Conceptual design of the beam source for the DEMO Neutral Beam Injectors

Abstract

DEMO (DEMOnstration Fusion Power Plant) is a proposed nuclear fusion power plant that is intended to follow the ITER experimental reactor. The main goal of DEMO will be to demonstrate the possibility to produce electric energy from the fusion reaction. The injection of high energy neutral beams is one of the main tools to heat the plasma up to fusion conditions. A conceptual design of the Neutral Beam Injector (NBI) for the DEMO fusion reactor, is currently being developed by Consorzio RFX in collaboration with other European research institutes. High efficiency and low recirculating power, which are fundamental requirements for the success of DEMO, have been taken into special consideration for the DEMO NBI. Moreover, particular attention has been paid to the issues related to reliability, availability, maintainability and inspectability. A conceptual design of the beam source for the DEMO NBI is here presented featuring 20 sub-sources (two adjacent columns of 10 sub-sources each), following a modular design concept, with each sub-source featuring its radio frequency driver, capable of increasing the reliability and availability of the DEMO NBI. Copper grids with increasing size of the apertures have been adopted in the accelerator, with three main layouts of the apertures (circular apertures, slotted apertures and frame-like apertures for each sub-source). This design, permitting to significantly decrease the stripping losses in the accelerator without spoiling the beam optics, has been investigated with a self-consistent model able to study at the same time the magnetic field, the electrostatic field and the trajectory of the negative ions. Moreover, the status on the R&D carried out in Europe on the ion sources is presented.

Towards powerful negative ion beams at the test facility ELISE for the ITER and DEMO NBI systems

“…Within EUROfusion, the 'European Consortium for the Development of Fusion Energy', a conceptual design of the beam source for DEMO is being developed [3,25] in the Work Package Heating and Current Drive (WPHCD) under the Power Plant Physics and Technology (PPPT) activities to fulfill in the best way the requirements on a neutral beam injector for the DEMO fusion reactor [26]. The requirements placed on the ion source are close to the ones for ITER.…”

“…The requirements placed on the ion source are close to the ones for ITER. In principle, the source module is based on the modular RF source concept whereas the route of having a large expansion chamber powered by multiple drivers is followed as well as the route of having individual smaller sources (up to 20) [25]. Besides the RAMI issues which need to be fulfilled by all components of the machine, specific R&D topics for the ion source have been identified as well [27] and are part of the WPHCD R&D work programme.…”

Research, Design, and Development Needed to Realise a Neutral Beam Injection System for a Fusion Reactor

“…In the following sections of this chapter, each of the aforementioned aspects is discussed more in detail and some suggestions given as to how problems arising from each aspect may be resolved and the parameters of the future injectors achieved. However it is important to understand that although various basic conceptual designs of an injector to be used on a fusion reactor have been considered [1][2][3], no concept has been chosen, and no serious engineering design of any concept has been carried out. Experience with the design of the neutral beam systems has shown that many aspects of the conceptual design are changed significantly during the engineering design phase.…”

Focus on sources of negatively charged ions

“…The future of fusion power requires a major step to establish the relevant economical and energetic efficiencies and feasibility. The conceptual design of the NBI of the DEMOnstration fusion power plant (DEMO) developed within the heating and current drive work package of EUROfusion [34] is introduced [35]. An example on the activities on smaller test facilities is given by McAdams et al (Culham Centre for Fusion Energy), in which an RF-driven volume source is used to systematically investigate the limits of neutralization and energy recovery.…”