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Surface Physics with Positrons
A disadvantage of conventional EAES is the high secondary electron background and the high penetration depth of the electrons, both due to the high energetic primary electron beam.
To overcome these facts, in 1988 A. WEISS et al. performed for the first time Positron annihilation induced Auger electron spectroscopy (PAES).
The big advantages of PAES over EAES are the higher surface sensitivity, the low secondary electron background and the fact, that this technique is non-destructive.
The only disadvantage of PAES, the very low positron intensity of conventional 22Na based beams, is reduced at our spectrometer, since we are working with the high intensity positron source NEPOMUC at the FRM II.
At this facility a positron intensity of 107 e+/s with an energy of 15 eV is available.
With this high intensity, the measurement times for one spectrum has been reduced to typically a few hours compared to a few days for a spectrum recorded with a lab source.
Until now, there has been just a single TRHEPD experiment in operation worldwide. In order to benefit from the high beam intensity available at the neutron induced positron source Munich (NEPOMUC), we recently installed a new positron diffractometer at the positron beam line at MLZ.
Prof. Dr. Christoph Hugenschmidt
Phone: +49 (0)89 289-14609
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