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Below the first plot shows the energy distribution of the V1 and V4R2 algorithms while the second shows them overlapped. Visually, there appears to be very little difference between the two algorithms . There is a clear difference between the two peak finders. The (in fact, the overlapped plot is exactly the same). Although, the peak for the V4R2 distribution is clearly smaller than that for V1 and is wider on both the small and large tailsappears to be slightly taller. This algorithm resulted in a mean of 140141.65 93 ± 0.07 05 with a sigma of 108.58. It appears that although this algorithm rejects peaks that are mostly likely not photons which is beneficial, it does not show to be a better alternative to the V1 algorithm for single photon finding.60. This sigma is very slightly smaller than that of the V1 algorithm. This change is better explained in the following section.
The Effect of Peak Size
Since the square peak finder only find 4 pixel peaks, only the data for the V1 and V4R2 peak finder is shown below. This data consists of 30,837 peaks for the V1 algorithm and 30,982 988 peaks for the V4R2 algorithm found over 13 different sparse events. It can be seen for the 1 and 2 pixel peaks, the sigma is almost the same for each algorithm but for 3 and 4 pixel peaks, the difference is more significant. This is due to the filtering that the V4R2 algorithm does on the peaks as described before. So 3 and 4 pixel peaks for the V1 algorithm are instead 1 and 2 pixel peaks for the V4R2 algorithm and it's clear that this filtering is beneficial to the energy resolution although the benefit is slight. It'll be seen later that the number of peaks that are affected by this filtering is a very small percentage of the total number of peaks.
| V1 Peak Finder | V4R2 Peak Finder | ||||||||
| Pixels | Peaks | Mean | Error | Sigma | Peaks | Mean | Error | Sigma | |
|---|---|---|---|---|---|---|---|---|---|
| 1 | 7934 | 140.26 | 0.08 | 7.46 | 82418247 | 139140.0725 | 0.1008 | 87.7847 | |
| 2 | 16171 | 142.48 | 0.06 | 8.14 | 16235 | 141142.2045 | 0.0806 | 108.4113 | |
| 3 | 4069 | 141.47 | 0.16 | 9.86 | 3903 | 141.1239 | 0.2116 | 139.2975 | |
| 4 | 2663 | 146.38 | 0.19 | 9.72 | 2603 | 146.5033 | 0.2919 | 149.6964 | |
In principle, one can count photons by looking at individual pixel values but, in practice, this is difficult because it is a broad distribution. For event 397656, an event with about 3000 peaks, the energy of every pixel was plotted below.distribution of all pixels is shown below in a semilog plot. As can be seen, the distribution is quite broad and there is no clear one-photon peak.
Lining Up and Recombining Pixel Distributions
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