Characterization of electromagnetic fields in the aSPECT spectrometer and reduction of systematic errors [Elektronische Ressource] / Fidel Ayala Guardia

Characterization ofelectromagnetic fields in theaSPECT spectrometer andreduction of systematic errorsDissertationzur Erlangung des Grades“Doktor der Naturwissenschaften”am Fachbereich Physik, Mathematik und Informatikder Johannes Gutenberg-Universitätin Mainzvorgelegt vonFidel Ayala Guardiageboren in ValenciaMainz, im October 2011iiA mis padres,iiiivAbstractThe aSPECT spectrometer has been designed to measure, with high precision, therecoil proton spectrum of the free neutron decay. From this spectrum, the electron an-tineutrino angular correlation coefficient a can be extracted with high accuracy. The goalof the experiment is to determine the coefficient a with a total relative error smaller than0.3%, well below the current literature value of 5%.FirstmeasurementswiththeaSPECTspectrometerwereperformedintheForschungs-Neutronenquelle Heinz Maier-Leibnitz in Munich. However, time-dependent backgroundinstabilities prevented us from reporting a new value of a.The contents of this thesis are based on the latest measurements performed with theaSPECT spectrometer at the Institut Laue-Langevin (ILL) in Grenoble, France. In thesemeasurements, background instabilities were considerably reduced. Furthermore, diversemodifications intended to minimize systematic errors and to achieve a more reliable setupwere successfully performed . Unfortunately, saturation effects of the detector electronicsturned out to be too high to determine a meaningful result.