Design and analyses of a one-dimensional CFC calorimeter for SPIDER beam characterisation

In the framework of the activities for the design of Padova Research on Injector Megavolt Accelerated (PRIMA), the beam source experiment SPIDER (Source for the Production of Ions of Deuterium Extracted from RF plasma), (SPIDER)] has a key role for the next generation of sources for the ITER Neutral Beam Injectors (NBIs). The main purpose of SPIDER test facility is the investigation and optimisation of a negative ion beam produced by the full size ion source for ITER NBIs, aiming at fulfilling ITER requirements in terms of extracted negative ion current density, its spatial uniformity and co-extracted electron current. At the exit of the beam source the negative ion beam is composed of an array of 4 x 4 beamlet groups, each one made of 16 x 5 beamlets. In order to study and optimise the beam uniformity and extracted ion current density, a movable calorimeter has been developed. The thermal image of the beamlet footprints that appears on the rear side of the calorimeter panels is observed by thermal cameras, which permit to reconstruct the beam shape. The calorimeter is V-shaped and composed of two panels made of one-dimensional Carbon Fibre Composite (CFC) tiles that can intercept the beam up to 10 s at its full power. The panel support system can remotely move forward/backward and can open/close the panels, in vacuum. The CFC can sustain the high heat power loads (up to 20 MW/m(2)) and the fibres are oriented along the thickness in order to transmit a clear image through the tiles enhanced by very low thermal conductivity in the in-plane directions. Each tile is electrically insulated to give a measure of the ion current reaching it and it is instrumented with a thermocouple array for absolute calibration of thermal camera measurements. According to the physical and mechanical requirements, a feasibility analysis has been carried out and a preliminary design has been concluded. This paper gives an overview of the design and thermal and structural analyses. (C) 2010 RFX. Published by Elsevier B.V. All rights reserved.