Low-to-High Confinement Transition Mediated by Turbulence Radial Wave Number Spectral Shift in a Fusion Plasma.
نویسندگان
چکیده
A new model for the low-to-high (L-H) confinement transition has been developed based on a new paradigm for turbulence suppression by velocity shear [G. M. Staebler et al., Phys. Rev. Lett. 110, 055003 (2013)]. The model indicates that the L-H transition can be mediated by a shift in the radial wave number spectrum of turbulence, as evidenced here, for the first time, by the direct observation of a turbulence radial wave number spectral shift and turbulence structure tilting prior to the L-H transition at tokamak edge by direct probing. This new mechanism does not require a pretransition overshoot in the turbulent Reynolds stress, shunting turbulence energy to zonal flows for turbulence suppression as demonstrated in the experiment.
منابع مشابه
Decorrelation of edge plasma turbulence at the transition from low- to high-confinement mode in the DIII–D Tokamak
The modification of turbulence in the edge plasma of the DIII–D tokamak at the transition from the low to the high mode of confinement is investigated with a phase-contrast imaging diagnostic. The amplitude and radial correlation length of the turbulence in the confinement region decrease at the transition, whereas the decorrelation time increases. The transition w Ž . x model of Biglari, Diamo...
متن کاملREVIEW ARTICLES Effects of E3B velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices*
One of the scientific success stories of fusion research over the past decade is the development of the E3B shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L ~low! to H ~high! transition. This concept has the universality ...
متن کاملGlobal energy confinement scaling predictions for the kinetically stabilized tandem mirror
Transport is studied for the kinetically stabilized tandem mirror, an attractive magnetic confinement device for achieving a steady-state burning plasma. For a magnetohydrodynamic stable system, three different radial transport models with Bohm, gyro-Bohm, and electron temperature gradient ETG scaling are derived. As a conservative estimate, numerical coefficients in the models are taken to be ...
متن کاملExperimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas
Self-regulation between structure and turbulence, which is a fundamental process in the complex system, has been widely regarded as one of the central issues in modern physics. A typical example of that in magnetically confined plasmas is the Low confinement mode to High confinement mode (L-H) transition, which is intensely studied for more than thirty years since it provides a confinement impr...
متن کاملStudy of edge turbulence in dimensionally similar laboratory plasmas
Comparative studies between a toroidal low-temperature plasma and drift-Alfvén-wave simulations were carried out in order to investigate the microscopic structure of turbulence. The dimensionless plasma parameters in the TJ-K torsatron [Krause 2002] are similar to those in the edge of a fusion plasma. At the same time the fluctuations can be fully diagnosed by probe arrays. Fluctuation spectra ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Physical review letters
دوره 116 9 شماره
صفحات -
تاریخ انتشار 2016