Das Vakuumschulen‐Zertifikat

Certification of Vacuum Trainings This article describes the certification process for quality assurance of vacuum trainings by the German Vacuum Society (DVG). This quality certification was established in 2014. The first certification has been completed, another is ongoing. The certification ensures all participants a certain level of teaching and learning content in both theoretical and practical parts of the trainings. The applicants are assessed by a team of auditors named by the DVG. The procedure also includes discussion about possible improvements. The spectrum of training courses that can be certified covers general vacuum trainings and special training like leak detection, coating technologies, or mass spectrometry. For further information please contact Dr. Michael Wahl, Tel. +49 631 205‐73‐3333, E‐Mail wahl@ifo.uni‐kl.de     

Development of superconducting absorbers for CRESST light detectors

An important aspect of dark matter search experiments is the active background reduction by identification of the type of particle interacting in the detector. In CRESST this is achieved by a simultaneous detection of heat and light produced by an interaction in a scintillating crystal. The overall light collection efficiency is a crucial parameter in order to achieve enough sensitivity to measure the small fraction of the deposited energy that is emitted as scintillation light. For this purpose, a thin superconducting lead film deposited on sapphire substrates has been tested as an alternative light absorber to a silicon absorber. The first results already show a better light absorption of the lead film. Other superconducting films are also being analyzed.     

Phase-field simulation of irradiated metals: Part I: Void kinetics

We present a phase-field model of void formation and evolution in irradiated metals by spatially and temporally evolving vacancy and self-interstitial concentration fields. By incorporating a coupled set of Cahn–Hilliard and Allen–Cahn equations, the model captures the processes of point defect generation and recombination, annihilation of defects at sinks, as well as void nucleation and growth in the presence of grain boundaries. Illustrative results are presented that characterize the rate of void growth or shrinkage due to supersaturated vacancy or interstitial concentrations, void nucleation and growth kinetics due to cascade-induced defect production, as well as void denuded and peak zones adjacent to grain boundaries.     

Modifizierung unpolarer Polymeroberflächen

Modification of non‐polar polymer surfaces In numerous technological relevant processes the adhesion in compound systems is of central importance. It concerns for example surface coatings and the manufacturing of composites. Particular problems result at the compounding of polyolefins, silicones and fluoropolymers due to their very low surface energy. The modification of such polymer surfaces with the aim of functionalisation and with it of increasing the surface energy results in an improvement of adhesion properties of the materials. A well‐established procedure, particularly in the automotive industry, is the flame treatment of the surfaces. However, a defined chemical modification of the surface depends on many parameters and thus is very difficult to standardize. A defined change of the surface can be better achieved through a targeted plasma treatment, in which in our case the surface is stabilized by a subsequent wet chemical process step.     

Efficient performance analysis of newly proposed sleep-mode mechanisms for IEEE 802.16m in case of correlated downlink traffic

There is a considerable interest nowadays in improving energy efficiency of wireless telecommunications. The sleep-mode mechanism in WiMAX (IEEE 802.16) and the discontinuous reception (DRX) mechanism of LTE are prime examples of energy saving measures. Recently, Samsung proposed some modifications on the sleep-mode mechanism, scheduled to appear in the forthcoming IEEE 802.16m standard, aimed at minimizing the signaling overhead. In this work, we present a performance analysis of this proposal and clarify the differences with the standard mechanism included in IEEE 802.16e. We also propose some special algorithms aimed at reducing the computational complexity of the analysis.     

Highly Anisotropic Steel Processed by Selective Laser Melting

For additive manufacturing of metals, selective laser melting can be employed. The microstructure evolution is directly influenced by processing parameters. Employing a high energy laser system, samples made from austenitic stainless steel were manufactured. The microstructure obtained is characterized by an extremely high degree of anisotropy featuring coarse elongated grains and a 〈001〉 texture alongside the build direction during processing. Eventually, the anisotropy of the microstructure drastically affects the monotonic properties of the current material.