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Supervisory control system for superconducting magnet power supplies in JT-60SA is designed and developed. This system is in charge of many kinds of control; discharge sequence control, real-time magnet current control, data acquisition, machine protection and human safety. In the design, communication interface has to be optimized according to all requirements. The most important feature is real-time control with 4 kHz which is required for equilibrium control of plasma. In order to satisfy this requirement, reflective memory (RFM) network is applied for high speed data sharing with multiple controllers. This paper describes the architecture of the control system and the operation of the power supply system under the supervision.

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.

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.

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.

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.

Questa pubblicazione rappresenta il “conceptual design report” per una sorgente a radiofrequenza di tipo CARM (Cyclotron auto resonance maser) operante a 250 GHz e progettata per attività di ricerca sul plasma. Lo studio è finalizzato alla pianificazione della costruzione di un dispositivo di tipo CARM nel Centro ENEA di Frascati, nell’ambito di ricerche concernenti la fusione nucleare. Le attività contemplate nel progetto raccolgono assieme differenti competenze tradizionalmente presenti all’interno dell’ENEA e, oltre la già citata fusione, riguardano la scienza e tecnologia degli acceleratori di particelle, la gestione e il trasporto dei fasci di particelle cariche, la superconduttività. Il documento prende in considerazione i vari particolari del progetto ed è diviso in due parti. La prima include la descrizione generale dell’intero sistema, tra l’altro presentando le ragioni a supporto della scelta del CARM, i presupposti teorici, le ragioni della la scelta dei parametri di operazione e le prestazioni attese dalla sorgente stessa. Nella seconda parte del testo sono riportati i dettagli costruttivi e ogni aspetto è adeguatamente descritto negli annessi tecnici: il progetto del catodo, la formazione e il trasporto del fascio di elettroni; le caratteristiche della alimentazione elettrica e della linea formatrice di impulso; il magnete superconduttore e le caratteristiche della cavità del CARM; lo sviluppo dei codici di calcolo per l’analisi delle prestazioni RF della sorgente., We present the conceptual design for a Cyclotron Auto Resonance Maser source, operating at 250 GHz and conceived for Plasma Fusion research ac- tivities. The study discussed here is aimed at planning the construction of such a device at the ENEA Frascati Center, within the framework of the researches pertaining to the Fusion department. This foreseen activity gather together different skills traditionally present in the Agency and including Fusion, ac- celerator technology, beam handling and transport, superconductivity. . . The report covers the different details of the project and is devided in two parts. The first contains a general description of the entire system, furthermore it describes the motivations underlying the choice of the de- vice, the relevant theoretical foundations, the reasons for the choice of the operating parameters and the expected performances of the source. In the second part the project details are reported and each constituting item is properly described in the technical annexes. We discuss indeed the cathode design and the electron beam shaping and transport, we report on the power supply and electrical pulse forming line, on the Superconduct- ing magnet and CARM cavity characteristics. Finally we discuss the code development effort for the analysis of the radiation output performances.

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)

OCEM and ENEA gained a wide experience in the design and experimental characterization of fast and accurate switching systems for high DC currents, as required to supply magnets and superconductors. The exploited idea consists in inserting an electronic switch in parallel to a light electromechanical switch in air to combine the benefits of both devices. The electronic switch is turned on and off to support the electromechanical commutations limiting their jitter and the arcs that would reduce the system lifetime. During the already performed tests, DC currents up to 20 kA were diverted in less than 100 mks with good repeatability. In case of emergency, the current can be interrupted in few tens of milliseconds. A resistor can be inserted in parallel to the switch to discharge inductive loads or to produce desired overvoltages (a voltage up to 5 kV was reached in this configuration). Specific circuits were designed to preserve the components from transient voltage overshoots. This switching system is expected to work for 10000 operations without major maintenance. The developed solutions may be extended to many relevant applications as particle accelerators and HVDC networks., Proceedings of the 25th Russian Particle Accelerator Conf., RuPAC2016, St. Petersburg, Russia

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)

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)

The Divertor Tokamak Test (DTT) facility, construction starting at Frascati, Italy, is designed to test different solutions for divertor in view of DEMO. A preliminary analysis of the error fields (EFs) assumed a simplified model of rigid and independent displacements and rotations. A methodology based on the first order truncated Taylor expansion has been applied, linking the displacement parameters and the EFs within the required ac-curacies. A system of in-vessel copper coils has been designed to counteract EFs and the ampere-turns necessary to force them back within the request limits has been calculated. Here, the details of the analysis have been provided.

The paper reports the results of the test and modelling activities carried out on large commercial supercapacitor cells at high current. Four commercials cells, with rated capacitance of 3000 F and rated voltage of 2.7 V, are considered. All cells are submitted to consecutive charge/discharge cycles at constant current. A test current in the range 80-130 A is used, which is comparable with the maximum operating current (up to 150 A) that the cells can reach in practical operations. A circuit model of the cells, able to reproduce the most relevant dynamic behavior, with a good compromise between accuracy, simplicity and robustness of the model's parameters, is also developed and validated against the experimental data. It is shown that all the investigated commercial cells are characterized by similar phenomena and comply with the same circuit model. Moreover, it is shown that the circuit parameters of the cells are in the same range and are weakly dependent on the test current. The obtained circuit parameters are accurately reported for all the cells and made fully accessible to users.