A Numerical Study of the Wavelength Dependence in an Off-Plane XUV Monochromator : Bachelor of Science Degree Thesis

Abstract: In this thesis the work is based around the HELIOS (High Energy Laser Induced Overtone Source) laboratory, a facility at the Division of Molecular and Condensed Matter Physics at the Department of Physics and Astronomy, Uppsala University, Sweden. HELIOS generates XUV (extreme ultraviolet) photon pulses with energies between 15-70 eV and pulse lengths shorter than 50 fs. It is believed that the grating in the monochromator of the lab introduces a chirp, meaning that the different constituent energies of the pulse will be ordered in an non homogeneous way. Since the lab is striving to create as short pulses with as high temporal resolution as possible, learning more about any effects that might change the pulse is of great interest. If the source of the chirp effect is known then possible countermeasures can start being discussed. To investigate the pulse a numerical ray trace is performed for a XUV pulse passing through the monochromator using the BeamFour© software. A pulse consisting of 49500 rays with mean energy 40 eV and FWHM 0.5 eV was traced, but no clear dependence between wavelength and the pulse length could be observed. This seems to indicate that there either is no chirp present in the monochromator or that it is of such a small order that higher certainty (more rays) will be required to observe it.