How to Measure the Half Life of 234mPa - with MCA system
For this part of the exercise, you will use a NaI detector connected to a Multi-Channel Analyser (MCA) to determine the disintegration rate of 234mPa. An alternative and more direct, but "old-fashion" method, is to use a GM-tube connected directly to a simple counter. It's described here.
If you look at the radiation from 234mPa (look it up in your nuclear chart!) you will notice that 234mPa only emitts very weak gamma-rays. However, due to the high-energy beta-particle we can still measure 234mPa since this high-energy particle will be able to penetrate through the protective shield around the NaI and interact with the NaI crystal. Alternatly, we could mount e.g. a plastic detector (NE 102A or similar) on a PM-tube and use this instead. The results will largely be the same (but the NaI is more sensitve to gamma-background, which add uncertainty to the background subtraction).