Electron-beam transmission through a micrometer-sized tapered-glass capillary: Dependence on incident energy and angular tilt angle

Abstract

An experimental study of 500- and 1000-eV incident electrons transmitted through a micrometer-sized funnel-shaped (tapered) glass capillary with inlet diameter 0.80 mm, outlet diameter 0.10 mm, and a length of 35 mm is reported. The properties of the electron beam transmitted were measured as a function of the emerging angle and the incident energy dependence. The angular profiles were found to be comprised of up to three peaks for both 500 and 1000 eV showing evidence for transmission going straight through the capillary without interacting with the walls (direct), as well as transmission resulting from Coulomb deflection of the electrons from a negative charge patch or by scattering from nuclei close to the surface of the capillary (indirect). The energy spectra show that elastically transmitted electrons dominate at 500 eV for increasing sample tilt angles up to \ensuremath{\sim}5.0\ifmmode^\circ\else\textdegree\fi{}, while inelastic processes dominate for 1000 eV already at tilt angles of \ensuremath{\sim}1.0\ifmmode^\circ\else\textdegree\fi{}. The angular width of the emitted electrons was found to constitute a narrow beam for direct (\ensuremath{\sim}0.4\ifmmode^\circ\else\textdegree\fi{}) and indirect (0.6\ifmmode^\circ\else\textdegree\fi{} for 500 eV and 1.0\ifmmode^\circ\else\textdegree\fi{} for 1000 eV) transmission for both energies with the widths decreasing for the largest tilt angles measured and approaching the inherent resolution (\ensuremath{\sim}0.3\ifmmode^\circ\else\textdegree\fi{}) of the electron analyzer.