Principles of Radiation Detection

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Principles of Radiation Detection

• Operational Radiological Safety Course
• U.S. Army Chemical Biological Radiological
  Nuclear School
• Edwin R. Bradley Radiological Lab
• 031RDB01

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Terminal Learning Objective

• Action Identify the principles of radiation
  detection
• Condition In a classroom environment, given
  PowerPoint slides
• Standards Identify the 2 principles of radiation
  detection and the characteristics of sensitive
  detectors

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Administrative Data

• Safety Requirement None
• Risk Assessment Low
• Environmental Considerations None
• Evaluation Students must score at least 70
  (80 for BOLC) on the end-of-course written test.

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Two Main Principles of Radiation Detection

• Electrical collection of ions
• Air Ionization
• Gas Ionization
• Scintillation
• Light Production

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Ionization Chamber

• Electrical collection of ions
• No gas amplification (air)
• Used to measure dose rate
• Sensitive to environmental changes

http//www.drct.com/specials/eberline.htm
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Gas Filled Detector (1)
() Anode
Resistor
(-) Cathode
-

Battery or High Voltage
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Gas Filled Detector (2)

e-
() Anode
Resistor
(-) Cathode
-

Battery or High Voltage
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Gas Filled Detector (3)
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Gas Filled Detector (4)

e-
() Anode
Resistor
(-) Cathode
-

Battery or High Voltage
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Gas Filled Detector (5)

() Anode
Resistor
VIR
(-) Cathode
e-
-

Battery or High Voltage
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GAS FILLED DETECTORRESPONSE
Log of Electrical Signal
Applied Tube Potential (Voltage)
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Geiger Mueller Counter

• Most common type of detector
• Gas amplification
• Multiplication factor 108-1010
• Long dead time
• Energy dependence
• Variety of uses
• Count rate
• Dose/Dose rate
• Surface activity

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Gas Filled Detector

• AN/VDR-2
• Beta/Gamma Probe
• Measures and detects gamma photon energy
• Detects moderate to high energy Beta
• particle emission
• Neon-halogen gas (Gas Ionization)
• Display µGy and µGyph to Gy and Gyph
• Operates in GM region

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Gas Filled Detector

• AN/PDR 77
• Beta/Gamma Probe
• Measures and detects gamma photon energy
• Detects moderate to high energy Beta
• particle emission
• Neon-halogen gas
• Display 0 999K mR/h
• Operates in GM region

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Proportional Counters

• Alpha-Beta discrimination
• Gas multiplication 106
• Low dead time
• Used in labs and neutron detectors

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Proportional Counters
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Scintillation Detector(Light Production)
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Scintillation Detector(Light Production)
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Scintillation Detector

• AN/PDR 77
• Alpha Probe (Zinc Sulfide (ZnS) Scintillator)
• Measures and detects alpha particle
  radiation in disintegrations per minute (dpm).

X-ray Probe (Sodium Iodide (NaI) Scintillator)
Primary use to detect fission isotopes
Measures and detects Pu239 U235 x-ray (17
keV 60 keV average energies from the daughter
products of Pu239 and U235).
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Liquid Scintillation

• Low energy beta and alpha
• Solvent mixed with scintillating material
• Very low background
• Laboratory instrument

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Liquid Scintillation
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Multi-Channel Analysis
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Multi-Channel Analysis
identiFINDER
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Thermoluminescent Dosimeter

• Stores absorbed energy
• Crystalline material
• Read by heating and detecting emitted light
• Primary occupational dosimeter

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Thermoluminescent Dosimeter
Whole Body and Wrist TLD Holders
Panasonic UD-802AS Dosimeter
Harshaw DXT-RAD Ring TLD
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Semi Conductor Detectors

• High energy resolution
• Low efficiency for gamma (Diode Detector)
• High efficiency for gamma (Ge Detector)
• Must be liquid nitrogen cooled (PINS)

http//www.missouri.edu/glascock/naafig5.gif
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Semi Conductor Detectors
High-purity Germanium
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Summary

• Principles of radiation detection
• Electrical collection of ions
• Gas ionization
• Air ionization
• Scintillation - Light production
• Characteristics of sensitive detectors
• Dense detecting medium
• High efficiency
• Low background