bluuebunny/crossref_metadata_2025 huggingface dataset:
Implications of the enhanced Brewer‐Dobson circulation in European Centre for Medium‐Range Weather Forecasts reanalysis ERA‐40 for the stratosphere‐troposphere exchange of ozone in global chemistry transport models
Authors: van Noije T. P. C. , Eskes H. J. , van Weele M. , van Velthoven P. F. J.
Published: October 2004

The European Centre for Medium‐Range Weather Forecasts 45‐year reanalysis (ERA‐40) exhibits an enhanced Brewer‐Dobson circulation, as is demonstrated for the year 1997 by examining the air mass transport across the 100‐hPa level and the tropopause. On the basis of a linearized ozone (Linoz) scheme for stratospheric chemistry it is estimated that the corresponding net downward transport of ozone to the lowermost stratosphere and the troposphere would be a factor 2–3 too high. Different methods are evaluated to simulate the downward transport of stratospheric ozone in tropospheric chemistry transport models driven by ERA‐40 meteorology. The synthetic ozone (Synoz) model, which is sometimes used to constrain the influx of stratospheric ozone by imposing its chemical production rate in the middle stratosphere, in the case of ERA‐40 leads to an unacceptable depletion of the upper troposphere/lower stratosphere region, with nearly halved ozone concentrations at 100 hPa. A better alternative is to constrain the zonal mean concentrations in the lower stratosphere by relaxation to an ozone climatology. If ozone is relaxed down to 100 hPa in the extratropics, the net downward transport of ozone is reduced by more than a factor of 2. Finally, we investigate to what extent the circulation bias persists in the forecasts of the reanalysis. The use of forecasts beyond the 6‐hour “first guess” in combination with relaxation yields a further reduction of the stratosphere‐troposphere exchange of ozone, the 100‐hPa flux approaching the range of observational estimates. An additional advantage of using forecasts is that the exchange of chemical constituents other than ozone is improved concurrently.
Evaluation of CO simulations and the analysis of the CO budget for Europe
Authors: Pfister G. , Pétron G. , Emmons L. K. , Gille J. C. , Edwards D. P. , Lamarque J.‐F. , Attie J.‐L. , Granier C. , Novelli P. C.
Published: October 2004

CO is a well‐suited indicator for the transport of pollutants in the troposphere on a regional and global scale. For the study presented here, simulations of CO concentrations from a global chemistry transport model (MOZART‐2), with the CO being tagged according to the emission type and the source region, have been used to diagnose the contributions of different processes and regions to the CO burden over Europe. Model simulations have been performed with both a priori emissions and an optimized set of CO surface emissions derived from the inversion of CO retrievals of the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument. The annual mean difference between the modeled and the observed CO at 850 hPa over Europe is −38 ± 13 ppb with the a priori set of emissions and −7 ± 7 ppb when the optimized emissions are employed in the model. The general difficulties arising from an intercomparison of remote sensing data with model simulations are discussed. Besides data from MOPITT, ground‐based CO measurements have been employed in the evaluation of the model and its emissions. The comparisons show that the model represents the background conditions as well as large‐scale transport relatively well. The budget analysis reveals the predominant impact of the European emissions on CO concentrations near the surface, and a strong impact of sources from Asia and North America on the CO burden in the free troposphere over Europe. On average, the largest contribution (67%) to the anthropogenic (fossil and biofuel sources, biomass burning) CO at the surface originates from regional anthropogenic sources, but further significant impact is evident from North America (14%) and Asia (15%). With increasing altitude, anthropogenic CO from Asia and North America gains in importance, reaching maximum contributions of 32% for North American CO at 500 hPa and 50% for Asian CO at 200 hPa. The impact of European emissions weakens with increasing altitude (8% at 500 hPa).
Characterization of summertime microwave emissivities from the Special Sensor Microwave Imager over the conterminous United States
Authors: Ruston Benjamin C. , Vonder Haar Thomas H.
Published: October 2004

Retrievals of microwave land emissivity have been performed for three summer seasons (June–August) over the conterminous United States for the years of 2000, 2001, and 2002. These retrievals use observations from the Special Sensor Microwave Imager to construct a database from which means and channel correlations of land emissivity can be computed, needed for variational retrievals of atmospheric parameters. In addition, the study establishes a range of values that must be reproducible by forward emissivity models. Embedded in the retrieval is an infrared‐based cloud‐clearing algorithm and land surface temperature retrieval. The land surface temperature retrieval employs vegetation and soil databases to index infrared spectral reflectance measurements to a given location. Analysis reveals that the land surface temperature dominates the total error in microwave emissivity, with the largest contribution coming from impacts of subpixel and undetected clouds, and interpolation error of 3‐hourly land surface temperature to the time of the satellite overpass. A practical microwave emissivity error estimate is 2% for all frequencies less than 85 GHz, within a natural summertime variability of 5%. A clearly polarized signature from the surface is present in the 19 GHz frequencies over terrain characterized as predominantly bare ground, with the scattering by vegetation and small‐scale roughness effects reducing this polarized signal at higher frequencies and over more densely vegetated areas.
CB1 receptor agonist and heroin, but not cocaine, reinstate cannabinoid‐seeking behaviour in the rat
Authors: Spano M Sabrina , Fattore Liana , Cossu Gregorio , Deiana Serena , Fadda Paola , Fratta Walter
Published: October 2004

We recently provided evidence for a functional link between cannabinoid and opioid endogenous systems in relapse to heroin‐seeking behaviour in rats. In the present study, we aimed at investigating whether the previously observed cross‐talk between cannabinoids and opioids could be extended to mechanisms underlying relapse to cannabinoid‐seeking behaviour after a prolonged period of abstinence.

In rats previously trained to intravenously self‐administer the synthetic cannabinoid receptor (CB1) agonist WIN 55,212‐2 (12.5 μg kg−1 inf−1) under a fixed ratio (FR1) schedule of reinforcement, noncontingent nonreinforced intraperitoneal (i.p.) priming injections of the previously self‐administered CB1 agonist (0.25 and 0.5 mg kg−1) as well as heroin (0.5 mg kg−1), but not cocaine (10 mg kg−1), effectively reinstate cannabinoid‐seeking behaviour following 3 weeks of extinction.

The selective CB1 receptor antagonist SR 141716A (0.3 mg kg−1 i.p.) does not reinstate responding when given alone, but completely prevents the cannabinoid‐seeking behaviour triggered by WIN 55,212‐2 or heroin primings.

The nonselective opioid antagonist naloxone (1 mg kg−1 i.p.) has no effect on operant behaviour per sè, but significantly blocks cannabinoid‐ and heroin‐induced reinstatement of cannabinoid‐seeking behaviour.

These results provide the first evidence of drug‐induced reinstatement of cannabinoid‐seeking behaviour, and further strengthen previous findings on a cross‐talk between the endogenous cannabinoid and opioid systems in relapse mechanisms to drug‐seeking.

British Journal of Pharmacology (2004) 143, 343–350. doi:10.1038/sj.bjp.0705932
Cardiovascular activity of rasagiline, a selective and potent inhibitor of mitochondrial monoamine oxidase B: comparison with selegiline
Authors: Abassi Zaid A , Binah Ofer , Youdim Moussa B H
Published: October 2004

Selegiline is used for treating Parkinson's disease. Despite its efficacy, the clinical use of selegiline in combination with L‐dihydroxphenylalanine in Parkinsonian patients is hampered by cardiovascular complications, such as hypotension. This study was designed to compare in rats the cardiovascular effects of selegiline and rasagiline, their metabolites L‐methamphetamine and aminoindan (TVP‐136), respectively, and the second rasagiline metabolite non‐monoamine oxidase (MAO) inhibitor TVP‐1022 (N‐propargyl‐1S(−)aminoindan).

Intravenous (i.v.) administration of selegiline and rasagiline (1 mg kg−1) to anaesthetized rats (thiobutabarbital, 100 mg kg−1, i.p.) did not affect mean arterial pressure (MAP), carotid blood flow (CBF) or carotid vascular resistance (CVR). Selegiline (10 mg kg−1, i.v.) decreased MAP, CBF and increased CVR. In contrast, rasagiline (10 mg kg−1, i.v.) caused a small transient decrease in MAP, while CBF and CVR were unchanged.

L‐methamphetamine (1 mg kg−1, i.v.) administration provoked a dramatic and long‐lasting depressor response, decreased CBF and increased CVR. In contrast, injection of aminoindan or TVP‐1022 at a similar dose produced gradual nonsignificant decreases in MAP and CBF.

Chronic oral treatment (21 days) of awake rats with selegiline at 10 mg kg−1 decreased systolic blood pressure (SBP), diastolic blood pressure (DBP), and MAP, whereas heart rate was unaffected. Since the effective MAO‐B inhibitory and clinical dose of rasagiline is about one‐tenth that of selegiline, administration of 1 mg kg−1 day−1 rasagiline resulted in moderate decreases in SBP, DBP, and MAP, which were significantly lower than those caused by the 10 mg kg−1 day−1 dose of selegiline.

These findings indicate that rasagiline, when given at doses equivalent to selegiline, is less likely to be hypotensive.

British Journal of Pharmacology (2004) 143, 371–378. doi:10.1038/sj.bjp.0705962
Spin transfer by spin injection between both interfaces of a Ni nanowire
Authors: Wegrowe J.-E. , Dubey M. , Wade T. , Drouhin H.-J. , Konczykowski M.
Published: October 2004

Magnetization switching provoked by spin injection is studied in Ni nanowires of various sizes and morphologies. The response of the magnetization to current injection is measured as a function of the amplitude of the current, the temperature, and the symmetry of the interfaces. The efficiency of the response of the magnetization of spin injection is a decreasing function of the temperature, does not depend on the current sign, and occurs only in the case of asymmetric interfaces. It is shown that the switching provoked by spin injection is not affected by the presence of a magnetic domain inside the layer. Some consequences in terms of spin transfer or exchange torque are discussed.
Measurement of the internal magnetic field of plasmas using an alpha particle source
Authors: Zweben S. J. , Darrow D. S. , Ross P. W. , Lowrance J. L. , Renda G.
Published: October 2004

The internal magnetic fields of plasmas can be measured under certain conditions from the integrated v×B deflection of MeV alpha particles emitted by a small radioactive source. The alpha source and large-area alpha particle detector would be located inside the vacuum vessel but outside the plasma. Alphas with a typical energy of 5.5 MeV (241Am) can reach the center of almost all laboratory plasmas and magnetic fusion devices, so this method can potentially determine the q(r) profile of tokamaks or spherical toris (STs). Orbit calculations, background evaluations, and conceptual designs for such α v×B (or “AVB”) detector are described.
Fast ion millimeter wave collective Thomson scattering diagnostics on TEXTOR and ASDEX upgrades
Authors: Michelsen S. , Korsholm S. B. , Bindslev H. , Meo F. , Michelsen P. K. , Tsakadze E. L. , Egedal J. , Woskov P. , Hoekzema J. A. , Leuterer F. , Westerhof E.
Published: October 2004

Collective Thomson scattering (CTS) diagnostic systems for measuring fast ions in TEXTOR and ASDEX Upgrade are described in this article. Both systems use millimeter waves generated by gyrotrons as probing radiation and the scattered radiation is detected with heterodyne receivers having 40 spectral channels at TEXTOR and 50 spectral channels at ASDEX Upgrade. The antenna patterns of probe and receiver, both steerable, determine size and location of the measuring volume, and the direction of the resolved fast ion velocity. With overmoded transmission lines, consisting of waveguides and quasioptical mirrors, the antenna patterns depend on the alignment of the entire transmission line. Alignment is aided by visible laser beams relayed by small optical mirrors, inserted in the quasioptical mirrors.
Cyclic-N3. I. An accurate potential energy surface for the ground doublet electronic state up to the energy of the A22/2B1 conical intersection
Authors: Babikov Dmitri , Zhang Peng , Morokuma Keiji
Published: October 2004

A sophisticated adiabatic ground electronic state potential energy surface for a pure nitrogen ring (cyclic-N3) molecule is constructed based on extensive high-level ab initio calculations and accurate three-dimensional spline representation. Most of the important features of the potential energy surface are presented using various reduced dimensionality slices in internal hyperspherical coordinates as well as full dimensional isoenergy surfaces. Very significant geometric phase effects are predicted in the spectra of rotational-vibrational states of cyclic-N3.
Fizeau interferometer for measurement of plasma electron current
Authors: Brower D. L. , Ding W. X. , Deng B. H. , Mahdavi M. A. , Mirnov V. , Prager S. C.
Published: October 2004

A high-resolution, vertically viewing far-infrared polarimeter-interferometer system is currently used on the Madison symmetric torus (MST) reversed-field pinch (RFP) to measure the plasma electron density and toroidal current density via Faraday rotation. In this article, we propose a scheme to measure the well-known Fizeau effect, whereby through modest modification of the existing apparatus, the line-integrated poloidal current density can also be directly measured. This parameter is important, since the RFP toroidal magnetic field is largely determined by currents flowing within the plasma. The Fizeau effect is a phase shift of an electromagnetic wave associated with movement of a dielectric medium. This motion can be related directly to the plasma electron current. Determining the Fizeau effect involves measurement of the phase shift between two collinear, orthogonally polarized, counterpropagating laser beams. Estimates indicate a phase shift of ∼2° is expected for typical MST parameters, well within the existing system resolution.
High-resolution compact Johann crystal spectrometer with the Livermore electron beam ion trap
Authors: Robbins D. L. , Chen H. , Beiersdorfer P. , Faenov A. Ya. , Pikuz T. A. , May M. J. , Dunn J. , Smith A. J.
Published: October 2004

A compact high-resolution (λ/Δλ≈10 000) spherically bent crystal spectrometer in the Johann geometry was recently installed and tested on the Lawrence Livermore National Laboratory SuperEBIT electron beam ion trap. The curvature of the mica (002) crystal grating allows for higher collection efficiency compared to the flat and cylindrically bent crystal spectrometers commonly used on the Livermore electron beam ion traps. The spectrometer’s Johann configuration enables orientation of its dispersion plane to be parallel to the electron beam propagation. Used in concert with a crystal spectrometer, whose dispersion plane is perpendicular to the electron beam propagation, the polarization of x-ray emission lines can be measured.
Compact imaging Bragg spectrometer for fusion devices
Authors: Bertschinger G. , Biel W. , Jaegers H. , Marchuk O.
Published: October 2004

A compact imaging x-ray spectrometer has been designed for tokamaks and stellarators to measure the plasma parameters at different spatial chords. It has been optimized for high spectral resolution and high sensitivity. High spectral resolution is obtained by using solid state detectors and minimizing the imaging errors of the spherical crystals. It is shown, that using spherical crystals the solid angle and hence the throughput can be increased significantly, without compromising the spectral resolution. The design is useful for the measurement of the spectra of He- and H-like ions from Si to Kr. The spectral resolution is sufficient for the measurement of plasma parameters. The temporal resolution is high enough for transport studies by gas puff and laser ablation experiments. The design is based on a modified Johann spectrometer mount, utilizing a spherically bent crystal instead of the cylindrically bent crystal in the traditional Johann mount. The astigmatism of the wavelength selective reflection on the spherical crystal is applied to obtain imaging of an extended plasma source on a two-dimensional detector. For each element, a separate crystal is required, only in few cases, a crystal can be used for the spectra of two elements. For the spectra of most of the He-like ions from Si up to Kr, suitable crystal cuts have been found on quartz, silicon and germanium crystals with Bragg angles in a small interval around the design value of 53.5°. All of the crystals have the same radius. They are fixed on a rotational table. The distance to the detector is adjusted by an x–y table to fit to the Rowland circle.
First tritium operation of ITER-prototype VUV spectroscopy on JET
Authors: Coffey I. H. , Barnsley R. ,   JET EFDA Contributors
Published: October 2004

Results from tritium operation of the VUV survey spectrometer on the JET tokamak are presented. The instrument, located outside the biological shield and offset from a direct plasma 1-o-s for maximum radiation protection, was operational during the trace tritium campaign (TTE) at JET. No discernible increase in detector background noise levels were detected for total neutron rates of up to 1×1017/s, demonstrating the shielding effectiveness of the configuration. Some tritium retention in the detector microchannel plate was measurable, but has not hampered subsequent operations. As a reference the unshielded detector of a close-coupled XUV instrument was operated during TTE (the spectrometer itself was valved off from the JET vessel). This was exposed to neutron fluxes of ∼109/cm2 s, in excess of those predicted for the corresponding instrument on ITER (107–108/cm2 s). A corresponding increase in the background level equivalent to ∼5% of the detector dynamic range was measured. This demonstration of the shielding effectiveness of the SPRED configuration during DT operations, coupled with the tolerable noise levels measured in the SOXMOS detector, give confidence in the planned implementation of such instruments in ITER.
Diagnostic neutral beam injector and associated diagnostic systems for the TJ-II stellarator device
Authors: McCarthy K. J. , Balbín R. , López-Fraguas A. , García A. , Carmona J. M. , Sánchez J. , Ivanov A. A.
Published: October 2004

A diagnostic neutral beam injector, based on the DINA-5F injector, is under development for the highly flexible TJ-II stellarator. The principal goals are to obtain spatially resolved charge-exchange recombination spectroscopy and neutral particle analysis measurements along the plasma minor radius and to stimulate opportunities for new physics studies. We first summarize relevant TJ-II characteristics and the considerations addressed when defining this compact system, for instance, the steps taken to minimize the impact of ferromagnetic shielding on magnetic configurations. We then outline the main aspects of the system and associated diagnostics. In particular, we highlight a bidirectional fiber-optic based multichannel spectrometer for obtaining Doppler measurements with high spatial resolution.
Fast neutral lithium beam probing of the edge region of the spherical tokamak ETE
Authors: Oliveira R. M. , Ueda M. , Berni L. A. , Iguchi H.
Published: October 2004

The close relationship between the behavior of the edge plasma characteristics and the global confinement in discharges in tokamaks has been extensively explored in recent years. A 15 keV lithium beam with 80% neutralization efficiency, using a high ion current density emitter and a modified Pierce gun design for extraction of ions, was developed for edge studies on the spherical tokamak ETE—(major radius R=0.30 m, aspect ration A=1.5, designed plasma current of 200 kA with a torodial magnetic field up to 0.4 T). Already in the calibration phase this diagnostics confirmed to be an efficient experimental tool, allowing accurate measurements of the fast varying pressure of the discharges in ETE. The measurement of the temporal evolution of the density of the plasma edge with fast neutral lithium beam is in accordance with data from Langmuir probe for the region near the limiter and the one made by the Thomson scattering for the inner region.
Digital processing of solid state detector signals in pellet charge exchange measurements on LHD
Authors: Goncharov P. R. , Ozaki T. , Sudo S. , Tamura N. , Isobe M. , Group TESPEL Group, and LHD Experimental , Sasao M. , Saida T. , Krasilnikov A. V. , Sergeev V. Yu.
Published: October 2004

Radially resolved measurements of the plasma ion distribution function by detecting charge exchange neutrals from an impurity pellet ablation cloud require a fast operating energy analyzer working at high count rates to build several spectra during the pellet flight. Currently a solid state detector in the pulse height analysis (PHA) mode is used for such measurements on the Large Helical Device. Traditional PHA techniques cannot provide the operating speed required for a good spatial resolution. An algorithm has been proposed based on digital processing of noisy data series containing charge-sensitive preamplifier signals with discontinuities corresponding to incident particles. The algorithm employs the modified Tikhonov regularization and the successive detection–estimation of signal increments at discontinuity points. Such an approach allows one to realize an ultrafast particle energy spectroscopy by taking advantage of detector/preamplifier capabilities without limiting the system throughput by subsequent electronics.
Testing LaMgAl11O19 crystal for x-ray spectroscopy
Authors: Chen H. , Beiersdorfer P. , Baronova E. O. , Kalashnikova I. I. , Stepanenko M. M.
Published: October 2004

We investigated the properties of the rare earth crystal LaMgAl11O19 and its application to soft x-ray spectroscopy. Its relative reflectivity and half-width rocking curve were measured to up to the reflection order of 28. In addition, a comparative measurement of the iron L-shell soft x-ray line emission was made on the EBIT-I Livermore electron beam ion trap by fielding the LaMgAl11O19 crystal side by side with a rubidium hydrogen phthalate crystal in a flat crystal spectrometer. From these measurements, reflectivity and spectral resolving power were determined.
Time-of-flight energy analyzer for the plasma potential measurements by a heavy ion beam diagnostic
Authors: Nedzelskiy I. S. , Malaquias A. , Gonçalves B. , Silva C. , Varandas C. A. F. , Cabral J. A. C.
Published: October 2004

A time-of-flight (TOF) technique for the plasma potential measurements by a heavy ion beam diagnostic (HIBD) with a multiple cell array detector has been elaborated on tokamak ISTTOK as an alternative to the traditional electrostatic energy analyzer. This article describes the design and operation of a four-channel TOF energy analyzer (TOFEA). First results of plasma potential measurements by TOFEA are presented proving the feasibility of this technique in experiments with HIBD.
Neutron measurements on Joint European Torus using an NE213 scintillator with digital pulse shape discrimination
Authors: Esposito B. , Bertalot L. , Marocco D. , Riva M. , Kaschuck Y. , Skopintsev S. , Zimbal A. , Reginatto M. , Schuhmacher H. , Adams J. M. , Murari A. , workprogram Contributors to the EFDA-JET
Published: October 2004

A digital pulse shape discrimination system (DPSD) has been used in conjunction with collimated NE213 scintillators for neutron spectroscopic measurements at high count rates (MHz range) in Joint European Torus discharges (DD and DT fueled, neutral beam injection and rf heated). The system, developed at ENEA-Frascati, is based on a commercial 200 MHz 12-bit analog to digital transient recorder card, which digitizes the direct output signal from the anode of a photomultiplier. Among the unique features of this DPSD system are the possibility of postexperiment data reprocessing, high count rate operation, and simultaneous neutron and gamma (γ) spectroscopy. Separation between γ and neutron (n) events is performed by means of dedicated software exploiting the charge comparison method; separate n and γ pulse height distributions are obtained and an example of neutron spectrum unfolding is shown. Implications of the DPSD in future neutron diagnostic systems on large and next step tokamaks are discussed.
Low-frequency noise and charge transport in light-emitting diodes with quantum dots
Authors: Dobrzanski Lech
Published: October 2004

In this experimental study, we have compared low-frequency (LF) noise and transport characteristics of light-emitting diodes (LEDs) with InAs quantum dots embedded in the In0.15Ga0.85As matrix with diodes of similar epitaxial structure without dots. Quantum dot (QD) and quantum well (QW) diodes have the p-i-n structure. At cryogenic temperatures, the LEDs with quantum dots exhibit pure excess tunneling transport mechanism, which originates from the energy levels introduced by quantum dots into the band gap of the intrinsic region. In the LEDs without quantum dots, an excess tunneling current was observed for small current densities. At a higher bias, another transport mechanism dominates, whose features can be explained by the Fowler-Nordheim (FN) tunneling. The low-frequency noise associated with the excess tunneling current is of 1∕f type and its power spectral density depends on the bias as S1∝I. In the diodes without dots, the relation S1∝I2 is valid at the bias, where the current transport mechanism is of Fowler-Nordheim type. In both cases, the considered noise spectral densities do not depend on temperature. We derived the explanation of the observed noise features for the QD and the QW devices on the basis of formulas for fundamental and nonfundamental noise sources, respectively. We measured the LF noise of the light emitted by idodes at room temperature and it appeared that it is a shot noise, which is not correlated with electrical noise.
Annealing behavior of oxygen in-diffusion from SiO2 film to silicon substrate
Authors: Abe T. , Yamada-Kaneta H.
Published: October 2004

Diffusion behavior of oxygen at (near) the Si∕SiO2 interface was investigated. We first oxidized the floating-zone-grown silicon substrates, and then annealed the SiO2-covered substrates in an argon ambient. We examined two different conditions for oxidation: wet and dry oxidation. By the secondary-ion-mass spectrometry, we measured the depth profiles of the oxygen in-diffusion of these heat-treated silicon substrates: We found that the energy of dissolution (in-diffusion) of an oxygen atom that dominates the oxygen concentration at the Si∕SiO2 interface depends on the oxidation condition: 2.0 and 1.7eV for wet and dry oxidation, respectively. We also found that the barrier heights for the oxygen diffusion in argon anneal were significantly different for different ambients adopted for the SiO2 formation: 3.3 and 1.8eV for wet and dry oxidation, respectively. These findings suggest that the microscopic behavior of the oxygen atoms at the Si∕SiO2 interface during the argon anneal depends on the ambient adopted for the SiO2 formation.
Production and loss mechanisms of SiClX etch products during silicon etching in a high density HBr∕Cl2∕O2 plasma
Authors: Cunge G. , Kogelschatz M. , Sadeghi N.
Published: October 2004

Si Cl X  (X=0–2) radicals’ concentrations have been measured by broadband ultraviolet absorption spectroscopy during the etching of 200mm diameter silicon wafers in HBr∕Cl2∕O2 plasmas. We report the variations of the concentrations of these radicals as a function of the radio frequency (rf) source power and rf-bias power. The silicon wafer etch rate is measured simultaneously. From the measured radicals densities and using electron impact ionization cross sections found in the literature, the densities of SiClX+ ions are calculated and are found to be in good agreement with ion densities measured by mass spectrometry. The upper limit for the SiCl2 radical concentration is calculated from the wafer etch rate. By comparison with the measured SiCl2 radical concentration it is concluded that SiCl2 radicals should also be produced by the reactor walls due to the etching of silicon containing species adsorbed on the reactor walls. Finally, using electron impact dissociation cross sections, the densities of SiCl and Si are calculated from the measured densities of SiCl2 and SiCl, respectively. The comparison between the calculated and measured values of SiClX densities allowed us to conclude that SiCl (and Si) are produced both in the gas phase by electron impact dissociation of SiCl2 (SiCl) radicals and at the reactor wall surfaces by the neutralization and reflection of ≈50% of the flux of SiCl+ (Si+) ions impinging on these surfaces. At the same time SiCl and Si are estimated to be lost (adsorption and abstraction reactions) on the reactor walls with a probability ranging between 0.2 and 1.
Elastic and elastic-plastic analysis of multilayer thin films:Closed-form solutions
Authors: Hu Y. Y. , Huang W. M.
Published: October 2004

The stress and curvature induced by temperature fluctuation in multilayer thin film structures have been investigated extensively in the past. However, most of the previous efforts were focused on the elastic deformation range. In this paper, first we propose a simple approach to derive the closed-form solutions in multilayer thin film structures in the elastic range. Subsequently, approximate solutions are obtained for very thin multilayer films. The condition that the film stress is of the same sign is identified for bilayer cases. The investigation is then extended into the elastic-plastic deformed films in bilayer structures. Closed-form solutions of the maximum, average, and minimum film stresses and curvatures are obtained for plastically deformed films. It is concluded that for an error within ±10% as compared with that of Stoney equation, it is required that the thickness ratio should be about 0.1 or less for whatever elastic or elastic-plastic analysis. In addition, the result of a case study reveals that the yield start point may be estimated as a linear function of temperature in the elastic-plastic deformation range.
Design and optimization of GaAs∕AlGaAs heterojunction infrared detectors
Authors: Esaev D. G. , Rinzan M. B. M. , Matsik S. G. , Perera A. G. U.
Published: October 2004

Design, modeling, and optimization principles for GaAs∕AlGaAs heterojunction interfacial workfunction internal photoemission (HEIWIP) infrared detectors for a broad spectral region are presented. Both n-type and p-type detectors with a single emitter or multiemitters, grown on doped and undoped substrates are considered. It is shown that the absorption, and therefore responsivity, can be increased by optimizing the device design. Both the position and the strength of the responsivity peaks can be tailored by varying device parameters such as doping and the thickness. By utilizing a resonant cavity architecture, the effect of a buffer layer on the response is discussed. Model results, which are in good agreement with the experimental results, predict an optimized design for a detector with a peak response of 9A∕W at 26μm with a zero response threshold wavelength λ0=100μm. For a λ0=15μm HEIWIP detector, background limited performance temperature (BLIP temperature), for 180° field of view (FOV) is expected around 80K. For a λ0=70μm optimized design, a highly doped n-type substrate could increase the peak detectivity from 1.7×1010to3.4×1010Jones at a FOV=180° operated at temperatures below T<TBLIP=13K. Intrinsic response times on the order of picoseconds are expected for these detectors.
Probe characterization of high-current driven metal plasma in a vacuum-arc rail gun
Authors: Vijayan T. , Roychowdhury P. , Venkatramani N.
Published: October 2004

The characteristics of metal plasma launched by high-current electric arc in a vacuum-arc rail gun are determined by employing electrical and magnetic probes. These measurements are validated by results from theoretical simulations. The arc coupled nonlinear circuit equations are solved simultaneously with the Newtonian arc motion and revealed the undercritically damped behavior of the arc current identical to the arc-current signal recorded by the Rogowski magnetic probe. Similarly the arc velocity and displacement derived from the signatures of B-dot probes are shown to concur closely with the results of J×B propulsion from simulation. The heating of plasma is formulated in a three-electron population regime with direct arc energy coupling through magnetohydrodynamic, ion-acoustic, Coulomb, and neutral interactions. This results in high temperature (Te) of hundreds of eV in the arc as revealed by the simulation. Hence Te of the rapidly cooling and equilibrating plasma that emerged from the muzzle is high around 80–90eV, which is confirmed by Langmuir electric probe measurements. Density ne of this metal plasma is shown to be in the range 4×1021–6×1021m−3 and includes multiple ion charge states. The exit velocity of the plasma measured by a pair of Langmuir probes is close to 2.2×106cm∕s and matched well with the arc velocity determined by the B-dot probes and the results from simulation.
Toroidal interferometer/polarimeter density measurement system on ITER
Authors: Kondoh T. , Costley A. E. , Sugie T. , Kawano Y. , Malaquias A. , Walker C. I.
Published: October 2004

In order to measure the line integrated electron density on the International Thermonuclear Experimental Reactor (ITER), a vibration-compensated five-channel CO2 laser interferometer/polarimeter system is being developed. The design of the interferometer/polarimeter has been improved from the previous design, which used a CO2 laser (wavelength, λ=10.6 μm) and a CO laser (λ=5.3 μm), on the basis of experience gained with a dual CO2 system (λ=10.6 and 9.27 μm) on JT−60U. The JT−60U system gives good reliability for both interferometry and polarimetry operation. The performance of the dual CO2 laser is expected to meet the requirements for measurements on ITER (accuracy; 1%, time resolution; 1 ms).
Nucleation versus spinodal decomposition in phase formation processes in multicomponent solutions
Authors: Schmelzer Jürn W. P. , Abyzov Alexander S. , Möller Jörg
Published: October 2004

In the present paper, some further results of application of the generalized Gibbs’ approach [J. W. P. Schmelzer et al., J. Chem. Phys. 112, 3820 (2000); 114, 5180 (2001); 119, 6166 (2003)] to describing new-phase formation processes are outlined. The path of cluster evolution in size and composition space is determined taking into account both thermodynamic and kinetic factors. The basic features of these paths of evolution are discussed in detail for a simple model of a binary mixture. According to this analysis, size and composition of the clusters of the newly evolving phase change in an unexpected way which is qualitatively different as compared to the classical picture of nucleation-growth processes. As shown, nucleation (i.e., the first stage of cluster formation starting from metastable initial states) exhibits properties resembling spinodal decomposition (the size remains nearly constant while the composition changes) although the presence of an activation barrier distinguishes the nucleation process from true spinodal decomposition. In addition, it is shown that phase formation both in metastable and unstable initial states near the classical spinodal may proceed via a passage of a ridge of the thermodynamic potential with a finite work of the activation barrier even though (for unstable initial states) the value of the work of critical cluster formation (corresponding to the saddle point of the thermodynamic potential) is zero. This way, it turns out that nucleation concepts—in a modified form as compared with the classical picture—may govern also phase formation processes starting from unstable initial states. In contrast to the classical Gibbs’ approach, the generalized Gibbs’ method provides a description of phase changes both in binodal and spinodal regions of the phase diagram and confirms the point of view assuming a continuity of the basic features of the phase transformation kinetics in the vicinity of the classical spinodal curve.
Spontaneous three-dimensional nanostructure formation of perfluoroalkyl terminated liquid crystal: A molecular dynamics simulation study
Authors: Yoneya Makoto , Nishikawa Etsushi , Yokoyama Hiroshi
Published: October 2004

Structure formation of a perfluoroalkyl terminated liquid crystal molecule was studied by molecular dynamics simulations. Two distinct structures with smectic-C-like layers and with bundles (blocks) of collapsed layers were spontaneously formed depending on the simulation temperatures. The bundles in the latter structure were somewhat positionally ordered (with respect to the small angle spots in its structure function) and orientationally isotropic overall even though the molecules making each bundle were well oriented. These characteristics of the simulated system well correspond to the cubic phase of the real system, and an even more precisely correspond to the proposed cubic structure model [M. Yoneya, E. Nishikawa, and H. Yokoyama, J. Chem. Phys. 120, 3699 (2004)] with respect to its hierarchical structure.
An optical-optical double resonance experiment in LiH molecules: Lifetime measurements in the C state
Authors: Bouloufa N. , Cabaret L. , Luc P. , Vetter R. , Luh W. T.
Published: October 2004

An optical-optical double resonance sub-Doppler experiment is used to measure short nonradiative lifetimes in the C 1Σ+ state of LiH. These lifetimes are expected to result from the strong electronic interaction between the C 1Σ+ state and the continuum of the A 1Σ+ state and to vary with the vibrational quantum number, from nanoseconds to milliseconds [F. Gemperlé and F. X. Gadéa, J. Chem. Phys. 110, 11197 (1999)]. The experimental setup combines a molecular beam of LiH, a first cw laser beam locked to a given A-X absorption line, and a second cw laser beam scanned over C-A absorption profiles. Analysis of these absorption profiles in terms of Voigt profiles shows that their Lorentzian components significantly vary with the vibrational quantum numbers of the C state. Nonradiative decay rates deduced this way are systematically larger than the calculated ones but their variations are similar. Coherent saturation effects cannot be invoked to explain this discrepancy.
Low-lying electronic states of the Ti2 dimer: Electronic absorption spectroscopy in rare gas matrices in concert with quantum chemical calculations
Authors: Hübner O. , Himmel H.-J. , Manceron L. , Klopper W.
Published: October 2004

Absorption spectra were measured for Ti2 in Ne and Ar matrices. The spectra give evidence for several electronic transitions in the region between 4000 and 10 000 cm−1 and provide important information about some excited electronic states of Ti2 in proximity to the ground state. The vibrational fine structure measured for these transitions allowed to calculate the force constants and the anharmonicity of the potential energy curves of the excited states, and to estimate changes in the internuclear Ti-Ti distances relative to the electronic ground state. The quantum chemical studies confirm the previously suggested Δ3g state as the ground state of Ti2. The equilibrium bond distance is calculated to be 195.4 pm. The calculated harmonic frequency of 432 cm−1 is in good agreement with the experimental value of 407.0 cm−1. With the aid of the calculations it was possible to assign the experimentally observed transitions in the region between 4000 and 10 000 cm−1 to the 1 3Πu←3Δg, 1 3Φu←3Δg, 2 3Πu←3Δg, 2 3Φu←3Δg, and Δ3u←Δ3g excitations (in the order of increasing energy). The calculated relative energies and harmonic frequencies are in pleasing agreement with the experimentally obtained values, with deviations of less than 5% and 2%, respectively. The bond distances estimated on the basis of the experimental spectra tally satisfactorily with the predictions of our calculations.
Thermally tunable filter for terahertz range based on a one-dimensional photonic crystal with a defect
Authors: Němec H. , Duvillaret L. , Garet F. , Kužel P. , Xavier P. , Richard J. , Rauly D.
Published: October 2004

A high-quality smart filter for terahertz range with relative tunability reaching 20% has been demonstrated. The filter is based on a narrow transmission band, which originates from a defect mode that appears due to insertion of a single crystal of KTaO3 into otherwise periodic one-dimensional photonic crystal. Frequencies of defect modes are controlled by the refractive index of the defect: their high tunability is achieved by the strong temperature dependence of the dielectric properties of KTaO3. The low losses of KTaO3 lead to a high peak transmission of the filter. Influence of the defect losses on the properties of the filter is also discussed.
Control and monitoring system for fusion neutron spectroscopy on the Joint European Torus
Authors: Tardocchi M. , Gorini G. , Palma D. , Sozzi C. , Källne J. , Conroy S. , Ericsson G. , Giacomelli L. , Glasser W. , Henriksson H. , Hjalmarsson A. , Ronchi E. , Sjöstrand H. , Weiszflog M. , Popovichev S. ,   JET-EFDA contributors
Published: October 2004

A new control and monitoring (C&M) system is being developed for the TOFOR and MPRu fusion neutron spectrometers within the Joint European Torus enhancement program. The system, which is an evolution of the existing C&M system of the MPR spectrometer, consists of a controlled pulsed light source distributed by an optical fiber network to all photomultiplier tubes used in the plastic scintillator based spectrometers. The light source is a green Nd:LSB solid-state laser complemented by blue light emitting diode sources. Pulse height distributions for each detection channel are recorded to set the spectrometers to prescribed working points and monitor deviations. Absolute reference is obtained complementing the controlled light source with radioactive sources. In this article we report on the C&M prototype design and component tests for the MPRu spectrometer. The results show that the laser and the associated optics provide a controlled light pulse of intensity covering a dynamic range of more than four orders of magnitude. The choice of optical fiber diameters is critical for achieving the desired stability and uniformity of the light intensity collected by each MPRu detector.
Heavy ion beam probe development for the plasma potential measurement on the TUMAN-3M tokamak
Authors: Askinazi L. G. , Kornev V. A. , Lebedev S. V. , Tukachinsky A. S. , Zhubr N. A. , Dreval N. B. , Krupnik L. I.
Published: October 2004

The peculiarities of the heavy ion beam probe implementation on the small aspect ratio tokamak TUMAN-3M are analyzed. The toroidal displacement of beam trajectory due to the high Ipl/Btor ratio is taken into account when designing the layout of the diagnostic. Numerical calculation of beam trajectories using realistic configuration of TUMAN-3M magnetic fields and parabolic plasma current profile resulted in proper adjustment of probing and detection parameters (probing ion material, energy, entrance angles, detector location, and orientation). Secondary ion energy analyzer gain functions G and F were measured in situ using neutral hydrogen puffed in the tokamak vessel as a target for secondary ions production. The detector unit featured split-plate design and had additional electrodes for secondary electron emission suppression. As a result, the diagnostic is now capable of plasma potential evolution measurement and is sensitive enough to trace the potential profile evolution at the L-H mode transition.
Mixed-sector intermediate Hamiltonian Fock-space coupled cluster approach
Authors: Landau Arie , Eliav Ephraim , Ishikawa Yasuyuki , Kaldor Uzi
Published: October 2004

An alternative formulation of the intermediate Hamiltonian Fock-space coupled cluster scheme developed before is presented. The methodological and computational advantages of the new formulation include the possibility of using a model space with determinants belonging to different Fock-space sectors. This extends the scope of application of the multireference coupled cluster method, and makes possible the use of quasiclosed shells (e.g., p2, d4) as reference states. Representative applications are described, including electron affinities of group-14 atoms, ionization potentials of group-15 elements, and ionization potentials and excitation energies of silver and gold. Excellent agreement with experiment (a few hundredths of an electronvolt) is obtained, with significant improvement (by a factor of 5–10 for p3 states) over Fock-space coupled cluster results. Many states not reachable by the Fock-space approach can now be studied.
Time-dependent four-component relativistic density functional theory for excitation energies
Authors: Gao Jun , Liu Wenjian , Song Bo , Liu Chengbu
Published: October 2004

Time-dependent four-component relativistic density functional theory within the linear response regime is developed for calculating excitation energies of heavy element containing systems. Since spin is no longer a good quantum number in this context, we resort to time-reversal adapted Kramers basis when deriving the coupled Dirac-Kohn-Sham equation. The particular implementation of the formalism into the Beijing density functional program package utilizes the multipolar expansion of the induced density to facilitate the construction of the induced Coulomb potential. As the first application, pilot calculations on the valence excitation energies and fine structures of the rare gas (Ne to Rn) and Group 12 (Zn to Hg) atoms are reported. To the best of our knowledge, it is the first time to be able to account for spin–orbit coupling within time-dependent density functional theory for excitation energies.
Photoassociation spectroscopy of ultracold Cs below the 6P3/2 limit
Authors: Pichler Marin , Chen Hongmin , Stwalley William C.
Published: October 2004

High precision photoassociation spectroscopy is performed in ultracold cesium gas, with detunings as large as 51 cm−1 below the Cs(6S1/2)+Cs(6P3/2) asymptote. Trap-loss fluorescence detection is used for detecting the photoassociation to excited state ultracold molecules. Long vibrational progressions are assigned to electronic states of 0g−, 0u+, and 1g symmetry. The spectral data are fitted to a LeRoy-Bernstein equation, in order to obtain the effective coefficients of the leading long-range interaction term (C3/R3) and the relative vibrational quantum numbers measured down from dissociation. Additionally we present evidence for perturbations between the 0g− state and the dark 2u state.
Utility of a baffled Langmuir probe for applications to edge plasma and turbulence characterization in stellarator plasma
Authors: Guttenfelder W. , Lechte C. , Koepke M. E. , Demidov V. I.
Published: October 2004

Baffles are obstacles that shield plasma electrons from being collected by a floating probe by virtue of a small electron gyroradius compared to a large ion gyroradius. A baffled probe floats at space potential if the baffling results in equal electron and ion saturation currents. With such a probe, potential fluctuations can be monitored locally with minimal plasma perturbation. The performance is documented in the edge of a stellarator plasma.