# Aspect Ratio Scaling of Ideal No-wall Stability Limits in High Bootstrap Fraction Tokamak Plasmas

## Abstract

Recent experiments in the low aspect ratio National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 (2000) 557] have achieved normalized beta values twice the conventional tokamak limit at low internal inductance and with significant bootstrap current. These experimental results have motivated a computational re-examination of the plasma aspect ratio dependence of ideal no-wall magnetohydrodynamic stability limits. These calculations find that the profile-optimized no-wall stability limit in high bootstrap fraction regimes is well described by a nearly aspect ratio invariant normalized beta parameter utilizing the total magnetic field energy density inside the plasma. However, the scaling of normalized beta with internal inductance is found to be strongly aspect ratio dependent at sufficiently low aspect ratio. These calculations and detailed stability analyses of experimental equilibria indicate that the nonrotating plasma no-wall stability limit has been exceeded by as much as 30% in NSTX in a high bootstrap fraction regime.

- Authors:

- Publication Date:

- Research Org.:
- Princeton Plasma Physics Lab., NJ (US)

- Sponsoring Org.:
- USDOE Office of Science (SC) (US)

- OSTI Identifier:
- 820210

- Report Number(s):
- PPPL-3908

TRN: US0305723

- DOE Contract Number:
- AC02-76CH03073

- Resource Type:
- Technical Report

- Resource Relation:
- Other Information: PBD: 25 Nov 2003

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ASPECT RATIO; BOOTSTRAP CURRENT; ENERGY DENSITY; INDUCTANCE; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; STABILITY; STABILITY, IDEAL HYDROMAGNETIC; TOKAMAKS, NSTX

### Citation Formats

```
Menard, J E, Bell, M G, Bell, R E, Gates, D A, Kaye, S M, LeBlanc, B P, Maingi, R, Sabbagh, S A, Soukhanovskii, V, Stutman, D, and the NSTX National Research Team.
```*Aspect Ratio Scaling of Ideal No-wall Stability Limits in High Bootstrap Fraction Tokamak Plasmas*. United States: N. p., 2003.
Web. doi:10.2172/820210.

```
Menard, J E, Bell, M G, Bell, R E, Gates, D A, Kaye, S M, LeBlanc, B P, Maingi, R, Sabbagh, S A, Soukhanovskii, V, Stutman, D, & the NSTX National Research Team.
```*Aspect Ratio Scaling of Ideal No-wall Stability Limits in High Bootstrap Fraction Tokamak Plasmas*. United States. doi:10.2172/820210.

```
Menard, J E, Bell, M G, Bell, R E, Gates, D A, Kaye, S M, LeBlanc, B P, Maingi, R, Sabbagh, S A, Soukhanovskii, V, Stutman, D, and the NSTX National Research Team. Tue .
"Aspect Ratio Scaling of Ideal No-wall Stability Limits in High Bootstrap Fraction Tokamak Plasmas". United States. doi:10.2172/820210. https://www.osti.gov/servlets/purl/820210.
```

```
@article{osti_820210,
```

title = {Aspect Ratio Scaling of Ideal No-wall Stability Limits in High Bootstrap Fraction Tokamak Plasmas},

author = {Menard, J E and Bell, M G and Bell, R E and Gates, D A and Kaye, S M and LeBlanc, B P and Maingi, R and Sabbagh, S A and Soukhanovskii, V and Stutman, D and the NSTX National Research Team},

abstractNote = {Recent experiments in the low aspect ratio National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40 (2000) 557] have achieved normalized beta values twice the conventional tokamak limit at low internal inductance and with significant bootstrap current. These experimental results have motivated a computational re-examination of the plasma aspect ratio dependence of ideal no-wall magnetohydrodynamic stability limits. These calculations find that the profile-optimized no-wall stability limit in high bootstrap fraction regimes is well described by a nearly aspect ratio invariant normalized beta parameter utilizing the total magnetic field energy density inside the plasma. However, the scaling of normalized beta with internal inductance is found to be strongly aspect ratio dependent at sufficiently low aspect ratio. These calculations and detailed stability analyses of experimental equilibria indicate that the nonrotating plasma no-wall stability limit has been exceeded by as much as 30% in NSTX in a high bootstrap fraction regime.},

doi = {10.2172/820210},

journal = {},

number = ,

volume = ,

place = {United States},

year = {2003},

month = {11}

}