LB Det A Dead Time
Due to the difficulty in getting the activity ratios to match the expected values, I decided to investigate the dead time of the detector in use (Detector A). Below is a table of values used to generate the plot. This will also give the reader a good idea of what the dead times are for certain count rates.
| Count Rate (Hz) | % Dead |
| 129.47 +/- 7.84 | 0.24 +/- 0.10 |
| 154.33 +/- 10.36 | 0.29 +/- 0.11 |
| 194.83 +/- 8.36 | 0.41 +/- 0.11 |
| 253.69 +/- 14.05 | 0.51 +/- 0.18 |
| 257.11 +/- 11.24 | 0.53 +/- 0.14 |
| 338.8 +/- 11.68 | 0.65 +/- 0.15 |
| 477.61 +/- 15.06 | 0.84 +/- 0.16 |
| 619.3 +/- 10.56 | 1.34 +/- 0.18 |
| 680.83 +/- 17.5 | 1.33 +/- 0.23 |
| 807.37 +/- 15.85 | 1.55 +/- 0.18 |
| 889.6 +/- 16.22 | 1.65 +/- 0.34 |
| 1051.33 +/- 26.74 | 1.92 +/- 0.26 |
| 1213.93 +/- 23.62 | 2.26 +/- 0.33 |
| 1389.45 +/- 24.75 | 2.53 +/- 0.31 |
| 1628.47 +/- 17.17 | 3.06 +/- 0.30 |
| 2084.6 +/- 33.77 | 3.95 +/- 0.42 |
| 2576.5 +/- 31.53 | 5.06 +/- 0.39 |
| 3058.20 +/- 35.62 | 5.87 +/- 0.54 |
| 3362.13 +/- 23.12 | 6.59 +/- 0.43 |
| 4067.2 +/- 45.37 | 8.18 +/- 0.66 |
| 4564.37 +/- 61.94 | 9.09 +/- 0.60 |
| 5511.6 +/- 64.60 | 10.86 +/- 0.85 |
Below is a plot of the data
Improved Measurement
Since the initial measurement of the dead time had a high error associated with the fluctuating of the count rate, a different measurement was made to try and minimized the error. This measurement was taken by using Ba-133 sources on detector A at the IAC. The source was placed at some position in front of the detector, then data was collected. For the next run the source was moved closer to the detector. A larger source was used as well in this manner to try and reach the higher dead times. The measurement gives the number of counts seen in some solid angle. I will compare this with theory by using the fact that the solid angle can be written as
We can also calculate the theoretical activity of the source. Using this we can find a theoretical rate of photons incident in the solid angle, or
Once the theoretical rate has been found, take a ratio between the measured rate and the theoretical rate to get the percent dead time, or