[en] Cubic boron nitride (CBN) crystals of graded particle size are chemically cleaned and disposed in a protective metal cup together with a mass of substrate source material and a concentration of metal for providing an alloy for infusing and wetting the walls of capillary-size voids. The CBN content is increased in density to greater than 70 percent by volume, and placed within a semi-isostatic system of finely divided powder. Pressure in the range of from about 20,000 to about 100,000 psi is applied semi-isostatically to the system and thereby to the metal cup and its contents. Heat and pressure are then simultaneously applied to the semi-isostatic system. Liquefied infusing and wetting alloy enters the interstices between the CBN crystals to bond them together. The entire system is cooled and the strong composite body of metal-bonded CBN directly bonded to a substrate is recovered therefrom

[en] A series of polycrystalline samples of high transition temperature superconductors were studied by pulsed nuclear magnetic resonance methods. From Cu⁶³ NMR on La_1.83Sr_0.17CuO₄, the Korringa constant 14±1Ks and a minimum gap energy 2Δ(O)/k_B T_c = 1.3 ± 0.2 are found. A comparison of these results with the larger gap reported from other experiments indicates that there is substantial anisotropy in the pairing interaction. Fluorinated superconductors with nominal compositions, La_1.8Sr_0.2Cu(O_0.95F_0.05)₄ and YBa₂Cu₃O_xF(x∼6), were prepared by solid state reaction techniques. F¹⁹ NMR and Cu^63,65 NQR spectra were obtained. In both materials Korringa behavior of the F¹⁹ spin-lattice relaxation was observed in the normal state indicating that fluorine is in a weak metallic environment. NMR results on YBaCuOF sample show that 85% of the expected amount of fluorine is incorporated in a single metallic phase which becomes superconducting at 92K. Analysis of neutron scattering implies that fluorine must substitute for oxygen. Combined with the NMR results this suggests that the most likely possibility is that fluorine resides on an apecal oxygen site. Significant frequency shifts of the Tl^205,203 NMR were observed in the superconducting state of Tl₂Ba₂Ca₂Cu₃O_10+δ. Measurements at two different magnetic fields indicate that the origin of these shifts is mainly due to the field distribution associated with vortices in the mixed state. The NMR linewidth is dominated by field inhomogeneity of the vortex lattice in the mixed state from which the temperature dependence of the penetration depth has been deduced

[en] Our experience with model-based accelerator control started at SPEAR. Since that time nearly all accelerator beamlines have been controlled using model-based application programs, for example, PEP and SLC at SLAC. In order to take advantage of state-of-the-art hardware and software technology, the design and implementation of the accelerator control programs have undergone radical changes with time. Consequently, SPEAR, PEP and SLC all use different control programs. Since many of these application programs are embedded deep into the control system, they had to be rewritten each time. Each time this rewriting has occurred a great deal of time and effort has been spent on training physicists and programmers to do the job. Now, we have developed an integrated system called GOLD (Genetic Orbit and Lattice Debugger) for debugging and correcting trajectory errors in accelerator lattices. The system consists of a lattice modeling program (COMFORT), a beam simulator (PLUS), a graphical workstation environment (micro-VAX) and an expert system (ABLE). This paper will describe some of the features and applications of our integrated system with emphasis on the automation offered by expert systems. 5 refs

[en] The computer code COMFORT, developed for the online control of machine functions at the SLC, has recently undergone several modifications to overcome some of its limitations. This note describes the reasons for these changes, the methods employed, some test results and the applications of the new version of the program

[en] The PEP RF system will be required to operate over a wide range of conditions, often with much heavier beam loading than in SPEAR. Since coupling loops are not readily changeable, it may be necessary to introduce other elements, such as an E-H tuner, into the system to provide flexibility for matching the klystron load requirements and simultaneously suppressing the Robinson instability. In this paper the steady state circuit relations are presented and a criterion for the Robinson instability is derived in a form which defines regions of stability in the parameter space. 2 figs

[en] Our experience with model based accelerator control started at SPEAR. Since that time nearly all accelerator beam lines have been controlled using model-based application programs, for example, PEP and SLC at SLAC. In order to take advantage of state-of-the-art hardware and software technology, the design and implementation of the accelerator control programs have undergone radical change with time. Consequently, SPEAR, PEP, and SLC all use different control programs. Since many of these application programs are imbedded deep into the control system, they had to be rewritten each time. Each time this rewriting has occurred a great deal of time and effort has been spent on training physicists and programmers to do the job. Now, we have developed these application programs for a fourth time. This time, however, the programs we are developing are generic so that we will not have to do it again. We have developed an integrated system called GOLD (Generic Orbit and Lattice Debugger) for debugging and correcting trajectory errors in accelerator lattices. The system consists of a lattice modeling program (COMFORT), a beam simulator (PLUS), a graphical workstation environment (micro-VAX) and an expert system (ABLE). This paper will describe some of the features and applications of our integrated system with emphasis on the automation offered by expert systems. 5 refs

[en] Commissioning particle beam line is usually a very time-consuming and labor-intensive task for accelerator physicists. To aid in commissioning, we developed a model-based expert system that identifies error-free regions, as well as localizing beam line errors. This paper will give examples of the use of our system for the SLC commissioning. 8 refs., 5 figs

[en] In the highly unlikely event of a loss of cooling accident in a LWR followed by failure of certain engineered safety features of the reactor system, the core may eventually melt due to the generation of decay heat. If the safety features of the reactor system fail to arrest the accident within the vessel, the molten core debris (corium) will fall into the reactor cavity and attack the concrete walls and floor. The heat transferred from the core melt to concrete can lead to concrete decomposition accompanied by gas generation, which along with direct heating of the atmosphere will lead to a pressure rise in the containment. The cooling rate of the core melt and the amount of gas generated by concrete decomposition will also affect the degree to which fission products may be released from the melt. A semiempirical correlation for calculating the downward heat transfer coefficient is derived based on periodic contact between the liquid pool and the underlying solid. The experimental data on interfacial heat transfer between bubble agitated immiscible layers are reviewed and a new model is proposed. The proposed downward and interfacial heat transfer models have been incorporated into an integral analysis code, CORCON/Mod1, developed by Sandia Laboratories. A simplified containment model based on thermal equilibrium among all materials within the containment is developed, and is integrated with the modified CORCON/Mod1. The combined model, called CORCELL, is used to study the impact of Corium/Concrete Interaction on containment pressurization

[en] A mass of diamond crystals in contact with a mass of eutectiferous silicon-rich alloy and a silicon nitride ceramic substrate are disposed in a container and placed within a pressure transmitting powder medium. Pressure is applied to the powder medium resulting in substantially isostatic pressure being applied to the container and its contents sufficient to dimensionally stabilize the container and its contents. The resulting shaped substantially isostatic system of powderenveloped container is hot-pressed whereby fluid eutectiferous silicon-rich alloy is produced and infiltrated through the interstices between the diamond crystals and contacts the contacting face of the silicon nitride substrate sufficiently producing, upon cooling, an adherently bonded integral composite

[en] In a postulated severe light water reactor (LWR) accident, the interaction of corium with the concrete reactor cavity is an important part of the accident analysis. The immiscible metallic and oxidic phases will be separated into two layers due to the large density difference. The interfacial heat transfer between these immiscible layers is important in characterizing the corium/concrete interaction. In this paper, the data on the surface renewal mechanism for heat transfer between bubble agitated immiscible liquid layers is reviewed. A modified version of Szekely's correlation is proposed. The predictions of the new correlation compare favorably with the experimental data of water/mercury and oil/wood's metal. A simple model based on the hydrodynamic stability of a liquid jet is proposed to model the conditions for bubble induced entrainment. The proposed model can predict the published experimental observation of entrainment in an oil/water system and not in a water/mercury system. By applying the model to corium/concrete interaction, it is concluded that the bubble induced entrainment would not occur in corium/concrete interaction