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[en] High quality, refractory metal, oxide coatings are required in a variety of applications such as laser optics, micro-electronic insulating layers, nano-device structures, electro-optic multilayers, sensors and corrosion barriers. A common oxide deposition technique is reactive sputtering because the kinetic mechanism vaporizes almost any solid material in vacuum. Also, the sputtered molecules have higher energies than those generated from thermal evaporation, and so the condensates are smoother and denser than those from thermally-evaporated films. In the typical sputtering system, target erosion is a factor that drives machine availability. In some situations such as nano-layered capacitors, where the device's performance characteristics depends on thick layers, target life becomes a limiting factor on the maximizing device functionality. The keen interest to increase target utilization in sputtering has been addressed in a variety of ways such as target geometry, rotating magnets, and/or shaped magnet arrays. Also, a recent sputtering system has been developed that generates a high density plasma, directs the plasma beam towards the target in a uniform fashion, and erodes the target in a uniform fashion. The purpose of this paper is to characterize and compare niobia films deposited by two types of high target utilization sputtering sources, a rotating magnetron and a high density plasma source. The oxide of interest in this study is niobia because of its high refractive index. The quality of the niobia films were characterized spectroscopically in optical transmission, ellipsometrically, and chemical stoichiometry with X-ray photo-electron spectroscopy. The refractive index, extinction coefficients, Cauchy constants were derived from the ellipsometric modeling. The mechanical properties of coating density and stress are also determined
[en] Typical users of the International Criticality Safety Evaluation Project (ICSBEP) Handbook have specific criteria to which they desire to find matching experiments. Depending on the application, those criteria may consist of any combination of physical or chemical characteristics and/or various neutronic parameters. The ICSBEP Handbook contains a structured format helping the user narrow the search for experiments of interest. However, with nearly 4300 different experimental configurations and the ever increasing addition of experimental data, the necessity to perform multiple criteria searches have rendered these features insufficient. As a result, a relational database was created with information extracted from the ICSBEP Handbook. A users interface was designed by OECD and DOE to allow the interrogation of this database. The database and the corresponding users interface are referred to as DICE. DICE currently offers the capability to perform multiple criteria searches that go beyond simple fuel, physical form and spectra and includes expanded general information, fuel form, moderator/coolant, neutron-absorbing material, cladding, reflector, separator, geometry, benchmark results, spectra, and neutron balance parameters. DICE also includes the capability to display graphical representations of neutron spectra, detailed neutron balance, sensitivity coefficients for capture, fission, elastic scattering, inelastic scattering, nu-bar and mu-bar, as well as several other features.
[en] Against the background of the European Union's Gas Directive, and the emergence of new players and markets in Europe's gas sector, this paper explores how company actions could shape the future for the gas industry. Starting with an examination of company strategies this paper develops three scenarios for the future: a 'Gradual Transformation' scenario where a single European gas market develops that is essentially oligopolistic in nature; a 'Vertical Integration' scenario, where upstream and downstream gas companies merge to form a vertically integrated gas supplier; and a 'Pull the Plug' scenario, where the current market structure decomposes into a competitive market. These scenarios are examined in terms of their impact on gas prices, demand and the distribution of gas rent along the supply chain. The paper highlights the fact that the EU's gas Directive is not sufficient for the introduction of competition into Europe's gas markets, but that company actions will be the key determinant, and they may favour alternative market structures. (Author)
[en] The 40Ca(13C, 14N)39K reaction at 60 and 68 MeV has been investigated in the no-recoil approximation to the DWBA. Reorientation effects arising from the quadrupole moments of 14N and 39K were found to be small. The use of spin-orbit components in the optical potentials was found to shift the phase of the angular distribution into agreement with experiment, while maintaining a fit to be elastic data. This was understood from a generalization of the Strutinsky model. For the 40Ca(13C, 12C)41Ca reaction at 60 and 68 MeV a smaller shift in phase was obtained which was desirable, but the damping of the magnitude of the oscillations was disturbing. (Auth.)
[en] The 2 x 2 array HEU-Re experiment was performed on the Planet universal critical assembly machine on November 4th, 2003 at the Los Alamos Critical Experiments Facility (LACEF) at Los Alamos National Laboratory (LANL). For this experiment, there were 10 1/2 units, each full unit containing four HEU foils and two rhenium foils. The top unit contained only two HEU foils and two rhenium foils. A total of 42 HEU foils were used for this experiment. Rhenium is a desirable cladding material for space nuclear power applications. This experiment consisted of HEU foils interleaved with rhenium foils and is moderated and reflected by polyethylene plates. A unit consisted of a polyethylene plate, which has a recess for rhenium foils, and four HEU foils in a single layer in the top recess of each polyethylene plate. The Planet universal criticality assembly machine has been previously used in experiments containing HEU foils interspersed with SiO2 (HEU-MET-THERM-001), Al (HEU-MET-THERM-008), MgO (HEU-MET-THERM-009), Gd foils (HEU-MET-THERM-010), 2 x 2 x 26 Al (HEU-MET-THERM-012), Fe (HEU-MET-THERM-013 and HEU-MET-THERM-015), 2 x 2 x 23 SiO2 (HEU-MET-THERM-014), 2 x 2 x 11 hastalloy plates (HEU-MET-THERM-016), and concrete (HEU-MET-THERM-018). The 2 x 2 array of HEU-Re is considered acceptable for use as a benchmark critical experiment.
[en] The systematic energy dependence of recently published surface- transparent potentials is shown to be affected very little by the coupling to the first excited 2+ state in 28Si, although the elastic scattering cross sections depend quite strongly on the coupling
[en] Purpose: Complex intensity modulated arc therapy tends to spread low dose to normal tissue(NT)regions to obtain improved target conformity and homogeneity and OAR sparing.This work evaluates the trade-offs between PTV homogeneity and reduction of the maximum dose(Dmax)spread to NT while planning of IMRT,VMAT and Tomotherapy. Methods: Ten prostate patients,previously planned with step-and-shoot IMRT,were selected.To fairly evaluate how PTV homogeneity was affected by NT Dmax constraints,original IMRT DVH objectives for PTV and OARs(femoral heads,and rectal and bladder wall)applied to 2 VMAT plans in Pinnacle(V9.0), and Tomotherapy(V4.2).The only constraint difference was the NT which was defined as body contours excluding targets,OARs and dose rings.NT Dmax constraint for 1st VMAT was set to the prescription dose(Dp).For 2nd VMAT(VMAT-NT)and Tomotherapy,it was set to the Dmax achieved in IMRT(~70-80% of Dp).All NT constraints were set to the lowest priority.Three common homogeneity indices(HI),RTOG-HI=Dmax/Dp,moderated-HI=D95%/D5% and complex-HI=(D2%-D98%)/Dp*100 were calculated. Results: All modalities with similar dosimetric endpoints for PTV and OARs.The complex-HI shows the most variability of indices,with average values of 5.9,4.9,9.3 and 6.1 for IMRT,VMAT,VMAT-NT and Tomotherapy,respectively.VMAT provided the best PTV homogeneity without compromising any OAR/NT sparing.Both VMAT-NT and Tomotherapy,planned with more restrictive NT constraints,showed reduced homogeneity,with VMAT-NT showing the worst homogeneity(P<0.0001)for all HI.Tomotherapy gave the lowest NT Dmax,with slightly decreased homogeneity compared to VMAT. Finally, there was no significant difference in NT Dmax or Dmean between VMAT and VMAT-NT. Conclusion: PTV HI is highly dependent on permitted NT constraints. Results demonstrated that VMAT-NT with more restrictive NT constraints does not reduce Dmax NT,but significantly receives higher Dmax and worse target homogeneity.Therefore, it is critical that planners do not use too restrictive NT constraints during VMAT optimization.Tomotherapy plan was not as sensitive to NT constraints,however,care shall be taken to ensure NT is not pushed too hard.These results are relevant for clinical practice.The biological effect of higher Dmax and increased target heterogeneity needs further study