# Nonextensive statistics and the sheath criterion in collisional plasmas

## Abstract

The Bohm criterion in an electropositive plasma containing nonextensively distributed electrons and warm ions is investigated by using a steady state two-fluid model. Taking into account the ion-neutral collisions and finite temperature of ions, a modified Bohm criterion is derived which limits both maximum and minimum allowable velocity of ions at the sheath edge (u{sub 0i}). It is found that the degree of nonextensivity of electrons (q) and temperature of positive ions (T{sub i}) affect only the lower limit of the entrance velocity of ions into the sheath while the degree of ion collisionality (α) influences both lower and upper limits of the ion velocities at the sheath edge. In addition, depending on the value of q, it is shown that the minimum velocity of positive ions at the sheath edge can be greater or smaller than its Maxwellian counterpart. Moreover, it is shown that, depending on the values of α and T{sub i}, the positive ions with subsonic velocity may enter the sheath for either q > 1 or −1 < q < 1. Finally, as a practical application, the density distribution of charged particles in the sheath region is studied for different values of u{sub 0i}, and it is shown that monotonical reduction ofmore »

- Authors:

- Physics Department of K. N. Toosi University of Technology, 15418-49611, Tehran (Iran, Islamic Republic of)

- Publication Date:

- OSTI Identifier:
- 22408035

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 1; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BOHM CRITERION; CATIONS; COLLISIONAL PLASMA; COLLISIONS; ELECTRONS; FLOW MODELS; ION DENSITY; ION TEMPERATURE; PLASMA SHEATH; STATISTICS; STEADY-STATE CONDITIONS; VELOCITY

### Citation Formats

```
Hatami, M. M., E-mail: m-hatami@kntu.ac.ir.
```*Nonextensive statistics and the sheath criterion in collisional plasmas*. United States: N. p., 2015.
Web. doi:10.1063/1.4906355.

```
Hatami, M. M., E-mail: m-hatami@kntu.ac.ir.
```*Nonextensive statistics and the sheath criterion in collisional plasmas*. United States. doi:10.1063/1.4906355.

```
Hatami, M. M., E-mail: m-hatami@kntu.ac.ir. Thu .
"Nonextensive statistics and the sheath criterion in collisional plasmas". United States.
doi:10.1063/1.4906355.
```

```
@article{osti_22408035,
```

title = {Nonextensive statistics and the sheath criterion in collisional plasmas},

author = {Hatami, M. M., E-mail: m-hatami@kntu.ac.ir},

abstractNote = {The Bohm criterion in an electropositive plasma containing nonextensively distributed electrons and warm ions is investigated by using a steady state two-fluid model. Taking into account the ion-neutral collisions and finite temperature of ions, a modified Bohm criterion is derived which limits both maximum and minimum allowable velocity of ions at the sheath edge (u{sub 0i}). It is found that the degree of nonextensivity of electrons (q) and temperature of positive ions (T{sub i}) affect only the lower limit of the entrance velocity of ions into the sheath while the degree of ion collisionality (α) influences both lower and upper limits of the ion velocities at the sheath edge. In addition, depending on the value of q, it is shown that the minimum velocity of positive ions at the sheath edge can be greater or smaller than its Maxwellian counterpart. Moreover, it is shown that, depending on the values of α and T{sub i}, the positive ions with subsonic velocity may enter the sheath for either q > 1 or −1 < q < 1. Finally, as a practical application, the density distribution of charged particles in the sheath region is studied for different values of u{sub 0i}, and it is shown that monotonical reduction of the positive ion density distribution occurs only when the velocity of positive ions at the sheath edge lies between two above mentioned limits.},

doi = {10.1063/1.4906355},

journal = {Physics of Plasmas},

number = 1,

volume = 22,

place = {United States},

year = {Thu Jan 15 00:00:00 EST 2015},

month = {Thu Jan 15 00:00:00 EST 2015}

}