HIGH-RESOLUTION X-RAY SENSOR FOR NON DESTRUCTIVE EVALUATION

Nondestructive evaluation (NDE) using X-rays is becoming indispensable for detecting microdefects in new materials currently used in aerospa ce and other engineering disciplines. Existing X-ray sensors pose limi tations on the speed of operation due to persistence of the sensor and a problematic tradeoff between the sensor thickness and spatial resol ution. To address these limitations we are developing a large area str uctured CsI(TI) imaging sensor for NDE using CCD based radiographic an d computed tomographic systems. The sensor is formed by vapor depositi on of CsI(TI) onto a specially designed fiberoptic substrate. Our work has produced X-ray sensors with a factor of 4.5 greater light output, at least three orders of magnitude faster decay time response, and gr eater spatial resolution (16% modulation transfer function, MTF(f), at 14 linepairs per millimeter (lp/mm)) compared to the currently used h igh density Tb2O3 doped fiberoptic glass scintillators. These performa nce advances will address the limitations of existing detector technol ogy by producing high quality images and fast scan times required for real-time NDE inspection. Performance measurements for prototype CsI(T I) scintillator converters are presented. With these new sensors the d evelopment of larger area fiberoptic taper based CCD detectors with mi llisecond data acquisition capabilities and high spatial resolution su itable for NDE applications will be possible.