The influence of magnetic-field gradients and boundaries on double-layer formation in capacitively coupled plasmas

Schröder, T.; Grulke, O.; Klinger, T.

doi:10.1209/0295-5075/97/65002

Cited by 6 publications

(6 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Numerical simulation also suggests the formation of current free double layer to be predominantly controlled by the increased ion loss in the diverging magnetic field region [29]. On the other hand, in the experiment of [22] locations of geometric expansion and maximum of magnetic field gradient are both varied and it is shown that stronger double layer is observed only when both these expansion points coincide. Therefore, the role of magnetic expansion with respect to geometric expansion is not yet fully understood.…”

Section: Introductionmentioning

confidence: 83%

“…Various aspects of the plasma double layers have been investigated thoroughly during the last three decadesexperimentally [9,[15][16][17][18][19][20][21][22][23][24][25], theoretically [26,27] as well as in simulation [28][29][30]. Of the different types of plasmas that produce double layer potential structure, the one that has gained tremendous interest amongst many researchers [13,18,19,21,22] is the expanding helicon plasma where plasma is produced by helicon discharge in a source chamber and it is diffused to a diffusion chamber of larger diameter in an expanding magnetic configuration. In 2003, Charles et al [16] first reported double layer formation in such a device.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Ghosh¹,

Chattopadhyay²,

Ghosh³

et al. 2017

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

Transition from single to multiple axial potential structure (MAPS) formation is reported in expanding helicon plasma. This transition is created by forming a cusp magnetic field at the downstream after the expansion throat. Two distinct potential drops are separated by a uniform axial potential zone. Non-uniform axial density distribution exists in expanding helicon systems. A cusp-like field nourishes both the axial density gradients sufficient enough for the formation of these two distinct potential drops. It is also shown that both single and multiple axial potential structures are observed only when both geometric and magnetic expansions closely coincide with each other. Coexistence of these two expansions at the same location enhances plasma expansion which facilitates deviation from Boltzmann distribution and violates quasi-neutrality locally.

show abstract

Section: Introductionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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

Ghosh¹,

Chattopadhyay²,

Ghosh³

et al. 2017

J. Phys. D: Appl. Phys.

View full text Add to dashboard Cite

show abstract

“…Few studies have directly addressed how the location of the geometric expansion relative to the magnetic field would effect the creation of the axial potential structure known to accelerate a supersonic ion beam or the formation of the high density conics downstream. To our knowledge, only two studies have reported comparisons of the axial characteristics of low-pressure expanding plasmas between cases in which the geometric expansion is and is not colocated with the diverging magnetic field [25,26]. The study by Schröder et al used the linear plasma device VINETA to assess the creation and position of double layer potential structures under different magnetic field and geometric conditions.…”

Section: Introductionmentioning

confidence: 99%

Separating the location of geometric and magnetic expansions in low-pressure expanding plasmas

Bennet

Charles

Boswell

2018

Plasma Sources Sci. Technol.

View full text Add to dashboard Cite

A geometric expansion and sharply diverging magnetic field are typically colocated in lowpressure expanding plasma devices to enhance diffusion and drive ion acceleration through the creation of sharply decreasing axial potential profiles. In this study we assess the ion and electron transport for cases in which the geometric expansion is and is not colocated with the diverging magnetic field through the inclusion of a pyrex extension tube, displacing the geometric expansion further downstream. Measurements on axis demonstrate that a directional, accelerated ion population is still created when the the extension tube is included, however the beam has a lower velocity and density than the standard case. The change in beam characteristics is linked to variations in the source density profile which results in a smaller potential drop that is stretched over a larger axial distance. The modification in the source density is found to result from the increased residence time of hot electrons situated on radial magnetic field lines that would normally ionise high density conics downstream of the source, typically reported as a hollow density profile.

show abstract

“…Extensive measurements [1][2][3][4][5][6][7] and analysis [8][9][10][11] of beam formation in current-free double layers (CFDLs) have been performed since the first beam observations in inductively coupled helicon plasmas. [12][13][14] Such beams are typically observed a short distance after the source plasma has flowed into an expansion chamber downstream from the source.…”

Section: Introductionmentioning

confidence: 99%

A comparison of ion beam measurements by retarding field energy analyzer and laser induced fluorescence in helicon plasma devices

et al. 2015

View full text Add to dashboard Cite

Both Laser-Induced Fluorescence (LIF) and Retarding Field Energy Analyzers (RFEA) have been applied to the investigation of beams formed in inductively coupled helicon plasmas. While the LIF technique provides a direct measurement of the velocity distribution in the plasma, the RFEA measures ion flux as a function of a retarding potential. In this paper, we present a method to compare the two techniques, by converting the LIF velocity distribution to an equivalent of a RFEA measurement. We applied this method to compare new LIF and RFEA measurements in two different experiments; the Hot Helicon Experiment (HELIX)-Large Experiment on Instabilities and Anisotropies (LEIA) at West Virginia University and Njord at University of Tromsø. We find good agreement between beam energies of the two methods. In agreement with earlier observations, the RFEA is found to measure ion beams with densities too low for the LIF to resolve. In addition, we present measurements of the axial development of the ion beam in both experiments. Beam densities drop exponentially with distance from the source, both in LIF and RFEA measurements. The effective quenching cross section from LIF in LEIA is found to be r b;Ã ¼ 4 Â 10 À19 m 2 , and the effective beam collisional cross sections by RFEA in Njord to be r b ¼ 1:7 Â 10 À18 m 2. V

show abstract

The influence of magnetic-field gradients and boundaries on double-layer formation in capacitively coupled plasmas

Cited by 6 publications

References 27 publications

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

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

Separating the location of geometric and magnetic expansions in low-pressure expanding plasmas

A comparison of ion beam measurements by retarding field energy analyzer and laser induced fluorescence in helicon plasma devices

Contact Info

Product

Resources

About