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  • 1
    Electronic Resource
    Electronic Resource
    Design and fabrication of a vacuum ultraviolet pinhole camera based on thin phosphor screens (abstract) : 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. 952-952 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact and highly sensitive pinhole camera has been developed for acquiring broadband vacuum ultraviolet (VUV) emission profiles of plasmas in the TJ-II. Its principal purpose is to obtain profiles with sufficiently high resolution so as to aid in the search for topological structures in stellarator plasmas. It can also be used to support experiments such as impurity injection by laser ablation. The original and purpose-designed camera reported here provides optimum sensitivity over a broad spectral range. In the camera vacuum chamber, plasma radiation passes through a pinhole and a filter before impinging on a 5×30 mm area of a P-46 phosphor screen. Thin screens of this material were extensively characterized using calibrated monochromatic VUV sources and it was found that their response is maximized when operated in reflection mode.1 Luminescent light emitted from the vacuum side of the screen is then focused by a toroidal mirror (the pinhole is cut in its center) onto the outside of a quartz window which is mounted on the side of camera. Finally, this intermediate image is relayed onto the surface of a gated and intensified linear photodiode array (25 μm by 25 mm) having 700 active pixels. This system is capable of obtaining radial VUV profiles every 12 ms and of recording them in ≥100 ns. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1323493
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  • 2
    Electronic Resource
    Electronic Resource
    Feasibility study of a method to measure the ECRH field in the plasma interior (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. 504-504 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The precise measurement of the power absorption in some ECRH plasma experiments can be plagued with many practical problems, which makes the direct validation of any theoretical model difficult. In the present work, the feasibility of a method to directly measure the electric field at the predicted resonant position is carried out. From the electric field it is possible to compute the local density power carried by the microwave beam and, hence, deduce the power deposition profile. The method based on measuring the ratio of near and far satellite intensities of He I lines, already used in cold plasma discharges,1 presents challenging problems when applied to a hotter plasma. The electric field is estimated using ray tracing calculations in the TJ-IU torsatron. The field is locally obtained in the plasma from the dispersion relation and the estimations for the injected power (200 kW) show that the effect of the microwave field can be non-negligible on the He I lines. An experimental setup to explore this idea in the TJ-IU torsatron will be described. The low densities of this device and the use of a signal-to-noise subtraction technique make this method feasible according to our preliminary estimation. The difficulties encountered and the results obtained will be reported.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147616
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  • 3
    Electronic Resource
    Electronic Resource
    Design of luminescent detectors for 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. 680-682 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We outline designs for several rare-earth-based phosphor powder detector systems for monitoring the broadband VUV plasma radiation in the TJ-II torsatron device. These include a global radiation detector, a detector with temporal and spectral resolution, and a third with radial scanning capabilities. We describe the selection of a phosphor powder for this application having good response from the soft x ray to the VUV, a fast response time, and the capability of operation at high temperatures. In addition, we give details of a method developed in-house for depositing thin uniform layers of powder on glass substrates for use as phosphor screens. Finally, we present some detector test results obtained in the plasma of the TJ-I U torsatron. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147718
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  • 4
    Electronic Resource
    Electronic Resource
    A vacuum-ultraviolet and x-ray linear camera for high-temperature plasmas (2002)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 283-288 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a prototype linear vacuum-ultraviolet x-ray pinhole camera based on the luminescence of a phosphor screen working in reflection mode. The luminescence emitted by the phosphor, in response to radiation selected by a broadband filter, is detected using a 1024 pixel intensified linear array detector. By operating this detector with integration times from 20 to 50 ms, random plasma fluctuations can be smeared out, so that structures related to the magnetic topology can be searched for. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1435844
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  • 5
    Electronic Resource
    Electronic Resource
    A toroidal focusing mirror based vacuum ultraviolet diagnostic for TJ-II : 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. 312-315 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a vacuum ultraviolet spectrometer having spatial, spectral, and temporal resolution capabilities that is being built as a diagnostic for the TJ-II flexible heliac device. The system is based around a renovated 0.5 m radius Rowland circle grazing incidence duochromator and will cover the wavelength range from 300 to 2000 Å with good spatial resolution. A toroidal mirror used at grazing incidence, mounted on a specially designed mounting positioned between the plasma and spectrometer, will permit ∼80% of the bean shaped plasma cross section to be scanned with spatial resolution on the order of 10 mm. In addition, filters and slits are incorporated to tailor the incident light beam. The duochromator was coupled directly to the TJ-II during the machine start up phase to check the good operation of the duochromator. These data have been fed back into the design program in order to optimize the instrument design. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149345
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of phosphors for broadband plasma emission detectors : 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. 534-536 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A comparative study of several luminescent materials which have potential interest for broadband plasma radiation detectors covering the vacuum ultraviolet (VUV) and x-ray ranges has been carried out. Among the studied phosphors Y2O2S:Tb (P-45) exhibits the highest sensitivity, which has been seen to be more than one order of magnitude higher than the standard VUV phosphor-sodium salicylate, over the whole spectral range. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146343
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    On a nonintrusive spectroscopic method to determine fluctuating electric fields in hot plasmas (abstract) : 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. 4617-4617 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A nonintrusive method to measure low level stochastic electric fields in hot plasmas is being investigated in the TJ-I tokamak (R=30 cm, a=10 cm, Ip〈60 kA, BT〈1.5 T). It is based on the measurement of ion temperature of particles with different masses, i.e., protons and impurities, by the Doppler line width of their emission lines. It is hypothesized that its difference is due to gross mass motion produced by E˜×B. As a guide for data interpretation, we compare our results with typical values of fluctuating electric fields obtained by Langmuir probes at the plasma periphery. The ion temperatures of representative impurities like C V and O V, have been measured by the Doppler line width of near UV lines 2271 and 2781 A(ring), respectively. The proton temperature has been measured analyzing the Hβ and Hα line wings whose emission is due to highly energetic neutrals. Results of fluctuating electric fields obtained by this method as a function of radius and plasma density will be presented. The deduced fluctuating electric fields are higher at the plasma periphery than at the plasma center and in the latter much higher at low than at high densities. An approach to distinguish between radial and poloidal electric field fluctuations is being addressed by modeling experimental results with a simulation code.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143687
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  • 9
    Electronic Resource
    Electronic Resource
    A code for calculating spectral line shapes in tokamaks and assisting in experimental data interpretation : 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. 5196-5198 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A code for calculating the actual spectral line shapes in magnetically confined plasmas of the tokamak type is described. The code determines the resulting line shape averaged along the line-of-sight of the spectrometer, starting from prescribed thermal temperature, ion emissivity, and flow profiles, for a plasma immersed in a magnetic field. In addition, the influence on the impurity linewidths of nonthermal fluctuating velocities due to fluctuating electric fields and to possible magnetic fluctuations is also included. Typical applications of the code to spectral data analysis in the TJ-I tokamak are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143427
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  • 10
    Electronic Resource
    Electronic Resource
    A multi-channel spectroscopic system for measuring impurity ion temperatures and poloidal rotation velocities in TJ-II : 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. 971-974 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article, we report on the hardware and software of an eight-channel, high-resolution, spectroscopic diagnostic system that has been built for the TJ-II flexible heliac. This system is currently being used on TJ-II to measure impurity ion temperature and poloidal rotation using passive emission spectroscopy. The principal features of the diagnostic include independent focusing of its channels, high sensitivity for performing Doppler measurements in low-density ECR-heated plasmas, as well as a flexible and fast in-house-developed software program for performing integrated data reduction and analysis. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1326008
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