[en] The aim of the KArlsruhe TRItium Neutrino experiment is to improve the current neutrino mass sensitivity limit to 0.2 eV/c"2 (90%C.L.). For that, the required proof of suitability of several components for a low pressure tritium atmosphere is furnished. In addition, an optical design for an e-gun is developed and the resulting electron rate is calculated. Also, a final Rear Wall with temporally stable and homogeneous work function is developed and characterized within the scope of this thesis.

[en] The KArlsruhe TRItium Neutrino-Experiment KATRIN will perform a model-independent measurement of the antineutrino mass by the examination of the beta electron energy spectrum of a gaseous molecular tritium source. To achieve the desired sensitivity of 0.2 eV/c"2 (90 % CL) the plasma potential of the tritium gas must be temporally and spatially stable within 20 meV. Therefore, the work function of the so called Rear Wall which probably defines the plasma potential must be known even more precisely and the temporal changes must be investigated. A common instrument to measure the work function of a surface with a precision of a few meV is a Kelvin Probe. Such a system was built up at the Tritium Laboratory Karlsruhe. In the talk the working principle of a Kelvin Probe and the setup are presented. In addition first work function measurements of Rear Wall candidates are discussed.

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[en] The aim of the Karlsruhe Tritium Neutrino (KATRIN) experiment is the model-independent measurement of the anti-neutrino mass. KATRIN measures the endpoint region of the electron energy spectrum of tritium beta decay where a non-vanishing neutrino mass has an influence on the shape of the spectrum. The beta electrons are produced in a windowless gaseous tritium source. In order to reach the design sensitivity of 200 meV/c² (90% C.L.) the tritium concentration of the inlet gas is continuously monitored by a laser Raman system with 0.1% statistical uncertainty. The system uses an optical measurement cell which is located in-line in the tritium loop of KATRIN. Tritium resistant optical coatings on all windows surfaces of the measurement cell are necessary to maintain a reliable and almost maintenance-free nonstop operation of the Raman system over 5 years of KATRIN measurements. However the up to now employed electron-beam deposited coatings were damaged after about 3 months of contact with a high purity tritium gas atmosphere (∝200 mbar, >90% purity). Therefore commercially available coating types are currently being tested in a dedicated COAting Test EXperiment (COATEX) by repeated exposures to tritium gas and subsequent measurements of their optical properties. In this talk an overview of COATEX is given, and results from the first series of exposures are presented.

[en] For a wide range of high-precision experiments in physics, well-defined electric potentials for achieving high measurement accuracies are required. An accurate determination of the electric potential is crucial for the measurement of the neutrino mass (KATRIN) as well as the measurement of the e"- anti ν_e correlation coefficient a in free neutron decay (aSPECT). Work function fluctuations on the electrodes lead to uncertainties in the distribution of the electric potential. For aSPECT, the electric potential has to be known at an accuracy of 10 mV. However, due to the patch effect of gold, work function fluctuations of several 100 meV can occur. Therefore, the work function distributions of the gold-plated electrodes have been measured using a Kelvin probe. Furthermore, the change of work function distributions over time as well as the influence of relative humidity on the work function measurement have been investigated. For aSPECT, the work function distributions of the gold-plated electrodes have been measured using a Kelvin probe. Due to the patch effect of gold, work function fluctuations of up to 160 meV occur. This would lead to a significant uncertainty of the potential barrier, which should be known at an accuracy of 10 mV. Furthermore, the change of work function distributions over time as well as the influence of relative humidity on the work function measurement have been investigated.

[en] High precision experiments at low energies are used in several areas of fundamental physics. Examples are, a.o., high precision beta decay experiments and experiments using Penning traps for mass measurements or for g-factor measurements. The knowledge of the potentials and potential differences inside these experiments is crucial to achieve the desired sensitivities. However, the potentials are modified by the work function of the electrodes, which can show fluctuations of of several hundred meV, both spatially and temporally. For the low energy precision experiments aSPECT and KATRIN we have commissioned and studied a scanning Kelvin probe system to investigate the work function fluctuations of gold surfaces on different substrates. Since the Kelvin probe is a relative method, also photoelectron spectroscopy was performed additionally to obtain information on the absolute work functions. The temporal stability of the work functions of the surfaces was also tested, as well as the influence of standard cleaning procedures for ultra-high vacuum applications and bake-out. This poster presents the results of these measurements.