bluuebunny/crossref_metadata_2025 huggingface dataset:
Objective or Subjective ‘Ought’?
Authors: HANSSON SVEN OVE
Published: February 2010

The prescriptive ‘ought’ has both an objective and a subjective interpretation. In the objective sense, what one ought to do depends on what is actually true. In the subjective sense it depends on what one believes to be true. Ordinary usage seems to vacillate between these two interpretations. An example (the indecisive terrorist) is used to show that a subjective ought statement can have a determinate truth-value in situations where the corresponding objective ought statement has no truth-value, not even an unknowable one. Therefore the subjective ought is not definable in terms of the objective ought. However, definability in the other direction is not excluded by this argument.
A Critique of Sumner's Account of Welfare
Authors: TUPA ANTON
Published: February 2010

Wayne Sumner, in the first six chapters of his excellent book Welfare, Happiness and Ethics, argues for what he calls an authentic life satisfaction theory of welfare. Somewhat generally, Sumner's theory of welfare is a sophisticated subjective account that treats one's happiness of a certain sort, and in the right conditions, as enhancing one's welfare. In this essay, I critically explore Sumner's account of welfare. I argue that Sumner's arguments for his own account of welfare, when followed to their logical conclusion, support a position which is slightly, but significantly, different from his own position. Additionally, I argue that Sumner's account of welfare has several counter-intuitive implications. I conclude that his account is seriously flawed.
J. S. Mill's Conception of Utility
Authors: SAUNDERS BEN
Published: February 2010

Mill's most famous departure from Bentham is his distinction between higher and lower pleasures. This article argues that quality and quantity are independent and irreducible properties of pleasures that may be traded off against each other – as in the case of quality and quantity of wine. I argue that Mill is not committed to thinking that there are two distinct kinds of pleasure, or that ‘higher pleasures’ lexically dominate lower ones, and that the distinction is compatible with hedonism. I show how this interpretation not only makes sense of Mill but allows him to respond to famous problems, such as Crisp's Haydn and the oyster and Nozick's experience machine.
Some Further Thoughts on Sidgwick's Epistemology
Authors: DEIGH JOHN
Published: February 2010

This article is a reply to Anthony Skelton's ‘On Sidgwick's Demise: A Reply to Professor Deigh’. Professor Skelton, in his article, makes several objections to the account of Sidgwick's epistemology I presented in my earlier article ‘Sidgwick's Epistemology’. I answer these objections by further explaining my account.
Tracing a morphosyntactic change in Quebec French: the non-standard conditional in si-clauses
Authors: LEBLANC CARMEN L.
Published: February 2010

We follow the trajectory of a change in progress in Québec French. The study is based on interviews with speakers born between 1895 and 1965. The results show an increase in conditional morphology in thesi-clauses of hypothetical complexes. After WWII, the conditional becomes the quantitative norm. The analysis of a number of demographic and socio-economic factors reveals that the usage likely originated in the working class male group. Today, use of the conditional is generalised in the community and it is the preferred form for the younger speakers; only the most educated hold on to the old rule.
Impact of farmers' practices and seed systems on the genetic structure of common sorghum varieties in Kenya and Sudan
Authors: Rabbi Ismail Y. , Geiger Hartwig H. , Haussmann Bettina I. G. , Kiambi Dan , Folkertsma Rolf , Parzies Heiko K.
Published: February 2010

To understand the effect of different farming systems on the dynamics of diversity of sorghum (Sorghum bicolor(L.) Moench) crop, genetic structure of widely used landraces and modern varieties collected from two contrasting agroecosystems, in eastern Sudan and western Kenya, were analysed with 16 polymorphic microsatellite markers. A total of 1104 accessions, grouped into 46 samples from individual farmers, were genotyped. Cluster analysis of the samples from the two countries displayed contrasting patterns. Most strikingly, differently named landraces from western Kenya formed widely overlapping clusters, indicating weak genetic differentiation, while those from eastern Sudan formed clearly distinguishable groups. Similarly, samples of the modern variety from Sudan displayed high homogeneity, whereas the most common modern variety from western Kenya was very heterogeneous. The high degree of fragmentation of farmlands of western Kenya, coupled with planting of different sorghum varieties in the same fields, increases the likelihood of inter-variety gene flow. This may explain the low genetic differentiation between the differently named landraces and heterogeneity of the modern variety from western Kenya. This study highlights the important role of farmers in shaping the genetic variation of their crops and provides population parameter estimates allowing forecasting of the fate of ‘modern’ germplasm (conventional or genetically modified) when introduced into subsistence farming systems.
Maximizing the accuracy of image‐based surface sediment sampling techniques
Authors: Graham David J. , Rollet Anne‐Julia , Piégay Hervé , Rice Stephen P.
Published: February 2010

Recent years have seen increased interest in automated methods, utilizing photographs collected with a handheld digital camera, for determining the grain size distribution of coarse river sediments. Such methods are as precise as traditional field methods and have considerable time and cost advantages. Nevertheless, several unresolved issues pertaining to their deployment remain to be addressed. Using data sets collected from seven gravel bed rivers, this paper examines four key issues: (1) the minimum area required to obtain a representative sample, (2) the effect of lower‐end truncation on grain size percentiles, (3) the effect of river bed structure such as imbrication and hiding, and (4) the potential benefits of using individual particle measurements rather than the number (or mass) of particles per size class to calculate percentiles. It is demonstrated that sampling areas of between 50 and 200 times that of the largest grain are adequate to achieve percentile errors of <10% (in mm). The appropriateness of lower‐end truncation depends on the study aims and sediment properties. It has a limited effect on higher percentiles, except where sand is a major constituent. Understanding the influence of bed structure on image‐derived size information is complicated by the absence of error‐free benchmarks against which accuracy may be evaluated, but it is likely that other errors are more important. The use of individual particle measurements to calculate percentiles in preference to classified data is shown to have a small, but appreciable, effect on precision. These results will assist practitioners in making appropriate operational decisions to maximize data quality using image‐based grain size data capture.
Temperature variation through 2000 years in China: An uncertainty analysis of reconstruction and regional difference
Authors: Ge Q.‐S. , Zheng J.‐Y. , Hao Z.‐X. , Shao X.‐M. , Wang Wei‐Chyung , Luterbacher Juerg
Published: February 2010

Twenty‐three published proxy temperature series over China spanning the last 2000 years were selected for an uncertainty analysis in five climate regions. Results indicated that, although large uncertainties are found for the period prior to the 16th century, high level of consistency were identified in all regions during the recent 500‐years, highlighted by the two cold periods 1620s–1710s and 1800s–1860s, and the warming during the 20th century. The latter started in Tibet, Northwest and Northeast, and migrated to Central East and Southeast. The analysis also indicates that the warming during the 10–14th centuries in some regions might be comparable in magnitude to the warming of the last few decades of the 20th century which was unprecedented within the past 500 years.
Ocean chemistry and atmospheric CO2sensitivity to carbon perturbations throughout the Cenozoic
Authors: Stuecker Malte F. , Zeebe Richard E.
Published: February 2010

We assess the response of atmospheric CO2(pCO2) and ocean chemistry to carbon perturbations, placing modern carbon‐cycle sensitivity in the context of the Cenozoic. We use the carbon‐cycle model LOSCAR to study the effect of perturbations over the past 67 Ma. Our results indicate that atmospheric CO2and surface ocean pH were slightly more sensitive to carbon perturbations during the Miocene (∼15 Ma ago) compared to modern conditions and less sensitive during the earlier part of the Cenozoic. We find that the sensitivity to carbon input at the Paleocene‐Eocene boundary (∼56 Ma ago) was most likely lower compared to modern conditions. Further, we show that the Cenozoic evolution of steady statepCO2and seawater Mg/Ca ratios is critical for the system's sensitivity to a carbon release.
First basin‐wide experimental results on N2 fixation in the open Mediterranean Sea
Authors: Ibello Valeria , Cantoni Carolina , Cozzi Stefano , Civitarese Giuseppe
Published: February 2010

The Mediterranean Sea presents several biogeochemical anomalies compared to the global ocean. An unbalanced N budget, high nitrate/phosphate ratios in subsurface waters and low 15N/14N ratios in particulate and dissolved nitrogen suggest a significant occurrence of N2 fixation. This study presents, for the first time, a basin‐wide overview of direct measurements of N2 fixation, with values in the North Atlantic for comparison, during late spring 2007. Very low N2 fixation rates (0.052 ± 0.031 nmols N l−1d−1) were observed in all sub‐regions of the Mediterranean, in contrast to the higher values measured in the North Atlantic (0.300 ± 0.115 nmols N l−1d−1). Higher phosphorus (inorganic or organic) concentrations were not associated with higher N2 fixation rates. Low 15N/14N ratios in particulate organic nitrogen (from −2.10 to +4.11‰), associated with low N2 fixation rates, suggest that other N sources, such as atmospheric inputs, fuel the Mediterranean ecosystem.
Large sea ice outflow into the Nares Strait in 2007
Authors: Kwok R. , Toudal Pedersen L. , Gudmandsen P. , Pang S. S.
Published: February 2010

Sea ice flux through the Nares Strait is most active during the fall and early winter, ceases in mid‐ to late‐winter after the formation of ice arches along the strait, and re‐commences after breakup in summer. In 2007, ice arches failed to form. This resulted in the highest outflow of Arctic sea ice in the 13‐year record between 1997 and 2009. The 2007 area and volume outflows of 87 × 103 km2 and 254 km3 are more than twice their 13‐year means. This contributes to the recent loss of the thick, multiyear Arctic sea ice and represents ∼10% of our estimates of the mean ice export at Fram Strait. Clearly, the ice arches control Arctic sea ice outflow. The duration of unobstructed flow explains more than 84% of the variance in the annual area flux. In our record, seasonal stoppages are always associated with the formation of an arch near the same location in the southern Kane Basin. Additionally, close to half the time another ice arch forms just north of Robeson Channel prior to the formation of the Kane Basin arch. Here, we examine the ice export with satellite‐derived thickness data and the timing of the formation of these ice arches.
Seismic cycle stress change in western Taiwan over the last 270 years
Authors: Mouyen M. , Cattin R. , Masson F.
Published: February 2010

The island of Taiwan is affected by intense seismic activity, which includes large events as the disastrous 1999 Chi‐Chi earthquake. To improve seismic hazard assessment in this area, we estimate the effect of both interseismic loading and major events since 1736 on the state of stress of major active faults. We focus our approach on western Taiwan, which is the most densely populated part of Taiwan. We pay a specific attention to faults geometry and to both interseismic and coseismic slip distributions. Our results suggest that both earthquakes and interseismic loading before 1999 increase the Coulomb stress in the north‐western part of the Chelungpu fault, a region which experienced the highest coseismic slip during the Chi‐Chi earthquake. More importantly our results reveal a Coulomb stress increase in the southern part of the Changhua thrust fault, below a densely populated area.
Anisotropic transport rates in heterogeneous porous media
Authors: Engdahl Nicholas B. , Weissmann Gary S.
Published: February 2010

We applied a recently developed method of aquifer characterization, which combines geophysics and geostatistics to create several heterogeneous realizations of a shallow fluvial aquifer that contain representations of sedimentary bounding surfaces. The influence of such small‐scale (several centimeters) features on subsurface transport was investigated using high‐resolution groundwater models of each of the subsurface realizations. Flow and transport through the models was simulated parallel, perpendicular, and at an oblique angle to paleoflow. The simulated transport rates showed directionally dependent tendencies and were found to be fastest parallel to paleoflow and slowest perpendicular to paleoflow. Homogeneous and geostatistical realizations with nearly identical mean hydraulic conductivity values were unable to reproduce the directional behavior. Transport was also simulated across three different length scales in the long direction of the model (parallel to paleoflow). The simulated breakthrough of all simulations was fitted using the advection‐dispersion equation, but breakthrough was approximated more accurately with a non‐Fickian solution. The results of this study show that the rate of transport in heterogeneous sediments depends on the direction of flow relative to bedding and is sensitive to the length scale that transport is simulated across.
Special positive birefringence properties of mesogen-jacketed liquid crystalline polymer films for optical compensators
Authors: Chen Si , Zhang Lan-Ying , Guan Xiao-Lin , Fan Xing-He , Shen Zhihao , Chen Xiao-Fang , Zhou Qi-Feng
Published: February 2010

Special positive birefringence optical compensative films were constructed from mesogen-jacketed liquid crystalline polymers. The heterocyclic groups present in the structure easily advance the birefringence properties. The title compounds have positive birefringence values of up to 0.0350.
Simulation of cesium injection and distribution in rf-driven ion sources for negative hydrogen ion generation
Authors: Gutser R. , Fantz U. , Wünderlich D.
Published: February 2010

Cesium seeded sources for surface generated negative hydrogen ions are major components of neutral beam injection systems in future large-scale fusion experiments such as ITER. Stability and delivered current density depend highly on the cesium conditions during plasma-on and plasma-off phases of the ion source. The Monte Carlo code CSFLOW3D was used to study the transport of neutral and ionic cesium in both phases. Homogeneous and intense flows were obtained from two cesium sources in the expansion region of the ion source and from a dispenser array, which is located 10 cm in front of the converter surface.
ITEP MEVVA ion beam for reactor material investigation
Authors: Kulevoy T. , Kuibeda R. , Kropachev G. , Kozlov A. , Chalyh B. , Aleev A. , Fertman A. , Nikitin A. , Rogozhkin S.
Published: February 2010

Since 2008 the ion beam irradiation modeling experiments for the testing of reactor materials radiation hardness are under development at the ITEP heavy ion RFQ injector with MEVVA ion source. Ion beam irradiation method has certain advantages for such tests. One of them is high speed of defect formation. Moreover, the irradiated samples can be investigated by traditional investigation methodic because they have not radioactivity induced. The special sample support with electrostatic deflector was constructed and installed at the injector output. The result of ion beam dynamics simulation throughout the deflector as well as the detailed description of the test facility is presented. The first experimental results are presented as well. They have been demonstrated promising results.
Nb
3
Sn
superconducting magnets for electron cyclotron resonance ion sources
Authors: Ferracin P. , Caspi S. , Felice H. , Leitner D. , Lyneis C. M. , Prestemon S. , Sabbi G. L. , Todd D. S.
Published: February 2010

Electron cyclotron resonance (ECR) ion sources are an essential component of heavy-ion accelerators. Over the past few decades advances in magnet technology and an improved understanding of the ECR ion source plasma physics have led to remarkable performance improvements of ECR ion sources. Currently third generation high field superconducting ECR ion sources operating at frequencies around 28 GHz are the state of the art ion injectors and several devices are either under commissioning or under design around the world. At the same time, the demand for increased intensities of highly charged heavy ions continues to grow, which makes the development of even higher performance ECR ion sources a necessity. To extend ECR ion sources to frequencies well above 28 GHz, new magnet technology will be needed in order to operate at higher field and force levels. The superconducting magnet program at LBNL has been developing high field superconducting magnets for particle accelerators based on Nb3Sn superconducting technology for several years. At the moment, Nb3Sn is the only practical conductor capable of operating at the 15 T field level in the relevant configurations. Recent design studies have been focused on the possibility of using Nb3Sn in the next generation of ECR ion sources. In the past, LBNL has worked on the VENUS ECR, a 28 GHz source with solenoids and a sextupole made with NbTi operating at fields of 6–7 T. VENUS has now been operating since 2004. We present in this paper the design of a Nb3Sn ECR ion source optimized to operate at an rf frequency of 56 GHz with conductor peak fields of 13–15 T. Because of the brittleness and strain sensitivity of Nb3Sn, particular care is required in the design of the magnet support structure, which must be capable of providing support to the coils without overstressing the conductor. In this paper, we present the main features of the support structure, featuring an external aluminum shell pretensioned with water-pressurized bladders, and we analyze the expected coil stresses with a two-dimensional finite element mechanical model.
Recent advances in plasma devices based on plasma lens configuration for manipulating high-current heavy ion beams
Authors: Dobrovolskiy A. , Dunets S. , Evsyukov A. , Goncharov A. , Gushenets V. , Litovko I. , Oks E.
Published: February 2010

We describe new results of development of novel generation cylindrical plasma devices based on the electrostatic plasma lens configuration and concept of electrons magnetic insulation. The crossed electric and magnetic fields plasma lens configuration provides us with the attractive and suitable method for establishing a stable plasma discharge at low pressure. Using plasma lens configuration in this way some cost-effective plasma devices were developed for ion treatment and deposition of exotic coatings and the effective lens was first proposed for manipulating high-current beams of negatively charged particles. Here we describe operation and features of these plasma devices, and results of theoretical consideration of mechanisms determining their optimal operation conditions.
Generation of high currents of carbon ions with the use of subnanosecond near-infrared laser pulses
Authors: Krása J. , Velyhan A. , Margarone D. , Krouský E. , Ullschmied J. , Skála J. , Láska L. , Jungwirth K. , Rohlena K.
Published: February 2010

Emission of carbon currents reaching values up to 2 A/cm2 at a distance of 1 m from the laser ion source driven by the subnanosecond Prague Asterix Laser System operated at a fundamental wavelength of 1315 nm is reported. Graphite targets were exposed to intensities up to 5×1016 W/cm2 varying both the laser energy and the position of the laser beam focus with respect to the target surface. The maximum energy gain of carbon ions was ≈1 MeV/u. At high laser intensities the shape of time-of-flight spectra is also formed by plasma outbursts, whose growth correlates with the oscillatory self-focusing of the laser beam.
Review of polarized ion sources (invited)
Authors: Zelenski A.
Published: February 2010

Recent progress in polarized ion sources development is reviewed. New techniques for production of polarized H− ion (proton), D− (D+), and H3e++ ion beams are discussed. Feasibility studies of these techniques are in progress at BNL and other laboratories. Polarized deuteron beams will be required for the polarization program at the Dubna Nuclotron and at the deuteron electric dipole moment experiment at BNL. Experiments with polarized H3e++ ion beams are a part of the experimental program at the future electron ion collider.
Current capabilities and future needs for semiconductor ion implantation (invited)
Authors: Renau A.
Published: February 2010

For many years the largest commercial application for particle accelerators has been semiconductor ion implantation. These tools differ from other accelerators in many respects. In particular they are automated to a very high degree and, in addition to technical performance requirements their success depends on other key metrics including productivity, availability and cost of ownership. These tools also operate with a large variety of species, four orders of magnitude of energy range and five orders of magnitude of dose range. The ion source is a key component of implanters with its own performance metrics that include beam current, lifetime, and materials cost. In this paper, we describe the primary applications for ion implantation and some of the beam line architectures that are used. We describe the ion source that has evolved for this application. Some key future challenges for implanter ion source development are also discussed.
Experimental study for 15–20 mA dc H− multicusp source
Authors: Zhang Tianjue , Jia Xianlu , Lv Yinlong , Zou Jian , Guan Fengping , Wu Longcheng , Pan Gaofeng , Liu Gengshou , Lin Jun , Ge Tao , Yao Hongjuan , Wang Zhenhui , An Shizhong
Published: February 2010

Recently, a new H- source and test stand was developed at CIAE. The design of this new source is based on the experience on our previous 10–15 mA H− ion source and the source at TRIUMF. Major efforts include the study of the virtual filter magnetic field, confining magnetic field, filament shape and location, the vacuum improvement on the extracting area, the extraction optics, new control and interlock system of the power supplies. More than 15 mA of H-beam was obtained for 36 h with stability of ±0.5%. The normalized emittance of 0.48π mm mrad (4 rms normalized emittance) were measured with ∼8 mA dc beam. Further experimental studies are proceeding in an effort to reach 20 mA with reasonable emittance at this moment. More study plans are conducted, e.g., building a longer source body and using cesium injection to get better emittance, which will be presented as a separate paper at this conference.
Design and construction of a compact microwave proton source for a proton linac
Authors: Hong I. S. , Park B. S. , Jang J. H. , Kwon H. J. , Cho Y. S. , Hwang Y. S.
Published: February 2010

A 100 MeV, 20 mA proton linear accelerator is being developed by the Proton Engineering Frontier Project at the Korea Atomic Energy Research Institute. 20 MeV acceleration system using radio frequency quadrupole and drift tube linac was already developed and has been tested. To operate this acceleration system with a long time, more reliable proton source is needed. A compact microwave proton source was proposed and has been designed and constructed as a prototype ion source for the 100 MeV proton linear accelerator. The design of microwave power injection system is based on the microwave proton injector at LANL and CEA. The wave power from a 2.45 GHz, 2 kW magnetron source is introduced into a compact plasma chamber with 7 cm diameter and 5 cm length through a standard tapered, double-ridged waveguide (WRD250) and a quartz window. The microwave power supply is installed on high voltage platform. Axial magnetic fields up to 1 kG can be provided with a water-cooled solenoid coil. A single-hole three electrode extraction system is designed for an extraction current up to 30 mA at a 50 kV extraction voltage. The design and initial operations of the proton source are presented.
Plasma potential and energy spread determination using ion beams extracted from an electron cyclotron resonance source
Authors: Harris P. R. , Meyer F. W.
Published: February 2010

We have obtained estimates of plasma potentials and energy spreads characterizing an electron cyclotron resonance ion source plasma under different source conditions. Our estimates are obtained from analysis of ion beams extracted from the ion source at 10 kV that are subsequently decelerated into a floating surface scattering chamber where their current intensity incident on a solid sample is measured as function of retardation voltage. The deceleration occurs outside the measurement chamber, permitting beam current measurements in a field-free region. Absence of grids in the deceleration section avoids potential issues of field penetration. The behavior of our deceleration optics was modeled with SIMION. The simulation indicated a linear beam attenuation dependence close to full retardation where the beam current goes to zero. Deviations from this linear dependence observed close to zero beam energy give information on the initial energy spread of the ions extracted from the source. Our decelerated beams measurements are compared with recent in situ probe results and external beams results based on magnetic analysis.
Time profile of ion pulses produced in a hot-cavity laser ion source
Authors: Liu Y. , Beene J. R. , Havener C. C. , Vane C. R. , Geppert Ch. , Gottwald T. , Kessler T. , Wies K. , Wendt K.
Published: February 2010

The time spreads of Mn ions produced by three-photon resonant ionization in a hot-cavity laser ion source are measured. A one-dimensional ion-transport model is developed to simulate the observed ion time structures. Assuming ions are generated with a Maxwellian velocity distribution and are guided by an axial electric field, the predictions of the model agree reasonably well with the experimental data and suggest that the ions are radially confined in the ion source and a substantial fraction of the ions in the transport tube are extracted.
Frame independence of the fundamental length in relativistic quantum field theory
Authors: Nagamachi S. , Brüning E.
Published: February 2010

Some time ago we proposed a relativistic quantum field theory with a fundamental length in terms of tempered ultrahyperfunctions [Brüning, E. and Nagamachi, S., “Relativistic quantum field theory with a fundamental length,” J. Math. Phys. 45, 2199 (2004); e-print arXiv:math-ph/0804.1663; “Solutions of a linearized model of Heisenberg’s fundamental equation II,” J. Math. Phys. 49, 052304 (2008)]. The definition of the fundamental length by Brüning and Nagamachi [“Relativistic quantum field theory with a fundamental length,” J. Math. Phys. 45, 2199 (2004)] seems to depend on the Lorentz frame which is used to define it. In this article we show that this is actually not the case. In addition we discuss in some detail the geometric and analytic realization of the fundamental length and point out some important difference to standard relativistic quantum field theory in the sense of Gårding and Wightman.
Plasma meniscus and extraction electrode studies of the ISIS H− ion source
Authors: Lawrie S. R. , Faircloth D. C. , Letchford A. P. , Gabor C. , Pozimski J. K.
Published: February 2010

In order to reduce the emittance and increase the transported beam current from the ISIS Penning-type H− ion source, improvements to the extraction system are required. This ion source is currently being commissioned on the front end test stand at the Rutherford Appleton Laboratory, which demands higher extraction energies, higher beam currents, and smaller emittances. To facilitate this, the present geometry requires optimization. This paper details the experimental and simulation studies performed of the plasma meniscus and the possible electrode geometry modifications needed to extract the highest quality beam.
Stability study of all-permanent-magnet electron cyclotron resonance ion source
Authors: Yoshida K. , Nara T. , Saitoh Y. , Yokota W.
Published: February 2010

Beam intensity fluctuation was investigated using an electron cyclotron resonance ion source of an all-permanent-magnet type under development for highly stable beam intensity. While the source achieved a stability of better than 3.2% by strict regulation of the coolant temperature change within ±0.1 °C, the intensity varies strongly with intentional changes in the temperature of the plasma chamber coolant. The influence of the temperature on chamber expansion, magnetic field strength, and vacuum was measured or estimated in detail. The result shows that a slight change in vacuum and magnetic field strength has considerable influence on the intensity fluctuation.
Production of electron cyclotron resonance plasma by using multifrequencies microwaves and active beam profile control on a large bore electron cyclotron resonance ion source with permanent magnets
Authors: Kato Yushi , Watanabe Takeyoshi , Matsui Yuuki , Hirai Yoshiaki , Kutsumi Osamu , Sakamoto Naoki , Sato Fuminobu , Iida Toshiyuki
Published: February 2010

A new concept on magnetic field with all magnets on plasma production and confinement has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure. The magnetic field configuration is constructed by a pair of magnets assembly, i.e., comb-shaped magnet which cylindrically surrounds the plasma chamber. The resonance zones corresponding to the fundamental ECR for 2.45 GHz and 11–13 GHz frequencies are constructed at different positions. The profiles of the plasma parameters in the ECR ion source are different from each frequency of microwave. Large bore extractor is set at the opposite side against the microwave feeds. It is found that differences of their profiles also appear at those of ion beam profiles. We conducted to launch simultaneously multiplex frequencies microwaves controlled individually, and tried to control the profiles of the plasma parameters and then those of extracted ion beam.
The computation of finite-time Lyapunov exponents on unstructured meshes and for non-Euclidean manifolds
Authors: Lekien Francois , Ross Shane D.
Published: February 2010

We generalize the concepts of finite-time Lyapunov exponent (FTLE) and Lagrangian coherent structures to arbitrary Riemannian manifolds. The methods are illustrated for convection cells on cylinders and Möbius strips, as well as for the splitting of the Antarctic polar vortex in the spherical stratosphere and a related point vortex model. We modify the FTLE computational method and accommodate unstructured meshes of triangles and tetrahedra to fit manifolds of arbitrary shape, as well as to facilitate dynamic refinement of the FTLE mesh.
Commissioning of the new H− source for Linac4
Authors: Kronberger M. , Küchler D. , Lettry J. , Midttun Ø. , O’Neil M. , Paoluzzi M. , Scrivens R.
Published: February 2010

As part of the CERN accelerator complex upgrade, a new linear accelerator for H− (Linac4) will start its operation in 2014. The source for this linac will be a 2 MHz rf driven H− source which is a copy of the very successful source from DESY. In this paper the design and the first results of the commissioning are reported. The commissioning has progressed successfully, and no major obstacles have been identified which will prevent reaching the goal of 80 mA H− beam current, 45 keV beam energy, 0.4 ms pulse length, and 2 Hz repetition rate. The source is producing up until now a stable beam of 23 mA, 35 keV, and with a repetition rate of 0.83 Hz.
Strain engineered segregation regimes for the fabrication of thin Si1−xGex layers with abrupt n-type doping
Authors: Berbezier I. , Ayoub J. P. , Ronda A. , Oehme M. , Lyutovich K. , Kasper E. , Di Marino M. , Bisognin G. , Napolitani E. , Berti M.
Published: February 2010

We implement a low temperature (LT) growth technique for achieving abrupt n-type doping profiles in order to match the vertical scaling of modulation doped field effect transistor fully depleted structures. We use strain engineering of Ge rich Si1−xGex layers at LTs to suppress dopant segregation and to fully incorporate antimony in ultrathin Si1−xGex layers. We show that, only in the LT terrace-mediated kinetically limited regime, segregation is controlled by strain. At higher temperatures, in the step-edge mediated kinetically limited regime, segregation becomes independent of strain and at even higher temperatures, segregation follows the classical equilibrium behaviour mainly controlled by reduction of surface energy and not by strain.
Fabrication of advanced La-incorporated Hf-silicate gate dielectrics using physical-vapor-deposition-based in situ method and its effective work function modulation of metal/high-k stacks
Authors: Arimura Hiroaki , Oku Yudai , Saeki Masayuki , Kitano Naomu , Hosoi Takuji , Shimura Takayoshi , Watanabe Heiji
Published: February 2010

Lanthanum (La) incorporation into Hf-silicate high-permittivity (high-k) gate dielectrics was conducted using a physical-vapor-deposition (PVD)-based in situ method. PVD-grown metal Hf, La, and Hf–La alloys on base SiO2 oxides received in situ annealing to form high-quality HfLaSiO dielectrics, and subsequent deposition of metal gate electrodes was carried out to fabricate advanced metal/high-k gate stacks without breaking vacuum. The in situ method was found to precisely control La content and its depth profile and to tune the effective work function of metal/high-k stacks. Remarkable leakage current reduction of almost seven orders of magnitude compared with conventional poly-Si/SiO2 stacks and excellent interface properties comparable to an ideal SiO2/Si interface were also achieved at an equivalent oxide thickness of around 1.0 nm. Our x-ray photoelectron spectroscopy analysis revealed that, as previously suggested, effective work function modulation due to La incorporation is attributed to the interface dipole (or localized sheet charge) at the bottom high-k/SiO2 interface, which is crucially dependent on the La content at the interface. Moreover, it was found that high-temperature annealing causing interface oxide growth leads to redistribution of La atoms and forms the uppermost La-silicate layer at the metal/high-k interface by releasing the dipole moment at the bottom high-k/SiO2 interface. Based on these physical and electrical characterizations, the advantages and process guidelines for La-incorporated dielectrics were discussed in detail.
The challenge of unity wall plug efficiency: The effects of internal heating on the efficiency of light emitting diodes
Authors: Heikkilä Oskari , Oksanen Jani , Tulkki Jukka
Published: February 2010

We develop a self-consistent model to describe the internal heating of high power light emitting diodes (LEDs) and use this model to simulate the operation of GaAs–AlGaAs double heterostructure LEDs. We account for the heating by nonradiative recombination processes in the simulations and solve self-consistently the steady state junction temperature. Based on the simulation results, we discuss the plausibility of unity conversion efficiency in LEDs and also the mechanisms underlying the efficiency droop. We show that the rise in the junction temperature limits the light output available from LEDs and further degrades the efficiency of operation at high operating currents. In addition to high power applications we study the optimal operating point and discuss the methods to increase the efficiency of LEDs toward the thermodynamical limits.
Temperature dependence of electric and dielectric behaviors of Ni/polyvinylidene fluoride composites
Authors: Xu Hai-Ping , Dang Zhi-Min , Bing Nai-Ci , Wu Yi-Hua , Yang Dan-Dan
Published: February 2010

Composites of polyvinylidene fluoride (PVDF) filled with metallic particles of nickel (Ni) were prepared via a blending and hot-molding technique. Rescaled temperature dependence of electric and dielectric behaviors of Ni/PVDF composites were studied at wide content ranges. Results show that there is significant positive temperature coefficient effect and giant dielectric constant as the concentration of Ni is near the percolation threshold. The nonuniform distribution of filler particles in PVDF host is observed from the scanning electron microscope micrograph since they are aggregated in amorphous regions of PVDF and form a network of conducting chains. Two relaxation peak regions of dielectric constant are observed from −10 to 40 °C and from 100 to 150 °C, which can be attributed to the contribution of polar effect of PVDF. The percolation theory, the thermal expansion model, and the simple concept of polarization in the capacitors are employed to explain these experimental results.
Structural analysis of silicon carbon nitride films prepared by vapor transport-chemical vapor deposition
Authors: Awad Y. , El Khakani M. A. , Scarlete M. , Aktik C. , Smirani R. , Camiré N. , Lessard M. , Mouine J.
Published: February 2010

Amorphous silicon carbon nitride (a-SiCN:H) films were synthesized using vapor transport-chemical vapor deposition technique. Poly(dimethylsilane) was used as a single source for both Si and C. NH3 gas diluted in Ar is used as a source for nitrogen. The composition and bonding states are uniquely characterized with respect to NH3/Ar ratio by Fourier transform infrared spectroscopy (FTIR) and x-ray photoelectron spectroscopy (XPS). Spectral deconvolution is used to extract the individual components of the FTIR and XPS spectra. For instance, the FTIR spectra show a remarkable drop in the intensity of SiC vibration accompanied by the formation of further bonds including SiN, CN, CN, CN, and NH with increasing NH3/Ar ratio. Moreover, the XPS spectra show the existence of different chemical bonds in the a-SiCN:H films such as SiC, SiN, CN, CN, and CC. Both FTIR and XPS data demonstrate that the chemical bonding in the amorphous matrix is more complicated than a collection of single SiC SiN, or SiH bonds.
Self-masking controlled by metallic seed layer during glass dry-etching for optically scattering surfaces
Authors: Hein E. , Fox D. , Fouckhardt H.
Published: February 2010

During reactive ion etching in a high density Ar/CF4 plasma, nonvolatile halogen compounds are generated on the glass surface and act as statistically distributed micromasks. As a consequence surface roughness occurs, which can be used as additional surface functionality in certain classes of applications, where defined optical scattering is desired. The glass etch process described in this contribution enables user-defined scattering characteristics. The deposition of a thin metallic layer of Cu on top of the samples before dry-etching provides an additional seed for the production of micromasks, resulting in higher reproducibility. By varying the etch parameters a multitude of different surface morphologies can be realized both on borosilicate glasses and on fused silica.
Jump properties of the tip magnetic field of a notch in a melt-processes yttrium-barium-copper-oxide bulk
Authors: Zhang Xing-Yi , Zhou Jun , Zhou You-He
Published: February 2010

We report on a direct measurement of the magnetic field properties at the tip of a notch in melt-processed Y1Ba2Cu3O7−x bulks. In the case of the fixed notch angle, when the notch length increases and reaches a critical value, the tip magnetic field will increase and exceed the initial value of the sample without a notch. In the case of fixed notch length which is equal to the radius of superconducting bulk, the tip magnetic field increases at first and then decreases as the notch angle is over 90°. In addition, the rules of the change in the interaction force between the bulk superconductor and magnet are also reported. A simple physical model is used to interpret these experimental phenomena qualitatively.
Electronic structure, phonons, and thermal properties of ScN, ZrN, and HfN: A first-principles study
Authors: Saha Bivas , Acharya Jagaran , Sands Timothy D. , Waghmare Umesh V.
Published: February 2010

With a motivation to understand microscopic aspects of ScN, ZrN, and HfN relevant to the thermoelectric properties of nitride metal/semiconductor superlattices, we determine their electronic structure, vibrational spectra and thermal properties using first-principles calculations based on density functional theory with a generalized gradient approximation of the exchange correlation energy. We find a large energy gap in the phonon dispersions of metallic ZrN and HfN, but a gapless phonon spectrum for ScN spanning the same energy range, this suggests that a reduced thermal conductivity, suitable for thermoelectric applications, should arise in superlattices made with ScN and ZrN or ScN and HfN. To obtain an electronic energy band gap of ScN comparable to experiment, we use a Hubbard correction with a parameter U (=3.5 eV). Anomalies in the acoustic branches of the phonon dispersion of ZrN and HfN, manifested as dips in the bands, can be understood through the nesting of Fermi surface determined from our calculations. To connect with transport properties, we have determined effective masses of ScN and determined their dependence on the U parameter. Using the relaxation time approximation in the Boltzmann transport theory, we estimate the temperature dependence of the lattice thermal conductivity and discuss the chemical trends among these nitrides.
Nanocrystalline diamond as an electronic material: An impedance spectroscopic and Hall effect measurement study
Authors: Bevilacqua Mose , Tumilty Niall , Mitra Chiranjib , Ye Haitao , Feygelson Tatayana , Butler James E. , Jackman Richard B.
Published: February 2010

Nanocrystalline diamond (NCD) has been grown using a nanodiamond seeding technique, leading to a dense form of this material, with grain sizes around 100 nm. The electrical properties of both intrinsic and lightly boron-doped NCD have been investigated using impedance spectroscopy and Hall effect measurements. For intrinsic material, both grain boundaries and grains themselves initially contribute to the frequency dependant impedance values recorded. However, boundary conduction can be removed and the films become highly resistive. Interestingly, the ac properties of these films are also excellent with a dielectric loss value ∼0.004 for frequencies up to 10 MHz. The dielectric properties of these NCD films are therefore as good as high quality large grain polycrystalline diamond films. In the case of boron-doped material, p-type material with good carrier mobility values (10–50 cm2/V s) can be produced at carrier concentrations around 1017 cm−3.
Theoretical study for the reaction of CH3CN with O(P3)
Authors: Sun Jingyu , Tang Yizhen , Jia Xiujuan , Wang Fang , Sun Hao , Feng Jingdong , Pan Xiumei , Hao Lizhu , Wang Rongshun
Published: February 2010

The low-lying triplet and singlet potential energy surfaces of the O(P3)+CH3CN reaction have been studied at the G3(MP2)//B3LYP/6-311+G(d,p) level. On the triplet surface, six kinds of pathways are revealed, namely, direct hydrogen abstraction, C-addition/elimination, N-addition/elimination, substitution, insertion, and H-migration. Multichannel Rice–Ramsperger–Kassel–Marcus theory and transition-state theory are employed to calculate the overall and individual rate constants over a wide range of temperatures and pressures. It is predicted that the direct hydrogen abstraction and C-addition/elimination on triplet potential energy surface are dominant pathways. Major predicted end products include CH3+NCO and CH2CN+OH. At atmospheric pressure with Ar and N2 as bath gases, CH3C(O)N (IM1) formed by collisional stabilization is dominated at T<700 K, whereas CH3 and NCO produced by C-addition/elimination pathway are the major products at the temperatures between 800 and 1500 K; the direct hydrogen abstraction leading to CH2CN+OH plays an important role at higher temperatures in hydrocarbon combustion chemistry and flames, with estimated contribution of 64% at 2000 K. Furthermore, the calculated rate constants are in good agreement with available experimental data over the temperature range 300–600 K. The kinetic isotope effect has also been calculated for the triplet O(P3)+CH3CN reaction. On the singlet surface, the atomic oxygen can easily insert into C–H or C–C bonds of CH3CN, forming the insertion intermediates s-IM8(HOCH2CN) and s-IM5(CH3OCN) or add to the carbon atom of CN group in CH3CN, forming the addition intermediate s-IM1(CH3C(O)N); both approaches were found to be barrierless. It is indicated that the singlet reaction exhibits a marked difference from the triplet reaction. This calculation is useful to simulate experimental investigations of the O(P3)+CH3CN reaction in the singlet state surface.
Localized sagittal modes of variable transverse and longitudinal components in one-dimensional phononic crystals
Authors: Castro-Arce L. , Manzanares-Martínez B. , Ramos-Mendieta F.
Published: February 2010

In this paper, we study the polarization states of the localized sagittal modes in a solid/solid one-dimensional phononic crystal with a defect layer. We have found that the well defined polarization of these modes, either transverse or longitudinal, for propagation in the direction of periodicity is completely modified for the case of oblique propagation. Thus for practical applications the polarization—the transverse/longitudinal component rate—of the defect modes will depend on the angle of incidence. For calculations, we use the supercell method; the criterion of energy balance is employed to determine the polarization state of all the acoustic waves. The results show the existence of localized elastic modes in the band gaps and resonant vibrations inside the allowed bands. By analyzing the amplitude profiles, we conclude that the displacement localization of both transverse and longitudinal components can be different. Consequently, the polarization of the transmission peaks could depend on the thickness of the sample. The interesting effect of change in polarization (from quasitransverse to quasilongitudinal) of some transmission peaks as function of the angle of incidence is reported. Calculations were made for an Epoxy/Sn superlattice with Zn as defect layer.
Neodymium doping in UV-IR transparent ferroelectric BaMgF4
Authors: Víllora E. G. , Molina P. , Álvarez S. , García-Santizo J. V. , Ramírez M. O. , Shimamura K. , Bausá L. E.
Published: February 2010

The incorporation of Nd3+ in the ferroelectric fluoride BaMgF4 crystal is investigated for its potential application as self-frequency-converter solid state laser. Low temperature high-resolution optical spectroscopy shows that Nd3+ is located at two well distinguished sites referred as A and B. The whole set of energy levels in the excited F43/2, I411/2, and ground I49/2 states are identified for both Nd3+ sites and their crystallographic location in BaMgF4 lattice is discussed. The radiative lifetime of the F43/2 metastable laser level is obtained to be 1430 and 800 μs for site A and B, respectively, and the luminescence quantum efficiency of the F43/2 metastable state for the dominant A site is 87%. The possibility of annihilating the contribution of the B site in the optical spectrum is demonstrated by means of the incorporation Na+ into the crystal.