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Book Determination of Equilibrium and Stability Characteristics of Low aspect Ratio Spherical Torus Plasmas in the PEGASUS Toroidal Experiment

Download or read book Determination of Equilibrium and Stability Characteristics of Low aspect Ratio Spherical Torus Plasmas in the PEGASUS Toroidal Experiment written by Sontag Aaron and published by . This book was released on 2002 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Operational Regimes of the National Spherical Torus Experiment

Download or read book Operational Regimes of the National Spherical Torus Experiment written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Physics Basis for a Spherical Torus Power Plant

Download or read book Physics Basis for a Spherical Torus Power Plant written by S. C. Jardin and published by . This book was released on 1999 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Progress in Understanding Error field Physics in NSTX Spherical Torus Plasmas

Download or read book Progress in Understanding Error field Physics in NSTX Spherical Torus Plasmas written by and published by . This book was released on 2010 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: The low aspect ratio, low magnetic field, and wide range of plasma beta of NSTX plasmas provide new insight into the origins and effects of magnetic field errors. An extensive array of magnetic sensors has been used to analyze error fields, to measure error field amplification, and to detect resistive wall modes in real time. The measured normalized error-field threshold for the onset of locked modes shows a linear scaling with plasma density, a weak to inverse dependence on toroidal field, and a positive scaling with magnetic shear. These results extrapolate to a favorable error field threshold for ITER. For these low-beta locked-mode plasmas, perturbed equilibrium calculations find that the plasma response must be included to explain the empirically determined optimal correction of NSTX error fields. In high-beta NSTX plasmas exceeding the n=1 no-wall stability limit where the RWM is stabilized by plasma rotation, active suppression of n=1 amplified error fields and the correction of recently discovered intrinsic n=3 error fields have led to sustained high rotation and record durations free of low-frequency core MHD activity. For sustained rotational stabilization of the n=1 RWM, both the rotation threshold and magnitude of the amplification are important. At fixed normalized dissipation, kinetic damping models predict rotation thresholds for RWM stabilization to scale nearly linearly with particle orbit frequency. Studies for NSTX find that orbit frequencies computed in general geometry can deviate significantly from those computed in the high aspect ratio and circular plasma cross-section limit, and these differences can strongly influence the predicted RWM stability. The measured and predicted RWM stability is found to be very sensitive to the E x B rotation profile near the plasma edge, and the measured critical rotation for the RWM is approximately a factor of two higher than predicted by the MARS-F code using the semi-kinetic damping model.

Book Physics Results from the National Spherical Torus Experiment

Download or read book Physics Results from the National Spherical Torus Experiment written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Spherical Torus Experiment (NSTX) at the Princeton Plasma Physics Laboratory is designed for studying toroidal plasma confinement at very low aspect-ratio, A= R/a= 0.85m/0.68m[approximately] 1.25, with cross-section elongation up to 2.2 and triangularity up to 0.5, for plasma currents up to 1 MA and vacuum toroidal magnetic fields up to 0.6 T on axis. Conducting plates are installed close to the plasma on the outboard side to stabilize kink modes. This should permit operation with toroidal-[beta] approaching 40%[1]. The plasmas will be heated by up to 6 MW High-Harmonic Fast Waves (HHFW) at a frequency 30 MHz and by 5 MW of 80 keV deuterium Neutral Beam Injection. Inductive plasma startup can be supplemented by the process of Coaxial Helicity Injection (CHI).

Book New Capabilities and Results for the National Spherical Torus Experiment

Download or read book New Capabilities and Results for the National Spherical Torus Experiment written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The National Spherical Torus Experiment (NSTX) produces plasmas with toroidal aspect ratio as low as 1.25, which can be heated by up to 6 MW High-Harmonic Fast Waves and up to 7 MW of deuterium Neutral Beam Injection. Using new poloidal fields coils, plasmas with cross-section elongation up to 2.7, triangularity 0.8, plasma currents Ip up to 1.5 MA and normalized currents Ip/a·BT up to 7.5 MA/m·T have been achieved. A significant extension of the plasma pulse length, to 1.5 s at a plasma current of 0.7 MA, has been achieved by exploiting the bootstrap and NBI-driven currents to reduce the dissipation of poloidal flux. Inductive plasma startup has been supplemented by Coaxial Helicity Injection (CHI) and the production of persistent current on closed flux surfaces by CHI has now been demonstrated in NSTX. The plasma response to magnetic field perturbations with toroidal mode numbers n = 1 or 3 and the effects on the plasma rotation have been investigated using three pairs of coils outside the vacuum vessel. Recent studies of both MHD stability and of transport benefitted from improved diagnostics, including measurements of the internal poloidal field using the motional Stark effect (MSE). In plasmas with a region of reversed magnetic shear in the core, now confirmed by the MSE data, improved electron confinement has been observed.

Book Compressional Alfvin Eigenmode Dispersion in Low Aspect Ratio Plasmas

Download or read book Compressional Alfvin Eigenmode Dispersion in Low Aspect Ratio Plasmas written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent observations of new fast ion beam driven instabilities in MHz frequency range in National Spherical Torus experiments (NSTX) are suggested to be Compressional Alfvin Eigenmodes (CAEs). A new theory of CAEs applicable to low aspect ratio toroidal plasmas is developed based on the ballooning representation for the poloidal dependence of the perturbed quantities. In agreement with observations, the analytical theory predicts that CAEs are discrete modes with frequencies correlated with the characteristic Alfvin velocity of the plasma. Plasma equilibrium structure is essential to determine accurately the dispersion of CAEs. The mode structure is localized in both the minor radius and the poloidal directions on the low magnetic field side.

Book Current Profile Reconstruction Using X ray Imaging on the PEGASUS Toroidal Experiment

Download or read book Current Profile Reconstruction Using X ray Imaging on the PEGASUS Toroidal Experiment written by Kevin Tritz and published by . This book was released on 2002 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Non inductive Startup of the Pegasus Spherical Torus Using Localized Washer gun Current Sources

Download or read book Non inductive Startup of the Pegasus Spherical Torus Using Localized Washer gun Current Sources written by Nicholas Walter Eidietis and published by . This book was released on 2007 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Engineering Design of the National Spherical Torus Experiment

Download or read book Engineering Design of the National Spherical Torus Experiment written by C. Neumeyer and published by . This book was released on 2000 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Operational Limits in the National Spherical Torus Experiment

Download or read book Operational Limits in the National Spherical Torus Experiment written by S. M. Kaye and published by . This book was released on 2000 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: