The RF negative ion source NIO1[1], built at Consorzio RFX in Padua (Italy), is aimed to investigate general issues on ion source physics in view of the full-size ITER injector MITICA [2-3] as well as DEMO relevant solutions, like energy recovery and alternative neutralization systems, crucial for neutral beam injectors in future fusion experiments. NIO1 has been designed to produce 9 H- beamlets (in a 3x3 pattern) of 15mA each and 60keV, using a three electrodes system downstream the plasma source. At the moment the source is at its early operational stage [4] and only operation at low power and low beam energy is possible. In particular NIO1 presents a too strong set of SmCo co-extraction electron suppression magnets (CESM) in the extraction grid (EG) that will be replaced by a weaker set of Ferrite magnets. A completely new set of magnets will be also designed and mounted on the new EG[5] that will be installed next year, replacing the present one. In this paper, the finite element code OPERA 3D is used to investigate the effects of the three sets of magnets on beamlet optics. A comparison of numerical results with measurements will be provided where possible. Both operations in oxygen and hydrogen gases will be compared in the investigation.
Finite elements numerical codes as primary tool to improve beam optics and support measurements in NIO1
Serianni G
2016
Abstract
The RF negative ion source NIO1[1], built at Consorzio RFX in Padua (Italy), is aimed to investigate general issues on ion source physics in view of the full-size ITER injector MITICA [2-3] as well as DEMO relevant solutions, like energy recovery and alternative neutralization systems, crucial for neutral beam injectors in future fusion experiments. NIO1 has been designed to produce 9 H- beamlets (in a 3x3 pattern) of 15mA each and 60keV, using a three electrodes system downstream the plasma source. At the moment the source is at its early operational stage [4] and only operation at low power and low beam energy is possible. In particular NIO1 presents a too strong set of SmCo co-extraction electron suppression magnets (CESM) in the extraction grid (EG) that will be replaced by a weaker set of Ferrite magnets. A completely new set of magnets will be also designed and mounted on the new EG[5] that will be installed next year, replacing the present one. In this paper, the finite element code OPERA 3D is used to investigate the effects of the three sets of magnets on beamlet optics. A comparison of numerical results with measurements will be provided where possible. Both operations in oxygen and hydrogen gases will be compared in the investigation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
