X-ray equipment in which the focal spot size is less than 100 µm is referred to as microfocus unit. Advanced micro-focus units have a focal spot size as low as 5 µm which is achieved by focussing the electron beam on the target in combination with sufficient cooling to avoid overheating and damaging the system.
Microfocus radiography facilitates the observation of minute details within the object through production of magnified X-ray images, which in turn enhances the flaw detection capability which improves reliability in comparison to conventional radiography. Micro-focus X-ray systems having focal spots that approach a point source are useful in obtaining very high resolution images due to the negligible penumbra effect.
The X-ray source generates a continuous beam of X-rays from the very small focal point. The beam passes through the sample placed on the manipulator turntable, and casts an X-ray projection onto the detector sensor. The sensor converts the transmitted X-ray projection into a visible greyscale image, which is displayed on a monitor. The magnification of the sample depends on its position between the X-ray source and detector. Moving the sample towards the X-ray source increases the magnification and improves the spatial resolution by increasing the number of pixels over which the X-ray image is projected. Even when operating at maximum magnification, the microfocus X-ray spot ensures the image is always sharp. The associated software enables contrast enhancement and image integration.
TWI Resources
X-Tek HMX225 micro-focus advanced X-ray system
Features:
- 5-10 µm focal spot reflection target X-ray source
- 25 to 225kV, 0-2000 µA, 225 Watt
- 5-axis fully programmable manipulator
- Maximum scan area: 450x450mm
- Geometric magnification: Up to x160
- System magnification: Up to: x400
- Feature recognition: Down to 5µm
Benefits
- Image enlargement
- Improved radiographic contrast
- Reliable detection of micro features
Applications
- Inspection of integrated circuits and PCBs
- Inspection of high quality castings and weld material
- Tube to tube sheet weld inspection
- Inspection of composites and ceramics for micro-voids and structural inhomogeneity
- Inspection of inaccessible areas
- Inspection of aero engine turbine blades to detect hairline cracks
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