Two density peaks in low magnetic field helicon plasma

Wang, Y.; Zhao, Guanghui; Liu, Z. W.; Ouyang, Jiting; Chen, Q.

doi:10.1063/1.4930287

Cited by 21 publications

(20 citation statements)

References 24 publications

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“…If one observes at the fixed end, the helicon waves propagating at opposite direction will show in the opposite rotation. Additionally, the discharge transition shown in figure 3 is also similar to that in uniform magnetic field [20] in which the discharge is supposed to be caused by the surface non-resonance mode conversion of TG wave. Recently, Ganguli et al [2,6] reported the mechanism of surface absorption by TG waves is similar to Samrai's work [10] that the efficient RF absorption could also occur through TG waves which are excited near the plasma boundary and absorbed quickly.…”

supporting

confidence: 54%

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

Wang

Zhao

Niu

2017

Plasma Sci. Technol.

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In this work, the reversal of radial glow distribution induced by reversed magnetic field is reported. Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction, it seems such a phenomenon in theory appears impossible. However, according to the diagnostic of the helicon waves by magnetic probe, it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves, i.e., the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field. It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution. The appearance of the traveling wave does not only improve the discharge strength, but also determines the transition of the discharge mode.

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supporting

confidence: 54%

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

Wang

Zhao

Niu

2017

Plasma Sci. Technol.

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“…However, no radial probe sweeps were performed at these low I Coils values in order to obtain radial n r profiles. Density peaks at low magnetic fields have been noticed earlier in different experiments (Shamrai & Taranov 1996;Chen 2003;Cho 2006;Lafleur, Charles & Boswell 2010a,b;Barada et al 2013;Wang et al 2015). Studies of this phenomenon have not yet provided an exact physical explanation, but several suggestions point to a helicon mode or a Trivelpiece-Gould (TG) mode which causes the plasma production to increase at a low axial magnetic field.…”

Section: Resultsmentioning

confidence: 88%

“…2013; Wang et al. 2015). Studies of this phenomenon have not yet provided an exact physical explanation, but several suggestions point to a helicon mode or a Trivelpiece–Gould (TG) mode which causes the plasma production to increase at a low axial magnetic field.…”

Section: Resultsmentioning

confidence: 99%

Effect of permanent magnets on plasma confinement and ion beam properties in a double layer helicon plasma source

Varberg

Fredriksen

2019

J. Plasma Phys.

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The work described in this article was carried out to investigate how permanent magnets (PM) affect the plasma confinement and ion beam properties in an inductively coupled plasma which expands from a helicon source. The cylindrical plasma device Njord has a 13 cm long and 20 cm wide stainless steel port connecting the source chamber and the diffusion chamber. The source chamber has an axial magnetic field produced by two coils, with magnetic field lines expanding into the diffusion chamber. Simulations have shown that the field lines leaving the edge of the source hit the port wall, causing a loss of electrons in this section. In the experiments performed in this work, PMs were added around the port walls near the exit of a plasma source and the effect was investigated experimentally by means of a retarding field energy analyser probe. The plasma potential, ion density and ion beam parameters were estimated, and the results with and without the PMs were compared. The results showed that the plasma density in the centre can in some cases be doubled, and the density at the edges of the plasma increased significantly with PMs in place. Although the plasma potential was slightly affected, and the beam velocity dropped by ${\sim}$ 10 %, the ion beam flux increased by a factor of 1.5.

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“…1, which has been described in detail elsewhere. [16] Briefly, the discharge system consists of a quartz cylinder (34 cm in length and 7 cm in inner diameter) with one end connected to a diffusion chamber (30 cm in length and 33 cm in inner diameter), and the other end of the tube is sealed by a dielectric plate (polytetrafluoroethylene, PTFE). The discharge gas is pure argon at a pressure of 0.35 Pa.…”

Section: Experimental Setup and Diagnosticsmentioning

confidence: 99%

“…[6][7][8][9][10][11][12][13][14][15] In recent years, the multiple lowfield density peaks were reported. [14,16] Helicon plasma generated in a non-uniform magnetic field was also addressed in previous research. [17][18][19] For example, Virko et al [20] examined the plasma characteristics and wave structures in m = 0 helicon discharge operated in a non-uniform magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Modulation of absorption manner in helicon discharges by changing profile of low axial magnetic field

Zhao¹,

Wang²,

Niu³

et al. 2017

Chinese Phys. B

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The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 13.56-MHz power source in 0.35-Pa argon environment. The peak of the external non-uniform magnetic field (B ex ) along the axis is observed in a range from 0 Gs to 250 Gs (1 Gs = 10 −4 T), where the electron density varies from 0.5×10 16 m −3 to 9×10 16 m −3 . When B ex is located near the tube upper end sealed by a dielectric plate, or near the tube bottom end connected with a diffusion chamber, the plasmas are centralized in the tube in the former case while the strong luminance appears between the edge of the tube and the axial line in the latter case. When B ex is located in the middle of the antenna, moreover, an effective resistance (R eff ) peak appears apparently with increasing magnetic field. The glow moves toward first the edge of the tube and then the two antenna legs as the magnetic field increases. The discharge in this case is caused by the absorption of Trivelpiece-Gould (TG) wave. It is suggested that B ex is located in the middle of the antenna to obtain a higher efficiency of power transfer.

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Two density peaks in low magnetic field helicon plasma

Cited by 21 publications

References 24 publications

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

Effect of permanent magnets on plasma confinement and ion beam properties in a double layer helicon plasma source

Modulation of absorption manner in helicon discharges by changing profile of low axial magnetic field

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