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Papers by Klemens Mosshammer
Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021), 2021
The High Energy Stereoscopic System (H.E.S.S.) is an array of five Imaging Atmospheric Cherenkov ... more The High Energy Stereoscopic System (H.E.S.S.) is an array of five Imaging Atmospheric Cherenkov Telescopes located in the Khomas Highland of Namibia. H.E.S.S. observes gamma rays above tens of GeV by detecting the Cherenkov light that is produced when Very High Energy gamma rays interact with the Earth's atmosphere. The H.E.S.S. Data Acquisition System (DAQ) coordinates the nightly telescope operations, ensuring that the various components communicate properly and behave as intended. It also provides the interface between the telescopes and the people on shift who guide the operations. The DAQ comprises both the hardware and software, and since the beginning of H.E.S.S., both elements have been continuously adapted to improve the data-taking capabilities of the array and push the limits of what H.E.S.S. is capable of. Most recently, this includes the upgrade of the entire computing cluster hosting the DAQ software, and the accommodation of a new camera on the large 28m H.E.S.S. telescope. We discuss the performance of the upgraded DAQ and the lessons learned from these activities.
The Cherenkov Telescope Array (CTA) project is the initiative to build the next-generation gamma-... more The Cherenkov Telescope Array (CTA) project is the initiative to build the next-generation gamma-ray observatory. With more than 100 telescopes planned to be deployed in two sites, CTA is one of the largest astronomical facilities under construction. The Array Control and Data Acquisition (ACADA) system will be the central element of on-site CTA Observatory operations. The mission of the ACADA system is to manage and optimize the telescope array operations at each of the CTA sites. To that end, ACADA will provide all necessary means for the efficient execution of observations, and for the handling of the several Gb/s generated by each individual CTA telescope. The ACADA system will contain a real-time analysis pipeline, dedicated to the automatic generation of science alert candidates based on the inspection of data being acquired. These science alerts, together with external alerts arriving from other scientific installations, will permit ACADA to modify ongoing observations at sub...
The Cherenkov Telescope Array is the future ground-based facility for gamma-ray astronomy at very... more The Cherenkov Telescope Array is the future ground-based facility for gamma-ray astronomy at very-high energies. The CTA Observatory will comprise more than 100 telescopes and calibration devices that need to be centrally managed and synchronized to perform the required scientific and technical activities. The operation of the array requires a complex Supervisory Control and Data Acquisition (SCADA) system, named Array Control and Data Acquisition (ACADA), whose quality level is crucial for maximizing the efficiency of the CTA operations. In this contribution we aim to present the Quality Assurance (QA) strategy adopted by the ACADA team to fulfill the quality standards required for the creation and usage of ACADA software. We will describe the QA organization and planned activities, together with the quality models and the related metrics defined to comply with the required quality standards. We will describe the procedures, methods and tools which will be applied in order to guara...
Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021), 2021
Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observati... more Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observations over the past decade have surprisingly revealed almost two hundred VHE emitters which appear to act as cosmic particle accelerators. These sources are an important component of the Universe, influencing the evolution of stars and galaxies. At the same time, they also act as a probe of physics in the most extreme environments known-such as in supernova explosions, and around or after the merging of black holes and neutron stars. However, the existing experiments have provided exciting glimpses, but often falling short of supplying the full answer. A deeper understanding of the TeV sky requires a significant improvement in sensitivity at TeV energies, a wider energy coverage from tens of GeV to hundreds of TeV and a much better angular and energy resolution with respect to the currently running facilities. The next generation gamma-ray observatory, the Cherenkov Telescope Array Observatory (CTAO), is the answer to this need. In this talk I will present this upcoming observatory from its design to the construction, and its potential science exploitation. CTAO will allow the entire astronomical community to explore a new discovery space that will likely lead to paradigm-changing breakthroughs. In particular, CTA has an unprecedented sensitivity to short (sub-minute) timescale phenomena, placing it as a key instrument in the future of multi-messenger and multi-wavelength time domain astronomy. I will conclude the talk presenting the first scientific results obtained by the LST-1, the prototype of one CTA telescope type-the Large Sized Telescope, that is currently under commission.
Software and Cyberinfrastructure for Astronomy V, Jul 6, 2018
The Cherenkov Telescope Array (CTA) will be the next-generation ground-based instrument for detec... more The Cherenkov Telescope Array (CTA) will be the next-generation ground-based instrument for detecting veryhigh energy gamma rays. It will consist of roughly 100 telescopes of different sizes and designs. In addition, a variety of auxiliary instrumentation will be part of the array. The Observation Execution System (OES) is the software system in charge of operating and monitoring all telescopes and devices, applying short-term observation schedules depending on the hardware status and environmental conditions and handling the data. Motivated by the wealth of tasks to accomplish and requirements to fulfil, a software development procedure is conceived for the development of OES. Part of this development process is the application of software testing procedures. These procedures range from unit tests up to system tests and stress tests. In this contribution, the software development process and the application of static and dynamic code analysis tools are described.
Physical Review B, 2014
We present a theory of magnetotransport through an electronic orbital, where the electron spin in... more We present a theory of magnetotransport through an electronic orbital, where the electron spin interacts with a (sufficiently) large external spin via an exchange interaction. Using a semiclassical approximation, we derive a set of equations of motions for the electron density matrix and the mean value of the external spin that turns out to be highly nonlinear. The dissipation via the electronic leads is implemented in terms of a quantum master equation that is combined with the nonlinear terms of the spin-spin interaction. With an anisotropic exchange coupling a variety of dynamics is generated, such as self-sustained oscillations with parametric resonances or even chaotic behavior. Within our theory we can integrate a Maxwell-demon-like closed-loop feedback scheme that is capable of transporting particles against an applied bias voltage and that can be used to implement a spin filter to generate spin-dependent oscillating currents of opposite directions.
Physical Review B, 2012
We present a theory of magnetotransport through a system of two coupled electronic orbitals, wher... more We present a theory of magnetotransport through a system of two coupled electronic orbitals, where the electron spin interacts with a (large) local magnetic moment via an exchange interaction. For the physical realization of such a setup we have in mind, for example, semiconductor quantum dots coupled to an ensemble of nuclear spins in the host material or molecular orbitals coupled to a local magnetic moment. Using a semiclassical approximation, we derive a set of Ehrenfest equations of motion for the electron density matrix and the mean value of the external spin (Landau equations): Due to the spin coupling they turn out to be nonlinear and, importantly, also coherences between electron states with different spin directions need to be considered. The electronic spin-polarized leads are implemented in form of a Lindblad-type dissipator in the infinite bias limit. We have solved this involved dynamical system numerically for various isotropic and anisotropic coupling schemes. For isotropic spin coupling and spin-polarized leads we study the effect of current-induced magnetization of the attached spin and compare this with a single quantum dot setup. We further demonstrate that an anisotropic coupling can lead to a rich variety of parametric oscillations in the average current reflecting the complicated interplay between the Larmor precession of the external spin and the dissipative coherent dynamics of the electron spin.
Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021), 2021
The High Energy Stereoscopic System (H.E.S.S.) is an array of five Imaging Atmospheric Cherenkov ... more The High Energy Stereoscopic System (H.E.S.S.) is an array of five Imaging Atmospheric Cherenkov Telescopes located in the Khomas Highland of Namibia. H.E.S.S. observes gamma rays above tens of GeV by detecting the Cherenkov light that is produced when Very High Energy gamma rays interact with the Earth's atmosphere. The H.E.S.S. Data Acquisition System (DAQ) coordinates the nightly telescope operations, ensuring that the various components communicate properly and behave as intended. It also provides the interface between the telescopes and the people on shift who guide the operations. The DAQ comprises both the hardware and software, and since the beginning of H.E.S.S., both elements have been continuously adapted to improve the data-taking capabilities of the array and push the limits of what H.E.S.S. is capable of. Most recently, this includes the upgrade of the entire computing cluster hosting the DAQ software, and the accommodation of a new camera on the large 28m H.E.S.S. telescope. We discuss the performance of the upgraded DAQ and the lessons learned from these activities.
The Cherenkov Telescope Array (CTA) project is the initiative to build the next-generation gamma-... more The Cherenkov Telescope Array (CTA) project is the initiative to build the next-generation gamma-ray observatory. With more than 100 telescopes planned to be deployed in two sites, CTA is one of the largest astronomical facilities under construction. The Array Control and Data Acquisition (ACADA) system will be the central element of on-site CTA Observatory operations. The mission of the ACADA system is to manage and optimize the telescope array operations at each of the CTA sites. To that end, ACADA will provide all necessary means for the efficient execution of observations, and for the handling of the several Gb/s generated by each individual CTA telescope. The ACADA system will contain a real-time analysis pipeline, dedicated to the automatic generation of science alert candidates based on the inspection of data being acquired. These science alerts, together with external alerts arriving from other scientific installations, will permit ACADA to modify ongoing observations at sub...
The Cherenkov Telescope Array is the future ground-based facility for gamma-ray astronomy at very... more The Cherenkov Telescope Array is the future ground-based facility for gamma-ray astronomy at very-high energies. The CTA Observatory will comprise more than 100 telescopes and calibration devices that need to be centrally managed and synchronized to perform the required scientific and technical activities. The operation of the array requires a complex Supervisory Control and Data Acquisition (SCADA) system, named Array Control and Data Acquisition (ACADA), whose quality level is crucial for maximizing the efficiency of the CTA operations. In this contribution we aim to present the Quality Assurance (QA) strategy adopted by the ACADA team to fulfill the quality standards required for the creation and usage of ACADA software. We will describe the QA organization and planned activities, together with the quality models and the related metrics defined to comply with the required quality standards. We will describe the procedures, methods and tools which will be applied in order to guara...
Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021), 2021
Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observati... more Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observations over the past decade have surprisingly revealed almost two hundred VHE emitters which appear to act as cosmic particle accelerators. These sources are an important component of the Universe, influencing the evolution of stars and galaxies. At the same time, they also act as a probe of physics in the most extreme environments known-such as in supernova explosions, and around or after the merging of black holes and neutron stars. However, the existing experiments have provided exciting glimpses, but often falling short of supplying the full answer. A deeper understanding of the TeV sky requires a significant improvement in sensitivity at TeV energies, a wider energy coverage from tens of GeV to hundreds of TeV and a much better angular and energy resolution with respect to the currently running facilities. The next generation gamma-ray observatory, the Cherenkov Telescope Array Observatory (CTAO), is the answer to this need. In this talk I will present this upcoming observatory from its design to the construction, and its potential science exploitation. CTAO will allow the entire astronomical community to explore a new discovery space that will likely lead to paradigm-changing breakthroughs. In particular, CTA has an unprecedented sensitivity to short (sub-minute) timescale phenomena, placing it as a key instrument in the future of multi-messenger and multi-wavelength time domain astronomy. I will conclude the talk presenting the first scientific results obtained by the LST-1, the prototype of one CTA telescope type-the Large Sized Telescope, that is currently under commission.
Software and Cyberinfrastructure for Astronomy V, Jul 6, 2018
The Cherenkov Telescope Array (CTA) will be the next-generation ground-based instrument for detec... more The Cherenkov Telescope Array (CTA) will be the next-generation ground-based instrument for detecting veryhigh energy gamma rays. It will consist of roughly 100 telescopes of different sizes and designs. In addition, a variety of auxiliary instrumentation will be part of the array. The Observation Execution System (OES) is the software system in charge of operating and monitoring all telescopes and devices, applying short-term observation schedules depending on the hardware status and environmental conditions and handling the data. Motivated by the wealth of tasks to accomplish and requirements to fulfil, a software development procedure is conceived for the development of OES. Part of this development process is the application of software testing procedures. These procedures range from unit tests up to system tests and stress tests. In this contribution, the software development process and the application of static and dynamic code analysis tools are described.
Physical Review B, 2014
We present a theory of magnetotransport through an electronic orbital, where the electron spin in... more We present a theory of magnetotransport through an electronic orbital, where the electron spin interacts with a (sufficiently) large external spin via an exchange interaction. Using a semiclassical approximation, we derive a set of equations of motions for the electron density matrix and the mean value of the external spin that turns out to be highly nonlinear. The dissipation via the electronic leads is implemented in terms of a quantum master equation that is combined with the nonlinear terms of the spin-spin interaction. With an anisotropic exchange coupling a variety of dynamics is generated, such as self-sustained oscillations with parametric resonances or even chaotic behavior. Within our theory we can integrate a Maxwell-demon-like closed-loop feedback scheme that is capable of transporting particles against an applied bias voltage and that can be used to implement a spin filter to generate spin-dependent oscillating currents of opposite directions.
Physical Review B, 2012
We present a theory of magnetotransport through a system of two coupled electronic orbitals, wher... more We present a theory of magnetotransport through a system of two coupled electronic orbitals, where the electron spin interacts with a (large) local magnetic moment via an exchange interaction. For the physical realization of such a setup we have in mind, for example, semiconductor quantum dots coupled to an ensemble of nuclear spins in the host material or molecular orbitals coupled to a local magnetic moment. Using a semiclassical approximation, we derive a set of Ehrenfest equations of motion for the electron density matrix and the mean value of the external spin (Landau equations): Due to the spin coupling they turn out to be nonlinear and, importantly, also coherences between electron states with different spin directions need to be considered. The electronic spin-polarized leads are implemented in form of a Lindblad-type dissipator in the infinite bias limit. We have solved this involved dynamical system numerically for various isotropic and anisotropic coupling schemes. For isotropic spin coupling and spin-polarized leads we study the effect of current-induced magnetization of the attached spin and compare this with a single quantum dot setup. We further demonstrate that an anisotropic coupling can lead to a rich variety of parametric oscillations in the average current reflecting the complicated interplay between the Larmor precession of the external spin and the dissipative coherent dynamics of the electron spin.