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  • 1
    Electronic Resource
    Electronic Resource
    Near-threshold electron emission from impact of slow van der Waals clusters and fullerene ions on clean gold (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 8254-8261 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Atomically clean polycrystalline gold has been bombarded by slow cluster ions (N2)+n (n≤120), Ne+n (n≤100), and Cq+60,70 (q=1–4) at kinetic energies from the apparent electron emission thresholds up to 6 kV times the cluster charge (qe). The resulting electron yields have been derived from the corresponding electron emission statistics. Grossly different electron yields were found for different cluster species of about equal masses and velocities, which is attributed to different partitions of the initial cluster kinetic energy among (a) inelastic binary collision processes involving cluster constituents and surface atoms, and (b) intramolecular vibrational excitation in the cluster ions (where possible). We found emission threshold velocities of ∼1×104 m/s, which is a lower velocity than where emission was observed in most other studies previously conducted. For (N2)+n cluster ions, clear evidence for a nonlinear behavior (i.e., increasing electron emission per cluster constituent with increasing cluster size) has been found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.465651
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  • 2
    Electronic Resource
    Electronic Resource
    Electron emission from clean gold bombarded by slow Auq+ (q=1–3) ions (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8198-8200 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Total electron yields for impact of slow singly, doubly, and triply charged gold ions on a clean polycrystalline gold surface have been precisely determined via current measurements for incident ions and emitted electrons. Results of this study are of relevance for a proposed method to establish a new mass standard by determining atomic mass via accumulation of ions to amounts that can be weighed with high accuracy. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373519
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  • 3
    Electronic Resource
    Electronic Resource
    A highly sensitive quartz-crystal microbalance for sputtering investigations in slow ion–surface collisions (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 3696-3700 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A quartz-crystal microbalance technique for measuring total sputter yields in ion–surface collisions is described. The electronic circuit to drive the quartz crystal ensures low noise and high frequency stability. By measuring total sputter yields for impact of singly charged ions on LiF target films a sensitivity limit of 0.5% of a monolayer per minute could be achieved. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149979
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  • 4
    Electronic Resource
    Electronic Resource
    Helium doped hydrogen or deuterium beam as cost effective and simple tool for plasma spectroscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 3723-3727 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Energetic neutral particles from neutral beam heating systems are widely used for active spectroscopic measurements of key plasma parameters in fusion experiments. Both the plasma discharges and the neutral beam systems are normally operated with hydrogen or deuterium. Helium beams are used in dedicated diagnostic beam lines as they offer deeper penetration and are subject to less background radiation and enable resonant double charge exchange with alpha particles. Neutral beam systems using pure helium either require specialized helium gas pumping with a pumping speed in excess of 1000 m3/h or are restricted to short pulses (normally less than 1 s). A doped hydrogen/helium beam combines the requirements for plasma heating and diagnostics without the need for sophisticated helium pumping. A small flow of helium gas is injected into the plasma source for the time helium particles are required. The helium current is typically 10% of the total extracted current. The reduction in heating power of the doped beam can be kept below 5%. The small amount of helium gas does not cause an excessive pressure rise along the beam line and does not reduce the reliability of the beam heating system. Doped deuterium/helium beams have been successfully tested and routinely used at JET. The Hel beam emission spectra obtained with a doped deuterium/helium beam produce sufficiently strong visible lines for spectroscopic applications. Furthermore, the simultaneous availability of helium and hydrogenic particles in the beam allows us to extend spectroscopic measurements to another atomic system and hence cross-check results from helium beams with those from hydrogenic beams. The only investment required is an additional helium gas inlet system into the ion source. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289678
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  • 5
    Electronic Resource
    Electronic Resource
    A 2.45-GHz electron cyclotron resonance multi-mA Li+ ion gun for fusion plasma diagnostics : Proceedings of the 5th international conference on ion sources (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1094-1096 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the purpose of neutral-lithium beam tokamak–plasma diagnostics we have developed a compact, high current (several tens of mA/cm2) 2.45-GHz electron cyclotron resonance (ECR) Li+ plasma ion source in coaxial geometry, coupled to a helium-buffered lithium feeding system working according to the heat pipe principle. The accel–decel-type ion extraction system features either seven holes or one single aperture. First experimental results for the extractable Li+ and He+ ions in both cw and pulsed-mode operations are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145074
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  • 6
    Electronic Resource
    Electronic Resource
    Fast lithium-beam spectroscopy of tokamak edge plasmas (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2285-2292 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Plasma-wall interaction and impurity transport processes in the outermost region of magnetically confined hot plasmas (the so-called plasma edge) must be well understood for successful development of future thermonuclear fusion reactors. To this goal, sufficiently detailed edge plasma diagnostics are in great demand. By injecting a fast Li beam into the edge plasma region, a great number of information can be obtained with excellent space and time resolution. This so-called Li-beam plasma spectroscopy gives access not only to edge plasma density profiles from the collisionally excited Li atoms, but also to the impurity concentration and temperature profiles via line emission induced by electron capture from the injected Li atoms by the impurity ions. Full utilization of all capabilities requires a reliable data base for the atomic collision processes involving injected Li atoms and plasma constituents (i.e., electrons, hydrogen ions, and relevant impurities in their various charge states), since a precise modeling of Li beam attenuation and excited-state composition has to be made for evaluating desired plasma properties from the related spectroscopical measurements. The most recent methodical improvement permits a fully consistent determination of absolute edge plasma density profiles by measuring only relative LiI line emission profiles. This is of special interest for investigating rapid edge plasma density fluctuations in connection with, e.g., ELMs, L-H mode transition, turbulence or edge cooling by impurity injection. This paper describes the capabilities of Li-beam edge plasma spectroscopy by way of illustrative examples from measurements at the tokamak experiment TEXTOR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144460
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  • 7
    Electronic Resource
    Electronic Resource
    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
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144274
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  • 8
    Electronic Resource
    Electronic Resource
    A versatile electron detector for studies on ion-surface scattering (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 1653-1657 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An innovative electron detector geometry for measuring electron multiplicities and absolute total electron yields from particle-induced electron emission is described. This setup has been successfully applied in coincidence measurements of slow singly and multiply charged ion-induced electron emission from a clean monocrystalline gold surface at grazing incidence of projectile ions. We describe characteristic features and operation of the electron detector which may also prove useful in various other experimental situations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149647
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  • 9
    Electronic Resource
    Electronic Resource
    Single-stage 5 GHz ECR-multicharged ion source with high magnetic mirror ratio and biased disk : Proceedings of fifth international conference on ion sources (1994)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1091-1093 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A low-cost, single-stage 5 GHz electron cyclotron resonance (ECR) multicharged ion source (MCIS) has been constructed for various atomic collision experiments. It features an axial magnetic field with a mirror ratio of up to five, and a magnetic hexapole field produced by a simple Nd–Fe–B permanent-magnet assembly. A disk probe axially mounted near the ECR resonance zone opposite to the ion extraction, and negatively biased with respect to the ECR plasma potential, permits reduction of the appropriate neutral feeding gas pressure by an order of magnitude, resulting in greatly improved ion charge state distributions, as normally offered by two-stage ECR–MCIS only. We present performance data for multicharged ion production from Ar and N2, including measured ion current emittances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145073
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  • 10
    Electronic Resource
    Electronic Resource
    Surface-induced dissociation of singly and multiply charged fullerene ions (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 5053-5057 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Collisions of singly and multiply charged ions C60z+ (z=1,2,3,4,5) with a hydrocarbon-covered stainless steel surface have been investigated; product ions of fragmentation and pickup reactions were determined as a function of the collision energy (100–500 eV) and the projectile charge z. All ions scattered off the surface are singly charged. The extent of fragmentation increases with the collision energy and the projectile charge. However, the increase of fragmentation with the charge of the projectile is less pronounced than expected from a full conversion of electronic energy, gained in the neutralization process, into internal energy of the ion. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1288032
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