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6 Cards in this Set

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When a fraction of an irradiated crystal stores a fraction of its energy and this is released in the form of light upon heating what is this phenomenon called?
thermoluminescence or TLD for thermoluminescencent dosimeters
how are electrons "trapped' in the crystal?
between the valence and conduction band. why do pure crystals have poor TLD properties and what can be done to make them better?
pure crystals have clear area between valence and conduction bands. by introducing an impurity, electron traps are created
_____________ is the immediate release of light by material when receiving energy from ionizing radiation and _______________ is delayed emission of energy as light
Fluorescence is the immediate release of light by material when receiving energy from ionizing radiation and phosphorescence is delayed emission of energy as light
How is a TLD read?
It is heated and the light emitted is plotted against temperature, with different peaks representing energy levels, what is this called?
glow curve
What is annealing and why is it necessary?
one of the problems of a TLD is that it has a memory since not all of the trapped electrons are released. they have to be reset to a ground state by heating, for example a Lithium Flouride TLD is heated for 1 hr at 400 deg C then 24 hrs at 80 deg C. this is the annealing cycle
What are the 7 advantages of a lithium flouride TLD
1. useful over a wide range of doses
2. can be made into a variety of forms
3. effective atomic number similar to soft tissue
4. stored energy is stable for six months or more
5. reusable
6 accurate to 3%
7. small enough to put in places where a chamber cannot be placed(like body cavities)
list 2 disadvantages
1. no permanent record
2. must be annealed