Attenuation of Beta Particles


In this experiment we will study the attenuation of beta particles in aluminium, using a radioactive source and a Geiger counter detector.

The source used is strontium-\(90\) which undergoes \(\beta^{-}\) decay into yttrium-\(90\) with decay energy \(0.546\) MeV and half-life \(28.79\) years.

Each decay emits an electron (\(\mathrm{e}^{-}\)) and an electron anti-neutrino (\(\mskip 1.5mu \overline{\mskip-1.5mu \nu_{\mathrm{e}}\mskip-1.5mu }\mskip 1.5mu \)). Neutrinos have negligible probability of interacting with matter. Electrons, however, lose kinetic energy as they interact electromagnetically with matter. So, they can only travel a certain distance, or range, before they come to rest.


The absorption of \(\beta\) rays is given approximately by Beer’s Law

\begin{equation} I_{x}=I_{0}\,\exp\left(\mu\,x\right)\nonumber \\ \end{equation}