arXiv subjects

A. Lopatin

Publications and source records attributed to A. Lopatin.

4 recordsLinked to original sources

arXiv2013

The H.E.S.S. central data acquisition system

The High Energy Stereoscopic System (H.E.S.S.) is a system of Imaging Atmospheric Cherenkov Telescopes (IACTs) located in the Khomas Highland in Namibia. It measures cosmic gamma rays of very high energies (VHE; >100 GeV) using the Earth's atmosphere as a calorimeter. The H.E.S.S. Array entered Phase II in September 2012 with the inauguration of a fifth telescope that is larger and more complex than the other four. This paper will give an overview of the current H.E.S.S. central data acquisition (DAQ) system with particular emphasis on the upgrades made to integrate the fifth telescope into the array. At first, the various requirements for the central DAQ are discussed then the general design principles employed to fulfil these requirements are described. Finally, the performance, stability and reliability of the H.E.S.S. central DAQ are presented. One of the major accomplishments is that less than 0.8% of observation time has been lost due to central DAQ problems since 2009.

astro-ph.IM↗

arXiv2012

Towards a Flexible Array Control and Operation Framework for CTA

The Cherenkov Telescope Array (CTA) \cite{CTA:2010} will be the successor to current Imaging Atmospheric Cherenkov Telescopes (IACT) like H.E.S.S., MAGIC and VERITAS. CTA will improve in sensitivity by about an order of magnitude compared to the current generation of IACTs. The energy range will extend from well below 100 GeV to above 100 TeV. To accomplish these goals, CTA will consist of two arrays, one in each hemisphere, consisting of 50-80 telescopes and composed of three different telescope types with different mirror sizes. It will be the first open observatory for very high energy $γ$-ray astronomy. The Array Control working group of CTA is currently evaluating existing technologies which are best suited for a project like CTA. The considered solutions comprise the ALMA Common Software (ACS), the OPC Unified Architecture (OPC UA) and the Data Distribution Service (DDS) for bulk data transfer. The first applications, like an automatic observation scheduler and the control software for some prototype instrumentation have been developed.

astro-ph.IM↗

arXiv2007

Microscopic theory of thermal phase slips in clean narrow superconducting wires

We consider structure of a thermal phase-slip center for a simple microscopic model of a clean one-dimensional superconductors in which superconductivity occurs only within one conducting channel or several identical channels. Surprisingly, the Eilenberger equations describing the saddle-point configuration allow for exact analytical solution in the whole temperature and current range. This solution allows us to derive a closed expression for the free-energy barrier, which we use to compute its temperature and current dependences.

cond-mat.supr-con↗

arXiv1998

Large-N treatment of the Abrikosov transition at low temperatures

We investigate the influence of order parameter fluctuations on the transition between normal and mixed superconducting states at low temperatures. We show that in case of clean quasi-two-dimensional superconductors the transition can be described by the functional of the Ginzburg-Landau type. We consider the large-N generalization of this functional and using the lowest Landau level approximation we get the large-N equations which describe the phase transition. In case of physical dimensionality we found that the transition is of the first order. The fluctuations significantly affect the temperature dependence of the upper critical field.

cond-mat.supr-con↗