Negative Ion Beam Characterisation in BATMAN by mini - STRIKE: Improved Design and New Measurements

The ITER project requires additional heating provided by two injectors of neutral beams resulting from the neutralisation of accelerated negative ions. To study and optimise negative ion production, t he 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 calorimete r STRIKE, whose main components are one - directional carbon fibre carbon composite tiles. Some prototype tiles have been employed in 2012 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. As the BATMAN beamlets are superposed at the measurement position, about 1m from the grounded grid, an actively cooled copper mask is located in front of the tiles; holes in the mask create an artificial beamlet structure. Recently the mini - STRIKE has been updated, taking into account the results obtained in the first campaign. In particular the spatial resolution of the system has been improved by increasing the number of the copper mask holes. Moreover a custom measurement system h as been realized for the thermocouple signals and employed in BATMAN in view of its use in SPIDER. The present contribution gives a description of the new design of the system as well as of the thermocouple measurements system and its field test. A new ser ies of measurements has been carried out in BATMAN. The results of the BATMAN beam characterisation in different experimental conditions are presented, including a campaign with varying vessel pressure to investigate the effect of space charge compensation.