The ITER project requires additional heating provided by two neutral beam injectors using accelerated negative deuterium ions. As the beam requirements (1MeV particle energy, 40A accelerated current for one hour) have never been experimentally met, a test facility is under construction at Consorzio RFX, which hosts two experiments: SPIDER, full-size 100 kV ion source prototype, and MITICA, 1 MeV full-size ITER injector prototype. Since diagnostics in ITER injectors will be mainly limited to thermocouples, due to neutron and gamma radiation and to limited access, it is crucial to get from more accessible experiments a wider knowledge of the key parameters of source plasma and beam, obtained using several complementary diagnostics assisted by modelling. The set of diagnostics in SPIDER and MITICA has been selected and designed with this goal. The ion source parameters are measured by the combination of optical emission spectroscopy, assisted by collisional radiative model, thermocouples for heat load and electrostatic probes for electron density and temperature, together with cavity ring down spectroscopy for HÂ? density and laser absorption spectroscopy for cesium density. These measurements over multiple lines-of-sight will provide the information on the spatial distribution of the parameters over the source extension. The beam profile uniformity and its divergence are studied with beam emission spectroscopy, complemented by visible tomography and neutron imaging, which are novel techniques, while an instrumented calorimeter based on custom mono-directional carbon fiber composite tiles observed by infrared cameras will measure the beam footprint on short pulses with highest spatial resolution. All heated components will be monitored with thermocouples: as these will likely be the only measurements available in ITER injectors, their capabilities will be investigated by comparison with other techniques. SPIDER and MITICA diagnostics will be described with a focus on their rationale, key solutions and most original and effective implementations.
A suite of diagnostics to validate and optimize the prototype ITER neutral beam injector
Pasqualotto Roberto
2017
Abstract
The ITER project requires additional heating provided by two neutral beam injectors using accelerated negative deuterium ions. As the beam requirements (1MeV particle energy, 40A accelerated current for one hour) have never been experimentally met, a test facility is under construction at Consorzio RFX, which hosts two experiments: SPIDER, full-size 100 kV ion source prototype, and MITICA, 1 MeV full-size ITER injector prototype. Since diagnostics in ITER injectors will be mainly limited to thermocouples, due to neutron and gamma radiation and to limited access, it is crucial to get from more accessible experiments a wider knowledge of the key parameters of source plasma and beam, obtained using several complementary diagnostics assisted by modelling. The set of diagnostics in SPIDER and MITICA has been selected and designed with this goal. The ion source parameters are measured by the combination of optical emission spectroscopy, assisted by collisional radiative model, thermocouples for heat load and electrostatic probes for electron density and temperature, together with cavity ring down spectroscopy for HÂ? density and laser absorption spectroscopy for cesium density. These measurements over multiple lines-of-sight will provide the information on the spatial distribution of the parameters over the source extension. The beam profile uniformity and its divergence are studied with beam emission spectroscopy, complemented by visible tomography and neutron imaging, which are novel techniques, while an instrumented calorimeter based on custom mono-directional carbon fiber composite tiles observed by infrared cameras will measure the beam footprint on short pulses with highest spatial resolution. All heated components will be monitored with thermocouples: as these will likely be the only measurements available in ITER injectors, their capabilities will be investigated by comparison with other techniques. SPIDER and MITICA diagnostics will be described with a focus on their rationale, key solutions and most original and effective implementations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
