Housing

Made of cast or fabricated Aluminum. Functions :

• Control scatter and leakage radiation (lead coating)

• Insure X-Ray beam pre-collimation thru outlet port window

• Supply (HV sockets) and Insulates High Voltage (oil)

• Supply filament currents to the insert

• Collect anode current

• Provide insert cooling (oil bath)

• Provide oil cooling (natural convection, air blower, water cooler or built-in or remote heat exchanger)

• Achieve insert rotor rotation (stator wiring, squirrel motor type)

• Equipped with safety switches (temperature and/or pressure) and with an oil expansion device (plastic bellow)

• Insert
• 

Insert

Is made of 3 main components :

Frame

Is made of highly heat resistant glass or metal

• Maintain vacuum

• Hold cathode and anode in proper position (Focal spot position and inter electrodes insulation gap)

• Provide insulation between anode (+) and cathode (-). With metal frame insulation is achieved by ceramic insulators.

• Cathode
• Anode
• 

Cathode

• Filament (helicoidal tungsten wire) provides electrons stream

• Focusing cup condenses electron on focal spot

• Mechanically assembled with microns precision to secure focal spot sizes and coincidence

Anode

Anode is mounted on a rotor

• Anode surface is made of tungsten (Mo or Rh for Mammo application)

• Anode is eventually backed up with graphite to increase its heat storage capacity

• Rotor is mounted on ball bearings assembly. Balls and races are silver coated

X-Ray generation (click for audio)

• Filament helical wire is run with heating currents (up to 7 Amps)

• Filament temperature thus becomes very high (> 2000°C) and a "cloud" of electrons is available as the surface of the filament

• When High Voltage is applied between cathode and anode, electrons are extracted from the filament and accelerated into the inter-electrodes spacing.Acceleration transfers energy to them..

• Focusing cup acts as an electromagnetical lens and the electron beam is condensed on the focal spot

• When electrons penetrate anode surface they produced X-Ray radiations and generate heat

• As more than 99% of the electron energy is transformed into heat, focal spot temperature increases very quickly

• Anode is rotating in order to "cool down" the focal spot, ie heat is transferred on a whole anode track surface and not only on a single spot.

• X-Ray are emitted in 360° direction from the focal spot. Only one part of the X-Ray beam is selected, thru the outlet port window which is a precollimation device

• Heat is transferred from the focal spot to track, and then from the track into the core of the anode. (that can withstand up to 1400°C).

• Anode is then transferring its heat by thermal radiations (directly into the housing oil thru the glass frame )

• Soft algorithm of the HV generator real time calculates tube components temperatures (focal spot, track, anode, bearing, oil, etc ... ) to make sure tube operates only within its design margin ranges.

• Focusing cup
• Anode
• Frame
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