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Accurate reporting of mercury concentration requires a detailed model that includes experimental parameters that vary, such as: pressure, temperature, concentration, absorption cross-section, and isotopic structure etc. During this quarter a theoretical model has been developed to model the 253.7 nm mercury transition. In addition, while testing the interferent species SO{sub 2}, SRD was able to determine the absorption cross-section experimentally and add this to the theoretical model. Assuming that the baseline losses are due to the mirror reflectivity and SO{sub 2}, SRD can now determine the concentrations of both mercury and SO{sub 2} from the data taken. For the CRD instrument to perform as a continuous emission monitor it will be required to monitor mercury concentrations over extended periods of time. The stability of monitoring mercury concentrations over time with the CRD apparatus was tested during the past quarter. During a test which monitored the mercury concentration every 2 seconds it was found that the standard deviation, of a signal from about 1.25 ppb Hg, was only 30 ppt. SRD continued interferent gas testing during this past quarter. This included creating a simulated flue gas composed of the gases tested individually by SRD. The detection limits for mercury, although dependent on the concentration of SO{sub 2} in the simulated gas matrix, remained well below the ppb range. It was determined that for the gases tested the only measurable changes in the baseline level occurred for SO{sub 2} and mercury. Speciation studies continued with mercury chloride (HgCl{sub 2}). This included checking for spectral speciation with both Hg and HgCl{sub 2} present in the CRD cavity. There was no observable spectral shift. Also a pyrolysis oven was incorporated into the gas delivery system both for tests with HgCl{sub 2} as well as atomization of the entire gas stream. The pyrolysis tests conducted have been inconclusive thus far.

ABSTRACTRadiation damage has been studied in natural rock salt from various localities, including potential repository sites. In the 100 to 300 C range the damage consists of point defects, primarily F-centers, and colloidal metal sodium particles. With increasing dose the F-centers grow to a saturation level, reached at 107 –108 rad, that decreases with increasing temperature to a negligible level at 300 C. Colloid concentration vs. irradiation-time curves follow nucleation and growth curves accurately described by C tn, or C(dose)n, relations at large irradiation times. For fourteen samples,n = 1.85± 0.18 but the values of C vary by a factor of more than 103. The constant C is related to the sample strain, the impurity and void content, dose rate, and possibly other factors. The currently available data indicate that rock salt adjacent to radioactive waste canisters, at a temperature of 150 C, will contain between 0.01 and 10 mole percent of sodium metal when the total dose reaches 1010 rad.

The heat deposition in a blanket is concentrated near the first wall. Uniform liquid-metal velocity in a self-cooled blanket is unattractive, because it leads to low mixed-mean temperature rise through the blanket and reduced power conversion efficiency. The objective of MHD flow control is to use the electromagnetic forces to produce a non-uniform velocity distribution which gives a uniform temperature distribution over the thickness of the blanket. Three methods of MHD flow control are presented here and the MHD pressure drops corresponding to the three methods are compared. One of the methods, although successful at achieving nonuniform velocity profiles, permits a large circulation of electric current which produces a high pressure drop. The analytical results do not indicate a clear choice between the other two methods. The analytical results do point to possible difference in heat transfer performance with the two methods.

Wilson Loop symmetry breaking is considered on a spacetime of the form M/sub 4/ x K, where M/sub 4/ is a four dimensional spacetime and K is an internal space with non-trivial and finite fundamental group. We show in a simple model that the different vacua obtained by breaking a non-Abelian gauge group by Wilson loops are separated in the space of gauge potentials by a finite energy barrier. An interpolating gauge configuration between these vacua has been constructed and it has been shown to have minimum energy. Finally, some implications of this construction are discussed.

The focus of the Phase 1 effort concerned further development of ZnO buffer layers. This work included further optimization of the metal-organic chemical vapor deposition (MOCVD) growth process and investigations of the interaction of zinc and oxygen with the absorber layers. Although much of the work had been done with Siemens' CIS material prior to this reporting period, a process for growing ZnO buffer layers on Siemens' CIGSS absorber had not been developed. The authors determined that a two-step procedure involving raising the substrate temperature to 250 C in nitrogen and then growing the buffer layer at 100 C works well with CIGSS material. Through collaboration with the Institute of Energy Conversion (IEC), completed cells with efficiencies in the 11% to 12% range were fabricated with the following structure: RF n-ZnO/i-ZnO/CIGSS. Cells with this structure were included as part of the Transient team studies. Cells were subjected to dark storage at 80 C, followed by a light soak at 40 C at IEC. Illuminated I-V curves taken at each stage of the study determined that these cells do not degrade under dark-storage conditions, which had been observed for Siemens cells with CdS buffer layers. To understand the reaction of zincmore » and oxygen with the absorber layers, secondary ion mass spectroscopy (SIMS) depth concentration profiles were obtained for i-ZnO/CIS structures through collaboration with Angus Rockett at the University of Illinois. SIMS profiles were obtained for ZnO films grown on polycrystalline CIS and epitaxial CIS films grown on GaAs. Comparison of the profiles strongly suggests that zinc and oxygen diffuse into the CIS along grain boundaries during the MOCVD growth process. It is also proposed that excess zinc along grain boundaries may result in the grain boundaries being n-type, which can result in enhanced loss currents. This model is consistent with the apparent requirement that cell structures with MOCVD buffer layers must undergo an aging process in air before efficient cells can be obtained. Future studies will investigate processes that allow the aging step to be eliminated.« less

The completion of the 5-MW Pilot Power Plant at the Raft River Geothermal Test Site, modification of the similar, binary cycle Prototype Power Plant, and the water treatment program that studies environmentally safe ways to inhibit corrosion and scaling in geothermal power plants and investigates corrosion resistant materials are summarized. Studies of binary geothermal cycles using mixed hydrocarbon working fluids are described as part of the continuing search for ways to produce low-cost electricity from moderate-temperature geothermal fluids. Progress is reported on studies of direct contact heat exchanger concepts, heat rejection systems, and primary heat exchangers with augmentation. As part of the now-ended series of aquaculture experiments, an unsuccessful attempt to incubate common carp embryos in geothermal waters is reported. An experiment in revegetating disturbed land at Raft River is mentioned and progress on DOE's new User Coupled Confirmation Drilling Program is described. An estimate is presented of the amount of hydrothermal energy that could be produced by the year 2000, with and without Federal assistance, for electric generation and direct applications such as industrial process heat. Progress is reported on the Marketing Assistance Program, through which technical information and assistance is provided potential users and developers of geothermal resources.more » Also reported is progress in DOE's Program Opportunity Notice (PON) Program demonstration projects and Program Research and Development Announcement (PRDA) Program study projects.« less

Photosynthetic light-harvesting proceeds by the collection and highly efficient transfer of energy through a network of pigment-protein complexes. Inter-chromophore electronic couplings and interactions between pigments and the surrounding protein determine energy levels of excitonic states and dictate the mechanism of energy flow. The excitonic structure (orientation of excitonic transition dipoles) of pigment-protein complexes is generally deduced indirectly from x-ray crystallography in combination with predictions of transition energies and couplings in the chromophore site basis. Here, we demonstrate that coarse-grained excitonic structural information in the form of projection angles between transition dipole moments can be obtained from polarization-dependent two-dimensional electronic spectroscopy of an isotropic sample, particularly when the nonrephasing or free polarization decay signal rather than the photon echo signal is considered. The method provides an experimental link between atomic and electronic structure and accesses dynamical information with femtosecond time resolution. In an investigation of the Fenna-Matthews-Olson complex from green sulfur bacteria, energy transfer connecting two particular exciton states in the protein is isolated as being the primary contributor to a cross peak in the nonrephasing 2D spectrum at 400 fs under a specific sequence of polarized excitation pulses. The results suggest the possibility of designing experiments using combinations of tailored polarization sequencesto separate and monitor individual relaxation pathways.

[1] The coupling of a super-Alfvenic plasma expansion in a magnetized background plasma is examined. Such coupling plays an important role in several high-energy, quasi-neutral, plasma configurations; the focus here is on High Altitude Nuclear Explosions (HANEs). Fully 3-D Kinetic Ion Simulation Modeling (KISM) reveals, for some initial conditions, strong coupling of the debris to the magnetized background ionosphere even though all collision processes between the ions have been neglected. The interaction dynamics are found to be altered dramatically for small changes in initial conditions. A slight increase in the ion charge density of the background plasma allows the debris ions to decouple and slip through the magnetized background. These decoupled ions in the expanding plasma then follow trajectories typical of single particle motion. The salient features of this process, guided by 1-D simulations, lead to two thresholds for the onset of decoupling. The first threshold depends on the ratio of the charge density of the expanding plasma to that of the background plasma. The second threshold is evident when the expanding plasma has a finite pulse length comparable to the gyroradius of the energized background ions.