TIME-OF-FLIGHT PAES SYSTEM

 

Positron annihilation induced Auger electron spectroscopy (PAES) has been shown to have unique advantages over conventional Auger techniques, including the ability to eliminate the secondary electron background under low energy Auger peaks and the ability to selectively probe the top-most atomic layer [1]. Recently, Suzuki et al. have demonstrated that the time-of-flight technique, in which the entire energy spectrum is collected simultaneously, can be used in PAES measurements to significantly increase the data acquisition rate in comparison with single channel energy analyzers[2]. We present the design of a new magnetically guided, time-of-flight (T-O-F) PAES spectrometer which should be capable of acquiring data at a rate ~100 times greater than the existing single energy channel PAES systems at UT Arlington, while maintaining an energy resolution of 3 %. Our system will differ from the pulsed beam system of Suzuki et al. in that it will make use of a DC positron beam and will rely on the detection of annihilation gamma rays with a BaF2 detector to provide a timing signal. Trajectories of the incident primary positrons and the resulting Auger electrons have been simulated for the new system using the SIMION, charged-particle trajectory program. The results of these ray tracings will be described along with details of design parameters and projected system performance.

(Supported by the Welch Foundation and NSF-9502459.)

[1] A. Weiss et al., Phys. Rev. Lett. 61 (1988) 2245.

[2] R. Suzuki et al., Appl. Surf. Sci. 100/101 (1996) 297.


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