Sökning: "Emission spectra"

Visar resultat 6 - 10 av 202 avhandlingar innehållade orden Emission spectra.

1. 6. Photospheric emission in gamma-ray bursts

   Författare :Christoffer Lundman; Felix Ryde; Stephan Rosswog; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : This thesis considers emission from gamma-ray bursts (GRBs), the most powerful explosions known in the Universe. Most GRBs are likely associated with the final stages of stellar evolution, where the core of a massive star collapses, and gives birth to a highly compact object such as a neutron star or black hole. LÄS MER

3. 7. Gamma-Ray Emission from Galaxy Clusters : DARK MATTER AND COSMIC-RAYS

   Författare :Anders Pinzke; Lars Bergström; Olaf Reimer; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Galaxy clusters; gamma-rays; cosmic-rays; dark matter; High energy astrophysics; Högenergiastrofysik; teoretisk fysik; Theoretical Physics;

   Sammanfattning : The quest for the first detection of a galaxy cluster in the high energy gamma-ray regime is ongoing, and even though clusters are observed in several other wave-bands, there is still no firm detection in gamma-rays. To complement the observational efforts we estimate the gamma-ray contributions from both annihilating dark matter and cosmic-ray (CR) proton as well as CR electron induced emission. LÄS MER

4. 8. Photospheric emission in gamma ray bursts : Analysis and interpretation of observations made by the Fermi gamma ray space telescope

   Författare :Shabnam Iyyani; Felix Ryde; David Burrows; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; gamma ray bursts; photosphere; radiation mechanism; Theoretical Physics; teoretisk fysik;

   Sammanfattning : The large flashes of radiation that are observed in GRBs are generally believed to arise in a relativistic jetted outflow. This thesis addresses the question of how and where in the jet this radiation is produced. LÄS MER

5. 9. Simulation of Core-Level Spectra of H-bonded Systems

   Författare :Iurii Zhovtobriukh; Lars G.M. Pettersson; Anders Nilsson; Marcus Lundberg; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; water; x-ray absorption; non-resonant x-ray emission; damped linear response theory; time-dependent density functional theory; semi-classical approximation to Kramers-Heisenberg formula; Reverse Monte-Carlo; kemisk fysik; Chemical Physics;

   Sammanfattning : The thesis consists of three related projects where attempts have been made to simulate X-Ray Absorption (XAS) spectra of water and hexagonal ice, static non-resonant X-ray Emission (XES) spectrum of water and to apply the semi-classical approximation to Kramers-Heisenberg formula (SCKH) formalism to calculate the non-resonant XES spectrum of water and methanol. The first project is devoted to an investigation of the performance of damped response theory in combination with the DFT electronic structure method (CPP-DFT) in XAS spectrum simulations of liquid water. LÄS MER

7. 10. Neutron Emission Spectrometry for Fusion Reactor Diagnosis : Method Development and Data Analysis

   Författare :Jacob Eriksson; Göran Ericsson; Carl Hellesen; Sean Conroy; Andreas Dinklage; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; fusion; plasma diagnostics; neutron spectrometry; TOFOR; MPRu; tokamak; JET; fast ions; fuel ion density; relativistic kinematics; Fysik med inriktning mot tillämpad kärnfysik; Physics with specialization in Applied Nuclear Physics;

   Sammanfattning : It is possible to obtain information about various properties of the fuel ions deuterium (D) and tritium (T) in a fusion plasma by measuring the neutron emission from the plasma. Neutrons are produced in fusion reactions between the fuel ions, which means that the intensity and energy spectrum of the emitted neutrons are related to the densities and velocity distributions of these ions. LÄS MER