On-axis parallel ion speeds near mechanical and magnetic apertures in a helicon plasma device

Sun, Xuan; Cohen, Samuel A.; Scime, Earl; Miah, Mahmood

doi:10.1063/1.2121347

Cited by 32 publications

(31 citation statements)

References 32 publications

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“…In a series of experiments on the Magnetized Nozzle eXperiment, multiple double layers were intentionally created by introducing grounded apertures upstream from a magnetic nozzle. 17 Axially resolved LIF measurements demonstrated that ions accelerated in the sheath formed by the aperture traveled nearly 30 cm to the magnetic nozzle where they were further accelerated by the double layer at the magnetic nozzle. Between the grounded aperture and the magnetic nozzle, a single accelerated ion population and the background ions created beyond the aperture were both observed with LIF.…”

Section: Lif Measurements Of Multiple Ion Beamsmentioning

confidence: 99%

Spontaneous ion beam formation in the laboratory, space, and simulation

et al. 2013

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We present experimental evidence for the spontaneous formation of multiple double layers within a single divergent magnetic field structure. Downstream of the divergent magnetic field, multiple accelerated ion populations are observed. The similarity of the accelerated ion populations observed in these laboratory experiments to ion populations observed in the magnetosphere and in numerical simulations suggests that the observation of a complex ion velocity distribution alone is insufficient to distinguish between simple plasma expansion and magnetic reconnection. Further, the effective temperature of the aggregate ion population is significantly larger than the temperatures of the individual ion population components, suggesting that insufficiently resolved measurements could misidentify multiple beam creation as ion heating. Ions accelerated in randomly oriented electric fields that mimic heating would have an ion heating rate dependent on the ion charge and mass that is qualitatively consistent with recent experimental observations of ion heating during magnetic reconnection. V C 2013 AIP Publishing LLC. [http://dx

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Section: Lif Measurements Of Multiple Ion Beamsmentioning

confidence: 99%

Spontaneous ion beam formation in the laboratory, space, and simulation

et al. 2013

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“…It was named current-free double layer (CFDL), as it formed self-consistently without external current forcing. The CFDLs formed in these experiments have later been repeated in a number of helicon devices [2][3][4][5][6][7][8][9]. As a result of a potential the drop set up between the source and the diffusion chamber an ion beam is formed.…”

Section: Introductionmentioning

confidence: 99%

RFEA Measurements of High-Energy Electrons in a Helicon Plasma Device with Expanding Magnetic Field

Gulbrandsen

Fredriksen

2017

Front. Phys.

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In the inductively coupled plasma of the Njord helicon device we have, for the same parameters as for which an ion beam exists, measured a downstream population of high-energy electrons emerging from the source. Separated measurements of energetic tail electrons was carried out by Retarding Field Energy Analyzer (RFEA) with a grounded entrance grid, operated in an electron collection mode. In a radial scan with the RFEA pointed toward the source, we found a significant population of high-energy electrons just inside the magnetic field line mapping to the edge of the source. A second peak in high-energy electrons density was observed in a radial position corresponding to the radius of the source. Also, throughout the main column a small contribution of high-energy electrons was observed. In a radial scan with a RFEA biased to collect ions a localized increase in the plasma ion density near the magnetic field line emerging from the plasma near the wall of the source was observed. This is interpreted as a signature of high-energy electrons ionizing the neutral gas. Also, a dip in the floating potential of a Langmuir probe is evident in this region where high-energy electrons is observed.

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“…In plasma applications, a directed ion flux is used to obtain an efficient momentum exhaust for electric propulsion, e.g., variable specific impulse magnetoplasma rocket, 4 and to achieve high aspect ratios in material processing ͑plasma etching͒. [5][6][7] Diverging magnetic field configurations are often used to obtain a unidirectional flow, [8][9][10][11][12][13] where we may anticipate that the magnetization of ions breaks down in the low magnetic field region. For realizing and controlling the plasma flow, it is important to have the knowledge on flow structure in the low magnetic field region, in which the detachment of ion stream line from the magnetic field line takes place.…”

Section: Introductionmentioning

confidence: 99%

Experimental studies on ion acceleration and stream line detachment in a diverging magnetic field

et al. 2010

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The flow structure of ions in a diverging magnetic field has been experimentally studied in an electron cyclotron resonance plasma. The flow velocity field of ions has been measured with directional Langmuir probes calibrated with the laser induced fluorescence spectroscopy. For low ion-temperature plasmas, it is concluded that the ion acceleration due to the axial electric field is important compared with that of gas dynamic effect. It has also been found that the detachment of ion stream line from the magnetic field line takes place when the parameter ͉f ci L B / V i ͉ becomes order unity, where f ci , L B , and V i are the ion cyclotron frequency, the characteristic scale length of magnetic field inhomogeneity, and the ion flow velocity, respectively. In the detachment region, a radial electric field is generated in the plasma and the ions move straight with the E ϫ B rotation driven by the radial electric field.

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On-axis parallel ion speeds near mechanical and magnetic apertures in a helicon plasma device

Cited by 32 publications

References 32 publications

Spontaneous ion beam formation in the laboratory, space, and simulation

Spontaneous ion beam formation in the laboratory, space, and simulation

RFEA Measurements of High-Energy Electrons in a Helicon Plasma Device with Expanding Magnetic Field

Experimental studies on ion acceleration and stream line detachment in a diverging magnetic field

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