Automatic measurement of the nonlinearity parameter B/A in liquid media |
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Authors: | Saito Shigemi Kim Jung-Ho Nakamura Kiyoshi |
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Institution: | School of Marine Science and Technology, Tokai University, Shimizu-Ku, Shizuoka 424-8610, Japan. ssaito@scc.u-tokai.ac.jp |
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Abstract: | Using a 19-MHz focused Gaussian beam generated by a LiNbO(3) plate with an inverted polarization layer coupled to an acoustic lens, a method to automatically measure the nonlinearity parameter B/A in liquid media is presented. A liquid sample is poured into a cylindrical cell set with a glass tube on the lens surface. The focusing source emits burst waves. A tungsten rod immersed in the sample so that the top surface is normal to the beam axis behaves as a perfect reflector. The position of the reflector to maximize the amplitude receiving the returned wave determines the sound speed c of the sample. The amplitude measurement for the waves returned from the lens-sample interface and the reflector surface leads to the determination of the density rho and attenuation coefficient alpha, respectively. Then the B/A is finally derived by summarizing the measured result of the 38-MHz second harmonic amplitude contained in the sound returned back from the reflector, together with rho, c and alpha. All these are automatically processed in a short time less than 2 min with the performance of computer controlled instruments. |
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