  The AXSIS project (Attosecond X-ray Science: Imaging and Spectroscopy) aims
to develop a THz-driven compact X-ray source for applications e.g. in chemistry
and biology by using ultrafast coherent diffraction imaging and spectroscopy.
The key components of AXSIS are the THz-driven electron gun and THz-driven
dielectric loaded linear accelerator as well as an inverse Compton scattering
scheme for the X-rays production. This paper is focused on the prototype of the
THz-driven electron gun which is capable of accelerating electrons up to tens
of keV. Such a gun was manufactured and tested at the test-stand at DESY. Due
to variations in gun fabrication and generation of THz-fields the gun is not
exactly operated at design parameters. Extended simulations have been performed
to understand the experimentally observed performance of the gun. A detailed
comparison between simulations and experimental measurements is presented in
this paper.
