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The tokamak JT-60SA is presently under construction in Naka (Japan) as a joint collaboration between Europe and Japan on the field of nuclear fusion research, in the framework of the Broader Approach Agreement. According to the international agreement, the different systems composing JT-60SA are supplied by European and Japanese institutions. In particular the four Switching Network Units (SNU) for the Central Solenoid (CS) of JT-60SA have been procured by ENEA. The design, manufacturing and factory test activities have been completed in 2016, and after the delivery in Naka the SNU have been installed and successfully commissioned in 2017. After an overview on the main technical characteristics of the SNU and the key aspects of their design, this paper describes the activities performed on-site, highlighting the results obtained during the final acceptance tests and comparing them with the design simulation and the factory test results.

JT-60SA is a Superconducting Tokamak in the framework of the Broader Approach Agreement (BAA) between Europe and Japan. For this International Project, both the Italian National Agency for New Technology, Energy and Sustainable Economic Development (ENEA) and the French Alternative Energies and Comissariat à l’Energie Atomique et aux Energies alternatives (CEA) have to provide overall twelve AC/DC pulse poloidal superconducting magnet power supplies (almost all rated for ±20 kA and ±1 kV). Each of them is equipped with a crowbar protection system. The crowbar system’s first function is to carry the current that is flowing through the superconducting coils and protects the AC/DC power converter from over-voltages, internal/external severe faults and in case of earthquakes. The current capability type test of crowbar system required a maximum peak current of ±26 kA and a maximum specific energy I2t = 4,6 GA2s for TF SCMPS. Finally the crowbar system and DC bus-bars were subjected to seismic tests in laboratory.

Development of the ECH/CD system for JT-60SA has been progressed. (i) A full length (~7 m) mock-up of the mirror steering structure of the launcher has been successfully tested in vacuum. The required life without maintenance, which is 105 cycles for the poloidal steering range of 60° and 104 cycles for toroidal beam steering range of 30°, has been achieved. A newly introduced solid lubricant enabled the smooth movement of the steering shaft. (ii) The temperature rise distribution of aluminum waveguides has been measured at high-power of 0.5 MW. It is in the range from 0.2 to 1.2 °C per 1 MJ transmission and acceptable for 1 MW/100 s transmission required in JT-60SA. (iii) The preparation of the JT-60SA ECH/CD system toward first plasma experiment is smoothly progressing by the above results and the successful gyrotron development., 27th IAEA Fusion Energy Conference (FEC 2018)

The Power Supply system for Resistive Wall Modes (RWM) control in the JT-60SA experiment is an Italian in-kind contribution to JT-60SA within the Broader Approach Agreement. A very efficient control of RWM is necessary to access plasma currents with high βN values (3-5) sustained for a hundred seconds, as foreseen in the JT-60SA research plan. The development of the whole RWM control system (coils, power supplies and control) went through several steps of optimization; the final coil configuration is made of three toroidal rings of six coils placed on the plasma side of the a stabilizing plate, inside the vacuum vessel; the coils are individually fed by dedicated power amplifiers, controlled in real time. A key aspect highlighted by the physics studies was the need of a very fast reaction of the control system to prevent an excessive growth of the plasma instabilities and to limit the power required for their control. The main requirements for the power amplifiers were a peak current of 300 A, output voltage of 240 V, bandwidth of 3 kHz and a latency shorter than 50 μs. The satisfaction of so fast dynamics was addressed via an R&D program which led to an innovative design solution adopting hybrid Silicon-Silicon Carbide (Si-SiC) semiconductor for the power amplifiers and to the development of a new sophisticated inverter on-board control. The schedule of the procurement was finalized in 2015 and was articulated in a relatively longer phase, for the detailed design, prototype development and testing, with respect to the manufacturing due to the high level of innovation. The delivery to Japan is expected in September 2018. An overview of the main phases of the development and realization of this advanced system, the first in fusion experiments adopting SiC semiconductors, will be presented., 30th edition of the Symposium on Fusion Technology (SOFT 2018)

Magnet power supply (PS) system of JT-60SA is being implemented within the Broader Approach Agreement aiming to achieve first plasma in 2020. The system consists of several components such as DC power supply, switching network unit, quench protection circuit and motor-generator. All the components have their own internal controller (LCC) for stand-alone operation so the individual commissioning are in progress and almost completed. The next step scheduled is a combination test with all components in which supervisory control system manage LCCs remotely. The supervisory system covers the following roles: 1) machine status monitoring; 2) discharge sequence management; 3) real-time reference waveforms management; 4) data acquisition; 5) machine protection; 6) human safety. The supervisory system consists of several subsystems; PS supervising computer (PS-SC), PS programmable logic controller (PS-PLC), PS internal protection system(PS-IPS) and PS safety interlock system (PS-SIS). PS-SC covers the primary roles in 1) – 4) which is built on CompactPCIs with real-time OS INtime. PS-SC and LCCs are linked through a Reflective Memory (RM) network to share common data in real-time (4 kHz). PS-SC is also linked to the upstream JT-60SA supervisory control system (SCSDAS) via another RM network as an interface for the power supply internal control systems. During discharge sequence, PS-SC also manages motor-generator speed, AC circuit breakers OPEN/CLOSE status with a controller PS-PLC and magnets current according to request from SCSDAS. PS-IPS covers the function of 5) which is implemented on FPGA. PS-IPS is connected to LCCs via fiber optical and hard-wired signals. In case of emergency events such as magnet quench and earth quake, PS-IPS commands to shut down the magnets currents immediately. PS-SIS plays the role in 6) such as status and permission of fence OPEN/CLOSE and grounding switch for maintenance. In this presentation, overview and development of the supervisory system are described., 30th edition of the Symposium on Fusion Technology (SOFT 2018)

JT-60SA is a superconducting tokamak in the framework of the broader approach agreement between Europe and Japan. For this international project among its various procurements, the Italian National Agency for new technology energy and sustainable economic development (ENEA) is providing four ac/dc converters for the central solenoid (CS) superconducting magnets, two ac/dc converters for the equilibrium field (EF) superconducting magnets, and two ac/dc converters for the fast plasma position control coils (FPPCC). Furthermore, ENEA is also providing six converter transformers of which four are of the dry type for FPPCC power supplies (PSs) and two of oil type for CS PSs. CS/EF PSs feed poloidal superconducting magnets of JT-60SA, whose purpose is the generation of strong magnetic fields able to induce and confine the plasma current in a prefixed geometrical configuration. The control system of CS/EF PSs has to be able to reproduce in real-time a reference current or voltage profile, known as “scenario” and these are particularly critical in these systems for the high currents required and for the high magnetic energy stored in the superconducting magnets. All performed type tests, carried out in accordance to the IEC60146 Standards, pointed toward a good dynamic behavior of the control system both for forward and for reverse rectifier bridges, assuring the smooth transitions between different operating modes: single mode, circulating current mode and dual mode. This is the focus of this paper.

The Power Supply system for Resistive Wall Modes (RWM) control in the JT-60SA experiment is an Italian in-kind contribution to JT-60SA within the Broader Approach Agreement. A very efficient control of RWM is necessary to access plasma currents with high ?N values (3-5) sustained for a hundred seconds, as foreseen in the JT-60SA research plan. The development of the whole RWM control system (coils, power supplies and control) went through several steps of optimization; the Ynal coil conYguration consists in three toroidal rings of six coils placed on the plasma side of the stabilizing plate, inside the vacuum vessel; the coils are individually fed by dedicated power ampliYers, controlled in real time. A key aspect highlighted by the physics studies was the need of a very fast reaction of the control system to prevent an excessive growth of the plasma instabilities and to limit the power required for their control. The main requirements for the power ampliYers were a peak current of 300 A, output voltage of 240 V, bandwidth of 3 kHz and a latency shorter than 50 ?s. The fulYllment of such a fast dynamics was addressed via an R&D program which led to an innovative design solution adopting hybrid Silicon-Silicon Carbide (Si-SiC) semiconductor for the power ampliYers and to the development of a new sophisticated inverter on-board control. The schedule of the procurement was Ynalized in 2015 and was articulated in a relatively longer phase, for the detailed design, prototype development and testing, in comparison with the manufacturing phase, due to the high level of innovation. The delivery to Japan is expected in September 2018. An overview of the main phases of the development and realization of this advanced system, the Yrst in fusion experiments adopting SiC semiconductors, will be presented.

Magnet power supply (PS) system of JT-60SA is being implemented within the Broader Approach Agreement aiming to achieve Vrst plasma in 2020. The system consists of several components such as DC power supply, switching network unit, quench protection circuit and motor-generator. All the components have their own internal controller (LCC) for stand-alone operation so the individual commissioning are in progress and almost completed. The next step scheduled is a combination test with all components in which supervisory control system manage LCCs remotely. The supervisory system covers the following roles: 1) machine status monitoring; 2) discharge sequence management; 3) real-time reference waveforms management; 4) data acquisition; 5) machine protection; 6) human safety. The supervisory system consists of several subsystems; PS supervising computer (PS-SC), PS programmable logic controller (PSPLC), PS internal protection system(PS-IPS) and PS safety interlock system (PS-SIS). PS-SC covers the primary roles in 1) - 4) which is built on CompactPCIs with real-time OS INtime. PS-SC and LCCs are linked through a Re_ective Memory (RM) network to share common data in real-time (4 kHz). PS-SC is also linked to the upstream JT-60SA supervisory control system (SCSDAS) via another RM network as an interface for the power supply internal control systems. During discharge sequence, PS-SC also manages motor-generator speed, AC circuit breakers OPEN/CLOSE status with a controller PS-PLC and magnets current according to request from SCSDAS. PS-IPS covers the function of 5) which is implemented on FPGA. PS-IPS is connected to LCCs via Vber optical and hard-wired signals. In case of emergency events such as magnet quench and earth quake, PS-IPS commands to shut down the magnets currents immediately. PS-SIS plays the role in 6) such as status and permission of fence OPEN/CLOSE and grounding switch for maintenance. In this presentation, overview and development of the supervisory system are described.

JT-60SA is an international tokamak being built in Naka (Japan) as a joint collaboration between Europe and Japan for the applied researches on the use of nuclear fusion as a new energy source. The procurement of the different systems composing JT-60SA is managed as in-kind contribution shared between European and Japanese institutions. The procurement of the Switching Network Units (SNUs) for the Central Solenoids (CS) is supported by Europe. After a four-year design and manufacturing in Europe, the JT-60SA CS SNUs and the related components were delivered to Japan in October 2016. This presentation describes the activities for the on-site installation, commissioning and tests of this procurement., 17th International Conference on Environment and Electrical Engineering (EEEIC2017)

JT-60SA is a Superconducting Tokamak in the framework of the Broader Approach Agreement between Europe and Japan. For this International Project among its various procurements, the Italian National Agency for New Technology Energy and Sustainable Economic Development (ENEA) is providing: four AC/DC converters for the central solenoid superconducting magnets (CS1, CS2, CS3 and CS4 PSs rated ±20 kA and ±1 kV); two AC/DC converters for the Equilibrium Field superconducting magnets (EF1 and EF6 PSs rated in the range +10 kA -20 kA and ±1 kV); and two AC/DC converters Fast Plasma Position Control Coils (rated ±5 kA and ±1 kV). Furthermore, ENEA is also providing six converter transformers of which: four dry type for FPPCC PSs and two oil type for CS PSs. These systems, being procured by ENEA through a contract signed in August 2013 with Industrial Suppliers (Poseico and Jema in Join-Venture), have been already constructed and they are in advanced testing phase. The basic devices of a CS/EF PS consist in: a thyristors rectifier or base PS, a converter transformer, a crowbar (to protect by over-voltages and/or over-currents); whereas the load of the CS/EF PS is a Super-Conducting Magnet, whose purpose is the generation of strong magnetic fields able to induce and confine the plasma current in a prefixed geometrical configuration. This requires that the control system of CS/EF PSs is able to comply with a reference current profile, known as “scenario”. The scenarios are particularly critical in these systems for the high currents required and hence for the high magnetic energy stored. The installed total electric power in JT-60SA is about 400 MVA, with a peak of reactive power equal to 330 MVAR and an energy consumption up to 1.5 GJ. The main characteristics of CS/EF base thyristor rectifier are: 4-quadrant AC/DC converter 12-pulses with circulating current in back-to-back configuration, with a DC current of ±20 kA, a DC voltage of 1 kV and an accuracy of ±1%. The design phase was completed in 2015, the construction of all EF/CS PSs was completed in 2016 whereas all PSs were tested in 2016 except EF PSs that are currently ongoing. All performed type tests were carried out both in closed loop feedback current control and in open loop feed forward voltage control and in accordance to the IEC60146 Standards. The electric load used for these tests the consists of three inductances connected in series, whole resulting values of 3.3mH and 3mΩ. The measure electric scheme is fed by the 30kV electric power grid and by an autotransformer, that offers the possibility to increase or decrease the voltage that is going to the converter transformers, that power the EF/CS PS. These tests, made at full current, pointed out a good dynamic behaviour of the control system both for forward and for reverse rectifier bridges, assuring the smooth transitions between different operating modes: single mode, circulating current mode and dual mode. This is the focus of the paper. The complete systems will be delivered to Japan by 2017., 27th IEEE Symposium on Fusion Engineering (SOFE-2017)

Switching Network Units (SNUs) are inserted in the power supply circuits of modern tokamaks for plasma initiation. In the framework of the “Broader Approach” agreement, the four SNUs for the superconducting modules of the JT-60SA Central Solenoid will be procured by European Union through the Italian Agency ENEA.The design is based on the synchronized operations of a light electromechanical contactor and of a static switch to combine the benefits of both devices. The adopted solutions could be extended to many fusion and industrial applications. A SNU was able to divert to a breakdown resistance (from 0.25 Ω to 3.75 Ω) currents up to 20 kA, producing a voltage drop up to 5 kV in less than 100 µs with a transient overvoltage limited to about 200 V.The tests showed good performance repeatability for all the SNUs. The accuracy of all the breakdown resistors was well within ±2%. Specific tests showed that they could dissipate much more than 360 MJ., 29th Symposium on Fusion Technology (SOFT2016)

Efficient control of Resistive-Wall-Modes (RWM) is mandatory in JT-60SA, the satellite tokamak under construction in Naka (Japan), since one of its main objectives is to reach steady-state high-beta plasmas. The RWM control system is based on a set of 18 in-vessel sector coils, placed on the plasma side of a conductive wall and independently fed by a dedicated fast power supply system (RWM-PS). This is the first PS system for fast control of plasma instabilities in fusion experiments adopting SiC semiconductors. The paper will give an overview of the whole final design with particular emphasis on the newest features and on the interface issues for an efficient integration with the JT-60SA power and control systems., 29th Symposium on Fusion Technology (SOFT2016)

JT-60SA is a Superconducting Tokamak in the framework of the Broader Approach Agreement (BAA) between Europe and Japan. For this International Project, both the Italian National Agency for New Technology, Energy and Sustainable Economic Development (ENEA) and the French Alternative Energies and Comissariat à l’Energie Atomique et aux Energies alternatives (CEA) have to provide overall twelve AC/DC pulse poloidal superconducting magnet power supplies (almost all rated for ±20 kA and ±1 kV). Each of them is equipped with a crowbar protection system. The crowbar system’s first function is to carry the current that is flowing through the superconducting coils and protects the AC/DC power converter from over-voltages, internal/external severe faults and in case of earthquakes. The current capability type test of crowbar system required a maximum peak current of ±26 kA and a maximum specific energy I2t = 4,6 GA2s for TF SCMPS. Finally the crowbar system and DC bus-bars were subjected to seismic tests in laboratory., 29th Symposium on Fusion Technology (SOFT2016)