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  • 1
    Electronic Resource
    Electronic Resource
    Deterministic diffusion in almost integrable systems (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 6 (1996), S. 519-527 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Diffusion processes are usually associated with randomness in the system. In this paper we show that deterministic diffusion processes can also occur in systems with zero entropy that mimic chaos with any precision without being mathematically chaotic. A random walk model is used to predict the behavior of the diffusion coefficient. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166199
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  • 2
    Electronic Resource
    Electronic Resource
    A spectroscopical measure for the exploration of phase space (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 8 (1998), S. 682-687 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Many nonintegrable systems have eigenstates that typically require numerous basis states to represent them. We develop a criterion to judge the extent to which phase space is explored by the spectrum of such a Hamiltonian. Our criterion uses the eigenvalues rather than the eigenfunctions and is based on identifying a direct relation between the intensity of Shnirelman's peak and the localization length. We illustrate our procedure by applying it to the spectrum of two prototypical nonintegrable systems, the kicked rotor and the kicked top. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166350
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  • 3
    Electronic Resource
    Electronic Resource
    TJ-II data retrieving by means of a client/server model : 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. 498-501 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The database of the TJ-II flexible heliac is centralized in a Unix server. This computer also commands the on-line processes related to data acquisition during TJ-II discharges: programming of measurement systems, connectivity with control systems, data visualization, and computations. The server has to provide access to the data so that signal analysis can be performed by local users or even from remote hosts. Data retrieving is accomplished by means of a client/server architecture in which two data servers are permanently running in the background of the Unix computer. One of them serves data requests from local clients and the other one sends data to remote clients. The communication protocol in both cases has been developed by using TCP/IP and Berkeley sockets. The client part consists of a set of routines (FORTRAN and C callable), which, in a transparent way, provide connectivity with the servers. This structure allows access to TJ-II data exactly in the same way from any computer, hiding not only specific aspects of the database, but hardware architecture of the server computer as well. In addition, the remote access makes it possible to distribute computations and to reduce the load on the Unix server from analysis and visualization tasks. At present, this software is running in four different environments: the Unix server itself, various types of Unix workstations, a CRAY J90 and a CRAY T3E. Finally, due to the fact that visualization is essential for TJ-II data analysis, a powerful and a very flexible visualization tool has been developed. It is a point and click application based on X Window/Motif. Data access is carried out through the client/server processes mentioned above and the software runs in the client computer. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149283
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  • 4
    Electronic Resource
    Electronic Resource
    Software architecture of data acquisition control process during TJ-II operation : 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. 959-962 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Data from the diagnostics on the TJ-II device will be collected by several independent systems linked to local area networks (LANs). Some of these systems will consist of digitizers based on well-known standards: CAMAC, VME, VXI, etc. Other allowable systems would be personal computers or workstations with direct control over a specific diagnostic. In principal, any equipment capable of being linked in a LAN can be used as a controller for data collection. All systems will be programmed from a central computer. In this computer, an application program will allow the set up of data acquisition in any system. This will be achieved by communicating systems through a network standard protocol: TCP/IP. The central computer will also centralize the database of discharges. For this purpose, immediately after a discharge, data will be sent from the autonomous systems to the main computer. The latter will coordinate data reception, organize discharge information, and compress data. Data will be transferred rapidly so all diagnostic signals will be available to users for immediate analysis. The computer processes outlined here will provide an application program to provide users with an interface for all operations related to data acquisition, fast signal analysis, and remote control of diagnostics. A second functionality will be the management of TJ-II discharge database. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147725
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  • 5
    Electronic Resource
    Electronic Resource
    Integration of autonomous systems for remote control of data acquisition and diagnostics in the TJ-II device : 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. 963-966 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The data acquisition system for TJ-II will consist of a central computer, containing the data base of the device, and a set of independent systems (personal computers, embedded ones, workstations, minicomputers, PLCs, and microprocessor systems among others), controlling data collection, and automated diagnostics. Each autonomous system can be used to isolate and manage specific problems in the most efficient manner. These problems are related to data acquisition, hard (μs–ms) real time requirements, soft (ms–s) real time requirements, remote control of diagnostics, etc. In the operation of TJ-II, the programming of systems will be carried out from the central computer. Coordination and synchronization will be performed by linking systems to local area networks. Several Ethernet segments and FDDI rings will be used for these purposes. Programmable logic controller devices (PLCs) used for diagnostic low level control will be linked among them through a fast serial link, the RS485 Profibus standard. One VME crate, running on the OS-9 real time operating system, will be assigned as a gateway, so as to connect the PLCs based systems with an Ethernet segment. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147726
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  • 6
    Electronic Resource
    Electronic Resource
    Encoding technique for high data compaction in data bases of fusion devices (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 4154-4160 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: At present, data requirements of hundreds of Mbytes/discharge are typical in devices such as JET, TFTR, DIII-D, etc., and these requirements continue to increase. With these rates, the amount of storage required to maintain discharge information is enormous. Compaction techniques are now essential to reduce storage. However, general compression techniques may distort signals, but this is undesirable for fusion diagnostics. We have developed a general technique for data compression which is described here. The technique, which is based on delta compression, does not require an examination of the data as in delayed methods. Delta values are compacted according to general encoding forms which satisfy a prefix code property and which are defined prior to data capture. Several prefix codes, which are bit oriented and which have variable code lengths, have been developed. These encoding methods are independent of the signal analog characteristics and enable one to store undistorted signals. The technique has been applied to databases of the TJ-I tokamak and the TJ-IU torsatron. Compaction rates of over 80% with negligible computational effort were achieved. Computer programs were written in ANSI C, thus ensuring portability and easy maintenance. We also present an interpretation, based on information theory, of the high compression rates achieved without signal distortion. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147544
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  • 7
    Electronic Resource
    Electronic Resource
    Measurement of density and temperature fluctuations using a fast-swept Langmuir probe : 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. 4605-4607 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Density and temperature fluctuations have been measured in the proximity of the velocity shear location of the TJ-I tokamak using a fast-swept Langmuir probe technique. From the current voltage characteristic we have determined the electron temperature and the density in a time scale which is small compared with the relevant times of the turbulence. Evidence of substantial temperature fluctuations has been found near the shear location.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143682
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  • 8
    Electronic Resource
    Electronic Resource
    Code for time-resolved x-ray pulse analysis at high count rates for short tokamak discharges : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3268-3270 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The measurement of soft x-ray spectrum in fusion plasmas allows for information on the nature of electron distribution, identification of impurity contents, calculation of electron temperature, estimation of Zeff, etc. All these measurements can be performed with a semiconductor detector. By amplifying the signal and using it as input to a multichannel analyzer (MCA), the spectrum is obtained. This kind of measurement does not have the desirable property of temporal resolution unless several detection chains are used or a special hardware is developed. In this paper, a method is presented to reach that type of resolution. This method requires only one measurement chain and the substitution of the MCA for a digitizer and mass storage. The digitized signal is stored in a computer, which will be the input for the several codes developed with the purpose of performing all the tasks of an MCA. These codes allow any number of time windows, of any length, along the digitized signal. Furthermore, in this way, it is possible to process one signal several times with different input parameters. Results in the TJ-I Tokamak (R0=0.3 m; a=0.1 m; BT〈1.9 T; IP〈70 kA) are shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141610
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  • 9
    Electronic Resource
    Electronic Resource
    A spectroscopic method to directly measure nonthermal velocity fluctuations (abstract) : 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. 447-447 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A spectroscopic method to directly measure the nonthermal velocity fluctuations is being studied in the TJ-I tokamak. The method is based on converting velocity in intensity fluctuations by subtracting the signals received at two symmetric positions of a spectral emission line. This is accomplished by means of a multichannel detector in which the channels respond to the line intensity at different wavelengths and positions within a single spectral line. A multichannel plate photomultiplier, with an anode split in 8×8 parts, is optically coupled by means of an anamorphic optical system, to the focal plane of a 1 m spectrometer where the image of a spectral line is formed. Some individual anodes are grouped to configurate four acquisition channels which are fled into four current amplifiers. The 100 kHz bandwidth signals are stored in a digital oscilloscope connected to a VAX computer, where the signals are processed. A simple simulation allows us to relate the differential signal between symmetrical channels to velocity in cases where the radial extension of the emitting ion is comparable to the radial correlation length of the turbulence causing the velocity fluctuations. The influence of the detection statistics on the measurement is analyzed. Preliminary results obtained in the TJ-I tokamak, using this system, will be presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146376
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  • 10
    Electronic Resource
    Electronic Resource
    A fully programmable data acquisition system for the TJ-I and TJ-IU devices : 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. 4806-4808 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new data acquisition system has been developed for the TJ-I tokamak and the TJ-IU torsatron. This system is based on the VME standard and it is controlled by an MC68020 microprocessor. This scheme is similar to the ones existing at CERN and used in high-energy physics experiments. [On-line Computing Group, Valet-Plus Operation Guide, Data handling, CERN DD Division OC Group]. The data acquisition system consists of 60 independent, fully programmable channels. Each channel has its own analog-to-digital converter (ADC) with a resolution of ten bits and a RAM memory of 128 kbytes (kB). A digital-to-analog converter is also included for providing an analog output in order to display the stored signal on oscilloscopes. The maximum sampling rate achievable with the ADC used is 500 Ksamples/s, which is equivalent to a sampling period of 2 μs. Each channel is programmed to have its own sampling period (in 400-ns steps), and to use the amount of storage required according to the sampling period and the pulse length, up to a maximum of 128 kB. The system controls not only the 7680 kB corresponding to the memory of the 60 channels, but a RAM buffer of 4 MB as well. The system is linked to a local ETHERNET network in order to send the recorded data to the disks of a VAX/VMS computer, where the data are available for analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143569
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