Instrumentation Flashcards
____ is sensed by detecting the ionizations of gas molecules produced by deposition of energy during radiation’s passage. (Gas Filled Detectors)
Radiation
_____ radiation interacts with the e- structure of an atom
Ionization
______ the energy required to knock e- out of its orbit ( the energy of the radiation must be greater than the binding energy of the e-)
Ionization energy
____ positive charged gas molecule and an e- that are produced as a result of ionization.
Ion pair
A gas filled detector contains 2 electrodes
-Positive electrodes(anode)
-Negative (cathode)
A gas filled detector is filled with what gases?
He,Ne,Ar,H or air
Why are noble gases used instead of of air
They are more dense- it gives them a greater probability of interaction better efficiency
The atmosphere of the gas is usually increased to ______
5 to 12 times more gas within the detectors
Voltage source does what to the electrodes
Applies a voltage
Current measuring device:
Measures current coming from the electrodes
How does a gas detector work ? Steps
- Radiation enters the chamber and causes an ion pair
- Ion pair is produced from the interaction of radiation with an e- from the gas
- Due to the voltage placed on the electrodes an positive gas molecule is attracted to the cathode
- E- is attracted to the anode
- When the e- and gas molecule reach the perspective electrodes a charge is produced
- The charges produce a current( amps)
- The current is being measured
- The amount of current measured is proportional to the strength of the radiation (stronger radiation means higher current)
There are 3 types of gas filled detectors that we use:
- Ionization chambers
- Proportional chambers
- GM Detectors
The voltage applied to the gas filled doctor determines the one we use
What does the voltage curve shows:
As you increase voltage what happens to the number of ion pairs produced(more are produced)
Each type of radiation has an amount of ionizing force a higher amount of ionizing force produces more
Ion pairs
Alpha has a higher ionizing force than
Beta( alpha produced 100 time more ion pairs than beta)