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| Master Thesis | GSI-2024-00516 |
2023
Abstract: The gas injection system, referred to as the System for Measuring Overlap With Gas(SMOG2), used in the Large Hadron Collider beauty (LHCb) experiment at CERN,employs storage cells to provide gas targets for collision experiments. In the next stageof development, the LHCSpin project aims to establish a polarized atomic hydrogen gastarget through the utilization of an amorphous carbon-coated storage cell.At the Nuclear Physics Institute of the Jülich research center, an atomic beam sourcecapable of generating a polarized atomic hydrogen beam was available, along with aLamb-shift polarimeter capable of measuring the nuclear polarization of hydrogen atomsand molecules. These resources facilitated an in-depth exploration of the propertiesof such a storage cell, with a specific focus on assessing the recombination rate ofpolarized atoms and the polarization preservation on carbon surfaces. Additionally, anovel beam chopper design was introduced to investigate the impact of the Lyman-αradiation induced desorption recombination process.Results of mass spectrometry measurements, conducted using a Wien filter in combinationwith a Faraday cup, confirmed the absence of a dominant superficial water layer andrevealed the beam chopper’s limitations in effectively reducing atomic beam and photonintensity. Utilizing transition units alongside a spin filter, polarization measurementsfor atomic hydrogen showed a recombination rate ranging from 95.8% to 100% and amaximum vector polarization of −0.606 ± 0.002. In the case of molecular hydrogen,measurements indicated a maximum polarization of −0.54±0.01. The observed characteristicsalign with fit parameters derived from a mathematical model describing the lossof polarization due to surface interactions.These findings emphasize the feasibility of employing carbon-coated storage cells aswater-repellent, polarized molecular gas targets in accelerator experiments. Leveragingthe high-energy ion beam delivered by the Large Hadron Collider creates possibilitiesfor conducting spin physics experiments that were previously beyond reach.
Note: Masterarbeit, FH Aachen, 2023
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Appears in the scientific report 2024
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