No abstract

then it is found that N -1.2 for the south beam and 2.4 for the north beam. In 11 534 the correlation is not as good but a value of N ~ 1.2 is obtained.In conclusion it can be said that the time and spatially resolved 2co 0 and |co 0 measurements have begun to provide the data necessary for an understanding of the laser-beam-plasma interactions occurring in the region of the critical surface. The spatial resolution of the 2u> 0 and f u) 0 streaked results provides critical and quarter-critical surface trajectories. This gives information on the hydrodynamics of the ablation region. Time-resolved scale lengths provide information for absorption studies. Intensity histories of the plasma emissions should yield information on the processes that lead to the plasma emissions.This work is supported by the Laser FusionCostley and co-workers 1 * 2 recently reported on measurements of the spectral distribution and the polarization of the synchrotron radiation emitted by the CLEO and TRF tokamak plasmas (parallel and perpendicular to the major radius) over a frequency band (30 GHz

The paper presents a study of impurity transport in ohmically heated TFTR plasmas by computer modelling of VUV line emissions from impurities injected using the laser blow-off technique. The results are sensitive to uncertainties in the ionization and recombination rates used in the modelling and, therefore, only a spatially averaged diffusion coefficient and parameterized convective velocity can be measured. Measurements of these transport parameters are presented for deuterium and helium discharges with Ip = 0.8−2.5 MA, n̄e = (0.6-6.0) × 1019 m−3 and Zeff = 2-6. The diffusion coefficients are found to be in the range of 0.5-1.5 m2 · s−1, considerably larger than neoclassical values. Non-zero inward convective velocities are necessary to fit the data in most cases. No dependence of the diffusion coefficient on injected element, working gas species or plasma current is found, but, at a given current, the diffusion coefficient in plasmas near the density limit is smaller by approximately a factor of two than in discharges with n̄e < 3 × 1019 m−3.

Electron heat transport on TFTR and other tokamaks is several orders of magnitude larger than neoclassical calculations predict. Despite considerable effort, there is still no clear theoretical understanding of this anomalous transport. The electron temperature profile, Te(r), has shown a marked consistency on many machines for a wide range of plasma parameters and heating profiles. This could be an important clue as to the process responsible for this enhanced thermal transport. In the first section of the paper the result is presented that TFTR electron temperature profile shapes are even more constrained than previous models of profile consistency suggested. The profile shapes, Te(r)/Te(a/2), are found to be invariant (for r > 0.4 a) for a wide range of parameters, including q(a). In the second section, an experiment is discussed which uses a fast current ramp to transiently decouple the current density profile, J(r), and the Te(r) profiles. From this experiment, it has been determined that the J(r) profile can be strongly modified with no measurable effect on the electron temperature profile shape. Thus, while the electron temperature profile is apparently constrained, the current profile is not.