Low-energy Pulsed Electron Beam System For Momentum Spectrometer To Build And Debug

There are a number of physical processes that can occur during collisions between molecules and low energy electrons, e.g. ionization, excitation and dis-sociated to name some. Research into the details of these processes with improve our understanding of molecular structure. Moreover such research will provide much needed data for the cross-sections of the above mentioned processes. These processes, along with others, all occur in the diverter region of Tokamaks and need to be understood to obtain a good model of the plasma in this region. One of the most important tools for research concerning such molecular processes in the Recoil-Ion Momentum Spectrometer, RIMS. Using RIMS, complete momentum information for all the products in an electron-molecule collision can be measured and hence a complete picture of the collision can be deduced. The work present-ed in this thesis concerns the development of a pulsed electron beam system for low energy electron-molecule collision studies at the RIMS at the Shanghai EBIT laboratory. The thesis is written in three sections as follows:Ⅰ. Introduce the basic principles of the electron gun. Introduce the Kimball ELG-2 electron gun and discuss installation and optimization of the gun operation. Use the Field Precision codes to aid in the optimization of the gun operation. Finally run the gun under 1 ns pulsed beam extraction conditions through coupling the gun with an external pulse generator.Ⅱ. An introduction to the electron optics needed to aid in coupling the elec-tron gun with the RIMS, including a discussion of the different classes and charac-teristics of electrostatic lenses. Design suitable electrostatic lenses to optimize the electron beam shape under the conditions/environment of the Shanghai RIMS. Finally a discussion of the design and implementation of a duel Faraday cup is given. For more information about the beam, also design the dual-cup Faraday cup. And then test them.Ⅲ. Mounting of the low energy pulsed electron beam injection system at the RIMS is discussed. Finally the whole system was tested in collisions between low energy electrons and molecules from the supersonic gas jet target.