APPARATUS FOR THE DIRECT RECORDING OF ULTRASONIC ATTENUATION IN SOLIDS
BOEING SCIENTIFIC RESEARCH LABS SEATTLE WA
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Effort is devoted to the measurement of acoustic losses in solids, primarily single crystals, at ultrasonic frequencies. In this type of experiment a pulse of r-f energy excites a quartz transducer bonded to the sample which in turn sends a pulse of ultrasound through the sample. The acoustic pulse is reflected from the sample end, travels back to the transducer and the reciprocal effect occurs. As a basic unit for this measurement the Sperry Ultrasonic Attenuation Comparator is used. This unit is a combination transmitter-receiver capable of delivering rf pulses over the frequency range 10-200 mc, containing a 60 mc meterodyne receiver with 8 mc bandwidth, and a calibrated exponential wave generator for attenuation measurements. The attenuation is essentially the logarithm of the ratio of the amplitudes of any two echoes, the procedure is to choose two convenient ones, detect their peaks, logarithmically amplify these, and then take the difference which is plotted on the x-y plotter against the suitable parameter.