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  • 1
    Electronic Resource
    Electronic Resource
    New tokamak physics and next step devices versus present limits of diagnostics (invited) (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 397-402 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In recent years the necessity of understanding the physics concerning new tokamak results has clearly shown the limits of the actual diagnostic capability of existing devices, in terms of reliability, precision, spatial localization, and temporal resolution of measurements. This appears even more evident when next-step tokamak devices are considered. For example, the formation and evolution of the plasma internal transport barriers and the regulation of its positions by a detailed tailoring of the current spatial profile and plasma heating gives demanding requests to a complex set of diagnostics including motional Stark effect as well as incoherent Thomson scattering (ITS). The measurement of detachment of plasma in a divertor puts some requirements on a dedicated ITS. The rotational stabilization of ideal magnetohydrodynamic modes puts some important accent to the plasma rotation measurements. The coherent (or collective) Thomson scattering giving ion temperature can be useful in a prototype fusion reactor to monitor the ignition process. A state-of-the-art review for these diagnostics is carried out trying to outline the perspectives that are seen from the point of view of physics studies. A discussion of the present limits is presented and new directions of development identified, since a step foreward in the physics studies implies a parallel refinement and/or new conception of diagnostic equipment. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149478
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  • 2
    Electronic Resource
    Electronic Resource
    Avalanche photodiodes operating parameter optimization for the Frascati Tokamak Upgrade Thomson scattering system (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. 699-699 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measured figures (linearity, avalanche gain, frequency response, and noise) of the avalanche photodiodes (APD) detectors used on the FTU Thomson scattering system (FTU-TS) are reported. This investigation on the APD figures is motivated by the necessity of knowing their values over a wide range of input signals, and also of checking the validity of McIntyre model of APD noise, since using this model the experimental signal-to-noise ratio is calculated. From the noise analysis, a method of optimization of the detection system sensitivity is derived, leading to the optimization of the signal-to-noise ratio over the entire FTU-TS system. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147910
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  • 3
    Electronic Resource
    Electronic Resource
    Thomson scattering system on FTU tokamak: Calibration, operation, resultsa) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1167-1170 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Frascati tokamak upgrade (FTU) Thomson scattering system is employed for the measurement of the electron temperature and density spatial profiles along the vertical torus diameter in 19 spatial points up to ten times in a single plasma discharge with a spatial resolution ranging from 2 cm in the central region to 4 cm in the plasma edge. The radiation source is a Nd:YLF laser at 1053 nm. The scattered radiation is collected by two objectives: the first looks at the plasma center, the second at the plasma edge. Bundles of optical fibers in the focal plane of the objectives carry the scattered light from the tokamak hall to a set of 19 interference filter polychromators, whose transmission is 70% and the rejection of the stray light at the laser wavelength is 1/107. The detectors are avalanche photodiodes with a NEP of the order of 10−13 W/(Hz)1/2 at 1053 nm. The absolute calibration for the electron density measurement has been carried out by Raman scattering on hydrogen and deuterium. Examples of temporal evolution of Te and ne spatial profiles are presented for ohmic plasma heating, lower hybrid current drive, and pellet injection experiment. A comparison between scattering data with interferometer for the density measurement, and ECE for the electron temperature shows agreement between the diagnostics. The system is controlled by two computers: a real-time computer for the laser settings, while the detection system parameters and data acquisition are managed using CAMAC by the data acquisition system (DAS) of FTU. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145999
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  • 4
    Electronic Resource
    Electronic Resource
    Antenna decoupling requirements in a gyrotron collective Thomson scattering diagnostic (CTS) (abstract)a) : 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. 430-430 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The required rejection ratio of the stray light in a CTS, respect to the launching power is investigated, for obtaining useful signal-to-noise ratio. This problem is faced considering the central gyrotron frequency f0, as well as the in-band stray light raising from the spurious mode of the gyrotron and amplified cyclotron emission (the so-called gyrotron noise), falling into the scattered light spectrum. The statistical nature of the gyrotron noise in the scattering band is important because the required decoupling is obtained using the S/N formula where the fluctuation of the plasma radiation and the gyrotron noise fluctuation appears. It turns out that the total decoupling required at f0 is of the order of or greater than 80 dB, while in the scattering band could be less than 40 dB. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146369
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  • 5
    Electronic Resource
    Electronic Resource
    Thomson scattering system on FTU tokamak: Calibration, operation, results (abstract)a) : 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. 500-500 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Frascati tokamak upgrade (FTU) Thomson scattering system is employed for the measurement of the electron temperature and density spatial profiles along the vertical torus diameter in 19 spatial points up to ten times in a single plasma discharge with a spatial resolution ranging from 2 cm in the central region to 4 cm in the plasma edge. The radiation source is a Nd:YLF laser at 1053 nm. The scattered radiation is collected by two objectives: the first looks at the plasma center, the second at the plasma edge. Bundles of optical fibers in the focal plane of the objectives carry the scattered light from the tokamak hall to a set of 19 interference filter polychromators, whose transmission is 70% and the rejection of the stray light at the laser wavelength is 1/107. The detectors are avalanche photodiodes with a NEP of the order of 10−13 W/(Hz)1/2 at 1053 nm. The absolute calibration for the electron density measurement has been carried out by Raman scattering on hydrogen and deuterium. Examples of temporal evolution of Te and ne spatial profiles are presented for ohmic plasma heating, lower hybrid current drive, and pellet injection experiment. A comparison between scattering data with interferometer for the density measurement, and ECE for the electron temperature shows agreement between the diagnostics. The system is controlled by two computers: a real-time computer for the laser settings, while the detection system parameters and data acquisition are managed using CAMAC by the data acquisition system of FTU. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146329
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  • 6
    Electronic Resource
    Electronic Resource
    Fe i density measurements by laser induced fluorescence spectroscopy : 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. 597-599 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The density of Fe atoms produced by bombardment of a stainless steel target by Ar+ ions was measured by laser induced fluorescence (LIF) using a tunable dye laser. The excitation transition involved was a 5D4→y 5D04 (λ=302.064 nm); measurements of the fluorescence signal, from the y 5D04→a 5F5 decay (λ=382.043 nm), were made by varying the laser power incident on Fe atoms by means of grey filters. An absolute calibration of the detection system allowed the determination of the number of the emitting atoms, versus the incident power. So the experimental curve of the fraction of total pumped atoms versus the saturation parameter was obtained. On the other hand, that fraction can be calculated by using standard rate equations for LIF process involving three level atoms. The result is strongly dependent on the model for the pumping laser pulse, particularly (as expected) at low incident power level. Assuming a realistic Gaussian temporal dependence for the radiation field energy flux at frequency v, i.e., U (vt) ∼ Uv0te−t2 and calculating the fraction of atoms pumped by the incident pulse, an agreement better than assuming a square time dependence for U(v,t) was found. The measurement sensitivity limit is 109 atoms/cm3 when LIF diagnostic on FTU is considered including plasma emission background. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146298
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  • 7
    Electronic Resource
    Electronic Resource
    Proposal for a new electron temperature diagnostic for fusion reactors : 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. 798-801 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The possibility of determining the plasma electron temperature by measuring the depolarization of the radiation scattered by the high temperature fusion reactor plasma is explored in this article. A numerical calculation based on the theory of the article [Sov. J. Plasma Phys. 7, 669 (1981)] in the case of 90° scattering, with the incident radiation linearly polarized and the polarization plane at 45° with respect to the scattering plane, is carried out. The result is that there is a one to one relationship between plasma electron temperature and depolarization, being independent from the detection wavelength. As an example electron density and temperature of 1020 m−3 and 20 keV, respectively, are taken, a wavelength and energy of the incident radiation pulse of 1064 nm and 8 J, respectively, and for a wavelength detection range of 1050–660 nm, a depolarization value of 0.19 and an estimated error on it of 1.7% are found, if the scattering volume is 2 cm long and the collection solid angle is 7.85×10−3 sr. A prototype of the diagnostic apparatus based on beamsplitting Thompson prism is proposed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149414
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  • 8
    Electronic Resource
    Electronic Resource
    MoI density measurements by laser induced fluorescence spectroscopy : 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. 921-924 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The density of molybdenum atoms produced by sputtering of a TZM (molybdenum) target by Ar+ ions is measured by laser induced fluorescence (LIF) using tunable dye laser. The excitation transition involved is a7S3−z5P30 at 345.64 nm, while the fluorescence signal is from the decay z5P30−a5S2 at 550.6 nm. The LIF measurements are carried out by varying the laser power incident on Mo atoms by means of neutral density filters. An absolute calibration of the detection system together with the realization of a well defined optical probe volume allows for the determination of the density of the emitting atoms. An evaluation of LIF diagnostic performance on Frascati Tokamak upgrade put a lower limit of 2.5×1014 atoms/m3 on the detectable local density of MoI close to the toroidal limiter. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149440
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  • 9
    Electronic Resource
    Electronic Resource
    Zeff spatial profiles from Bremsstrahlung emission in the near infrared spectral region : 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. 925-927 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measurements of plasma radiation in the infrared (IR) BREM_IR range (λ=978 nm, Δλ=38 nm), at 16 horizontal lines of sight intersecting the central vertical chord of the [Frascati Tokamak Upgrade (FTU) R=0.935 m, a=0.3 m, B=4–8 T], from z=−0.22 m below, to z=0.08 m above the equatorial plane, are performed using the detection system of the Thomson scattering apparatus [F. Orsitto et al., Appl. Opt. 34, 2712 (1995)] (TS). The measured BREM_IR intensity is equal I(z)=〈ZeffGne2/Te1/2〉 where 〈〉 means line average. For determining the Zeff, the Gaunt factor (G) is needed, and the Born–Elwert formula is used. The Zeff spatial profiles are determined using the plasma temperature (Te) and density (ne) measured by the TS, DCN interferometer, and Abel inverted intensity profiles. Zeff(r) versus time behavior in FTU discharges is presented for krypton injection experiments aimed to investigate the particle confinement behavior during strong injection of impurities. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149462
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  • 10
    Electronic Resource
    Electronic Resource
    Review of possibilities for a collective Thomson scattering system on ITER : 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. 686-688 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Different scenarios for measuring the alpha particle distribution in ITER by means of a collective Thomson scattering experiment are reviewed. As a result of this analysis, two possible methods are selected, respectively using a 10.6 μm laser (tangential geometry) and a 65–70 GHz gyrotron (backscattering). © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147673
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