Further improvements on TRACE 3-D

TRACE 3-D, an interactive beam-dynamics program that calculates the envelopes of a bunched beam (including linear space-charge forces) through a user-defined transport system, has undergone several upgrades in physics, coding, and capabilities. Recent modifications include centroid tracking (and misalignment capabilities) and an improved beam description that allows study of some nonlinear effects such as wakefields. The Fortran code has been made portable and runs on numerous platforms. It can be used with a variety of graphics packages. The additional beamline elements, new commands, expanded fitting capabilities, improved beam description, and coding modifications have extended TRACE 3-D`s usefulness and applicability to the accelerator community. These changes are documented in the third edition of TRACE 3-D Documentation

Securing tropical forest carbon: the contribution of protected areas to REDD

Forest loss and degradation in the tropics contribute 6-17% of all greenhouse gas emissions. Protected areas cover 217.2 million ha (19.6%) of the world's humid tropical forests and contain c. 70.3 petagrams of carbon (Pg C) in biomass and soil to 1 m depth. Between 2000 and 2005, we estimate that 1.75 million ha of forest were lost from protected areas in humid tropical forests, causing the emission of 0.25-0.33 Pg C. Protected areas lost about half as much carbon as the same area of unprotected forest. We estimate that the reduction of these carbon emissions from ongoing deforestation in protected sites in humid tropical forests could be valued at USD 6,200-7,400 million depending on the land use after clearance. This is >1.5 times the estimated spending on protected area management in these regions. Improving management of protected areas to retain forest cover better may be an important, although certainly not sufficient, component of an overall strategy for reducing emissions from deforestation and forest degradation (REDD

High energy beam transport beamline for LEDA

Here the authors describe the High Energy Beam Transport (HEBT) for the Low Energy Demonstration Accelerator (LEDA), which is part of the Accelerator Production of Tritium (APT) project. The authors used the TRACE 3-D linear design code for the first-order design and performed r-z and 3-D particle-in-cell (PIC) simulations to study the beam distribution and halo. TRACE 3-D predicts rms beam properties well. The PIC simulations are important for determining the presence of beam halo, which is present for some tunes. They propose halo experiments to help validate the simulation codes for modeling nonlinear space charge

Plasmon oscillations in ellipsoid nanoparticles: beyond dipole approximation

The plasmon oscillations of a metallic triaxial ellipsoid nanoparticle have been studied within the framework of the quasistatic approximation. A general method has been proposed for finding the analytical expressions describing the potential and frequencies of the plasmon oscillations of an arbitrary multipolarity order. The analytical expressions have been derived for an electric potential and plasmon oscillation frequencies of the first 24 modes. Other higher orders plasmon modes are investigated numerically.Comment: 33 pages, 12 figure

High-temperature phase stability of hafnium aluminate films for alternative gate dielectrics

Hafnium aluminate films with different compositions were deposited at room temperature by jet vapor deposition. The as-deposited films were amorphous. After annealing at 1100 degreesC, the microstructure of the films was analyzed by high-resolution transmission electron microscopy, electron diffraction and electron energy loss spectroscopy (EELS). The crystalline phase in pure HfO2 films was monoclinic. With an increase in the Al content in the films, the amount of metastable HfO2 with a tetragonal distorted fluorite structure increased. In addition, the grain sizes decreased, making the detection of crystallization by x-ray diffraction difficult. No crystalline Al2O3 phase could be unambiguously detected in electron diffraction patterns in films with up to 30 mol % Al2O3. However, an Al-rich intergranular phase was identified by EELS. Films with similar to64 mol % Al2O3 crystallized as tetragonal HfO2 and metastable cubic Al2O3 with the spinel structure. The complex microstructures of the films should be considered in the interpretation of their dielectric and electrical properties after high temperature anneals. (C) 2004 American Institute of Physics