Prototype of a radiation hard resistive bolometer for ITER

The prototype of a radiation hard resistive bolometer has been produced. This prototype bolometer was installed in ASDEX Upgrade to test its viability and long term stability in a tokamak environment. The prototype bolometer with platinum meanders and absorber on an amorphous silicon nitride substrate and the original standard Kapton bolometer used on ASDEX Upgrade and JET with gold meanders and absorber were calibrated as a function of temperature. The temperature coefficients of the gold and platinum meander resistances are found to have the same value to within 5%. Heat diffusion simulations of the bolometer foils, using the dimensions, specific heat, density and thermal conductivity of the components, were carried out to calculate the cooling time constant and heat capacity of the foils. These calculated values are in agreement with those measured to within 15%. In accordance with these simulations, the prototype bolometer is a factor of 2 more sensitive than the original bolometer and the cooling time constant of the prototype was about a factor of 2 smaller than the original bolometer. The design considerations involved in producing this bolometer foil are discussed and recommendations for future development work are outlined.