Agilent 5DX Service Guide 8-17
5DX Series 3 Imaging Subsystem Components
X-ray Tube Pressure Vessel
The X-ray Tube Pressure Vessel contains the X-ray Tube and the X-ray Tube
Electronics. The X-ray Tube Pressure Vessel is filled with an inert dielectric gas
at a pressure of 60 psi. The dielectric gas is an insulator used to protect the X-ray
Tube from internal arcing.
X-ray Tube
The X-ray Tube assembly is comprised of the following components:
• Cathode — The cathode provides the source of electron emissions for the X-
ray Tube. The cathode is heated by a cathode filament that is potted in a
ceramic casing and is electrically isolated from the cathode. The cathode
filament provides a source of heat that excites the molecules of the cathode
material. The hot cathode emits electrons that are accelerated as the electron
beam through an anode then focused and deflected onto an X-ray Target.
• Accelerator — The -160 kilovolt dc source voltage generates a difference in
potential between the cathode and the anode, creating an electric field. This
electric field is segmented into four equal field zones. These cascaded zones
accelerate and help shape the electron beam.
• Focus Grid — The focus grid provides preliminary focal alignment of the
electrons emitted by the cathode. The value of the focus grid voltage is set at
the factory and should not be adjusted.
• Control Grid — The emission of elections from the cathode is regulated by a
control grid, positioned between the cathode and the anode. A voltage is
applied to the control grid, known as a “bias” voltage. This bias controls the
field between the cathode and anode, thereby controlling the flow of electrons.
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As the bias voltage applied to the Control Grid is increased, less
electrons are emitted from the Cathode. The inverse is true when the
bias voltage applied is decreased.
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