This document discusses various types of personal dosimeters used to measure radiation exposure, including film badges, pocket chambers, pocket dosimeters, and TLDs (thermoluminescent dosimeters). Film badges use multiple filters and sensitive films to measure different types of radiation. Pocket chambers and dosimeters can measure accumulative doses more frequently but require charging. TLDs measure light emitted from crystals when heated to determine exposure and can store doses over long periods. The document provides details on the components, operation, advantages, and disadvantages of each dosimeter type.

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2. Prepared by :
Seyedeh Shabnam Mousavi
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3. Summary
 Introduction of dosimetery
Introduction of personal dosimeters
 Film badge - structure
- advantage & disadvantages
- function
Pocket chamber - structure
- reading & charging
Pocket dosimeter - structure
- reading & charging
 TLD
New device for personal dosimetry 3

4. Ionization radiation
Not audible, not visible
Product ion , biological effects happen with delay
Dosimetery : description of radiation beam &
effects on environment
Exposure: producted pair ion in the air(Rontgen)
Dose & Kerma : absorbed dose per Kg (Gy)
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5. Dose
Absorbed dose
Equivalent dose
Effective dose
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6. Principle of radiation protection
Time
Distance
Shielding
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7. Permitted dose limit
Staff: 20 mSv
Public : 1 mSv
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8. Personal monitoring
 People who are exposed by ionizing radiation need
personal monitoring programs.
 Personnel should wear dosimeter when the
possibility of such exposure exists.
 Personal monitoring isn’t radiation protection
instrument ; but it is a method for measuring
radiation.
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9. Types :
 Film badge
 Pocket dosimeter
 Pocket chamber
 TLD
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10. Film badge
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11. Introduction
 The primary personal dosimetry instrument
Determining x-ray , gamma, beta, and neutron
 Is changed for twice a month
Range of radiation: 5-500 mR
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12. Outside structure
Badge : holder with 8 filters
 Part for the consumer profile
 Clamp
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13. Badge
Protecting the film during use
 Filters are placed on both the back & front of the
holder
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14. Inside structure
 Film : measuring radiation through density
Opening window : determine beta beams
 7 filters : allow some energy types to pass,
while blocking others
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15. Film
 At the core of a dosimeter badge
 Reacting to radiation & is surrounded by a case
to prevents from light & moisture
 A badge contain:
- several films of different sensitivities
OR
- single film with multiple emulsion coating
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16. Filter
 Choosing filter depend on the kind of
radiation
The purpose of using them is determining
types of radiation
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17. Filter cont.
 Plastic filter : 50 mg/cm²
Plastic filter : 300 mg/cm²
 Alloy of Al & Cu
 Alloy of Cd & Pb
 Alloy of Sn & Pb
 Lead border
 Indium
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18. Advantages
Inexpensive
Easy to use
Providing a permanent record
Requiring no technical knowledge
Less vulnerable than the other methods of
dosimetry
Determining the types & amount of radiation
energy to predict the biological consequences
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19. Advantages cont.
 Show the direction of radiation
 Judging the standards of environment
Distinguish the primary radiation from scatter
 High spatial resolution
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20. Disadvantage
 Non reusable
 Failure to detect low-energy beams
 It is not accurate for any exact measurement
 Isn’t used for long time
 Less sensitivity in comparison with the other
personal dosimeter devises
 No immediate diagnosis
Sensitivity decrease outside the energy range
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21. How do you use them?
 Its number is specified for a person
 Badge shouldn’t have more or less part
 Film must not have holes
 Film-badge is worn in front of the chest
 Film-badge must not exposure by ionizing
beam when you don’t use it.
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22. Operation
 Film-badge measure radiation when ionizing
radiation confront with silver halide
 Film density is depend on quantity of radiation
 Photoelectrical densitometer read film density
 Small change of emulsion cause large change in
quantity repliment to radiation
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23. Relation between radiation & density
curve
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24. Any question?
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25. Dosimetry by pocket instrument
Is useful when exposure needs to be monitored
more frequently
 Measure accumulative doses
 Quantities x-ray , gamma & even beta & neutron
 2 types: pocket chamber & pocket dosimeter
 Dimensions: length: 4.5 inch , diameter: 0.6 inch
 Weight : 250 grams
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26. Pocket chamber
(indirect reading dosimeter)
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27. Outward structure
 Aluminum cap
 Aluminum terminal head
 Low atomic number wall
 Clip
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28. Inside structure
 Act as an air-filled condenser like thimble -
chamber
 Calibrated by Cs , Co , Ra gamma radiation
 Insulator is penetrated at one end to serve as
charging contact
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29. Inside structure cont.
Has 2 electrodes:
- aluminum rod as central electrode
- chamber’s outer wall as second electrode
 The central electrode was suspended at each
end with a polyethylene insulator
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30. How it works ?
 Voltage depressure is the base of pocket chamber
 Electrical discharge is proportional to ionization
 Pocket chambers need to be charge after reading
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31. How we read & charge
pocket chamber?
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32. Correct dosimeter placement
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33. Looking to indicator
& microscopic scale
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34. Dosimeter reset by charging
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35. User can manipulate charger knob to
reset indicator( upscale, downscale)
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36. Reading & Charging
pocket dosimeter (Cont.)
 No batteries required
 Charging with electro physiologic crystals
 Has a lever & button
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37. Pocket dosimeter
(direct reading)
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38. Inside structure
 Small ionizing chamber
 Lens & scale
 Movable fiber
 Charging contact
 Graphite inner wall
 Central wire anode with metal coated quartz fiber
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39. Outward structure
 Walls is made of aluminum or some of plastics
 Clip
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40. How it works?
 charge of anode by positive potential
distributed between wire & fiber
 quartz fiber deflected by electrostatic
repulsion
 Greater charge cause greater deflection
Radiation produce ionization and electron
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41. How it works? (Cont.)
 electrons attracted to , & collected by
positively charged central anode
 electron collection reduce the net positive
charge
In result, quartz fiber return to right position
 Fiber movement is proportional to ionization
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42. Reading & Charging
pocket dosimeter
Pointing dosimeter at a light source
Looking through lenses
Fiber is viewed on a graduated translucent
scale
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43. Reading & Charging
pocket dosimeter
(Cont.)
 Pocket dosimeters charge by handheld
charger through squeezing the lever
 Dosimeter placed in or remove from charger
by pulling a trigger
 Clamping action hold dosimeter
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44. pocket chamber vs. pocket dosimeter
 pocket chamber needs to reader instrument
 pocket dosimeters are larger
Pocket dosimeter are more energy dependent
 pocket chambers were far less expensive
 pocket chamber is more reliable
 chamber dosimeter have to be charged every
time they were read
For military purposes chamber dosimeter is
desirable
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45. Properties
 Is absolute , stable, directional dependence &
user friendly device
 Accuracy: within ±1% of true exposure
 Ranges: 0-200 mRem , 0-600 mRem
 Temperature range: -20 °C – 50 °C
 Relative humidity: up to 90%
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46. Advantages
 Reading exposure frequently
 They are reusable
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47. Disadvantages
They discharge automatically
 They are affected by charge leakage & natural
radiation
 They can’t record permanent dose
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48. Any question?
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49. TLD
Thermo luminescent dosimeter
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50. Introduction
 A thermo luminescent dosimeter, or TLD, is a type
of radiation dosimeter.
 A TLD measures ionizing radiation exposure by
measuring the amount of visible light emitted from a
crystal in the detector when the crystal is heated.
 The amount of light emitted is dependent upon the
radiation exposure.
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51. TLD material
Lithium fluoride
Lithium borate
Calcium fluoride
Calcium sulfate
Calcium ferrate
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52. TLD forms
common types of TLD are:
Bulk granulated
Compressed pellets or “chips”
 Teflon matrix
Single-crystal plates
Powder enclosed in plastic tubing that can be heated
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53. TLD machines
 TLD reader
 Heater
 Photo multiplier tube
 Electronic system
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54. Personal dosimetery by TLD
 Ability to store doses over long periods.
 It can be read by automated system and is fast.
 It can be held in film badge holder.
 Low doses can be measured.
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55. Advantages
 Small size
 Wide useful dose range, from a few millirads to ~103 rad
 Economy. Reusability usually reduces cost per reading
 TLD phosphors can normally be reused many times until they
become permanently damaged by radiation, heat or
environment.
 Readout convenience
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56. Disadvantages
 low Precision
 Loss of information if heated
 Fading
 Reader instability
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57. New devices for personal dosimetry
digital electronic dosimeter
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58. Thanks
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