Detectors Flashcards
What do detectors do
Count amount of interactions and dose delivered to the patient
What do ionisation chambers do?
Ionization chambers essentially measure radiation by creating an electric current when radiation passes through them. This current tells us how much radiation there is.
How does an ionisation chamber work?
Big chamber full of air
And radiation is fired in the volume of air.
There’s two electrons each side , anode and cathode.
The neg ions go to anode and pos to to cathode.
The ammeter gives a reason of how many neg ions are collected and that is the xrays emitted.
What is a GIEGER MULLER TUBE
a gas filled detector that detects radiation but not exposure.
It needs very high voltage.
Made of metal
How does is a GM tube created
Tube is filled with argon gas
Voltage is applied to the wire in the middle
Particles enter the tube and oils electron from Argos gas
Election is attracted to wire and rushed through it hitting other electrons creating an avalanche.
Creating a pulse which can be calculated.
What is the dead time and recovery time in a GM tube like
No pulses can be produced after dead time.
So it’s only produces a limited till the recovery time elapses.
Not an accurate count of electrons.
This means it’s ineffective.
Disadvantages and advantages of a GM tubes
Advantage:
Rapid,
Large output signal
Sensitive
Disadvantage:
Energy dependence
Doesn’t measure exposure
Long dead time
