Overview on electrical issues faced during the SPIDER experimental campaigns

SPIDER is the full-scale prototype of the ion source of the ITER Heating Neutral Beam Injector, where negative ions of Hydrogen or Deuterium are produced by a RF generated plasma and accelerated with a set of grids up to ~100 keV. The Power Supply System is composed of high voltage dc power supplies capable of handling frequent grid breakdowns, high current dc generators for the magnetic filter field and RF generators for the plasma generation. During the first 3 years of SPIDER operation different electrical issues were discovered, understood and addressed thanks to deep analyses of the experimental results supported by modelling activities. The paper gives an overview on the observed phenomena and relevant analyses to understand them, on the effectiveness of the short-term modifications provided to SPIDER to face the encountered issues and on the design principle of long-term solutions to be introduced during the currently ongoing long shutdown.Comment: 8 pages, 12 figures. Presented at SOFT 202

Experimental Validation of the 3-D Molecular Flow Code AVOCADO

In the framework of the activities for Padova Research on ITER Megavolt Accelerator (PRIMA), the knowledge of the background gas density distribution in the neutral beam components is a very important aspect, which plays a role in their performances. The adaptable rarefied instrumented atmosphere for neutral injection applications (ARIANNA) experiment has been set up as a complementary service for the modeling activity of the ion beam source for the neutral beam injector. It reproduces the layout of a typical beam source, in which the ion source and grids are integrated. ARIANNA supported the development and validation of the AVOCADO code, which has been created to simulate molecular flow and density gas distribution in 3-D geometry by view factor technique. The validation activity was aimed at demonstrating the capability to correlate the mass flow to the pressure difference, and the correctness of the pressure distribution in the volume. This paper presents the ARIANNA experimental setup and the subsystems involved in the vacuum production and measurement, and compares AVOCADO results obtained, while modeling the ARIANNA device with the experimental data

1 MV power supplies integration issues in MITICA experiment, the ITER Heating Neutral Beam Injector prototype

MITICA, the full scale prototype of ITER Heating Neutral Beam Injector required to heat up ITER plasma with 16.5 MW injected power, is under realization at the Neutral Beam Test Facility (NBTF) in Padova (Italy) with the contributions of JApanese and EUropean Domestic Agencies (JADA and EUDA, respectively). The objective of MITICA is to produce a 16.5 MW neutral beam, obtained by accelerating negative Deuterium ions up to 1 MeV for a total ion current of 40 A and then neutralized.MITICA Power Supply (PS), installed from 2016 to 2019, includes several non-standard equipment, with ratings well beyond the present industrial standard for insulation voltage level (-1 MVdc) and dimensions:- the Acceleration Grid Power Supply (AGPS), composed of five DC Generators (DCG) rated for -200kVdc each, connected in series to produce -1 MVdc acceleration voltage;- the Ion Source and Extraction Power Supply system (ISEPS);- the large air insulated Faraday cage (High Voltage Deck1, HVD1) hosting ISEPS and connected to the Transmission Line (TL) through an air-to-SF6 Bushing (High Voltage Bushing Assembly, HVBA);- a 100 m gas (SF6) insulated TL, connecting AGPS and ISEPS to the beam source installed inside the vacuum vessel through- the SF6-to-vacuum HV Bushing (HVB).The definition of the interfaces both between components supplied by the different DA’s and towards the buildings has been studied and finalized as far as possible during the design phase. Nevertheless, during the installation phase some issues emerged and had to be solved, minimizing modifications of the components already manufactured. The paper deals with the experience gained during the installation activities, focusing on solutions to interface the aforementioned equipment with NBTF buildings according to the stringent dimensional requirements and to the electrical insulation issues of the TL from the buildings. In particular, the solutions adopted to realize the electrical and mechanical interfaces between the TL and the HVBA are described in detail

Detailed design of the RFX-mod2 machine load assembly

Contén: 1. Fundamentos -- 2. Posibilidad y efectividad -- 3. La fábrica del mundo real -- 4. Filosofía de la naturaleza. Teoría especial de las categorías : Categorías dimensionales, categorías cosmológicas -- 5. Filosofía de la naturaleza. Teoría especial de las categorías : Categorías organológicas. El pensar teleológic

Design concepts of machine upgrades for the RFX-mod experiment

After 10 years of operation since its major modification, an upgrade of the RFX-mod experiment is presently under design. The scientific objective is the improvement of 3D physics studies through a more robust transition to higher confinement regimes in both Reversed Field Pinch (RFP) and Tokamak configuration obtained thanks to an advanced system for the active control of MHD instabilities. The main design driver requirements for this machine upgrade are the removal of the present resistive vacuum vessel and the enhancement of the 'shell-plasma proximity', to reduce the deformation of the last close magnetic surface and to improve the self-organized helical plasma regimes. The fulfillment of these requirements implies a major change of the internal components of the machine such as the replacement of the whole first wall, the change of the support system of the stabilizing shell and the modification of the present toroidal support structure to provide the function of vacuum barrier. In combination, other components of the machine will be upgraded, such as magnets and power supply, diagnostic systems and a NBI will be integrated. The paper presents an overview of the engineering design of the new components and highlights the critical aspects of the new torus assembly