bluuebunny/crossref_metadata_2025 huggingface dataset:
A new Greenland ice core chronology for the last glacial termination
Authors: Rasmussen S. O. , Andersen K. K. , Svensson A. M. , Steffensen J. P. , Vinther B. M. , Clausen H. B. , Siggaard‐Andersen M.‐L. , Johnsen S. J. , Larsen L. B. , Dahl‐Jensen D. , Bigler M. , Röthlisberger R. , Fischer H. , Goto‐Azuma K. , Hansson M. E. , Ruth U.
Published: March 2006

We present a new common stratigraphic timescale for the North Greenland Ice Core Project (NGRIP) and GRIP ice cores. The timescale covers the period 7.9–14.8 kyr before present and includes the Bølling, Allerød, Younger Dryas, and early Holocene periods. We use a combination of new and previously published data, the most prominent being new high‐resolution Continuous Flow Analysis (CFA) impurity records from the NGRIP ice core. Several investigators have identified and counted annual layers using a multiparameter approach, and the maximum counting error is estimated to be up to 2% in the Holocene part and about 3% for the older parts. These counting error estimates reflect the number of annual layers that were hard to interpret, but not a possible bias in the set of rules used for annual layer identification. As the GRIP and NGRIP ice cores are not optimal for annual layer counting in the middle and late Holocene, the timescale is tied to a prominent volcanic event inside the 8.2 kyr cold event, recently dated in the DYE‐3 ice core to 8236 years before A. D. 2000 (b2k) with a maximum counting error of 47 years. The new timescale dates the Younger Dryas‐Preboreal transition to 11,703 b2k, which is 100–150 years older than according to the present GRIP and NGRIP timescales. The age of the transition matches the GISP2 timescale within a few years, but viewed over the entire 7.9–14.8 kyr section, there are significant differences between the new timescale and the GISP2 timescale. The transition from the glacial into the Bølling interstadial is dated to 14,692 b2k. The presented timescale is a part of a new Greenland ice core chronology common to the DYE‐3, GRIP, and NGRIP ice cores, named the Greenland Ice Core Chronology 2005 (GICC05). The annual layer thicknesses are observed to be log‐normally distributed with good approximation, and compared to the early Holocene, the mean accumulation rates in the Younger Dryas and Bølling periods are found to be 47 ± 2% and 88 ± 2%, respectively.
Carbon emissions from a temperate peat fire and its relevance to interannual variability of trace atmospheric greenhouse gases
Authors: Poulter Benjamin , Christensen Norman L. , Halpin Patrick N.
Published: March 2006

The contribution of wildfire in peatlands outside of boreal and tropical regions to interannual variability of global carbon emissions has been relatively little studied. There are 0.19 to 0.88 million km2of localized peat deposits in the temperate zone (30–50° latitude) where drainage and climate change may affect the status of this potentially large carbon pool. For example, in the coastal plain of North Carolina, USA, where wildfire is common, over 325 teragrams of carbon (Tg C) are stored in peat deposits up to 5 m deep. We estimated carbon emissions for a temperate peatland fire in North Carolina using remote sensing to reconstruct burn severity and topographic lidar to constrain peat burn depths. Total carbon emissions for the fire ranged from 1 to 3.8 Tg, with spatially heterogeneous patterns of carbon fluxes (0.2 to 11 kg C m−2) responding to variation in vegetation type, peat burn depth, soil substrate (mineral or organic), and fire severity. To maintain a carbon sink in this region at the current rates of carbon sequestration (0.109 to 0.127 kg C m−2yr−1) we estimated a fire return interval of greater than 20–80 years. Continued drainage and future drought could decrease the fire return interval to less than 20 years or increase peat burn depths thereby converting these peatlands into a net carbon source. On a global scale, this study suggests that temperate peatland fires may emit up to 0.32 petagrams of carbon during drought years, a significant contribution to interannual greenhouse gas variability.
Residues in the first transmembrane domain of theCaenorhabditis elegansGABAAreceptor confer sensitivity to the neurosteroid pregnenolone sulfate
Authors: Wardell Bryan , Marik Purba S , Piper David , Rutar Tina , Jorgensen Erik M , Bamber Bruce A
Published: March 2006

The GABAAreceptor is a target of endogenous and synthetic neurosteroids. Little is known about the residues required for neurosteroid action on GABAAreceptors. We have investigated pregnenolone sulfate (PS) inhibition of theCaenorhabditis elegansUNC‐49 GABA receptor, a close homolog of the mammalian GABAAreceptor.

The UNC‐49 locus encodes two GABA receptor subunits, UNC‐49B and UNC‐49C. UNC‐49C is sensitive to PS but UNC‐49B is not sensitive. By analyzing chimeric receptors and receptors containing site‐directed mutations, we identified two regions required for PS inhibition.

Four residues in the first transmembrane domain are required for the majority of the sensitivity to PS, but a charged extracellular residue at the end of the M2 helix also plays a role. Strikingly, mutation of one additional M1 residue reverses the effect of PS from an inhibitor to an enhancer of receptor function.

Mutating the M1 domain had little effect on sensitivity to the inhibitor picrotoxin, suggesting that these residues may mediate neurosteroid action specifically, and not allosteric regulation in general.

British Journal of Pharmacology(2006)148, 162–172. doi:10.1038/sj.bjp.0706719
The in vivo synaptic plasticity mechanism of EGb 761‐induced enhancement of spatial learning and memory in aged rats
Authors: Wang Yongfu , Wang Lei , Wu Jing , Cai Jingxia
Published: March 2006

It has not been uniform to date that the Ginkgo biloba extracts enhance cognitive function in aged animals, and the mechanisms of action remain difficult to elucidate. In this study, the Morris water maze task and electrophysiological methods were used to study the effects of repeated daily administration of EGb 761, a standardized extract from G. biloba leaves, on hippocampal‐dependent spatial learning and memory and synaptic plasticity of aged rats.

The adult subjects perform the Morris water maze task better than aged rats, as a cellular mechanism, the hippocampal long‐term potentiation (LTP) elicited from adult animals is robust (139.29±2.7%).

In addition, the spatial learning and memory of aged rats that had been fed on an EGb 761‐supplemented diet (60 mg kg−1) for 30 days were significantly better than those of control aged rats. The magnitude of LTP (116.63±3.6%) recorded in vivo from the hippocampus CA1 area of aged rats was significantly enhanced by EGb 761 (60 mg kg−1).

In conclusion, the spatial learning and memory of aged rats is worse than that of young subjects, and EGb 761, acting as a ‘cognitive enhancer’, has benefit on synaptic plasticity and cognition in aged rats. The present data further confirmed that enhancement of synaptic plasticity of the hippocampus might ameliorate the deficit in spatial learning and memory in aged rats.

British Journal of Pharmacology (2006) 148, 147–153. doi:10.1038/sj.bjp.0706720
Characterization of TRIUMF dc H− ion sources for enhanced brightness
Authors: Hwang Y. S. , Cojocaru G. , Yuan D. , McDonald M. , Jayamanna K. , Kim G. H. , Dutto G.
Published: March 2006

At TRIUMF, H− ion sources have been characterized on a teststand to improve the understanding of their performance. Measured beam characteristics such as current, emittance, and e∕H− ratio were correlated with source conditions as a function of relevant plasma parameters. Plasma densities, temperatures, and plasma potentials were measured with a Langmuir probe and correlated with beam properties for different confining magnetic fields and different values of arc power and gas pressure. The mechanism of beam extraction was studied by correlating plasma potential profiles with the corresponding plasma electrode bias voltages obtained from optimizing ion source outputs. Experiments with collar biasing and noble gas mixing were unsuccessful because of undesirable plasma potential profiles.
Status report on the design and construction of the Superconducting Source for Ions at the National Superconducting Cyclotron Laboratory/Michigan State University
Authors: Zavodszky P. A. , Arend B. , Cole D. , DeKamp J. , Machicoane G. , Marti F. , Miller P. , Moskalik J. , Ottarson J. , Vincent J. , Zeller A. , Kazarinov N. Yu.
Published: March 2006

A status report of the design and fabrication of a new, fully superconducting electron cyclotron resonance ion source will be presented. The Superconducting Source for Ions (SuSI) first will operate at 18+14.5GHz microwave frequencies. A short description of the magnet structure and the injection and extraction hardware will be presented. Several innovative solutions are described, which will allow maximum flexibility in tuning SuSI in order to match the acceptance of the coupled cyclotrons. Details of an ultrahigh temperature inductive oven construction are given as well as a description of the low-energy beam transport line.
Negative-ion implantation into thin SiO2 layer for defined nanoparticle formation
Authors: Tsuji Hiroshi , Arai Nobutoshi , Gotoh Naoyuki , Minotani Takashi , Ishibashi Toyoji , Okumine Tetsuya , Adachi Kouichiro , Kotaki Hiroshi , Gotoh Yasuhito , Ishikawa Junzo
Published: March 2006

Two methods to form nanoparticles at a certain depth in a thin oxide layer by negative-ion implantation into the oxide layer of silicon substrate have been investigated. One method is by implantation at a low energy and the other is by a thermal diffusion after implantation. Regarding the low-energy implantation, about 1keV of ion energy is required. In general, a surface charge-up of the oxide layer arises from a positive-ion implantation to affect ion penetration depth. In this research, we used negative ion implantation because of its advantage of almost “charge-up-free” feature, even for insulating materials. We obtained delta-layered gold nanoparticles (Au NPs) in a 25nm thick SiO2 layer on Si by the low-energy implantation method of gold negative ions at 1keV. The center depth and an average diameter of the delta-layered Au NPs were 5nm and 7nm, respectively. As by the thermal diffusion after implantation, silver negative ions were implanted into 25nm thick SiO2∕Si at 10keV with 5×1015ions∕cm2 at room temperature. Implanted atoms diffused from the implanted site, depending on annealing temperature. Only after annealing at 700°C, delta-layered silver nanoparticles (Ag NPs) were obtained near the interface of SiO2∕Si.
ECRIS operation with multiple frequencies
Authors: Vondrasek R. C. , Scott R. , Pardo R. C.
Published: March 2006

The 10.5GHz electron cyclotron resonance ion source (ECRIS) at Argonne National Laboratory has been utilizing a 10.5GHz klystron and an 11–13GHz traveling wave tube amplifier (TWTA) for beam production in two-frequency heating mode. The beam intensities obtained from the source with two-frequency heating have shown a factor of 2 improvement over single-frequency heating for the higher charge states. Following a simple logic that an increased number of resonance zones leads to enhanced source performance, a 14GHz klystron was added to the source configuration enabling the plasma to be simultaneously excited with three discrete frequencies. In studies with three-frequency heating when compared to two-frequency heating, the beam intensity for O7+ increased from 70.4to84.2eμA, Kr23+ (mass 86, 99.9% enriched) increased from 3.5to7.2eμA, and Xe28+ (mass 136, 60% enriched) increased from 7.9to12.2eμA. A rf power combiner was added to the TWTA so that it could be driven simultaneously with two frequencies. With the TWTA operating at 10.85 and 12.66GHz, the intensities of O6+ increased 80% and O7+ doubled compared to single-frequency operation, further demonstrating the multiple frequency heating effect except in this instance with a single transmitter.
H
−
extraction from electron-cyclotron-resonance-driven multicusp volume source operated in pulsed mode
Authors: Svarnas P. , Bacal M. , Auvray P. , Béchu S. , Pelletier J.
Published: March 2006

H 2 microwave (2.45GHz) pulsed plasma is produced from seven elementary electron cyclotron resonance sources installed into the magnetic multipole chamber “Camembert III” (École Polytechnique—Palaiseau) from which H− extraction takes place. The negative-ion and electron extracted currents are studied through electrical measurements and the plasma parameters by means of electrostatic probe under various experimental conditions. The role of the plasma electrode bias and the discharge duty cycle in the extraction process is emphasized. The gas breakdown at the beginning of every pulse gives rise to variations of the plasma characteristic parameters in comparison with those established at the later time of the pulse, where the electron temperature, the plasma potential, and the floating potential converge to the values obtained for a continuous plasma. The electron density is significantly enhanced in the pulsed mode.
Charge state breeding of radioactive ions with an electron cyclotron resonance ion source at TRIUMF
Authors: Ames F. , Baartman R. , Bricault P. , Jayamanna K. , McDonald M. , Olivo M. , Schmor P. , Yuan D. H. L. , Lamy T.
Published: March 2006

Efficient primary ion sources at ISOL facilities normally produce singly charged ions. This limits the usable mass range for postacceleration due to the A∕Q acceptance of the accelerator. At the ISAC facility at TRIUMF an A∕Q below 7 is desired to avoid further stripping. Thus, charge state breeding is necessary if higher masses are to be accelerated. A 14 GHz ECRIS “PHOENIX” booster has been chosen as a breeder. In order to investigate and optimize its performance under ISAC conditions it has been set up at a test bench equipped with a standard ISAC target-ion-source to produce singly charged ions. A series of measurements has been performed with the noble gases Ar, Kr, and Xe. Efficiencies of more than 6% in the maximum of the charge state distribution after mass separation have been obtained and the emittance of the extracted beam and breeding times have been measured. This article gives a status report on the ongoing measurements.
KVI Lamb-shift polarimeter
Authors: Beijers J. P. M. , Kremers H. R. , Kalantar-Nayestanaki N.
Published: March 2006

The design and operation of a Lamb-shift polarimeter is discussed. This polarimeter is used to measure the polarization of proton and deuteron beams extracted from the KVI polarized-ion source. The major components of the Lamb-shift polarimeter (LSP) are described in some detail. These include the deceleration lens system, cesium neutralization oven, spin filter, metastable-atom detection system, and the solenoid. Typical operating parameters of the LSP will be given together with some representative spin-polarization measurements. The design criterion of measuring the polarization of a H+ or D+ beam within 60 s and with a statistical uncertainty smaller than 2% has been met.
Development of a plasma ion source for next-generation facilities
Authors: Cheikh Mhamed M. , Lau C. , Essabaa S. , Arianer J. , Bajeat O. , Croizet H. , Ducourtieux M. , Lefort H.
Published: March 2006

The ionization by radial electron neat adaptation (IRENA) ion source has been designed to operate under unprecedented radiation conditions generated by next-generation facilities such as SPIRAL-2 and EURISOL. The design and development of this next-generation-facility ion source will be presented and discussed.
Improvement of beam uniformity by magnetic filter optimization in a Cs-seeded large negative-ion source
Authors: Hanada M. , Seki T. , Takado N. , Inoue T. , Tobari H. , Mizuno T. , Hatayama A. , Dairaku M. , Kashiwagi M. , Sakamoto K. , Taniguchi M. , Watanabe K.
Published: March 2006

The influence of magnetic filter configuration on the beam uniformity was examined to improve beam uniformity in a large Cs-seeded negative-ion source. By reducing the filter strength of the transverse magnetic field used in a typical negative-ion source, the beam uniformity was largely improved with the improvement of the plasma uniformity while the beam intensity was kept to be nearly constant. However, the coextracted electron current greatly increased. To suppress the coextracted electron current, a tent-shaped magnetic filter was applied together with modifications in the cusp magnets to form a typical multicusp positive-ion source arrangement. The uniformity in longitudinal beam profile was improved with the deviation of local beam intensity within 16% that was nearly equal to the deviation obtained at 50Gcm of the transverse filter strength. In the meantime, the coextracted electron current was kept to be the same as the H− ion current. The present result suggests that the uniformity of H− ion-beam profile is affected by the uniformity of atoms or protons in the source plasma, which are the primary species of negative ions under Cs-seeded surface production.
Plasma diagnostic tools for optimizing negative hydrogen ion sources
Authors: Fantz U. , Falter H. D. , Franzen P. , Speth E. , Hemsworth R. , Boilson D. , Krylov A.
Published: March 2006

The powerful diagnostic tool of optical emission spectroscopy is used to measure the plasma parameters in negative hydrogen ion sources based on the surface mechanism. Results for electron temperature, electron density, atomic-to-molecular hydrogen density ratio, and gas temperature are presented for two types of sources, a rf source and an arc source, which are currently under development for a neutral beam heating system of ITER. The amount of cesium in the plasma volume is obtained from cesium radiation: the Cs neutral density is five to ten orders of magnitude lower than the hydrogen density and the Cs ion density is two to three orders of magnitude lower than the electron density in front of the grid. It is shown that monitoring of cesium lines is very useful for monitoring the cesium balance in the source. From a line-ratio method negative ion densities are determined. In a well-conditioned source the negative ion density is of the same order of magnitude as the electron density and correlates with extracted current densities.
Development of an H−-ion source for the high-intensity proton accelerator (J-PARC)
Authors: Oguri H. , Ueno A. , Namekawa Y. , Ikegami K.
Published: March 2006

A cesium-free tungsten-driven H−-ion source was fabricated and is under testing for the Japan Proton Accelerator Research Complex. Optimization of the filament shape and the positions of the plasma confinement and electron suppression magnets is being performed. An H−-ion beam of 28mA was obtained at an arc discharge power of 40kW. The emittance was measured for an H−-ion beam with 50keV energy and 20mA intensity. The measured values of the normalized rms emittance were 0.18 (horizontal plane) and 0.15 (vertical plane) πmmmrad.
Enhancement of H− extraction from a compact source by streaming neutral gas injection
Authors: Mendenilla Alexander , Takahashi Hidenori , Kasuya Toshiro , Wada Motoi
Published: March 2006

A new negative ion extraction geometry with streaming neutral gas injector (SNGI) was tested in its performance to enhance negative hydrogen ion (H−) at low operational pressure. The experiments were performed using a test ion source equipped with a SNGI having the wall perpendicular to the gas emission holes. The results showed that the SNGI was capable of reducing the operating pressure of the ion source from 0.14to0.07Pa. At 0.14Pa, the operation using the SNGI produced 20% more negative ions than the operation without SNGI. A compact ion source was constructed with a smaller SNGI and having a tapered wall for the gas injection nozzles. The neutral density distribution within the central region of the SNGI within the ion source was simulated using direct simulation Monte Carlo (DSMC) method. It was realized that the neutral density distribution produced by the SNGI with the tapered wall was at most 35% lower than a SNGI structure without the taper.
Improved ion extraction from an electron cyclotron resonance ion source by a metal-dielectric-extraction electrode
Authors: Schachter L. , Dobrescu S. , Stiebing K. E.
Published: March 2006

The goal of the experiment was to study the influence and the physics of the boundary region (between the plasma and the extraction potential) with direct impact on the source ion-beam output. A specially processed high-emissive metal-dielectric structure was installed on the extraction electrode of the Frankfurt 14GHz electron cyclotron resonance ion source (ECRIS), forming a so-called metal-dielectric- (MD) extraction electrode. The emissive layer of the disk faced the plasma; its inner hole was about the size of the normal extraction hole of the ECRIS. The output of the ECRIS in the presence of the MD electrode was compared with the outputs for the standard configuration (overall stainless-steel plasma chamber) and with the same plasma chamber with the radial wall covered by a highly electron emissive MD liner that raise the plasma electron density and temperature. The charge state distributions of the argon ions extracted from the source show an important increase of the ion beam for the high charge states as compared to the standard situation whereas the low charge states are less reduced than in the case of the presence of a MD liner. Due to the special position of the dielectric layer, the MD electrode introduces a new effect, which is connected to its property of becoming a positively charged surface under electron and ion bombardment. The MD electrode creates a quasiconfinement of the peripheral ions in the extraction, those ions that are normally lost to a conducting extraction electrode.
H
−
source developments at CERN
Authors: Hill C. E. , Küchler D. , Mastrostefano C. , O’Neil M. , Scrivens R. , Steiner T.
Published: March 2006

Future CERN programs for the large hadron collider (LHC) and the isotope online separator (ISOLDE) require increasing the beam intensity and brightness from the proton synchrotron booster (PSB). This could be achieved by charge-exchange injection with phase-space painting into the PSB acceptance from a higher energy H− linac. A new injector will require a high performance, high reliability, negative hydrogen-ion source. This article will present the results achieved so far with a prototype microwave-driven source operated with three different magnetic structures (multicusp, solenoidal, and a combination of both). The experiments were carried out with different mixing gases, different chamber inserts, and under a wide range of operational conditions.
Intensity improvements of pulsed source of polarized negative hydrogen ions
Authors: Belov A. S. , Netchaeva L. P. , Turbabin A. V.
Published: March 2006

The intensity of a polarized negative hydrogen ion source of the Institute for Nuclear Research of the Russian Academy of Sciences has been increased due to the decrease of the destruction of polarized negative hydrogen ions in plasma ionizer and the improvements in the atomic beam stage of the source. A polarized H− ion current of 3.8mA peak with pulse duration of 170μs full width at half maximum at 5Hz repetition rate has been obtained. An unpolarized D− ion current extracted from the plasma ionizer together with a polarized ion beam was 70mA, and the respective electron current was ∼150mA. The efficiency of the conversion of polarized hydrogen atoms into polarized negative hydrogen ions reached 12%. The polarization of the H− beam has been measured to be 0.91±0.03. The figure of merit P2I of the polarized negative hydrogen ion beam obtained has record value of 3.15mA.
Comparison of particle-in-cell simulation with experiment for the transport system of the superconducting electron cyclotron resonance ion source VENUS
Authors: Todd D. S. , Leitner D. , Leitner M. , Lyneis C. M. , Qiang J. , Grote D. P.
Published: March 2006

The three-dimensional, particle-in-cell code WARP has been enhanced to allow end-to-end beam dynamics simulations of the VENUS beam transport system from the extraction region, through a mass-analyzing magnet, and up to a two-axis emittance scanner. This article presents the first results of comparisons between the simulation and experimental data. A helium beam (He+ and He2+) is chosen as an initial comparison beam due to its simple mass spectrum. Although a number of simplifications are made for the initial extracted beam, aberration characteristics appear in simulations that are also present in experimental phase-space current-density measurements. Further, measurements of phase-space tilt indicate that simulations must have little or no space-charge neutralization along the transport system to best agree with experiment. In addition, recent measurements of triangular beam structure immediately after the source are presented. This beam structure is related to the source magnetic confinement fields and will need to be taken into account as the initial beam approximations are lifted.
Direct 1+ to n+ method for production of radioactive alkaline ions
Authors: Eleon C. , Tuske O. , Gaubert G. , Pacquet J. Y. , Dubois M. , Saint Laurent M. G. , Jardin P. , Cornell J. , Leroy R. , Villari A. C. C. , Maunoury L.
Published: March 2006

In the frame of the production of radioactive ion beams by isotope separator on line method, a new principle of target∕ion-source system has been developed at GANIL to produce multicharged ions of alkalis. The principle consists of a surface ionization source associated to a multicharged electron-cyclotron-resonance ion source (ECRIS) named NANOGAN III [R. Leroy et al., AIP Conf. Proc. 749, 137 (2004)] presently used to produce radioactive ions of gas on Système de Production d’Ions Radioactifs Accélérés en Ligne partie I. The singly charged ions are injected in the multicharged ion source without mass separation, through a very short beam line including several stages of acceleration, focusing, deceleration, and rf injection. The first tests showed a good behavior of the ECRIS with the new rf coupling. A study of the surface ionization source is in progress in order to improve its coupling to the 1+ beam line.
Bias voltage and corrosion effects in rf ovens in electron cyclotron resonance ion source
Authors: Cavenago M. , Galatá A. , Kulevoy T. , Petrenko S.
Published: March 2006

Induction-heated miniaturized ovens were successfully coupled to electron cyclotron resonance ion sources for the production of copper and silver ion beams. Experiments with tin and praseodymium ion beams are here presented; some preliminary tests for titanium are also described. In the latter case (and in general over a 1800K temperature) a molybdenum rf coil is used. The results with tin show currents comparable to silver (after obvious correction for isotopic abundance), with some operational difficulty due to frequent pouring of liquid sample out of crucible. The effects of a bias voltage Vb applied to the Sn sample are reported. Cold sputter probes are compared. The results with praseodymium show lower currents than tin and large sensitivity to mixing gas used: nitrogen emerged as the best compromise against oxygen (possibly because this oxidizes the sample) and against inert noble gases. Optimal bias voltage for Pr (Vb from −50to−300V) is much smaller than for silver (Vb≅−1kV).
Electrostatics of nanowire transistors with triangular cross sections
Authors: Vashaee Daryoosh , Shakouri Ali , Goldberger Joshua , Kuykendall Tevye , Pauzauskie Peter , Yang Peidong
Published: March 2006

The electrostatic properties of nanowire field effect transistors with triangular cross sections were investigated. The Poisson equation was solved for these structures; furthermore, two properties of the nanowire field effect transistors, the gate capacitance and current versus gate voltage, were calculated. The simulation results yielded the type, mobility, and concentration of the carriers, as well as the Ohmic contact resistance of the wire transistor. We examined how wire capacitance depends on various parameters: wire diameter, gate oxide thickness, charge density, and shape. It is shown that the capacitance of a triangular nanowire is less than that of a cylindrical nanowire of the same size, which could be significant in structures with thin gate oxides. The simulation results were compared with the previously reported experimental data on GaN nanowires.
Global equilibrium in electron cyclotron resonance ion sources
Authors: Cavenago M.
Published: March 2006

In electron cyclotron resonance ion sources (ECRISs) the neutral gas density ng is typically smaller than the plasma density, which is the opposite of many other source cases, for example, radio-frequency ion source for H (plus or minus) production. For the latter, a global model of equilibrium between ambipolar diffusion and ionization gives a firm prediction of the electron temperature Th. With the purpose of obtaining firm predictions also for ECRIS plasmas, the difficulty of a highly charged ion distribution and of a more complicated model of ambipolar potential ϕ is here taken into account. Using an approximate solution for the highly charged ion density, the global balance equations are written and discussed as a function of ϕ, of the gas density ng, and of the electron temperature Th. Some examples of the application of equilibrium balance laws to a typical ECRIS are given.
Cybele: A large size ion source of modular construction for the Tore-Supra diagnostic injector
Authors: Simonin A. , Garibaldi P.
Published: March 2006

A 70keV 40A hydrogen beam injector has been developed at Cadarache for plasma diagnostic purpose (MSE and charge exchange) on the Tore-Supra tokamak. This injector routinely operates with a large size ion source (the so-called Pagoda ion source) which does not completely fulfill all the requirements necessary for the present experiments. As a consequence, the development of a new ion source (called Cybele) has been underway whose objectives are a high accelerated proton fraction (>80%), current density of 160mA∕cm2, and uniform illumination of the extraction surface (within ±5%) for long shot operation (from 1to100s). The main particularity of Cybele is the modular construction; it is composed of five, vertically juxtaposed modules, geometrically arranged to fit the curved extraction surface of the injector, which ensures the geometrical focusing of the neutral beam 7m downstream, at the entrance to the tokamak. Cybele will be tested first for positive-ion production for the Tore-Supra injector and later in negative-ion production mode; its modular concept could be advantageous to ensure plasma uniformity over the very large extraction surface (∼1m2) of the ITER neutral beam injector. A prototype module (the Drift source) has already been developed and optimized [A. Simomin et al., Rev. Sci. Instrum. 70, 4542 (1999)] both for positive- and negative-ion productions. It has met the ITER ion source requirements in terms of D− current density (200A∕m2), source pressure (0.3Pa), uniformity, and arc efficiency (0.015AD−∕kW).
Advanced direct current negative-ion source for accelerator use
Authors: Belchenko Yu. , Gusev I. , Khilchenko A. , Kvashnin A. , Rashchenko V. , Sanin A. , Savkin V. , Zubarev P.
Published: March 2006

Status of direct current hydrogen negative-ion source development for tandem accelerator is described. The electrodes enforcing its water cooling and introducing of the electrons’ interception permitted to increase the source discharge power and to obtain regularly the H−-ion beam with energy >25kV and current up to 15mA.
New developments in rf-driven multicusp H− ion sources
Authors: Peters J.
Published: March 2006

rf H− sources are in permanent use for accelerators such as HERA and the SNS. The stability and H− current of these sources depend very much on the transition region between plasma and extractor. The physics of the extraction plasma region was the subject of very detailed investigations with special sets of collars, cones, and Langmuir probe measurements. The measured changes in H− current depend on the dimensions of the inserts in the transition region. They are summarized in a graph in order to make them compar able to measurements done in Japan and USA. Recently it was possible to measure the H− distribution in a rf source both with and without extraction voltage for the first time.
High current carbon beam production with direct plasma injection scheme
Authors: Okamura Masahiro , Kashiwagi Hirotsugu , Sakakibara Kazuhiko , Takano Jumpei , Hattori Toshiyuki , Hayashizaki Noriyosu , Jameson Robert A. , Yamamoto Kazuo
Published: March 2006

We have been studying a new heavy-ion production technique called “direct plasma injection scheme,” DPIS, since 2000. A new radio frequency quadrupole (RFQ) designed especially for the DPIS was commissioned in 2004 and very intense carbon beam was successfully obtained, reaching more than 60mA accelerated current from the RFQ. Most of the contents of the accelerated beam was carbon 4+ as verified by beam analysis.
Temperature measurements in plasmas produced by high-power lasers interacting with solid targets
Authors: Torrisi L. , Gammino S. , Picciotto A. , Margarone D. , Laska L. , Krasa J. , Rohlena K. , Wolowski J.
Published: March 2006

One of the main goals of the study of plasmas generated by short or ultrashort laser pulses is the estimation of a complex parameter as the evaluation of the plasma temperature. Considering the laser-target and laser-plasma interactions as nonequilibrium processes, it is not possible to define a unique plasma temperature because the behavior of the different subsystems such as ions, electrons, neutral particles, and photons is not uniformly correlated, and the physical parameters can be different in different values of the plasma plume. In this work different experimental setups and techniques and different empirical and theoretical approaches are compared by using a Nd:YAG laser with an intensity of 1010W∕cm2 and an iodine laser with an intensity of 1015–1016W∕cm2. Time-of-flight measurements have been performed with an ion-energy analyzer and by using a number of Faraday cups in order to measure the velocity and the kinetic energy of ions and electrons emitted by the plasma. The obtained results have been relevant to confirm that by using a Nd:YAG laser the plasma ion temperature in the plasma core is about 400eV. The electron emission indicates the presence of hot electrons with an energy of about 1keV. These results will be compared with the ones obtained with the powerful iodine laser at Prague Asterix Laser System.
Particle-in-cell modeling of negative-ion transport and extraction processes in a hydrogen negative-ion source
Authors: Hatayama A. , Matsumiya T. , Sakurabayashi T. , Bacal M.
Published: March 2006

To understand the effect of the magnetic field on the H− extraction, the temporal behavior and spatial structure of the electrostatic potential near the plasma grid have been studied in detail by particle-in-cell simulation in the collisionless limit. Also, a parameter study of the dependence of the extracted H− current on the magnetic field has been done. The results show that the intrinsic physical mechanism to enhance H− extraction is possibly explained by the difference in dynamics between electrons and ions and by the resultant ambipolar electric field under the presence of the “weak” magnetic field.
Numerical modeling of the transport process of negative-ion plasmas in photodetachment measurement
Authors: Mizuno T. , Nakata S. , Takado N. , Matusmiya T. , Sakurabayashi T. , Hatayama A. , Bacal M.
Published: March 2006

In order to measure negative-ion temperature, the experimental result of the negative-ion recovery ratio from the two-laser photodetachment is usually fitted with the theoretical curve derived from the ballistic kinetic theory of negative ions. The particle-in-cell (PIC) code with a one-dimensional slab model has been developed to analyze the effect of the ambipolar electric field, which is neglected in the ballistic theory, on the negative-ion recovery. The preliminary results of the PIC simulation indicate that our PIC code is a useful tool for the analyses of the negative-ion recovery in the photodetachment.
Cavity nucleation and delamination during adhesive transfer of a thin viscoelastic film
Authors: McSwain Rachel L. , Shull Kenneth R.
Published: March 2006

A model acrylic copolymer system was used to study the processes involved in the transfer of a thin viscoelastic film from a weakly adhesive elastomeric substrate to a more strongly adhesive surface. The film consisted of a layer of acrylic diblock copolymer micelles that was spun cast onto a silicone elastomer from a suspension in butanol. A circular portion of the layer was transferred to a hemispherical glass indenter with which it was brought into contact. The transfer of the film during tensile loading of the indenter began with nucleation of a cavity at the film/elastomer interface and was followed by delamination of the film at this interface. Statistical variations in cavity nucleation for identical loading conditions were quantified by defining a Weibull modulus similar to that used to describe the failure of brittle materials. The average energy release rate required for cavity nucleation at a fixed induction time increased with film thickness in a way that is consistent with the existence of a critical value of the hydrostatic tension at the film/substrate interface. This critical hydrostatic tension was comparable in magnitude to the elastic modulus of the substrate and was about ten times the elastic modulus of the thin film.
Electron beam ion source for highly charged ion production in a continuous regime
Authors: Kuznetsov G. , Batazova M.
Published: March 2006

It seems feasible to strip ions to charge state q>20 during two traverses along the high-density electron beam in a continuous regime. The singly charged ions decelerated before the extractor electrode can be injected into the electron beam through the aperture in an electron collector. The further deceleration to thermal energies can be done by the controlled potential on the drift tube, shaping this drift tube and by Coulomb interaction with electrons in a beam. The injected ions travel along the drift tube, decelerate, turn around, and travel back towards the electron collector. We estimate the travel time of ions inside the electron beam with a length of 2m to be τ=(0.5–5.0)×10−3s. With electron beam current density J=1000A∕cm2 the ionization factor can reach Jτ=(0.5–5.0)C∕cm2, which is sufficient for producing ions with charge states of 10–30 (depending on the species). Such device can be efficient for producing ions of short-lived isotopes. It utilizes an electron gun with high electrostatic compression and subsequent adiabatic Brillouin focusing.
Simulation of gridded broad-beam ion sources for ultra-precise surface processing
Authors: Jankuhn St. , Scholze F. , Hartmann E. , Neumann H.
Published: March 2006

Multiaperture multigrid broad-beam ion sources are applied for quite different purposes, which impose rather different demands on their broad-beam properties. In view of the great complexity of these ion–technological devices, a corresponding adaptation can only be accomplished with the aid of a flexible simulation tool. By breaking down the concomitant processes into consecutive fractional steps, the well-approved solver kernels [particle-in-cell (PIC) as an alternative to ray tracing] and dedicated complementary routines for external magnetic fields, molecular gas flow, etc., can be composed to a methodological variant of greatest adequacy and numerical stability in the context of the envisaged specific objective. For devising a source for ultraprecise surface processing, a PIC treatment proves exceedingly efficient in generating homogeneous and low-emittance broad beams. The advantages are exemplified which a PIC treatment reveals in all the consecutive stages of plasma excitation, ion extraction, broad-beam formation with neutralization, and ion–target interaction.
Analysis of laser-produced heavy ions for direct plasma injection scheme
Authors: Sakakibara K. , Okamura M. , Kondrashev S. , Hattori T. , Kashiwagi H. , Kanesue T.
Published: March 2006

To accelerate highly charged intense ion beam, we have developed the direct plasma injection scheme (DPIS) with laser ion source. In this scheme an ion beam from a laser ion source is injected directly to a radio frequency quadrupole (RFQ) linac without a low energy beam transport (LEBT) line and then beam losses in the LEBT can be avoided. We achieved high current acceleration of carbon ions (60mA) by DPIS with the RFQ specially designed for high current heavy ions. As the next step we will use heavier elements such as Al, Fe, and Ta as targets in laser ion source (using high power laser, for example, glass laser) for DPIS and will examine properties of laser-produced plasma for highly charged ion production.
Resolution blur of latent acid image and acid generation efficiency of chemically amplified resists for electron beam lithography
Authors: Kozawa Takahiro , Tagawa Seiichi
Published: March 2006

Acid generation processes of chemically amplified resists for electron beam (EB) lithography are different from those of chemically amplified photoresists. Although acid generators decompose mainly via their excited state in photoresists, they decompose through electron attachment in EB resists. This difference causes significant blur (degradation of contrast) in latent acid images of EB resists because typical acid generators can react with low-energy electrons (∼0eV). It has been widely accepted that the contrast is strongly correlated to line edge roughness. We examined the magnitude of blur intrinsic to the reaction mechanism of chemically amplified EB resists by a simulation based on the reaction mechanism. The acid generation efficiency per ionization (secondary electron generation) was also theoretically estimated. The resolution blur and efficiency of current organic resist materials are considered to lie within 4.6–10.3nm and 0.39–0.85, respectively.
Improvement of trace element analysis system using RIKEN electron cyclotron resonance ion source and linear accelerator
Authors: Kidera M. , Nakagawa T. , Takahashi K. , Enomoto S. , Igarashi K. , Fujimaki M. , Ikezawa E. , Kamigaito O. , Kase M. , Goto A. , Yano Y.
Published: March 2006

We have developed a new analytical system that consists of an electron cyclotron resonance ion source (RIKEN 18 GHz ECRIS) and a RIKEN heavy ion linear accelerator (RILAC). This system is called trace element analysis using electron cyclotron resonance ion source and RILAC (ECRIS-RILAC-TEA). ECRIS-RILAC-TEA has several advantages as described in the work of Kidera et al. [AIP Conf. Proc. 749, 85 (2005)]. However, many experimental results during the last several years revealed a few problems: (1) large background contamination in the ECRIS, particularly at the surface of the plasma chamber wall, (2) high counting of the ionization chamber and the data taking system that is monitored by the direct beam from the accelerator, and (3) difficulty in the selection of the pilot sample and pilot beam production from the ECRIS for the purpose of normalization. In order to overcome these problems, we conducted several test experiments over the past year. In this article, we report the experimental results in detail and future plans for improving this system.
Ion beam formation in a gas-dynamic electron cyclotron resonance ion source
Authors: Sidorov A. , Bokhanov A. , Izotov I. , Razin S. , Skalyga V. , Zorin V. , Balabaev A. , Kondrashev S. , Geller R. , Lamy T. , Sortais P. , Thuillier T. , Spädtke P.
Published: March 2006

Generation of quasistationary flows of multicharged ions with a current density of up to 1A∕cm2 from a dense electron cyclotron resonance plasma confined in a magnetic trap under the quasi-gas-dynamic regime has been achieved [Golubev et al., Trans. Fusion Sci. Technol. 47, 345 (2005)]. This technique provides opportunities for extracting high current multicharged ion beams. The present research is concerned with experimental and theoretical investigations of two ion extraction systems for the gas-dynamic ion sources. (1) Single-aperture system. In this case, there is a principal possibility to obtain ion beams with low emittance by using a small-diameter aperture for extraction. Here we describe investigations aimed at creating nitrogen ion beams (the main ion in the spectrum is N2+) with currents of up to 6.5mA through a 1.5mm aperture in the plasma electrode. (2) Multiaperture system. Such systems provide significantly higher beam currents. First results of testing an extractor with five apertures are presented in this article.
Modified miniature metal vapor vacuum arc source for the Shanghai electron beam ion trap
Authors: Du Guangtian , Guo Panlin , Huang Manli , Gong Peirong , Li Jimin , Zhang Yao , Fu Yunqing , Zou Yaming
Published: March 2006

A modified miniature metal vapor vacuum arc ion source has been developed for the Shanghai electron beam ion trap. Several kinds of elements have been tested to extract lowly charged ions, such as Fe, Au, Ge, Mo, Ti, Al, and Cu. Besides high enough ion beam current and a short pulse width, we focus on the operation reliability, long term operation, and convenience of use.
Properties of a dielectric probe for scanning near-field millimeter-wave microscopy
Authors: Kume Eiji , Sakai Shigeki
Published: March 2006

The characteristics of a dielectric probe for scanning near-field millimeter wave microscopy are presented in this paper. The dielectric probe was fabricated from Teflon and shaped like a cone. The beam profile of the millimeter-wave radiated from the tip of the Teflon probe was measured by three-dimensional scanning using a different Teflon probe. The 93.5 GHz millimeter wave was focused on the tip of the probe at the wavelength level, and the millimeter-wave power was found to decrease exponentially with distance from the tip, the same as a near-field wave.
Ablation study in the capillary discharge of an electrothermal gun
Authors: Keidar Michael , Boyd Iain D.
Published: March 2006

In this paper, we study the ablation phenomena associated with the operation of a capillary discharge for an electrothermal gun. Electrothermal-chemical (ETC) guns are used for enhancement of ignition and combustion of an energetic propellant. One of the major components of the ETC system is a plasma source based on a capillary discharge. In this paper, a model of the capillary discharge is developed. In this model, primary attention is paid to the ablation phenomenon. Different characteristic subregions near the ablated surface, namely, a space-charge sheath, a Knudsen layer, and a hydrodynamic layer, are considered. In this formulation, the ablation rate is determined by the parameters at the edge of the Knudsen layer. The kinetic approach is used to determine the parameters at the interface between the kinetic Knudsen layer and the hydrodynamic layer. Coupling the solution of the nonequilibrium Knudsen layer with the hydrodynamic layer provides a self-consistent solution for the ablation rate. According to the model predictions, the peak electron temperature is about 1.4 eV, the polyethylene surface temperature is about 700 K, and the pressure is about 10 MPa. It is found that the ablation rate increases with the capillary length. The ablated mass and the predicted total pressure agree with previous experimental observations.