toc1955's video: Radioactivity: exponential decay measurement

(Adolf Cortel, October 2013) Another nice example of how useful is the ionization chamber designed by Charles Wenzel (www.techlib.com) is the measurement of half-life of Radon-220. When a thorium ore is inside a can it releases the radioactive gas Rn-220. A syninge is used to inject some mililiters of air enriched in Rn-220 into the ionization chamber. Radon decays quickly (half-life 55 s) into a Polonium-216 with the emission of an alpha particle and immediately (half-life 0.16 s) polonium decays to Pb-212 emitting another alpha particle. The exponential decay coresponding to the whole process (as if Rn-220 decayed with a double alpha emission) is recorded using a Vernier SensorDAQ. A simple Labview program finds the best fitting exponential V(t) to the data. Once the exponent is known the half-life of radon is calculated . The results are very goog, with values in the range 50 to 57 s.