A Wire Calorimeter for the SPIDER Beam: Experimental Tests and Feasibility Study

To study and optimise negative ion production and acceleration, in view of the use of neutral beam injectors in the ITER project, the SPI DER test facility (particle energy 100keV; beam current 50A, divided into 1280 beamlets) is under construction in Padova, with the aim of testing beam characteristics and to verify the source proper operation by means of several diagnostic systems. An arr ay of tungsten wires, directly exposed to the beam and consequently heated to high temperature, is used in similar experiments at IPP - Garching to provide a qualitative investigation of the beam optics, which is one of the most important issues. The present contribution gives a description of an experimental investigation of the behaviour of tungsten wires under high heat loads in vacuum. Samples of tunsten wires are heated by electrical currents and the emitted light is recorded by a camera in the 400 - 1100n m wavelength range. Simultaneously, the voltage applied to the wire is measured to study the influence of temperature on emissivity. Previous literature is applied to the interpretation of the measurements. The feasibility study of a wire calorimeter for S PIDER is finally proposed; to this purpose, the expected behaviour of tungsten with the two - dimensional beam profile in SPIDER is numerically addressed.