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151.
e/p separation study using the ISS-CREAM top and bottom counting detectors
Y. Amarea, D. Angelaszek, S. C. Kang, N. Anthony, G. H. Choi, M. Chung, M. Copley, L. Derome, L. Eraud, C. Falana, Jon Paul Lundquist, 2019, published scientific conference contribution

Abstract: Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) is an experiment for studying the origin, acceleration, and propagation mechanisms of high-energy cosmic rays. The ISS-CREAM instrument was launched on the 14th of August 2017 to the ISS aboard the SpaceX-12 Dragon spacecraft. The Top and Bottom Counting Detectors (TCD/BCD) are parts of the ISS-CREAM instrument and designed for studying electron and gamma-ray physics. The TCD/BCD each consist of an array of 20 × 20 photodiodes on a plastic scintillator. The TCD/BCD can separate electrons from protons by using the difference between the shapes of electromagnetic and hadronic showers in the high energy region. The Boosted Decision Tree (BDT) method, which is a deep learning method, is used in this separation study. We will present results of the electron/proton separation study and rejection power in various energy ranges.
Found in: ključnih besedah
Summary of found: ...the origin, acceleration, and propagation mechanisms of high- energy cosmic rays. The ISS-CREAM instrument was launched...
Keywords: instrumentations, high energy cosmic rays, particle detectors, composition
Published: 08.02.2021; Views: 1145; Downloads: 0
.pdf Fulltext (2,14 MB)

152.
Calibration of the underground muon detector of the Pierre Auger Observatory
Lukas Zehrer, Marko Zavrtanik, Danilo Zavrtanik, Serguei Vorobiov, Marta Trini, Samo Stanič, Jon Paul Lundquist, Andrej Filipčič, A. Aab, 2021, original scientific article

Abstract: To obtain direct measurements of the muon content of extensive air showers with energy above 10[sup]16.5 eV, the Pierre Auger Observatory is currently being equipped with an underground muon detector (UMD), consisting of 219 10 m[sup]2-modules, each segmented into 64 scintillators coupled to silicon photomultipliers (SiPMs). Direct access to the shower muon content allows for the study of both of the composition of primary cosmic rays and of high-energy hadronic interactions in the forward direction. As the muon density can vary between tens of muons per m[sup]2 close to the intersection of the shower axis with the ground to much less than one per m[sup]2 when far away, the necessary broad dynamic range is achieved by the simultaneous implementation of two acquisition modes in the read-out electronics: the binary mode, tuned to count single muons, and the ADC mode, suited to measure a high number of them. In this work, we present the end-to-end calibration of the muon detector modules: first, the SiPMs are calibrated by means of the binary channel, and then, the ADC channel is calibrated using atmospheric muons, detected in parallel to the shower data acquisition. The laboratory and field measurements performed to develop the implementation of the full calibration chain of both binary and ADC channels are presented and discussed. The calibration procedure is reliable to work with the high amount of channels in the UMD, which will be operated continuously, in changing environmental conditions, for several years.
Found in: ključnih besedah
Summary of found: ...muon content of extensive air showers with energy above 10[sup]16.5 eV, the Pierre Auger Observatory...
Keywords: ultra-high energy cosmic rays, extensive air showers (EAS), EAS muonic component, Pierre Auger Observatory, underground muon detector, detector calibration
Published: 14.04.2021; Views: 1291; Downloads: 82
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153.
154.
Anaerobic treatment of excess yeast and waste ethanol from alcohol free beer production for increase of renewable energy use in brewing industry
Goran Lukić, Mario Panjicko, Gregor Drago Zupančič, 2020, published scientific conference contribution

Abstract: In the presented paper we have investigated how large quantities of excess yeast and periodical releases of waste ethanol influence the operation of the anaerobic treatment process in a UASB reactor. The process was tested in a pilot-scale reactor with a design organic load of 16.0 kg/m3/day of COD. Through various stages of the experiment, several possible scenarios were tested, excess yeast was added continuously with concentrations up to 3 vol. %, whereas waste ethanol was added in batches of up to 0.8 % of daily volume load several days a week. The intent was to test real conditions in the treatment process. The whole experiment lasted for 77 days, where the maximum organic load of 24.72 kg/m3/day was successfully achieved with no adverse effects on the efficiency of the reactor performance although it significantly surpassed the design load. The COD efficiency at maximum OLR was 83.1 %, whereas the average was 88.0 %. The average biogas production rate increased from 2,044 m3/m3/day to 4.927 m3/m3/day. The microbial community structure analysis showed significant shifts only in the archaeal community (25 – 30 %) as a good adaptation to the addition of substrates. Monitoring the model brewery in applying the addition of yeast and ethanol to the wastewater treatment showed a 110 % increase in biomethane production. The consequence of the increased biomethane production is that the natural gas substitute ratio could be increased from the current average of 10.7 % to potentially 20.1 %, which is a substantial step towards the goal of renewable energy use.
Found in: ključnih besedah
Keywords: anaerobic digestion, biogas, brewery yeast, renewable energy, waste ethanol
Published: 10.06.2021; Views: 1143; Downloads: 5
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155.
An economic analysis of biomass potential as an opportunity to increase the share of biogas production for energy purposes in Slovenia
Stefan Dabižljević, 2021, master's thesis

Abstract: One of the biggest global problems, the solution of being put in front of the scientists around the world, is endangering the environment. To preserve it, the transition from non-renewable to renewable energy sources is a rational and necessary solution. One of the energy sources with great potential in the future is biomass. In the master’s thesis, we have studied the economic analysis of the possibility of obtaining energy from biogas in Slovenia for the production of which biomass is used. For the study to be successful, it was necessary to analyse the situation in the field of renewable energy sources and biogas in the European Union and Slovenia to obtain a general picture for further analysis. By analysing the available data from previous years, we gained insight into the situation in the given area. The master’s thesis aims to show that although Slovenia has been facing the problem of a decreasing number of biogas power plants for years, the implementation of a system for obtaining energy from biogas is an economically and environmentally viable investment. The economic analysis was done for a 1 MW plant. The choice of plant size and power was made based on the Kepner-Tregoe method and the method of comparing alternatives. For the project duration of 30 years, through cash flows, as well as through various economic indicators, such as the presentation of loan calculations with a certain interest rate, internal rate of return, repayment period method, present project value, etc., the economic side of the investment is presented, which aims to show the profitability of the project.
Found in: ključnih besedah
Keywords: Renewable energy sources, biomass, biogas, economic analysis, investment, project
Published: 07.09.2021; Views: 1053; Downloads: 52
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156.
Extrapolating FR-0 radio galaxy source properties from propagation of multi-messenger ultra-high energy cosmic rays
Chiara Righi, Giacomo Bonnoli, Fabrizio Tavecchio, Paolo Da Vela, Anita Reimer, Margot Boughelilba, Serguei Vorobiov, Lukas Merten, Jon Paul Lundquist, 2021, published scientific conference contribution

Abstract: Recently, it has been shown that relatively low luminosity Fanaroff-Riley type 0 (FR-0) radio galaxies are a good candidate source class for a predominant fraction of cosmic rays (CR) accelerated to ultra-high energies (UHE, E>10[sup]18 eV). FR-0s can potentially provide a significant fraction of the UHECR energy density as they are much more numerous in the local universe than more energetic radio galaxies such as FR-1s or FR-2s (up to a factor of ∼5 with z≤0.05 compared to FR-1s). In the present work, UHECR mass composition and energy spectra at the FR-0 sources are estimated by fitting simulation results to the published Pierre Auger Observatory data. This fitting is done using a simulated isotropic sky distribution extrapolated from the measured FR-0 galaxy properties and propagating CRs in plausible extragalactic magnetic field configurations using the CRPropa3 framework. In addition, we present estimates of the fluxes of secondary photons and neutrinos created in UHECR interactions with cosmic photon backgrounds during CR propagation. With this approach, we aim to investigate the properties of the sources with the help of observational multi-messenger data.
Found in: ključnih besedah
Keywords: jetted active galaxies, FR-0 radiogalaxies, ultra-high energy cosmic rays, extragalactic magnetic fields, UHECR propagation, UHECR interactions, cosmogenic photons, cosmogenic neutrinos
Published: 16.08.2021; Views: 762; Downloads: 0
.pdf Fulltext (2,04 MB)

157.
FR-0 jetted active galaxies
Chiara Righi, Jon Paul Lundquist, Giacomo Bonnoli, Fabrizio Tavecchio, Serguei Vorobiov, Paolo Da Vela, Anita Reimer, Margot Boughelilba, Lukas Merten, 2021, published scientific conference contribution

Abstract: Fanaroff-Riley (FR) 0 radio galaxies form a low-luminosity extension to the well-established ultra-high-energy cosmic-ray (UHECR) candidate accelerators FR-1 and FR-2 galaxies. Their much higher number density — up to a factor five times more numerous than FR-1 with z ≤ 0.05 — makes them good candidate sources for an isotropic contribution to the observed UHECR flux. Here, the acceleration and survival of UHECR in prevailing conditions of the FR-0 environment are discussed. First, an average spectral energy distribution (SED) is compiled based on the FR0CAT. These photon fields, composed of a jet and a host galaxy component, form a minimal target photon field for the UHECR, which will suffer from electromagnetic pair production, photo-disintegration, photo-meson production losses, and synchrotron radiation. The two most promising acceleration scenarios based on Fermi-I order and gradual shear acceleration are discussed as well as different escape scenarios. When an efficient acceleration mechanism precedes gradual shear acceleration, e.g., Fermi-I orothers, FR-0 galaxies are likely UHECR accelerators. Gradual shear acceleration requires a jet Lorentz factor of Gamma>1.6, to be faster than the corresponding escape. In less optimistic models, a contribution to the cosmic-ray flux between the knee and ankle is expected to be relatively independent of the realized turbulence and acceleration.
Found in: ključnih besedah
Summary of found: ...form a low-luminosity extension to the well-established ultra-high- energy cosmic-ray (UHECR) candidate accelerators FR-1 and FR-2...
Keywords: jetted active galaxies, FR-0 radiogalaxies, ultra-high energy cosmic rays, cosmic ray acceleration, cosmic ray energy losses
Published: 16.08.2021; Views: 709; Downloads: 0
.pdf Fulltext (1,13 MB)

158.
Application of machine learning techniques for cosmic ray event classification and implementation of a real-time ultra-high energy photon search with the surface detector of the Pierre Auger Observatory
Lukas Zehrer, 2021, doctoral dissertation

Abstract: Despite their discovery already more than a century ago, Cosmic Rays (CRs) still did not divulge all their properties yet. Theories about the origin of ultra-high energy (UHE, > 10^18 eV) CRs predict accompanying primary photons. The existence of UHE photons can be investigated with the world’s largest ground-based experiment for detection of CR-induced extensive air showers (EAS), the Pierre Auger Observatory, which offers an unprecedented exposure to rare UHE cosmic particles. The discovery of photons in the UHE regime would open a new observational window to the Universe, improve our understanding of the origin of CRs, and potentially uncloak new physics beyond the standard model. The novelty of the presented work is the development of a "real-time" photon candidate event stream to a global network of observatories, the Astrophysical Multimessenger Observatory Network (AMON). The stream classifies CR events observed by the Auger surface detector (SD) array as regards their probability to be photon nominees, by feeding to advanced machine learning (ML) methods observational air shower parameters of individual CR events combined in a multivariate analysis (MVA). The described straightforward classification procedure further increases the Pierre Auger Observatory’s endeavour to contribute to the global effort of multi-messenger (MM) studies of the highest energy astrophysical phenomena, by supplying AMON partner observatories the possibility to follow-up detected UHE events, live or in their archival data.
Found in: ključnih besedah
Keywords: astroparticle physics, ultra-high energy cosmic rays, ultra-high energy photons, extensive air showers, Pierre Auger Observatory, multi-messenger, AMON, machine learning, multivariate analysis, dissertations
Published: 27.10.2021; Views: 1006; Downloads: 42
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159.
Two-integral distribution functions in axisymmetric galaxies: Implications for dark matter searches
Piero Ullio, Mihael Petač, 2019, original scientific article

Abstract: We address the problem of reconstructing the phase-space distribution function for an extended collisionless system, with known density profile and in equilibrium within an axisymmetric gravitational potential. Assuming that it depends on only two integrals of motion, namely the energy and the component of the angular momentum along the axis of symmetry Lz , there is a one-to-one correspondence between the density profile and the component of the distribution function that is even in Lz, as well as between the weighted azimuthal velocity profile and the odd component. This inversion procedure was originally proposed by Lynden-Bell and later refined in its numerical implementation by Hunter and Qian; after overcoming a technical difficulty, we apply it here for the first time in presence of a strongly flattened component, as a novel approach of extracting the phase-space distribution function for dark matter particles in the halo of spiral galaxies. We compare results obtained for realistic axisymmetric models to those in the spherical symmetric limit as assumed in previous analyses, showing the rather severe shortcomings in the latter. We then apply the scheme to the Milky Way and discuss the implications for the direct dark matter searches. In particular, we reinterpret the null results of the Xenon1T experiment for spin-(in)dependent interactions and make predictions for the annual modulation of the signal for a set of axisymmetric models, including a self-consistently defined corotating halo.
Found in: ključnih besedah
Summary of found: ...only two integrals of motion, namely the energy and the component of the angular momentum...
Keywords: dark matter, astrophysics of galaxies, high energy physics, phenomenology
Published: 01.10.2021; Views: 735; Downloads: 0
.pdf Fulltext (1,22 MB)

160.
Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations
Emmanuel Nezri, Julien Lavalle, Arturo Núñez-Castiñeyra, Mihael Petač, 2021, original scientific article

Abstract: Signal predictions for galactic dark matter (DM) searches often rely on assumptions regarding the DM phase-space distribution function (DF) in halos. This applies to both particle (e.g. p-wave suppressed or Sommerfeld-enhanced annihilation, scattering off atoms, etc.) and macroscopic DM candidates (e.g. microlensing of primordial black holes). As experiments and observations improve in precision, better assessing theoretical uncertainties becomes pressing in the prospect of deriving reliable constraints on DM candidates or trustworthy hints for detection. Most reliable predictions of DFs in halos are based on solving the steady-state collisionless Boltzmann equation (e.g. Eddington-like inversions, action-angle methods, etc.) consistently with observational constraints. One can do so starting from maximal symmetries and a minimal set of degrees of freedom, and then increasing complexity. Key issues are then whether adding complexity, which is computationally costy, improves predictions, and if so where to stop. Clues can be obtained by making predictions for zoomed-in hydrodynamical cosmological simulations in which one can access the true (coarse-grained) phase-space information. Here, we test an axisymmetric extension of the Eddington inversion to predict the full DM DF from its density profile and the total gravitational potential of the system. This permits to go beyond spherical symmetry, and is a priori well suited for spiral galaxies. We show that axisymmetry does not necessarily improve over spherical symmetry because the (observationally unconstrained) angular momentum of the DM halo is not generically aligned with the baryonic one. Theoretical errors are similar to those of the Eddington inversion though, at the 10-20% level for velocity-dependent predictions related to particle DM searches in spiral galaxies. We extensively describe the approach and comment on the results.
Found in: ključnih besedah
Summary of found: ...cosmology, nongalactic astrophysics, astrophysics of galaxies, high energy physics...
Keywords: galaxy dynamics, dark matter experiments, dark matter simulations, dark matter theory, cosmology, nongalactic astrophysics, astrophysics of galaxies, high energy physics
Published: 01.10.2021; Views: 754; Downloads: 31
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