To reach fusion conditions and to control the plasma configuration in ITER, the next step in thermonuclear fusion research, two heating and current-drive neutral beam injectors (NBIs) will supply 17MW each, by accelerating negative hydrogen or deuterium ions to 1MeV. The requirements of ITER NBIs (40A negative H or D ions for 1 hour) have never been simultaneously attained. So in the dedicated Neutral Beam Test Facility (NBTF) at Consorzio RFX (Italy) the performances of the ITER NBI (divergence <7mrad, aiming <2mrad) will be studied and optimised. The NBTF includes two experiments: MITICA, full-scale ITER NBI prototype, and SPIDER, full-scale prototype of the ITER NBI source with 100keV particle energy. SPIDER aim is to investigate source uniformity (over a 1m×2m area), negative ion current density and beam optics; MITICA will address the issues related with the accelerator, including high voltage holding in vacuum. The present contribution will briefly outline the activities and the experiments carried out in the SPIDER beam source during its first year of operation with volume generation of negative ions. In order to extend the source pressure range and to provide a thorough investigation of the properties of the early SPIDER beams, a mask was installed in the accelerator, leaving only isolated beamlets (for a total number of ~100 beamlets out of 1280). The investigation of the efficiency of RF coupling to the plasma in different configurations of the RF circuits, is presented. During the first extraction of negative particles from the source, the features of the co-extracted electrons were studied and correlated with the plasma parameters. Particularly, the magnetic filter field effectiveness in reducing the co-extracted electron current was verified; correspondingly, the decrease of the plasma emissivity was studied as well as the influence on the negative ion current. Finally the first characterisation of the SPIDER beam, in terms of beamlet divergence and deflection, is proposed and compared with numerical models while varying the source parameters; the negative ion beam exhibits values of current density and optics similar to those expected in volume operation. As for MITICA, installation of the plants is well advanced. High voltage tests of the accelerator power supplies up to 1.2MV started in 2018, by subsequently adding the various components provided by different domestic agencies; these tests should be completed in autumn 2019. The integrated tests of the power supply system, at full power on dummy load, are planned for the first half of 2020. Afterwards, before installing the beam source and the beam line components, the power supplies and the vessel, together with an electrostatic mock-up, will be employed to gain experience on high voltage holding in vacuum, which is one of the main issues to be addressed in MITICA.
First operation in SPIDER and the path to complete MITICA
Serianni G;Toigo V;
2019
Abstract
To reach fusion conditions and to control the plasma configuration in ITER, the next step in thermonuclear fusion research, two heating and current-drive neutral beam injectors (NBIs) will supply 17MW each, by accelerating negative hydrogen or deuterium ions to 1MeV. The requirements of ITER NBIs (40A negative H or D ions for 1 hour) have never been simultaneously attained. So in the dedicated Neutral Beam Test Facility (NBTF) at Consorzio RFX (Italy) the performances of the ITER NBI (divergence <7mrad, aiming <2mrad) will be studied and optimised. The NBTF includes two experiments: MITICA, full-scale ITER NBI prototype, and SPIDER, full-scale prototype of the ITER NBI source with 100keV particle energy. SPIDER aim is to investigate source uniformity (over a 1m×2m area), negative ion current density and beam optics; MITICA will address the issues related with the accelerator, including high voltage holding in vacuum. The present contribution will briefly outline the activities and the experiments carried out in the SPIDER beam source during its first year of operation with volume generation of negative ions. In order to extend the source pressure range and to provide a thorough investigation of the properties of the early SPIDER beams, a mask was installed in the accelerator, leaving only isolated beamlets (for a total number of ~100 beamlets out of 1280). The investigation of the efficiency of RF coupling to the plasma in different configurations of the RF circuits, is presented. During the first extraction of negative particles from the source, the features of the co-extracted electrons were studied and correlated with the plasma parameters. Particularly, the magnetic filter field effectiveness in reducing the co-extracted electron current was verified; correspondingly, the decrease of the plasma emissivity was studied as well as the influence on the negative ion current. Finally the first characterisation of the SPIDER beam, in terms of beamlet divergence and deflection, is proposed and compared with numerical models while varying the source parameters; the negative ion beam exhibits values of current density and optics similar to those expected in volume operation. As for MITICA, installation of the plants is well advanced. High voltage tests of the accelerator power supplies up to 1.2MV started in 2018, by subsequently adding the various components provided by different domestic agencies; these tests should be completed in autumn 2019. The integrated tests of the power supply system, at full power on dummy load, are planned for the first half of 2020. Afterwards, before installing the beam source and the beam line components, the power supplies and the vessel, together with an electrostatic mock-up, will be employed to gain experience on high voltage holding in vacuum, which is one of the main issues to be addressed in MITICA.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
