# The beta limit in the DIII-D tokamak

## Abstract

The combination of high power deuterium neutral beam injection and operation with high current double-null divertor discharges has enabled increasingly high values of both toroidal and normalized beta ({beta}{sub T} and {beta}{sub N} respectively) to be obtained in the DIII-D tokamak. The highest achieved values are {beta}{sub T} = 9.3% and {beta}{sub N} = 5%-m-T/MA, obtained indifferent discharges. Here, {beta}{sub T} = ({integral}PdV/V)/(B{sup 2}/{mu} {sub 0}) is the volume average beta and {beta}{sub N} = {beta}{sub T}/(I/aB) where a is the minor radius of the discharge, B is the vacuum toroidal magnetic field at the geometric center of the discharge, P is the plasma pressure, V is the discharge volume, and I is the plasma current. It is expected that when the beta reaches a threshold value an ideal instability will occur, either the low toroidal mode number (n) ideal kink mode or the high-n, ideal ballooning mode. If all other obstacles to achieving high values of beta are overcome, it is generally postulated that the insurmountable limit to beta will be the stability threshold of one of these modes. According to Troyon-Sykes scaling, this limit to {beta}{sub N} is a constant (C{sub {beta}}) with a value which depends onmore »

- Authors:

- Publication Date:

- Research Org.:
- General Atomics, San Diego, CA (USA)

- Sponsoring Org.:
- DOE/ER

- OSTI Identifier:
- 6825208

- Report Number(s):
- GA-A-20063; CONF-900602-11

ON: DE90011896; TRN: 90-016480

- DOE Contract Number:
- AC03-89ER51114

- Resource Type:
- Conference

- Resource Relation:
- Conference: 17. European conference on controlled fusion and plasma heating, Amsterdam (Netherlands), 25-29 Jun 1990

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DOUBLET REACTORS; BETA RATIO; BALLOONING INSTABILITY; DIVERTORS; MAGNETIC FIELDS; INSTABILITY; PLASMA INSTABILITY; PLASMA MACROINSTABILITIES; THERMONUCLEAR REACTORS; TOKAMAK TYPE REACTORS; 700101* - Fusion Energy- Plasma Research- Confinement, Heating, & Production

### Citation Formats

```
Ferron, J R, Chu, M S, Helton, F J, Howl, W, Kellman, A G, Lao, L L, Lazarus, E A, Lee, J K, Osborne, T H, Stambaugh, R D, Strait, E J, Taylor, T S, and Turnbull, A D.
```*The beta limit in the DIII-D tokamak*. United States: N. p., 1990.
Web.

```
Ferron, J R, Chu, M S, Helton, F J, Howl, W, Kellman, A G, Lao, L L, Lazarus, E A, Lee, J K, Osborne, T H, Stambaugh, R D, Strait, E J, Taylor, T S, & Turnbull, A D.
```*The beta limit in the DIII-D tokamak*. United States.

```
Ferron, J R, Chu, M S, Helton, F J, Howl, W, Kellman, A G, Lao, L L, Lazarus, E A, Lee, J K, Osborne, T H, Stambaugh, R D, Strait, E J, Taylor, T S, and Turnbull, A D. Sun .
"The beta limit in the DIII-D tokamak". United States.
```

```
@article{osti_6825208,
```

title = {The beta limit in the DIII-D tokamak},

author = {Ferron, J R and Chu, M S and Helton, F J and Howl, W and Kellman, A G and Lao, L L and Lazarus, E A and Lee, J K and Osborne, T H and Stambaugh, R D and Strait, E J and Taylor, T S and Turnbull, A D},

abstractNote = {The combination of high power deuterium neutral beam injection and operation with high current double-null divertor discharges has enabled increasingly high values of both toroidal and normalized beta ({beta}{sub T} and {beta}{sub N} respectively) to be obtained in the DIII-D tokamak. The highest achieved values are {beta}{sub T} = 9.3% and {beta}{sub N} = 5%-m-T/MA, obtained indifferent discharges. Here, {beta}{sub T} = ({integral}PdV/V)/(B{sup 2}/{mu} {sub 0}) is the volume average beta and {beta}{sub N} = {beta}{sub T}/(I/aB) where a is the minor radius of the discharge, B is the vacuum toroidal magnetic field at the geometric center of the discharge, P is the plasma pressure, V is the discharge volume, and I is the plasma current. It is expected that when the beta reaches a threshold value an ideal instability will occur, either the low toroidal mode number (n) ideal kink mode or the high-n, ideal ballooning mode. If all other obstacles to achieving high values of beta are overcome, it is generally postulated that the insurmountable limit to beta will be the stability threshold of one of these modes. According to Troyon-Sykes scaling, this limit to {beta}{sub N} is a constant (C{sub {beta}}) with a value which depends on the limiting ideal instability, plasma profiles, and wall stabilization. Previous tokamak experiments have found operational limits representing C{sub {beta}} values from 2.8 to 3.5, associated with several types of instabilities. Experimental data is presented in this paper that demonstrates that over a wide range of plasma current, in DIII-D the value of C{sub {beta}} is larger than 3.5.},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {1990},

month = {4}

}