Date of Award
T. J. Reddish
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A cyclical electrostatic device, referred to as an Electron Recycling Spectrometer (ERS) for charged particles is described and demonstrated. The system has been developed with storing electrons with typical kinetic energies of tens of eV. The orbital path for the electrons is 0.65 m long and defined through the application of design voltages to two series of cylindrical lenses inserted between two identical hemispherical deflector analyzers. The ERS design concept exploits the very low scattering cross sections in electron-molecule collisions, where the majority of electrons do not interact with the target. Unscattered electrons are collected and passed back through the ERS for another collision opportunity in the interaction region.
The design of the charged particle optics and the basic operating characteristics of the storage ring are discussed. An overall transfer matrix is formed for the ERS by individual transfer matrices of charged particle optics. The conditions of stability within the ERS are extracted from the fundamental inequality involving the trace of the total transfer matrix. The stability lies within a region in a resonant-like pattern, defined by the focal lengths of the electrostatic lenses.
Electron orbit spectra are displayed for a number of ERS operating conditions. Exponential decay rates, average orbit time, and mean electron energy are presented for each spectrum. Analysis was performed by fitting each orbit or "peak distribution" with a Gaussian curve. The noble gases helium and argon were used as the scattering target for electron detection. Ionization spectra provide long term storage times, as an electron beam must be present in the system to produce an ion species. The optimal ion storage exponential decay lifetime achieved is - 55 μs, which is target gas pressure limited and corresponds to - 200 orbits of the 0.65 m orbital circumference for a drop in particle yield of e *. Studies of beam dynamics were performed, analyzing the width evolution of each peak as a function of orbit number. Separate modes were observed that are non-linear with respect to the orbit number.
* i.e. the base of the natural logarithm
Tessier, David Ronald, "The Development of an Electrostatic Storage Ring for Low Energy Electrons" (2008). Electronic Theses and Dissertations. 8284.