Ch.9 Review Questions Flashcards
Why must an X-ray tube be vacuumed of all gas?
So that
What is the approximate efficiency of X-ray productions by an X-ray tube?
.5 %
What type of X-ray tube uses a wire mesh to hold back the space charge until exposure?
Grid controlled tubes
Name three things that happen during Bucky radiography when the rotor switch is depressed.
The filament heats
The anode disc spins
The Bucky oscillates
Name the process that provides a source of free electrons in the X-ray tube.
Thermionic emission
What is the focusing cup usually made of?
Molybdenum or nickel
What element is added to the tungsten filament to extend its life?
Thorium
What element is added to the tungsten focal track to help balance the spin of the anode disc?
Rhenium
By what ratio is the electron beam narrowed by the time it reaches the anode?
1/20th
Molybdenum is used for the anode shank because it is a ____ conductor of heat and a ____ conductor of electricity.
Poor, good
What are the typical spin rates in rpm for standard rotoring? High speed rotoring?
3400 rpm
10000 and greater rpm
A the X-ray tube ages what is the ever louder shushing sound made after each exposure?
Warped ball bearings
The copper anode cylinder in the tube and the stator windings outside the tube together form what?
Induction motor
Why are high mA stations not accessible when a small focal spot is engaged?
There are limitations on the heat capacity for the filaments chosen
As an X-ray tube ages the effective mA produced at the filament_____. ( increases, decreases, stays the same)
Increases
