Characterizing the energy resolution of Bloch beamline.

Abstract: The Bloch beamline on 1.5 GeV ring at MAX IV Laboratory is dedicated to measure electronic structure of materials using the technique angle resolved photoelectron spectroscopy (ARPES) and spin resolved photoelectron spectroscopy (spin-ARPES). The main goal of the thesis is to experimentally determine, the energy resolution of the Bloch beamline at 21 eV and 62 eV as a function of the exit slit opening using total ion measurements. To achieve this, one has to first make sure that there was no roll misalignment of the grating. The reason being, if there is a roll misalignment, the beam exiting from the monochromator will move sideways when the grating pitch is changed to choose different energies. This sideway motion has to be then compensated by changing the pitch angle of the optical element after the monochromator. The first part of the work is to characterize, the pitch change required of the above mentioned optical element after the monochromator as a function of the grating pitch, so the photon beam goes along the correct path. This data was then used to evaluate with a simple model the grating roll error based on the relationship between pitch angle correction of the mentioned optical element and the grating pitch angle. The validity of the model was checked with a ray tracing method before correcting for the grating misalignment. After re-alignment (by the beamline staff), the beam movement was negligible and one could proceed with the experiment to determine the beamline energy resolution at 21 eV and 62 eV using total ion yield measurements.