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You searched for +publisher:"Texas A&M University" +contributor:("Melconian, Daniel G"). Showing records 1 – 2 of 2 total matches.

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Texas A&M University

1. Alfonso, Marisa Christina. Development of Online Chemistry for Rutherfordium (Element 104): Commissioning of a Gas Stopper and Extraction Chromatography of Rutherfordium Homologs (Zirconium and Hafnium).

Degree: PhD, Chemistry, 2016, Texas A&M University

The chemical and physical properties of the heaviest elements are of particular interest because relativistic effects increase as proton number squared. Transactinides, elements where relativistic effects are expected to be the largest, do not exist naturally; they are produced via fusion-evaporation reactions. The products of these reactions must be degraded down to sub-eV energies for chemical studies. At the Cyclotron Institute at Texas A&M University, a device for the thermalization of fusion-evaporation reaction products, the Recoil Transfer Chamber (RTC), has been designed, fabricated, and characterized. The design of this device is based on a gas stopper previously used at the National Superconducting Cyclotron Laboratory. This device uses a combination of laminar gas flow and static electric field to effectively transport the thermalized ions to the appropriate chemistry experiment. The RTC’s efficiency was determined using products of the 118Sn(40Ar, 6n)152Er reaction. An efficiency of 34 ± 5% was directly measured. Additionally, extraction chromatographic systems for the future chemical characterization of Rf were optimized offline. Trace quantities of long-lived radioactive homologs of Rf, 89Zr (t1/2 = 78.41 hr) and 175Hf (t1/2 = 70 d), were used to mimic the “one-atom-at-a-time” nature of transactinide chemistry. The extraction behavior of Zr and Hf was studied in HCl, HNO3, and H2SO4 using TEVA (a trioctyl and tridecyl methyl ammonium-based resin) and UTEVA (a diamyl amylphosphonate-based resin). Batch uptake studies were performed to determine which systems could separate Zr and Hf. Both resins showed the most promise in an HCl media. A separation factor of 18 ± 8 in 8.4 M HCl was measured using TEVA, while a separation factor of greater than 9.4 in 5.6 M HCl was measured using UTEVA. Offline, both TEVA and UTEVA column studies in HCl had good intergroup separation and showed viability for future extraction chromatographic studies of Rf. Advisors/Committee Members: Yennello, Sherry J (advisor), Folden III, Charles M (advisor), Clearfield, Abraham (committee member), Melconian, Daniel G (committee member).

Subjects/Keywords: recoil transfer chamber; gas stopper; gas catcher; heavy elements; fusion-evaporation reactions; column chromatography; extraction; zirconium; hafnium; rutherfordium

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Alfonso, M. C. (2016). Development of Online Chemistry for Rutherfordium (Element 104): Commissioning of a Gas Stopper and Extraction Chromatography of Rutherfordium Homologs (Zirconium and Hafnium). (Doctoral Dissertation). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/159020

Chicago Manual of Style (16th Edition):

Alfonso, Marisa Christina. “Development of Online Chemistry for Rutherfordium (Element 104): Commissioning of a Gas Stopper and Extraction Chromatography of Rutherfordium Homologs (Zirconium and Hafnium).” 2016. Doctoral Dissertation, Texas A&M University. Accessed March 23, 2019. http://hdl.handle.net/1969.1/159020.

MLA Handbook (7th Edition):

Alfonso, Marisa Christina. “Development of Online Chemistry for Rutherfordium (Element 104): Commissioning of a Gas Stopper and Extraction Chromatography of Rutherfordium Homologs (Zirconium and Hafnium).” 2016. Web. 23 Mar 2019.

Vancouver:

Alfonso MC. Development of Online Chemistry for Rutherfordium (Element 104): Commissioning of a Gas Stopper and Extraction Chromatography of Rutherfordium Homologs (Zirconium and Hafnium). [Internet] [Doctoral dissertation]. Texas A&M University; 2016. [cited 2019 Mar 23]. Available from: http://hdl.handle.net/1969.1/159020.

Council of Science Editors:

Alfonso MC. Development of Online Chemistry for Rutherfordium (Element 104): Commissioning of a Gas Stopper and Extraction Chromatography of Rutherfordium Homologs (Zirconium and Hafnium). [Doctoral Dissertation]. Texas A&M University; 2016. Available from: http://hdl.handle.net/1969.1/159020


Texas A&M University

2. Fustero, Joseph G. Mcnp6 Code Development for One Dimensional Position Sensitive Thermal Neutron Detectors.

Degree: MS, Nuclear Engineering, 2017, Texas A&M University

The development of position sensitive thermal neutron detectors (PSD’s) began soon after the initial development of early model thermal neutron detectors. One dimensional (1D) PSD’s report not only neutron counts but the axial position of the neutron interaction within the detector gas volume. These detectors maintain a high level of fidelity except when the neutron interaction takes place close to the gas-shell boundary. The use of PSD’s in order to characterize the spatial distribution of the thermal neutron field will become more commonplace as the technology has become less expensive. These experiments, however, must be validated against simulation results in order to assure their quality. The stochastic radiation transport code MCNP6 was used in order to provide these simulation results due to its large user base and its compatibility with the Parallel Deterministic Transport (PDT) code. It was found that it is possible to use MCNP6 to accurately simulate 1D PSD’s without heavily editing the source code. MCNP6 was used to simulate both the position of the neutron interaction as well as the predicted detector response due to the charge generation resultant of this interaction. This was done by writing a TALLYX modification to the default energy deposition F6 tally for charged particles which result from a neutron interaction. Additionally, it was found that using the PTRAC particle tracing utility for events contributing to the F6 tally for the cell corresponding to the detector gas volume was also appropriate for determining the location of the neutron interaction and the corresponding detector response due to charge collection on the anode wire. These simulations were run for a line detector test problem, a modified already completed impurity model experiment, and a future localized source experience. For all of these simulations the expected spatial distribution (including symmetries) and notable physical features (wall effect due to surface leakage of heavy charged particles) was observed. The computational expense did not differ significantly from a simulation using the default MCNP6 tallies. Advisors/Committee Members: McClarren, Ryan G (advisor), Perez-Nunez, Delia (advisor), Adams, Marvin L (committee member), Melconian, Daniel G (committee member).

Subjects/Keywords: Neutron detection; position sensitive detector

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Fustero, J. G. (2017). Mcnp6 Code Development for One Dimensional Position Sensitive Thermal Neutron Detectors. (Masters Thesis). Texas A&M University. Retrieved from http://hdl.handle.net/1969.1/169607

Chicago Manual of Style (16th Edition):

Fustero, Joseph G. “Mcnp6 Code Development for One Dimensional Position Sensitive Thermal Neutron Detectors.” 2017. Masters Thesis, Texas A&M University. Accessed March 23, 2019. http://hdl.handle.net/1969.1/169607.

MLA Handbook (7th Edition):

Fustero, Joseph G. “Mcnp6 Code Development for One Dimensional Position Sensitive Thermal Neutron Detectors.” 2017. Web. 23 Mar 2019.

Vancouver:

Fustero JG. Mcnp6 Code Development for One Dimensional Position Sensitive Thermal Neutron Detectors. [Internet] [Masters thesis]. Texas A&M University; 2017. [cited 2019 Mar 23]. Available from: http://hdl.handle.net/1969.1/169607.

Council of Science Editors:

Fustero JG. Mcnp6 Code Development for One Dimensional Position Sensitive Thermal Neutron Detectors. [Masters Thesis]. Texas A&M University; 2017. Available from: http://hdl.handle.net/1969.1/169607

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