Study of Au and graphite thin films by MeV ultrafast electron diffraction for use as a beam diagnostic tool

MeV ultrafast electron diffraction (MUED) is a pump-probe structural characterization technique to investigate material dynamics in the ultrashort range. It utilizes a Ti:Sapph ultrashort laser and an ultrashort relativistic electron beam to study the dynamic response of the material structure. Electron beam instabilities currently limit the applicability and accuracy of MUED, hindering the use of single shot measurements.

In this work, we studied Au and graphite films with MUED for different pump-probe delay times and laser fluences in single shot mode. Au samples are standards with known lattice constants, hence enabling the indirect characterization of the electron beam. Graphite films were also employed and structure dynamics were investigated as a function of the number of layers. This thorough study will enable the use of these materials as a diagnostic tool for MUED and possibly other applications. The instrument will be extended to hold a second sample chamber to obtain concurrent diffraction patterns of either Au or graphite and the material system of interest. This will allow to perform shot-to-shot pattern normalization to improve the accuracy of MUED.