Design development of SPIDER and MITICA experiments, prototypes of the ITER neutral beam injectors

Operation of the ITER project, the largest thermonuclear fusion experiment, will require a mix of heating systems with the aim of supplying the plasma with additional power so that ITER can demonstrate the sustainability of the fusion reactions with a Q factor ranging from 5 to 10 in a stationary condition. Among the heating systems, neutral beams, obtained from accelerated negative ions, will be injected. Two neutral beam injectors (NBIs) are planned, delivering a total of 33 MW in a stationary condition up to one hour. Each injector is required to accelerate at 1 MV a 40 A deuterium ion current at the exit of the last accelerating grid. Such requirements have never been achieved simultaneously. To minimise risks and time to provide ITER with reliable NBIs, the ITER Organization and the ITER parties involved in the development of the NBIs (EU, Japan and India) have strongly endorsed the experimental demonstration and optimisation of critical components and systems. Within this framework, a dedicated test facility named PRIMA (Padova Research on ITER Megavolt Accelerator) is being built at Consorzio RFX in Padua, Italy, with adaptation of the 400 kV power substation. The PRIMA facility will host two experimental test stands. The SPIDER device (Source for the Production of Ions of Deuterium Extracted from Rf plasma) is a full-size negative ion source aiming at demonstrating the capability to create and extract a negative ion current up to approximately 50/60 A on a wide surface (more than 1 m2) with a uniformity within the 10%. MITICA (Megavolt ITer Injector and Concept Advancement) will be the prototype of the full ITER injector and will test all components and overall design at the required operational specifications including the capability of 1 MV voltage holding at low pressure. The experimental effort is supported by a complete set of diagnostics, specific for the test facility and unavailable on the ITER NBIs, and is supplemented by numerical simulation activities devoted to the optimisation of the accelerator optics, taking into account various operational scenarios, and to the computation of the particle trajectories, allowing the estimation of heat loads and currents on the various surfaces. All the experimental plants and components of SPIDER are ready for the procurement phase. Most of the design for the procurement of MITICA plants and components are well developed and close to being ready for starting of procurement. The design will be completed within the next two years. A number of laboratories are cooperating with Consorzio RFX to the success of this enterprise: CCFE- Culham IPP-Garching, KIT- Karlsruhe, and other European research institutions, together with the Japanese and the Indian Domestic Agencies. In this contribution the most recent developments of the test stands will be described as well as some design solutions of the main components and systems. Finally the planning of the overall facility will be presented. This work was set up in collaboration and financial support of F4E.