Components of an X-ray tube

Question 1

What is the Tube insert?

Answer 1

An inner housing vacuum around the inner components

Question 2

What is the cathode block?

Answer 2

This is the negative terminal of the tube

Question 3

What is the Filament?

Answer 3

A linear spiral mounted in the focusing cup which has its own electrical supply to produce the space charge

Question 4

Name 5 features of the filament

Answer 4

• Made of tungsten
• High melting point
• Ductile
• Low work function
• Low vapour pressure

Question 5

What is the Focusing Cup?

Answer 5

Elongated deep open structure connected to highly negative output which holds electrons around the
filament as a space charge aswell as repelling electrons from filament

Question 6

Name the two different sizes of filament inside the

focussing cup

Answer 6

Fine focus

Broad focus

Question 7

What other function can the focusing cup be used for?

Answer 7

As a switch

Question 8

What does increasing the charge on the focussing cup do?

Answer 8

Holds electons in a cloud near the focussing cup, when the charge on the focussing cup is reduced this allows the electrons to flood across the x-ray tube instantly

Question 9

Name 5 features of the Stationary Anode

Answer 9

• Made of tungsten
• High melting point
• Low vaporisation pressure
• High atomic number
• Can form a durable block

Question 10

Increasing the anode angle does what the the anode heel effect?

Answer 10

Decreases Andone heel effect

They are inversely proportional

Question 11

The Rotating Anode is made of 3 sections, what are they?

Answer 11

Focal track
Disc
Disc backing

Question 12

How is Anode rotation achieved?

Answer 12

Electromagnetic induction from an alternating current producing a magnetic field

Question 13

What is the Glass envelope?

Answer 13

Evacuated container which provides electrical insulation

Question 14

Name 5 features of the Glass envelope

Answer 14

• Borosilicate glass
• Heat resistant
• Strong
• Electrical insulator
• Radiolucent

Question 15

Name 5 features of the Tube Housing?

Answer 15

• Aluminium or mild steel
• Securely contains the oil
• Radiation protection
• Provides tube port
• Electrical safety

Question 16

What is Extra Focal or Off-focus Radiation?

Answer 16

Extrafocal radiation is radiation that is produced from the interactions of electrons with any parts of the x-ray tube which are NOT the focal spot

Question 17

What is Leakage Radiation?

Answer 17

This is radiation that emerges from the tube housing rather than the tube port, lead is in the housing to reduce the amount of leakage radiation

Question 18

Name 3 ways the X-ray tube cools down?

Answer 18

The heat is radiated away from the anode target when it spins

Thermal energy is conducted away along the (stationary) anode block

The oil that surrounds the insert removes heat away from the tube insert by convection