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A 250-GHz CARM (Cyclotron Auto Resonance Maser) oscillator experiment driven by an induction linac

Description: A 250-GHz Cyclotron Auto Resonance Maser (CARM) oscillator has been designed and constructed and will be tested using a 1-kA, 2-MeV electron beam produced by the induction linac at the Accelerator Research Center (ARC) facility of Lawrence Livermore National Laboratory (LLNL). The oscillator circuit was made to operate in the TE{sub 11} mode at ten times cutoff using waveguide Bragg reflectors to create an external cavity Q of 8000. Theory predicts cavity fill times of less than 30 ns (pulse length) and efficiencies approaching 20% is sufficiently low transverse electron velocity spreads are maintained (2%).
Date: September 14, 1990
Creator: Caplan, M.; Kulke, B.; Bubp, D.G. (Lawrence Livermore National Lab., CA (USA)); McDermott, D. & Luhmann, N. (California Univ., Los Angeles, CA (USA))

300 Degree C GaN/AlGaN Heterojunction Bipolar Transistor

Description: A GaN/AIGaN heterojunction bipolar transistor has been fabricated using C12/Ar dry etching for mesa formation. As the hole concentration increases due to more efficient ionization of the Mg acceptors at elevated temperatures (> 250oC), the device shows improved gain. Future efforts which are briefly summarized. should focus on methods for reducing base resistance.
Date: October 14, 1998
Creator: Abernathy, C. R.; Baca, A. G.; Cho, H.; Chow, P. P.; Han, J.; Hichman, R. A. et al.

3D visualization of port simulation.

Description: Affordable and realistic three dimensional visualization technology can be applied to large scale constructive simulations such as the port simulation model, PORTSIM. These visualization tools enhance the experienced planner's ability to form mental models of how seaport operations will unfold when the simulation model is implemented and executed. They also offer unique opportunities to train new planners not only in the use of the simulation model but on the layout and design of seaports. Simulation visualization capabilities are enhanced by borrowing from work on interface design, camera control, and data presentation. Using selective fidelity, the designers of these visualization systems can reduce their time and efforts by concentrating on those features which yield the most value for their simulation. Offering the user various observational tools allows the freedom to simply watch or engage in the simulation without getting lost. Identifying the underlying infrastructure or cargo items with labels can provide useful information at the risk of some visual clutter. The PortVis visualization expands the PORTSIM user base which can benefit from the results provided by this capability, especially in strategic planning, mission rehearsal, and training. Strategic planners will immediately reap the benefits of seeing the impact of increased throughput visually without keeping track of statistical data. Mission rehearsal and training users will have an effective training tool to supplement their operational training exercises which are limited in number because of their high costs. Having another effective training modality in this visualization system allows more training to take place and more personnel to gain an understanding of seaport operations. This simulation and visualization training can be accomplished at lower cost than would be possible for the operational training exercises alone. The application of PORTSIM and PortVis will lead to more efficient planning overall and ultimately increase port utilization and throughput, decreasing ...
Date: June 14, 1999
Creator: Horsthemke, W. H.; Macal, C. M. & Nevins, M. R.

50x50 GeV Muon Collider Beam Collimation

Description: A summary of different techniques and systems to scrape beam halo in a 50 x 50 GeV {mu}{sup +}{mu}{sup -} collider is presented. Such systems are installed in a special utility section with optics specifically designed to meet both the requirements of the scraping system and of injection. Results froma realistic Monte Carlo simulation (STRUCT-MARS) show that a system consisting of steel absorbers several meters in length suppresses halo-induced backgrounds in the collider detector by more than three orders of magnitude. The heat load in superconducting magnets near the scraper system can be reduced to tolerable levels by appropriate collimator design and location. This reduction applies to both injection and collider mode of operation. Also discussed is extraction of halo particles using electrostatic deflectors and bent crys-tals, although neither appears to be effective for a muon collider at this energy.
Date: April 14, 1999
Creator: Drozhdin, A. I.; Johnstone, C. J.; Mokhov, N. V.; Garen, A. A. & Biryukov, V. M.

Additional Interface Corner Toughness Data for an Adhesively-Bonded Butt Joint

Description: Over a period of 15 months, five sets of adhesively-bonded butt joints were fabricated and tested. This previously unreported data is used to assess the variability of measured interface corner toughness values, K{sub ac}, as well as the dependence of K{sub ac} on surface preparation. A correlation between K{sub ac} and the size of the adhesive failure zone is also noted.
Date: April 14, 1999
Creator: Guess, T.R. & Reedy, E.D.

Adjustment of the (235)U Fission Spectrum

Description: The latest nuclear data are used to examine the sensitivity of the least squares adjustment of the {sup 235}U fission spectrum to the measured reaction rates, dosimetry cross sections, and prior spectrum covariance matrix. All of these parameters were found to be very important in the spectrum adjustment. The most significant deficiency in the nuclear data is the absence of a good prior covariance matrix. Covariance matrices generated from analytic models of the fission spectra have been used in the past. This analysis reveals some unusual features in the covariance matrix produced with this approach. Specific needs are identified for improved nuclear data to better determine the {sup 235}U spectrum. An improved {sup 235}U covariance matrix and adjusted spectrum are recommended for use in radiation transport sensitivity analyses.
Date: September 14, 1999
Creator: GRIFFIN,PATRICK J. & WILLIAMS,J.G.

Alternative repository criticality-control strategies for fissile uranium wastes

Description: Methods to prevent long term, disposal site nuclear criticality from fissile uranium isotopes in wastes were investigated. Long term refers to the time period after waste package (WP) failure and the subsequent loss of geometry and chemistry control within the WP. The preferred method of control was found to be the addition of sufficient depleted uranium to each WP so that the uranium enrichment is reduced to < 1 wt % {sup 235}U and < 0.66 wt % {sup 233}U in {sup 238}U.
Date: April 14, 1998
Creator: Forsberg, C.W.

Analysis of In-Situ Vibration Monitoring for End-Point Detection of CMP Planarization Processes

Description: This paper details the analysis of vibration monitoring for end-point control in oxide CMP processes. Two piezoelectric accelerometers were integrated onto the backside of a stainless steel polishing head of an IPEC 472 polisher. One sensor was placed perpendicular to the carrier plate (vertical) and the other parallel to the plate (horizontal). Wafers patterned with metal and coated with oxide material were polished at different speeds and pressures. Our results show that it is possible to sense a change in the vibration signal over time during planarization of oxide material on patterned wafers. The horizontal accelerometer showed more sensitivity to change in vibration amplitude compared to the vertical accelerometer for a given polish condition. At low carrier and platen rotation rates, the change in vibration signal over time at fixed frequencies decreased approximately &frac12; - 1 order of magnitude (over the 2 to 10 psi polish pressure ranges). At high rotation speeds, the vibration signal remained essentially constant indicating that other factors dominated the vibration signaL These results show that while it is possible to sense changes in acceleration during polishing, more robust hardware and signal processing algorithms are required to ensure its use over a wide range of process conditions.
Date: May 14, 1999
Creator: Hetherington, Dale L.; Lauffer, James P.; Shingledecker, David M.; Stein, David J. & Wyckoff, Edward E.

Analysis of Strategies to Improve Heliostat Tracking at Solar Two

Description: This paper investigates dhlerent strategies that can be used to improve the tracking accuracy of heliostats at Solar Two. The different strategies are analyzed using a geometrical error model to determine their performance over the course of a day. By using the performance of heliostats in representative locations of the field aad on representative days of the year, an estimate of the annual performance of each strategy is presented.
Date: January 14, 1999
Creator: Jones, S. A. & Stone, K. W.

Anisotropy in Hydrogenated Amorphous Silicon Films as Observed Using Polarized FTIR-ATR Spectroscopy

Description: We used polarized attenuated total reflection (ATR) measurements together with Fourier transform infrared (FTIR) spectroscopy to investigate the vibrational spectra of hydrogenated amorphous silicon (a-SiH{sub x}) films 0.5-1.0 microns in thickness. We deposited the films using hot-wire or plasma-enhanced chemical vapor deposition methods (HWCVD or PECVD, respectively) on crystalline silicon and cadmium telluride substrates. Our ATR technique gave a spectral range from 2100-400 cm{sup -1}, although the Si-H wagging mode absorption band at 640 cm{sup -1} was somewhat distorted in the a-SiHx/Si samples by impurity and lattice absorption in the silicon ATR substrates. We report the identification of a Si-O-C impurity band with maximum intensity at 1240-1230 cm{sup -1}. The assignment of this band to a Si-O-C vibration is supported by secondary-ion mass spectrometry (SIMS) measurements. Our polarized FTIR-ATR spectra of HWCVD and PECVD a-SiH{sub x} films on &lt;111&gt; Si ATR substrates show that the impurity dipoles ar e oriented strongly parallel to the film growth direction. The wagging mode absorbance band is more intense in the film plane. This trend is less pronounced for the Si-H stretching vibrations. These observations are consistent with some degree of anisotropy or medium-range order in the films. The anisotropy in the Si-H bands may be related to residual stress in the films. Our scanning electron microscopy (SEM) analyses of the samples offer additional evidence of bulk structural anisotropy in the a-SiH{sub x}/Si films. However, the Si-O-C impurity band was not observed in the polarized ATR-FTIR spectra of the a-SiH{sub x}/CdTe samples, thus indicating that the Si substrates influence formation of the impurity in the a-SiH{sub x}/Si films.
Date: May 14, 1999
Creator: Webb, J. D.; Gedvilas, L. M.; Crandall, R. S.; Iwaniczko, E.; Nelson, B. P.; Mahan, A. H. et al.

Application of probabilistic risk assessment methods to incinerator design and permitting

Description: The Consolidated Incineration Facility at the Savannah River Site is designed without emergency flue gas vents. The main components of this 18 million btu/hr facility are a rotary kiln and secondary combustion chamber, each with a code allowable internal pressure of 15 psig. The facility is designed to treat mixed waste. During the early stages of design it was judged on a qualitative basis that potential eventsthat might produce damaging overpressures were not credible. When these findings were questioned during subsequent design reviews, a probabilistic risk assessment was undertaken to provide a quantitative basis for decision making. The result was identification of design conditions leading to relatively high frequencies for a few event sequences in which the allowable pressure might be exceeded. Risk assessment assumptions and results were reviewed with design engineers and relatively simple improvements were identified that collectively reduced the frequency of overpressure to an acceptable level. This experience showed that the use of formalized risk assessment techniques can provide valuable insight leading to timely and cost-effective improvements in facility design and operating procedures. In this case, the program of analysis and follow-on improvements provided justification for incinerator operation without thermal relief devices.
Date: February 14, 1993
Creator: Brown, E. A.; McAfee, D. E. & Aabye, D. C.

Application of probabilistic risk assessment methods to incinerator design and permitting

Description: The Consolidated Incineration Facility at the Savannah River Site is designed without emergency flue gas vents. The main components of this 18 million btu/hr facility are a rotary kiln and secondary combustion chamber, each with a code allowable internal pressure of 15 psig. The facility is designed to treat mixed waste. During the early stages of design it was judged on a qualitative basis that potential eventsthat might produce damaging overpressures were not credible. When these findings were questioned during subsequent design reviews, a probabilistic risk assessment was undertaken to provide a quantitative basis for decision making. The result was identification of design conditions leading to relatively high frequencies for a few event sequences in which the allowable pressure might be exceeded. Risk assessment assumptions and results were reviewed with design engineers and relatively simple improvements were identified that collectively reduced the frequency of overpressure to an acceptable level. This experience showed that the use of formalized risk assessment techniques can provide valuable insight leading to timely and cost-effective improvements in facility design and operating procedures. In this case, the program of analysis and follow-on improvements provided justification for incinerator operation without thermal relief devices.
Date: February 14, 1993
Creator: Brown, E.A.; McAfee, D.E. (Westinghouse Savannah River Co., Aiken, SC (United States)) & Aabye, D.C. (Science Applications International Corp., Oak Ridge, TN (United States))

Approaches to instrument design at pulsed neutron sources

Description: A number of tools are used in the design of scattering instruments for pulsed neutron sources. Initial design is based largely on simple analytical calculations. More complicated analytical calculations and Monte Carlo simulations come into play as the design is optimized to maximize the data rate and to improve the data quality. Examples are used to illustrate the relative roles of these different computational tools. Areas are also identified where appropriate computational tools are currently lacking.
Date: April 14, 1997
Creator: Crawford, R.K.

Assembly planning at the micro scale

Description: This paper investigates a new aspect of fine motion planning for the micro domain. As parts approach 1--10 {micro}m or less in outside dimensions, interactive forces such as van der Waals and electrostatic forces become major factors which greatly change the assembly sequence and path plans. It has been experimentally shown that assembly plans in the micro domain are not reversible, motions required to pick up a part are not the reverse of motions required to release a part. This paper develops the mathematics required to determine the goal regions for pick up, holding, and release of a micro-sphere being handled by a rectangular tool.
Date: May 14, 1998
Creator: Feddema, J.T.; Xavier, P. & Brown, R.

Assessing Cumulative Thermal Stress in Fish During Chronic Exposure to High Temperature

Description: As environmental laws become increasingly protective, and with possible future changes in global climate, thermal effects on aquatic resources are likely to receive increasing attention. Lethal temperatures for a variety of species have been determined for situations where temperatures rise rapidly resulting in lethal effects. However, less is known about the effects of chronic exposure to high (but not immediately lethal) temperatures and even less about stress accumulation during periods of fluctuating temperatures. In this paper we present a modeling framework for assessing cumulative thermal stress in fish. The model assumes that stress accumulation occurs above a threshold temperature at a rate depending on the degree to which the threshold is exceeded. The model also includes stress recovery (or alleviation) when temperatures drop below the threshold temperature as in systems with large daily variation. In addition to non-specific physiological stress, the model also simulates thermal effects on growth.
Date: November 14, 1999
Creator: Bevelhimer, M.S. & Bennett, W.R.

An Assessment of carbon reduction technology opportunities in the petroleum refining industry.

Description: The refining industry is a major source of CO{sub 2} emissions in the industrial sector and therefore in the future can expect to face increasing pressures to reduce emission levels. The energy used in refining is impacted by market dictates, crude quality, and environmental regulations. While the industry is technologically advanced and relatively efficient opportunities nevertheless exist to reduce energy usage and CO{sub 2} emissions. The opportunities will vary from refinery to refinery and will necessarily have to be economically viable and compatible with each refiner's strategic plans. Recognizing the many factors involved, a target of 15-20% reduction in CO{sub 2} emissions from the refining sector does not appear to be unreasonable, assuming a favorable investment climate.
Date: September 14, 1998
Creator: Petrick, M.

ASTM Standards for Reactor Dosimetry and Pressure Vessel Surveillance

Description: The ASTM standards provide guidance and instruction on how to field and interpret reactor dosimetry. They provide a roadmap towards understanding the current ''state-of-the-art'' in reactor dosimetry, as reflected by the technical community. The consensus basis to the ASTM standards assures the user of an unbiased presentation of technical procedures and interpretations of the measurements. Some insight into the types of standards and the way in which they are organized can assist one in using them in an expeditious manner. Two example are presented to help orient new users to the breadth and interrelationship between the ASTM nuclear metrology standards. One example involves the testing of a new ''widget'' to verify the radiation hardness. The second example involves quantifying the radiation damage at a pressure vessel critical weld location through surveillance dosimetry and calculation.
Date: September 14, 1999
Creator: GRIFFIN, PATRICK J.

Atomic-Scale Engineering of the SiC-SiO{sub 2} Interface

Description: We report results from three distinct but related thrusts that aim to elucidate the atomic-scale structure and properties of the Sic-SiO{sub 2} interface. (a) First-principles theoretical calculations probe the global bonding arrangements and the local processes during oxidation; (b) Z-contrast atomic-resolution transmission electron microscopy and electron-energy-loss spectroscopy provide images and interface spectra, and (c) nuclear techniques and electrical measurements are used to profile N at the interface and determine interface trap densities.
Date: November 14, 1999
Creator: Buczko, R.; Chung, G.; Di Ventra, M.; Duscher, G.; Feldman, L.C.; Huang, M.B. et al.

Australia Remote Monitoring Project (ARMP)

Description: As a result of the Safeguards Arrangement between the US Department of Energy (DOE) and the Australian Safeguards and Non-Proliferation Office (ASNO) concerning international safeguards R and D, ASNO and Sandia National Laboratories (SNL) have agreed to jointly develop a remote monitoring system at the HIFAR reactor, Lucas Heights, Australia. The HIFAR reactor is a high flux research reactor operated by the Australian Nuclear Science and Technology Organization (ANSTO). The objective of the system is to remotely monitor the entire Material Balance Area (MBA) AS-A to include: fresh fuel the reactor core; spent fuel in the cropping/irradiation pond, international pond, dry spent fuel storage facility, and Dounreay flasks; and spent fuel during designated transport. The purpose is to reduce on-site inspection effort at the HIFAR reactor.
Date: July 14, 1999
Creator: Atencio, Carmella; Busse, James; Carlson, John; Dickerson, Dawn; Ffrost, Brian; Gaillour, Marsha et al.

B decays in the upsilon expansion

Description: Theoretical predictions for B decay rates are rewritten in terms of the Upsilon meson mass instead of the b quark mass, using a modified perturbation expansion. The theoretical consistency is shown both at low and high orders. This method improves the behavior of the perturbation series for inclusive and exclusive decay rates, and the largest theoretical error in the predictions coming from the uncertainty in the quark mass is eliminated. Applications to the determination of CKM matrix elements, moments of inclusive decay distributions, and the {bar B} {yields} X{sub s}{gamma} photon spectrum are discussed.
Date: December 14, 1999
Creator: Ligeti, Zoltan

Back-side emissions from filtered gold targets

Description: An investigation of the rapid rise time of incoherent x-ray emission from targets heated by an ultra-short pulse (USP) high-intensity optical laser was conducted for use as the x-ray source for inner- shell photo-ionized (ISPI) x ray lasing. Previous studies considered front-side x-ray emission; however, ISPI x-ray lasing requires a filtered x-ray source. Modeling using the hydrodynamics/atomic kinetics code LASNEX of a 40 fs USP driving laser with an intensity of 10 exp(17W/CM2) incident on a flat target of thin Au layered on a Be filter is presented. The filter has a modest influence on the x- ray emission of the Au via conduction cooling but has a large effect on the backside spectrum by removing low energy x rays as the Au emission passes through the filter. The use of such a filtered source is shown to provide the needed x rays to achieve high gain in C at 45A.
Date: August 14, 1997
Creator: Moon, S. J. & Eder, D.C.

The Bethe surface of liquid water.

Description: The Bethe surface of liquid water, earlier calculated using a semi-empirical model, is compared with recent available data from IXS-experiments (inelastic X-ray scattering; Compton scattering of high energy photons) in liquid water. No alarming discrepancy is found on a global view of the Bethe surface. The extrapolation to the optical limit (viz., at zero momentum transfer) is shown and the reliability of these data is discussed in detail.
Date: October 14, 1998
Creator: Dingfelder, M.

BNL Activities in Advanced Neutron Source Development: Past and Present

Description: Brookhaven National Laboratory has been involved in advanced neutron sources almost from its inception in 1947. These efforts have mainly focused on steady state reactors beginning with the construction of the first research reactor for neutron beams, the Brookhaven Graphite Research Reactor. This was followed by the High Flux Beam Reactor that has served as the design standard for all the subsequent high flux reactors constructed worldwide. In parallel with the reactor developments BNL has focused on the construction and use of high energy proton accelerators. The first machine to operate over 1 GeV in the world was the Cosmotron. The machine that followed this, the AGS, is still operating and is the highest intensity proton machine in the world and has nucleated an international collaboration investigating liquid metal targets for next generation pulsed spallation sources. Early work using the Cosmotron focused on spallation product studies for both light and heavy elements into the several GeV proton energy region. These original studies are still important today. In this report we discuss the facilities and activities at BNL focused on advanced neutron sources. BNL is involved in the proton source for the Spallation Neutron source, spectrometer development at LANSCE, target studies using the AGS and state-of-the-art neutron detector development.
Date: June 14, 1998
Creator: Hastings, J.B.; Ludewig, H.; Montanez, P.; Todosow, M.; Smith, G.C. & Larese, J.Z.