Wuppertal 2015 – wissenschaftliches Programm

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AKBP: Arbeitskreis Beschleunigerphysik

AKBP 2: PWA / TNSA I

AKBP 2.2: Vortrag

Montag, 9. März 2015, 14:15–14:30, BZ.08.04 (HS 2)

Highly sensitive pulsed spectrometer for laser excited and field extracted electrons — •Stephan Mingels, Vitali Porshyn, Dirk Lützenkirchen-Hecht, and Günter Müller — Physics Department, University of Wuppertal

We have completed an ultra-high vacuum system for investigations of cathodes in a triode configuration under high electric fields E (up to ∼100 MV/m) and pulsed tunable laser illumination (3.5 ns, 10 Hz, hν=0.5-5.9 eV, >0.3 mJ) [1]. Measurements of the cathode current by a picoammeter and of the electron energy by a spectrometer for DC as well as laser-pulsed beams are enabled. The cathodes can be 3D-positioned with µm precision and cooled or heated in the range of 77-400 K. System commissioning with DC field emission from a W tip yielded a work function φ of 4.7 eV and a spectrometer resolution of <10 meV. Precise determination of the emitter temperature from the spectra at low currents (down to 60 nA) demonstrated the high sensitivity of the system. The suitability for laser-pulsed beams was shown with photoemission from a n-GaP(100) wafer. Quantum efficiency QE(hν) measurements at low E revealed expected band structure effects and φ values of 3.5-4.6 eV depending on the actual oxide layer. In order to develop novel highly brilliant electron sources, the suitability of various materials for photo-induced field emission by indirect (QE(hν,E)) and direct electron spectroscopy will be performed next.

[1] S. Mingels et al., submitted to Rev. Sci. Instrum.

Funded by the BMBF joint research project 05K13PX2.