ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Experimental determination of gap scaling in a plasma opening switch (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3790-3796 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments were performed to investigate the coupling between a ∼0.5 μs conduction-time, ∼0.5 MA conduction-current plasma opening switch (POS), and an electron-beam (e-beam) diode. Electrical diagnostics provided measurements of the voltage at the oil-vacuum insulator and at the diode as well as anode and cathode currents on the generator and load sides of the POS. These measurements were combined with a flow impedance model to determine the POS gap over a range of conduction times and e-beam diode impedances, and for two POS-to-load distances. A comparison of the inferred POS gap at peak power with the critical gap for magnetic insulation indicates that the POS gap is always saturated in both switch-limited and load-limited regimes. This POS gap-size scaling with load impedance is consistent with an opening mechanism dominated by erosion and not J×B forces. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287914
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A new kind of light-generation mechanism: Incandescent radiation from clusters (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 607-613 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel technique to generate hot refractory metal clusters is explained. A regenerative chemical cycle is used to form small clusters inside a microwave-excited high-pressure discharge which heats the clusters to 4700 K (rhenium) or 3800 K (tungsten). The discharge's emission spectrum exhibits a strong continuum, which is the incandescent radiation of clusters. The spectral shapes of the continua and the positions of their maxima (Re: 550 nm; W: 700 nm) are characteristic of the refractory metal. A first theoretical description of the clusters' radiation can be based on the Mie theory. Measurements of emission and absorption coefficients are performed to determine the optical properties and temperatures of the clusters. The existence of clusters with an average size of about 2.5 nm is proved by a laser scattering experiment. The properties of the cluster radiation, especially the continuous spectrum and the high luminous efficiency, are attractive for lighting applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355274
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Charged particle flow in plasma-filled pinched-electron-beam diodes (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 2274-2286 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma-filled pinched-electron-beam diode experiments have been performed on the Gamble II (1.5 MV, 800 kA, 60 ns) pulsed power generator at Naval Research Laboratory. These plasma-filled diode (PFD) experiments show three phases of behavior: a low impedance phase followed by a phase of rapidly increasing impedance that culminates in a relatively constant vacuum impedance phase. The duration of the low impedance phase as well as the final operating impedance depends on the prefill plasma density. The charged particle flow in the PFD is studied with one-dimensional (1-D) and two-dimensional (2-D) simulation models. These simulation models show the formation of growing sheaths at both electrodes during the low impedance phase. The end of the low impedance phase in the simulations coincides with the two sheaths meeting in the center of the anode-cathode (A-K) gap. Based on these observations, an analytic model was developed that treats the low impedance phase as symmetric bipolar sheaths. The analytical model adequately predicts the duration of the low impedance phase predicted by the 1-D simulation model. Differences between the bipolar model and the experiments or 2-D simulations can be explained in terms of magnetized sheaths which enhance the ion current over the bipolar level and cause the sheath to grow faster than the bipolar model. During the rapidly increasing impedance phase, the simulations show that the cathode sheath quickly expands to completely fill the A-K gap. At this time, charged particle flow in the simulation models are consistent with the vacuum gap spacing. Experimentally, the higher density, longer conduction time, PFD shots exhibited a significantly lower final impedances than predicted by 2-D simulations. This difference is probably caused by expanding electrode surface plasmas produced by the interaction of the plasma source with one or both electrode surfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354711
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Self-pinched transport of an intense proton beam (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 346-358 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion beam self-pinched transport (SPT) experiments have been carried out using a 1.1-MeV, 100-kA proton beam. A Rutherford scattering diagnostic and a LiF nuclear activation diagnostic measured the number of protons within a 5 cm radius at 50 cm into the transport region that was filled with low-pressure helium. Time-integrated signals from both diagnostics indicate self-pinching of the ion beam in a helium pressure window between 35 and 80 mTorr. Signals from these two diagnostics are consistent with ballistic transport at pressures above and below this SPT pressure window. Interferometric measurements of electron densities during beam injection into vacuum are consistent with ballistic transport with co-moving electrons. Interferometric measurements for beam injection into helium show that the electron density increases quadratically with pressure through the SPT window and roughly linearly with pressure above the SPT window. The ionization fraction of the helium plateaus at about 1.5% for pressures above 80 mTorr. In the SPT window, the electron density is 3 to 20 times the beam density. Numerical simulations of these beam transport experiments produce results that are in qualitative agreement with the experimental measurements. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873803
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Plasma opening switch conduction scaling (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3893-3901 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma opening switch (POS) experiments performed on the Hawk generator [Commisso et al., Phys. Fluids B 4, 2368 (1992)] (750 kA, 1.2 μs) determine the dependence of the conduction current and conduction time on plasma density, electrode dimensions, and current rise rate. The experiments indicate that for a range of parameters, conduction is controlled by magnetohydrodynamic (MHD) distortion of the plasma, resulting in a low density region where opening can occur, possibly by erosion. The MHD distortion corresponds to an axial translation of the plasma center-of-mass by half the initial plasma length, leading to a simple scaling relation between the conduction current and time, and the injected plasma density and POS electrode dimensions that is applicable to a large number of POS experiments. For smaller currents and conduction times, the Hawk data suggest a non-MHD conduction limit that may correspond to electromagnetohydrodynamic (EMH) field penetration through the POS plasma. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871018
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Gap formation processes in a high-density plasma opening switch (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 299-309 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A gap opening process in plasma opening switches (POS) is examined with the aid of numerical simulations. In these simulations, a high density (ne=1014–5×1015 cm−3) uniform plasma initially bridges a small section of the coaxial transmission line of an inductive energy storage generator. A short section of vacuum transmission line connects the POS to a short circuit load. The results presented here extend previous simulations in the ne=1012–1013 cm−3 density regime. The simulations show that a two-dimensional (2-D) sheath forms in the plasma near a cathode. This sheath is positively charged, and electrostatic sheath potentials that are large compared to the anode–cathode voltage develop. Initially, the 2-D sheath is located at the generator edge of the plasma. As ions are accelerated out of the sheath, it retains its original 2-D structure, but migrates axially toward the load creating a magnetically insulated gap in its wake. When the sheath reaches the load edge of the POS, the POS stops conducting current and the load current increases rapidly. At the end of the conduction phase a gap exists in the POS whose size is determined by the radial dimensions of the 2-D sheath. Simulations at various plasma densities and current levels show that the radial size of the gap scales roughly as B/ne, where B is the magnetic field. The results of this work are discussed in the context of long-conduction-time POS physics, but exhibit the same physical gap formation mechanisms as earlier lower density simulations more relevant to short-conduction-time POS. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871106
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    On the flow in the unobstructed space between shrouded corotating disks (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1760-1770 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model of a computer hard disk drive was constructed and measurements of the air flow in the unobstructed space between a pair of disks were obtained. The disks were centrally clamped to a common hub, and rotated within an axisymmetric (cylindrical) enclosure or shroud. Measurements of the circumferential velocity component were made at five radial locations and three rotation rates (Ω=300, 1200, and 3600 rpm) using a laser-Doppler velocimeter. The resulting mean and rms circumferential velocity profiles are presented and discussed. The data show that the circumferential velocity component profiles are fairly uniform in the axial direction in the space between the disks, except near the shroud where the flow is strongly sheared. The circumferential velocity peaks at a critical radius. Between the hub and the critical radius location the flow is in solid body rotation. Between the critical radius and the shroud the circumferential velocity decreases to zero, gradually at first and then very quickly as the shroud is approached. Analysis based on simplified force balance considerations facilitates the interpretation of the experimental observations and leads to improved understanding of the complex flow phenomena. Numerical calculations of the present configuration assuming axisymmetric steady flow were performed by Chang et al. (submitted to Int. J. Heat Mass Transfer). These calculations show reasonable agreement with the averaged velocity data but, for the reasons discussed, fail to reproduce features of the rms distribution associated with nonturbulent flow unsteadiness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857703
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Characterization of a microsecond-conduction-time plasma opening switch (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2368-2376 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents data and analyses from which emerges a physical picture of microsecond-conduction-time plasma opening switch operation. During conduction, a broad current channel penetrates axially through the plasma, moving it toward the load. Opening occurs when the current channel reaches the load end of the plasma, far from the load. During conduction, the axial line density in the interelectrode region is reduced from its value with no current conduction as a result of radial hydrodynamic forces associated with the current channel. A factor of 20 reduction is observed at opening in a small, localized region between the electrodes. When open, the switch plasma behaves like a section of magnetically insulated transmission line with an effective gap of 2 to 3 mm. Increasing the magnetic field in this gap by 50% results in an improvement of 50% in the peak load voltage and load current rise time, to 1.2 MV and 20 nsec, respectively. An erosion opening mechanism explains the inferred gap growth rate using the reduced line density at opening. Improved switch performance results when the maximum gap size is increased by using a rising load impedance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860207
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Erratum: "Theoretical modeling and experimental characterization of a rod-pinch diode" [Phys. Plasmas 8, 4618 (2001)] (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 3643-3643 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1493795
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Theoretical modeling and experimental characterization of a rod-pinch diode (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4618-4636 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The rod-pinch diode consists of an annular cathode and a small-diameter anode rod that extends through the hole in the cathode. With high-atomic-number material at the tip of the anode rod, the diode provides a small-area, high-yield x-ray source for pulsed radiography. The diode is operated in positive polarity at peak voltages of 1 to 2 MV with peak total electrical currents of 30–70 kA. Anode rod diameters as small as 0.5 mm are used. When electrode plasma motion is properly included, analysis shows that the diode impedance is determined by space-charge-limited current scaling at low voltage and self-magnetically limited critical current scaling at high voltage. As the current approaches the critical current, the electron beam pinches. When anode plasma forms and ions are produced, a strong pinch occurs at the tip of the rod with current densities exceeding 106 A/cm2. Under these conditions, pinch propagation speeds as high as 0.8 cm/ns are observed along a rod extending well beyond the cathode. Even faster pinch propagation is observed when the rod is replaced with a hollow tube whose wall thickness is much less than an electron range, although the propagation mechanism may be different. The diode displays well-behaved electrical characteristics for aspect ratios of cathode to anode radii that are less than 16. New physics understanding and important properties of the rod-pinch diode are described, and a theoretical diode current model is developed and shown to agree with the experimental results. Results from numerical simulations are consistent with this understanding and support the important role that ions play. In particular, it is shown that, as the ratio of the cathode radius to the anode radius increases, both the Langmuir–Blodgett space-charge-limited current and the magnetically limited critical current increase above previously predicted values. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1403016
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...