Study of axial double layer in helicon plasma by optical emission spectroscopy and simple probe

Zhao, Guanghui; Zhu, Wanying; Chen, Qiang; Tan, Chang; Ouyang, Jiting

doi:10.1088/2058-6272/aab4f1

Cited by 15 publications

(17 citation statements)

References 35 publications

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“…The experiment setup of helicon discharge is shown in figure 1(a); this has been used in our previous works [21][22][23][24]. Briefly, the setup consists of a vacuum chamber and vacuum pump group, an RF power source and matching network, a couple of magnetic field coils, a helical antenna and water cooling.…”

Section: Methodsmentioning

confidence: 99%

“…The floating electrostatic probe [21], as shown in figure 4, is connected to an electrostatic voltmeter through a radio frequency filter circuit to obtain the floating potential V f . The RF circuit can filter out AC signals of 13.56 and 27.12 MHz.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…In our previous work [21], it was demonstrated that DLs can be formed near the magnetic field gradient in wavecoupled (W-) mode in argon helicon plasma, and the magnetic field is one of the most important factors for DL. In this study, we try to confirm the decisive role of the gradient of the external magnetic field on the formation and structure of DL in discharge plasma.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of double layer in argon helicon plasma and magnetized DC discharge plasma

Cui¹,

Han²,

He³

et al. 2022

Plasma Sci. Technol.

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We present in this paper the comparison of an electric double layer (DL) in argon helicon plasma and magnetized direct current (DC) discharge plasma. DL in high-density argon helicon plasma of 13.56 MHz RF discharge was investigated experimentally by a floating electrostatic probe and local optical emission spectroscopy (LOES). The DL characteristics at different operating parameters, including RF power (300–1500 W), tube diameter (8–60 mm), and external magnetic field (0–300 G), were measured. For comparison, DL in magnetized plasma channel of a DC discharge under different conditions was also measured experimentally. The results show that in both cases, DL appears in a divergent magnetic field where the magnetic field gradient is the largest and when the plasma density is sufficiently high. DL strength (or potential drop of DL) increases with the magnetic field in two different structures. It is suggested that the electric DL should be a common phenomenon in dense plasma under a gradient external magnetic field. DL in magnetized plasmas can be controlled properly by magnetic field structure and discharge mode (hence the plasma density).

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Section: Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Comparison of double layer in argon helicon plasma and magnetized DC discharge plasma

Cui¹,

Han²,

He³

et al. 2022

Plasma Sci. Technol.

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show abstract

“…A ceramic collimator was designed and installed on the head of the optical fiber. The spatial resolution of this OES assembly was less than 5 mm, and was described in detail in our previous works [4,19,20]. For a brief introduction here, a light-proof ceramic collimator was designed and mounted on the head of the optical fiber.…”

Section: Experimental Apparatusmentioning

confidence: 99%

“…Due to the advantages of high density, electrodeless design, and multiple operation modes, helicon plasmas are gaining more and more attention as thrusters or plasma sources in spacecraft propulsion [1][2][3][4]. In helicon plasmas, the electron characteristics are very important because electrons are the medium for neutral particles and plasmas.…”

Section: Introductionmentioning

confidence: 99%

Electron population properties with different energies in a helicon plasma source

Zhang¹,

Zhang²,

Tang³

et al. 2020

Plasma Sci. Technol.

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The characteristics of electrons play a dominant role in determining the ionization and acceleration processes of plasmas. Compared with electrostatic diagnostics, the optical method is independent of the radio frequency (RF) noise, magnetic field, and electric field. In this paper, an optical emission spectroscope was used to determine the plasma emission spectra, electron excitation energy population distributions (EEEPDs), growth rates of low-energy and high-energy electrons, and their intensity jumps with input powers. The 56 emission lines with the highest signal-to-noise ratio and their corresponding electron excitation energy were used for the translation of the spectrum into EEEPD. One discrete EEEPD has two clear different regions, namely the low-energy electron excitation region (neutral lines with threshold energy of 13–15 eV) and the high-energy electron excitation region (ionic lines with threshold energy ≥19 eV). The EEEPD variations with different diameters of discharge tubes (20 mm, 40 mm, and 60 mm) and different input RF powers (200–1800 W) were investigated. By normalized intensity comparison of the ionic and neutral lines, the growth rate of the ionic population was higher than the neutral one, especially when the tube diameter was less than 40 mm and the input power was higher than 1000 W. Moreover, we found that the intensities of low-energy electrons and high-energy electrons jump at different input powers from inductively coupled (H) mode to helicon (W) mode; therefore, the determination of W mode needs to be carefully considered.

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Design and testing of a Mini-RF plasma thruster with permanent magnets

Sun,

Zhang,

Zhang

2024

J Electr Propuls

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Compared with traditional electric propulsion, RF plasma thruster have attracted much attention due to their characteristics of no electrodes, long life, and high ionization rate. In recent years, the development of micro-nano satellites has put forward requirements for the miniaturization, modularization, and integration of satellite thrusters, and the miniaturization of RF plasma thrusters has a broad prospect. In this paper, a mini-RF plasma thruster with a discharge chamber inner diameter of 10 mm is designed, and a magnetic field is generated around it by two annular samarium cobalt permanent magnets. The discharge state and plasma parameters of the mini-RF thruster are tested using optical emission spectrometry (OES) and target thrust stand. In the experiment, we changed the flow rate of argon gas, the presence or absence of a magnetic field, the power of the RF source and analyzed the effects of these factors on the mode transition, plasma density, electron temperature, and thrust. According to the experimental results, it is found that the magnetic field (maximum strength 0.14T) helps to increase the plasma density at low power but delay the jump power threshold of the CCP-ICP.

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Study of axial double layer in helicon plasma by optical emission spectroscopy and simple probe

Cited by 15 publications

References 35 publications

Comparison of double layer in argon helicon plasma and magnetized DC discharge plasma

Comparison of double layer in argon helicon plasma and magnetized DC discharge plasma

Electron population properties with different energies in a helicon plasma source

Design and testing of a Mini-RF plasma thruster with permanent magnets

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