1. Principles of Radiation Detection
Operational Radiological Safety Course
U.S. Army Chemical Biological Radiological & Nuclear School
Edwin R. Bradley Radiological Lab
031RDB01

2. 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

3. 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.

4. Two Main Principles of Radiation Detection
Electrical collection of ions
Air Ionization
Gas Ionization
Scintillation
Light Production

5. Ionization Chamber Electrical collection of ions
No gas amplification (air)
Used to measure dose rate
Sensitive to environmental changes
Battery or High Voltage
Resistor
(-) Cathode + -
(+) Anode e-

6. Gas Filled Detector (1) (+) Anode Resistor (-) Cathode - +
Battery or High Voltage

7. Gas Filled Detector (2) + e- (+) Anode Resistor (-) Cathode - +
Battery or High Voltage

8. Gas Filled Detector (3) e- (+) Anode Resistor (-) Cathode - +
Battery or High Voltage
Resistor
(-) Cathode + -
(+) Anode e-

9. Gas Filled Detector (4) + e- (+) Anode Resistor (-) Cathode - +
Battery or High Voltage

10. Gas Filled Detector (5) V=IR + (+) Anode Resistor (-) Cathode e- - +
Battery or High Voltage

11. GAS FILLED DETECTOR RESPONSE
Breakdown Region
Geiger Mueller Region
Log of Electrical Signal
Proportional Region
Ionization Region
Recombination
Applied Tube Potential (Voltage)

12. Geiger Mueller Counter
Most common type of detector
Gas amplification
Multiplication factor
Long dead time
Energy dependence
Variety of uses
Count rate
Dose/Dose rate
Surface activity
Battery or High Voltage
Resistor
(-) Cathode + -
(+) Anode e-

13. 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

14. 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

15. Proportional Counters
Alpha-Beta discrimination
Gas multiplication 106
Low dead time
Used in labs and neutron detectors
Alpha+Beta
Beta
Electrical Signal
Background

16. Proportional Counters

17. Scintillation Detector (Light Production)+ -
Scintillator
Photo Cathode
Focusing cup
Dynodes HV
Resistor

18. Scintillation Detector (Light Production)+ -
Scintillator
Photo Cathode
Focusing cup
Dynodes HV
Resistor e-

19. 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).

20. Liquid Scintillation Counter
Low energy beta and alpha
Solvent mixed with scintillating material
Very low background
Laboratory instrument + -
Photo multiplier tube
Liquid Scintillation Counter
Counting Circuit
LSC Vial

21. Liquid Scintillation

22. Multi-Channel Analysis
Channel Number (Energy)
Number of Counts
Photo Peak
Compton Edge

23. Multi-Channel Analysis
identiFINDER

24. Thermoluminescent Dosimeter
Stores absorbed energy
Crystalline material
Read by heating and detecting emitted light
Primary occupational dosimeter

25. Thermoluminescent Dosimeter
Whole Body and Wrist TLD Holders
Panasonic UD-802AS Dosimeter
Harshaw DXT-RAD Ring TLD

26. Semi Conductor Detectors
High energy resolution
Low efficiency for gamma (Diode Detector)
High efficiency for gamma (Ge Detector)
Must be liquid nitrogen cooled (PINS)

27. Semi Conductor Detectors
High-purity Germanium

28. 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