Development of the 174 GHz collective Thomson scattering diagnostics at Wendelstein 7-X

Ponomarenko, S.; Moseev, D.; Stange, T.; Krier, L.; Stordiau, P.; Braune, H.; Gantenbein, G.; Jelonnek, J.; Kuleshov, A.; Laqua, H. P.; Lechte, C.; Marsen, S.; Nielsen, S. K.; Oosterbeek, J. W.; Plaum, B.; Ragona, R.; Rasmussen, J.; Ruess, T.; Salewski, M.; Thumm, M.; Zimmermann, J.; ,

doi:10.1063/5.0174444

Cited by 7 publications

(2 citation statements)

References 29 publications

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“…These improvements lowered the noise temperature of the 174 GHz CTS receiver to around 2 eV down from around 8 eV for the 140 GHz case. A detailed characterization of the new receiver is reported separately [26].…”

Section: Jinst 19 C03056mentioning

confidence: 99%

“…• Values of integrated spectra do not fall back to the initial values in the beginning of the overlap sweep. The ECE background never goes to zero and remains in the range 20-70 eV [23,26]. During the gyrotron-on period a process of slight absorption of the 174 GHz probing beam and re-emission in a broader spectral range takes place at the plasma edge.…”

Section: Overlap Sweepmentioning

confidence: 99%

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Commissioning and first results of the 174 GHz collective Thomson scattering diagnostic at Wendelstein 7-X

Moseev,

Ponomarenko,

Laqua

et al. 2024

J. Inst.

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Collective Thomson Scattering (CTS) diagnostics measure the scattering spectrum of monochromatic incident radiation off collective fluctuations in the plasma. In this contribution, we present the first results from the upgraded CTS diagnostic at Wendelstein 7-X (W7-X) operating in the frequency range between 172 and 176 GHz. This frequency range allows for minimization of noise originating from the electron cyclotron emission in the plasma. Consequently, the good signal-to-noise ratio allows measurements of fast ions or bulk plasma parameters with higher temporal resolution compared with the previously used 140 GHz system.

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Section: Jinst 19 C03056mentioning

confidence: 99%

Section: Overlap Sweepmentioning

confidence: 99%

Commissioning and first results of the 174 GHz collective Thomson scattering diagnostic at Wendelstein 7-X

Moseev,

Ponomarenko,

Laqua

et al. 2024

J. Inst.

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Towards absolutely calibrated ECE Michelson measurements in EC heated plasmas at W7-X

Oosterbeek,

Stern,

Chaudhary

et al. 2024

EPJ Web Conf.

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A Michelson Interferometer is in use at Wendelstein 7-X (W7-X) to probe the Electron Cyclotron Emission (ECE) spectrum [1], [2], [3]. During the past operational campaign (OP2.1), 2nd and 3rd harmonic ECE power density spectra have been routinely recorded in the presence of X2and O2-mode Electron Cyclotron Resonance Heating (ECRH). However, combination of the particular notch filter arrangement and high transmission line losses have thus far prevented overall calibration using a hot source cold source exposure at the input antenna. As an alternative, the response of the individual components is measured and summed. While reasonable numbers on electron temperature are obtained in X2-mode polarisation, interaction between front-end components is neglected and large error bars must be assumed. But the information on the individual components, together with synthetic modelling and data from experiment (OP2.1), has been used to design a new front-end with improved S/N. This optimisation is discussed in this paper with focus on notch filter selection, a new transmission line (Tx-line) and a novel combined quasi-optical taper / polarizer tuner.

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Spectral decomposition for collective Thomson scattering based on an improved genetic algorithm

Zhang,

Lan,

Zeng

et al. 2024

Review of Scientific Instruments

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Collective Thomson scattering (CTS) is a diagnostic technique that obtains ion temperature and ion composition of plasma by spectral decomposition from scattering spectra. Bayesian estimation and least squares fitting are usually applied in this spectral decomposition process. Nevertheless, these spectral decomposition methods strongly rely on measurements of other diagnostic systems, and the measurement errors of other systems would influence the spectral decomposition results. In this article, an improved genetic algorithm is applied to decompose the scattering spectra of CTS. By analyzing the sensitivity of plasma parameters, the width and slope of the scattering spectrum are found to be strongly associated with ion temperature. Based on this correlation relation, a new fitness function is designed to provide a more precise estimation of ion temperature. Meanwhile, adaptive crossover and mutation operators are introduced to solve the premature convergence problem. This improved genetic algorithm with the new fitness function can obtain a more precise ion temperature from scattering spectra of CTS and does not rely on the measurement of other diagnostic systems, which has an extensive application prospect in data processing of CTS.

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Development of the 174 GHz collective Thomson scattering diagnostics at Wendelstein 7-X

Cited by 7 publications

References 29 publications

Commissioning and first results of the 174 GHz collective Thomson scattering diagnostic at Wendelstein 7-X

Commissioning and first results of the 174 GHz collective Thomson scattering diagnostic at Wendelstein 7-X

Towards absolutely calibrated ECE Michelson measurements in EC heated plasmas at W7-X

Spectral decomposition for collective Thomson scattering based on an improved genetic algorithm

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