Dynamics of low energy electrons transmitting through straight glass capillary: Tilt angle dependence

Abstract

<sec>It is a hot topic that using glass capillary to focus and shape the charged particle beam, for it is inexpensive and simple. There are the cases that single glass capillaries are used to make the microbeam of the positive ions. When it comes to electrons, their transmitting through insulating capillaries is complex and the attempt to use the glass capillary to produce electron beams in the size of micrometer needs further exploring.</sec><sec>In this paper, the charging-up process of the 900-eV electrons transmitting through a glass capillary with the grounded conductive-coated outer surface is reported. Two-dimensional angular distributions of the transmitted electrons and their time evolutions are measured for the cases of various tilt angles of glass tube. It is found that there are a considerable number of transmitted electrons at the tilt angle exceeding the geometrical opening angle (1°) of the glass tube. The intensity of transmitted electrons for large tilt angle (i.e. –1.15°) can be considered as first falling to zero, then keeping zero for a long time, finally rising to a certain stable value. Correspondingly, the angular distribution center experiences moving towards negative-positive-negative-settled. The energy losses are measured for various tilt angles. The larger the tilt angles, the larger the energy loss of transmitted electrons is. To better understand the physics behind the observed phenomena, the simulations of the energy loss for transmitted electrons at various tilt angles are performed by the Monte Carlo method. The comparation between the simulated energy losses and the measured energy losses shows that the experimental results are well explained by multiple deflections from the wall.</sec>