Nanosecond interferometry

The plume development in MD simulations can only be followed up to a few nanoseconds after the pulse, which is not enough to compare the data with various experimental techniques (such as MALDI, TOF-MS, shadowgra-phy, interferometry, or for PLD). The long-term plume expansion is then modeled by the direct simulation Monte Carlo method, which was recently applied to systems relevant to MALDI [112]. 

The analysis of the transmission of the film during irradiation suggests that decomposition of the triazene chromophore occurs during irradiation. The decomposition of the chromophore in the film should result in changes of the surface topography. Therefore another time-resolved method was applied that can give this information. This technique is nanosecond interferometry, which allows the observation of the surface morphology with nanosecond resolution. 

The experimental setup for the nanosecond interferometry experiments has been described previously [198, 199], except for a novel improved optical configuration. The optical configurations are illustrated in Figs. 32a and b, which are called surface and internal configurations, respectively. The surface configuration is the same as that in the previous works [198, 199], while the internal configuration is a novel design. 

Another method that can give complementary information to interferometry is nanosecond shadowgraphy. Shadowgraphy directly shows the speed of ablated fragments and yields information about the size of the ejected fragments. Solid fragments can result in contamination of the optics and remaining polymer surface. This is probably due to the incomplete decomposition of the polymer. To avoid this kind of contamination in microfabrica-... 

The other group of methods includes those that are based on the registration of the state originated after the shock wave reflection from a barrier. For instance, the detonation pressure m be determined on the basis of the measurement of a thin metal plate firee-surface velocity. The plate free-surface velocity can be determined using optical methods or the electrocontact type of probes and oscilloscope technique. The methods based on the determination of the shock wave velocity through an inert material, e.g., the Aquarium test, are also included in this group. The time resolution of these methods may be on a nanoseconds scale, and even less than a nanosecond, e.g., w en laser interferometry technique is used. Since the processes in the shock fi-ont occur on a nanosecond scale, the present-day techniques are still inadequate to study the detonation wave shock front. 

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