ABSTRACT
I. Beek, K. J. Varganel, J. Sneider2, Z. T6th2, P. Deal 'Budapest University of Technology and Economics,Departinent of Atomic Physics, Surface Physics Laboratory
H-11 l l Budapest XI., Budafialci at 8. Hungary 'General Electric Hungary Inc. Consumer and Industrial
H-1340 Budapest XIII., Vaci at 73-77. Hungary Contact: ildiko.beck@mailbox.hu
INTRODUCTION AND EXPERIMENTAL In this work we present one of the most important factors affecting the operability of high-pressure sodium lamps manufactured by General Electric Hungary Inc. Consumer and Industrial. We investigated the electron emission properties, the work function of the tungsten electrodes. We studied the following three aspects of this parameter: (1) sintering temperature of cathodes (1500°C - 1700°C), (2) lamp operation time (Oh — 12000h) and (3) comparison of the work function of cold-end cathodes to the hot-end cathodes. The investigations have been carried out by Kelvin Probe Method and by a combined Auger Electron Spectrometer (AES)-Work Function Spectrometer (WFS) system. The widely used Kelvin Probe Method is an indirect technique to measure average work function of a lmm2 area of the cathode tip, related to a flat and clean Au electrode crystal vibrated by a constant frequency [1]. In order to investigate the local work function by WFS in selected points of cathode tips the low kinetic energy region (0-30 eV) of secondary electron energy spectrum is used [2, 3]. The work function change is calculated using the tangent method described by Scholtes [4]. The analysis of chemical composition has been carried out by AES on tips of the tungsten electrodes. The AES and WFS measurements were performed by means of VG Microtech LEG200 electron gun of 200 nm spot diameter, primary energy: 4 keV in ultra high vacuum. The measurements were carried out at the Surface Physics Laboratory of Budapest University of Technology and Economics, Hungary.
