Fiber optic probe hydrophone

Figure 8. Comparison of the cavitation pressure (top) and density (bottom) of water as a function of temperature obtained with acoustic method and water inclusions in quartz used as Berthelot tubes. The symbols represent acoustic method with calibration by static pressure method (open diamonds [43] and solid diamonds [52]), acoustic method with fiber optic probe hydrophone (solid bullets [51]), water Inclusions In quartz (open squares [45]). In the lower panel, cavitation of an inclusion during melting is also included (black filled square [92]) and light and dark arrows indicate isothermal and isochorlc paths, respectively. Solid lines are the binodals. Lower panel reproduced with permission from Ref. [52].

Berthelot method in water inclusions in quartz [45]. The inclusions appear to give a much more negative Pcav But one has to remember that the liquid density only is known (assuming that the inclusions keep a constant volume and remain sealed), and that the pressure is deduced with an extrapolated EoS. Therefore, a direct measurement of the liquid density at the nucleation threshold has been performed in the acoustic experiment [52], thanks to a fiber optic probe hydrophone [51], Figure 8b presents a comparison of the acoustic and inclusion measurements in terms of density. The solid bullets are direct measurements acquired with the hydrophone and they compare well in trend and magnitude with pressure estimates that were converted to density with an EoS, but the major discrepancy with the inclusions is persistent. 

A. Arvengas, K. Davitt, and F. Caupin, Fiber optic probe hydrophone for the shufy of acoustic cavitation in water, Rev. Sci. Instrum. 82(3), 034904 (2011). 

Staudenraus, J. and Eisenmenger, W. (1993) Fiber-optic probe hydrophone for ultrasonic and shock-wave measurements in water, Ultrasonics, 31, 267-73. 

Zhou, Y., Zhai, L., Simmons, R. and Zhong, P. (2006) Measurement of high intensity focused ultrasound fields by a fiber optic probe hydrophone, J. Acoust. Soc Am., 120, 676-85. 

Although these acoustical probes can be made very small they will always slightly disturb the ultrasonic field. Just as in the case of coated thermal probes, the response signal depends on the nature and size of the probe, thus it is important that the microphones are carefully calibrated. They are however widely used, especially to calibrate medical ultrasonic equipment. Recently, very small and sensitive devices using PVDF membranes [68,69] or fiber optics [70] have been described. PVDF has piezoelectric properties and miniature membrane hydrophones (about 0.5 mm in diameter) are available. Fiber optic probes can even be smaller and a spatial resolution of 0.1 mm has been claimed [70],... 

---