Radiation Detectors

ę Brooke Clarke 2006 - 2011

Types of Radiation
Detector Types
    Ionization Chamber
    Dose Meters
    Bicron Surveyor 50
    The Polonium Pen
    Elektor PIN Diode Kit
    Electronic Goldmine Kit
    PocketGeiger (Japan)
    Liquid Scintillation Analyzer
Decay Times & the Sun

Types of Radiation

There are three common types of radiation: Alpha, Beta and Gamma.  They have different abilities of penetration.  Alpha is blocked by thin aluminum foil or just about anything.  Beta and Gamma will penetrate much more depending on their energy.  No known radiation is strong enough to penetrate the earth at it's center and go all the way through.
Ionizing radiation units -

Detector Types


These are the most common "Geiger Counter" sensors.  They are biased with enough voltage so that when an atomic particle gets into the gas it causes an avalanche.  The size of the output pulse is the same no matter what the energy of the input particle.  Although it's possible to turn down the voltage so that the output pulse has a relation to the input particle energy, the operation is then no longer called Geiger Mueller. 

There is a plateau in the count rate vs. applied voltage plot for a G-M tube and it should be operated on the plateau, not above or below.  The recomended voltage for most tubes is in the 500 to 900 volt area.

After the particle leaves the tube there is a recovery time.  If another particle enters the tube before the recovery time has passed the tube will conduct continuously.  This is bad because most Geiger counters will show zero when in fact they should be showing full scale.

The common G-M tube is a metallic cylinder with a wire insulated in the center.  One end typically has a mica window to allow alpha particles to enter.  But the end area is much smaller than the active area of a pancake type G-M tube.  Pancake G-M tubes are much more sensitive to alpha as well as beta and gamma rays than the cylindrical type tubes.

The end of a "hot dog" type G-M tube or the face of a "pancake" tube typically has a thin mica window.  Ideally for the detection of alpha particles there would be no window, but then the gas in the tube would except.  The density of the window puts a limit on the energy level of the alpha particles that can get into the tube (typically around 3 Mev).

Google "Geiger Mueller"

The sensivity of a G-M type tube can be greatly increased by adding more electrodes.
2397071 Radiation Detector, Gerhard Herzog (Texaco -  oil wells) - multiple cathode disks and multiple anode wires
2397072 Radiation Detector - multiple cathode disks and multiple anode wires
2397073 Radiation Detector - 5 to 10 times more sensitive than G-M tube, uses more electrodes, but has some volumes where the field is zero, hence there's a better way
2397074 Radiation Detector - very rugged
2397075 Radiation Detector - minimizes anode to cathode leakage (noise)

2873399 Radiation Detector - has no zero field volumes so is somewhat more sensitive than 5 to 10 times a G-M tube
2599352 Radiation Detector - greater cathode area by adding fins - more sensitive
2649554 Radiation Indicator, Anton - (beta & gamma dosemeter)
2699513 Radiation Detector -multiple anode wires in addition to increased cathode area


Some crystal or plastic that generates a photon of light when hit by a particle is coupled with a photo multiplier tube and both enclosed in a light tight package.  The output pulse is proportional to the energy of the input particle.

Ionization Chamber

An insulating chamber with some gas the ionizes under the influence of strong radiation.  Many of the surplus civil defense survey meters (often erroneously called geiger counters) use this type of detector.


This is a hand held magnifier focused on a screen made of Silver activated Zinc Sulfide and with an alpha emitter source like Po-210 Polonium (Anti-Static Brush) or AM-241 (Smoke Detector).  With a night adapted eye you can see the scintillation.  These show up on eBay, new from United Nuclear, old from antique instrument dealers.


There are many other ways of detecting atomic radiation.

Dose Meters

While Geiger counters measure the rate (i.e. counts per minute) a dose meter adds up the counts giving a total exposure.  These are usually in the form of badges that may have photographic film or electronic integrators or pen shaped electrometers.


One way to detect X-Rays is to use a Scintillator coupled to a photomultiplier tube in a light tight manner.  This was the method used on first generation CAT scanners.  The problem is that you can only have a small number of these around the circumference of a circle and so the spacial resolution is low.  GE developed X-Ray sensors using Xenon gas that can have many more sensors in the same space where there were only a few photomultiplier types.  As of 2008 this is a hot bed of activity since CAT is the prefered method of imaging many things in the human body (i.e. is prefered over MRI which is good for other things).
4031396 X-ray Detector, GE - multiple anode wires in a curved chamber for CAT scanner
4707607 High Resolution X-Ray Detector, GE - an even higher resolution detector using a flow of Xenon gas through the curved chamber for CAT scanner
7355181 Radiological imaging apparatus and radiological imaging method and radiological imaging support method, Hitachi - combines CAT and PET images
US 2007/0147576 A1 - X-Ray CT Apparatus and an Image Controlling Method Thereof, Toshiba - An X-ray CT apparatus and image controlling method thereof that achieves a higher time resolution tomography image on a region of interest (ROI) of an object while reducing a total amount of X-ray irradiation exposure.


Bicron Surveyor 50

Uses pancake G-M tube.  Ranges 0 - 0.5,  0 - 5 & 0 - 50 mR/hour.  9 volt battery.  Meter and when turned on clicks from speaker.


Military uses two hot dog type G-M types.  Started out in the early 1950s as an all tube instrument and has gone through many variations and now is mostly solid state and powered by 6 "D" batteries.

The Polonium Pen (Tech Lib web page)

The idea for this comes from the fact that Alexander Litvinenko (Wiki) died of radiation poisoning when Polonium (Wiki) was put in his drink.
Polonium is also found in cigarette smoke and some sea food.

Elektor PIN Diode Kit

The first article about using a PIN diode as an Gamma particle detector appeared in the June 2011 issue and was followed up with the final kit article in the November 2011 issue.  Note:  The pre-programmed microcontroller and other IC are on the other side of the black foam.
Elektor Improved
              PIN Diode Radiation Meter

Electronic Goldmine Kit

This kit was developed to make use of the Russian glass GM tube (Type SI 39 ) but the kit can be used with the SBM-10, SBM-19, SBM-20 and SBM-21, LND 713 & LND 714 GM tubes.

What's  needed:
PCB and parts kit by Electronic Goldmine p/n: G18410 (Chaney Electronic Kits p/n: G18410) - no GM tube, no box
Russian Geiger Counter Tube. Type SI 39, Electronic Goldmine p/n: G19129
Hammond 1593QBK box
Electronic Goldmine G18410
          Geiger Counter Kit

PocketGeiger Type 4 (Japan)

Based on using Photo diode as radiation detector.  Designed as low cost option for people near Fukushima nuclear plant.
Uses First Sensor AG (Germany)  X100-7 -
on order 1 Aug 2013  arrived 14 Aug 2013

This Type 4 pocket Geiger counter arrived as a fully assembled unit complete with the necessary apple audio cable.
Note: there are no internal batteries, it gets it's power from the iDevice sending out a very loud audio signal.
So that can work there are some Settings that need to be checked (my default settings were correct).

Reads in counts per minute (cpm) and micro Sievert (Wiki).

Then you load either the free Pocket Geiger app or the $7 Pro Pocket Geiger app.
How do they differ?

The counts per minute divided by 53 is the uSv/hour number.
Not sure how they came up with that calibration?

It takes 5 minutes to get a result.

Background Count (Wiki)
1.80 cpm
0.03+/-0.01 uSv/h
Pocket Geiger
                  Counter iPod Touch normal background
Am-241 both top and bottom (Wiki)
16.41 cpm
0.31+/-0.03 uSv/h
52.9 counts/uSv/h
Pocket Geiger Counter
                  iPod Touch Am-241
CS-137 (Wiki)
874.58 cpm
16.49 +/- 2.49 uSv/h
53.03 counts/uSv/h
Pocket Geiger Counter
                  iPod Touch CS-137

Autunite (Wiki)
248.59 cpm
4.69+/- 0.13 uSv/h
53.0 counts/uSv/h
Pocket Geiger Counter
                  iPod Touch Autunite
Vaseline Glass (Wiki)
6.40 cpm
0.12+/-0.02 uSv/h
53.3 counts/uSv/h
Pocket Geiger Counter
                  iPod Touch Vaseline Glass
Depleted Uranium (Wiki) with lead shield
48.04 cpm
0.91+/-0.06 uSv/h
52.8 counts/uSv/h
Pocket Geiger Counter
                  iPod Touch Depleted Uranium with lead shiled
Banana (Wiki: Banana Equivalent Dose)
3.00 cpm
0.06+/-0.01 uSv/h
50 counts/uS/h
Pocket Geiger
                  Counter iPod Touch Banana

Depleted Uranium (Wiki) without lead shield
Pocket Geiger Counter iPod Touch Depleted
                Uranium without lead shiled


The manual is on line.

These were on eBay selling for about the same price as the LND 712 tube.


Geiger Counter .............................  250 / 374+ 
    Design .................................  D10 / 47
    In nuclear reactions ...................  376 / 254

Geiger Muller Tube .........................  313 / 93
    Survey meter ...........................  250 / 374+
    With circuit ...........................  250 / 374+
1181423 Apparatus for Measuring Rontgen Rays, May 2, 1916, K Bangert, 250/385.1 ; 313/523; 313/93
1589833 Measuring Device for Electromagnetic Waves, H Behnken, June 22, 1926, 313/538 ; 250/374; 313/93; 378/207; 378/82; 378/98 - X-Ray detector
1855669 Method and Apparatus for the Measurement of Radiation Intensity, April 26, 1932, 250/377 ; 313/93; 324/109; 324/702; 324/97
1961708 System for Influencing an Electric Current by Irradiation, F M Penning, June 5, 1934, 250/214.1 ; 313/538; 313/93; 315/150; 315/157; 315/337
1961717 Ray Intensity Meter System, C H Thomas, June 5, 1934, 378/97 ; 250/214R; 250/382; 313/601; 313/93; 315/150; 315/157; 315/234; 315/241R; 361/175
1995018 Gas Filled Tube, H J Spanner, March 19, 1935 313/592 ; 313/253; 313/594; 313/93; 315/105; 315/268
2257827 Electron Discharge Tube, G J Weissenberg, October 7, 1941, 445/35 ; 313/149; 313/355; 313/485; 313/93; 427/111; 427/74
2390965 Central Electrode Support, S A Scherbatskoy, December 11, 1945, 250/374 ; 174/152E; 250/256; 313/246; 313/247; 313/255; 313/292; 313/318.01; 313/357; 313/545; 313/93
2521315 Geiger Tube, J A Victoreen, September 5, 1950, 313/93 ; 313/278; 313/286; 313/290; 313/552 - improved quenching
2542440 Geiger Tube, J A Victoreen, February 20, 1951, 313/93 ; 220/2.3R; 313/247; 313/281 - Mica end window
249064 Receiver for Telephones, R M Lockwood, November 1, 1881, 181/167
454941 Phonograph Recorder or Reproducer, T A Edison, June 30, 1891, 181/162 ; 181/170
2159628 Telephone Transmitter, E G Danielson, May 23, 1939, 381/174 ; 181/167; 264/320; 425/DIG.56
2475603 Geiger Counter Structure, H Friedman, July 12, 1949, 313/93 ; 313/312; 313/622

Sampling and recording dose rate meter 250/374 ; 250/376; 250/377
4859853 Solid Gamma Ray Dosimeter which measures radiation in terms of absorption in a material different from the detector material
5665970 Directional Radiation Detector and Imager
4853163 Method of controlling discharge of stored electric charge in plastic objects and forming Lichtenberg figures in plastic objects 264/406 ; 264/101; 264/162; 264/340; 264/341; 264/40.1; 264/78; 428/13

Liquid Scintillation Analyzer

In the book Physics for Future Presidents, Richard Muller talks about measuring alcohol beverages for mandatory radiation so that it can be confirmed they were made from plant material and not from oil.  Here are some patents for doing that:
4220855 Scintillation counter with rotatable light seal, Packard Instrument Company, Inc., Sep 2, 1980, 250/328 - hardware
4555629 Method and apparatus for determination of sample homogeneity in scintillation counting, Packard Instrument Company, Inc., Nov 26, 1985, 250/362, 250/369, 250/328
                about data processing
4628205 Regionless multiple label scintillation counting, Packard Instrument Company, Inc., Dec 9, 1986, 250/361.00R, 250/328, 250/364 -
                DPM for two different radionuclides based on calibration quench curves
4633088 Reverse sum quench measurement using a liquid scintillation counter, Packard Instrument Company, Inc., Dec 30, 1986,
                 250/369, 250/364, 250/361.00R, 250/363.09, 250/363.01, 250/362
                math in support of the quench curves
4651006 For counting sample optical events resulting from the radioactive decay, Packard Instrument Company, Inc., Mar 17, 1987,
                250/362, 250/363.07, 250/363.01, 250/369, 250/366
                A method and apparatus for separating background events from valid sample events - dual phototubes & coincidence detector
5483070 Scintillation counter, Packard Instrument Company, Jan 9, 1996, 250/366, 250/362, 250/364, 250/369
A scintillation measurement system for measuring optical events produced by scintillators in response to the radioactive decay of a constituent or constituents of a sample to be measured comprises a sample support for positioning a sample in a sample well; a bismuth germanate (BGO) scintillation crystal, such as Bi4 Ge3 O12, located adjacent the sample well; a plurality of photodetectors located outside the bismuth germanate crystal for detecting optical events occurring in the sample well or in the bismuth germanate crystal and converting those optical events into electrical pulses; and a pulse analyzing system for receiving the electrical pulses from the photodetectors and determining whether such pulses represent α, β or γ events. This system can be used with samples containing α, β and γ emitters, or any combination thereof.               


These are legally available on the internet.  I keep them in a can that's marked as Radioactive as a safety measure.
Radiosactive Sample

Samples Table


CS-137 Radioactive
                  Isotope sample

Depleted Uranium
Depleted Uranium sample

Geo on DU

UN Report on DU

30,000 CPM (X100 Range)

                  Syrveyo 50, Pancake Probe & Depleted Uranium
                  without lead shiled 30,000 CPM
500 CPM with lead shield (X1 range)
Bicron Syrveyo
                  50, Pancake Probe & Depleted Uranium with lead
                  shield: 500 CPM
Vaseline Glass
Vaseline Glass Radioactive sample


Am-241 Am-241

80,000+ Counts/minute
Different source, much lower strength  20,000 counter/minute

                  military tubes
1. U.S. Army, U.S. Navy, Type JAN CW 1B22 Cont NXSA 8805,
Western Electric, Accepted March 1945 -
AN/APS-4, 16-T-51222, 1 Vac. Tube, V(5)6, Etc., JAN-1B22, Part of Item 078 Ext web pages: 1B22, 1B22 spark gap Contains Ra-226

2. NSN: 5960-188-3531, One Ea. Electron Tube, JAN CAHG 1B46,
Mfg by Chatham Electronics, Div of Tung-Sol Electric, Inc.,
Date Packed 12/58, For Use In: FX-1, TT-1, TXC-1 only
Ext web pages: 1B46, 1B46 voltage regulator Contains Ra-226

3. Radioisotope CS 137, Activity 0.9 uc ea, 1 Spark Gap, TG 202,
Mfd by Signalite Inc., Pkd 1/67 Ext web pages: TG-202

4. Spark Gap
By Product Material Cs-137, <5μc each, Mfd by Signalite Inc., Pkd 10/70
TG-30  Ext web page: TG-30

1B22: 682.56 cpm, 12.87 ÁSv/h
1B46: 31.22 cpm, 0.59 ÁSv/h
                          Tube Top
1B46 Tube Top
TG-202: 48.24 cpm, 0.91ÁSv/h
TG-30: 132.90 cpm, 2.51ÁSv/h

Note photos are not to any scale.  The 1B22 is the largest tube by far.

Radiation measurements made with iPod & Pocket Geiger

Decay Times & the Sun

An article appeared in the Stanford News about work done at Purdue by Ephraim Fischbach.
The strange case of solar flares and radioactive elements - that suggests that there may be a correlation between the rotational position of the Sun's core and the decay rate for some isotopes.  The article mentions:
Half Life
manganese-54 312.03 days or 26.9E6 sec
cesium-137 30.17 years
silicon-32 170 years or 5.4E9 sec
radium-226 1601 years

manganese-54 looks like the shortest half life that was mentioned and it's available from United Nuclear:
Here's their table of Disk Sources which has some isotopes that have a shorter half life:
Cobalt57            270 days
Zinc65                244 days
Polonium210 138 days (also available as a needle source)

So in the disk sources Polonium-210 has the shortest half life.

Barium133 1uCi 10.7 years Gamma: 81.0, 356.0
Cadmium109 1uCi 453 days Gamma: 88.0
Cesium137 1uCi 30.1 years Gamma: 32, 661.6
Beta: 511.6, 1173.2
Cesium137 5uCi 30.1 years Gamma: 32, 661.6
Beta: 511.6, 1173.2
Cesium137 10uCi 30.1 years Gamma: 32, 661.6
Beta: 511.6, 1173.2
Cobalt57 1uCi 270 days Gamma: 122.1
Cobalt60 1uCi 5.27 years Gamma: 1173.2, 1332.5
Europium152 1uCi 13.5 years Gamma: 121.8, 344.3, 1408.0
Manganese54 1uCi 312 days Gamma: 834.8
Sodium22 1uCi 2.6 years Gamma: 511.0, 1274.5
Strontium90 0.1uCi 28.5 years Beta: 546.0
Thallium204 1uCi 3.78 years Beta: 763.4
Polonium210 0.1uCi 138 days Alpha: 5304.5
Zinc65 1uCi 244 days Gamma: 511.0, 1115.5


Buying a radiation detection instrument - Detecting Radiation -
Cold War Civil Defense Museum - a lot of information on those yellow painted geiger counters and related stuff.
Dangerous Laboratories - Radiation Detection -
Table of Nuclides -
Radiation Decay -
Gamma-ray Burst Real-time Sky Map -
Radioactive electron tubes -
Charlie Thompson's Buda Seismic Observatory Radiation Detection - neat DIY info
Welcome to albert-cordova - Radiation Units
Paul's RADIAC Showcase -
Spectrum Techniques -
N. Wood Counter Laboratory, Inc. - BF3 Neutron Proportional Detectors - Proportional Gamma Detectors - GM Detectors
Oak Ridge Associated Universities - Health Physics Historical Instrumentation Museum Collection - Military Radiac Instruments - Library (huge)
NukeAlert -key chain size -patent 6897448 - uses a CdS photo cell to detect light from Scintillator very low dc power drain and simple circuit
Gama Scout - same battery life as the NukeAlert but uses LND712 GM tube, larger and with panel and computer interface.   Comes in 3 models: Traditional, Alert, and Online
Rad Detect - key chain size - PIN diode + scintillator and light sensor
Pocket Rad - counter, ore samples
GotHotRocks - ore samples
United Nuclear - Scientific Equipment & Supplies - Am-241 source not listed on isotopes page
Rad Pro Calculator - on line
TENORM - Links - Technologically-Enhanced Naturally Occurring Radioactive Material
Old Style GEIGER Counters - Refurbish PRI scintillation counters - Battery Adapter
K0FF - Index of /k0ff - Testing various GM tubes  
Home Built Scintillation Counters and Multichannel Analyzers (MCAs) - mods to existing equipment
Armadillo - low cost scintillator for gamma ray spectrometry - made by Super Ocean Light in Japan
Radioactive Electron Tubes
How Hot Are Your Rocks? Radioactivity in Uranyl-Activated Fluorescent Minerals - combines radioactivity and UV - Facebook: Fluorescent Minerals - including uranium glass

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page created  19 Jan 2006.