Intro: Detecting Cosmic Muons in a Simple Can
This time we are trying to detect muons created through collisions of the cosmis radiation with particles of our atmosphere.
Muons are elementary particles belonging to the group of the leptons (falsely also named µ-meson) with a "middle" mass (207 times heavier than an electron). They have an average half life of just 2.2 µsek. To pass the atmosphere (20km) it takes more than 67 µsek even with the Speed of light. Therefore muons shouldn't be detected on ground, but we do. The reason is, that moving clocks go slower. For the fast muons time goes slower and so they can reach the ground. This can be seen from the two different decay-Graphs. Muons decay in electrons (Positrons) and neutrinos.
Step 1: Parts You Need
To detect the muons you just need
a light-proof can like mine used for car-colours
- a photo-multiplier-tube (PMT) [you can get some on ebay f.e. http://www.ebay.com/itm/Hamamatsu-R580-PMT-38mm-1-5-inch-Photomultiplier-Tube-/141764749329?hash=item2101d66811]
- a high voltage power supply for the PMT [you can take a Commercial product or build your own based on a CCFL-module like I did]
- detection-electronics including an amplifier and a comparator [also selfmade]
- a counter [http://www.ebay.com/itm/6-Digit-Red-LED-Counter-Pa...]
- an oscilloscope to control the signals
- bnc-cable etc.
Step 2: Why Water?
Goes a particle through a material faster than light the so-called cherenkov-radiation is emitted. In water (refractive index n = 4/3) the speed of light is c_medium = c_vacuum / n_medium = 300.000 / (4/3) = 225.000 km/s.
So if a muon goes through water with a velocity faster than 225.000 km/s cherenkov-light will be emitted by the muon. This light can be detected with the PMT and the "light"-pulses counted.
By the way cherenkov-light can be seen in nuclear power plants too. In the cooling pool for the old fuel rods the nuclear radiation consisting of neutrons and other particles is responsable for that...
Step 3: Results
To be sure that the muons cause the peaks I made three rounds. First I took the empty can and counted the pulses within 10 minutes (53). Than I filled the can with distilled water and measured once more. Now I was able to detect 81 pulses within 10 min. After this I poured out the can and repeated the measurement with the result of 46 peaks. So water increased the number of pulses significantly, heureka ;-)
Maybe you're interested in my other Videos: https://www.youtube.com/user/stopperl16/videos
Thank's for spending your time.