Anomalous events
(a) This plot shows a small number of "fast events" (red points) with scintillation times shorter than the gamma-ray calibration curve (blue line). It is similar to figure 5 except that logarithmic axes are used. (b) The same data plotted as event rate versus energy: the anomalous events (red) are clearly discriminated from higher-energy events due to alpha-particles (blue). This plot is similar to figure 4 except both axes are logarithmic. The event rate for gamma-rays is about 100 times higher and is not shown.