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  • 1
    Electronic Resource
    Electronic Resource
    Investigation of the ETA-BETA II plasma edge by surface analysis of collector probes (1991)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 13 (1991), S. 435-453 
    Details
    ISSN: 0392-6737
    Keywords: Integrated electronics ; VLSI ; Plasma interactions ; Plasma diagnostic techniques and instrumentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary To investigate the ion flux escaping from the plasma and the impurity flux released by the wall, collector probes made of graphite, silicon and titanium have been exposed to the deuterium plasma confined in the toroidal device ETA BETA II. The damages on the collector surfaces have been surveyed by a scanning electron microscopy (SEM) apparatus. The deuterium and impurity retention have been measured by elastic recoil detection (ERD) and Rutherford backscattering spectroscopy (RBS) techniques respectively. The implantation build-up has been investigated as a function of the exposure time. The deuterium dose in graphite saturates after a few discharges, whereas the metal impurities exhibit a linear increase in time. The deuterium flux and its radial dependence, inferred from the implanted concentrations, have been compared with those measured by Langmuir probes. Metal impurities have been identified and their relative abundances have been compared with the material wall composition. The impurity flux is found consistent with the global content in the plasma derived by spectroscopic measurements. The deuterium dose measured in different samples has been related to the backscattering coefficient of the materials. Finally, to investigate the damage on sample probes facing the plasma particle flow, erosion probes made of vitreous graphite with silver implanted at a fixed depth have been exposed to the plasma and the thickness change after exposure recovered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02452128
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of a DC magnetron sputtering device (2005)
    Bradford : Emerald
    Compel 24 (2005), S. 261-270 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Purpose - The aim of this paper is to obtain an extensive experimental characterization of a DC magnetron sputtering device used for plasma processing of materials. Design/methodology/approach - Models and measurements are combined for an interdisciplinary characterization of a DC magnetron sputtering device. Langmuir probes are used for the plasma characterization; the magnetic field is measured by using Hall probes and the data are used to validate a magnetostatic three-dimensional numerical analysis of the device; precision mechanical measurements are done for the target erosion profile and the results are related to a simple estimation formula; a simple model is proposed for the target heating. Findings - Data on magnetic and electric fields, electron temperature and density, plasma potential and target erosion are provided. An estimation of the target heating is proposed. Finally, an application concerning thin film deposition is reported. Research limitations/implications - Measurement of the target surface temperature for the validation of the proposed target heating estimation has not been done. Originality/value - In the field of the electromagnetic processing of materials, the reported extensive device characterization is a valuable set of information for an optimized utilization of DC magnetron sputtering devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321640510571282
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  • 3
    Electronic Resource
    Electronic Resource
    Improved confinement and transport studies in the reversed field experiment (RFX) : 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. 1830-1836 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents results obtained on the Reversed Field eXperiment, RFX [G. Rostagni, Fusion Engineering and Design 25, 301 (1995)], on the study of local transport properties of the RFP configuration both in the standard regime and during improved confinement phases obtained with poloidal current drive. The plasma core is dominated by magnetic turbulence, as indicated by both energy and particle transport analysis. Diffusivity decreases toward the edge and is reduced in the core at high Lundquist number. The edge region is apparently not affected by dynamo mode turbulence and determines global confinement in standard operation. Particle and heat diffusivity in this region show a favorable dependence with increasing density. The most interesting feature of the edge region of RFX consists of a sheared radial electric field with shearing rate comparable to that observed in tokamaks. Indications of turbulence reduction in the shear layer have been obtained. Enhanced energy confinement has been produced by pulsed poloidal current drive (PPCD). A clear reduction of the dynamo activity has been observed with a decrease of core thermal diffusivity to level comparable to the edge and global confinement improvement up to a factor of 3. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873441
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental evidence of long-range correlations and self-similarity in plasma fluctuations : 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. 1885-1892 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To better understand long time transport dynamics, techniques to investigate long-range dependences in plasma fluctuations have been applied to data from several confinement devices including tokamaks, stellarators, and reversed field pinch. The results reveal the self-similar character of the edge plasma fluctuations. This implies that the tail of the autocorrelation function decays as a power law and suggests that there is a superdiffusive component of the anomalous transport. Rescaled fluctuation and turbulent flux spectra from different devices also show a strong similarity. For a range of parameters corresponding to the tokamak ohmic regime and equivalent power for other devices, the spectral decay index may show a universal character.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873490
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  • 5
    Electronic Resource
    Electronic Resource
    Relaxation phenomena and on axis q limit in a reversed field pinch (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1489-1496 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For sustained discharges at high values of the pinch parameter aitch-theta large disturbances appear on the plasma current, loop voltage, and toroidal magnetic field signals. An increase of both plasma resistance and magnetohydrodynamic (MHD) activity measured at the edge is observed. The onset of such phenomena is found at values of aitch-theta〉1.5 and the amplitude of the disturbances increases with aitch-theta. The oscillations are interpreted as the effect of major current redistributions occurring periodically in the central region of the plasma. Relating experimental field profiles and aitch-theta values, the effect of the current redistribution is the recovery of the on axis q value when a lower limit is exceeded. From the experimental measurements such a lower limit has been found to be approximately q(0)≥2a/(3R).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866262
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  • 6
    Electronic Resource
    Electronic Resource
    A fast moving diagnostic system on the RFX experiment : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 403-406 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A fast rotating graphite arm equipped with two Langmuir probes has been developed to investigate the temperature, density, and plasma potential profiles at the edge in the reversed field pinch experiment RFX. The system, driven by an electromagnetic torque, allows a 5 cm radial insertion in about 20 ms with a magnetic field of 0.3 T. The motion of the arm takes place on a plane having an angle of 45° with respect to the direction of the poloidal magnetic field. The probe collecting area is constant during the movement. The initial and final positions of the graphite arm are monitored by electrical contacts. To reconstruct the motion of the equipment, an equivalent lumped-constant network has been developed. The equivalent resistance and inductance are measured before each discharge. By this system radially resolved measurements of edge plasma parameters in a single RFX plasma discharge have been obtained. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149310
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  • 7
    Electronic Resource
    Electronic Resource
    Langmuir and heat flux probes for RFX : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4711-4713 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A movable limiter made of graphite and instrumented with an array of Langmuir and heat flux probes has been developed for the reversed field pinch experiment RFX. The limiter is mushroom shaped and designed to be exposed to the edge plasma for a discharge duration ≈250 ms. The distribution of the probes on the limiter surface allows simultaneous collection, in a single discharge, of edge parameters at different angles and radial positions. A bellows drive system with three degrees of freedom allows the instrumented limiter to be rotated and translated to investigate the spatial structure of the edge plasma. Cables and feedthroughs have been designed for 1-kV voltage and 5-A current. The power supply provides an output voltage ±100 V and a maximum current 4 A. Specific software has been developed for the automatic analysis of the Langmuir probes data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143615
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  • 8
    Electronic Resource
    Electronic Resource
    Automatic fast fitting of single Langmuir probe characteristics on RFX : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 365-368 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An array of single Langmuir probes is routinely used in the RFX reversed field pinch for time-resolved measurements of edge electron density and temperature. In order to allow an automatic analysis of the large number of current–voltage characteristics, three different methods have been developed, which consider restricted subsets of data with voltage lower than an upper cutoff value. The first one determines this limiting voltage by a neural network based technique, combined with criteria for the rejection of too noisy characteristics. In the second one a standard fitting routine is applied repeatedly to the data while varying the upper cutoff voltage. The third one consists of a numerical technique, where the best fit is obtained by minimizing a properly defined cost function. An error index is also calculated, which allows the reliability of the results to be easily estimated. The best results have been achieved using the last two methods.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147831
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  • 9
    Electronic Resource
    Electronic Resource
    Target emission probe for suprathermal electron detection : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 431-433 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and preliminary results of a target emission probe (TEP), applied to the continuous detection of suprathermal electrons in the edge of fusion plasmas, is presented in this paper. This diagnostic, developed for the RFX reversed field pinch experiment, is based on the measurement of the x-ray emission from a material target, exposed to the edge plasma, due to the bremsstrahlung of the electrons. The diagnostic has been successfully tested in RFX and a clear indication of the presence of a mostly unidirectional fast electron flow in the RFX plasma edge has been found. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146370
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  • 10
    Electronic Resource
    Electronic Resource
    Experimental measurements and modelling of the structure of the radial electric field in RFX (2000)
    Springer
    Czechoslovak journal of physics 50 (2000), S. 1387-1396 
    Details
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The experimental determination of the radial electric field E r and the associated E × B drift velocity at the edge of RFX is presented and possible mechanisms responsible for its generation are discussed. E r measurements by means of an array of Langmuir probes and those deduced from Doppler spectroscopy of impurity lines agree fairly well. In particular the rotation velocity of the plasma edge has been determined from the Doppler shift of a C III emission line. The observation of other ions characterised by different radial positions, such as B IV and C V, has allowed an estimate of the velocity shear. Typical values of plasma rotation at the edge are around 10 km/s while the velocity shear is of the order of (105–106)s−1 in the spontaneous layer, a few cm thick, usually observed in standard discharges. Plasma rotation has been artificially modified by both positive and negative edge biasing and the associated increase or decrease of the fluid velocity is well in agreement with the radial electric field change. The modification of E r during edge biasing and Pulsed Poloidal Current Drive (PPCD) are also reported and interpreted within a momentum balance model. Analytical and self-consistent Monte Carlo models at the plasma edge suggest that impurities have a relevant role in the generation of the radial electric field, due to their relatively large Larmor radius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022843529120
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