916 research outputs found
Experimental Mapping and Benchmarking of Magnetic Field Codes on the LHD Ion Accelerator
No full textThe megavolt ITER injector concept advancement neutral injector test facility will be constituted by
a RF-driven negative ion source and by an electrostatic Accelerator, designed to produce a negative
Ion with a specific energy up to 1 MeV. The beam is then neutralized in order to obtain a focused
17 MW neutral beam. The magnetic configuration inside the accelerator is of crucial importance for
the achievement of a good beam efficiency, with the early deflection of the co-extracted and stripped
electrons, and also of the required beam optic quality, with the correction of undesired ion beamlet
deflections. Several alternative magnetic design concepts have been considered, comparing in detail
the magnetic and beam optics simulation results, evidencing the advantages and drawbacks of each
solution both from the physics and engineering point of view. © 2012 American Institute of Physics
A possible nature of breathing plasmas
No full textA model for "breathing" plasmas observed in the large helical device [Y. Takeiri , Plasma Phys. Controlled Fusion 42, 147 (2000)] is proposed. It takes into account the synergism of radiation losses from both low-Z (carbon, oxygen) and high-Z (iron) impurities in the plasma power balance. (C) 2000 American Institute of Physics. [S1070- 664X(00)01411-7]
Physics and engineering studies on the MITICA accelerator: comparison among possible design solutions
No full textConsorzio RFX in Padova is currently using a comprehensive set of numerical and analytical codes, for the physics and engineering design of the SPIDER (Source for Production of Ion of Deuterium Extracted from RF plasma) and MITICA (Megavolt ITER Injector Concept Advancement) experiments, planned to be built at Consorzio RFX.
This paper presents a set of studies on different possible geometries for the MITICA accelerator, with the objective to compare different design concepts and choose the most suitable one (or ones) to be further developed and possibly adopted in the experiment. Different design solutions have been discussed and compared, taking into account their advantages and drawbacks by both the physics and engineering points of view
Prospect Toward Steady-State Helical Fusion Reactor Based on Progress of LHD Project Entering the Deuterium Experiment Phase
No full text0000-0001-7569-6717Large Helical Device (LHD) is one of the world largest superconducting fusion experiment devices, having demonstrated its inherent advantage for steady-state operation since the start of experiments in 1998. LHD has also demonstrated reliable operation of the large-scale superconducting magnet system for almost two decades. Development of the challenging heating systems, such as negative-ion-based neutral beam injection (NBI), high-power and high-frequency electron cyclotron heating, and steady-state ion cyclotron heating, have led to wide-ranging physics and engineering achievements. LHD has progressed to the next stage, that is, the deuterium experiment starting in March 2017, which should further extend plasma parameters toward reactor-relevant regime. For establishing firm basis for designing steady-state helical fusion reactor, advanced physics research, such as on isotope effect, energetic particle confinement, and plasma-wall interaction, will be intensively performed in the deuterium experiments. In an engineering aspect, the upgrade of NBI system has been carried out in preparation to the deuterium experiment, and it should contribute to future NBI development for fusion reactors including ITER. For enhancement of the particle control, the closed divertor system has been installed with pumping capability. Diagnostics for neutron measurements are newly developed and installed for the deuterium experiment. Aligned with all the progress of LHD project in terms of engineering and physics aspects, the conceptual design activity of the LHD-type helical fusion reactor, FFHR-d1, has been programmatically conducted. In parallel to the design study, engineering research and development for the component development have been performed, including those based on employing challenging ideas such as high-temperature superconductor, liquid metal ergodic divertor, and molten-salt breeder blanket. The present status of LHD project entering the deuterium experiment phase is overviewed with putting emphasis on the engineering aspects, and then the engineering research and development activities toward steady-state helical fusion reactor are described.journal articl
Sensitivity Analysis of the Off-Normal Conditions of the SPIDER Accelerator
No full textIn the context of the development of the 1 MV neutral beam injector for the ITER tokamak [1], the study on beam formation and acceleration has considerable importance. This effort includes the ion source and accelerator SPIDER (Source for Production of Ions of Deuterium Extracted from an Rf plasma) ion source, planned to be built in Padova, and designed to extract and accelerate a 355 A/m2 current of H- (or 285 A/m2 D-) up to 100 kV [2][3]. Exhaustive simulations were already carried out during the accelerator optimization leading to the present design [4]. However, as it is expected that the accelerator shall operate also in case of pre-programmed or undesired off-normal conditions, the investigation of a large set of off-normal scenarios is necessary. These analyses will also be useful for the evaluation of the real performances of the machine, and should help in interpreting experimental results, or in identifying dangerous operating conditions.
The present contribution offers an overview of the results obtained during the investigation of these off-normal conditions, by means of different modeling tools and codes. The results, showed a good flexibility of the device in different operating conditions. Where the consequences of the abnormalities appeared to be problematic further analysis were addressed
Modeling activities on the negative-ion-based Neutral Beam Injectors of the Large Helical Device
No full textAt the National Institute for Fusion Science (NIFS) large-scaled negative ion sources
have been widely used for the Neutral Beam Injectors (NBIs) mounted on the Large Helical Device
(LHD), which is the world-largest superconducting helical system. These injectors have achieved
outstanding performances in terms of beam energy, negative-ion current and optics, and represent a
reference for the development of heating and current drive NBIs for ITER.
In the framework of the support activities for the ITER NBIs, the PRIMA test facility, which
includes a RF-drive ion source with 100 keV accelerator (SPIDER) and a complete 1 MeV Neutral
Beam system (MITICA) is under construction at Consorzio RFX in Padova.
An experimental validation of the codes has been undertaken in order to prove the accuracy of the
simulations and the soundness of the SPIDER and MITICA design. To this purpose, the whole set
of codes have been applied to the LHD NBIs in a joint activity between Consorzio RFX and NIFS,
with the goal of comparing and benchmarking the codes with the experimental data. A description
of these modeling activities and a discussion of the main results obtained are reported in this pape
Optics of the NIFS negative ion source test stand by infrared calorimetry and numerical modelling
No full textConfinement Improvement in High-ion Temperature Plasmas Heated with High-energy Negative-NBI in LHD
No full text"The increase in the ion temperature due to transport improvement has been observed in plasmas heated with high-energy negative-NBI, in which electrons are dominantly heated, in Large Helical Device (LHD). When the centrally focused ECRH is superposed on the NBI plasma, the ion temperature is observed to rise, accompanied by formation of the electron-ITB. This is ascribed to the ion transport improvement with the transition to the neoclassical electron root with a positive radial electric field. In high-Z plasmas, the ion temperature is increased with an increase in the ion heating power, and reaches 13.5keV. The central ion temperature increases with an increase in a gradient of the electron temperature in an outer plasma region of rho=0.8, suggesting the ion transport improvement in the outer plasma region induced by the neoclassical electron root. These results indicate the effectiveness of the electron-root scenario for obtaining high-ion temperature plasmas in helical systems."research repor
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