Fast-Ion Dynamics in the TEXTOR Tokamak Measured by Collective Thomson Scattering

Bindslev, H.; Nielsen, S. K.; Porte, L.; Hoekzema, J.A.; Korsholm, S. B.; Méo, F.; Michelsen, Poul; Michelsen, S.; Oosterbeek, J.W.; Tsakadze, E.L.; Westerhof, E.; Woskov, P.

doi:10.1103/physrevlett.97.205005

Cited by 101 publications

(71 citation statements)

References 35 publications

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“…At relatively large frequency shifts, here roughly beyond ±0.5 GHz, CTS measurements provide information about fast, nonthermal ion populations, e.g. from neutral beam heating [4][5][6][7][8][9][10][11][12][13][14] or from fusion reactions in future experiments with burning plasmas [15][16][17][18][19] . At lower frequency shifts, in the bulk ion region of the spectrum, CTS measurements provide information about thermal ion populations including properties such as the ion temperature and drift a) mspe@fysik.dtu.dk velocity (i.e.…”

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confidence: 99%

Resolving the bulk ion region of millimeter-wave collective Thomson scattering spectra at ASDEX Upgrade

Stejner

Nielsen

Jacobsen

et al. 2014

Review of Scientific Instruments

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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 obtained 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.

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confidence: 99%

Resolving the bulk ion region of millimeter-wave collective Thomson scattering spectra at ASDEX Upgrade

Stejner

Nielsen

Jacobsen

et al. 2014

Review of Scientific Instruments

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“…Current in-line ECE and collective Thomson scattering 15,16 ͑CTS͒ diagnostics on TEXTOR achieve a temporal resolution of up to 0.1 MHz and a dynamic range of ϳ26 dB. However, the total frequency range is limited by the number of channels and the fixed bandwidth of the detector channels.…”

Section: Introductionmentioning

confidence: 99%

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

Thoen

Bongers

Westerhof

et al. 2009

Review of Scientific Instruments

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. A fast Fourier transform ͑FFT͒ 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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“…The recent development of high-power radiation sources such as megawatt-class gyrotrons and the associated transmission/antenna system make it possible to detect the scattered electromagnetic waves by electron density fluctuations associated with the thermal ion motion in plasmas [1].…”

Section: Introductionmentioning

confidence: 99%

Identification of Spurious Modes of High-Power 77-GHz Gyrotron for Collective Thomson Scattering in LHD

Ogasawara

Kubo

Nishiura

et al. 2012

Plasma and Fusion Research

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Frequency measurements at 74-80 GHz were conducted for the identification and suppression of spurious modes from the 77-GHz gyrotron, which was originally introduced as a power source for electron cyclotron resonance heating and is now also used as a probe beam for the collective Thomson scattering (CTS) diagnostic. The spurious modes are excited as the gyrotron output power is turned on and off by controlling the anode voltage. These modes are harmful for the CTS diagnostic, even though their power is less than approximately 50 dB below than that of the main mode. The measured frequency of one of the spurious modes is approximately 74.7 GHz. The cavity structure, starting current calculation, and mode competition calculation suggest that the spurious mode is the TE 17,6 mode. The result is important for optimizing the gyrotron operation as a CTS probe beam and suppressing or minimizing the spurious mode excitation.

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Fast-Ion Dynamics in the TEXTOR Tokamak Measured by Collective Thomson Scattering

Cited by 101 publications

References 35 publications

Resolving the bulk ion region of millimeter-wave collective Thomson scattering spectra at ASDEX Upgrade

Resolving the bulk ion region of millimeter-wave collective Thomson scattering spectra at ASDEX Upgrade

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

Identification of Spurious Modes of High-Power 77-GHz Gyrotron for Collective Thomson Scattering in LHD

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