Showing papers by "Joachim Schulz published in 2003"

DoseSim: Microsoft-Windows graphical user interface for using synchrotron x-ray exposure and subsequent development in the LIGA process

Abstract: The LIGA process, which combines x-ray lithography with electroplating and moulding, is a technique used worldwide for the fabrication of high aspect ratio microstructures. In the first step (x-ray lithography), a resist layer is applied to a metal-coated substrate, which is then patterned by shadow printing through an x-ray mask with synchrotron radiation. The second step consists in dissolving the exposed parts or the unexposed parts, of a positive and negative resist, respectively, in an organic developer. A graphical user interface has been developed, working under Windows, which meets the necessary requirements of a LIGA x-ray beamline. The code currently permits the computation of synchrotron radiation from bending magnets, the effects of the optical properties of materials, and the necessary parameters for the resist exposure. Also, this program is highly flexible and allows the user to access many annexed calculation possibilities, for example, optimization of the absorber thickness for a desired dose after the absorber, filter possibilities for a desired ratio top dose/bottom dose, calculation of the necessary time to develop the exposed resist. The comparison of results of this code and data used by different x-ray LIGA centers will be given. A general overview of the possibilities of this program will be presented.

Observation of elastic scattering effects on photoelectron angular distributions in free Xe clusters

Abstract: We report an observation of substantial deviations in the photoelectron angular distribution for photoionization of atoms in free Xe clusters compared to the case of photoionization of free atoms. The cross section, however, seems not to vary between the cluster and free atoms. This observation was made in the vicinity of the Xe 4d Cooper minimum, where the atomic angular distribution is known to vary dramatically. The angular distribution of electrons emitted from atoms in the clusters is more isotropic than that of free atoms over the entire kinetic energy range studied. Furthermore, the angular distribution is more isotropic for atoms in the interior of the clusters than for atoms at the surface. We attribute this deviation to elastic scattering of the outgoing photoelectrons. We have investigated two average cluster sizes, (N) approximate to 4000 and 1000 and found no significant differences between these two cases. (Less)

Energy absorption of free rare gas clusters irradiated by intense VUV pulses of a free electron laser

Abstract: As one of the first experiments at the free electron laser of the TESLA Test Facility (TTF) the Coulomb explosion of Xenon clusters irradiated with high intensity pulses at a wavelength of 98 nm has been observed. Classical trajectory calculations have been performed in order to illuminate the energy absorption process. Comparison with typical parameters in the infrared regime shows that above barrier ionization is suppressed due to the fast oscillating field and thermionic ionization prevails.

Linear dichroism of the 4f photoemission in the giant resonance of atomic europium

Abstract: The linear dichroism in the $4f$ photoelectron spectra of atomic Eu excited at photon energies in the range of the giant $4d\ensuremath{-}4f$ resonance have been determined. Dramatic changes of the dichroism have been observed when tuning the photon energy through the giant resonance. The dichroism patterns are compared to the predictions of a model based on LS coupling which takes the interaction of the discrete resonances with the ionization continua into account.

Acrylate based adhesive, its use and a process for connecting two objects

Abstract: An adhesive comprising (wt.%): a solution of polymethyl methacrylate (PMMA) (10-20) in glycidyl methacrylate (GMA) (10-50) and monomethyl methacrylate (MMA) (30-80) and a radical starter is new. An Independent claim is included preparation of the adhesive by applying at least one of two components at the adhesive site to be bonded, followed by polymerization, where one of the components is PMMA and the other is Si, a metal, glass, or ceramic.