The energy scales of the two silicon detectors were calibrated with 241Am sources, which were attached to the diffuser and hence could be removed during the muon beam measurements.
Figure 8.1 illustrates the calibration spectra for one of the silicon detector (Si2) taken with the source. Measurement with no target present in the system is shown in Fig. 8.1(a) which had a full width half maximum resolution of about 40 keV. This is partly due to the resolution of the source itself, and the detector resolution may be better. The spectrum in Fig. 8.1(b), on the other hand, was taken with 2 T, or about 6.8 Ci of tritium present (Target II-14 in Table 4.4 in page ). The effect of tritium caused the peak width to be about 65 keV, due to the decay background.
Since energy spectroscopy is not the purpose of our experiments, the absolute energy scale was not very crucial. However, as we found in the thickness measurements in Section 3.3, the change in the detector temperature could cause significant variation in the energy gain, hence frequent calibration was performed to ensure the relative stability of the energy scale. In addition, the fusion signal itself, whose energy is well known, could provide the calibration information.