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

University essay from Uppsala universitet/Molekyl- och kondenserade materiens fysik

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.

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