Study of a low energy pulsed electron beam extraction system

A pulsed low energy (<100 keV) large cross-section ion induced secondary emission electron gun has been developed to decompose gaseous pollutants such as NOx. The emitted electron beam has been extracted through a thin foil supported by an aluminum honeycomb (depth 8 mm and area 64.5 cm/sup 2/) that serves as a partition between electron gun and atmospheric pressure processing chamber. In this paper, we report a design and construction of a robust electron window as well as performance of two commercial polymer foils (SiO/sub 2/ coated polyethylene and aluminum coated Mylar) as a window material. The performance of these polymer foils are compared with conventional aluminum foil in terms of various extraction mechanisms such as energy deposition, electron transmission, mechanical and thermal loadings etc. Both the polymer foils have been judged to be consistent with mechanical requirements but aluminum coated Mylar window showed high electron transmission (78%) comparing to SiO/sub 2/ coated polyethylene (64%) and aluminum (45%) window of same thickness (12 /spl mu/m) at 100 kV. The improved current transmission through the new window enhances the electrical efficiency of the electron gun up to 58.7% (from 33%).