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  • 1
    Electronic Resource
    Electronic Resource
    Temperature fluctuations and plasma edge turbulence in the Brazilian tokamak TBR (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 971-977 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To investigate the tokamak turbulence, a set of Langmuir probes and a triple probe have been designed and used in the TBR [J. Fusion Energy 12, 529 (1993)] to measure average and fluctuating values of density, potential, and temperature of the plasma edge. The obtained results showed a significant influence of the temperature fluctuations in the transport parameters. Namely, taking into account this influence, the density and plasma potential power spectra were obtained, and the turbulence parameters reevaluated. Furthermore, the computed cross-power-spectra showed appreciable linear correlation, and the cross-bispectra showed a quadratic mode coupling between temperature fluctuations and other quantities. Significant bicoherence between these fluctuations was observed. Finally, for a fluctuation monitored at two probe points, no preferential direction for energy cascading was detected. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871802
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of resonant magnetic perturbations on plasma edge turbulence (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 329-336 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work reports alterations on plasma-edge equilibrium profiles and on edge turbulence, and anomalous transport induced by resonant perturbing magnetic fields in the TBR (Brazilian Tokamak) tokamak [J. Fusion Energy 12, 295 (1993)]. Thus, these perturbations have reduced the equilibrium parameters and the spectral power of the fluctuations and enhanced their phase velocity. They have also reduced the particle flux at the plasma edge. All these electrostatic edge parameters have been computed by taking into account temperature fluctuation corrections. Although the perturbation slightly affected just the linear correlation between electrostatic fluctuations, its bispectral analysis shows a reduction of the quadratic mode coupling. Furthermore, the energy transferred between different spectral components, with and without the magnetic perturbation, did not have the same direction for all fluctuations. Finally, the normal probability distribution functions of the fluctuations show significant non-Gaussian features, although the fluctuating potential distribution became near Gaussian with the magnetic perturbation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872093
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  • 3
    Electronic Resource
    Electronic Resource
    Time-resolved analysis of Mirnov oscillations (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3710-3715 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We discuss the application of time-resolved spectral analysis to interpret the magnetohydrodynamic or Mirnov oscillations in tokamaks. As an example, the technique is applied to analyze the Mirnov oscillations measured in the small tokamak TBR-1 with and without external helical perturbations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143602
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  • 4
    Electronic Resource
    Electronic Resource
    A complex probe for measurements of turbulence in the edge of magnetically confined plasmas (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 4418-4423 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: To improve the turbulence characterization and the estimation of the transport processes at the plasma edge, we designed and installed, in the Brazilian tokamak (TBR), a complex probe that consisted of five single Langmuir probes, a four-channel triple probe, and magnetic probes. In this work, we describe in detail this diagnostic system and present experimental examples of simultaneously measured plasma parameters and electrostatic and magnetic turbulent fluctuations in the TBR tokamak. This procedure permits to investigate any coupling between these two kinds of oscillations. Furthermore, our results confirmed that corrections due to electron temperature fluctuations are relevant for turbulence characterization. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148406
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  • 5
    Electronic Resource
    Electronic Resource
    Electrostatic ion probe for tokamak-plasma-edge diagnostic (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2205-2209 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electrostatic probe for ion temperature and density measurements was built and tested in the scrape-off region of the TBR-1 small tokamak. The main parameters involved in the design and details of the construction of the probe are presented. The electron discrimination and the probe efficiency for ion detection were checked by measuring the probe current as a function of the collector retraction length for a constant voltage. The results for the ion temperature and density obtained from the characteristic curves are discussed and compared with previous measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138683
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  • 6
    Electronic Resource
    Electronic Resource
    Signal analysis of transients in pulsed photoacoustic spectroscopy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 363-373 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A finite difference model was constructed to describe the origin of the complex transients in pulsed photoacoustic spectroscopy signals. With inclusion of boundary conditions and material interfaces, the model is shown to give qualitative agreement with experimental transients. The model provides insight into the results of varying the photoacoustic-cell materials and/or geometric configuration for cell optimization. The transients are found to contain significant information regarding resonant modes in the photoacoustic cell assembly. The transient signal behavior is explained in terms of these resonant cavity modes, and it is determined which cell cavities are relevant to a given time segment of the signal. Analytical detection limits are correlated with each point on the transient signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144258
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  • 7
    Electronic Resource
    Electronic Resource
    Simultaneous measurement of ion and electron temperatures in the scrape-off layer of a small tokamak (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2700-2708 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes a system composed of an electrostatic ion probe associated with an electronic circuit designed and constructed to be used in the scrape-off layer of the TBR-1 tokamak for simultaneous measurements of local electron and ion temperatures. The electronic circuit is discussed. Details of the mechanical structure and dimensions of the probe can be found in another article [Rev. Sci. Instrum. 57, 2205 (1986)]. The circuit is composed of a sweep generator followed by an amplifier. The sweep time can be varied from 50 μs to 50 ms and the probe voltage amplitude from 0 to 200 V. The circuit supplies a maximum current of 250 mA, is short-circuit protected, and provides cable capacitance neutralization. The ion current is detected by a current transformer sensitive to currents as low as 20 μA. The total probe current is measured by the voltage drop in a resistor inserted in the circuit. The system has been tested in the TBR-1 boundary plasma and showed good performance with a time resolution better than 500 μs. The obtained results showed that, for TBR-1 boundary plasma, the ion temperature is about two times the electron temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1142203
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  • 8
    Electronic Resource
    Electronic Resource
    Micro-Raman study of polydioxolane/LiClO4 and NaClO4 electrolytes (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3352-3354 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A micro-Raman study of polydioxolane (PDXL)/NaClO4 and PDXL/LiClO4 polymeric electrolytes has been carried out in a wide range of salt concentration, at room temperature. The ion–ion interactions and the precipitation of salt microcrystals in the host polymer have been evidenced by means of a line shape analysis of the band associated to the totally symmetric stretching mode (ν1) of the ClO4− anion. The Raman spectra results reveal changes of the crystallinity of the PDXL/MCLO4 systems which are directly related to the salt concentration. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115244
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  • 9
    Electronic Resource
    Electronic Resource
    Remote photoacoustic measurements in aqueous solutions using an optical fiber (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3729-3732 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A photoacoustic spectrometer was developed for remote optical absorption measurements in aqueous solutions using an 85-m optical fiber to deliver pulsed tunable dye laser radiation to a sample cuvette located in a glove box. The spectrometer was tested using aqueous solutions of praseodymium ions. Beer's law was verified down to a concentration of 8×10−6M for an equivalent absorptance of 3.2×10−5 cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141544
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  • 10
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    Intrinsic dielectric properties of magnetodielectric La2CoMnO6 (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-06-05
    Description: Manganite with a double perovskite structure is an attractive material because of its interesting magnetoelectric and dielectric responses. In particular, colossal dielectric constant (CDC) behavior has been observed in La 2 CoMnO 6 (LCMO) at radio frequencies and at room temperature. In this paper, we used infrared-reflectivity spectroscopy to study a LCMO ceramic obtained through a modified Pechini's method to determine the phonon contribution to the intrinsic dielectric response of the system and to investigate the CDC origin. The analysis of the main polar modes and of the obtained phonon parameters indicate that the CDC effect of LCMO is of pure extrinsic origin. In addition, we estimated the dielectric constant and the quality factor of the material in the microwave region to be ε′ s  ∼ 16 and Q u  × f  ∼ 124 THz, which verifies that LCMO is appropriate for application in microwave devices and circuitry.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics (AIP)
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