Co-60 Spectra

SiPM 2 (channel 0) and SiPM 4 (channel 1) were placed in their delrin holders on opposite sides of the WLS fiber of scintillator 1-74-1. No optical coupling grease was used when placing the fiber in the scintillator sample. Each event was self-triggered when both SiPM were above the trigger threshold of 8320. When the Co-60 source was present, it was placed 10 cm from the plastic.

Table 1: Explanation of runs used.
Run	Source	Number of events	Data file
1	background	10k	130725_sipm2+4_background_8320threshold_WLSfiber.dat
2	Co-60	10k	130725_sipm2+4_co-60_8320threshold_WLSfiber.dat
3	Co-60	100k	130725_sipm2+4_co-60_8320threshold_wlsfiber_x10.dat

Background

The background run was previously analyzed in the Ce-137 spectra. The histograms in Figure 1 exclude pulses with a baseline standard deviation greater than 7 or with secondary pulses present.

Figure 1: Area under the pulse for background using SiPM 2 only, SiPM 4 only, and SiPM 2 and 4 combined.

Short Run

Figure 2: Area under the pulse for the short run with Co-60 for SiPM 2 only, SiPM 4 only, and SiPM 2 and 4 combined.

The histograms of Figure 2 exclude pulses with a baseline standard deviation greater than 7 or with secondary pulses present.

Figure 3: Comparison between Co-60 (short run) spectrum and the background spectrum.

Long Run

Figure 4: Area under the pulse for the long run with Co-60 for SiPM 2 only, SiPM 4 only, and SiPM 2 and 4 combined.

The histograms of Figure 4 exclude pulses with a baseline standard deviation greater than 7 or with secondary pulses present.

Figure 5: Comparison between Co-60 (long run) and background spectra.

The Co-60 (long run) histogram in Figure 5 has been scaled by 1/10 to match the total number of events taken in the background run.