Scheelite Coupled Photodiode X-Ray Sensor Designing and Characterization

Abstract

Efficient detection of un-attenuated and attenuated x-rays intensities is crucial to reconstruct 3D volume in a Computed Tomography (CT) machine employed for Non-Destructive Testing. In this study, an x-ray sensor is developed and characterized to be used with an existing X-ray Io device by evaluating its linearity and operating range. The sensor is developed by using Photodiode BPX61 from Siemens coupled with Sheelite (Calcium Tungstate [CaWO4]) scintillator. Sheelite illuminate by exposure of x-rays and BPX61 converts illuminated light into relative current signal. The current signal is amplified and for further processing transmitted to x-ray Io device virtual instrument which consist of a PIC microcontroller and a Personal Computer (PC). As the x-ray intensity depend upon x-ray tube voltage and current, the linearity and operating range of developed sensor is evaluated by performing special experiments in which the two quantities (tube voltage and current) are accreting one at a time while keeping the other constant. Using normalized values obtained from Oscilloscope and HyperTerminal measurements, the conversion time error is observed and reduced thus increasing linear and operating regions.