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Villigen, Switzerland

Willendrup P.,Technical University of Denmark | Farhi E.,ILL | Knudsen E.,Technical University of Denmark | Filges U.,PSI | Lefmann K.,Copenhagen University
Journal of Neutron Research | Year: 2014

The McStas neutron ray-tracing simulation package is a collaboration between Risø DTU, ILL, University of Copenhagen and the PSl. During its lifetime, McStas has evolved to become the world leading software in the area of neutron scattering simulations for instrument design, optimisation, virtual experiments. McStas is being actively used for the design-update of the European Spallation Source (ESS) in Lund. This paper includes an introduction to the McStas package, recent and ongoing simulation projects. Further, new features in releases McStas 1.12c and 2.0 are discussed. © 2014 - IOS Press and the authors. All rights reserved. Source

Reliable leak detection is of high importance for liquid metal targets. For the PSI Megapie target two novel approaches had been pursued: a thermocouple-based leak detector and one employing capacity sensors with impedance read out. Whereas the temperature based leak detector performed according to expectations, severe degradation of the impedance probes occurred during the irradiation period of Megapie. The electrical characteristics of the chosen insulator material ZrO2 stabilized by 1% Y2O3 showed massive changes over time and they exhibited strong dependence on the prevailing environment conditions. Three different contributions to effective electrical conductivity in the supposed insulator could be identified: a prompt radiation induced, a temperature induced, and most probably a gas induced change in conductivity. These components, both increases and decreases in bulk conductivity of the insulating slabs in the impedance probes, demonstrated some cross-dependence on each other. The alterations in conductivity and the mutual influence of the identified factors changed with the irradiation time and the probable exposure to gaseous radiolysis products at the location close to the beam entrance window of the liquid metal target. A phenomenological and qualitative description of the observed effects as they evolved during Megapie operation is presented. © 2009 Elsevier B.V. All rights reserved. Source

Ludeke A.,PSI
IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference | Year: 2014

Reliability is defined as the ability of a system or component to perform its required functions under stated conditions for a specified period of time [1]. If we are talking about accelerator reliability then we have to know what the required functions are. Many accelerator facilities restrict their analysis to the beam availability: how reliable is beam provided to the users? We will show that this metrics is often not fully adequate. Specific metrics can be much more useful to allow you to optimize your facility to the needs of your users. The three accelerator user facilities at PSI will serve as examples for these happy-user-indexes. Copyright © 2014 CC-BY-3.0 and by the respective authors. Source

Benedicto A.,CIEMAT | Missana T.,CIEMAT | Degueldre C.,PSI
Science of the Total Environment | Year: 2013

Colloids (ex. nanoparticles) may be relevant in contaminant migration in groundwater if the contaminant is strongly adsorbed onto colloids and they are stable in the environment.An integrated study of Se(IV) sorption and TiO2 colloid stability was performed in this work. This integrated study includes the experimental analysis and modelling of Se(IV) sorption onto TiO2 particle surface and the evaluation of the influence of adsorbed Se(IV) on TiO2 stability.Results indicated that low ionic strength and acid pH favour both high Se(IV) sorption and TiO2 colloid stability. However, at medium-high surface occupancy, sorbed Se(IV) highly affected TiO2 colloid stability. Anion adsorption decreases the positive surface charge shifting the TiO2 isoelectric point, thus promoting particle aggregation under acid pH.Nevertheless, the application of the single particle counting technique allowed determination of the presence of a significant fraction of TiO2 nanoparticles which are highly susceptible to migrate even under favourable conditions for aggregation. Therefore, although part of the TiO2 is disabled for migration by sorbed Se at acid conditions, still a considerable percentage that remains disaggregated could move together with Se. The developed Se(IV) sorption model can inform about the extent and type of sorption under specific geochemical conditions. © 2013 Elsevier B.V. Source

Ludeke A.,PSI
IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference | Year: 2014

Third generation light sources do aim for a very high reliability of the accelerator. This contribution describes the reliability reporting of the Swiss Light Source at the Paul Scherrer Institut, as it has been performed in the past decade. We will highlight the importance of a formal reporting on the accelerator reliability to support the long term optimization of the reliability of an accelerator facility. Copyright © 2014 CC-BY-3.0 and by the respective authors. Source

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