# Turbulence in the cylindrical slab

## Abstract

The cylindrical slab was the first and simplest model of intrinsically unstable microturbulence. The Helimak is an experimental realization of this model. Although finite, it is sufficiently large to escape boundary effects, with dimensionless parameters similar to those of a tokamak edge or scrape off layer. The essential drive is interchange-like, a pressure gradient with unfavorable magnetic curvature, leading to a non-linearly saturated state of large-amplitude turbulence, Δn{sub rms}/n ∼ 0.5. The nonlinear processes governing this saturation are unique, unlike any of those posited for the much weaker turbulence typical of confined plasma, e.g., in a tokamak. Neither linear stability theory, quasi-linear theory, zonal flows, nor flow shear stabilization is consistent with the observations. The mechanisms determining the non-linearly saturated state constitute an important challenge to our understanding of strongly nonlinear systems.

- Authors:

- Institute of Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)

- Publication Date:

- OSTI Identifier:
- 22303626

- Resource Type:
- Journal Article

- Journal Name:
- Physics of Plasmas

- Additional Journal Information:
- Journal Volume: 21; Journal Issue: 9; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; CYLINDRICAL CONFIGURATION; NONLINEAR PROBLEMS; PLASMA; PLASMA SCRAPE-OFF LAYER; PRESSURE GRADIENTS; STABILITY; STABILIZATION; TOKAMAK DEVICES; TURBULENCE

### Citation Formats

```
Gentle, K. W., Rowan, W. L., Williams, C. B., and Brookman, M. W.
```*Turbulence in the cylindrical slab*. United States: N. p., 2014.
Web. doi:10.1063/1.4894687.

```
Gentle, K. W., Rowan, W. L., Williams, C. B., & Brookman, M. W.
```*Turbulence in the cylindrical slab*. United States. doi:10.1063/1.4894687.

```
Gentle, K. W., Rowan, W. L., Williams, C. B., and Brookman, M. W. Mon .
"Turbulence in the cylindrical slab". United States. doi:10.1063/1.4894687.
```

```
@article{osti_22303626,
```

title = {Turbulence in the cylindrical slab},

author = {Gentle, K. W. and Rowan, W. L. and Williams, C. B. and Brookman, M. W.},

abstractNote = {The cylindrical slab was the first and simplest model of intrinsically unstable microturbulence. The Helimak is an experimental realization of this model. Although finite, it is sufficiently large to escape boundary effects, with dimensionless parameters similar to those of a tokamak edge or scrape off layer. The essential drive is interchange-like, a pressure gradient with unfavorable magnetic curvature, leading to a non-linearly saturated state of large-amplitude turbulence, Δn{sub rms}/n ∼ 0.5. The nonlinear processes governing this saturation are unique, unlike any of those posited for the much weaker turbulence typical of confined plasma, e.g., in a tokamak. Neither linear stability theory, quasi-linear theory, zonal flows, nor flow shear stabilization is consistent with the observations. The mechanisms determining the non-linearly saturated state constitute an important challenge to our understanding of strongly nonlinear systems.},

doi = {10.1063/1.4894687},

journal = {Physics of Plasmas},

issn = {1070-664X},

number = 9,

volume = 21,

place = {United States},

year = {2014},

month = {9}

}