1993•Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIERequires access
Computer simulation of electron optical characteristics of accelerating tube for high-voltage electron microscope
Toshimi Ohye, Chiaki Morita, Hiroshi Shimoyama
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Abstract
Numerical calculations were conducted on the electron optical characteristics of the accelerating tube (AT) for the high voltage electron microscope. The emitted electrons are firstly accelerated to V0 by the TE gun or the FE gun and finally to Va by the AT which consists of 34 electrodes with the inner diameter of 33 mm and has the overall length of 1423 mm. The AT is treated as a thick electrostatic accelerating lens. Several electron optical problems arising from a combination of the AT with a thermionic emission (TE) gun or a field emission (FE) gun are studied. For the TE gun the aberration effect of the AT lens is found to be safely neglected for any combination of Va and V0. In the case of the FE gun, on the other hand, the aberration effect of the AT lens can not be neglected and deteriorates the brightness of the beam. This situation can be overcome by placing an electron lens between the FE gun and the AT.