Transition from single to multiple axial potential structure in expanding helicon plasma

Ghosh, S.; Chattopadhyay, P. K.; Ghosh, Joydeep; Pal, Rabindranath; Bora, D.

doi:10.1088/1361-6463/aa5068

Cited by 15 publications

(15 citation statements)

References 42 publications

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“…It is also observed that this high-density plasma source could be a viable option for electric propulsion systems, and has received great attention in the helicon double layer thruster community [10][11][12]. Its current-free nature in lowcollisional, magnetically expanding, inductive-or wave-mode discharges distinguishes helicon double layers [12][13][14] from other current-driven double layers. The DL in the plateau region of mirror magnetic field topology was also investigated [5,15].…”

Section: Introductionmentioning

confidence: 99%

“…In a brief communication, an emissive probe wire was proposed by Lafleur et al [25] to take measurements of the potential in an expanding helicon plasma. Recently Ghosh et al [14] also used the emissive probe to measure multiple DLs. Sahu et al [15] used a new RF-compensated Langmuir probe structure to acquire the plasma potential from the maximum of the first order differential of the current-voltage curve.…”

Section: Introductionmentioning

confidence: 99%

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

Zhao¹,

Zhu²,

Chen³

et al. 2018

Plasma Sci. Technol.

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Electron heating in a high-density helicon discharge B Clarenbach, M Krämer and B Lorenz -Thrust measurements in a low-magnetic field mode in the HDLT J Ling, M D West, T Lafleur et al. -Time-dependent gas density and temperature in Ar B Clarenbach, B Lorenz, M Krämer et al. - AbstractIn this work we used a passive measurement method based on a high-impedance electrostatic probe and an optical emission spectroscope (OES) to investigate the characteristics of the double layer (DL) in an argon helicon plasma. The DL can be confirmed by a rapid change in the plasma potential along the axis. The axial potential variation of the passive measurement shows that the DL forms near a region of strong magnetic field gradient when the plasma is operated in wavecoupled mode, and the DL strength increases at higher powers in this experiment. The emission intensity of the argon atom line, which is strongly dependent on the metastable atom concentration, shows a similar spatial distribution to the plasma potential along the axis. The emission intensity of the argon atom line and the argon ion line in the DL suggests the existence of an energetic electron population upstream of the DL. The electron density upstream is much higher than that downstream, which is mainly caused by these energetic electrons.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Zhao¹,

Zhu²,

Chen³

et al. 2018

Plasma Sci. Technol.

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“…1 The ion beam appears in low pressure, expanding helicon plasmas regardless of source size, magnetic field ratio (upstream to downstream), and overall magnetic field strength. [2][3][4][5] The spontaneous creation of ion beams in an expanding plasma is of particular relevance to the development of helicon source plasma thrusters, 6,7 to solar wind acceleration models, 8 and to particle acceleration processes during magnetic reconnection. 9 Soon after their discovery, various researchers proposed explanations for the ion beam creation process that focused on current-free, double layers (DLs) as the phenomenon responsible for the ion beams.…”

Section: Introductionmentioning

confidence: 99%

Pressure dependence of an ion beam accelerating structure in an expanding helicon plasma

et al. 2018

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We present measurements of the parallel ion velocity distribution function and electric field in an expanding helicon source plasma plume as a function of downstream gas pressure and radial and axial positions. The ion beam that appears spontaneously in the plume persists for all downstream pressures investigated, with the largest parallel ion beam velocities obtained for the lowest downstream pressures. However, the change in ion beam velocity exceeds what would be expected simply for a change in the collisionality of the system. Electric field measurements confirm that it is the magnitude of the potential structure responsible for accelerating the ion beam that changes with downstream pressure. Interestingly, the ion density radial profile is hollow close to the end of the plasma source for all pressures, but it is hollow at downstream distances far from the source only at the highest downstream neutral pressures.

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“…Ghosh et al created the transition from single to multiple axial potential structure by forming a cusp magnetic field in the downstream of the diffusion chamber. They pointed out that only when geometric and magnetic expansions closely coincide with each other could single and multiple DL‐like structures appear [24]. Charles [25] found a two‐dimensional (2D) high‐density conic along the most diverging magnetic field lines exiting the source in helicon plasma device, which was also reported by Saha et al [26] that radial density profile in the downstream was peaked on the periphery appearing a hollow profile.…”

Section: Introductionmentioning

confidence: 88%

Effect of magnetic field on double layer in argon helicon plasma

et al. 2020

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The electric double layer in argon helicon plasma by using floating electrostatic probe and local optical emission spectroscopy under different external magnetic field was investigated. Results show that electrons generated in the plasma source can be magnetized by the magnetic field and transported by the gradient of diverging magnetic field in the diffusion chamber, giving rise to the hollowed distribution of electron temperature. The electron temperature on axis has a sudden decrease, leading to the sudden decrease of plasma density as well as the plasma potential, forming a double layer structure. The position of double layer moves along with the position of diverging magnetic field, and the potential drop increases along with the strength of magnetic field. The structure of the external magnetic field plays the decisive factor for the double layer in helicon plasma.

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Transition from single to multiple axial potential structure in expanding helicon plasma

Cited by 15 publications

References 42 publications

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

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

Pressure dependence of an ion beam accelerating structure in an expanding helicon plasma

Effect of magnetic field on double layer in argon helicon plasma

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