Laser-aided diagnostics of JT-60SA Y. Ohtani, H. Sasao, M. Akimitsu, H. Sakai, H. Tojo, et al. Journal of Instrumentation, 2025 JT-60SA is currently the world's largest superconducting tokamak. It accelerates the realization of fusion energy by supporting ITER exploitation and complementing it in addressing key physics and engineering issues for DEMO reactors. The main targets of JT-60SA are breakeven-equivalent high-temperature deuterium plasmas and high- β steady-state plasmas. To achieve these goals, laser-aided diagnostics with high spatial resolution are essential for detailed physics studies. In Operation Phase 1, a tangential single-chord two-color CO 2 laser interferometer was installed. The data acquisition and processing system featured fringe-jump detection and real-time processing, enabling density feedback control. In the upcoming operational phases, a CO 2 laser polarimeter and Thomson scattering diagnostics will be implemented in Operation Phase 2, followed by the installation of phase-contrast imaging in Operation Phase 3. This paper summarizes the measurement results from the first operational phase and outlines the design and current status of the other three diagnostics.
A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors Andrea Murari, Riccardo Rossi, Teddy Craciunescu, Jesús Vega, J. Mailloux, et al. Nature Communications, 2024 The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
Recent progress of JT-60SA project toward plasma operation Hiroshi Shirai, Koji Takahashi, Enrico Di Pietro Nuclear Fusion, 2024 Superconducting tokamak JT-60SA plays an essential role in fusion research and development by supporting and complementing ITER project, providing directions to the DEMO design activity and fostering next generation scientists and engineers. Since the incident of the Equilibrium Field coil #1 during the Integrated Commissioning (IC) in March 2021, both EU and JA Implementing agencies (IAs) have examined how to ensure safety operation of JT-60SA by mitigating the risk of possible discharge occurrence inside the cryostat. Based on the experience of the Global Paschen tests, the IAs have established a strategy of risk mitigation measures, which is a combination of (i) reinforcement of insulation, (ii) avoiding unnecessary voltage application to the coil systems and (iii) immediate de-energization of the coils when deteriorated vacuum condition is detected. Thanks to the considerable efforts of the Integrated Project Team (IPT) members, the IC restarted in May 2023. After the confirmation of superconducting state of coil systems (TF, EF and CS), the coil energization test and the plasma operation (OP-1) starts. The first plasma was successfully achieved on 23 October 2023 with a limited value of applied voltage and current to the coils. The plasma configuration control will be also confirmed with low plasma current and low auxiliary heating power conditions. Based on the IO-F4E-QST collaboration, activities of JT-60SA have been shared with the IO and provided an important lesson learned for ITER assembly and commissioning, and will provide an outstanding contribution to fusion research at large. After OP-1, Maintenance & Enhancement phase 1 (M/E-1) starts from January 2024, in which in-vessel components are installed, and heating system and diagnostic system are extensively upgraded to allow high power heating experiment planned in OP-2. In order to make the best use of JT-60SA, newly organized JT-60SA experiment team will refine the research plan in the future high heating power operation phase.
Collection optics of JT-60SA edge Thomson scattering diagnostic F. A. D’Isa, A. Fassina, L. Giudicotti, S. Soare, H. Tojo, et al. Review of Scientific Instruments, 2024 The mission of the JT-60SA project is to complement ITER’s capabilities by addressing the fundamental physics and engineering challenges necessary to develop a practical and reliable fusion power plant. Diagnostics play a pivotal role in achieving this mission, especially the Thomson Scattering (TS) diagnostic systems developed by a collaborative Japan–EU team. The edge Thomson scattering of JT-60SA is tailored to measure the low field side outer region of the plasma, in particular, to resolve the electron temperature Te and density ne. The collection optics of the edge TS system have a critical role in meeting the required field of view and spatial resolution despite the limited space. This work presents a comprehensive optomechanical design of the optics assembly, whose main features are telecentricity and compactness, highlighting its capabilities. The tests undertaken to verify its performance: focal plane identification, thermal cycle, and magnification, are described.
Plasma physics and control studies planned in JT-60SA for ITER and DEMO operations and risk mitigation M Yoshida, G Giruzzi, N Aiba, J F Artaud, J Ayllon-Guerola, et al. Plasma Physics and Controlled Fusion, 2022 A large superconducting machine, JT-60SA has been constructed to provide major contributions to the ITER program and DEMO design. For the success of the ITER project and fusion reactor, understanding and development of plasma controllability in ITER and DEMO relevant higher beta regimes are essential. JT-60SA has focused the program on the plasma controllability for scenario development and risk mitigation in ITER as well as on investigating DEMO relevant regimes. This paper summarizes the high research priorities and strategy for the JT-60SA project. Recent works on simulation studies to prepare the plasma physics and control experiments are presented, such as plasma breakdown and equilibrium controls, hybrid and steady-state scenario development, and risk mitigation techniques. Contributions of JT-60SA to ITER and DEMO have been clarified through those studies.
Completion of JT-60SA construction and contribution to ITER Y. Kamada, E. Di Pietro, M. Hanada, P. Barabaschi, S. Ide, et al. Nuclear Fusion, 2022 Construction of the JT-60SA tokamak was completed on schedule in March 2020. Manufacture and assembly of all the main tokamak components satisfied technical requirements, including dimensional accuracy and functional performances. Development of the plasma heating systems and diagnostics have also progressed, including the demonstration of the favourable electron cyclotron range of frequency (ECRF) transmission at multiple frequencies and the achievement of long sustainment of a high-energy intense negative ion beam. Development of all the tokamak operation control systems has been completed, together with an improved plasma equilibrium control scheme suitable for superconducting tokamaks including ITER. For preparation of the tokamak operation, plasma discharge scenarios have been established using this advanced equilibrium controller. Individual commissioning of the cryogenic system and the power supply system confirmed that these systems satisfy design requirements including operational schemes contributing directly to ITER, such as active control of heat load fluctuation of the cryoplant, which is essential for dynamic operation in superconducting tokamaks. The integrated commissioning (IC) is started by vacuum pumping of the vacuum vessel and cryostat, and then moved to cool-down of the tokamak and coil excitation tests. Transition to the super-conducting state was confirmed for all the TF, EF and CS coils. The TF coil current successfully reached 25.7 kA, which is the nominal operating current of the TF coil. For this nominal toroidal field of 2.25 T, ECRF was applied and an ECRF plasma was created. The IC was, however, suspended by an incident of over current of one of the superconducting equilibrium field coil and He leakage caused by insufficient voltage holding capability at a terminal joint of the coil. The unique importance of JT-60SA for H-mode and high-β steady-state plasma research has been confirmed using advanced integrated modellings. These experiences of assembly, IC and plasma operation of JT-60SA contribute to ITER risk mitigation and efficient implementation of ITER operation.
Physics requirements for the VUV survey spectrometer intended for the divertor radiation monitoring on JT-60SA 46th Eps Conference on Plasma Physics Eps 2019, 2019
Test chip for the development and evaluation of test structures for measuring stress in metal interconnect IEEE International Conference on Microelectronic Test Structures, 2004
Calibration and optimization of interconnect based MEMS test structures for predicting thermo-mechanical stress in metallization Annual Proceedings Reliability Physics Symposium, 2004
Experimental research on the evolution of a preserved homologous dura mater graft in posterior scleral consolidation Revista Medico Chirurgicala A Societatii De Medici Si Naturalisti Din Iasi, 1988
