Re: What is the absorption coefficient of aluminium using beta particles?

The reason that you cannot find a correct value is because there is no 
one single value for the absorption coefficient. It depends on the 
elemental composition and density of the material, and on the initial 
energy of the beta ray. One problem with your experiment is that beta 
rays are not emitted with just one energy, but with a spread of 
energies up to a maximum which is characteristic of the particular 
decay. What you are looking for is properly called the "mass 
absorption coefficient". What you will find is a curve for electrons or 
beta rays in unit density material, plotted with energy on the x-axis 
and the mass absorption coefficient on the y-axis. To find the answer 
for a given absorber and energy, you pick the value corresponding to 
the energy, and multiply by the density of the absorbing material you 
are using. That gives you the absorption coefficient for that energy 
only. Higher energy betas penetrate more than lower energy ones, 
out to the maximum range for the maximum energy particles in the 
beta-ray spectrum. A discussion if this phenomenon, and probably 
the curve also, should be found in any college-level text on nuclear 
physics.