josh webster march 17, 2014 - wordpress.com · 2014-03-22 · a look ahead… •history/backstory...

Josh Webster

March 17, 2014

A Look Ahead…

• History/Backstory

– What is radiation?

– Why detect radiation?

• Main Types of Detectors

• The Geiger-Müller Device: An in Depth Look

• Building a Geiger-Müller Counter: My Spring Break Project

3/17/2014 Radiation Detection - Josh Webster 2

History

3/17/2014 Radiation Detection - Josh Webster

Ernest Rutherford - half-life, α, β, γ (1908 N.P.)

Wilhem Röntgen - X-rays (1901 1st physics N.P.)

Other notable contributions by: Marie & Pierre Curie, J.J. Thomson, Frederick Soddy

http://s2.germany.travel/media/microsites_media/german_originality/heritage/famouspeople/famouspeople_start/W-C-Roentgen01_RET_1024x768.jpg

http://en.wikipedia.org/wiki/File:Ernest_Rutherford_cropped.jpg

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Henri Becquerel - Spontaneous radioactivity

(1903 N.P.) http://en.wikipedia.org/wiki/File:Portrait_of_Antoine-Henri_Becquerel.jpg

What is radiation?

• Electromagnetic waves & particle radiation

• Gamma rays and X-rays (both high energy photons) are forms of electromagnetic radiation. Alpha and beta are types of particle radiation.

• Alpha particles occur in alpha decay when an atomic nucleus emits an alpha particle (He nucleus).

• Beta particles occur in beta decay and are electrons/positrons emitted from an atomic nucleus.


http://www.sat.dundee.ac.uk/gif/spectrum.png

Sources of Radiation

• Cosmic rays from supernovae, gamma ray bursts, quasars, active galactic nuclei

• The Sun - infrared, UV, X-ray (mostly blocked)


http://www.technology.org/texorgwp/wp-content/uploads/2013/07/llama-magnetic-fields.jpg

http://chemwiki.ucdavis.edu/@api/deki/files/816/atmosphere-nasa.gov.jpg

Sources of Radiation Continued…

• α from elements Z (proton #) ≥ 52.

• α, β, γ from elements with Z > 83.


http://www.physics-experiments.com/photos/uranium%20radioactive%20decay.jpg

Radiation Penetration


http://en.wikipedia.org/wiki/File:Alfa_beta_gamma_radiation_penetration.svg

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Why detect radiation?

• For science, safety, and because it’s fun!

• Determine how much of a sample will be left after a given amount of time. (i.e. radio-carbon dating)

• Discover new particles or learn more about known particles


Three Types of Detectors


• Particle Track Devices • Ionization Detectors • Scintillation Detectors

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Particle Track Device


http://www.scifun.ed.ac.uk/pages/pp4ss/pp4ss-cloud_chamber.html

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Ionization Detector


http://spmphysics.onlinetuition.com.my/2013/08/geiger-muller-tube.html

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Scintillation Detector


http://en.wikipedia.org/wiki/File:Scintillation_Counter_Schematic.jpg

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The Geiger-Müller Device: An in Depth Look


• Townsend Avalanche Effect • Geiger Plateau • Tube Types

Townsend Avalanche Effect


http://en.wikipedia.org/wiki/File:Spread_of_avalanches_in_G-M_tube.jpg

Geiger Plateau


Credit: Josh Webster

Types of Geiger-Müller Tubes


Tube type is critical! Alpha particles can’t pass through thick walled tubes.

Glass tubes provide an alternative.

http://www.cooking-hacks.com/documentation/tutorials/geiger-counter-raspberry-pi-radiation-sensor-board

Building a Geiger-Müller Counter: My Spring Break Project

• What You’ll Need • Assembly • Final Touches


What You’ll Need


• Kit or design for the board & parts • I bought a kit from

https://sites.google.com/site/diygeigercounter/ (GK-B5 $49)

• Also added the LCD ($5.50) • Geiger-Müller tube (SBM-20 @ ~$20) • Soldering iron (preferably adjustable) • 0.022” solder and solder wick • Battery and connector/wires • Digital voltmeter • Wire cutter/stripper • Mini flat head screwdriver • Flat wire cutter or finger nail clipper • Helping hands is nice • Possibly needle nose pliers and

tweezers

Assembly


2. Double check before soldering 1. Inspect parts 3. Start soldering

4. Inspect soldering 5. Back to soldering… 6. Inspect when done soldering

Finished Circuit Board Close-Up


Testing


Connect battery, tube, and LCD. Then test with background and known source.

~1308 CPM w/ thorium test source.

12-36 CPM (counts per minute) from background radiation.

Final Touches


• Housing • Power switch • Other switches

can be added: • Click/Mute/

Tone • Display

on/off • Tube select

Conclusion

• Radiation is occurring all around us.

• There are various types of radiation.

• There are varying types of detecting equipment.

• Radiation detection equipment has advanced scientific knowledge and understanding.

• For $100 and a Saturday you can build your own detector and begin exploring radioactivity


References

• DIYGeigerCounter, GK-B5 Build Instructions, Retrieved March 8, 2014 from: https://dl.dropboxusercontent.com/u/3572198/GK%20v5.3/GK%20Build%20Instructions%20v5-2%20v5-3.pdf

• Flakus, F.N., Detecting and measuring ionizing radiation – a short history, Retrieved March 10, 2014 from: http://www.iaea.org/Publications/Magazines/Bulletin/Bull234/23405043136.pdf

• Wikipedia, Geiger Counter, Retrieved March 9, 2014 from: http://en.wikipedia.org/wiki/Geiger_counter#History

• Wikipedia, Radiation, Retrieved March 10, 2014 from: http://en.wikipedia.org/wiki/Radiation#Discovery

• Wikipedia, Scintillation Counter, Retrieved March 10, 2014 from: http://en.wikipedia.org/wiki/Scintillation_counter

• Wikipedia, Henri Becquerel, Retrieved March 11, 2014 from: http://en.wikipedia.org/wiki/Henri_Becquerel


Questions?


josh webster march 17, 2014 - wordpress.com · 2014-03-22 · a look ahead… •history/backstory...

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