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Gegelia J.,Johannes Gutenberg University Mainz | Gegelia J.,High Energy Physics Institute | Scherer S.,Johannes Gutenberg University Mainz
Journal of Physics A: Mathematical and Theoretical | Year: 2010

By means of a simple scalar field theory it is demonstrated that the Lagrange formalism and Ostrogradsky's Hamilton formalism in the presence of higher derivatives, in general, do not lead to the same results. While the two approaches are equivalent at the classical level, differences appear due to quantum corrections. © 2010 IOP Publishing Ltd. Source

Tejedor L.A.,Complutense University of Madrid | Boix J.,High Energy Physics Institute | Dubois F.,Complutense University of Madrid | Konno Y.,Kyoto University | And 3 more authors.
IEEE Transactions on Nuclear Science | Year: 2013

Photomultiplier transit time variation due to different high-voltage settings is a significant problem that degrades the performance of the systems that try to recognize fast image patterns in arrays of this type of photosensors. This effect is especially harmful for the performance of the trigger system of Cherenkov telescope cameras. With the aim of overcoming this effect, an electronic system has been designed, manufactured, and tested. This system can reduce the delay differences by introducing the appropriate variable delay for each photomultiplier (PMT), which is calculated by making use of a delay meter specially designed for this application. The specifications of the system have been defined by means of simulations and the measurements fulfill the requirements. The circuits used in this delay compensation system, as well as the simulations and measurements of the prototypes, are presented in this paper. © 2013 IEEE. Source

Tejedor L.A.,Complutense University of Madrid | Barcelo M.,High Energy Physics Institute | Boix J.,High Energy Physics Institute | Herranz D.,Complutense University of Madrid | And 5 more authors.
IEEE Transactions on Nuclear Science | Year: 2013

Arrays of Cherenkov telescopes typically use multi-level trigger schemes to keep the rate of random triggers from the night sky background low. At a first stage, individual telescopes produce a trigger signal from the pixel information in the telescope camera. The final event trigger is then formed by combining trigger signals from several telescopes. In this paper we present a Cherenkov telescope trigger scheme based on the analog pulse information of the pixels in a telescope camera. Advanced versions of all components of the system have been produced and a working prototype has been tested, showing in most cases features which surpass previous designs in terms of compactness, low noise, short delay, low power consumption and flexibility to be adapted to different observation conditions. Finally, issues related to integrating the trigger system in a telescope camera and in the whole array will be dealt with. © 1963-2012 IEEE. Source

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