The Xray Tube Head Flashcards
What charge does the cathode have?
Negative
What charge does the anode have?
Positive
Where are electrons produced?
At the cathode
What is the cathode?
A coiled wire filament made of tungsten
How are electrons produced?
The cathode filament is heated by a small electrical current and releases a cloud of electrons
What is the process that causes the cathode to release electrons?
Thermionic emission
Why is tungsten used as the cathode filament?
It has a night atomic number, 74, and therefore has many electrons
It has a very night me,ting point, 3380c, and so can safely be heated
It has helpful mechanical properties which mean that fine, coiled filaments can be made
What needs to be used between the tungsten filament and the mains power when heating the filament?
a step down transformer
How is the electron could made to travel from the filament to the target?
by applying a hight electrical potential difference between the filament and the target
When the potential difference is applied what happens to the filament?
It becomes a cathode (negatively charged) and repels the electrons
What happens to the target when the potential difference is applied?
it becomes and anode (positively charged) and attracts electrons
What is the focusing cup surrounding the filament made of?
Molybdenum
How does the focusing cup work?
creating a negative charge and repelling the electrons and guiding them into a narrow beam
What are milliamperes (mA)?
The measurement of the electric current created by the electrons across the tube
how is the total number of electrons emitted calculated?
multiplying the mA by the duration of exposure (s) = mAs
