Y. Nunoya

Test of the ITER central solenoid model coil and CS insert

The Central Solenoid Model Coil (CSMC) was designed and built from 1993 to 1999 by an ITER collaboration between the U.S. and Japan, with contributions from the European Union and the Russian Federation. The main goal of the project was to establish the superconducting magnet technology necessary for a large-scale fusion experimental reactor. Three heavily instrumented insert coils were built to cover a wide operational space for testing. The CS Insert, built by Japan, was tested in April-August of 2000. The TF Insert, built by Russian Federation, will be tested in the fall of 2001. The NbAl Insert, built by Japan, will be tested in 2002. The testing takes place in the CSMC Test Facility at the Japan Atomic Energy Research Institute, Naka, Japan. The CSMC was charged successfully without training to its design current of 46 kA to produce 13 T in the magnet bore. The stored energy at 46 kA was 640 MJ. This paper presents the main results of the CSMC and the CS Insert testing-magnet critical parameters, ac losses, joint performance, quench characteristics and some results of the post-test analysis.

Test Results and Investigation of Tcs Degradation in Japanese ITER CS Conductor Samples

Japan Atomic Energy Agency (JAEA) has fabricated and tested the four conductor samples composed of high performance strands manufactured by the bronze-route process for the ITER Central Solenoid (CS) conductor. The current sharing temperature (Tcs) electrically assessed at 45.1 K and 10.85 T along the cycling loading at 48.8 kA and 10.85 T initially were 6.0 K and 6.1 K, and then 5.3 K and 5.5 K after 6000 cycles for the first SULTAN sample named JACS01, respectively. As results of second SULTAN sample named JACS02, the Tcs values initially were 7.2 K and 6.8 K, and then 6.6 K and 6.1 K after 10000 cycles for each conductor, respectively. The Tcs degradation was not saturated at the end of the test campaign. From the destructive observation, the large bending at the low transverse loading side in the high field zone was observed. The strand buckling and accumulating by slipping between the cable and the jacket are considered.

Status of Conductor Qualification for the ITER Central Solenoid

The ITER central solenoid (CS) must be capable of driving inductively 30 000 15 MA plasma pulses with a burn duration of 400 s. This implies that during the lifetime of the machine, the CS, comprised of six independently powered coil modules, will have to sustain severe and repeated electromagnetic cycles to high current and field conditions. The design of the CS calls for the use of cable-in-conduit conductors made up of and pure copper strands, assembled in a five-stage, rope-type cable around a central cooling spiral that is inserted into a circle-in-square jacket made up of a special grade of high manganese stainless steel. Since cable-in-conduit conductors are known to exhibit electromagnetic cycling degradation, prior to the launch of production, the conductor design and potential suppliers must be qualified through the successful testing of full-size conductor samples. These tests are carried out at the SULTAN test facility. In this paper, we report the results of the on-going CS conductor performance qualification and we present the options under consideration for the different modules constituting the CS coil.

ITER CS model coil and CS insert test results

The inner and outer modules of the central solenoid model coil (CSMC) were built by US and Japanese home teams in collaboration with European and Russian teams to demonstrate the feasibility of a superconducting central solenoid for ITER and other large tokamak reactors. The CSMC mass is about 120 t; OD is about 3.6 m and the stored energy is 640 MJ at 36 kA and peak field of 13 T. Testing of the CSMC and the CS insert took place at Japan Atomic Energy Research Institute (JAERI) from mid March until mid August 2000. This paper presents the main results of the tests performed,.

Test Results From the PF Conductor Insert Coil and Implications for the ITER PF System

In this paper we report the main test results obtained on the Poloidal Field Conductor Insert coil (PFI) for the International Thermonuclear Experimental Reactor (ITER), built jointly by the EU and RF ITER parties, recently installed and tested in the CS Model Coil facility, at JAEA-Naka. During the test we (a) verified the DC and AC operating margin of the NbTi Cable-in-Conduit Conductor in conditions representative of the operation of the ITER PF coils, (b) measured the intermediate conductor joint resistance, margin and loss, and (c) measured the AC loss of the conductor and its changes once subjected to a significant number of Lorentz force cycles. We compare the results obtained to expectations from strand and cable characterization, which were studied extensively earlier. We finally discuss the implications for the ITER PF system.

Test of the ITER TF insert and Central Solenoid Model Coil

The Central Solenoid Model Coil (CSMC) was designed and built by ITER collaboration between the European Union, Japan, Russian Federation and the United States in 1993-2001. Three heavily instrumented insert coils have been also built for testing in the background field of the CSMC to cover a wide operational space. The TF Insert was designed and built by the Russian Federation to simulate the conductor performance under the ITER TF coil conditions. The TF Insert Coil was tested in the CSMC Test Facility at the Japan Atomic Energy Research Institute, Naka, Japan in September-October 2001. Some measurements were performed also on the CSMC to study effects of electromagnetic and cooldown cycles. The TF Insert coil was charged successfully, without training, in the background field of the CSMC to the design current of 46 kA at 13 T peak field. The TF Insert met or exceeded all design objectives, however some interesting results require thorough analyses. This paper presents the overview of main results of the testing - magnet critical parameters, joint performance, effect of cycles on performance, quench and some results of the post-test analysis.

First test results for the ITER central solenoid model coil

Abstract The largest pulsed superconducting coils ever built, the Central Solenoid (CS) Model Coil and Central Solenoid Insert Coil were successfully developed and tested by international collaboration under the R&D activity of the International Thermonuclear Experimental Reactor (ITER), demonstrating and validating the engineering design criteria of the ITER Central Solenoid coil. The typical achievement is to charge the coil up to the operation current of 46 kA, and the maximum magnetic field to 13 T with a swift rump rate of 0.6 T/s without quench. The typical stored energy of the coil reached during the tests was 640 MJ that is 21 times larger than any other superconducting pulsed coils ever built. The test have shown that the high current cable in conduit conductor technology is indeed applicable to the ITER coils and could accomplish all the requirements of current sharing temperature, AC losses, ramp rate limitation, quench behavior and 10 000-cycle operation.

Test Results of the Third Japanese SULTAN Sample

Many full size conductors for the ITER TF coils have been tested at the SULTAN test facility in Switzerland for conductor qualification. JAEA tested two samples and two kinds of Nb3Sn strands were evaluated through the tests. Now another sample named JATF3 has been tested, which uses two other kinds of Nb3Sn strands. The strands satisfy the critical current density Jc requirement, but results of the conductor test were lower than our expectation. After the test, JAEA has been investigating the reason by X-ray CT scan and destructive inspection, and has found a possible reason.

Characterization of ITER

Japan Atomic Energy Agency has developed four types of strand which can be used in the ITER TF coils. One is a strand made by an internal tin process strand and the others are bronze process strands. The achieved critical current density is more than 790 in the bronze process strands and more than 980 in the internal tin process strand under 4.2 K temperature and 12 T magnetic field and there is hysteresis loss of less than 770 mJ/cc under 3 T cycle. Since these strands are utilized with an external strain, it is necessary to evaluate strain dependency to confirm the ITER conductor design. An apparatus to measure the strain dependency was newly developed. It has a horseshoe-shaped ring to produce uniform axial compressive or tensile strain along the strand length, a strand being soldered on the outer surface of the ring. The detailed strand characteristics were investigated subjecting the developed strands to a magnetic field from 10 T to 13 T, a strain from about 0.8% to 0.5%, and a temperature from 4.2 K to the critical temperature. When the critical current is normalized to that under the conditions where strain is intrinsically zero, the bronze process strands exhibit better performance than the internal tin process strand. However, the three bronze process strands do not exhibit the same -strain characteristics. Two types of scaling relations are applied to the data, and good expressions of strand performance were obtained by the least square method within 3 A as RMS.

\hbox{Nb}_{3}\hbox{Sn}

The central solenoid (CS) model coil program is in progress with an international collaboration under the frame of the ITER-EDA. The purpose of the CS insert coil is to test the performance of the ITER-CS conductor. The CS insert coil is installed in the bore of the CS model coil and tested at a magnetic flux density of 13 T. The installation work is underway with the inner and outer module of the CS model coil. The superconducting characteristics of the CS conductor, the critical current and the current sharing temperature are evaluated under the operating load. The AC loss characteristics of the conductor are also evaluated under pulsed magnetic field. The fabrication of the CS insert coil was completed on May 1999. The winding tools and the results of the winding of CS insert coil are reported. The heat treatment for Nb/sub 3/Sn processing was performed successfully with no SAGBO (stress accelerated grain boundary oxidation). The procedure of the heat treatment is also reported.