Tsuneo Kikuchi

Calorimetric method for measuring high ultrasonic power using water as a heating material

The present study shows the calorimetric method for measuring high ultrasonic power using water as the heating material. In recent years, at the National Metrology Institute of Japan (NMIJ), an ultrasonic power primary standard of from 1 mW to 15 W has been established by the radiation force balance (RFB) method. Conventionally, the RFB method is widely used for ultrasonic power measurement, but this method is not suitable for very high power measurement due to thermal damages to the absorbing targets. High power ultrasonic standards, however, are being required by medical HITU measurements and in the sonochemistry industry. In order to meet these requirements, we have started to develop an ultrasonic power standard between 15 W and 200 W. Our final goal is an ultrasonic power standard of up to 500 W. The calorimetric method is an alternative ultrasonic power measurement method to the RFB method. We have adopted this method and use water as the heating material. Water has excellent features as a standard material, because the physical properties of water are well known. In the present study, we present an experimental system and the results for an ultrasonic power standard of up to 100 W. The measured ultrasonic power agreed well with the NMIJ primary standard up to 25 W.

Preparation of NbC/sub x/N/sub 1-x/ Josephson junctions with TiN/sub x/ barriers

This paper presents the preparation process and the characteristics of titanium nitride films and nonhysteretic NbC_xN_1-x,/TiN_x/NbC_xN_1-x SNS junctions using TiN_x as the barrier material. Structural studies show that TiN_x films prepared by rf sputtering at room temperature have a preferential orientation of TiN(111) phase, while those grown at higher substrate temperatures are (200)-oriented. Resistivilies of the TiN_x films range from 4SμΩ·cm to 1lOμΩ·cm, depending on the values of N₂ partial pressure. Polycrystalline NbC_xN<sub1-x</sub> films with high T_c have been grown on TiN_x films by rf sputtering. NbC<sub>N_1-x/TiN_x/NbC_xN_l-x trilayer junctions with various dimensions and TiN_x thicknesses have been fabricated. Current-voltage characteristics of the junction with a 130nm-thick TIN_x barrier show nonhysteiretic behavior and strong critical current modulatilon with applied magnetic field, suggesting the characteristics of a Josephson SNS large junction. The I_cR_N product and the critical current density J_c of a 5μm x 5μm junction at 4.2K are estimated to be 30μV and 36kA/cm², respectively.

Estimation of Cavitation Sensor with Hydrothermally Synthesized Lead Zirconate Titanate Film on Titanium Cylindrical Pipe: Spatial Distribution of Acoustic Cavitation Field and Basic Characteristics of Cavitation Sensor

We developed a small cavitation sensor by the deposition of a hydrothermally synthesized lead zirconate titanate (PZT) polycrystalline film on a Ti hollow cylindrical pipe. The spatial distributions of acoustic cavitation generated in a vessel of 150 kHz sonoreactor were measured by using our cavitation sensor. We estimated the spatial distribution of acoustic cavitation by using the broad band integrated voltage (BIV) calculated from the output signal of our cavitation sensor. A similar spatial distribution of the BIV to a sonochemical luminescence pattern could be observed in the measured results. Our fabricated cavitation sensor could be applied to the measurement of sound pressure in a high-intensity ultrasound field with acoustic cavitation for a period longer than 150 without damage. We measured the spatial distribution and directivity of the receiving sensitivity for the characterization of our cavitation sensor. It is suggested from the measured results that the BIV and the cavitation signal included in the output signal from the cavitation sensor are based on the acoustic cavitation generated in the cylindrical hollow of our cavitation sensor.

A method for measuring the frequency response of photodetector modules using twice-modulated light

In this paper, a novel method is proposed for measuring the frequency response of a photodetector (PD) and its associated amplifier, which is called a PD module in this paper, by using light whose intensity is modulated twice. A distinctive feature of the twice-modulated light is that it contains two frequency components that essentially have equal intensities. A measurement system was constructed consisting of an He-Ne laser source and two acoustooptic modulators to verify the method. This study shows the resolution to a problem caused by the use of acoustooptic modulators (AOMs). This method can be readily used for determining the frequency responses of a PD module in the frequency range of up to tens of megaHertz.

Frequency characteristics of receiving sensitivity and waveform of an anti-acoustic cavitation hydrophone

Novel anti-cavitation hydrophones were fabricated by depositing a hydrothermally synthesized lead zirconate titanate polycrystalline film on the back of a titanium plate. These hydrophones were not damaged by the measurement of the acoustic field formed by a high-intensity focused ultrasound (HIFU) device. The hydrophones were designed using Masons equivalent circuit and by numerical simulation to improve their receiving characteristics for the measurement of the HIFU device. High receiving sensitivity with flat frequency characteristics was obtained by using a backing material with a specific acoustic impedance of about 20 × 106 kg/(m2 s) [Rayl]. We developed a new type of hydrophone using a tin and titanium rods as backing materials, which have specific acoustic impedances of 24 × 106 and 27 × 106 kg/(m2 s), respectively. The fabricated anti-cavitation hydrophone showed wide frequency characteristics of the receiving sensitivity. Furthermore, we observed the output waveform with distortion due to nonlinear propagation using the fabricated anti-cavitation hydrophone. This hydrophone was not damaged by exposure to a high-intensity acoustic field of an ultrasound cleaner under acoustic cavitation for duration of about ten times longer than the conventional commercial hydrophone.

Quantitative Estimation of the Amount of Fibrosis in the Rat Liver Using Fractal Dimension of the Shape of Power Spectrum

This paper describes the quantitative measurement of the amount of fibrosis in the rat liver using the fractal dimension of the shape of power spectrum. The shape of the power spectrum of the scattered echo from biotissues is strongly affected by its internal structure. The fractal dimension, which is one of the important parameters of the fractal theory, is useful to express the complexity of shape of figures such as the power spectrum. From invitro experiments using rat liver, it was found that this method can be used to quantitatively measure the amount of fibrosis in the liver, and has the possibility for use in the diagnosis of human liver cirrhosis.

Ultrasonic Power Measurement by the Radiation Force Balance Method –Experimental Results using Burst Waves and Continuous Waves–

Results of ultrasonic power measurements using a radiation force balance system constructed at National Institute of Advanced Industrial Science and Technology (AIST) are described. The aim of this research is to establish the ultrasonic power standard for medical ultrasonics. The experimental results of the linearity of the system under 1 mW to about 60 mW for the continuous and the burst waves are presented. It is also confirmed that the measured ultrasonic power is not affected by the repetition rate of the burst wave.

Investigation of Output Signal from Cavitation Sensor by Dissolved Oxygen Level and Sonochemical Luminescence

We investigated the relationships between the broadband integrated voltage (BIV) calculated from the high-frequency components of broadband noise produced by acoustic cavitation in an output signal, the dissolved oxygen (DO) level which is one of generation conditions for cavitation, and sonochemical luminescence which is a chemical reaction induced by cavitation. As a result, BIV was changed by the DO level in distilled water. Also, a correlation was found between BIV and sonochemical luminescence. This indicated that BIV has the potential to be used as an index of the amount of generated cavitation.

Effects of Ultrasound Exposure Time on Nanometer-Sized Diamond Particles Dispersion

We investigated the improvement in the dispersion of nanometer-sized diamond particles by change of ultrasound exposure time. As the results, the dispersion of the diamond particles improved with increasing ultrasound exposure time. The average particle size of the diamond particles of 5 µm decreased to less than 100 nm at ultrasound exposure times of 300 and 1200 s. Also, the diamond particles at 300 and 1200 s had a narrow particle size distribution in the nanometer range. The zeta potential on the diamond particles increased to about 30 mV at an ultrasound exposure time longer than 900 s.

Influence of Ultrasonic Nonlinear Propagation on Hydrophone Calibration Using Two-Transducer Reciprocity Method

In this study, the influence of ultrasonic nonlinear propagation on hydrophone calibration by the two-transducer reciprocity method is investigated quantitatively using the Khokhlov–Zabolotskaya–Kuznetsov (KZK) equation. It is proposed that the correction for the diffraction and attenuation of ultrasonic waves used in two-transducer reciprocity calibration can be derived using the KZK equation to remove the influence of nonlinear propagation. The validity of the correction is confirmed by comparing the sensitivities calibrated by the two-transducer reciprocity method and laser interferometry.