First Negative Ion Beam Profile Measurements by the Diagnostic Calorimeter STRIKE

The ITER project requires additional heating provided by two injectors of neutral beams resulting from the neutralization of acceleratednegative ions. To study and optimise negative ion production, the SPIDER test facility (particle energy 100keV; beam current 50A) is under construction in Padova, with the aim of testing beam characteristics and to verify the source proper operation.The SPIDER beam will be characterised by the instrumented calorimeter STRIKE, whose main components are one-directional carbon fibre carbon composite tiles. Some prototype tiles have been employed as a small-scale version (mini-STRIKE) of the entire system to investigate the features of the beam of the device BATMAN at IPP-Garching. The present contribution gives a description of the mini-STRIKE, which is made of two tiles arranged in the vertical direction and exposed perpendicularly to the beamin order to characterise the vertical beam profile. The measurement position is about 1m from the accelerator, where the beamlets composing the beam are largely overlapping. To provide local measurements of the beam features, in front of the tiles an actively cooled copper mask was located provided with some apertures. Calorimetry of the mask was performed, whereas the temperature map on the rear side of the tiles was measured by a thermal camera and compared to some local thermocouple measurements. Indicationson the beam are also provided by a thermocouple installed on the mask. The first results of the investigation of the BATMAN beam are described in various operating conditions. The data analysis is presented, including the dependence of the beam featureson plasma grid voltage, extraction voltage, radiofrequency power and filling pressure. This work was set up in collaboration and financial support of F4E.