Characterisation and calibration of a scintillating fibre detector with > 4000 multi-anode photomultiplier channels

In the Kaos spectrometer at the Mainz Microtron a high-resolution coordinate detector for high-energy particles is operated. It consists of scintillating fibres with diameters of 4000 multi-anode photomultiplier channels. It is one of the most modern focal-plane detectors for magnetic spectrometers world-wide. To correct variations in the detection efficiency, caused by the different gains and the different optical transmittances, a fully automated off-line calibration procedure has been developed. The process includes the positioning of a radioisotope source alongside the detector plane and the automated acquisition and analysis of the detector signals. It was possible to characterise and calibrate each individual fibre channel with a low degree of human interaction.Comment: Nucl. Instrum. Meth. A (2012

Remote surface damage detection on rotor blades of operating wind turbines by means of infrared thermography

Wind turbines are constantly exposed to wind gusts, dirt particles and precipitation. Depending on the site, surface defects on rotor blades emerge from the first day of operation on. While erosion increases quickly with time, even small surface defects can affect the performance of the wind turbine. Consequently, there is demand for an easily applicable remote monitoring method for rotor blades that is capable of detecting surface defects at an early stage. In this work it is investigated if infrared thermography (IRT) can meet these requirements by visualizing differences in the thermal transport and the corresponding surface temperature of the wall-bounded flow.Firstly, a validation of the IRT method compared to stereoscopic particle image velocimetry measurements is performed comparing both types of experimental results for the boundary layer of a flat plate. Then, the main characteristics of the flow in the wake of generic surface defects on different types of lifting surfaces are studied both experimentally and numerically: temperature gradients behind protruding surface defects on a flat plate and a DU 91-W2-250 profile are studied by means of IRT. The same is done with the wall shear stress from Reynolds-averaged Navier–Stokes simulations of a wind turbine blade. It is consistently observed, both in the experiments and the simulations, that turbulent wedges are formed on the flow downstream of generic surface defects. These wedges provide valuable information about the kind of defects that generate them. At last, experimental and numerical performance measures are taken into account for evaluating the aerodynamic impact of surface defects on rotor blades. We conclude that the IRT method is a suitable remote monitoring technique for detecting surface defects on wind turbines at an early stage.</p

Measurement of polarization transfer in the quasi-elastic 40Ca(e⃗,e′p⃗)^{40}{\rm Ca}(\vec{e},e' \vec{p}) process

Polarization transfer to a bound proton in polarized electron knock-out reactions, $\mathrm{A}(\vec{e},e^{\prime}\vec{p})$, is a powerful tool to look for in-medium modification of the bound proton. It requires comparison to calculations which consider the many-body effects accompanying the quasi-free process. We report here measured components $P_x^{\prime}$, $P_z^{\prime}$, and their ratio $P_x^{\prime}/P_z^{\prime}$, of polarization transfer to protons bound in $^{40}\mathrm{Ca}$, which is described well by the shell model and for which reliable calculations are available. While the calculations capture the essence of the data, our statistical precision allows us to observe deviations which cannot be explained by simple scaling, including by varying the proton electromagnetic form factor ratio $G_E/G_M$. We further explore the deviations of the ratio of the polarization transfer components from that of a free proton, $(P_x^{\prime}/P_z^{\prime})_{\rm A}/(P_x^{\prime}/P_z^{\prime})_{\rm H}$, and its dependence on the bound-proton virtuality