X-ray Imaging Questions & Answers

Why choose an MFX (microfocus x-ray) source?

Microfocus x-ray source tubes are used in industrial and scientific applications such as 3D parts inspection, µ-CT imaging, and CT metrology. They are generally distinguished from the more common x-ray source tubes used in security, medical, and food inspection applications by the size of the focal spot which generates the x-rays. There isn’t a hard definition of MFX, but it is generally accepted that a focal spot less than 100 µm is in the MFX range. For example, Hamamatsu has an MFX (L10711) with a focal spot size down to 0.25 µm, which is about 1/100th the width of a human hair. (Click here to see our MFX products.)

Three significant components are needed for high-resolution imaging: small focal spot of the MFX, magnification of the object (i.e., bringing the object close to the MFX), and the resolution of the flat panel sensor or camera. Since magnification is greatly improved with a very small focal spot, the MFX actually strongly contributes to 2 of these 3 attributes. So MFX is needed whenever very high resolution imaging is required.

Figure 1. Bringing the object closer to the x-ray source achieves high magnification, and using an MFX source results in a sharper magnified image.

What is the difference between sealed- and open-type MFX?

In a sealed-type MFX tube, the cathode and anode target components are inside a vacuum glass envelope which cannot be broken open. Sealed-type tubes tend to have larger focal spot sizes, are extremely robust, and are generally used in factory environments and where compact design is needed.

In an open-type MFX tube, the cathode and anode target are in a special housing that is externally vacuum-pumped, allowing the components to be accessed for maintenance. This allows the open-source tube to be driven harder (higher kV) at smaller focal spot sizes since the user will be able to replace components that tend to wear out faster at these harder conditions. However, the users must have a significant level of x-ray sophistication to do so.

Figure 2. Sealed-type MFX (left) and open-type MFX (right).

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Meet the engineers

Andrew Fay is an Applications Engineer specializing in x-ray sources, detectors, and imaging software. He has extensive knowledge of and experience in x-ray components and complete imaging solutions for medical and industrial applications. When not helping customers implement Hamamatsu’s latest x-ray technology, Andrew enjoys spending time with his family, landscape design, visiting art museums, and playing golf.

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