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Structural change of ions induced by collision with a neutral has been studied in a guided ion beam tandem mass spectrometer, using Time‐Of‐Flight measurements and SIMION simulation. The exothermic catalytic isomerization of HOC+ to HCO+ is used to explore the new methodology. Isomerization is catalyzed via a proton transport mechanism through the interplay of a neutral molecule, the catalyst. Four different potential catalysts, Ne, D2, CH4, and C18O, were studied at different collision energies. SIMION simulation of the ion path and collision in the instrument leads to the highlight of a specific signature related to the catalytic isomerization in the time‐of‐flight spectra. This signature is used to identify the experimental conditions where isomerization takes place. Only C18O, at low collision energies, gives a clear signature of catalytic isomerization, and a quantitative estimate of the catalyzed isomerization cross‐section and rate constant is derived. This new methodology is sensitive to clear presence of catalyzed isomerization and can be used in instruments designed for cross‐section measurements, provided low collision energy is used and ion bunching is available. [ABSTRACT FROM AUTHOR]

The effect of the applied voltage and magnetic field on the defining slot in focusing and energy distribution of the primary filament electron beam was studied theoretically. In this work, SIMION 8.1 software was used to determine the best operational conditions for focusing and the distribution of the electron beam in the ion source system. Furthermore, the Larmor radius on the slot was calculated in two dimensions for different values of magnetic flux density. The results showed that the values of flux density and slot voltage play an effective role in improving the dimensions of beam spot and energy distribution in the source. The dimensions of beam spot were reduced by about 71% at voltage value of slot 75 volt and flux density 780 G. In addition; the kinetic energy distribution for electrons were computed at different magnetic flux and obtaining a homogeneous beam energy. The results of this research support the calculations of plasma source designers. [ABSTRACT FROM AUTHOR]

We explore the spatial distribution of ions in a linear multipole radio-frequency ion trap by ion-trajectory simulation using the SIMION software. As a typical example, a two-dimensional column density is characterised for Ag2+ ions stored in several types of the trap. Taking into account the effects of the space charge and ion–buffer He collisions, we are able to reproduce a ring profile of an ion distribution experimentally observed for a linear octopole trap at a high density of ions close to the space-charge limit. This simulation demonstrates also that the profile of the ion distribution is dependent on the number of ions stored and the temperature of a buffer He gas. As for a quadrupole trap, an ion distribution is shown to be located around the central axis of the trap as observed by experiment. An influence of the electrode structure is also discussed for the quadrupole trap. [ABSTRACT FROM AUTHOR]

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Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fast ion beams delivered by tandem Van de Graaff accelerators intrinsically have an energy width, Δ E P / E P , due to the voltage ripple of the accelerator, the production mechanism of the highly charged ions inside the tank of the accelerator, as well as geometrical considerations related to the propagation of the ion beam. The ion beam energy width directly affects the experimental resolution and thus its value should be considered in experiments and the corresponding data analysis. Here, we present a method for determining the energy width of ion beams delivered by tandem Van de Graaff accelerators, based on high resolution Auger projectile electron spectroscopy combined with data analysis via Monte Carlo simulations within the SIMION ion optics package. [ABSTRACT FROM AUTHOR]

The under-construction FRIB-EDM 3 -instrument was designed to study polar radioactive molecules (such as RaF) in transparent cryogenic solids by laser spectroscopy. The instrument is divided into a frontend- and a backend section. The frontend accepts an aqueous sample from isotope harvesting and provides a mass-separated molecular ion beam in an ultra-high vacuum environment. In the backend, the ions are guided into alkali-metal vapor and the resulting neutrals are co-deposited in a solid argon matrix to perform laser spectroscopy. This work addresses the frontend of the instrument. The efficient ionization of harvested radioisotopes from aqueous samples is achieved with a spray-ionization method. Subsequently, the molecular ion beam is analyzed by mass-to-charge ratio by a quadrupole mass filter. To verify the feasibility of the approach, numerical simulations with the COMSOL and SIMION packages have been conducted. While the former was applied to study transport in ion funnels, the latter was used to investigate ion beam transmission through the lower pressure sections. Following promising simulation results, a first experimental setup is under construction. [ABSTRACT FROM AUTHOR]

BackgroundThe electrostatic lens plays an important role in obtaining high quality focused electron/ion/slow positron beams with high spatial resolution and brightness. A novel electric lens, composed of simplified electrode structures with tube diameter gradually decreasing, is proposed for focusing charged particle beams with low energy and large spot size.PurposeThis study aims to investigate the beam dynamics of this designed electrostatic lens for validation.MethodsBased on overall structure of electric lens focusing system, the charged particle optical simulation software SIMION was employed to optimize the parameters of this focusing system. Then combined with electron beam experiments, the key technologies involved in the electronic lens were studied in detail, including influencing factors, their distributions, and the focusing performance of the lens.ResultsThe results show that the large transverse space of the initial electron beam can be compressed effectively by arranging the electrode structure and electric potential of the lens, with focusing efficiencies exceeding 80%.ConclusionsThe focusing method proposed in this study has significant lateral compression advantages with wide application prospects in many focusing scenarios of different charged particle beams, such as reactor positron sources.

Drift tube is one of the core components of proton transfer reaction mass spectrometer (PTR-MS). Technical innovation of the drift tube is one of the important ways to improve the performance of the instrument. In recent years, focusing drift tube (FDT) has been paid more and more attention because of its high ion utilization ratio. In this work, the design and simulation of a FDT combined with a radio frequency quadrupole and a resistor glass tube was reported. The quadrupole was used to provide an RF focusing field, and the resistor glass tube was used to generate a uniformly distributed DC gradient electric field. Based on the designed 3D structure, the simulation model was built in SIMION 8.1 and the parameters such as the diameter of the quadrupole, the frequency and the voltage amplitude of the RF field were simulated systematically with three kinds of ions (m/z 19, 55 and 100). The results showed that the introduction of the RF field was very effective in reducing the radius of the ion beam, and the rod with larger diameter was beneficial to improve the ion focusing efficiency, especially for the ions with low mass-charge ratio. When the frequency was about 2 MHz, the focusing efficiency was the highest. With the increase of the voltage amplitude, the radius of ion beam decreased rapidly and finally tended to smooth. In addition, more than 85% of the ions could successfully pass through the sampling orifice with a diameter of 1.0 mm, and the transport efficiency was about 28 times higher than that of the traditional drift tube. In this study, structural design, SIMION modeling and ion transmittance of RF quadrupole focusing drift tube (RFQ-FDT) were described in detail, hoping to provide some technical support for follow-up research.

Drift tube is one of the core components of proton transfer reaction mass spectrometer (PTR-MS). Technical innovation of the drift tube is one of the important ways to improve the performance of the instrument. In recent years, focusing drift tube (FDT) has been paid more and more attention because of its high ion utilization ratio. In this work, the design and simulation of a FDT combined with a radio frequency quadrupole and a resistor glass tube was reported. The quadrupole was used to provide an RF focusing field, and the resistor glass tube was used to generate a uniformly distributed DC gradient electric field. Based on the designed 3D structure, the simulation model was built in SIMION 8.1 and the parameters such as the diameter of the quadrupole, the frequency and the voltage amplitude of the RF field were simulated systematically with three kinds of ions (m/z 19, 55 and 100). The results showed that the introduction of the RF field was very effective in reducing the radius of the ion beam, and the rod with larger diameter was beneficial to improve the ion focusing efficiency, especially for the ions with low mass-charge ratio. When the frequency was about 2 MHz, the focusing efficiency was the highest. With the increase of the voltage amplitude, the radius of ion beam decreased rapidly and finally tended to smooth. In addition, more than 85% of the ions could successfully pass through the sampling orifice with a diameter of 1.0 mm, and the transport efficiency was about 28 times higher than that of the traditional drift tube. In this study, structural design, SIMION modeling and ion transmittance of RF quadrupole focusing drift tube (RFQ-FDT) were described in detail, hoping to provide some technical support for follow-up research. [ABSTRACT FROM AUTHOR]

A novel design of an ionisation vacuum gauge is presented, aiming to achieve predictable sensitivity and high accuracy in high and the ultra-high vacuum range. The proposed design features a belt-like electron beam emitted from a linear filament, following a circular trajectory between two cylindrical electrodes, resembling a cylindrical analyser. The proposed design offers several key upsides: a precisely defined electron beam trajectory with reduced susceptibility to path variations, effective electron collection in a Faraday cup able to contain secondary emissions and backscattered electrons, and the inclusion of a suppressor grid in front of the ion collector to eliminate ion-induced secondary electron emission. These features are expected to secure high stability of the gauge and the low pressure limit. An in-depth description of the design is presented, along with the discussions on simulations of the key components that provide the improved performance. • Novel ionisation gauge design to achieve high accuracy and long term stability. • Circular electron trajectories with reduced susceptibility to variations. • Faraday cup electrode enhances accuracy with effective capture secondary particles. • Suppressor grid reduces IISEY ensuring ion current measurement stability. • Very good agreement between the simulated and experimental sensitivity. [ABSTRACT FROM AUTHOR]

Abstract The effects of the gap distance between the electrodes and the extraction voltage on the spot, shape and the kinetic energy distribution of the argon ions were studied theoretically for a diode extraction system. The results showed that under specific conditions, a good focusing to ion- beam was found, where the dimensions of the ion spot were reduced by about 28.6% at gap distance 8 mm and extraction voltage -35 kV with best controlled for hitting ion to the extraction electrode. Also, a homogenous kinetic energy distribution of the beam can be found at distance between 10 mm and 25 mm. [ABSTRACT FROM AUTHOR]

Electron Guns are considered as important and useful devices in electron scattering studies. So far, different models of these guns have been designed. In this paper, using the computational code SIMION- 8.0 3D we simulate a low energy electron gun which is appropriate for the electron collision process. This computational code may be used to correct the canonical properties of electrostatic lenses and also to calculate the imposed voltages on the optical components of the electron gun. Moreover, by applying this code the location and diameter of all the apertures (electrodes) and also the tracing of the electron beams through the electrostatic lenses can be determined. The designed electron gun system accelerates and focuses the electrons leaving a thermionic emitter to an interaction domain (target) in a wide range of variable final energy.

Toroidal ion traps show promise for miniaturized mass spectrometers. However, because of the geometry of the trap, there remains a lack of understanding about the electric field and its effect on the motion of trapped ions. As an approach to this problem, solutions to the Laplace equation in a toroidal coordinate system can be used to characterize the electric potential distribution. The symmetric 2nd order solution of the second kind, or toroidal quadrupole, was previously explored for an ion trap. Non-ideal features in the stability diagram were similar to that for conventional ion traps with higher-order field contributions. To eliminate or reduce these non-ideal features, other solutions to the Laplace equation, including higher-order solutions, can be added to the toroidal quadrupole. The toroidal hexapole (T3) improves the stability diagram by reducing the jagged features at the stability apex and reducing the β r  + 2 β z  = 2 resonance line when the A 3 coefficient of the toroidal hexapole is in the range of 2.75. The β r  = 1/2 resonance line is eliminated by the A 3 coefficient of 1 or greater for the toroidal hexapole. The β r  = 2/3 resonance line is not present in the viewed voltage range when the A 3 coefficient is between 3.5 and 4.75, and the β r  +  β z  = 1 resonance line becomes evident in this same range with the toroidal hexapole contribution is greater than 4.25. The toroidal octopole (T4) and decapole (T5) give no clear trend in variation of the non-ideal features in the stability diagram. The electrode geometry and stability diagram were very sensitive to small additions of the toroidal dipole (T1). The addition of a toroidal hexapole component to the toroidal quadrupole provides improvement in ion trapping, and is expected to play an important role in optimizing the performance of all types of toroidal ion trap mass spectrometers. [ABSTRACT FROM AUTHOR]

In zero-degree Auger projectile spectroscopy (ZAPS), electrons are measured with high energy resolution at 0° with respect to the beam direction and state-selective cross sections can be determined. However, for Auger electrons from long -lived projectile states such as the 1 s 2 s 2 p 4 p j (with lifetimes ranging from ns to ms depending on atomic number Z p and total angular momentum J ) these zero-degree electrons are emitted all along the projectile path towards the spectrometer making their detection solid angle Δ Ω ¯ and therefore their cross section difficult to determine. To date, Δ Ω ¯ has been modeled theoretically leading to significant corrections of the determined cross sections. Here, using ZAPS, we experimentally determine Δ Ω ¯ using the 1 s 2 2 s 2 p     P 3 metastable component of 17.5 MeV O 4+ and 6.6 MeV C 2+ Be-like ion beams. Both the long-lived 1 s 2 s 2 p     P 4 state and the similarly configured prompt 1 s ( 2 s 2 p     P 3 )     P 2 (also known as the P − 2 ) state are readily produced by 1 s ionization in a cascade-free environment in the ratio of 2:1, according to spin statistics. This allows for the determination of Δ Ω ¯ for the P 4 state in relation to the known point solid angle Δ Ω 0 of the prompt P − 2 state. Using this technique new results are obtained with our hemispherical deflector analyzer (HDA), as well as from the re-analysis of the older ZAPS measurements of Lee et al. (1992) [26] which used a two-stage parallel plate analyzer (2PPA). SIMION electro-optical simulations for both spectrometers and geometrical calculations for the 2PPA are compared to our experimental results and found in acceptable agreement. The ramifications of these results on recent 2 p capture measurements using ( 1 s 2 s     S 3 ) C 4+ and F 7+ ions involving the production of 1 s 2 s 2 p     P 4 states are discussed. [ABSTRACT FROM AUTHOR]

The article describes the commissioning and technical development of the Weak Interaction Studies with 32Ar Decay (WISArD) experiment, installed at the radioactive ion-beam facility ISOLDE/CERN. The experiment aims to extend the present limits on scalar and tensor currents in the weak interaction and hence search for physics beyond the Standard Model. The evaluation of these limits relies on measuring the proton energy in beta-delayed proton emission, sensitive to both the beta-neutrino angular correlation coefficient a β ν and the Fierz interference term b. The method tries to improve previous studies by considering the positron-proton coincidences when determining the kinematic shift in the energy of the emitted protons. Using this coincidence technique, the a β ν and b coefficients will be measured at the per mil level. Simulations were employed to optimize the ion beam transport efficiency and validate proof-of-principle results obtained in November 2018 (Nov2018). Upgrades are ongoing, and we are looking into improvements to the overall performance of the setup. [ABSTRACT FROM AUTHOR]

The study of an ion beam transport mechanism contributes to the production of a good quality ion beam with a higher current and better beam emittance. The simulation of an ion beam provides the basis for optimizing the extraction system and the acceleration gap for the ion source. In order to extract an ion beam from an ion source, a carefully designed electrode system for the required beam energy must be used. In our case, a self-extracted penning ion source is used for ion generation, extraction and acceleration with a single accelerating gap for the production of neutrons. The characteristics of the ion beam extracted from this ion source were investigated using computer code SIMION 8.0. The ion trajectories from different locations of the plasma region were investigated. The simulation process provided a good platform for a study on optimizing the extraction and focusing system of the ion beam transported to the required target position without any losses and provided an estimation of beam emittance.

The use of mixed-state ionic beams in collision dynamics investigations is examined. Using high resolution Auger projectile spectroscopy involving He-like ( 1 s 2 1 S , 1 s 2 s 3 , 1 S ) mixed-state beams, the spectrum contributions of the 1 s 2 s 3 S metastable beam component is effectively separated and clearly identified. This is performed with a technique that exploits two independent spectrum measurements under the same collision conditions, but with ions having quite different metastable fractions, judiciously selected by varying the ion beam charge-stripping conditions. Details of the technique are presented together with characteristic examples. In collisions of 4 MeV B 3 + with H 2 targets, the Auger electron spectrum of the separated 1 s 2 s 3 S boron beam component allows for a detailed analysis of the formation of the 1 s 2 s ( 3 S ) n l 2 L states by direct n l transfer. In addition, the production of hollow 2 s 2 p 1 , 3 P doubly- and 2 s 2 p 2 2 D triply-excited states, by direct excitation and transfer-excitation processes, respectively, can also be independently studied. In similar mixed-state beam collisions of 15 MeV C 4 + with H 2 , He, Ne and Ar targets, the contributions of the 1 s 2 , 1 s 2 s 3 , 1 S beam components to the formation of the 2 s 2 p 3 , 1 P states by double-excitation, 1 s → 2 p excitation and transfer-loss processes can be clearly identified, facilitating comparisons with theoretical calculations.

The comparisons between the optical properties of two types of electrostatic quadrupole lenses with the same dimensions and operation conditions are made. The optimum voltages of the electrodes which give the stigmatic image for both focusing planes with are calculated. The calculations are carried out for point-to-point focusing mode. The effects of changing the electrode shape on the optical properties of the lenses are investigated, where the magnification, electron-beam trajectories, and aberration figures are studied, and the comparisons are made. The effects of variation the object and image positions with respect to lens are studied and the comparison between the results for the two lens systems is done. The results show that the electrode shape of the lens play important role in the imaging properties of the electrostatic quadrupole doublet lens systems, especially in the aberrations figures at the image plane. The b-type electrostatic quadrupole doublet lens system gives the best imaging properties in comparison with a-type. [ABSTRACT FROM AUTHOR]

The ion beam extraction system for various ion sources must be designed and evaluated using optimized parameters such as the gap distance between electrodes, applied voltage, and beam properties, using several different programs. SIMION, a 3-D simulation program, can transport various particles at once, and it is useful for simulating beam trajectories from the ion source and the beam line. PBGUNS can be used to calculate the effect of the gap between the plasma electrode and the extraction electrode on the ion beam properties. We propose combining the SIMION and PBGUNS results to compensate for problems in the calculation for the plasma. The calculation result from PBGUNS is utilized to perform ion beam extraction, which is close to the plasma model in SIMION, which can be used to easily simulate beam trajectories and model electrodes. We proposed a simulation method using SIMION to develop a model using plasma information from the PBGUNS result. [ABSTRACT FROM PUBLISHER]

This study reports the optimization of the first stages of a MEMS-based, microfabricated time-of-flight mass spectrometer. The authors present an acceptable match between simulations and experimental results. It validates the use of simulations as a time efficient approach as to predict optimal experimental set points. Chips with three differently meshed ionization grids have been tested and show a significant impact of the grid size on both ionization and extraction. An optimal trade-off is found for 3 mm × 3 mm grid, with about 5 × 10 −6 ion/atom ionization efficiency and over 50% extraction rate. Optimized parameters for ion focussing are found faster with the help of simulations as the experimental optimal settings are found near the predicted simulated voltages. A total ionic current of hundreds of picoamperes is measured, confirming the potential of this electron-impact ion source as the first step of the full time-of-flight mass spectrometer integrated on a single MEMS chip. [ABSTRACT FROM AUTHOR]

An electrostatic accelerator tube capable of accelerating proton, deuteron, alpha beam and heavier ions up to an energy of 150keV has been designed and constructed. This tube can be operated with a Cockroft-Walton type high voltage generator. The construction of the tube is important from two different standpoints. First, because it will initiate the use of low energy accelerators for both scientific and industrial development in country and also this step will lead the country toward approaching the accelerator design technology, an issue which has been severely overlooked for the past few decades. The present accelerator tube consists of 11 different electrodes forming 3 cylindrical lenses, i.e., extractor lens, focusing lens and cooling lens. An accelerator column which includes 7 collimating lenses follows the cooling lens. The tube can accelerate 2H+ up to an energy of 150keV. The accelerator column was successfully tested for the high vacuum and the voltage up to 150kV. A radio frequency type ion source was used to check the performance of the tube. Measurements demonstrated that a beam current close to 850µA can be readily obtained in the present system.

This paper simulates the performance of a cylindrical electrostatic analyzer specially devised to measure the energy spectra of electrons precipitating in the South Atlantic Magnetic Anomaly (SAMA). Unlike its counterparts built to operate in the auroral region, the dimensions of this analyzer were designed to maximize the geometric factor, and to be the first experiment dedicated to measure the much lower fluxes in the equatorial ionosphere. The geometric factor of the analyzer was calculated based on the numerical simulation of electron trajectories coming from a calibration beam using the package SIMION 8.0. Positive and negative voltages applied to the inner and outer plates were compared to examine the analyzer’s response, showing small but visible differences. Simulations at the lower and higher ends of the energy spectrum showed similar geometric factors [ G ] as expected with [G]/E_{\mathrm {peak}} \sim 2.9\times 10^{\mathrm {-3}} (cm ^{2}\cdot {\mathrm{ sr}}$ ) and \Delta E/E_{\mathrm {peak}} \sim 0.29 . These results are in good agreement with semianalytical and empirical estimates. Comparisons with two analyzers designed for measurements in the auroral region showed that the simulated geometric factors are about one order of magnitude larger. Flux estimates based on aeronomic effects over the SAMA indicate that the number of counts should be sufficiently above noise level with the present analyzer design. [ABSTRACT FROM AUTHOR]

Although toroidal ion traps are being used more widely in miniaturized mass spectrometers, there is a lack of fundamental understanding of how the toroidal electric field affects ion motion, and therefore, the ion trap's performance as a mass analyzer. Toroidal harmonics, which represent solutions to the Laplace equation in a toroidal coordinate system, may be useful to understand these devices. This paper reports on SIMION simulations of ion trapping and ion motion in a time-varying electric potential representing the symmetric, second-order toroidal harmonic of the second kind—the solution most analogous to the conventional, Cartesian quadrupole. Simulations show that this potential, which we call the toroidal quadrupole, is similar to that of the Cartesian quadrupole in its ability to trap ions. The stability diagram for the toroidal quadrupole shares similarities with that of both the quadrupole ion trap (QIT) and the quadrupole mass filter (QMF), but has several minor differences including a series of chasms and a portion of the boundary that is diffuse. [ABSTRACT FROM AUTHOR]

The accurate determination of the electron yield of a metastable projectile Auger state necessitates the careful evaluation of the corresponding effective solid angle, i.e. the geometrical solid angle convoluted with the decay time of the metastable state. Recently, we presented (Doukas et. al., 2015) SIMION Monte Carlo type simulations of the effective solid angle for long lived projectile Auger states (lifetime τ ∼ 10 - 9 – 10 - 5 s ) recorded by a hemispherical spectrograph with injection lens and position sensitive detector in the direction of the projectile ion. These results are important for the accurate evaluation of the 1 s 2 s 2 p P 4 / 2 P ratio of K-Auger cross sections whose observed non-statistical production by electron capture into He-like ions, recently a field of interesting interpretations, awaits final resolution. Here we expand and systematize our investigation using the same techniques to expose universal behaviors of the effective solid angle covering life times of 1 s 2 s 2 p P 4 states for all first row ions. Our results are also compared to purely geometrical calculations of the solid angle that omit the lensing effects and serve as a benchmark for a deeper insight into the effect. [ABSTRACT FROM AUTHOR]

Hot cathode ionisation gauges are the only reliable pressure measurement devices suitable for both high and ultra-high vacuum measurement. These devices are characterized by low accuracy that is hardly better than 20%. The sources of loss of accuracy are documented in the literature although their quantification and details are not fully understood. In the present work, simulations of Bayard-Alpert and extractor gauges were performed under the influence of uniform magnetic fields up to 30 Gs. Results are in qualitative agreement with measurements taken previously with the Bayard-Alpert gauge. Both gauges are sensitive to low intensity magnetic fields which may be present in vacuum chambers. However, the extractor gauge proved to be more stable in the presence of a magnetic field due to its ring-shaped cathode. • Operation of Bayard-Alpert and extractor gauges is affected by magnetic fields. • Good agreement between BA gauge simulations and previous experiments was achieved. • Magnetic fields up to 30 Gs can introduce measuring errors of 5–30%. • Simulations revealed higher stability of extractor gauge compared to BA gauge. [ABSTRACT FROM AUTHOR]

Simulation of IMS systems is important for gaining insight into the role of its geometric and operational parameters. Using two simulation programs, SIMION and LORENTZ, this study looks into questions pertaining to miniaturization, dimensional disparity across different geometrical axes, and the drift cell medium, both gas and liquid phase. Additionally, we address key physics issues related to space-charge effects and induced current by varying gate pulse width and input charge. This study determines the comparative merits of the two simulation programs, from both computational effectiveness and efficiency standpoints. We explain the necessary techniques for applying these programs to IMS, and we describe similarities and differences of the methods of the programs and how they affect their suitability for simulation of IMS. [ABSTRACT FROM AUTHOR]

The CATS (Cylindrical And Tiny Spectrometer) electrostatic optics geometry features multiple nested cylindrical analysers to simultaneously measure multiple energies of electron and multiple energies of ion in a configuration that is targeted at miniaturisation and MEMS fabrication. In the prototyped model, two configurations of cylindrical analyser were used, featuring terminating side-plates that caused particle trajectories to either converge (C type) or diverge (D type) in the axial direction. Simulations show how these different electrode configurations affect the particle focussing and instrument parameters; C-type providing greater throughputs but D-type providing higher resolving powers. The simulations were additionally used to investigate unexpected plate spacing variations in the as-built model, revealing that the k -factors are most sensitive to the width of the inter-electrode spacing at its narrowest point. [ABSTRACT FROM AUTHOR]

In Fourier transform ion cyclotron resonance spectrometry (FT-ICR MS) the ion magnetron motion is not usually directly measured, yet its contribution to the performance of the FT-ICR cell is important. Its presence is manifested primarily by the appearance of even-numbered harmonics in the spectra. In this work, the relationship between the ion magnetron motion in the ICR cell and the intensities of the second harmonic signal and its sideband peak in the FT-ICR spectrum is studied. Ion motion simulations show that during a cyclotron motion excitation of ions which are offset to the cell axis, a position-dependent radial drift of the cyclotron center takes place. This radial drift can be directed outwards if the ion is initially offset towards one of the detection electrodes, or it can be directed inwards if the ion is initially offset towards one of the excitation electrodes. Consequently, a magnetron orbit diameter can increase or decrease during a resonant cyclotron excitation. A method has been developed to study this behavior of the magnetron motion by acquiring a series of FT-ICR spectra using varied post-capture delay (PCD) time intervals. PCD is the delay time after the capture of the ions in the cell before the cyclotron excitation of the ion is started. Plotting the relative intensity of the second harmonic sideband peak versus the PCD in each mass spectrum leads to an oscillating 'PCD curve". The position and height of minima and maxima of this curve can be used to interpret the size and the position of the magnetron orbit. Ion motion simulations show that an off-axis magnetron orbit generates even-numbered harmonic peaks with sidebands at a distance of one magnetron frequency and multiples of it. This magnetron offset is due to a radial offset of the electric field axis versus the geometric cell axis. In this work, we also show how this offset of the radial electric field center can be corrected by applying appropriate DC correction voltages to the mantle electrodes of the ICR cell while observing the signals of the second harmonic peak group. The field correction leads to a definite performance increase in terms of resolving power and mass accuracy, and the mass spectrum contains intensity-minimized even-numbered harmonics. This is very important in the case of high performance cells, particularly the dynamically harmonized cell, since the magnetron motion can severely impair the averaging effect for dynamic harmonization and can therefore reduce the resolving power. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Development of small, field-portable mass spectrometers has enabled a rapid growth of in-field measurements on mobile platforms. In such in-field measurements, unexpected signal variability has been observed by the authors in portable ion traps with internal electron ionization. The orientation of magnetic fields (such as the Earth's) relative to the ionization electron beam trajectory can significantly alter the electron flux into a quadrupole ion trap, resulting in significant changes in the instrumental sensitivity. Instrument simulations and experiments were performed relative to the earth's magnetic field to assess the importance of (1) nonpoint-source electron sources, (2) vertical versus horizontal electron beam orientation, and (3) secondary magnetic fields created by the instrument itself. Electron lens focus effects were explored by additional simulations, and were paralleled by experiments performed with a mass spectrometer mounted on a rotating platform. Additionally, magnetically permeable metals were used to shield (1) the entire instrument from the Earth's magnetic field, and (2) the electron beam from both the Earth's and instrument's magnetic fields. Both simulation and experimental results suggest the predominant influence on directionally dependent signal variability is the result of the summation of two magnetic vectors. As such, the most effective method for reducing this effect is the shielding of the electron beam from both magnetic vectors, thus improving electron beam alignment and removing any directional dependency. The improved ionizing electron beam alignment also allows for significant improvements in overall instrument sensitivity. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this paper, we present the design of a linear neutron source based on the concept of inertial electrostatic confinement fusion. The source mainly comprises of a concentric coaxial cylindrical grid assembly housed inside a double walled cylindrical vacuum chamber, a gas injection system, a high voltage feedthrough and a high voltage negative polarity power supply. The inner grid will be kept at a high negative potential with respect to the outer grid that will be grounded. The effect of grid transparency on electric potential distribution and ion trajectories has been studied using SIMION. A diffuse deuterium plasma will be initially created by making filament discharge and subsequently, on application of high negative voltage to the inner grid, deuterons will be accelerated towards the axis of the device. These deuterons will oscillate in the negative potential and consequently fuse in between the grids to produce neutrons. This source is expected to produce 10 7 –10 8 neutrons/s. The proposed linear neutron source will be operated both in the continuous and pulse modes and it will be utilized for a few near term applications namely fusion reactor material studies and explosive detection. [ABSTRACT FROM AUTHOR]

Electrodynamic ion funnels are used to enhance the transmission of ions in electrospray-based ion injection systems in 0.1 to 30 Torr pressure range. Jet disrupters are commonly employed to prevent droplets and high pressure jets from entering subsequent vacuum regions. This study presents the simulation and testing of an ion funnel containing a jet disrupter using computational fluid dynamics (CFD) and SIMION ion trajectory simulations. Traditional modeling approaches have utilized approximations for the bulk fluid flow fields without including the time-varying nature of the turbulent flow present in the system, thus yielding idealized results. In this study, the fluid flow fields are calculated using CFD. In an effort to include time dependence, a random velocity vector, whose magnitude is proportional to the square root of the turbulence kinetic energy, was calculated at each time step and added to the velocity of the background gas. These simulations predicted that the transmitted ion current is effectively modulated by the variation of the jet disrupter voltage. The addition of the random velocity vector produced results that closely matched the experiments. The simulations yielded the dependence of the transmission on the jet disrupter voltage, and the voltage necessary for maximum ion throughput was accurately predicted. In addition, the magnitude of the predicted transmission closely matched that of the experimental results. This modeling approach could be extended to similar ion transport and filtering systems in which the effects of turbulent fluid flow cannot be ignored. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Simulations show that significant ion losses occur within the commercial electrospray ionization-field asymmetric waveform ion mobility spectrometer (ESI-FAIMS) interface owing to an angular desolvation gas flow and because of the impact of the FAIMS carrier gas onto the inner rf (radio frequency) electrode. The angular desolvation gas flow diverts ions away from the entrance plate orifice while the carrier gas annihilates ions onto the inner rf electrode. A novel ESI-FAIMS interface is described that optimizes FAIMS gas flows resulting in large improvements in transmission. Simulations with the bromochloroacetate anion showed an improvement of ~9-fold to give ~70% overall transmission). Comparable transmission improvements were attained experimentally for six peptides (2+) in the range of m/z 404.2 to 653.4 at a chromatographic flow rate of 300 nL/min. Selected ion chromatograms (SIC) from nano-LC-FAIMS-MS analyses showed 71% (HLVDEPQNLIK, m/z 653.4, 2+) to 95% (LVNELTEFAK, m/z 582.3, 2+) of ion signal compared with ion signal in the SIC from LC-MS analysis. IGSEVYHNLK (580.3, 2+) showed 24% more ion signal compared with LC-MS and is explained by enhanced desolvation in FAIMS. A 3-10 times lower limits of quantitation (LOQ) (<15% RSD) was achieved for chemical noise limited peaks with FAIMS. Peaks limited by ion statistics showed subtle improvement in RSD and yielded comparable LOQ to that attained with nano-LC-MS (without FAIMS). These improvements were obtained using a reduced FAIMS separation gap (from 2.5 to 1.5 mm) that results in a shorter residence time (13.2 ms ± 3.9 ms) and enables the use of a helium free transport gas (100% nitrogen). [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

A new ELectrostAtic Storage Ring (ELASR) has been designed and built at the King Abdulaziz City for Science and Technology (KACST), in Riyadh, Saudi Arabia. It was developed to be the core of a new storage ring laboratory for atomic and molecular physics at KACST. ELASR follows the standard design of the pioneering storage ring ELISA and it thereby features a racetrack single-bend shaped ring. Complementary simulation code packages were used to work out the design under the requirements of the projected experiments. This paper reports a short description of the ELASR storage ring through an overview of its design and construction.

We have simulated the design and performance of the simplified coaxial ion trap – a dual ion trap mass spectrometer consisting of an outer simplified toroidal trap and an inner cylindrical trap. The device can perform tandem mass analysis by initially trapping ions in the toroidal region, and then transferring ions mass-selectively to the cylindrical region where they can be fragmented, isolated, and mass-scanned. The key benefit of the coaxial trap is the ability to store and retain the original ion population in the toroidal region while tandem mass analysis is being done in the cylindrical region for a selected mass. This study models a miniaturized simplified coaxial ion trap using the ion trajectory simulation software, SIMION, and characterizes its performance in terms of mass resolution and selectivity of transfer from toroidal to cylindrical regions, ion ejection direction from the toroidal trap, and trapping efficiency in the cylindrical trap. Mass resolution was maximized with a slightly positive octopole term in the toroidal trapping region, and the desired inward radial ejection of ions was achieved with a positive hexapole term. We demonstrate the possibility to obtain an optimized electric field for a given aspect ratio of the toroidal trap by varying only three geometric parameters. Simulated mass resolution from the optimized geometry was 0.3 Da for aspect ratio 8. The trapping efficiency was found to be affected by RF and AC voltages, RF phase, as well as the pressure. A mismatch between the kinetic energy of transferred ions and the RF phase in the cylindrical trap at the time of transfer was found to account for most of the ion loss during transfer. The intricate dependence of trapping efficiency on a number of operational variables was found to lead to trade-offs between itself and other operational parameters such as mass resolution and transfer efficiency. The results demonstrate successful operation of the simplified coaxial trap and reveal the geometric and operational constraints to be considered in its operation. [Display omitted] • Simplified coaxial ion trap consists of concentric toroidal and cylindrical traps. • Mass-selective ion transfer is possible between toroidal and cylindrical regions. • Tandem mass analysis possible while retaining other ions in the toroidal region. • Toroidal trap electric field optimized using geometric parameters. • Mass resolution and radial inward ejection of ions optimized in toroidal trap. [ABSTRACT FROM AUTHOR]

Three-dimensionally (3D) resolved ion trajectory calculations within the complex viscous flow field of an atmospheric pressure ion source are presented. The model calculations are validated with spatially resolved measurements of the relative sensitivity distribution within the source enclosure, referred to as the distribution of ion acceptance (DIA) of the mass analyzer. In previous work, we have shown that the DIA shapes as well as the maximum signal strengths strongly depend on ion source operational parameters such as gas flows and temperatures, as well as electrical field gradients established by various source electrode potentials (e.g., capillary inlet port potential and spray shield potential). In all cases studied, distinct, reproducible, and, to some extent, surprising DIA patterns were observed. We have thus attempted to model selected experimental operational source modes (called operational points) using a validated computational flow dynamics derived 3D-velocity field as an input parameter set for SIMION/SDS, along with a suite of custom software for data analysis and parameter set processing. Despite the complexity of the system, the modeling results reproduce the experimentally derived DIA unexpectedly well. It is concluded that SIMION/SDS in combination with accurate computational fluid dynamics (CFD) input data and adequate analysis software is capable of successfully modeling operational points of an atmospheric pressure ion (API) source. This approach should be very useful in the computer-aided design of future API sources. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: A new electrostatic storage ring for beams at energies up to 30keV·q is currently under development at the National Centre for Mathematics and Physics (NCMP), King Abdulaziz City for Science and Technology (KACST). The ring design is based on the existing electrostatic storage rings, but stretches significantly beyond them in that it shall form the core of a unique flexible experimental facility at KACST. The lattice of this ring has been designed in a way that enables the use of state-of-the-art experimental methods to study electron–ion, laser-ion, and ion-neutral beams interactions. The lattice design also allows for a future upgrade of the ring to a double storage ring structure that would enable ion–ion beam interactions to be performed. In this paper, we present the design of this ring with a focus on beam dynamics calculations for the 7° single-bend racetrack layout. The study is principally based on the SIMION8 program. We complemented this study further by using purpose-written routine and MAD-X simulation code. An in-depth investigation into beam stability under consideration of non-linear field components in the electrostatic optical elements, is presented. Finally, different working points and stability regions are discussed. [Copyright &y& Elsevier]

For the comprehensive simulation of ion trajectories including reactive collisions at elevated pressure conditions, a chemical reaction simulation (RS) extension to the popular SIMION software package was developed, which is based on the Monte Carlo statistical approach. The RS extension is of particular interest to SIMION users who wish to simulate ion trajectories in collision dominated environments such as atmospheric pressure ion sources, ion guides (e.g., funnels, transfer multi poles), chemical reaction chambers (e.g., proton transfer tubes), and/or ion mobility analyzers. It is well known that ion molecule reaction rate constants frequently reach or exceed the collision limit obtained from kinetic gas theory. Thus with a typical dwell time of ions within the above mentioned devices in the ms range, chemical transformation reactions are likely to occur. In other words, individual ions change critical parameters such as mass, mobility, and chemical reactivity en passage to the analyzer, which naturally strongly affects their trajectories. The RS method simulates elementary reaction events of individual ions reflecting the behavior of a large ensemble by a representative set of simulated reacting particles. The simulation of the proton bound water cluster reactant ion peak (RIP) in ion mobility spectrometry (IMS) was chosen as a benchmark problem. For this purpose, the RIP was experimentally determined as a function of the background water concentration present in the IMS drift tube. It is shown that simulation and experimental data are in very good agreement, demonstrating the validity of the method. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

We propose a novel scheme for monitoring the transition between deflagration and 'detonation-like' behavior of small-scale explosive samples-in-vacuum subjected to short duration shock stimuli. Our approach relies on measuring the chemical identities and velocity distributions of the gaseous species produced by such samples; e.g. the relatively low velocity expansion-quenched reaction intermediates produced by deflagration versus the hyperthermal thermodynamically stable molecules generated by the termination of a detonation wave at an explosive-vacuum interface. We demonstrate our ability to detect such species by time-of-flight mass spectrometry (TOFMS) using fast Al atoms produced by laser ablation of aluminum metal. Extensive SIMION simulations of ion trajectories in our mass spectrometer lead to a semi-quantitative model connecting the system operating parameters and the velocity-dependent neutral species detection efficiency. We present a method for correcting our data for these detection biases, and for transforming them into neutral species velocity and kinetic energy distributions. We also present preliminary TOFMS data of hyperthermal organic molecular species produced by direct laser ablation/ignition of thin-film nitrocellulose samples. [ABSTRACT FROM AUTHOR]

Abstract: Particle trapping in the nano aerosol mass spectrometer (NAMS) is investigated through a combination of modeling and experimental measurements to understand and optimize the trapping process. In the NAMS, charged nanoparticles pass through an aerodynamic lens, digital ion guide (DIG) and field adjusting lens (FAL) prior to entering a digital ion trap (DIT) where they are captured and subsequently analyzed. The DIT is operated with a square wave potential applied to the ring electrode. SIMION modeling was used to study particle motion from the exit aperture of the DIG into the DIT. Several parameters were characterized including particle starting position, kinetic energy, trajectory and FAL design. A new FAL assembly was designed to increase the number of trapped particles. The new design was found to increase the rate that ambient particles are analyzed by over an order of magnitude. With the new design, an ambient aerosol concentration (dN/dlog d m) of 1×103 cm−3 yields approximately 2–3 particles analyzed per minute. [Copyright &y& Elsevier]