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Title: Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade

Abstract

We first describe the improved receiving system of the diagnostic experiment of millimeter-wave collective Thomson scattering being run on the Frascati Tokamak Upgrade (FTU), and then discuss some peculiar problems and new operating procedures related to the investigation of strong anomalous spectra of nonthermal origin, many-orders-of-magnitude stronger than the ion thermal feature merged in them, systematically observed in the experimentation, and finally ascribed to a perturbation of the gyrotron that generates the probing beam. Arguments in favor of a more general valence of the solutions actuated for the specific case of FTU are finally given.

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ;  [1];  [2];  [3];  [4]
  1. Istituto di Fisica del Plasma, CNR-ENEA-Euratom Association, Via R. Cozzi 53, 20125 Milan (Italy)
  2. (Russian Federation)
  3. (Italy)
  4. (United Kingdom)
Publication Date:
OSTI Identifier:
20953419
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 78; Journal Issue: 4; Other Information: DOI: 10.1063/1.2719197; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAMS; DISTURBANCES; FT TOKAMAK; IONS; PLASMA; PLASMA CONFINEMENT; SPECTROSCOPY; THOMSON SCATTERING

Citation Formats

Tartari, U., Grosso, G., Granucci, G., Gandini, F., Garavaglia, S., Grossetti, G., Simonetto, A., Mellera, V., Muzzini, V., Lubyako, L., Shalashov, A., Orsitto, F. P., Ciccone, G., Volpe, F., Institute of Applied Physics, Russian Academy of Sciences, Ulyanova Street 46, 603950 Nizhny Novgorod, CRE-ENEA, Euratom-ENEA Association, Via E. Fermi 45, 00044 Frascati, and Culham Science Centre, UKAEA-EURATOM Association, Abingdon, Oxfordshire, OX14 3DB. Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade. United States: N. p., 2007. Web. doi:10.1063/1.2719197.
Tartari, U., Grosso, G., Granucci, G., Gandini, F., Garavaglia, S., Grossetti, G., Simonetto, A., Mellera, V., Muzzini, V., Lubyako, L., Shalashov, A., Orsitto, F. P., Ciccone, G., Volpe, F., Institute of Applied Physics, Russian Academy of Sciences, Ulyanova Street 46, 603950 Nizhny Novgorod, CRE-ENEA, Euratom-ENEA Association, Via E. Fermi 45, 00044 Frascati, & Culham Science Centre, UKAEA-EURATOM Association, Abingdon, Oxfordshire, OX14 3DB. Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade. United States. doi:10.1063/1.2719197.
Tartari, U., Grosso, G., Granucci, G., Gandini, F., Garavaglia, S., Grossetti, G., Simonetto, A., Mellera, V., Muzzini, V., Lubyako, L., Shalashov, A., Orsitto, F. P., Ciccone, G., Volpe, F., Institute of Applied Physics, Russian Academy of Sciences, Ulyanova Street 46, 603950 Nizhny Novgorod, CRE-ENEA, Euratom-ENEA Association, Via E. Fermi 45, 00044 Frascati, and Culham Science Centre, UKAEA-EURATOM Association, Abingdon, Oxfordshire, OX14 3DB. Sun . "Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade". United States. doi:10.1063/1.2719197.
@article{osti_20953419,
title = {Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade},
author = {Tartari, U. and Grosso, G. and Granucci, G. and Gandini, F. and Garavaglia, S. and Grossetti, G. and Simonetto, A. and Mellera, V. and Muzzini, V. and Lubyako, L. and Shalashov, A. and Orsitto, F. P. and Ciccone, G. and Volpe, F. and Institute of Applied Physics, Russian Academy of Sciences, Ulyanova Street 46, 603950 Nizhny Novgorod and CRE-ENEA, Euratom-ENEA Association, Via E. Fermi 45, 00044 Frascati and Culham Science Centre, UKAEA-EURATOM Association, Abingdon, Oxfordshire, OX14 3DB},
abstractNote = {We first describe the improved receiving system of the diagnostic experiment of millimeter-wave collective Thomson scattering being run on the Frascati Tokamak Upgrade (FTU), and then discuss some peculiar problems and new operating procedures related to the investigation of strong anomalous spectra of nonthermal origin, many-orders-of-magnitude stronger than the ion thermal feature merged in them, systematically observed in the experimentation, and finally ascribed to a perturbation of the gyrotron that generates the probing beam. Arguments in favor of a more general valence of the solutions actuated for the specific case of FTU are finally given.},
doi = {10.1063/1.2719197},
journal = {Review of Scientific Instruments},
number = 4,
volume = 78,
place = {United States},
year = {Sun Apr 15 00:00:00 EDT 2007},
month = {Sun Apr 15 00:00:00 EDT 2007}
}
  • 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. {copyright} {ital 1997more » American Institute of Physics.}« less
  • 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. {copyright} {ital 1997more » American Institute of Physics.}« less
  • Collective Thomson scattering (CTS) measurements provide information about the composition and velocity distribution of confined ion populations in fusion plasmas. The bulk ion part of the CTS spectrum is dominated by scattering off fluctuations driven by the motion of thermalized ion populations. It thus contains information about the ion temperature, rotation velocity, and plasma composition. To resolve the bulk ion region and access this information, we installed a fast acquisition system capable of sampling rates up to 12.5 GS/s in the CTS system at ASDEX Upgrade. CTS spectra with frequency resolution in the range of 1 MHz are then obtainedmore » through direct digitization and Fourier analysis of the CTS signal. We here describe the design, calibration, and operation of the fast receiver system and give examples of measured bulk ion CTS spectra showing the effects of changing ion temperature, rotation velocity, and plasma composition.« less
  • Collective Thomson scattering on alpha density fluctuations in ignited plasma regimes is investigated with reference to a promising candidate source as the mm-wave gyrotron and a representative ITER-like plasma regime. It is shown that a number of intrinsic limitations characterize each of the equatorial scattering geometries selected as more promising, namely a backscattering geometry at {ital f}{sub 0}=80 GHz and two similar quasiorthogonal geometries at {ital f}{sub 0}=180 GHz. A lack of spatial resolution typical of the former geometry has to be contrasted with a significant limitation in plasma access typical of the remaining geometries. Other relevant differences concern themore » requirements in terms of gyrotron power, acceptable stray radiation levels, etc. Special emphasis is given in the work to a discussion of ECE noise, on which the feasibility itself of the alpha collective scattering diagnostics at mm-waves largely depends in the plasma regimes considered. {copyright} {ital 1996 American Institute of Physics.}« less
  • Collective Thomson scattering (CTS) diagnostic systems for measuring fast ions in TEXTOR and ASDEX Upgrade are described in this article. Both systems use millimeter waves generated by gyrotrons as probing radiation and the scattered radiation is detected with heterodyne receivers having 40 spectral channels at TEXTOR and 50 spectral channels at ASDEX Upgrade. The antenna patterns of probe and receiver, both steerable, determine size and location of the measuring volume, and the direction of the resolved fast ion velocity. With overmoded transmission lines, consisting of waveguides and quasioptical mirrors, the antenna patterns depend on the alignment of the entire transmissionmore » line. Alignment is aided by visible laser beams relayed by small optical mirrors, inserted in the quasioptical mirrors.« less