Results of experiments investigating the performance of the JET Mark IIA divertor are reported and compared to the performance of its Mark I predecessor. The principal e ect of reducing the divertor width increasing closure was to increase pumping for both deuterium and impurities while reducing upstream neutral pressure. Neither the orientation of the divertor target relative to the divertor plasma nor the width of the divertor had a major in uence on core plasma performance in ELMy H-modes. Changing the core triangularity and thus the edge magnetic shear modi es the ELM frequency in ELMy H-mode plasmas thereby c hanging the peak divertor power loading. The integrated performance of the core and divertor plasmas is reviewed with a view to extrapolation to the requirements of ITER. The con nement of JET ELMy H-modes with hot, medium density edges is good and follows gyro-Bohm scaling. The impurity content of these discharges is low and within the ITER requirements. When one attempts to raise the density with deuterium gas fuelling the ELM frequency increases and the con nement, especially in the edge, decreases. Good con nement can be achieved in JET either by producing a large edge pedestal, typically in discharges with neutral beam heating or by centrally peaked heating with ICRH schemes. Large amplitude, Type I ELMs, which are present in all discharges with a large edge pedestal, would result in unacceptable divertor plate erosion when scaled to ITER. Since the power deposition pro le due to heating in ITER is calculated to be intermediate between JET NB and RF heating pro les, it is likely that operation in ITER with small ELMs in order to reduce rst wall loading will result in degraded con nement compared to present d a y scaling laws.

No abstract

No abstract

Simulation of electrothermal launchers is extended to include nonideal plasma effects. The simulation is compared to experimental data obtained from the SIRENS facility, for the measurable quantity of ablation depth as a function of the input discharge energy [IEEE Trans. Plasma Sci. PS-17, 386 (1989)]. The plasma model for nonideal plasma is based on the evaluation of a non-Debye radius due to incomplete screening of the shielding cloud around a charged particle. The consistent and necessary transport and thermodynamic functions for weakly nonideal plasmas are included in the time-dependent set of governing equations. In this paper a semiempirical scaling law for the fraction of blackbody radiation that is transmitted through the ablating vapor for Lexan insulators under high heat flux conditions is also presented.

No abstract