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Sparks in MSGCs can be induced by strongly ionizing particles that damage the anodes. In MSGCs combined with GEMs, the MSGC gain can be reduced below the sparking threshold. However, occasionally discharges in the GEM can produce large secondary sparks at the MSGC. We discuss the dependence of the spark rate on geometrical and electrical parameters of the detectors. Different gas mixtures are compared. The most efficient way to avoid secondary sparks is to reduce the electric field between GEM and MSGC to below 6.6kV/cm. We present first results from a robust alternative to MSGCs, the groove detector.

We have measured the spark rate as a function of voltages and geometric parameters and investigated the damage to Au, Al, Cr, W and Rh electrodes. Measurements of the spark signals compare well with simulations. We propose a new device, the Macro Gap Chamber.

Disc brake manufacturing for railway vehicles has become a popular fieldfor assessing the possibilities of MMC application during recent years. The substitution of conventional ferrous materials by light alloys allows for a significant reduction in the rotating masses in a vehicle bogie which leads to a decrease in energy consumption. The use of conventional aluminium casting alloys is not suitable to solve this. Castable MMC materials are a highly promising alternative. Under economic pressure MMC solutions are required to be not only mechanically superior but also cost effective, and due to the low ductility of these particle reinforced materials there is a needfor new concepts. Locally optimised discs consist of a ductile carrier (body) with wear resistant rubbing surfaces. This led to several prototype disc brakes being manufactured by various casting processes. This paper gives an overview of the state of the art and newly developed manufacturing routes and materials, metallic and non-metallic, for rail disc brake applications.

In general losses of optical of less than 1 % cannot be measured precisely with the best-established techniques (e.q. two-beam spectroscopy). However, it is possible to measure losses in the 0.0001 - 0.5 % range with high accuracy using cavity enhanced spectroscopy (CES) methods. Such low losses can be measured with CES, due to an increased interaction path way with the object. The Cavity Ring-Down (CRD) technique takes advantage of the CES method and transforms the optical loss information into the time domain. Two types of CRD setups for spectrally resolved loss measurement of laser mirrors will be presented. The first setup uses a tunable laser system for serial detection of the reflectivity spectra. The second method determines the spectral losses using a super continuum source. Here, simultaneous excitation and a spectrometer based camera system for separate detection of several wavelengths is used. Results will be shown and compared with direct absorption measurements of the same sample.