Kahn Outline Chapter 3: Production Of X-Rays

Front 1

Describe "Thermionic emission"

Back 1

When the tungston filament "cathode" is heated it emits electrons

Front 2

Describe "Heel effect"

Back 2

The attenuation of the x-ray beam as it passes through the target.

Front 3

Describe Rectification

Back 3

Since the anode is positive with respect to the cathode only through half the voltage cycle, thetube current flows through only that half of the cycle. During the next half-cycle, the voltage re-verses and the current cannot flow in the reverse direction. Thus, the tube current and the x-rays Since the anode is positive with respect to the cathode only through half the voltage cycle, thetube current flows through only that half of the cycle. During the next half-cycle, the voltage re-verses and the current cannot flow in the reverse direction. Thus, the tube current and the x-rays

Front 4

Describe the Bremsstrahlung x-ray process

Back 4

The process of bremsstrahlung (braking radiation) is the result of radiative "collision" (interaction) between a high-speed electron and a nucleus. The electron while passing a nucleus may be deflected from its path by the action of Coulomb forces of attraction and lose energy as bremsstrahlung. As the electron, with its associated electromagnetic field, passes in the vicinity of a nucleus, it suffers a sudden deflection and acceleration. As a result, a part or all of its energy is dissociated from it and propagates in space as electromagnetic radiation.The

Front 5

Describe the Characteristic x-ray process

Back 5

An electron, with kinetic energy E0, may interact with the atoms of the target by ejecting an orbital electron, such as a K, L, or M electron, leaving the atom ionized. The original electron will recede from the collision with energy E0 - ΔE where Δ E is the energy given to the orbital electron.

Front 6

What is Brems efficiency affected by?

Back 6

The efficiency of x-ray production varies with Z^2 of the target material.
Efficiency = 9 X 10 ^-10 ZV

Front 7

How does filtration affect a poly energetic beam?

Back 7

Add filtration enriches the beam with higher-energy photons by absorbing the lower-energy components of the spectrum. As the filtration is increased, the transmitted beam hardens, i.e., it achieves higher average energy and therefore greater penetrating power.

Front 8

How dose filtration affect a mono energetic beam?

Back 8

Even if the x-ray tube were to be energized with a constant potential, the x-ray beam would still be heterogeneous in energy because of the multiple bremsstrahlung process that result in different energy photons.

Front 9

What is "Output" and what affects it?

Back 9

The "output" of an x-ray machine can also be expressed in terms of the ionization it produces in air.
As the voltage increases, the output increases, however, it is much greater than that given by a linear relationship.

Front 10

What is "Exposure" and what affects it?

Back 10

The quantity of ionizations per unit mass of air.
There is a linear relationship between exposure rate and tube current.