radiation.
This is the dominant X-ray production process and produces
a wide spectrum of X-ray energies up to the accelerating voltage.
A high energy electron can eject electrons from a target atom. The
resulting atom is unstable as it has a "hole" in one of
its inner electron orbits. In order to return to a stable state
the atom shuffles its electrons to fill the hole and releases an
X-ray. This process is called characteristic X-ray emission because
the energy of the resulting X-rays depends upon the target material.
In our x-ray sources, electrons emitted from a fine wire are accelerated
by up to 225 thousand volts. These high-energy electrons are then
focused by a magnetic lens on to a spot on a metallic target, as
shown:
a. filament
b. electron beam
c. magnetic lens
d. target
Obtaining a sharp, high-resolution real time x-ray
image requires a very small spot size. If the x-ray spot size is
too large, unsharp regions are created in the x-ray image, as shown:
Moving the sample closer to the x-ray source
increases the magnification of the resulting image:
|
Back
