Modern precision neutrino experiments like Double Chooz require a highly efficient trigger system in order to reduce systematic uncertainties. The trigger and timing system of the Double Chooz experiment was designed according to this goal. The Double Chooz trigger system is driven by the basic idea of triggering on multiple thresholds according to the total visible energy and additionally triggering on the number of active photomultiplier tubes (PMTs) in the detector. To do so, the trigger system continuously monitors the analogue signals from all PMTs in the detector. The amplitudes of these PMT-signals are summed for groups of certain PMTs (group signals) and for all PMTs (sum signal), respectively. The group signals are discriminated by two thresholds for each input channel and four thresholds for the sum signal. The resulting signals are processed by the trigger logic unit which is implemented in a FPGA. In addition to the proper trigger, the trigger system provides a common clock signal for all subsequent data acquisition systems to guarantee a synchronous readout of the Double Chooz detectors. The present design of the system provides a high flexibility for the applied logic and settings, making it useful for experiments other than Double Chooz. The Double Chooz trigger and timing system was installed and commissioned in 2011. This article describes the hardware of the trigger and timing system. Furthermore the setup, implemented trigger logic and performance of the trigger and timing system for the Double Chooz experiment is presented.

The influence of heat treatments and Ca additions on the corrosion behaviour of HPDC AM50 was studied using potentiodynamic polarisation technique in bi‐distilled water at pH=8. Heat treatments caused a considerable modification of the polarisation behaviour, which manifested itself in a wide range of passivity in the anodic branch. During heat treatments, the Mg solid solution was enriched from 2 wt.% to 4 wt.% Al due to the partial dissolution of the β‐phase. This enabled the comprehensive formation of a double‐structured passive layer during polarisation. Only minor effect of Ca additions (0.7 wt.%) on the corrosion behaviour of AM50 was observed.

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