Fusion cutting, typically using nitrogen assist gas, is used for cutting stainless steel and requires a smaller focal spot
with low divergence.
On one hand, the best resolution tube to see the smallest features will have the smallest focal spot
, but this puts a lot of electrons into a very small area on the target and means very high current densities.
Spatial resolution in CT is primarily determined by the pixel size of the detector, the ratio of the distance between the source and the object and the object and the detector (geometric magnification), and the X-ray focal spot
size (Goldman 2007; Romans 2011; Staude & Goebbels 2011).
(a) Determine the distance from the focal spot
[a.sub.1] to the virtual detector [vd.sub.1].
Chen, "Improve spatial resolution by modeling finite focal spot
(MFFS) for industrial CT reconstruction," Optics Express, vol.
With this metalens, the transverse distance of the focal spots
of two orthogonal polarization states is about 10-bit units (2 mm), as shown in Figures 4(b) and 4(c).
Besides the physical dimension of the detector, the focal spot
size of the lens mechanism is another factor that can cause signal fall-off.
Measuring the acoustic impedance with a 230-MHz transducer would be time-consuming and have a more localized reading, however, because the focal spot
size of the transducer is so much smaller.
NFF arrays essentially exploit the extreme flexibility of array antennas to control the side lobe level, shape the -3 dB focal spot
, implement multifocus antennas, and electronically scan the focal point.
For the single-focus excitation, we used nonresonant/resonant galvano mirror pair scanner (128 lines, 125 frames/s) to scan the focal spot
. For the multifocus excitation, we used a microlens array scanner (128 lines, 1000 fps).
With its optimally designed optical system, it provides a smaller focal spot
diameter while maintaining a long depth of focus(1).
This allows a quick temperature balance, essential for a stable position of the focal spot
and a stable operation that limits additional thermal expansion of the tube.