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[Photograph of Alpha Phi Omega at Sing]
Photograph of Alpha Phi Omega performing onstage in Sing at Hardin-Simmons University. They wear matching costumes that includes red vests and bow ties with varying hats.
Date:
1990
Creator:
unknown
Object Type:
Photograph
System:
The Portal to Texas History
Intramolecular condensation reactions of {alpha}, {omega}- bis(triethoxy-silyl)alkanes. Formation of cyclic disilsesquioxanes
Under acidic sol-gel polymerization conditions, 1,3-bis(triethoxysilyl)-propane (1) and 1,4-bis(triethoxysilyl)butane (2) were shown to preferentially form cyclic disilsesquioxanes 3 and 4 rather than the expected 1,3-propylene- and 1,4-butylene-bridged polysilsesquioxane gels. Formation of 3 and 4 is driven by a combination of an intramolecular cyclization to six and seven membered rings, and a pronounced reduction in reactivity under acidic conditions as a function of increasing degree of condensation. The ease with which these relatively unreactive cyclic monomers and dimers are formed (under acidic conditions) helps to explain the difficulties in forming gels from 1 and 2. The stability of cyclic disilsesquioxanes was confirmed withe the synthesis of 3 and 4 in gram quantities; the cyclic disilsesquioxanes react slowly to give tricyclic dimers containing a thermodynamically stable eight membered siloxane ring. Continued reactions were shown to perserve the cyclic structure, opening up the possibility of utilizing cyclic disilsesquioxanes as sol-gel monomers. Preliminary polymerization studies with these new, carbohydrate-like monomers revealed the formation of network poly(cyclic disilsesquioxanes) under acidic conditions and polymerization with ring-opening under basic conditions.
Date:
August 1, 1996
Creator:
Loy, Douglas A.; Carpenter, Joseph P.; Myers, Sharon A.; Assink, Roger A.; Small, James H.; Greaves, John et al.
Object Type:
Article
System:
The UNT Digital Library
Omega phase formation in shock-loaded zirconium
A shock recovery experiment and post-shock mechanical measurements were conducted on high-purity Zr. Mechanical properties of the Zr samples before and after the shock loading are compared and discussed in terms of the substructure evolution during the shock loading. Metastable {omega}-phase was found in the Zr sample following shock-loading to 7 GPa. A new orientation relationship between the {alpha} and {omega} phases was derived which does not agree with those previously reported in hydrostatic pressure experiments. A mechanism is proposed for the observed {alpha} {yields} {omega} transformation.
Date:
August 1, 1993
Creator:
Song, Shihong & Gray, G. T., III
Object Type:
Report
System:
The UNT Digital Library
Omega phase formation in titanium and titanium alloys
Although the response of titanium alloys to dynamic loading is receiving increased attention in the literature (particularly in the area of shear-band formation), a more limited experimental database exists concerning the detailed structure/property relationships of titanium alloys subjected to shock loading. In this study, preliminary results concerning the influence of alloy chemistry on the property of omega-phase formation and its structure in three titanium alloys are presented. The influence of shock-wave deformation on the phase stability and substructure evolution of high-purity (low-interstitial) titanium, A-70 (3700 ppm oxygen) titanium, and Ti-6Al-4V were probed utilizing real-time velocity interferometry (VISAR) and soft'' shock-recovery techniques. VISAR wave profiles of shock-loaded high-purity titanium revealed the omega-phase pressure-induced transition to occur at approximately 10.4 GPa. Wave profile measurements on A-70 Ti shocked to pressures up to 35 GPa and Ti-6Al-4V shocked to pressures up to 25 GPa exhibited no evidence of a three-wave structure indicative of a pressure-induced phase transition. Neutron and X-ray diffractometry and TEM analysis confirmed the presence of retained {omega}-phase in the electrolytic-Ti and the absence of {omega}-phase in the shock-recovered A-70 Ti and Ti-6Al-4V. Suppression of the {alpha}-{omega} phase transition in A-70 Ti, containing a high interstitial oxygen content, is seen to …
Date:
January 1, 1992
Creator:
Gray, G. T., III; Morris, C. E. & Lawson, A. C.
Object Type:
Article
System:
The UNT Digital Library
Omega phase formation in titanium and titanium alloys
Although the response of titanium alloys to dynamic loading is receiving increased attention in the literature (particularly in the area of shear-band formation), a more limited experimental database exists concerning the detailed structure/property relationships of titanium alloys subjected to shock loading. In this study, preliminary results concerning the influence of alloy chemistry on the property of omega-phase formation and its structure in three titanium alloys are presented. The influence of shock-wave deformation on the phase stability and substructure evolution of high-purity (low-interstitial) titanium, A-70 (3700 ppm oxygen) titanium, and Ti-6Al-4V were probed utilizing real-time velocity interferometry (VISAR) and ``soft`` shock-recovery techniques. VISAR wave profiles of shock-loaded high-purity titanium revealed the omega-phase pressure-induced transition to occur at approximately 10.4 GPa. Wave profile measurements on A-70 Ti shocked to pressures up to 35 GPa and Ti-6Al-4V shocked to pressures up to 25 GPa exhibited no evidence of a three-wave structure indicative of a pressure-induced phase transition. Neutron and X-ray diffractometry and TEM analysis confirmed the presence of retained {omega}-phase in the electrolytic-Ti and the absence of {omega}-phase in the shock-recovered A-70 Ti and Ti-6Al-4V. Suppression of the {alpha}-{omega} phase transition in A-70 Ti, containing a high interstitial oxygen content, is seen to …
Date:
May 1, 1992
Creator:
Gray, G. T., III; Morris, C. E. & Lawson, A. C.
Object Type:
Article
System:
The UNT Digital Library
Alfvenic behavior of alpha particle driven ion cyclotron emission in TFTR
Ion cyclotron emission (ICE) has been observed during D-T discharges in the Tokamak Fusion Test Reactor (TFTR), using rf probes located near the top and bottom of the vacuum vessel. Harmonics of the alpha cyclotron frequency ({Omega}{sub {alpha}}) evaluated at the outer midplane plasma edge are observed at the onset of the beam injection phase of TFTR supershots, and persist for approximately 100-250 ms. These results are in contrast with observations of ICE in JET, in which harmonics of {Omega}{sub {alpha}} evolve with the alpha population in the plasma edge. Such differences are believed to be due to the fact that newly-born fusion alpha particles are super-Alfvenic near the edge of JET plasmas, while they are sub-Alfvenic near the edge of TFTR supershot plasmas. In TFTR discharges with edge densities such that newly-born alpha particles are super-Alfvenic, alpha cyclotron harmonics are observed to persist. These results are in qualitative agreement with numerical calculations of growth rates due to the magnetoacoustic cyclotron instability.
Date:
July 1, 1995
Creator:
Cauffman, S.; Majeski, R. & McClements, K.G.
Object Type:
Report
System:
The UNT Digital Library
Alpha Particle Destabilization of the Toroidicity-Induced Alfven Eigenmodes
The high frequency, low mode number toroidicity-induced Alfven eigenmodes (TAE) are shown to be driven unstable by the circulating and/or trapped {alpha}-particles through the wave-particle resonances. Satisfying the resonance condition requires that the {alpha}-particle birth speed v{sub {alpha}} {ge} v{sub A}/2{vert bar}m-nq{vert bar}, where v{sub A} is the Alfven speed, m is the poloidal model number, and n is the toroidal mode number. To destabilize the TAE modes, the inverse Landau damping associated with the {alpha}-particle pressure gradient free energy must overcome the velocity space Landau damping due to both the {alpha}-particles and the core electrons and ions. The growth rate was studied analytically with a perturbative formula derived from the quadratic dispersion relation, and numerically with the aid of the NOVA-K code. Stability criteria in terms of the {alpha}-particle beta {beta}{sub {alpha}}, {alpha}-particle pressure gradient parameter ({omega}{sub {asterisk}}/{omega}{sub A}) ({omega}{sub {asterisk}} is the {alpha}-particle diamagnetic drift frequency), and (v{sub {alpha}}/v{sub A}) parameters will be presented for TFTR, CIT, and ITER tokamaks. The volume averaged {alpha}-particle beta threshold for TAE instability also depends sensitively on the core electron and ion temperature. Typically the volume averaged {alpha}-particle beta threshold is in the order of 10{sup {minus}4}. Typical growth rates of the …
Date:
October 1, 1990
Creator:
Cheng, C. Z.
Object Type:
Report
System:
The UNT Digital Library
[Calibration methods for neutron diagnostics at Omega]. DOE/NLUF final report
The investigation of Calibration Methods for Neutron Diagnostics at Omega is still underway. The data shown here is a compilation of measurements taken at Omega during the time of the grant. The data set has been updated with additional information taken this year. The neutron yield from an ICF event was determined by measuring the activity of an aluminum sample activated by target-produced DT neutrons. The radioactive nuclei {sup 24}Na and {sup 27}Mg, which were produced via the {sup 27}Al(n,{alpha}){sup 24}Na and {sup 27}Al(n,p){sup 27}Mg direct reactions, beta decay to excited states of {sup 24}Mg and {sup 27}Al respectively. These excited states then emitted gamma rays as the nuclei de-excite to their respective ground states. The gamma rays are detected and counted. From their numbers the neutron yield is determined.
Date:
January 15, 1998
Creator:
Padalino, S.
Object Type:
Report
System:
The UNT Digital Library
Inhomogeneous primordial nucleosynthesis and new abundance constraints on {Omega}{sub b}h{sup 2}
We discuss the upper limit to the baryonic contribution to the closure density. We consider effects of new observational and theoretical uncertainties in the primordial light element abundances, and the effects of fluctuation geometry on the inhomogeneous nucleosynthesis yields. We also consider implications of the possible detection of a high D/H abundance in a Lyman-{alpha} absorption cloud at high redshift and the implied chemical evolution effects of a high deuterium abundance. We show that there exists a region of the parameter space for inhomogeneous models in which a somewhat higher baryonic contribution to the closure density is possible than that allowed in standard homogeneous models. This result is contrary to some other recent studies and is due to both geometry and recently revised uncertainties in primordial light-element abundances, particularly {sup 7}Li. We find that the presently adopted abundance constraints are consistent with a contribution of baryons to the closure density as high as {Omega}{sub b}h{sub 50}{sup 2} {le} 0.11 ({eta} {le} 7 {times} 10{sup {minus}10}). This corresponds to a 20% increase over the limit from standard homogeneous models ({Omega}{sub b}h{sub 50}{sup 2} {le} 0.08, {eta} {le} 5.8 {times} 10{sup {minus}10}). With a high deuterium abundance the upper limits for the …
Date:
July 20, 1995
Creator:
Mathews, G. J.; Kajino, T. & Orito, M.
Object Type:
Report
System:
The UNT Digital Library
In-situ spatially resolved x-ray diffraction mapping of the alpha to beta to alpha transformation in commercially pure titanium arc welds
Spatially Resolved X-Ray Diffraction (SRXRD) is used to map the {alpha}{r_arrow}{beta}{r_arrow}{alpha} phase transformation in the heat affected zone (HAZ) of commercially pure titanium gas tungsten arc welds. In-situ SRXRD experiments were conducted on arc welds using a 200 pm diameter x-ray beam at Stanford Synchrotron Radiation Laboratory (SSRL). A map was created which identifies six HAZ microstructural regions that exist between the liquid weld pool and the base metal during welding. The first region is single phase {beta}-Ti that forms in a 2- to 3-mm band adjacent to the liquid weld pool. The second region is back transformed {alpha}-Ti that forms behind the portion of the HAZ where {beta}-Ti was once present at higher temperatures. The third region is completely recrystallized {alpha}-Ti that forms in a 2- to 3-mm band surrounding the single phase {beta}-Ti region. Recrystallized {alpha}-Ti was observed by itself and also with varying amounts of {beta}-Ti. The fourth region of the weld is the partially transformed zone where {alpha}-Ti and {beta}-Ti coexist during welding. The fifth region is directly behind the partially transformed zone and consists of a mixture of recrystallized and back transformed {alpha}-Ti The sixth region is farthest from the weld pool and consists of …
Date:
May 15, 1998
Creator:
Elmer, J. W., LLNL
Object Type:
Article
System:
The UNT Digital Library
Current 3 {omega} large optic test procedures and data analysis for the quality assurance of National Ignition Facility
A reliable metric is required to describe the damage resistance of large aperture 3{omega} transmissive optics for the National Ignition Facility (NIF) laser. The trend from single site testing to the more statistically valid Gaussian scanning test requires a well modeled experimental procedure, accurate monitoring of the test parameters, and careful interpretation of the resulting volumes of data. The methods described here provide reliable quality assurance data, as well as intrinsic damage concentration information used to predict the performance expected under use conditions. This paper describes the equipment, test procedure, and data analysis used to evaluate large aperture 3{omega} optics for the NIF laser.
Date:
December 22, 1998
Creator:
Schwartz, S; Feit, M D; Kozlowski, M R & Mouser, R P
Object Type:
Article
System:
The UNT Digital Library
Early-time measurements of laser-plasma conditions in OMEGA-Upgrade ICF Targets. Final report, April 1, 1997--March 31, 1998
Under this FY-97 NLUF grant, we primarily carried out spectral line and continuum diagnostics at early times and in the coronal region of the plasma using our flat-field grazing-incidence spectrograph, improved to incorporate time resolution at wavelengths extending below the carbon K-absorption edge using a gated microchannel plate detector. These experiments were carried out on the OMEGA facility. Fifty-nine beams were focused onto the target, providing nominally 18 kJ of energy in a 1 ns pulse for an irradiance of {approximately}2{times}10{sup 14}/cm{sup 2}. Some beam smoothing, provided by spectral dispersion, was used, but may not have been particularly effective alone, i.e., without the presence of distributed phase plates in the beams. The plastic microballoon targets were nominally 900 {mu}m in diameter with 10- and 20-{mu}m thick walls, and were filled with neon to a pressure of 10 atm. Overcoatings of Mg and Al in thicknesses ranging from 0.2 to 4 {mu}m were applied. A 1-{mu}m thick layer of CH was added in some early shots to reduce the rate of expansion of the metallic coatings. In the extreme ultraviolet (euv) spectral region, we observed n=3 to n=2 emissions from Li-, He- and H-like ions from the Mg and Al coatings. …
Date:
April 4, 1998
Creator:
Griem, H. R. & Elton, R. C.
Object Type:
Report
System:
The UNT Digital Library
Real-Time Monitoring of Alpha Emissions. Final report, FY 1994
A technology is being developed for on-line, real-time monitoring of mixed and low-level incinerator stacks for levels of airborne alpha activity. The Large-Volume Flow Thru Detector System uses a detector composed of multiple parallel plates of scintillating material fabricated so that the entire stack gas stream flows directly through the inter-plate volume. This report is largely a compilation of 3 reports on background reduction, once-through flow tests, and the aeronautical/mechanical engineering work. The full text of each report is included as an appendix.
Date:
December 31, 1994
Creator:
Gritzo, R.; Fowler, M. & Wouters, J.
Object Type:
Report
System:
The UNT Digital Library
A Contribution of Tipler's Omega Point Theory to Near-Death Studies
Article presenting Frank Tipler's concepts and arguments, and highlighting the value of his orientation for near-death studies. Tipler's work takes the steam out of scientific rejection of religious, spiritual, or noetic phenomena, and makes it possible to accept these phenomena while maintaining a strictly scientific posture.
Date:
Autumn 1999
Creator:
Crumbaugh, James C.
Object Type:
Article
System:
The UNT Digital Library
[Pamphlet: Dee Dee Warwick]
Program for a musical jazz performance featuring singer DeeDee Warwick and hosted by the Junior Black Academy of Arts and Letters on October 15-16, 1999, at the Muse Cafe Theatre.
Date:
October 1999
Creator:
Junior Black Academy of Arts and Letters
Object Type:
Pamphlet
System:
The UNT Digital Library
New approaches to the preparation of P(alpha)MS beads as mandrels for NIF-scale target capsules
We report on a new method using heated density gradient columns for preparing spherical poly({alpha} - methylstyrene) (P{alpha}MS) bead mandrels for inertial confinement fusion spherical shell targets. Using 1,2 propane diol/glycerol mixtures, stable density gradient columns for supporting P{alpha}MS beads can be prepared at temperatures as high as 150 {degrees}C. At these temperatures plasticized commercial beads become fluid and spherical, however loss of the plasticizer and very low molecular weight components of the bead due to limited solubility in the column fluid leads to surface finish problems. We also present results on P{alpha}MS beads prepared in an aqueous bath batch mode. Using these techniques beads with maximum out-of-rounds less than 5 {micro}m have been produced.
Date:
October 20, 1998
Creator:
Buckley, S R; Cook, R C; Fearon, E & Letts, S A
Object Type:
Article
System:
The UNT Digital Library
Early-time measurements of laser-plasma conditions in omega-upgrade ICF targets. Semi-annual report, October 1, 1997--March 31, 1998
Since arrival of FY-98 funding under this grant in December, we have been preparing for our first series of experiments under this grant at the University of Rochester Laboratory for Laser Energetics (LLE) on the Omega laser facility, now scheduled the week beginning May 4, 1998. We will again be fielding our flat-field, grazing-incidence extreme-ultraviolet (euv) spectrograph with a four-channel gated-stripline microchannel plate (MCP) detector, which is mounted on the outside of the vacuum chamber approximately 60 inches from the center. In addition, we will be using for the first time our newly constructed flat field spectrograph covering the spectral range of 30-250 {angstrom} (hv = 50-400 eV), designed to fit into a Ten Inch Manipulator (TIM). As such, it can be located closer to the central target position, with an expected enhancement in sensitivity of at least a factor-of-ten. It is the preparation of this instrument that mainly has occupied our attention so far in this grant period and discussed in this report.
Date:
April 4, 1998
Creator:
Griem, H. R. & Elton, R. C.
Object Type:
Report
System:
The UNT Digital Library
Early-time measurements of soft x-ray emission in an omega-upgrade laser-produced plasma. Semi-annual report, October 1, 1996--March 31, 1997
Beginning in January 1997 (following arrival of the FY-97 funding) we have been preparing for our first series of experiments under this grant at the University of Rochester Laboratory for Laser Energetics (LLE) on the Omega Upgrade laser facility, now scheduled to commence June 2, 1997. For these experiments we have purchased (just arrived) a four-channel gated-stripline microchannel plate (MCP) detector to be coupled to our soft x-ray flat-field grazing incidence spectrograph used previously at LLE. This will permit time-resolved `snapshots` of the complete spectra with a resolution to times as short as 180 ps per strip. An advantage of this technique over the streak camera used previously is the lack of any carbon absorbers such as in the thin plastic cathode required for the streak camera. This eliminates absorption in the 30-44 {angstrom} spectral region in which we are interested for intermediate-Z target materials such as Mg, Al and Si. An auxiliary turbomolecular-drag pump has also been installed in order to obtain the necessary vacuum for optimum MCP operation.
Date:
March 31, 1997
Creator:
Griem, H. R.; Elton, R. C. & Welch, B. L.
Object Type:
Report
System:
The UNT Digital Library
LLE 1995 annual report, October 1994--September 1995
The fiscal year ending September 1995 (FY95) concluded the third year of the cooperative agreement (DE-FC03-92SF19460) with the U.S. Department of Energy (DOE). This report summarizes research at the Laboratory for Laser Energetics (LLE) and reports on the successful completion of the OMEGA Upgrade. Previous annual reports describe the OMEGA Upgrade design. The preliminary design for the system was complete in October 1989 and the detailed design started in October 1990. The original 24-beam OMEGA system was decommissioned in December 1992 as construction for the OMEGA Upgrade began. We discuss the initial performance results (p. 99) of the upgraded OMEGA laser system. All acceptance tests were completed, and we demonstrated that all 60 beams can irradiate a target with more energy and better beam balance than was required by DOE`s acceptance criteria. We are most proud that all program milestones were met or exceeded, and that the system was completed on time and on budget.
Date:
January 1, 1996
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Final Report: Measurements of Core Conditions, Implosion Symmetry, and Anomaloes Acceleration Mechanisms on Omega through Charged Particle Spectroscopy, November 1, 1997 - December 31, 1998
This work concerns the first spectroscopic measurements of energetic charged particles on Omega. Individual line profiles include D-3He protons (14.7 MeV) and alphas (3.6 MeV), D-T alphas (3.5 MeV), D-D protons (3.0 MeV), and D-D tutons (1.0 MeV)
Date:
October 19, 1999
Creator:
Petrasso, R. & Li, C. K.
Object Type:
Report
System:
The UNT Digital Library
Two-stream cyclotron radiative instabilities due to the marginally mirror-trapped fraction for fustion alphas in tokamaks
It is shown here that the marginally mirror-trapped fraction of the newly-born fusion alpha particles in the deuterium-tritium (DT) reaction dominated tokamak plasmas can induce a two-stream cyclotron radiative instability for the fast Alfven waves propagating near the harmonics of the alpha particle cyclotron frequency {omega}{sub c{alpha}}. This can explain both the experimentally observed time behavior and the spatially localized origin of the fusion product ion cyclotron emission (ICE) in TFTR at frequencies {omega} {approx} m{omega}{sub c{alpha}}.
Date:
July 1, 1995
Creator:
Arunasalam, V.
Object Type:
Report
System:
The UNT Digital Library
LLE 1997. Annual report, October 1996--September 1997
The fiscal year ending September 1997 (FY97) concluded the fifth year of the cooperative agreement (DE-FC03-92SF19460) with the U.S. Department of Energy (DOE). This report summarizes research at the Laboratory for Laser Energetics (LLE) and is the final report for the first five years of the cooperative agreement. In September 1997, the cooperative agreement was renewed for an additional five years. We summarize our research during FY97, the operation of the National Laser Users` Facility (NLUF), and the education of high school, undergraduate, and graduate students in LLE programs. A general introduction to LLE`s experimental physics program and a report on recent results are found on pp. 161-167. This article includes a useful summary of the system`s operational capabilities and system parameters after three years of operation. Direct-drive inertial confinement fusion requires precise drive uniformity, the control of hydrodynamic instabilities during the implosion of the fusion target, and accurate target fabrication and characterization. The article summarizes a wide variety of experiments relating to direct-drive laser fusion, from high-yield implosion experiments to planar and spherical Rayleigh-Taylor experiments, laser-imprinting experiments, and laser-plasma interaction experiments. A detailed analysis of the equation of motion for an electron in a plane wave is presented beginning …
Date:
January 1, 1998
Creator:
unknown
Object Type:
Report
System:
The UNT Digital Library
Group velocity effects in broadband frequency conversion on OMEGA. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports
The powerful lasers needed for ICF can only produce light in the infrared wavelengths. However, the one micron wavelength produced by the neodymium glass that powers OMEGA and other lasers used for fusion research does not efficiently compress the fuel pellet. This happens because the infrared light is not well absorbed by the target, and because of the creation of suprathermal electrons. These suprathermal electrons preheat the fuel, adding extra resistance to compression. To eliminate these problems associated with longer wavelengths of light, the process of frequency converting the laser beam was invented. This process efficiently converts the initial beam to a beam which has three times the frequency and one third the wavelength. The third-harmonic beam, in the UV range, has a better absorption rate. The PV-WAVE computer program that the author has written has shown that increasing the frequency of SSD (Smoothing by Spectral Dispersion) on OMEGA to approximately 10 GHz as planned will not hurt the third harmonic generation conversion efficiency significantly. The increased bandwidth and increased frequency of SSD will make the laser beams that strike the target on OMEGA much smoother and more uniform than ever before. Therefore it is both safe and advisable to …
Date:
March 1, 1999
Creator:
Grossman, P.
Object Type:
Report
System:
The UNT Digital Library
An analysis of the uncertainty in temperature and density estimates from fitting model spectra to data. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports
Temperature and density histories of direct-drive laser fusion implosions are important to an understanding of the reaction`s progress. Such measurements also document phenomena such as preheating of the core and improper compression that can interfere with the thermonuclear reaction. Model x-ray spectra from the non-LTE (local thermodynamic equilibrium) radiation transport post-processor for LILAC have recently been fitted to OMEGA data. The spectrum fitting code reads in a grid of model spectra and uses an iterative weighted least-squares algorithm to perform a fit to experimental data, based on user-input parameter estimates. The purpose of this research was to upgrade the fitting code to compute formal uncertainties on fitted quantities, and to provide temperature and density estimates with error bars. A standard error-analysis process was modified to compute these formal uncertainties from information about the random measurement error in the data. Preliminary tests of the code indicate that the variances it returns are both reasonable and useful.
Date:
March 1, 1999
Creator:
Schubmehl, M.
Object Type:
Report
System:
The UNT Digital Library