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Transcript of 1 Principles of Radiation Detection Operational Radiological Safety Course U.S. Army Chemical...
11
Principles of Radiation Principles of Radiation DetectionDetection
Operational Radiological Safety CourseOperational Radiological Safety CourseU.S. Army Chemical Biological Radiological & Nuclear SchoolU.S. Army Chemical Biological Radiological & Nuclear School
Edwin R. Bradley Radiological LabEdwin R. Bradley Radiological Lab031RDB01031RDB01
44
Two Main Principles of Two Main Principles of Radiation DetectionRadiation Detection
Electrical collection of ionsElectrical collection of ions– Air IonizationAir Ionization– Gas IonizationGas Ionization
ScintillationScintillation– Light ProductionLight Production
55
Ionization ChamberIonization Chamber
Electrical collection of ionsElectrical collection of ions
No gas amplification (air)No gas amplification (air)
Used to measure dose rateUsed to measure dose rate
Sensitive to environmental changesSensitive to environmental changes
http://www.drct.com/specials/eberline.htm
Battery or High Voltage
Resistor (-) Cathode
+ -
(+) Anode
e-
+
66
Gas Filled Detector (1)Gas Filled Detector (1)
Battery or High Voltage
Resistor (-) Cathode
(+) Anode
+ -
77
Battery or High Voltage
Resistor (-) Cathode
+ -
(+) Anode
e-+
Gas Filled Detector (2)Gas Filled Detector (2)
88
Gas Filled Detector (3)Gas Filled Detector (3)
Battery or High Voltage
Resistor (-) Cathode
+ -
(+) Anodee-
+
99
Gas Filled Detector (4)Gas Filled Detector (4)
Battery or High Voltage
Resistor (-) Cathode
+ -
(+) Anodee-
+
1010
Gas Filled Detector (5)Gas Filled Detector (5)
Battery or High Voltage
Resistor (-) Cathode
+ -
(+) Anode
e-
+
V=IR
1111
Log
of E
lect
rical
Sig
nal
Applied Tube Potential (Voltage)
Recombination
GAS FILLED DETECTORGAS FILLED DETECTORRESPONSERESPONSE
Ionization Region
Proportional Region
Geiger Mueller Region
Breakdown Region
1212
Geiger Mueller CounterGeiger Mueller CounterMost common type of detectorMost common type of detector Gas amplification Gas amplification Multiplication factor 10Multiplication factor 1088-10-101010
Long dead timeLong dead timeEnergy dependenceEnergy dependenceVariety of usesVariety of uses– Count rateCount rate– Dose/Dose rateDose/Dose rate– Surface activitySurface activity
Battery or High Voltage
Resistor(-) Cathode
+ -
(+) Anodee-
+
1313
AN/VDR-2AN/VDR-2
Beta/Gamma ProbeBeta/Gamma Probe
Measures and detects gamma photon energyMeasures and detects gamma photon energy
Detects moderate to high energy BetaDetects moderate to high energy Beta
particle emissionparticle emission
Neon-halogen gas (Gas Ionization)Neon-halogen gas (Gas Ionization)
Display Display µGy and µGyph to Gy and GyphµGy and µGyph to Gy and Gyph
Operates in GM regionOperates in GM region
Gas Filled DetectorGas Filled Detector
1414
AN/PDR 77AN/PDR 77
Beta/Gamma ProbeBeta/Gamma Probe
Measures and detects gamma photon Measures and detects gamma photon energyenergy
Detects moderate to high energy BetaDetects moderate to high energy Beta
particle emissionparticle emission
Neon-halogen gasNeon-halogen gas
Display Display 0 – 999K mR/h0 – 999K mR/h
Operates in GM regionOperates in GM region
Gas Filled DetectorGas Filled Detector
1515
Proportional CountersProportional Counters
Alpha-Beta discriminationAlpha-Beta discrimination
Gas multiplication 10Gas multiplication 1066
Low dead timeLow dead time
Used in labs and neutron detectorsUsed in labs and neutron detectors
Alpha+BetaBeta
Beta
Alpha+Beta
Elec
trica
l Sig
nal
Background
1616
Proportional CountersProportional Counters
1717
Scintillation DetectorScintillation Detector(Light Production)(Light Production)
+
-
Scintillator
Photo Cathode
Focusing cup
Dynodes
HV
Resistor
1818
Scintillation DetectorScintillation Detector(Light Production)(Light Production)
+
-
Scintillator
Photo Cathode
Focusing cup
Dynodes
HV
Resistor
e-
e-
1919
AN/PDR 77AN/PDR 77
Alpha Probe (Zinc Sulfide (ZnS) Scintillator)Alpha Probe (Zinc Sulfide (ZnS) Scintillator) Measures and detects alpha particle radiation in disintegrations per minute (dpm).Measures and detects alpha particle radiation in disintegrations per minute (dpm).
Scintillation DetectorScintillation Detector
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).
2020
Liquid ScintillationLiquid Scintillation
Low energy beta and alphaLow energy beta and alpha
Solvent mixed with scintillating materialSolvent mixed with scintillating material
Very low backgroundVery low background
Laboratory instrumentLaboratory instrument
+
-
+
-
Photo multiplier tubePhoto multiplier tube
Liquid Scintillation CounterCounting Circuit
LSC Vial
2121
Liquid ScintillationLiquid Scintillation
2222
Multi-Channel AnalysisMulti-Channel Analysis
Channel Number (Energy)
Num
ber
of C
ount
s
Photo Peak
Compton Edge
2323identiFINDER
Multi-Channel AnalysisMulti-Channel Analysis
2424
Thermoluminescent DosimeterThermoluminescent Dosimeter
Stores absorbed energyStores absorbed energy
Crystalline materialCrystalline material
Read by heating and detecting emitted Read by heating and detecting emitted lightlight
Primary occupational dosimeterPrimary occupational dosimeter
2525
Panasonic UD-802AS Dosimeter
Whole Body and Wrist TLD Holders
Harshaw DXT-RAD Ring TLD
Thermoluminescent DosimeterThermoluminescent Dosimeter
2626
Semi Conductor DetectorsSemi Conductor DetectorsHigh energy resolutionHigh energy resolution
Low efficiency for gamma (Diode Detector)Low efficiency for gamma (Diode Detector)
High efficiency for gamma (Ge Detector)High efficiency for gamma (Ge Detector)
Must be liquid nitrogen cooled (PINS)Must be liquid nitrogen cooled (PINS)
http://www.missouri.edu/~glascock/naafig5.gif
2727
High-purity Germanium
Semi Conductor DetectorsSemi Conductor Detectors
2828
SummarySummary
Principles of radiation detectionPrinciples of radiation detection– Electrical collection of ionsElectrical collection of ions
Gas ionizationGas ionization
Air ionizationAir ionization
– Scintillation - Light productionScintillation - Light production
Characteristics of sensitive detectorsCharacteristics of sensitive detectors– Dense detecting mediumDense detecting medium– High efficiencyHigh efficiency– Low backgroundLow background