MOPD50
Bergische Universität Wuppertal, Wuppertal, Germany
Highly brilliant electron sources are crucial for the performance of future free electron lasers[1]. Photo-induced field emission (PFE) might combine the high peak currents of photo cathodes with the low emittance of field emitted electrons. Previous investigations of PFE were performed on tip cathodes and yielded a high brilliance B ≤ 1x1013 A/m2rad2 but only low currents I ≤ 2.9 A and parasitic field emission [2]. We are investigating PFE from flat cathodes in an UHV system for PFE spectroscopy with a resolution of less than 50 meV [3]. Electric fields of up to 400 MV/m can be applied, and pulsed tunable laser illumination of the cathode (0.5 - 5.9 eV photon energy, 1-15 mJ in 3.5 ns pulses, 10 Hz repetition rate) are available. First indications of Schottky-induced photo emission and PFE on flat polycrystalline Au samples were obtained. Measurements of quantum efficiency at continuously varied photon energies revealed strong resonances, which hint for certain band structure transitions. Detailed measurements on single-crystalline Au and Ag samples including electron spectra are ongoing, and the results will be presented at the conference.
[1] D.H. Dowell et al., Nucl. Instr. And Meth. Phys. A 622, 685-697 (2010)
[2] R. Ganter et al., PRL 100, 064801 (2008)
[3] B. Bornmann et al., Rev. Sci. Instrum. 83, 013302 (2012)
