| 摘要 |
An entrance grid is positioned in the incident beam path of a DC beam positron lifetime spectrometer. The difference between the potentials applied to the sample and the entrance grid provides simultaneous acceleration of both the primary positrons and the secondary electrons. The result is a reduction in the time spread induced by variation of the secondary electron energy. The spectrometer also includes a means for path separation of the incoming positrons and the outgoing secondary electrons from the sample in the non-acceleration range. The result is a positron lifetime spectrometer with a wide time range representing exponential decay functions of annihilation radiation intensity, and an improved time resolution. Results to date show that a valid time range of more than 300 nsec, a time resolution of 570 psec, and a signal-to-noise ratio of 3300 have been achieved.
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