Automated control system for HgI2 crystals growth

Abstract

We describe the control system developed for the automated growth of HgI2 crystals, mainly used for X and gamma radiation detectors. The system includes instrumentation for the precise measurement of the growth furnace temperatures and for their control, both needed to fulfill the strict requirements of the vapour phase crystal growth. A video camera and a VME grabber module allow the detection of the crystal nucleation and pattern recognition. This image analysis is used as input for the control actions. A VME based computer (MVM147SA-1 from Motorola) running a real time OS9 operating system performs: data collection, instrumentation programming, image acquisition, data analysis and control of the whole system making use of a highly structured software. The image analysis is done by means of a perceptron neural net classifier using a parameter invariant representation of the objects detected in the segmented images.