A NEW DESIGN OF A SEMICONDUCTOR BOLOMETER ON RIGID SUBSTRATE FOR FUSION PLASMA DIAGNOSTICS

A new, fast, and very sensitive semiconductor bolometer has been desig ned and developed for the measurement of radiative energy losses in fu sion devices in which the hard radiation level is not too high. Specia l care was taken in the design of the bolometer to simplify both the c onstruction technology and the installation in fusion devices. The maj or novelty of this bolometer is the use of a low thermal conductivity rigid substrate, instead of the typical thin foil stretched on a rigid frame. In spite of large detector-substrate contact area, the cooling time constant reaches values as high as 150 ms. The rigid substrate a llows the detector to be very robust and reliable; moreover, the monol ithic integration of array structures is straightforward. The detector has been fabricated with a thin-film multilayer technology achieving very low thermal capacitance (< 2 mJ/K) and very low response time (< 5 mus). High responsivity (20 V/W) is obtained using GeO(x) thin film with a high thermal coefficient of the electrical resistance (-4.5%/K) as sensing thermistor.