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  • 1
    Digitale Medien
    Digitale Medien
    Proton beam targets shot on PBFA-II : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4779-4781 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: In recent proton beam experiments on PBFA-II, foam-filled gold targets and gas-filled spherical exploding pushers were shot as physics targets. Surrounding these targets were gold foils used to characterize the beam. The target fabrication and characterization are presented in this paper.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1143560
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  • 2
    Digitale Medien
    Digitale Medien
    Modeling the ion-source performance of an electron-beam ion trap (invited) : Proceedings of the fourth International Conference on Ion Sources (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2806-2811 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Several key features of the electron-beam ion trap (EBIT) enable it to provide superior ion-source performance for many applications requiring ultra-high-charged ions. This paper briefly reviews these features and the operating conditions in the existing EBITs. The present performance of the EBIT as an ion source is demonstrated by producing and extracting ions up to Th80+ and U70+ at microsecond-wide ion beam pulses of about 104 ions per second. Using as examples the production of U92+, U90+, and Dy66+, modeling results are presented to show how the fundamental processes limit the quality and quantity of ions that can be obtained from an upscaled EBIT.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1142812
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  • 3
    Digitale Medien
    Digitale Medien
    Measurements and code comparison of wave dispersion and antenna radiation resistance for helicon waves in a high density cylindrical plasma source (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 703-712 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Helicon wave dispersion and radiation resistance measurements in a high density (ne(approximate)1019−1020 m−3) and magnetic field (B〈0.2 T) cylindrical plasma source are compared to the results of a recently developed numerical plasma wave code [I. V. Kamenski and G. G. Borg, Phys. Plasmas 3, 4396 (1996)]. Results are compared for plasmas formed by a double saddle coil antenna and a helical antenna. In both cases, measurements reveal a dominance of the m=+1 azimuthal mode to the exclusion of most other modes; in particular, no significant m=−1 mode was observed. The helical antenna, designed to launch m〈0 and m〉0 modes in opposite directions along the field, resulted in an axially asymmetric discharge with very little plasma on the m〈0 side of the antenna. For both antennas, good agreement of the antenna radiation resistance and wave dispersion with the model was obtained. It is concluded that unshielded antennas formed from current loops with an important |m|=1 component for the conditions of our experiment, couple most of their power to the m=+1 helicon mode and thus have negligible parasitic, nonhelicon plasma loading. This result greatly simplifies calculations of power balance in these sources by identifying the helicon as the mode by which energy is transferred to the plasma. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.873307
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  • 4
    Digitale Medien
    Digitale Medien
    Anisotropic effective mass and scattering of electrons in mismatched heteroepitaxial films (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 6542-6549 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: InP layers grown epitaxially on silicon substrates show a pronounced anisotropy of the transverse magnetoresistance. We use this effect to study the ensuing anisotropy of the effective mass and scattering mechanisms of electrons. We investigated samples with an electron concentration from 7×1016 to 9.6×1017 cm−3 at temperatures ranging from 4.2 to 30 K in magnetic fields of up to 15 T. The sample with the lowest electron concentration showed an anisotropic negative magnetoresistance which we attribute to weak localization. This allows the characteristic times for inelastic scattering (coherence time) and for spin–orbit interaction to be determined. For the InP layers on Si of higher electron concentration we measured for the first time Shubnikov-de Haas oscillations, showing again anisotropy of the effective mass and of the Dingle temperature. We quantitatively ascribe differences from the bulk values to biaxial mechanical strain, distorting the Fermi sphere of bulk material to an ellipsoid. We assume that the observed anisotropies are due to a preferential orientation of crystal defects as a result of differences in the thermal expansion coefficient of the InP film and the Si substrate. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.370159
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  • 5
    Digitale Medien
    Digitale Medien
    Projection x-ray microscope powered by highly charged ions (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 204-209 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Recombination of slow highly charged ions at the surface of a target foil can be used as a source of x rays for a projection x-ray microscope. In a first test of this concept, a low emittance beam of Ar18+ and Ar17+ ions from an electron beam ion trap was focused with einzel lenses to a 20 μm full width at half maximum spot on a beryllium target foil. The 3 keV x rays from radiative deexcitation of the ions were used to obtain a magnified image of an electroformed nickel mesh with 20 μm resolution by projection onto a CCD camera. Prospects for substantial improvements in resolution and intensity are discussed. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1148496
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  • 6
    Digitale Medien
    Digitale Medien
    Confinement in a cryogenic penning trap of highest charge state ions from EBIT (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3472-3478 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: The retrapping of highly charged Xe44+ and Th68+,72+ ions extracted from an "electron-beam ion trap'' (EBIT) is demonstrated after injection of the ions into RETRAP, a cryogenic Penning trap (up to 6 T magnetic field) currently with an open cylinder design. Ion extraction in a short pulse (5–20 μs) from EBIT, essential for efficient retrapping, is employed. The ions are slowed down upon entering a deceleration tube mounted above the trap within the magnetic field. The potential is then rapidly (100 ns) decreased, enabling low-energy ions to enter the trap. Capture efficiencies up to 25% are observed via detection of the delayed ion release pulse with a detector below the trap. Signal voltages induced in a tuned circuit due to single and multiple ions have been observed by tuning the ion resonant axial oscillation frequencies for different ions. Results from transporting and retrapping of the ions, as well as their detection, are described and the trapping efficiency is discussed. The motivation for these studies is to cool the trapped very highly charged ions to low temperatures (〈4 K) in order to perform ultrahigh-resolution precision spectroscopy, collision studies at ultralow energies, and to observe phase transitions in Coulomb clusters of highly charged ions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1144525
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  • 7
    Digitale Medien
    Digitale Medien
    Distinction between multicharged ion species with equal q/m (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 3499-3502 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We present a new technique for selective, highly sensitive, absolute detection of different multiply charged ion species with equal charge-to-mass ratios in mixed multicharged ion beams. This is achieved by exploiting the statistics of potential electron emission as induced by the ion beams on a clean metal surface. The applicability of the method is illustrated by way of different practical examples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1144274
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  • 8
    Digitale Medien
    Digitale Medien
    In-plane effective mass of electrons in InGaAs/InP quantum wells (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2828-2830 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We measured the in-plane effective mass for electrons in multiquantum wells in InGaAs/InP by the Shubnikov–de Haas effect. We varied the well width from 8.6 down to 2.3 nm where the enhancement of the effective mass is predicted to be very pronounced. The electron concentration was in the range of 3×1011 cm−2, so that band filling can be neglected. The variation of the effective mass from 0.045 to 0.067m0 is in accordance with current theories. We discuss the effect of the interface roughness and ionized impurities on the scattering times as found from our experiments. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.358694
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  • 9
    Digitale Medien
    Digitale Medien
    COMPARISON OF THE EFFECTS OF DEPOLARIZING AGENTS AND NEUROTRANSMITTERS ON REGIONAL CNS CYCLIC GMP LEVELS IN VARIOUS'ANIMALS (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 26 (1976), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract— The effects of 121 mm-K+, 10 mm-glutamate, 5 mm-GABA, 1 mm-glycine, 0.1 mm-NE, and 1–10 μmACh on cyclic GMP levels in tissue slices prepared from cerebral cortex and cerebellum of mouse, rabbit, guinea-pig, cat, and rat were studied. Basal levels of cyclic GMP in the cerebella of mice, guinea-pigs and cats were 4–15 and 70 pmol/mg prot in rat, whereas in the cerebral cortex of the same animals, levels were only 0.6–2 pmol/mg prot. In contrast, basal levels of the cyclic nucleotide were 1–2 pmol/mg prot in both of these regions in rabbit brain. Only 121 mm-K+ was capable of increasing cyclic GMP levels in all the tissues studied. Elevations ranged from 30% in rat cerebral cortex to 2800% in mouse cerebellum. Glutamate produced a 30–1000% rise of cyclic GMP levels in all tissues except rabbit cerebellum. NE elevated levels of cyclic nucleotide 2- to 3-fold in slices of cerebellum from all species studied but had no effect in cerebral cortex. GABA and glycine had no effect in any tissue except mouse cerebellum. ACh had no consistent effect on levels of cyclic GMP in any brain region investigated. These results suggest that mechanisms regulating cyclic GMP levels in mammalian CNS vary among brain regions and among animal species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1976.tb01506.x
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  • 10
    Digitale Medien
    Digitale Medien
    Retention and supply of zebra mussel larvae in a large river system: importance of an upstream lake (2004)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 49 (2004), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 1. Persistence of zebra mussel populations in river systems probably depends upon the presence of upriver sites capable of hosting self-recruiting adult populations that act as sources of larvae. In this paper we examine the importance of Lake Pepin, a natural riverine lake in the Upper Mississippi River, as an upriver source of larvae to the downstream populations of zebra mussels.2. Field studies and modelling suggest that Lake Pepin plays a major role in maintaining zebra mussel populations in the Upper Mississippi River. Long water residence times in Lake Pepin allow for self-recruitment under the right hydraulic conditions. Larval abundance was low to absent upstream of the lake but increased dramatically downriver in all 3 years of the study. Travel time estimates in the Upper Mississippi River show that newly fertilised larvae drifting out of Lake Pepin can contribute substantially to the major downstream peak in larval abundance. In contrast, backwater and other off-channel sites are unlikely to drive main-channel abundance patterns. Larval abundances in off-channel sites were less than or equal to those in the main channel.3. A key factor in assessing the importance of Lake Pepin as a source population was the abundance of early stage, unshelled larvae. Studies that consider only abundances of older shelled stages (visible by cross polarised lighting) may yield misleading results. Results of this study suggest that efforts to control zebra mussels in the Upper Mississippi River should focus on controlling adult populations within Lake Pepin and reducing or eliminating larvae exiting the lake.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.2004.01237.x
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