Tingzhi Zhou

Design of the HTS Current Leads for ITER

Following the design, fabrication and test of a series of trial leads, designs of the three types of current leads required for ITER have been developed, and targeted trials of specific features are in progress on the way to fabrication and testing of prototype units. These leads are of the hybrid type with a cold section based on the use of high temperature superconductor (HTS) and a resistive section cooled by forced flow of helium gas, optimized for operation at 68 kA, 55 kA and 10 kA. The leads incorporate relevant features of the large series of current leads developed and constructed for the CERN-LHC, relevant features of the trial leads built for ITER, and additional features required to fully satisfy the exigent constraints of ITER with regard to cooling, insulation, and interfaces to feeder and powering systems. In this report a description of the design of the leads is presented, together with plans for the preparation of prototype manufacture and testing at ASIPP.

Test Results of 52/68 kA Trial HTS Current Leads for ITER

High Temperature Superconductor (HTS) current leads provide the transition of the current transfer system from room temperature to the 4.5 K. For the ITER superconducting magnet system, a total of 60 HTS current leads are required, with a total nominal current capacity of 2.64 MA. By the use of HTS leads significant power savings can be achieved during the operation of the ITER magnet system. Based on the functional specification by the ITER Organization (IO), ASIPP manufactured and tested a first pair of trial HTS current leads for the ITER coils. The cryogenic test of these 68 kA and 52 kA trial HTS leads was performed at ASIPP using the cryoplant and power supplies of the EAST Tokamak. The following paper presents the results of the tests and concludes with a discussion of the design features of the next generation prototype of the ITER HTS leads based on the results of the trial lead tests.

Design of the ITER TF Magnet Feeder Systems

The International Thermonuclear Experimental Reactor (ITER) superconducting magnet system requires current supplies from 10 kA to 68 kA. The components relating the electrical power and cryogens through the warm-cold barrier to the ITER magnets are the so-called feeders. In total there are 31 such feeders for the ITER magnet system, 9 of them necessary for the toroidal field magnet system are called TF feeders. Each feeder consists of three main units: the In-Cryostat Feeder (ICF), the Cryostat Feed-Through (CFT) and the S-Bend Box (SBB)/Coil Terminal Box (CTB) assembly. This paper presents the latest design of the TF feeder components.

R&D Towards HTS Current Leads for ITER

The ITER Organization (IO) and the Institute of Plasma Physics at the Chinese Academy of Sciences (ASIPP) are jointly developing the 68 kA current leads using High Temperature Superconductors for the superconducting Toroidal Field (TF) magnet system of the International Thermonuclear Experimental Reactor, ITER. The proposed design consists of a conventional helium cooled heat exchanger operating between 65 K and 320 K and an HTS module covering the low temperature end using Bi-2223 tapes. The first HTS current lead prototypes will be tested in the EAST tokamak facility at ASIPP. This paper discusses the design of the first, 68 kA, TF HTS lead, which is the main emphasis of this first stage of the ITER current lead development program.

Progress in Design, Analysis, and Manufacturing Studies of the ITER Feeders

The feeder design has been improved by the feeder teams at the ITER Organization (IO) and the Institute of Plasma Physics, Chinese Academy of Science (ASIPP) by incorporating the results of mechanical and thermal analyses as well as the system integration and assembly tolerances in the present CAD model. The feeder design is being finalized progressively, and will be delivered to the Chinese Domestic Agent (CNDA) for further procurement arrangement (PA) activities. Pre-PA manufacturing studies and tests performed at ASIPP have been effective in clarifying feeder design feasibility and component manufacturability. This paper reports the recent advancements on feeder design, analysis and manufacturing studies.

High Voltage Test of ITER Feeder Components Under Paschen Condition

As an important method of quality confirmation for the ITER Feeder system insulated components, high voltage test at Paschen condition need to be carried out once after these components are manufactured. The Paschen test is much more efficient for detecting the micro cracks or defects in solid multi-composite high polymer insulation materials than the conventional high voltage test done in atmospheric condition, and almost without any damage for the qualified components. For this purpose and the task agreement of Feeder R&D with ITER IO, a cryogenic vacuum Paschen test facility, which was modified by the Feeder prototype of Coil Termination Box (CTB), was established in ASIPP (China) in October of 2010, it is suitable to test typical critical high voltage components in Feeder, such as S-bend busbar, superconducting joint, and current lead. The test voltage can be up to 30 kV and provide pressure lower than 10-3. This paper describes the detailed configurations of the insulation mock-ups for Feeder and the test facility, also presents and discusses the test procedure and results acquired up to now.

Development of the Coil Terminal Boxes for the ITER Magnet Feeder Systems

The nuclear radiation levels, magnetic fields and general access restrictions in the ITER Tokamak are such that it is undesirable to place remote control helium supply valves close to the coils. The Coil Terminal Boxes (CTB), which are further away from the coils, are therefore designed for easy access and contain as much as possible the components needing maintenance, such as the cryo-valves. The CTBs also house the electrical cold-warm transitions with the HTS current leads and the NbTi feeder busbars. Also most of the feeder instrumentation is located in the CTB. Based on the functional specification by ITER, ASIPP has manufactured and tested a prototype CTB for the ITER magnet system. This test allowed for the verification of the mechanical design of the cryostat and the thermal shield design. Following a discussion of the ITER CTB design, with particular emphasis on the concepts of flow distribution for the large ITER magnet system, considering safety and maintenance, this paper will also present the results of the prototype CTB development.

Status of Design and R&D for the ITER Feeder System Procurement in China

The Procurement of the feeder system for The International Thermonuclear Experimental Reactor (ITER) tokamak device started in ASIPP (China) in 2006. The relevant tasks of structural design and analysis have now come to an end, but the R&D activities started in 2009 for critical feeder components and key technology are still ongoing. Following the signature of the Procurement Arrangement between China and the ITER Organization (IO) in 2010, a great number of R&D tasks have been launched with the purpose of testing and verifying the original design, leading to design changes and optimizations. This paper mainly discusses the progress of the feeder design and R&D activities; it also presents some test results.

Key Components of the ITER Magnet Feeders

Now that ITER is entering construction, many of its systems are in the final stages of design and analysis. Among them the 31 feeders, which will be supplied in-kind by the Chinese ITER partner. The feeders supply the electrical power and cryogens through the warm-cold barrier to the ITER superconducting magnet systems. They are complex systems with their independent cryostats and thermal shields, densely packed with many components, such as the current feeds, the cryogenic valves and High-Voltage (HV) instrumentation hardware. Some of the feeder components are particularly critical and have been designed with great care. Among them the High-Temperature Superconductor (HTS) current leads, designed for unprecedented currents, the 30 kV class, Paschen-hard HV insulation and the bus bar support system, designed to react the multi-ton Lorentz-forces from the bus bars at minimal heat load. This paper discusses the design challenges for these (and other) key components of the ITER magnet feeders.

Development of 12 kA HTS Current Lead for Accelerator Magnet Test Application

A pair of 12 kA HTS current leads has been developed with a nitrogen vapor cooled resistive section and a stainless steel shunted HTS section using Bi2223/AgAu matrix tapes at the Institute of Plasma Physics, Chinese Academy of Science. These two leads, which need to transfer 21 kA in a short time, are intended as replacement leads for the accelerator magnet test program at the Joint Institute of Nuclear Research in Dubna. The structure design of the current leads is described. The test results are reported and discussed in this paper.