Name & decribe main components of Xray tube

• Negatively charged electrode
• Contains the FILAMENT (coiled tungsten wire)
• Contains the FOCUSING CUP (nickel, negatively charged)
• Two filaments: small/fine + largeroad focus
• 3 supply leads: 1 fine, 1 broad, 1 focusing cup
• Offset to face the anode target track

• Positively charged electrode
• ANODE DISC: molybdenum body + carbon graphite backing
• ANODE TARGET: 90% tungsten + 10% rhenium, sits on bevelled edge
• ANODE STEM: molybdenum, narrow cross-section
• ROTOR: copper, driven by stator coils
• BEARINGS: steel coated with lead or silver

• TUNGSTEN (W)
• Thin coiled wire
• Coiled = large surface area in small space

• Made of NICKEL
• Carries a NEGATIVE charge
• Same polarity as electrons → repels and focuses them

• 90% TUNGSTEN
• 10% RHENIUM
• Sits in the bevelled edge of the anode disc

• MOLYBDENUM body — half the density of tungsten, high heat capacity
• CARBON GRAPHITE backing — increases heat capacity to ~4000°C
• Graphite draws heat away from the target

• Pure mineral OIL
• Acts as electrical insulator
• Acts as coolant
• Prevents sparking (arcing) between insert and housing

• LEAD — 3mm lining
• Absorbs stray and off-focus radiation
• Ensures only the primary beam exits via the tube window

• BOROSILICATE GLASS — good electrical insulator, rounded shape prevents static build-up
• OR METAL — with ceramiclass insulation sections between cathode and anode ends
• Contains a BERYLLIUM WINDOW at the primary beam exit point

• Made of COPPER
• Driven by the rotating magnetic field of the STATOR coils (outside the envelope)
• Induction motor principle

• Steel ball bearings coated with LEAD or SILVER for lubrication
• Oil CANNOT be used — it would evaporate in the vacuum
• Lead/silver are solid-state lubricants that work in a vacuum

• High melting point (3387°C) — survives intense heating
• Ductile — can be drawn into a very fine coiled wire
• Low vapour pressure — minimal vapour released into vacuum when hot
• Low work function — electrons escape well below the melting point

• Coiling gives a LARGE SURFACE AREA in a SMALL VOLUME
• More surface area = more electrons emitted per unit time
• Concentrates heat efficiently for thermionic emission

• Surrounds the filament
• Carries high negative potential equal to the filament
• Same charge as electrons → REPELS them inward
• Sharp edges create an electric field that narrows the beam
• Focuses electrons as a beam toward the focal spot on the anode target
• Without it: electrons would scatter in all directions

• Molybdenum: half the density of tungsten — manageable mass for rotation
• Molybdenum: higher heat capacity than tungsten alone
• Molybdenum: melting point 2600°C — adequate for the disc body
• Carbon graphite backing: increases heat capacity to ~4000°C
• Graphite actively draws heat away from the target toward the disc body

• Rhenium is more ELASTIC than pure tungsten
• Improves thermal expansion tolerance
• The target expands and contracts with repeated heating without cracking
• Reduces pitting of the focal track over time
• Extends tube lifespan

• ELECTRICAL INSULATOR: prevents sparking between the insert and housing
• COOLANT: conducts heat away from the insert by convection
• PREVENTS ARCING: fills all air gaps — air gaps allow electrical discharge

• Flexible rubber diaphragm in the tube housing
• Allows oil to EXPAND and CONTRACT as it heats and cools
• Prevents excessive pressure build-up inside the housing
• Linked to a MICROSWITCH — activates if oil overheats → locks out further exposures