Ion Trapping Effect Research Articles

Observation and mitigation of ion trapping in Indus-2

The presence of trapped ions in electron storage rings causes considerable degradation in the performances of the beam, such as increase in beam size, reduction in beam lifetime, shifting of betatron tune, beam instabilities etc. This paper discusses the effects of ion trapping and its mitigation in Indus-2 electron storage ring. Ion-induced instability generating partial beam loss is one of the main barriers in higher beam current accumulation in any electron storage ring. Though there are several techniques to clear the ions from the electron beam path, in Indus-2, it is addressed mainly by filling the storage ring in partial bunch filling pattern. In order to improve the electron beam performance and to mitigate the ion-related problem, a suitable bunch filling pattern has been determined. The theoretical prediction and the result of optimal bunch filling pattern are presented in this paper.

Nonlinear behavior of double ion beam distributions

We study the stability and nonlinear evolution of differential streaming between core and beam protons based on the analysis of a nonlinear kinetic dispersion relation and using hybrid simulations describing the self-consistent decay of Alfvén-cyclotron waves. The effects of ion trapping by ion acoustic waves and pitch-angle scattering induced by decay of the Alfvéen-cyclotron waves are discussed.

Improved bias-temperature instability characteristics in SiC metal-oxide-semiconductor devices with aluminum oxynitride dielectrics

Significant improvement of bias-temperature instability characteristics in SiC-based metal-oxide-semiconductor (MOS) devices was demonstrated with high-permittivity aluminum oxynitride (AlON) dielectrics deposited on thin thermal oxides. AlON/SiO2 stacked dielectrics were found to be beneficial not only for reducing gate leakage current but also for suppressing diffusion of positively charged ions, leading to stable SiC-MOS characteristics even under strong electric fields and high temperatures. Unlike the prompt electric-field-induced ion migration in thermally grown and sputter-deposited SiO2 dielectrics, the ion drift for the stacked gate dielectrics was confined within the thin SiO2 underlayers owing to low ion diffusivity in AlON layers. Impacts of mobile ions on interface properties of SiC-MOS devices and effects of intentional ion trapping within the AlON layers were also systematically investigated.

Uptake of organic emergent contaminants in spath and lettuce: an in vitro experiment.

Although a myriad of organic microcontaminants may occur in irrigation waters, little attention has been paid to their incorporation in crops. In this work, a systematic approach to assess the final fate of both ionizable and neutral organic contaminants taken up by plants is described. In vitro uptake of triclosan (TCS), hydrocinnamic acid (HCA), tonalide (TON), ibuprofen (IBF), naproxen (NPX), and clofibric acid (CFA) were studied in lettuce ( Lactuca sativa L) and spath ( Spathiphyllum spp.) as model plants. After 30 days incubation, analyte depletion from the culture medium was 85-99% (lettuce) and 51-81% (spath). HCA, NPX, and CFA exhibited the highest depletion rate in both plant species. Lettuce plant tissue analysis revealed an accumulation of all compounds except for HCA. These compounds reached a peak in tissue concentration followed by a sudden drop, probably due to the plant detoxification system and analyte depletion from the culture medium. Kinetic characterization of the uptake and detoxification processes was fitted to a pseudo-first-order rate. Compounds with a carboxylic group in their structure exhibited higher uptake rates, possibly due to the contribution of an ion trap effect. Molecular weight and log K(ow) played a direct role in uptake in lettuce, as proven by the significant correlation of both properties to depletion and by the correlation of molecular weight to kinetic uptake rates.

Activity-Based Concept for Transport and Partitioning of Ionizing Organics

Ionizing chemicals, including pesticides, pharmaceuticals, and personal care products, are care products, are widely used chemicals of commerce and have been detected in the environment in large numbers. These "ionics" are subject to a variety of processes, such as dissociation, ion trap, and electrical interactions with organic matter and biota. Conventional chemodynamic concepts and models designed to treat neutral compounds do not necessarily address these processes. A new system of equations, based on activity and analogous to the fugacity approach, is suggested to describe the fate of organic ionics. The total concentration of all molecule species in a bulk compartment is determined from the product of activity 'a' and a bulk activity capacity 'B'. The concentration ratio between compartments in equilibrium depends on the activity ratio and the capacity ratio. Changes in partitioning due to pH, ionic strength, and the ion trap effect are quantified. The calculation is illustrated for two pharmaceuticals, namely the monovalent acid ibuprofen and the monovalent base trimethoprim, in a multimedia lake system. Trimethoprim is neutral at high pH but ionized at low pH, while ibuprofen exhibits the opposite. The concentration ratios of air and biota to water are shown to depend on pH. The activity approach may be used to describe transport and partitioning of multivalent ionizable organic compounds and to build multimedia fate models.

Quantification of ion trapping effect of carbon nanomaterials in liquid crystals

We have determined the ion trapping coefficients of carbon nanomaterials in liquid crystals through the analysis of capacitance–voltage response. The ion trapping coefficient is defined as the ability to trap impurity ions for each carbon nanomaterial and can be used as a referable value to select proper carbon nanomaterials as dopants in liquid crystals. The characterized nanomaterials include multi-wall carbon nanotubes, carbon nanofibers, carbon nanocoils, single-wall carbon nanotubes and fullerenes, respectively. It is found that the multi-wall carbon nanotubes with a tube length of 5–15 μm have the largest ion trapping coefficient and hence serve as the best dopant to suppress the liquid crystal hysteresis.

Effects of ion-ion collisions and inhomogeneity in two-dimensional kinetic ion simulations of stimulated Brillouin backscattering

Two-dimensional simulations with the BZOHAR [B. I. Cohen, B. F. Lasinski, A. B. Langdon, and E. A. Williams, Phys. Plasmas 4, 956 (1997)] hybrid code (kinetic particle ions and Boltzmann fluid electrons) have been used to investigate the saturation of stimulated Brillouin backscatter (SBBS) instability, including the effects of ion-ion collisions and inhomogeneity. Two types of Langevin-operator, ion-ion collision models were implemented in the simulations. In both models the collisions are functions of the local ion temperature and density, but the collisions have no velocity dependence in the first model. In the second model the collisions are also functions of the energy of the ion that is being scattered so as to represent a more physical Fokker-Planck collision operator. Collisions decorrelate the ions from the acoustic waves in SBS, which disrupts ion trapping in the acoustic wave. Nevertheless, ion trapping leading to a hot ion tail and two-dimensional physics that allows the SBS ion waves to nonlinearly scatter, remain important saturation mechanisms for SBBS in a high-gain limit over a range of ion collisionality. Ion-ion collisions tend to increase ion-wave dissipation, which decreases the gain exponent for stimulated Brillouin backscattering; and the peak Brillouin backscatter reflectivities decrease with increasing collisionality in the simulations for velocity-independent collisions and very weakly decrease for the range of Fokker-Planck collisionality considered. SBS backscatter in the presence of a spatially nonuniform plasma flow is also investigated. Simulations show that, depending on the sign of the spatial gradient of the flow relative to the backscatter, ion trapping effects that produce a nonlinear frequency shift can enhance (autoresonance) reflectivities relative to anti-autoresonant configurations, in agreement with theoretical arguments.

Modelling of minority ion cyclotron current drive during the activated phase of ITER

Neoclassical tearing modes, triggered by the long-period sawteeth expected in tokamaks with large non-thermal α-particle populations, may impose a severe β limit on experiments with large fusion yields and on reactors. Sawtooth destabilization by localized current drive could relax the β limit and improve plasma performance. 3He minority ion cyclotron current drive around the sawtooth inversion radius has been planned for ITER. Several ion species, including beam injected D ions and fusion born α particles, are however also resonant in the plasma and may represent a parasitic absorption of RF power.Modelling of minority ion cyclotron current drive in an ITER-FEAT-like plasma is presented, including the effects of ion trapping, finite ion drift orbit widths, wave-induced radial transport and the coupled evolution of wave fields and resonant ion distributions. The parasitic absorption of RF power by the other resonant species is concluded to be relatively small, but the 3He minority current drive is nevertheless negligible due to the strong collisionality of the 3He ions and the drag current by toroidally counter-rotating background ions and co-rotating electrons. H minority current drive is found to be a significantly more effective alternative.

Effects of ion trapping on crossed-laser-beam stimulated Brillouin scattering

An analysis of the effects of ion trapping on ion acoustic waves excited by the stimulated Brillouin scattering of crossing intense laser beams is presented. Ion trapping alters the dispersion of ion acoustic waves by nonlinearly shifting the normal mode frequency and by reducing the ion Landau damping. This in turn can influence the energy transfer between two crossing laser beams in the presence of plasma flows such that stimulated Brillouin scattering (SBS) occurs. The same ion trapping physics can influence the saturation of SBS in other circumstances. A one-dimensional analytical model is presented along with reasonably successful comparisons of the theory to results from particle simulations and laboratory experiments. An analysis of the vulnerability of the National Ignition Facility Inertial Confinement Fusion point design [S. W. Haan et al., Fusion Sci. Technol. 41, 164 (2002)] is also presented.

Mechanism-based design of parasite-targeted artemisinin derivatives: synthesis and antimalarial activity of new diamine containing analogues.

The potent antimalarial activity of chloroquine against chloroquine-sensitive strains can be attributed, in part, to its high accumulation in the acidic environment of the heme-rich parasite food vacuole. A key component of this intraparasitic chloroquine accumulation mechanism is a weak base "ion-trapping" effect whereupon the basic drug is concentrated in the acidic food vacuole in its membrane-impermeable diprotonated form. By the incorporation of amino functionality into target artemisinin analogues, we hoped to prepare a new series of analogues that, by virtue of increased accumulation into the ferrous-rich vacuole, would display enhanced antimalarial potency. The initial part of the project focused on the preparation of piperazine-linked analogues (series 1 (7-16)). Antimalarial evaluation of these derivatives demonstrated potent activity versus both chloroquine-sensitive and chloroquine-resistant parasites. On the basis of these observations, we then set about preparing a series of C-10 carba-linked amino derivatives. Optimization of the key synthetic step using a newly developed coupling protocol provided a key intermediate, allyldeoxoartemisinin (17) in 90% yield. Further elaboration, in three steps, provided nine target C-10 carba analogues (series 2 (21-29)) in good overall yields. Antimalarial assessment demonstrated that these compounds were 4-fold more potent than artemisinin and about twice as active as artemether in vitro versus chloroquine-resistant parasites. On the basis of the products obtained from biomimetic Fe(II) degradation of the C-10 carba analogue (23), we propose that these analogues may have a mode of action subtly different from that of the parent drug artemisinin (series 1 (7-16)) and other C-10 ether derivatives such as artemether. Preliminary in vivo testing by the WHO demonstrated that four of these compounds are active orally at doses of less than 10 mg/kg. Since these analogues are available as water-soluble salts and cannot form dihydroartemisinin by P450-catalyzed oxidation, they represent useful leads that might prove to be superior to the currently used derivatives, artemether and artesunate.

Modelling uptake into roots and subsequent translocation of neutral and ionisable organic compounds

A study on uptake of neutral and dissociating organic compounds from soil solution into roots, and their subsequent translocation, was undertaken using model simulations. The model approach combines the processes of lipophilic sorption, electrochemical interactions, ion trap, advection in xylem and dilution by growth. It needs as input data, apart from plant properties, log KOW, pKa and the valency number of the compound, and pH and chemical concentration in the soil solution. Equilibrium and dynamic (steady-state) models were tested against measured data from several authors, including non-electrolytes as well as weakly acidic and weakly basic compounds. Deviations from the measured values led to further development of the model approach: sorption in the central cylinder may explain the small transpiration stream concentration factor of lipophilic compounds. For non-electrolytes, the model predicted uptake and translocation with high accuracy. For acids and bases, the tendency of the results was satisfactory. The dynamic model and the equilibrium approach gave similar results for the root concentration factor. The calculation of the transpiration stream concentration factor was more accurate with the dynamic model, but still gave deviations up to factor of ten or more. The dominating process for monovalent weak electrolytes was found to be the ion trap effect. © 2000 Society of Chemical Industry

Observations of the coherent beam-ion interaction in the CESR storage ring

The coherent interaction between the electron beam and trapped ions in the Cornell Electron/positron Storage Ring (CESR) has been seen by shaking the beam and observing the resulting beam oscillation amplitude. A linear theory is developed which enables the calculation of ion densities from the experimental measurements. Nonlinearities in the beam-ion force are shown to be important in understanding the ion trapping effects including frequency shifts of the betatron sideband resonances.

A48 Balancing treatment assignments in trials with large number of centers

Nanocomposites comprises of nano sized zinc oxide (ZnO, size ~10 nm) particles and ferroelectric liquid crystal (FLC) material have been prepared and studied. The concentration of the dopant (ZnO nanoparticles) in FLC matrix varied from 0.0 to 1 wt%. Distinct nanocomposites have been used to fabricate memory device and studied through dielectric spectroscopy, optical microscopy and electro-optical methods to explore electro-optic and memory parameters. Experimental results reveal that doping of ZnO nanoparticles in FLC leads to long lasting memory and low deriving voltage in nanocomposites. The achieved prolonged memory effect in nanocomposites may attribute to the charge transfer at the interfaces. Another reason, application of applied field may lead to ion trapping effect at ZnO surface which in turn minimize the depolarized field and enhance the memory effect in nanocomposites.

Dissociative excitation of CF4, CCl4, and chlorofluoromethanes by collisions with argon and helium active species

Dissociative excitation of CFnCl4–n (n=0–4) by collisions with Ar and He active species has been studied by observing uv and visible emissions in the Ar and He afterglows. Emissions from such excited fragments as Cl*, Cl*2, CF*, CCl*, CCl+*, ArCl*, CF*2, CCl*2, CFCl*, and CF*3 were observed. New continuous bands which may be related to Cl*2, CFCl*, CCl*n(n=2,3), and CCl+*n(n=2,3) were found in the reactions of CFCl3 and CCl4. The effects of ion trapping and SF6 addition into the discharge flow indicated that the excited species were produced from primary reactions by the metastable Ar(3P2) and He(2 3S) atoms and (Ar+)* and He+ ions and/or secondary reactions via electron–ion recombination processes. The emission rate constants have been determined for the primary reactions of Ar(3P2), He(2 3S), and He+ with CFnCl4–n (n=0–3). A comparison between the observed emission rate constants and known total quenching rate constants indicated that dissociative excitation processes are minor exit channels (≤4.6%).

Fetal and Maternal Placental and Nonplacental Clearances of Metoclopramide in Chronically Instrumented Pregnant Sheep

The placental and nonplacental clearances of metoclopramide were studied in nine chronically instrumented, near-term pregnant sheep using a two-compartment open model. Metoclopramide was administered to the ewe and fetus on separate occasions as an initial iv bolus loading dose followed by a constant-rate infusion, with steady-state maternal and fetal plasma concentrations being obtained by 45min. Following the maternal infusions, metoclopramide reached average steady-state concentrations of 50.0 ± 20.2 ng/mL in the ewe and 27.1 ± 8.6 ng/mL in the fetus, with a mean fetal-to-maternal concentration ratio of 0.57 ± 0.14. The ability of the fetus to eliminate metoclopramide by nonplacental routes appears to be responsible for this ratio being less than unity, rather than differential protein binding and ion-trapping effects. Mean steady-state concentrations were 13.8 ± 4.5 and 253.7 ± 92.1 ng/mL in the ewe and fetus, respectively, after fetal drug administration. Metoclopramide was bound significantly less to fetal (39.5 ± 8.9%) than to maternal (49.5 ± 7.9%) plasma proteins, with values similar to that reported for humans (≈40%). Clearance of metoclopramide across the placenta from the fetus to the ewe (6.2 ± 2.4 L/h/kg) was significantly greater than that in the reverse direction (4.3 ± 1.3 L/h/kg) and accounted for ≈80% of total fetal drug elimination. This may be explained by the higher percentage of fetal cardiac output to the placenta and the flow-limited transfer of this compound. Nonplacental routes (e.g., renal, hepatic) were responsible for only ≈20% of total fetal drug elimination (7.9 ± 2.9 L/h/kg), but, they comprised the major source (≈95%) of total maternal drug clearance (2.9 ± 0.4 L/h/kg). Neither maternal nor fetal drug administration resulted in any consistent or significant cardiorespiratory or behavioral effects in the fetal lamb, even though very high concentrations were obtained in fetal plasma following fetal dosing.

High beam current storage at low energy for compact synchrotron radiation rings (invited)

A study of high beam current storage at a low energy is being conducted on the compact electron storage ring NIJI-1. In general, it is said that the stored beam lifetime is rapidly shortened as the beam energy decreases, and the high beam current storage is difficult to obtain. However, a stored beam current above a 350 mA was obtained at an injection energy of 100 MeV, and the lifetime of the stored beam is considerably long. For example, e-folding lifetime is about 2 h at 100 MeV. In this paper, we estimate the beam current decay rate due to the residual gas scattering, the ion trapping effect, and the Touschek effect, and make clear these contributions to the beam lifetime. It was clear that the Touschek lifetime is lengthened according to the bunch size growth, which is roughly explained by the longitudinal coupled bunch instability.

Ion-Clearing System of UVSOR Storage Ring

An ion-clearing system consisting of DC and RF electrodes was installed to cure an ion-trapping effect in the UVSOR, a 600-MeV electron storage ring. In experimental studies of their effectiveness, it was found that the simultaneous use of both electrodes is essential for clearing ions.

Mechanisms of mixed cation effects in β-alumina

From X-ray crystal structure refinements of Na/K and Na/Ag β-aluminas, it is shown that mixed-cation effects in conductivity can arise either from a blocking effect, or from ion-trapping (complexation) effects. The diversity of behaviour is influenced by the selective occupation of Beevers-Ross, anti Beevers-Ross and mid-oxygen sites. By contrast in glass, the more uniform mixed-alkali effect points to a “universal” mechanism which is briefly discussed.

Ion-Trapping Effect in UVSOR Storage Ring

UVSOR is an electron-stage ring dedicated to vacuum ultraviolet synchrotron radiation research. The first beam was stored in the ring in November 1983, and from that time on, efforts have been devoted to improving the performance of the ring. Some inconvenient phenomena have been found during the accelerator studies. One of the most serious problems is the growth of the vertical size of the electron beam. This phenomenon is explained by the ion-trapping effect, in which the ions trapped in the electron beam change the operating point of the storage ring and enhance the coupling between horizontal and vertical oscillations, resulting in a considerable increase in the vertical beam size. This ion trapping was successfully cured by the RF knockout method, which excited the betatron oscillation.

Beam Properties of UVSOR Storage Ring

UVSOR constructed at the IMS (Institute for Molecular Science) is an electron storage ring dedicated to synchrotron radiation research in molecular science and its related fields. The first beam was stored on 10th Nov. in 1983. From that time on, efforts have been devoted to improvement of the performance of the ring. During the accelerator studies, some inconvenient phenomena were found. One of the big problems is ion trapping effect. Trapped ions change the operating point and enhance the coupling between horizontal and vertical oscillations. As a result, the beam height is enlarged considerably at high beam current. The beam is shaken slightly in the vertical plane and the electrostatic clearing field is applied to solve this problem. The bunch length is somewhat longer than the expected value. This effect is also a problem to be solved.