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A low-energy multipole line cusp ion source with two-grid extraction system has been developed and characterized for studying the role of the charge exchange processes on ion beam extraction, transport, and neutralization. The ion source is operated for extraction of Ar+ ion beam of current 50–240 mA at energies 850–1650 eV. The characterization of the ion beam is carried out at various axial positions along a 200–815-mm beam path with a background pressure of 4– $20\times10$ −5 Torr. An 11-channel Faraday cup array is used to measure the radial profiles of ion current density and angular beam divergence at these positions. The beam divergences are found to be in the range of 6°–15° for beam perveance of 0.50– $3.75\times10$ −9 AV−3/2. The attenuation of ion beam current along the beam path is observed due to the charge exchange neutralization of the energetic ions in the presence of high background pressure. Since ion current density along the beam path can be reduced by both the charge exchange processes and beam divergence, the accounting of beam particles, i.e., energetic ions and neutrals, at larger distances is difficult by the measurements of ion current density using the Faraday cup alone. The flux of energetic particles (energetic ions and fast neutrals) is therefore obtained by a thrust measurements on a beam target fixed at a distance of 800 mm from the ion source. The neutralization of the ion beam obtained by the emission of electrons from a hot filament neutralizer is also investigated in the presence of the charge exchange processes. Space-charge neutralization is provided initially by the secondary electrons emitted from the vessel walls or by the charge exchange processes even without the neutralizer operating at the desired temperature. However, the current neutralization is achieved only by the electrons emitted from the hot filament neutralizer operating in a space-charge-limited mode.

Research in ITER grade magnetic confinement fusion uses high power radio frequency sources and accelerated neutral particles to heat the plasma to fusion temperature. These devices require high voltage DC power supplies in the range of several tens of kilovolts at a power level of few megawatts. Pulse step modulation technique is widely used to generate high voltage by cascading bulk numbers of low voltage switched power modules, offers a minimum ripple with microsecond order transient response and low let-through energy in case of load fault. However, the power quality and reliability of these systems still need enhancement for compatibility with an industrial environment. In a conventional diode rectifier-based switched power module, current drawn from the multisecondary transformer is highly distorted affecting transformer performance, leading to deploy higher capacity with enhanced thermal management. A novel concept of pulsewidth modulated (PWM) rectifiers in pulse step modulated power supplies is attempted for the first time with comparative analysis over conventional diode rectifiers, quoting an example of dual output high voltage power supply. Articles also discuss the development of a laboratory-scale prototype of the switched power supply module utilizing a PWM rectifier.

A solid state High Frequency (HF) 1 MHz, 40 kW source is intended for plasma formation in a neutral beam source by inductive coupling of RF power. An important design feature of such an HF source is its ability to sustain large transient swings of load (due to impedance transition on microsecond time scales). A 40 kW High Frequency Power Supply (HFPS) has been configured with multiple Class-D H-bridge inverters modules by using latest generation switching semiconductors. Each module is capable of delivering 3 kW of power, then magnetic combiners and an LC tuning network provides a 1 MHz sinusoidal output to a 50 Ω standard load. The developed prototype power supply has been coupled to a single-driver RF ion source test bed ROBIN in IPR to characterize the system with actual load conditions. In a recent experimental campaign, tuning of matching network parameters helped to strike and sustain plasma over the pressure range of 1 Pa to 0.42 Pa with forward power of 37 kW to 22 kW. An additional impedance matching network was implemented to map the power supply impedance (50 Ω) with the impedance offered from the source (>90 Ω seen at PS end). A configurable frequency with resolution (∼1 kHz) helped to achieve a power factor close to unity. Experiments helped to study the behavior of the power supply in scenarios of dynamic (plasma) impedance. Auto-tunable frequency for matching the varying load is being implemented in the HF power supply.

Ion Cyclotron High Voltage Power Supply (IC-HVPS) with dual output (27kV & 15kV, 3MW) is operational at ITER-India lab with a 1.5 MW Diacrode based RF source to be used for ICRF (Ion Cyclotron RF) system. The controller for ICHVPS is designed with LabVIEW Real-time (RT) PXI controller to support all control and monitoring operations of the Pulse Step Modulation (PSM) based power supply. Besides regulation of output voltage, the controller supports all essential features like, fast dynamics, low ripple and protection for source and loads. This is managed by close integration between RT system and FGPA (Field Programmable Gate Array) inside the controller. Two types of data transfers inside the RT controller are implemented, 1) Between FPGAs and RT controller, 2) Between internal algorithms. RT controller and FPGAs are interconnected through PXI bus. Critical functions, signal generations, monitoring & data acquisition and interfaces are assigned to FPGAs. All these processes are managed by Real Time Operating System (RTOS) installed in the controller. Most of the processes initiated by RT controller ends up performing certain task by invoking the algorithm inside FPGA directing some action to outer interfaces. Some of the process routines are implemented for managing the internal algorithms. This paper discusses different techniques used mostly for transfer of information between RT controller and FPGAs. Information includes critical signals, data, measurements, commands and configuration required for internal algorithms. Algorithms use various methods like DMA-FIFOs, local variables, arrays, Trigger lines to transfer information. RT-FIFOs are used to handle bulk data in runtime to improve performance. Methods have been chosen carefully to fulfill critical requirements, balancing the available resources while managing limitations. Discussion also includes some specific choices made for synchronized and asynchronous transmission of parallel and sequential data.

Pulse Step Modulation (PSM) based High Voltage Power Supplies (HVPSs) are widely used in fusion research and other applications viz. broadcast transmitters, particle accelerators and neutral beam injectors because of inherent advantages of modular structure, high accuracy and efficiency, low ripple and fast dynamics. Typical Ion Cyclotron Radio Frequency (IC RF) system composed of cascaded connection of Driver stage (130 kW RF output) and End stage (1500 kW RF Output) would need two power supplies. A novel concept of tapping two outputs from single PSM based HVPS is attempted for the first time. PSM based 3 MW HVPS is developed with dual output to feed anode voltage of Driver (up to 18 kV) and Final Stage (up to 27 kV). Controller for the HVPS is designed to suit requirements during local operation and remote operation. In Local operation mode, protection interlocks with in the HVPS are integrated while remote mode has additional interlocks from IC RF Amplifiers system. Field integration of the controller is achieved through fiber optical links to avoid Electro-Magnetic interferences. Present article discusses initial experience of dual output HVPS with IC RF amplifiers, pre-integration validation campaigns including qualification for energy limits. The paper also presents the performance of HVPS at full rated capacity of 2800 kW continuous duty to support 1.5 MW IC RF system.

A Dual output (27 kV & 15 kV), 3 MW Ion Cyclotron High Voltage Power Supply (IC-HVPS) has been installed and integrated with a Diacrode based RF source to be used for ICRF (Ion Cyclotron RF) system. The IC-HVPS Controller is based on LabVIEW Real-time PXI controller, which supports all control and monitoring operations of the PSM based power supply. The controller supports all essential features like, fast dynamics, low ripple and protection for source and loads. EPICS (Experimental Physics and Industrial Control Systems) is an open source software widely accepted in scientific community as supervisory distributed control system including CODAC (Control, Data Access and Communication) for ITER. However interface with LabVIEW RT systems is not fully mature yet. Evolving interface requirements of platforms like EPICS with IC-HVPS control has been assessed and implemented for monitoring purpose. A test case was implemented to identify compatibility, feasibility, consistency and performance of EPICS server with Input Output Controller (IOCs) implemented in Real-time controller. This paper discusses integration of EPICS IOCs and LabVIEW based Real-time Controller along with an analysis on limitations imposed by such integration.

Mega watt particle accelerators like Neutral Beam Injectors draw electrical power for Plasma formation, Ion Extraction at elevated potential of ~100kV, infact the water cooling lines, gas feed lines are also floating at 100kV. Usually power supplies, hydraulic/gas feed station of typical Injector are placed in a separate building/location. In such a scenario, large coaxial transmission lines are used to support power transport, hydraulic & gas feed lines, providing electrical isolation of 100kV. This paper presents electrostatic analysis for the complex configuration of large transmission line. Specially designed profiles to provide electrical isolation within permissible limits of electric stress. Further HVDC test results showing behaviour of Transmission line over longer exposure of 3600s are also presented.

Heating neutral beam (HNB) injectors, necessary to achieve burning conditions and to control plasma instabilities in ITER, are characterized by such demanding parameters that a neutral beam test facility (NBTF) dedicated to their development and optimization is being realized in Padua (Italy) with direct contributions from the Italian government (through Consorzio RFX as the host entity) and the ITER international organization (with kind contributions from the ITER domestic agencies of Europe, Japan and India) and technical and scientific support from various European laboratories and universities. The NBTF hosts two experiments: SPIDER, devoted to ion source optimization for the required source performance, and MITICA, the full-size prototype of the ITER HNB, with an ion source identical to SPIDER. This paper gives an overview of the progress towards NBTF realization, with particular emphasis on issues discovered during this phase of activity and on solutions adopted to minimize the impact on the schedule and maintain the goals of the facilities. The realization of MITICA is well advanced; operation is expected to start in 2023 due to the long procurement time of the in-vessel mechanical components. The beam source power supplies, operating at 1 MV, are in an advanced phase of realization; all high-voltage components have been installed and the complex insulation test phase began in 2018. At the same time, construction and installation of SPIDER plant systems was successfully completed with their integration into the facility. The mechanical components of the SPIDER ion source were installed inside the vessel and connected to the plants. Integrated commissioning with the control, protection and safety systems ended positively and the first experimental phase has begun. The first results of the SPIDER experiment, with data from operational diagnostics, and the plans for the 1 MV insulation tests on the MITICA high-voltage components are presented.

Controlled fusion is the huge energy source and able to cater the future electricity needs. To achieve controlled fusion, wide variety of power supplies are being used at experimental level, mainly categorized as converters for supplying superconducting magnets and converters for plasma heating and current drive (H&CD) systems. Power converters for supplying super conducting coils are generating very high dc current (in kA range) while high dc voltage (∼ 30–1000 kV) is required for heating and current drive systems. Present article describes stringent performance requirements demanded by H&CD system and reason for adopting Pulse Step Modulation (PSM) based or modular inverter based High Voltage Power Supply (HVPS). Article also discuss case study of PSM based HVPS along with associated challenges appearing at operation modes. A glimpse of few important behavior of H&CD load and possible solution also discussed at the end.

Power Transformers with more than one secondary winding are not uncommon in industrial applications. But new classes of applications where very large number of independent secondaries are used are becoming popular in controlled converters for medium and high voltage applications. Cascade H-bridge medium voltage drives and Pulse Step Modulation (PSM) based high voltage power supplies are such applications. Regulated high voltage power supplies (Fig.1) with 35-100 kV, 5-10 MW output range with very fast dynamics (μS order) uses such transformers. Such power supplies are widely used in fusion research. Here, series connection of isolated voltage sources with conventional switching semiconductor devices is achieved by large number of separate transformers or by single unit of multi-secondary transformer. Naturally, a transformer having numbers of secondary windings (~40) on single core is the preferred solution due to space and cost considerations. For design and simulation analysis of such a power supply, the model of a multi-secondary transformer poses special problem to any circuit analysis software as many simulation softwares provide transformer models with limited number (3-6) of secondary windings. This article discusses a more detailed representation of flux coupled magnetic model with saturable core properties to simulate actual transformers very close to its observed parameters in test and actual usage.

The realization of the ITER Neutral Beam Test Facility (NBTF) and the start the experimental phase are important tasks of the fusion roadmap, since the target requirements of injecting to the plasma a beam of Deuterium atoms with a power up to 16.5 MW, at 1MeV of energy and with a pulse length up to 3600s have never been reached together before. The ITER NBTF, called PRIMA (Padova Research on ITER Megavolt Accelerator), is hosted in Padova, Italy; it includes two experiments: MITICA, the full-scale prototype of the ITER injector and SPIDER, the full-size negative ion source. The realization promoted by the ITER organization is carried out with the contribution of the European Union, channeled through the Joint Undertaking for ITER (F4E), of the Consorzio RFX which hosts the Test Facility, the Japanese and the Indian ITER Domestic Agencies (JADA and INDA) and several European laboratories, such as IPP-Garching, KIT-Karlsruhe, CCFECulham, CEA-Cadarache. The early start of operation of PRIMA experiments is urgent because sufficient experimental time is necessary to face and solve the issues related to the achievement of the desired performance in time for the ITER operation, requiring NBI since the beginning. Substantial progresses have been recently achieved: the buildings construction, begun in October 2012, has been completed by the end of 2015 and the installation of some components has been started since the end of 2014. The SPIDER realization is well advanced: the installation phase is proceeding in good agreement with the general plan; it is expected to be almost completed by the end of 2016. In parallel, the commissioning of the SPIDER power supply (PS) and auxiliary plant systems is being proceeding. Tests at full power and remote control are planned, including also those addressed to reproduce the grid breakdowns and to test the relevant protections. The design of the MITICA injector components was completed in 2015their procurement is being made through a number of tenders, some of them already launched. The HV Power Supply system of the MITICA 1MV accelerator, provided by JADA, was delivered on site in December 2015. The challenging installation of these components, including the step-up transformers and the SF6 gas insulated transmission line, started soon after and will go on throughout 2016. The present phase, with the PRIMA buildings continuously filled with new components, with the installation activities progressing and with also the commissioning and testing phase starting represents a substantial step forward toward the main target. The paper will describe the main challenges the Project Team has dealt during this phase and the important feedback derived for the ITER HNB systems both from the technical and the organizational standpoints.

SPIDER is one of two projects of the ITER Neutral Beam Test Facility under construction in Padova, Italy, at the Consorzio RFX premises. It will have a 100 keV beam source with a full-size prototype of the radiofrequency ion source for the ITER neutral beam injector (NBI) and also, similar to the ITER diagnostic neutral beam, it is designed to operate with a pulse length of up to 3600 s, featuring an ITER-like magnetic filter field configuration (for high extraction of negative ions) and caesium oven (for high production of negative ions) layout as well as a wide set of diagnostics. These features will allow a reproduction of the ion source operation in ITER, which cannot be done in any other existing test facility. SPIDER realization is well advanced and the first operation is expected at the beginning of 2018, with the mission of achieving the ITER heating and diagnostic NBI ion source requirements and of improving its performance in terms of reliability and availability. This paper mainly focuses on the preparation of the first SPIDER operations - integration and testing of SPIDER components, completion and implementation of diagnostics and control and formulation of operation and research plan, based on a staged strategy

The ITER Neutral Beam Test Facility (NBTF), called PRIMA (Padova Research on ITER Megavolt Accelerator), is hosted in Padova, Italy and includes two experiments: MITICA, the full-scale prototype of the ITER heating neutral beam injector, and SPIDER, the full-size radio frequency negative-ions source. The NBTF realization and the exploitation of SPIDER and MITICA have been recognized as necessary to make the future operation of the ITER heating neutral beam injectors efficient and reliable, fundamental to the achievement of thermonuclear-relevant plasma parameters in ITER. This paper reports on design and R&D carried out to construct PRIMA, SPIDER and MITICA, and highlights the huge progress made in just a few years, from the signature of the agreement for the NBTF realization in 2011, up to now - when the buildings and relevant infrastructures have been completed, SPIDER is entering the integrated commissioning phase and the procurements of several MITICA components are at a well advanced stage

Regulated high-voltage power supplies (RHVPSs) are important power sources in high-power heating and current drive systems for a tokamak. Along with high power at output, these power supplies meet the requirements of fast dynamics (on the order of few microseconds), low ripple factor, and good output regulation. A development overview is presented for RHVPS ranging from 14 to 80 kV at several-megawatt power with typical output results. Having extensive tests performed with an 80-kV 75-A RHVPS, it is being regularly used for a neutral beam injector (NBI) at the Institute for Plasma Research (IPR). A large number of identical and series-connected switched power modules (SPMs) are fed from multisecondary transformers. Pulse step modulation control applied to an insulated-gate bipolar transistor switch within SPMs regulates output. Different rise and fall times of voltage can be set from few microsecond to millisecond range. Fast detection of instantaneous overcurrent reduces turnoff time within 2 μs. Due to higher frequency of ripple at higher voltages, output filter component value is of smaller order, which, in turn, limits fault energy below 10 J. The development of RHVPS at IPR started by making a functional prototype at lower rating (14 kV; 35 A) to have an experience in testing design concepts. This was divided in various activities like selection of topology, selection and design of different subparts, e.g., control, switching power converters with protections, and multisecondary transformers. Having successful results and testing all functional parameters on prototype, a series of RHVPSs at higher ratings (up to 80 kV), are developed and installed for NBI and radio-frequency heating system. The design details for each subsystem along with results are discussed.

High voltage power supply (HVPS) based on pulse step modulation (PSM) topology has already demonstrated its ability for broadcast transmitters, accelerators using radio frequency (RF) source and neutral beam injectors. Typical ion cyclotron resonant heating (ICRH) system composed of cascaded connection of driver stage and end stage would need two power supplies. A novel concept of tapping two outputs from single PSM based HVPS is attempted for the first time. A PSM based HVPS is developed with dual output to feed driver and end stages of a high power RF amplifier. This article discusses the development of a HVPS, capable to provide 14–18 kV, 250 kW to driver stage and 16–27 kV, 175–105 A, 2800 kW to end stage RF amplifier chain. Here dual output are controlled independently by single FPGA based PXI controller which support all pros of PSM based HVPS like low ripple, fast dynamics and very short time to turn-off. Discussed HVPS supports non-linear demand from ICRH system i.e. lower current (105 A) at higher voltage (27 kV) and higher current (175 A) at lower voltage (18 kV), which developed as indoor compact solution. As an add-on specification, HVPS facilitates 1 kHz RF power modulation. The HVPS is composed of two cast resin multi-secondary transformers (CRT), 48 numbers of switched power supply (SPS) modules; FPGA/real time based controller and other auxiliaries including passive protection devices. Present article describes technical details of HVPS components which are manufactured to IEC standards. HVPS with dual output is an effective replacement to conventional solutions, as it offers optimized solution for equipment bulk as well as economy.

Pulse step modulation (PSM)-based high-voltage power supplies have played a significant role in fusion research. In many cases, multisecondary transformers are used for generation of tens of kilovolt range outputs with fast (microsecond-order) transient response. In this scheme, large numbers of isolated voltage sources are connected in series to generate the output. Isolated voltage sources can be achieved by a large number of separate transformers or by a single unit of multisecondary transformer. Naturally, a transformer having numbers of secondary windings (40) on a single core is the preferred solution for PSM topology due to its space and cost consideration. For design and simulation analysis of such a power supply, the model of a multisecondary transformer poses special problem to any circuit analysis software. While many simulation software packages provide transformer models with limited number (3-6) of secondary windings, they still fail to predict the actual observed results from a manufactured unit. This paper discusses the difficulties in modeling, step by step with representative schemes of multisecondary transformer, and advantages/disadvantages of each scheme with simulation results. Finally, a model using flux-coupled cores as basic building blocks is proposed; this model is able to simulate actual transformers very close to its observed parameters in test and actual usage.

The diagnostic neutral beam (DNB) line shall be used to diagnose the He ash content in the D–T phase of the ITER machine using the charge exchange recombination spectroscopy (CXRS). Implementation of a successful DNB at ITER requires several challenges related to the production, neutralization and transport of the neutral beam over path lengths of 20.665 m, to be overcome. The delivery is aided if the above effects are tested prior to onsite commissioning. As DNB is a procurement package for INDIA, an ITER approved Indian test facility, INTF, is under construction at Institute for Plasma Research (IPR), India and is envisaged to be operational in 2015. The timeline for this facility is synchronized with the RADI, ELISE (IPP, Garching), SPIDER (RFX, Padova) in a manner that best utilization of configurational inputs available from them are incorporated in the design. This paper describes the facility in detail and discusses the experiments planned to optimise the beam transmission and testing of the beam line components using various diagnostics.

The RF heating and current drive (H&CD) systems to be installed for the ITER fusion machine are the electron cyclotron (EC), ion cyclotron (IC) and, although not in the first phase of the project, lower hybrid (LH). These systems require high voltage, high current power supplies (HVPS) in CW operation. These HVPS should deliver around 50 MW electrical power to each of the RF H&CD systems with stringent requirements in terms of accuracy, voltage ripple, response time, turn off time and fault energy. The PSM (Pulse Step Modulation) technology has demonstrated over the past 20 years its ability to fulfill these requirements in many industrial facilities and other fusion reactors and has therefore been chosen as reference design for the IC and EC HVPS systems. This paper describes the technical specifications, including interfaces, the resulting constraints on the design, the conceptual design proposed for ITER EC and IC HVPS systems and the current status.

The RF heating and current drive (H&CD) systems that are to be installed in ITER during the construction phase, are the electron cyclotron (EC) and ion cyclotron (IC) systems. They are complex assemblies of high voltage power supplies (HVPS), RF generators, transmission lines and antennas. Their design and integration are constrained by many interfaces, both internal, between the subsystems, and external, with the other ITER systems. In addition, some components must be compatible with a nuclear environment and are classified as Safety Important Component. This paper describes the processes implemented in ITER to ensure proper integration.

An ion extractor system has been designed for the steady state superconducting tokamak (SST-1) neutral beam injector (NBI) for an experiment using a prototype ion source with fully integrated regulated high voltage power supply (RHVPS) and data acquisition and control system (DACS) developed at Institute for Plasma Research (IPR) to obtain experience of NB operation. The extractor system is capable of extracting positive hydrogen ion beam of ∼10 A current at ∼20 kV. This paper presents the beam optics study for detailed design of an ion extraction system which could meet this requirement. It consists of 3 grid accel–decel system, each of the grid has 217 straight cylindrical holes of 8 mm diameter. Grids are placed on a specially designed G-10 block; a fiber reinforc plastic (FRP) isolator of outer diameter of 820 mm and 50 mm thickness. Provisions are made for supplying high voltage to the grid system through the embedded feed-throughs. Extractor system has been fabricated, mounted on the SST-1 neutral beam injector and has extracted positive hydrogen ion beam of 4 A at 20 kV till now.

We present characteristics of a 5 MW ion source for SST-1 neutral beam injector. Before the source could be tested for its performance, it was conditioned by 480 arc discharges of 1 s and beam extraction of hydrogen species at various beam voltages ranging between 19 kV and 56 kV. Breakdown free beam extraction could be secured only after about 3000 beam second extraction. The ion source is capable of delivering 1.7 MW of neutral beam power at 55 kV with horizontal and vertical focal length of 5.4 m and 7 m respectively. Beam divergence is ∼0.97°. Steady-state beam energy of 31 MJ at 41 kV was achieved during 14 s long beam extraction. We have not noticed any deterioration of beam parameters, including beam divergence during long pulse operation. These results indicate that 0.5 MW of neutral beam power at 30 kV required for heating of plasma in SST-1 can be delivered.

The Indian Test Facility (INTF) for Neutral Beams is designed with the objective to not only test the performance of an ion source but also to characterize the transmission of the Neutral Beam to a length of 20.66 m and thereby generate adequate database on the quality of the beam that is required for the CXRS diagnostics for measurement of Helium ash content in the fusion plasma.

Multisecondary transformers are used at the input stage of modular high voltage power supplies. These power supplies are used in various steady state and pulsed applications, typical examples are neutral beam injectors, rf and microwave devices [N. Tomljenovic et al., Solid power supplies for Gyrotron and NBI sources, Fusion Technol., 1992; H.-U. Boksberger et al., The solid state TEXTOR high voltage neutral beam accelerator power supplies, in: Proceedings of the 11th SOFE, Austin, 1985, p. 679]. This paper presents a systematic study of the interactions of the transformer secondary winding stray capacitances [S. Austen Stigant, The J&P Transformer Book, Butterworths, London, 10th ed., pp. 498–500] and their behavior on the switching frequency of the power supply. Results from simulation and experiments on a pair of 300 kV A, 415/330 V (20 secondaries), 30 kV dc isolation transformers used for generating a regulated 14 kV dc, 35 A output are presented. Additional dielectric losses ∼13% of the total transformer loss and voltage swings at the switching frequency of the semiconductor devices are observed. Possible effects on the performance of the transformer and the design considerations are discussed. Constructional features and other observations related to the multisecondary transformers are also discussed.

The ITER project requires additional heating by two neutral beam injectors, each accelerating to 1 MV a 40 A beam of negative deuterium ions, to deliver to the plasma a power of about 17 MW for one hour. As these requirements have never been experimentally met, it was recognized as necessary to setup a test facility, PRIMA (Padova Research on ITER Megavolt Accelerator), in Italy, including a full-size negative ion source, SPIDER, and a prototype of the whole ITER injector, MITICA, aiming to develop the heating injectors to be installed in ITER. This realization is made with the main contribution of the European Union, through the Joint Undertaking for ITER (F4E), the ITER Organization and Consorzio RFX which hosts the Test Facility. The Japanese and the Indian ITER Domestic Agencies (JADA and INDA) participate in the PRIMA enterprise; European laboratories, such as IPP-Garching, KIT-Karlsruhe, CCFE-Culham, CEA-Cadarache and others are also cooperating. Presently, the assembly of SPIDER is on-going and the MITICA design is being completed. The paper gives a general overview of the test facility and of the status of development of the MITICA and SPIDER main components at this important stage of the overall development; then it focuses on the latest and most critical issues, regarding both physics and technology, describing the identified solutions.

This article describes hardware and software solutions to a need which is comprised of (i) acquisition of a large volume of high speed data with multiple time scales, (ii) control of various operational parameters of device and diagnostics, and (iii) processing and management of the acquired data for a large volume plasma device. The solution relies on the base of a VXI bus and uses a standard PC with a Windows 98/NT operating system and C as the programming language. The system is networked with the existing network with the result of allowing a large data storage space of processing facilities from any terminal in the laboratory.

High Frequency Power supply (HFPS) is used for various applications like AM Transmitters, metallurgical applications, Wireless Power Transfer, RF Ion Sources etc. The Ion Source for a Neutral beam Injector at ITER-India uses inductively coupled power source at High Frequency (~1 MHz). Switching converter based topology used to generate 1 MHz sinusoidal output is expected to have advantages on efficiency and reliability as compared to traditional RF Tetrode tubes based oscillators. In terms of Power Electronics, thermal and power coupling issues are major challenges at such a high frequency. A conceptual design for a 200 kW, 1 MHz power supply and a prototype design for a 600 W source been done. The prototype design is attempted with Class-E amplifier topology where a MOSFET is switched resonantly. The prototype uses two low power modules and a ferrite combiner to add the voltage and power at the output. Subsequently solution with Class-D H-Bridge configuration have been evaluated through simulation where module design is stable as switching device do not participate in resonance, further switching device voltage rating is substantially reduced. The rating of the modules is essentially driven by the maximum power handling capacity of the MOSFETs and ferrites in the combiner circuit. The output passive network including resonance tuned network and impedance matching network caters for soft switching and matches the load impedance to 50ohm respectively. This paper describes the conceptual design of a 200 kW high frequency power supply and experimental results of the prototype 600 W, 1 MHz source.

The neutral beam injector of steady state superconducting tokamak (SST1-NBI) at IPR is designed for injecting upto 1.7 MW of neutral beam (Ho, 30-55 keV) power to the tokamak plasma for heating and current drive. Operations of the positive ion source (PINI or Plug-In-Neutral-Injector) of SST1-NBI were carried out on the NBI test stand. The PINI was operated at reduced gas feed rate of 2-3 Torr l/s, without using the high speed cryo pumps. Experiments were conducted to achieve a stable beam extraction by optimizing operational parameters namely, the arc current (120-300 A), acceleration voltage (16-40 kV), and a suitable control sequence. The beam divergence, power density profiles, and species fractions (H(+):H2(+):H3(+)) were measured by using the diagnostics such as thermal calorimetry, infrared thermography, and Doppler shift spectroscopy. The maximum extracted beam current was about 18 A. A further increase of beam current was found to be limited by the amount of gas feed rate to the ion source.

The paper presents the complete engineering design of steady neutral beam injector, with emphasis on the deviation in the design from conventional short pulse injectors.

This paper presents the control system overview, hardware, software and network for Data acquisition and Control system for steady state neutral beam injector (NBIDACS) to be used for heating of plasma in steady state superconducting tokamak (SST-1). The task for NBIDACS is not only to safely deliver 1.7 MW of neutral beams at 55 keV H° a period of 1000 s with 16.7% duty cycle but also to acquire the data related to house keeping of the system and its auxiliaries and diagnostics which determine the quality and parameters of the beam. Major issues concerning the design of the system stem from operation duty cycle of 1000 s ON/5000 s OFF. This calls for use of intelligent techniques not only for managing a large amount (100 MB) of data per shot but also to obtain failsafe, reliable control system and to archive the recorded data.

The Neutral Beam Injector of SST-1 (Steady-state Superconducting Tokamak-1) uses Filamented Ion Sources with AC heating. A regulated filament power supply is essential to maintain constant filament temperature, beam current and plasma. This paper presents the design and performance of AC-to-AC converters for the filament power supply system. A 24 phase heater supply is used to minimize the ripple on plasma density. The front-end converter circuit at the input maintains the total current harmonic distortion of line within 5% and power factor at unity with 10kVA power. A PWM inverter along with output filters generates the three-phase output. Three phase AC output is controllable from 0-415V (rms), 400Hz, sinusoidal. The secondary from a single-phase step down transformer (ratio 12:1) placed at the output of the converter is connected to one filament. The stability at the output is 0.1 % for line or load fluctuations with 20 mSec transient response. Overall efficiency is approximately 90%. Eight power supplies, all capable of being synchronized with an external phase reference trigger pulse are used to generate a 24-phase filament heating system for the ion source. The PWM generation carrier waveform is generated by a digital scheme, with a start trigger for each cycle. The control is matched to meet the filament temperature stability with compensation for actual current in the filament.

A positive ion neutral injector capable in delivering 5MW (55kV, 90A) ion beam power is being operated for SST-1 neutral beam injection (NBI). SST-1 Neutral beam injection systems has various components on beam line like ion source, neutralizer, deflection magnet, ion dump, beam dump etc. A Thermocouples based diagnostics is being used for Power density distribution, Beam alignment and System protection. Temperature of beam line components rises when beam passes through them. In order to measure the rise in temperature and estimating beam power profile, beam line components are instrumented with thermocouples (TCs). The thermocouples, which are all K (nickel-chromium/nickel-aluminum) type, have their hot junctions on ground so as to respond quickly to temperature changes. Here `the ground' means beam line components, which in turn are connected to the single reference point of the electrical circuit. The beam itself is dumped on these parts so TCs are subject to severe voltage transients up to few hundred volts. We developed a signal conditioning and data acquisition system to measure the voltage developed across the thermocouples due to rise in temperature. This signal conditioning and data acquisition system is capable in truly producing the temperature rise in presence of voltage transients, high voltage switching during breakdowns. Raw signal from each of these thermocouples is first processed in signal condition cards and then acquired on data acquisition system. This paper presents the scheme of signal conditioning system and obtained results in detailed.

Regulated High Voltage Power Supplies (RHVPS) are developed at the Institute for Plasma Research (IPR) for Neutral beam and RF heating applications of Steady-state Superconducting Tokomak (SST-1) up to 80 kV, 130A rating. They deliver power to loads that have very low fault energy tolerance; thereby protection of load is mandatory. At each stage special diagnosis is necessary to protect power supply components. Also, output fault protection is done so that fault energy is not more than 10J. Multi-secondary transformers (2 numbers, each at 5.6 MVA rating with 40 outputs) may get damaged even for overload at any one of their secondary, while remaining secondaries carry very less current or no current. Special technique is applied to sense and diagnose this fault in addition to routine overload sensing. Electronic means are used for fast detection and isolating RHVPS from utility supply. This paper describes overall RHVPS power scheme along with output fault protection and internal fault diagnosis system and test results thereof.

Pulse Step Modulation based High voltage power supply has played significant role in fusion research. Multi-Secondary transformers are invariably used for generation of tens of kV range outputs with fast (µS order) transient response. In this scheme, large numbers of isolated voltage sources are connected in series to generate the output. Isolated voltage sources can be achieved by large number of separate transformers or by single unit of multi-secondary transformer. Naturally, a transformer having numbers of secondary windings (∼40) on single core is the preferred solution due to its space and cost consideration. For design and simulation analysis of such a power supply, the model of a multi-secondary transformer poses special problem to any circuit analysis software. While many simulation softwares provide transformer models with limited number (3–6) of secondary windings, they still fail to predict the actual observed results from a manufactured unit. This paper discusses the difficulties in modelling, step by step with representative schemes of multi-secondary transformer, advantages/disadvantages of each scheme with simulation results. Finally, a model using flux coupled cores as basic building block is proposed, this model is able to simulate actual transformers very close to its observed parameters in test and actual usage.

The Ion Cyclotron Heating and Current Drive (IC H & CD) system for ITER will provide Radio frequency (RF) heating and current drive to the ITER plasma. This system is designed to provide 20 MW into the plasma using frequencies in the range of 40 MHz to 55 MHz, which could be upgraded to 40 MW in future. This paper presents the recent development of the IC H&CD system configuration in the ITER Tokamak complex & auxiliary buildings with developed interfaces.

This paper describes the ITER ICRF system main requirements and the latest developments for its different parts which are to be procured by the ITER Parties. The built in margins will allow reaching the requirements on a large parameter range, or delivering more power in a restricted range.

The paper presents the design and performance of the discharge power supply for the ion source of the long pulse neutral beam injector. The dc output is 10-160 V, 100 A (max.) with peak ripple less than 400 mV at rated load. Long term stability is better than 0.1% with very fast turn on time (20 /spl mu/s) and turn off time (2 /spl mu/s). Settling time is less than 40 ms to /spl plusmn/2% of final value. 24 such power supplies are used for one ion source. The control is matched to meet the discharge dynamics. The design uses novel features in power electronics, these are discussed and performance results are presented.

Regulated High Voltage Power Supplies (RHVPS) are commonly used in high-energy particle accelerators. RHVPS is a modular power supply in which kV level modules (40 or 80#) are cascaded to generate desired level of voltage/power [1]. One of the most challenging tasks involved is to provide input power to number of rectifier modules with required isolation (inter-winding and winding to ground). This is accomplished by deploying multi-secondary (large numbers, say 40 secondaries) transformers. This RHVPS concept was realized for the first time in the country with development of oil filled multi-secondary transformer. A pair of 3.3MVA, 11kV/ (940Vx40) has been successfully demonstrated, isolation of 6kVDC (inter-winding) and 160kVDC (all secondary to ground) tested. The next generation power supplies are unitized with indoor installations. This has created the demand for dry type multi-secondary transformers in compliance with safety regulations. This paper presents manufacturing issues and testing of the prototype resin cast coil. On the manufactured prototype, inter-winding isolation is tested up to 6kVDC and 125kVDC with respect to ground.

This paper presents operational experience of integrated control of the arc-filament and High-voltage power supply of Steady State Tokamak (SST)-1 NBI system using Versa Module Europa (VME) system on prototype Ion source. The control algorithm is implemented on the VxWorks operating system using 'C' language. This paper also describes the operating sequence and controls on power supply system. Discharge and Filament power supplies are controlled in such a way so that necessary discharge current can be available in Ion Source. The discharge current is controlled by manipulating the filament current. Close loop control is implemented on each filament power supply with feedback from Discharge Current to control the overall discharge inside the ion source. Necessary actions for shut OFF and subsequent Turn ON are also taken during breakdowns between the Grids of the ion source. Total numbers of breakdowns are also monitored. Shot is terminated, if the breakdown count is higher than the set value. This control system can be programmed to restart High-voltage power supply within 5mS after breakdown occurs. This control system is capable to handle the all types of dynamics in the system. This paper also presents results of experiment.

This article describes the control system for a 5MW ion source of the NBI (neutral beam injector) for steady-state superconducting tokamak-1 (SST-1). The system uses both hardware and software solutions. It comprises a DAS (data acquisition system) and a control system. The DAS is used to read the voltage and current signals from eight filament heater power supplies and 24 discharge power supplies. The control system is used to adjust the filament heater current in order to achieve an effective control on the discharge current in the plasma box. The system consists of a VME (Verse Module Eurocard) system and C application program running on a VxWorks™ real-time operating system. A PID (proportional, integral, and differential) algorithm is used to control the filament heater current. Experiments using this system have shown that the discharge current can be controlled within 1% accuracy for a PID loop time of 20ms. Response of the control system to the pressure variation of the gas in the chamber has also...

Regulated high-voltage power supplies (RHVPSs) have been developed at Institute for Plasma Research and utilized for neutral beam and radio-frequency heating applications of the steady-state superc...

This paper presents the design calculations for the ion deflection system for the SST-1 NBI system. The main design driver for engineering this system has been long pulse compatibility with the heat load.