Location

Williamsburg, VA

Start Date

1-1-1986 12:00 AM

Description

The thermoacoustic microscope [1–9] uses a modulated particle beam (electrons, photons or ions) as a heat source on (or near) the surface of the sample, and a piezoelectric transducer attached elsewhere on the sample as a detector of acoustic waves generated by the beam. The modulation frequency is typically 103 to 107 Hz, so the acoustic signal is in the sonic to ultrasonic range. These acoustic signals are used to produce images of surface and near surface features of the solid by scanning the source over the face of the sample. In order to make full use of this type of microscope as a quantitative NDE tool, one must be able to interpret the images in terms of the physical properties of the features being imaged. The interpretation of an image resulting from variations in, say, the elastic constants as if it were caused by variations in, say, thermal expansion coefficient, could lead to totally incorrect conclusions about the nature of a defect. This paper summarizes a theoretical analysis which can form a basis for assessing the relative importance of different contrast mechanisms.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

5A

Chapter

Chapter 2: Inversion, Imaging and Reconstruction

Section

Imaging and Reconstruction

Pages

439-445

DOI

10.1007/978-1-4615-7763-8_45

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Contrast Mechanisms in the Thermoacoustic Microscope

Williamsburg, VA

The thermoacoustic microscope [1–9] uses a modulated particle beam (electrons, photons or ions) as a heat source on (or near) the surface of the sample, and a piezoelectric transducer attached elsewhere on the sample as a detector of acoustic waves generated by the beam. The modulation frequency is typically 103 to 107 Hz, so the acoustic signal is in the sonic to ultrasonic range. These acoustic signals are used to produce images of surface and near surface features of the solid by scanning the source over the face of the sample. In order to make full use of this type of microscope as a quantitative NDE tool, one must be able to interpret the images in terms of the physical properties of the features being imaged. The interpretation of an image resulting from variations in, say, the elastic constants as if it were caused by variations in, say, thermal expansion coefficient, could lead to totally incorrect conclusions about the nature of a defect. This paper summarizes a theoretical analysis which can form a basis for assessing the relative importance of different contrast mechanisms.