Kaizhong Ding

Photoluminescence and Raman scattering of silicon nanocrystals prepared by silicon ion implantion into SiO2 films

Photoluminescence (PL) and Raman spectra of silicon nanocrystals prepared by Si ion implantion into SiO2 layers on Si substrate have been measured at room temperature. Their dependence on annealing temperature was investigated in detail. The PL peaks observed in the as-implanted sample originate from the defects in SiO2 layers caused by ion implantation. They actually disappear after thermal annealing at 800 degrees C. The PL peak from silicon nanocrystals was observed when thermal annealing temperatures are higher than 900 degrees C. The PL peak is redshifted to 1.7 eV and the intensity reaches maximum at the thermal annealing temperature of 1100 degrees C. The characterized Raman scattering peak of silicon nanocrystals was observed by using a right angle scattering configuration. The Raman signal related to the silicon nanocrystals appears only in the samples annealed at temperature above 900 degrees C. It further proves the formation of silicon nanocrystals in these samples

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.

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.

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.

R&D on 52-kA HTS Current Lead at ASIPP

The Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) is experienced in the design and fabrication of high-temperature superconductor (HTS) current leads such as those successfully used in the Experimental Advanced Superconducting (EAST) Tokamak. The aim of the 52-kA trial lead was to develop a prototype for the leads supplying the poloidal field and central solenoid magnets of ITER. This lead differs from former HTS current leads and from another trial (68 kA) lead developed in parallel for the toroidal field magnet, in that it features a foil-type heat exchanger, a helium-cooled transition section, and a binary shunt made of stainless steel and phosphor bronze. The 52-kA trial lead was fabricated and tested in the EAST Tokamak facility. Results of the test are presented. An analysis of these results indicates that the design concepts introduced are validated. The test also served to validate the HTS stacks that equipped the lead. These were supplied by InnoST.

Design and Qualification of Joints for ITER Magnet Busbar System

The joints connecting the ITER magnet busbars and coils utilize the twin-box “shaking hands” concept: inside a helium leak tight box, a bare cable is pressed in an indium-tinned copper base. To form the joint, two boxes are tightly compressed against each other on the copper side with a layer of indium in between. This concept was chosen to address the different requirements of the joints: to provide low electrical resistance without degradation and need of maintenance during ITER lifecycle, to sustain cyclic electromagnetic and pressure loads, to be easily dismountable in case of failure, to be tolerant to manufacturing and assembly misalignments, to provide low coolant flow impedance, and to limit ac losses and at the same time to facilitate current redistribution in the busbars. This paper presents the design; the key results of the electromagnetic, thermal, and stress analysis; and the major manufacturing and qualification steps. The latter includes cryogenic fatigue test of the joint welds and joint resistance measurements.

New Facility for the Cryogenic Test of ITER Current Leads at ASIPP

Based on the procurement agreement signed by the ITER IO and the Chinese domestic agency, the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) will produce the 60 single high-temperature superconducting (HTS) current leads in-kind for ITER. All of the ITER HTS current leads will be cold tested before assembly in the coil feeder systems. Therefore, a dedicated test facility was built in 2011 and completed in 2014 to perform the factory acceptance test of the HTS current leads. This paper describes the design of the test facility and its key components, including the cryogenic system, the power supply system, and the data acquisition as well as quench detection system. As an example, some results of the ITER HTS current lead prototype test campaigns will be shown.

Manufacture and Test of ITER 10-kA HTSCL Prototypes

10 kA High Temperature Superconducting Current Leads (HTSCL) are designed to carry current for the ITER Correction Coils (CC). Current leads provide the transition from 4.5 K low temperature to room temperature. Before the supply of the HTS current lead series, a pair of prototypes was manufactured and tested in 2014 based on the quality control and test requirements from the ITER Organization (IO). This paper summarizes the major design features of the prototypes, followed by a discussion of the manufacturing and testing.

Design and Development of 16-kA HTS Current Lead for HMFL 45-T Magnet

The High Magnetic Field Laboratory developed a 45-T hybrid magnet. To test this magnet, a new pair of high-temperature superconducting current leads rated at 16 kA were developed. This paper addresses the design and test of those current leads. To minimize heat loads at the cold end, Bi-2223 high-temperature superconductors were used. The foil-type main heat exchanger is cooled by 77-K liquid nitrogen (LN2) and gas nitrogen (GN2). The busbar for International Thermonuclear Experimental Reactor, an Nb-Ti low-temperature superconducting (LTS) cable, is used to connect the magnet coil for easy access to the LTS cable. The insulation on the current lead was designed on the test target of 10 kV.