Synchrotron Radiation Based Study of X-Ray Absorption of Flame Generated Nanoparticles

摘要

This report results from a contract tasking University of Rennes I as follows: The contractor will perform a study of soot growth and nucleation by a time-resolved synchrotron radiation based x-ray absorption method'. A gaseous fuel burner will be constructed that will allow a stable flame to be produced. It is here proposed to perform synchrotron-based experiments in which the mobility of the charged species can be studied. Such measurement is possible since the synchrotron radiation has a well-defined time structure and pump-probe type experiments can be performed. In order to do this correctly however, it is desirable to perform the experiments under vacuum and so a pre-mixed type of flame will be used. The burner assembly will be mounted in a vacuum chamber that can be mounted on the synchrotron radiation experimental bench. It is proposed to use cryopumping in order to achieve the high pumping rates necessary to allow a flame to burn in vacuum. (Cryopumping rates are typically 101/sec per square centimeter of cryosurface). In addition to the mobility experiments, it is proposed to examine the effects of incident wavelength on the absorption process in order to compare the results so obtained with existing models of x-ray absorption by graphite dust particles. The goal of this work is to study the influence of the incident x-ray wavelength on the absorption process. The experimentation will be performed at the University of Rennes using the UV lasers in their laboratory. These will be used to investigate the thermal ionization of soot particles. The experiment will also be tried at the Vacuum Ultra Violet undulator beamline SU5 at the LURE synchrotron in Paris. If scheduling permits, this experiment will be performed using UV light in the 5-40 eV range.