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2,089 - 2,101 of
2,101
Ultra-Bright X-Ray Generation Using Inverse Compton Scattering of Picosecond CO(2) Laser Pulses.
Laser-Compton scattering with picosecond CO{sub 2} laser pulses is proposed for generation of high-brightness x-rays. The interaction chamber has been developed and the experiment is scheduled for the generation of the x-rays of 4.7 keV, 10{sup 7} photons in 10-ps pulse width using 50-MeV, 0.5-nC relativistic electron bunches and 6 GW CO{sub 2} laser.
Date:
March 1, 1999
Creator:
Tsunemi, A.; Endo, A.; Pogorelsky, I.; Ben-Zvi, Ilan; Kusche, K.; Skaritka, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Ultraviolet radiation climatology of the Earth`s surface and lower atmosphere. Final report
Ultraviolet (UV) radiation is the driving force of tropospheric chemistry and is furthermore detrimental to most living tissues. A three year modeling program was carried out to characterize the UV radiation in the lower atmosphere, with the objective of development a climatology of UV biologically active radiation, and of photo-dissociation reaction rates that are key to tropospheric chemistry. A comprehensive model, the Tropospheric Ultraviolet-Visible (TUV) model, was developed and made available to the scientific community. The model incorporates updated spectroscopic data, recent advances in radiative transfer theory, and allows flexible customization for the needs of different users. The TUV model has been used in conjunction with satellite-derived measurements of total atmospheric ozone and cloud amount, to develop a global climatology of UV radiation reaching the surface of the Earth. Initial validation studies are highly encouraging, showing that model predictions agree with direct measurements to ca. 5--10% at times when environmental conditions are well known, and to 10--30% for monthly averages when local environmental conditions can only be estimated remotely from satellite-based measurements. Additional validation studies are continuing.
Date:
March 1, 1999
Creator:
Madronich, S. & Stamnes, K.
Object Type:
Report
System:
The UNT Digital Library
Unrestricted release measurements with ambient air ionization monitors
Radiation monitoring systems based on the long-range alpha detection (LRAD) technique, such as the BNFL Instruments IonSens{trademark}, provide a single contamination measurement for an entire object rather than the more familiar individual readings for smaller surface areas. The LRAD technique relies on the ionization of ambient air molecules by alpha particles, and the subsequent detection of these ions, rather than direct detection of the alpha particles themselves. A single monitor can detect all of the ions produced over a large object and report a total contamination level for the entire surface of that object. However, both the unrestricted release limits specified in USDOE Order 5400.5 (and similar documents in other countries), and the definitions of radioactive waste categories, are stated in terms of contamination per area. Thus, conversion is required between the total effective contamination as measured by the LRAD-based detector and the allowable release limits. In addition, since the release limits were not written assuming an averaging detector system, the method chosen to average the assumed contamination over the object can have a significant impact on the effective sensitivity of the detector.
Date:
March 1, 1999
Creator:
MacArthur, D.; Gunn, R.; Dockray, T. & Luff, C.
Object Type:
Report
System:
The UNT Digital Library
Upgrade of the CEBAF acceleration system
Long-term plans for CEBAF at Jefferson Lab call for providing 12 GeV in the middle of the next decade and 24 GeV after 2010. Such energies can be achieved within the existing footprint by fully populating the accelerator tunnel with cryomodules capable of twice the operating voltage of the existing ones within the same length. In particular, this requires the development of superconducting cavities capable of operating at gradients above 12 MV/m and Q{approximately}10{sup 10}. An R&D program for the development of the cryomodules is under way and will be presented, as well as various options for the upgrade path.
Date:
March 1, 1999
Creator:
Team, J.R. Delayen for the Upgrade Cryomodule Development
Object Type:
Article
System:
The UNT Digital Library
Use of Activated Charcoal for {sup 220}Rn Adsorption for Operations Associated with the Uranium Deposit in the Auxiliary Charcoal Bed at the Molten Salt Reactor Experiment Facility
Measurements have been collected with the purpose of evaluating the effectiveness of activated charcoal for the removal of {sup 220}Rn from process off-gas at the Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory. A series of bench-scale tests were performed at superficial flow velocities of 10, 18, 24, and 33 cm/s (20, 35, 47, and 65 ft/min) with a continuous input concentration of {sup 220}Rn in the range of 9 x 10{sup 3} pCi/L. In addition, two tests were performed at the MSRE facility by flowing helium through the auxiliary charcoal bed uranium deposit. These tests were performed so that the adsorptive effectiveness could be evaluated with a relatively high concentration of {sup 220}Rn. In addition to measuring the effectiveness of activated charcoal as a {sup 220}Rn adsorption media, the source term for available {sup 220}Rn in the deposit is actually available for removal and that the relative activity of fission gases is very small when compared to {sup 220}Rn. The measurement data were then used to evaluate the expected effectiveness of a proposed charcoal adsorption bed consisting of a right circular cylinder having a diameter of 43 cm and a length of 91 cm (17 in. I.D. …
Date:
March 1, 1999
Creator:
Coleman, R.L.
Object Type:
Report
System:
The UNT Digital Library
The use of design-of-experiments methodology to optimize polymer capsule fabrication. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports
Future inertial-fusion experiments on Omega will utilize {approximately} 1 mm-diameter cryogenic targets that have a {approximately} 100-{micro}m-thick, uniformly-frozen fuel layer on their interior. It is desired that they have a stress-free wall thickness < 1 {micro}m and an rms surface roughness < 20 nm. A design-of-experiments (DOE) approach was used to characterize a glow-discharge-polymerization coater built at LLE to fabricate smooth, stress-free capsules with submicron wall thicknesses. The DOE approach was selected because several parameters can be changed simultaneously in a manner which allows the minimum number of runs to be performed to obtain statistically-relevant data. Planar, silicon substrates were coated with {approximately} 3--5 {micro}m of polymer and profilometry was used to determine the coating rate, the film stress, and the surface roughness. The coating rate was found to depend on the trans-2-butene/hydrogen ratio, the total gas-flow rate, the total chamber pressure, and the RF power. In addition, a two-parameter interaction between the total pressure and the RF power also affects the coating rate. The film stress depends on the total chamber pressure and the total mass-flow rate. The surface roughness is independent of the parameters studied. Preliminary results indicate that capsules can be produced rapidly without affecting the smoothness …
Date:
March 1, 1999
Creator:
Lai, L.
Object Type:
Report
System:
The UNT Digital Library
The use of propagation path corrections to improve regional seismic event location in western China
In an effort to improve the ability to locate seismic events in western China using only regional data, the authors have developed empirical propagation path corrections (PPCs) and applied such corrections using both traditional location routines as well as a nonlinear grid search method. Thus far, the authors have concentrated on corrections to observed P arrival times for shallow events using travel-time observations available from the USGS EDRs, the ISC catalogs, their own travel-tim picks from regional data, and data from other catalogs. They relocate events with the algorithm of Bratt and Bache (1988) from a region encompassing China. For individual stations having sufficient data, they produce a map of the regional travel-time residuals from all well-located teleseismic events. From these maps, interpolated PPC surfaces have been constructed using both surface fitting under tension and modified Bayesian kriging. The latter method offers the advantage of providing well-behaved interpolants, but requires that the authors have adequate error estimates associated with the travel-time residuals. To improve error estimates for kriging and event location, they separate measurement error from modeling error. The modeling error is defined as the travel-time variance of a particular model as a function of distance, while the measurement error …
Date:
March 1, 1999
Creator:
Steck, L. K.; Cogbill, A. H. & Velasco, A. A.
Object Type:
Article
System:
The UNT Digital Library
Using Servers to Enhance Control System Capability
Many traditional control systems include a distributed collection of front end machines to control hardware. Back end tools are used to view, modify and record the signals generated by these front end machines. Software servers, which are a middleware layer between the front and back ends, can improve a control system in several ways. Servers can enable on-line processing of raw data, and consolidation of functionality. In many cases, data retrieved from the front end must be processed in order to convert the raw data into useful information. These calculations are often redundantly performed by different programs, frequently offline. Servers can monitor the raw data and rapidly perform calculations, producing new signals which can be treated like any other control system signal, and can be used by any back end application. Algorithms can be incorporated to actively modify signal values in the control system based upon changes of other signals, essentially producing feedback in a control system. Servers thus increase the flexibility of a control system. Lastly, servers running on inexpensive UNIX workstations can relay or cache frequently needed information, reducing the load on front end hardware by functioning as concentrators. Rather than many back end tools connecting directly to …
Date:
March 1, 1999
Creator:
Bickley, M.; Bowling, B. A.; Bryan, D. A.; Zeijts, J. van; White, K. S. & Witherspoon, S.
Object Type:
Article
System:
The UNT Digital Library
Vacuum-compatible standard diffuse source, manufacture and calibration
Los Alamos National Laboratories has completed the design, manufacture and calibration of a vacuum-compatible, tungsten lamp, integrated sphere. The light source has been calibrated at the National Institute of Standards and Technology (NIST) and is intended for use as a calibration standard for remote sensing instrumentation. Calibration 2{sigma} uncertainty varied with wavelength from 1.21% at 400 nm and 0.73% at 900 nm, to 3.95% at 2,400 nm. The inner radius of the Spectralon-coated sphere is 21.2 cm with a 7.4 cm square exit aperture. A small satellite sphere is attached to the main sphere and its output coupled through a stepper motor driven aperture. The variable aperture allows a constant radiance without effecting the color temperature output from the main sphere. The sphere`s output is transmitted into a vacuum test environment through a fused silica window that is an integral part of the outer housing of the vacuum shell assembly. The atmosphere within this outer housing is composed of 240 K nitrogen gas, provided by a custom LN{sub 2} vaporizer unit. Use of the nitrogen gas maintains the internal temperature of the sphere at a nominal 300 K {+-}10{degree}. The calibrated spectral range of the source is 0.4 {micro}m through …
Date:
March 1, 1999
Creator:
Byrd, D. A.; Atkins, W. H.; Bender, S. C.; Christensen, R. W. & Michaud, F. D.
Object Type:
Article
System:
The UNT Digital Library
Vacuum simulation of RF cavities to optimize pump configurations
The pressure history in the components of an rf linac has been modeled using Mathematica.[1] Specifically the Cavity Coupled Drift Tube Linac (CCDTL) and Cavity Coupled Linac (CCL) sections of the Accelerator Production of Tritium (APT) plant [2] have been modeled in order to predict the optimal pump configuration over the 224 meter length. The pressure history in up to 43 sub-volumes within three representative modules (about three meters long) is analyzed in detail. Included in our model are time-dependent outgassing rates and pressure-dependent pump speeds. With this information, we solve for the pressure history during roughing and with turbo and ion pumps. The number and size of each pump is optimized to achieve the desired pressure with minimal costs.
Date:
March 1, 1999
Creator:
Shen, S. & Tung, L. S.
Object Type:
Article
System:
The UNT Digital Library
Veterans' Benefits Claims: Further Improvements Needed in Claims-Processing Accuracy
A letter report issued by the General Accounting Office with an abstract that begins "Pursuant to a congressional request, GAO reviewed the Department of Veterans Affairs' (VA) regional offices' (RO) accuracy in processing disability claims, focusing on: (1) the extent of improvements made by the Systematic Technical Accuracy Review (STAR) system in measuring claims-processing accuracy; (2) additional efforts needed to strengthen the system; and (3) challenges the Veterans Benefits Administration (VBA) faces in meeting goals for improving claims-processing accuracy."
Date:
March 1, 1999
Creator:
United States. General Accounting Office.
Object Type:
Report
System:
The UNT Digital Library
Washing of Rocky Flats Combustible Residues (Conducted March - May 1995)
The scope of this project is to determine the feasibility of washing plutonium-containing combustible residues using ultrasonic disruption as a method for dislodging particulate. Removal of plutonium particulate and, to a lesser extent, solubilized plutonium from the organic substrate should substantially reduce potential fire, explosion or radioactive release hazards due to radiolytic hydrogen generation or high flammability. Tests were conducted on polypropylene filters which were used as pre-filters in the rich-residue ion-exchange process at the Los Alamos Plutonium Facility. These filters are similar to the Ful-Flo{reg_sign} cartridges used at Rocky Flats that make up a substantial fraction of the combustible residues with the highest hazard rating. Batch experiments were run on crushed filter material in order to determine the amount of Pu removed by stirring, stirring and sonication, and stirring and sonication with the introduction of Pu-chelating water-soluble polymers or surfactants. Significantly more Pu is removed using sonication and sonication with chelators than is removed with mechanical stirring alone.
Date:
March 1, 1999
Creator:
Barr, Mary E.; Schake, Ann R.; Romero, David A. & Jarvinen, Gordon D.
Object Type:
Report
System:
The UNT Digital Library
Winning, March 1999
Pamphlet containing information about Texas Lottery winners, scratch-off prizes, new games, and more.
Date:
March 1999
Creator:
Texas Lottery Commission
Object Type:
Journal/Magazine/Newsletter
System:
The Portal to Texas History