Atomic lifetime measurements of highly charged ions (open access)

Atomic lifetime measurements of highly charged ions

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Date: May 21, 2008
Creator: Trabert, E.
Object Type: Book
System: The UNT Digital Library
Comparison of Cluster Lensing Profiles with Lambda CDM Predictions (open access)

Comparison of Cluster Lensing Profiles with Lambda CDM Predictions

We derive lens distortion and magnification profiles of four well known clusters observed with Subaru. Each cluster is very well fitted by the general form predicted for Cold Dark Matter (CDM) dominated halos, with good consistency found between the independent distortion and magnification measurements. The inferred level of mass concentration is surprisingly high, 8 < c{sub vir} < 15 (<c{sub vir}> = 10.39 {+-} 0.91), compared to the relatively shallow profiles predicted by the {Lambda}CDM model, c{sub vir} = 5.06 {+-} 1.10 (for <M{sub vir}> = 1.25 x 10{sup 15} M{sub {circle_dot}}/h). This represents a 4{sigma} discrepancy, and includes the relatively modest effects of projection bias and profile evolution derived from N-body simulations, which oppose each other with little residual effect. In the context of CDM based cosmologies, this discrepancy implies some modification of the widely assumed spectrum of initial density perturbations, so clusters collapse earlier (z {ge} 1) than predicted (z < 0.5) when the Universe was correspondingly denser.
Date: May 21, 2008
Creator: Broadhurst, Tom; U., /Tel Aviv; Umetsu, Keiichi; /Taipei, Inst. Astron. Astrophys.; Medezinski, Elinor; U., /Tel Aviv et al.
Object Type: Article
System: The UNT Digital Library
A table-top femtosecond time-resolved soft x-ray transient absorption spectrometer (open access)

A table-top femtosecond time-resolved soft x-ray transient absorption spectrometer

A laser-based, table-top instrument is constructed to perform femtosecond soft x-ray transient absorption spectroscopy. Ultrashort soft x-ray pulses produced via high-order harmonic generation of the amplified output of a femtosecond Ti:sapphire laser system are used to probe atomic core-level transient absorptions in atoms and molecules. The results provide chemically specific, time-resolved dynamics with sub-50-fs time resolution. In this setup, high-order harmonics generated in a Ne-filled capillary waveguide are refocused by a gold-coated toroidal mirror into the sample gas cell, where the soft x-ray light intersects with an optical pump pulse. The transmitted high-order harmonics are spectrally dispersed with a home-built soft x-ray spectrometer, which consists of a gold-coated toroidal mirror, a uniform-line spaced plane grating, and a soft x-ray CCD camera. The optical layout of the instrument, design of the soft x-ray spectrometer, and spatial and temporal characterization of the high-order harmonics are described. Examples of static and time-resolved photoabsorption spectra collected on this apparatus are presented.
Date: May 21, 2008
Creator: Leone, Stephen; Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E. & Leone, Stephen R.
Object Type: Article
System: The UNT Digital Library
New Quarkonium Results from the BABAR experiment (open access)

New Quarkonium Results from the BABAR experiment

New BABAR results on B mesons and quarkonia are presented: an analysis of B{sup +} {yields} X(3872)K{sup +} and B{sup 0} {yields} X(3872)K{sup 0} decays with X(3872) {yields} J/{psi}{pi}{sup +}{pi}{sup -}, a precise measurement of the B mass difference {Delta}m{sub B} = m(B{sup 0}) -m(B{sup +}) and a study of hadronic transition between {Upsilon} mesons.
Date: May 21, 2008
Creator: Arnaud, Nicolas & Collaboration, representing the BABAR
Object Type: Article
System: The UNT Digital Library
Rick Sawicki Interview for Dartmouth Engineer Magazine (open access)

Rick Sawicki Interview for Dartmouth Engineer Magazine

In this issue Rick Sawicki answers the question--What is your role as chief engineer on this project? His reply is--There are two major roles for the Chief Engineer position: (1) to assure that the engineering that is being performed for the project is safely completed in full compliance with all federal, state and Lawrence Livermore National Laboratory policies, standards and procedures and (2) as needed, address special engineering issues as they arise assuring that their resolution is completed in the safest, most effective manner consistent with the project's budget and schedule constraints. Currently the project is nearing completion. Many activities are rapidly coming to a conclusion and many new, complex systems are being activated. I am presently playing a major role in coordinating these activities so that the work can be executed safely and efficiently and the project will complete on schedule. He also answers the following questions: (1) What is the timetable to have this facility up and running for experimentation; (2) Where is the facility; (3) How large is your team of designers, engineers, etc.; (4) What are the means of achieving nuclear fusion; (5) What are the special engineering challenges of this project; (6) How close are …
Date: May 21, 2008
Creator: Sawicki, R
Object Type: Article
System: The UNT Digital Library
Thermal Flammable Gas Production from Bulk Vitrification Feed (open access)

Thermal Flammable Gas Production from Bulk Vitrification Feed

The baseline bulk-vitrification (BV) process (also known as in-container vitrification ICV™) includes a mixer/dryer to convert liquid low-activity waste (LAW) into a dried, blended feed for vitrification. Feed preparation includes blending LAW with glass-forming minerals (GFMs) and cellulose and drying the mixture to a suitable dryness, consistency, and particle size for transport to the ICVTM container. The cellulose is to be added to the BV feed at a rate sufficient to destroy 75% of the nitrogen present as nitrate or nitrite. Concern exists that flammable gases may be produced during drying operations at levels that could pose a risk. The drying process is conducted under vacuum in the temperature range of 60 to 80°C. These flammable gases could be produced either through thermal decomposition of cellulose or waste organics or as a by-product of the reaction of cellulose and/or waste organics with nitrate or the postulated small amount of nitrite present in the waste. To help address the concern about flammable gas production during drying, the Pacific Northwest National Laboratory (PNNL) performed studies to identify the gases produced at dryer temperatures and at possible process upset conditions. Studies used a thermogravimetric analyzer (TGA) up to 525°C and isothermal testing up …
Date: May 21, 2008
Creator: Scheele, Randall D.; McNamara, Bruce K. & Bagaasen, Larry M.
Object Type: Report
System: The UNT Digital Library
Simultaneously Bound Guests and Chiral Recognition: a Chiral Self-Assembled Supramolecular Host Encapsulates Hydrophobic Guests (open access)

Simultaneously Bound Guests and Chiral Recognition: a Chiral Self-Assembled Supramolecular Host Encapsulates Hydrophobic Guests

None
Date: May 21, 2008
Creator: Hastings, Courtney; Pluth, Michael; Biros, Shannon; Bergman, Robert & Raymond, Kenneth
Object Type: Article
System: The UNT Digital Library
Correlation Analysis of TEM Images of Nanocrystal Molecules (open access)

Correlation Analysis of TEM Images of Nanocrystal Molecules

Quantitative characterizataion of images of naocrystals and nanostructures is a challenging but important task. The development and optimization of methods for the construction of complex nanostructures rely on imaging techniques. Computer programs were developed to quantify TEM images of nanocrystal/DNA nanostructures, and results are presented for heterodimers annd trimers of gold nanocrystals. The programs presented here have also been used to analyze more complex trimers and tetramers linked by branched DNA, as well as for structures made from attaching gold nanocrystals to CdSe/ZnS core-shell quantum dots. This work has the additional goal of enabling others to quickly and easily adapt the methods for their own use.
Date: May 21, 2008
Creator: Micheel, Christine; Zanchet, Daniele & Alivisatos, A. Paul
Object Type: Article
System: The UNT Digital Library
Electron Bernstein Wave Emission and Mode Conversion Physics on NSTX (open access)

Electron Bernstein Wave Emission and Mode Conversion Physics on NSTX

NSTX is a spherical tokamak (ST) that operates with ne up to 1020 m-3 and BT less than 0.6 T, cutting off low harmonic electron cyclotron (EC) emission widely used for Te measurements on conventional aspect ratio tokamaks. The electron Bernstein wave (EBW) can propagate in ST plasmas and is emitted at EC harmonics. These properties suggest thermal EBW emission (EBE) may be used for local Te measurements in the ST. Practically, a robust Te(R,t) EBE diagnostic requires EBW transmission efficiencies of > 90% for a wide range of plasma conditions. EBW emission and coupling physics were studied on NSTX with an obliquely viewing EBW to O-mode (B-X-O) diagnostic with two remotely steered antennas, coupled to absolutely calibrated radiometers. While Te(R,t) measurements with EBW emission on NSTX were possible, they were challenged by several issues. Rapid fluctuations in edge ne scale length resulted in > 20% changes in the low harmonic B-X-O transmission efficiency. Also, B-X-O transmission efficiency 2 during H-modes was observed to decay by a factor of 5-10 to less than a few percent. The B-X-O transmission behavior during H-modes was reproduced by EBE simulations that predict that EBW collisional damping can significantly reduce emission when Te < …
Date: May 21, 2008
Creator: Diem, S J; Caughman, J B; Efthimion, P; Kugel, H; LeBlanc, B P; Preinhaelter, J et al.
Object Type: Article
System: The UNT Digital Library
Comparison of Edge Plasma Perturbation During ELM Control Using One vs Two Toroidal Rows of RMP Coils in ITER Similar Shaped Plasmas on DIII-D (open access)

Comparison of Edge Plasma Perturbation During ELM Control Using One vs Two Toroidal Rows of RMP Coils in ITER Similar Shaped Plasmas on DIII-D

Large Type-I edge localized modes (ELMs) were suppressed by n = 3 resonant magnetic perturbations (RMPs) from a set of internal coils (I-coil) in plasmas with an ITER similar shape at the ITER pedestal collisionality, {nu}*{sub e} {approx} 0.1 and low edge safety factor (q{sub 95} {approx} 3.6), with either a single toroidal row of the internal RMP coils or two poloidally separated rows of coils. ELM suppression with a single row of internal coils was achieved at approximately the same q{sub 95} surface-averaged perturbation field as with two rows of coils, but required higher current per coil. Maintaining complete suppression of ELMs using n = 3 RMPs from a single toroidal row of internal coils was less robust to variations in input neutral beam injection torque than previous ELM suppression cases using both rows of internal coils. With either configuration of RMP coils, maximum ELM size is correlated with the width of the edge region having good overlap of the magnetic islands from vacuum field calculations.
Date: May 21, 2008
Creator: Fenstermacher, M. E.; Evans, T. E.; Osborne, T. H.; Schaffer, M. J.; deGrassie, J. S.; Gohil, P. et al.
Object Type: Article
System: The UNT Digital Library