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6 Cards in this Set
- Front
- Back
- 3rd side (hint)
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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?
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thermoluminescence or TLD for thermoluminescencent dosimeters
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how are electrons "trapped' in the crystal?
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between the valence and conduction band. why do pure crystals have poor TLD properties and what can be done to make them better?
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pure crystals have clear area between valence and conduction bands. by introducing an impurity, electron traps are created
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_____________ is the immediate release of light by material when receiving energy from ionizing radiation and _______________ is delayed emission of energy as light
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Fluorescence is the immediate release of light by material when receiving energy from ionizing radiation and phosphorescence is delayed emission of energy as light
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How is a TLD read?
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It is heated and the light emitted is plotted against temperature, with different peaks representing energy levels, what is this called?
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glow curve
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What is annealing and why is it necessary?
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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
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What are the 7 advantages of a lithium flouride TLD
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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 |
