02_Zhang_optical_dc - IEEE Transactions on Dielectrics and...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
IEEE Transactions on Dielectrics and Electrical Insulation Vol. 9, No. 2, April 2002 187 Optical Studies of Surface Discharge under dc Voltage in Vacuum G. J. Zhang, X. R. Wang, Z. Yan School of Electrical Engineering Xi’an Jiaotong University Xi’an, 710049 P.R.China Y. S. Liu, M. Okada, K. Yasuoka, and S. lshii Department of Electrical and Electronic Engineering Tokyo Institute of Technology Tokyo, 152-8552 Japan ABSTRACT Utilizing a high-sensitivity photomultiplier tube (PMT) and an intensified charge coupled device (ICCD) camera, the light emission from the surface of polytetraflu- oroethylene (PTFE) and alumina ceramic samples was investigated in vacuum un- der a stepped dc voltage in order to study the initiation and development of surface discharge. Different from the classical electrode contact by butting electrodes on a sample directly, to achieve a fine contact between electrodes and the surface of a sample, the metalized electrodes were employed by sputtering two additional gold contacts on each sample in advance. The two types of materials showed quite dif- ferent optical characteristics. It was suggested that there were several processes possibly related to the initiation mechanism of the surface discharge. Besides the field electron emission from the cathode triple junction (CTJ) for the classical electrode contact, there were charge injection and transport in the surface states of dielectrics, and charge trapping and detrapping phenomena. Electroluminescence (EL) emission was emitted due to the radiative recombination of electrons and holes injected. These processes were strongly dependent on the electrode contact manner and the surface states of insulating materials. 1 INTRODUCTION surface discharge across a solid insulator in vacuum A is a complicated surface/interface phenomenon that depends on many parameters. Historically, influential fac- tors such as the waveform of the applied voltage, profile, material and surface condition of insulators, and structure of electrodes, etc., have been investigated in detail [1,21. Its initiation mechanism has been considered to be a field emission of electrons from the cathode triple junction (CTJ, the interface of metal cathode, insulator and vac- uum) into vacuum, giving rise to the secondary electron emission (SEE) due to the impact of emitted electrons on insulator surface [3,4] and subsequently the surface charg- ing phenomena [5,6]. Another widely accepted model was based on the rapid charge detrapping from localized sites and the corresponding relaxation of polarization energy [7,81. However, a generalized mechanism for all aspects of experimental observations has not yet been proposed, and the physical origin of the complex phenomena is still puz- zling. The initiation and development of the surface discharge is strongly dependent on the local electric field at the CTJ, which is not only determined by the microscopic shape of the electrode, but the space charge distribution near the electrode. Charge injection from an electrical contact be-
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 06/11/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

Page1 / 7

02_Zhang_optical_dc - IEEE Transactions on Dielectrics and...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online