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.

Introduction

The ITER Central Solenoid (CS) Model Coil Program [1] has been carried out since 1992 as one of the largest R&D programs in the ITER Engineering Design Activity in an international collaboration among the ITER Joint Central Team (JCT), EU, Japan, Russia and US. In the program, the CS Model Coil (CSMC) and the CS Insert have been developed and tested in order to verify the magnet technology that will allow the ITER magnets to be built with confidence. It is expected to provide the validation of design and analysis tools, the demonstration of industrial manufacturing methods, the performance of each component integrated in the magnet and the demonstration of reliable operation.

Fabrication of the CSMC and CS Insert adopted a commingle-fabrication task sharing; all participants shared the fabrication of the Nb₃Sn cable-in-conduit superconducting cables (24.6 tons). The US provided Incoloy 908 [2] as a conductor jacket material. The EU assembled the cables and the jacket into the conductors. The US assembled the CSMC Inner Module (10 layers) [3], and Japan assembled the Outer Module (eight layers) [4] and the CS Insert (one layer) [5]. Their configuration and major parameters are shown in Fig. 1 and Table 1, respectively. The CSMC is the largest pulsed superconducting magnet ever built with a stored energy of 640 MJ, at the operational current of 46 kA. Japan assembled these coil components coaxially as the CSMC and CS Insert in around 5 months within a 6.5-m diameter and 9.5-m high vacuum tank, as shown in Fig. 2, at the CSMC Test Facility [6] located at the Japan Atomic Energy Research Institute, Naka.

The cooldown of the coil system (total cold mass of 180 tons) was initiated by the end of November 1999 but a cold leak was detected at a coil temperature of around 20 K after around 500 h. Then the cooldown was cancelled, followed by warming up the coil. After the leak was repaired, the cooldown was resumed on March 13, 2000. The electric performance test was started in April and was successfully completed on August 18, followed by the coil warm-up which was finished by the end of August. The test implemented a total of about 350 charging runs and around 400 sensors continuously monitored the coil performance by the computer data acquisition system, accumulating a huge amount of test data. The cryogenic system also provided a stable 4-K condition through the test campaign without any problems. This paper introduces the test program, typical achieved operation, and the results of preliminary analysis.