Expected headings
"Construction"
"Principal elements"
"Additional elements"
"Other parts of an x-ray system"
"Function"
"Filament (cathode) and target (anode)"
"Anode rotor and induction stator"
"Tube envelope"
"Tube window"
"Coolant"
"Tube housing"
"Generator"
"The filament/cathode and target/anode are contained in the envelope, which provides vacuum, support and electrical insulation. The envelope is made of glass (Pyrex or borosilicate glass) 8, ceramic, or metal 4. A glass envelope is more prone to failure because tungsten filament vapourises and coats the surface of the glass, altering the electric potential of the tube, and resulting in the formation of an electric arc, causing tube failure. A metal envelope maintains the electric potential across the tube, making it less likely to fail. Thus, most high-output x-ray tubes use metal envelopes 6."