Operator Manual / 2. Safety
26
2.8 X-ray generation principles
X-rays in VOTI X-ray scanners are produced in an X-ray generator. Inside the generator is a vacuum tube containing a
tungsten filament cathode, and an anode that is also made of tungsten. A current is passed through the cathode,
causing it to heat up and emit electrons. Voltage is applied across the cathode and anode, which causes the electrons
to accelerate towards the anode. When the electrons strike the anode, their kinetic energy is absorbed, and some of it
is released again in the form of X-rays. A rough diagram of the apparatus is as follows:
Figure 5 - X-Ray Generation Operating Principle
The value of the voltage applied determines the energy of the X-rays produced. In the case of a VOTI scanner, this
voltage is usually 160 kV. The current passing through the cathode determines the quantity of X-ray photons
produced. The cathode current in a VOTI scanner is usually between 550 µA and 1 mA.
The X-ray generator is shielded to prevent radiation from escaping, except through a funnel that directs X-rays
towards the tunnel of the scanner. The funnel and the tunnel of the item scanner are also lined to prevent X-rays
from escaping.
© VOTI2020 / 900116-001
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