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|  Radiological Assessor Training
DOE-HDBK-1141-2001
Instructor's Guide
III. X-ray machines
Show OT 12.5.
A. Components
Obj. 2
Describe the basic components of
X-ray devices have been in existence for about
an x-ray machine.
100 years. Although there are many different
designs of x-ray machines, they all have the
same basic components. These include a
source of electrons, an electrical potential
difference to accelerate the electrons, and an
anode, or target for the accelerated electrons to
strike.
Usually, the source of electrons in an x-ray
The number of electrons moving
machine is a thin wire filament from which
across the x-ray tube, or the tube
electrons are emitted when it is heated by a
current, is adjusted on the x-ray
machine control panel with the
large electrical current. Controlling the current
milliAmpere (mA) control. In
through the filament, then, becomes a way to
some x-ray machines, the mA
control the number of electrons available for
may be fixed, and not adjustable
by the operator.
The electrical potential difference between the
cathode (filament) and the anode (or target) is
the force that accelerates the electrons. The
larger the potential difference, the more kinetic
energy the electrons will acquire. The potential
difference is measured in units of kilovolts (kV).
The energy of the electrons is measured in units
of kilo electron volts (keV), with one electron volt
Electrons interact in the target by
being the amount of energy required to move
one of the following mechanisms:
one electron through a potential difference of
one volt.
Excitation
Ionization
Bremsstrahlung
The accelerated electrons then strike the anode
(or target). The target may consist of various
materials, depending on the purpose and design
of the x-ray tube. X-ray production is most
efficient in high atomic number targets, like
tungsten.
Module 12 4
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