Library

Notes: The evolution of surface morphologies of films prepared by ion-based deposition techniques has been investigated by atomic force microscopy. Two deposition processes, filtered arc deposition (FAD) and ion-beam-assisted deposition, where low-energy (〈100 eV) ion irradiation and high-energy (several tens of keV) ion-beam bombardment concurrent with film growth were involved, respectively, have been employed to prepare TiN and Al films. Comparative studies on the effect of energetic ions on the development of topography have been performed between the low-ion-energy regime and high-ion-energy regime. In addition, the relationship between topography and mechanical properties of thin films has been revealed, by involving thin films prepared by thermal evaporation deposition (TED), where almost all depositing particles are neutral. In the images of the TED TiN and Al films, a large number of porous and deep boundaries between columnar grains was observed, suggesting a very rough and loose surface. In contrast, the FAD films exhibited much denser surface morphologies, although still columnar. The root-mean-square roughness of the FAD films was less than 1 A(ring). Hardness test and optical parameter measurement indicated that the FAD films were much harder and, in the case of optical films, much more transparent than the TED films, which was considered to arise from the denser surface morphologies rather than crystallization of the films. The high density and super smoothness of the FAD films, and the resultant mechanical and optical properties superior to those of the TED films, were attributed to the enhancement of surface migration of the deposited adatoms in the FAD process, which could provide intensive low-energy ion irradiation during film growth. As for topography modification by high-energy ion-beam bombardment concurrent with film growth, in addition to the increase of surface diffusion due to elastic collision and thermal spikes, physical sputtering must be considered while explaining the development of the film topography. Both surface migration enhancement and sputtering played important roles in the case of high-energy heavy-ion-beam bombardment, under which condition surface morphology characterized by dense columns with larger dimension and deep clean boundaries was formed. However, under high-energy light-ion-beam bombardment, the sputtering was dominant, and the variation of sputtering coefficient with position on the surface of growing film led to the formation of cones. © 1996 American Institute of Physics.

Notes: . This paper uses new estimates of metropolitan factor demand and output supply functions to study how federal, state, and local fiscal policies affect metropolitan economies. We illustrate our work with findings for ten metropolitan areas in five states for changes in state corporate income taxes, local property taxes, the federal corporate income tax, an investment tax credit, interest rates, public capital stocks, output prices, and tax and regulatory policies affecting gross wages. It is clear from these simulations that a policy that is nominally the same everywhere will have repercussions that vary widely across regions and cities.

Notes: . In this study we use a translog profit function and iterate seemingly unrelated regressions to estimate a system of factor demand and output supply functions for metropolitan economies. Our sample includes all metropolitan areas defined by the Census in 1977 for the period 1962 to 1982. Estimation shows that all price elasticities are elastic and that the signs are as expected. These results hold true for virtually all model specifications. Our findings indicate that federal, state, and local tax policies have significant impacts on factor demand and output supply. Public investment plays a positive and significant, but small, role in increasing output and in complementing other factors, although this influence has declined over time. Additionally, capital provided by the private sector has a substantially larger impact on output and employment than does capital provided by the public sector.

Notes: High yields of highly charged ions are produced with electron beam ion sources (EBISs) operated in a batch or pulsed mode, yielding small duty cycles. An EBIS operated in a continuous, dc, or leaky mode can produce continuous, "dc'' ion beams, although with substantially lower yields especially for the higher charge states. This article introduces the leaky batch mode and the dc batch mode of operation which combine the high duty cycles obtained with leaky or dc modes with the high yields of highly charged ions obtained with batch modes. The leaky batch mode produces ion beams with duty cycles as high as 90% with ion yields as high as 70% of the most efficient batch mode. The dc batch mode delivers constant intensity (dc) ion beams during 50% of the time with ion yields as high as 98% of the most efficient batch mode. When the dc batch mode is combined with the stretcher mode proposed by Becker, the dc batch mode will allow for dc ion beams of constant intensity with yields close to the most efficient batch mode. © 1996 American Institute of Physics.

Notes: Time-resolved electron-beam diagnostics have been developed for use with free-electron lasers (FELs) and associated electron sources, based on the techniques of secondary electron emission and optical transition radiation (OTR). The 32-channel OTR detector forms part of a high-resolution (0.18%) electron spectrometer with a time resolution of 50 ns. Variable-magnification optics allow the spectrometer to view single-macropulse spectra with widths in the range of 0.2%–7%; wider spectra are taken with several momentum settings. Design criteria for the spectrometer are presented, and experience of operating with the diagnostics over a range of FEL physics experiments is summarized. The spectrometer is used, in conjunction with optical diagnostics, in studies at FELIX of efficiency enhancement, pulse chirping, and stepped-undulator operation. © 1996 American Institute of Physics.

Notes: An automated system for determinations of transport current–voltage (I–V) characteristics as a function of temperature (25–125 K), magnetic field (0–1.6 T), and magnetic field orientation (−125 to +145°) is described. Currents of up to 100 A are applied either as a continuous ramp or as pulses of 2–100 ms duration. A closed-cycle helium refrigerator provides a rapid (∼45 min), convenient, cost effective, cooldown from 300 to 25 K. Control of current, temperature, magnetic field, and field orientation is fully automated and requires no user interaction. The characterization of performance of a ceramic superconductor typically involves several temperatures, fields, and orientations and requires 8–30 h to complete. © 1996 American Institute of Physics.

Notes: A breaking of the up–down symmetry due to the inductive electric field Eφ is analyzed in detail for particles describing quasibanana orbits in the large aspect ratio approximation. Time-independent and time-dependent electric fields are considered. In the first case it is proved that the classical ∇B drift and the breaking of up–down symmetry due to Eφ lead to a net inward radial drift, which agrees with the well-known Ware pinch formula. The weak points of previous treatments of the Ware pinch, e.g. taking only leading terms in the Taylor expansion of Aφ, are discussed. Yet the results obtained here lead to the same pinch formula, even for banana orbits with a large amplitude of poloidal angle and for more general conditions than previously considered. A more general formula for a time-dependent Eφ has also been found. Our results show from a very general basis that the corresponding polarization type of drift does not play any role in the inward pinch; however, the second time derivative of the inductive electric field Eφ could significantly increase or decrease the usual Ware pinch. © 1996 American Institute of Physics.

Notes: A method to obtain long lengths of flexible, biaxially oriented substrates with smooth, chemically compatible surfaces for epitaxial growth of high-temperature superconductors is reported. The technique uses well established, industrially scalable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers (metal and/or ceramic) to yield chemically compatible surfaces. Epitaxial YBa2Cu3Ox films grown on such substrates have critical current densities exceeding 105 A/cm2 at 77 K in zero field and have field dependencies similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for the fabrication of long lengths of high-Jc wire capable of carrying high currents in high magnetic fields and at elevated temperatures. © 1996 American Institute of Physics.

Notes: The refractive index n, extinction coefficient k, and optical band gap Eopt of nitrogen incorporated amorphous carbon films α-C:N have been investigated by spectroscopic ellipsometry. The effect of the incorporated nitrogen on the bonding configuration of carbon atoms has been discussed in term of the optical behavior of the films. The results show that nitrogen incorporation into the films stabilizes the tetrahedral bonds of carbon atoms, resulting in lower values of both n and k. However, if the nitrogen incorporation is accomplished by means of excessive N+ ion bombardment, the formed α-C:N films possess zero gap and are more "graphitelike.'' © 1996 American Institute of Physics.

Notes: The responses to salt stress in NFT (nutrient film) hydroponics of ‘Chinese Spring’ wheat and a number of its aneuploids involving the chromosomes of homoeologous group 5 were studied. This showed that the absence of chromosome 5D allowed plants to survive better than in the euploid condition. Much of this response could be related to the effects of Vrn3, which conditions the spring habit of ‘Chinese Spring’. The ability to survive relatively high levels of stress was promoted by the group 5 homoeologue from Thinopyrum bessarabicum.