Entwicklung eines bipolaren flugzeuggetragenen Aerosolmassenspektrometers

The aim of this thesis is the development of an aerosol mass spectrometer designed to determine aerosols in upper troposphere and the lowermost stratosphere. The instrument named SPLAT (Single Particle Laser Ablation Time of flight mass spectrometer) was developed for the integration in a research aircraft for a flight altitude of about 10 km. The SPLAT system should be able to provide information about the size and the chemical composition of an individual aerosol particle from ambient air. The knowledge of this parameter is of relevance, because of its important role for heterogeneous chemical reactions, for ozone depletion and for cloud formation. Direct effects of aerosol particles, like e.g. scattering and absorption of sunlight, may cause a negative or positive forcing of climate in dependence of size and composition. A differentially pumped inlet system separates the particles from the gas phase within the SPLAT system. At high vacuum conditions the sizing takes place through a laser ray configuration. Two laser rays measure the velocity of every individual particle. The velocity depends an the aerodynamic diameter of the particle. Further, the laser configuration triggers an excimer laser. A pulse of the excimer laser vaporizes and ionizes the particle when it reaches the middle of the mass spectrometer. To determine the mass of the ions formed, they are detected in a time-of-flight mass spectrometer. Both the negative and positive ions of a particle can be detected, because of the bipolar construction of the mass spectrometer. Thereby for the first time extensive studies of the size and the chemical composition of individual aerosol particles are possible for in-flight conditions. The efficiency of the instrument was verified in numerous laboratory measurements with particles of known diameter and known chemical composition. These measurements are further used to calibrate the Instrument. The participation in the MINOS field campaign an the island of Crete yielded the first measurements in ambient aerosol particles