X-Rays

X-Ray Diagram X-Ray Diagram. The heavy metal target is normally tungsten. X-rays are close to 1% efficient so a lot of care needs to be taken on cooling.

X-ray production

The heater ‘boils off’ electrons by thermionic emission.
These are then accelerated to very high velocities by the p.d. between the heater filament and anode.
They are collimated by the focussing anode.
The tube is evacuated so the electrons travel in straight lines and collide with a tungsten target (the anode) embedded in a copper block.
The resulting deceleration produces an enormous amount of heat (up to 99% of the energy input) and also X-rays, which emerge from a window in the lead housing.

Manipulating the X-ray spectra

Changing the heavy metal component changes where you get the metal specific spikes
The intensity of the X-ray beam depends on the number of electrons striking the target per second and is controlled by the filament current and operating p.d.
The penetrating power of the x-rays (i.e. their maximum energy) is determined by the speed of the electrons and thus the accelerating voltage.
The greater the accelerating voltage (voltage across the cathode and anode) the smaller the wavelength or higher the photon energy of the x-rays that are produced and the greater the penetrating power.
Increasing the filament current or voltage will liberate more electrons so more electrons collide with the target per second.

Formula
So the greater the fraction of energy that the electrons lose the smaller
the wavelength of the emitted x-rays

Intensity
The minimum wavelength of x-rays that are produced depends entirely on the maximum energy of the photons that are decelerated when they hit the target.
where are known constants plank, speed of light, charge of electron and V is pd

Changing Materials
As the proton number is increased: E max remains constant, as it's a function of the voltage;

The total intensity (the area under the graph) will change because there is a greater
probability of a collision between the incoming electron and the electron shells.
The more protons, the more electrons; The characteristic lines are shifted to higher photon energies.

Attenuation of x-rays
When X-rays pass through matter they are absorbed and scattered and therefore the beam is attenuated. This attenuation can be calculated using the equation: $µ$ Where :

I = intensity at a depth x
I_0 = intensity at the surface
µ = the attenuation coefficient with units m^-1

Half Value Thickness
This is the thickness of the material which is needed to reduce the intensity (I) of the X ray beam to one half the intensity of the incident radiation (Io). Formula :
$µ$

Therapeutic use of X-Ray
X-ray therapy is where high-energy radiation from x-rays is used to kill cancer cells and shrink tumors.

Diagnostic use of X-Ray
You can look for soft tissue by using a contrast medium to change the density of the soft tissue