X-Ray Tubes (2) Flashcards
How are x-rays developed?
Generated when an electron is accelerated and decelerated rapidly - interacts with dense atomic particles (tungsten target)
Prior to 1913 most x-ray tubes were referred to as___.
Gas tubes due to the fact that they generally contained a high amount of residual gases.
prior 1913 x-ray tubes were
- unreliable (fluctuations in gas temp and pressure)
- max energy 130kV
- taget material = platinum
What are the different types of x-ray tubes?
- bipolar
- unipolar
- rotating anode tube
Bipolar x-ray tubes
- most common
- most portable
- built-in high voltage transformer
- 150-450kV max
different housing can emit 4000kV max
Unipolar x-ray tubes
only cathode has a potential difference, anode is at ground potential
Rotating Anode Tubes
Rotating target self-cools by constantly rotating
exposures can be performed in “fractions” of seconds
list the X-Ray tube controls
- Milliamperage (mA)
- Kilovoltage (kV)
- timer
What does the mA control do?
Governs the amount of electricity going to the negative cathode.
1amp = 6.3x10¹⁸ electrons through a conductor per second
most tubes are limited to 10mA
What does the kV control do?
Governs the energy potential between the negative cathode and positive anode.
voltage that moves electrons (current) through the circuit, higher voltage = faster moving electrons.
amount of voltage required to move 1amp of current through the circuit per second.
What does the Timer control do?
Governs the duration for the x-ray shot.
longer the tube is energized the more x-rays will penetrate the part and more photons will reach the film.
Two types of X-ray Generation
AC (alternating current)
Constant Potential Systems
What are AC x-rays?
Alternating current is the power supply for the x-ray tube, but the current will only produce x-rays during 1/2 of the 1/60th second AC cycle
- valiance in energy levels
- needs filters
What are Constant Potential System x-rays?
tube rectifiers convert AC supply into a rectified AC that resemble a DC current
- uniform stream of mono-energetic radiation.
What are fashion tubes?
X-Ray Tubes that make use of AC for the production of x-rays in short bursts or pulses dependant on the frequency of AC applied.
What are Rectifiers?
Used to convert the AC power supply to emulate uniformity or DC.