Speaker
Description
Radiation detections and radio isotope identification are of paramount importance in DAE. Cadmium Zinc Telluride (CZT) with its wide band gap (1.56 eV) and high electron density is an apt material for compact radiation detectors to be used at room temperature in comparison to HpGe which requires cryo cooling. CZT single crystals are grown using travelling heater method by a modified high temperature solution growth in excess of Tellurium. The growth process yields 20 mm diameter and 100 mm long single crystal boules from which useful elements of dimensions 10 mm X 10 mm X 5 mm are harvested after identifying regions with Te inclusion size less than 5 microns with uniform distribution using IR transmission microscopy. Subsequently, the surface states of these elements are modified by chemical etching and gold electrodes are deposited in a quasi-hemispherical (QH) geometry to maximise the electron collection efficiency. Using these gold-electroded CZT elements, along with a preamplifier, shaping amplifier and multichannel analyser battery powered portable gamma-ray spectrometers have been demonstrated with energy resolution of 2.8 % at 662 keV gamma-ray from 137Cs source. Piezoelectric crystals with high piezo-electric coefficient and electro-mechanical coupling are high in demand. Lead zinc niobate – lead titanate (PZN-PT) is one such material exhibiting a piezo-coefficient (d33) of 2100 pm/V and an electro-mechanical coupling coefficient (k33) of 91%. We have developed a novel bottom cooling high temperature solution growth method which enables the growth of crystals upto 30 mm width and weighing over 100 grams. These crystals are crystallographically oriented to exploit their anisotropic piezoelectric properties. The oriented crystals are cut into various dimensions depending on their intended applications, electroded and poled. These poled elements have been successfully tested for a prototype surface acoustic wave (SAW) device
