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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1054-1056 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A volume source, based on the high efficiency ion source (HIEFS), is being developed for D+ production in steady state operation. The source will be optimized for the extraction of atomic deuterium ions with high current densities. It was found that a maximum deuterium ion beam current density of 210 mA/cm2 can be achieved with a D+ fraction above 90%. At an extraction voltage of 35 kV and with an aperture radius of 4 mm, the source delivers 61 mA D+. After a description of the source and the experimental setup, the results of detailed studies of the beam composition in dependence of the plasma parameters are presented. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1249-1251 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source is planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 μm patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of a rf-generated plasma. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1012-1014 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: For the European spallation source, a volume source based on the high efficiency source is being developed. The source will be optimized to produce high current densities in pulsed operation. A pulse generator delivering 1–1.5 ms pulses was installed. Furthermore, cesium was supplied to the plasma generator from an external oven. The cesium injection was optimized for a low e/H− ratio and a high current. We obtained a current density of 70 mA/cm2. This way, with an aperture radius of 4.25 mm, an H− current of 40 mA was extracted at an extraction voltage of 22 kV. After a description of the source and the experimental setup, measurements of the beam current density and the e/H− ratio will be presented in this article. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 836-838 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: For the International Fusion Materials Irradiation Facility (IFMIF) scenario, a 140 mA deuterium beam in continuous wave (cw) mode with an atomic yield of above 85% is required. The normalized root-mean-square emittance should be less than 0.2 π mm mrad at the entrance of a RFQ. As part of a conceptual design for IFMIF, a new ion source has been developed and is tested at the Institut für Angewandte Physik in Frankfurt. The ion source is of the volume type with a tungsten cathode driving the discharge. Both cw and pulsed mode are possible and were studied. First experiments were carried out with deuterium. 80 mA deuterons with a D+ fraction of above 90% were extracted [A. Maser et al., Rev. Sci. Instrum. 67, 1054 (1996)]. In order to avoid neutron generation by the d–d reaction, hydrogen was used instead of deuterium later on. As far as the ion source and plasma production processes are concerned, the use of hydrogen instead of deuterium is equivalent because of their similar atomic shells. Recently, a 200 mA proton beam at 55 kV was extracted in cw mode (according to Child–Langmuir, 200 mA H+ corresponds to 140 mA D+) with a H+ fraction of 93%. This article will give a detailed description of the ion source and the essential experimental results. Especially, the influence of important physical parameters (such as discharge current and strength of the filter field) on the H+ fraction was studied. By using different kinds of auxiliary gases, the influence on the H+ fraction and the noise level were investigated, too. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 1039-1041 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A new version of the high efficiency source is being developed for the European Spallation Source. The goal of these experiments is to produce a nearly pure H− ion beam with a low electron to H− ratio and high current (70 mA). To achieve this, the discharge chamber is divided into two parts of different plasma parameters by means of a filter magnetic field. Furthermore, the plasma chamber is aligned unsymmetrically with respect to the z axis of the extractor. We obtained a current density of 10 mA/cm2 for an arc power as small as 1 kW. In preliminary experiments, a beam of 10 mA was extracted at an extraction voltage of 8 kV (1.8% impurities). Measurements of the beam current density, electron to H− ratio, and the ion composition for a wide range of discharge conditions will be presented in this article. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 6898-6910 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The title reaction is studied using guided ion beam mass spectrometry. Absolute reaction cross sections are measured as a function of kinetic energy from thermal to 40 eV, and three endothermic product channels are observed. The dominant SiF++SiF3 channel is only slightly endothermic, while the SiF+3 +SiF and SiF+2 +SiF2 channels have much higher thresholds. The SiF+3 cross section magnitude is about half that of SiF+, while the SiF+2 cross section is an order of magnitude smaller than that of SiF+. A second feature which appears in the SiF+2 cross section is due to dissociation of SiF+3 . There is evidence that SiF+ and SiF+3 are produced via a direct mechanism. Competition between these two channels is interpreted in terms of molecular orbital correlations and qualitative potential energy surfaces. One surface is found to correlate only with the SiF+3 +SiF channel, while another correlates diabatically with this channel and adiabatically with the SiF++SiF3 channel. Competition on this latter surface has an energy dependence which is consistent with the Landau–Zener model. Reaction thresholds are analyzed to yield 298 K heats of formation for SiFx and SiF+x species. From an evaluation of these and literature values, we recommend the following values: ΔH0f(SiF+) =170.4±2.2 kcal/mol, IP(SiF)=7.54±0.16 eV, ΔH0f (SiF3)=−258±3 kcal/mol, and IP(SiF3)=9.99±0.24 eV.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1521-1529 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The endothermic reaction of Al+ with O2 is studied using a guided ion-beam apparatus. The reaction cross section is measured as a function of kinetic energy from 0 to 20 eV. The threshold energy for the reaction, E0, is determined from an empirical model to be 3.64±0.04 eV. Phase space calculations of the cross section performed with E0 as the only adjustable parameter yield a similar result, E0=3.60±0.02 eV, and predict the absolute magnitude of the reaction cross section within experimental error. We conservatively quote the threshold energy as 3.62±0.12 eV which is somewhat higher than the thermodynamic threshold calculated using literature thermochemistry, 3.40±0.16 eV. This may indicate that a slight barrier to the reaction exists, or that AlO+ is produced in an excited state, or that the literature thermochemistry needs revision. Our results suggest D00 (AlO+)≥1.50±0.12 eV and I.P.(AlO)≤9.75±0.13 eV.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1066-1068 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A volume source based on the high efficiency source is being developed for heavy ion production. Bismuth was chosen for exemplifying investigations because of its low melting point. The ion source is driven by an arc discharge ionizing bismuth atoms which are evaporated from an oven inside the source chamber. It has been optimized to produce a beam with a fraction of singly ionized bismuth above 92%. A multiaperture extraction system was built consisting of seven holes with a radius of 3 mm each. For that system, the perveance limit was achieved at a beam current of 70 mA and an extraction voltage of 27.5 kV. The corresponding emission current density amounts to 35 mA/cm2. This value was obtained for an arc power of only 280 W. Furthermore, the emittance of a beam extracted from the multiaperture extraction system has been determined with a high power emittance scanner. It amounts to 0.27π mm mrad (80%, normalized, 4 rms). In this case, the emittance of a single beam is 0.017π mm mrad. This article will give a detailed description of both the source and the experimental setup. In addition, various dependencies between the plasma parameters and the beam composition are presented. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 2213-2224 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Guided ion-beam techniques are used to measure the cross sections for reaction of SiF4 with Ar+, Ne+, and He+ from thermal to 50 eV. Charge transfer followed by loss of F atoms are the sole processes observed. All SiF+x (x=0–4) products are observed, except for SiF+4 from reaction with Ne+ and He+, and Si+ from reaction with Ar+. At high energies, the dominant products are SiF+3 in the Ar system, and SiF+ in both the Ne and He systems. There is some evidence in the Ne system for an excited state of SiF+3 at 5.7 eV. In the Ar+ and Ne+ reactions, the observed energetics are consistent with literature thermochemistry, but with He+, reaction barriers are observed. A value of ΔH0f,298 (SiF+3)=−30.1±0.9 kcal/mol is derived, which is in agreement with previous values but is much more precise. The observed product distributions and energetics are explained by consideration of the potential energy surfaces and the difference in ionization potentials of the rare gases. Finally, the relationships of these reactions to plasma deposition and etching are discussed.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2296-2302 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Guided ion-beam techniques are used to measure the cross sections for reaction of CF4 with Ar+, Ne+, and He+ from thermal to 50 eV. Dissociative charge transfer followed by successive loss of F atoms are the major processes observed. Only CF+x (x=1–3) products are observed in the reactions of Ar+ and Ne+. With He+, in addition to the CF+x products, both C+ and F+ are seen at high kinetic energies. Reaction rates for these reactions are also given and compared with previous measurements. It is found that the energy dependence of the cross sections can be understood by considering the energies needed to access specific electronic states of the CF+4 ion.
    Materialart: Digitale Medien
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