Spherical tokamak with a plasma center column

Journal Article · Sat Apr 15 04:00:00 EDT 2006 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.2195381· OSTI ID:20782750

Tang, X Z; Boozer, A H ^[1]

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1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

Low aspect ratio toroidal pinches such as the standard (q>1) and the ultralow q (q<1) spherical tori or tokamaks (ST), would have a far more robust reactor engineering design if a plasma center column (PCC) can be used in place of a material center post. Biased electrodes across the plasma center column would drive a plasma current to produce the toroidal magnetic field in lieu of the toroidal field (TF) coils. The operation of such a device is naturally divided into two distinct phases: formation by driven relaxation under magnetic helicity injection and sustainment by auxiliary current drive and heating such as rf and neutral beam injection (NBI). The initial design constraints of a ST-PCC experiment are primarily motivated by the formation rather than the sustainment physics. With a Taylor-relaxed plasma as the baseline case, it is shown that three essential factors guide the design. First, the flux amplification factor determines the aspect ratio of the ST-PCC. Second, the plasma shaping in general and plasma elongation in particular gives the most freedom in shaping the q profile of the relaxed plasma. Two examples are the standard spherical tokamak with q>1 throughout the plasma and the ultralow q (ULQ) spherical tokamak with q much less than unity for the bulk of the plasma. Third, the vacuum bias magnetic flux plays the second most important role in modifying the q profile. As an example, it is shown how the bias flux can be designed to delineate a standard spheromak experiment from that of an ULQ ST-PCC. These physics understandings help define the design space of the ST-PCC experiments and directions for optimization.

• OSTI ID: 20782750
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 4 Vol. 13; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ASPECT RATIO
BEAM INJECTION HEATING
DESIGN
ELECTRIC CURRENTS
ELONGATION
HELICITY
MAGNETIC FIELDS
MAGNETIC FLUX
OPTIMIZATION
PINCH EFFECT
PLASMA
PLASMA BEAM INJECTION
PLASMA CONFINEMENT
RADIATION TRANSPORT
RELAXATION
RF SYSTEMS
SPHEROMAK DEVICES
THERMONUCLEAR REACTORS