3 research outputs found
Recommended from our members
Difference in electron thermal diffusivity and profile between interior and exterior of TFTR L-mode plasmas
The local properties such as scale lengths of the electron density (L{sub n{sub e}}), temperature (L{sub T{sub e}}), and pressure (L{sub p{sub e}}), and the electron thermal diffusivity {chi}{sub e}(r) (m{sup 2}/s) for r/a > 0.3 have been studied for TFTR L-mode discharges under the assumption of {chi}{sub e} = {chi}{sub i}. The scale lengths and the electron thermal diffusivity in the interior 0.3 < r/a < 0.55 are significantly different from those on the exterior 0.55 < r/a < 0.8. following are some examples (temperatures in keV, other quantities in MKS units). In the interior (0.3 < r/a < 0.55), most of the scale lengths were constant or a weakly dependent on radius, and {chi}{sub e} can be expressed as (with correlation coefficient R = 0.61), {chi}{sub e}(r) = 1.44 {times} 10{sup 18}(r/a){sup 1.0}T{sub e}(r){sup 0.1}q(r){sup 0.1}/n{sub e}{sup 0.9}(r). In the exterior region (0.55 < r/a < 0.8), the scale lengths decrease monotonically, and {chi}{sub e} can be described as (with R = 0.68), {chi}{sub e}(r) = 2.3 {times} 10{sup 3}(r/a){sup 1.7}T{sub e}(r){sup 0.7}q(r){sup 0.8}/n{sub e}{sup 0.2}(r). It is interesting to note the negative n{sub e} dependence of {chi}{sub e} in the interior and the positive T{sub e} dependence of {chi}{sub e} in the exterior
Recommended from our members
Neoclassical transport of energetic minority tail ions generated by ion-cyclotron resonance heating in tokamak geometry
Neoclassical transport of energetic minority tail ions, which are generated by high powered electromagnetic waves of the Ion Cyclotron Range of Frequencies (ICRF) at the fundamental harmonic resonance, is studied analytically in tokamak geometry. The effect of Coulomb collisions on the tail ion transport is investigated in the present work. The total tail ion transport will be the sum of the present collision-driven transport and the wave-driven transport, which is due to the ICRF-wave scattering of the tail particles as reported in the literature. The transport coefficients have been calculated kinetically, and it is found that the large tail ion viscosity, driven by the localized ICRF-heating and Coulomb slowing-down collisions, induces purely convective particle transport of the tail species, while the energy transport is both convective and diffusive. The rate of radial particle transport is shown to be usually small, but the rate of radial energy transport is larger and may not be negligible compared to the Coulomb slowing-down rate. 18 refs., 2 figs
Recommended from our members
Burning plasmas
The fraction of fusion-reaction energy that is released in energetic charged ions, such as the alpha particles of the D-T reaction, can be thermalized within the reacting plasma and used to maintain its temperature. This mechanism facilitates the achievement of very high energy-multiplication factors Q, but also raises a number of new issues of confinement physics. To ensure satisfactory reaction operation, three areas of energetic-ion interaction need to be addressed: single-ion transport in imperfectly symmetric magnetic fields or turbulent background plasmas; energetic-ion-driven (or stabilized) collective phenomena; and fusion-heat-driven collective phenomena. The first of these topics is already being explored in a number of tokamak experiments, and the second will begin to be addressed in the D-T-burning phase of TFTR and JET. Exploration of the third topic calls for high-Q operation, which is a goal of proposed next-generation plasma-burning projects. Planning for future experiments must take into consideration the full range of plasma-physics and engineering R D areas that need to be addressed on the way to a fusion power demonstration