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  • 1
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Detailed measurements of the ion velocity distribution function are used to test representations of the electrostatic degrees of freedom of slightly non-Maxwellian plasmas. It is found that fluid theory does not describe the data very well because there exist multiple closely spaced kinetic electrostatic modes. New wave branches appear that theoretically should persist as weakly damped modes even with Te∼Ti. Both a sum over discrete dispersion relations and the Case–Van Kampen spectral representation can be used to provide working descriptions of the data, but the latter has certain advantages. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
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    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 1253-1262 
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Spectral line shifts have been observed in the Dα transition of neutral deuterium in the Alcator C-mod [I. H. Hutchinson, Proceedings of the IEEE 13th Symposium on Fusion Engineering (IEEE, Piscataway, 1990), Vol. 1, p. 13] tokamak and interpreted as Doppler shifts due to a neutral flow of approximately 5×103 m/s. The emission originates from plasma at the inner wall, as indicated by the Zeeman patterns of the transition. The direction of the flow changes when the plasma transitions from a limited to a diverted configuration. In all cases, the flows are directed toward the point of contact with the wall or divertor plate. Narrow spectral profiles have been observed for the Dα transition near the midplane and within the divertor. Temperatures not higher than 0.86 eV are indicated for the divertor measurements. A difference in plasma conditions for separate locations along a single line of sight has been observed. © 2001 American Institute of Physics.
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  • 3
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 3448-3458 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Virtually all practical applications for intense ion beams require that the beam pulses be generated at high repetition rates. This paper reports the development of the first high pulse rate, long-lived ion beam diode. It is a magnetically insulated diode which has produced ∼75 keV proton and carbon beam pulses of 1.0–2.5 A/cm2 and 100 ns duration at up to 90 Hz in four pulse bursts. It has also produced 125 keV, 5 A/cm2 Ar beams at a steady 1 pulse per 30 s for over 1000 pulses between failures in many runs. This diode employs a magnetically confined anode plasma ion source, and the high repetition rate pulsed power systems are based upon saturable magnetic switching. © 1995 American Institute of Physics.
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  • 4
    Digitale Medien
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 342-344 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A magnetic spectrometer has been constructed and used to measure energy distributions of intense proton beams in the range ∼0.3–2.5 MeV from ion diodes. Rutherford scattering foils are used to attenuate the beam before magnetic analysis. CR-39 track detectors provide time-integrated records, while an array of p-i-n diode detectors provides time-resolved data at discrete energies. The spectrometer was calibrated in the range between 0.3 and 2.0 MeV with monoenergetic protons from a Van de Graaff accelerator. The overall precision of this calibration is better than ±10 keV. Spectral measurements of intense proton beams transported in low-pressure gases are presented. © 1995 American Institute of Physics.
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  • 5
    Digitale Medien
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 912-912 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A novel, spatially resolved diagnostic is being developed to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as is envisioned for ion-driven inertial confinement fusion. The diagnostic technique uses laser-induced fluorescence spectroscopy, and can be varied to measure either small or large fields. Small fields, as expected in ballistic beam transport, produce Zeeman shifts, ΔλZ, much smaller than the transition linewidth Δλ. High sensitivity to measure these sub-Doppler shifts is achieved by a variation on the Babcock technique.〈citeref RID="R1" STYLE="SUPERIOR"〉1 Large fields, as expected in self-pinched beam transport, produce ΔλZ larger than Δλ. These ΔλZ will be resolved using a Fabry–Pérot interferometer, in a novel technique similar to that for small fields. Results from benchtop experiments using calibrated B fields for the small-field technique will be presented. Available results from a proof-of-principle experiment for the large-field technique will also be presented.© 1999 American Institute of Physics.
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  • 6
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    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5108-5117 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A recently developed high pulse rate intense ion beam diode has been exploited to measure the relative density profile of electrons in the ion diode's acceleration gap as a function of time. This diode was magnetically insulated and it produced 100 keV Ar+ beams at up to 4 A/cm2 using an active anode plasma ion source. The diode also had a backfill of 10−2 Torr of He that was collisionally excited by energetic electrons in the acceleration gap. When the excited He atoms radiatively decayed, the emitted light was measured and used to deduce the relative electron density profile with space and time resolution. The profile was peaked toward the center of the gap and dropped off significantly toward both the anode and the cathode. The absence of electron density near the physical cathode is evidence for magnetic field profile modification from the diamagnetic drift of the electrons in the diode. With a macroscopic electric field of order 100 kV/cm, the electron current takes many tens of nanoseconds, from the moment the cathode begins to emit, to reach the Child–Langmuir current. The extent to which this limit is exceeded depends strongly on the profile of the insulating magnetic field and appears to be dominated by the dynamics of the electron flow in the diode gap. In contrast, the delay between when electrons are first observed in the gap spectroscopically and when the ion beam is first formed is independent of the magnetic field profile. This delay is about the time that it takes an argon ion to transit the acceleration gap, suggesting that ion inertia is the rate limiting factor. © 1998 American Institute of Physics.
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  • 7
    Digitale Medien
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 12-16 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Modifications to a multianode position-sensitive electron detector employed for time-resolved electron energy loss spectroscopy (TREELS), aimed at reducing interchannel crosstalk, improving response uniformity, and increasing the maximum supportable event rate, are described. The critical importance of the resolution of the electron-dispersing element in determining the multiplex advantage of multidetector analyzers is explored, and its relevance to the maximum attainable multiplex advantage in TREELS is discussed.
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  • 8
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1032-1035 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A novel, spatially and temporally resolved diagnostic is being developed to measure small B fields by detecting Zeeman shifts much smaller than the transition linewidth. This diagnostic technique will be used to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as envisioned for particle beam fusion. High sensitivity is achieved by a variation on the Babcock technique using laser-induced fluorescence (LIF) spectroscopy. The LIF from a J=1→0 transition in a probe species is viewed parallel to B. In this direction, ΔM=0 fluorescence is not observed, while ΔM=±1 fluorescence is right- and left-circularly polarized and can be measured separately using polarization filters. If a narrow-band pump laser is tuned to a half-maximum point of the unsplit transition line, the presence of the magnetic field shifts one of the ΔM=±1 absorption transitions into resonance with the laser and shifts the other transition further out of resonance. For small field strengths, the difference in the fluorescence signals is proportional to the Zeeman split. © 1997 American Institute of Physics.
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