Week 3: Power Generation, Circuitry and Tube Components

Question 1

AC Current

Answer 1

The power coming from the wall (alternating current). Incoming AC current will be three phase power (three different waves of power are combined so that the potential never fully drops to zero).

Question 2

Main Circuit

Answer 2

Provides modified power to the x-ray tube. Voltage must be increased by using a series of transformers. Once AC current has been modified and increased for x-ray production it myst be rectified which turn AC to DC current.

Question 2

DC Current

Answer 2

What is needed for x-ray production. Direct current.

Question 3

Filament Circuit

Answer 3

Provides modified power to the filament. Only contains a step down transformer to decrease voltage so amperage can be increased. Lots of amperage needed to supply lots of electrons to the filament.

Question 4

Rectification

Answer 4

The process of turning AC power into DC power. Takes the second (useless to us) part of the wave and applies it to the tube for use in x-ray production.

Question 5

Protective Housing

Answer 5

Composed of cast steel and line with lead. Controls leakage and scatter radiation, isolates the high voltage components and provides a means to cool the tube through insulating oil.

Question 6

Envelope

Answer 6

Encases the cathode and anode assembly, excluding stair. Made of heart resistant pyrex or metal and maintains a high vacuum for radiation production. Photons leave through window segment.

Question 7

Cathode Assembly

Answer 7

Negative charge, produces thermionic cloud. Made of the filament, focusing cup and wiring.

Question 8

The Filament

Answer 8

Provides resistance to cause thermionic cloud = thermionic emission. Made of metals like rhenium, molybdenum or tungsten which have high melting points and are hard to vaporize.

Question 9

The Focusing Cup

Answer 9

Focuses the electron stream toward the anode. Required to keep the negatively charged electron cloud together until the voltage is applied to the tube.

Question 10

Anode Assembly

Answer 10

Positively charged, target surface where x-rays are produced. Conducts high voltage back into the circuitry. Made of anode, stator and rotor.

Question 11

Rotating Anode

Answer 11

Rotates for better heat dissipation, 5-13 cm in diameter. Molybdenum or graphite base and middle layers, graphite base layer and rhenium alloyed tungsten target layer.

Question 12

Focal Track

Answer 12

Circular path on the anode struck by the electrons.

Question 13

Target or Focal Spot

Answer 13

The area of the focal track being struck by electrons at a given time during exposure.

Question 14

Stator

Answer 14

Series of electromagnets, only part of the assembly outside of the glass envelope. The high voltage of exposure would destroy the electromagnets so it sits outside. Electromagnetic effect causes rotor to turn by creating a magnetic field.

Question 15

Rotor

Answer 15

Inside glass envelope, affected by the electromagnetic field to case anode to turn. Attached to the anode by molybdenum shaft and moves on silver plated steel ball bearings.

Question 16

Off Focus Radiation

Answer 16

X-ray photons that are not produced at the focal spot. Some have enough energy to go through the window and strike the object being images = ghost image. Does not contribute to detail.