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Space Radiation Environment And Radiation Hardness Assurance Tests Of Electronic Components To Be Used In Space MissionsAmutkan, Ozge 01 July 2010 (has links) (PDF)
Space radiation is significantly harmful to electronic Components. The operating time, duration and orbit of the space mission are affected by the characteristic of the radiation environment. The aging and the performance of the electronic components are modified by radiation. The performance of the space systems such as electronic units, sensors, power and power subsystem units, batteries, payload equipments, communication units, remote sensing instruments, data handling units, externally located units,
and propulsion subsystem units is determined by the properly functioning of various electronic systems. Such systems are highly sensitive against space radiation.
The space radiation can cause damage to electronic components or functional failure on the electronics. A precisely methodology is needed to ensure that space radiation is not a threat on the functionality and performance of the electronics during their operational lives. This methodology is called as &rdquo / Radiation Hardness Assurance&rdquo / . In
this thesis, the hardening of electronics against space radiation is discussed.
This thesis describes the space radiation environments, physical mechanisms, effects of space radiation, models of the space radiation environment, simulation of the Total
Ionizing Dose, and &rdquo / Radiation Hardness Assurance&rdquo / which covers Total Ionizing Dose and Single Event Effects testing and analyzing of the electronics.
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Lepton Flavor Violation In The Two Higgs Doublet ModelSundu, Hayriye 01 June 2007 (has links) (PDF)
The lepton flavor violating interactions are interesting in the sense that they are sensitive the physics beyond the standard model and they ensure considerable information about the restrictions of the free parameters, with the help of the possible accurate measurements. In this work, we investigate the lepton flavor
violating H+ ! W+l and the lepton flavor conserving H+ ! W+l decays in the general two Higgs doublet model and we estimate decay widths of these decays. After that, we analyze lepton
flavor violating decay !
i in the same model and calculate its branching ratio. We observe that the
experimental results of the processes under consideration can give comprehensive
information about the physics beyond the standard model and the existing free
parameters.
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Scalar Mesons In Radiative Phi-meson Decays Into Charged K-meson StatesOzturk, Fahri 01 June 2008 (has links) (PDF)
The role of $f_{0}(980)$ and
$a_{0}(980)$ scalar meson intermediate states in the mechanism of
radiative $phi (1020)$ meson decay into two charged $K (494)$
mesons and a photon $phirightarrow K^{+} + K^{-} + gamma$ is
investigated. For the contribution of scalar meson intermediate
state two models are considered. In the kaon-loop model, the scalar
meson intermediate state couples the final state to the initial
$phi$ meson through a charged kaon-loop. The second model, called
no-structure model, consist of point-like coupling of intermediate
scalar meson state to the initial state. It is found that in the
kaon-loop model, scalar meson intermediate state results in a
considerable modification of the pure Bremsstrahlung photon
spectrum.
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Properties Of Light And Heavy Baryons In Light Cone Qcd Sum Rules FormalismAzizi, Kazem 01 March 2009 (has links) (PDF)
In this thesis, we investigate the masses, form factors and magnetic dipole moments of some light octet, decuplet and heavy baryons containing a single heavy quark in the framework of the light cone QCD sum rules. The magnetic dipole moments can be measured considering radiative transitions within a multiplet or between multiplets.
Analyzing the transitions among the baryons and calculating the above mentioned parameters can give us insight into the structure of those baryons. In analyzing the aforementioned processes, the transition form factors play a crucial role. In this thesis, the form factors for these transitions are calculated using the light cone QCD sum rules approach.
In the limit when the light quark masses are equal, mu = md = ms, QCD has an SU(3) flavour symmetry which can be used to classify the light baryons. This classification results in the light decuplet, octet and singlet baryons. The baryons containing single heavy quark, on the other hand, can be classified according to the spin of the light degrees of freedom in the heavy quark limit, mQ -> / infinity. QCD at low energies, when the baryons are formed, is a non-perturbative theory. Hence, for phenomenology of the baryons, the QCD sum rules as a more powerful non-perturbative approach is
used.
Understanding the properties of nucleons is one of the main objectives of QCD. To investigate the properties of the nucleons, the axial N-Delta(1232) transition form factors
are calculated within the light cone QCD sum rules method. A comparison of our results on those form factors with the predictions of lattice QCD and quark model is presented. The nucleon electromagnetic form factors are also calculated in the same framework using the most general form of the nucleon interpolating current. Using two forms of the distribution amplitudes (DA&rsquo / s), predictions for the form factors are presented and compared with existing experimental data. It is shown that our results describe the existing experimental data remarkably well.
Another important property of the baryons is their magnetic moments. The magnetic moments of the heavy Xi_Q (Q = b or c) baryons containing a single charm or bottom quark are calculated within the light cone QCD sum rules approach. A comparison of our results with the predictions of other approaches, such as relativistic and nonrelativistic quark models, hyper central model, Chiral perturbation theory, soliton and skyrmion models is presented. Moreover, inspired by the results of recent experimental discoveries for charm and bottom baryons, the masses and magnetic moments of the heavy baryons with J^2P = 3/2^+ containing a single heavy quark are studied also within the light cone QCD sum rules method. Our results on the masses of heavy
baryons are in good agreement with predictions of other approaches, as well as with the existing experimental values. Our predictions on the masses of the states, which
are not experimentally discovered yet, can be tested in the future experiments. A comparison of our results on the magnetic moments of these baryons and the hyper
central model predictions is also presented.
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Nuclear Spinodal Instabilities In Stochastic Mean-field ApproachesEr, Nuray 01 August 2009 (has links) (PDF)
Nuclear spinodal instabilities are investigated in non-relativistic
and relativistic stochastic mean-field approaches for charge
asymmetric and charge symmetric nuclear matter. Quantum statistical
effect on the growth of instabilities are calculated in
non-relativistic approach. Due to quantal effects, in both symmetric
and asymmetric matter, dominant unstable modes shift towards longer
wavelengths and modes with wave numbers larger than the Fermi
momentum are strongly suppressed. As a result of quantum statistical
effects, in particular at lower temperatures, amplitude of density
fluctuations grows larger than those calculated in semi-classical
approximation.
Relativistic calculations in the semi-classical limit are compared
with the results of non-relativistic calculations based on
Skyrme-type effective interactions under similar conditions. A
qualitative difference appears in the unstable response of the
system: the system exhibits most unstable behavior at higher baryon
densities around $rho_{B}=0.4 rho_{0}$ in the relativistic
approach while most unstable behavior occurs at lower baryon
densities around $rho_{B}=0.2 rho_{0}$ in the non-relativistic
calculations.
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Spinodal Instabilities In Symmetric Nuclear Matter Within A Density-dependent Relativistic Mean-field ApproachDanisman, Betul 01 August 2011 (has links) (PDF)
The nuclear matter liquid-gas phase transition is expected to be a signal of nuclear
spinodal instabilities as a result of density fluctuations. Nuclear spinodal
instabilities in symmetric nuclear matter are studied within a stochastic relativistic
density-dependent model in semi-classical approximation. We use two
parameterization for the Lagrange density, DDME1 and TW sets. The early
growth of density fluctuations is investigated by employing relativistic Vlasov
equation based on QHD and discussed the cluster size of the condensations
from the early growth of density correlation functions. Expectations are that
hot nuclear matter behaves unstable around &rho / b &asymp / &rho / 0/4 (below the saturation
density) and at low temperatures. We therefore present our results at low temperature
T=1 MeV and at higher temperature T=5 MeV, and also at a lower
initial baryon density &rho / b = 0.2 &rho / 0 and a higher value &rho / b = 0.4 &rho / 0 where unstable
behavior is within them.
Calculations in density-dependent model are compared with the other calculations
obtained in a relativistic non-linear model and in a Skyrme type nonivrelativistic model. Our results are consistent with them. Qualitatively similar
results show that the physics of the quantities are model-independent. The size
of clusterization is estimated in two ways, by using half-wavelength of the most
unstable mode and from the width of correlation function at half maximum. Furthermore,
the average speed of condensing fragments during the initial phase of
spinodal decomposition are determined by using the current density correlation
functions.
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Analysis Of Kappa Meson In Light Cone Qcd Sum RulesBaytemir, Gulsen 01 September 2011 (has links) (PDF)
In the present work some hadronic properties of the scalar &kappa / meson are studied.
Using the QCD sum rules approach, which is a nonperturbative method, the
mass and the overlap amplitude of this meson are calculated. As well as the
mass and the overlap amplitude, &kappa / &rarr / K^+&pi / ^&minus / decay is also studied. For this
decay the coupling constant g_&kappa / K^+&pi / ^&minus / is obtained using light cone QCD sum rules
which is an extension of the QCD sum rules method. Moreover, the coupling
constant is calculated using the experimental decay width and it is compared
with the value obtained in light cone QCD sum rules approach. The result of
the calculation of g_&kappa / K^+&pi / ^&minus / , the one obtained from light cone QCD sum rules
approach, is also applied to acquire the f_0 &minus / &sigma / scalar mixing angle, &theta / s, using
the ratio g^2 (&kappa / &rarr / K^+&pi / ^&minus / )/g^2 (&sigma / &rarr / &pi / &pi / ) obtained from experimental decay width.
The value of scalar mixing angle is also compared with its experimental results.
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名古屋大学前歩道放射線の多様性と天然放射線通路標識(Radio Guide-way)の提案Kataoka, Ryosuke, Tanaka, Tsuyoshi, 片岡, 良輔, 田中, 剛 03 1900 (has links)
第23回名古屋大学年代測定総合研究センターシンポジウム平成22(2010)年度報告
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Novel neutron detectorsBurgett, Eric Anthony 04 May 2010 (has links)
A new set of thermal neutron detectors has been developed as a near term 3He tube replacement. The zinc oxide scintillator is an ultrafast scintillator which can be doped to have performance equal to or superior to 3He tubes. Originally investigated in the early 1950s, this room temperature semiconductor has been evaluated as a thermal neutron scintillator. Zinc oxide can be doped with different nuclei to tune the band gap, improve optical clarity, and improve the thermal neutron detection efficiency. The effects of various dopant effects on the scintillation properties, materials properties, and crystal growth parameters have been analyzed. Two different growth modalities were investigated: bulk melt grown materials as well as thin film scintillators grown by metalorganic chemical vapor deposition (MOCVD). MOCVD has shown significant advantages including precise thickness control, high dopant incorporation, and epitaxial coatings of neutron target nuclei.
Detector designs were modeled and simulated to design an improved thermal neutron detector using doped ZnO layers, conformal coatings and light collection improvements including Bragg reflectors and photonic crystal structures. The detectors have been tested for crystalline quality by XRD and FTIR spectroscopy, for scintillation efficiency by photo-luminescence spectroscopy, and for neutron detection efficiency by alpha and neutron radiation tests. Lastly, a novel method for improving light collection efficiency has been investigated, the creation of a photonic crystal scintillator. Here, the flow of optical light photons is controlled through an engineered structure created with the scintillator materials. This work has resulted in a novel radiation detection material for the near term replacement of 3He tubes with performance characteristics equal to or superior to that of 3He.
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The origin of 26Al in the GalaxyKnödlseder, Jürgen 24 November 1997 (has links) (PDF)
The history of recent galactic nucleosynthesis activity can be studied by <br />measurements of the 1.809 MeV gamma-ray line arising from the decay of <br />radioactive 26Al.<br />The COMPTEL telescope aboard the Compton Gamma-Ray Observatory, launched on <br />April 5, 1991, permits for the first time an extensive investigation of the <br />1.8 MeV radiation throughout the entire sky.<br />The aim of this thesis is to infer the galactic distribution of 26Al from <br />these measurements and to identify the dominant sources of this <br />radioactive isotope.<br /><br />The first part of the thesis is dedicated to the reconstruction of <br />the 1.8 MeV intensity distribution from the measured data.<br />It is demonstrated that the use of conventional deconvolution <br />algorithms, like maximum likelihood or maximum entropy inversion, <br />leads to lumpy, noise-dominated intensity distributions.<br />Nevertheless, simulations can help to assess the uncertainties in the <br />reconstructed images, which permits the scientific exploitation of the <br />recovered skymaps.<br />Alternatively, a multiresolution approach is proposed, which largely <br />reduces the uncertainties in the reconstructed 1.8 MeV intensity <br />distribution.<br />In summary, 1.8 MeV emission is mainly concentrated towards the <br />galactic plane, which clearly demonstrates that the bulk of 26Al is of <br />galactic rather than local origin.<br />However, distinct emission features towards Cygnus, Carina, and the <br />Auriga-Camelopardalis-Perseus region are inconsistent with a smooth <br />galactic 1.8 MeV emission profile, pointing towards a massive star <br />origin of 26Al.<br /><br />The second part of the thesis consists of a multi-wavelength <br />comparison of COMPTEL 1.8 MeV data which aims in the <br />identification of the origin of galactic 26Al.<br />For the comparison, a rigorous Bayesian analysis is applied, which <br />is the only consistent framework that allows inference based on the <br />comparison.<br />It turned out that the 1.8 MeV distribution follows very closely <br />the distribution of free electrons in the Galaxy which is traced by <br />thermal bremsstrahlung, observable in the microwave domain.<br />The similarity of the 1.8 MeV intensity distribution to the<br />thermal bremsstrahlung distribution implies a direct proportionality <br />between the 26Al and the massive star column densities, which strongly <br />supports that massive stars are the origin of galactic 26Al.<br />In particular, ONeMg-novae and AGB stars can be excluded as dominant <br />26Al sources since their galactic distribution is not expected to <br />correlate with the distribution of free electrons.<br /><br />The correlation between 26Al and free electrons established, the <br />analysis of 1.8 MeV gamma-ray line emission can complement our knowledge <br />about star formation and the distribution of ionized gas throughout <br />the entire Galaxy. <br />While COMPTEL made the first step in providing the first all-sky map <br />in the light of the 1.809 MeV line, INTEGRAL, the next generation gamma-ray spectrometer, will allow a detailed study of current star formation <br />in the Galaxy.
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