R.A. Olstad

Continuous fabrication of high‐temperature superconductor coated metal fiber and multifilamentary wire

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.

High power millimeter wave experiment of ITER relevant electron cyclotron heating and current drive system

High power, long pulse millimeter (mm) wave experiments of the RF test stand (RFTS) of Japan Atomic Energy Agency (JAEA) were performed. The system consists of a 1 MW/170 GHz gyrotron, a long and short distance transmission line (TL), and an equatorial launcher (EL) mock-up. The RFTS has an ITER-relevant configuration, i.e., consisted by a 1 MW-170 GHz gyrotron, a mm wave TL, and an EL mock-up. The TL is composed of a matching optics unit, evacuated circular corrugated waveguides, 6-miter bends, an in-line waveguide switch, and an isolation valve. The EL-mock-up is fabricated according to the current design of the ITER launcher. The Gaussian-like beam radiation with the steering capability of 20°-40° from the EL mock-up was also successfully proved. The high power, long pulse power transmission test was conducted with the metallic load replaced by the EL mock-up, and the transmission of 1 MW/800 s and 0.5 MW/1000 s was successfully demonstrated with no arcing and no damages. The transmission efficiency of the TL was 96%. The results prove the feasibility of the ITER electron cyclotron heating and current drive system.

Fabrication of long length Bi-2223 superconductor tape using continuous electrophoretic deposition on round and flat substrates

We have developed a continuous fabrication process for producing long lengths of Bi-2223 superconductor tapes. The process involves sequentially electrophoretically depositing and sintering superconductor and then silver layers on a substrate, followed by rolling and thermal processing. Both round and flat silver substrates have been used. Bi-2223 tapes made using flat silver substrates require only a few processing steps. Transport critical current densities at 77K in zero applied magnetic field exceeding 20000 A/cm2 have been obtained.

Progress on design and testing of corrugated waveguide components for ITER ECH&CD transmission lines

The performance requirement of 1 (possibly 2) MW cw at 170 GHz for ITER electron cyclotron heating & current drive transmission line components is much more demanding than the 1 MW, 5 to 10 s performance, generally at 110 GHz, that has been demonstrated on present devices. The high ITER heat loads will require enhanced cooling and, for some components, new or modified designs. In addition to thermal management issues, the components must be designed to have very low losses in order to meet the ITER transmission line efficiency requirements. Testing at representative ITER conditions of some components has been initiated at the JAEA 170 GHz gyrotron test stand at Naka, Japan. In addition, testing of a complete prototype ITER transmission line is planned in order to validate the designs for use on ITER. The design changes that are being made for the various components to assure low loss transmission and acceptable component temperatures are presented.

High-power corrugates waveguide components for mm-wave fusion heating systems

Considerable progress has been made over the last year in the U.S., Japan, Russia, and Europe in developing high power long pulse gyrotrons for fusion plasma heating and current drive. These advanced gyrotrons typically operate at a frequency in the range 82 GHz to 170 GHz at nearly megawatt power levels for pulse lengths up to 5 s. To take advantage of these new microwave sources for fusion research, new and improved transmission line components are needed to reliably transmit microwave power to plasmas with minimal losses. Over the last year, General Atomics and collaborating companies (Spinner GmbH in Europe and Toshiba Corporation in Japan) have developed a wide variety of new components which meet the demanding power, pulse length, frequency, and vacuum requirements for effective utilization of the new generation of gyrotrons. These components include low-loss straight corrugated waveguides, miter bends, miter bend polarizers, power monitors, waveguide bellows, de breaks, waveguide switches, dummy loads, and distributed windows. These components have been developed with several different waveguide diameters (32, 64, and 89 mm) and frequency ranges (82 GHz to 170 GHz). This paper describes the design requirements of selected components and their calculated and measured performance characteristics.

Design and high power testing of ITER ECH&CD transmission line components

The ITER Electron Cyclotron Heating and Current Drive (ECH&CD) transmission line components will need to be suitable for 1–2 MW cw operation. The high heat loads compared to existing transmission lines will require enhanced cooling and, for some components, new or modified designs. Testing at representative ITER conditions of key components has been carried out at the JAEA 170 GHz gyrotron test stand at Naka. Preliminary test results and a discussion of new ITER-relevant components are presented.

Progress on design and testing of ITER ECH&CD transmission line components

The performance requirement of 1 (possibly 2) MW cw at 170 GHz for ITER Electron Cyclotron Heating and Current Drive transmission line components is much more demanding than the performance that has been demonstrated on present devices. The high ITER heat loads will require enhanced cooling and, for some components, new or modified designs. In addition to thermal management issues, the components must be designed to have very low losses in order to meet the ITER transmission line efficiency requirements. Testing at representative ITER conditions of some components (waveguide switch, waveguides, miter bends, gate valve, and waveguide window) has been initiated at the JAEA 170 GHz gyrotron test stand at Naka, Japan. Results obtained on additional tests of GA components at JAEA will be presented. These additional components include a DC break, polarizer miter bends, arc detector miter bend, very low loss miter bends, and a waveguide switch. In addition, the US ITER Project Office (USIPO) plans to test a complete prototype ITER transmission line in order to validate the designs for use on ITER, and GA is providing some components to the USIPO for initial tests.

Recent advancements in ECH transmission line components for ITER and other devices

General Atomics continues to adapt its mm-wave transmission line components to meet the ever-more demanding requirements for DIII-D, ITER and other fusion devices in Japan and Europe. Components that are addressed include components for 1 to 2 MW CW operation and remote steering launcher waveguides.

Fabrication of long length Bi-2223 superconductor tape using a continuous electrophoretic coating process

We have developed a unique fabrication process for producing long lengths of Bi-2223 superconductor tapes. The process uses a continuous electrophoretic coating technique for sequentially depositing superconductor and silver layers on a substrate, by heat treating and rolling steps. The process offers a number of advantages over competing techniques.<<ETX>>

Designs of new components for ITER ECH&CD transmission lines

The ITER Electron Cyclotron Heating and Current Drive (ECH&CD) transmission line components will need to be suitable for 2 MW cw operation and have high transmission efficiency. The high heat loads compared to existing transmission lines will require enhanced cooling and, for some components, new or modified designs. Portions of the transmission line between the closure plate and the tritium barrier window have special design considerations to assure that tritium from the tokamak plasma does not leak into the tokamak building. Design aspects of new components meeting the ITER requirements are presented.