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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 630-637 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3586-3591 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 593-594 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2975-2977 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 198-200 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low pressure chemical vapor deposition (CVD) process of SiO2 from SiH4 and O2 has been analyzed. For deposition at pressures ranging from 10−3 to 3 Torr, with no carrier gas, the process is dominated by fast gas-phase reactions. In situ analytical techniques, such as mass spectrometry and high-resolution electron energy loss spectroscopy, indicate that hydroxyl groups are reaction products and are imbedded into the growing oxide at temperatures from 300 to 600 °C. Presence of these groups is detrimental to the electrical properties of metal-oxide-semiconductor (MOS) structures, e.g., by causing low-field breakdown and by increasing the interface state density. Low-pressure (SiH4/O2) oxides are thus principally not well suited for gate-oxide applications because of their underlying chemistry.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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].
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3262-3264 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 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.
    Type of Medium: Electronic Resource
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