Coherent magnetic field fluctuations and locked modes in a reversed-field pinch

Journal Article · Mon Mar 01 00:00:00 EST 1993 · Physics of Fluids B; (United States)

DOI:https://doi.org/10.1063/1.860939· OSTI ID:6817104

Brunsell, P R; Yagi, Y; Hirano, Y; Maejima, Y; Shimada, T ^[1]

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1. Plasma Section, Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba, Ibaraki 305 (Japan)

Magnetic field fluctuations have been measured in the TPE-1RM20 reversed-field pinch [in [ital Plasma] [ital Physics] [ital and] [ital Controlled] [ital Nuclear] [ital Fusion] [ital Research], [ital Proceedings] [ital of] [ital the] 14[ital th] [ital International] [ital Conference], 1992, Wuerzburg (International Atomic Energy Agency, Vienna, 1992) Paper IAEA-CN-56/C-4-3]. The dominant modes are [ital m]=1/[ital n]=7--9, resonant near the axis. The fluctuations are coherent, corresponding to nearly continuous rigid body rotation with poloidal and toroidal frequencies of [ital f][sub [theta]]=130--170 kHz and [ital f][sub [phi]]=11--14 kHz, respectively. Discrete dynamo events (in which toroidal magnetic flux is generated) of two different types are observed at high values of pinch parameter ([Theta][gt]1.6). The first type is triggered by a single, wall-locked [ital m]=1/[ital n]=7 mode. The slowing down of the mode rotation is in rough agreement with a simulation which assumes the effect of induced eddy current in the vacuum liner. In the subsequent relaxation event, the locked mode decays and the [ital m]=1 spectrum cascades to higher-[ital n] modes. However, in some cases the saturated [ital m]=1/[ital n]=7 mode exists for periods up to [ital t]=0.4 msec, resembling single helicity Ohmic states. The second type of event is characterized by phase locking of several [ital m]=1/[ital n]=7--9 modes and the appearance of large [ital m]=0/[ital n]=1--5 modes. Mode rotation continues through the event, similar to the normal machine operating condition.

• OSTI ID: 6817104
• Journal Information: Physics of Fluids B; (United States), Vol. 5:3; ISSN 0899-8221
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
PINCH DEVICES
FLUCTUATIONS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
RELAXATION
RESONANCE
REVERSE-FIELD PINCH
TEARING INSTABILITY
FLUID MECHANICS
HYDRODYNAMICS
INSTABILITY
MECHANICS
PINCH EFFECT
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
THERMONUCLEAR DEVICES
VARIATIONS
700340* - Plasma Waves
Oscillations
& Instabilities- (1992-)