Pulse radar reflectometry for fusion plasma diagnostics

Shevchenko, V. F.; Petrov, A. A.; Петров, В. Г.

doi:10.1007/bf02101330

Cited by 23 publications

(14 citation statements)

References 1 publication

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“…We will select a central frequency ω 0 and designate the corresponding value of L as L 0 . From equations ( 8)- (10) one then obtains:…”

Section: Analytical Considerationsmentioning

confidence: 99%

“…Equations (10) and (15) rely on a number of simplifications. First of all, a linear background density profile (and magnetic field profile in the case of X-mode) does not describe realistic plasma conditions.…”

Section: Analytical Considerationsmentioning

confidence: 99%

“…Once a set of 3000 delay times for each density perturbation amplitude was obtained for a linear n 0 profile, the delay r.m.s. was computed and compared to the prediction given by equation (10).…”

Section: Numerical Integrationmentioning

confidence: 99%

“…The radar pulse reflectometry technique was proposed and employed for density profile measurements [10].The diagnostic has the benefit of operating in the time-domain, making it possible to directly measure the delay of the reflected pulses and to separate them from parasitic reflections and scattering away from the cut-off.…”

Section: Introductionmentioning

confidence: 99%

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A method for density fluctuation measurements using pulse reflectometry

2023

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An analytical 1D model based on the WKB approximation is used to study the properties of a short pulse reflectometry diagnostic in a magnetic fusion device. Expressions linking the pulse delay with the parameters of the turbulence near the cut-off layer are derived for both ordinary and extraordinary polarizations of the probing beam. These results are used to develop a method for measuring the turbulence amplitude and the radial correlation length. The analytical conclusions and the proposed method are validated using full-wave numerical modelling. The latter is also used to study the limitations of the method and potential experimental effects not included in the reduced model.

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“…We will select a central frequency ω 0 and designate the corresponding value of L as L 0 . From equations ( 8)- (10) one then obtains:…”

Section: Analytical Considerationsmentioning

confidence: 99%

Section: Analytical Considerationsmentioning

confidence: 99%

Section: Numerical Integrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A method for density fluctuation measurements using pulse reflectometry

2023

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“…SPR does also feature unique technical challenges. SPR prototypes were successfully demonstrated by Shevchenko et al 2 , Heijnen et al 3 , and Tokuzawa et al 4 in the nineties but none are operational today. SPR was traditionally implemented by combining a discrete number of fixed frequency oscillators, sending sequential nsscale pulses of increasing frequency, and measuring the round-trip group delays using analog pulse-detection systems.…”

Section: Introductionmentioning

confidence: 99%

V-band nanosecond-scale pulse reflectometer diagnostic in the TCV tokamak

Cabrera

Coda

Porte

et al. 2019

Review of Scientific Instruments

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This article describes the realization of a novel approach to short pulse (∼1ns) reflectometry (SPR) recently implemented in the TCV tokamak. Taking advantage of a fast arbitrary waveform generator and vectornetwork-analyzer extension modules, the design offers flexibility regarding pulse output frequency, duration, and repetition rate. Such flexibility allows the instrument to overcome traditional SPR spatial sampling limitations while reducing hardware complexity. In order to measure the group-delay of ns-scale pulses, both traditional analog and novel digital sampling techniques have been explored. A group-delay range resolution of 17ps (2.6mm) in average over the V-band has been achieved with both timing techniques against a waveguide mirror featuring 10dB power fluctuations. Direct pulse sampling during L-mode plasmas shows that reflected pulse widths increase only by 4% in average. However, pulse width dispersion does occur in L-mode plasmas and leads to an increase in the group-delay uncertainty up to 40ps (6mm). Raw histograms of group-delay data show interesting qualitative changes from L to H-mode. Frequency spectra of group-delay data allow the identification of macroscopic density fluctuations as well as edge quasi-coherent modes during ELM-free H-modes. Lastly, fast changes to the density profile have been measured with microsecond time resolution and sub-cm spatial resolution in both O and X-mode polarizations.

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Status and Prospects of Pulse Radar Reflectometry on the Start Tokamak

Shevchenko

1998

Diagnostics for Experimental Thermonuclear Fusion Reactors 2

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Pulse radar reflectometry for fusion plasma diagnostics

Cited by 23 publications

References 1 publication

A method for density fluctuation measurements using pulse reflectometry

A method for density fluctuation measurements using pulse reflectometry

V-band nanosecond-scale pulse reflectometer diagnostic in the TCV tokamak

Status and Prospects of Pulse Radar Reflectometry on the Start Tokamak

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