Frequency tailored transducers

By employing this technique, the frequency range best suited for a particular material can be automatically estimated and utilized for inspection, without the need to employ a tailor-made transducer. Consequently, a single wide-band transducer can be used to get near-optimal inspection results for a wide range of materials. 

The ultrasound fields are generated by a focused, MRI compatible piezoelectric transducer (19). The physical characteristics of the transducer determine the size of the focal spot and can be tailored for the experimental needs. For example, we have performed successful experiments with 100-mm diameter, 80-mm radius of curvature transducers with a frequency of 0.7 MHz (see Note 1). 

As with all systems which operate using piezoelectric transducers, optimum performance is obtained at a fixed frequency. For most commercial probe systems such a frequency is 20 kHz and, although it is possible to drive them at their overtones i.e. 40 or 80 kHz), the power dissipation at overtones is very much reduced. In order to operate successfully at different frequencies, it is best to purchase individual amplifier-horn systems tailored to one s individual requirements. 

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