Beta limit due to m/n = 2/1 tearing mode onset in the DIII-D hybrid scenario

Journal Article · Tue Jan 01 00:00:00 EST 2008 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/48/1/015005· OSTI ID:1170913

La Haye, R. J. ^[1]; Politzer, P. A. ^[1]; Brennan, D. P. ^[2]

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1. General Atomics, San Diego, CA (United States)
2. Univ. of Tulsa, OK (United States)

The performance (β_N ≈ 3, q₉₅ ≈ 4.4, f_BS ≈ 0.5, H₈₉ > 2) of hybrid scenario plasmas in DIII-D is limited by m/n = 2/1 tearing modes. Unlike conventional plasmas, the linear dependence scaling of the global beta for onset of the instability with normalized local ion gyroradius ρ_i^* is modified as the n = 1 ideal kink beta limit is approached, suggesting that small island neoclassical tearing mode (NTM) threshold physics does not impose the dominant criterion for NTM stability. The hybrid scenario tends to go unstable just at or below the no wall n = 1 ideal kink beta limit of about 4l. Experimentally 4l_i decreases with beta as 4l_i ≈ 5.7 β_N^-1/2. Thus the 'ceiling' in beta due to coupling of tearing to the ideal kink comes down as beta is increased. Scaling of the tearing unstable beta that combines both NTM threshold physics and a pole in Δ'r due to coupling to the ideal kink is presented

• Sponsoring Organization: USDOE Office of Science (SC), Fusion Energy Sciences (FES)
• OSTI ID: 1170913
• Journal Information: Nuclear Fusion, Vol. 48, Issue 1; ISSN 0029-5515
• Publisher: IOP Science
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY