Ratio of counts for single versus multiple events, over the time of the mission for the data used in this paper. Values integrated between successive “detector annealings” are shown: these are performed roughly every six months to recover spectral resolutions after degradation due to cosmic-ray bombardment. Detector failures occurred after 3rd, 4th, 12th, and 15th annealings. Step changes after annealing 15 and 19 reflect a reduction of the detector high voltage (4 to 3 to 2.5 kV) which assists the needs of prolonged operations.