Search

The avoidance of any moving parts in a microthruster exhibits a great potential for low-noise thrust generation in the micronewton range. This is required, e.g., for scientific missions that need attitude and orbit control systems with exquisite precision. Laser ablation propulsion offers the opportunity of permanent inertia-free, electro-optical delivery of laser energy to access the propellant entirely without moving it. New propellant is accessed by ablating the previous surface in layers, essentially damaging the surface with a laser over and over again. The resulting surface properties for different fluences and scanning patterns were investigated for multiple layers of aluminum, copper, and gold. The pulse-length-specific issues of various ablation mechanisms such as vaporization, spallation, and phase explosion are accounted for by the use of a 10-ps laser system and a 500-ps laser system. We show that the surface roughness produced with 500-ps laser pulses is approximately twice the surface roughness generated by using 10-ps laser pulses. Furthermore, with 500-ps pulses, the surface roughness shows low dependency on the fluence for carefully chosen scanning parameters. Therefore, we conclude that laser pulse duration differences in the picosecond and nanosecond regimes will not necessarily alter surface roughness properties.

Im Rahmen dieser Arbeit wurde die Spallationsreaktion 56Fe + p in inverser Kinematik in Hinblick auf die vollständige Identifikation der schweren Restkerne untersucht. Zur Durchführung des Experiments an der GSI in Darmstadt wurde ein ringabbildender Cerenkov-Zähler zur Geschwindigkeitsmessung eingesetzt. Zur Integration in die Datenaufnahme wurde eine neue schnelle Auslese-Elektronik entwickelt und im Experiment erfolgreich eingesetzt. Die Impulsmessung erfolgte über das ALADiN-Spektrometer, für das ein neues Software-Paket zur Impulsrekonstruktion erstellt wurde. Aus den Daten des Experiments konnten massenaufgelöst Wirkungsquerschnitte und Geschwindigkeitsverteilungen für über 100 Isotope berechnet und mit empirischen Modellen sowie anderen Experimenten zur Spallation verglichen werden. Die im Experiment gewonnenen Erkenntnisse erlauben gezielte Verbesserungen beim Aufbau des neuen R3B-Spektrometers an FAIR. In this work the spallation reaction 56Fe + p was investigated in inverse kinematics with regard to complete identification of the heavy residues. A ring imaging Cerenkov counter was used for velocity measurements in the experimental setup located at GSI in Darmstadt. A new fast readout electronic was developed and has been operated successfully in the experiment. Momentum reconstruction was carried out with the ALADiN spectrometer and a new software package written for this purpose. Cross sections and velocity distributions for more than 100 mass separated isotopes could be extracted from the dataset and compared with empirical models and other spallation experiments. The experiencies gained in this experiment will be used for systematic improvements in the setup of the new spectrometer R3B at FAIR.