Title: An apparatus architecture for femtosecond transmission electron microscopy,
Abstract: The motion of electrons in or near solids, liquids and gases can be tracked
by forcing their ejection with attosecond x-ray pulses, derived from
femtosecond lasers. The momentum of these emitted electrons carries the imprint
of the electronic state. Aberration corrected transmission electron microscopes
have observed individual atoms, and have sufficient energy sensitivity to
quantify atom bonding and electronic configurations. Recent developments in
ultrafast electron microscopy and diffraction indicate that spatial and
temporal information can be collected simultaneously. In the present work, we
push the capability of femtosecond transmission electron microscopy (fs-TEM)
towards that of the state of the art in ultrafast lasers and electron
microscopes. This is anticipated to facilitate unprecedented elucidation of
physical, chemical and biological structural dynamics on electronic time and
length scales. The fs-TEM numerically studied employs a nanotip source,
electrostatic acceleration to 70 keV, magnetic lens beam transport and
focusing, a condenser-objective around the sample and a terahertz temporal
compressor, including space charge effects during propagation. With electron
emission equivalent to a 20 fs laser pulse, we find a spatial resolution below
10 nm and a temporal resolution of below 10 fs will be feasible for pulses
comprised of on average 20 electrons. The influence of a transverse electric
field at the sample is modelled, indicating that a field of 1 V/$\mu$m can be
resolved.