to an explosion hydrodynamic one takes place when the radiation power density increases from 10{sup 8} to 10{sup 9} W cm{sup -2}. The resultant experimental information is extremely important for the laser deposition of metal nanostructures under atmospheric conditions, which is possible only for power densities of 10{sup 8}–10{sup 9} W cm{sup -2}. (interaction of laser radiation with matter)

  15. Boron- and phosphorus-doped polycrystalline silicon thin films prepared by silver-induced layer exchange

    SciTech Connect

    Antesberger, T.; Wassner, T. A.; Jaeger, C.; Algasinger, M.; Kashani, M.; Scholz, M.; Matich, S.; Stutzmann, M.


    Intentional boron and phosphorus doping of polycrystalline silicon thin films on glass prepared by the silver-induced layer exchange is presented. A silver/(titanium) oxide/amorphous silicon stack is annealed at temperatures below the eutectic temperature of the Ag/Si system, leading to a complete layer exchange and simultaneous crystallization of the amorphous silicon. Intentional doping of the amorphous silicon prior to the exchange process results in boron- or phosphorus-doped polycrystalline silicon. Hall effect measurements show carrier concentrations between 2 Multiplication-Sign 10{sup 17} cm{sup -3} and 3 Multiplication-Sign 10{sup 20} cm{sup -3} for phosphorus and 4 Multiplication-Sign 10{sup 18} cm{sup -3} to 3 Multiplication-Sign 10{sup 19} cm{sup -3} for boron-doped layers, with carrier mobilities up to 90 cm{sup 2}/V s.

  16. Preliminary design for a standard 10 sup 7 bit Solid State Memory (SSM)

    NASA Technical Reports Server (NTRS)

    Hayes, P. J.; Howle, W. M., Jr.; Stermer, R. L., Jr.


    A modular concept with three separate modules roughly separating bubble domain technology, control logic technology, and power supply technology was employed. These modules were respectively the standard memory module (SMM), the data control unit (DCU), and power supply module (PSM). The storage medium was provided by bubble domain chips organized into memory cells. These cells and the circuitry for parallel data access to the cells make up the SMM. The DCU provides a flexible serial data interface to the SMM. The PSM provides adequate power to enable one DCU and one SMM to operate simultaneously at the maximum data rate. The SSM was designed to handle asynchronous data rates from dc to 1.024 Mbs with a bit error rate less than 1 error in 10 to the eight power bits. Two versions of the SSM, a serial data memory and a dual parallel data memory were specified using the standard modules. The SSM specification includes requirements for radiation hardness, temperature and mechanical environments, dc magnetic field emission and susceptibility, electromagnetic compatibility, and reliability.

  17. A thin-collector Bayard-Alpert gauge for 10/sup -12/ Torr vacuum

    SciTech Connect

    Hseuh, H.C.; Lanni, C.


    The changes in the sensitivity (S) and the equivalent X-ray limit (P/sub x/) of several Bayard-Alpert gauges (BAGs) were studied when the size of the collectors was reduced from 125 to 50 and when different mounting envelopes were used. Based on this study, 400 custom BAGs with 50 collector were purchased from a vendor. The S and the P/sub x/ of these thin-collector BAGs were also measured.

  18. The afterglow of GRB 130427A from 1 to 10{sup 16} GHz

    SciTech Connect

    Perley, D. A.; Cenko, S. B.; Corsi, A.; Tanvir, N. R.; Wiersema, K.; Levan, A. J.; Kann, D. A.; Greiner, J.; Sonbas, E.; Zheng, W.; Clubb, K. I.; Zhao, X.-H.; Bai, J.-M.; Chang, L.; Bremer, M.; Castro-Tirado, A. J.; Fruchter, A.; Göğüş, E.; Güver, T.; and others


    We present multiwavelength observations of the afterglow of GRB 130427A, the brightest (in total fluence) gamma-ray burst (GRB) of the past 29 yr. Optical spectroscopy from Gemini-North reveals the redshift of the GRB to be z = 0.340, indicating that its unprecedented brightness is primarily the result of its relatively close proximity to Earth; the intrinsic luminosities of both the GRB and its afterglow are not extreme in comparison to other bright GRBs. We present a large suite of multiwavelength observations spanning from 300 s to 130 days after the burst and demonstrate that the afterglow shows relatively simple, smooth evolution at all frequencies, with no significant late-time flaring or rebrightening activity. The entire data set from 1 GHz to 10 GeV can be modeled as synchrotron emission from a combination of reverse and forward shocks in good agreement with the standard afterglow model, providing strong support to the applicability of the underlying theory and clarifying the nature of the GeV emission observed to last for minutes to hours following other very bright GRBs. A tenuous, wind-stratified circumburst density profile is required by the observations, suggesting a massive-star progenitor with a low mass-loss rate, perhaps due to low metallicity. GRBs similar in nature to GRB 130427A, inhabiting low-density media and exhibiting strong reverse shocks, are probably not uncommon but may have been difficult to recognize in the past owing to their relatively faint late-time radio emission; more such events should be found in abundance by the new generation of sensitive radio and millimeter instruments.

  19. P-type conductivity in annealed strontium titanate

    SciTech Connect

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.


    In this study, Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO3, or STO) samples that were annealed at 1200°C. Room temperature mobilities above 100 cm>2/Vs were measured, an order of magnitude higher than those for electrons (5-10 cm>2/Vs). Average hole densities were in the 10<sup>9-10<sup>10sup> cm>-3 range, consistent with a deep acceptor.

  20. Long term operation of the 100-cm{sup 2} class single cell of MCFC

    SciTech Connect

    Tanimoto, Kazumi; Yanagida, Masahiro; Kojima, Toshikatsu


    The R&D on Molten Carbonate Fuel Cell (MCFC) is proceeding as one of the New Sun Shine Project sponsored by Japanese government. In ONRI (Osaka National Research Institute), the tested MCFCs were assembled with the state-of-the-art components and operated under the load condition for 40000 hours and 34000 hours. We analyzed the performance reduction.

  1. The stability of sodalite in the system NaAlSiO sub 4 -NaCl

    SciTech Connect

    Sharp, Z.D. ); Helffrich, G.R. ); Bohlen, S.R. ); Essene, E.J. )


    The reaction sodalite = {beta}-nepheline + NaCl (s) was reversed in solid-medium apparatus and the reaction sodalite = carnegieite + NaCl (l) was reversed at 1 bar (1,649-1,652 K). The experimental reversals between 923 K and 973 K can be fit with a dP/dT of {minus}11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO{sub 4}-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1,650 K can be generated if the 61.7 J/mol{center dot}K entropy contribution is included in the S{sup 0}{sub 298} of sodalite. This entropy contribution must be removed below 973 K for the experiments to fit with calculations. Previously unreported thermodynamic data estimated in this study are {Delta}G{sup 0}{sub 298} for sodalite ({minus}12,697 kJ/mol) and carnegieite (NaAlSiO{sub 4}) ({minus}1,958 kJ/mol), S{sup 0}{sub 298} of carnegieite (129.6 J/mol{center dot}K) and compressibility of NaCl{sub liquid} (V{sup P}{sub 298} (cm{sup 3}) = 31.6{center dot}(1 - 24.7{center dot}10{sup {minus}3}{center dot}P + 800{center dot}10{sup {minus}6}{center dot}P{sup 2}))(T in K; P in kbar). Sodalite is a high-temperature, low-pressure phase, stable well above the solidus in sodic silica-undersaturated magmas enriched in NaCl, and its presence constrains NaCl activities in magmas. Estimates of minimum NaCl (l) activities in the Mont St-Hilaire sodalite syenites are 0.05 at 1,073 K and 0.13 at 1,273 K. Density calculations are consistent with the field observations that sodalite phenocrysts will float in a nepheline syenite liquid. This explains the enrichment of sodalite in the upper levels of the sodalite syenites at Mont St.Hilaire and elsewhere.

  2. Temperature Dependent Capacitance-Voltage And Deep Level Transient Spectroscopy Study Of Self-Assembled Ge Quantum Dots Embedded In P-type Silicon

    SciTech Connect

    Rangel-Kuoppa, Victor-Tapio; Chen Gang; Jantsch, Wolfgang


    Temperature dependent Capacitance-Voltage (TCV) and Deep Level Transient Spectroscopy (DLTS) techniques were used to study how Ge Quantum Dots (QDs) embedded in Silicon trap charge. Atomic Force Microscopy (AFM) is used to obtain the density of QDs, which is in the order of 3x10{sup 11} cm{sup -2}. Three shallow levels, with activation energies of 40, 65 and 90 meV, and densities around 10{sup 16} cm{sup -3}, are found and are related to Boron. Four deep levels, with activation energies of 110, 150, 330 and 380 meV, and densities between 2x10{sup 15} cm{sup -3} and 5x10{sup 15} cm{sup -3}, are also found. TCV results suggest they are related to the Ge QDs.

  3. Electrical properties of semiconductor quantum dots

    SciTech Connect

    Kharlamov, V. F. Korostelev, D. A.; Bogoraz, I. G.; Milovidova, O. A.; Sergeyev, V. O.


    A method, which makes it possible to obtain semiconductor particles V Almost-Equal-To 10{sup -20} cm{sup 3} in volume (quantum dots) with a concentration of up to 10{sup 11} cm{sup -2} and electrical contacts to each of them, is suggested. High variability in the electrical properties of such particles from a metal oxide (CuO or NiO) after the chemisorption of gas molecules is found.

  4. Comparison of the optical parameters of a CaF{sub 2} single crystal and optical ceramics

    SciTech Connect

    Palashov, O V; Khazanov, E A; Mukhin, I B; Mironov, I A; Smirnov, A N; Dukel'skii, K V; Fedorov, Pavel P; Osiko, Vyacheslav V; Basiev, Tasoltan T


    Single crystal and optical ceramic CaF{sub 2} samples are studied by the method of thermally induced depolarisation of laser radiation at 1076 nm. The absorption coefficients of the single crystal and ceramics are estimated as {alpha} < 4.5x10{sup -4} cm{sup -1} and {alpha} < 1.33x10{sup -3} cm{sup -1}, respectively. (letters)

  5. Preclosure radiological safety analysis for accident conditions of the potential Yucca Mountain Repository: Underground facilities; Yucca Mountain Site Characterization Project

    SciTech Connect

    Ma, C.W.; Sit, R.C.; Zavoshy, S.J.; Jardine, L.J.; Laub, T.W.


    This preliminary preclosure radiological safety analysis assesses the scenarios, probabilities, and potential radiological consequences associated with postulated accidents in the underground facility of the potential Yucca Mountain repository. The analysis follows a probabilistic-risk-assessment approach. Twenty-one event trees resulting in 129 accident scenarios are developed. Most of the scenarios have estimated annual probabilities ranging from 10{sup {minus}11}/yr to 10{sup {minus}5}/yr. The study identifies 33 scenarios that could result in offsite doses over 50 mrem and that have annual probabilities greater than 10{sup {minus}9}/yr. The largest offsite dose is calculated to be 220 mrem, which is less than the 500 mrem value used to define items important to safety in 10 CFR 60. The study does not address an estimate of uncertainties, therefore conclusions or decisions made as a result of this report should be made with caution.



    Balt, R.O.


    A method is described for conducting mechanical operations necessitating the use of a lubricant in a medium operaject to reactor irradiation of 0.5 x 10/ sup 12/ to 1 x 10/sup 12/ neut rons/ cm/sup 2//sec. A thiopolyether lubricant such as 16, 19-dioxa-13, 22-dithiatetratriacontane is used. (AEC)

  7. Electrical and morphological properties of CdTe films synthesized by the method of molecular deposition

    SciTech Connect

    Mayorov, V. A. Yafaysov, A. M.; Bogevolnov, V. B.; Radanstev, V. F.


    Films of cadmium telluride are synthesized by molecular deposition on the substrates made of graphite, mica, and Si. Homogeneous photosensitive layers with the area 65 cm{sup 2} and thickness from 0.5 to 5 {mu}m and hole concentration of 6.3 x 10{sup 16} cm{sup -3} (300 K) are obtained.

  8. Rotationally resolved spectroscopy of a librational fundamental band of hydrogen fluoride tetramer

    SciTech Connect

    Blake, Thomas A.; Sharpe, Steven W.; Xantheas, Sotiris S.


    The rotationally resolved spectrum of a fundamental band of hydrogen fluoride tetramer has been recorded using a pulsed slit-jet, diode laser spectrometer. The band has a parallel rotational structure and is assigned as the H-F out-of-plane libration fundamental with A{sub u} symmetry. Ninety-five ground state combination differences were fit to a symmetric top Hamiltonian to give the following ground state rotational constants: B{sup ''}=0.132 081(7) cm{sup -1}, D{sub J}{sup ''}=7.1(7)x10{sup -7} cm{sup -1}, D{sub JK}{sup ''}=-9(2)x10{sup -7} cm{sup -1}, H{sub JJJ}{sup ''}=6(2)x10{sup -10} cm{sup -1}, H{sub JJK}{sup ''}=9(7)x10{sup -10} cm{sup -1}, H{sub JKK}{sup ''}=-1.3(8)x10{sup -10} cm{sup -1}. A total of 190 transitions were fit to determine the upper state spectroscopic constants: v{sub 4}=714.7849(1) cm{sup -1}, B{sup '}=0.129 634(5) cm{sup -1}, {delta}(C-B)=0.001 344 cm{sup -1}, D{sub J}{sup '}=6.4(5)x10{sup -7} cm{sup -1}, D{sub JK}{sup '}=-4.5(6)x10{sup -7} cm{sup -1}, {delta}D{sub K}=2.92(8)x10{sup -6} cm{sup -1}, H{sub JJJ}{sup '}=3(1)x10{sup -10} cm{sup -1}, H{sub JKK}{sup '}=-1.55(6)x10{sup -8} cm{sup -1}; {delta}H{sub KKK}=-4.65(6)x10{sup -8} cm{sup -1}. Furthermore, a perpendicular band centered at 752.7 cm{sup -1} was observed. The band has a rotational line spacing that gives an approximate B{sup ''} value of 0.132 cm{sup -1}; it has been assigned as the E{sub u} symmetry, H-F in-plane libration fundamental of the HF tetramer. Finally, a parallel band was observed at 741.0 cm{sup -1} with B{sup ''}=0.076 cm{sup -1} and has been assigned as the A{sup ''} symmetry, H-F out-of-plane libration fundamental of the HF pentamer. Structural parameters and harmonic vibrational frequencies are estimated from first-principles, correlated MP2 and CCSD(T) calculations. These are the largest calculations performed to date for this system with respect to both orbital basis set and level of electron correlation. The CCSD(T) harmonic frequencies are, in particular

  9. Electron mobility in very low density GaN/AlGaN/GaN heterostructures

    SciTech Connect

    Manfra, M.J.; Baldwin, K.W.; Sergent, A.M.; Molnar, R.J.; Caissie, J.


    We report on the transport properties of a tunable two-dimensional electron gas (2DEG) confined at the lower interface of a GaN/Al{sub 0.06}Ga{sub 0.94}N/GaN heterostructure grown by plasma-assisted molecular beam epitaxy on semi-insulating GaN templates prepared by hydride vapor phase epitaxy. Using an insulated gate Hall bar structure, the electron density is continuously tuned from {approx}2x10{sup 12} down to 1.5x10{sup 11} cm{sup -2}. At T=300 mK, the 2DEG displays a maximum mobility of 80 000 cm{sup 2}/V s at a sheet density of 1.75x10{sup 12} cm{sup -2}. At low densities, the mobility exhibits a power law dependence on density -{mu}{approx}n{sub e}{sup {alpha}}, with {alpha}{approx}1.0, over the range of 2x10{sup 11}-1x10{sup 12} cm{sup -2}. In this density regime, the mobility is no longer limited by alloy scattering and long-range Coulomb scattering dominates. We discuss the dominant scattering mechanisms that presently limit low temperature mobility at electron densities below 1x10{sup 12} cm{sup -2}.

  10. Plasma resistivity measurements in the Wisconsin levitated octupole

    SciTech Connect

    Brouchous, D. A.


    Resistivity measurements parallel to the magnetic field were made on gun injected plasmas ranging in density from 10/sup 9/cm/sup -3/ to 10/sup 1/parallelcm/sup -3/ in the Wisconsin levitated octupole with toroidal and poloidal magnetic fields. The 10/sup 9/cm/sup -3/ plasma was collisionless with lambda/sub mfp/ > 100 mirror lengths, had T/sub e/ = 10 eV, T/sub i/ = 30 eV and was found to have anomalous resistivity scaling like eta = ..sqrt..T/sub e//n/sub e/ when E/sub parallel/ > E/su c/ is the Dreicer critical field. The 10/sup 12/cm/sup -3/ plasma was collisional with lambda/sub mfp/ < mirror length, had T/sub e/ = T/sub i/ approx. = .2 eV and was found to have Spitzer resistivity when E/sub parallel/ < E/sub c/.

  11. The use of perfluorocarbon tracer (PFT) technology to determine fine leaks in hermeticity testing of semiconductor devices

    SciTech Connect

    Dietz, R.N.


    The BNL-developed perfluorocarbon tracer (PFT) technology includes a rapid-response real-time (5-second) analyzer (COPS) which can detect PFT concentrations as low as 1 {times} 10{sup {minus}11} mL/mL and a concentrating analyzer (DTA) which can measure down to 1 {times} 10{sup {minus}12} mL of PFT--separately quantifying up to 4 PFTs in a 6-min cycle time or less. Based on this technology, experimental leak- rate design concepts are proposed for determining the effectiveness (hermeticity) of the seal of semiconductor devices with internal cavities from 0.01 to 1 mL. The concept is based on pressurizing with PFT-containing air for 60 seconds, purging with PFT-free air for 60 seconds, pressure pulsing with air or He to extract the PFT leaked into the internal volume, and finally detecting the PFT vapor concentration with one of the two instruments. The COPS analyzer can quantify gross leaks from 1 {times} 10{sup {minus}7} to 1 {times} 10{sup {minus}3} mL/s in just 3 minutes for the complete test. The more-sensitive concentrating analyzer (DTA) can quantify fine leaks from 0.2 {times} 10{sup {minus}8} to 1 {times} 10{sup {minus}3} mL/s in just 12 minutes for the complete test; the latter procedure includes two determinations per test. 5 refs., 2 tabs.

  12. P-type conductivity in annealed strontium titanate

    SciTech Connect

    Poole, Violet M.; Corolewski, Caleb D.; McCluskey, Matthew D.


    Hall-effect measurements indicate p-type conductivity in bulk, single-crystal strontium titanate (SrTiO{sub 3}, or STO) samples that were annealed at 1200°C. Room-temperature mobilities above 100 cm{sup 2}/V s were measured, an order of magnitude higher than those for electrons (5-10 cm{sup 2}/V s). Average hole densities were in the 10{sup 9}-10{sup 10} cm{sup −3} range, consistent with a deep acceptor.

  13. High mobility two-dimensional hole system in GaAs/AlGaAs quantum wells grown on (100) GaAs substrates

    SciTech Connect

    Manfra, M.J.; Pfeiffer, L.N.; West, K.W.; Picciotto, R. de; Baldwin, K.W.


    We report on the transport properties of a high mobility two-dimensional hole system (2DHS) confined in GaAs/AlGaAs quantum wells grown by molecular-beam epitaxy on the (100) surface of GaAs. The quantum wells are modulation doped with carbon utilizing a resistive filament source. At T=0.3 K and carrier density p=1x10{sup 11} cm{sup -2}, a mobility of 10{sup 6} cm{sup 2}/Vs is achieved. At fixed carrier density p=10{sup 11} cm{sup -2}, the mobility is found to be a nonmonotonic function of the quantum well width. The mobility peaks at 10{sup 6} cm{sup 2}/Vs for a 15-nm well and is reduced for both smaller and larger well widths for these (100) samples. The mobility anisotropy is found to be small. Mobility along [011] is approximately 20% higher than along the [011] direction. In addition, the low-temperature carrier density is found to have low sensitivity to light. The hole density increases by only {approx}10% after exposure to red light at T=4.2 K. In structures designed for a lower carrier density of 3.6x10{sup 10} cm{sup -2}, a mobility of 800 000 cm{sup 2}/Vs is achieved at T=15 mK.

  14. Mass composition of 10{sup 17}- to 10{sup 18}-eV primary cosmic rays according to data on the lateral distribution of radio emission from extensive air showers

    SciTech Connect

    Kalmykov, N. N. Konstantinov, A. A.; Vedeneev, O. V.


    Experimental data obtained for the lateral distribution of radio emission from extensive air showers (EAS) at the array of Moscow State University (30-34 MHz) and the LOPES array (40-80 MHz) were comparedwith the results of calculations performed within amicroscopic approach based on aMonte Carlo simulation of EAS (CORSIKA code). The same experimental data were used to reconstruct the distribution of the depth of the EAS maximum at cosmic-ray energies in the range of 1017-1018 eV. The energy dependence of the depth of the EAS maximum was constructed for the case of data from the LOPES array, and the mass composition of cosmic rays was estimated for this case. From the resulting dependences, it follows that the mass composition shows a trend toward becoming lighter in the energy range being considered.

  15. Neutrino emission by the pair, plasma, and photo processes in the Weinberg-Salam model

    SciTech Connect

    Schinder, P.J.; Schramm, D.N.; Witta, P.J.; Margolis, S.H.; Tubbs, D.L.


    The results of numerical integrations of the rates and emissivities of the photo, pair, and plasma neutrino emission mechanisms in the Weinberg-Salam theory of the weak interaction are presented. The range of densities 10 gm cm/sup -3/ less than or equal to rho < 10/sup 14/ gm cm/sup -3/ and the temperature range 10/sup 8/K less than or equal to T less than or equal to 10/sup 11/K are considered. Fitting formulae, similar to those provided by Beaudet, Petrosian, and Salpeter, which reproduce the numerical result for the total emissivity to within 20% in the temperature range 10/sup 8.2/K less than or equal to T less than or equal to 10/sup 11/K are presented. 24 refs., 21 figs., 1 tab.

  16. The role of impurities in LP-MOCVD grown gallium nitride

    SciTech Connect

    Hwang, C.Y.; Li, Y.; Schurman, M.J.; Mayo, W.E.; Lu, Y.; Stall, R.A.


    The authors have investigated the relationship of the Hall electron mobility to the background carrier concentration in low pressure MOCVD grown GaN. The highest electron mobility (400 cm{sup 2}/V{center_dot}s) of the unintentionally doped GaN was obtained at a carrier concentration of 1 {times} 10{sup 17} cm{sup {minus}3} and samples with carrier concentrations lower than this exhibited lower mobilities. SIMS analysis shows C and O concentrations in the range of 2--3 {times} 10{sup 16} cm{sup {minus}3} and H in the 2--3 {times} 10{sup 17} cm{sup {minus}3} range. Structural defects, stoichiometry and impurities in the GaN films grown under different conditions are investigated to understand their relationship to the electron Hall mobilities. In particular, different growth temperatures and pressures were used to grow undoped GaN and modify the background doping effect of the impurities.

  17. Portable TXRF Spectrometer with 10{sup -11}g Detection Limit and Portable XRF Spectromicroscope with Sub-mm Spatial Resolution

    SciTech Connect

    Kunimura, Shinsuke; Hatakeyama, So; Sasaki, Nobuharu; Yamamoto, Takashi; Kawai, Jun


    A portable total reflection X-ray fluorescence (TXRF) spectrometer that we have developed is applied to trace elemental analysis of water solutions. Although a 5 W X-ray tube is used in the portable TXRF spectrometer, detection limits of several ppb are achieved for 3d transition metal elements and trace elements in a leaching solution of soils, a leaching solution of solder, and alcoholic beverages are detected. Portable X-ray fluorescence (XRF) spectromicroscopes with a 1 W X-ray tube and an 8 W X-ray tube are also presented. Using the portable XRF spectromicroscope with the 1 W X-ray tube, 93 ppm of Cr is detected with an about 700 {mu}m spatial resolution. Spatially resolved elemental analysis of a mug painted with blue, red, green, and white is performed using the two portable spectromicroscopes, and the difference in elemental composition at each paint is detected.

  18. Frequency Stability of 1x10(sup -13) in a Compensated Sapphire Oscillator Operating Above 77K

    NASA Technical Reports Server (NTRS)

    Dick, G. J.; Santiago, D. G.; Wang, R. T.


    We report on the design and test of a whispering gallery sapphire resonator for which the dominant (WGH(sub n11)) microwave mode family shows frequency-stable, compensated operation for temperatures above 77 kelvin. The resonator makes possible a new ultra-stable oscillator (USO) capability that promises performance improvements over the best available crystal quartz oscillators in a compact cryogenic package.

  19. Frequency Stability of 1X10(sup -13) in a Compensated Sapphire Oscillator Operating Above 77 K

    NASA Technical Reports Server (NTRS)

    Santiago, D. G.; Dick, G. J.; Wang, R. T.


    We report on a frequency-stable temperature compensated sapphire oscillator (CSO) at temperatures above 77 K. Previously, high stability in sapphire oscillators had only been obtained with liquid helium cooling.

  20. Evolution Of Surface Topography On GaAs(100) And GaAs(111) At Normal And Oblique Incidence Of Ar{sup +}-Ions

    SciTech Connect

    Venugopal, V.; Basu, T.; Garg, S.; Majumder, S.; Sarangi, S. N.; Som, T.; Das, P.; Bhattacharyya, S. R.; Chini, T. K.


    Nanoscale surface structures emerging from medium energy (50-60 keV)Ar{sup +}-ion sputtering of p-type GaAs(100) and semi-insulating GaAs(111) substrates have been investigated. For normally incident 50 keV Ar{sup +}-ions of fluence 1x10{sup 17} ions/cm{sup 2} on GaAs(100) and GaAs(111) features in the form of nanoscale pits/holes without short range ordering are observed with densities 5.2x10{sup 9} /cm{sup 2} and 5.9x10{sup 9} /cm{sup 2}, respectively along with irregularly shaped patches of islands. For GaAs(111) on increasing the influence to 5x10{sup 17} /cm{sup 2} the pit density increases marginally to 6.2x10{sup 9} /cm{sup 2}. For 60 deg. off-normal incidence of 60 keV Ar.{sup +}-ions of fluence 2x10{sup 17} ions/cm{sup 2} on GaAs(100) microscale wavelike surface topography is observed. In all cases well-defined nanodots are absent on the surface.

  1. Specific features of transmutational doping of {sup 30}Si-enriched silicon crystals with phosphorus: Studies by the method of electron spin resonance

    SciTech Connect

    Baranov, P. G.; Ber, B. Ya.; Godisov, O. N.; Il'in, I. V. Ionov, A. N.; Kaliteevskii, A. K.; Kaliteevskii, M. A.; Lazebnik, I. M.; Safronov, A. Yu.; Pohl, H.-J.; Riemann, H.; Abrosimov, N. V.; Kop'ev, P. S.; Bulanov, A. D.; Gusev, A. V.


    Electron spin resonance (ESR) is used to study the neutron transmutation doping of silicon crystals enriched with {sup 30}Si isotope: phosphorus donors and radiation defects produced in the course of transmutational doping are observed. The ESR signals related to the phosphorus uncontrolled impurity in {sup 30}Si before transmutational doping (the P concentration is {approx}10{sup 15} cm{sup -3}) and phosphorus introduced by neutron irradiation with doses {approx}1 x 10{sup 19} cm{sup -2} and {approx}1 x 10{sup 20} cm{sup -2} (the P concentrations are {approx}5 x 10{sup 16} and {approx}7 x 10{sup 17} cm{sup -3}, respectively) are studied. As a result of drastic narrowing of the phosphorus ESR lines in {sup 30}Si, the intensity of lines increased appreciably, which made it possible to measure the phosphorus concentration in the samples with a small volume (down to 10{sup -6} mm{sup -3}). The methods for determining the concentration of P donors from hyperfine structure in the ESR spectra of isolated P atoms, exchange-related pairs, and clusters that consist of three, four, and more P donors are developed. In the region of high concentrations of P donors, in which case the hyperfine structure disappears, the concentration of P donors was estimated from the exchange-narrowed ESR line.


    SciTech Connect

    Heinke, C. O.; Tomsick, J. A.; Yusef-Zadeh, F.; Grindlay, J. E.


    We have identified two moderately bright, rapidly variable transients in new and archival X-ray data near the Galactic center. Both objects show strong, flaring variability on timescales of tens to thousands of seconds, evidence of N{sub H} variability, and hard spectra. XMMU J174445.5-295044 is seen at 2-10 keV fluxes of 3 x 10{sup -11} to <10{sup -12} erg cm{sup -2} s{sup -1}, with N{sub H} at or above 5 x 10{sup 22} cm{sup -2}, by XMM-Newton, Chandra, and Suzaku. A likely Two Micron All Sky Survey (2MASS) counterpart with K{sub S} = 10.2 shows colors indicative of a late-type star. CXOU J174042.0-280724 is a likely counterpart to the fast hard transient IGR J17407-2808. Chandra observations find F{sub X} (2-10 keV) {approx}10{sup -12} erg cm{sup -2} s{sup -1}, with large N{sub H} variations (from 2 x 10{sup 22} to >2 x 10{sup 23} cm{sup -2}). No 2MASS counterpart is visible, to K{sub S} >13. XMMU J174445.5-295044 seems likely to be a new symbiotic star or symbiotic X-ray binary, while CXOU J174042.0-280724 is more mysterious, likely an unusual low-mass X-ray binary.

  3. Electronic properties and deep traps in electron-irradiated n-GaN

    SciTech Connect

    Brudnyi, V. N.; Verevkin, S. S.; Govorkov, A. V.; Ermakov, V. S.; Kolin, N. G.; Korulin, A. V.; Polyakov, A. Ya.; Smirnov, N. B.


    The study is concerned with the effect of electron irradiation (with the energies E = 7 and 10 MeV and doses D = 10{sup 16}-10{sup 18} cm{sup -2}) and subsequent heat treatments in the temperature range 100-1000 Degree-Sign C on the electrical properties and the spectrum of deep traps of undoped (concentration of electrons n = 1 Multiplication-Sign 10{sup 14}-1 Multiplication-Sign 10{sup 16} cm{sup -3}), moderately Si-doped (n = (1.2-2) Multiplication-Sign 10{sup 17} cm{sup -3}), and heavily Si-doped (n = (2-3.5) Multiplication-Sign 10{sup 18} cm{sup -3}) epitaxial n-GaN layers grown on Al{sub 2}O{sub 3} substrates by metal-organic chemical vapor deposition. It is found that, on electron irradiation, the resistivity of n-GaN increases, this is due to a shift of the Fermi level to the limiting position close to E{sub c} -0.91 eV. The spectrum of deep traps is studied for the initial and electron-irradiated n-GaN. It is shown that the initial properties of the irradiated material are restored in the temperature range 100-1000 Degree-Sign C, with the main stage of the annealing of radiation defects at about 400 Degree-Sign C.

  4. Neutron-transmuted carbon-14 in neutron-irradiated GaN: Compensation of DX-like center

    SciTech Connect

    Ida, T.; Oga, T.; Kuriyama, K.; Kushida, K.; Xu, Q.; Fukutani, S.


    The transmuted-C related luminescence and net carrier concentration are studied by combining photoluminescence, liquid scintillation, and Raman scattering. GaN single crystal films grown by metalorganic-vapor-phase epitaxy are irradiated with fast and thermal neutrons at fluxes of 3.9 × 10{sup 13} cm{sup −2}s{sup −1} and 8.15 × 10{sup 13} cm{sup −2}s{sup −1}, respectively. Irradiation time is 48 hours. The calculated {sup 72}Ge and {sup 14}C concentrations are 1.24 × 10{sup 18} cm{sup −3} and 1.13 × 10{sup 18} cm{sup −3}, respectively. The transmuted {sup 14}C is detected by the liquid scintillation method to survey β-rays emitted in the process of {sup 14}C decays from {sup 14}N. Tritium ({sup 3}H) is also emitted by a (n,t) reaction of {sup 14}N due to the neutron irradiation above 4.5 MeV. Photoluminescence relating to C, DX-like center of Ge and yellow luminescence band are observed in 1000 °C annealed NTD-GaN. The free electron concentration estimated from Raman scattering is 4.97 × 10{sup 17} cm{sup −3}. This value is lower than that from the transmuted Ge concentration, suggesting the compensation due to the transmuted {sup 14}C acceptors.

  5. Recycler ring conceptual design study

    SciTech Connect

    Jackson, G.


    The Tevatron Collider provides the highest center of mass energy collisions in the world. To fully exploit this unique tool, Fermilab is committed to a program of accelerator upgrades for the purpose of increasing the Collider luminosity. Over the past 7 years the luminosity has been increased from a peak of 1.6{times}10{sup 30}cm{sup {minus}2}sec{sup {minus}1} in 1989 to over 3{times}10{sup 31}cm{sup {minus}2}sec{sup {minus}1} during 1995. The Main Injector will supply a larger flux of protons for antiproton production and more intense proton bunches for use in the Collider, and this is expected to increase the peak luminosity to close to 1{times}10{sup 32}cm{sup {minus}2}sec{sup {minus}1}. Further increases in luminosity will require additional upgrades to the Fermilab accelerator complex. This report documents the design of a new fixed-energy storage ring to be placed in the Main Injector tunnel which will provide an initial factor of 2 increase to 2{times}10{sup 32}cm{sup {minus}2}sec{sup {minus}1}, and ultimately provide the basis for an additional order of magnitude luminosity increase up to 1{times}10{sup 33}cm{sup {minus}2}sec{sup {minus}1}.

  6. First results on lower hybrid current drive at 2. 45 GHz in ASDEX

    SciTech Connect

    Leuterer, F.; Soldner, F.X.; Buechse, R.; Carlson, A.; Eberhagen, A.; Fahrbach, H.; Gehre, O.; Hassenpflug, F.; Herrmann, W.; Janeschitz, G.; Kornherr, M.; Luce, T.; McKormick, K.; Monaco, F.; Muenich, M.; Murmann, H.; Pelicano, M.; Steuer, K.; Zouhar, M. ); Bartiromo, R.; DeAngelis, R.; Pericoli, V.; Santini, F.; Tuccillo, A. ); Bernabei, S.; Forrest, C. ); ASDEX-team


    A new lower hybrid system with 2.45 GHz/3 MW/1 sec has started operation on ASDEX. Current drive effects have been identified up to a density of {bar n}{sub e}=4.7 {center dot} 10{sup 13} cm{sup {minus}3}. Full current drive at I{sub p}=420 kV was achieved up to a density of {bar n}{sub e}=2.1 {center dot} 10{sup 13} cm{sup {minus}3}. The effeciency was maximum at {bar n}{sub e}=1.35 {center dot} 10{sup 13} cm{sup {minus}3} and reached {eta}=1.46 (10{sup 13} cm{sup {minus}3} {center dot} A {center dot} m/W). The electron temperature is peaking and reached peak values up to 6 keV, while the electron density profile flattens. Sawteeth have been stabilized up to a density of {bar n}{sub e}=3.4 {center dot} 10{sup 13} cm{sup {minus}3}. The global confinement times decreases with increasing rf-power. The scaling can be described by an offset linear relation. At low density global confinement is better during the LH-phase than in the OH-phase at the same total power input.

  7. Investigation of epitaxial silicon layers as a material for radiation hardened silicon detectors

    SciTech Connect

    Li, Z.; Eremin, V.; Ilyashenko, I.; Ivanov, A.; Verbitskaya, E.; CERN RD-48 ROSE Collaboration


    Epitaxial grown thick layers ({ge} 100 micrometers) of high resistivity silicon (Epi-Si) have been investigated as a possible candidate of radiation hardened material for detectors for high-energy physics. As grown Epi-Si layers contain high concentration (up to 2 {times} 10{sup 12} cm{sup {minus}3}) of deep levels compared with that in standard high resistivity bulk Si. After irradiation of test diodes by protons (E{sub p} = 24 GeV) with a fluence of 1.5 {times} 10{sup 11} cm{sup {minus}2}, no additional radiation induced deep traps have been detected. A reasonable explanation is that there is a sink of primary radiation induced defects (interstitial and vacancies), possibly by as-grown defects, in epitaxial layers. The ``sinking`` process, however, becomes non-effective at high radiation fluences (10{sup 14} cm{sup {minus}2}) due to saturation of epitaxial defects by high concentration of radiation induced ones. As a result, at neutron fluence of 1 {times} 10{sup 14} cm{sup {minus}2} the deep level spectrum corresponds to well-known spectrum of radiation induced defects in high resistivity bulk Si. The net effective concentration in the space charge region equals to 3 {times} 10{sup 12} cm{sup {minus}3} after 3 months of room temperature storage and reveals similar annealing behavior for epitaxial as compared to bulk silicon.

  8. Investigation of epitaxial silicon layers as a material for radiation hardened silicon detectors

    SciTech Connect

    Li, Z.; Eremin, V.; Ilyashenko, I.; Ivanov, A.


    Epitaxial grown thick layers (>100 {mu}m) of high resistivity silicon (Epi-Si) have been investigated as a possible candidate of radiation hardened material for detectors for high-energy physics. As grown Epi-Si layers contain high concentration (up to 2{center_dot}10{sup 12} cm{sup {minus}3}) of deep levels compared with that in standard high resistivity bulk Si. After irradiation of test diodes by protons (E{sub p} = 24 GeV) with a fluence of 1.5{center_dot}10{sup 11} cm{sup {minus}2}, no additional radiation induced deep traps have been detected. A reasonable explanation is that there is a sink of primary radiation induced defects, in epitaxial layers. The {open_quotes}sinking{close_quotes} process, however, becomes non-effective at high radiation fluences (10{sup 14} cm{sup {minus}2}) due to saturation of epitaxial defects by high concentration of radiation induced ones. As a result, at neutron fluence of 1{center_dot}10{sup 14}cm{sup {minus}2} the deep level spectrum corresponds to well-known spectrum of radiation induced defects in high resistivity bulk Si. The net effective concentration in the space charge region equals to 3{center_dot}10{sup 12} cm{sup {minus}3} after 3 months of room temperature storage and reveals similar annealing behavior for epitaxial as compared to bulk silicon.

  9. Optical evaluation of multichannel radiative transitions originating from {sup 4}G{sub 5/2} level of Sm{sup 3+} in heavy-metal-gallate glasses

    SciTech Connect

    Zhang, J.; Yang, D. L.; Gong, H.; Lin, H.; Pun, E. Y. B.


    Conventional visible and novel infrared (IR) emissions of Sm{sup 3+} in heavy-metal-gallate glasses (Li{sub 2}O-K{sub 2}O-BaO-PbO-Bi{sub 2}O{sub 3}-Ga{sub 2}O{sub 3}, LKBPBG for short) with low phonon energy have been observed. Judd-Ofelt parameters {Omega}{sub 2} (3.00x10{sup -20} cm{sup 2}), {Omega}{sub 4} (5.19x10{sup -20} cm{sup 2}), and {Omega}{sub 6} (1.69x10{sup -20} cm{sup 2}) indicate a higher asymmetry and stronger covalent environment in the optical glasses. For the visible fluorescence bands peaked at 564, 601, 648, and 710 nm, the maximum stimulated emission cross-sections ({sigma}{sub e}) were derived to be 1.35x10{sup -22}, 9.21x10{sup -22}, 9.58x10{sup -22}, and 3.91x10{sup -22} cm{sup 2}, respectively, the values are larger than those in phosphate, oxyfluoroborate, tellurite, and calibo glasses obviously. The observed 1185 nm IR emission lies in the low-loss window of telecommunication system, and the maximum value of {sigma}{sub e} for this band was obtained to be 6.09x10{sup -23} cm{sup 2}. The characterization of multichannel radiative transitions of Sm{sup 3+} in LKBPBG glasses is beneficial in exposing its potential applications in visible and IR optoelectronic devices.

  10. Pesticides sensing by surface plasmon resonance

    SciTech Connect

    Kalabina, N.A.; Ksenevich, T.I.; Beloglazov, A.A.; Nikitin, P.I.


    High toxicity of pesticides and their wide use in agriculture, represent a general danger for environmental welfare and could become a real threat to life. Screening of pesticides in the environment has become very important during last years due to low threshold values for pesticides in drinking water. An optical biosensor has been developed for detection of pesticides, based on surface plasmon resonance (SPR) technique. Concentration of the pesticides was measured in liquid or gas. The authors specially originated organic film on a disposable element. A setup on the base of the Kretschmann arrangement was improved by using a computer-controlled angular scanning system. The detection concentration limit of dinitrophenole (DNP) was 10{sup {minus}9} M. Some samples exhibited effect down to 10{sup {minus}11} M of DNP. The results obtained provide reason for further development of SPR sensor as applied to pesticides monitoring.

  11. Sorption of americium in tuff and pure minerals using synthetic and natural groundwaters

    SciTech Connect

    Triay, I.R.; Meijer, A.; Cisneros, M.R.; Miller, G.G.; Mitchell, A.J.; Ott, M.A.; Hobart, D.E.; Palmer, P.D.; Perrin, R.E.; Aguilar, R.D.


    The distribution of Am between selected solid and liquid phases has been studied using initial {sup 241}Am solutions with a molarity smaller than 1 {times} 10{sup {minus}11}. The synthetic and natural groundwaters used have pH values in the 7--8 range and a total alkalinity of approximately 1 mN which is mainly due to bicarbonate. Mass spectrometric isotope dilution was utilized to determine the amount of Am in the solution phase initially and after equilibrium was attained. Using this sensitive technique, 7 {times} 10{sup 8} atoms of {sup 241}Am were accurately measured. Our results indicate that the percent of Am lost to the walls of the container in the absence of geologic material varies from 35 to 84. The Am sorption coefficient determined is on the order of 10{sup 3} ml/g for clinoptilolite, 10{sup 4} ml/g for tuff consisting mainly of alkali feldspar and cristobalite, and 10{sup 5} ml/g for romanechite. 12 refs.

  12. Properties of iron-doped multicrystalline silicon grown by the float-zone technique

    SciTech Connect

    Ciszek, T.F.; Wang, T.H.; Ahrenkiel, R.K.; Matson, R.


    Multicrystalline Fe-doped Si ingots were float-zoned from high-purity feed rods. Fe was introduced by pill-doping, which gives uniform impurity content for small segregation coefficients (k {approximately} 10{sup {minus}5} for Fe in Si). Fe concentrations were calculated from the initial weight of the Fe pill, the molten zone geomet and the growth parameters. Values in the range of 10{sup 12}-10{sup 16} atoms/cm{sup 3} were targeted. No additional electrically active dopants were introduced. Minority charge carrier lifetime (via YAG-laser-excited, 430-MHz ultra-high-frequency-coupled, photoconductive decay) was measured on the ingots, and wafers were cut to examine grain structure and electron-beam-induced current response of grain boundaries. Observed lifetimes decreased monotonically with increasing Fe content for similar grain sizes (from {approximately}10 {mu}s to 2 {mu}s for < 10{sup {minus}3} cm{sup 2} grains, from {approximately}30 {mu}s to 2 {mu}s for {approximately}5 x 10{sup {minus}3} cm{sup 2} grains, and from {approximately}300 {mu}s to 2 {mu}s for > 10{sup {minus}2} cm{sup 2} grains) as the Fe content increased to 1 {times} 10{sup 16} atoms/cm{sup 3}.

  13. Strain evolution in Si substrate due to implantation of MeV ion observed by extremely asymmetric x-ray diffraction

    SciTech Connect

    Emoto, T.; Ghatak, J.; Satyam, P. V.; Akimoto, K.


    We studied the strain introduced in a Si(111) substrate due to MeV ion implantation using extremely asymmetric x-ray diffraction and measured the rocking curves of asymmetrical 113 diffraction for the Si substrates implanted with a 1.5 MeV Au{sup 2+} ion at fluence values of 1x10{sup 13}, 5x10{sup 13}, and 1x10{sup 14}/cm{sup 2}. The measured curves consisted of a bulk peak and accompanying subpeak with an interference fringe. The positional relationship of the bulk peak to the subpeak and the intensity variation of those peaks with respect to the wavelengths of the x rays indicated that crystal lattices near the surface were strained; the lattice spacing of surface normal (111) planes near the surface was larger than that of the bulk. Detailed strain profiles along the depth direction were successfully estimated using a curve-fitting method based on Darwin's dynamical diffraction theory. Comparing the shapes of resultant strain profiles, we found that a strain evolution rapidly occurred within a depth of approx300 nm at fluence values between 1x10{sup 13} and 5x10{sup 13}/cm{sup 2}. This indicates that formation of the complex defects progressed near the surface when the fluence value went beyond a critical value between 1x10{sup 13} and 5x10{sup 13}/cm{sup 2} and the defects brought a large strain to the substrate.

  14. Processing and evaluation of the AGS Booster ultra-high vaccum system

    SciTech Connect

    Hseuh, H.C.; Mapes, M.; Schnitzenbaumer, P.; Shen, B.; Sikora, R.; Stattel, P.


    The AGS Booster is a synchrotron for the acceleration of both protons and heavy ions. To minimize the beam loss due to charge exchange of the partially stripped, low {Beta} very heavy ions with the residual gas molecules, pressure of low 10{sup {minus}11} Torr is required for the 200 m booster ring. To achieve this ultra high vacuum, chemical cleaning, vacuum furnace degassing and insitu bake were employed for all chambers and beam components. Using these procedures, vacuums of low 10{sup {minus}11} Torr have been routinely achieved during the testing of individual half cells and beam components, and during the commissioning of the vacuum sectors. In this paper, the design and layout of chambers, flanges and bakeout hardware is briefly described. The vacuum processing of different components and the results of bakeout and evaluation are summarized. The experience gained during the construction and commissioning of this ultra-high vacuum system is also given. 3 refs., 3 figs., 1 tab.

  15. AGS proposal: A new search for very rare K{sub L} decays

    SciTech Connect

    Heinson, A.; Molzon, W.R.; Diwan, M.


    The authors propose to carry out a new search for the decays K{sub L} {r_arrow} {mu}e and K{sub L} {r_arrow} ee, building upon the experience and reusing some of the equipment from the recently completed Expt. 791. They also improve the K{sub L} {r_arrow} {mu}{mu} branching ratio measurement. The final E791 single event sensitivity for K{sub L} {r_arrow} {mu}e will be about 1--2 {times} 10{sup {minus}11} (corresponding to a 90% CL limit of roughly 3--5 {times} 10{sup {minus}11}). The new experiment will reach a single event sensitivity below 10{sup {minus}12} and if no events are observed, will set an upper limit of about 2 {times} 10{sup {minus}12}. A few K{sub L} {r_arrow} ee events should be observed, if it occurs at the Standard model level, or more if a new physics process contributes to this decay. About 10,000 K{sub L} {r_arrow} {mu}{mu} decays will also be observed. The experiment will take the novel approach of stopping the neutral beam in a beam stop (or plug) near the upstream end of the spectrometer. A beam test with the beam plug in place will be necessary in the 1991 SEB cycle in order to establish the efficacy of this approach. Another novel feature will be the operation of a tracking detector (probably scintillating fibers) inside the vacuum decay region. The improvements over E791 can be identified as due to: increased beam (approximately a factor of 4, made possible by the Booster), increased acceptance (more than a factor of 2), and improvements in various efficiencies (more than a factor of 2). More precise comparison to E791 is made within this proposal.

  16. Time-resolved electron thermal conduction by probing of plasma formation in transparent solids with high power subpicosecond laser pulses

    SciTech Connect

    Vu, B.T.V.


    This dissertation work includes a series of experimental measurements in a search for better understanding of high temperature (10{sup 4}-10{sup 6}K) and high density plasmas (10{sup 22}-10{sup 24}cm{sup {minus}3}) produced by irradiating a transparent solid target with high intensity (10{sup 13} - 10{sup 15}W/cm{sup 2}) and subpicosecond (10{sup {minus}12}-10{sup {minus}13}s) laser pulses. Experimentally, pump and probe schemes with both frontside (vacuum-plasma side) and backside (plasma-bulk material side) probes are used to excite and interrogate or probe the plasma evolution, thereby providing useful insights into the plasma formation mechanisms. A series of different experiments has been carried out so as to characterize plasma parameters and the importance of various nonlinear processes. Experimental evidence shows that electron thermal conduction is supersonic in a time scale of the first picosecond after laser irradiation, so fast that it was often left unresolved in the past. The experimental results from frontside probing demonstrate that upon irradiation with a strong (pump) laser pulse, a thin high temperature ({approximately}40eV) super-critical density ({approximately}10{sup 23}/cm{sup 3}) plasma layer is quickly formed at the target surface which in turn becomes strongly reflective and prevents further transmission of the remainder of the laser pulse. In the bulk region behind the surface, it is also found that a large sub-critical ({approximately}10{sup 18}/cm{sup 3}) plasma is produced by inverse Bremsstrahlung absorption and collisional ionization. The bulk underdense plasma is evidenced by large absorption of the backside probe light. A simple and analytical model, modified from the avalanche model, for plasma evolution in transparent materials is proposed to explain the experimental results. Elimination of the bulk plasma is then experimentally illustrated by using targets overcoated with highly absorptive films.

  17. Electron Emission from Slightly Oxidized Depleted Uranium Generated by its Own Radioactivity Measured by Electron Spectroscopy, and Electron-Induced Dissociation and Ionization of Hydrogen Near its Surface.

    SciTech Connect

    Siekhaus, W J; Nelson, A J


    Energy dependent electron emission (counts per second) between zero and 1.4 keV generated by the natural reactivity of uranium was measured by an electrostatic spectrometer with known acceptance angle and acceptance area. The electron intensity decreases continuously with energy, but at different rates in different energy regimes, suggesting that a variety of processes may be involved in producing the observed electron emission. The spectrum was converted to energy dependent electron flux (e-/cm{sup 2} s) using the assumption that the emission has a cosine angular distribution. The flux decreased rapidly from {approx}10{sup 6}/cm{sup 2}s to {approx}10{sup 5}/cm{sup 2}s in the energy range from zero to 200 eV, and then more slowly from {approx}10{sup 5}/cm{sup 2}s to {approx}3*10{sup 4}/cm{sup 2} s in the range from 200 to 1400 eV. The energy dependent electron mean free path in gases together with literature cross sections for electron induced reactions were used to determine the number of ionization and dissociation reactions per cm{sup 2}s within the inelastic mean free path of electrons, and found to be about 1.3*10{sup 8}/cm{sup 2}s and 1.5*10{sup 7}/cm{sup 2}s, respectively, for hydrogen. An estimate of the number of ionization and dissociation reactions occurring within the total range, rather than the mean free path of electrons in gases resulted in 6.2*10{sup 9}/cm{sup 2}s and 1.3*10{sup 9}/cm{sup 2}s, respectively. The total energy flux carried by electrons from the surface is suspiciously close to the total possible energy generated by one gram of uranium. A likely source of error is the assumption that the electron emission has a cosine distribution. Angular distribution measurements of the electron emission would check that assumption, and actual measurement of the total current emanating from the surface are needed to confirm the value of the current calculated in section II. These results must therefore be used with caution - until they are confirmed


    SciTech Connect

    Tripathi, Shruti; Misra, R.; Dewangan, G. C.; Cheeran, J.; Abraham, S.; Philip, N. S.


    We analyze Suzaku and XMM-Newton data of the highly variable Seyfert 2, IRAS 18325-5926. The spectra of the source are well modeled as a primary component described as an absorbed power law and a secondary power-law component which is consistent with being scattered emission from an on-axis extended highly ionized medium. We show that while the primary component varies on a wide range of timescales from 10{sup 4}-10{sup 8} s, the scattered emission is variable only on timescales longer than 10{sup 5} s. This implies that the extent of the scattering medium is greater than 10{sup 16} cm. The ratio of the scattered to primary flux ({approx}0.03) implies a column density for the scattering medium to be {approx}10{sup 23} cm{sup -2}. We argue that for such a medium to be highly ionized it must be located less than 10{sup 17} cm from the X-ray source. Thus, we localize the position and extent of scattering region to be {approx}a few Multiplication-Sign 10{sup 16} cm, with an average particle density of {approx}10{sup 6} cm{sup -3}. We consider the physical interpretation of these results, and as an aside we confirm the presence of a broad iron line emission in both the XMM-Newton and Suzaku observations.


    SciTech Connect

    Shi, Yong; Helou, George; Armus, Lee


    We estimate the abundance of Compton-thick (CT) active galactic nuclei (AGNs) based on our joint model of X-ray and infrared backgrounds. At L{sub rest2-10{sub keV}} > 10{sup 42} erg s{sup –1}, the CT AGN density predicted by our model is a few ×10{sup –4} Mpc{sup –3} from z = 0 up to z = 3. CT AGNs with higher luminosity cuts (>10{sup 43}, 10{sup 44}, and 10{sup 45} erg s{sup –1}) peak at higher redshift and show a rapid increase in number density from z = 0 to z ∼ 2-3. The CT AGN to all AGN ratio appears to be low (2%-5%) at f{sub 2-10{sub keV}} > 10{sup –15} erg s{sup –1} cm{sup –2} but rises rapidly toward fainter flux levels. The CT AGNs account for ∼38% of the total accreted supermassive black hole mass and contribute ∼25% of the cosmic X-ray background spectrum at 20 keV. Our model predicts that the majority (90%) of luminous and bright CT AGNs (L{sub rest2-10keV} > 10{sup 44} erg s{sup –1} or f{sub 2-10{sub keV}} > 10{sup –15} erg s{sup –1} cm{sup –2}) have detectable hot dust 5-10 μm emission, which we associate with a dusty torus. The fraction drops for fainter objects, to around 30% at L{sub rest2-10{sub keV}} > 10{sup 42} erg s{sup –1} or f{sub 2-10{sub keV}} > 10{sup –17} erg s{sup –1} cm{sup –2}. Our model confirms that heavily obscured AGNs (N{sub H{sub I}} > 10{sup 23} cm{sup –2}) can be separated from unobscured and mildly obscured ones (N{sub H{sub I}} < 10{sup 23} cm{sup –2}) in the plane of observed frame X-ray hardness versus mid-IR/X-ray ratio.

  20. Metabolic responses to subacute toxicity of trace metals in a marine microalga (Thalassiosira weissflogii) measured by calorespirometry

    SciTech Connect

    Reinfelder, J.R.; Jablonka, R.E.; Cheney, M.


    Metabolic responses to the subacute toxicities of Cd, Cu, and Zn were measured in the coastal marine diatom Thalassiosira weissflogii using calorespirometry. Respiratory heat production and oxygen consumption rates were measured in diatom cells grown with concentrations of Cd{sup 2+} (10{sup {minus}12} to 10{sup {minus}8} M), Cu{sup 2+} (10{sup {minus}13.8} to 10{sup {minus}9.8} M), and Zn{sup 2+} (10{sup {minus}10.9} to 10{sup {minus}6.9} M). Respiratory heat rates in cells grown with elevated, but non-growth-rate-inhibiting free Cu{sup 2+} ion concentrations (10{sup {minus}11.8} to 10{sup {minus}9.8} M) were up to 40% higher and oxygen consumption rates were 50 to 75% lower than control ([Cu{sup 2+}] = 10{sup {minus}13.8} M) cells indicating a subacute depression of respiratory efficiency in Cu-exposed cells. Exposure to elevated free Cd{sup 2+} concentrations (10{sup {minus}10} to 10{sup {minus}8} M) caused dramatic short-term (hours) increases (five- to eight-fold) in respiratory oxygen consumption rates, which returned to normal in acclimated cells, suggesting a transient disruption of metabolism upon Cd exposure. Zinc did not significantly affect either respiratory parameter up to a free Zn concentration of 10{sup {minus}7.9} M, above which diatom growth rate was significantly reduced. The subacute toxic effects of Cd and Cu were more pronounced in low Mn than in Mn-replete cells, consistent with proposed Mn-Cd, -Cu antagonisms in marine phytoplankton. The range of free Cu{sup 2+} ion concentrations in coastal waters is similar to that found to cause a decrease in respiratory efficiency in T. weissflogii, thus coastal marine diatoms may be subject to the subacute metabolic toxicity of Cu. Free Cd{sup 2+} concentration in coastal waters are below those found to cause transient subacute stress in T. weissflogii. calorespirometry proved to be a sensitive tool for the assessment of the subacute toxicity of contaminant trace metals.

  1. Temperature dependences of the contact resistivity in ohmic contacts to n{sup +}-InN

    SciTech Connect

    Sachenko, A. V.; Belyaev, A. E.; Boltovets, N. S.; Brunkov, P. N.; Jmerik, V. N.; Ivanov, S. V.; Kapitanchuk, L. M.; Konakova, R. V. Klad’ko, V. P.; Romanets, P. N.; Saja, P. O.; Safryuk, N. V.; Sheremet, V. N.


    The temperature dependences of the contact resistivity (ρ{sub c}) of ohmic contacts based on the Au-Ti-Pd-InN system are measured at an InN doping level of 2 × 10{sup 18} cm{sup −3} in the temperature range of 4.2–300 K. At temperatures T > 150 K, linearly increasing dependences ρ{sub c}(T) are obtained. The dependences are explained within the mechanism of thermionic current flow through metal shunts associated with dislocations. Good agreement between theoretical and experimental dependences is achieved assuming that the flowing current is limited by the total resistance of the metal shunts, and the density of conductive dislocations is ∼5 × 10{sup 9} cm{sup −2}. Using the X-ray diffraction method, the density of screw and edge dislocations in the structure under study is measured: their total density exceeds 10{sup 10} cm{sup −2}.

  2. Nanostructures from hydrogen implantation of metals.

    SciTech Connect

    McWatters, Bruce Ray; Causey, Rion A.; DePuit, Ryan J.; Yang, Nancy Y. C.; Ong, Markus D.


    This study investigates a pathway to nanoporous structures created by hydrogen implantation in aluminum. Previous experiments for fusion applications have indicated that hydrogen and helium ion implantations are capable of producing bicontinuous nanoporous structures in a variety of metals. This study focuses specifically on hydrogen and helium implantations of aluminum, including complementary experimental results and computational modeling of this system. Experimental results show the evolution of the surface morphology as the hydrogen ion fluence increases from 10{sup 17} cm{sup -2} to 10{sup 18} cm{sup -2}. Implantations of helium at a fluence of 10{sup 18} cm{sup -2} produce porosity on the order of 10 nm. Computational modeling demonstrates the formation of alanes, their desorption, and the resulting etching of aluminum surfaces that likely drives the nanostructures that form in the presence of hydrogen.

  3. Cr{sup 4+}:YAG as passive Q-switch and Brewster plate in a pulsed Nd:YAG laser

    SciTech Connect

    Shimony, Y.; Burshtein, Z.; Kalisky, Y.


    The authors demonstrate the performance of a Nd:YAG laser, passively Q-switched with a Cr{sup 4+}:YAG plate, which plays the double role of a passive Q-switch ad a Brewster plate. The Brewster plate configuration contributes an intracavity loss of approximately 3.2 {times} 10{sup {minus}3} cm{sup {minus}1} along the cavity length. Losses contributed by the active Cr{sup 4+} ions in the plate relate to their excited state absorption. A freshly measured transmission saturation curve of Cr{sup 4+}:YAG suggests a ground state absorption cross section {sigma}{sub gs} = (8.7 {+-} 0.8) {times} 10{sup {minus}19} cm{sup 2}, and an excited state absorption cross section {sigma}{sub es} = (2.2 {+-} 0.2) {times} 10{sup {minus}19} cm{sup 2} of the Cr{sup 4+} ions at {lambda} = 1,064 nm.

  4. Deactivation of krypton atoms in the metastable 5s({sup 3}P{sub 2}) state in collisions with krypton and argon atoms

    SciTech Connect

    Zayarnyi, D A; L'dov, A Yu; Kholin, I V


    The collision deactivation of the metastable 5s[3/2]{sub 2}{sup o}({sup 3}P{sub 2}) state of krypton atoms is studied by the absorption probe method in electron-beam-excited high-pressure Ar-Kr mixtures with a low krypton content. The rate constants of plasma-chemical reactions Kr* + Kr + Ar {yields} Kr{sub 2}* + Ar [(4.1{+-}0.4)x10{sup -33} cm{sup 6} s{sup -1}] and Kr* + 2Ar {yields} ArKr* + Ar (less than 10{sup -35} cm{sup 6} s{sup -1}) are measured for the first time and the rate constant of the reaction Kr* + Ar {yields} products + Ar [(3.8{+-}0.4)x10{sup -15} cm{sup 3} s{sup -1}] is refined. (active media)

  5. Deactivation of xenon atoms in the 6s resonant state in collisions with xenon and helium atoms

    SciTech Connect

    Zayarnyi, D A; Semenova, Ludmila V; Ustinovskii, N N; Kholin, I V; Chugunov, A Yu


    The absorption probing method was used to investigate collisional deactivation of the 6s[3/2]{sub 1}{sup 0}({sup 3}P{sub 1}) state of the xenon atom in high-pressure He - Xe mixtures with a low xenon concentration. Measurements were made of the rate constants of the following plasma-chemical reactions: Xe* + Xe + He {yields} Xe{sub 2}* + He [(2.1 {+-} 0.2) x 10{sup -32} cm{sup 6}s{sup -1}], Xe* + 2He {yields} HeXe* + He (less than 10{sup -35} cm{sup 6}s{sup -1}), and Xe* + He {yields} products + He (less than 3 x 10{sup -15} cm{sup 3}s{sup -1}). (active media)

  6. Deep-level emissions influenced by O and Zn implantations in ZnO

    SciTech Connect

    Zhao, Q.X.; Klason, P.; Willander, M.; Zhong, H.M.; Lu, W.; Yang, J.H.


    A set of bulk ZnO samples implanted with O and Zn at various densities were investigated by photoluminescence. The implantation concentration of O and Zn is varied between 1x10{sup 17}/cm{sup 3} and 5x10{sup 19}/cm{sup 3}. The samples were thermally treated in an oxygen gas environment after the implantation. The results clearly show the influence of O and Zn implantations on the deep-level emission. By comparing the photoluminescence spectra for the samples with different implantations, we can conclude that the V{sub Zn} is responsible to the observed deep-level emission. In addition, a novel transition at the emission energy of 3.08 eV at 77 K appears in the O-implanted sample with 5x10{sup 19}/cm{sup 3} implantation concentration. The novel emission is tentatively identified as O-antisite O{sub Zn}.

  7. Effect of extreme radiation fluences on parameters of SiC nuclear particle detectors

    SciTech Connect

    Ivanov, A. M. Lebedev, A. A.; Strokan, N. B.


    Detectors based on modern CVD-grown films were irradiated with 8 MeV protons at a fluence of 3 x 10{sup 14} cm{sup -2}. The concentration of primary radiation defects was {approx}10{sup 17} cm{sup -3}, which is three orders of magnitude higher than the concentration of the initially present uncompensated donors. The resulting deep compensation of SiC enabled measurements of detector parameters in two modes: under reverse and forward bias. The basic parameters of the detectors degraded by no more than a factor of 1.7, compared with the fluence of 1 x 10{sup 14} cm{sup -2}. However, there appeared a polarization voltage, which indicates that a space charge is accumulated by radiation defects.

  8. Instability of characteristics of SiC detectors subjected to extreme fluence of nuclear particles

    SciTech Connect

    Ivanov, A. M. Strokan, N. B.; Bogdanova, E. V.; Lebedev, A. A.


    The operation of detectors irradiated with 8-MeV protons at a fluence of 3 x 10{sup 14} cm{sup -2} has been studied. The detectors were based on modern CVD-grown n-4H-SiC films with a concentration of uncompensated donors equal to {approx}2 x 10{sup 14} cm{sup -3} and a thickness of 55 {mu}m. The high concentration of primary radiation defects ({approx}2 x 10{sup 17} cm{sup -3}) determined the deep compensation of the films. The basic characteristics of the detectors-pulse amplitude and resolution-exhibited temporal instability. This effect is due to prolonged capture of nonequilibrium carriers by radiation centers and the resulting appearance of a polarization voltage in the bulk of the detector. The kinetics of attainment of steady values by the quantities specified above was analyzed.

  9. Critical oxygen concentration in hydrogenated amorphous silicon solar cells dependent on the contamination source

    SciTech Connect

    Woerdenweber, Jan; Merdzhanova, Tsvetelina; Gordijn, Aad; Stiebig, Helmut; Beyer, Wolfhard


    For hydrogenated amorphous silicon (a-Si:H) solar cells, the critical concentration of a given impurity defines the lowest concentration which causes a decay of solar cell efficiency. Values of 2-5x10{sup 19} cm{sup -3} are commonly found for the critical oxygen concentration (C{sub O}{sup crit}) of a-Si:H. Here we report a dependence of C{sub O}{sup crit} on the contamination source. For state-of-the-art a-Si:H solar cells prepared at the same plasma deposition conditions, we obtain with a (controllable) chamber wall leak C{sub O}{sup crit} approx2x10{sup 19} cm{sup -3} while for a leak in the gas supply line a higher C{sub O}{sup crit} of approx2x10{sup 20} cm{sup -3} is measured. No such dependence is observed for nitrogen.

  10. Review and assessment of measured values of the nonlinear refractive-index coefficient of fused silica

    SciTech Connect

    Milam, D.


    The literature describes more than 30 measurements, at wavelengths between 249 and 1550 nm, of the absolute value of the nonlinear refractive-index coefficient of fused silica. Results of these experiments were assessed and best currently available values were selected for the wavelengths of 351, 527, and 1053 nm. The best values are (3.6{plus_minus}0.64){times}10{sup {minus}16} cm{sup 2}/W at 351 nm, (3.0{plus_minus}0.35){times}10{sup {minus}16} cm{sup 2}/W at 527 nm, and (2.74{plus_minus}0.17){times}10{sup {minus}16} cm{sup 2}/W at 1053 nm. {copyright} 1998 Optical Society of America

  11. P-type InGaN across the entire alloy composition range

    SciTech Connect

    Wang, K.; Araki, T.; Katsuki, T.; Yu, K. M.; Mayer, M. A.; Ager, J. W. III; Walukiewicz, W.; Alarcon-Llado, E.; Nanishi, Y.


    A systematic investigation on Mg doped and undoped InGaN epilayers grown by plasma-assisted molecular beam epitaxy has been conducted. Single phase InGaN alloys across the entire composition range were synthesized and Mg was doped into In{sub x}Ga{sub 1-x}N (0.1 {<=} x {<=} 0.88) epilayers up to {approx}10{sup 20}/cm{sup 3}. Hall effect, thermopower, and electrochemical capacitance voltage experimental results demonstrate the realization of p-type InGaN across the entire alloy composition range for properly Mg doped InGaN. Hole densities have been measured or estimated to be in the lower {approx}10{sup 18}/cm{sup 3} range when the net acceptor concentrations are in the lower {approx}10{sup 19}/cm{sup 3} range across the composition range.

  12. Permanent optical doping of amorphous metal oxide semiconductors by deep ultraviolet irradiation at room temperature

    SciTech Connect

    Seo, Hyungtak; Cho, Young-Je; Bobade, Santosh M.; Park, Kyoung-Youn; Choi, Duck-Kyun; Kim, Jinwoo; Lee, Jaegab


    We report an investigation of two photon ultraviolet (UV) irradiation induced permanent n-type doping of amorphous InGaZnO (a-IGZO) at room temperature. The photoinduced excess electrons were donated to change the Fermi-level to a conduction band edge under the UV irradiation, owing to the hole scavenging process at the oxide interface. The use of optically n-doped a-IGZO channel increased the carrier density to approx10{sup 18} cm{sup -3} from the background level of 10{sup 16} cm{sup -3}, as well as the comprehensive enhancement upon UV irradiation of a-IGZO thin film transistor parameters, such as an on-off current ratio at approx10{sup 8} and field-effect mobility at 22.7 cm{sup 2}/V s.

  13. Electrical properties of Zinc-Tin diarsenide (ZnSnAs{sub 2}) irradiated with H{sup +} ions

    SciTech Connect

    Brudnyi, V. N. Vedernikova, T. V.


    The results of studying the electrical properties and isochronous annealing of p-ZnSnAs{sub 2} irradiated with H{sup +} ions (energy E = 5 MeV, dose D = 2 x 10{sup 16} cm{sup -2}) are reported. The limiting electrical characteristics of irradiated material (the Hall coefficient R{sub H} (D){sub lim} {approx} -4 x 10{sup 3} cm{sup 3} C{sup -1}, conductivity {sigma} (D){sub lim} {approx} 2.9 x 10{sup -2} {omega}{sup -1} cm{sup -1}, and the Fermi level position F{sub lim} {approx} 0.58 eV above the valence-band top at 300 K) are determined. The energy position of the 'neutral' point for the ZnSnAs{sub 2} compound is calculated.

  14. A compact laser head with high-frequency stability for Rb atomic clocks and optical instrumentation

    SciTech Connect

    Affolderbach, Christoph; Mileti, Gaetano


    We present a compact and frequency-stabilized laser head based on an extended-cavity diode laser. The laser head occupies a volume of 200 cm{sup 3} and includes frequency stabilization to Doppler-free saturated absorption resonances on the hyperfine components of the {sup 87}Rb D{sub 2} lines at 780 nm, obtained from a simple and compact spectroscopic setup using a 2 cm{sup 3} vapor cell. The measured frequency stability is {<=}2x10{sup -12} over integration times from 1 s to 1 day and shows the potential to reach 2x10{sup -13} over 10{sup 2}-10{sup 5} s. Compact laser sources with these performances are of great interest for applications in gas-cell atomic frequency standards, atomic magnetometers, interferometers and other instruments requiring stable and narrow-band optical sources.

  15. Atomic layer deposition of Al-incorporated Zn(O,S) thin films with tunable electrical properties

    SciTech Connect

    Park, Helen Hejin; Jayaraman, Ashwin; Heasley, Rachel; Yang, Chuanxi; Hartle, Lauren; Gordon, Roy G.; Mankad, Ravin; Haight, Richard; Gunawan, Oki; Mitzi, David B.


    Zinc oxysulfide, Zn(O,S), films grown by atomic layer deposition were incorporated with aluminum to adjust the carrier concentration. The electron carrier concentration increased up to one order of magnitude from 10{sup 19} to 10{sup 20} cm{sup −3} with aluminum incorporation and sulfur content in the range of 0 ≤ S/(Zn+Al) ≤ 0.16. However, the carrier concentration decreased by five orders of magnitude from 10{sup 19} to 10{sup 14} cm{sup −3} for S/(Zn+Al) = 0.34 and decreased even further when S/(Zn+Al) > 0.34. Such tunable electrical properties are potentially useful for graded buffer layers in thin-film photovoltaic applications.

  16. Effect of molarity on properties of spray pyrolysed SnO{sub 2}:F thin films

    SciTech Connect

    Deepu, D. R. Kartha, C. Sudha Vijayakumar, K. P.


    Fluorine doped tin oxide (FTO) thin films were prepared by using automated Chemical Spray Pyrolysis (CSP) machine and the effect of concentration of the precursors on the conductivity and transmittance of the films were studied. The resistivity (ρ) and mobility (μ) are in the range of 10{sup −3}–10{sup −4} Ω-cm and 8.2–13.5 cm{sup 2}V{sup −1}s{sup −1} respectively. The electron density lies between 3.4 × 10{sup 20} and 6.6×10{sup 20} cm{sup −3}. The film transmittance varies between 70 to 80% and the films shows very good reflectivity in the IR-NIR region. Prepared films can be used as transparent electrodes in photo voltaic and optoelectronic devices.

  17. p type doping of zinc oxide by arsenic ion implantation

    SciTech Connect

    Braunstein, G.; Muraviev, A.; Saxena, H.; Dhere, N.; Richter, V.; Kalish, R.


    p type doping of polycrystalline ZnO thin films, by implantation of arsenic ions, is demonstrated. The approach consisted of carrying out the implantations at liquid-nitrogen temperature ({approx}-196 deg. C), followed by a rapid in situ heating of the sample, at 560 deg. C for 10 min, and ex situ annealing at 900 deg. C for 45 min in flowing oxygen. p type conductivity with a hole concentration of 2.5x10{sup 13} cm{sup -2} was obtained using this approach, following implantation of 150 keV 5x10{sup 14} As/cm{sup 2}. A conventional room-temperature implantation of 1x10{sup 15} As/cm{sup 2}, followed by the same ex situ annealing, resulted in n type conductivity with a carrier concentration of 1.7x10{sup 12} cm{sup -2}.

  18. Minority carrier lifetime in iodine-doped molecular beam epitaxy-grown HgCdTe

    SciTech Connect

    Madni, I.; Umana-Membreno, G. A.; Lei, W.; Gu, R.; Antoszewski, J.; Faraone, L.


    The minority carrier lifetime in molecular beam epitaxy grown layers of iodine-doped Hg{sub 1−x}Cd{sub x}Te (x ∼ 0.3) on CdZnTe substrates has been studied. The samples demonstrated extrinsic donor behavior for carrier concentrations in the range from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3} without any post-growth annealing. At a temperature of 77 K, the electron mobility was found to vary from 10{sup 4} cm{sup 2}/V s to 7 × 10{sup 3} cm{sup 2}/V s and minority carrier lifetime from 1.6 μs to 790 ns, respectively, as the carrier concentration was increased from 2 × 10{sup 16} cm{sup −3} to 6 × 10{sup 17} cm{sup −3}. The diffusion of iodine is much lower than that of indium and hence a better alternative in heterostructures such as nBn devices. The influence of carrier concentration and temperature on the minority carrier lifetime was studied in order to characterize the carrier recombination mechanisms. Measured lifetimes were also analyzed and compared with the theoretical models of the various recombination processes occurring in these materials, indicating that Auger-1 recombination was predominant at higher doping levels. An increase in deep-level generation-recombination centers was observed with increasing doping level, which suggests that the increase in deep-level trap density is associated with the incorporation of higher concentrations of iodine into the HgCdTe.

  19. Ionic conductivity of Bi{sub 2}Ni{sub x}V{sub 1−x}O{sub 5.5−3x/2} (0.1 ≤ x ≤ 0.2) oxides prepared by a low temperature sol-gel route

    SciTech Connect

    Rusli, Rolan; Patah, Aep Prijamboedi, Bambang Ismunandar; Abrahams, Isaac


    Solid oxides fuel cells (SOFCs) is one technology that could contribute toward future sustainable energy. One of the most important components of an SOFC is the electrolyte, which must have high ionic conductivity. Cation substitution of vanadium in Bi{sub 4}V{sub 2}O{sub 11} yields a family of fast oxide ion conducting solids known collectively as the BIMEVOXes (bismuth metal vanadium oxide), which have the potential to be applied as electrolytes in SOFCs. The purpose of this work is to study the effect of Ni concentration, when used as a dopant, on the ionic conductivity of Bi{sub 2}Ni{sub x}V{sub 1−x}O{sub 5.5−3x/2} (BINIVOX) oxides (0.1 ≤ x ≤ 0.2) when prepared by a sol gel method. The gels were calcined at 600 °C for 24 h to produce pure BINIVOX. These oxides were found to exhibit the γ-phase structure with tetragonal symmetry in space group I4/mmm. Ionic conductivity of BINIVOX at 300 °C were 6.9 × 10{sup −3} S cm{sup −1}, 1.2 × 10{sup −3} S cm{sup −1}, and 8.2 × 10{sup −4} S cm{sup −1}, for x = 0.1; 0.15; and 0.2; respectively; and at 600 °C were 1.1 × 10{sup −1} S cm{sup −1}, 5.3 × 10{sup −2} S cm{sup −1}, and 2.8 ×10{sup −2} S cm{sup −1}, for x = 0.1; 0.15; and 0.2; respectively.

  20. Heating of the magnetic-ion spin system in modulation doped ZnMnSe/ZnBeSe quantum wells by means of photoexcitation.

    SciTech Connect

    Keller, D.; Astakhov, G. V.; Yakovlev, D. R.; Barrick, T.; Crooker, S. A.; Hansen, L.; Ossau, W.; Molenkamp, L. W.


    Heating of the spin system of magnetic ions by means of photoexcited carriers has been studied in modulation-doped (Zn,Mn)Se/(Zn,Be)Se quantum well structures with different electron densities varying from about 10{sup 9} to 5.5 x 10{sup 11} cm{sup -2}. The elevated temperature of the magnetic ions manifests in a reduced Zeeman splitting of the carriers already for low excitation densities. The efficiency of the heating decreases with increasing electron concentration.

  1. Bose-Einstein condensation of {sup 86}Sr

    SciTech Connect

    Stellmer, Simon; Grimm, Rudolf; Tey, Meng Khoon; Schreck, Florian


    We report on the attainment of Bose-Einstein condensation of {sup 86}Sr. This isotope has a scattering length of about +800a{sub 0} and thus suffers from fast three-body losses. To avoid detrimental atom loss, evaporative cooling is performed at low densities around 3x10{sup 12} cm{sup -3} in a large volume optical dipole trap. We obtain almost pure condensates of 5x10{sup 3} atoms.

  2. Crystallographically oriented Zn nanocrystals formed in ZnO by Mn{sup +}-implantation

    SciTech Connect

    Li, Y. J.; Zhang, B.; Lu, W.; Wang, Y.; Zou, J.


    The nanostructural characteristics of ZnO implanted with Mn{sup +} to doses ranging from 1x10{sup 15} to 1x10{sup 17} cm{sup -2} are systematically studied for both as-implanted and postannealed cases. The detailed structural characterizations confirmed that the Mn{sup +} implantation and postannealing result in (1) the formation of crystallographically orientated Zn nanocrystals in the ZnO matrix and (2) Mn atoms occupy the Zn sites in ZnO.

  3. Parameters for a Super-Flavor-Factory

    SciTech Connect

    Seeman, J.T.; Cai, Y.; Ecklund, S.; Novokhatski, A.; Seryi, A.; Sullivan, M.; Wienands, U.; Biagini, M.; Raimondi, P.; /Frascati


    A Super Flavor Factory, an asymmetric energy e{sup +}e{sup -} collider with a luminosity of order 10{sup 36} cm{sup -2} s{sup -1}, can provide a sensitive probe of new physics in the flavor sector of the Standard Model. The success of the PEP-II and KEKB asymmetric colliders in producing unprecedented luminosity above 10{sup 34} cm{sup -2} s{sup -1} has taught us about the accelerator physics of asymmetric e{sup +}e{sup -} collider in a new parameter regime. Furthermore, the success of the SLAC Linear Collider and the subsequent work on the International Linear Collider allow a new Super-Flavor collider to also incorporate linear collider techniques. This note describes the parameters of an asymmetric Flavor-Factory collider at a luminosity of order 10{sup 36} cm{sup -2} s{sup -1} at the Y(4S) resonance and about 10{sup 35} cm{sup -2} s{sup -1} at the {tau} production threshold. Such a collider would produce an integrated luminosity of about 10,000 fb{sup -1} (10 ab{sup -1}) in a running year (10{sup 7} sec) at the Y(4S) resonance. In the following note only the parameters relative to the Y(4S) resonance will be shown, the ones relative to the lower energy operations are still under study.

  4. Measurements of the Ultraviolet Fluorescence Cross Sections and Spectra of Bacillus Anthracis Simulants

    SciTech Connect

    Stephens, J.R.


    Measurements of the ultraviolet autofluorescence spectra and absolute cross sections of the Bacillus anthracis (Ba) simulants Bacillus globigii (Bg), Bacillus megaterium (Bm), Bacillus subtilis (Bs), and Bacillus cereus (Bc) were measured. Fluorescence spectra and cross sections of pine pollen (Pina echinata) were measured for comparison. Both dried vegetative cells and spores separated from the sporulated vegetative material were studied. The spectra were obtained by suspending a small number (<10) of particles in air in our Single Particle Spectroscopy Apparatus (SPSA), illuminating the particles with light from a spectrally filtered arc lamp, and measuring the fluorescence spectra of the particles. The illumination was 280 nm (20 nm FWHM) and the fluorescence spectra was measured between 300 and 450 nm. The fluorescence cross section of vegetative Bg peaks at 320 nm with a maximum cross section of 5 X 10{sup -14} cm{sup 2}/sr-nm-particle while the Bg spore fluorescence peaks at 310 nm with peak fluorescence of 8 X 10{sup -15} cm{sup 2}/sr-nm-particle. Pine pollen particles showed a higher fluorescence peaking at 355 nm with a cross section of 1.7 X 10{sup -13} cm{sup 2}/sr-nm-particle. Integrated cross sections ranged from 3.0 X 10{sup -13} for the Bg spores through 2.25 X 10{sup -12} (cm{sup 2}/sr-particle) for the vegetative cells.

  5. Methods of enhancing conductivity of a polymer-ceramic composite electrolyte


    Kumar, Binod


    Methods for enhancing conductivity of polymer-ceramic composite electrolytes are provided which include forming a polymer-ceramic composite electrolyte film by a melt casting technique and uniaxially stretching the film from about 5 to 15% in length. The polymer-ceramic composite electrolyte is also preferably annealed after stretching such that it has a room temperature conductivity of from 10.sup.-4 S cm.sup.-1 to 10.sup.-3 S cm.sup.-1. The polymer-ceramic composite electrolyte formed by the methods of the present invention may be used in lithium rechargeable batteries.

  6. Cold {sup 52}Cr elastic and inelastic collision-rate determination using evaporative cooling analysis

    SciTech Connect

    Nguyen, Scott V.; Carvalho, Robert de; Doyle, John M.


    Elastic and inelastic collision-rate constants of {sup 52}Cr in the temperature range of 20 mK to 1 K are inferred from the evaporative cooling of buffer gas loaded atomic chromium. Using a model that describes the dynamics of the trapped chromium cloud during evaporation, we find g{sub el}=2.15(+2.5,-1.2)x10{sup -10} cm{sup 3}/s and g{sub in}=1.36(+1.2,-0.7)x10{sup -12} cm{sup 3}/s, consistent with theory but in disagreement with previously reported measurements.

  7. Upper limits on phiphi production in 350-GeV/c proton-beryllium collisions

    SciTech Connect

    Yamanouchi, T.; Brown, B.C.; Brown, C.N.; Dixon, R.L.; Ito, A.S.; Jostlein, H.; Lederman, L.M.; Ueno, K.; Coutrakon, G.B.; Finley, D.A.; McCarthy, R.L.


    We have established a sensitive upper limit on phiphi resonance production by 350-GeV/c protons incident on a beryllium target. The 90%-confidence-level upper limit varies from 1.5 x 10/sup -30/ cm/sup 2//nucleon at M/sub phiphi/=2.8 GeV/c/sup 2/ to 6.0 x 10/sup -32/ cm/sup 2//nucleon at M/sub phiphi/=3.4 GeV/c/sup 2/. We observe no evidence of the eta/sub c/.

  8. Transient loss of plasma from a theta pinch having an initially reversed magnetic field

    SciTech Connect

    Heidrich, J. E.


    The results of an experimental study of the transient loss of plasma from a 25-cm-long theta pinch initially containing a reversed trapped magnetic field are presented. The plasma, amenable to MHD analyses, was a doubly ionized helium plasma characterized by an ion density N/sub i/ = 2 x 10/sup 16/ cm/sup -3/ and an ion temperature T/sub i/ = 15 eV at midcoil and by N/sub i/ = 0.5 x 10/sup 16/ cm/sup -3/ and T/sub i/ = 6 eV at a position 2.5 cm beyond the end of the theta coil.

  9. Subpicosecond high-brightness uv laser system

    SciTech Connect

    Gibson, R.B.


    A laser system that produces intense subpicosecond pulses of 248 nm light is under development. Ultrashort pulses are generated in the visible in a synchronously-pumped mode-locked dye oscillator, heterodyned into the uv by two KDP crystals, and amplified in a chain of KrF* amplifiers. Front end output of 5 is amplified to 20 mJ and focused to peak intensities of order 10/sup 17/ W cm/sup -2/. Additional amplification is expected to permit experiments at intensities >10/sup 20/ W cm/sup -2/.

  10. Near UV atmospheric absorption measurements of column abundances during Airborne Arctic Stratospheric Expedition, January-February 1989: 3. BrO observations

    SciTech Connect

    Wahner, A.; Callies, J.; Dorn, H.P.; Platt, U.; Schiller, C. )


    Column abundances of BrO were measured during the Airborne Arctic Stratospheric Expedition from January 6 to February 9, 1989 by near UV absorption spectroscopy. BrO was detected during early flights by scattered sunlight observations during twilight and direct moon light observations during the night. The daytime vertical column abundances of BrO varied between 2 {times} 10{sup 13} cm{sup {minus}2} and 13 {times} 10{sup 13} cm{sup {minus}2} and are consistent with observed OClO column abundances and chemical model calculations. The nighttime presence of BrO suggests different vertical profiles of BrO and ClO.

  11. Solid composite electrolytes for lithium batteries


    Kumar, Binod; Scanlon, Jr., Lawrence G.


    Solid composite electrolytes are provided for use in lithium batteries which exhibit moderate to high ionic conductivity at ambient temperatures and low activation energies. In one embodiment, a polymer-ceramic composite electrolyte containing poly(ethylene oxide), lithium tetrafluoroborate and titanium dioxide is provided in the form of an annealed film having a room temperature conductivity of from 10.sup.-5 S cm.sup.-1 to 10.sup.-3 S cm.sup.-1 and an activation energy of about 0.5 eV.

  12. The Electrical Properties of Co-Doped ZnO Thin Films

    SciTech Connect

    Hamid, H. A.; Abdullah, M. J.; Aziz, A. A.


    Codoped ZnO thin films were prepared on silicon (111) substrates by cosputtering of aluminium rods and zinc target using DC magnetron sputtering followed by heat treatment at 400 deg. C for 1 hour at different ratios of oxygen and nitrogen gas. Results indicate that gas ratios influenced the film conduction properties, which had the lowest resistivity of 7.985x10{sup -3} cm{sup -3} and highest carrier concentration of 6.89x10{sup 21} cm{sup -3}.

  13. Spectrally resolved four-wave mixing experiments on bulk GaAs with 14-fs pulses

    SciTech Connect

    Wehner, M.U.; Steinbach, D.; Wegener, M.; Marschner, T.; Stolz, W.


    We investigate the coherent dynamics at the band edge of GaAs at low temperatures for carrier densities ranging from 4.3{times}10{sup 14} cm{sup {minus}3} to 4.4{times}10{sup 17} cm{sup {minus}3} by means of spectrally resolved transient four-wave mixing with 14-fs pulses. At large nonequilibrium carrier densities we observe oscillations with an energy-dependent oscillation period related to interference among continuum states. The experimental findings are compared with a simple model. This comparison delivers a weak energy dependence of dephasing in the initial buildup phase of screening. {copyright} {ital 1996 Optical Society of America.}

  14. Population inversion in a stationary recombining plasma

    SciTech Connect

    Otsuka, M.


    Population inversion, which occurs in a recombining plasma when a stationary He plasma is brought into contact with a neutral gas, is examined. With hydrogen as a contact gas, noticeable inversion between low-lying levels of H as been found. The overpopulation density is of the order of 10/sup 8/ cm/sup -3/, which is much higher then that (approx. =10/sup 5/ cm/sup -3/) obtained previously with He as a contact gas. Relations between these experimental results and the conditions for population inversion are discussed with the CR model.

  15. Methods of enhancing conductivity of a polymer-ceramic composite electrolyte

    NASA Technical Reports Server (NTRS)

    Kumar, Binod (Inventor)


    Methods for enhancing conductivity of polymer-ceramic composite electrolytes are provided which include forming a polymer-ceramic composite electrolyte film by a melt casting technique and uniaxially stretching the film from about 5 to 15% in length. The polymer-ceramic composite electrolyte is also preferably annealed after stretching such that it has a room temperature conductivity of from 10.sup.-4 S cm.sup.-1 to 10.sup.-3 S cm.sup.-1. The polymer-ceramic composite electrolyte formed by the methods of the present invention may be used in lithium rechargeable batteries.

  16. Magneto-transport of an electron bilayer system in an undoped Si/SiGe double-quantum-well heterostructure

    SciTech Connect

    Laroche, Dominique; Huang, ShiHsien; Nielsen, Erik; Liu, Chee Wee; Li, Jiun -Yun; Lu, Tzu -Ming


    We report the design, the fabrication, and the magneto-transport study of an electron bilayer system embedded in an undoped Si/SiGe double-quantum-well heterostructure. Additionally, the combined Hall densities (n Hall ) ranging from 2.6 × 10<sup>10sup> cm>-2 to 2.7 × 10<sup>11 cm>-2 were achieved, yielding a maximal combined Hall mobility (μHall ) of 7.7 × 10<sup>5 cm>2/(V • s) at the highest density. Simultaneous electron population of both quantum wells is clearly observed through a Hall mobility drop as the Hall density is increased to nHall > 3.3 × 10<sup>10 sup>cm-2, consistent with Schrödinger-Poisson simulations. Furthermore, the integer and fractional quantum Hall effects are observed in the device, and single-layer behavior is observed when both layers have comparable densities, either due to spontaneous interlayer coherence or to the symmetric-antisymmetric gap.

  17. The effect of neutron irradiation and annealing temperature on the electrical properties and lattice constant of epitaxial gallium nitride layers

    SciTech Connect

    Boyko, V. M.; Verevkin, S. S.; Kolin, N. G. Korulin, A. V.; Merkurisov, D. I.; Polyakov, A. Y.; Chevychelov, V. A.


    Effect of irradiation with high reactor-neutron fluences ({Phi} = 1.5 Multiplication-Sign 10{sup 17}-8 Multiplication-Sign 10{sup 19} cm{sup -2}) and subsequent heat treatments in the temperature range 100-1000 Degree-Sign C on the electrical properties and lattice constant of epitaxial GaN layers grown on an Al{sub 2}O{sub 3} substrate is considered. It is shown that, with the neutron fluence increasing to (1-2) Multiplication-Sign 10{sup 18} cm{sup -2}, the resistivity of the material grows to values of about 10{sup 10} {Omega} cm because of the formation of radiation defects, and, with the fluence raised further, the resistivity passes through a maximum and then decreases to 2 Multiplication-Sign 10{sup 6} {Omega} cm at 300 K, which is accounted for by the appearance of a hopping conductivity via deep defects in the overlapping outer parts of disordered regions. With the neutron fluence raised to 8 Multiplication-Sign 10{sup 19} cm{sup -2}, the lattice constant c increases by 0.38% at a nearly unchanged parameter a. Heat treatment of irradiated samples at temperatures as high as 1000 Degree-Sign C does not fully restore the lattice constant and the electrical parameters of the material.

  18. Donor and acceptor concentrations in degenerate InN

    SciTech Connect

    Look, D.C.; Lu, H.; Schaff, W.J.; Jasinski, J.; Liliental-Weber, Z.


    A formalism is presented to determine donor (N{sub D}) and acceptor (N{sub A}) concentrations in wurtzitic InN characterized by degenerate carrier concentration (n) and mobility ({mu}). The theory includes scattering not only by charged point defects and impurities, but also by charged threading dislocations, of concentration N{sub dis}. For an 0.45-{micro}m-thick InN layer grown on Al{sub 2}O{sub 3} by molecular beam epitaxy, having N{sub dis} = 5 x 10{sup 10} cm{sup -2}, determined by transmission electron microscopy, n(20 K) = 3.5 x 10{sup 18} cm{sup -3}, and {mu}(20 K) = 1055 cm{sup 2}/V-s, determined by Hall-effect measurements, the fitted values are N{sub D} = 4.7 x 10{sup 18} cm{sup -3} and N{sub A} = 1.2 x 10{sup 18} cm{sup -3}. The identities of the donors and acceptors are not known, although a comparison of N{sub D} with analytical data, and also with calculations of defect formation energies, suggests that a potential candidate for the dominant donor is H.

  19. Effects of growth temperature on Mg-doped GaN grown by ammonia molecular beam epitaxy

    SciTech Connect

    Hurni, Christophe A.; Lang, Jordan R.; Burke, Peter G.; Speck, James S.


    The hole concentration p in Mg-doped GaN films grown by ammonia molecular beam epitaxy depends strongly on the growth temperature T{sub GR}. At T{sub GR}=760 Degree-Sign C, GaN:Mg films showed a hole concentration of p=1.2 Multiplication-Sign 10{sup 18} cm{sup -3} for [Mg]=4.5 Multiplication-Sign 10{sup 19} cm{sup -3}, while at T{sub GR}=840 Degree-Sign C, p=4.4 Multiplication-Sign 10{sup 16} cm{sup -3} for [Mg]=7 Multiplication-Sign 10{sup 19} cm{sup -3}. Post-growth annealing did not increase p. The sample grown at 760 Degree-Sign C exhibited a low resistivity of 0.7 {Omega}cm. The mobility for all the samples was around 3-7 cm{sup 2}/V s. Temperature-dependent Hall measurements and secondary ion mass spectroscopy suggest that the samples grown at T{sub GR}>760 Degree-Sign C are compensated by an intrinsic donor rather than hydrogen.

  20. Amorphous tin-cadmium oxide films and the production thereof


    Li, Xiaonan; Gessert, Timothy A


    A tin-cadmium oxide film having an amorphous structure and a ratio of tin atoms to cadmium atoms of between 1:1 and 3:1. The tin-cadmium oxide film may have an optical band gap of between 2.7 eV and 3.35 eV. The film may also have a charge carrier concentration of between 1.times.10.sup.20 cm.sup.-3 and 2.times.10.sup.20 cm.sup.-3. The tin cadmium oxide film may also exhibit a Hall mobility of between 40 cm.sup.2V.sup.-1 s.sup.-1 and 60 cm.sup.2V.sup.-1 s.sup.-1. Also disclosed is a method of producing an amorphous tin-cadmium oxide film as described and devices using same.

  1. A pressurized ion chamber monitoring system for environmental radiation measurements utilizing a wide-range temperature-compensated electrometer

    SciTech Connect

    Stevenick, W. Van . Environmental Measurements Lab.)


    The performance of a complete pressurized ion chamber (PIC) radiation monitoring system is described. The design incorporates an improved temperature-compensated electrometer which is stable to [+-]3 [center dot] 10[sup [minus]16] A over the environmental range of temperature ([minus]40 to +40 C). Using a single 10[sup 11] [Omega] feed-back resistor, the electrometer accurately measures currents over a range from 3 [center dot] 10[sup [minus]15] A to 3 [center dot] 10[sup [minus]11] A. While retaining the sensitivity of the original PIC system (the instrument responds readily to small background fluctuations on the order of 0.1 [mu]R h[sup [minus]1]), the new system measures radiation levels up to the point where the collection efficiency of the ion chamber begins to drop off, typically [approximately]27 pA at 1 mR h[sup [minus]1]. A data recorder and system controller was designed using the Tattletale[trademark] Model 4A computer. Digital data is stored on removable solid-state, credit-card style memory cards.

  2. Analysis of instability growth and collisionless relaxation in thermionic converters using 1-D PIC simulations

    SciTech Connect

    Kreh, B.B.


    This work investigates the role that the beam-plasma instability may play in a thermionic converter. The traditional assumption of collisionally dominated relaxation is questioned, and the beam-plasma instability is proposed as a possible dominant relaxation mechanism. Theory is developed to describe the beam-plasma instability in the cold-plasma approximation, and the theory is tested with two common Particle-in-Cell (PIC) simulation codes. The theory is first confirmed using an unbounded plasma PIC simulation employing periodic boundary conditions, ES1. The theoretically predicted growth rates are on the order of the plasma frequencies, and ES1 simulations verify these predictions within the order of 1%. For typical conditions encountered in thermionic converters, the resulting growth period is on the order of 7 {times} 10{sup {minus}11} seconds. The bounded plasma simulation PDP1 was used to evaluate the influence of finite geometry and the electrode boundaries. For this bounded plasma, a two-stream interaction was supported and resulting in nearly complete thermalization in approximately 5 {times} 10{sup {minus}10} seconds. Since the electron-electron collision rate of 10{sup 9} Hz and the electron atom collision rate of 10{sup 7} Hz are significantly slower than the rate of development of these instabilities, the instabilities appear to be an important relaxation mechanism.

  3. Model Calculations of Continuous-Wave Laser Ionization of Krypton

    SciTech Connect

    Bret D. Cannon


    This report describes modeling of a scheme that uses continuous-wave (CW) lasers to ionize selected isotopes of krypton with high isotopic selectivity. The models predict that combining this ionization scheme with mass spectrometric measurement of the resulting ions can be the basis for ultra-sensitive methods to measure {sup 85}Kr in the presence of a 10{sup 11} excess of the stable krypton isotopes. Two experimental setups are considered in this model: the first setup is for krypton as a static gas, the second is for krypton in an atomic beam. In the static gas experiment, for a total krypton press of 10{sup {minus}4} torr and 10 W of power in the cavity, the model predicts a total krypton ion current of 4.6 x 10{sup 8} s{sup {minus}1} and for a {sup 85}Kr/Kr of 10{sup {minus}11} a {sup 85}Kr ion current of 3.5 s{sup {minus}1} or about 10,000 per hour. The atomic beam setup allowed higher isotopic selectivity; the model predicts a {sup 85}Kr ion current of 18 s{sup {minus}1} or 65,000 per hour.

  4. Interaction of graphite with a hot, dense deuterium plasma

    SciTech Connect

    Desko, J.C. Jr.


    The erosion of ATJ-S graphite caused by a hot, dense deuterium plasma has been investigated experimentally. The plasma was produced in an electromagnetic shock tube. Plasma characteristics were typically: ion temperature approx. = 800 eV (approx. 1 x 10/sup 7/ /sup 0/K), number density approx. = 10/sup 16//cm/sup 3/, and transverse magnetic field approx. = 1 tesla. The energetic ion flux, phi, to the sample surfaces was approx. 10/sup 23/ ions/cm/sup 2/-sec for a single pulse duration of approx. 0.1 usec. Sample surfaces were metallographically prepared and examined with a scanning electron microscope before and after exposure.

  5. Temperature stability of gamma-ray-induced effects in glassy arsenic trisulfide

    SciTech Connect

    Shpotyuk, O.I.


    The author studied the effect of low-temperature annealing (up to the softening point) on the energy dependences of the optical absorption coefficient ..cap alpha.. in the region of Urbach's edge (..cap alpha.. < 10/sup 2/ cm/sup -1/) and the microhardness H of glassy arsenic trisulfide irradiated with gamma rays from a CO/sup 60/ source (absorbed dosages of 10/sup 6/-10/sup 7/ Gy). Bulk samples of As/sub 2/S/sub 3/, obtained by direct synthesis in evacuated ampuls consisting of especially pure components, were used.

  6. High quality transparent conducting oxide thin films


    Gessert, Timothy A.; Duenow, Joel N.; Barnes, Teresa; Coutts, Timothy J.


    A transparent conducting oxide (TCO) film comprising: a TCO layer, and dopants selected from the elements consisting of Vanadium, Molybdenum, Tantalum, Niobium, Antimony, Titanium, Zirconium, and Hafnium, wherein the elements are n-type dopants; and wherein the transparent conducting oxide is characterized by an improved electron mobility of about 42 cm.sup.2/V-sec while simultaneously maintaining a high carrier density of .about.4.4e.times.10.sup.20 cm.sup.-3.

  7. Optimization study for an epithermal neutron beam for boron neutron capture therapy at the University of Virginia Research Reactor

    SciTech Connect

    Burns, T.D. Jr.


    The non-surgical brain cancer treatment modality, Boron Neutron Capture Therapy (BNCT), requires the use of an epithermal neutron beam. This purpose of this thesis was to design an epithermal neutron beam at the University of Virginia Research Reactor (UVAR) suitable for BNCT applications. A suitable epithermal neutron beam for BNCT must have minimal fast neutron and gamma radiation contamination, and yet retain an appreciable intensity. The low power of the UVAR core makes reaching a balance between beam quality and intensity a very challenging design endeavor. The MCNP monte carlo neutron transport code was used to develop an equivalent core radiation source, and to perform the subsequent neutron transport calculations necessary for beam model analysis and development. The code accuracy was validated by benchmarking output against experimental criticality measurements. An epithermal beam was designed for the UVAR, with performance characteristics comparable to beams at facilities with cores of higher power. The epithermal neutron intensity of this beam is 2.2 {times} 10{sup 8} n/cm{sup 2} {center_dot} s. The fast neutron and gamma radiation KERMA factors are 10 {times} 10{sup {minus}11}cGy{center_dot}cm{sup 2}/n{sub epi} and 20 {times} 10{sup {minus}11} cGy{center_dot}cm{sup 2}/n{sub epi}, respectively, and the current-to-flux ratio is 0.85. This thesis has shown that the UVAR has the capability to provide BNCT treatments, however the performance characteristics of the final beam of this study were limited by the low core power.

  8. Einstein X-ray observations of Proxima Centauri and the surrounding region

    SciTech Connect

    Haisch, B.M.; Linsky, J.L.; Harnden, F.R. Jr.; Rosner, R.; Seward, F.D.; Vaiana, G.S.


    We report the first detection of both quiescent and flaring soft X-ray emission from a dMe flare star, Proxima Centauri (dM5e). The data are analyzed for temporal variability and spectral characteristics. The quiescent state is characterized by a mean X-ray luminosity of approx.1.5 x 10/sup 27/ ergs s/sup -1/, corresponding to a mean surface flux of approx.7 x 10/sup 5/ ergs cm/sup -2/ s/sup -1/, and an inferred temperature of approx.4 x 10/sup 6/ K. The flare we have detected has a peak flux of approx.7.4 x 10/sup 27/ ergs s/sup -1/ and a peak temperature of approx.17 x 10/sup 6/ K. We discuss implications of these data for models of the quiescent and flare coronae of dMe stars.

  9. Extended soft x-ray source in Delphinus: H2027+19

    SciTech Connect

    Stern, R.A.; Charles, P.A.; Walker, B.C.; Nugent, J.J.; Garmire, G.P.


    We report the detection of an extended (approx.3/sup 0/) source of soft X-ray emission. H2027+19, observed with the HEAO 1 A-2 experiment. The object emits primarily in the 0.16--0.4 keV band, with a total flux in this band of approx.2 x 10/sup -11/ ergs cm/sup -2/ S/sup -1/. Although our data can be formally modeled with two discrete sources, a detailed analysis suggests that this alternative is not likely to be the case. We fine that both simple continuum and coronal plasma models provide good fits to the observed pulse-height spectrum. The source parameters are restricted to 10/sup 5.8/ 10/sup 6.5/K, N/sub x/<10/sup 21.3/ cm/sup -2/ (Raymond and Smith plasma), and 10/sup 5.8/10/sup 7.0/, N/sub x/<10/sup 21.2/ (exponential+Gaunt factor) at the 90% confidence level. The most likely physical models are either that the source is an old supernova remnant or that it is a region of enhanced soft X-ray emission surrounding an H I cloud imbedded in a cornal plasma, as suggested by Hayakawa et al. for the Lupus Loop.

  10. RF plasma source for heavy ion beam charge neutralization

    SciTech Connect

    Efthimion, Philip C.; Gilson, Erik; Grisham, Larry; Davidson, Ronald C.; Yu, Simon S.; Logan, B. Grant


    Highly ionized plasmas are being used as a medium for charge neutralizing heavy ion beams in order to focus the ion beam to a small spot size. A radio frequency (RF) plasma source has been built at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The goal is to operate the source at pressures {approx} 10{sup -5} Torr at full ionization. The initial operation of the source has been at pressures of 10{sup -4}-10{sup -1} Torr and electron densities in the range of 10{sup 8}-10{sup 11} cm{sup -3}. Recently, pulsed operation of the source has enabled operation at pressures in the 10{sup -6} Torr range with densities of 10{sup 11} cm{sup -3}. Near 100% ionization has been achieved. The source has been integrated with the NTX facility and experiments have begun.


    SciTech Connect

    Muccino, M.; Ruffini, R.; Bianco, C. L.; Izzo, L.; Penacchioni, A. V.; Pisani, G. B.


    GRB 090510, observed by both Fermi and AGILE satellites, is the first bright short-hard gamma-ray burst (GRB) with an emission from the keV up to the GeV energy range. Within the Fireshell model, we interpret the faint precursor in the light curve as the emission at the transparency of the expanding e {sup +} e {sup -} plasma: the Proper-GRB. From the observed isotropic energy, we assume a total plasma energy E{sup tot}{sub e{sup +}e{sup -}}=(1.10{+-}0.06) Multiplication-Sign 10{sup 53} erg and derive a Baryon load B = (1.45 {+-} 0.28) Multiplication-Sign 10{sup -3} and a Lorentz factor at transparency {Gamma}{sub tr} = (6.7 {+-} 1.6) Multiplication-Sign 10{sup 2}. The main emission {approx}0.4 s after the initial spike is interpreted as the extended afterglow, due to the interaction of the ultrarelativistic baryons with the CircumBurst Medium (CBM). Using the condition of fully radiative regime, we infer a CBM average spherically symmetric density of (n{sub CBM}) = (1.85 {+-} 0.14) Multiplication-Sign 10{sup 3} particles cm{sup -3}, one of the highest found in the Fireshell model. The value of the filling factor, 1.5 Multiplication-Sign 10{sup -10}{<=}R{<=}3.8 Multiplication-Sign 10{sup -8}, leads to the estimate of filaments with densities n{sub fil} = n{sub CBM}/R approx. (10{sup 6}-10{sup 14}) particles cm{sup -3}. The sub-MeV and the MeV emissions are well reproduced. When compared to the canonical GRBs with (n{sub CBM}) Almost-Equal-To 1 particles cm{sup -3} and to the disguised short GRBs with (n{sub CBM}) Almost-Equal-To 10{sup -3} particles cm{sup -3}, the case of GRB 090510 leads to the existence of a new family of bursts exploding in an overdense galactic region with (n{sub CBM}) Almost-Equal-To 10{sup 3} particles cm{sup -3}. The joint effect of the high {Gamma}{sub tr} and the high density compresses in time and 'inflates' in intensity the extended afterglow, making it appear as a short burst, which we here define as a 'disguised short GRB by excess

  12. Dy{sup 3+}-doped Ga–Sb–S chalcogenide glasses for mid-infrared lasers

    SciTech Connect

    Zhang, Mingjie; Yang, Anping; Peng, Yuefeng; Zhang, Bin; Ren, He; Guo, Wei; Yang, Yan; Zhai, Chengcheng; Wang, Yuwei; Yang, Zhiyong; Tang, Dingyuan


    Highlights: • Novel Ga–Sb–S chalcogenide glasses doped with Dy{sup 3+} ions were synthesized. • The glasses show good thermal stability and excellent infrared transparency. • The glasses show low phonon energy and intense mid-infrared emissions. • The mid-infrared emissions have high quantum efficiency. • The mid-infrared emissions have large stimulated emission cross sections. - Abstract: Novel Ga–Sb–S chalcogenide glasses doped with different amount of Dy{sup 3+} ions were prepared. Their thermal stability, optical properties, and mid-infrared (MIR) emission properties were investigated. The glasses show good thermal stability, excellent infrared transparency, very low phonon energy (∼306 cm{sup −1}), and intense emissions centered at 2.95, 3.59, 4.17 and 4.40 μm. Three Judd–Ofelt intensity parameters (Ω{sub 2} = 8.51 × 10{sup −20} cm{sup 2}, Ω{sub 4} = 2.09 × 10{sup −20} cm{sup 2}, and Ω{sub 6} = 1.60 × 10{sup −20} cm{sup 2}) are obtained, and the related radiative transition properties are evaluated. The high quantum efficiencies and large stimulated emission cross sections of the MIR emissions (88.10% and 1.11 × 10{sup −20} cm{sup 2} for 2.95 μm emission, 75.90% and 0.38 × 10{sup −20} cm{sup 2} for 4.40 μm emission, respectively) in the Dy{sup 3+}-doped Ga–Sb–S glasses make them promising gain materials for the MIR lasers.

  13. Simultaneous X-ray, ultraviolet, optical, and radio observations of the flare star Proxima Centauri

    SciTech Connect

    Haisch, B.M.; Linsky, J.L.; Slee, O.B.; Siegman, B.C.; Nikoloff, I.; Candy, M.; Harwood, D.; Verveer, A.; Quinn, P.J.; Wilson, I.; Page, A.A.; Higson, P.; Seward, F.D.


    We report on a coordinated program involving X-ray, ultraviolet, optical, and radio observations of the dM5e flare star Proxima Centauri. We detected one major X-ray flare event with L/sub x/(0.2--4.0 keV)roughly-equal6.0 x 10/sup 27/ ergs s/sup -1/, T = 1.7 x 10/sup 7/ K, and EM = 7.5 x 10/sup 50/ cm/sup -3/ during the rise phase and L/sub x/roughly-equal7.4 x 10/sup 27/ ergs s/sup -1/, T = 1.2 x 10/sup 7/ K, and EM = 12.0 x 10/sup 50/ cm/sup -3/ during the decay phase. This is the first detection of a time-resolved stellar X-ray flare that shows changes in its spectral flux distribution. We detected no ultraviolet, optical or radio emission corresponding to this flare, but we did detect a total of five optical and 12 possible radio flares, including one event with simultaneous radio and optical emission. We interpret the absence of optical and ultraviolet emission at the time of the X-ray flare in terms of an arch model in which the flare cools predominently by X-ray radiation. The observed 20 min expotential cooling time is consistent with an electron density of 1.0 x 10/sup 11/ cm/sup -3/ during the decay phase and a flare of total arch length of ..pi.. x 10/sup 10/ cm, comparable to the size of the star itself. We conclude that we have observed an X-ray flare more like a typical strong solar flare than heretofore seen on a flare star.

  14. Phenomenological constraints on accretion of non-annihilating dark matter on the PSR B1257+12 pulsar from orbital dynamics of its planets

    SciTech Connect

    Iorio, Lorenzo


    We analytically compute the effects that a pulsar's mass variation, whatever its physical origin may be, has on the standard Keplerian changes Δτ{sub Kep} in the times of arrival of its pulses due to potential test particle companions, and on their orbital dynamics over long time scales. We apply our results to the planetary system of the PSR B1257+12 pulsar, located in the Galaxy at ∼ 600 pc from us, to phenomenologically constrain a putative accretion of non-annihilating dark matter on the hosting neutron star. By comparing our prediction for Δτ{sub M-dot/M} to the root-mean-square accuracy of the timing residuals δ(Δτ) = 3.0μs we find for the mass variation rate M-dot /M ≤ 1.3 × 10{sup −6} yr{sup −1}. Actually, considerations related to the pulsar's lifetime, of the order of Δt ∼ 0.8 Gyr, and to the currently accepted picture of the formation of its planets point toward a tighter constrain on the mass accretion rate, i.e. M-dot /M ≤ 10{sup −9} yr{sup −1}. Otherwise, the planets would have formed at about 300–700 au from PSR B1257+12, i.e. too far with respect to the expected extension of 1–2 au of the part of the protoplanetary disk containing the solid constituents from which they likely originated. In fact, an even smaller upper limit, M-dot /M ≤ 10{sup −11} yr{sup −1}, would likely be more realistic to avoid certain technical inconsistencies with the quality of the fit of the timing data, performed by keeping the standard value M = 1.4M{sub s}un fixed for the neutron star's mass. Anyway, the entire pulsar data set should be re-processed by explicitly modeling the mass variation rate and solving for it. Model-dependent theoretical predictions for the pulsar's mass accretion, in the framework of the mirror matter scenario, yield a mass increment rate of about 10{sup −16} yr{sup −1} for a value of the density of mirror matter ρ{sub dm} as large as 10{sup −17} g cm{sup −3} = 5.6 × 10{sup 6} GeV cm{sup −3}. Such a

  15. Excited-state absorption in the lasing wavelength region of Alexandrite

    SciTech Connect

    Shand, M.L.; Walling, J.C.


    The excited-state absorption cross section sigma/sub 2/ /sub a/ (E) in the gain wavelength region of alexandrite has been determined and is shown to limit the vibronic laser range at both high and low energy. The maximum in vibronic laser emission is due to a minimum in sigma/sub 2/ /sub a/ (E) near 13 000 cm/sup -1/. sigma/sub 2/ /sub a/ (E) is less than 10/sup -20/ cm/sup 2/ between 12 000 and 14 000 cm/sup -1/.

  16. Cell for determination of tritium concentration by liquid radiometer

    SciTech Connect

    Antonenko, G.I.; Savina, V.I.; Egurneva, T.B.


    An optimized cell is described for determination of tritium concentration in the form of tritiated water by a liquid scintillation radiometer at a level of 10/sup 4/ Bq/m/sup 3/. The cell is made of Teflon and has a wall thickness of 0.8-1.0 mm. The useful capacity of the cell is 45 cm/sup 3/ (5 cm/sup 3/ of tritiated water and 40 cm/sup 3/ of ZhS-81 liquid scintillator).

  17. Investigation of deep level defects in epitaxial semiconducting zinc sulpho-selenide. Progress report, June 15, 1980-June 14, 1981

    SciTech Connect

    Wessels, B.W.


    High conductivity ZnSe single crystalline films have been heteroepitaxially deposited on GaAs substrates using open tube chemical vapor transport. Unintentionally doped films had net donor densities of 10/sup 14/ - 10/sup 16/ cm/sup -3/ and resistivities of 1 to 10/sup 3/ ohm cm. Resistivity was found to be strongly dependent upon zinc partial pressure during deposition. Electron mobilities of the order of 50 to 200 cm/sup 2//V sec were observed which suggested that the films are highly compensated. Properties of the deep level defects in heteroepitaxially grown ZnSe have been investigated using transient capacitance spectroscopy. A series of electron traps were observed with activation energies of 0.33, 0.35, 0.42, 0.71 and 0.86 eV in Au/ZnSe Schottky diodes. Trap concentration ranged from 10/sup 12/ to 10/sup 14/ cm/sup -3/ and depended on the zinc partial pressure. A model for the defect structure of ZnSe was proposed. Growth studies of ZnS/sub x/Se/sub 1-x/ on GaAs were begun.

  18. Experimental and theoretical evaluation of density sensitive N VII, Ar XIV and Fe XXII line ratios

    SciTech Connect

    Chen, H; Beiersdorfer, P; Heeter, L A; Liedahl, D A; Naranjo-Rivera, K L; Trabert, E; Gu, M F; Lepson, J K


    The line ratios of the 2p-3d transitions in the B-like spectra Ar XIV and Fe XXII have been measured using the electron beam ion traps at Livermore. Radiative-collisional model calculations show these line ratios to be sensitive to the electron density in the ranges ne = 10{sup 10} to 10{sup 12} cm{sup -3} and ne = 10{sup 13} to 10{sup 15} cm{sup -3}, respectively. In our experiment, the electron beam density of about 10{sup 11} cm{sup -3} was varied by about a factor of 5. Our data show a density effect for the line doublet in Ar XIV, and good agreement with theory is found. The relative intensity of the Fe XXII doublet shows good agreement with our predicted low density limit. The N VI K-shell spectrum was used to infer the actual electron density in the overlap region of ion cloud and electron beam, and systematic measurements and calculations of this spectrum are presented as well. The Ar XIV and Fe XXII spectra promise to be reliable density diagnostics for stellar coronae, complementing the K-shell diagnostics of helium-like ions.

  19. Anomalous ion damage behavior in ZnSe

    SciTech Connect

    Yu, K.M.; Bourret-Courchesne, E.D.


    The structural properties of ZnSe damaged by 180 keV Zn ions are studied for a wide range of ion dose (10{sup 13}{endash}10{sup 16}/cm{sup 2}) using ion channeling techniques. We found that ZnSe cannot be rendered amorphous by implantation at either room temperature (RT) or liquid nitrogen temperature (LNT) in the range of doses investigated. For lower ion doses (10{sup 13}{endash}10{sup 14}/cm{sup 2}), ZnSe samples implanted at LNT result in less damage than those implanted at RT by as much as an order of magnitude. Moreover, no simple point defect or amorphous clusters are found in the implanted ZnSe. For high implant doses ({approx_gt}10{sup 14}/cm{sup 2}), the samples are still monocrystalline but become highly defective with extended defects. Our results also suggests that point defects in the ZnSe created during implantation may be mobile at or below RT and that they may migrate rapidly under ion irradiation. {copyright} {ital 1996 American Institute of Physics}

  20. Contacts for high-resistivity (Cd,Mn)Te crystals

    SciTech Connect

    Witkowska-Baran, M.; James, R.; Mycielski, A.; Kochanowska, D.; Szadkowski, A.J.; Jakiela, R.; Witkowska, B.; Kaliszek, W.; Domagala, J.; Lusakowska, E.; Domukhovski, V.; Dybko, K.; Cui, Y.; and James, R.B.


    Semi-insulating (Cd,Mn)Te crystals offer a material that may compete well with the commonly used (Cd,Zn)Te crystals for manufacturing large-area X- and gamma-ray detectors. The Bridgman growth method yields good quality, high-resistivity (10{sup 9} - 10{sup 10} {Omega} {center_dot} cm) crystals of (Cd,Mn)Te:V. Doping the as-grown crystals with the compensating agent vanadium ({approx} 10{sup 16} cm{sup -3}) ensures their high resistivity; thereafter, annealing them in cadmium vapors reduces the number of cadmium vacancies. Applying the crystals as detectors necessitates having satisfactory electrical contacts. Accordingly, we explored various techniques of ensuring good electrical contacts to these semi-insulating (Cd,Mn)Te crystals, assessing metallic layers, monocrystalline semiconductor layers, and amorphous (or nanocrystalline) semiconductor layers. We found that ZnTe heavily doped ({approx} 10{sup 18} cm{sup -3}) with Sb, and CdTe heavily doped ({approx} 10{sup 17} cm{sup -3}) with In, proved satisfactory semiconductor contact layers. They subsequently enabled us to establish good contacts (with only narrow tunneling barriers) to the Au layer that usually constitutes the most external contact layer. We outline our technology of applying electrical contacts to semi-insulating (Cd,Mn)Te, and describe some important properties.


    EPA Science Inventory

    Using a relative rate method, rate constants have been measured at 296 ? 2 K for the gas-phase reactions of OH radicals with 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, and 2-methyl-2,4-pentanediol, with rate constants (in units of 10<SUP>-12 cm>3 molecule

  2. Measured neutron carbon kerma factors from 14. 1 MeV to 18 MeV

    SciTech Connect

    Deluca, P.M. Jr.; Barschall, H.H.; Haight, R.C.; McDonald, J.C.


    For A-150 tissue-equivalent plastic, the total neutron kerma is dominated by the hydrogen kerma. Tissue kerma is inferred with reasonable accuracy by normalization to the kerma factor ratio between tissue and A-150 plastic. Because of the close match in the hydrogen abundance in these materials, the principal uncertainty is due to the kerma factors of carbon and oxygen. We have measured carbon kerma factor values of 0.183 +- 0.015 10/sup -8/ cGy cm/sup 2/ and 0.210 +- 0.16 10/sup -8/ cGy cm/sup 2/ at 14.1-MeV and 15-MeV neutron energy, respectively. A preliminary value of 0.297 +- 0.03 10/sup -8/ cGy cm/sup 2/ has been determined at 17.9 MeV. A recent microscopic cross section measurement of the (n,n'3..cap alpha..) reaction in carbon at 14.1-MeV energy gives a kerma factor of 0.184 +- 0.019 10/sup 8/ cGy cm/sup 2/ in agreement with the present result. 9 refs., 4 figs., 2 tabs.

  3. Thin film polymeric gel electrolytes


    Derzon, D.K.; Arnold, C. Jr.; Delnick, F.M.


    Novel hybrid thin film electrolytes, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities {approx_equal}10{sup {minus}3}{Omega}{sup {minus}1} cm{sup {minus}1} are useful as electrolytes for rechargeable lithium batteries. 1 fig.

  4. High-energy high-luminosity µ+ µ- collider design

    SciTech Connect

    Palmer, Robert B.; Fernow, Richard; Gallardo, Juan C.; Lee, Y. Y.; Torun, Yagmur; Neuffer, David; Winn, David


    We discuss the design of a high luminosity (10<sup>35 cm>-2 s-1), high energy (2 + 2 TeV) µ+µ- collider, starting from the proton accelerator needed to generate the muon beams and proceeding through the muon storage ring.

  5. Searching for New Physics at SuperB: The Super Flavor Factory

    SciTech Connect

    Hitlin, David


    SuperB - a Super Flavor Factory, an electron-positron collider with a luminosity of 10{sup 36} cm{sup -2} s{sup -1}, can conduct unique sensitive searches for New Physics effects such as lepton flavor violation and new sources of CP violation in the quark and lepton sectors.

  6. Potential for measurement of the tensor polarizabilities of nuclei in storage rings by the frozen spin method

    SciTech Connect

    Silenko, Alexander J.


    The frozen spin method can be effectively used for a high-precision measurement of the tensor electric and magnetic polarizabilities of the deuteron and other nuclei in storage rings. For the deuteron, this method would provide the determination of the deuteron's polarizabilities with absolute precision of the order of 10{sup -43} cm{sup 3}.

  7. Single- and double-electron-capture collision of C{sup q+} (q=3,4) with CO at keV energies

    SciTech Connect

    Gao Hui; Kwong, Victor H.S.


    Absolute total single- and double-electron-capture cross sections for C{sup q+} (q=3,4) with CO have been measured at {approx}0.5 keV/amu using a reflection-time-of-flight mass spectrometer with a laser ablation ion source. The single- and double-electron-capture cross sections for C{sup 3+} with CO at 423{+-}48 eV/amu are found to be (0.96{+-}0.12)x10{sup -15} cm{sup 2} and (0.99{+-}0.13)x10{sup -15} cm{sup 2}, respectively. The single- and double-electron-capture cross sections for C{sup 4+} with CO at 565{+-}65 eV/amu are measured to be (3.16{+-}0.42)x10{sup -15} cm{sup 2} and (1.05{+-}0.21)x10{sup -15} cm{sup 2}, respectively. This suggests that double capture should not be ignored in modeling the emission from cascading processes in comet atmosphere.

  8. Density scaling of an optically pumped lithium negative ion source

    SciTech Connect

    McGeoch, M.W.; Schlier, R.E.


    An experiment is described in which a high density of lithium negative ions (1 x 10/sup 10/ cm/sup -3/) is generated by dissociative attachment of electrons to optically pumped lithium molecules. During a three microsecond period up to 7% of electrons are attached. The possibilities for increased Li/sup -/ density are explored.

  9. Annealing studies of heteroepitaxial InSbN on GaAs grown by molecular beam epitaxy for long-wavelength infrared detectors

    SciTech Connect

    Patra, Nimai C.; Bharatan, Sudhakar; Li Jia; Iyer, Shanthi


    We report the effect of annealing on the structural, vibrational, electrical, and optical properties of heteropepitaxially grown InSbN epilayers on GaAs substrate by molecular beam epitaxy for long-wavelength infrared detector applications. As-grown epilayers exhibited high N incorporation in the both substitutional and interstitial sites, with N induced defects as evidenced from high resolution x-ray diffraction, secondary ion mass spectroscopy, and room temperature (RT) micro-Raman studies. The as-grown optical band gap was observed at 0.132 eV ({approx}9.4 {mu}m) and the epilayer exhibited high background carrier concentration at {approx}10{sup 18} cm{sup -3} range with corresponding mobility of {approx}10{sup 3} cm{sup 2}/Vs. Ex situ and in situ annealing at 430 Degree-Sign C though led to the loss of N but improved InSb quality due to effective annihilation of N related defects and other lattice defects attested to enhanced InSb LO phonon modes in the corresponding Raman spectra. Further, annealing resulted in the optical absorption edge red shifting to 0.12 eV ({approx}10.3 {mu}m) and the layers were characterized by reduced background carrier concentration in the {approx}10{sup 16} cm{sup -3} range with enhanced mobility in {approx}10{sup 4} cm{sup 2}/Vs range.

  10. Surface segregation as a means of gettering Cu in liquid-phase-epitaxy silicon thin layers grown from Al-Cu-Si solutions

    SciTech Connect

    Wang, T.H.; Ciszek, T.F.; Reedy, R.; Asher, S.; King, D.


    The authors demonstrate that, by using the natural surface segregation phenomenon, Cu can be gettered to the surface from the bulk of silicon layers so that its concentrations in the liquid-phase-epitaxy (LPE) layers are much lower than its solubility at the layer growth temperature and the reported 10{sup 17} cm{sup {minus}3} degradation threshold for solar-cell performance. Secondary-ion mass spectroscopy (SIMS) analysis indicates that, within a micron-deep sub-surface region, Cu accumulates even in as-grown LPE samples. Slower cooling after growth to room temperature enhances this Cu enrichment. X-ray photoelectron spectroscopy (XPS) measurement shows as much as 3.2% Cu in a surface region of about 50 {Angstrom}. More surface-sensitive, ion-scattering spectroscopy (ISS) analysis further reveals about 7% of Cu at the top surface. These results translate to an areal gettering capacity of about 1.0 x 10{sup 16} cm{sup {minus}2}, which is higher than the available total-area density of Cu in the layer and substrate (3.6 x 10{sup 15} cm{sup {minus}2} for a uniform 1.2 x 10{sup 17}cm{sup {minus}3} Cu throughout the layer and substrate with a total thickness of 300 {mu}m).

  11. The SuperB project

    SciTech Connect

    Lesiak, Tadeusz


    This paper presents a very short review of the SuperB project which aims to construct a new generation flavour factory with a designed luminosity of at least 10{sup 36} cm{sup -2} s{sup -1}. The main issues related to the physics programme, together with the description of the conceptual design of the accelerator and detector are briefly discussed.

  12. Low dislocation GaN via defect-filtering, self-assembled SiO2-sphere layers.

    SciTech Connect

    Wang, George T.; Li, Qiming


    The III-nitride (AlGaInN) materials system forms the foundation for white solid-state lighting, the adoption of which could significantly reduce U.S. energy needs. While the growth of GaN-based devices relies on heteroepitaxy on foreign substrates, the heteroepitaxial layers possess a high density of dislocations due to poor lattice and thermal expansion match. These high dislocation densities have been correlated with reduced internal quantum efficiency and lifetimes for GaN-based LEDs. Here, we demonstrate an inexpensive method for dislocation reduction in GaN grown on sapphire and silicon substrates. This technique, which requires no lithographic patterning, GaN is selectively grown through self-assembled layers of silica microspheres which act to filter out dislocations. Using this method, the threading dislocation density for GaN on sapphire was reduced from 3.3 x 10{sup 9} cm{sup -2} to 4.0 x 10{sup 7} cm{sup -2}, and from the 10{sup 10} cm{sup -2} range to {approx}6.0 x 10{sup 7} cm{sup -2} for GaN on Si(111). This large reduction in dislocation density is attributed to a dislocation blocking and bending by the unique interface between GaN and silica microspheres.

  13. Depth uniformity of electrical properties and doping limitation in neutron-transmutation-doped semi-insulating GaAs

    SciTech Connect

    Satoh, M.; Kuriyama, K. ); Kawakubo, T. )


    Depth uniformity of electrical properties has been evaluated for neutron-transmutation-doped (NTD), semi-insulating GaAs irradiated with thermal neutrons of 1.5{times}10{sup 18} cm{sup {minus}2} by the van der Pauw method combined with iterative etching of the surface. In NTD-GaAs wafers (thickness {similar to}410 {mu}m) annealed for 30 min at 700 {degree}C, the depth profiles of the resistivity, the carrier concentration, and the Hall mobility show constant values of 1{times}10{sup {minus}2} {Omega} cm, 2.0{times}10{sup 17} cm{sup {minus}3}, and 3100 cm{sup 2}/V s, respectively, within an experimental error of 5%. In an annealing process, the redistribution and/or the segregation of NTD impurities is not observed. We also discuss the limitations of low-level NTD in semi-insulating GaAs. It is suggested that the activation of the NTD-impurities below {similar to}1{times}10{sup 16} cm{sup {minus}3} is mainly restricted by the presence of the midgap electron trap (EL2).

  14. Damped acceleration cavities

    SciTech Connect

    Palmer, R.B.


    Structures with slots to strongly damp higher order longitudinal and transverse modes should allow the use, in linear colliders, of multiple bunches, and thus attain luminosities of over 10/sup 34/cm/sup /minus/2/sec/sup /minus/1/. Preliminary measurements on model structures suggest that such damping can be achieved. 10 refs., 9 figs.

  15. Monopole search using an accelerator detector

    SciTech Connect

    Ahrenes, L.A.; Aronson, S.H.; Connolly, P.L.; Erickson, T.E.; Gibbard, B.G.; Montag, M.; Murtagh, M.J.; Murtagh, S.J.; Terada, S.; Thorndike, A.M.


    A neutrino detector at the Brookhaven AGS has been used to investigate the feasibility of using an already constructed apparatus for GUT monopole searches. A flux limit (90%CL) of 5.2 x 10/sup -12/ cm/sup -2/ sec/sup -1/ str/sup -1/ was found. The limitations of such an approach are discussed.

  16. Sinterless Formation Of Contacts On Indium Phosphide

    NASA Technical Reports Server (NTRS)

    Weizer, Victor G.; Fatemi, Navid S.


    Improved technique makes it possible to form low-resistivity {nearly equal to 10(Sup-6) ohm cm(Sup2)} electrical contacts on indium phosphide semiconductor devices without damaging devices. Layer of AgP2 40 Angstrom thick deposited on InP before depositing metal contact. AgP2 interlayer sharply reduces contact resistance, without need for sintering.

  17. Hydrothermal synthesis of mesoporous VO{sub 2}·½(H{sub 2}O) nanosheets and study of their electrical properties

    SciTech Connect

    Soltane, L.; Sediri, F.; Gharbi, N.


    Highlights: ► Sheet-like nanocrystalline VO{sub 2}·½(H{sub 2}O) was synthesized by a hydrothermal route. ► Reaction time is key factor for structure and morphology. ► Electrical properties were also studied. ► Conductivity value goes from 75 10{sup −6} Ω{sup −1} cm{sup −1} at 298 K to 68 10{sup −5} Ω{sup −1} cm{sup −1} at 386 K. -- Abstract: Layered sheet-like nanocrystalline VO{sub 2}·½(H{sub 2}O) has been synthesized by hydrothermal process using V{sub 2}O{sub 5} as vanadium source and 2-phenylethylamine as a reducing agent and a structure-directing template. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption/desorption isotherms have been used to characterize the structure, morphology and composition of the materials. Electrical conductivity measurements showed that the as synthesized VO{sub 2}·½(H{sub 2}O) nanosheets has a conductivity value which goes from 75 × 10{sup −6} Ω{sup −1} cm{sup −1} at 298 K, to 68 10{sup −5} Ω{sup −1} cm{sup −1} at 386 K with activation energy of 0.24 eV.


    SciTech Connect

    Aota, Takuhiro; Aikawa, Yuri; Inoue, Tsuyoshi


    Recent Atacama Large Millimeter/submillimeter Array observations of young protostellar objects detected warm SO emission, which could be associated with a forming protostellar disk. In order to investigate if such warm gas can be produced by accretion shock onto the forming disk, we calculate the sputtering and thermal desorption of various grain-surface species in one-dimensional shock waves. We find that thermal desorption is much more efficient than the sputtering in the post-shock region. While H{sub 2}O can be thermally desorbed, if the accretion velocity is larger than 8 km s{sup –1} with the pre-shock gas number density of 10{sup 9} cm{sup –3}, SO is desorbed if the accretion velocity ≳2 km s{sup –1} and ≳4 km s{sup –1}, with the pre-shock density of 10{sup 9} cm{sup –3} and 10{sup 8} cm{sup –3}, respectively. We also find that the column density of hydrogen nuclei in warm post-shock gas is N {sub warm} ∼ 10{sup 21} cm{sup –2}.


    SciTech Connect

    Seeman, John T


    The present B-factories PEP-II and KEKB have reached luminosities of 3-4 x 10{sup 33}/cm{sup 2}/s and delivered integrated luminosity at rates in excess of 4fb{sup -1} per month [1,2]. The recent turn on of these two B-Factories has shown that modern accelerator physics, design, and engineering can produce colliders that rapidly reach their design luminosities and deliver integrated luminosities capable of frontier particle physics discoveries. PEP-II and KEK-B with ongoing upgrade programs should reach luminosities of over 10{sup 34}/cm{sup 2}/s in a few years and with more aggressive improvements may reach luminosities of order 10{sup 35}/cm{sup 2}/s by the end of the decade. However, due to particle physics requirements, the next generation B-Factory may require significantly more luminosity. Initial parameters of a very high luminosity e{sup +}e{sup -} B-Factory or Super B-Factory (SBF) are being developed incorporating several new ideas from the successful operation of the present generation e{sup +}e{sup -} accelerators [3,4]. A luminosity approaching 10{sup 36}/cm{sup 2}/s{sup -1} appears possible. Furthermore, the ratio of average to peak luminosity may be increased by 30% due to continuous injection. The operation of this accelerator will be qualitatively different from present e{sup +}e{sup -} colliders due to this continuous injection.

  20. Features of the electrical conductivity of TlInSe{sub 2} under photoexcitation and X-ray excitation

    SciTech Connect

    Madatov, R. S. Najafov, A. I.; Mustafayev, Yu. M.; Gazanfarov, M. R.; Movsumova, I. M.


    The current–voltage characteristics of TlInSe{sub 2} crystals under photoexcitation and X-ray excitation are studied. The parameters of the trap, which are equal to N{sub t} = 5 × 10{sup 16} cm{sup –3}, n{sub t} = 4.5 × 10{sup 12} cm{sup –3}, and ΔE{sub t} = 0.42 eV, are calculated. The calculated values of N{sub t} and n{sub t} before and after X-ray excitation are equal to 3 × 10{sup 16} cm{sup –3} and 3.2 × 10{sup 12} cm{sup –3}, respectively. The dependences of the X-ray conductances on the radiation intensity are studied for TlInSe{sub 2} crystals at various accelerating voltages V{sub a} and it is determined that the X-ray conductance K{sub σ} decreases exponentially as the accelerating voltage V{sub a} and radiation dose increase.

  1. Radiation environment and shielding for the GEM experiment at the SSC

    SciTech Connect

    Diwan, M.; Fisyak, Y.; Mokhov, N.


    We have performed a comprehensive study of the radiation environment for the proposed GEM detector at the SSC. As a result of this study, we have developed a shielding scenario that will ensure that the detector will operate with its design performance for at least 10 years at the luminosity of 10{sup 33} cm{sup {minus}2}s{sup {minus}1}.

  2. Attainment of a high gain in a disk amplifying stage with neodymium phosphate glass elements

    SciTech Connect

    Voronich, Ivan N; Garanin, Sergey G; Zaretskii, Aleksei I; Ignat'ev, Ivan V; Kirillov, G A; Murugov, Vasilii M; Osin, Vladimir A; Sukharev, Stanislav A; Charukhchev, Aleksandr V


    An efficient reflecting coating made of a MIRO foil with an oxide layer is fabricated, which enhances the reflection of radiation of pump lamps in the head of a high-power neodymium laser and allows a gain g{sub 0}=5x10{sup -2} cm{sup -1} to be achieved. (lasers)

  3. Control of extended high-voltage electric discharges in atmospheric air by UV KrF-laser radiation

    SciTech Connect

    Zvorykin, V D; Levchenko, A O; Ustinovskii, N N


    Experiments in the commutation of extended ({approx}1-m long) high-voltage (up to 390 kV) electric discharges were carried out with the aid of 100-ns long UV pulses of the GARPUN KrF laser, in which we demonstrated a one-and-a-half-fold lengthening of the discharge gap broken down in the presence of laser illumination. Total control of discharge trajectory along the direction of the laser beam was observed for a radiation energy of {approx}300 mJ (the corresponding intensity I = 5x10{sup 8} W cm{sup -2} and its attendant initial electron density Ne {approx} 10{sup 11} cm{sup -3}) and partial control for an energy of 40 mJ (I = 7x10{sup 7} W cm{sup -2}, Ne {approx} 8x10{sup 9} cm{sup -3}) with a 100% probability of breakdown. We discuss the advantages of employing a UV laser for active lightning protection in comparison with IR lasers and ultrashort-pulse laser systems. (interaction of laser radiation with matter)

  4. Method of preparing thin film polymeric gel electrolytes


    Derzon, Dora K.; Arnold, Jr., Charles


    Novel hybrid thin film electrolyte, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities .apprxeq.10.sup.-3 .OMEGA..sup.-1 cm.sup.-1 are useful as electrolytes for rechargeable lithium batteries.

  5. Method of preparing thin film polymeric gel electrolytes


    Derzon, D.K.; Arnold, C. Jr.


    Novel hybrid thin film electrolyte is described, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities {approx_equal}10{sup {minus}3}{Omega}{sup {minus}1}cm{sup {minus}1} are useful as electrolytes for rechargeable lithium batteries. 1 fig.

  6. Thin film polymeric gel electrolytes


    Derzon, Dora K.; Arnold, Jr., Charles; Delnick, Frank M.


    Novel hybrid thin film electrolyte, based on an organonitrile solvent system, which are compositionally stable, environmentally safe, can be produced efficiently in large quantity and which, because of their high conductivities .apprxeq.10.sup.-3 .OMEGA..sup.-1 cm.sup.-1 are useful as electrolytes for rechargeable lithium batteries.

  7. The CDF LEVEL3 trigger

    SciTech Connect

    Carroll, T.; Joshi, U.; Auchincloss, P.


    CDF is currently taking data at a luminosity of 10{sup 30} cm{sup -2} sec{sup -1} using a four level event filtering scheme. The fourth level, LEVEL3, uses ACP (Fermilab`s Advanced Computer Program) designed 32 bit VME based parallel processors (1) capable of executing algorithms written in FORTRAN. LEVEL3 currently rejects about 50% of the events.


    SciTech Connect

    Edwards, J. L.; Ziurys, L. M.


    Millimeter and sub-millimeter molecular-line observations of planetary nebula (PN) NGC 6537 (Red Spider) have been carried out using the Sub-Millimeter Telescope and the 12 m antenna of the Arizona Radio Observatory in the frequency range 86-692 GHz. CN, HCN, HNC, CCH, CS, SO, H{sub 2}CO, HCO{sup +} and N{sub 2}H{sup +}, along with the J = 3 {yields} 2 and 6 {yields} 5 lines of CO and those of several isotopologues, were detected toward the Red Spider, estimated to be {approx}1600 yr old. This extremely high excitation PN evidently fosters a rich molecular environment. The presence of CS and SO suggest that sulfur may be sequestered in molecular form in such nebulae. A radiative transfer analysis of the CO and CS spectra indicate a kinetic temperature of T{sub K} {approx} 60-80 K and gas densities of n(H{sub 2}) {approx} 1-8 Multiplication-Sign 10{sup 5} cm{sup -3} in NGC 6537. Column densities of the molecules in the nebula and their fractional abundances relative to H{sub 2} ranged from N{sub tot} {approx} 10{sup 16} cm{sup -2} and f {approx} 10{sup -4} for CO, to {approx}7 Multiplication-Sign 10{sup 11} cm{sup -2} and f {approx} 8 Multiplication-Sign 10{sup -9} for the least abundant species, N{sub 2}H{sup +}. For SO and CS, N{sub tot} {approx} 2 Multiplication-Sign 10{sup 12} cm{sup -2} and 10{sup 13} cm{sup -2}, respectively, with f {approx} 10{sup -7} and 2 Multiplication-Sign 10{sup -8}. It was also found that HCN/HNC Almost-Equal-To 2. A low {sup 12}C/{sup 13}C ratio of {approx}4 was measured, indicative of hot-bottom burning. These results, coupled with past observations, suggest that molecular abundances in PNe are governed principally by the physical and chemical properties of the individual object and its progenitor star, rather than nebular age.

  9. Plasma expansion into a waveguide created by a linearly polarized femtosecond laser pulse

    SciTech Connect

    Lemos, N.; Grismayer, T.; Cardoso, L.; Figueira, G.; Dias, J. M.


    We demonstrate the efficient generation of 4 mm and 8 mm long plasma waveguides in hydrogen and helium. These waveguides have matching spots sizes for 13 to 34 μm laser beams. The plasma waveguides are created by ultra-short laser pulses (sub-picosecond) of moderate intensities, ∼10{sup 15}–10{sup 16} W cm{sup −2}, that heat the plasma to initial temperatures of tens of eV in order to create a hot plasma column that will expand into a plasma waveguide. We have determined that the main heating mechanism when using fs laser pulses and plasma densities ∼10{sup 18–19} cm{sup −3} is Above Threshold Ionization. Detailed time and space electron density measurements are presented for the laser produced plasma waveguides.

  10. Ultra-low density InAs quantum dots

    SciTech Connect

    Dubrovskii, V. G. Cirlin, G. E.; Brunkov, P. A.; Perimetti, U.; Akopyan, N.


    We show that InAs quantum dots (QDs) can be grown by molecular beam epitaxy (MBE) with an ultralow density of sin 10{sup 7} cm{sup -2} without any preliminary or post-growth surface treatment. The strain-induced QD formation proceeds via the standard Stranski-Krastanow mechanism, where the InAs coverage is decreased to 1.3-1.5 monolayers (MLs). By using off-cut GaAs (100) substrates, we facilitate the island nucleation in this subcritical coverage range without any growth interruption. The QD density dependences on the InAs coverage are studied by photoluminescence, atomic force microscopy, transmission electron microscopy, and are well reproduced by the universal double exponential shapes. This method enables the fabrication of InAs QDs with controllable density in the range 10{sup 7}-10{sup 8} cm{sup -2}, exhibiting bright photoluminescence.

  11. High-purity, isotopically enriched bulk silicon

    SciTech Connect

    Ager III, J.W.; Beeman, J.W.; Hansen, W.L.; Haller, E.E.; Sharp, I.D.; Liao, C.; Yang, A.; Thewalt, M.L.W.; Riemann, H.


    The synthesis and characterization of dislocation-free, undoped, single crystals of Si enriched in all 3 stable isotopes is reported: {sup 28}Si (99.92%), {sup 29}Si (91.37%), and {sup 30}Si (89.8%). A silane-based process compatible with the relatively small amounts of isotopically enriched precursors that are practically available was used. The silane is decomposed to silicon on a graphite starter rod heated to 700-750 C in a recirculating flow reactor. A typical run produces 35 gm of polycrystalline Si at a growth rates of 5 {micro}m/min and conversion efficiency >95%. Single crystals are grown by the floating zone method and characterized by electrical and optical measurements. Concentrations of shallow dopants (P and B) are as low as mid-10{sup 13} cm{sup -3}. Concentrations of C and O lie below 10{sup 16} and 10{sup 15} cm{sup -3}, respectively.

  12. Magnetic trap for thulium atoms

    SciTech Connect

    Sukachev, D D; Sokolov, A V; Chebakov, K A; Akimov, A V; Kolachevskii, N N; Sorokin, Vadim N


    For the first time ultra-cold thulium atoms were trapped in a magnetic quadrupole trap with a small field gradient (20 Gs cm{sup -1}). The atoms were loaded from a cloud containing 4x10{sup 5} atoms that were preliminarily cooled in a magneto-optical trap to the sub-Doppler temperature of 80 {mu}K. As many as 4x10{sup 4} atoms were trapped in the magnetic trap at the temperature of 40 {mu}K. By the character of trap population decay the lifetime of atoms was determined (0.5 s) and an upper estimate was obtained for the rate constant of inelastic binary collisions for spin-polarised thulium atoms in the ground state (g{sub in} < 10{sup -11}cm{sup 3} s{sup -1}). (magnetic traps)

  13. Plasma effects in high frequency radiative transfer

    SciTech Connect

    Alonso, C.T.


    This paper is intended as a survey of collective plasma processes which can affect the transfer of high frequency radiation in a hot dense plasma. We are rapidly approaching an era when this subject will become important in the laboratory. For pedagogical reasons we have chosen to examine plasma processes by relating them to a particular reference plasma which will consist of fully ionized carbon at a temperature kT=1 KeV (10/sup 70/K) and an electron density N = 3 x 10/sup 23/cm/sup -3/, (which corresponds to a mass density rho = 1 gm/cm/sup 3/ and an ion density N/sub i/ = 5 x 10/sup 22/ cm/sup -3/). We will consider the transport in such a plasma of photons ranging from 1 eV to 1 KeV in energy. Such photons will probably be frequently used as diagnostic probes of hot dense laboratory plasmas.

  14. Search for nuclearites using the MACRO detector

    SciTech Connect

    Ahlen, S.; Ambrosio, M.; Antolini, R.; Auriemma, G.; Baker, R.; Baldini, A.; Barbarino, G.C.; Barish, B.C.; Battistoni, G.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bisi, V.; Bloise, C.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, P.; Campana, D.; Carboni, M.; Cecchini, S.; Cei, F.; Chiarella, V.; Chiera, C.; Cobis, A.; Cormack, R.; Corona, A.; Coutu, S.; DeCataldo, G.; Dekhissi, H.; DeMarzo, C.; De Vincenzi, M.; Di Credico, A.; Diehl, E.; Erriquez, O.; Favuzzi, C.; Ficenec, D.; Forti, C.; Foti, L.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giubellino, P.; Grassi, M.; Green, P.; Grillo, A.; Guarino, F.; Gustavino, C.; Habig, A.; Heinz, R.; Hong, J.T.; Iarocci, E.; Katsavounidis, E.; Kearns, E.; Klein, S.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Lee, C.; Levin, D.; Lipari, P.; Liu, G.; Liu, R.; Longo, M.J.; Ludlam, G.; Mancarella, G.; Mandrioli, G.; Margiotta-Neri, A.; Marin, A.; Marini, A.; Martello, D.; Martellotti, G.; Marzari Chiesa, A.; Masera,


    A negative search using 1/12 of the eventual MACRO detector has yielded nuclearite flux limits of 1.1[times]10[sup [minus]14] cm[sup [minus]2] sr[sup [minus]1] s[sup [minus]1] for 10[sup [minus]10][lt][ital m][lt]0.1 g, and 5.5[times]10[sup [minus]15] cm[sup [minus]2] sr[sup [minus]1] s[sup [minus]1] for [ital m][gt]0.1 g. We have modified the formula of De Rujula and Glashow for the light yield of nuclearites to include the uv light absorbed and reemitted in the visible region, and proved that the MACRO sensitivity extends almost to the escape velocity of the Earth. Our flux limit, therefore, can be used to address nuclearites that are possibly trapped in the solar system.

  15. Photoelectric and electrical properties of soluble polyphenylquinolines containing an oxygen or phenylamine bridge group between quinoline moieties

    SciTech Connect

    Aleksandrova, E. L.; Svetlychnyi, V. M. Miagkova, L. A.; Nekrasova, T. N.; Tameev, A. R.; Vannikov, A. V.; Kudryavtsev, V. V.


    Photoelectric and electrical properties of polyphenylquinolines differing in the structure of donor bridge groups between quinoline moieties have been studied. It is demonstrated that films of the polymers synthesized exhibit a photosensitivity at the level of 10{sup 5} cm{sup 2} J{sup -1} (integrated sensitivity 5 x 10{sup -4} lx{sup -1} . s{sup -1}), with a quantum yield of carrier photogeneration of 0.07 and a carrier drift mobility on the order of 10{sup -6} cm{sup 2} V{sup -1} s{sup -1}. The fact that the electron and hole drift mobilities in polyphenylquinoline with a phenylamine bridge group are balanced makes the polymer promising for development of film-type devices based on the bipolar conductivity of a material (e.g., single-layer light-emitting diode)

  16. Thermal property measurements in a fresh pumice flow at Mt. St. Helens

    SciTech Connect

    Hardee, H.C.


    A thermal penetrator that was air dropped into a freshly emplaced pumice flow at Mt. St. Helens yielded information on the in-situ thermal properties of the pumice. The in-situ conductivity-density-specific heat product at a depth of 60 cm was found to be 7.24 x 10/sup -5/ cal/sup 2/cm//sup 4/ s- /sup 0/C/sup 2/ at an average pumice temperature of 200 /sup 0/C. Using this data, values for the average in-situ thermal conductivity (2.9 x 10/sup -4/ cal/cm-s-/sup 0/C) and thermal diffusivity (1.2 x 10/sup -3/ cm/sup 2//s) were estimated. These thermal properties are of use in studies of pumice cooling and in the interpretation of infrared remote sensing data.

  17. Production of high-density capacitive plasma by the effects of multihollow cathode discharge and high-secondary-electron emission

    SciTech Connect

    Ohtsu, Y.; Fujita, H.


    High-density capacitively coupled plasma with electron density of 10{sup 11} cm{sup -3} was produced with the effects of the multihollow cathode discharge and the high-secondary-electron emission from radio frequency (rf)-biased electrode using Ar gas. It was found that the optimum pressure was around 3-15 Pa. In the case of only multihollow cathode discharge, the plasma density increased from 1.2x10{sup 10} to 8x10{sup 10} cm{sup -3} with the increasing distance z from the cathode electrode for 5 mm

  18. Study of PbTe p-Type Doping With BaF{sub 2}

    SciTech Connect

    Mengui, U. A.; Rappl, P. H. O.; Diaz, B.; Closs, H.; Ueta, A. Y.; Abramof, E.


    We investigate here the electrical and structural properties of PbTe layers doped with BaF{sub 2}. The layers were grown on (111)BaF{sub 2} substrates by molecular beam epitaxy. The nominal doping level, defined as the beam flux ratio between BaF{sub 2} and PbTe, was varied from 0.02 to 1%. The hole concentration increases monotonously from 5x10{sup 17} to 1x10{sup 19} cm{sup -3} as the doping level is raised from 0.02 to 0.4%, and saturates at p approx10{sup 19} cm{sup -3} for higher doping levels. This result demonstrates that PbTe can be effectively p-type doped with BaF{sub 2}. Even for the highest doping levels, the PbTe layers remained with a good structural quality, as evidenced by the (222) x-ray rocking curves.

  19. Defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy, studied by means of low-energy ion treatment

    SciTech Connect

    Izhnin, I. I. Izhnin, A. I.; Fitsych, E. I.; Smirnova, N. A.; Denisov, I. A.; Pociask, M.; Mynbaev, K. D.


    Treatment with low-energy ions and measurements of electrical parameters of samples have been used to study the defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy. The films contain neutral defects supposedly associated with tellurium nanoinclusions. Ion treatment electrically activates these defects, with a high concentration of donor centers ({approx}10{sup 17} cm{sup -3}) created in the films. These defects decompose in {approx}10{sup 3} min of aging at room temperature. Then the properties of the material are determined by the concentration of residual donors, which is found to be very low (down to {approx}10{sup 14} cm{sup -3}) for the films under study.

  20. Versatile, high-sensitivity faraday cup array for ion implanters


    Musket, Ronald G.; Patterson, Robert G.


    An improved Faraday cup array for determining the dose of ions delivered to a substrate during ion implantation and for monitoring the uniformity of the dose delivered to the substrate. The improved Faraday cup array incorporates a variable size ion beam aperture by changing only an insertable plate that defines the aperture without changing the position of the Faraday cups which are positioned for the operation of the largest ion beam aperture. The design enables the dose sensitivity range, typically 10.sup.11 -10.sup.18 ions/cm.sup.2 to be extended to below 10.sup.6 ions/cm.sup.2. The insertable plate/aperture arrangement is structurally simple and enables scaling to aperture areas between <1 cm.sup.2 and >750 cm.sup.2, and enables ultra-high vacuum (UHV) applications by incorporation of UHV-compatible materials.

  1. Impact of ethylene carbonate on ion transport characteristics of PVdF-AgCF{sub 3}SO{sub 3} polymer electrolyte system

    SciTech Connect

    Austin Suthanthiraraj, S.; Joice Sheeba, D.; Joseph Paul, B.


    The ionic transport in thin film plasticized polymer electrolytes based on polyvinylidene fluoride (PVdF) as the polymer host, silver triflate (AgCF{sub 3}SO{sub 3}) as salt and ethylene carbonate (EC) as plasticizer prepared by solution casting technique has been reported. Addition of silver triflate has resulted in an increase in the room temperature (298 K) electrical conductivity of the polymer from 10{sup -6} to 10{sup -5} S cm{sup -1} whereas incorporation of EC as the plasticizer has further enhanced the conductivity value by an order of magnitude to 10{sup -4} S cm{sup -1} owing to the possible decrease in crystallinity of the polymer matrix as revealed by the detailed temperature-dependent complex impedance, silver ionic transference number, Fourier transform infrared and X-ray diffraction measurements.

  2. Photophysical properties of indolo[3,2-b]carbazoles as a promising class of optoelectronic materials

    SciTech Connect

    Svetlichnyi, V. M.; Alexandrova, E. L.; Miagkova, L. A.; Matushina, N. V.; Nekrasova, T. N.; Tameev, A. R.; Stepanenko, S. N.; Vannikov, A. V.; Kudryavtsev, V. V.


    The photophysical properties of new synthesized indolocarbazoles, i.e., indolo[3,2-b]carbazole and its derivatives, have been comparatively analyzed. It is shown that their photosensitivity (total photosensitivity to (5-8) x 10{sup -2} (lx s){sup -1}, spectral photosensitivity {approx}10{sup 5} cm{sup 2} J{sup -1}, and free carrier photogeneration quantum yield of 0.1) and transport (effective mobility in 5,11-dioctyl indolo[3,2-b]carbazole is more than 10{sup -5} cm{sup 2}/(V s)) parameters significantly exceed those of pentacene, which, among molecular media (organic crystals), exhibits the highest carrier photogeneration quantum yields. The high photoluminescence intensity of synthesized indolo[3,2-b]carbazole derivatives shows promise for their applicability in electroluminescent devices.

  3. Gold and silver in stream sediments from reconnaissance of 3 x 10/sup 5/ KM/sup 2/ of the western United States

    SciTech Connect

    Van Konynenburg, R.A.; McMillan, G.G.; Higgins, G.H.


    As part of the National Uranium Resource Evaluation (NURE) Program, Lawrence Livermore National Laboratory analyzed about 30,000 stream sediment samples from selected areas of the western United States for numerous chemical elements. The analysis was performed by neutron activation. Data for the concentrations of gold and silver for the samples in which they were detected are presented. Gold was detected in 310 samples, and silver in 19. Latitudes and longitudes are given for the sites from which these samples were taken.

  4. Strong vortex core pinning and Barkhausen-free magnetization response in thin Permalloy disks induced by implantation of 1 × 10{sup 4} Ga{sup +} ions

    SciTech Connect

    Fani Sani, F. E-mail:; Losby, J. E.; Diao, Z.; Parsons, L. C.; Burgess, J. A. J.; Hiebert, W. K.; Freeman, M. R. E-mail:; Vick, D.


    Artificial vortex core pinning sites are induced in thin Permalloy disks by point exposure to as few as 10 000 ions from a focused Ga{sup +} beam. These pinning sites yield a first-order change in the magnetization response of the disk. A single site can keep the vortex core pinned over an applied field range comparable to the vortex annihilation field of the unaltered disk. Several widely separated sites can work together to keep the core pinned in one place, while the Barkhausen effect is eliminated from the magnetization curve over a range approaching the saturation moment of the disk.

  5. Mechanism for the generation of 10[sup 9] G magnetic fields in the interaction of ultraintense short laser pulse with an overdense plasma target

    SciTech Connect

    Sudan, R.N. )


    The physical mechanism for the generation of very high dc'' magnetic fields in the interaction of ultraintense short laser pulse with an overdense plasma target originates in the spatial gradients and nonstationary character of the ponderomotive force. A set of model equations to determine the evolution of the dc'' fields is derived and it is shown that the dc'' magnetic field is of the same order of magnitude as the high frequency laser magnetic field.

  6. Geologic form and setting of a hydrothermal vent field at latitude 10/sup 0/56'N, East Pacific Rise: a detailed study using Angus and Alvin

    SciTech Connect

    McConachy, T.F.; Ballard, R.D.; Mottl, M.J.; Von Herzen, R.P.


    A hydrothermal vent field, here called the Feather Duster site, occurs on the eastern marginal high near the edge of a narrow (95-m) and shallow (15-20-m) axial graben, within an area dominated by sheet flows and collapse features. The sheet flows are intermediate in relative age between younger fluid-flow lavas on the floor of the axial graben and older pillow (constructional) lavas on the marginal highs. Hydrothermal activity occurs in two zones within a 65 by 45 m area. The main zone is located where a fissure system and sulfide-sulfate chimneys vent warm (9-47/sup 0/C) and hot (347/sup 0/C) hydrothermal fluids. Here, two mounds of massive sulfide totaling about 200 t are forming. One occurs at the base of a 3-m-high scarp which is the wall of a drained lava lake; the other is perched on top of the scarp. 19 references, 4 figures.

  7. Heavy ion collisions with A = 10/sup 57/: Aspects of nuclear stability and the nuclear equation of state in coalescing neutron-star binary systems

    SciTech Connect

    Mathews, G.J.; Wilson, J.R.; Evans, C.R.; Detweiler, S.L.


    The dynamics of the final stages of the coalescence of two neturon stars (such as the binary pulsar PSR 1913+16) is an unsolved problem in astrophysics. Such systems are probably efficient generators of gravitational radiation, and may be significant contributors to heavy-element nucleosynthesis. The input physics for the study of such systems is similar to that required for the strudy of heavy-ion collision hydrodynamics; e.g., a finite temperature nuclear equation of state, properties of nuclei away from stability, etc. We discuss the development of a relativistic hydrodynamics code in three spatial dimensions for the purpose of studying such neutron-star systems. The properties of the mass-radius relation (determined by the nuclear equation of state) may lead to a proposed mechanism by which hot, highly neutronized matter is ejected from the coalescing stars. This material is photodisintegrated into a free (mostly) neutron gas which may subsequently experience rapid-neutron capture (r-process) nucleosynthesis. 15 refs., 4 figs.

  8. Percutaneous absorption of (7. 10-/sup 14/C)benzo(a)pyrene and (7,12-/sup 14/C)dimethylbenz(a)anthracene in mice

    SciTech Connect

    Sanders, C.L.; Skinner, C.; Gelman, R.A.


    The percutaneous penetration, tissue distribution, and excretion of /sup 14/C-labeled benzo(a)pyrene (BaP) and dimethylbenz(a)anthracene (DMBA) were studied in mice. Both BaP and DMBA rapidly penetrated the skin and were excreted more in the feces than in the urine. The proportion of BaP or DMBA absorbed was less with increasing applied dose due to apparent saturation of the uptake process. Uptake from the dorsal skin of the nose was similar to uptake from the dorsal nuchal skin. 24 references.

  9. Fractographic examination of ferritic alloy Charpy specimens at a fluence of 6 x 10/sup 22/ n/cm/sup 2/

    SciTech Connect

    Gelles, D.S.; Hu, W.L.


    The fracture surfaces of thirteen Charpy specimens have been examined by scanning electron microscopy and several of these have been measured for hardness. The specimen series irradiated in the AD-2 test, second discharge includes HT-9 base metal in two product forms, and Modified 9Cr-1Mo base metal and weld metal, fluences include 13 and 26 dpa and irradiation temperatures cover the range 390/sup 0/C to 550/sup 0/C. Fracture appearance is found to be insensitive to irradiation fluence, whereas significant differences could be found in product form. It is concluded that irradiation does not encourage a new fracture mechanism such as temper embrittlement. Failure is controlled by the microstructure generated prior to irradiation.

  10. Studies of Pulsed Plasma-Ion Streams During Their Free Propagation And Interaction With Carbon-Tungsten Targets In PF-1000 Facility

    SciTech Connect

    Skladnik-Sadowska, E.; Malinowski, K.; Marchenko, A.; Sadowski, M. J.; Scholz, M.; Karpinski, L.; Paduch, M.; Zielinska, B.; Gribkov, V. A.


    The paper presents results of recent experimental studies within the PF-1000 plasma-focus facility [1], which were performed during the free propagation of pulsed plasma-ion streams inside the vacuum chamber, and during their interaction with different targets. Optical spectra were recorder by means of a Mechelle registered 900 spectrometer operated with some delays in relation to the discharge current peculiarity (dip) and with exposition varied from 100 ns to 100 {mu}s. The recorded spectral lines were used to estimate the density of the free-propagating plasma stream. The electron concentration, as estimated from the Stark broadening of the D{sub {beta}} line recorded at a distance of z = 30 cm from the electrode ends, changed from about 4x10{sup 17} cm{sup -3} to 2x10{sup 16} cm{sup -3} in about 30 {mu}s. Analogous spectroscopic measurements were carried out in experiments performed with targets made of carbon and sintered tungsten, which were placed at a distance of 15 cm from the electrode outlet, where q = 10{sup 10} W/cm{sup 2}, and at a distance of 30 cm, where q = 10{sup 9} W/cm{sup 2}. Particular attention was paid to investigation of a plasma layer formed in the front of the target. In that case the electron density, as estimated on the basis of carbon-and deuterium-ion lines, changed from about 3x10{sup 18} cm{sup -3} to 3x10{sup 16} cm{sup -3} in 30 {mu}s. For the target made of the sintered tungsten, which was placed at a distance of 30 cm, the recorded optical spectr a showed intense D{sub {alpha}} and D{sub {beta}} lines as well as CII-CIV lines, which covered tungsten (WI and WII) lines.


    SciTech Connect

    Henley, David B.; Shelton, Robin L.


    We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on {approx}4/5 of our sight lines. The temperature is fairly uniform (median = 2.22 Multiplication-Sign 10{sup 6} K, interquartile range = 0.63 Multiplication-Sign 10{sup 6} K), while the emission measure and intrinsic 0.5-2.0 keV surface brightness vary by over an order of magnitude ({approx}(0.4-7) Multiplication-Sign 10{sup -3} cm{sup -6} pc and {approx}(0.5-7) Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively, with median detections of 1.9 Multiplication-Sign 10{sup -3} cm{sup -6} pc and 1.5 Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.

  12. {ital p}-type ion-implantation doping of Al{sub 0.75}Ga{sub 0.25}Sb with Be, C, Mg, and Zn

    SciTech Connect

    Zolper, J.C.; Klem, J.F.; Howard, A.J.; Hafich, M.J.


    {ital p}-type ion-implantation doping of Al{sub 0.75}Ga{sub 0.25}Sb is reported. The surface morphology and electrical properties of Al{sub 0.75}Ga{sub 0.25}Sb are shown by atomic force microscopy and Hall measurements to be degraded after rapid thermal annealing of 650{degree}C. Implantation of Be and Mg results in sheet hole concentrations twice that of the implanted acceptor dose of 1{times}10{sup 13} cm{sup {minus}2} following a 600{degree}C anneal. This is explained in terms of double acceptor or antisite defect formation. Implanted C acts as an acceptor but also demonstrates excess hole conduction attributed to implantation-induced defects. Implanted Zn requires higher annealing temperatures than Be and Mg to achieve 100{percent} effective activation for a dose of 1{times}10{sup 13} cm{sup {minus}2} probably as a result of more implantation-induced damage created from the heavier Zn ion. Secondary ion mass spectroscopy of as-implanted and annealed Be, Mg, and C samples are presented. Diffusion of implanted Be (5{times}10{sup 13} cm{sup {minus}2}, 45 keV) is shown to have an inverse dependence on temperature that is attributed to a substitutional-interstitial diffusion mechanism. Implanted Mg (1{times}10{sup 14} cm{sup {minus}2}, 110 keV) shows dramatic redistribution and loss at the surface of up to 56{percent} after a 600{degree}C anneal. Implanted C (2.5{times}10{sup 14} cm{sup {minus}2}, 70 keV) displays no redistribution even after a 650{degree}C anneal. This work lays the foundation for using ion-implantation doping in high performance AlGaSb/InGaSb-based {ital p}-channel field-effect transistors.

  13. Irradiation-assisted stress corrosion cracking of model austenitic stainless steel.

    SciTech Connect

    Chung, H. M.; Ruther, W. E.; Strain, R. V.; Shack, W. J.; Karlsen, T. M.


    Slow-strain-rate tensile (SSRT) tests were conducted on model austenitic stainless steel (SS) alloys that were irradiated at 289 C in He. After irradiation to {approx}0.3 x 10{sup 21} n {center_dot} cm{sup 2} and {approx} 0.9 x 10{sup 21} n {center_dot} cm{sup -2} (E > 1 MeV), significant heat-to-heat variations in the degree of intergranular and transgranular stress corrosion cracking (IGSCC and TGSCC) were observed. At {approx}0.3 x 10{sup 21} n {center_dot} cm{sup -2}, a high-purity heat of Type 316L SS that contains a very low concentration of Si exhibited the highest susceptibility to IGSCC. In unirradiated state, Types 304 and 304L SS did not exhibit a systematic effect of Si content on alloy strength. However, at {approx}0.3 x 10{sup 21} n {center_dot} cm{sup -2}, yield and maximum strengths decreased significantly as Si content was increased to >0.9 wt.%. Among alloys that contain low concentrations of C and N, ductility and resistance to TGSCC and IGSCC were significantly greater for alloys with >0.9 wt.% Si than for alloys with <0.47 wt.% Si. Initial data at {approx}0.9 x 10{sup 21} n {center_dot} cm{sup -2} were also consistent with the beneficial effect of high Si content. This indicates that to delay onset of and reduce susceptibility to irradiation-assisted stress corrosion cracking (IASCC), at least at low fluence levels, it is helpful to ensure a certain minimum concentration of Si. High concentrations of Cr were also beneficial; alloys that contain <15.5 wt.% Cr exhibited greater susceptibility to IASCC than alloys with {approx}18 wt.% Cr, whereas an alloy that contains >21 wt.% Cr exhibited less susceptibility than the lower-Cr alloys under similar conditions.

  14. Performance assessment of zircon as a waste form for excess weapons plutonium under deep borehole burial conditions

    SciTech Connect

    Weber, W.J.; Ewing, R.C.; Lutze, W.


    Zircon (ZrSiO{sub 4}) is proposed as a waste form for excess weapons-grade plutonium. Zircon is an extremely durable ceramic that is often found as an accessory mineral in Precambrian terranes with ages up to 4 billion years. The chemical durability of zircon in groundwater far exceeds that of other waste forms, as modeled leach rates may be as low as 10{sup {minus}11} g/m{sup 2}d. At least 10 wt% Pu can substitute for Zr in zircon. Self-radiation damage from alpha decay leads to a crystalline-to-amorphous transformation that is modeled as a function of time and temperature for deep borehole conditions. Based on the results of this assessment, zircon could meet all necessary durability and criticality criteria required for a Pu waste form. The types of data used in this analysis are generally not available for other crystalline ceramics or glasses.

  15. The Super Fixed Target beauty facility at the SSC

    SciTech Connect

    Lau, Kwong; The SFT Collaboration


    The rationale for pursuing beauty physics at the SSC in a fixed target configuration is described. The increased beauty production cross section at the SSC, combined with high interaction rate capability of the proposed detector, results in 10{sup 10{minus}11} produced BB events per year. The long decay length of the B hadrons ({approx_equal} 10 cm) allows direct observation of B decays in the high resolution silicon microstrip vertex detector. To optimize the operation of the proposed beauty spectrometer and the SSC, parasitic extraction of attendant or artificially generated large amplitude protons using crystal channeling is proposed and explored. The large sample of fully reconstructed B events allows detailed studies of various CP violating decays with requisite statistics to confront the standard model. The CP physics potential of the proposed experiment is evaluated and compared with alternative approaches, such as symmetric e{sup +}e{sup {minus}} B Factories and specialized hadron colliders.

  16. Design and operation of the AGS Booster Ionization Profile Monitor

    SciTech Connect

    Stillman, A.N.; Thern, R.E.; Van Zwienen, W.H.; Witkover, R.L.


    The AGS Booster Ionization Profile Monitor (IPM) must operate in a vacuum of about 3 {times} 10{sup {minus}11} Torr. The ultra-high vacuum imposes certain requirements on detector gain and restrictions on construction techniques. Each detector is a two-stage micro-channel plate with an integral substrate containing sixty-four printed anodes. Formed electrodes provide uniform collection fields without the use of resistors, which would be unacceptable in these vacuum conditions. An ultra-violet light calibrates the detector in its permanent mounting. An extra set of electrodes performs a first order correction to the perturbations imposed by the horizontal and vertical collection electrodes. This paper will present details of the design of the profile monitor and recent operational results. 4 refs., 6 figs.

  17. Design and operation of the AGS Booster Ionization Profile Monitor

    SciTech Connect

    Stillman, A.N.; Thern, R.E.; Van Zwienen, W.H.; Witkover, R.L.


    The AGS Booster Ionization Profile Monitor (IPM) must operate in a vacuum of about 3 {times} 10{sup {minus}11} Torr. The ultra-high vacuum imposes certain requirements on detector gain and restrictions on construction techniques. Each detector is a two-stage micro-channel plate with an integral substrate containing sixty-four printed anodes. Formed electrodes provide uniform collection fields without the use of resistors, which would be unacceptable in these vacuum conditions. An ultra-violet light calibrates the detector in its permanent mounting. An extra set of electrodes performs a first order correction to the perturbations imposed by the horizontal and vertical collection electrodes. This paper will present details of the design of the profile monitor and recent operational results. 4 refs., 6 figs.

  18. Finite-element-method expectation values for correlated two-electron wave functions

    SciTech Connect

    Ackermann, J.


    The Schroedinger equation for the ground state of correlated two-electron atoms is treated by an accurate finite-element method (FEM) yielding energy eigenvalues of {minus}2.903 724 377 021 a.u. for the helium atom and {minus}0.527 751 016 532 a.u. for the hydrogen ion H{sup {minus}}. By means of an adaptive multilevel grid refinement the FEM energy eigenvalue is improved to a precision of 1{times}10{sup {minus}11} a.u., which is comparable to results obtained with sophisticated global basis sets. The local and overall precision of the FEM wave function approximation is studied and discussed. Benchmark values for the expectation values {l_angle}{ital r}{sup 2}{r_angle}, {l_angle}{ital r}{r_angle}, {l_angle}1/{ital r}{r_angle}, and {l_angle}1/{ital r}{sub 12}{r_angle} are presented.

  19. Design of the AGS Booster Ionization Profile Monitor

    SciTech Connect

    Stillman, A.N.; Thern, R.E.; Witkover, R.L.; Van Zwienen, W.H.


    The AGS Booster Ionization Profile Monitor (IPM) must operate in a vacuum of about 3 {times} 10{sup {minus}11} Torr. The ultra-high vacuum imposes certain requirements on detector gain and restrictions on construction techniques. Each detector is a two-stage microchannel plate with an integral substrate containing sixty-four printed anodes. Formed electrodes provide uniform collection fields without the use of resistors, which would be unacceptable in these vacuum conditions. An ultra-violet light calibrates the detector in its permanent mounting. An extra set of electrodes performs a first order correction to the perturbations imposed by the horizontal and vertical collection electrodes. This paper will present details of the design of the profile monitor. 4 refs., 2 figs.

  20. Gallium self-diffusion in gallium arsenide: A study using isotope heterostructures

    SciTech Connect

    Wang, Lei; Hsu, L.; Haller, E.E. |; Erickson, J.W.; Fischer, A.; Eberl, K.; Cardona, M.


    Ga self-diffusion was studied with secondary-ion mass spectroscopy in {sup 69}GaAs/{sup 71}GaAs isotope heterostructures grown by molecular beam epitaxy on GaAs substrates. Results show that the Ga self- diffusion coefficient in intrinsic GaAs can be described accurately with D = (43{+-}25 cm{sup 2}s{sup -1})exp(-4.24{+-}0.06 eV/k{sub B}T) over 6 orders of magnitude between 800 and 1225 C under As-rich condition. Experimental results combined with theoretical calculations strongly suggest Ga vacancy being the dominant native defect controlling the diffusion. No significant doping effects were observed in samples where the substrates were doped with Te up to 4x10{sup 17}cm{sup -3} or Zn up to 1x10{sup 19}cm{sup -3}.

  1. Study of residual background carriers in midinfrared InAs/GaSb superlattices for uncooled detector operation

    SciTech Connect

    Haugan, H. J.; Elhamri, S.; Szmulowicz, F.; Ullrich, B.; Brown, G. J.; Mitchel, W. C.


    The midinfrared 7 ML InAs/8 ML GaSb superlattices (SLs) were grown by molecular beam epitaxy at growth temperatures between 370 and 430 deg. C in order to study the intrinsic characteristic of background carriers. Grown SLs were all residual p type with carrier densities in the low 10{sup 11} cm{sup -2}, and a minimum density of 1.8x10{sup 11} cm{sup -2} was obtained from the SL grown at 400 deg. C. With increasing growth temperature, the in-plane carrier mobility decreased from 8740 to 1400 cm{sup 2}/V s due to increased interfacial roughness, while the photoluminescence intensity increased sixfold due to a decrease in the nonradiative defect densities.

  2. Interface trap density and mobility extraction in InGaAs buried quantum well metal-oxide-semiconductor field-effect-transistors by gated Hall method

    SciTech Connect

    Chidambaram, Thenappan; Madisetti, Shailesh; Greene, Andrew; Yakimov, Michael; Tokranov, Vadim; Oktyabrsky, Serge; Veksler, Dmitry; Hill, Richard


    In this work, we are using a gated Hall method for measurement of free carrier density and electron mobility in buried InGaAs quantum well metal-oxide-semiconductor field-effect-transistor channels. At room temperature, mobility over 8000 cm{sup 2}/Vs is observed at ∼1.4 × 10{sup 12} cm{sup −2}. Temperature dependence of the electron mobility gives the evidence that remote Coulomb scattering dominates at electron density <2 × 10{sup 11} cm{sup −2}. Spectrum of the interface/border traps is quantified from comparison of Hall data with capacitance-voltage measurements or electrostatic modeling. Above the threshold voltage, gate control is strongly limited by fast traps that cannot be distinguished from free channel carriers just by capacitance-based methods and can be the reason for significant overestimation of channel density and underestimation of carrier mobility from transistor measurements.

  3. Nitriding of a tool steel with an electron-beam-excited plasma

    SciTech Connect

    Shoyama, H.; Hishida, T.; Hara, T.; Dake, Y.; Mori, T.; Nagai, H.; Hori, M.; Goto, T.


    Nitriding of a tool steel was carried out with an electron-beam-excited plasma (EBEP). EBEP is sustained with energetic electron beams over the pressure range of 10{sup -3}-10{sup 1} Pa by electron-impact ionization. Samples whose temperatures were controlled by electric radiant heater were exposed to EBEP. A nitrided layer of 100 {mu}m and a surface hardness of 1000 HV(0.1) were achieved for tool steel SKD61 (JIS) at 800 K and a treatment time of 3 h. In order to measure the density of nitrogen atoms in EBEP, a vacuum ultraviolet absorption spectroscopy system was used. It was found that the density of nitrogen atoms increased from 10{sup 11} to 10{sup 12} cm{sup -3} linearly with an increase of electron beam current from 2 to 20 A.

  4. Neutrino emissivity from e sup minus synchrotron and e sup minus e+ annihilation processes in a strong magnetic field: General formalism and nonrelativistic limit

    SciTech Connect

    Kaminker, A.D.; Levenfish, K.P.; Yakovlev, D.G. ); Amsterdamski, P.; Haensel, P. )


    A general formalism is developed for calculating the neutrino emissivities of synchrotron and {ital e}{sup {minus}}{ital e+} annihilation radiations in a plasma in the presence of a large magnetic field {ital B}{similar to}10{sup 12}--10{sup 14} G. As a first step, the formalism is used to calculate the synchrotron and annihilation radiations from a nonrelativistic electron plasma (density {rho}{approx lt}10{sup 6} g cm{sup {minus}3}, temperature {ital T}{approx lt}6{times}10{sup 9} K) including the cases of nondegenerate and degenerate electrons, and of quantizing and nonquantizing magnetic fields. We conclude that these processes can be important for neutrino production in a hot plasma of neutron star envelopes.

  5. Dielectric behavior of Ar{sup +} implanted CR-39 polymer

    SciTech Connect

    Shekhawat, Nidhi; Sharma, Annu; Aggarwal, Sanjeev; Deshpande, S. K.; Nair, K. G. M.


    The frequency dependent dielectric response of Ar{sup +} implanted CR-39 specimens has been studied. Samples were implanted with 130 keV Ar{sup +} ions to various doses ranging from 5x10{sup 14} to 1x10{sup 16} cm{sup -2}. The frequency response of dielectric constant (e) and dielectric loss has been studied both in the pristine and argon ion implanted samples of CR-39 polymer in the frequency range 10{sup 4} to 10{sup 8} Hz. Structural changes produced in CR-39 specimens due to implantation have been studied using Attenuated total reflectance (ATR) Fourier transform infrared spectroscopic technique. Results of dielectric analysis indicate the lowering in dielectric constant ({epsilon}') and similar behavior of dielectric loss with increase in ion fluence. An attempt has been made to correlate these changes produced in the dielectric properties of implanted specimens with the structural changes produced due to implantation.

  6. Open-circuit voltage, fill factor, and efficiency of a CdS/CdTe solar cell

    SciTech Connect

    Kosyachenko, L. A. Grushko, E. V.


    The dependences of the open-circuit voltage, fill factor, and efficiency of the thin-film CdS/CdTe solar cell on the resistivity {rho} and carrier lifetime {tau} in the absorbing CdTe layer were studied. In the common case in which the uncompensated acceptor concentration and the electron lifetime in the CdTe layer are within 10{sup 15}-10{sup 16} cm{sup -3} and 10{sup -10}-10{sup -9} s, the calculation results correspond to the achieved efficiency of the best thin-film CdS/CdTe solar cells. It was shown that, by decreasing {rho} and increasing {tau} in the absorbing CdTe layer, the open-circuit voltage, fill factor, and efficiency can be substantially increased, with their values approaching the theoretical limit for such devices.

  7. Study of transport properties with relativistic ponderomotive effect in two-electron temperature plasma

    SciTech Connect

    Sen, Sonu Dubey, A.; Varshney, Meenu Asthana; Varshney, Dinesh


    In the present paper we make an analytical investigation to study transport properties with relativistic ponderomotive effect in two-electron temperature plasma. Using fluid model the two-electron temperature are introduced through relativistic ponderomotive force for the transportation of two species of electrons. Applying WKB and paraxial ray approximation the nonlinear dielectric constant and self-focusing equation is evaluated and analyzed with experimental relevance. Numerical calculations are made for different concentration of electron density (10{sup 19}−10{sup 21} per cm{sup 3}) at arbitrary values of laser intensity in the range 10{sup 18}−10{sup 21} W/cm{sup 2}. For a minimum radius depending on the initial conditions it is oscillating between a minimum and maximum value. The hot electrons leading to the increase of the on-axis transportation and favorable effect on relativistic self-focusing.

  8. Cross focusing of two laser beams and plasma wave excitation

    SciTech Connect

    Gupta, M.K.; Sharma, R.P.; Gupta, V.L.


    This article presents the cross focusing of two high power laser beams in a plasma when relativistic and ponderomotive nonlinearities are operative. The effect of electron density modification changes the critical power significantly in contrast to (only) relativistic case. The plasma wave generation at the difference frequency and particle acceleration has also been studied. In a typical case when laser wavelengths are 1047 and 1064 nm and electron density 1.9x10{sup 19} cm{sup -3}, the maximum electron plasma wave power flux comes out to be 6x10{sup 17} W/cm{sup 2} (laser power P{sub 1}=3.6x10{sup 18} W/cm{sup 2} and P{sub 2}=3.2x10{sup 18} W/cm{sup 2})


    SciTech Connect

    Lockman, Felix J.; Free, Nicole L.; Shields, Joseph C.


    The Green Bank Telescope has been used to search for 21 cm H I emission over a large area between the galaxies M31 and M33 in an attempt to confirm at 9.'1 angular resolution the detection by Braun and Thilker of a very extensive neutral gas 'bridge' between the two systems at the level N{sub HI} Almost-Equal-To 10{sup 17} cm{sup -2}. We detect H I emission at several locations up to 120 kpc in projected distance from M31, at least half the distance to M33, with velocities similar to that of the galaxies, confirming the essence of the Braun and Thilker discovery. The H I does not appear to be associated with the extraplanar high-velocity clouds of either galaxy. In two places we measure N{sub HI} > 3 Multiplication-Sign 10{sup 18} cm{sup -2}, indicative of concentrations of H I with {approx}10{sup 5} M{sub Sun} on scales {approx}< 2 kpc, but over most of the field we have only 5{sigma} upper limits of N{sub HI} {<=} 1.4 Multiplication-Sign 10{sup 18} cm{sup -2}. In very deep measurements in two directions H I lines were detected at a few 10{sup 17} cm{sup -2}. The absence of emission at another location to a 5{sigma} limit N{sub HI} {<=} 1.5 Multiplication-Sign 10{sup 17} cm{sup -2} suggests that the H I bridge is either patchy or confined to within {approx}125 kpc of M31. The measurements also cover two of M31's dwarf galaxies, And II and And XV, but in neither case is there evidence for associated H I at the 5{sigma} level of 1.4 Multiplication-Sign 10{sup 4} M{sub Sun} for And II and 9.3 Multiplication-Sign 10{sup 3} M{sub Sun} for And XV.

  10. Polymer-based solar cells having an active area of 1.6 cm{sup 2} fabricated via spray coating

    SciTech Connect

    Scarratt, N. W.; Griffin, J.; Zhang, Y.; Lidzey, D. G.; Wang, T.; Yi, H.; Iraqi, A.


    We demonstrate the fabrication of polymer solar cells in which both a PEDOT:PSS hole transport and a PCDTBT:PC{sub 71}BM photoactive layer are deposited by spray-casting. Two device geometries are explored, with devices having a pixel area of 165 mm{sup 2} attaining a power conversion efficiency of 3.7%. Surface metrology indicates that the PEDOT:PSS and PCDTBT:PC{sub 71}BM layers have a roughness of 2.57 nm and 1.18 nm over an area of 100 μm{sup 2}. Light beam induced current mapping reveals fluctuations in current generation efficiency over length-scales of ∼2 mm, with the average photocurrent being 75% of its maximum value.


    SciTech Connect

    Haggard, Daryl; Cool, Adrienne M.; Heinke, Craig O.; Van der Marel, Roeland; Anderson, Jay; Cohn, Haldan N.; Lugger, Phyllis M. E-mail:


    We report a sensitive X-ray search for the proposed intermediate-mass black hole (IMBH) in the massive Galactic cluster, {omega} Centauri (NGC 5139). Combining Chandra X-ray Observatory data from Cycles 1 and 13, we obtain a deep ({approx}291 ks) exposure of the central regions of the cluster. We find no evidence for an X-ray point source near any of the cluster's proposed dynamical centers, and place an upper limit on the X-ray flux from a central source of f{sub X}(0.5-7.0 keV) {<=}5.0 Multiplication-Sign 10{sup -16} erg cm{sup -2} s{sup -1}, after correcting for absorption. This corresponds to an unabsorbed X-ray luminosity of L{sub X}(0.5-7.0 keV) {<=}1.6 Multiplication-Sign 10{sup 30} erg s{sup -1}, for a cluster distance of 5.2 kpc, Galactic column density N{sub H} = 1.2 Multiplication-Sign 10{sup 21} cm{sup -2}, and power-law spectrum with {Gamma} = 2.3. If a {approx}10{sup 4} M{sub sun} IMBH resides in the cluster's core, as suggested by some stellar dynamical studies, its Eddington luminosity would be L{sub Edd} {approx}10{sup 42} erg s{sup -1}. The new X-ray limit would then establish an Eddington ratio of L{sub X}/L{sub Edd} {approx}< 10{sup -12}, a factor of {approx}10 lower than even the quiescent state of our Galaxy's notoriously inefficient supermassive black hole Sgr A*, and imply accretion efficiencies as low as {eta} {approx}< 10{sup -6}-10{sup -8}. This study leaves open three possibilities: either {omega} Cen does not harbor an IMBH or, if an IMBH does exist, it must experience very little or very inefficient accretion.

  12. Spectroscopic studies of magnesium plasma produced by fundamental and second harmonics of Nd:YAG laser

    SciTech Connect

    Haq, S. U. Ahmat, L.; Mumtaz, M.; Nadeem, A.; Shakeel, Hira; Mahmood, S.


    In the present experimental work, laser induced magnesium plasma has been characterized using plasma parameters. The plasma has been generated by the fundamental (1064 nm) and second harmonics (532 nm) of Nd:YAG laser. The plasma parameters such as electron temperature and electron number density have been extracted using Boltzmann plot method and Stark broadened line profile, respectively. The laser irradiance dependence and spatial behavior of electron temperature and number density in laser induced magnesium plasma have been studied. The electron temperature as a function of laser irradiance (0.5 to 6.5 GW/cm{sup 2}) ranges from (9.16–10.37) × 10{sup 3 }K and (8.5–10.1)× 10{sup 3 }K, and electron number density from (0.99–1.08) × 10{sup 16} cm{sup −3} and (1.04–1.22) × 10{sup 16}cm{sup −3} for 1064 and 532 nm, respectively. These parameters exhibit fast increase at low laser irradiance and slow increase at high irradiance. The spatial distribution of electron temperature and electron number density shows same decreasing trend up to 2.25 mm from the target surface. The electron temperature and number density decrease from (9.5–8.6) × 10{sup 3 }K, (1.27–1.15) × 10{sup 16}cm{sup −3} and (10.56–8.85)× 10{sup 3 }K, (1.08–0.99) × 10{sup 16} cm{sup −3} for 532 nm and 1064 nm laser ablation wavelengths, respectively.


    SciTech Connect

    Grcevich, Jana; Putman, Mary E E-mail:


    We examine the H I content and environment of all of the Local Group dwarf galaxies (M {sub tot} < 10{sup 10} M {sub sun}), including the numerous newly discovered satellites of the Milky Way and M31. All of the new dwarfs, with the exception of Leo T, have no detected H I. The majority of dwarf galaxies within {approx}270 kpc of the Milky Way or Andromeda are undetected in H I (<10{sup 4} M {sub sun} for Milky Way dwarfs), while those further than {approx}270 kpc are predominantly detected with masses {approx}10{sup 5} to 10{sup 8} M {sub sun}. Analytical ram-pressure arguments combined with velocities obtained via proper motion studies allow for an estimate of the halo density of the Milky Way at several distances. This halo density is constrained to be greater than 2x 10{sup -4}-3 x 10{sup -4} cm{sup -3} out to distances of at least 70 kpc. This is broadly consistent with theoretical models of the diffuse gas in a Milky Way-like halo and is consistent with this component hosting a large fraction of a galaxy's baryons. Accounting for completeness in the dwarf galaxy count, gasless dwarf galaxies could have provided at most 2.1 x 10{sup 8} M {sub sun} of H I gas to the Milky Way, which suggests that most of our Galaxy's star formation fuel does not come from accreted small satellites in the current era.

  14. Effect of electron and proton irradiation on characteristics of SiC surface-barrier detectors of nuclear radiation

    SciTech Connect

    Ivanov, A. M. Strokan, N. B.; Kozlovskii, V. V.; Lebedev, A. A.


    Structures with a Schottky barrier based on CVD-grown 4H-SiC films were irradiated with 8 MeV protons and 900 keV electrons. The maximum fluences were 10{sup 14} and 3 x 10{sup 16} cm{sup -2}, respectively. It was found that, in the case of electrons, the primarily introduced radiation defects are closely spaced Frenkel pairs. Changes in the electrical characteristics of the structures were compared. Capacitance methods and nuclear spectrometry were employed. The latter technique was used to determine the charge collection efficiency under pulsed ionization with {alpha}-particles. It was determined that, under proton irradiation, the charge collection efficiency steadily decreases as the fluence increases. For electrons, the efficiency remains unchanged in the fluence range (1-3) x 10{sup 16} cm{sup -2}. However, a fluence of 3 x 10{sup 16} cm{sup -2} leads to a pronounced increase in the non-uniformity of charge transport conditions throughout the sample volume.

  15. Effect of electron and proton irradiation on characteristics of SiC surface-barrier detectors of nuclear radiation

    SciTech Connect

    Ivanov, A. M. Strokan, N. B.; Kozlovskii, V. V.; Lebedev, A. A.


    Structures with a Schottky barrier based on CVD-grown 4H-SiC films were irradiated with 8 MeV protons and 900 keV electrons. The maximum fluences were 10{sup 14} and 3 Multiplication-Sign 10{sup 16} cm{sup -2}, respectively. It was found that, in the case of electrons, the primarily introduced radiation defects are closely spaced Frenkel pairs. Changes in the electrical characteristics of the structures were compared. Capacitance methods and nuclear spectrometry were employed. The latter technique was used to determine the charge collection efficiency under pulsed ionization with {alpha}-particles. It was determined that, under proton irradiation, the charge collection efficiency steadily decreases as the fluence increases. For electrons, the efficiency remains unchanged in the fluence range (1-3) Multiplication-Sign 10{sup 16} cm{sup -2}. However, a fluence of 3 Multiplication-Sign 10{sup 16} cm{sup -2} leads to a pronounced increase in the non-uniformity of charge transport conditions throughout the sample volume.

  16. Neutron star solutions in perturbative quadratic gravity

    SciTech Connect

    Deliduman, Cemsinan; Ekşi, K.Y.; Keleş, Vildan E-mail:


    We study the structure of neutron stars in R+βR{sup μν}R{sub μν} gravity model with perturbative method. We obtain mass-radius relations for six representative equations of state (EoSs). We find that, for |β| ∼ 10{sup 11} cm{sup 2}, the results differ substantially from the results of general relativity. Some of the soft EoSs that are excluded within the framework of general relativity can be reconciled for certain values of β of this order with the 2 solar mass neutron star recently observed. For values of β greater than a few 10{sup 11} cm{sup 2} we find a new solution branch allowing highly massive neutron stars. By referring some recent observational constraints on the mass–radius relation we try to constrain the value of β for each EoS. The associated length scale (β){sup 1/2} ∼ 10{sup 6} cm is of the order of the the typical radius of neutron stars, the probe used in this test. This implies that the true value of β is most likely much smaller than 10{sup 11} cm{sup 2}.

  17. Magneto-optical trap for metastable helium at 389 nm

    SciTech Connect

    Koelemeij, J.C.J.; Stas, R.J.W.; Hogervorst, W.; Vassen, W.


    We have constructed a magneto-optical trap (MOT) for metastable triplet helium atoms utilizing the 2 {sup 3}S{sub 1}{yields}3 {sup 3}P{sub 2} line at 389 nm as the trapping and cooling transition. The far-red-detuned MOT (detuning {delta}=-41 MHz) typically contains few times 10{sup 7} atoms at a relatively high ({approx}10{sup 9} cm{sup -3}) density, which is a consequence of the large momentum transfer per photon at 389 nm and a small two-body loss rate coefficient (2x10{sup -10} cm{sup 3}/s<{beta}<1.0x10{sup -9} cm{sup 3}/s). The two-body loss rate is more than five times smaller than in a MOT on the commonly used 2 {sup 3}S{sub 1}{yields}2 {sup 3}P{sub 2} line at 1083 nm. Furthermore, laser cooling at 389 nm results in temperatures somewhat lower than those achieved using 1083 nm. The 389-nm MOT exhibits small losses due to two-photon ionization, which have been investigated as well.

  18. Low Radioactivity Argon Dark Matter Search Results from the DarkSide-50 Experiment

    SciTech Connect

    Agnes, P.


    Our DarkSide-50 dark matter search reports the first results obtained using a target of lowradioactivity argon extracted from underground sources. The experiment is located at the Laboratori Nazionali del Gran Sasso and uses a two-phase time projection chamber as a detector. A total of 155 kg of low radioactivity argon has been obtained, and we have determined that underground argon is depleted in 39Ar by a factor (1.4 ±0.2) x 10<sup>3 relative to atmospheric argon. The underground argon was also found to contain (2.05 ± 0.13)mBq=kg of 85Kr. We also found no evidence for dark matter in the form of WIMPs in 70.9 live-days of data with a fiducial mass of (36.9 ± 0.6) kg. When combined with our preceding search with an atmospheric argon target, we set a 90% C.L. upper limit on the WIMP-nucleon spin-independent cross section of 2.0 x 10<sup>-44 cm>2 (8.6 x 10<sup>-44 cm>2, 8.0 x 10<sup>-43 cm>2) for a WIMP mass of 100 GeV=c2 (1TeV=c2, 10TeV=c2).

  19. Deep Level Defect Studies in MOCVD-Grown In(x)Ga(1-x)As(1-y)N(y) Films Lattice-Matched to GaAs

    SciTech Connect

    Allerman, A.A.; Boeckl, J.J.; Jones, E.D.; Kaplar, R.J.; Kurtz, S.R.; Kwon, D.; Ringel, S.A.


    Deep level defects in MOCVD-grown, unintentionally doped p-type InGaAsN films lattice matched to GaAs were investigated using deep level transient spectroscopy (DLTS) measurements. As-grown p-InGaAsN showed broad DLTS spectra suggesting that there exists a broad distribution of defect states within the band-gap. Moreover, the trap densities exceeded 10{sup 15} cm{sup {minus}3}. Cross sectional transmission electron microscopy (TEM) measurements showed no evidence for threading dislocations within the TEM resolution limit of 10{sup 7} cm{sup {minus}2}. A set of samples was annealed after growth for 1800 seconds at 650 C to investigate the thermal stability of the traps. The DLTS spectra of the annealed samples simplified considerably, revealing three distinct hole trap levels with energy levels of 0.10 eV, 0.23 eV, and 0.48 eV above the valence band edge with trap concentrations of 3.5 x 10{sup 14} cm{sup {minus}3}, 3.8 x 10{sup 14} cm {sup {minus}3}, and 8.2 x 10{sup 14} cm{sup {minus}3}, respectively. Comparison of as-grown and annealed DLTS spectra showed that post-growth annealing effectively reduced the total trap concentration by an order of magnitude across the bandgap. However, the concentration of a trap with an energy level of 0.48 eV was not affected by annealing indicating a higher thermal stability for this trap as compared with the overall distribution of shallow and deep traps.

  20. Helium measurements of pore-fluids obtained from SAFOD drillcore

    SciTech Connect

    Ali, S.; Stute, M.; Torgersen, T.; Winckler, G.; Kennedy, B.M.


    {sup 4}He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4-6 times on each sample, and indicate a bulk {sup 4}He diffusion coefficient of 3.5 {+-} 1.3 x 10{sup -8} cm{sup 2}s{sup -1} at 21 C, compared to previously published diffusion coefficients of 1.2 x 10{sup -18} cm{sup 2}s{sup -1} (21 C) to 3.0 x 10{sup -15} cm{sup 2}s{sup -1} (150 C) in the sands and clays. Correcting the diffusion coefficient of {sup 4}He{sub water} for matrix porosity ({approx}3%) and tortuosity ({approx}6-13) produces effective diffusion coefficients of 1 x 10{sup -8} cm{sup 2}s{sup -1} (21 C) and 1 x 10{sup -7} (120 C), effectively isolating pore fluid {sup 4}He from the {sup 4}He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8 {+-} 0.4% (SD, n=4) and mudstones 3.1 {+-} 0.8% (SD, n=4).

  1. Two proton-conductive hybrids based on 2-(3-pyridyl)benzimidazole molecules and Keggin-type heteropolyacids

    SciTech Connect

    Wei, Mei-Lin Wang, Yu-Xia; Wang, Xin-Jun


    Two proton-conductive organic/inorganic complexes were constructed by Keggin-type heteropolyacids and 2-(3-pyridyl)benzimidazole molecules. Single-crystal X-ray diffraction analyses revealed that two complexes crystallized in the monoclinic space group P2{sub 1}/c, exhibited different unit cell parameters, and presented different hydrogen-bonded networks constructed by 2-(3-pyridyl)benzimidazole molecules, [PMo{sub 12}O{sub 40}]{sup 3−} anions and solvent molecules. The results of thermogravimetric analyses suggest that two supramolecular complexes have different thermal stability based on the different hydrogen-bonded networks. Two complexes at 100 °C under 35–98% relative humidity showed a good proton conductivity of about 10{sup −3} S cm{sup −1}. The proton conductivities of two complexes under 98% relative humidity both increase on a logarithmic scale with temperature range from 25 to 100 °C. At 100 °C, both complexes showed poor proton conductivities of 10{sup −8}–10{sup −9} S cm{sup −1} under acetonitrile or methanol vapor. - Graphical abstract: Two molecular hybrids constructed by Keggin-type heteropolyacids and 2-(3-pyridyl)benzimidazole molecules showed good proton conductivities of 10{sup −3} S cm{sup −1} at 100 °C under 35–98% relative humidity. Display Omitted - Highlights: • 2-(3-Pyridyl)benzimidazole could form hydrogen bonds via the N–H groups. • Heteropolyacids have suitable characteristics to be used excellent proton conductors. • Two proton-conductive hybrids based on Keggin HPAs and 3-PyBim were constructed. • The structures were determined by using single-crystal X-ray diffraction data. • They showed good proton conductivities of 10{sup −3} S cm{sup −1} at 100 °C under 35–98% RH.

  2. Microstructure of hardened and softened zirconia after xenon implantation

    SciTech Connect

    Fleischer, E.L.; Norton, M.G.; Zaleski, M.A. ); Hertl, W. ); Carter, C.B.; Mayer, J.W. )


    Ion-channeling and transmission electron microscopy (TEM) techniques were used to examine the microstructure of single-crystal Y{sub 2}O{sub 3} stabilized cubic zirconia (YSZ) after implantation with 240 keV Xe{sup +} ions. The observed microstructure was related to Knoop indentation hardness measurements. These measurements showed an increase in hardness for low ion-doses, reaching some maximum value, then a decrease in hardness at higher doses. In the hardening regime, below 7.5{times}10{sup 15} Xe{sup +}/cm{sup 2}, point defects and dislocation networks were observed by TEM. Ion-channeling showed a corresponding increase in damage as a function of ion-dose. For doses between 7.5{times}10{sup 15} and 3{times}10{sup 16} Xe{sup +}/cm{sup 2} the hardness falls, and the amount of damage, measured with ion-channeling, reaches a limiting value at less than complete damage. In this dose range the Xe concentration continues to increase beyond the dose where the amount of damage saturates. For high doses, greater than 3{times}10{sup 16} Xe{sup +}/cm{sup 2}, where softening of the zirconia occurs, additional reflections appear in the electron diffraction pattern that are consistent with the lattice parameter of solid Xe. A diffuse ring is also visible; this is believed to be due to the presence of fluid Xe. Both ion-channeling and TEM show that a significant amount of monocrystalline zirconia remains even up to doses of 1{times}10{sup 17} Xe{sup +}/cm{sup 2}. There is also evidence for the presence of recrystallized zirconia at the high doses. Since so much crystalline material remains, it seems that amorphization of the zirconia is not the dominant cause of the softening at high doses.

  3. Effects of gamma-ray irradiation on dislocations in sodium nitrate single crystals

    SciTech Connect

    Solnick-Legg, H.; Herley, P.J.; Levy, P.W.


    The topography of the etch pits formed on the (100) cleavage surfaces of unirradiated and irradiated NaNO/sub 3/ single crystals has been studied. The principal etch pit alignments are consistent with dislocation families of the type (100) (011), (211) (011), and (111) (011). The pit density increases from 1.4 (+-0.2) x 10/sup 4//cm/sup 2/ at zero dose to 7.3 (+-0.2) x 10/sup 5//cm/sup 2/ at 5.0 x 10/sup 8/ rad. With increasing dose the pit density distribution narrows and clusters at 1.0 x 10/sup 6/ pits/cm/sup 2/ at doses above 5.0 x 10/sup 8/ rad. Above this dose radiolytic-induced micro bumps or structures are observed that precede the onset of radiolytic decomposition that is visible at 2.5 x 0/sup 9/ rad. These asymmetric structures appear to nucleate at the same sites as the chemically created etch pits and are aligned in the same principal directions. These observations indicate that dislocations are important sites for nucleating radiation induced decomposition and internal radiolytic gas generation. 12 references, 9 figures, 1 table.

  4. Dissociative recombination of the cation and dication of CO{sub 2}

    SciTech Connect

    Seiersen, K.; Al-Khalili, A.; Heber, O.; Jensen, M. J.; Nielsen, I. B.; Pedersen, H. B.; Safvan, C. P.; Andersen, L. H.


    Dissociative recombination of CO{sub 2} ions has been studied at the heavy-ion storage ring ASTRID. Electrons were scattered on both singly and doubly charged positive ions of the molecule, and the absolute cross sections were measured in the energy range of 10{sup -3}-10{sup 1} eV. Thermal rate coefficients of {alpha}(CO{sub 2}{sup +}) =(6.5{+-}1.9)x10{sup -7}x(300/T[K]){sup 0.8} cm{sup 3} s{sup -1} and {alpha}(CO{sub 2}{sup 2+}) =(6.2{+-}2.1)x10{sup -7}x(300/T[K]){sup 0.5} cm{sup 3} s{sup -1} were extracted. Furthermore, branching ratios for molecular breakup into neutral product channels have been measured using a grid technique. The branching ratios were measured at {approx}0 eV for CO{sub 2}{sup +}, and in the entire energy range from 10{sup -3} eV to 50 eV for CO{sub 2}{sup 2+}. This measurement reveals pronounced structure in the CO{sub 2}{sup 2+} branching ratios.

  5. Raman measurements in silica glasses irradiated with energetic ions

    SciTech Connect

    Saavedra, R. Martin, P.; Vila, R.; León, M.; Jiménez-Rey, D.; Girard, S.; Boukenter, A.; Ouerdane, Y.


    Ion irradiation with energetic He{sup +} (2.5 MeV), O{sup 4+} (13.5 MeV), Si{sup 4+} (24.4 MeV) and Cu{sup 7+} (32.6 MeV) species at several fluences (from 5 × 10{sup 12} to 1.65 × 10{sup 15} ion/cm{sup 2}) were performed in three types of SiO{sub 2} glasses with different OH content (KU1, KS-4V and Infrasil 301). After ion implantation the Raman spectra were measured and compared with the spectra of unirradiated samples. Irradiated samples of the three fused silica grades exhibit changes in the broad and asymmetric R-band (ω{sub 1} around 445 cm{sup −1}), in D{sub 1} (490 cm−1) and D{sub 2} (605 cm{sup −1}) bands associated to small-membered rings. The D{sub 2} band shows an increase with increasing fluences for different ions, indicating structural changes. Raman spectra of ion-irradiated samples were compared with the spectra of neutron irradiated samples at fluences 10{sup 17} n/cm{sup 2} and 1018 n/cm{sup 2}. Macroscopic surface cracking was detected, mainly at fluences corresponding to deposited energies between 10{sup 23} eV/cm{sup 3} and 10{sup 24} eV/cm{sup 3} (after ion beam shutdown)


    SciTech Connect

    Wheeler, J. Craig; Johnson, Vincent E-mail:


    We explore the potential cumulative energy production of stellar-mass black holes in early galaxies. Stellar-mass black holes may accrete substantially from the higher density interstellar media (ISMs) of primordial galaxies, and their energy release would be distributed more uniformly over the galaxies, perhaps providing a different mode of energy feedback into young galaxies than central supermassive black holes. We construct a model for the production and growth of stellar-mass black holes over the first few gigayears of a young galaxy. With the simplifying assumption of a constant density of the ISM, n {approx} 10{sup 4}-10{sup 5} cm{sup -3}, we estimate the number of accreting stellar-mass black holes to be {approx}10{sup 6} and the potential energy production to be as high as 10{sup 61} erg over several billion years. For densities less than 10{sup 5} cm{sup -3}, stellar-mass black holes are unlikely to reach their Eddington limit luminosities. The framework we present could be incorporated in numerical simulations to compute the feedback from stellar-mass black holes with inhomogeneous, evolving ISMs.

  7. Multichannel transition emissions of Dy{sup 3+} in fiber-adaptive germanium tellurite glasses

    SciTech Connect

    Li, Y. H.; Chen, B. J.; Lin, H.; Pun, E. Y. B.


    Multichannel transition visible and near-infrared (NIR) fluorescences have been captured in Dy{sup 3+}-doped fiber-adaptive Na{sub 2}O-ZnO-PbO-GeO{sub 2}-TeO{sub 2} glasses. The maximum stimulated emission cross-sections {sigma}{sub em-max} were derived to be 0.33 Multiplication-Sign 10{sup -21}, 3.66 Multiplication-Sign 10{sup -21}, and 0.67 Multiplication-Sign 10{sup -21} cm{sup 2} for conventional visible emissions assigned to {sup 4}F{sub 9/2}{yields}{sup 6}H{sub J} (J = 15/2, 13/2, and 11/2) transitions, respectively. Infrequent multi-peak NIR emissions were recorded in the spectral range of 900-1500 nm, among which the values of {sigma}{sub em-max} were solved to be 1.05 Multiplication-Sign 10{sup -22} and 1.56 Multiplication-Sign 10{sup -22} cm{sup 2} for {approx}1.02 and {approx}1.18 {mu}m emission bands. Internal quantum efficiency for the {sup 4}F{sub 9/2} level and external quantum yield for visible emissions of Dy{sup 3+} were determined to be 88.44% and 12.38%, severally. Effective multichannel radiative emissions reveal a potential in developing fiber-lighting sources, tunable lasers, and NIR optical amplifiers.

  8. Progress in Antiproton Production at the Fermilab Tevatron Collider

    SciTech Connect

    Pasquinelli, Ralph J.; Drendel, Brian; Gollwitzer, Keith; Johnson, Stan; Lebedev, Valeri; Leveling, Anthony; Morgan, James; Nagaslaev, Vladimir; Peterson, Dave; Sondgeroth, Alan; Werkema, Steve; /Fermilab


    Fermilab Collider Run II has been ongoing since 2001. During this time peak luminosities in the Tevatron have increased from approximately 10 x 10{sup 30} cm{sup -2}sec{sup -1} to 300 x 10{sup 30} cm{sup 02}sec{sup -1}. A major contributing factor in this remarkable performance is a greatly improved antiproton production capability. Since the beginning of Run II, the average antiproton accumulation rate has increased from 2 x 10{sup 10}{anti p}/hr to about 24 x 10{sup 10}{anti p}/hr. Peak antiproton stacking rates presently exceed 28 x 10{sup 10}{anti p}/hr. The antiproton stacking rate has nearly doubled since 2005. It is this recent progress that is the focus of this paper. The process of transferring antiprotons to the Recycler Ring for subsequent transfer to the collider has been significantly restructured and streamlined, yielding additional cycle time for antiproton production. Improvements to the target station have greatly increased the antiproton yield from the production target. The performance of the Antiproton Source stochastic cooling systems has been enhanced by upgrades to the cooling electronics, accelerator lattice optimization, and improved operating procedures. In this paper, we will briefly report on each of these modifications.

  9. Electron beam processing of ZnGeP{sub 2}: A nonlinear optical material for the infrared

    SciTech Connect

    Schunemann, P.G.; Drevinsky, P.J.; Ohmer, M.C.; Mitchel, W.C.; Fernelius, N.C.


    Zinc germanium phosphide, an important frequency-conversion material for producing mid-infrared lasers, is plagued by a defect-related absorption band extending from the fundamental edge (0.62 microns) to {approximately}3 microns. The level of absorption varies with melt composition, and can be reduced by post-growth annealing treatments. In these experiments, further reduction of the near-band-edge absorption was achieved by irradiating with 1--1.5 MeV electrons at cumulative fluence levels up to 2.75 {times} 10{sup 18}cm{sup {minus}2}. Ge-rich, ZnP{sub 2}-rich, and both as-grown and annealed stoichiometric crystals were studied. The near-edge absorption of the higher-loss, nonstoichiometric samples decreased monotonically with each subsequent irradiation, whereas the absorption in the lower-loss, stoichiometric samples was minimized after cumulative electron fluences of 2 {times} 10{sup 18}cm{sup {minus}2} and 1 {times} 10{sup 18}cm{sup {minus}2} for as-grown and annealed material respectively, The minimum absorption coefficient achieved at 1 {micro}m was {approximately}4.4 cm{sup {minus}1} in both stoichiometric samples, representing a factor two decrease for the as-grown crystal. Further exposure after reaching saturation served only to increase the losses at longer wavelengths.

  10. Studies of laser wakefield structures and electron acceleration in underdense plasmas

    SciTech Connect

    Maksimchuk, A.; Reed, S.; Bulanov, S. S.; Chvykov, V.; Kalintchenko, G.; Matsuoka, T.; McGuffey, C.; Mourou, G.; Naumova, N.; Nees, J.; Rousseau, P.; Yanovsky, V.; Krushelnick, K.; Matlis, N. H.; Kalmykov, S.; Shvets, G.; Downer, M. C.; Vane, C. R.; Beene, J. R.; Stracener, D.


    Experiments on electron acceleration and optical diagnostics of laser wakes were performed on the HERCULES facility in a wide range of laser and plasma parameters. Using frequency domain holography we demonstrated single shot visualization of individual plasma waves, produced by 40 TW, 30 fs laser pulses focused to the intensity of 10{sup 19} W/cm{sup 2} onto a supersonic He gas jet with plasma densities n{sub e}<10{sup 19} cm{sup -3}. These holographic 'snapshots' capture the variation in shape of the plasma wave with distance behind the driver, and resolve wave front curvature seen previously only in simulations. High-energy quasimonoenergetic electron beams were generated using plasma density in the range 1.5x10{sup 19}{<=}n{sub e}{<=}3.5x10{sup 19} cm{sup -3}. These experiments demonstrated that the energy, charge, divergence, and pointing stability of the beam can be controlled by changing n{sub e}, and that higher electron energies and more stable beams are produced for lower densities. An optimized quasimonoenergetic beam of over 300 MeV and 10 mrad angular divergence is demonstrated at a plasma density of n{sub e}{approx_equal}1.5x10{sup 19} cm{sup -3}. The resultant relativistic electron beams have been used to perform photo-fission of {sup 238}U with a record high reaction yields of {approx}3x10{sup 5}/J. The results of initial experiments on electron acceleration at 70 TW are discussed.

  11. Interpretation of brine-permeability tests of the Salado Formation at the Waste Isolation Pilot Plant site: First interim report

    SciTech Connect

    Beauheim, R.L. ); Saulnier, G.J. Jr.; Avis, J.D. )


    Pressure-pulse tests have been performed in bedded evaporites of the Salado Formation at the Waste Isolation Pilot Plant (WIPP) site to evaluate the hydraulic properties controlling brine flow through the Salado. Hydraulic conductivities ranging from about 10{sup {minus}14} to 10{sup {minus}11} m/s (permeabilities of about 10{sup {minus}21} to 10{sup {minus}18} m{sup 2}) have been interpreted from nine tests conducted on five stratigraphic intervals within eleven meters of the WIPP underground excavations. Tests of a pure halite layer showed no measurable permeability. Pore pressures in the stratigraphic intervals range from about 0.5 to 9.3 MPa. An anhydrite interbed (Marker Bed 139) appears to be one or more orders of magnitude more permeable than the surrounding halite. Hydraulic conductivities appear to increase, and pore pressures decrease, with increasing proximity to the excavations. These effects are particularly evident within two to three meters of the excavations. Two tests indicated the presence of apparent zero-flow boundaries about two to three meters from the boreholes. The other tests revealed no apparent boundaries within the radii of influence of the tests, which were calculated to range from about four to thirty-five meters from the test holes. The data are insufficient to determine if brine flow through evaporites results from Darcy-like flow driven by pressure gradients within naturally interconnected porosity or from shear deformation around excavations connecting previously isolated pores, thereby providing pathways for fluids at or near lithostatic pressure to be driven towards the low-pressure excavations. Future testing will be performed at greater distances from the excavations to evaluate hydraulic properties and processes beyond the range of excavation effects.

  12. Differential stress, strain rate, and temperatures of mylonitization in the Ruby Mountains, Nevada: Implications for the rate and duration of uplift

    SciTech Connect

    Hacker, B.R.; An Yin; Christie, J.M. ); Snoke, A.W. )


    Knowledge of the magnitude of the differential stress during the formation of mylonitic rocks provides constraints on mechanical and thermal models for the exhumation of the metamorphosed footwalls of major low-angle detachment faults. The authors have analyzed the differential flow stress during the mylonitization of quartoze rocks in the Ruby Mountains, Nevada, using grain-size piezometers and kinetic laws for grain growth. Quartzites from mylonitic shear zones in Lamoille Canyon and Secret Creek gorge have grain sizes of 91-151 {mu}m and 42-64 {mu}m, respectively. The peak temperature during mylonitization was 630 {plus minus} 50C, and analysis of grain-growth kinetics indicates that mylonitization continued during cooling to temperatures {le}450C. Quartz grain-size piezometers suggest that the mylonitization occurred under differential stresses of 38-64 MPa, or maximum shear stresses of 19-32 MPa. Extrapolation of quartzite flow laws indicates that the mylonitization occurred at strain rates between 10{sup {minus}10} and 10{sup {minus}13} s{sup {minus}1}; arguments presented in the paper suggest that the likely range of strain rates is 10{sup {minus}11} to 10{sup {minus}12} s{sup {minus}1}. These strain rates are compatible with displacement rates of the order of 23 mm yr{sup {minus}1} along a 1.5-km-thick simple shear zone. Such a shear zone dipping 15{degree} would produce an uplift rate of 5.8 km/m.y. and a horizontal extension rate of 22 km/m.y. This uplift rate indicates that midcrustal mylonitic rocks could have been lifted up along a 1.5-km-thick simple shear zone dipping 15{degree} in 2.6 m.y.

  13. Electron attachment to MoF{sub 6}, ReF{sub 6}, and WF{sub 6}; reaction of MoF{sub 6}{sup -} with ReF{sub 6} and reaction of Ar{sup +} with MoF{sub 6}

    SciTech Connect

    Friedman, Jeffrey F.; Stevens, Amy E.; Miller, Thomas M.; Viggiano, A.A.


    Rate constants were measured for electron attachment to MoF{sub 6}, ReF{sub 6}, and WF{sub 6} in 133 Pa of helium gas using a flowing-afterglow Langmuir-probe apparatus. The experiment is a thorny one because the molecules tend to form oxide impurities on feedline surfaces and because of thermal decomposition of MoF{sub 6} on surfaces as the gas temperature is increased. The electron attachment rate constant for MoF{sub 6} is (2.3{+-}0.8)x10{sup -9} cm{sup 3} s{sup -1} at 297 K; only MoF{sub 6}{sup -} is formed in the temperature range of 297-385 K. The rate constant increases with temperature up to the point where decomposition becomes apparent. Electron attachment to ReF{sub 6} occurs with a rate constant of (2.4{+-}0.8)x10{sup -9} cm{sup 3} s{sup -1} at 297 K; only ReF{sub 6}{sup -} is produced. MoF{sub 6}{sup -} reacts with ReF{sub 6} to form ReF{sub 6}{sup -} on essentially every collision, showing definitively that the electron affinity of ReF{sub 6} is greater than that of MoF{sub 6}. A rate constant of (5.0{+-}1.3)x10{sup -10} cm{sup 3} s{sup -1} was measured for this ion-molecule reaction at 304 K. The reverse reaction is not observed. The reaction of Ar{sup +} with MoF{sub 6} was found to produce MoF{sub 5}{sup +}+F, with a rate constant of (1.8{+-}0.5)x10{sup -9} cm{sup 3} s{sup -1}. WF{sub 6} attaches electrons so slowly at room temperature that the attachment rate was below detection level ({<=}10{sup -12} cm{sup 3} s{sup -1}). By 552 K, the attachment rate constant reaches a value of (2{+-}1)x10{sup -10} cm{sup 3} s{sup -1}.

  14. Beat wave current drive experiment on the Davis Diverted Tokamak (DDT). Final report

    SciTech Connect

    Hwang, D.Q.; Horton, R.D.; Rogers, J.H. |


    The beatwave current drive experiment is summarized. The first phase of the experiment was the construction of the microwave sources and the diagnostics needed to demonstrate the beat wave effects, i.e. the measurement of the electrostatic plasma wave produced by the beating of two high intensity electromagnetic waves. In order to keep the cost of the experiments to a minimum, a low density filament plasma source (10{sup 8}) to (10{sup 10} particles cm{sup {minus}3}) was employed and the magnetic field in the toroidal plasma was produced by a dc power supply.

  15. Neutrino induced muons in Soudan 2.

    SciTech Connect

    DeMuth, D. M.; Soudan 2 Collaboration


    The neutrino-induced muon rate underground has been measured at Soudan 2. To discriminate from the intense background of atmospheric muons we consider only the through-going muons which originate from horizontal direction ({minus}0.14 < cos{theta} < 0.14). We calculate the horizontal, neutrino-induced muon rate at Soudan 2 from an exposure of 1.23 x 10{sup 8} s as {Phi}{sub {nu}{mu}} = (3.45 {+-} 0.52 {+-} 0.61) x 10{sup {minus}13} (cm{sup 2} sr s){sup {minus}1}.

  16. Processes of chemoionization in the course of inflammation of a methane-oxygen mixture by a high-current gliding surface discharge in a closed chamber

    SciTech Connect

    Artem’ev, K. V.; Berezhetskaya, N. K.; Kossyi, I. A. Misakyan, M. A.; Popov, N. A.; Tarasova, N. M.


    Results are presented from experiments on the inflammation of a stoichiometric methane-oxygen mixture by a high-current multielectrode spark-gap in a closed cylindrical chamber. It is shown that, in both the preflame and well-developed flame stages, the gas medium is characterized by a high degree of ionization (n{sub e} ≈ 10{sup 12} cm{sup −3}) due to chemoionization processes and a high electron-neutral collision frequency (ν{sub e0} ≈ 10{sup 12} s{sup −1})

  17. Cationic exchange membrane for the zinc-ferricyanide battery. Final report

    SciTech Connect

    Pemsler, J.P.; Dempsey, M.D.


    In this one year effort of research into supported-liquid-membrane (SLM) separators for the zinc-ferricyanide battery systems, at least one SLM separator (80% LT27/M80 on 0.13 mm PTFE), has been found that approaches the required specifications with separator resistance in the 2 to 3 ohm-cm/sup 2/ range, 1 x 10/sup -3/ mmoles Fe/h-cm/sup 2/ iron transport and 2 x 10/sup -4/ mmoles Zn/h-cm/sup 2/ zinc transport. This separator is still being tested in a 60-cm/sup 2/ zinc-ferricyanide battery and is exhibiting encouraging results.

  18. A chemical bonding model for photo-induced defects in hydrogenated amorphous silicon (a-Si:H): Intrinsic and extrinsic reaction pathways

    SciTech Connect

    Lucovsky, G.; Yang, H.


    In device grade a-Si:H photo- or light-induced defect generation is an intrinsic effect for impurity concentrations of oxygen and nitrogen below about 10{sup 19} to 10{sup 20} cm{sup {minus}3}; however, at higher concentrations it increases with increasing impurity content. Charged defect configurations are identified by empirical chemistry and are studied by ab initio calculations. This paper addresses: (1) the chemical stability of charged defects; (2) the reaction pathways for defect metastability; and (3) the transition between extrinsic and intrinsic behavior.

  19. Wrought stainless steel compositions having engineered microstructures for improved heat resistance


    Maziasz, Philip J [Oak Ridge, TN; Swindeman, Robert W [Oak Ridge, TN; Pint, Bruce A [Knoxville, TN; Santella, Michael L [Knoxville, TN; More, Karren L [Knoxville, TN


    A wrought stainless steel alloy composition includes 12% to 25% Cr, 8% to 25% Ni, 0.05% to 1% Nb, 0.05% to 10% Mn, 0.02% to 0.15% C, 0.02% to 0.5% N, with the balance iron, the composition having the capability of developing an engineered microstructure at a temperature above C. The engineered microstructure includes an austenite matrix having therein a dispersion of intragranular NbC precipitates in a concentration in the range of 10.sup.10 to 10.sup.17 precipitates per cm.sup.3.

  20. Reproducing continuous radio blackout using glow discharge plasma

    SciTech Connect

    Xie, Kai; Li, Xiaoping; Liu, Donglin; Shao, Mingxu; Zhang, Hanlu


    A novel plasma generator is described that offers large-scale, continuous, non-magnetized plasma with a 30-cm-diameter hollow structure, which provides a path for an electromagnetic wave. The plasma is excited by a low-pressure glow discharge, with varying electron densities ranging from 10{sup 9} to 2.5 × 10{sup 11} cm{sup −3}. An electromagnetic wave propagation experiment reproduced a continuous radio blackout in UHF-, L-, and S-bands. The results are consistent with theoretical expectations. The proposed method is suitable in simulating a plasma sheath, and in researching communications, navigation, electromagnetic mitigations, and antenna compensation in plasma sheaths.

  1. Search for the Dirac Monopole with 30-bev Protons

    DOE R&D Accomplishments Database

    Purcell, E.M.; Collins, G.B.; Fujii, T.; Hornbostel, J.; Turkot, F.


    A search was made at the Brookhaven alternating gradient synchrotron for magnetic monopoles produced either in collisions of 30-Bev protons with light nuclei, or produced by gamma rays secondary to these protons in the Coulomb field of protons or of carbon nuclei. In runs using 5.7 x 10{sup 15} circulating protons, no monopole-like event was found. This implies an upper limit for production in protonnucleon interactions of about 2 x 10{sup -40} cm{sup 2}. Experimental limits are also derived for the photoproduction of pole pairs. (auth)

  2. Extreme ionization of Xe clusters driven by ultraintense laser fields

    SciTech Connect

    Heidenreich, Andreas; Last, Isidore; Jortner, Joshua


    We applied theoretical models and molecular dynamics simulations to explore extreme multielectron ionization in Xe{sub n} clusters (n=2-2171, initial cluster radius R{sub 0}=2.16-31.0 A ring ) driven by ultraintense infrared Gaussian laser fields (peak intensity I{sub M}=10{sup 15}-10{sup 20} W cm{sup -2}, temporal pulse length {tau}=10-100 fs, and frequency {nu}=0.35 fs{sup -1}). Cluster compound ionization was described by three processes of inner ionization, nanoplasma formation, and outer ionization. Inner ionization gives rise to high ionization levels (with the formation of (Xe{sup q+}){sub n} with q=2-36), which are amenable to experimental observation. The cluster size and laser intensity dependence of the inner ionization levels are induced by a superposition of barrier suppression ionization (BSI) and electron impact ionization (EII). The BSI was induced by a composite field involving the laser field and an inner field of the ions and electrons, which manifests ignition enhancement and screening retardation effects. EII was treated using experimental cross sections, with a proper account of sequential impact ionization. At the highest intensities (I{sub M}=10{sup 18}-10{sup 20} W cm{sup -2}) inner ionization is dominated by BSI. At lower intensities (I{sub M}=10{sup 15}-10{sup 16} W cm{sup -2}), where the nanoplasma is persistent, the EII contribution to the inner ionization yield is substantial. It increases with increasing the cluster size, exerts a marked effect on the increase of the (Xe{sup q+}){sub n} ionization level, is most pronounced in the cluster center, and manifests a marked increase with increasing the pulse length (i.e., becoming the dominant ionization channel (56%) for Xe{sub 2171} at {tau}=100 fs). The EII yield and the ionization level enhancement decrease with increasing the laser intensity. The pulse length dependence of the EII yield at I{sub M}=10{sup 15}-10{sup 16} W cm{sup -2} establishes an ultraintense laser pulse length

  3. Millimeter observations of CS, HCO{sup +}, and CO toward five planetary nebulae: following molecular abundances with nebular age

    SciTech Connect

    Edwards, J. L.; Ziurys, L. M.; Cox, E. G.


    Millimeter and sub-millimeter observations of CO, CS, and HCO{sup +} have been conducted toward five planetary nebulae (PNe: K4-47, NGC 6537 (Red Spider), M2-48, NGC 6720 (Ring), and NGC 6853 (Dumbbell)), spanning an age range of 900-10,000 yr, using the Sub-Millimeter Telescope and the 12 m antenna of the Arizona Radio Observatory. The J = 5 → 4, J = 3 → 2, and J = 2 → 1 transitions of CS at 245, 147, and 98 GHz, as well as the J = 3 → 2 and J = 1 → 0 lines of HCO{sup +} at 268 and 89 GHz, were detected toward each source. At least three rotational transitions of CO have also been observed, including the J = 6 → 5 and J = 4 → 3 lines at 691 and 461 GHz. CS had not been definitively identified previously in PNe, and new detections of HCO{sup +} were made in four of the five nebulae. From a radiative transfer analysis of the CO and CS data, kinetic temperatures of T {sub K} ∼ 10-80 K and gas densities of n(H{sub 2}) ∼ 0.1-1 × 10{sup 6} cm{sup –3} were determined for the molecular material in these sources. Column densities for CO, CS, and HCO{sup +} were N {sub tot} ∼ 0.2-5 × 10{sup 16} cm{sup –2}, N {sub tot} ∼ 0.4-9 × 10{sup 12} cm{sup –2}, and N {sub tot} ∼ 0.3-5 × 10{sup 12} cm{sup –2}, respectively, with fractional abundances, relative to H{sub 2}, of f ∼ 0.4-2 × 10{sup –4}, f ∼ 1-4 × 10{sup –8}, and f ∼ 1 × 10{sup –8}, with the exception of M2-48, which had f(HCO{sup +}) ∼ 10{sup –7}. Overall, the molecular abundances do not significantly vary over a duration of 10,000 yr, in contrast to predictions of chemical models. The abundances reflect the remnant asymptotic giant branch shell material, coupled with photochemistry in the early PN phase. These observations also suggest that PNe eject substantial amounts of molecular material into the diffuse interstellar medium.

  4. Radiation trapping in rubidium optical pumping at low buffer-gas pressures

    SciTech Connect

    Rosenberry, M. A.; Reyes, J. P.; Gay, T. J.; Tupa, D.


    We have made a systematic study of rubidium optical pumping in a simple cylindrical cell geometry with a high-power 10 W diode laser array, low magnetic fields, and buffer-gas pressures of less than 50 torr. We have determined rubidium polarizations experimentally for H{sub 2}, N{sub 2}, He, and Ar buffer gases, with Rb number densities from 10{sup 12} to 10{sup 13} cm{sup -3}. Comparison to a relatively simple optical pumping model allows us to extract useful information about radiation trapping and quenching effects.

  5. High dislocation density of tin induced by electric current

    SciTech Connect

    Liao, Yi-Han; Liang, Chien-Lung; Lin, Kwang-Lung; Wu, Albert T.


    A dislocation density of as high as 10{sup 17} /m{sup 2} in a tin strip, as revealed by high resolution transmission electron microscope, was induced by current stressing at 6.5 x 10{sup 3} A/ cm{sup 2}. The dislocations exist in terms of dislocation line, dislocation loop, and dislocation aggregates. Electron Backscattered Diffraction images reflect that the high dislocation density induced the formation of low deflection angle subgrains, high deflection angle Widmanstätten grains, and recrystallization. The recrystallization gave rise to grain refining.

  6. Photoelectric Effect at Ultrahigh Intensities

    SciTech Connect

    Sorokin, A. A.; Bobashev, S. V.; Feigl, T.; Tiedtke, K.; Wabnitz, H.; Richter, M.


    In the spectral range of the extreme ultraviolet at a wavelength of 13.3 nm, we have studied the photoionization of xenon at ultrahigh intensities. For our ion mass-to-charge spectroscopy experiments, irradiance levels from 10{sup 12} to 10{sup 16} W cm{sup -2} were achieved at the new free-electron laser in Hamburg FLASH by strong beam focusing with the aid of a spherical multilayer mirror. Ion charges up to Xe{sup 21+} were observed and investigated as a function of irradiance. Our surprising results are discussed in terms of a perturbative and nonperturbative description.

  7. Discovery of reversible photochromism in titanium dioxide using photoacoustic spectroscopy. Implications for the investigation of light-induced charge-separation and surface redox processes in titanium dioxide

    SciTech Connect

    Highfield, J.G.; Graetzel, M.


    Utilizing a conventional photoacoustic spectrometer in a pump-probe arrangement, band-gap excitation of powdered titanium dioxide in a moist, oxygen-free atmosphere results in a strong photochromic response, characteristic of small polaron formation. The reactivity and remarkable lifetime of such excited species are demonstrated in their subsequent dark reduction of methylviologen. Results from two independent methods indicate carrier densities in the range 10/sup 19/-10/sup 20/ cm/sup -3/. Electron-hole recombination follows first-order kinetics, suggesting that detrapping of surface-trapped holes is rate controlling. The presence of water vapor delays the recombination process, extending decay constants from seconds to minutes.

  8. First Demonstration of Electron Scattering Using a Novel Target Developed for Short-Lived Nuclei

    SciTech Connect

    Suda, T.; Wakasugi, M.; Emoto, T.; Ito, S.; Wang, S.; Yano, Y.; Ishii, K.; Kurita, K.; Kuwajima, A.; Tamae, T.; Noda, A.; Shirai, T.; Tongu, H.


    We carried out a demonstrative electron scattering experiment using a novel ion-trap target exclusively developed for short-lived highly unstable nuclei. Using stable {sup 133}Cs ion as a target, this experiment completely mimicked electron scattering off short-lived nuclei. Achieving a luminosity higher than 10{sup 26} cm{sup -2} s{sup -1} with around only 10{sup 6} trapped ions on the electron beam, the angular distribution of elastic scattering was successfully measured. This experiment clearly demonstrates that electron scattering off rarely produced short-lived nuclei is practical with this target technique.

  9. Study of ablation by laser irradiation of plane targets at wavelengths 1. 05, 0. 53, and 0. 35. mu. m

    SciTech Connect

    Key, M.H.; Toner, W.T.; Goldsack, T.J.; Kilkenny, J.D.; Veats, S.A.; Cunningham, P.F.; Lewis, C.L.S.


    Ablation by laser irradiation at wavelengths lambda = 1.05, 0.53, and 0.35 has been studied from analysis of time-resolved x-ray spectra of layered targets and of ion emission. Irradiance was varied in the range 2 x 10/sup 13/ to 2 x 10/sup 15/ W cm/sup -2/ with constant laser power and variable focal spot size. Deductions include the effect of lateral energy transport from small focal spots and ablation rates and ablation pressures obtained both in the limit of negligible transport and when lateral transport is significant. Advantages of short wavelengths for ablatively driven implosions are quantified.

  10. Plasma conditions generated by interaction of a high brightness, prepulse free Raman amplified KrF laser pulse with solid targets

    SciTech Connect

    Riley, D.; Gizzi, L.A.; Khattak, F.Y.; Mackinnon, A.J.; Viana, S.M.; Willi, O. )


    A high brightness, Raman amplified KrF laser has been used to irradiate solid targets with 12 ps laser pulses at intensities above 10[sup 15] W/cm[sup 2] without the presence of a preformed plasma caused by low level amplified spontaneous emission prepulse. Time-resolved x-ray spectroscopy of the [ital K]-shell emission from aluminum was used to infer electron densities in excess of 10[sup 23] cm[sup [minus]3] at temperatures of several hundred electronvolts.

  11. Influence of an electric field on near-surface processes in laser processing of metals

    SciTech Connect

    Vasil'ev, S V; Ivanov, A Yu


    It is shown that by varying the external electric field with different polarity from 0 to 10{sup 6} V m{sup -1} in the course of laser processing with the mean radiation flux density {approx}10{sup 6} W cm{sup -2} the change in the evolution features of the plasma torch at the surface of some metals (Cu, Al, Sn, Pb) at early stages is quantitative rather than qualitative. At the same time the characteristic size of the target material droplets, carried out from the irradiated zone, becomes essentially (by several times) smaller as the amplitude of the external electric field strength grows, independently of its polarity. (laser technologies)

  12. Photodissociation rates of OH, OD, and CN by the interstellar radiation field

    SciTech Connect

    Nee, J.B.; Lee, L.C.


    The photoabsorption cross sections for OH, OD, and CN in the vacuum ultraviolet region are measured. The cross sections for the hydroxyl radicals are of the order of 10/sup -17/ cm/sup -2/, but the photoabsorption for CN is so low that only an upper limit of 2 x 10/sup -18/ is obtained. The molecular photodissociative processes are discussed. The photodissociation cross sections are inferred from the photoabsorption cross sections. On the basis of the measured data, the photodissociation rates by the interstellar radiation field are computed and discussed.

  13. Three-photon absorption of radiation from a Ti:sapphire laser by methylstyrylbenzene

    SciTech Connect

    Meshalkin, Yu P; Svetlichnyi, Valerii A; Svetlichnaya, N N; Kopylova, T N


    It is shown that 2,2'-di-methylstyrylbenzene (bis-MSB) at a concentration of 10{sup -3} M in 1-methyl-2-pyrrolidone can fluoresce at 420 nm upon excitation by a 708-nm femtosecond Ti:sapphire laser. The dependence of the fluorescence intensity on the excitation power proved to be cubic. The three-photon absorption cross section of bis-MSB was estimated as (1.61{+-}0.10)x10{sup -79} cm{sup 6} s{sup 2} phot{sup -2}. bis-MSB is recommended as a cubic standard to normalise laser powers in three-photon measurements. (nonlinear optical phenomena)

  14. Scattering due to Schottky barrier height spatial fluctuation on two dimensional electron gas in AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Li, Huijie; Liu, Guipeng Wei, Hongyuan; Jiao, Chunmei; Wang, Jianxia; Zhang, Heng; Dong Jin, Dong; Feng, Yuxia; Yang, Shaoyan Wang, Lianshan; Zhu, Qinsheng; Wang, Zhan-Guo


    A scattering mechanism related to the Schottky barrier height (SBH) spatial fluctuation of the two dimensional electron gas (2DEG) in AlGaN/GaN heterostructures is presented. We find that the low field mobility is on the order of 10{sup 4}–10{sup 6} cm{sup 2}/Vs. The 2DEG transport properties are found to be influenced by both the mobility and 2DEG density variations caused by the SBH fluctuation. Our results indicate that a uniform Schottky contact is highly desired to minimize the influence of SBH inhomogeneity on the device performance.

  15. Positron plasma control techniques for the production of cold antihydrogen

    SciTech Connect

    Funakoshi, R.; Hayano, R. S.; Amoretti, M.; Macri, M.; Testera, G.; Variola, A.; Bonomi, G.; Bowe, P. D.; Hangst, J. S.; Madsen, N.; Canali, C.; Carraro, C.; Lagomarsino, V.; Manuzio, G.; Cesar, C. L.; Charlton, M.; Joergensen, L. V.; Mitchard, D.; Werf, D. P. van der; Doser, M.


    An observation of a clear dependence of antihydrogen production on positron plasma shapes is reported. For this purpose a plasma control method has been developed combining the plasma rotating-wall technique with a mode diagnostic system. With the help of real-time and nondestructive observations, the rotating-wall parameters have been optimized. The positron plasma can be manipulated into a wide range of shapes (aspect ratio 6.5{<=}{alpha} < or approx. 80) and densities (1.5x10{sup 8}{<=}n < or approx. 7x10{sup 9} cm{sup -3}) within a short duration (25 s) compatible with the ATHENA antihydrogen production cycle.

  16. A near infrared organic photodiode with gain at low bias voltage

    SciTech Connect

    Campbell, Ian H; Crone, Brian K


    We demonstrate an organic photodiode with near infrared optical response out to about 1100 run with a gain of {approx}10 at 1000 run under 5V reverse bias. The diodes employ a soluble naphthalocyanine with a peak absorption coefficient of {approx}10{sup 5} cm{sup -1} at 1000 nm. In contrast to most organic photodiodes, no exciton dissociating material is used. At zero bias, the diodes are inefficient with an external quantum efficiency of {approx} 10{sup -2}. In reverse bias, large gain occurs and is linear with bias voltage above 4V. The observed gain is consistent with a photoconductive gain mechanism.

  17. Effect of the active-ion concentration on the lasing dynamics of holmium fibre lasers

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A


    The lasing dynamics of fibre lasers with a core based on quartz glass doped with holmium ions to concentrations in the range of 10{sup 19}-10{sup 20} cm{sup -3} is investigated. It is shown that fibre lasers with a high concentration of active holmium ions generate pulses, but a decrease in the holmium concentration changes the lasing from pulsed to cw regime. At the same time, a decrease in the active-ion concentration and the corresponding increase in the fibre length in the cavity reduce the lasing efficiency. (lasers)

  18. Effect of active-ion concentration on holmium fibre laser efficiency

    SciTech Connect

    Kurkov, Andrei S; Sholokhov, E M; Marakulin, A V; Minashina, L A


    We have measured the fraction of holmium ions that relax nonradiatively to the ground level as a result of interaction at a metastable level in optical fibres with a silica-based core doped with holmium ions to 2 x 10{sup 19} - 2 x 10{sup 20} cm{sup -3}. The percentage of such ions has been shown to depend on the absolute active-ion concentration. The fibres have been used to make a number of 2.05-{mu}m lasers, and their slope efficiency has been measured. The laser efficiency decreases with increasing holmium concentration in the fibres (lasers)


    SciTech Connect

    Aykutalp, A.; Spaans, M. E-mail:


    The initial mass function (IMF) of the first (Population III) stars and Population II (Pop II) stars is poorly known due to a lack of observations of the period between recombination and reionization. In simulations of the formation of the first stars, it has been shown that, due to the limited ability of metal-free primordial gas to cool, the IMF of the first stars is a few orders of magnitude more massive than the current IMF. The transition from a high-mass IMF of the first stars to a lower-mass current IMF is thus important to understand. To study the underlying physics of this transition, we performed several simulations using the cosmological hydrodynamic adaptive mesh refinement code Enzo for metallicities of 10{sup -4}, 10{sup -3}, 10{sup -2}, and 10{sup -1} Z{sub sun}. In our simulations, we include a star formation prescription that is derived from a metallicity-dependent multi-phase interstellar medium (ISM) structure, an external UV radiation field, and a mechanical feedback algorithm. We also implement cosmic ray heating, photoelectric heating, and gas-dust heating/cooling, and follow the metal enrichment of the ISM. It is found that the interplay between metallicity and UV radiation leads to the coexistence of Pop III and Pop II star formation in non-zero-metallicity (Z/Z{sub sun} {>=} 10{sup -2}) gas. A cold (T < 100 K) and dense ({rho} > 10{sup -22} g cm{sup -3}) gas phase is fragile to ambient UV radiation. In a metal-poor (Z/Z{sub sun} {<=} 10{sup -3}) gas, the cold and dense gas phase does not form in the presence of a radiation field of F{sub 0} {approx} 10{sup -5}-10{sup -4} erg cm{sup -2} s{sup -1}. Therefore, metallicity by itself is not a good indicator of the Pop III-Pop II transition. Metal-rich (Z/Z{sub sun} {>=} 10{sup -2}) gas dynamically evolves two to three orders of magnitude faster than metal-poor gas (Z/Z{sub sun} {<=} 10{sup -3}). The simulations including supernova explosions show that pre-enrichment of the halo does not affect

  20. Limits on the abundance and coupling of cosmic axions

    SciTech Connect

    DePanfilis, S.; Melissinos, A.C.; Moskowitz, B.E.; Rogers, J.T.; Semertzidis, Y.K.; Wuensch, W.U.; Halama, H.J.; Prodell, A.G.; Fowler, W.B.; Kerns, Q.


    We report preliminary results from a search for galactic axions in the mass range 4.5 < m/sub a/ < 5.0 For an axion line width GAMMA/sub a/ less than or equal to 8 x 10/sup -13/ eV, we obtain the experimental limit (g/sub a..gamma gamma../m/sub a/)/sup 2/rho/sub a/ < 1.4 x 10/sup -41/. The theoretical prediction is (g/sub a..gamma gamma../m/sub a/)/sup 2/rho/sub a/ = 3.9 x 10/sup -44/ with the local galactic axion density rho/sub a/ = 300 MeV/cm/sup 3/. We have also searched for the presence of a continuous spectrum of light pseudoscalar particles; assuming that the local galactic axion density is composed of axions with masses uniformly distributed between 4.5 and 5.0, we find that g/sub a..gamma gamma../ < 2 x 10/sup -30/ MeV/sup 1/2/ cm/sup 3/2/ approx. = 10/sup 11/ GeV/sup -1/. Limits have also been set on the production of light pseudoscalar x particles; we find g/sub x..gamma gamma../ < 10/sup -24/ MeV/sup 1/2/ cm/sup 3/2/ approx. = 10/sup -5/ GeV/sup -1/ for 0< m/sub x/ less than or equal to 20 refs., 7 figs., 1 tab.


    SciTech Connect

    Chiaki, Gen; Yoshida, Naoki; Nozawa, Takaya


    In a low-metallicity gas, rapid cooling by dust thermal emission is considered to induce cloud fragmentation and play a vital role in the formation of low-mass stars ({approx}< 1 M{sub Sun }) in metal-poor environments. We investigate how the growth of dust grains through accretion of heavy elements in the gas phase onto grain surfaces alters the thermal evolution and fragmentation properties of a collapsing gas cloud. We directly calculate grain growth and dust emission cooling in a self-consistent manner. We show that MgSiO{sub 3} grains grow sufficiently at gas densities n{sub H} = 10{sup 10}, 10{sup 12}, and 10{sup 14} cm{sup -3} for metallicities Z = 10{sup -4}, 10{sup -5}, and 10{sup -6} Z{sub Sun }, respectively, where the cooling of the collapsing gas cloud is enhanced. The condition for efficient dust cooling is insensitive to the initial condensation factor of pre-existing grains within the realistic range of 0.001-0.1, but sensitive to metallicity. The critical metallicity is Z{sub crit} {approx} 10{sup -5.5} Z{sub Sun} for the initial grain radius r{sub MgSiO{sub 3,0}}{approx}<0.01 {mu}m and Z{sub crit} {approx} 10{sup -4.5} Z{sub Sun} for r{sub MgSiO{sub 3,0}}{approx}>0.1 {mu}m. The formation of a recently discovered low-mass star with extremely low metallicity ({<=}4.5 Multiplication-Sign 10{sup -5} Z{sub Sun }) could have been triggered by grain growth.

  2. Growth of detector-grade CZT by Traveling Heater Method (THM): An advancement

    SciTech Connect



    In this present work we report the growth of Cd{sub 0.9}Zn{sub 0.1}Te doped with In by a modified THM technique. It has been demonstrated that by controlling the microscopically flat growth interface, the size distribution and concentration can be drastically reduced in the as-grown ingots. This results in as-grown detector-grade CZT by the THM technique. The three-dimensional size distribution and concentrations of Te inclusions/precipitations were studied. The size distributions of the Te precipitations/inclusions were observed to be below the 10-{micro}m range with the total concentration less than 10{sup 5} cm{sup -3}. The relatively low value of Te inclusions/precipitations results in excellent charge transport properties of our as-grown samples. The ({mu}{tau}){sub e} values for different as-grown samples varied between 6-20 x 10{sup -3} cm{sup 2}/V. The as-grown samples also showed fairly good detector response with resolution of {approx}1.5%, 2.7% and about 3.8% at 662 keV for quasi-hemispherical geometry for detector volumes of 0.18 cm{sup 3}, 1 cm{sup 3} and 4.2 cm{sup 3}, respectively.

  3. Fourier-transform spectroscopy and potential construction of the (2){sup 1}Π state in KCs

    SciTech Connect

    Birzniece, I.; Nikolayeva, O.; Tamanis, M.; Ferber, R.


    The paper presents an empirical pointwise potential energy curve (PEC) of the (2){sup 1}Π state of the KCs molecule constructed by applying the Inverted Perturbation Approach routine. The experimental term values in the energy range E(v′, J′) ∈ [15 407; 16 579] cm{sup −1} involved in the fit were based on Fourier-Transform spectroscopy data obtained with 0.01 cm{sup −1} accuracy from the laser-induced (2){sup 1}Π → X{sup 1}Σ{sup +} fluorescence spectra. Buffer gas Ar was used to facilitate the appearance of rotation relaxation lines in the spectra, thus enlarging the (2){sup 1}Π data set and allowing determination of the Λ-splitting constants. The data set included vibrational v′ ∈ [0, 28] and rotational J′ ∈ [7, 274] quantum numbers covering about 67% of the potential well. The present PEC reproduces the overall set of data included in the fit with a standard deviation of 0.5 cm{sup −1}. The obtained value of the Λ-doubling constant q = + 1.8 × 10{sup −6} cm{sup −1} for J′ > 50 and v′ ∈ [0, 6] is in an excellent agreement with q = + 1.84 × 10{sup −6} cm{sup −1} reported in Kim, Lee, and Stolyarov [J. Mol. Spectrosc. 256, 57-67 (2009)].

  4. Effects of copper excess and copper deficiency on the structural and electrical properties of bulk Cu{sub x}SnSe{sub 3} with x=1.6–2.2

    SciTech Connect

    Wubet, Walelign; Kuo, Dong-Hau


    Effects of the Cu variation on the morphological, structural, and electrical properties of bulk Cu{sub x}SnSe{sub 3} (CTSe) with x=1.6–2.2 have been investigated. Dense CTSe pellets with grains of 3–4 µm were obtained after sintering at 550 °C. All CTSe pellets showed a dominant p-type behavior. CTSe at x=2.0 with a hole concentration (n{sub p}) of 1.02×10{sup 18} cm{sup −3} and Hall mobility (μ) of 225 cm{sup 2}/V/s had a highest conductivity (σ) of 39 S/cm. CTSe at x=1.6 with n{sub p} of 5.0×10{sup 17} cm{sup −3} and of 11 cm{sup 2}/V/s had a lowest of 0.90 S/cm. The explanation, based upon vacancies and antisite defects, for the changes in electrical property with the Cu content is supported by the data from lattice parameter. The study in bulk properties of CTSe and its defects is helpful for selecting the suitable absorber composition to fabricate thin film solar cells. - Graphical abstract: Cu{sub 2}SnSe{sub 3} is an absorber candidate for solar cells. The Cu stoichiometry on electrical properties, which is important for CIGS and CZTS, is investigated and the Cu-deficiency composition is recommended. - Highlights: • Cu{sub x}SnSe{sub 3} (CTSe) bulks with 1.6≤x≤2.2 were prepared by reactive sintering. • Cu{sub 2}SnSe{sub 3} with n{sub p} of 1.02×10{sup 18} cm{sup −3} and μ of 225 cm{sup 2}/V/s had highest σ of 39 S/cm. • Cu{sub 1.6}SnSe{sub 3} with n{sub p}=5.0×10{sup 17} cm{sup −3} and μ=11 cm{sup 2}/V/s had lowest σ=0.90 S/cm. • Lower n{sub p} at CTSe at x=1.6 is related to the formation of the Sn-to-Cu defect. • The drop in n{sub p} for CTSe at x=2.2 indicates V{sub Sn}{sup 4−} dominates over Cu{sub Sn}{sup 3−} defect.

  5. Process for growing epitaxial gallium nitride and composite wafers


    Weber, Eicke R.; Subramanya, Sudhir G.; Kim, Yihwan; Kruger, Joachim


    A novel growth procedure to grow epitaxial Group III metal nitride thin films on lattice-mismatched substrates is proposed. Demonstrated are the quality improvement of epitaxial GaN layers using a pure metallic Ga buffer layer on c-plane sapphire substrate. X-ray rocking curve results indicate that the layers had excellent structural properties. The electron Hall mobility increases to an outstandingly high value of .mu.>400 cm.sup.2 /Vs for an electron background concentration of 4.times.10.sup.17 cm.sup.-3.

  6. Two-dimensional electron gas in monolayer InN quantum wells

    SciTech Connect

    Pan, Wei; Dimakis, Emmanouil; Wang, George T.; Moustakas, Theodore D.; Tsui, Daniel C.


    We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in monolayer InN quantum wells embedded in GaN barriers. The electron density and mobility of the two-dimensional electron system (2DES) in these InN quantum wells are 5×10<sup>15 cm>-2 and 420 cm>2 /Vs, respectively. Moreover, the diagonal resistance of the 2DES shows virtually no temperature dependence in a wide temperature range, indicating the topological nature of the 2DES.

  7. Measurements of the helium propagation at 4.4 K in a 480 m long stainless steel pipe

    SciTech Connect

    Hseuh, H.C.; Wallen, E.


    The Relativistic Heavy Ion Collider (RHIC), with two concentric rings 3.8 km in circumference, uses superconducting magnets to focus the high energy beams. Each sextant of RHIC will have continuous cryostats up to 480 m in length housing the magnets and the cold beam pipes. For an acceptable lifetime of the stored beam, the pressure in the cold beam pipe will be < 10{sup {minus}11} Torr. The characteristics of He pressure front propagation due to He leaks will be of importance for beam lifetimes and for vacuum monitoring due to the high vapor pressure of He at 4.4 K, even with small surface coverage. The travel of the He pressure fronts along a 480 m long, 6.9 cm I.D. stainless steel beam pipe cooled to 4.4 K has recently been measured during the RHIC first sextant test. The experiment was carried out over a 12-day period by bleeding in a calibrated He leak of 3 {times} 10{sup {minus}5} Torr{center_dot}l/s (20 C) while measuring the He pressures along this 480 m cold tube at {approximately} 30 m intervals. The measured speed of the pressure fronts and the pressure profiles are summarized and compared with the calculated ones.

  8. Measurements of the helium propagation at 4.4 K in a 480 m long stainless steel pipe

    SciTech Connect

    Hseuh, H.C.; Wallen, E.


    The relativistic heavy ion collider (RHIC), with two concentric rings 3.8 km in circumference, uses superconducting magnets to focus the high energy beams. Each sextant of RHIC will have continuous cryostats up to 480 m in length housing the magnets and the cold beam pipes. For an acceptable lifetime of the stored beam, the pressure in the cold beam pipe will be {lt}10{sup {minus}11} Torr. The characteristics of He pressure front propagation due to He leaks will be of importance for beam lifetimes and for vacuum monitoring due to the high vapor pressure of He at 4.4 K, even with small surface coverage. The travels of the He pressure fronts along a 480 m long, 6.9 cm I.D. stainless steel beam pipe cooled to 4.4 K have recently been measured during the RHIC first sextant test. The experiment was carried out over a 12-day period by bleeding in a calibrated He leak of 3{times}10{sup {minus}5}Torrl/s (20{degree}C) while measuring the He pressures along this 480 m cold tube at approximately 30 m intervals. The measured speed of the pressure fronts and the pressure profiles are summarized and compared with the calculated ones. {copyright} {ital 1998 American Vacuum Society.}

  9. Second harmonic generation studies of ozone depletion reactions on ice surfaces under stratospheric conditions

    SciTech Connect

    Geiger, F.M.; Tridico, A.C.; Hicks, J.M.


    Hypochlorous acid, HOCl, an important species in the proposed heterogeneous mechanism for stratospheric ozone depletion, has been observed directly at submonolayer amounts on a single crystalline basal ice surface at 155-188 K, using the nonlinear optical method second harmonic generation. The ice is held in equilibrium with its vapor pressure. Second harmonic generation signals form 290 to 310 nm spectroscopically characterize the species and enable the authors to follow isothermal desorption kinetics in situ. HOCl desorbs as a single species with a {Delta}G*{sub des} = 48 {+-} 4 kJ/mol, close to the cohesive energy of ice itself. The lifetime of HOCl on the clean ice surface at 185 K is estimated to be 4 s and the equilibrium surface coverage at 10{sup {minus}11} Torr HOCl to be around 4 x 10{sup 11} molecules/cm{sub 2}, corresponding to about 0.1% of a monolayer. However, these same measurements performed on ice predosed with varying amounts of HNO{sub 3}show that the HOCl lifetime is lengthened by coadsorbed HNO{sub 3}, depending on the HNO{sub 3} surface density.

  10. Influence of stress intensity and loading mode on intergranular stress corrosion cracking of Alloy 600 in primary waters of pressurized water reactors

    SciTech Connect

    Rebak, R.B.; Szklarska-Smialowska, Z. . Fontana Corrosion Center)


    The steam generator in a pressurized water reactor (PWR) of a nuclear power plant consists mainly of a shell made of carbon (C) steel and tubes made of alloy 600 (UNS N06600). However, alloy 600 suffers environmentally induced cracking with exposure to high-temperature primary water. The susceptibility of alloy 600 to integranular stress corrosion cracking (IGSCC) was investigated as a function of the level of applied stresses and mode of loading. Constant load tests were conducted with specimens prepared from thin wall tubes, and constant deformation tests were conducted using specimens prepared from plates. With tubes exposed to primary water at 330 C, the crack propagation rate (CPR) was found to increase from 1 [times] 10[sup [minus]11] m/s at a stress intensity (K[sub i]) of 10 MPa[radical]m to 1 [times] 10[sup [minus]9] at K[sub i] = 60 MPa[radical]m. CPR obtained using compact specimens prepared from plates were 1 order of magnitude lower than values measured in tubes at the same temperature and in the same solution at each stress intensity. The corollary was that values of crack propagation and threshold stress intensities obtained using compact specimens could not be extrapolated to the behavior of thin wall tubes.

  11. Blast furnace slag-modified grouts for in situ stabilization of chromium-contaminated soil

    SciTech Connect

    Allan, M.L.; Kukacka, L.E.


    Blast furnace slag-modified grouts were used to stabilize soils contaminated with trivalent and hexavalent chromium. Slag content, grout/soil ratio and water/cementitious material ratio were varied to determine the effects on leachability of chromium, permeability and compressive strength. Slag-modified grouts successfully stabilized Cr(VI)-contaminated soil to give low leachability, thereby allowing omission of the pretreatment stage to reduce Cr(VI) to Cr(III) necessary with lime and ordinary Portland cement stabilization procedures. Leachability of both Cr(III) and Cr(VI) decreased with increasing slag content. The permanence of leach resistance is enhanced by higher slag levels in grout. Compressive strength of grout-treated soil ranges from 6 to 36 MPa and permeability is of the order of 10{sup {minus}11} to 10{sup {minus}7} cm/s, depending on mix proportions. Slag-modified grouts have potential for in situ stabilization of Cr(III)- or Cr(VI)-contaminated landfills.

  12. Heavy ion acceleration at the AGS: Present and future plans

    SciTech Connect

    Lee, Y.Y.


    The Brookhaven AGS is alternating gradient synchrotron, 807 meters in circumference, which was originally designed for only protons. Using the 15 MV Brookhaven Tandem Van de Graaff as an injector, the AGS started to accelerate heavy ions of mass lighter than sulfur. Because of the relatively poor vacuum (/approximately/10/sup /minus/8/ Torr), the AGS is not able to accelerate heavier ions which could not be fully stripped of electrons at the Tandem energy. When the AGS Booster, which is under construction, is completed the operation will be extended to all species of heavy ions including gold and uranium. Because ultra-high vacuum (/approximately/10/sup /minus/11/ Torr) is planned, the Booster can accelerate partially stripped elements. The operational experience, the parameters, and scheme of heavy ion acceleration will be presented in detail from injection to extraction, as well as future injection into the new Relativistic Heavy Ion Collider (RHIC). A future plan to improve intensity of the accelerator will also be presented. 5 figs., 4 tabs.

  13. Metallothionein as a biomarker of environmental metal exposure: Species-dependent effects

    SciTech Connect

    Benson, W.H.; Watson, C.F. ); Baer, K.N. )


    Because of the paucity of data concerning the induction of MT following stress in teleosts, the present investigation focused on the influence of cadmium and environmental stressors (cold, hypoxia) on MT induction in bluegill sunfish, Lepomis macrochirus. Following cadmium exposure (10 ug/L, 48 hr), significant increases in the Cd content of the MT-like fraction in both teleost gill (85{plus minus} 11 nmol {times} 10{sup {minus}2}) and liver (38 {plus minus} 3 nmol {times} 10{sup {minus}2}) were observed as compared to control gill and liver. Exposure to environmental stressors, such as cold and hypoxia had profound effects on the Zn and Cu content of metal-binding proteins in the gill. Following cold and hypoxic stress, Zn content significantly decreased in all metal-binding fractions, except the LMW fraction after cold stress. Likewise, the Cu content significantly decreased in the HMW and MT-like protein fraction, but increased in the LMW fraction following treatment in cold and hypoxic stresses. In contrast, no significant alterations were observed in the hepatic MT-like protein fraction as a result of treatment with environmental stressors. These findings indicate that teleost liver MT-like protein is influenced to a greater degree by metal exposure than by environmental stressors, as compared to gill MT-like protein. Therefore, hepatic MT-like protein appears promising as a biomarker for metal exposure in teleost species.

  14. Materials erosion and redeposition studies at the PISCES-facility: net erosion under redeposition

    SciTech Connect

    Hirooka, Y.; Goebel, D.M.; Conn, R.W.; Leung, W.K.; Campbell, G.A.


    Simultaneous erosion and redeposition of copper and 304 stainless steel under controlled and continuous plasma (D,He,Ar) bombardment has been investigated in the PISCES-facility, which generates typical edge-plasma conditions of magnetic fusion devices. The plasma bombardment conditions are: incident ion flux in the range from 10/sup 17/ to 10/sup 18/ ions/sec/cm/sup 2/, ion bombarding energy of 100 eV, electron temperature in the range from 5 to 15 eV, plasma density in the range from 10/sup 11/ to 10/sup 13/ cm/sup -3/, target temperature in the range from 300 to 900K, and the total ion fluence in the range from 10/sup 20/ to 10/sup 22/ ions/cm/sup 2/. The net erosion yield under redeposition is found to be significantly smaller than the classical sputtering yield data. A first-order modeling is attempted to interpret the erosion and redeposition behavior of materials under plasma bombardment. It is pointed out both theoretically and experimentally that the mean free path for electron impact ionization of the sputtered material is the key parameter to control the overall mechanism of erosion and redeposition. Strongly modified surface morphologies of bombarded targets are observed and indicate a retrapping effect.

  15. Optical limiting effects in nanostructured silicon carbide thin films

    SciTech Connect

    Borshch, A A; Starkov, V N; Volkov, V I; Rudenko, V I; Boyarchuk, A Yu; Semenov, A V


    We present the results of experiments on the interaction of nanosecond laser radiation at 532 and 1064 nm with nanostructured silicon carbide thin films of different polytypes. We have found the effect of optical intensity limiting at both wavelengths. The intensity of optical limiting at λ = 532 nm (I{sub cl} ∼ 10{sup 6} W cm{sup -2}) is shown to be an order of magnitude less than that at λ = 1064 nm (I{sub cl} ∼ 10{sup 7} W cm{sup -2}). We discuss the nature of the nonlinearity, leading to the optical limiting effect. We have proposed a method for determining the amount of linear and two-photon absorption in material media. (nonlinear optical phenomena)

  16. Results From the DAFNE High Luminosity Test

    SciTech Connect

    Milardi, C.; Alesini, D.; Biagini, M.E.; Boni, R.; Boscolo, M.; Bossi, F.; Buonomo, B.; Clozza, A.; Delle Monache, G.; Demma, T.; Di Pasquale, E.; Di Pirro, G.; Drago, A.; Gallo, A.; Ghigo, A.; Guiducci, S.; Ligi, C.; Marcellini, F.; Mazzitelli, G.; Murtas, F.; Pellegrino, L.; /Frascati /Novosibirsk, IYF /CERN /INFN, Cosenza /INFN, Rome /KEK, Tsukuba /Orsay, LAL /Rome U. /Pisa U. /INFN, Pisa /INFN, Rome3 /SLAC


    The DAPHNE collider, based on a new collision scheme including Large Piwinsky angle and Crab-Waist, has been successfully commissioned and is presently delivering luminosity to the SIDDHARTA detector. Large crossing angle and Crab-Waist scheme proved to be effective in: (1) Increasing luminosity, now a factor 2.7 higher than in the past; and (2) controlling transverse beam blow-up due to the beam-beam. Work is in progress to reach the ultimate design luminosity goal 5.0 {center_dot} 10{sup 32} cm{sup -2}s{sup -1}. The new collision scheme is the main design concept for a new project aimed at building a Super-B factory that is expected to achieve a luminosity of the order of 10{sup 36} cm{sup -2} s{sup -1} and it has been also taken into account to upgrade one of the LHC interaction regions.

  17. Nonequilibrium atmospheric pressure plasma with ultrahigh electron density and high performance for glass surface cleaning

    SciTech Connect

    Iwasaki, Masahiro; Matsudaira, Yuto; Hori, Masaru; Inui, Hirotoshi; Kano, Hiroyuki; Yoshida, Naofumi; Ito, Masafumi


    We produced a nonequilibrium atmospheric pressure plasma by applying an alternative current between two electrodes. The gas temperature and electron density were evaluated using optical emission spectroscopy. It was found that the plasma had gas temperatures from 1800 to 2150 K and ultrahigh electron densities in the order of 10{sup 16} cm{sup -3}. A remarkably high oxygen radical concentration of 1.6x10{sup 15} cm{sup -3} was obtained at a 1% O{sub 2}/Ar gas flow rate of 15 slm (standard liters per minute). Contact angles below 10 deg. were obtained in the process of glass cleaning with a plasma exposure time of 23 ms.

  18. Blistering of implanted crystalline silicon by plasma hydrogenation investigated by Raman scattering spectroscopy

    SciTech Connect

    Duengen, W.; Job, R.; Mueller, T.; Ma, Y.; Fahrner, W. R.; Keller, L. O.; Horstmann, J. T.; Fiedler, H.


    Czochralski silicon wafers were implanted with H{sup +} ions at a dose of 1x10{sup 16} cm{sup -2} followed by hydrogen plasma treatments at different temperatures. The minimum hydrogen implantation dose required for silicon surface exfoliation of 3x10{sup 16} H{sup +}/cm{sup 2} without further hydrogen incorporation was reduced to one-third by subsequent plasma hydrogenation. The corresponding local vibrational modes of hydrogen molecules, vacancy-hydrogen complexes, and Si-H bonds on surfaces have been analyzed by micro-Raman scattering spectroscopy to investigate blistering and platelet formation. The surface profile has been studied by atomic force microscopy and scanning electron microscopy. The plasma treated samples were annealed to investigate the mechanism and applicability of the induced exfoliation. <111>-platelet formation occurred below plasma hydrogenation temperatures of 350 deg. C. At temperatures above 450 deg. C, <100>-platelet nucleation induced blistering.

  19. Ion Implanted Ge:B Far Infrard Blocked Impurity BandDetectors

    SciTech Connect

    Beeman, J.W.; Goyal, S.; Reichertz, L.A.; Haller, E.E.


    Ge Blocked Impurity Band (BIB) photoconductors have the potential to replace stressed Ge:Ga photoconductors for far-infrared astronomical observations. A novel planar BIB device has been fabricated in which ion-implanted boron is used to form the blocking and absorbing layers of necessary purity and compensation. The effect of doping in the infrared active layer on the far-infrared photoconductive response has been studied, and the optimum doping concentration is found to be {approx} 4 x 10{sup 16} cm{sup -3}. Devices doped near this concentration show good blocking characteristics with low dark currents. The spectral response extends to {approx} 45 cm{sup -1}, clearly showing the formation of an impurity band. Under low background testing conditions these devices attain a responsivity of 0.12 A/W and NEP of 5.23 x 10{sup -15} W/Hz{sup -1/2}.

  20. Modified Johnson model for ferroelectric lead lanthanum zirconate titanate at very high fields and below Curie temperature.

    SciTech Connect

    Narayanan, M.; Tong, S.; Ma, B.; Liu, S.; Balachandran, U.


    A modified Johnson model is proposed to describe the nonlinear field dependence of the dielectric constant ({var_epsilon}-E loop) in ferroelectric materials below the Curie temperature. This model describes the characteristic ferroelectric 'butterfly' shape observed in typical {var_epsilon}-E loops. The predicted nonlinear behavior agreed well with the measured values in both the low- and high-field regions for lead lanthanum zirconate titanate films. The proposed model was also validated at different temperatures below the ferroelectric-to-paraelectric Curie point. The anharmonic coefficient in the model decreased from 6.142 x 10{sup -19} cm{sup 2}/V{sup 2} to 2.039 x 10{sup -19} cm{sup 2}/V{sup 2} when the temperature increased from 25 C to 250 C.

  1. Nature of Defects Induced by Au Implantation in Hexagonal Silicon Carbide Single Crystals

    SciTech Connect

    Gentils, Aurelie; Barthe, Marie-France; Egger, Werner; Sperr, Peter


    Pulsed-slow-positron-beam-based positron lifetime spectroscopy was used to investigate the nature of vacancy defects induced by 20 MeV Au implantation in single crystals 6H-SiC. Preliminary analysis of the data shows that at lower fluence, below 10{sup 14} cm{sup -2}, a positron lifetime of 220 ps has been obtained: it could be associated with the divacancy V{sub Si}-V{sub C} in comparison with the literature. At higher fluence, above 10{sup 15} cm{sup -2}, a positron lifetime of 260-270 ps, increasing with the incident positron energy, has been observed after decomposition of the lifetime spectra. By comparison with lifetime calculations, open-volumes such as quadrivacancy (V{sub Si}-V{sub C}){sub 2} clusters could be associated with this value.

  2. Monte Carlo simulation of electron swarms in nitrogen in uniform E times B fields

    SciTech Connect

    Raju, G.R.G.; Dincer, M.S. )


    The motion of electrons in nitrogen in uniform {ital E} {times} {ital B} fields is simulated using the Monte Carlo technique for 240 {le}= {ital E/N} {le} 600 Td (1 Td = 1 {times} 10{sup {minus}17} V cm{sup 2}) and 0 {le} {ital B/N} {le} 0.45 {times} 10{sup {minus}17} T cm{sup 3}. The electron-molecule collision cross sections adopted are the same cross sections as those used previously for the numerical solution of the Boltzmann equation. The swarm parameters obtained from the Monte Carlo simulation are compared with the Boltzmann solution and with the experimental data available in the literature. In relation to {ital E} {times} {ital B} fields, it is concluded that the Monte Carlo approach provides an independent method of substantiating the validity of the equivalent electric field approach.

  3. Continuous wave cavity ring-down spectroscopy for velocity distribution measurements in plasma

    SciTech Connect

    McCarren, D.; Scime, E.


    We report the development of a continuous wave cavity ring-down spectroscopic (CW-CRDS) diagnostic for real-time, in situ measurement of velocity distribution functions of ions and neutral atoms in plasma. This apparatus is less complex than conventional CW-CRDS systems. We provide a detailed description of the CW-CRDS apparatus as well as measurements of argon ions and neutrals in a high-density (10{sup 9} cm{sup −3} < plasma density <10{sup 13} cm{sup −3}) plasma. The CW-CRDS measurements are validated through comparison with laser induced fluorescence measurements of the same absorbing states of the ions and neutrals.

  4. Transport and recombination channels in undoped microcrystalline silicon studied by ESR and EDMR

    SciTech Connect

    Will, D.; Lerner, C.; Fuhs, W.; Lips, K.


    The authors present a detailed study of ESR and spin-dependent transport (EDMR) on {micro}c-Si. They identify to different types of defects at g = 2.0055({+-}3) and g = 2.0044({+-}5) and study their influence on transport and recombination by stepwise annealing the samples. They find that transport is not controlled by defects if N{sub D} < 10{sup 18} cm{sup {minus}3}. For N{sub D} > 10{sup 18} cm{sup {minus}3} a dramatic decrease of the conductivity is found and they identify a hopping contribution in transport. To explain their ESR and EDMR results they propose a simple model where most defects are distributed at the surface of the columns and transport is along percolation paths. They also observe minor metastable changes of the defect density which are assigned to adsorption of atmospheric oxygen.

  5. Helium-ion-induced release of hydrogen from graphite

    SciTech Connect

    Langley, R.A.


    The ion-induced release of hydrogen from AXF-5Q graphite was studied for 350-eV helium ions. The hydrogen was implanted into the graphite with a low energy (approx.200 eV) and to a high fluence. This achieved a thin (approx.10-nm), saturated near-surface region. The release of hydrogen was measured as a function of helium fluence. A model that includes ion-induced detrapping, retrapping, and surface recombination was used to analyze the experimental data. A value of (1.65 +- 0.2) x 10/sup -16/ cm/sup 2/ was obtained from the detrapping cross section, and a value of (0.5 to 4) x 10/sup -14/ cm/sup 4//atoms was obtained for the recombination coefficient. 11 refs., 4 figs.

  6. Response function stability of single crystal diamond detectors to 14 MeV neutrons

    SciTech Connect

    Zbořil, Miroslav Zimbal, Andreas


    Detectors based on single crystal synthetic diamond show promise as neutron spectrometers for the ITER project. In this work, the stability of the response function of two diamond detectors was tested at the Physikalisch-Technische Bundesanstalt (PTB) accelerator using a 14 MeV neutron field and a method of time-resolved fluence monitoring. In addition, measurements at the PTB ion-microbeam were made to investigate the charge collection properties of the detectors in more detail. The {sup 12}C(n,α){sup 9}Be peak response of one of the detectors was found to be stable within 1% after irradiation with a neutron fluence of 8 × 10{sup 9} cm{sup −2}. The absolute value of the peak response of this detector was determined as 8.65(26) × 10{sup −5} cm{sup 2}.

  7. Surface transfer doping of diamond by MoO{sub 3}: A combined spectroscopic and Hall measurement study

    SciTech Connect

    Russell, Stephen A. O. Crawford, Kevin G.; Moran, David A. J.; Cao, Liang; Qi, Dongchen; Tallaire, Alexandre; Wee, Andrew T. S.


    Surface transfer doping of diamond has been demonstrated using MoO{sub 3} as a surface electron acceptor material. Synchrotron-based high resolution photoemission spectroscopy reveals that electrons are transferred from the diamond surface to MoO{sub 3}, leading to the formation of a sub-surface quasi 2-dimensional hole gas within the diamond. Ex-situ electrical characterization demonstrated an increase in hole carrier concentration from 1.00 × 10{sup 13}/cm{sup 2} for the air-exposed hydrogen-terminated diamond surface to 2.16 × 10{sup 13}/cm{sup 2} following MoO{sub 3} deposition. This demonstrates the potential to improve the stability and performance of hydrogen-terminated diamond electronic devices through the incorporation of high electron affinity transition metal oxides.

  8. Observation of relativistic effects in collective Thomson scattering

    SciTech Connect

    Ross, J S; Glenzer, S H; Palastro, J P; Pollock, B B; Price, D; Divol, L; Tynan, G R; Froula, D H


    We observe relativistic modifications to the Thomson scattering spectrum in a traditionally classical regime: v{sub osc}/c = eE{sub 0}/cm{omega}{sub 0} << 1 and T{sub e} < 1 keV. The modifications result from scattering off electron-plasma fluctuations with relativistic phase velocities. Normalized phase velocities v/c between 0.03 and 0.12 have been achieved in a N{sub 2} gas-jet plasma by varying the plasma density from 3 x 10{sup 18} cm{sup -3} to 7 x 10{sup 19} cm{sup -3} and electron temperature between 85 eV and 700 eV. For these conditions, the complete temporally resolved Thomson scattering spectrum including the electron and ion features has been measured. A fully relativistic treatment of the Thomson scattering form factor has been developed and shows excellent agreement with the experimental data.

  9. 7Be Solar Neutrino Measurement with KamLAND

    SciTech Connect

    The KamLAND Collaboration; Gando, A.; Gando, Y.; Hanakago, H.; Ikeda, H.; Inoue, K.; Ishidoshiro, K.; Ishikawa, H.; Kishimoto, Y.; Koga, M.; Matsuda, R.; Matsuda, S.; Mitsui, T.; Motoki, D.; Nakajima, K.; Nakamura, K.; Obata, A.; Oki, A.; Oki, Y.; Otani, M.; Shimizu, I.; Shirai, J.; Suzuki, A.; Tamae, K.; Ueshima, K.; Watanabe, H.; Xu, B. D.; Yamada, S.; Yamauchi, Y.; Yoshida, H.; Kozlov, A.; Takemoto, Y.; Yoshida, S.; Grant, C.; Keefer, G.; McKee, D. W.; Piepke, A.; Banks, T. I.; Bloxham, T.; Freedman, S. J.; Fujikawa, B. K.; Han, K.; Hsu, L.; Ichimura, K.; Murayama, H.; O'Donnell, T.; Steiner, H. M.; Winslow, L. A.; Dwyer, D.; Mauger, C.; McKeown, R. D.; Zhang, C.; Berger, B. E.; Lane, C. E.; Maricic, J.; Miletic, T.; Learned, J. G.; Sakai, M.; Horton-Smith, G. A.; Tang, A.; Downum, K. E.; Tolich, K.; Efremenko, Y.; Kamyshkov, Y.; Perevozchikov, O.; Karwowski, H. J.; Markoff, D. M.; Tornow, W.; Detwiler, J. A.; Enomoto, S.; Heeger, K.; Decowski, M. P.


    We report a measurement of the neutrino-electron elastic scattering rate of 862 keV {sup 7}Be solar neutrinos based on a 165.4 kton-day exposure of KamLAND. The observed rate is 582{+-}90 (kton day){sup -1}, which corresponds to a 862 keV {sup 7}Be solar neutrino flux of (3.26{+-}0.50) x 10{sup 9} cm{sup -2}s{sup -1}, assuming a pure electron flavor flux. Comparing this flux with the standard solar model prediction and further assuming three flavor mixing, a e survival probability of 0.66{+-}0.14 is determined from the KamLAND data. Utilizing a global three flavor oscillation analysis, we obtain a total {sup 7}Be solar neutrino flux of (5.82{+-}0.98) x 10{sup 9} cm{sup -2}s{sup -1}, which is consistent with the standard solar model predictions.

  10. Characterization of ι-carrageenan and its derivative based green polymer electrolytes

    SciTech Connect

    Jumaah, Fatihah Najirah; Mobaraka, Nadhratun Naiim; Ahmad, Azizan; Ramli, Nazaruddin


    The new types of green polymer electrolytes based on ι-carrageenan derivative have been prepared. ι-carrageenan act as precursor was reacted with monochloroacetic acid to produce carboxymethyl ι-carrageenan. The powders were characterized by Attenuated Total Reflection Fourier Transform infrared (ATR-FTIR) spectroscopy and {sup 1}H nuclear magnetic resonance (NMR) to confirm the substitution of targeted functional group in ι-carrageenan. The green polymer electrolyte based on ι-carrageenan and carboxymethyl ι-carrageenan was prepared by solution-casting technique. The films were characterized by electrochemical impedance spectroscopy to determine the ionic conductivity. The ionic conductivity ι-carrageenan film were higher than carboxymethyl ι-carrageenan which 4.87 ×10{sup −6} S cm{sup −1} and 2.19 ×10{sup −8} S cm{sup −1}, respectively.

  11. Carrier mediated reduction of stiffness in nanoindented crystalline Si(100)

    SciTech Connect

    Kataria, S. Dhara, Sandip Dash, S.; Tyagi, A. K.


    We report the observation of carrier mediated decrease in the stiffness of crystalline (c)-Si(100) under nanoindentation. The apparent elastic moduli of heavily doped (∼1 × 10{sup 21} cm{sup −3}) p- and n-type c-Si are observed to be lower by 5.3%–7.5% than the estimated value for intrinsic (∼1 × 10{sup 14} cm{sup −3}) c-Si. The deviation observed with respect to elastic modulus remarkably matches with the estimated value while considering the electronic elastic strain effect on carrier concentration as an influence of negative pressure coefficient of band gap for Si (Γ-X). The value is predominantly higher than the reported value of a decrease of 1%–3% in stiffness as an effect of impurity in c-Si.

  12. Plasma resonances in a microwave-driven microdischarge

    SciTech Connect

    Xue, J.; Urdahl, R. S.; Cooley, J. E.


    This work investigates resonances in a capacitively coupled, low pressure krypton microdischarge operated at 2.5 GHz. A circuit model for the device, which has a length dimension of approximately 1 mm, calculates impedance values for a range of electron densities. The model results predict several 'parallel' and 'series' resonances at the driving frequency when the electron density is approximately 8 x 10{sup 11} cm{sup -3} and 5 x 10{sup 12} cm{sup -3}. The series resonance occurs when the resistance approaches the output impedance of the radio-frequency signal source, minimizing the reflected power. These resonances explain an experimentally observed jump in intensity with increasing input power.

  13. Deep level transient spectroscopy in plasma-assisted molecular beam epitaxy grown Al{sub 0.2}Ga{sub 0.8}N/GaN interface and the rapid thermal annealing effect

    SciTech Connect

    Park, Young S.; Lee, Minyoung; Jeon, Kiyoung; Im, Hyunsik; Yoon, Im T.; Shon, Yoon; Park, C. J.; Cho, Hoon Y.; Han, Myung-Soo


    We investigated deep-level traps formed in Al{sub 0.2}Ga{sub 0.8}N/GaN heterostructures grown using plasma-assisted molecular beam epitaxy and by performing deep level transient spectroscopy (DLTS). Two electron traps with activation energies of E{sub c}-150 meV and E{sub c}-250 meV were observed, and their capture cross-sections ({sigma}{sub T}) were estimated to be 2.0x10{sup -18} cm{sup 2} and 1.1x10{sup -17} cm{sup 2}, respectively. Different behaviors in the dependence of DLTS on filling pulse length confirm that the traps originated from N vacancies and dislocations. The amplitude of the dislocation-induced DLTS signal was reduced significantly by high-temperature rapid thermal annealing under N{sub 2} ambient after hydrogen treatment due to the reduction in dislocation density.

  14. The development of the Next Linear Collider at SLAC

    SciTech Connect

    Ruth, R.D.


    At SLAC, we are pursuing the design of a Next Linear Collider (NLC) which would begin with a center-of-mass energy of 0.5 TeV and be upgradable to at least 1.0 TeV, and possibly 1.5 TeV. The luminosity is designed to be 10{sup 33} cm{sup {minus}2}s{sup {minus}1} at the lower energy and 10{sup 34} cm{sup {minus}2}s{sup {minus}1} at the top energy. In this paper, we discuss the accelerator physics issues which are important in our approach, and also the present state of the technology development. We also review the impact that the SLC has had in the evolution of our basic approach.

  15. Saturation of the Two-Plasmon Decay Instability in Long-Scale-Length Plasmas Relevant to Direct-Drive Inertial Confinement Fusion

    SciTech Connect

    Froula, D. H.; Yaakobi, B.; Hu, S. X.; Chang, P-Y.; Craxton, R. S.; Edgell, D. H.; Follett, R.; Michel, D. T.; Myatt, J. F.; Seka, W.; Short, R. W.; Solodov, A.; Stoeckl, C.


    Measurements of the hot-electron generation by the two-plasmon-decay instability are made in plasmas relevant to direct-drive inertial confinement fusion. Density-scale lengths of 400 {micro}m at n{sub cr}/4 in planar CH targets allowed the two-plasmon-decay instability to be driven to saturation for vacuum intensities above ~3.5 x 10{sup 14} W cm{sup -2}. In the saturated regime, ~1% of the laser energy is converted to hot electrons. The hot-electron temperature is measured to increase rapidly from 25 to 90 keV as the laser beam intensity is increased from 2 to 7 x 10{sup 14} W cm{sup -2}. This increase in the hot-electron temperature is compared with predictions from nonlinear Zakharov models.

  16. Recovery of the chemical ordering in L1{sub 0} MnAl epitaxial thin films irradiated by 2 MeV protons

    SciTech Connect

    Anuniwat, Nattawut; Cui, Yishen; Wolf, Stuart A.; Lu, Jiwei; Weaver, Bradley D.


    Epitaxial MnAl films with a high chemical ordering were synthesized and characterized during a series of irradiations by 2 MeV protons (H{sup +}). The chemical ordering was first reduced to a minimum at a total fluence (TF) of 1 Multiplication-Sign 10{sup 15} H{sup +}/cm{sup 2}, and consequently was recovered at the final total fluence of 2 Multiplication-Sign 10{sup 15} H{sup +}/cm{sup 2}. We attributed the recovery of chemical ordering to thermal effects and the enhanced diffusion caused by the high energy protons. In addition, the damages by the protons have little effect on the magnetic scattering processing in MnAl characterized by the anomalous Hall effect.

  17. Supercontinuum generation in thulium-doped fibres

    SciTech Connect

    Kurkov, Andrei S; Kamynin, V A; Tsvetkov, V B; Sadovnikova, Ya E; Marakulin, A V; Minashina, L A


    Supercontinuum generation in thulium-doped fibres under pumping at 1.59 {mu}m is investigated. Amplification of supercontinuum in the range of 1.8--2.0 {mu}m is found for a fibre doped to a level of 2 Multiplication-Sign 10{sup 19} cm{sup -3}. For a fibre with an activator concentration of 2 Multiplication-Sign 10{sup 20} cm{sup -3} amplification is also observed in the (2.1 - 2.45)-{mu}m band, which suggests the occurrence of the {sup 3}H{sub 4} {yields} {sup 3}H{sub 5} optical transition in the fibre. The occupation of the {sup 3}H{sub 4} level can be explained by cooperative effects. (optical fibres, lasers and amplifiers. properties and applications)

  18. Interaction Region Upgrades of e+ e- B-Factories

    SciTech Connect

    Sullivan, M.; /SLAC


    Both the PEP-II and KEKB B-Factories have plans to upgrade their Interaction Regions (IRs) in order to improve luminosity performance. Last summer PEP-II added cooling to the IR beam pipe in order to increase beam currents thereby raising the luminosity. In addition, PEP-II is working on a design that modifies the permanent magnets near the Interaction Point (IP) for an even higher luminosity increase. KEKB is also planning an improvement to their IR that will decrease the detector beam pipe radius. In addition, KEK has a design to increase the luminosity of KEKB to 1 x 10{sup 35} cm{sup -2} sec{sup -1} which includes changes to the IR. PEP-II is also investigating the feasibility of a 1 x 10{sup 36} cm{sup -2} sec{sup -1} luminosity design. I summarize these various upgrades and concentrate on issues common to the different designs.

  19. 132 ns Bunch Spacing in the Tevatron Proton-Antiproton Collider

    SciTech Connect

    Holmes, S.D.; Holt, J.; Johnstone, J.A.; Marriner, J.; Martens, M.; McGinnis, D.


    Following completion of the Fermilab Main Injector it is expected that the Tevatron proton-antiproton collider will be operating at a luminosity in excess of 5{times}10{sup 3l} cm{sup {minus}2} with 36 proton and antiproton bunches spaced at 396 nsec. At this luminosity, each of the experimental detectors will see approximately 1.3 interactions per crossing. Potential improvements to the collider low beta and rf systems could push the luminosity beyond 10{times}10{sup 3l} cm{sup {minus}2}sec{sup {minus}1}, resulting in more than three interactions per crossing if the bunch separation is left unchanged. This paper discusses issues related to moving to {approx}100 bunch operation, with bunch spacings of 132 nsec, in the Tevatron. Specific scenarios and associated hardware requirements are described.

  20. Scientific opportunities with advanced facilities for neutron scattering

    SciTech Connect

    Lander, G.H.; Emery, V.J.


    The present report documents deliberations of a large group of experts in neutron scattering and fundamental physics on the need for new neutron sources of greater intensity and more sophisticated instrumentation than those currently available. An additional aspect of the Workshop was a comparison between steady-state (reactor) and pulsed (spallation) sources. The main conclusions were: (1) the case for a new higher flux neutron source is extremely strong and such a facility will lead to qualitatively new advances in condensed matter science and fundamental physics; (2) to a large extent the future needs of the scientific community could be met with either a 5 x 10/sup 15/ n cm/sup -2/s/sup -1/ steady state source or a 10/sup 17/ n cm/sup -2/s/sup -1/ peak flux spallation source; and (3) the findings of this Workshop are consistent with the recommendations of the Major Materials Facilities Committee.

  1. Enhanced hard x-ray emission from microdroplet preplasma

    SciTech Connect

    Anand, M.; Kahaly, S.; Ravindra Kumar, G.; Krishnamurthy, M.; Sandhu, A.S.; Gibbon, P.


    We perform a comparative study of hard x-ray emission from femtosecond laser plasmas in 15 {mu}m methanol microdroplets and Perspex target. The hard x-ray yield from droplet plasmas is {approx_equal}68 times more than that obtained from solid plasmas at 2x10{sup 15} W cm{sup -2}. A 10 ns prepulse at about 5% of the main pulse appears to be essential for hard x-ray generation from droplets. Hot electron temperature of 36 keV is measured from the droplets at 8x10{sup 14} W cm{sup -2}, whereas a three times higher intensity is needed to obtain similar hot electron temperatures from Perspex plasmas. Particle-in-cell simulations with very long scale-length density profiles support experimental observations.

  2. Determination of the global recombination rate coefficient for the ISX-B Tokamak

    SciTech Connect

    Langley, R.A.; Howe, H.C.


    The global recombination rate coefficient for hydrogen has been measured for the ISX-B tokamak vacuum vessel for various surface conditions. The measurements were performed by observing the rate of decrease of gas pressure in the vessel during a glow discharge. The parameters of the glow discharge and the complete experimental method are described. Previously published analytic and numerical models are used for data analysis. The effects of surface contamination on the results are described. For ''unclean'' wall conditions sigmak/sub r/ = 1.8 x 10/sup -28/ cm/sup 4//atom.s at 296 K and increases to sigmak/sub r/ = 4.4 x 10/sup -28/ cm/sup 4//atoms.s for ''clean'' conditions and remains constant until subsequent exposure to air.

  3. Computer simulation of plasma behavior in open-ended linear theta machines. Scientific report 81-5

    SciTech Connect

    Stover, E. K.


    Zero-dimensional and one-dimensional fluid plasma computer models have been developed to study the behavior of linear theta pinch plasmas. Computer simulation results generated from these codes are compared with data obtained from two theta pinch experiments so that significant machine plasma behavior can be identified. The experiments examined are a collisional experiment, T/sub i/ approx. 50 eV, n/sub e/ approx. 10/sup 17/ cm/sup -3/, where the plasma mean-free-path was significantly less than the plasma column length, and a hot ion species experiment, T/sub i/ approx. 3 keV, n/sub e/ approx. 10/sup 16/ cm/sup -3/, where the ion mean-free-path was on the order of the plasma column length.

  4. Ionically conductive thin polymer films prepared by plasma polymerization; Preparation and characterization of ultrathin films having fixed sulfonic acid groups with only one mobile species

    SciTech Connect

    Ogumi, Z.; Uchimoto, Y.; Takehara, Z. ); Foulkes, F.R. . Dept. of Chemical Engineering and Applied Chemistry)


    Ultrathin solid polymer electrolyte membranes containing sulfonic ester groups were prepared by polymerization of methyl benzenesulfonate and octamethylcyclotetrasiloxane in a glow discharge plasma. The sulfonic ester groups of the plasma polymer were transformed to lithium sulfonate groups by treatment with lithium iodide. Hybridization of this plasma polymer containing the lithium sulfonate groups with poly(ethylene oxide) (average Mw 300) resulted in the formation of a single lithium ion conductive film. The hybrid polymer electrolyte films were about 1 {mu}m thick, pinhole-free, adherent to various substrates, and showed ionic conductivities at 60{degrees}C of the order of 10{sup {minus} 6} S cm{sup {minus} 1} (10{sup 2} {Omega} cm{sup 2} resistance per unit area of as-prepared solid polymer electrolyte). This material shows promise for electrochemical applications such as all solid-state lithium batteries, sensors, and electrochemical display devices.

  5. Radiative power and electron cooling rates for oxygen in steady-state and transient plasmas at densities beyond the coronal limit

    SciTech Connect

    Keane, C.; Skinner, C.H.


    We have developed a time-dependent, collisional-radiative model to calculate radiative power and electron cooling rates for oxygen at intermediate densities (10/sup 16/ cm/sup -3/ less than or equal to n/sub e/ less than or equal to 10/sup 20/ cm/sup -3/) where the usual coronal approximation is not valid. Large differences from coronal values are predicted. The behavior of the steady-state radiative power loss coefficient, L/sub Z, is investigated as the electron density is increased. Generalized power loss coefficients applicable to transient plasmas are derived and applied to ionizing and recombining oxygen plasmas. Time-dependent effects are found to play a large role both in terms of the total radiated power and the net electron energy loss rate. 41 refs., 11 figs.

  6. The growth of n-type GaSb by metal-organic chemical vapor deposition : effects of two-band conduction on carrier concentrations and donor activation.

    SciTech Connect

    Cederberg, Jeffrey George; Biefeld, Robert Malcolm


    n-type GaSb has been prepared by metal-organic chemical vapour deposition with tellurium donors using diethyltelluride as the dopant precursor. The maximum carrier concentration achieved was 1.7 x 10{sup 18} cm{sup -3}, as measured by van der Pauw-Hall effect measurements, for an atomic tellurium concentration of 1.8 x 10{sup 19} cm{sup -3}. The apparent low activation of tellurium donors is explained by a model that considers the effect of electrons occupying both the {Lambda} and L bands in GaSb due to the small energy difference between the {Lambda} and L conduction band minima. The model also accounts for the apparent increase in the carrier concentration determined by van der Pauw-Hall effect measurements at cryogenic temperatures.

  7. Characterization of Si volume- and delta-doped InGaAs grown by molecular beam epitaxy

    SciTech Connect

    Fedoryshyn, Y.; Kaspar, P.; Jaeckel, H.; Beck, M.


    Bulk InGaAs layers were grown at 400 deg. C lattice-matched to InP semi-insulating substrates by molecular beam epitaxy. Si doping of the layers was performed by applying volume- and delta-doping techniques. The samples were characterized by capacitance-voltage, van der Pauw-Hall, secondary ion mass spectroscopy and photoluminescence measurements. Good agreement in terms of dependence of mobility and Burstein-Moss shift shift on doping concentration in samples doped by the two different techniques was obtained. Amphoteric behavior of Si was observed at doping concentrations higher than {approx}2.9x10{sup 19} cm{sup -3} in both delta- and volume-doped samples. Degradation of InGaAs crystalline quality occurred in samples with Si concentrations higher than {approx}4x10{sup 19} cm{sup -3}.

  8. Quantum dot Ge/TiO{sub 2} heterojunction photoconductor fabrication and performance

    SciTech Connect

    Church, Carena P.; Carter, Sue A.; Muthuswamy, Elayaraja; Kauzlarich, Susan M.; Zhai, Guangmei


    Spun cast TiO{sub 2}-Ge quantum dot (QD) heterojunction type photodetectors have been fabricated and characterized, with interest paid to photocurrent enhancements related to device design. Performance as a function of absorber layer thickness, QD size, and back contact is investigated. We have achieved ultra-thin (∼200 nm) devices with photocurrents at 0.5 V of 10{sup −4} A cm{sup −2} while the thickest devices have photocurrents at 0.5 V of 10{sup −2} A cm{sup −2} with on-off ratios >100, which represents 5 orders of magnitude increase in photocurrents over previously fabricated Ge QD devices. At 0.5 V bias, the currents in our devices are competitive with thin-film Ge photovoltaics.

  9. Bidirectional propagation of cold atoms in a 'stadium'-shaped magnetic guide

    SciTech Connect

    Wu Saijun; Rooijakkers, Wilbert; Striehl, Pierre; Prentiss, Mara


    We demonstrate the bidirectional propagation of more than 10{sup 7} atoms ({sup 87}Rb) around a 'stadium'-shaped magnetic ring that encloses an area of 10.9 cm{sup 2}, with a flux density exceeding 10{sup 11} atom s{sup -1} cm{sup -2}. Atoms are loaded into the guide from a two-dimensional (and higher) magneto-optical trap at one side of the 'stadium'. An optical standing wave pulse is applied to increase the propagation velocity of atoms along the waveguide. The atom sample fills the entire ring in 200 ms when counterpropagating atom sections of the original atom cloud recombine at their initial positions after a full revolution.

  10. Carbon implantation in Al(sub x)Ga{sub 1{minus}x}As

    SciTech Connect

    Pearton, S.J.; Abernathy, C.R.


    Maximum hole densities of 4 {times} 10{sup 18} cm{sup {minus}3} were produced in Al{sub 0.3}Ga{sub 0.7}As by C + Ga implantation and subsequent annealing at {approximately} 800 C. The activation efficiency decreases with increasing AlAs mole fraction and the use of higher temperatures for the Ga co-implantation due to a reduced vacancy concentration under these conditions. The C diffusivity is {ge} 2 {times} 10{sup {minus}13} cm{sup 2}sec{sup {minus}1} at 950 C in implanted Al{sub 0.3}Ga{sub 0.7}As, demonstrating that C is a much more thermally stable acceptor than Be, Mg, or Zn.

  11. Performance and reproducibility enhancement of HgCdTe molecular beam epitaxy growth on CdZnTe substrates using interfacial HgTe/CdTe superlattice layers

    SciTech Connect

    Chang Yong; Zhao Jun; Abad, Hisham; Grein, Christoph H.; Sivananthan, Sivalingam; Aoki, Toshihiro; Smith, David J.


    Interfacial layers including HgTe/CdTe superlattices (SLs) were introduced during the molecular-beam epitaxy growth of HgCdTe on CdZnTe (211)B substrates. Transmission-electron-microscopic observations show that the SLs smooth out the substrates' surface roughness during growth, and can also bend or block threading dislocations in a way that prevents their propagation from the substrate into the functional HgCdTe epilayers. An average etch pit density value in the low-10{sup 5} cm{sup -2} range was reproducibly achieved in long wavelength HgCdTe samples, with the best value being 4x10{sup 4} cm{sup -2}. Photoconductive decay lifetime measurements give values approaching theoretical limits, as determined by the intrinsic radiative and Auger recombination mechanisms. The use of such interfacial layers thus leads to enhanced growth yields and material properties.

  12. Ordering and disordering of doped Ga[sub 0. 5]In[sub 0. 5]P

    SciTech Connect

    Kurtz, S.R.; Olson, J.M.; Friedman, D.J.; Kibbler, A.E.; Asher, S. )


    The band gap of Ga[sub 0.5]In[sub 0.5]P is reported as a function of doping level and growth rate. The lowest band gaps are obtained for hole concentrations of about 2 x 10[sup 17] cm[sup [minus]3]. For samples doped p-type above 1 x 10[sup 18] cm[sup [minus]3], the band gap increases dramatically, regardless of growth rate. This effect is shown to be the result of disordering during growth rather than a change in the equilibrium surface structure with doping. The doping level dependence of the band gap of Ga[sub 0.5]In[sub 0.5]P samples grown at higher and lower growth rates differs for selenium and zinc doping even though the effects of high doping are the same for both dopants. 22 refs., 3 figs.

  13. The problem of uniformity of properties of 4H-SiC CVD films

    SciTech Connect

    Ivanov, A. M. Strokan, N. B.; Scherbov, N. A.; Lebedev, A. A.


    Nonuniformities of electrical properties of 4H-SiC CVD films have been revealed using physicochemical reactions occurring upon introduction of radiation-induced structural defects. Primary knocked-on atoms and vacancies actively interact with impurities and defects of the starting material and thereby form the final system of radiation centers. The samples were irradiated with 900-keV electrons and 8-MeV protons at doses not leading to conductivity compensation (<7.5 x 10{sup 12} cm{sup -2}) and a dose of 6 x 10{sup 14} cm{sup -2} causing deep compensation. Despite their area-averaging nature, capacitance methods demonstrated that characteristics of samples {approx}3 mm in size are not identical. The nuclear spectrometry technique, which enables microprobing of samples, demonstrated individual behavior of separate parts of a film with areas of tens of square micrometers.

  14. Spectrometry of the Rutherford backscattering of ions and the Raman scattering of light in GaS single crystals irradiated with 140-keV H{sub 2}{sup +} ions

    SciTech Connect

    Garibov, A. A.; Madatov, R. S.; Komarov, F. F.; Pilko, V. V.; Mustafayev, Yu. M.; Akhmedov, F. I.; Jakhangirov, M. M.


    The methods of the Raman scattering of light and Rutherford backscattering are used to study the degree of structural disorder in layered GaS crystals before and after irradiation with 140-keV H{sub 2}{sup +} ions. It is shown that the distribution of the crystal’s components over depth is homogeneous; for doses as high as 5 × 10{sup 15} cm{sup −2}, the stoichiometric composition of the compound’s components is retained. The experimental value of the critical dose for the beginning of amorphization amounts to about 5 × 10{sup 15} cm{sup −2} and is in accordance with the calculated value. The results obtained by the method of the Raman scattering of light confirm conservation of crystalline structure and the start of the amorphization process.

  15. Inelastic cross sections for positron scattering from atomic hydrogen

    SciTech Connect

    Weber, M.; Hofmann, A.; Raith, W.; Sperber, W.; Jacobsen, F.; Lynn, K.G.


    Positronium formation (Ps) cross sections for positrons impinging on atomic hydrogen were measured in the impact energy range from 13eV to 255eV at the High Intensity Positron (HIP) beam at Brookhaven National Laboratory (BNL). The Ps-formation cross section was found to rise rapidly from the threshold at 6.8eV to a maximum value of (2.98 {plus_minus} 0.18) {times} 10{sup {minus}16} cm{sup 2} for {approx} 15eV positrons. By 75eV it drops below the detection limit of 0.17 {times} 10{sup {minus}16} cm{sup 2} which is the present level of statistical uncertainty. The experiment was modified to enable the measurement of doubly differential scattering cross sections.

  16. Characteristics of the three-half-turn-antenna-driven RF discharge in the Uragan-3M torsatron

    SciTech Connect

    Grigor’eva, L. I.; Chechkin, V. V. Moiseenko, V. E.; Grekov, D. L.; Pavlichenko, R. O.; Lozin, A. V.; Tarasov, I. K.; Kulaga, A. Ye.; Zamanov, N. V.; Tretiak, K. K.; Kozulya, M. M.; Beletskii, A. A.; Kasilov, A. A.; Mironov, Yu. K.; Romanov, V. S.; Voitsenya, V. S.


    In the ℓ = 3 Uragan-3M torsatron hydrogen plasma is produced by RF fields in the Alfvén range of frequencies (ω ≤ ω{sub ci}). The initial (target) plasma with the line-averaged density of units 10{sup 12} cm{sup −3} is produced by a frame antenna with a broad spectrum of generated parallel wavenumbers. After this, to heat the plasma and bring its density to ∼10{sup 13} cm{sup –3}, another, shorter wavelength three-half-turn antenna with large transverse currents is used. The behavior of the density, electron temperature, and loss of the plasma supported by the three-half-turn antenna is studied depending on the RF power fed to the antenna and initial values of the density and electron temperature supplied by the frame antenna.

  17. Photodetectors on the basis of Ge/Si(001) heterostructures grown by the hot-wire CVD technique

    SciTech Connect

    Shengurov, V. G. Chalkov, V. Yu.; Denisov, S. A.; Alyabina, N. A.; Guseinov, D. V.; Trushin, V. N.; Gorshkov, A. P.; Volkova, N. S.; Ivanova, M. M.; Kruglov, A. V.; Filatov, D. O.


    The fabrication of photodetectors for the wavelength range of communications λ = 1.3–1.55 µm on the basis of Ge/Si(001) heterostructures with thick (∼0.5 µm) Ge layers grown by the hot-wire technique at reduced growth temperatures (350°C) is reported. The single-crystal Ga layers are distinguished by a low density of threading dislocations (∼10{sup 5} cm{sup –2}). The photodetectors exhibit a rather high quantum efficiency (∼0.05 at λ = 1.5 µm and 300 K) at moderate reverse saturation current densities (∼10{sup –2} A cm{sup –2}). Thus, it is shown that the hot-wire technique offers promise for the formation of integrated photodetectors for the wavelength range of communications, especially in the case of limitations on the conditions of heat treatments.

  18. Formation of ZnTe:Cu/Ti Contacts at High Temperature for CdS/CdTe Devices (Presentation)

    SciTech Connect

    Gessert, T. A.; Asher, S.; Johnston, S.; Duda, A.; Young, M. R.; Moriarty, T.


    The conclusions of this report are that Cu diffusion from a ZnTe:Cu contact causes good and bad things. The good (Cu in CdS < low 10{sup 18} cm{sup -3})--increase in CdTe N{sub A}-N{sub D} that leads to V{sub oc} and FF improvement. The bad (Cu in CdS > low 10{sup 18} cm{sup -3})--(1) possibly decreased of shunt resistance (?); (2) depletion width in CdTe can become too narrow for optimum current collection at J{sub MPP}; (3) donor reduction in CdS (significant FF loss in LIV); and (4) excessive Cu diffusion into CdS readily observed by red-light bias QE.

  19. Concentration quenching of rhodamine 6G fluorescence in the adsorbed state

    SciTech Connect

    Zemskii, V.I.; Meshkovskii, I.K.; Sokolov, I.A.


    Porous glass to which molecules of organic dyes have been added is a promising active solid medium for tunable lasers. The spectroluminescent characteristics of samples of porous glass activated with rhodamine 6G molecules have been studied. It is shown that molecules of rhodamine 6G adsorbed in porus glass retain their capacity for fluorescence with a high quantum yield. Fixation of rhodamine 6G molecules on the pore walls interferes with their association in the concentration range up to 10/sup 19/ cm/sup -3/. Concentration quenching of fluorescence is observed starting with a concentration of dye molecules of 5 x 10/sup 15/ cm/sup -3/; this is explained by inductive-resonance energy transfer between monomeric molecules under conditions of inhomogeneous broadening of the electronic spectra of the adsorbed molecules.

  20. Interaction of divalent plutonium and curium

    SciTech Connect

    Mikheev, N.B.; Kazakevich, M.Z.; Rumer, I.A.


    It has been established that at plutonium concentrations ranging from 10/sup -5/ to 10/sup -4/ mole % the oxidation potentials of the Pu/sup 3 +//Pu/sup 2 +/ and Cm/sup 3 +//Cm/sup 2 +/ pairs increased by 0.15-0.2 V due to the dimerization of Pu/sup 2 +/ and the formation of mixed dimers of plutonium and curium. Promethium(2+) does not have a similar ability to form mixed dimers owing to the fact that Pm/sup 2 +/ does not have a free d electron. The oxidation potential of the Pm/sup 3 +//Pm/sup 2 +/ pair does not vary in the presence of massive quantities of plutonium

  1. Low-cost, high-efficiency solar cells utilizing GaAs-on-Si technology. Annual subcontract report, 1 August 1991--31 July 1992

    SciTech Connect

    Vernon, S.M.


    This report describes work to develop technology to deposit GaAs on Si using a nucleation layer of atomic-layer-epitaxy-grown GaAs or AlAs on Si. This ensures two-dimensional nucleation and should lead to fewer defects in the final GaAs layer. As an alternative, we also developed technology for depositing GaAs on sawtooth-patterned Si. Preliminary studies showed that this material can have a very low defect density, {approximately} 1 {times} 10{sup 5} cm{sup {minus}5}, as opposed to our conventionally grown GaAs on SL which has a typical defect density of over 1 {times}10{sup 7} cm{sup {minus}2}. Using these two now methods of GaAs-on-Si material growth, we made solar cells that are expected to show higher efficiencies than those of previous cells.

  2. Low-cost, high-efficiency solar cells utilizing GaAs-on-Si technology

    SciTech Connect

    Vernon, S.M. )


    This report describes work to develop technology to deposit GaAs on Si using a nucleation layer of atomic-layer-epitaxy-grown GaAs or AlAs on Si. This ensures two-dimensional nucleation and should lead to fewer defects in the final GaAs layer. As an alternative, we also developed technology for depositing GaAs on sawtooth-patterned Si. Preliminary studies showed that this material can have a very low defect density, [approximately] 1 [times] 10[sup 5] cm[sup [minus]5], as opposed to our conventionally grown GaAs on SL which has a typical defect density of over 1 [times]10[sup 7] cm[sup [minus]2]. Using these two now methods of GaAs-on-Si material growth, we made solar cells that are expected to show higher efficiencies than those of previous cells.

  3. Electrical Characteristics and Interface Properties of III Nitride-Based Metal-Insulator-Semiconductor Structure

    SciTech Connect

    Mahyuddin, A.; Hassan, Z.; Yusof, Y.; Cheong, K. Y.


    In this work, III-Nitride based metal-insulator-semiconductor (MIS) structure has been studied using AlN/GaN heterostructures on Si (111) with AlN buffer layer grown by plasma-assisted molecular beam epitaxy (MBE). The structural and electrical characteristics of the films were studied through high resolution x-ray diffraction (HRXRD), capacitance-voltage (C-V) and current-voltage (I-V) measurements. The value of flat-band voltage was -0.7 V. A total fixed oxide charge density of 2.73x10{sup 11} cm{sup -2} was estimated. Terman's method was used to obtain the density of interface state in the MIS structure. The analysis showed low interface state density values of 3.66x10{sup 11} cm{sup -2} eV{sup -1}.


    SciTech Connect

    Wright, J; Ferguson, B; Peters, B; Mcwhorter, S


    A compact two-gas sensor based on quartz enhanced photoacoustic spectroscopy (QEPAS) was developed for trace methane and ammonia quantification in impure hydrogen. The sensor is equipped with a micro-resonator to confine the sound wave and enhance QEPAS signal. The normalized noise-equivalent absorption coefficients (1{sigma}) of 2.45 x 10{sup -8} cm{sup -1}W/{radical}Hz and 9.1 x 10{sup -9} cm{sup -1}W/{radical}Hz for CH{sub 4} detection at 200 Torr and NH{sub 3} detection at 50 Torr were demonstrated with the QEPAS sensor configuration, respectively. The influence of water vapor on the CH{sub 4} channel was also investigated.

  5. Temporal evolution of nanoporous layer in off-normally ion irradiated GaSb

    SciTech Connect

    Datta, D. P.; Garg, S. K.; Som, T.; Kanjilal, A.; Sahoo, P. K.; Kanjilal, D.


    Room temperature irradiation of GaSb by 60 keV Ar{sup +}-ions at an oblique incidence of 60° leads to simultaneous formation of a nanoporous layer and undulations at the interface with the underlying substrate. Interestingly, with increasing ion fluence, a gradual embedding of the dense nanoporous layer takes place below ridge-like structures (up to the fluence of 1 × 10{sup 17} ions cm{sup −2}), which get extended to form a continuous layer (at fluences ≥4 × 10{sup 17} ions cm{sup −2}). Systematic compositional analyses reveal the co-existence of Ga{sub 2}O{sub 3} and Sb{sub 2}O{sub 3} in the surface layer. The results are discussed in terms of a competition between ion-induced defect accumulation and re-deposition of sputtered atoms on the surface.

  6. Dissociative electron attachment to C{sub 2}F{sub 5} radicals

    SciTech Connect

    Haughey, Sean A.; Field, Thomas A.; Langer, Judith; Shuman, Nicholas S.; Miller, Thomas M.; Friedman, Jeffrey F.; Viggiano, A. A.


    Dissociative electron attachment to the reactive C{sub 2}F{sub 5} molecular radical has been investigated with two complimentary experimental methods; a single collision beam experiment and a new flowing afterglow Langmuir probe technique. The beam results show that F{sup -} is formed close to zero electron energy in dissociative electron attachment to C{sub 2}F{sub 5}. The afterglow measurements also show that F{sup -} is formed in collisions between electrons and C{sub 2}F{sub 5} molecules with rate constants of 3.7 Multiplication-Sign 10{sup -9} cm{sup 3} s{sup -1} to 4.7 Multiplication-Sign 10{sup -9} cm{sup 3} s{sup -1} at temperatures of 300-600 K. The rate constant increases slowly with increasing temperature, but the rise observed is smaller than the experimental uncertainty of 35%.

  7. Low Band Gap Thiophene-Perylene Diimide Systems with Tunable Charge Transport Properties

    SciTech Connect

    Balaji, Ganapathy; Kale, Tejaswini S.; Keerthi, Ashok; Della Pelle, Andrea M.; Thayumanavan, S.; Vallyaveettil, Surech


    Perylenediimide-pentathiophene systems with varied architecture of thiophene units were synthesized. The photophysical, electrochemical, and charge transport behavior of the synthesized compounds were studied. Both molecules showed a low band gap of ~1.4 eV. Surprisingly, the molecule with pentathiophene attached via β-position to the PDI unit upon annealing showed a predominant hole mobility of 1 × 10<sup>-4 cm>2 V-1 s-1 whereas the compound with branched pentathiophene attached via β-position showed an electron mobility of 9.8 × 10<sup>-7 cm>2 V-1 s-1. This suggests that charge transport properties can be tuned by simply varying the architecture of pentathiophene units.

  8. Decoherence mechanisms of Landau level THz excitations in two dimensional electron gases

    SciTech Connect

    Maissen, Curdin; Scalari, Giacomo; Faist, Jérôme; Reichl, Christian; Wegscheider, Werner


    We report coherent THz transmission measurements on different two dimensional electron gases (2DEGs) in magnetic field. The investigated 2DEGs form in GaAs/AlGaAs heterostructures. A short (1 ps) linearly polarized THz pulse is used to excite inter Landau level transitions. The circular polarized radiation emitted by the 2DEG is then measured by electro optic sampling of the linear component orthogonal to the pump pulse polarization. Here we present measurements on two high mobility samples with μ = 5×10{sup 6}cm{sup 2}/Vs and μ = 16×10{sup 6}cm{sup 2}/Vs respectively. The decay times of the emitted radiation are 5.5 ps and 9 ps respectively at 2 K.

  9. Pushing the limits of plasma length in inertial fusion laser-plasma interaction experiments

    SciTech Connect

    Froula, D; Divol, L; London, R; Michel, P; Berger, R L; Meezan, N; Neumayer, P; Ross, J; Wallace, R; Glenzer, S H


    We demonstrate laser beam propagation and low backscatter in laser produced hohlraum plasmas of ignition plasma length. At intensities I < 5 x 10{sup 14} W cm{sup -2} greater than 80% of the energy in a blue (3{omega}, 351 nm) laser is transmitted through a L=5-mm long, high-temperature (T{sub e} = 2.5 keV), high-density (n{sub e} = 5 x 10{sup 20} cm{sup -3}) plasma. These experiments show that the backscatter scales exponentially with plasma length which is consistent with linear theory. The backscatter calculated by a new steady state 3D laser-plasma interaction code developed for large ignition plasmas is in good agreement with the measurements.

  10. Spectroscopic investigation of the plasma in a hollow anode with an incorporated ferroelectric plasma source

    SciTech Connect

    Krokhmal, A.; Gleizer, J.Z.; Krasik, Ya.E.; Yarmolich, D.; Felsteiner, J.; Bernshtam, V.


    Spectroscopic measurements are reported of the plasma formed inside a hollow anode (HA) with a ferroelectric plasma source (FPS) incorporated in it. The HA was used as a cathode in a diode supplied by an accelerating pulse ({<=}300 kV, {<=}400 ns). It was found that the HA discharge (1.2 kA, 10 {mu}s) is accompanied by the formation of a dense ({approx_equal}8x10{sup 14} cm{sup -3}) plasma layer at the surface of the FPS. This surface plasma serves as a practically unlimited source of electrons. In the bulk of the HA plasma the density is {approx_equal}3x10{sup 13} cm{sup -3} and it remains the same during the accelerating pulse whereas the plasma electron temperature increases from 4 to 11 eV.

  11. Plasma density measurements in tungsten wire-array Z-pinches

    SciTech Connect

    Douglass, J. D.; Hammer, D. A.; Pikuz, S. A.; Shelkovenko, T. A.; Blesener, K. S.


    Measurements of the plasma density profile near the exploding wires in 1 MA tungsten (W) wire-array Z-pinches have been made using calibrated x-ray absorption. As many as 5 x-ray images per pulse were obtained between 65 and 160 ns after the start of the 100 ns rise time current pulse. Measured W ion densities range from above 10{sup 19}/cm{sup 3} close to the wire to {approx}10{sup 17}/cm{sup 3} about 1 mm away from the wire in the plasma stream. After accurate geometrical registration of the individual wires in each successive image in a pulse using the Genetic Algorithm, the temporal evolution of the axial modulation wavelength distribution of the ablation rate from the wires in each array and the global mass-ablation rate as a function of time are presented.

  12. Tungsten-doped tin oxide thin films prepared by pulsed plasma deposition

    SciTech Connect

    Huang Yanwei; Zhang Qun Li Guifeng; Yang Ming


    Transparent conductive oxide tungsten-doped tin oxide thin films were deposited on glass substrates from ceramic targets by the pulsed plasma deposition method. The structural, electrical and optical properties have been investigated as functions of tungsten doping content and oxygen partial pressure. The lowest resistivity of 2.1 x 10{sup -3} {omega}{center_dot}cm was reproducibly obtained, with carrier mobility of 30 cm{sup 2}V{sup -1}s{sup -1} and carrier concentration of 9.6 x 10{sup 19} cm{sup -3} at the oxygen partial pressure of 1.8 Pa. The average optical transmission was in excess of 80% in the visible region from 400 to 700 nm, with the optical band gap ranging from 3.91 to 4.02 eV.

  13. Materials properties and dislocation dynamics in InAsP compositionally graded buffers on InP substrates

    SciTech Connect

    Jandl, Adam Bulsara, Mayank T.; Fitzgerald, Eugene A.


    The properties of InAs{sub x}P{sub 1−x} compositionally graded buffers grown by metal organic chemical vapor deposition are investigated. We report the effects of strain gradient (ε/thickness), growth temperature, and strain initiation sequence (gradual or abrupt strain introduction) on threading dislocation density, surface roughness, epi-layer relaxation, and tilt. We find that gradual introduction of strain causes increased dislocation densities (>10{sup 6}/cm{sup 2}) and tilt of the epi-layer (>0.1°). A method of abrupt strain initiation is proposed which can result in dislocation densities as low as 1.01 × 10{sup 5} cm{sup −2} for films graded from the InP lattice constant to InAs{sub 0.15}P{sub 0.85}. A model for a two-energy level dislocation nucleation system is proposed based on our results.

  14. Dopant and carrier concentration in silicon, in equilibrium with SiP precipitates

    SciTech Connect

    Solmi, S.; Parisini, A.; Armigliato, A.; Angelucci, R.


    The methods recently reported to study the equilibria hi the Si-As system, were extended to the Si-P. On this line the behaviour of Silicon slices very heavily implanted with 1.5 x 10{sup 17} P{sup +}/cm{sup 2}, was followed by transmission electron microscopy (TEM) and secondary neutral mass spectrometry (SNMS) after annealing at 800, 850, 900 and 1000 C. Precipitation of large monoclinic, and partially orthorhombic, SiP takes place hi the most heavily doped region. From the shape of the SNMS profiles in the dissolution stage of these precipitates, we determined for the First time, the concentration C{sub e} of P hi equilibrium with the conjugate phase: C. = 2.45 x 10{sup 23} exp (- 0.62/ kT) cm{sup -3}, were kT is in eV.

  15. High-energy 4{omega} probe laser for laser-plasma experiments at nova

    SciTech Connect

    Glenzer, S. H., LLNL


    For the characterization of inertial confinement fusion plasmas we implemented a high-energy 4{omega} probe laser at the Nova laser facility. A total energy of > 50 Joules at 4{omega}, a focal spot size of order 100 {micro}m, and a pointing accuracy of 100 {micro}m was demonstrated for target shots. This laser provides intensities of up to 3 x 10{sup 14}W cm{sup -2} and therefore fulfills high-power requirements for laser-plasma interaction experiments. The 4{omega} probe laser is now routinely used for Thomson scattering. Successful experiments were performed in gas-filled hohlraums at electron densities of n{sub e} > 2 X 10{sup 21}cm{sup -3} which represents the highest density plasma so far being diagnosed with Thomson scattering.

  16. Bunch Pattern With More Bunches in PEP-II

    SciTech Connect

    Colocho, W.S.; Decker, F.-J.; Novokhatski, A.; Sullivan, M.K.; Wienands, U.; /SLAC


    The number of bunches in the PEP-II B-Factory has increased over the years. The luminosity has followed roughly linearly that increase or even faster since we have also lowered the spot size at the interaction point. The recent steps from 939 bunches in June of 2003 to about 1320 in February 2004 (and 1585 in May) should have been followed by a similar rise in luminosity from 6.5 {center_dot} 10{sup 33} l/cm{sup 2} {center_dot} 1/s to 9.1 {center_dot} 10{sup 33} 1/cm{sup 2} {center_dot} 1/s (or even 11 {center_dot} 10{sup 33} 1/cm{sup 2} {center_dot} 1/s in May). This didn't happen so far and a peak luminosity of ''only'' 7.3 {center_dot} 10{sup 33} 1/cm{sup 2} {center_dot} 1/s (or 9.2 {center_dot} 10{sup 33} 1/cm{sup 2} {center_dot} 1/s in May) was achieved with less bunch currents. By filling the then partially filled by-3 pattern to a completely filled by-3 pattern (1133 bunches) we should get 7.9 {center_dot} 10{sup 33} 1/cm{sup 2} {center_dot} 1/s with scaled currents of 1400 mA (HER) on 1900 mA (LER). We were typically running about 1300 mA on 1900 mA with 15% more bunches in February (and 1550 mA on 2450 mA with 40% more bunches in May). The bunch pattern is typically by-2 with trains of 14 bunches out of 18 (or 67 out of 72). The parasitic beam crossings or electron cloud effects might play a role at about a 5-10% luminosity loss. Also the LER x-tune could be pushed further down to the 1/2 integer in the by-3 pattern. On the other hand, we might not push the beam-beam tune shift as hard as in June of 2003 since we have started trickle injection and therefore might avoid the highest peak luminosity which probably has a higher background.

  17. Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors

    SciTech Connect

    Bandaru, Jordana


    Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer (< 10{sup 13} cm{sup -3}) approximately 1 mm thick grown on a heavily doped active layer ({approx} 10{sup 16} cm{sup -3}) approximately 20 mm thick. Epilayers were grown using liquid phase epitaxy (LPE) of germanium out of lead solution. The effects of the crystallographic orientation of the germanium substrate on LPE growth modes were explored. Growth was studied on substrates oriented by Laue x-ray diffraction between 0.02{sup o} and 10{sup o} from the {l_brace}111{r_brace} toward the {l_brace}100{r_brace}. Terrace growth was observed, with increasing terrace height for larger misorientation angles. It was found that the purity of the blocking layer was limited by the presence of phosphorus in the lead solvent. Unintentionally doped Ge layers contained {approx}10{sup 15} cm{sup -3} phosphorus as determined by Hall effect measurements and Photothermal Ionization Spectroscopy (PTIS). Lead purification by vacuum distillation and dilution reduced the phosphorus concentration in the layers to {approx} 10{sup 14} cm{sup -3} but further reduction was not observed with successive distillation runs. The graphite distillation and growth components as an additional phosphorus source cannot be ruled out. Antimony ({approx}10{sup 16} cm{sup -3}) was used as a dopant for the active BIB layer. A reduction in the donor binding energy due to impurity banding was observed by variable temperature Hall effect measurements. A BIB detector fabricated from an Sb-doped Ge layer grown on a pure substrate showed a low energy photoconductive onset ({approx}6 meV). Spreading resistance measurements on doped layers revealed a nonuniform dopant distribution with Sb pile-up at the layer surface, which must be removed by chemomechanical polishing. Sb diffusion into the pure substrate was observed by Secondary Ion Mass Spectroscopy (SIMS) for epilayers grown at 650 C. The Sb concentration at the interface


    SciTech Connect

    Tenenbaum, E. D.; Woolf, N. J.; Ziurys, L. M.; Milam, S. N. E-mail: nwoolf@as.arizona.ed E-mail: Stefanie.N.Milam@nasa.go


    H{sub 2}CO, c-C{sub 3}H{sub 2}, and C{sub 2}H have been identified in the neutral envelope of the highly evolved planetary nebula (PN), the Helix (also know as NGC 7293). Emission from these species were detected toward a peak position in CO, 372'' east of the central star, using the facilities of the Arizona Radio Observatory (ARO). C{sub 2}H and c-C{sub 3}H{sub 2} were identified on the basis of their 3 mm transitions, measured with the ARO 12 m, while five lines of H{sub 2}CO were observed using the 12 m at 2 and 3 mm and the ARO Submillimeter Telescope at 1 mm. From a radiative transfer analysis of the formaldehyde emission, the molecular material was determined to have a density of n(H{sub 2}) approx3 x 10{sup 5} cm{sup -3}, with a kinetic temperature of T {sub kin} approx20 K. Column densities for C{sub 2}H, H{sub 2}CO, and c-C{sub 3}H{sub 2} of N {sub tot} approx1.4 x 10{sup 13} cm{sup -2}, 1.1 x 10{sup 12} cm{sup -2}, and 3 x 10{sup 11} cm{sup -2}, respectively, were derived, corresponding to fractional abundances relative to H{sub 2} of f (H{sub 2}CO) = 1 x 10{sup -7}, f (c-C{sub 3}H{sub 2}) = 3 x 10{sup -8}, and f (C{sub 2}H) = 1 x 10{sup -6} {sub .} The physical conditions found support the notion that molecules in evolved PNe survive in dense clumps in pressure equilibrium, shielded from photodissociation. The presence of H{sub 2}CO, c-C{sub 3}H{sub 2}, and C{sub 2}H, along with the previously observed species CN, HNC, HCN, and HCO{sup +}, indicates that a relatively complex chemistry can occur in the late stages of PN evolution, despite potentially destructive ultraviolet radiation. These molecules have also been observed in diffuse clouds, suggesting a possible connection between molecular material in evolved PNe and the diffuse ISM.


    SciTech Connect

    Zack, L. N.; Ziurys, L. M.


    Observations of CO, HCO{sup +}, and H{sub 2}CO have been carried out at nine positions across the Helix Nebula (NGC 7293) using the Submillimeter Telescope and the 12 m antenna of the Arizona Radio Observatory. Measurements of the J = 1 {yields} 0, 2 {yields} 1, and 3 {yields}2 transitions of CO, two transitions of HCO{sup +} (J = 1 {yields} 0 and 3 {yields}2), and five lines of H{sub 2}CO (J{sub Ka,Kc} = 1{sub 0,1} {yields} 0{sub 0,0}, 2{sub 1,2} {yields} 1{sub 1,1}, 2{sub 0,2} {yields} 1{sub 0,1}, 2{sub 1,1} {yields} 1{sub 1,0}, and 3{sub 0,3} {yields}2{sub 0,2}) were conducted in the 0.8, 1, 2, and 3 mm bands toward this highly evolved planetary nebula. HCO{sup +} and H{sub 2}CO were detected at all positions, along with three transitions of CO. From a radiative transfer analysis, the kinetic temperature was found to be T{sub K} {approx} 15-40 K across the Helix with a gas density of n(H{sub 2}) {approx} 0.1-5 Multiplication-Sign 10{sup 5} cm{sup -3}. The warmer gas appears to be closer to the central star, but high density material is distributed throughout the nebula. For CO, the column density was found to be N{sub tot} {approx} 0.25-4.5 Multiplication-Sign 10{sup 15} cm{sup -2}, with a fractional abundance of f (CO/H{sub 2}) {approx} 0.3-6 Multiplication-Sign 10{sup -4}. Column densities for HCO{sup +} and H{sub 2}CO were determined to be N{sub tot} {approx} 0.2-5.5 Multiplication-Sign 10{sup 11} cm{sup -2} and 0.2-1.6 Multiplication-Sign 10{sup 12} cm{sup -2}, respectively, with fractional abundances of f (HCO{sup +}/H{sub 2}) {approx} 0.3-7.3 Multiplication-Sign 10{sup -8} and f (H{sub 2}CO/H{sub 2}) {approx} 0.3-2.1 Multiplication-Sign 10{sup -7}-several orders of magnitude higher than predicted by chemical models. Polyatomic molecules in the Helix appear to be well-protected from photodissociation and may actually seed the diffuse interstellar medium.

  20. Good electrical contacts for high resistivity (Cd,Mn)Te crystals

    SciTech Connect

    Witkowska-Baran,M.; Mycielski, A.; Kochanowska, D.; Szadkowski, A. J.; Jakiela, r.; Witkowska, B.; Kaliszek, W.; Domagala, J.; Lusakowska, E.; Domukhovski, V.; Dybko, K.; Cui, Y.; James, R. B.


    We consider that semi-insulating (Cd,Mn)Te crystals may well successfully replace the commonly used (Cd,Zn)Te crystals as a material for manufacturing large-area X- and gamma-ray detectors. The Bridgman growth method yields good quality and high-resistivity (10{sup 9}-10{sup 10} {Omega}-cm) crystals of (Cd,Mn)Te:V. Doping with vanadium ({approx} 10{sup 16} cm{sup -3}), which acts as a compensating agent, and annealing in cadmium vapors, which reduces the number of cadmium vacancies in the as-grown crystal, ensure this high resistivity. Detector applications of the crystals require satisfactory electrical contacts. Hence, we explored techniques of ensuring good electrical contacts to semi-insulating (Cd,Mn)Te crystals. Our findings are reported here. Before depositing the contact layers, we prepared an 'epi-ready' surface of the crystal platelet by a procedure described earlier for various tellurium-based II-VI compound crystals. A molecular beam epitaxy (MBE) apparatus was used to deposit various types of contact layers: Monocrystalline semiconductor layers, amorphous- and nanocrystalline semiconductor layers, and metal layers were studied. We employed ZnTe heavily doped ({approx} 10{sup 18} cm{sup -3}) with Sb, and CdTe heavily doped ({approx} 10{sup 17} cm{sup -3}) with In as the semiconductors to create contact layers that subsequently enable good contact (with a narrow, tunneling barrier) to the Au layer that usually is applied as the top contact layer. We describe and discuss the technology and some properties of the electrical contacts to semi-insulating (Cd,Mn)Te.


    SciTech Connect

    Goodman, Michael L.; Judge, Philip G. E-mail:


    An MHD model of a hydrogen plasma with flow, an energy equation, NLTE ionization and radiative cooling, and an Ohm's law with anisotropic electrical conduction and thermoelectric effects is used to self-consistently generate atmospheric layers over a 50 km height range. A subset of these solutions contains current sheets and has properties similar to those of the lower and middle chromosphere. The magnetic field profiles are found to be close to Harris sheet profiles, with maximum field strengths {approx}25-150 G. The radiative flux F{sub R} emitted by individual sheets is {approx}4.9 Multiplication-Sign 10{sup 5}-4.5 Multiplication-Sign 10{sup 6} erg cm{sup -2} s{sup -1}, to be compared with the observed chromospheric emission rate of {approx}10{sup 7} erg cm{sup -2} s{sup -1}. Essentially all emission is from regions with thicknesses {approx}0.5-13 km containing the neutral sheet. About half of F{sub R} comes from sub-regions with thicknesses 10 times smaller. A resolution {approx}< 5-130 m is needed to resolve the properties of the sheets. The sheets have total H densities {approx}10{sup 13}-10{sup 15} cm{sup -3}. The ionization fraction in the sheets is {approx}2-20 times larger, and the temperature is {approx}2000-3000 K higher than in the surrounding plasma. The Joule heating flux F{sub J} exceeds F{sub R} by {approx}4%-34%, the difference being balanced in the energy equation mainly by a negative compressive heating flux. Proton Pedersen current dissipation generates {approx}62%-77% of the positive contribution to F{sub J} . The remainder of this contribution is due to electron current dissipation near the neutral sheet where the plasma is weakly magnetized.

  2. Methods for passivating silicon devices at low temperature to achieve low interface state density and low recombination velocity while preserving carrier lifetime


    Chen, Zhizhang; Rohatgi, Ajeet


    A new process has been developed to achieve a very low SiO.sub.x /Si interface state density, low recombination velocity S (<2 cm/s), and high effective carrier lifetime T.sub.eff (>5 ms) for oxides deposited on silicon substrates at low temperature. The technique involves direct plasma-enhanced chemical vapor deposition (PECVD), with appropriate growth conditions, followed by a photo-assisted rapid thermal annealing (RTA) process. Approximately 500-A-thick SiO.sub.x layers are deposited on Si by PECVD at C. with 0.02 W/cm.sup.-2 rf power, then covered with SiN or an evaporated thin aluminum layer, and subjected to a photo-assisted anneal in forming gas ambient at C., resulting in an interface state density in the range of about 1-4.times.10.sup.10 cm.sup.-2 eV.sup.-1, which sets a record for the lowest interface state density for PECVD oxides fabricated to date. Detailed analysis shows that the PECVD deposition conditions, photo-assisted anneal, forming gas ambient, and the presence of an aluminum layer on top of the oxides during the anneal, all contributed to this low value of interface state density Detailed metal-oxide semiconductor analysis and model calculations show that such a low recombination velocity S is the result of moderately high positive oxide charge (5.times.10.sup.11 -1.times.10.sup.12 cm.sup.-2) and relatively low midgap interface state density (1.times.10.sup.10 -4.times.10.sup.10 cm.sup.-2 eV.sup.-1). Photo-assisted anneal was found to be superior to furnace annealing, and a forming gas ambient was better than a nitrogen ambient for achieving a very low surface recombination velocity S.

  3. The helix nebula viewed in HCO{sup +}: Large-scale mapping of the J = 1 → 0 transition

    SciTech Connect

    Zeigler, N. R.; Zack, L. N.; Ziurys, L. M.; Woolf, N. J.


    The J = 1 → 0 transition of HCO{sup +} at 89 GHz has been mapped across the Helix Nebula (NGC 7293) with 70'' spatial resolution (1.68 km s{sup –1} velocity resolution) using the Arizona Radio Observatory 12 m telescope. This work is the first large-scale mapping project of a dense gas tracer (n(H{sub 2}) ∼ 10{sup 5} cm{sup –3}) in old planetary nebulae. Observations of over 200 positions encompassing the classical optical image were conducted with a 3σ noise level of ∼20 mK. HCO{sup +} was detected at most positions, often exhibiting multiple velocity components indicative of complex kinematic structures in dense gas. The HCO{sup +} spectra suggest that the Helix is composed of a bipolar, barrel-like structure with red- and blue-shifted halves, symmetric with respect to the central star and oriented ∼10° east from the line of sight. A second bipolar, higher velocity outflow exists as well, situated along the direction of the Helix 'plumes'. The column density of HCO{sup +} across the Helix is N {sub tot} ∼ 1.5 × 10{sup 10}-5.0 × 10{sup 11} cm{sup –2}, with an average value N {sub ave} ∼ 1 × 10{sup 11} cm{sup –2}, corresponding to an abundance, relative to H{sub 2}, of f ∼ 1.4 × 10{sup –8}. This value is similar to that observed in young PN, and contradicts chemical models, which predict that the abundance of HCO{sup +} decreases with nebular age. This study indicates that polyatomic molecules readily survive the ultraviolet field of the central white dwarf, and can be useful in tracing nebular morphology in the very late stages of stellar evolution.


    SciTech Connect

    Codella, C.; Fontani, F.; Gómez-Ruiz, A.; Vasta, M.; Viti, S.; Ceccarelli, C.; Lefloch, B.; Podio, L.; Caselli, P.


    We present the first detection of N{sub 2}H{sup +} toward a low-mass protostellar outflow, namely, the L1157-B1 shock, at ∼0.1 pc from the protostellar cocoon. The detection was obtained with the IRAM 30 m antenna. We observed emission at 93 GHz due to the J = 1-0 hyperfine lines. Analysis of this emission coupled with HIFI CHESS multiline CO observations leads to the conclusion that the observed N{sub 2}H{sup +}(1-0) line originated from the dense (≥10{sup 5} cm{sup –3}) gas associated with the large (20''-25'') cavities opened by the protostellar wind. We find an N{sub 2}H{sup +} column density of a few 10{sup 12} cm{sup –2} corresponding to an abundance of (2-8) × 10{sup –9}. The N{sub 2}H{sup +} abundance can be matched by a model of quiescent gas evolved for more than 10{sup 4} yr, i.e., for more than the shock kinematical age (≅2000 yr). Modeling of C-shocks confirms that the abundance of N{sub 2}H{sup +} is not increased by the passage of the shock. In summary, N{sub 2}H{sup +} is a fossil record of the pre-shock gas, formed when the density of the gas was around 10{sup 4} cm{sup –3}, and then further compressed and accelerated by the shock.

  5. Experimental and theoretical study of the ion-ion mutual neutralization reactions Ar{sup +}+SF{sub n}{sup -} (n=6, 5, and 4)

    SciTech Connect

    Bopp, Joseph C.; Miller, Thomas M.; Viggiano, Albert A.; Troe, Juergen


    The ion-ion mutual neutralization reactions Ar{sup +}+SF{sub n}{sup -}{yields}Ar+SF{sub n} (n=6, 5, and 4) have been studied in a flowing afterglow-Langmuir probe (FALP) apparatus at 300 K and 1 Torr of He buffer gas. Electron concentrations and product ion fractions were measured, and neutralization rate constants of 4.0x10{sup -8}, 3.8x10{sup -8}, and 4x10{sup -8} cm{sup 3} s{sup -1} for SF{sub 6}{sup -}, SF{sub 5}{sup -}, and SF{sub 4}{sup -}, respectively, were derived, with uncertainties of {+-}25% ({+-}35% for SF{sub 4}{sup -}). During the neutralization process, excited neutrals are generated that are able to dissociate to neutral fragments. In the case of SF{sub 6}, the formation of SF{sub 5} and SF{sub 4}, and similarly in the case of SF{sub 5}, the formation of SF{sub 4} and SF{sub 3} were observed and quantified. The mechanism of primary and secondary reaction was analyzed in detail, and rate constants for the dissociative electron attachments e{sup -}+SF{sub 5}{yields}F{sup -}+SF{sub 4} (k=3x10{sup -9} cm{sup 3} s{sup -1},{+-}40%) and e{sup -}+SF{sub 3}{yields}F{sup -}+SF{sub 2} (k=2x10{sup -8} cm{sup 3} s{sup -1},+400%,-75%) were also derived. The experimental ion-ion neutralization rate constants were found to be in good agreement with estimates from an optimum two-state double-passage Landau-Zener model. It was also found that energy partitioning in the neutralization is related to the extent of electronic excitation of Ar generated by the electron transfer processes.

  6. Neodymium Fluorescence Quenching by Hydroxyl Groups in Phosphate Laser Glasses

    SciTech Connect

    Ehrmann, P R; Carlson, K; Campbell, J H; Click, C A; Brow, R K


    Non-radiative losses due to OH fluorescence quenching of the Nd{sup 3+} {sup 4}F{sub 3/2} state are quantified over a range of OH concentrations from 4 x 10{sup 18}/cm{sup 3} to 4 x 10{sup 20}/cm{sup 3} and Nd doping levels from 0.4 to 9 x 10{sup 20}/cm{sup 3} in two K{sub 2}O-MgO-Al{sub 2}O{sub 3}-P{sub 2}O{sub 5} metaphosphate glasses having different K/Mg ratios ({approx}1/1 and 2/1). The quenching rate is found to vary linearly with the Nd and OH concentrations as predicted by Forster-Dexter theory. However, in contrast to theory the OH quenching rate extrapolates to a non-zero value at low Nd{sup 3+} doping levels. It is proposed that at low Nd{sup 3+} concentrations the OH is correlated with Nd sites in the glass. The quenching strength of OH on a per ion basis is found to be weak compared to other common transition metal impurities (e.g. Fe{sup 2+}, Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}). Nevertheless, OH dominates the Nd quenching in phosphate glass because under most processing conditions OH is present at concentrations 10{sup 2} to 10{sup 3} greater than transition metal ion impurities. A correlation of the quenching strength of OH and common metal impurity ions with the degree of spectral overlap of the impurity absorption bands and the four {sup 4}F{sub 3/2} to {sup 4}I{sub J} transitions shows good agreement.

  7. Judd-Ofelt analysis, frequency upconversion, and infrared photoluminescence of Ho{sup 3+}-doped and Ho{sup 3+}/Yb{sup 3+}-codoped lead bismuth gallate oxide glasses

    SciTech Connect

    Zhou Bo; Pun, Edwin Yue-Bun; Yang Dianlai; Huang Lihui; Lin Hai


    Ho{sup 3+}-doped and Ho{sup 3+}/Yb{sup 3+}-codoped lead bismuth gallate (PBG) oxide glasses were prepared and their spectroscopic properties were investigated. The derived Judd-Ofelt intensity parameters (OMEGA{sub 2}=6.81x10{sup -20} cm{sup 2}, OMEGA{sub 4}=2.31x10{sup -20} cm{sup 2}, and OMEGA{sub 6}=0.67x10{sup -20} cm{sup 2}) indicate a higher asymmetry and stronger covalent environment for Ho{sup 3+} sites in PBG glass compared with those in tellurite, fluoride (ZBLAN), and some other lead-contained glasses. Intense frequency upconversion emissions peaking at 547, 662, and 756 nm as well as infrared emissions at 1.20 and 2.05 mum in Ho{sup 3+}/Yb{sup 3+}-codoped PBG glass were observed, confirming that energy transfer between Yb{sup 3+} and Ho{sup 3+} takes place, and a two-phonon-assisted energy transfer from Yb{sup 3+} to Ho{sup 3+} ions was determined by the calculation using phonon sideband theory. The 1.20 mum emission observed was primarily due to the weak multiphonon deexcitation originated from the small phonon energy of PBG glass (approx535 cm{sup -1}). A large product of emission cross-section and measured lifetime (9.93x10{sup -25} cm{sup 2} s) was obtained for the 1.20 mum emission and the gain coefficient dependence on wavelength with population inversion rate (P) was performed. The peak emission cross-section for 2.05 mum emission was calculated to be 4.75x10{sup -21} cm{sup 2}. The relative mechanism of Ho{sup 3+}-doped and Ho{sup 3+}/Yb{sup 3+}-codoped PBG glasses on their spectroscopic properties was also discussed. Our results suggest that Ho{sup 3+}/Yb{sup 3+}-doped PBG glasses are a good potential candidate for the frequency upconversion devices and infrared amplifiers/lasers.

  8. Preliminary Langmuir probe results on the CTX gun experiment

    SciTech Connect

    Tuszewski, M.


    Preliminary results obtained with a double Langmuir probe in the Compact Toroid experiment facility confirm the existence of a gun plasma of n approx. 5 x 10/sup 14/ cm/sup -3/ and T approx. 10 eV lasting for approx. 250 to 400, which is consistent with interferometry and Thomson scattering data. The probe current characteristics as a function of voltage suggest non-Maxwellian features of the particles distribution functions.

  9. Determination of the microstructure of gas bubbles in highly purified water by measuring the elements of the laser radiation scattering matrix

    SciTech Connect

    Bunkin, Nikolai F; Suyazov, N V; Shkirin, A V; Ignat'ev, P S; Indukaev, K V


    Modulation interference microscopy and measurements of the elements of the light scattering matrix showed that doubly distilled water purified from solid impurities contains macroscopic scatterers in the form of micron clusters formed by polydisperse air bubbles with the effective radius 70-90 nm. The fractal dimension of clusters lies within 2.4-2.8 and their concentration is {approx}10{sup 6} cm{sup -3}. (radiation scattering)

  10. Cluster structure of stable dissolved gas nanobubbles in highly purified water

    SciTech Connect

    Bunkin, N. F. Suyazov, N. V.; Shkirin, A. V.; Ignat'ev, P. S.; Indukaev, K. V.


    Experiments using phase-modulation interference microscopy and Mueller-matrix polarimetry show that double-distilled water free of foreign solid matter contains macroscopic light scatterers. Numerical calculations suggest that these scatterers can be represented as micrometer-size clusters of polydisperse air bubbles with effective radii between 70 and 90 nm. The fractal dimension of the clusters varies from 2.4 to 2.8, and their concentration is on the order of 10{sup 6} cm{sup -3}.

  11. Production of centimeter-scale, high-density plasmas with a linear gas jet

    SciTech Connect

    Coverdale, C.A.; Darrow, C.B.; Jones, R.; Sawyer, W.; Crane, J.; Ditmire, T.; Perry, M.D. ); Filbert, P.C. )


    A novel linear gas jet has been developed and used to produce centimeter-scale, 10[sup 19] cm[sup [minus]3] electron density plasmas. Long regions of high density are important to many types of experiments, including x-ray laser and laser-plasma interaction studies. This new type of gas jet has been characterized by stimulated Raman backscatter emission from the plasma.

  12. DETECTIONS OF C{sub 2}H, CYCLIC-C{sub 3}H{sub 2}, AND H{sup 13}CN IN NGC 1068

    SciTech Connect

    Nakajima, T.; Takano, S.; Kohno, K.; Inoue, H.


    We used the Nobeyama 45 m telescope to conduct a spectral line survey in the 3 mm band (85.1-98.4 GHz) toward one of the nearest galaxies with an active galactic nucleus (AGN), NGC 1068, and the prototypical starburst galaxy NGC 253. The beam size of this telescope is {approx} 18'', which was sufficient to spatially separate the nuclear molecular emission from the emission of the circumnuclear starburst region in NGC 1068. We detected rotational transitions of C{sub 2}H, cyclic-C{sub 3}H{sub 2}, and H{sup 13}CN in NGC 1068. These are detections of carbon-chain and carbon-ring molecules in NGC 1068. In addition, the C{sub 2}H N = 1-0 lines were detected in NGC 253. The column densities of C{sub 2}H were determined to be 3.4 x 10{sup 15} cm{sup -2} in NGC 1068 and 1.8 x 10{sup 15} cm{sup -2} in NGC 253. The column densities of cyclic-C{sub 3}H{sub 2} were determined to be 1.7 x 10{sup 13} cm{sup -2} in NGC 1068 and 4.4 x 10{sup 13} cm{sup -2} in NGC 253. We calculated the abundances of these molecules relative to CS for both NGC 1068 and NGC 253, and found that there were no significant differences in the abundances between the two galaxies. This result suggests that the basic carbon-containing molecules are either insusceptible to AGN or are tracing cold (T{sub rot} {approx} 10 K) molecular gas rather than X-ray irradiated hot gas.

  13. The D0 upgrade trigger

    SciTech Connect

    Eno, S.


    The current trigger system for the D0 detector at Fermilab`s Tevatron will need to be upgraded when the Min Injector is installed and the Tevatron can operate at luminosities exceeding 10{sup 32} cm{sup {minus}2}s{sup {minus}1} and with a crossing time of 132 ns. We report on preliminary designs for upgrades to the trigger system for the Main Injector era.

  14. Confinement scaling and ignition in tokamaks

    SciTech Connect

    Perkins, F.W.; Sun, Y.C.


    A drift wave turbulence model is used to compute the scaling and magnitude of central electron temperature and confinement time of tokamak plasmas. The results are in accord with experiment. Application to ignition experiments shows that high density (1 to 2) . 10/sup 15/ cm/sup -3/, high field, B/sub T/ > 10 T, but low temperature T approx. 6 keV constitute the optimum path to ignition.

  15. Evidence for observation of underground muons from Cygnus X-3

    SciTech Connect

    Bartelt, J.; Courant, H.; Heller, K.; Heppelmann, S.; Joyce, T.; Peterson, E.A.; Marshak, M.L.; Ruddick, K.; Shupe, M.; Ayres, D.S.


    We have observed evidence for an average underground muon flux of approx. = 7 x 10/sup -11/ cm/sup -2/ s/sup -1/ which points back to the x-ray binary Cygnus X-3 and which exhibits the 4.8 h periodicity observed for other radiation from this source. These observations cannot be explained by conventional models of the propagation and interaction of cosmic rays. 13 refs., 2 figs.

  16. Polymeric Ionic Networks with High Charge Density: Solid-like Electrolytes in Lithium Metal Batteries

    SciTech Connect

    Zhang, Pengfei; Li, Mingtao; Jiang, Xueguang; Fang, Youxing; Veith, Gabriel M.; Sun, Xiao-Guang; Dai, Sheng


    Polymerized ionic networks (PINs) with six ion pairs per repeating unit are synthesized by nucleophilic-substitution-mediated polymerization or radical polymerization of monomers bearing six 1-vinylimidazolium cations. PIN-based solid-like electrolytes show good ionic conductivities (up to 5.32 × 10<sup>-3 S cm>-1 at 22 °C), wide electrochemical stability windows (up to 5.6 V), and good interfacial compatibility with the electrodes.

  17. Highly ionized plasma plume generation by long-pulse CO/sub 2/ laser irradiation of solid targets in strong axial magnetic fields

    SciTech Connect

    Hoffman, A L; Crawford, E A


    The present work utilizes high f number optics and is directed primarily at controlling the conditions in the magnetically confined plume. Typically, fully ionized carbon plasmas have been produced with 10/sup 18/ cm/sup -3/ electron densities and 100 to 150 eV electron temperatures. These carbon plasmas have been doped with high Z atoms in order to study ionization and emission rates at the above conditions.

  18. Phosphorus doping of 4H SiC by liquid immersion excimer laser irradiation

    SciTech Connect

    Ikeda, Akihiro; Nishi, Koji; Ikenoue, Hiroshi; Asano, Tanemasa


    Phosphorus doping of 4H SiC is performed by KrF excimer laser irradiation of 4H SiC immersed in phosphoric acid. Phosphorus is incorporated to a depth of a few tens of nanometers at a concentration of over 10{sup 20}/cm{sup 3} without generating significant crystal defects. Formation of a pn junction diode with an ideality factor of 1.06 is demonstrated.

  19. Refractory oxide hosts for a high power, broadly tunable laser with high quantum efficiency and method of making same


    Chen, Yok; Gonzalez, Roberto


    Refractory oxide crystals having high-quantum efficiency and high thermal stability for use as broadly tunable laser host materials. The crystals are formed by removing hydrogen from a single crystal of the oxide material to a level below about 10.sup.12 protons per cm.sup.3 and subsequently thermochemically reducing the oxygen content of the crystal to form sufficient oxygen anion vacancies so that short-lived F.sup.+ luminescence is produced when the crystal is optically excited.

  20. Refractory oxide hosts for a high power, broadly tunable laser with high quantum efficiency and method of making same


    Chen, Yok; Gonzalez, R.


    Refractory oxide crystals having high-quantum efficiency and high thermal stability for use as broadly tunable laser host materials. The crystals are formed by removing hydrogen from a single crystal of the oxide material to a level below about 10/sup 12/ protons per cm/sup 3/ and subsequently thermochemically reducing the oxygen content of the crystal to form sufficient oxygen anion vacancies so that short-lived F/sup +/ luminescence is produced when the crystal is optically excited.


    SciTech Connect



    A high-energy CO{sub 2} laser is channeled in a capillary discharge. Occurrence of guiding conditions at a relatively low plasma density (<10{sup 18} cm{sup -3}) is confirmed by MHD simulations. Divergence of relativistic electron beam changes depending on the plasma density. Counter-propagation of the electron and laser beams inside the plasma channel results in intense x-ray generation.


    SciTech Connect

    Plume, R.; Bergin, E. A.; Wang, S.; Crockett, N. R.; Phillips, T. G.; Lis, D. C.; Caux, E.; Comito, C.; Schilke, P.; Goldsmith, P. F.


    The large number of high-J lines of C{sup 18}O available via the Herschel Space Observatory provide an unprecedented ability to model the total CO column density in hot cores. Using the emission from all the observed lines (up to J = 15-14), we sum the column densities in each individual level to obtain the total column after correcting for the population in the unobserved states. With additional knowledge of source size, V{sub LSR}, and line width, and both local thermodynamic equilibrium (LTE) and non-LTE modeling, we have determined the total C{sup 18}O column densities in the Extended Ridge, Outflow/Plateau, Compact Ridge, and Hot Core components of Orion KL to be 1.4 Multiplication-Sign 10{sup 16} cm{sup -2}, 3.5 Multiplication-Sign 10{sup 16} cm{sup -2}, 2.2 Multiplication-Sign 10{sup 16} cm{sup -2}, and 6.2 Multiplication-Sign 10{sup 16} cm{sup -2}, respectively. We also find that the C{sup 18}O/C{sup 17}O abundance ratio varies from 1.7 in the Outflow/Plateau, 2.3 in the Extended Ridge, 3.0 in the Hot Core, and to 4.1 in the Compact Ridge. This is in agreement with models in which regions with higher ultraviolet radiation fields selectively dissociate C{sup 17}O, although care must be taken when interpreting these numbers due to the size of the uncertainties in the C{sup 18}O/C{sup 17}O abundance ratio.

  3. Production of high-density capacitively coupled radio-frequency discharge plasma by high-secondary-electron-emission oxide

    SciTech Connect

    Ohtsu, Yasunori; Fujita, Hiroharu


    High-density capacitively coupled radio-frequency plasma with electron density n{sub e}>10{sup 10} cm{sup -3} was produced using MgO electrodes with a high secondary-electron-emission coefficient. It was found that in the case of MgO electrodes, both plasma density and optical emission intensity were about one order of magnitude higher than those in the case of Al electrodes.

  4. Physics of a high-luminosity Tau-Charm Factory

    SciTech Connect

    King, M.E.


    This paper highlights the physics capabilities of a Tau-Charm Factory; i.e., high luminosity ({approximately}10{sup 33}cm{sup {minus}2}s{sup {minus}1}) e{sup +}e{sup {minus}} collider operating in the center-of-mass energy range of 3-5 GeV, with a high-precision, general-purpose detector. Recent developments in {tau} and charm physics are emphasized.

  5. Spectroscopic characteristics of chromium doped mullite glass-ceramics

    SciTech Connect

    Wojtowicz, A.J.; Meng, W.; Lempicki, A.; Beall, G.H.; Hall, D.W.; Chin, T.C.


    Characteristics of chromium doped mullite ceramics are discussed with reference to possible laser applications. Dominant features are attributed to large and inherent spectroscopic inhomogeneity of mullite. The spectroscopic data are analyzed using a generalized McCumber theory. The peak stimulated emission cross section is 0.54 x 10/sup -20/ cm/sup 2/. This, together with preliminary single-pass measurements, indicate that gain for mullite is about 2.6 times smaller than gain for alexandrite.

  6. Production of a large diameter hot-electron plasma by electron cyclotron resonance heating

    SciTech Connect

    Kawai, Y.; Sakamoto, K.


    A large diameter hot-electron plasma is produced by electron cyclotron resonance heating, using a slotted Lisitano coil as a launcher. It is found from detailed measurements of the plasma parameters that n/sub e/< or approx. =3 x 10/sup 11/ cm/sup -3/ and T/sub e/< or approx. =40 eV, with a diameter roughly-equal14 cm. High-energy tails with temperatures of more than 100 eV are observed.

  7. Growth of InP single crystals by liquid encapsulated Czochralski (LEC) using glassy-carbon crucibles

    SciTech Connect

    Oliveira, C.E.M. de; Miskys, C.R.; Carvalho, M.M.G. de


    Using a high pressure puller and Glassy-Carbon crucibles, undoped InP single crystals weighing 100g and with 25 mm diameter were grown in the <100> direction. The residual carrier concentration of samples, measure by the Van der Pauw method at 300K, was about 5 {times} 10{sup 15}cm{sup {minus}3}, result as good as those obtained with Quartz crucibles with the advantage that Glassy-Carbon crucibles are fully reusable.

  8. Operation of silicon microstrip detectors in a high radiation environment

    SciTech Connect

    Kapustinsky, J.S.; Alde, D.M.; Boissevain, J.G.; Jeppesen, R.G.; Lane, D.W.; Leitch, M.J.; Lillberg, J.W.; Lopez, T.A.; McGaughey, P.L.; Moss, J.M.; Peng, J.C. ); Brooks, B.M.; Isenhower, L.D.; Sadler, M.E. ); Lederman, L.M.; Schub, M.H. ); Brown, C.N.; Cooper, W.E.; Gounder, K.; Hsiung, Y.B.; Mishra, C.S. (Fermi National


    A Silicon Microstrip Spectrometer was recently installed and operated in an 800 GeV proton beamline at Fermilab as a major new component of experiment E789. The detectors received an estimated radiation exposure of up to 7.8 {times} 10{sup 12} minimum ionizing particles per cm{sup 2} over a period of two months. We report on the changes in detector performance that we have observed following preliminary data analysis. 5 refs., 4 figs.

  9. Long-pulse suprathermal discharges in the ASDEX tokamak

    SciTech Connect

    Fussmann, G.; Campbell, D.; Eberhagen, A.; Engelhardt, W.; Karger, F.; Keilhacker, M.; Klueber, O.; Lackner, K.; Sesnic, S.; Wagner, F.; Behringer, K.; Gehre, O.; Gernhardt, J.; Glock, E.; Haas, G.; Kornherr, M.; Lisitano, G.; Mayer, H.M.; Meisel, D.; Mueller, R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Rapp, H.; Ruhs, N.; Schneider, F.; Siller, G.; Steuer, K.


    Use of the ASDEX divertor permits the production of stable low-density discharges (n/sub e/> or approx. =10/sup 12/ cm/sup -3/) with extremely low resistivity lasting for more than 10 s. While the distribution functions of electrons and ions show suprathermal tails, runaway electrons in the megaelectronvolt range are found to disappear with decreasing density. There are indications that in these discharges the energy confinement is improved compared with ALCATOR scaling.

  10. Electrical properties of PbTe doped with BaF{sub 2}

    SciTech Connect

    Mengui, U. A.; Abramof, E.; Rappl, P. H. O.; Diaz, B.; Closs, H.; Senna, J. R.; Ueta, A. Y.


    We study here the p-type doping of PbTe with BaF{sub 2}. For the investigation, PbTe layers were grown on (111) BaF{sub 2} substrates by molecular beam epitaxy. The beam flux ratio between BaF{sub 2} and PbTe, defined as the nominal doping level, was varied from 0.02% to 1%. The hole density increases from 5x10{sup 17} to 1x10{sup 19} cm{sup -3} as the doping level rises from 0.02% to 0.4% and saturates at p{approx}10{sup 19} cm{sup -3} for higher levels. The saturation effect was attributed to self-compensation. The carrier concentration of all samples remained almost constant as the temperature was varied from 10 to 350 K, indicating that no thermal activation is present in the whole doping range. It suggests that the impurity level in PbTe doped with BaF{sub 2} remains resonant with the valence band, similar to the native defects behavior. The low-temperature mobility showed a pronounced reduction from 50 000 to 2 000 cm{sup 2}/V s as the doping level rises from 0.02% to 1%, mainly due to the substantial increase in the hole concentration. For temperatures higher than 80 K, the mobility was essentially limited by phonon scattering. Our results demonstrate that a controlled p-type doping of PbTe with BaF{sub 2} can be obtained up to 10{sup 19} cm{sup -3}.

  11. Improved dot size uniformity and luminescense of InAs quantum dots on InP substrate

    NASA Technical Reports Server (NTRS)

    Qiu, Y.; Uhl, D.


    InAs self-organized quantum dots have been grown in InGaAs quantum well on InP substrates by metalorganic vapor phase epitaxy. Atomic Force Microscopy confirmed of quantum dot formation with dot density of 3X10(sup 10) cm(sup -2). Improved dot size uniformity and strong room temperature photoluminescence up to 2 micron were observed after modifying the InGaAs well.

  12. Hydrothermal synthesis and electrical properties of NaNbO{sub 3}

    SciTech Connect

    Boukriba, M.; Sediri, F.; Gharbi, N.


    Graphical abstract: Display Omitted Highlights: ► Crystalline rhombohedral sodium niobate (r-NaNbO{sub 3}) were synthesized. ► Conductivity goes from 5.5 × 10{sup −6} Ω{sup −1} cm{sup −1} at 280 °C to 7.61 × 10{sup −4} Ω{sup −1} cm{sup −1} at 780 °C. ► Activation energies are in the order of 0.893, 0.507, 0.819 and 0.105 eV. -- Abstract: Triangular prism-like of crystalline rhombohedral sodium niobate (r-NaNbO{sub 3}) were prepared from Nb{sub 2}O{sub 5} in the presence of NaOH via a hydrothermal method at 180 °C for 6 h. Techniques X-ray diffraction, scanning electron microscopy, Fourier transform infrared, Raman and impedance spectroscopy have been used to characterize the structure, morphology, composition and electrical properties of the material. Electrical conductivity measurements showed that the as synthesized r-NaNbO{sub 3} triangular prism has a conductivity value which goes from 5.5 × 10{sup −6} Ω{sup −1} cm{sup −1} at 280 °C to 7.61 × 10{sup −4} Ω{sup −1} cm{sup −1} at 780 °C. The Arrhenius diagram is not linear; it presents four regions of conductivity. The corresponding activation energies are, respectively, in the order of 0.893, 0.507, 0.819 and 0.105 eV, deduced from the Arrhenius relation.

  13. Perspectives on Higher Luminosity B-Factories

    SciTech Connect

    Seeman, J


    The present B-factories PEP-II and KEKB have reached luminosities of 4-6 x 10{sup 33}/cm{sup 2}/s and delivered integrated luminosity at rates in excess of 6 fb{sup -1} per month [1,2]. The recent turn on of these two B-Factories has shown that modern accelerator physics, design, and engineering can produce colliders that rapidly reach their design luminosities and deliver integrated luminosities capable of frontier particle physics discoveries. PEP-II and KEK-B with ongoing upgrade programs should reach luminosities of over 10{sup 34}/cm{sup 2}/s in a few years and with more aggressive improvements may reach luminosities of order 4 x 10{sup 34}/cm{sup 2}/s by the end of the decade. However, due to particle physics requirements, the next generation B-Factory may require significantly more luminosity. Initial parameters of a very high luminosity e{sup +}e{sup -} B-Factory or Super B-Factory (SBF) are being developed incorporating several new ideas from the successful operation of the present generation e{sup +}e{sup -} accelerators [3,4]. A luminosity approaching 10{sup 36} cm{sup -2}s{sup -1} may be possible. Furthermore, the ratio of average to peak luminosity may be increased by 30% due to continuous injection. The operation of this new accelerator will be qualitatively different from present e{sup +}e{sup -} colliders due to this continuous injection.

  14. Electron scattering by acceptor centers in p-Ag{sub 2}Te at low temperatures

    SciTech Connect

    Aliev, F. F. Jafarov, M. B.; Askerova, G. Z.; Gojaev, E. M.


    Resonant electron scattering in p-Ag{sub 2}Te at acceptor concentrations N{sub a} < 4.2 x 10{sup 16} cm{sup -3} has been observed in the temperature range of 50-80 K. The contribution of the resonant scattering to the temperature dependences of the conductivity {sigma}(T) and thermopower {alpha}{sub 0}(T) has been calculated. It is shown that this contribution exceeds that of charge carrier scattering by acoustic phonons.

  15. Breakdown and discharges in dense gases governed by runaway electrons

    SciTech Connect

    Babich, L.P.


    The phenomenon of runaway electrons (REs) at high values of the ratio field intensity/gas number density {ital E}/{ital N} and {ital N} up to the Loshmidt number {ital N}{sub {ital L}}{approx_equal}2.7{times}10{sup 19} cm{sup {minus}3} is described. REs are shown to govern the breakdown and discharges at such condition. {copyright} {ital 1996 American Institute of Physics.}

  16. Poloidal OHMIC heating in a multipole

    SciTech Connect

    Holly, D.J.


    The feasibility of using poloidal currents to heat plasmas confined by a multipole field has been examined experimentaly in Tokapole II. The machine is operated as a toroidal octupole, with a time-varying toroidal magnetic field driving poloidal plasma currents I/sub plasma/ - 20 kA to give densities n/sub e/ - 10/sup 13/ cm/sup -3/ and temperatures T/sub e/ - 30 eV.

  17. Compact Magneto-optical Trap for Rubidium Atoms

    SciTech Connect

    Chapovsky, P.L.


    The characteristics of a magneto-optical trap (MOT) using small-diameter cooling laser beams are considered. Trapping and cooling of Rb atoms from the surrounding gas of warm atoms takes place in the trap. A compact (140 {mu}m) and stable atomic cloud is obtained with a density of 7 x 10{sup 10} cm{sup -3}, which is three orders of magnitude higher than the density of the surrounding gas.


    SciTech Connect

    Usman, S. M.; Murray, S. S.; Hickox, R. C.; Brodwin, M.


    We explore the connection between absorption by neutral gas and extinction by dust in mid-infrared (IR) selected luminous quasars. We use a sample of 33 quasars at redshifts 0.7 < z ≲ 3 in the 9 deg{sup 2} Boötes multiwavelength survey field that are selected using Spitzer Space Telescope Infrared Array Camera colors and are well-detected as luminous X-ray sources (with >150 counts) in Chandra observations. We divide the quasars into dust-obscured and unobscured samples based on their optical to mid-IR color, and measure the neutral hydrogen column density N {sub H} through fitting of the X-ray spectra. We find that all subsets of quasars have consistent power law photon indices Γ ≈ 1.9 that are uncorrelated with N {sub H}. We classify the quasars as gas-absorbed or gas-unabsorbed if N {sub H} > 10{sup 22} cm{sup –2} or N {sub H} < 10{sup 22} cm{sup –2}, respectively. Of 24 dust-unobscured quasars in the sample, only one shows clear evidence for significant intrinsic N {sub H}, while 22 have column densities consistent with N {sub H} < 10{sup 22} cm{sup –2}. In contrast, of the nine dust-obscured quasars, six show evidence for intrinsic gas absorption, and three are consistent with N {sub H} < 10{sup 22} cm{sup –2}. We conclude that dust extinction in IR-selected quasars is strongly correlated with significant gas absorption as determined through X-ray spectral fitting. These results suggest that obscuring gas and dust in quasars are generally co-spatial, and confirm the reliability of simple mid-IR and optical photometric techniques for separating quasars based on obscuration.

  19. Thermal resistance of ultra-small-diameter disk microlasers

    SciTech Connect

    Zhukov, A. E. Kryzhanovskaya, N. V.; Maximov, M. V.; Lipovskii, A. A.; Savelyev, A. V.; Shostak, I. I.; Moiseev, E. I.; Kudashova, Yu. V.; Kulagina, M. M.; Troshkov, S. I.


    The thermal resistance of AlGaAs/GaAs microlasers of the suspended-disk type with a diameter of 1.7–4 μm and InAs/InGaAs quantum dots in the active region is inversely proportional to the squared diameter of the microdisk. The proportionality factor is 3.2 × 10{sup −3} (K cm{sup 2})/W, and the thermal resistance is 120–20°C/mW.

  20. Deep traps in n-type GaN epilayers grown by plasma assisted molecular beam epitaxy

    SciTech Connect

    Kamyczek, P.; Placzek-Popko, E.; Zielony, E.; Gumienny, Z.; Zytkiewicz, Z. R.


    In this study, we present the results of investigations on Schottky Au-GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77 K–350 K. Undoped GaN layers were grown using the plasma-assisted molecular beam epitaxy technique on commercial GaN/sapphire templates. The quality of the epilayers was studied by micro-Raman spectroscopy (μ-RS) which proved the hexagonal phase and good crystallinity of GaN epilayers as well as a slight strain. The photoluminescence spectrum confirmed a high crystal quality by intense excitonic emission but it also exhibited a blue emission band of low intensity. DLTS signal spectra revealed the presence of four majority traps: two high-temperature and two low-temperature peaks. Using the Laplace DLTS method and Arrhenius plots, the apparent activation energy and capture cross sections were obtained. For two high-temperature majority traps, they were equal to E{sub 1} = 0.65 eV, σ{sub 1} = 8.2 × 10{sup −16} cm{sup 2} and E{sub 2} = 0.58 eV, σ{sub 2} = 2.6 × 10{sup −15} cm{sup 2} whereas for the two low-temperature majority traps they were equal to E{sub 3} = 0.18 eV, σ{sub 3} = 9.7 × 10{sup −18} cm{sup 2} and E{sub 4} = 0.13 eV, σ{sub 4} = 9.2 × 10{sup −18} cm{sup 2}. The possible origin of the traps is discussed and the results are compared with data reported elsewhere.