A collisional model of the plasma presheath

Scheuer, J.T.; Emmert, G.A.

doi:10.1063/1.866663

Cited by 47 publications

(40 citation statements)

References 12 publications

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“…Ions must fall through a presheath potential drops greater than T e =2e to reach the Bohm velocity when collisions are present. 5 For one ion species, Riemann 6 has shown that mobility limited ion flow in the presheath electric field results in the presheath potential profile can be approximated by eD/ T e % ffiffiffiffiffi ffi Dx k r ;…”

Section: Introductionmentioning

confidence: 99%

Experimental test of instability enhanced collisional friction for determining ion loss in two ion species plasmas

2011

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Recent experiments have shown that ions in weakly collisional plasmas containing two ion species of comparable densities approximately reach a common velocity at the sheath edge equal to the bulk plasma ion sound velocity. A recent theory [S. D. Baalrud, C. C. Hegna, and J. D. Callen, Phys. Rev. Lett. 103, 205002 (2009)] suggests that this is a consequence of collisional friction between the two ion species enhanced by the two stream instability. The theory finds that the difference in velocities at the sheath edge depends on the relative concentrations of the two ions. The difference in velocities is small, with both species approaching to the bulk sound velocity, when the concentrations are comparable, and is large, with each species reaching its own Bohm velocity, when the relative concentration differences are large. To test these findings, drift velocities of Ar and Xe ions were measured with laser-induced fluorescence in Ar-Xe and He-Xe plasmas and combined with ion acoustic wave and plasma potential data. In addition, electron temperature was varied by a Maxwell demon [K. R. MacKenzie et al., App. Phys. Lett. 18, 529 (1971)]. The predictions were found to be in excellent agreement with the experimental data. The generalized Bohm criterion in two ion species plasmas is also verified in a wider variety of relative ion concentrations.

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Section: Introductionmentioning

confidence: 99%

Experimental test of instability enhanced collisional friction for determining ion loss in two ion species plasmas

2011

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“…The constant collision frequency may be a reasonable approximation in low fields [7], where the relative velocity of the collision partners does not differ essentially from the thermal neutral velocity. Although Emmert [8] has considered collision frequency that is a function of speed, this model has been used in ion-ion Coulomb collisions. The model assumes ´Úµ Ú , which is a very poor approximation in the limit Ú ¼ .…”

Section: A Kinetic Formulationmentioning

confidence: 99%

“…These orbits are designated as 'trapped'. The solution of these 'trapped' orbits requires use of the continuity conditions (8) for orbits originating at Ü Ä and…”

Section: A Kinetic Formulationmentioning

confidence: 99%

A self-consistent kinetic modeling of a 1-D, bounded, plasma in equilibrium

Goswami

Ramachandran

2000

Pramana - J Phys

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A self-consistent kinetic treatment is presented here, where the Boltzmann equation is solved for a particle conserving Krook collision operator. The resulting equations have been implemented numerically. The treatment solves for the entire quasineutral column, making no assumptions about Ñ Ô AE Ä , where Ñ Ô is the ion-neutral collision mean free path and Ä the size of the device. Coulomb collisions are neglected in favour of collisions with neutrals, and the particle source is modeled as a uniform Maxwellian. Electrons are treated as an inertialess but collisional fluid. The ion distribution function for the trapped and the transiting orbits is obtained. Interesting findings include the anomalous heating of ions as they approach the presheath, the development of strongly non-Maxwellian features near the last Ñ Ô , and strong modifications of the sheath criterion.

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“…More complex shapes than planar have been considered, such as cylindrical and spherical objects [7,21,22], and trenches and holes [23,24]. Sheath models have been extended to include collisions [25,26]. The situation for HIPIMS is not as advanced.…”

Section: Special Casesmentioning

confidence: 99%

Physics of plasma‐based ion implantation & deposition (PBIID) and high power impulse magnetron sputtering (HIPIMS): A comparison

Anders

2008

Physica Status Solidi (a)

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The emerging technology of High Power Impulse Magnetron Sputtering (HIPIMS) has much in common with the more established technology of Plasma Based Ion Implantation & Deposition (PBIID): both use pulsed plasmas, the pulsed sheath periodically evolves and collapses, the plasma-sheath system interacts with the pulsedriving power supply, the plasma parameters are affected by the power dissipated, surface atoms are sputtered and secondary electrons are emitted, etc. Therefore, both fields of science and technology could learn from each other, which has not been fully explored. On the other hand, there are significant differences, too. Most importantly, the operation of HIPIMS heavily relies on the presence of a strong magnetic field, confining electrons and causing their ExB drift, which is closed for typical magnetron configurations. Second, at the high peak power levels used for HIPIMS, 1 kW/cm2 or greater averaged over the target area, the sputtered material greatly affects plasma generation. For PBIID, in contrast, plasma generation and ion processing of the surface (ion implantation, etching, and deposition) are considered relatively independent processes. Third, secondary electron emission is generally considered a nuisance for PBIID, especially at high voltages, whereas it is a critical ingredient to the operation of HIPIMS. Fourth, the voltages in PBIID are often higher than in HIPIMS. For the first three reasons listed above, modelling of PBIID seems to be easier and could give some guidance for future HIPIMS models, which, clearly, will be more involved.

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A collisional model of the plasma presheath

Abstract: Experimental studies of transverse metastable ion velocity distribution functions in the presheath of a weakly collisional argon plasma Phys. Plasmas 15, 083503 (2008);

Cited by 47 publications

References 12 publications

Experimental test of instability enhanced collisional friction for determining ion loss in two ion species plasmas

Experimental test of instability enhanced collisional friction for determining ion loss in two ion species plasmas

A self-consistent kinetic modeling of a 1-D, bounded, plasma in equilibrium

Physics of plasma‐based ion implantation & deposition (PBIID) and high power impulse magnetron sputtering (HIPIMS): A comparison

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