1. Session II.3.2 Part II Quantities and Measurements
Module 3 Principles of Radiation Detection and Measurement
Session 2 Proportional and GM Detectors
IAEA Post Graduate Educational Course
Radiation Protection and Safe Use of Radiation Sources

2. Overview
In this session we will discuss the principle of measuring radiation using proportional and Geiger Mueller detectors

3. Gas Filled Detectors
As indicated in the previous lecture, ion chambers are the simplest of all gas filled detectors
An electric field is used to collect all the ionizations (positive and negative charged particles) produced by the incident radiation in the gas volume

4. Regions of a Gas Filled Chamber
Recombination
Region
The proportional region is located where the voltage is high enough to produce secondary ionizations. The voltage causes the electrons liberated by the incident radiation to have enough energy that they are able to ionize additional atoms. Since these secondary ionizations were not produced by the incident radiation they do not carry any information relating to the incident radiation. The signal produced by these and the originally liberated electrons is “proportional” to the energy carried by the incident radiation but not equal to it.
When the voltage has been increased sufficiently, the electrons liberated by the initial incident radiation have enough energy to ionize other atoms and those electrons also are able to ionize additional atoms resulting in a chain reaction of ionizations until the entire volume has essentially been ionized. The result is an electronic pulse which is independent of the amount of energy initially deposited by the incident radiation. All types of radiation and all energies will produce the same effect if they interact with the atoms inside the chamber. This is the GM region.

5. Operating Regions of a Gas Filled Detector
Recombination
Ionization
Proportional
Limited Proportional
Geiger Mueller
Continuous Discharge

6. Gas Flow Proportional Chamber
In this proportional chamber, a continuous flow of gas enters the chamber. This gas is ionized by the radiation emitted from the sample placed within the chamber. The liberated electrons are collected by the wire loop anode in the center of the chamber.

7. Directional and Energy Response
This GM detector responds differently depending on the direction of the incident radiation. It also responds differently depending on the energy of the incident radiation. At low energies, the radiation cannot penetrate the walls of the detector. Since this type of detector has a very thin window at the end, radiation incident from that direction more readily enters the chamber.
However, the detector over-responds to the low energy photons since it was calibrated with high energy photons from 137Cs.

8. Sample Geiger Muller
(GM) Detectors

9. Bicron Surveyor 2000
0-0.2 mR/h to 0-2,000 mR/h cpm to 0-240,000 cpm Exposure accuracy within 10% (per NRC reg. guide 10.8) Meets or exceeds 10CFR35 for nuclear medicine
Surveyor 2000 is compact, with doserate and countrate scales and controls for response time and audio. X-ray and gamma ray exposures are measured by an internal GM detector, and alpha, beta, X- or gamma countrates using a suitable external probe operating at 900 V. High voltage check, anti-saturation and dead time compensation are included.

10. Bicron “Radiographer”
A portable survey meter with an internal energy-compensated GM detector, the Radiographer also features automatic dead time compensation, anti-saturation circuit and HV and battery checks
Three linear ranges: mR/h to mR/h
Response times optimized for each range
Energy compensated: 40 keV to 1.2 MeV
Weighs only 1 kg

11. Detector System (UWDS)
Eberline Underwater
Detector System (UWDS)
Detects high gamma fields underwater. Underwater detector, 65' watertight cable and a Survey Meter which features a large, backlit digital display with analog bar graph. Data logging (up to 256 data points), adjustable alarms, and built in speaker with click rate proportional to the count rate.
FEATURES - Energy compensated GM tube with a range of 10 mR/h to 10,000 R/h - Watertight detector down to 20m  
Detector Size 3.5 cm diameter x 23 cm long
Batteries - 2 standard "AA", 250 hrs with Alkaline, 500 hrs with Lithium
Simultaneous internal and external detector rate measurements          
OPTIONS - Stainless steel detector housing to facilitate easy decontamination  - "Smart Probe" with stored calibration parameters

12. Ludlum 44-9 “pancake” GM INDICATED USE: Alpha beta gamma survey
DETECTOR: Pancake type halogen quenched GM
WINDOW: 1.7 plus or minus 0.3 mg/cm2 mica
WINDOW AREA: Active - 15 cm2 ; Open - 12 cm2
EFFICIENCY(4 geometry): Typically 5% - C14; 22% - Sr90/Y90; 19% - Tc99;
32% - P32; 15% - Pu239
SENSITIVITY: Typically 3300 cpm/mR/hr (Cs137 gamma )
ENERGY RESPONSE: Energy dependent
DEAD TIME: Typically 80 microseconds
COMPATIBLE INSTRUMENTS: General purpose survey meters, ratemeters, and scalers
OPERATING VOLTAGE: 900 volts
CONNECTOR: Series "C" (others available )
CONSTRUCTION: Aluminum housing with beige polyurethane enamel paint
TEMPERATURE RANGE: -20oC to 50oC
SIZE: 4.6 cm H X 6.9 cm W X 27.2 cm L
WEIGHT: 0.5kg

13. Eberline Monitor 4 (pocket sized meter) FEATURES Compact Easy to Use
Low Cost
Carrying Case Included
DETECTOR
GM, uncompensated
RANGES
0.5, 5, 50 mR/h and 500, 5k, 50k cpm
OPTIONS
Energy Compensated GM

14. Eberline HP-210 Series GM “pancake”
Application/Type: Beta/Gamma surveys; GM, non energy compensated
Dead Time: 50 usec nominal
Mica Window Size/Thickness: diameter (4.4 cm); 1.4 to 2.0 mg/cm2
Background Sensitivity: ~3,600 cpm/mR/h (137Cs)
Beta/Gamma Efficiency: ~22% 137Cs, ~16% 60Co
Beta Efficiency (4): ~ 32% 90Sr/90Y, ~ 15% 99Tc, ~ 6% 14C
Alpha Efficiency (4): ~ 25% 241Am
CONFIGURATIONS
Model HP-210AL: Aluminum with 1:1 window to bkg ratio (0.7 kg)
Model HP-210L: Lead shielded with 4:1 window to bkg ratio (1.9 kg)
Model HP-210T: Tungsten shield with 4:1 window to bkg ratio (1.9 kg)
Window Area: Active - 15 cm2 Open - 12 cm2
Window: 1.7  0.3 mg/cm2 mica
Sensitivity: ~ 3,300 cpm/mR/hr (137Cs )
Beta Efficiency (4): ~ 22% 90Sr/Y; 19% 99Tc; 5% 14C; 32% 32P
Alpha Efficiency (4): ~ 15% 239Pu
Ludlum 44-40

15. Eberline HP-190A End Window GM
Application: Alpha/Beta/Gamma surveys
Detector Type: GM, non energy compensated, end window
Operating Voltage: 900 V +/- 50 V
Dead Time: 200 uSec nominal
Mica Window Size: 1.1 diameter (2.8 cm)
Mica Window Thickness: 1.4 to 2.0 mg/cm2
Gamma Sensitivity: ~ 2,500 cpm/mR/h (137Cs)
Beta Efficiency (4): ~ 35% 90Sr/90Y, ~ 25% 99Tc, ~ 10% 14C
Alpha Efficiency (4): ~ 6% 241Am
Operating Temp: -30o to +60oC
Housing: ABS plastic
Connector: BNC
Size: 3.9 x 12.4 cm
Weight: 156 g

16. Eberline HP-271 Energy Compensated GM
Application: Beta/Gamma exposure surveys
Detector Type: Energy compensated GM
Detector Range: 3 R/hr (with dead time correction)
Energy Range: 30 keV to 6 MeV
Operating Voltage: 900 V +/- 50V
Dead Time: 100 uSec nominal
Wall Material: Stainless steel
Wall Thickness: 30 mg/cm2 (tube only)
Gamma Sensitivity: ~1,200 cpm/mR/h (137Cs)
Operating Temp: -40o to +63o C
Housing: ABS plastic with sliding beta shield
Connector: BNC
Size: 3.5 x 15.2 cm
Weight: 142 g

17. Ludlum Model 2401P “pocket meter”
DETECTOR: Built-In Pancake GM
SENSITIVITY: ~ 3,300 cpm/mR/hr (137Cs gamma)
ENERGY RESPONSE: Energy dependent
METER DIAL: mR/hr; cpm; BAT OK
MULTIPLIERS: X1, X10, X100
LINEARITY: Reading within 10% of true value
AUDIO: Built in speaker (quiet position on main switch to silence audio)
CALIBRATION CONTROLS: Accessible from front of instrument
RESPONSE: Typically 5 seconds from 10% to 90% of final reading
POWER: 1 ea. 9 volt
BATTERY LIFE: Typically 250 hours with alkaline batteries (battery condition
can be checked on meter )
CONSTRUCTION: Aluminum housing with beige polyurethane enamel paint, and a recessed subsurface printed membrane front panel
TEMPERATURE RANGE: -20 C to 50 C
SIZE: 4.6 cm H X 8.4 cm W X 13.5 cm L
WEIGHT: 0.4 kg including batteries

18. Ludlum Model 3-97EP
Explosion Proof NaI(Tl) Gamma Scintillator & Energy-Compensated GM
INDICATED USE: Gamma Survey
DETECTORS: 2.5 cm X 2.5 cm NaI(Tl) scintillator
SENSITIVITY: Typically 175 cpm/microR/hr (Cs-137 gamma)
ENERGY RESPONSE: Energy dependent - Energy compensated GM
ENERGY RESPONSE: Within 15% of true value from 60 keV - 3 MeV
WORKING ENVIRONMENT: Explosion proof housing for extreme environments
METER DIAL: mR/hr, BAT TEST
MULTIPLIERS: X0.1, X1, X10, X100, X1k
LINEARITY: Reading within 10% of true value with detector connected
CALIBRATION CONTROLS: Located in meter housing
RESPONSE: 4 seconds from 10% to 90% of final reading
RESET: Push-button to zero meter
POWER: 2 each "C" cell batteries
BATTERY LIFE: Typically 450 hours with alkaline batteries
CONSTRUCTION: explosion proof housing
TEMPERATURE RANGE: -20o C to 50o C
SIZE/WEIGHT: 16.5cm H X 20.3cm W X 17.8cm L; 6.4 kg including batteries

19. Proportional
Counters

20. Eberline E600 Survey Meter
+ NRD Detector
GENERAL DESCRIPTION
The model E600/NRD Combines E-600 Survey Meter with NRD neutron REM detector. The NRD is a 23 cm-diameter, cadmium-loaded polyethylene sphere with a BF3 tube in the center. Energy response closely follows the theoretical dose from neutrons over the energy range from eV thermal to about 10 MeV. The BF3 tube allows excellent gamma rejection.
FEATURES
Measures Thermal Through Fast Neutrons
Gamma Rejection Up To 500 R/h
Direction Independent Measurements
Background Subtraction
Data Logging
COMBINED DETECTOR/METER
Size/Weight: cm x 22.9 cm x 22.9 cm; 8.16 Kg
Operating Temperature: -20oC to +50oC
Operating Humidity: Up to 95% non-condensing

21. Eberline E600 Survey Meter
+ NRD Detector
DETECTOR
Detector: BF3 Tube in 23 cm cadmium loaded polyethylene sphere
Plateau: Approximately 200 V with a slope of 5% per 100 V
Operating Voltage: Dependant on sensitivity of counter and cable length;
typically 1,600 to 2,000 V.
Directional Response: Within 10%
Energy Range: Thermal to approximately 10 MeV
Gamma Rejection: Up to 500 R/h. Rejection is dependant on voltage selected.
Factory default is 10 mR/h.
Sensitivity: Approximately 45 cpm/mrem/h (3,000 counts per mrem)
SURVEY METER (E-600)
Count Range: 1 to 1.3 million cpm
Response Times: Slow, Medium, Fast. Each time setting is programmable from 0 to 255 seconds.
Dead Time Correction: 0 to 255 sec
Operating Modes: Ratemeter, Scaler, Integration, Peak Trap, Background
Accumulation.

22. Eberline E600 Survey Meter Eberline E600 Survey Meter
+ NRD Detector
Eberline E600 Survey Meter
+ SHP-400A
(Data Logging RO-20)

23. Ludlum Model 15 (---)
End Window GM Detector for Alpha Beta and Gamma
BF3 Proportional Detector with Moderator for Neutron
4 Ranges - Total Counting Range from ,000 cpm
INDICATED USE: Fast and thermal neutron, alpha, beta-gamma survey
DETECTORS: Controlled by selector switch
NEUTRON: Model 42-9 BF3 proportional detector with
7.6 cm diameter cadmium lined moderator for fast neutrons
(remove detector from moderator for thermal neutrons)
ENERGY RESPONSE: Count response is not linear throughout
energy spectrum ( MeV)
SENSITIVITY: Typically 60 cpm/mrem/hr (AmBe fast neutrons)
GAMMA REJECTION: Less than 10 cpm through 10 R/hr
ALPHA BETA-GAMMA: Model 44-7 thin end window GM detector
WINDOW: 1.7 0.3 mg/cm2 mica
WINDOW AREA: Active cm Open cm2
EFFICIENCY(2 geometry): Typically 5% - 14C; 20% - 90Sr/90Y; 15% - 239Pu
SENSITIVITY: Typically 2100 cpm/mR/hr (137Cs gamma)

24. Ludlum Model 15 METER DIAL: 0 - 500 cpm, 0 - 2.5 kV, BAT TEST
MULTIPLIERS: X1, X10, X100, X1000
LINEARITY: Reading within 10% of true value
RESET: Push-button to zero meter
AUDIO: Built in speaker with ON/OFF switch (greater than 60 dB at 0.6 m)
CALIBRATION CONTROLS: Accessible from front of instrument (protective cover provided)
RESPONSE: Toggle switch for FAST (4 seconds) or SLOW (22 seconds) from 10% to 90% of final reading
POWER: 2 each "D" cell batteries (housed in sealed compartment that is
externally accessible)
BATTERY LIFE: Typically 600 hours with alkaline batteries (battery condition
can be checked on meter)
METER: 6.4cm arc, 1 mA analog type
CONSTRUCTION: aluminum with beige polyurethane enamel paint
TEMPERATURE RANGE: -20oC to 50oC
SIZE: 31.8cm H X 8.9cm W X 21.6cm L
WEIGHT: 3.7 kg including batteries

25. “air proportional alpha”
Ludlum Model 43-44
“air proportional alpha”
INDICATED USE: Alpha survey
WORKING ENVIRONMENT: Splashproof shields and
desiccant vented chamber for outdoor use
WINDOW: 0.4 mg/cm2 aluminized mylar
WINDOW AREA: Active - 76 cm2 Open - 50 cm2
EFFICIENCY(4 geometry): Typically 8% 239Pu
COMPATIBLE INSTRUMENTS: Models 12, 16, 18, 2000,2200, 2221, 2241, 2350
OPERATING VOLTAGE: Altitude sensitive
Sea level volts
2000 feet volts
5000 feet volts
7000 feet volts
CONSTRUCTION: Anodized aluminum body with aluminum screen (65% open)
TEMPERATURE RANGE: -20 C to 50 C
SIZE: 10.2 cm H X 6.4 cm W X 22.9 cm L
WEIGHT: 0.5kg

26. Ludlum Model 44-110 The Model 44-110 is a windowless 100 cm2
gas proportional detector for tritium detection
INDICATED USE: Tritium surface survey
WINDOW: Windowless
WINDOW AREA: Active cm2 Open cm2
EFFICIENCY (4): Typically 25% - H3
BACKGROUND: Typically 400 cpm
OPERATING VOLTAGE: Typically 1700 volts
COUNTER THRESHOLD SETTING: Typically 4 mV
RECOMMENDED COUNTING GAS: P-10 (10% methane, 90% argon)
GAS PURGE TIME: Approximately 20 seconds
CONNECTOR: Series "C"
CONSTRUCTION: Anodized aluminum housing
TEMPERATURE RANGE: -20o C to 50o C
SIZE: 12.4cm H X 11.7cm W X 22.9cm L
WEIGHT: 0.9kg

27. Where to Get More Information
Cember, H., Introduction to Health Physics, 3rd Edition, McGraw-Hill, New York (2000)
Firestone, R.B., Baglin, C.M., Frank-Chu, S.Y., Eds., Table of Isotopes (8th Edition, 1999 update), Wiley, New York (1999)
International Atomic Energy Agency, The Safe Use of Radiation Sources, Training Course Series No. 6, IAEA, Vienna (1995)