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  • 1
    Digitale Medien
    Digitale Medien
    Index of refraction and its temperature coefficient in CdSe0.18Te0.82 at 10.2 μm wavelength (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 593-594 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The index of refraction and its temperature dependence were measured at 10.22 μm on CdSe0.18Te0.82 grown by the Bridgman technique. The results are n=2.67±0.02 (different than the value expected from Vegard's law), and (1/n)(dn/dt)=(3.89±0.07)10−5 °C−1. The absorption coefficient of the sample has also been measured, α=(0.79±0.05) cm−1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357049
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  • 2
    Digitale Medien
    Digitale Medien
    Melt-front velocity in laser-induced melting (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6694-6700 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Laser melting processes have been studied extensively, particularly for semiconductor substrates. Values for the velocity of the melt front have been determined by several experimental methods, and also calculated in numerical simulations of the melting processes. The velocity of the melt both during melting and recrystallization is of direct consequences for the material properties of the laser treated zone. Hence, a clear understanding of the physical parameters involved is essential. For laser pulses of a Gaussian shape, and whose duration is longer than a few tens of nanoseconds, expressions are derived for the melt-front velocity for the general case and for the limiting case of a point source. In either case the velocity turns out to be nonconstant. Hence, experimentally reported values may only be regarded as indicative of the maximum velocity achievable. The simple closed-form analytical expressions obtained in the present study are amenable for a direct analysis of relevant experimental results. Comparison made with some available data reveals a general agreement between theory and experiment. Ultra high-speed photography is one possible technique that may enable observation of the varying velocity of the lateral melt front.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345106
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  • 3
    Digitale Medien
    Digitale Medien
    The effect of multiple laser pulses on damage to thin metallic films (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 630-637 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The mechanical effects due to the application of multiple laser pulses to thin metallic films are studied. Particular attention is paid to systems involving thin aluminum films deposited on an insulating substrate such as silica. This film/substrate combination is widely employed in silicon semiconductor technology. In building such devices laser energy is sometimes used for the purpose of cutting conducting lines, while in other applications it is used to effect linking between two levels of metallization. Both processes have been greatly facilitated by employing a multiple-pulse scheme. The mechanism responsible for this effect is discussed and it is shown how the present model leads to a good agreement between the measured and calculated quantities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351347
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  • 4
    Digitale Medien
    Digitale Medien
    Chemistry of fluorine in the oxidation of silicon (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2975-2977 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The chemical environment of fluorine in the oxide layer of metal-oxide-semiconductor (MOS) structures has been examined by surface analytical spectroscopies. HF treatment of Si(100) results in subsurface SiF formation. Upon oxidation, oxyfluoride moieties are formed with a significant accumulation of fluorine throughout the oxide layer. These changes are correlated to the electrical integrity of MOS interfaces by performing Fowler–Nordheim electron injection studies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104686
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  • 5
    Digitale Medien
    Digitale Medien
    Correlations of heat and momentum transport in the TFTR tokamak (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1300-1305 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Measurements of the toroidal rotation speed vφ(r) driven by neutral beam injection in tokamak plasmas and, in particular, simultaneous profile measurements of vφ, Ti, Te, and ne, have provided new insights into the nature of anomalous transport in tokamaks. Low-recycling plasmas heated with unidirectional neutral beam injection exhibit a strong correlation among the local diffusivities, χφ≈χi〉χe. Recent measurements have confirmed similar behavior in broad-density L-mode plasmas. These results are consistent with the conjecture that electrostatic turbulence is the dominant transport mechanism in the tokamak fusion test reactor tokamak (TFTR) [Phys. Rev. Lett. 58, 1004 (1987)], and are inconsistent with predictions both from test-particle models of strong magnetic turbulence and from ripple transport. Toroidal rotation speed measurements in peaked-density TFTR "supershots'' with partially unbalanced beam injection indicate that momentum transport decreases as the density profile becomes more peaked. In high-temperature, peaked-density plasmas the observed gradient scale length parameter ηtoti=d ln Ti/d ln ne correlates reasonably well with predictions of the threshold for exciting ion-temperature-gradient-driven turbulence (ITGDT), as would be expected for plasmas at marginal stability with respect to this strong transport mechanism. In L-mode plasmas where ITGDT is expected to be too weak to enforce marginal stability, ηtoti exceeds this threshold considerably. However, preliminary experiments have failed to observe a significant increase in ion heat transport when ηtoti was rapidly forced above ηc (the threshold for exciting ITGDT) using a perturbative particle source, as would have been expected for a plasma at marginal stability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859545
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  • 6
    Digitale Medien
    Digitale Medien
    An instrument for measuring the momentum flux from atomic and charged particle jets (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3586-3591 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We have developed an instrument to measure the momentum flux from an intense plasma stream for which the standard techniques used for low-pressure gases (〈10 Torr) at room temperature are unsuitable. With a response time of 〈 50 ms, this device, a plasma momentum meter, can measure forces of 10−5–103 N onto surfaces of different materials immersed in dense plasmas (n(approximately-greater-than)1012cm−3). Such forces are transmitted predominantly by ionic and neutral species, with 10's of eV's of kinetic energy, are accompanied by high heat fluxes, and are pulsed. The momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer, a capacitance-type pressure gauge. This protects the transducer from thermal damage, arcing, and sputtering. An absolute force calibration of the PMM to 1% accuracy has been made and is described. A flat carbon target has been used in measurements of the momentum flux of He, Ne, Ar, and Kr plasmas produced in a magnetized linear plasma device.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141575
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  • 7
    Digitale Medien
    Digitale Medien
    Instrument for measuring the momentum flux from atomic and charged particle jets (abstract) : Eighth topical conference on high—temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3148-3148 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: We have developed an instrument to measure the momentum flux from an intense plasma stream for which the standard techniques used for low-pressure gases (〈10 Torr) at room temperature are unsuitable. This device, a plasma momentum meter, can measure forces of 10−5–103 Newtons with a response time of 〈50 ms onto surfaces of different materials immersed in dense plasmas (n(approximately-greater-than)1012 cm−3). Such forces are transmitted predominantly by ionic and neutral species, with 10's of eV's of kinetic energy, are accompanied by high heat fluxes, and are pulsed. The momentum flux onto a biasable target plate is transferred via a suspended quartz tube onto a sensitive force transducer, a capacitance-type pressure gauge. This protects the transducer from thermal damage, arcing, and sputtering. An absolute force calibration of the PMM to 1% accuracy has been made and is described. A flat carbon target has been used in measurements of the momentum flux of He, Ne, Ar, and Kr plasmas produced in a magnetized linear plasma device.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141666
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  • 8
    Digitale Medien
    Digitale Medien
    PPPL Lorentz orbit code : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3262-3264 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A code that integrates the Lorentz force equation has been developed to trace a single charged particle's trajectory under the influence of toroidally symmetric magnetic fields found in tokamaks. This code is used primarily to design and estimate the efficiency of charged fusion product probes, which detect escaping energetic ions such as the 1 MeV tritons, 3 MeV protons, 15 MeV protons, and 3.5 MeV alphas created in TFTR. This interactive code has also been used as a teaching tool to illustrate classes of orbits such as trapped and passing, as well as subtle orbital motions, e.g., precession of banana orbits in tokamaks, or orbits in dipole magnetic field configuration. This paper describes the code as well as recent modifications which (1) include Shafranov shifts of the magnetic surfaces, (2) use more realistic current density profiles, and (3) allow modeling of the detector and limiters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141608
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  • 9
    Digitale Medien
    Digitale Medien
    High-beta operation and magnetohydrodynamic activity on the TFTR tokamak (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1287-1290 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Magnetohydrodynamic (MHD) activity within three zones (core, half-radius, and edge) of TFTR [Plasma Physics and Controlled Nuclear Fusion Research 1986 (IAEA, Vienna, 1987), Vol. 1, p. 51] tokamak plasmas are discussed. Near the core of the plasma column, sawteeth are often observed. Two types of sawteeth are studied in detail; one with complete, and the other with incomplete, magnetic reconnection. Their characteristics are determined by the shape of the q profile. Near the half-radius the m/n=3/2 and 2/1 resistive ballooning modes are found to correlate with a beta collapse. The pressure and the pressure gradient at the mode rational surface are found to play an important role in stability. MHD activity is also studied at the plasma edge during limiter H modes. The edge localized modes (ELM's) are found to have a precursor mode with a frequency between 50–200 kHz and a mode number m/n=1/0. The mode does not show a ballooning structure. While these instabilities have been studied on many other machines, on TFTR the studies have been extended to high pressure (plasma pressure greater than 4×105 Pa) and low collisionality [vi@B|(a/2)〈0.002, ve*(a/2)〈0.01].
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.859544
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  • 10
    Digitale Medien
    Digitale Medien
    Investigation of global Alfvén instabilities in the Tokamak Fusion Test Reactor (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2122-2126 
    Details
    ISSN: 1089-7666
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Toroidal Alfvén eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into plasmas at low magnetic field in the Tokamak Fusion Test Reactor (TFTR) [Proceedings of the 11th International Conference on Plasma Physics and Controlled Fusion Research (IAEA, Vienna, 1987), Vol. 1, p. 51]. The injection velocities were comparable to the Alfvén speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtoothlike behavior and the crashes always coincide with TAE bursts. This indicates ejection of fast ions from the plasma until these modes are stabilized. The dynamics of growth and stabilization were investigated at various plasma currents and magnetic fields. The results indicate that the instability can effectively clamp the number of energetic ions in the plasmas. The observed instability threshold is discussed in light of recent theories. In addition to these TAE modes, intermittent oscillations at three times the fundamental TAE frequency were observed by Mirnov coils, but no corresponding signal was found in BES. It appears that these high-frequency oscillations do not have a direct effect on the plasma neutron source strength.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.860462
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