Status of the Negative Ion Based Heating and Diagnostic Neutral Beams for ITER

摘要

The current baseline of ITER foresees 2 Heating Neutral Beam (HNB's) systemsbased on negative ion technology, each accelerating to 1 MeV 40 A of 13- and capable ofdelivering 16.5 MW of D° to the ITER plasma, with a 3rd HNB injector foreseen as anupgrade option [1]. In addition a dedicated Diagnostic Neutral Beam (DNB) accelerating60 A of If to 100 keV will inject .--15 A equivalent of H° for charge exchange recombinationspectroscopy and other diagnostics. Recently the RF driven negative ion source developed byIPP Garching has replaced the filamented ion source as the reference ITER design. The RFsource developed at IPP, which is approximately a quarter scale of the source needed forITER, is expected to have reduced caesium consumption compared to the filamented arcdriven ion source. The RF driven source has demonstrated adequate accelerated 13- and 1-1-current densities as well as long-pulse operation [2, 3]. It is foreseen that the HNB's and theDNB will use the same negative ion source. Experiments with a half ITER-size ion source areon-going at IPP and the operation of a full-scale ion source will be demonstrated, at fullpower and pulse length, in the dedicated Ion Source Test Bed (ISTF), which will be part ofthe Neutral Beam Test Facility (NBTF), in Padua, Italy. This facility will carry out thenecessary R&D for the HNB's for ITER and demonstrate operation of the full-scale HNBbeamline. An overview of the current status of the neutral beam (NB) systems and the chosenconfiguration will be given and the ongoing integration effort into the ITER plant will behighlighted. It will be demonstrated how installation and maintenance logistics haveinfluenced the design, notably the top access scheme facilitating access for maintenance andinstallation. The impact of the ITER Design Review and recent design change requests(DCRs) will be briefly discussed, including start-up and commissioning issues. The lowcurrent hydrogen phase now envisaged for start-up imposed specific requirements foroperating the HNB's at full beam power. It has been decided to address the shinethrough issueby installing wall armour protection, which increases the operational space in all scenarios.Other NB related issues identified by the Design Review process will be discussed and thepossible changes to the ITER baseline indicated.