Dresden 2003 – scientific programme
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VA: Vakuumphysik und Vakuumtechnik
VA 2: Vakuumverfahrenstechnik
VA 2.5: Talk
Monday, March 24, 2003, 16:10–16:30, HSZ105
Investigation of emission instabilities of liquid metal alloy ion sources — •Chavkat Akhmadaliev1, Lothar Bischoff1, Grehem L. R. Mair2, and Costas J. Aidinis2 — 1Forschungszentrum Rossendorf e.V., Bautzner Landstraße 128 (B6), 01328 Dresden, Germany — 2University of Athens, Department of Physics, Panepistimiopolis, Zografou, 157 84 Athens, Greece
Detailed investigations of the emission instabilities and their frequency spectra for Liquid Metal Alloy Ion Sources (LMAIS) wetted with Ga, AuGeSi and AuGe, were carried out. Ion sources with extracting electrode as well as without extractor were applied. The ion current from a collector electrode was amplified and converted into a voltage according to 200 mV/µA. Frequency spectra from 0 to 100 MHz were measured using a spectrum analyzer. Corresponding oscillograms of the emission current were obtained from a digital oscilloscope. The emission noise is a result of a droplet emission, and its terminal frequency appears to coincide with the frequency of vibrations of the sides of the liquid cone at high currents. The emitted droplets screen the source tip. This leads to a decreasing of the effective electric field and fluctuations of the emission process. The noise depends nonlinearly on the current. At 100 µA emission current the fluctuations amount to about 5 µA(rms). The alloy sources were heated up from 400 to 1100 oC and the dependence of the fluctuations on the temperature were obtained. With increasing of the temperature stronger fluctuations were registered. A better understanding of the instabilities on the liquid anodes are useful for deposition purposes.