Library

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
    Omegatron mass spectrometer for analysis of ion concentrations in hydrogenic plasmas : 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. 623-626 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe an omegatron-type mass spectrometer used for measurement of the molecular and atomic ion concentrations as well as the ion species temperatures in hydrogenic plasmas. The experiments were performed in the PISCES-A linear plasma experiment with electron densities n(approximate)1011–1012 cm−3, ion temperatures Ti(approximate)2–8 eV, electron temperatures Te(approximate)3–30 eV, and magnetic fields B=0.8–1.9 kG. The resulting mass spectra show clear evidence of atomic hydrogen H+, as well as of the molecular ions H2+ and H3+, with H+ and H3+ usually being dominant. It is found that large electron repeller voltages ((approximate)−200 V) are important for preventing electrons from entering the diagnostic region and ionizing the residual gas. The relative peak heights for the different ions are found to vary as a function of ion repeller voltage, probably due to differences in ion temperature. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310594
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A fast phosphor imaging diagnostic for two-dimensional plasma fluctuation measurements : 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. 953-956 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A plasma imaging diagnostic is being developed using a fast time response ZnO:Zn phosphor disk to image plasma density fluctuations in a two-dimensional (2D) region. The plasma sensor consists of an 8.9 cm diameter phosphor coated aluminum disk that is inserted into the plasma and is excited by incident electrons resulting in a cathodoluminescent emission image. The phosphor light distribution is then interpreted as plasma density fluctuations using sheath theory and the phosphor response function. The local luminance S of fluctuating phosphor light is dependent on the incident electron energy Ee and current density through the equation S(r,t)=e∫R(Ee)(v⋅n(circumflex))fe(r,v,t)d3v, where R(Ee) is the energy dependent response function of the phosphor. The phosphor persistence time of 1–10 μs (emulsion dependent) combined with fast intensified charge coupled device camera shutter speeds enables the imaging of plasma fluctuations on microsecond range time scales. Broadband turbulent phosphor light fluctuations (f≤500 kHz) have been measured with photodiode detectors and compared with Langmuir probe data. The 2D phosphor images show density profiles consistent with radial Langmuir probe measurements. Temporal and spatial resolution of the phosphor diagnostic enables 2D imaging of plasma turbulence and coherent modes. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1329658
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Disruption mitigation studies in DIII-D : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1872-1879 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data on the discharge behavior, thermal loads, halo currents, and runaway electrons have been obtained in disruptions on the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 2A 441 (1985)]. These experiments have also evaluated techniques to mitigate the disruptions while minimizing runaway electron production. Experiments injecting cryogenic impurity "killer" pellets of neon and argon and massive amounts of helium gas have successfully reduced these disruption effects. The halo current generation, scaling, and mitigation are understood and are in good agreement with predictions of a semianalytic model. Results from "killer" pellet injection have been used to benchmark theoretical models of the pellet ablation and energy loss. Runaway electrons are often generated by the pellets and new runaway generation mechanisms, modifications of the standard Dreicer process, have been found to explain the runaways. Experiments with the massive helium gas puff have also effectively mitigated disruptions without the formation of runaway electrons that can occur with "killer" pellets. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873445
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Particle confinement improvement during 2.45 GHz lower-hybrid current-drive experiments (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2288-2291 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Particle confinement behavior during 2.45 GHz lower-hybrid current drive has been investigated on the Versator II tokamak [Phys. Fluids 29, 1985 (1986)]. It is found that during combined Ohmic and rf current drive the global particle confinement time τp increases by up to a factor of 2 compared to purely Ohmically driven discharges, as observed in earlier 800 MHz experiments at lower densities n¯e ≤6×1012 cm−3. In the present experiments, τp increases have been observed at densities up to n¯e =2×1013 cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866113
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Particle confinement and the anomalous Doppler instability during combined inductive and lower-hybrid current drive (1986)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 29 (1986), S. 1985-1993 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Increases in average density have been observed during lower-hybrid current-drive experiments (LHCD) on the Versator II tokamak [Phys. Rev. Lett. 48, 152 (1982)], and on other LHCD experiments where inductive-Ohmic and lower-hybrid current drive are combined. In the present experiment it is found that this density increase is the result of an improvement in global particle confinement time τp in comparison to purely Ohmic discharges with similar plasma parameters. Furthermore, it is found that the improved confinement deteriorates when the anomalous Doppler relaxation instability of the anisotropic high-energy electron tail becomes unstable during LHCD, and the loss rate of tail electrons increases. However, energetic electron losses alone are at least an order of magnitude too small to explain this deterioration in particle confinement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.865626
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Experimental measurements of lower-hybrid wave propagation in the Versator II tokamak using microwave scattering (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2101-2112 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of 139 GHz microwave scattering experiments has been performed on the Versator II tokamak (B. Richards, Ph.D. thesis, Massachusetts Institute of Technology, 1981) to study the propagation of externally launched 0.8 GHz lower-hybrid waves. During lower-hybrid current drive, the launched waves are found to follow a highly directional resonance cone in the outer portion of the plasma. Wave power is also detected near the center of the plasma, and evidence of wave absorption is seen. Scattering of lower-hybrid waves in k space by density fluctuations appears to be a weak effect, although measurable frequency broadening by density fluctuations is found, Δω/ω=3×10−4. In the detectable range (2.5〈N(parallel)〈5.5) the N(parallel) spectra inferred from the scattering measurements are quite similar above and below the current drive density limit. Numerical modeling of these experiments using ray tracing is also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859622
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Measurement of suprathermal electron confinement by cyclotron transmission (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1421-1426 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The confinement time of suprathermal electrons is determined experimentally from the distribution function determined via wave transmission measurements. Measurements of the lowest moment of the distribution perpendicular to the B field as a function of the parallel electron momentum as well as the global input power allow the suprathermal electron confinement time (τse ) to be calculated during lower-hybrid and inductive current drive. Finite particle confinement is found to be the dominant energy loss term for the suprathermals and improves with plasma current and density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859566
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The anomalous Doppler instability during lower-hybrid current drive (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2110-2118 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The anomalous Doppler instability is investigated for two-dimensional velocity distributions f(v(parallel),v⊥) appropriate for lower-hybrid current drive. In this case, in contrast to the runaway electron problem, this mode becomes unstable at high density when the ratio ω2pe/ ω2ce is sufficiently large. Increasing the maximum velocity v2 of the rf (radio-frequency) plateau, v1≤v(parallel) ≤v2, is also a destabilizing influence. In this paper expressions are given for the growth rate of the electrostatic waves obeying the dispersion relation ω=ωpe (1+ω2pe/ ω2ce)−1/2 k(parallel)/k, employing both analytic expressions for f(v(parallel),v⊥) and numerical solutions for f from the two-dimensional Fokker–Planck equation. The analytical and numerical results are in close agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866146
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Measurement of the correlation spectrum of electrostatic potential fluctuations in an ECRH Helimak plasma (1993)
    Springer
    Journal of fusion energy 12 (1993), S. 289-293 
    Details
    ISSN: 1572-9591
    Keywords: Plasma turbulence ; anomalous transport ; plasma fluctuations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Measurements of the length and time scales of turbulent potential fluctuations were carried out on the MIT Versatile Toroidal Facility (VTF). Plasmas were produced by ECRF heating in a novel toroidal configuration which we have termed the Helimak. The configuration consists of a toroidal fieldB φ of approximately 800 gauss and a vertical fieldB z of typically 10 gauss, produced by a Helmholtz coil.T e is approximately 10 eV. The density exhibited a peaked profile havingn max ≈ 2×1010 cm−3 and a density gradient scale length of ∼10 cm. The fluctuation experiments were conducted using a mobile vertical array of eight Langmuir probes. At major radii outside the density peak, the vertical correlation lengths λc⊥ of fluctuations were found to be on the order of 5–10 cm for fluctuation frequencies below 3–8 kHz, and on the order of 1–2 cm at higher frequencies. At major radii on the inner slope of the density peak, a new feature appears in the spatial coherence function consisting of a second peak at a probe separation which scales linearly with vertical field. This observation indicates that these fluctuations have a correlation length on the order of 2πR 0∼600 cm in the direction parallel to the helical magnetic field lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01079672
    Library Location Call Number Volume/Issue/Year 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...