Atom-Probe Tomography APT

In this section, we review the basic principles of APT and explain how the technique has been used to analyse RPV steels. Several dedicated monographs provide more detailed information on the technique itself.  

APT relies on the combination of field evaporation, time-of-flight spectroscopy and position-sensitive detection. Electropolishing or focused 

As a first approximation, the radius of curvature of the needle tip, R, during field evaporation is given by  

The atom probe was invented in 1968 and, since then, there have been many improvements to the original design. Most have been used to characterise irradiated RPV steels and so it is appropriate to summarise the technological advances. The original ID atom probe had a detector placed behind a probe hole in the centre of an imaging channel plate and phosphor screen (Fig. 9.15). The probe hole diameter was 3mm which 

14 Schematic showing fieid evaporation process as function of appiied eiectric fieid or thermai puise from a iaser.  

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The last chapter is of paramount importance for the materials community -characterization. Prom electron microscopy to surface quantitative analysis techniques, and everything in between, this chapter provides a thorough description of modem techniques used to characterize materials. A flowchart is provided at the end of the chapter that will assist the materials scientist in choosing the most suitable technique(s) to characterize a particular material. In addition to comprehensive updates throughout the chapter, a new technique known as atom-probe tomography (APT) has been included in this edition. 

A.10.3.4 APT Atom Probe Tomography (APT) also called Tomographic Atom Probe (TAP) is a destmctive technique capable of providing elemental/isotopic... 

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