Developments Towards High-Resolution Muonic Atom X-ray Spectroscopy of Low-Z Elements : For precision measurements of absolute nuclear charge radii

Abstract: This Master's thesis investigates a method to measure atomic nuclei with record precision using muonic atom X-ray spectroscopy. In particular, 6Li is measured experimentally. The method used is independent from the previous most precise measurement of the 6Li nuclear charge radius which uses electron scattering. Measuring low-Z elements using muonic X-ray transitions requires excellent detectors which have so far been mostly optimised for higher energies. This project investigates methods to reach precision requirements for low-Z elements which can yield insight into nuclear structure models, and uses a Silicon Drift Detector (SDD) which is here characterised in detail and found to allow for significantly improved results over previous attempts. So far, the SDD and developed calibration scheme demonstrates a 3.7 eV precision compared to the target 0.5 eV. It appears to be limited by detector resolution, which also makes curve fitting difficult for complex line structures. A new method for generating calibration lines, X-ray fluorescence, is tested and shows good promise for future use. The planned use of a Metallic Magnetic Microcalorimeter will potentially improve results significantly, having a much-improved resolution over SDD's. Preliminary experimental results find ΔEµLi-6, 2p-1s = 18780.6 ± 15.7 eV, which is a factor of 4 improvement over the previous best measurement of this transition and the world's most precise measurement to date. While the uncertainty is larger than seen in designated calibration runs, it demonstrates the ability to perform high-precision muonic atom spectroscopy. With new detector technologies, this thesis finds no immediate obstacles to the target 0.5 eV precision.