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  • 1
    Electronic Resource
    Electronic Resource
    Fast bolometric diagnostic in the RFX reversed field pinch experiment : 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. 4714-4716 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Bolometric measurements are performed in the RFX reversed field pinch experiment by means of a low noise miniaturized multichannel metal resistor bolometer module. The first tests on RFX, an experiment with geometrical dimensions comparable with those of large tokamaks but characterized by a much faster plasma dynamics, show that this thin film bolometer can be operated with high bandwidth and high time resolution in very different fusion experiments. A new data analysis technique, which allows the derivation of the power absorbed by the bolometer at a high time resolution (Δt=3×10−5 s) for the study of fast phenomena is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143616
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  • 2
    Electronic Resource
    Electronic Resource
    First results of reverse field experiment vertical time-of-flight : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 607-610 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The charge exchange neutral particle outfluxes and ion temperature are important quantities for the determination of the power balances and the plasma's energetic content; therefore they constitute a long term issue of reversed field pinch research. In order to improve the experimental knowledge of these plasma quantities, in the reversed field experiment a vertical time-of-flight (TOF) neutral particle analyzer (NPA) has been recently installed. It sees the plasma along a vertical chord, whose impact parameter is about half radius, and it is meant to complement the other two NPAs, which are installed on the equatorial plane. In this article, the new vertical TOF is reported, with particular attention to its more original components. An "in situ" method to calibrate the electron multiplier gain absolutely is described in detail. The first measurements of the ion temperature are reported, showing the reliable operation of the system and the acceptable signal-to-noise ratio obtained up to now. The results are also compared with the measurements of the horizontal NPAs mainly in the experimental regime of high plasma density. Possible improvements of the new diagnostic and its use in combination with a neutral particle beam are also briefly described and discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1316760
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  • 3
    Electronic Resource
    Electronic Resource
    Soft x-ray and bolometric tomography in RFX (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1256-1260 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The article presents the design and the first results of a new eight camera, soft x-ray (SXR) and bolometric tomography which has been installed in RFX, a large (R=2 m, a=0.46 m), high current reverse field pinch experiment operating in Padova. The main features of the diagnostic, which has been designed with standards compatible with the requirements of large fusion experiments, are: (a) it allows simultaneous reconstruction of both SXR and total radiation emissivity structures with high spatial and time resolution (bandwidth up to 200 kHz for SXR and 10 kHz for bolometry). Moreover, computer controlled remote actions which interchange up to five material filters in front of the detectors allow the exploration of different energy ranges; (b) it can be easily decoupled from the machine without breaking the main vacuum and can be operated during first wall baking up to 300 °C thanks to a cooling circuit; (c) the detection chain is designed to measure very low signals [in the order of 1 nA for SXR diodes and of 100 μV for bolometers]; (d) it is equipped with a VME based 1 MHz data acquisition system which allows on-line processing of a large amount of data. To accomplish these features the diagnostic consists of eight fully remotely controlled manipulators which can insert eight photocameras, carrying 78 top-rated Si SXR and 48 miniaturized metal film bolometric detectors in their operating positions. Initial results are presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148054
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  • 4
    Electronic Resource
    Electronic Resource
    Soft x-ray and bolometric tomography in RFX (abstract) : 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. 761-761 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The article presents the design and the first results of a new eight camera, soft x-ray (SXR) and bolometric tomography which has been installed in RFX, a large (R=2 m, a=0.46 m), high current reverse field pinch experiment operating in Padova. The main features of the diagnostic, which has been designed with standards compatible with the requirements of large fusion experiments, are: (a) it allows simultaneous reconstruction of both SXR and total radiation emissivity structures with high spatial and time resolution (bandwidth up to 200 kHz for SXR and 10 kHz for bolometry). Moreover, computer controlled remote actions which interchange up to five material filters in front of the detectors allow the exploration of different energy ranges; (b) it can be easily decoupled from the machine without breaking the main vacuum and can be operated during first wall baking up to 300 °C thanks to a cooling circuit; (c) the detection chain is designed to measure very low signals [in the order of 1 nA for SXR diodes and of 100 μV for bolometers]; (d) it is equipped with a VME based 1 MHz data acquisition system which allows on-line processing of a large amount of data. To accomplish these features the diagnostic consists of eight fully remotely controlled manipulators which can insert eight photocameras, carrying 78 top-rated Si SXR and 48 miniaturized metal film bolometric detectors in their operating positions. Initial results are presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147911
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  • 5
    Electronic Resource
    Electronic Resource
    Signal processing and general purpose data acquisition system for on-line tomographic measurements : 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. 951-954 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: New analog signal conditioning electronics and data acquisition systems have been developed for the soft x-ray and bolometric tomography diagnostic in the reverse field pinch experiment (RFX). For the soft x-ray detectors the analog signal processing includes a fully differential current to voltage conversion, with up to a 200 kHz bandwidth. For the bolometers, a 50 kHz carrier frequency amplifier allows a maximum bandwidth of 10 kHz. In both cases the analog signals are digitized with a 1 MHz sampling rate close to the diagnostic and are transmitted via a transparent asynchronous xmitter/receiver interface (TAXI) link to purpose built Versa Module Europa (VME) modules which perform data acquisition. A software library has been developed for data preprocessing and tomographic reconstruction. It has been written in C language and is self-contained, i.e., no additional mathematical library is required. The package is therefore platform-free: in particular it can perform online analysis in a real-time application, such as continuous display and feedback, and is portable for long duration fusion or other physical experiments. Due to the modular organization of the library, new preprocessing and analysis modules can be easily integrated in the environment. This software is implemented in RFX over three different platforms: open VMS, digital Unix, and VME 68040 CPU. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147723
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Integration of magnetic and nonmagnetic measurements for current profile reconstruction in RFX : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 426-429 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A crucial issue in magnetically confined plasmas characterized by relevant internal current redistribution, such as high beta and low field toroidal devices, is the determination of their internal magnetic structure. The article presents a method for the integration of magnetic and nonmagnetic measurements in a model which considers a plasma described by stationary ideal magnetohydrodynamic equilibrium equations, with toroidal and poloidal plasma currents represented by distributed discrete filaments and current sheets. The model also includes the massive conductors representing the vessel, the shell, and the machine windings. The discrete current sets are determined by using as input data the total currents flowing in the plasma, in the windings and in the vessel, as deduced by external integral magnetic measurements. The obtained filamentary current sets are then adjusted by imposing further constraints. One of the constraints is given by the set of local magnetic field measurements provided by external pickup coils. A further and more significant constraint is imposed by far infrared polarimeter, which gives an integral condition for each implemented measurement chord. The method is validated by using experimental data from the reversed field pinch Reversed Field eXperiment, and the results suggest that the current density distribution is rather different from that usually predicted by conventional data inversion algorithms. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1316753
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  • 8
    Electronic Resource
    Electronic Resource
    An optimized multifoil soft x-ray spectrometer for the determination of the electron temperature with high time resolution : 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. 581-585 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In RFX a monitor for the measurement of the on-axis electron temperature with high temporal resolution has been designed and operated during the last experimental campaigns. It consists of four soft x-ray (SXR) diodes which observe the plasma through four beryllium filters of different thickness. In this article the main design issues are presented. The measured values of the temperature, computed both with the standard double foil method and with a fit of all the available signals, are reported, correlated with the main plasma parameters and briefly compared with the results of other diagnostics. The main causes of systematic error, the effect of the noise and the reliability of the results in various plasma conditions have been investigated. Dynamic evaluations of the temperature up to a maximum bandwidth of 5 kHz are described, confirming the potentialities of the technique to follow fast phenomena. Possible improvements of the diagnostic and future developments are also pointed out. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149342
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  • 9
    Electronic Resource
    Electronic Resource
    Multichord calibrated bolometer array for the RFX experiment : 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. 665-667 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new multichord bolometer array has been installed for the first time in the RFX experiment, a large machine designed to study plasma confinement at high current in the reversed field pinch configuration. The main purpose of the diagnostic is to provide emissivity spatial profiles with good time resolution for the measurement of the total radiated power. The detectors used are miniaturized metal foil bolometers which are mounted in a water cooled pinhole camera covered by a graphite shield. The bolometers can be absolutely calibrated in situ according to a technique originally developed for the Asdex tokamak. In order to prove the electrical calibration technique a blackened bolometer was optically irradiated with a monochromatic light over a wide spectral range with wave numbers from 2.7 up to 47 000 cm−1. In the visible and UV spectral range an absorptivity of 80% was measured while in the IR and far-infrared regions only 7% of the incoming light was absorbed by the bolometer foil. In the mm wavelength range less than 1% of the radiation was absorbed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146254
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  • 10
    Electronic Resource
    Electronic Resource
    Neural networks for real time determination of radiated power in JET (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 2038-2043 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article describes the use of neural networks (NNs) for the on-line computation of the radiated power in JET. The NNs have been trained using a database of about 120 discharges, for which the emitted power had been calculated via tomographic inversion of JET bolometric signals. In addition to the bolometric data, elongation and triangularity have been used as input to the NN, since these provide useful complementary information. Dedicated NNs have been designed for the determination of the total radiated power, the power from the bulk, and from the divertor region. All the NNs have been tested with a set of about 30 discharges with positive results. Moreover, the NNs can operate at full sampling speed and are therefore suited to follow edge localized modes and other rapid phenomena. The sensitivity of the NNs to failures in the input signals has also been tested, proving their robustness. Their possible use in feedback applications is finally briefly discussed. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1463714
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