Darmstadt 2016 – wissenschaftliches Programm

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AKBP: Arbeitskreis Beschleunigerphysik

AKBP 1: Injectors, Lasers I

AKBP 1.5: Vortrag

Montag, 14. März 2016, 15:00–15:15, S1/05 23

Explosive electron emission from flat Ge crystals — Vitali Porshyn, •Stephan Mingels, Dirk Lützenkirchen-Hecht, and Günter Müller — University of Wuppertal

During the search for photo-induced field emission from flat semiconductors, which might provide high brightness electron beams, we have found with our new ultra-high vacuum measurement system [1] explosive electron emission (EEE) from n-doped Ge crystals resulting in high current pulses of ∼100 A and ∼4 ns duration. This effect reproducibly appears in a narrow photon energy range of 3.2-3.6 eV with a quantum efficiency of up to 20%. Moreover, the EEE current does not depend on the surface field but on the extraction voltage (500-3000 V). EEE is a well known plasma-induced effect for locally heated metals resulting in a crater-like destruction of the surface [2]. For Ge, however, it appears at a factor of 20 lower power density (0.3 MW/cm²) of the pulsed laser, and each current pulse forms a new crater of ∼10 µm size. The measured EEE spectra show a similar FWHM (< 1 eV) as photo emitted electrons. Potential applications, e.g. in microwave tubes or gyrotrons, will be discussed.

[1] S. Mingels et al., Rev. Sci. Instr. 86, 043307 (2015).

[2] G.A. Mesyats, Plasma Phys. Control. Fusion 47, A109-A151 (2005).

Funded by the German Federal Ministry of Education and Research under project number 05K13PX2.