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70,620 Matching Results
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Observation of parity violation in the Omega- ---> Lambda K- decay
The {alpha} decay parameter in the process {Omega}{sup -} {yields} {Lambda}K{sup -} has been measured from a sample of 4.50 million unpolarized {Omega}{sup -} decays recorded by the HyperCP (E871) experiment at Fermilab and found to be [1.78 {+-} 0.19(stat) {+-} 0.16(syst)] x 10{sup -2}. This is the first unambiguous evidence for a nonzero {alpha} decay parameter, and hence parity violation, in the {Omega}{sup -} {Lambda}K{sup -} decay.
Date:
May 1, 2005
Creator:
Lu, L. C.; U., /Virginia; Burnstein, R. A.; Chakravorty, A.; Chen, Y. C.; Choong, W.-S. et al.
Object Type:
Article
System:
The UNT Digital Library
Devloping High Energy Radiography for HED Experiments on NIF and Omega-EP
High energy radiography capabilities are essential for many future DNT/HED experiments on NIF. We have been developing bright, high-energy (15-100 keV), high resolution (< 20 {micro}m), 1-D and 2-D radiography solutions for DNT experiments on NIF. In this LDRD, we have made significant progress utilizing high-energy, high-intensity, short-pulse lasers to generate hard K-{alpha} photons. High energy K-{alpha} sources are created by hot electrons interacting in the target fluor material after irradiation by lasers with intensity I{sub L} > 10{sup 17} W/cm{sup 2}. High resolution point projection 1-D and 2-D radiography have been achieved using {mu}-foil and {mu}-wire targets attached to low-Z substrate materials. The {mu}-wire size was 10 x 10 x 300 {micro}m on a 300 x 300 x 5 {micro}m CH substrate creating the point source size equivalent to these micro targets. This unique technique will utilize the NIF short pulse laser (ARC) as a backlighter suitable for the full range of DNT science experiments on NIF.
Date:
February 14, 2008
Creator:
Maddox, B.; Tommasini, R.; Remington, B.; Key, M. & Town, R.
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
[Letter from Geraldine Smedler to President and Members - April 13, 1987]
Letter from Geraldine Smedler to the San Antonio chapter of The Links, Inc. soliciting them for an advertisement in the program of events for their fund raiser and fashion show.
Date:
April 13, 1987
Creator:
Smedler, Geraldine
Object Type:
Letter
System:
The Portal to Texas History
[Letter from Geraldine Smedler to Friends - March 26, 1987]
Letter from Geraldine Smedler to the San Antonio chapter of The Links, Inc. inviting them to attend and support a fashion show, pageant, and fund raiser hosted by the San Antonio chapter of the Alpha Kappa Alpha Sorority.
Date:
March 26, 1987
Creator:
Smedler, Geraldine
Object Type:
Letter
System:
The Portal to Texas History
[Letter from Geraldine Smedler to Friends - March 26, 1987]
Letter from Geraldine Smedler to the San Antonio chapter of The Links, Inc. inviting them to attend and support a fashion show, pageant, and fund raiser hosted by the San Antonio chapter of the Alpha Kappa Alpha Sorority. Included is a blank form for buying advertisements in the event's program.
Date:
March 26, 1987
Creator:
Smedler, Geraldine
Object Type:
Letter
System:
The Portal to Texas History
[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
Charged Particle Spectroscopy on Omega (Final report)
Using the 2-MeV Van de Graaf Accelerator at SUNY Geneseo's Nuclear Structure Laboratory, a {sup 3}He-implanted tantalum target was bombarded by 450-keV deuterons to produce high energy protons via the {sup 3}He(d,p){sup 4}He reaction. A 1500-{micro}m surface barrier detector with a 3/16 inch diameter collimator was placed at 8.75 cm from the target and 135{sup o} from the incident beam. A movable arm was setup so that an array of aluminum filters of varying thicknesses could be rotated in front of the detector. A 6-{micro}m mylar filter was also mounted on the movable arm and was used to calibrate the detector as described in the CR-39 experiment report. Eight aluminum filters with thicknesses ranging from 250pm to 1100{micro}m were in turn rotated in front of the collimator and spectra were taken for each. The results are shown on the attached graphs. The theoretical curve for each graph was generated using TRIM The exact energy distribution of the proton beam incident on the target was not known; because no such spectrum could be taken due to the high count rate for elastically scattered deuterons. Instead, it was assumed that the incident beam had a distribution similar to that measured through the …
Date:
January 1, 2001
Creator:
Fletcher, K.; Padalino, S.; Schwartz, B.; Olsen, M.; Wakeman, T. & Petrasso, R.
Object Type:
Report
System:
The UNT Digital Library
FY12 LLNL OMEGA Experimental Programs
None
Date:
November 15, 2012
Creator:
Heeter, R.; Fournier, K.; Baker, K.; Celliers, P.; Fratanduono, D.; Hawreliak, J. et al.
Object Type:
Report
System:
The UNT Digital Library
Line-imaging velocimeter for shock diagnostics at the OMEGA laser facility
None
Date:
January 26, 2004
Creator:
Celliers, P M; Bradley, D K; Collins, G W; Hicks, D G; Boehly, T R & Armstrong, W J
Object Type:
Article
System:
The UNT Digital Library
[Fraternity student at the Omega Delta Phi Fraternity table]
Photograph of a fraternity student standing at the Chaotic Alpha Chi Chapter of Omega Delta Phi Fraternity table. The student is posing for his picture to be taken, dressed in his fraternities colors and holding up his fraternities' hand sign. The poster board is intricately designed as a castle, with colors of black and red. The photograph was taken during UNT's Founder's Day event, the celebration of UNT's birthday.
Date:
September 10, 2021
Creator:
Esparza, Anna
Object Type:
Photograph
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
FY13 LLNL OMEGA Experimental Programs
None
Date:
October 14, 2013
Creator:
Heeter, R. F.; Fournier, K. B.; Baker, K.; Brown, G. V.; Casey, D.; Celliers, P. et al.
Object Type:
Report
System:
The UNT Digital Library
Two Dimensional Simulations of Plastic-Shell, Direct-Drive Implosions on OMEGA
Multidimensional hydrodynamic properties of high-adiabat direct-drive plastic-shell implosions on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] are investigated using the multidimensional hydrodynamic code, DRACO. Multimode simulations including the effects of nonuniform illumination and target roughness indicate that shell stability during the acceleration phase plays a critical role in determining target performance. For thick shells that remain integral during the acceleration phase, target yields are significantly reduced by the combination of the long-wavelength ({ell} < 10) modes due to surface roughness and beam imbalance and the intermediate modes (20 {le} {ell} {le} 50) due to single-beam nonuniformities. The neutron-production rate for these thick shells truncates relative to one-dimensional (1-D) predictions. The yield degradation in the thin shells is mainly due to shell breakup at short wavelengths ({lambda} {approx} {Delta}, where {Delta} is the in-flight shell thickness). The neutron-rate curves for the thinner shells have significantly lower amplitudes and a fall-off that is less steep than 1-D rates. DRACO simulation results are consistent with experimental observations.
Date:
September 27, 2004
Creator:
Radha, P. B.; Goncharov, V. N.; Collins, T. B.; Delettrez, J. A.; Elbaz, Y.; Glebov, V. Y. et al.
Object Type:
Article
System:
The UNT Digital Library
Constraining |V(td)|/|V(ts)| Using Radiative Penguin B -> V(K*/rho/omega)gamma Decays
Exclusive radiative penguin B decays, B {yields} (K*{sup 0}/K*{sup +}) and B {yields} ({rho}/{omega}){gamma}, are flavor-changing neutral-current (FCNC) processes. Studies of these decays are of special interest in testing Standard Model (SM) predictions and searching for other beyond-the-SM FCNC interactions. Using 89 x 10{sup 6} B{bar B} pairs from BABAR, we measure the branching fraction ({Beta}), CP-asymmetry ({Alpha}), and isospin asymmetry ({Delta}{sub 0-}) of B {yields} (K*{sup 0}/K*{sup +}){gamma} as follows: {Beta}(B{sup 0} {yields} K*{sup 0}{gamma}) = 3.92 {+-} 0.20(stat.) {+-} 0.24(syst.); {Beta}(B{sup +} {yields} K*{sup +}{gamma}) = 3.87 {+-} 0.28(stat.) {+-} 0.26(syst.); {Alpha}(B {yields} K*{gamma}) = -0.013 {+-} 0.36(stat.) {+-} 0.10(syst.); {Delta}{sub 0-}(B {yields} K*{gamma}) = 0.050 {+-} 0.045(stat.) {+-} 0.028(syst.) {+-} 0.024(R{sup +/0}). The 90% confidence intervals for the CP-asymmetry and the isospin-asymmetry in the B {yields} K*{gamma} decay are given as: -0.074 < {Alpha}(B {yields} K*{gamma}) < 0.049, -0.046 < {Delta}{sub 0-} (B {yields} K*{gamma}) < 0.146. We also search for B {yields} ({rho}/{omega}){gamma} decays using 211 x 10{sup 6} B{bar B} pairs from BABAR. No evidence for these decays is found. We set the upper limits at 90% confidence level for these decays: {Beta}(B{sup 0} {yields} {rho}{sup 0}{gamma}) < 0.4 x 10{sup -6}; {Beta}(B{sup +}{yields} {rho}{sup …
Date:
March 8, 2006
Creator:
Tan, Ping
Object Type:
Report
System:
The UNT Digital Library
The Role of Ledge Nucleation/Migration in ''Omega'' Plate Thickening Behavior in Al-Cu-Mg-Ag Alloys
The thickening kinetics of {Omega} plates in an Al-4Cu-0.3Mg-0.2Ag (wt. %) alloy have been measured at 200 C, 250 C and 300 C using conventional transmission electron microscopy techniques. At all temperatures examined the thickening showed a linear dependence on time. At 200 C the plates remained less than 6nm in thickness after 1000h exposure. At temperatures above 200 C the thickening kinetics are greatly increased. Atomic resolution Z-contrast microscopy has been used to examine the structure and chemistry of the (001){sub {Omega}} {parallel} (111){sub {alpha}} interphase boundary in samples treated at each temperature. In all cases, two atomic layers of Ag and Mg segregation were found at the broad face of the plate. The risers of the growth ledges and the ends of the plates were free of segregation. No significant levels of Ag or Mg were detected inside the plate at any time. The necessary redistribution of Ag and Mg accompanying a migrating thickening ledge occurs at all temperatures and is not considered to play a decisive role in the excellent coarsening resistance exhibited by the {Omega} plates at temperatures up to 200 C. Plates transformed at 200 C rarely contained ledges and usually exhibited a strong vacancy …
Date:
March 16, 2001
Creator:
Hutchinson, C.R.
Object Type:
Article
System:
The UNT Digital Library
Analytical electron microscope study of the omega phase transformation in a zirconium-niobium alloy
The study of the as-quenched omega phase morphology shows that the domain size of Zr-15% Nb is on the order of 30 A. No alignment of omega domains along <222>..beta.. directions was observed and samples having undergone thermal cycling in thin foil form, did not develop a long-period structure of alternating ..beta.. and ..omega.. phases below the omega transformation temperature. (FS)
Date:
January 1, 1979
Creator:
Zaluzec, N. J.
Object Type:
Report
System:
The UNT Digital Library
Analytical electron microscope study of the omega phase transformation in a zirconium--niobium alloy
An in-situ study of the as-quenched omega phase transformation in Zr--15% Nb was conducted between the temperatures of 77 and 300/sup 0/K using analytical electron microscopy. The domain size of the omega regions observed in this investigation was on the order of 30 A, consistent with previous observations in this system. No alignment of omega domains along <222> directions of the bcc lattice was observed and in-situ thermal cycling experiments failed to produce a long period structure of alternating ..beta.. and ..omega.. phase regions as predicted by one theory of this transformation. Several techniques of microstructural analysis were developed, refined, and standardized. Grouped under the general classification of Analytical Electron Microscopy (AEM) they provide the experimentalist with a unique tool for the microcharacterization of solids, allowing semiquantitative to quantitative analysis of the morphology, crystallography, elemental composition, and electronic structure of regions as small as 20 A in diameter. These techniques have complications, and it was necessary to study the AEM system used in this work so that instrumental artifacts which invalidate the information produced in the microscope environment might be eliminated. Once these factors had been corrected, it was possible to obtain a wealth of information about the microvolume of …
Date:
June 1, 1979
Creator:
Zaluzec, N.J.
Object Type:
Report
System:
The UNT Digital Library
Destabilization of tokamak pressure-gradient driven instabilities by energetic alpha populations
Alpha particle populations can significantly alter existing MHD in stabilities in tokamaks through kinetic effects and coupling to otherwise stable shear Alfven waves. Here we consider resonances of the trapped alpha precessional drift with both the usual ballooning mode diamagnetic frequency ({omega}{sub *i}/2) and the toroidicity induced Alfven eigenmode (TAE). This is examined for noncircular tokamaks in the high-n ballooning limit using an isotropic alpha slowing down distribution and retaining the full energy and pitch angle dispersion in the alpha drift frequency. Applying this to CIT and ITER indicates that ballooning instabilities can persist at {Beta}'s below the ideal MHD threshold. These are especially dominated by the destabilization of the TAE mode. In addition, a hybrid fluid-particle approach for simulating alpha effects on pressure-gradient driven instabilities is described. 13 refs., 6 figs.
Date:
January 1, 1989
Creator:
Spong, D. A.; Holmes, J. A.; Leboeuf, J. N.; Christenson, P. J. & Michigan Univ., Ann Arbor, MI (USA). Dept. of Nuclear Engineering)
Object Type:
Article
System:
The UNT Digital Library
[News Script: Management consultant's new venture]
Script from the WBAP-TV/NBC station in Fort Worth, Texas, relating a news story.
Date:
November 27, 1970, 10:00 p.m.
Creator:
WBAP-TV (Television station : Fort Worth, Tex.)
Object Type:
Script
System:
The UNT Digital Library
[News Script: Okonite]
Script from the WBAP-TV/NBC station in Fort Worth, Texas, relating a news story about Ling-Temco-Vought Inc having bids for their divestment.
Date:
March 2, 1971, 6:00 p.m.
Creator:
WBAP-TV (Television station : Fort Worth, Tex.)
Object Type:
Script
System:
The UNT Digital Library
High statistics study of omega$sup 0$ production at 6 GeV/c
The spin-projected cross sections for $omega$$sup 0$ production at 6 GeV/ c were measured in a counter-spark chamber experiment at the Zero Gradient Synchrotron of Argonne National Laboratory. Results are presented for a sample of 25,000 $omega$$sup 0$ events, and critical tests are shown for any residual background. The reaction is dominated by the s-channel natural-parity helicity one projection (rho$sub 11$ + rho/sub 1-1) dsigma/dt which shows a turnover in the forward direction and no strong dip at t = 0.6 (GeV/c)$sup 2$. The unnatural- parity helicity-zero cross section rho$sub 00$ dsigma/dt shows no forward turnover suggesting a sizeable helicity-nonflip contribution. Comparisons are made with the predictions of a Regge exchange model with absorptive corrections. (auth)
Date:
January 1, 1975
Creator:
Shaevitz, M.H.
Object Type:
Thesis or Dissertation
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
Deformation Induced Hierarchical Twinning Coupled with Omega Transformation in a Metastable β-Ti Alloy
This article looks at hierarchical twinning in metastable body-centered cubic (bcc) β-titanium alloy on tensile deformation.
Date:
August 15, 2015
Creator:
Mantri, Srinivas Aditya; Sun, F.; Choudhuri, Deep; Alam, Talukder; Gwalani, Bharat; Prima, Frederic et al.
Object Type:
Article
System:
The UNT Digital Library