Long superconductor fibers have been continuously produced by electrophoretically depositing REBa2Cu3O7−x (where RE=Y or a selected rare-earth element) powder onto a metal substrate fiber and sintering, then electrophoretically depositing silver and sintering. After collecting the coated fiber on a take-up spool, the entire spool is batch-oxygenated to form the 90 K superconducting phase. Multiple fibers are then continuously unspooled and soldered into a copper channel to form the final multifilamentary high-temperature superconductor wire. Superconducting fibers over 1000 m long and multifilamentary wire 70 m long have been produced.

DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L–H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.

DII-D currently operates with a single-or double-null open divertor and graphite walls. Active particle control with a divertor cryopump has demonstrated density control, efficient helium exhaust, and reduction of the inventory of particles in the wall. Gas puffing of D2 and impurities has demonstrated reduction of the peak divertor heat flux by factors of 3-5 by radiation. A combination of active cryopumping and feedback-controlled D2 gas puffing has produced similar divertor heat flux reduction with density control. Experiments with neon puffing have shown that the radiation is equally-divided between a localized zone near the X-point and a mantle around the plasma core. The density in these experiments has also been controlled with cryopumping. These experimental results combined with modeling were used to develop the new Radiative Divertor for DIII-D. This is a double-null slot divertor with four cryopumps to provide particle control and neutral shielding for high-triangularity advanced tokamak discharges. UEDGE and DEGAS simulations, benchmarked to experimental data, have been used to optimize the design.

Homopolar motors are compact and, therefore, are attractive for use in a direct electric drive for a ship. The critical components for the motor are the brushes, the superconducting coils, and the power conversion system to produce the high current, low voltage DC required for the motor. A program is underway at General Atomics for the Office of Naval Research in which a 500 kW Test Stand Motor and a 3.7 MW Motor are being built for demonstration of the technology. The Test Stand Motor will use one superconducting coil and about 25% of the copper fiber brushes needed for the 3.7 MW motor. The latter will use the rotor from the Test Stand Motor, a full complement of brushes, and two superconducting coils. NbTi superconducting coils are being used, but the design allows for a direct transition to high temperature superconductors when it is cost effective and practical to do so. Selected features of the test facility and designs for both motors are discussed together with projections for motors at the 19 MW level in terms of size and weight.A 260 0-7803-7519-X/02/$17.00

This isa preprintof a paperto be presented at the EleventhInterna-tionalConference onPlasmaSurfaceInteractions inControlledFusion Devices,May23-27, 1994, Ibaraki-ken, Japan,andto be printedin the PROCEEDINGS.