The ITER project requires additional heating via injection of neutral beams, which will be provided by two injectors. Such high-power beams result from the neutralization of accelerated negative ions. To study and optimise negative ion production, the SPIDER test facility is under construction in Padova, with the aim of testing beam characteristics and to verify the source proper operation. The SPIDER beam has energy of 100 keV and current of 50 A. The instrumented calorimeter STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) has been developed for diagnostic purposes to characterise the SPIDER negative ion beam during short operation (several seconds). The most important measurements performed by STRIKE are: beam uniformity, stripping losses and beam divergence. They are obtained using different diagnostics: thermal cameras, current sensors, thermocouples and electrostatic sensors. STRIKE is subdivided into 16 tiles (one for each beamlet group) to reproduce the SPIDER beam source geometry and it is directly exposed to the beam. In particular, the beam uniformity evaluated with thermal measurements is compared to the uniformity evaluated with current measurements. This work presents the investigation of the influence on the response of STRIKE diagnostics due to secondary electrons and off-normal conditions. A set of electrostatic simulations will be shown, to assess the effect of the biasing of the calorimeter on the secondary electron trajectories and to study their effect on the current measurements. Moreover, thermal simulations concerning normal and off-normal beam conditions have been carried out and in particular the discretisation introduced by thermal cameras on thermal images will be discussed with regard to the reconstruction of the input data. This work was set up in collaboration and financial support of F4E.
Thermal and Electrostatic Simulations of STRIKE to Reconstruct the Features of the SPIDER Beam
Serianni G;Dalla Palma M;Pasqualotto R;Pomaro N;
2011
Abstract
The ITER project requires additional heating via injection of neutral beams, which will be provided by two injectors. Such high-power beams result from the neutralization of accelerated negative ions. To study and optimise negative ion production, the SPIDER test facility is under construction in Padova, with the aim of testing beam characteristics and to verify the source proper operation. The SPIDER beam has energy of 100 keV and current of 50 A. The instrumented calorimeter STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) has been developed for diagnostic purposes to characterise the SPIDER negative ion beam during short operation (several seconds). The most important measurements performed by STRIKE are: beam uniformity, stripping losses and beam divergence. They are obtained using different diagnostics: thermal cameras, current sensors, thermocouples and electrostatic sensors. STRIKE is subdivided into 16 tiles (one for each beamlet group) to reproduce the SPIDER beam source geometry and it is directly exposed to the beam. In particular, the beam uniformity evaluated with thermal measurements is compared to the uniformity evaluated with current measurements. This work presents the investigation of the influence on the response of STRIKE diagnostics due to secondary electrons and off-normal conditions. A set of electrostatic simulations will be shown, to assess the effect of the biasing of the calorimeter on the secondary electron trajectories and to study their effect on the current measurements. Moreover, thermal simulations concerning normal and off-normal beam conditions have been carried out and in particular the discretisation introduced by thermal cameras on thermal images will be discussed with regard to the reconstruction of the input data. This work was set up in collaboration and financial support of F4E.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
