Article on a spectroscopic investigation of fluorescence quenching agents and the effect of nitromethane on the fluorescence emission behavior of select cyclopenta-PAH, aceanthrylene, and fluorene derivatives.

Article on kinetics studies of the reactions of atomic chlorine and bromine with trimethylsilane and an ab initio investigation.

Yucca Mountain, the potential site of a repository for high-level radioactive waste, is situated in a region of natural and man-made seismicity. Underground openings excavated at this site must be designed for worker safety in the seismic environment anticipated for the preclosure period. This includes accesses developed for site characterization regardless of the ultimate outcome of the repository siting process. Experience with both civil and mining structures has shown that underground openings are much more resistant to seismic effects than surface structures, and that even severe dynamic strains can usually be accommodated with proper design. This paper discusses the design and performance of lined openings in the seismic environment of the potential site. The types and ranges of possible ground motions (seismic loads) are briefly discussed. Relevant historical records of underground opening performance during seismic loading are reviewed. Simple analytical methods of predicting liner performance under combined in situ, thermal, and seismic loading are presented, and results of calculations are discussed in the context of realistic performance requirements for concrete-lined openings for the preclosure period. Design features that will enhance liner stability and mitigate the impact of the potential seismic load are reviewed. The paper is limited to preclosure performance …

The potential repository system is intended to isolate high-level radioactive waste at Yucca Mountain. One subsystem that may contribute to achieving this objective is the sealing subsystem. This subsystem is comprised of sealing components in the shafts, ramps, underground network of drifts, and the exploratory boreholes. Sealing components can be rigid, as in the case of a shaft seal, or can be more compressible, as in the case of drift fill comprised of mined rockfill. This paper presents the preliminary seismic response of discrete sealing components in welded and nonwelded tuff. Special consideration is given to evaluating the stress in the seal, and the behavior of the interface between the seal and the rock. The seismic responses are computed using both static and dynamic analyses. Also presented is an evaluation of the maximum seismic response encountered by a drift seal with respect to the angle of incidence of the seismic wave. Mitigation strategies and seismic design considerations are proposed which can potentially enhance the overall response of the sealing component and subsequently, the performance of the overall repository system.

In dual-energy hydrogen imaging, the increase in hydrogen neutron cross-section at subthermal neutron energies is used to enhance the imaging of small amounts of hydrogen against a background of other absorbing materials by subtracting a tomographic image obtained for higher energy neutrons from that obtained for subthermal neutrons (picking energies such that the other absorbing materials have nearly the same cross-sections at both energies). This technique was used to provide dual-energy imaging of water in tuffaceous rock, with the goal being to track water flow through porous rock for site risk analysis of permanent disposal of radwaste. A feasibility experiment was conducted at the IPNS facility with coarse spatial resolution, yielding promising results.

Consideration of the technical feasibility of Yucca Mountain in Nevada as the site for a high-level nuclear waste repository has led to an intense debate regarding the economic, social, and political impacts of the repository. Impediments to the siting process mean that the nuclear waste problem is being resolved by adhering to the status quo, in which nuclear waste is stored at scattered sites near major population centers. To assess the merits of alternative siting strategies--including both the permanent repository and the status quo- we consider the variables that would be included in a model designed to select (1) the optimal number of disposal facilities, (2) the types of facilities (e.g., permanent repository or monitored retrievable facility), and (3) the geographic location of storage sites. The objective function in the model is an all-inclusive measure of social cost. The intent of the exercise is not to demonstrate the superiority of any single disposal strategy; uncertainties preclude a conclusive proof of optimality for any of the disposal options. Instead, we want to assess the sensitivity of a variety of proposed solutions to variations in the physical, economic, political, and social variables that influence a siting strategy.

These proceedings contain 18 papers presented at the meeting. While the majority of the papers (11) had to do with specific hydrogen production methods, other papers were related to hydrogen storage systems, evaluations of and systems analysis for a hydrogen economy, and environmental transport of hydrogen from a pipeline leak.

The purpose of a vertex detector is to measure position and angles of charged particle tracks to sufficient precision so as to be able to separate tracks originating from decay vertices from those produced at the interaction vertex. Such measurements are interesting because they permit the detection of weakly decaying particles with lifetimes down to 10{sup {minus}13} s, among them the {tau} lepton and charm and beauty hadrons. These two lectures are intended to introduce the reader to the different techniques for the detection of secondary vertices that have been developed over the past decades. The first lecture includes a brief introduction to the methods used to detect secondary vertices and to estimate particle lifetimes. It describes the traditional technologies, based on photographic recording in emulsions and on film of bubble chambers, and introduces fast electronic registration of signals derived from scintillating fibers, drift chambers and gaseous micro-strip chambers. The second lecture is devoted to solid state detectors. It begins with a brief introduction into semiconductor devices, and then describes the application of large arrays of strip and pixel diodes for charged particle tracking. These lectures can only serve as an introduction the topic of vertex detectors. Time and space …

The authors study the applicability of beam-beam deflection techniques as a tuning tool for asymmetric B factories, focusing on PEP-II as an example. Assuming that the closed orbits of the two beams are separated vertically at the interaction point by a local orbit bump that is nominally closed, they calculate the residual beam orbit distortions due to the beam-beam interaction. Difference orbit measurements, performed at points conveniently distant from the interaction point (IP), provide distinct signatures that can be used to maintain the beams in collision and perform detailed optical diagnostics at the IP. A proposal to test this method experimentally at the TRISTAN ring is briefly discussed. Because of their two-ring structure, asymmetric B factories are likely to require more diagnostics and feedback mechanisms than single-ring colliders in order to guarantee head-on collisions. In addition to the traditional techniques, however, the independence of the two beams allows one to envisage other kinds of beam diagnostics. In this article they investigate one such possibility, by looking at the closed orbit distortion produced by the beam-beam interaction when the beams do not collide exactly head-on. They base this investigation on an analytic model and strong-strong multiparticle simulations. Although the discussion uses …

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New measurements of the electric GE(Q2) and magnetic GM(Q2) form factors of the nucleons are reported. The proton data cover the Q2 range from 1.75 to 8.83 (GeV/c)2 and the neutron data from 1.75 to 4.00 (GeV/c)2, more than doubling the range of previous data. Scaled by the dipole fit, GD(Q2), the results forGMp(Q2) /¿pGD(Q2) decrease smoothly from 1.05 to 0.92, while GEp(Q2)/GD(Q2)is consistent with unity. The preliminary results for GMn(Q2) /¿nGD(Q2) are consistent with unity, while GEn is consistent with zero at all values of Q2.

The CEBAF accelerator can drive high power IR and UV FELs, if a high peak current source is added to the existing front end. We present a design for a high peak current injector which is compatible with simultaneous operation of the accelerator for cw nulear physics (NP) beam. The high peak current injector provides 60 A peak current in 2 psec long bunches carrying 120 pC charge at 7.485 MHz. At 10 MeV that beam is combined with 5 MeV NP beam (0.13pC, 2 psec long bunches at 1497 MHz) in an energy combination chicane for simultaneous acceleration in the injector linac. The modifications to the low-energy NP transport are described. Results of optical and beam dynamics calculations for both high peak current and NP beams in combined operation are presented.

Argonne National Laboratory has conducted analyses of failed components from nuclear power generating stations since 1974. The considerations involved in working with and analyzing radioactive components are reviewed here, and the decontamination of these components is discussed. Analyses of four failed components from nuclear plants are then described to illustrate the kinds of failures seen in service. The failures discussed are (a) intergranular stress corrosion cracking of core spray injection piping in a boiling water reactor, (b) failure of canopy seal welds in adapter tube assemblies in the control rod drive head of a pressure water reactor, (c) thermal fatigue of a recirculation pump shaft in a boiling water reactor, and (d) failure of pump seal wear rings by nickel leaching in a boiling water reactor.

LBL and LLNL propose to build, at LBL, the Induction Linac Systems Experiments (ILSE), the next logical step towards the eventual goal of a heavy-ion induction accelerator powerful enough to implode or drive'' inertial-confinement fusion targets. ILSE, although much smaller than a driver, will be the first experiment at full driver scale in several important parameters. Most notable among these are line charge density and beam cross section. Many other accelerator components and beam manipulations needed for an inertial fusion energy (IFE) driver will be tested. The ILSE accelerator and research program will permit experimental study of those beam manipulations required of an induction linac inertial fusion driver which have not been tested sufficiently in previous experiments, and will provide a step toward driver technology.

Coherent anti-Stokes Raman Spectroscopy (CARS) is used to study the plasma-assisted chemical vapor deposition (PACVD) of TiB{sub 2}. CARS is applied to the dominent species in an inductively coupled B{sub 2}H{sub 6}/Ar rf plasma. Axial concentration profiles of diborane and hydrogen are probed in the plasma. A five-step mechanism is developed. Photochemical initiation of the chemical reaction is considered. 16 refs, 5 figs.(DLC)

To study the effects of frequency on an electron cyclotron resonance (ECR) ion source, the LBL Advanced ECR ion source (designed to operate at 14 GHz) has been tested at 6.4, 10, and 14 GHz with one plasma chamber (ID = 6.0 cm), a permanent sextuple magnet ( closed sextuple'') with a field strength of 0.84 Tesla at the chamber wall, and no radial vacuum pumping. Pure oxygen was used as the running gas for a fair comparison. The source was tested as a single stage, as well as with cold electron injection using an electron gun in place of a conventional microwave-driven first stage. Higher frequency, with a higher axial magnetic field to ensure a closed ECR zone for electron heating, does give better performance. As demonstrated before, at each frequency electron injection led to about a factor of two increase in the high charge state oxygen beam intensity. The 14 GHz performance of the AECR source with the closed sextuple magnet was compared to the slotted sextuple'' (a plasma chamber with radial pumping slots of 7.0-cm dia and a weaker magnet of 0.64 Tesla at the chamber wall). Results show that a stronger sextuple magnet alone does not …

This report discusses for determining key static reactor physics parameters which have been developed by groups of experts (working groups) under the aegis of ANS-19, the ANS Reactor Physics Standards Committee. Following a series of sequential reviews, augmented by feedback from potential users, a proposed standard is brought into final form by the working group before it is adopted as a formal standard by the American National Standards Institute (ANSI); Reactor Physics standards are intended to provide guidance in the performance and qualification of complex sequences of reactor calculations and/or measurements and are regularly reviewed for possible updates and/or revisions. The reactor physics standards developed to date are listed and standards now being developed by the respective working groups are also provided.

Operating the Stanford Linear Collider (SLC) at 120Hz repetition rate requires the presence of two bunches in both the electron and the positron damping ring. The {pi}-mode instability, a coupled bunch instability where the two bunches oscillate with a phase difference of 180{degrees}, had been observed in both rings with low current thresholds of 7{sup *}10{sup 9} particles per bunch. To avoid the instability, the RF system had to be operated in ways which in general reduced the cavity gap voltages and required constant operational attention. For the 1992 running cycle a passive cavity was installed and successfully tested. It is tuned to the frequency of the lower synchrotron oscillation sideband of an odd revolution harmonic. The impedance of the cavity then damps {pi}-mode oscillations very similar to the Robinson damping provided by the main RF cavities which damps O-mode synchrotron oscillations. In this report we describe the motivation and physical considerations that led to the final design parameters and the experience obtained from the performance of these cavities.

The application of Fourier Transform Ion Cylcotron Resonance Mass Spectroscopy to precision atomic mass measurements is considered. Limits on the mass accuracy of this technique for atomic masses are discussed, and plans for future developments with application to fundamental weak interaction physics are presented.

Fenestration systems are major contributors to peak cooling loads in commercial buildings and thus to HVAC system costs, peak electric demand, and annual energy use. These loads can be reduced significantly through proper fenestration design and the use of daylighting strategies. However, there are very few documented applications of energy-saving daylighted buildings today, which suggests that significant obstacles to efficient fenestration and lighting design and utilization still exist. This paper reports results of the first phase of a utility-sponsored research, development, and demonstration project to more effectively address the interrelated issues of designing and implementing energy-efficient envelope and lighting systems. We hypothesize that daylighting and overall energy efficiency will not be achieved at a large scale until true building integration has been accomplished to some meaningful degree. Moving beyond the vague concept of intelligent' buildings long popular in the design sector, we attempt to integrate component technologies into functional systems in order to optimize the relevant building energy performance and occupant comfort parameters. We describe the first set of integrated envelope and lighting concepts we are developing using available component technologies. Emerging and future technologies will be incorporated in later phases. Because new hardware systems alone will not ensure optimal …

Large shifts of liquid arising from small changes in certain container shapes in zero gravity can be used as a basis for accurately determining contact angle. Canonical'' geometries for this purpose, recently developed mathematically, are investigated here computationally. It is found that the desired nearly- discontinuous'' behavior can be obtained and that the shifts of liquid have sufficient volume to be readily observed.

At the leaf level, under light saturating and light limiting conditions, it is shown that elevated atmospheric CO{sub 2} concentration not only alters the scale of the response of carbon gain to rising temperature, but can alter the direction of response. These points bring into serious question the value of any predictions of plant production which ignore not only the direct effect Of C0{sub 2} on carbon gain, but also the basic interactions of temperature, C0{sub 2} and 0{sub 3}. Whilst many factors may potentially diminish the enhancement of lightsaturated leaf photosynthetic rates with increase in atmospheric CO{sub 2} concentrations, no mechanism has so far been identified which could remove the parallel stimulation of light-limited photosynthesis.

We investigate the utility of accelerating during the nonadiabatic period surrounding the time of transition with an rf waveform modified by a second or third harmonic component to eliminate rf focusing. Simulation study shows this scheme not only to control momentum spread but also to have apparent advantage with respect to microwave instability. An experimental test has been initiated in the Fermilab Main Ring using a cavity at the third harmonic of the rf.

The cuprate superconductors are fascinating not only because of their technical promise, but also because of their structures, especially the anisotropy of the crystal lattice. There are some structural similarities among these compounds, but also significant differences. Measurements of the oxygen tracer diffusion coefficients have been carried out as a function of temperature, oxygen partial pressure, crystal orientation, and doping in the La-Sr-Cu-0, Y-Ba-Cu-0, and Bi-Sr-Ca-Cu-0 systems. These measurements have revealed a variety of defect mechanisms operating in these compounds; the exact nature of the mechanism depends on the details of the structure.