A surface-electrode quadrupole guide for electrons

This thesis reports on the design and first experimental
realization of a surface-electrode quadrupole guide for free
electrons. The guide is based on a miniaturized, planar electrode
layout and is driven at microwave frequencies. It confines
electrons in the near-field of the microwave excitation, where
strong electric field gradients can be generated without resorting
to resonating structures or exceptionally high drive powers. The
use of chip-based electrode geometries allows the realization of
versatile, microstructured potentials with the perspective of novel
quantum experiments with guided electrons. I present the design,
construction and operation of an experiment that demonstrates
electron confinement in a planar quadrupole guide for the first
time. To this end, electrons with kinetic energies from one to ten
electron-volts are guided along a curved electrode geometry. The
stability of electron guiding as a function of drive parameters and
electron energy has been studied. A comparison with numerical
particle tracking simulations yields good qualitative agreement and
provides a deeper understanding of the electron dynamics in the
guiding potential. Furthermore, this thesis gives a detailed
description of the design of the surface-electrode layout. This
includes the development of an optimized coupling structure to
inject electrons into the guide with minimum transverse excitation.
I also discuss the extension of the current setup to longitudinal
guide dimensions that are comparable to or larger than the
wavelength of the drive signal. This is possible with a modified
electrode layout featuring elevated signal conductors. Electron
guiding in the field of a planar, microfabricated electrode layout
allows the generation of versatile and finely structured guiding
potentials. One example would be the realization of junctions that
split and recombine a guided electron beam. Furthermore, it should
be possible to prepare electrons in low-lying quantum mechanical
oscillator states of the transverse guiding potential by matching
an incoming electron beam to the wave functions of these states.