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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new steady-state, low-energy, and high-flux ion beam test device has been developed to study erosion, re-deposition, and hydrogen retention mechanisms of plasma facing materials under high flux conditions. Source plasma was produced by electron cyclotron resonance discharge with 2.45 GHz microwave. Ion extraction was made by spherical multiaperture triode electrodes to obtain high ion flux at the focal point. Ion extraction aperture geometry was designed so that high current density can be obtained in the case of low energy (〈500 eV) by applying high deceleration voltage. It was demonstrated that low-energy and high-flux ion beam can be produced by increasing deceleration voltage with the fixed acceleration voltage (beam energy). In the case of hydrogen beam energy of 300 eV, beam power density has rapidly increased with a deceleration voltage over accel–decel ratio 4, and maximum beam flux is 4.1×1020 H/m2 s. On the other hand, maximum beam flux of 3.6×1021 H/m2 s was obtained for 3 keV hydrogen beam. These fluxes are much higher than that of conventional mass analyzed ion beam (〈1.0×1020 H/m2 s). © 2002 American Institute of Physics.
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Effects of the ambient gas in the ion drift space on the transport property of the low energy (155 eV) and high brightness beam are studied experimentally. A bucket ion source with single-aperture triode extraction is used. Beam characteristics such as the divergence angle and the current density are improved by the increase in the ambient gas pressure in the high brightness beam (high deceleration voltage, −2000 V), but not in the low brightness beam (low deceleration voltage, −600 V). The beam spreading due to the space charge of the ion beam is seen at the low ambient gas pressure when the central current density, which is measured at 35 cm downstream side from the electrode system, exceeds 5 μA/cm2. The electron density in the ion-beam plasma increases with the ambient gas pressure, but the space charge is not sufficiently neutralized by the electrons produced by the ambient gas atom ionization. © 1995 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3443-3447 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For low-energy plasma ion source (〈1 keV), the narrow acceleration gap and application of high accel–decel voltage ratio are useful for obtaining high brightness ion beam. This paper describes these effects in a triode multiaperture extraction system on the characteristics of geometrical focusing by aperture displacement experimentally. Beam parameters such as focal length and beam divergence were estimated from a two-dimensional (axial and radial) power density profile by a Gaussian beamlet model. It is found that this model agrees very well with the beam power density profile. The relation of focal length with aperture displacement roughly agrees with the analytical model derived by Conrad. However, the effective gap width for the model is not simply determined from the aperture geometry. © 1995 American Institute of Physics.
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  • 4
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We have used cDNA encoding D-amino acid oxidase, and genomic DNA encoding cephalosporin acylase from Fusarium solani and Pseudomonas diminuta, respectively, to construct a novel hybrid 7-aminocephalosporanic acid (7ACA) biosynthetic operon under the control of regulatory elements from the alkaline ...
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  • 5
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The effects of source plasma parameters and space charge neutralization on energy spread of very low energy and high perveance ion beam have been studied experimentally. Plasma parameters of a bucket source were changed by shorting an arc chamber and a positive electrode (a plasma electrode) to deteriorate electron confinement. Although the change of plasma potential reflected the beam energy and the change of energy spread was observed, the relation between the plasma parameters and energy spread is unclear. Space charge neutralization of the ion beam by supplying thermal electron and increasing gas pressure in beam transport region showed reduction of the energy spread. This result suggests that the space charge effects of the ion beam plays an important role in energy broadening. © 1996 American Institute of Physics.
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  • 6
    ISSN: 1436-2813
    Keywords: intractable ascites ; peritoneovenous (PV) shunting ; Denver-type shunting tube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A total oftwenty six peritoneovenous shuntings were performed in our department between 1978 and 1984, on twelve cirrhotic and ten cancerous patients with intractable ascites, using Pudenz, LeVeen or Denver type shunting tubes. Reduced ascites was noted postoperatively with statistical significance in both the cirrhotic group (p〈0.05) and the cancerous group (p〈0.01), of whom eight cirrhotic and seven cancerous patients exhibited an abdominal girth reduced by 9.7cm (a 10.9 per cent reduction) in two weeks. A larger urinary output was noted in 13 patients, with a mean increase of 587 ml/day compared with the pre-shunting output. These patients lost a mean weight of 6.13 kg in two weeks, while the non-reduced ascites group gained weight. The post-shunting serum albumin level was higher in the reduced ascites group. The mean functioning periods of the shunts were 5.1 and 2 months, respectively for the cirrhotic and cancerous patients whose shunts were patent. The patients’ outcome was shown to depend on the disease itself, with the exception of one patient who died of disseminated intravascular coagulopathy following shunting. In comparing several types of shunting systems, the Denver-type was proven as being the most unlikely to plug or malfunction because of its simpler structure.
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  • 7
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to produce high brightness beam at energies below 100 eV, the effects of high deceleration voltage in a triode extraction system and plasma potential have been studied. Although the application of high deceleration voltage caused beam spreading, beam brightness was increased at least up to accel–decel ratio of 80. It is found that the reduction of sheath potential of the source plasma caused the increase in beam brightness under high deceleration voltage condition. In particular, it is desirable to reduce sheath potential at the energy below 50 eV because this potential is comparable to external applied acceleration voltage. © 1996 American Institute of Physics.
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  • 8
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to obtain a high brightness ion beam from a plasma ion source in the low energy region (150 eV), the effects of sheath potential on the ion beam characteristics such as beam divergence and brightness have been studied experimentally. A bucket-type ion source (magnetic multicusp ion source) with an accel–decel triode extraction system is used for the experiment. Bias voltage between a discharge chamber and a positive (plasma) electrode is applied for sheath potential control. Two types of electrode systems have been examined, such as straight hole aperture (S type) and recessed hole aperture (R type), and have found that the effects of the bias voltage on the beam characteristics depend on the type of aperture and the deceleration voltage. For an S-type system, the application of bias voltage improves the beam performance in a low deceleration voltage (−600 V), but not in a high deceleration voltage (−1600 V). For an R-type system, almost no improvement is observed in all deceleration voltages. Although the highest brightness is obtained in a deceleration voltage of −1600 V without the application of bias voltage in the S-type system, the significant fraction of the intersecting beam to the electrodes is present in this case.
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  • 9
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The measurements of spatial profiles of primary electron (high-energy tail electron) density in a magnetic multicusp ion source have been made in the cases of different current directions of "T''-shaped filaments, and its effects on the beam extraction have been studied. The axial profiles of arc plasma parameters in the ion source were measured by use of a movable Langmuir probe. A high-energy tail electron density ntail is calculated from the electron energy distribution function derived from probe current-voltage characteristics using Druyvesteyn's method. It is confirmed that the axial profiles of tail electron density ntail relates to the location of primary electron emission. The results indicate that higher ion-beam current is observed in the case that ntail and equivalent electron temperature Tequ are higher near the plasma electrode.
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  • 10
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A polarization-sensitive laser-light-scattering method is developed for simultaneous in situ measurements of properties (size, size dispersion, density, and refractive index) of particulates formed in processing plasmas. The developed system is applied to observe the growth processes of particulates in a range of their size larger than about 10 nm in rf silane plasmas. A size, a size dispersion (logarithm of a standard deviation of size), a density, and a refractive index of particulates in the plasmas are found to be 10–200 nm, about 0.1, 107–109 cm−3 and about 3–5i, respectively. The former three of such values agree fairly well with ones deduced from scanning electron microscopic (SEM) observation. These particulates grow through three phases of nucleation and initial growth, rapid growth, and growth saturation. Coexistence of two size groups of particulates with narrow size dispersions during and after the rapid growth phase verified by the SEM observation may be explained by a model taking into account coagulation between oppositely charged particulates. © 1996 American Institute of Physics.
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