Low-reflection-coefficient liquid interfaces for system characterization

The use of liquid brominated hydrocarbons to form a planar reflecting inter face with water is described. Gravity-based planar reflecting surfaces with known reflection coefficients can be used in system characterization for q uantitative ultrasonics, and a set of surfaces with a range of reflection c oefficients allows calibration of the output power and receiver gain of ult rasonic imaging systems. The substances reported here are immiscible in wat er and form interfaces with water, resulting in a broad range of acoustic r eflection coefficients. Reflection coefficients were measured at temperatur es from 18-24 degreesC for "pure" substances and for mixtures of two bromin ated hydrocarbons. Results show that reflection coefficients are weakly dep endent on temperature and that, at a specific temperature, a significant ra nge of arbitrarily small reflection coefficients is available, in the case of the mixtures, by the appropriate choice of weight-percents of the two br ominated hydrocarbons.