Development and testing of a fast Fourier high dynamic-range spectral diagnostics for millimeter wave characterization

Thoen, D.J.; Goede, A.P.H.; Oosterbeek, J.W.; Westerhof, E.; Bongers, W.A.; Graswinckel, M.F.; Schüller, F.C.; TEXTOR, Team.; Bürger, A.; van Beveren, V.; de Baar, M.R.; van den Berg, M.A.; Hennen, B.A.

doi:10.1063/1.3244091

Journal Article

Development and testing of a fast Fourier high dynamic-range spectral diagnostics for millimeter wave characterization

Thoen, D. J. ; Bongers, W. A. ; Westerhof, E. ; Oosterbeek, J. W. ; de Baar, M. R. ; van den Berg, M. A. ; van Beveren, V. ; Bürger, A. ; Goede, A. P. H. ; Graswinckel, M. F. ; Hennen, B. A. ; Schüller, F. C. ; TEXTOR, T.FZJ*

2009
American Institute of Physics [S.l.]

Review of scientific instruments 80, (2009) [10.1063/1.3244091]

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Please use a persistent id in citations: http://hdl.handle.net/2128/16767 doi:10.1063/1.3244091

Abstract: A fast Fourier transform (FFT) based wide range millimeter wave diagnostics for spectral characterization of scattered millimeter waves in plasmas has been successfully brought into operation. The scattered millimeter waves are heterodyne downconverted and directly digitized using a fast analog-digital converter and a compact peripheral component interconnect computer. Frequency spectra are obtained by FFT in the time domain of the intermediate frequency signal. The scattered millimeter waves are generated during high power electron cyclotron resonance heating experiments on the TEXTOR tokamak and demonstrate the performance of the diagnostics and, in particular, the usability of direct digitizing and Fourier transformation of millimeter wave signals. The diagnostics is able to acquire 4 GHz wide spectra of signals in the range of 136-140 GHz. The rate of spectra is tunable and has been tested between 200,000 spectra/s with a frequency resolution of 100 MHz and 120 spectra/s with a frequency resolution of 25 kHz. The respective dynamic ranges are 52 and 88 dB. Major benefits of the new diagnostics are a tunable time and frequency resolution due to postdetection, near-real time processing of the acquired data. This diagnostics has a wider application in astrophysics, earth observation, plasma physics, and molecular spectroscopy for the detection and analysis of millimeter wave radiation, providing high-resolution spectra at high temporal resolution and large dynamic range.

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Note: The collaboration with Acqiris/Agilent is appreciated: Mr. Laurent Weber (Acqiris Switzerland) is acknowledged for his hardware support, and the Dutch representative of Acqiris (TTMS, Nieuw-Vennep) is acknowledged for their support and effort regarding the (testing) equipment. The help of Mr. Woskov has been greatly inspiring.This work, supported by the European Communities under the Contract of Association between EURATOM-FOM, was carried out within the framework of the European Fusion Program. The views and opinions expressed herein do not necessarily reflect those of the European Commission.

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