1. Geiger-Mueller Tubes
By: Daniel Hancock

2. How It Works
Gas-filled counter detects electron-ion pairs produced by a charged particle
Electrostatic field causes electrons to move to the anode and ions to the cathode
Produces electric pulse which is detected
Ionization, proportional, Geiger-mueller
[1]

3. In detail
The increase in electric field results in loss of proportionality until the counter reaches the GM region
Single ionizing event induces an electrical discharge along the length of the anode wire
Output pulse is large independent of energy deposited by ionizing particle
Has a long dead time, saturates counting rates above a few thousand particles per second
[2]

4. Electron Avalanche
Operates at electric fields above proportional region
Ultra violet photons induce electrical discharge
Avalanche spreads over the whole counter and leads to a complete discharge
Gas mixtures contain a noble gas mixed with ethyl alcohol or halogen
Acts as a quencher and eventually stops discharge
After discharge cant register another pulse
[3]

5. Things to keep in mind Data Analysis
Binomial distribution: random radioactive decay
Poisson distribution: determining background
Lab Safety
Radioactive sources
Wash hands afterwards
Don’t raise above 1000V
[4]

6. Real World Applications
GM counters are often used in instruments for radiation protection and monitoring
Can also be used for detecting alpha and beta particles
[5]

7. References [1] CRC press LLC ‘Nuclear Measurement’, 1999
[2] Melissinos ‘Experiment in Modern Physics’,1966, pg
[3] Kleinknecht ‘Detectors for Particle Radiation’, 1986, pg
[4] Taylor ‘Introduction to Error Analysis’,1982, pg. 230, 246
[5] muller-1-projeto.html
ecay/Counting%20Statistics%20122.pdf