H. Tsuji

Construction of ITER common test facility for CS model coil

Japan Atomic Energy Research Institute is constructing the International Thermonuclear Experimental Reactor common test facility for the Central Solenoid Model Coil which is around 180 tons, a forced-flow cooled magnet with the maximum pulsed operation of 2 T/s and generates the rated magnetic field of 13 T at 48 kA with stored energy of 668 MJ. The test facility consists of a coil vacuum chamber, a cryogenic system with the 5-kW refrigerator and 500-g/s cryogenic pump, two pairs of 50-kA current leads, two DC power supplies (50 kA and 60 kA) and two JT-60 pulsed power supplies (50 kA, /spl plusmn/4.5 kV and /spl plusmn/40 kA, /spl plusmn/1.5 kV). The facility will be demonstrating the refrigeration and operation of a fusion pulsed magnet and the design and construction will accumulate experience towards the construction of ITER.

Design and fabrication of superconducting cables for ITER central solenoid model coil

The Nb/sub 3/Sn cable is being fabricated for the central solenoid (CS) model coil under the ITER Engineering-Design Activity. The cable consists of about 1000 strands whose diameter is 0.81 mm. The design current is 48 kA at a magnetic field of 13 T. The 0.6-GJ CS model coil is operated in a pulse mode (0.5 T/s). The first trial fabrication of a 100-m dummy cable and a 20-m superconducting cable was completed successfully. The second trial fabrication of a 1000-m dummy cable was performed to establish the stable manufacturing procedure in January, 1995. The authors measured the AC losses of the full-sized conductor and could determine the cable coupling time constant. They analyzed the heat generation of the CS model coil and calculated the temperature rise of the cable for the model coil.

Design consideration of the ITER-TF coil with a react-and-wind technique using Nb/sub 3/Al conductor

The ITER-TF coil requires a generation of 12.5 T in a size of 12 m/spl times/18 m. For such a high field-large coil, the applicability of Nb/sub 3/Al conductors was considered with a react-and-wind technique which realizes high reliability and low cost for the coil fabrication. The maximum bending strain on the Nb/sub 3/Al conductor in use of this technique is 0.39%. I/sub c/ degradation due to the strain is expected to be below 5%. The limiting current is estimated as 65 kA for 60 kA operation current. AC loss in the TF coil with Nb/sub 3/Al conductor is almost the same as with Nb/sub 3/Sn conductor.

Design of the ITER central solenoid (CS) model coil

The Japan Atomic Energy Research Institute (JAERI) has been designing and developing the central solenoid (CS) model coil for International Thermonuclear Experimental Reactor (ITER). The CS model coil is composed of two modules and they will be manufactured by a United States Home Team and a Japanese Home Team. The coil winding method is two-conductors-in-hand and the coil, which has an inner diameter of 1.6 m and an outer diameter of 3.6 m, produces a maximum field of 13 T. The coil will be tested in the JAERI facility. This paper describes the coil design, manufacturing procedure, stress analysis on the winding pack and AC loss analysis.

Design of the Nb/sub 3/Al insert to be tested in ITER central solenoid model coil

Critical current of Nb/sub 3/Al is less sensitive to strain than Nb/sub 3/Sn. This characteristic makes a react-and-wind method applicable in a large dimension coil. By applying the react-and-rind method for toroidal field (TF) coil, technical difficulties in transfer of the conductor after reaction are eliminated and construction cost of magnet system can be reduced in comparison with a wind-react-insulate-transfer method. Therefore, the Nb/sub 3/Al conductor has large potential as candidate for the TF conductor. The experiment of a 60 kA-12.5 T Nb/sub 3/Al insert is projected to demonstrate applicability of the react-and-wind method with the Nb/sub 3/Al conductor. The react-and-wind method will be employed in the winding and 0.4% bending strain will be applied to the conductor. The major characteristics of the Nb/sub 3/Al insert are reported in this paper.

Domestic test result of the Japanese LCT coil

Japan Atomic Energy Research Institute (JAERI) has been preparing one D shape superconducting coil for the Large Coil Task. This paper describes mainly the results on domestic test which has been successfully carried out with a single test condition in JAERI this year. The main results, which were obtained during the test, are cool-down and warm-up characteristics, superconducting recovery characteristics, discharge characteristics, strain and displacement measurements, and heat load measurements. Before describing the results, the Japanese coil design parameters and the Superconducting Engineering Test Facility for the domestic test are shown in this paper.

Recent progress in the demo poloidal coil program

The fabrication of two 30-kA NbTi pulsed coils and one 10-kA Nb/sub 3/Sn coil with a total stored energy of 40 MJ is in progress as a part of the DPC (Demonstration Poloidal Coil) Program. All the Nb-Ti superconducting strands have been fabricated, and their loss time-constant has been measured at 0.32 ms at 7 T, which is well below the initial target of less than 1 ms. A novel winding technique is described for the large current conductor which provides good mechanical contact. >

Experimental results of the Nb/sub 3/Sn demo poloidal coil (DPC-EX)

In order to demonstrate the applicability of a Nb/sub 3/Sn conductor to pulsed poloidal coils for Tokamak fusion machines, the Nb/sub 3/Sn Demo Poloidal Coil (DPC-EX) has been fabricated and tested. DPC-EX, whose inner diameter is 1 m, consists of two double pancakes made by a react-and-wind technique. The coil has a flat cable-in-conduit conductor cooled by forced-flow helium. DPC-EX has been set up in the Demo Poloidal Coil Test Facility (DPCF). In the operation of the coils in series, DPC-EX has been ramped up to 17 kA in 1 s. The magnetic field at this point was 6.7 T, and pulsed operation at 6.7 T/s was thus demonstrated. An average current density of 37.2 A/mm/sup 2/ in the winding was achieved in this operation, and the AC loss of the coil was confirmed to be quite small.

Design of the prototype conductors for the Fusion Experimental Reactor

The prototype conductors of the toroidal coil for the Fusion Experimental Reactor have been investigated. Specifications of the conductor are as follows: forced flow cooling; rated current of 30 kA at 12 T and 4.2 K; margin of critical current of 2; current density in winding of 30-40 A/mm/sup 2/; inlet helium at 4.2 K and 4-10 bar; and minimum bending radius of 1.5 m. Three types of conductors were considered as candidates: a test module coil of FF type (hollow cooling type using test module coil Nb/sub 3/Sn conductor techniques); preformed armor type; and advanced disk type. Detailed design parameters and analysis results are given for the three candidate conductors. >

Pulsed field loss characteristics of the Japanese test coil for the large coil task

This paper describes some results of an analytical calculation and the measurements of a pulsed field loss on the Japanese LCT conductor. The conductor, whose aspect ratio is around 2.5, is wound edge wise to reduce the pulsed field loss. The Japanese LCT coil, with the conductor thus designed, was evaluated to have a pulsed field loss of about 19W. This includes the loss of the helium vessel under the normal LCT test with a pulsed field of 0 to 0.14T. In addition, the loss measurement has been carried out up to 25 T/s. Measured results on the relation between the loss of a single strand and that of a whole strand pack well supports the validity of the loss analysis which includes a newly arranged set of analytical equations.