How to Measure the Half Life of 234mPa
For this part of the exercise, you will use a GM-probe connected to a simple counter ("old fashion") to determine the disintegration rate of 234mPa. An alternative method, using a NaI detector and a MCA system is described here.
Before you get your sample, make sure you know exactly what to do. Test the counting procedure without a sample to ensure that this is the case.
- Make a god background measurement, i.e. use a long counting time (at least 30 min). It would be smart to start the background measurement before you prepare the radionuclide generator, as this will take at least one hour. Then you can start directly with the 234mPa measurements once the generator is ready.
Insertion of aluminum counting-vessel into a detector.
- Select a preset counting time of 60 s. Make a table in which you can write down your results.
- Get a stopwatch and learn how to use it.
- You will count your sample repeatedly in 60 s intervals in order to get the disintegration curve for 234mPa. Between each interval a break of 30 s is recommended for writing down the result, clearing the spectrum/counter and prepare for the next measurement. Make sure you write down the exact time you start each counting - do not cheat to fit your planned schedule, write down the actual time!
- Write down the total number of counts in the spectrum for each measurement.
- Repeat the 60 s countings until there is no more 234mPa left, then do a 600 s background measurement (remember to change the preset counting time).
- Repeat the measurement so you get two complete disintegration curves for 234mPa.