摘要 :
A Monte-Carlo simulation package is presented which has primarily been used to characterize ion bunching devices based on gas-filled (linear) Paul traps and Penning traps. The code calculates the motion of ions in the presence of ...
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A Monte-Carlo simulation package is presented which has primarily been used to characterize ion bunching devices based on gas-filled (linear) Paul traps and Penning traps. The code calculates the motion of ions in the presence of arbitrary electric and/or magnetic fields modeling the effect of the buffer gas by realistically simulating collisions between ions and buffer gas molecules. A summary of the algorithm is presented. Examples of applications of the code are discussed, which include the ion beam bunchers of ISOLTRAP, REXTRAP, LIST and LEBIT.
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This paper is devoted to study the expansion of a beam composed of packets of positively and negatively charged ions generated by alternating extraction and acceleration. This beam is extracted from an ion-ion plasma, i.e. the ele...
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This paper is devoted to study the expansion of a beam composed of packets of positively and negatively charged ions generated by alternating extraction and acceleration. This beam is extracted from an ion-ion plasma, i.e. the electron density is negligible compared to the negative ion density. The alternating acceleration of ions is ensured by two grids placed in the ion-ion plasma region. The screen grid in contact with the plasma is biased with a square voltage waveform while the acceleration grid is grounded. A two-dimensional particle-in-cell (2D-PIC) code and an analytical model are used to study the properties of the near-field plume downstream of the acceleration grid. It is shown that the possible operating bias frequency is delimited by an upper limit and a lower one that are in the low MHz range. The simulations show that alternating acceleration with bias frequencies close to the upper frequency limit for the system can achieve high ion exhaust velocities, similar to traditional gridded ion thrusters, and with lower beam divergence than in classical systems. Indeed, ion-ion beam envelope might be reduced to 15 degrees with 70% of ion flux contained within an angle of 3 degrees. Thus, this alternating acceleration method is promising for electric space propulsion.
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摘要 :
This paper is devoted to study the expansion of a beam composed of packets of positively and negatively charged ions generated by alternating extraction and acceleration. This beam is extracted from an ion-ion plasma, i.e. the ele...
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This paper is devoted to study the expansion of a beam composed of packets of positively and negatively charged ions generated by alternating extraction and acceleration. This beam is extracted from an ion-ion plasma, i.e. the electron density is negligible compared to the negative ion density. The alternating acceleration of ions is ensured by two grids placed in the ion-ion plasma region. The screen grid in contact with the plasma is biased with a square voltage waveform while the acceleration grid is grounded. A two-dimensional particle-in-cell (2D-PIC) code and an analytical model are used to study the properties of the near-field plume downstream of the acceleration grid. It is shown that the possible operating bias frequency is delimited by an upper limit and a lower one that are in the low MHz range. The simulations show that alternating acceleration with bias frequencies close to the upper frequency limit for the system can achieve high ion exhaust velocities, similar to traditional gridded ion thrusters, and with lower beam divergence than in classical systems. Indeed, ion-ion beam envelope might be reduced to 15 degrees with 70% of ion flux contained within an angle of 3 degrees. Thus, this alternating acceleration method is promising for electric space propulsion.
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This paper reviews recent progress in developing high current density ion sources for positive and negative halogen ion beams. These sources have produced $hbox{Cl}^{-}$ current densities almost eq
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The rational design of ion exchange membranes (IEMs) is becoming more pertinent as their usage becomes broader and as their staple applications (i.e., electrodialysis, flow batteries, and fuel cells) improve in commercial viabilit...
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The rational design of ion exchange membranes (IEMs) is becoming more pertinent as their usage becomes broader and as their staple applications (i.e., electrodialysis, flow batteries, and fuel cells) improve in commercial viability. Such efforts would be catalyzed by an improved fundamental understanding of ion transport in IEMs. This review discusses recent progress in modeling ion partitioning and diffusion in IEMs in an effort to relate IEM performance metrics to fundamental membrane properties over which researchers and membrane manufacturers possess direct and sometimes precise control. Central focus is given to the Donnan-Manning model for ion partitioning and the Manning- Meares model for ion diffusion in IEMs. These two frameworks, which are derived from Manning's counter-ion condensation theory for polyelectrolyte solutions, have been widely used within the IEM literature since their recent introduction. To explore this topic, the mathematical derivation of both models is revisited, followed by a survey of experimental and computational discussions of counter-ion condensation in IEMs. Alternative models which fulfill similar roles in predicting IEM transport properties are compared. This review concludes by highlighting the uniquely favorable positions of the Donnan-Manning and Manning-Meares models and discussing their prospects as leading predictors of IEM partitioning and diffusive properties.
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To better probe large biomolecular complexes, developments in mass spectrometry (MS) have focused on improving technologies used to generate, transmit, and measure high m/z ions. The additional tandemMS (MSn) capabilities of ion t...
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To better probe large biomolecular complexes, developments in mass spectrometry (MS) have focused on improving technologies used to generate, transmit, and measure high m/z ions. The additional tandemMS (MSn) capabilities of ion trap mass spectrometers (ITMS) facilitate experiments that facilitate probing complex biomolecular ions. In particular, charge reduction using gas-phase ion/ion reactions increase separation of charge states generated via electrospray ionization (ESI), which increases confidence in charge state assignments and therefore masses determined from the observed charge states. Current ITMS technologies struggle to generate and measure low charge states of large (>50 kDa) proteins and complexes because of power limitations associated with conventional high-frequency sine wave operation. Other approaches, including frequency scanning techniques and use of digital waveforms, reduce or eliminate some of these limitations. The work presented here studies five different operational modes for a quadrupole ion trap (QIT) mass spectrometer used to generate and measure low charge states of bovine serum albumin (BSA), pyruvate kinase (PK), and GroEL. While digital operation of a QIT presents limitations during the ion/ion reaction period of the experiment, it generally provided the best spectra in terms of resolution and signal at m/z > 50,000. (C) 2020 Elsevier B.V. All rights reserved.
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Negative ions have attractive features as drivers for inertial confinement fusion, because they will avoid electron cloud effects, and could be efficiently photodetached to neutrals after the final focus, which could also be benef...
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Negative ions have attractive features as drivers for inertial confinement fusion, because they will avoid electron cloud effects, and could be efficiently photodetached to neutrals after the final focus, which could also be beneficial in heating warm dense matter targets. The halogens have large electron affinities, and thus should be able to produce high current densities of relatively robust negative ions. Recent experiments comparing chlorine beams to argon beams using the same source, extraction optics, and diagnostics have demonstrated that Gl~- beams can be produced with similar emittance to Ar~+ beams, and with about 3/4 the current density from the same configuration. The observed effective beam temperature of about 1/3 eV, and the similarity of current densities show that negative halogen beams can meet the current density and emittance requirements of heavy ion fusion. The near equivalence of the Cl~1 and Cl~+ +Cl_~2 current densities reaching the Faraday cup after passage through a substantial line density of effluent gas demonstrates that beam losses in the higher vacuum of a heavy ion fusion accelerator should be acceptable. A number of lines of evidence show that negative ion-positive ion plasmas (hereafter ion-ion plasmas), composed primarily of negative and positive ions with a small population of electrons, were produced in the sources near the extractor plane. Since Cl, F, I, and Br should all show similar chemistry, any of these halogens should be suitable as fusion driver beams, and heating thin iodine or bromine foils may produce ion-ion plasmas in the warm dense matter regime.
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This study investigates the most suitable conditions for the combined separation of nickel and zinc ions from aqueous solution using triethylenetetramine (Trien) as a neutral organic chelating ligand and sodium dodecyl sulfate (SD...
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This study investigates the most suitable conditions for the combined separation of nickel and zinc ions from aqueous solution using triethylenetetramine (Trien) as a neutral organic chelating ligand and sodium dodecyl sulfate (SDS) as an anionic collector for ion flotation. The interaction of nickel ions with Trien at various pHs and Trien concentrations, and that of nickel ions with SDS, are studied spectrophotometrically. The results show that most suitable conditions for ion flotation are a pH of 9.7, a Trien/Ni(II) mole ratio of 2 and an SDS/Ni(II) mole ratio of 2. Flotation results for the nickel-zinc-SDS-Trien solution show that nickel ion removal is higher than that for zinc ions, indicating that the order of ion removal is opposite to the order of increasing crystal ionic radius. The stability constant of the nickel-Trien complex is greater than that for the zinc-Trien complex, leading to higher Trien interactions with nickel ions. At a pH of 9, the removal of nickel and zinc ions reaches a maximum of 88.4 and 79.9% respectively, corresponding to a 9% higher removal of nickel ions compared to zinc ions.
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Here we report on the reaction of rhenate anions (ReO3-) with multiply protonated peptide cations in a quadrupole linear ion trap mass spectrometer. These reactions effect the formation of an anion-cation complex that, upon collis...
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Here we report on the reaction of rhenate anions (ReO3-) with multiply protonated peptide cations in a quadrupole linear ion trap mass spectrometer. These reactions effect the formation of an anion-cation complex that, upon collisional activation, dissociates along the peptide backbone rather than by displacement of the anion. Cleavage of the peptide backbone, with anion retention, leads us to conclude the anion-cation complex must be tightly bound, most probably through coordination chemistry. We describe this chemistry and detail the possible application of such ion attachment reactions to the characterization of intact proteins.
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We have developed high-intensity negative ion sources, i.e. NIABNIS and rf-plasma sputter-type heavy negative ion sources, for material science applications. The operational principle of the sources is sputtered particle emission ...
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We have developed high-intensity negative ion sources, i.e. NIABNIS and rf-plasma sputter-type heavy negative ion sources, for material science applications. The operational principle of the sources is sputtered particle emission from an optimally cesiated surface. The sources can deliver ion beams of C~-, C_2~-, B_2~-, P~-, Si~-, Cu~-, Ag~-, Au~-, O~-, F~- and CN~- in the current range of several tens mic-roamperes to several milliamperes in dc mode. With these ion sources, we have investigated new negative ion implantation and deposition techniques. The negative ion implantation has the advantage of not charging-up the implanted surfaces of insulators or insulated materials. Thus, this technique can be used for surface modification of micrometer-sized powders without scattering, for nano-particles formation in insulator in the case of quantum devices and also for the nerve cell growth manipulation by precise control of the polymer surface bio-compatibility.
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