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In the ITER neutral beam (NB) system, deuterium negative ion beam with 1 MeV, 40 A for 3600 s is required for plasma heating and current drive. The NB Test Facility (NBTF) is now being constructed in Padova, Italy, to achieve such high requirement prior to the ITER operation. Japan procures DC 1 MV power supply (PS) components for the NBTF and the ITER NB. Since this PS consists of various kinds of component with 100 m long, manufacturing and factory test have been performed over five years, and shipping and installation have been proceeded in parallel step by step as presented in the last FEC [A]. The on-site assembling technique for such complicated 1MV PS components is one of challenges not only for the ITER NB but also typical electrical components. As recent progress in the last two years, completion of assembly and also high-voltage insulation test of DC 1 MV power supply components are reported.

In the ITER neutral beam (NB) system, deuterium negative ion beam with 1 MeV, 40 A for 3600 s is required for plasma heating and current drive. The NB Test Facility (NBTF) is now being constructed in Padova, Italy, to achieve such high requirement prior to the ITER operation. Japan procures DC 1 MV power supply (PS) components for the NBTF and the ITER NB. Since this PS consists of various kinds of component with 100 m long, manufacturing and factory test have been performed over five years, and shipping and installation have been proceeded in parallel step by step as presented in the last FEC [A]. The on-site assembling technique for such complicated 1MV PS components is one of challenges not only for the ITER NB but also typical electrical components. As recent progress in the last two years, completion of assembly and also high-voltage insulation test of DC 1 MV power supply components are reported.

The following results have been obtained in consequence of patho-morphological examination regarding the supplemental groove.1. Light microscopic observation of cross-sectioned supplemental grooves revealed that most of them were shallow in the form of plate or bowl. Some of the supplemental grooves had contents not described in the past and the structure of the contents was not clear under a light microscope. The contents were found in 22% of the supplemental grooves examined.2. The contents in supplemental grooves which were confirmed under a light microscope were found to consist of enamel itself when examined by means of an electron microscope. Microhardness measurements of this enamel showed less than one third the values of normal enamel. By means of microradiography, it was established that radiolucency of this enamel was, for the most part, much higher than normal enamel.3. It was ascertained that enamel with low hardness and high radiolucency constitutes the contents of supplemental grooves. Judging from its tissue properties, the contents were believed to be susceptible to attack by caries. This view was supported by the results of an investigation of caries sites in supplemental grooves., L’examen morpho-pathologique de sillons surnuméraires a donné les résultats suivants:1. En coupes transversales observées en microscopie classique, les sillons surnuméraires apparaissent peu profonds, en forme d’assiette ou de coupe. Dans certains, on trouve un contenu, non encore décrit dans la littérature et dont la structure n’apparaît pas nettement en microscopie classique. On trouve ce contenu dans 22% des sillons surnuméraires étudiés.2. Etudié en microscopie électronique à transmission, le contenu des sillons surnuméraires apparaît fait d’émail. Les mesures de dureté indiquent pour cet émail des valeurs inférieures d’un tiers à celles de l’émail normal. La microradiographie montre que cet émail est, en général, beaucoup moins radiodense que l’émail normal.3. Etant donné que le contenu des sillons surnuméraires s’est révélé être un émail de faible dureté et de faible radiodensité, on peut considérer que, par ses propriétés tissulaires, cet émail est sensible à l’attaque carieuse. Cette hypothèse est corroborée par les résultats de l’étude des sites carieux dans les sillons surnuméraires.

The ITER Heating Neutral Beam (HNB) injectors, one of the tools necessary both to achieve burning conditions and to control plasma instabilities, are characterized by such demanding parameters as to require the construction of a Neutral Beam Test Facility (NBTF) dedicated to their development and optimization. The NBTF was realized in Padua (Italy), with the direct contribution of the Italian government, through the Consorzio RFX as the host entity, IO, the in kind contributions of three Domestic Agencies (F4E, JADA, INDA) and the technical and scientific support of various European laboratories and universities. The NBTF hosts two experiments: SPIDER and MITICA. The former is devoted to the optimization of the HNB and DNB ion sources and to the achievement of the required source performances. MITICA is the full size prototype of the ITER HNB, with an ion source identical to the one used in SPIDER. This paper gives an overview of the progress of the NBTF realization with particular emphasis on issues discovered during this phase of activities and to the adopted solutions in order to minimize the impact on the schedule while maintaining the goals of the facilities. The realization of MITICA is well advanced; it is expected to enter into operation in 2023 due to the long procurement times of the in-vessel mechanical components. The power supply designed to operate at 1MV are in an advanced phase of realization; all the high voltage components have been installed and the complex insulation test phase has begun in 2018. The construction and installation of SPIDER plant systems was successfully completed with their integration into the facility. The mechanical components of the ion source were installed inside the vessel and connected to the plants. The integrated commissioning with control (CODAS), protection and safety systems ended positively and the first experimental phase began. Finally, the first results of the SPIDER experimentation and of the 1MV insulation tests on the MITICA high voltage components are presented.

The negative ion accelerators for the ITER neutral beam system has been designed by using the conventional beam codes for the positive ion accelerators because mechanism of meniscus formation of negative ions has not been clarified well. In this way, the operational window of the negative ion accelerators can be simply predicted, but the grid heat loading by peripheral beam (beam halo) could not be simulated. To understand the applicable range of the conventional codes to the negative ion accelerators, and then to understand the negative ion meniscus consequently, the benchmark tests between the conventional codes (BEAMORBT (BO) [1] and SLACCAD (SC)[2]) and the experiments have been performed under a joint experiment by RFX and QST on the Negative Ion Test Stand in Naka. Figure 1 shows one numerical results as an example with the grid configuration. The extraction voltage (Vext) is applied between the plasma grid (PG) and the extraction grid (EXG). The acceleration voltage (Vacc) is applied between EXG and the grounded grid (GG). Figure 2 shows the beam divergence angle as a function of Vext at Vacc of 20 kV. Vext with the minimum divergence angle are shown around 4.0 kV both in the numerical codes and the experimental result. The operational window can be predicted in the numerical codes. However, the absolute values of the divergence angle of the experiment was larger than those of the numerical result. One of reasons will be that the numerical code cannot represent the beam halo. Even in the numerical results, the divergence angle in the BO is slightly lower than that of the SC. To understand the meniscus effect to the beam divergence, the relationship between meniscus depth ?zmenis and beam divergence in the numerical results was compared as shown in Figure 3. The details are reported in the paper.

Chemically induced rearrangements of amphifunctional molecules have been demonstrated using strong nonuniform electric fields (10(8)-10(10) V m(-1)) induced in the vicinity of nanoscale asperities. Electrostatic interactions utilizing these rearrangements of alkylthiolates assembled on Au(111) result in the nanopatterning of raised nanostructure (1.5-9 nm high, 15-100 nm wide) arrays on a second time scale by manipulating an atomic force microscope (AFM) tip above the monolayer. It is suspected that, as a result of the oxidative cleavage initiated by a weak bias of the tip, the S end of the alkylthiolate chain carrying a sulfenium cation is attracted to the (lifting) tip, forming bi- and higher-layer structures in the vicinity of the tip apex. Stabilization of the multiple-layered structures is accomplished via mutual attraction and entanglement of hydrocarbon chains. The rearrangements suggest a novel and general approach for nanoscale architecture in self-assembled systems.

A high-beta, supersonic plasma flow plays a crucial role in MHD phenomena in space and fusion plasmas. There are a few experimental researches on production and control of a fast flowing plasma in spite of a growing significance in the magnetized-plasma flow dynamics. A magneto-plasma-dynamic arcjet (MPDA) is one of promising devices to produce a supersonic plasma flow and has been utilized as an electric propulsion device with a higher specific impulse and a relatively larger thrust. We have improved the performance of an MPDA to produce a quasi-steady plasma flow with a transonic and supersonic Mach number in a highly-ionized state. There are two methods in order to control an ion-acoustic Mach number of the plasma flow exhausted from an MPDA: one is to use a magnetic Laval nozzle to convert a thermal energy to a flow energy and the other is a combined system of an ion heating and a divergent magnetic nozzle. The former is an analogous method to a compressible air flow and the latter is the method proposed in an advanced thruster for a manned interplanetary space mission. We have clarified the plasma flow characteristics in various shapes of a magnetic field configuration. It was demonstrated that the Mach number of the plasma flow could increase up to almost 3 in a divergent magnetic nozzle field. This paper reports recent results on the flow field improvements: one is on a magnetic-Laval-nozzle effects observed at the muzzle region of the MPDA, and the other is on ICRF (ion-cyclotron-range of frequency) heating of a supersonic plasma by use of a helical antenna., 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France)

We investigated experimentally characteristics of an atmospheric pressure glow discharge(APGD) produced by cathode-pin and anode-plate electrodes with a flowing gas between the electrodes. An APGD is sustained by DC voltage applied between these electrodes with main and auxiliary gas flow. The nozzle position of the auxiliary gas flow is varied between the two electrodes. It is found at first time that the glow discharge current increased significantly when the auxiliary nozzle is set near the anode plate. This finding is very important to clarify the mechanism of a flow-stabilized APGD.

A high-beta, supersonic plasma flow plays a crucial role in MHD phenomena in space and fusion plasmas. There are a few experimental researches on production and control of a fast flowing plasma in spite of a growing significance in the magnetized-plasma flow dynamics. A magneto-plasma-dynamic arcjet (MPDA) is one of promising devices to produce a supersonic plasma flow and has been utilized as an electric propulsion device with a higher specific impulse and a relatively larger thrust. We have improved the performance of an MPDA to produce a quasi-steady plasma flow with a transonic and supersonic Mach number in a highly-ionized state. There are two methods in order to control an ion-acoustic Mach number of the plasma flow exhausted from an MPDA: one is to use a magnetic Laval nozzle to convert a thermal energy to a flow energy and the other is a combined system of an ion heating and a divergent magnetic nozzle. The former is an analogous method to a compressible air flow and the latter is the method proposed in an advanced thruster for a manned interplanetary space mission. We have clarified the plasma flow characteristics in various shapes of a magnetic field configuration. It was demonstrated that the Mach number of the plasma flow could increase up to almost 3 in a divergent magnetic nozzle field. This paper reports recent results on the flow field improvements: one is on a magnetic-Laval-nozzle effects observed at the muzzle region of the MPDA, and the other is on ICRF (ion-cyclotron-range of frequency) heating of a supersonic plasma by use of a helical antenna.

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.

ITER envisages the use of two heating neutral beam injectors plus an optional one as part of the auxiliary heating and current drive system, to reach the desired performances during its various phases of operation. The 16.5 MW expected neutral beam power per injector is several notches higher than worldwide existing facilities.In order to enable such development, a Neutral Beam Test Facility (NBTF) was established at Consorzio RFX, exploiting the synergy of two test beds, called SPIDER and MITICA. SPIDER is dedicated developing and char-acterizing large efficient negative ion sources at relevant parameters in ITER-like conditions: source and accel-erator located in the same vacuum where the beam propagates, immunity to electromagnetic interferences of multiple radio-frequency (RF) antennas, avoidance of RF-induced discharges on the outside of the source. Three years of experiments on SPIDER have addressed to the necessary design modifications to enable full perfor-mances. The source is presently under a long shut-down phase to incorporate learnings from the experimental campaign, in particular events/issues occurred during operation, which led to the identification of improvement opportunities/necessities (e.g. RF discharges, local burns, water leaks, other damages, configuration/design upgrades to maximize chances/margin to quest target parameters).Parallelly, developments on MITICA, the full-scale prototype of the ITER Neutral Beam Injector (NBI) featuring a 1 MV accelerator and ion neutralization, are underway including manufacturing of the beam source, accel-erator and the beam line components, while power supplies and auxiliary plants, already installed, are under final testing and commissioning.Integration, commissioning and tests of the 1 MV power supplies are essential for this first-of-kind system, unparalleled both in research and industry field. 1.2 MV dc insulating tests of high voltage components were successfully completed. The integrated test to confirm 1 MV output by combining invertor systems, DC gener-ators and transmission lines extracted errors/accidents in some components. To realize a concrete system for ITER, said events have been addressed and solutions for the repair and the improvement of the system were developed.Hence, NBTF is emerging as a necessary facility, due to the large gap with existing injectors, effectively dedicated to identify issues and find solutions to enable successful ITER NBI operations in a time bound fashion. The lessons learned during the implementation on NBTF and future perspectives are here discussed.

To reach fusion conditions and control the plasma configuration in ITER, the next step in tokamak fusion research, two neutral beam injectors (NBIs) will supply 16.5 MW each, by neutralizing accelerated negative hydrogen or deuterium ions. The requirements of ITER NBIs (40A/1 MeV D- ions for ≤1 h, 46A/870 keV H- ions for ≤1000 s) have never been simultaneously attained. So in the Neutral Beam Test Facility (NBTF, Consorzio RFX, Italy) the operation of the full-scale ITER NBI prototype (MITICA) will be tested and optimised up to full performances, focussing on accelerator (including voltage holding), beam optics, neutralisation, residual ion removal. The NBTF includes also the full-scale prototype of the ITER NBI source with 100 keV particle energy (SPIDER), for early investigation of: negative ion production and extraction, source uniformity, negative ion current density and beam optics. This paper will describe the main results of the first two years of SPIDER operation, devoted to characterizing plasma and beam parameters, including investigation of RF-plasma coupling efficiency and magnetic filter field effectiveness in reducing co-extracted electrons. SPIDER is progressing towards the first caesium injection, which aims at increasing the negative ion density. A major shutdown, planned for 2021, to solve the issues identified during the operation and to carry out programmed modifications, will be outlined. The installation of each MITICA power supply and auxiliary system is completed; in-vessel mechanical components are under procurement by Fusion for Energy (F4E). Integration, commissioning and test of the power supplies, procured by F4E and QST, as the Japanese Domestic Agency (JADA), will be presented. In particular, 1.0MV insulating tests were carried out step-by-step and successfully completed. In 2020 integrated tests of the power supplies on the accelerator dummy load started, including the assessment of their resilience to accelerator grid breakdowns using a short-circuit device located in vacuum. The aggressive programme, to validate the NBI design at NBTF and to meet ITER schedule (requiring NBIs in operation in 2032), will be outlined. Unfortunately, in 2020 the coronavirus disease infection affected the NBTF activities. A solution to proceed with integrated power tests despite the coronavirus is presented.

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

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.

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.