Application of the triple Langmuir probe to study local plasma parameters in the radiofrequency discharge that is placed in an additional applied magnetostatic field

Kozhevnikov, Vladimir Valentinovich; Melnikov, A. V.; Khartov, S. A.

doi:10.1063/5.0032306

Cited by 2 publications

(1 citation statement)

References 11 publications

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“…In the 1920s, Langmuir and Mott-Smith proposed a single probe capable of measuring various plasma parameters [2]. For a century, Langmuir probes have become the most important technical means in laboratory and space plasma diagnosis [5][6][7][8][9]. The Langmuir probe is easy to operate, just insert a conductor into the plasma, apply a scanning voltage on the metal electrode with a variable power supply, and measure the current on the electrode to obtain the current-voltage (I-V) characteristics.…”

Section: Introductionmentioning

confidence: 99%

A bidirectional long short-term memory network for electron density diagnostic with double probe

Wang,

Zhou,

et al. 2023

Meas. Sci. Technol.

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The double probe method is a plasma in situ diagnostic technology. Compared with Langmuir single probe, it has less influence on the background plasma and can obtain relatively accurate results. However, it can only collect some high-energy electrons in the plasma, and cannot directly measure the electron density (Ne). In this paper, a double probe Ne diagnosis approach based on Bidirectional Long Short-Term Memory (BLSTM) is proposed. After the training is completed, the accurate prediction of Ne can be realized by using the double probe data, which solves the problem that the double probe cannot directly measure Ne. In the plasma simulation environment of the laboratory, the plasma source is controlled to generate plasma with different densities, the current–voltage (I–V) characteristic data of the double probe at the same position are used as features, and the Ne calculated by the triple probe is used as the label to train the BLSTM model. The mean square error (MSE) is used as the loss function, the root mean square error (RMSE) and the prediction accuracy (Acc) are used as the evaluation indicators. The BLSTM network is evaluated according to the evaluation indicators and the hyperparameters are adjusted. After about 100 iterations, the RMSE of the BLSTM network to Ne can be reduced to about 0.03. The final network is evaluated on a separate test set. The results show that in the range of 2×1013 m-3 to 3×1014 m-3, the model can predict Ne more than 95% accurately. This approach extends the application of the double probe method and is of great significance for improving the accuracy of plasma diagnostic methods. If it is applied to ionospheric plasma diagnosis, it can reduce the amount of data collected by the probe and improve the spatial resolution of ionospheric detection.

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Section: Introductionmentioning

confidence: 99%

A bidirectional long short-term memory network for electron density diagnostic with double probe

Wang,

Zhou,

et al. 2023

Meas. Sci. Technol.

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Advancement of Langmuir probe-based laser photo-detachment technique for negative ion density measurement in a high-power helicon plasma source

Mukhopadhyay,

Bandyopadhyay,

Tyagi

et al. 2024

Review of Scientific Instruments

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In the pursuit of precise diagnostics for measuring negative ion density in a helicon plasma source (HPS), a new approach utilizing a radio frequency (RF) broadband transformer-based Langmuir probe is developed specifically for laser photo-detachment (LPD) analysis. This inductively coupled LPD technique is useful for high power RF systems in which capacitive RF noise is in the same scale as the pulsed photo-detachment signal. The signal acquired by this transformer-based probe is compared against the conventional Langmuir probe-based LPD technique, revealing a remarkable enhancement in signal fidelity through an improved signal-to-noise ratio (SNR) achieved by the RF broadband transformer methodology. In addition, the localized hydrogen negative ion density measurements obtained through this probe are harmoniously aligned with the line-averaged negative ion density derived from the cavity ringdown spectroscopy (CRDS) technique. These concurrence measurements highlight the RF broadband transformer-based approach’s accuracy in capturing localized negative ion density during helicon mode operation in an HPS setup. Furthermore, the correlation of negative ion density values with RF input exhibits a consistent trend in tandem with background plasma density. Notably, both CRDS and LPD measurements ascertain negative ion densities ranging from ∼5 to 6×1016 m−3 under an RF power of 500–700 W and a pressure of 8 × 10−3 mbar, all under the influence of a 55 G axial magnetic field. These specific parameters represent the optimal operational configuration for effective negative ion production with the present experimental HPS setup. Due to its better SNR, the RF broadband transformer-based Langmuir probe emerges as a useful tool for LPD diagnostics, particularly in the presence of pervasive RF noise.

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Application of the triple Langmuir probe to study local plasma parameters in the radiofrequency discharge that is placed in an additional applied magnetostatic field

Cited by 2 publications

References 11 publications

A bidirectional long short-term memory network for electron density diagnostic with double probe

A bidirectional long short-term memory network for electron density diagnostic with double probe

Advancement of Langmuir probe-based laser photo-detachment technique for negative ion density measurement in a high-power helicon plasma source

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