Automated control system for HgI/sub 2/ crystals growth

We describe the control system developed for the automated growth of HgI₂ crystals, mainly used for X and γ radiation detectors. The system includes instrumentation for the precise measurement of the growth furnace temperatures and for their control, both needed to fulfil 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