Test with two SiPM

Histogram Comparisons

SiPM 3 and SiPM 4 were placed in their delrin holders on opposite ends of scintillator 1-74-1 (with the wavelength shifting fiber) in the darkroom. Each event was self-triggered when both SiPMs passed a trigger threshold of 8400.

Table 1: Further run information.
Run	Number of Events	Source	Data file
1	6.9K	no source (background)	130718_sipm3+4_background_8400threshold.dat
2	10k	Ba-133 (3 cm from crystal)	130718_sipm3+4_ba-133_8400threshold.dat
3	10k	Ba-133 (1 cm from crystal)	130719_sipm3+4_ba-133_8400threshold.dat

Figure 1: Area under the pulse for the background run for SiPM 3 only, SiPM 4 only, and combined.

Figure 2: Pulse maximum for the background run for SiPM 3 only, SiPM 4 only, and combined.

All histograms above (Figures 1 and 2) exclude pulses with a baseline standard deviation greater than 7. The pulse area histograms (Figure 1) also excludes data with secondary pulses present.

Figure 3: Area under the pulse for the Ba-133 run for SiPM 3 only, SiPM 4 only, and combined.

Figure 4: Pulse maximum for the Ba-133 run for SiPM 3 only, SiPM 4 only, and combined.

All histograms above (Figures 3 and 4) exclude pulses with a baseline standard deviation greater than 7. The pulse area histograms (Figure 3) also excludes data with secondary pulses present.

Figure 5: Area under the pulse for the closer Ba-133 run for SiPM 3 only, SiPM 4 only, and combined.

Figure 6: Pulse maximum for the closer Ba-133 run for SiPM 3 only, SiPM 4 only, and combined.

All histograms above (Figures 5 and 6) exclude pulses with a baseline standard deviation greater than 7. The pulse area histograms (Figure 5) also excludes data with secondary pulses present.

Figure 7: Comparison of area under the pulse for each run.

Therefore, we think the second peak visible in the far run is background, and the main peak in the far and close runs are the Ba-133 peak.

Gain Matching

As seen in the comparison between SiPMs, each SiPM 3 and SiPM 4 have different gains. In order to add the pulses from these two SiPMs together, the data collected from SiPM 4 must be corrected to have the same gain as SiPM 3.

Data from the following runs were used (from Comparison of all four SiPM - Long Runs):
130709_sipm3_blueled_delayed-trig_10hz_100ns_x10_1.806kohm.dat
130710_sipm4_blueled_delayed-trig_10hz_100ns_x10_1.806kohm.dat

Figure 8: Gaussian fits to each pulse area photoelectron peak for SiPM 3 and SiPM 4.

The average difference between the location of subsequent photoelectron peaks for SiPM 3 is 714.207 and for SiPM 4 is 608.911. Therefore, the gain correction for the area under the pulse of SiPM 4 is 1.1728.

Figure 9: Gaussian fits to each pulse maximum photoelecton peak for SiPM 3 and SiPM 4.

The average difference between the location of subsequent photoelectron peaks for SiPM 3 is 45.6952 and for SiPM 4 is 47.233. Therefore, the gain correction for the pulse maximum of SiPM 4 is 0.9674.

All histograms above (Figures 1 and 2) exclude data with a baseline standard deviation greater than 27. The histograms of the pulse areas (Figure 1) also excludes data with secondary pulses.