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
    Broadband density fluctuation measurements using a heavy ion beam probe on the Texas Experimental Tokamak (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3360-3367 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Broad bandwidth (60 kHz ≤f≤500 kHz), long wavelength (k¯θ≤2 cm−1) density fluctuation measurements were made using a heavy ion beam probe on the Texas Experimental Tokamak (TEXT) [K. W. Gentle, Nucl. Technol./Fusion 1, 479 (1981)]. Fluctuation amplitudes and correlation length scalings do not correspond to linear or quasilinear drift wave theory. Power-weighted root-mean-square (rms) wave number estimates are much lower (〈k¯θ〉rmsρs≤0.1, ρs=[miTe]1/2/eB) than quasilinear theoretical expectations (k¯⊥ρs∼0.3). Core results indicate strong turbulence with a wave number spread, Δk∼k¯ at fixed frequency f, consistent with strong turbulence predictions, while edge results can be considered consistent with weak turbulence. In between the core and edge (0.6≤r/a≤0.8) is a transition region. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871170
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Radial electrostatic flux inferred from core measurements of potential and density fluctuations (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1278-1288 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Broadband potential fluctuations and electrostatic fluctuation induced particle flux have been measured in the core of a medium size tokamak plasma for the first time. Density fluctuations and wave numbers were simultaneously measured. Measurements indicate that radial electrostatic fluctuation induced particle flux in the core region, at the normalized radii of 0.17〈ρ〈0.38, due to modes with wave numbers less than 4 cm−1 is small in magnitude, is likely directed inward, and cannot account for particle flux predicted by the continuity equation and particle source codes. Estimates of electrostatic energy flux are also significantly less than values predicted via power balance analysis. Asymmetries in coherent density and potential fluctuation levels on closed flux surfaces are evident. Relative fluctuation levels ñ/n and φ˜ tend to increase with radius, and the fluctuations are Boltzmann-like in the region 0.17≤ρ≤0.38. The direction of mode propagation is in the electron diamagnetic drift direction. Corresponding phase velocities, vph∼3.5×105 cm/s, are similar to drift wave velocities. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1355674
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    An experimental counter-example to the local transport paradigm (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2292-2298 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The response of a tokamak discharge to a sharp drop in edge temperature differs significantly from that expected from typical local transport models in several important respects. Laser ablation of carbon induces large (ΔT/T≤70%), rapid (〈200 μs) electron temperature drops in the outermost region of the plasma, r/a≥0.9. This cold pulse proceeds through the outer plasma (r/a≥0.75), rapidly compared with power balance or sawtooth predictions. However, the pulse shrinks markedly thereafter, disappearing near r/a∼0.5. Within r/a∼0.3, the temperature rises promptly. The results are inconsistent with conventional local transport models; a nonlocal phenomenology, in which transport coefficients increase in the edge and decrease in the core, is suggested. The turbulence levels measured with a heavy ion beam probe increase near the edge but are unchanged in the core. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871252
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Evolution of the 2-MeV electrostatic energy analyzer for TEXT-Upgrade (abstract) : 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. 4582-4582 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The development of an electrostatic energy analyzer to be used with the 2-MeV heavy ion beam probe on the TEXT-Upgrade tokamak has presented several very interesting voltage breakdown phenomena. In order to maintain a 400-kV potential on large surface area plates (46.2 cm×152 cm) various configurations of support dielectrics, voltage feedthrough, plate materials, and plate geometry have been evaluated. Experimental evaluation of several designs and the resulting modifications leading to a working analyzer will be presented. This work was supported by the U.S. Department of Energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143675
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Enhanced sensitivity detectors for potential fluctuation measurements (abstract) : 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. 4578-4578 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method to improve the sensitivity of energy analyzers is being developed for use with heavy ion beam probes (HIBP). The method basically involves segmenting a single entrance slit into ten slits and modifying a detector. Theory and a simplified test shows that a factor of 10 improvement in sensitivity is possible. Previously, potential fluctuation measurements would have a signal to noise factor of unity when the rms fluctuation equaled 10−5×Vacc where Vacc is the accelerator voltage. The new 2-MeV HIBP on TEXT would be limited to potential fluctuations of greater than 20 Vrms when operating at full voltage. Measurements with the old system indicated that central potential fluctuations on TEXT were the order of 10 Vrms. The new detector should be able to measure down to 2 Vrms. A simplified geometry has been tested and showed a sensitivity as predicted, though a somewhat reduced range of operation. A test in an analyzer is planned. This work was supported by the U.S. Department of Energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143673
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Initial operation of the TEXT-Upgrade 2-MeV heavy ion beam probe (abstract) : 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. 4582-4582 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The new heavy ion beam probe diagnostic system on TEXT is presently operational at reduced energy. Thallium and cesium ion beams with energy up to 590 keV have been obtained using a single injection beamline and an energy analyzer that can be operated with low-energy beams only (≤590 keV). At full energy (up to 2 MeV) two injection beamlines and two energy analyzers (presently under construction) will allow access to 90% of the plasma cross section. Stable 2-MeV test beams with currents up to 10 μA have been obtained but not injected into the tokamak. The capacitive liner feedback control system allowed stable operations with ripple less than 100 V. Results of initial operations and preliminary measurements of density fluctuations are presented. This work is supported by the U. S. Department of Energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143676
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Broadband fluctuation wave number measurement technique using a heavy ion beam probe : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3058-3060 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The heavy ion beam probe (HIBP) measures localized density fluctuations in the plasma interior. These measurements can be used to calculate two point estimates of interior poloidal wave numbers. The results so far show wave numbers significantly lower than FIR scattering wave numbers and drift wave expectations. Experiments were performed on TEXT to look for possible sources of error in our wave number calculations. The HIBP effects that are considered the possible dominant error terms are finite sample volume size and path effect fluctuations as well as the possible existence of counter-propagating modes. An aperture experiment showed the presence of a finite sample volume effect, but not large enough to correct the measured wave numbers significantly. Simulations using HIBP data show that our processing techniques detect counter-propagating modes. Path effects are discussed. The error analysis so far shows the HIBP calculations to be accurate wave number measurements, but more study on path effects is needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141726
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    MHD magnetic fluctuation measurements using a heavy ion beam probe : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3061-3063 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes a technique for measuring magnetic fluctuations using a heavy ion beam probe (HIBP) and presents the results of the first experiment to measure locally the internal magnetic structure of MHD modes in a hot, tokamak plasma. In these experiments on the TEXT tokamak, the toroidal position of the HIBP beam at the detector is used to measure the toroidal component of the magnetic vector potential fluctuations, A˜φ, at a localized position in the plasma. In an axisymmetric system a purely local measurement is possible. However, the detection method employed and the asymmetries in the tokamak introduce path effects. The importance of the path effects is estimated through numerical simulations of the experiment, and it is found that in this experiment the path effects are small throughout much of the plasma. In addition, toroidal asymmetries reduce the signal amplitude, but do not greatly distort the radial profile. The accuracy of the numerical simulations and detection technique is tested in a plasma with a known A˜φ, with agreement obtained to within 5%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141727
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Poloidal asymmetry and gradient drive in core electron density and temperature fluctuations on the Texas Experimental Tokamak-Upgrade (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2013-2021 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron temperature and density fluctuations are measured in the core of the Texas Experimental Tokamak-Upgrade (TEXT-U) [P. H. Edmonds, E. R. Solano, and A. J. Wootton, in Proceedings of the 15th Symposium on Fusion Technology, Utrecht (Elsevier Science, Amsterdam, 1989), Vol. 1, p. 342] plasma across the poloidal cross section. The high spatial resolution of the heavy-ion beam probe (HIBP) and correlation radiometry of electron cyclotron emission (CRECE) reveal that both the density and temperature fluctuations are strongly poloidally asymmetric. Temperature fluctuation measurements indicate a broadband drift wave feature localized near the plasma equatorial plane on both the high- and low-field sides, which is consistent with density fluctuation measurements by far infrared (FIR) scattering. In contrast, the HIBP observes this feature localized only to the low-field side. Excellent spatial resolution allows us to investigate whether changes in the gradient affect the fluctuation amplitudes. We find that indeed, the temperature fluctuations increase with the electron temperature gradient. Results also link density fluctuations to changes in the density gradient. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871998
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Calibration and initial operation of the HIBP on the MST : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 564-567 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the first time, a heavy ion beam probe (HIBP) has been installed on a reversed field pinch, i.e., Madison symmetric torus (MST), to measure the plasma potential profile, potential, and electron density fluctuations, etc. The application of a HIBP on MST has presented new challenges for this diagnostic. The primary sources of difficulty are small access ports, high plasma, and, ultraviolet (UV) flux and a confining magnetic field produced largely by plasma currents. The requirement to keep ports small so as to avoid magnetic field perturbations led to the development of the cross-over sweep system. The effectiveness and calibration of this sweep system will be reported. In addition, this diagnostic is now operating with greater plasma/UV loading effects than most previous Rensselaer HIBPs. The plasma flux is reduced by using a magnetic suppression structure. The UV flux appears to be the dominant cause of the remaining loading, which is substantial. The magnetic field being largely produced by the plasma makes determination of measurement locations exclusively from trajectory calculations difficult. Initial operation results have shown that the magnetic field model we are using to calculate our ion trajectories has an inaccuracy of about 10%, and thus subsequent development of improved confining field models is important. Secondary signals have been detected, and the levels are smaller than that from the UV induced noises. Methods to increase the signal levels are discussed. A very rough estimation of the potential at a typical MST core location is 0.8–2 kV. Fluctuations in the frequency range 100–20 kHz have also been observed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310590
    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...