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MEASUREMENT OF IONIZING RADIATION. Measurement of Ionizing Radiation. Objectives Familiarization with Detection Mechanisms Identify the Correct Instrument for the Job. Detection Mechanisms. Gas Filled Detectors Scintillation Semiconductor. Gas Ionization Regions.

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Presentation Transcript
measurement of ionizing radiation2
Measurement of Ionizing Radiation
  • Objectives
    • Familiarization with Detection Mechanisms
    • Identify the Correct Instrument for the Job
detection mechanisms
Detection Mechanisms
  • Gas Filled Detectors
  • Scintillation
  • Semiconductor
gas ionization regions
Gas Ionization Regions
  • Pulse Amplitude vs. Applied Voltage
    • Ion Saturation
    • Proportional/Limited Proportional
    • Geiger-Mueller
ion saturation detectors
Ion Saturation Detectors
  • Common Detectors
    • Pocket Dosimeter
    • Ion Chamber
    • Pressurized Ion Chamber
pocket dosimeter
Pocket Dosimeter
  • Uses Charge Integration
  • Exposure Readout With Quartz Fiber Electroscope
  • Gamma/X-ray Only
  • Inexpensive
  • Poor Accuracy
ion chamber
Ion Chamber
  • Directly Quantifies Exposure Rate
  • Linear Energy Response
  • Gamma/X-ray/Beta(with window)
pressurized ion chamber
Pressurized Ion Chamber
  • Extremely Sensitive
  • Gamma/X-ray
  • High Background
  • Can be Expensive
proportional region detectors
Proportional Region Detectors
  • Common Detector
    • Gas Flow Proportional Counter
gas flow proportional counter
Gas Flow Proportional Counter
  • Can Integrate Source and Gas
  • Spectroscopy
  • Alpha/Beta/Low-Energy Gamma/X-ray
  • Can be Expensive
geiger mueller region detectors
Geiger-Mueller Region Detectors
  • Common Detector
    • Geiger Tube/G-M Counter
geiger tube
Geiger Tube
  • Pulse Amplitude Does Not Vary With Initiating Event
  • Output is Normally CPM
  • Non-Linear Energy Response
  • Can be Calibrated in Exposure Units
  • Alpha/Beta/Gamma/X-ray Depending on Window and Fill Gas
scintillation
Scintillation
  • Visible Light Produced After Excitation of a Substance
  • A Good Scintillator Converts a Large Fraction of Incident Radiation Energy Into Prompt Fluorescence
scintillation15
Scintillation
  • Zinc Sulfide used for alpha
  • Plastics and liquids used for Beta
  • Organic and inorganic crystals for x and gamma
  • Liquids used for all currently
scintillation detectors
Scintillation Detectors
  • Common Detectors
    • Solid Scintillator
      • Sodium Iodide, NaI
      • Thin Crystal NaI
      • Plastic
    • Liquid Scintillation Counter
solid scintillation detectors
Solid Scintillation Detectors
  • Thick Crystal Sodium Iodide
    • Extremely Sensitive
    • Used for Quantification and Identification
    • Gamma/High-Energy X-ray Only
    • Expensive
    • Poor Resolution
solid scintillation detectors18
Solid Scintillation Detectors
  • Thin Crystal Sodium Iodide
    • Good Sensitivity at Low-Energies
    • Low-Energy Gamma/X-ray Only
    • Highly Energy Dependent
    • High Background
solid scintillation detectors19
Solid Scintillation Detectors
  • Plastic Scintillator
    • Can be made into a Large-Volume Detector
    • Alpha/Beta/Gamma
    • Inexpensive
    • Low Light Output/Self-absorption a Problem
liquid scintillation counting
Liquid Scintillation Counting
  • Sample Integrated With Scintillator
  • Can be Highly Efficient
  • Widely Used for Low-Energy Beta Counting
  • Alpha/Beta
  • Quenching a Problem
semiconductors
Semiconductors
  • Electron-hole Pairs Created in a Semiconductor by a Charged Particle Generate the Signal
solid state detectors
Solid-State Detectors
  • Common Detectors
    • Silicon Diode
    • Lithium Drifted Silicon
    • High Purity Germanium
silicon diode
Silicon Diode
  • Charged Particle Spectroscopy
  • Superior Energy Resolution
  • Alpha/Heavy Ions
  • Limited to Small Sizes
  • Susceptible to Performance Degradation
lithium drifted silicon
Lithium Drifted Silicon
  • Low-Energy Photon Spectroscopy
  • Beta/Electron Detection and Spectroscopy
  • Superior Energy Resolution
  • Low-Energy Gamma/X-ray/Beta/Electrons
  • Must be Cooled With Liquid Nitrogen
  • Susceptible to Performance Degradation
high purity germanium detector
High Purity Germanium Detector
  • Gamma Ray Spectroscopy
  • Superior Energy Resolution
  • Gamma
  • Must be Cooled with Liquid Nitrogen
  • Susceptible to Performance Degradation