Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 21 for “"Doppler-broadening"”.
-
Doppler-Broadening of Light Nuclei Gamma-Ray Spectra
… of interest in explosives detection, are Doppler-broadened. This thesis focuses on the gamma ray spectra from the 4438 keV gamma ray in the 12C (n, n’γ) reaction wherein Doppler broadening was investigated. A graphite sample was exposed to 14 MeV neutrons and the 12C gamma ray spectra …
-
Windowed multipole : an efficient Doppler broadening technique for Monte Carlo
In this thesis, the windowed multipole method of Doppler broadening is developed from the multipole method. The multipole method is a pole and residue reformulation of the cross section data used in nuclear cross section data libraries. This form is advantageous as the Doppler broadened form is …
-
On-the-fly Doppler broadening using multipole representation for Monte Carlo simulations on heterogeneous clusters
… at many temperatures are required to account for Doppler effects, which can impose an unacceptably high overhead in computer memory. In this thesis, a novel approach, based on the multipole representation, is proposed to reduce the memory footprint for the cross sections with little loss of …
-
Measuring the Ion Temperature of a Plasma Jet Undergoing Instability-Driven Heating
… of plasma are inferred through analysis of the Doppler-broadening observed spectroscopically at relevant wavelengths. To improve measurements, this arrangement implements a unique assemblage of 54 fiber-optic cables organized into a systematic two-dimensional array that broadens the area of …
-
Millimeter-wave dynamics and control of Rydberg-Rydberg transitions
… the smaller lab-frame velocity reduces the Doppler broadening enough to allow for coherent manipulation of Rydberg states and a coherent coupling of an optical and millimeter-wave photon. I demonstrate this coherent coupling in an ensemble of barium atoms, and provide a theoretical …
-
A new unresolved resonance region methodology
… using the RML formalism and the Leal-Hwang Doppler broadening methodology. The effective cross sections calculated at the energy of reference are then used to construct probability tables in the unresolved resonance region. The RML cross section reconstruction algorithm has been rigorously …
-
Computational treatments for neutron resonance elastic scattering in Monte Carlo nuclear simulations
… sampling method--against the already verified Doppler broadening rejection correction (DBRC) treatment in the open-source OpenMC Monte Carlo neutron transport code being developed at the Massachusetts Institute of Technology. In an effort to improve computational efficiency, the optimal energy …
-
Calculating reaction rate derivatives in Monte Carlo neutron transport/
… derivatives due to the resolved resonance Doppler broadening effect. To demonstrate the utility of differential tallies, this thesis presents example computations of moderator density and fuel Doppler feedback coefficients in pressurized water reactor pincells. With differential tallies, …
-
Positron annihilation spectroscopy to understand defect formation and evolution in neutron-irradiated Fe-Cr model alloys
… positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy (DBS). This work focused on the latter. DBS can be used to gain information on the various types of defects present in a material system and this technique is sensitive to both defect size and defect concentration. …
-
Nuclear Computations under Uncertainty New methods to infer and propagate nuclear data uncertainty across Monte Carlo simulations
… sections and analytically compute their thermal Doppler broadening. This drastically reduces the memory footprint of nuclear data (at least 1,000-fold), without incurring additional computational costs. These contributions are documented in nine peer-reviewed journal articles (eight published and …
-
The Galaxy Velocity Function from MIGHTEE-HI Early Science Data
… of cosmic variance, instrumental linewidth broadening and Doppler linewidth broadening on the velocity function are quantified within the context of the limitations of the Early Science data. The MIGHTEE-H I Early Science velocity function is compared with the velocity functions from …
-
Positron interactions with oriented polymers and with chiral quartz crystals
… and right handed (RH) chiral quartz crystals. Doppler broadening energy spectra (DBES) of z-cut LH or RH quartz disks at different angles were also measured by an “S parameter” to probe the observed difference. It was found that obtained annihilation energy difference of DBES was in agreement …
-
Reproducing the line-shape of a Doppler-broadened Gamma-line in 10Be following the beta-decay of 11Li using Geant4
Doppler Shift Attenuation Methods (DSAM) are capable of determining very short lifetimes of excited states (from femtoseconds to picoseconds). Given the evolution of DSAM experiments and computational tools available to nuclear physicists, it is surprising that no standard implementation exists for …
-
Direct Ion-Temperature Measurements Using High-Resolution Inelastic X-ray Scattering
… temperature can be extracted through standard Doppler-broadening relationships. These truly model-independent lattice-temperature measurements enable unambiguous determination of thermodynamic behavior in metallic samples under extreme conditions. Using this platform, we performed a series of …
-
Some effects on polymers of low-energy implanted positrons
… of positronium (Ps) from the sample surface. In Doppler broadening of annihilation radiation (DBAR) experiments, it has been shown that in a longitudinal setup, the para-Ps (p-Ps) contribution to the photo-peak is detected as a narrow fly-away peak at the low-energy side of the 511-keV-line. In …
-
Far-infrared superradiance in methyl fluoride
… onset of swept superradiance or to the onset of Doppler broadening, and were shown to be due to changes in the dominant value of K. The question of the form of the tipping angle was left unsolved, as our values vary between the two cases, theta= 2N-1/2 and () 0 = 2 (uN)-1/2. The delay was found …
-
Shock Wave Dispersion in Weakly Ionized Gas
… formula for deconvolution of Stark and Doppler broadening. The local electric field inside the MW discharge was evaluated by using a simplified kinetic model. Dispersion of a shock wave in a MW discharge will most likely be applied in future technical solutions in aircraft design, or …
-
Quantum computing with naturally trapped sub-nanometre-spaced ions
… trapped inside the crystal lattice there is no Doppler broadening of the line-width. The coherence properties of these optical transitions is one of the features that makes these materials attractive for use as a solid-state platform for quantum computing, using these ions as qubits. Another …
-
Characterization of Argon and Ar/Cl<sub>2</sub> Plasmas Used for the Processing of Niobium Superconducting Radio-Frequency Cavities
… spectroscopy technique that measures the thermal Doppler broadening of spectral lines, from which the neutral gas temperature and lower state density of the transition can be evaluated. The two methods were conducted in tandem while external parameters that were empirically determined to be …
-
Plasma Heating By Alfven Wave In Field-Reversed Ion Ring Experiment
… of increased plasma ion kinetic energy by Doppler broadening of ion and neutral emission lines integrated across the plasma radius ii
Page 1 of 2