I carried out an experiment to calculate the half thickness (half value layer) of lead. The experiment was done using what i believe to be a Ba-133m source on this software: https://radiation-lab.software.informer.com
I am unsure of what the true gamma source is because it wrote Ba-133 on the program, but Ba-131 on the .csv file it produced.
My value for the half thickness came out to be about 4 mm. However, I am unable to find any sources to prove me right or wrong and perhaps even help identify which source I was truly using.
In page 4 of this pdf the hvl for lead using barium sources can be found, and they are nowhere near close to my value.
Any help is very much appreciated.