Ion Mass Separation Research Articles

Трехмерная ловушка с возбуждением колебаний ионов на границе устойчивости диаграммы Матье

Vibrations of charged particles in compositions of three-dimensional high-frequency quadrupole and static homogeneous electric fields in the stable region and in the vicinity of the stability boundary of the Mathieu diagram are investigated. Using a pseudopotential model of a rapidly oscillating field, it is shown that the motion of charged particles during linear scanning of a secular frequency is described by the Airy differential equation. Based on the properties of solutions of the Airy equation, a method of ion mass separation with resonant excitation of oscillations at the stability boundary of the Mathieu diagram has been developed. To implement the method, the ion-optical system of the three-dimensional trap is supplemented with corrective electrodes. Computer modeling has determined the optimal potentials of the correcting electrodes, at which the errors of the distributions of quadrupole and homogeneous fields do not exceed 10E-4 and 2·10E-3. Keywords: superposition of quadrupole and homogeneous fields, Airy differential equation, mode of resonant excitation of oscillations, three-dimensional ion trap with correcting electrodes.

Ion mass separation in crossed electric and magnetic fields as a part of the concept of spent nuclear fuel plasma separation

Presented results have been obtained to develop the concept of spent nuclear fuel plasma separation. The main task is to calculate trajectories of ions of the substance imitating spent nuclear fuel in crossed electric and magnetic fields. The 3D calculations have been made by the KARAT code in a single-particle approximation. The calculations have been performed for a number of combinations of azimuthal and axial magnetic fields and different electric fields configurations. Magnetic field is produced by 2 main coils with the characteristic field strength up to 1.4 kG and in several series with additional coil with the characteristic field strength up to 1.6 kG. Electric field is produced by 2 electrodes with electric potential up to 1 kV. The characteristic linear size of the calculation area is 100 cm. The characteristic size of injection region is 1 cm (up to 10 cm along main axis). Spatial position of the injection region and axis of the injection direction are varied. Injected particles are single-charged ions with energies from 0.2 to 3 eV with atomic masses A = 150 and 240, spreading angle is 60°. Calculations have revealed several options to realize a spatial separation of spent nuclear fuel ions.

Time-of-flight mass separation of ions in planar linear radiofrequency electric fields

The space-time focusing of ions in planar linear high-frequency electric fields was investigated. The possibility of the time-of-flight mass separation of ions in radiofrequency fields was demonstrated and the analytical parameters of this separation were evaluated. The results of the numerical simulation of a radiofrequency mass-reflectron with and without taking into account the space charge of ions were given.

Towards ion identification limit with the silicon telescopes of the FAZIA project

The response of Si-Si-CsI(Tl) and Si-CsI(Tl) telescopes with quality controlled detectors, developed within the FAZIA collaboration, is presented. The aim of the test experiment was to explore the capabilities of various solutions exploiting digital pulse shape analysis techniques for charge and mass separation of ions stopped in a single silicon layer, in order to decrease the identification threshold. It has been found that it is possible to fully discriminate the charge of stopped ions up to the maximum available Z (slightly over that of the beam, Z=54). The ΔE-E correlation, both from the first two silicon detectors and for Si+Si vs. CsI(Tl), can identify all the isotopes up to Z=25. The radiation damage effect on these FAZIA silicon detectors has been also studied. In particular, some results about the effect due to the punching-through and stopped Xe ions will be shown and discussed.

Mass separation of ions in a circular plasma flow

A condition is formulated for nonoverlapping focal spots for ions of various masses in axisymmetric plasma-optic separators with electrostatic ion focusing. It is established that a large spread of ion energies in a plasma flow can hinder the panoramic separation of ions in a common focal plane perpendicular to the axis of the initial plasma flow. For such a flow, a method for the ideal separation of three isotope ion species with masses M2 < M0 < M1 is proposed, according to which the ions with masses M1 and M2 are deposited on the inner and outer cylindrical collectors, respectively, while the ions of mass M0 are collected on the intermediate edge ring.

Catalytic reactions on platinum nanofacets: bridging the size and complexity gap

In this short review we present few selected sections of our own work on the catalytic reactions as studied on a nanoscale using the field emission and field ion microscopies (FEM/FIM) and the corresponding probe-hole techniques: magnetic field ion mass separation combined with the field ion appearance energy spectroscopy (FIAES) and an atom probe with a Wien-filter ion mass selection combined with the time of flight (ToF) and coincidence analyses. We focus on the CO respectively hydrogen oxidation on Pt nanofacets present on an apex of a Pt tip that serves as a model of a single catalytic pellet of a supported catalyst. Exhibiting a heterogeneous surface formed by different orientations, like a catalyst pellet, a Pt tip can be prepared and characterized with atomic resolution. Surface reactions in such a well-defined system can be monitored with a resolution of ≤ 2 nm by FEM or FIM and the reacting species originating from few selected surface sites can be analyzed by FIAES or ToF in a probe-hole experiment. By using the single tip the usual averaging of data over at least few catalytic pellets of the common array-type model catalyst is avoided and thus a “smoothing out” of the characteristics of the single particles can be eliminated. As a result, the correlation of processes on individual nanofacets and fluctuation effects can be studied in situ. Until now, the FIM/FEM techniques are known to be quite successful in studying the oscillating surface reactions on Pt and Rh surfaces. In the present review we concentrate, in turn, on the local reaction kinetics in the nanosized reaction systems as mirrored by spectroscopic measurements and on the fluctuation-induced deviations from the behaviour predicted by macroscopic rate laws.

Initial Trial of Plasma Mass Separation by Crossed Electric and Magnetic Fields

Using segmented concentric rings to produce a radial electric field, an initial trial experiment on ion mass separation in a magnetized plasma with low collisionality has been successfully carried out. With the increase in electric field or the decrease in magnetic field, the azimuthal flow velocity in the Xe plasma saturated and then it decayed due to the unconfined condition. On the other hand, the Ar plasma, whose mass is lighter than the Xe one, did not show this behavior in this operational region. These results are consistent with a particle orbit analysis and a simple calculation of the balances of forces.

Dynamic mass spectrometer for studies of organic and inorganic molecules

Experimental technique is described and relative cross-sections of direct and dissociative ionization of CO 2, C 4H 9OH, C 2H 5OH, CH 3OH, C 6H 12O 6 and C 7H 8 molecules by electron impact in the near-threshold energy range are obtained. The experiment is performed on a setup with ion mass separation based on a monopole mass spectrometer which is proved to be successful for such a sort of experiments. For the incident electron energy range from 7 to 35 eV the energy dependences of cross-section of appearance of the main molecule ions and the fragment ions formed due to its dissociation are given.

Ionization of Nitrogen, Oxygen, Water, and Carbon Dioxide Molecules by Near-Threshold Electron Impact

An experimental technique for measuring the cross sections of direct and dissociative ionization of N2, O2, H2O, and CO2 molecules by electron impact in the near-threshold energy range is described. The setup used in the experiments allows mass separation of ions with a monopole mass spectrometer. It is shown that such a setup can be used to advantage in separation experiments. For incident electron energies between 7 and 35 eV, the energy dependences of the cross sections of generation of parent ions and ion fragments due to parent molecule dissociation are obtained.

Liquid chromatography-mass spectrometry with collision-induced dissociation of conjugated metabolites of benzol[ a]pyrene

Benzo[a]pyrene (BP) metabolites conjugated with glutathione, cysteine-glycine, cysteine, N-acetylcysteine, and sulfuric and glucuronic acids have been studied by microcolumn liquid chromatography-electrospray mass spectrometry with collision-induced dissociation (CID) on a hybrid double focusing magnetic sector-orthogonal time-of-flight tandem mass spectrometer equipped with a focal plane array detector. Negative-ion electrospray mass spectra of the conjugated BP metabolites showed strong [M – H]− ions. When the array detector was used, spectra were obtained from femtomoles of sample infused at mass resolutions of 5000 (full width at half maximum). Cone voltage fragmentation spectra show [M-H]− ions and fragment ions indicative of the BP moiety and/or the conjugating group. Linked scan CID spectra at constant B/E were found to contain structurally informative product ions from infusion of as little as 1 pmol of sample. CID spectra were also recorded by using the double focusing sectors for precursor ion selection and the orthogonal time-of-flight analyzer for product ion mass separation. The method was applied to the analysis of conjugated BP metabolites in the urine of germ-free rats given a single intraperitoneal dose of BP.

Ion mass separation by use of spatial cyclotron resonance

Spatial cyclotron resonance of an ion beam in a wavy magnetic field is investigated to realize the separation of stable isotopes. To perform the experiment, a surface-ionizing lithium ion beam source, which is collisionless and charge-neutralized, has been developed. A wavy magnetic field is produced by setting two magnet-arrays face to face. At the resonance condition, clear scattering of the lithium ion beam is observed and the concentration of 6Li is obtained on a target.

Design and performance of a reflectron based time-of-flight secondary ion mass spectrometer with electrodynamic primary ion mass separation

In many secondary ion mass spectrometry (SIMS) investigations, the total number of generated secondary ions is limited by the amount of sample material available. This is the case in surface reaction studies as well as in organic and inorganic trace analysis or imaging SIMS. In such cases a time-of-flight mass spectrometer has some considerable advantages: quasisimultaneous detection of all masses, unlimited mass range, and very high transmission. We have developed a high-resolution reflectron based time-of-flight secondary ion mass spectrometer with a new electrodynamic mass separation and beam chopping technique based on a pulsed 90° deflection of the primary ion beam. A primary ion pulse width of less than 1.5 ns has been obtained. Second-order energy focusing in the flight path of the secondary ions is achieved by a two-stage reflectron. A mass resolution m/Δm=13 000 and a dynamic range of five orders of magnitude have been obtained with this instrument.

A ten-channel analyzer of atomic-particle energy spectra with mass separation over a wide energy range

A ten-channel analyzer with a wide energy range and mass separation of ions designed for the diagnostics of hot plasma in large thermonuclear machines with injection of fast-atom beams is described. The dynamic range of the device, i.e. the energy ratio of the particles registered simultaneously in the two extreme channels, is equal to 30. The maximum energy of registered particles is 80 keV, the minimum, about 200 eV. The energy widths of channels are 6–30%. The detectors are made on a basis of channeltrons with ion-electron converters. The efficiency for the detection of ions is ⪆ 90%. The analyzer has been calibrated with beams of hydrogen and deuterium atoms. The stripping of atoms is achieved using the stationary admission of nitrogen and/or the pulsed admission of helium into the stripping chamber. The efficiency for the detection of atoms with the analyzer is in the range 10 −4 (at 300 eV) to 2 × 10 −1 (at 50 keV). The analyzer has been applied successfully in Tokamak-10 (USSR), and installed in ASDEX (BRD), Wendelstein-7 A (BRD), Heliotron-E (Japan).

Electron-ion coincidence measurements of CH4

Measurements are reported of 10 keV electron scattering in CH4at low momentum transfers, in coincidence with the various ionic products. Ion mass separation was performed in a time-of-flight system with total transmission for fragments with dissociation energies up to 20 eV. Results have been obtained on the oscillator strengths for the formation of all ionic products for energy losses from the IP up to 80 eV. The present results confirm earlier electron-electron coincidence measurements of the photoionization efficiency (see ibid., vol.8, no.18, p.3007 (1975)) and extend them to higher energy. The oscillator strengths of the (1t2)-1, (2a1)-1and higher initial states of CH4+could be extracted separately from the data.

Ion Microprobe Analyzer with Wien Filter for Primary Ion Mass Separation

Ion Microprobe Analyzer with Wien Filter for Primary Ion Mass Separation