The Sepia years. 1951. Castaing’s thesis(1) : Genesis of a Non-Destructive and truly Quantitative Microanalysis method. 1958. The beginning of commercial microprobes : Early instruments had no computers and were lacking special analyzing crystals, but overall they were well designed. Modern features we are familiar with today, such as light element analysis, field emission gun, Energy Dispersive analysis, analysis of insulated material and scanning analysis, although not widely implemented, were discussed in scientific reviews even then(2) 1963. One of my early personal experience: The daring job of obtaining Castaing’s acceptance for his Cameca-buih EPMA at the University of Paris/Orsay.

From early models to present microprobes Early microprobes were developed, after WWII, in a world driven by metallurgy. They had few WD spectrometers, usually at low take off angle. However, the need for light element analysis and the fast growing use of EPMA in geology have sent the manufacturers back to the drawing board. Why ? The design of modern microprobes was a compromise between light optics, electron optics and higher take off angle X-ray spectrometry. There were three possible designs of X-ray path geometry : X-rays through the(final) lens, X-rays through the gap of the lens, X-rays outside the lens, hence three suppliers arose based on these concepts.

Present and future EPMA improvements. As in the initial era of EPMA newer applications will point the direction in which the electron microprobe of the future should evolve.