Determining the Half Life of 234mPa

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Before you plot the data subtract the background counts from each measurement and calculate the uncertainty for each point.

  1. Plot your measured data on a A3-sized semi-logarithmic paper. Your data should lie on a straight line (why?). Fit the best possible line through your data. Remember to plot the uncertainty also.
  2. Select a point on your fitted line from the left side (e.g. 1000 counts), note the corresponding time, t1.
  3. Now, divide the number of counts for t1 by 2 three times (for 1000 counts you get 125) and find the time, t2, your fitted line passed through this number of counts.
  4. The difference between t1 and t2 corresponds to three half lives (why?).
  5. Estimate the uncertainty in your fit by drawing two worst-case lines through your data, one with the steepest possible slope and one with the least possible slope. Analyse these lines in the same way as the main line - the respective half lives indicate your lower and upper uncertainty limits.