Algodoo

Anyone who has worked with radioactive materials will most likely know what a multichannel analyzer is and what it's used for. For those who have never heard of it, it is sort of a sophisticated Geiger counter that not only displays count rate, but also displays a spectrum of the energy levels of the radioactive material being analyzed. This device is commonly used by colleges and universities, as well as nuclear power plants and other industries that need to monitor nuclear radiation. The display provides a "fingerprint" of the radioactive material so that it can be identified.

I included a picture of a very common spectrum which is Cesium-137. My multichannel analyzer produces a rough approximation of a Cs-137 spectrum. I also provided a random generator that simulates background radiation. You can click on background only, or you can click on the Cesium-137 generator which generates the Cs-137 data along with the broad-spectrum background radiation. Click on either of them to turn off the radiation. You can also zero out the data to start acquiring over again. The horizontal scale is the "energy" channels, which go from channel 0 to channel 127 and they represent energies of zero to approximately 700 KeV. The vertical scale represents counts and is a maximum of 100 counts per channel. When any data point reaches a count of 100, data acquisition automatically stops.

You can learn more about this device by searching on multichannel analyzer or pulse height analyzer (which are different names for the same device).