Repository of University of Nova Gorica

Search the repository
A+ | A- | Help | SLO | ENG

Query: search in
search in
search in
search in
* old and bologna study programme


1 - 10 / 41
First pagePrevious page12345Next pageLast page
CR-ENTREES - Cosmic-Ray ENergy TRansport in timE-Evolving astrophysical Settings
Anita Reimer, Lukas Merten, Margot Boughelilba, Paolo Da Vela, Serguei Vorobiov, Jon Paul Lundquist, 2023, published scientific conference contribution

Abstract: In order to understand observable signatures from putative cosmic-ray (CR) sources in-source acceleration of particles, their energy and time-dependent transport including interactions in an evolving environment and their escape from source have to be considered, in addition to sourceto- Earth propagation. We present the code CR-ENTREES (Cosmic-Ray ENergy TRansport in timE-Evolving astrophysical Settings) that evolves the coupled time- and energy-dependent kinetic equations for cosmicray nucleons, pions, muons, electrons, positrons, photons and neutrinos in a one-zone setup of (possibly) non-constant size, with user-defined particle and photon injection laws. All relevant interactions, particle/photon escape and adiabatic losses are considered in a radiation-dominated, magnetized astrophysical environment that is itself evolving in time. Particle and photon interactions are pre-calculated using event generators assuring an accurate interactions and secondary particle production description. We use the matrix multiplication method for fast radiation and particle energy transport which allows also an efficient treatment of transport non-linearities due to the produced particles/photons being fed back into the simulation chain. Examples for the temporal evolution of the non-thermal emission from AGN jet-like systems with focus on proton-initiated pair cascades inside an expanding versus straight jet emission region, are further presented.
Keywords: cosmic rays (CRs), CR energy transport, CR interactions, modeling
Published in RUNG: 24.08.2023; Views: 167; Downloads: 2
.pdf Full text (442,19 KB)
This document has many files! More...

Efficient Modeling of Heavy Cosmic Rays Propagation in Evolving Astrophysical Environments
L. Merten, P. Da Vela, A. Reimer, M. Boughelilba, J. P. Lundquist, S. Vorobiov, J. Becker Tjus, 2023, published scientific conference contribution

Abstract: We present a new energy transport code that models the time dependent and non-linear evolution of spectra of cosmic-ray nuclei, their secondaries, and photon target fields. The software can inject an arbitrary chemical composition including heavy elements up to iron nuclei. Energy losses and secondary production due to interactions of cosmic ray nuclei, secondary mesons, leptons, or gamma-rays with a target photon field are available for all relevant processes, e.g., photo-meson production, photo disintegration, synchrotron radiation, Inverse Compton scattering, and more. The resulting x-ray fluxes can be fed back into the simulation chain to correct the initial photon targets, resulting in a non-linear treatment of the energy transport. The modular structure of the code facilitates simple extension of interaction or target field models. We will show how the software can be used to improve predictions of observables in various astrophysical sources such as jetted active galactic nuclei (AGN). Since the software can model the propagation of heavy ultrahigh-energy cosmic rays inside the source it can precisely predict the chemical composition at the source. This will also refine predictions of neutrino emissions –– they strongly depend on the chemical composition. This helps in the future to optimize the selection and analyses of data from the IceCube neutrino observatory with the aim to enhance the sensitivity of IceCube and reduce the number of trial factors.
Keywords: cosmic rays (CRs), CR energy transport, CR interactions, energy losses, modeling
Published in RUNG: 24.08.2023; Views: 173; Downloads: 2
.pdf Full text (1,12 MB)
This document has many files! More...

Time-of-flight photoconductivity investigation of high charge carrier mobility in Ti3C2Tx MXenes thin-film
Jurij Urbančič, Erika Tomsič, Manisha Chhikara, Nadiia Pastukhova, Vadym Tkachuk, Andraž Mavrič, Gvido Bratina, Egon Pavlica, 2023, original scientific article

Abstract: Charge transport through a randomly oriented multilayered network of two-dimensional (2D) Ti3C2Tx (where Tx is the surface termination and corresponds to O, OH and F) was studied using time-of-flight photoconductivity (TOFP) method, which is highly sensitive to the distribution of charge carrier velocities. We prepared samples comprising Ti3C2Tx with thickness of 12 nm or 6-monolayers. MXene flakes of size up to 16 μm were randomly deposited on the surface by spin-coating from water solution. Using TOFP, we have measured electron mobility that reached values up to 279 cm2/Vs and increase with electric-field in a Poole-Frenkel manner. These values are approximately 50 times higher than previously reported field-effect mobility. Interestingly, our zero-electric-field extrapolate approaches electron mobility measured using terahertz absorption method, which represents intra-flake transport. Our data suggest that macroscopic charge transport is governed by two distinct mechanisms. The high mobility values are characteristic for the intra-flake charge transport via the manifold of delocalized states. On the other hand, the observed Poole-Frenkel dependence of charge carrier mobility on the electric field is typical for the disordered materials and suggest the existence of an important contribution of inter-flake hopping to the overall charge transport.
Keywords: Charge transport in multilayered network of flakes, Time-of-flight photoconductivity, MXene exfoliation, High-mobility solution-cast thin-film, Semiconducting mxene
Published in RUNG: 31.03.2023; Views: 446; Downloads: 0
This document has many files! More...

Carbon nanoparticles assisted energy transport mechanism in leaves: A thermal lens study
Swapna Mohanachandran Nair Sindhu, 2019, original scientific article

Abstract: In the world of increasing population and pollution due to carbon emissions, the research for effective utilization of futile diesel soot for fruitful applications has become a necessity for a sustainable development. The contribution to pollution from vehicles and industries due to the aging of engines has caused a crisis. Carbon nanoparticles (CNPs) have been the subject of interest because of their good physical, chemical, and biological properties. The present work investigates the role of CNPs produced by internal combustion engines on the energy transport mechanism among leaf pigments using the sensitive and nondestructive single beam thermal lens technique. The studies reveal the absorption changes by various chlorophyll pigments with the concentration of CNPs sprayed on the leaves. Though for low concentrations CNPs lower the photon absorbance by chlorophyll pigments, the effect gets reversed at higher concentrations. The variation of thermal diffusivity with CNP concentration and its role in the energy transport mechanism among chlorophyll pigments are also studied. It is found that CNP concentrations of 625-2500mg/l are good for better intra-pigment energy transport leading to increased rate of photosynthesis and plant yield and thereby helping in attaining food security. The variation of CNP assisted energy transport among leaf pigments on the production of nicotinamide adenine dinucleotide phosphate (NADPH) and carbohydrates is also studied with ultraviolet (UV) and near-infrared (NIR) spectroscopy.
Keywords: carbon nanoparticle, soot, energy transport, thermal lens, photosynthesis
Published in RUNG: 05.07.2022; Views: 686; Downloads: 0
This document has many files! More...

Charge transport characterization of P3HT thin-film organic semiconductor : Written report: in fulfilment of diploma seminar 1FAF29 requirement
Matija Filipčič, 2021, research project (high school)

Abstract: The focus of this diploma seminar is to describe different types of charge transport theory and models used for finding mobility in semiconductors, more specifically focused on P3HT thin-film organic semiconductor. It also describes the time-of-flight method, which was used to measure the experimental data for P3HT with time dependent current I(t) curve. Another data set was obtained by performing Kinetic Monte Carlo (KMC) simulations using Miller-Abrahams hopping formalism. KMC was used to determine the material disorder, simulate I(t) curve and transit time for every charge carrier. Simulated data, different transit times and mobilities were then finally compared with experimental, in order to find agreements between the two.
Keywords: charge transport, P3HT, thin-film organic semiconductor
Published in RUNG: 15.09.2021; Views: 1683; Downloads: 0
This document has many files! More...

Search done in 0.06 sec.
Back to top