T. Brown

The KSTAR superconducting magnet system

The Korean Superconducting Tokamak Advanced Research (KSTAR) at the Korea Basic Science Institute in Taejon will be the first Tokamak with an advanced all superconducting magnet system, including toroidal field (TF), poloidal field (PF),and field error correction (FEC) coils. The conductors are all cable-in-conduit (CICC) superconductors with a single conduit similar to those in the International Thermonuclear Experimental Reactor (ITER).

The Trim Coils for the Wendelstein 7-X Magnet System

The magnet system of the fusion experiment Wendelstein 7-X (W7-X) consists of superconducting as well as normal conducting coils. 50 non planar superconducting coils are forming the main field, 20 planar superconducting coils allow varying the shape of the plasma. Inside of the plasma vessel 10 normal conducting control coils will be placed to modify the strike points of the plasma at the divertor. In addition a set of five normal conducting trim coils has been designed to allow the correction of error fields and to increase the experimental flexibility. The coils will be placed at the outer surface of the outer vessel of W7-X. Four out of five coils have identical size and shape. They have dimensions of 3.5 × 3.3 meters with 48 turns and will be operated with currents of up to 1.8 kA. The other coil type has a smaller size of 2.8 × 2.2 meters, but a higher number of turns and a higher operating current of 1.95 kA. Both types of trim coils will be made of square copper hollow profile with an integrated cooling channel. Five independent power supplies will be used to energize the coils. The present concept is based on four-quadrant power supplies. The control system will allow the local control as well as the remote control of the five power supplies from an external control room.

Systems analysis exploration of operating points for the Korean DEMO program

The Korean DEMO program is pursuing a steady state tokamak configuration to develop a fusion energy producing facility. Systems analysis is performed to determine its geometry and operating space available. After the plasma major radius and elongation is chosen, and the maximum toroidal magnetic field at the coil is established, the operating space can be explored with a range of assumptions. A database approach for the systems analysis is used that generates a large number of solutions, that can be used to examine sensitivities and parameter uncertainties.

The Wendelstein 7-X Trim Coil System

The magnet system of the fusion experimental device Wendelstein 7-X (W7-X) contains superconducting as well as normal conducting coils. Seventy superconducting coils are forming the steady state main field to confine the plasma. Inside of the plasma vessel, ten control coils, made of copper, will be placed to modify the strike points of the plasma at the divertor. In addition, a set of five normal conducting, water cooled trim coils will increase the experimental flexibility by providing a means to balance the divertor heat loads among the five field periods. The coils will be placed at the outer surface of the cryostat of W7-X. There are four coils (type A) with equal shape; the fifth coil (type B) has a slightly different shape due to space restrictions. The coils have dimensions of 3.5 × 3.3 m with 48 turns and will be operated with currents of up to 1.8 kA (type A). The other coil (type B) has a smaller size of 2.8 × 2.2 m, compensated by a higher number of turns and a higher operation current of 1.95 kA. Five independent power supplies are being fabricated to operate the coils with a maximum of flexibility. The concept is based on four-quadrant power supplies using Insulated-Gate-Bipolar-Transistors. The trim coil package consisting of the five coils plus the five power supplies is being designed and built in collaboration between IPP, Germany and PPPL, USA, partly funded by the Department of Energy.

Progress in developing the K-DEMO device configuration

K-DEMO is being studied by South Korean researchers as a follow-on to ITER and the next step toward the construction of a commercial fusion power plant. The K-DEMO mission defines a staged approach targeting operation with an initial testing phase for plasma facing components and critical operating systems to be followed by a second phase which centers on upgrading the in-vessel components for operation at 200 to 600 MWe with a planned 70% availability. This paper reviews the general arrangement of the K-DEMO device core, the novel configuration concept for the vertical maintenance of large in-vessel segments and describes the arrangement and maintenance of planned interfacing auxiliary systems and services - design features which impact the ability to operate with a staged mission strategy that ends with high availability operations.

Parameters and requirements of superconducting focusing quadrupoles for heavy ion fusion

In a heavy ion fusion driver, arrays of superconducting quadrupoles will transport parallel beams through a sequence of induction acceleration cells. The development of such arrays is a unique and challenging task. Since magnetic transport is one of the most expensive subsystems, economy of fabrication is a primary consideration. A compact design is essential to limit the size and cost of induction cores. Special edge coils have to be implemented to adjust the field in outer cells and terminate the magnetic flux. The development of superconducting magnets for both near term experiments and the ultimate driver application is actively pursued by the U.S. Heavy Ion Fusion Program. The main parameters and requirements are discussed, and the R&D status and plans are presented.

Metrology for the NCSX Project

The National Compact Stellerator Experiment (NCSX) is being constructed at the Princeton Plasma Physics Laboratory (PPPL) in partnership with the Oak Ridge National Laboratory (ORNL). The complex geometry and tight fabrication tolerances of the NCSXs non-planar coils and vacuum vessel necessitate the use of computerized, CAD-based metrology systems capable of very accurate and reasonably quick measurements. To date, multi-link, portable coordinate measuring machines (pCMM) are used in the fabrication of the non-planar coils. Characterization of the CNC machined coil winding form and subsequent positioning of the conductor centroid (to within +/-0.5 mm) are accomplished via multiple sets of detailed measurements. A laser tracker is used for all phases of work on the vacuum vessel including positioning magnetic diagnostics and vessel ports prior to welding. Future tasks requiring metrology include positioning of the magnet systems and assembly of the three vacuum vessel sub-assemblies onto the final machine configuration. This paper describes the hardware and software used for metrology, as well as the methodology for achieving the required dimensional control and will present an overview of the measurement results to date.

13 Adsorption of Gases and Electron-Spin Resonance of Sugar Charcoal

Electron-spin resonance has been measured at 9400 and 51.7 Mc. for a variety of charcoals heated to various temperatures. A very sharp resonance line has been observed by proper heat treatment and subsequent evacuation of the charcoal. Oxygen and nitric oxide adsorption at room temperature decrease the absorption intensity and widen the absorption band. Nitrogen and hydrogen have no effect at room temperature on the electron-spin resonance of the charcoal.

Progress in developing the STFNSF configuration

The design features developed for the Spherical Tokamak (ST) in the PPPL pilot plant study was used as the starting point in developing designs to meet the mission of a Fusion Nuclear Science Facility (FNSF) considering a range of machine sizes based on the influence of tritium consumption and maintenance strategies. The compact nature of a steady state operated ST device for this mission pushes operating conditions and places challenges in the design of components, device maintenance and the integration of supports and services. This paper reviews the general arrangement, design details and maintenance strategy of the ST-FNSF device core for a 1.6-m and 1.0-m device; operating points which bracket the region between purchasing and breeding tritium.

A preliminary conceptual design study for Korean fusion Demo Reactor magnets

As a continuation of initial conceptual design work for a steady-state Korean fusion DEMO Reactor (K-DEMO), a bit more detailed K-DEMO magnet conceptual design is being carried out. The size of the K-DEMO is only slightly bigger than the ITER and the major radius is around 6.8 m. But the peak field of toroidal field (TF) magnets is as high as ~16 T. Due to a stability issue, the TF magnets will be made of two different cable-in-conduit conductors (CICCs) for the high and relatively low field regions. Some engineering issues, including possible inter coil joint schemes, are discussed. Both CICCs for the TF magnets are designed by assuming the use of a currently available high performance Nb3Sn wire. Preliminary CICC design parameters are presented together with simulation results using the code GANDALF. A vertical maintenance scheme is being discussed for the K-DEMO and the location of poloidal field (PF) coils are recently set. However, a preliminary work on central solenoid (CS) coil has been carried out. The CS coils are designed to generate ~83 Wb of flux swing. Preliminary design parameters for the CS CICC are also presented.