Showing papers on "Time of flight published in 2003"

A C60 Primary Ion Beam System for Time of Flight Secondary Ion Mass Spectrometry: Its Development and Secondary Ion Yield Characteristics

Abstract: A buckminsterfullerene (C60)-based primary ion beam system has been developed for routine application in TOF-SIMS analysis of organic materials. The ion beam system is described, and its performance is characterized. Nanoamp beam currents of C60+ are obtainable in continuous current mode. C602+ can be obtained in pulsed mode. At 10 keV, the beam can be focused to less than 3 μm with 0.1 nA currents. TOF-SIMS studies of a series of molecular solids and a number of polymer systems in monolayer and thick film forms are reported. Very significant enhancement of secondary ion yields, particularly at higher mass, were observed using 10-keV C60+ for all samples other than PTFE, as compared to those observed from 10 keV Ga+ primary ions. Three materials (PS2000, Irganox 1010, PET) were studied in detail to investigate primary ion-induced disappearance (damage) cross sections to determine the increase in secondary ion formation efficiency. The C60 disappearance cross sections observed from monolayer film PS2000 an...

Application of time-sliced ion velocity imaging to crossed molecular beam experiments

Abstract: A three-dimensional (3D) ion velocity imaging method was developed to measure the product velocity distributions in crossed molecular beam experiments. While maintaining conventional two-dimension velocity mapping, the third velocity component was mapped linearly to the ion time of flight. A weak extraction field was used to spread the ion turnaround time to several hundred nanoseconds, which permits good resolution for selection of the longitudinal velocity. A fast gated (⩾5 ns) intensified charge coupled device camera was used to record time-sliced ion images. Calibration of the apparatus was done by measuring O+ images from the multiphoton dissociation/ionization of O2. The resolution in velocity achieved was about 1% (Δv/v) in slicing through the center of a Newton sphere. The overall performance was examined by observing product ion images from the F+CD4→DF+CD3 reaction. To detect CD3+ with kinetic energy release of about 1 eV, 50 ns time slicing provides sufficient velocity resolution, such that res...

Development of high-sensitivity ion trap ion mobility spectrometry time-of-flight techniques: a high-throughput nano-LC-IMS-TOF separation of peptides arising from a Drosophila protein extract.

Abstract: A linear octopole trap interface for an ion mobility time-of-flight mass spectrometer has been developed for focusing and accumulating continuous beams of ions produced by electrospray ionization. The interface improves experimental efficiencies by factors of approximately 50-200 compared with an analogous configuration that utilizes a three-dimensional Paul geometry trap (Hoaglund-Hyzer, C. S.; Lee, Y. J.; Counterman, A. E.; Clemmer, D. E. Anal. Chem. 2002, 74, 992-1006). With these improvements, it is possible to record nested drift (flight) time distributions for complex mixtures in fractions of a second. We demonstrate the approach for several well-defined peptide mixtures and an assessment of the detection limits is given. Additionally, we demonstrate the utility of the approach in the field of proteomics by an on-line, three-dimensional nano-LC-ion mobility-TOF separation of tryptic peptides from the Drosophila proteome.

Tandem time-of-flight mass spectrometer and method of use

Abstract: To provide comprehensive (i.e. rapid and sensitive) MS-MS analysis, the inventor employs a time-nested separation, using two time-of-flight (TOF) mass spectrometers. Parent ions are separated in a slow and long TOF1, operating at low ion energy (1 to l00eV), and fragment ions are mass analyzed in a fast and short TOF2, operating at much higher keV energy. Low energy fragmentation cell between TOF1 and TOF2 is tailored to accelerate fragmentation and dampening steps, mostly by shortening the cell and employing higher gas pressure. Since separation in TOF1 takes milliseconds and mass analysis in TOF2- microseconds, the invention provides comprehensive MS-MS analysis of multiple precursor ions per single ion pulse. Slow separation in TOF1 becomes possible with an introduction of novel TOF1 analyzers. The TOF-TOF could be implemented using a static TOF1, here described on the examples of spiratron, planar and cylindrical multi-pass separators with griddles spatial focusing ion mirrors. Higher performance is expected with the use of novel hybrid TOF 1 analyzers, combining radio frequency (RF) and quadratic DC fields. RF field retains low-energy ions within TOF 1 analyzer, while quadratic DC field improves resolution by compensate for large relative energy spread.

Electron kinetic energy measurements from laser irradiation of clusters

Abstract: We have measured electron kinetic energy spectra from the interaction of a low-density beam of noble-gas clusters with a high-intensity femtosecond laser pulse. Electron energies were measured both through their time of flight and through measurements of electron signals as a function of retarding voltages up to 7 kV. We have observed electrons with energies up to 6 keV and a sharp peak at an arrival time consistent with the detection of photons. The electrons had a broad angular distribution peaked along the polarization axis, while the sharp peak had an isotropic angular distribution. We attribute this sharp peak to uv, xuv, or x-ray photons formed as a result of the laser-cluster interaction and were unable to observe the two-lobed electron kinetic energy distribution reported by Shao et al. [Phys. Rev. Lett. 77, 3343 (1996)] with any combination of the laser and cluster parameters used.

A miniature laser ablation time-of-flight mass spectrometer for in situ planetary exploration

Abstract: We report the development and testing of a miniature mass spectrometer and ion source intended to be deployed on an airless planetary surface to measure the elemental and isotopic composition of rocks and soils. Our design concentrates at this stage on the proposed BepiColombo mission to the planet Mercury. The mass analyser is an axially symmetric reflectron time-of-flight design. The ion source utilizes a laser induced plasma, which is directly coupled into the mass analyser. Laser ablation gives high spatial resolution, and avoids the need for sample preparation. Our prototype instrument has a demonstrated mass resolution m/Δm (FWHM) in excess of 600 and a predicted dynamic range of better than four orders of magnitude. Isotopic fractionation effects are found to be minor. We estimate that a flight instrument would have a mass of 500 g (including all electronics), a volume of 650 cm3 and could operate on 3 W power.

Time of flight mass spectra of ions in plasmas produced by hypervelocity impacts of organic and mineralogical microparticles on a cosmic dust analyser

Abstract: The ionic plasma produced by a hypervelocity particle impact can be analysed to determine compositional informa- tion for the original particle by using a time-of-flight mass spectrometer. Such methods have been adopted on interplanetary dust detectors to perform in-situ analyses of encountered grains, for example, the Cassini Cosmic Dust Analyser (CDA). In order to more fully understand the data returned by such instruments, it is necessary to study their response to impacts in the laboratory. Accordingly, data are shown here for the mass spectra of ionic plasmas, produced through the acceleration of microparticles via a 2 MV van de Graa accelerator and their impact on a dimensionally correct CDA model with a rhodium target. The microparticle dusts examined have three dierent chemical compositions: metal (iron), organic (polypyrrole and polystyrene latex) and mineral (aluminosilicate clay). These microparticles have mean diameters in the range 0.1 to 1.6 m and their velocities range from 1-50 km s 1 . They thus cover a wide range of compositions, sizes and speeds expected for dust particles encountered by spacecraft in the Solar System. The advent of new low-density, microparticles with highly controllable attributes (composition, size) has enabled a number of new investigations in this area. The key is the use of a conducting poly- mer, either as the particle itself or as a thin overlayer on organic (or inorganic) core particles. This conductive coating permits ecient electrostatic charging and acceleration. Here, we examine how the projectile's chemical composition influences the ionic plasma produced after the hypervelocity impact. This study thus extends our understanding of impact plasma formation and detection. The ionization yield normalized to particle mass was found to depend on impact speed to the power (3.4 0.1) for iron and (2.9 0.1) for polypyrrole coated polystyrene and aluminosilicate clay. The ioization signal rise time was found to fall for all projectile materials from a few microseconds at low impact speeds (3 km s 1 ) to a few tenths of a microsecond at higher speeds (approximately 16 km s 1 for aluminosilicate particles and approximately 28 km s 1 for iron and polystyrene particles). At speeds greater than these the rise time was a constant few tenths of a microsecond independent of impact speed. The mass resolution of the time of flight spectrometer was found to be non-linear at high masses above 100 amu. It wasm=m= 5f orm= 1 amu and 40 for m= 200 amu. However, although at high masses most mass peaks had the resolution quoted, there were also occasional much narrower mass peaks observed, suggesting that at 250 to 280 amum=m= 80 to 100. The lower resolutions may be due to closely spaced mass peak signals eectively merging into one observed peak due to the (greater but still finite) resolution found for the isolated mass peaks. Complex mass spectra have been reproducibly obtained from a number of dierent projectiles that display many charged molecular fragments with masses up to 250 amu and with periodicities of 12-14 amu. These new studies reveal an extremely strong dependence of the time-of-flight mass spectra on the impact speed, particularly at low velocities (1-20 km s 1 ). In some impact velocity regimes it is possible to distinguish time-of-flight spectra originating from organic microparticles from those obtained from iron microparticles. However, such discrimination was not possible at high impact speeds, nor was it possible to distinguish between the time-of-flight spectra obtained for aluminosilicate particles from those obtained for iron projectiles.

Multiplexed orthogonal time-of-flight mass spectrometer

Abstract: A mass spectrometer and associated methods analyze an ion beam by accumulating ions for a sequence of time periods, and driving the accumulated ions in pulses Differing quantities of ions can be accumulated in the sequential pulses according to a pseudo-random sequence, and the slower ions are overtaken by the faster ions of a subsequent pulse A mass spectrum may be reconstructed from an overlapping ion detector signal using an inverse of a weighted simplex matrix or inverse Hadamard transform techniques

Time of flight mass spectrometer

Abstract: PROBLEM TO BE SOLVED: To improve detection sensitivity of ion by detecting the ion in a wider energy region while maintaining high resolution under a simple method. SOLUTION: In the time of flight mass spectrometer provided with the ion reflector an ion reflector has a plurality of thin electrodes and one terminal electrode, proper voltage is applied to each of these electrodes, a first stage of a high electric field having a fundamentally uniform electric field and a second stage of a low electric field having also a fundamentally uniform electric field are formed and electric field strength of the second stage is corrected so as to fundamentally increase on the side of the terminal electrode.

Time-of-flight mass analyzer with multiple flight paths

Abstract: A TOF mass analyzer having multiple flight paths is described. The TOF mass analyzer includes a pulsed ion source that generates a packet of ions and that accelerates the packet of ions. An ion deflector directs a first group of ions from the packet of ions to a first ion path, and a second group of ions to a second ion path for each of a first and second predetermined time interval after the pulsed ion source generates the packet of ions. A first TOF mass separator separates the first group of ions according to their mass to-charge ratio and a first detector is positioned to receive the first group of ions A second TOF mass separator separates a second group of ions according to their mass to-charge ratio and a second detector is positioned to receive the second group of ions. Additional ion paths may be employed, and any type of TOF mass separator may be used in each ion path.

Time of flight mass spectrometer employing a plurality of lenses focussing an ion beam in shift direction

Abstract: A multi reflecting time-of-flight mass spectrometer MR TOF MS 11. the flight path of ions from an ion source 12 to a receiver is folded along a trajectory by two parallel gridless electrostatic mirrors 15, elongated in the shift direction 7, orthogonal to the direction of reflection. A set of multiple lenses 17 is positioned in the drift space 14 between the mirrors to provide for spatial focusing of ions in the plane of the folded ion path. Each mirror consists of at least 4 electrodes 15C, 15E, 15L arranged and controlled so that to improve ion optics properties. Namely, in addition to time-of-flight focusing in energy and spatial focusing across the plane of the folded ion path, the mirrors also provide time-of-flight focusing with respect to the spatial spread of ions across the said plane. Because of improved spatial and time focusing, the MR TOF MS of the invention provides for a wider acceptance and confinement of ion beam along an extended folded ion path.

Using matrix peaks to map topography: increased mass resolution and enhanced sensitivity in chemical imaging.

Abstract: It is well known in secondary ion mass spectrometry (SIMS) that sample topography leads to decreased mass resolution. Specifically, the ion's time of flight is dependent on where it was generated. Here, using matrix-enhanced SIMS, it is demonstrated that, in addition to increasing the yield of intact pseudomolecular ions, the matrix allows the user to semiquantitatively record the topography of a sample. Through mapping the topography-related mass shifts of the matrix (which leads to decreased mass resolution), the analogous mass shifts of higher mass ions can be deconvoluted and higher resolution and greater sensitivity obtained. Furthermore, the semiquantitative topographical map obtained can be compared with any chemical images obtained, allowing the user to quickly ascertain whether local intensity maximums are due to topological features or represent genuine features of interest.

Laser Ablation of Titanium Metallic Targets: Comparison Between Theory and Experiment

Abstract: A model of plasma expansion with chemical kinetics has been developed and compared with the free-flow model describing the laser ablation plume of metallic titanium target. Optical emission spectroscopy has been used to obtain time of flight (TOF) spectra. The measured shift between Ti and Ti + TOF has been theoretically explained on the basis of the recombination process. Particular attention has been also focused on the dependence of TOF on some plume parameters such as initial speed, temperature, pressure, and plume extension.

Highly efficient time-of-flight spectrometer for studying low-energy secondary emission from dielectrics: Secondary-electron emission from LiF film

Abstract: A highly efficient time-of-flight electron spectrometer is described. An incident electron current of the order of 10−14 A makes it suitable for studying secondary emission from dielectric surfaces. A microchannel plate position-sensitive detector allows flight distance correction while keeping a large acceptance angle. Measured energy distribution curves of secondary electrons generated from a LiF film by 19–31 eV incident electrons demonstrate good energy resolution and reveal reproducible and stable emission features at 2.6±0.3 eV, 7.2±0.3 eV, and 10.3±0.3 eV.

Image processing of mass spectrometry data for using at multiple resolutions

Abstract: A Mass Spectrometer and method of data processing comprising a time of flight mass spectrometer (300) coupled to a processor (304) having a memory means (308) and data acquisition unit (306) for increasing data compression and enhancing the resolution of mass spectrometer data.

A Simple Multi-Turn Time of Flight Mass Spectrometer ‘MULTUM II’

Abstract: A new multi-turn time-of-flight mass spectrometer ‘MULTUM II’ was constructed. The ion optical system was simplified comparing with ‘MULTUM Linear plus’. The multi-turn part of the new instruments consisted of only four toroidal electric sector fields. The mean radius of cylindrical electric sector was 50 mm and the deflection angle was 157.1°. The total flight pass length of one cycle was 1.308 m. In a preliminary experiment, the mass spectra of Xe ion were measured and enhancement in mass resolution with increasing number of cycles was obserbed. The mass resolution 5100 at m/z 136 was achieved after 10 cycles.

Time of flight secondary ion mass spectrometry study of silicon nanoclusters embedded in thin silicon oxide layers

Abstract: Si nanoclusters have been formed by 5 keV Si+ implantation at a fluence of 1×1016 atoms/cm2 into a 200 A thin thermally grown SiO2 film on Si (100), followed by thermal treatment at 1000 °C with different annealing times. All the annealed samples show a broad photoluminescence spectrum with increasing intensity as function of annealing time. The use of a dual beam time of flight secondary ion mass spectrometry in negative mode with Cs+ ions at low energy for sputtering allows us to observe variations in Si− signal due to excess of silicon atoms introduced by implantation. With the high sensitivity achieved using this instrumental configuration it is possible to follow Sin− signals which give information about the chemical enviroment of the Si atoms. The possibility of studying the time evolution of the nucleation and growth of nanoclusters has been investigated.

Calculation and measurement of the time-of-flight spread in a hemispherical electron energy analyzer

Abstract: We have determined the transit time distribution of electrons passing a high resolution hemispherical energy analyzer. Comparison of our measured results with analytical expressions reveals that differing transit times between electrons of equal kinetic energy mainly build up on the Kepler-type orbits on which the electrons travel through the hemispheres. To facilitate the measurements, we have installed a position sensitive electron detector capable of single event detection into our spectrometer. This device is based on a delay-line anode. We briefly report on the energy resolution achieved in comparison with a slower readout system via a fluorescent screen. The transit time distribution is important in coincidence experiments, where electrons detected in the hemispherical analyzer are to be related to events in other detectors. We discuss the feasibility of electron–electron coincidence experiments using a hemispherical detector plus a time-of-flight drift tube for energy discrimination of an electron pair.

A resonant electron capture time-of-flight MS with trochoidal electron monochromator.

Abstract: A prototype electron monochromator (EM) reflectron time-of-flight (TOF) mass spectrometer has been constructed and demonstrated to record resonant electron capture (REC) mass spectra of electron-capturing compounds. The electron energy is ramped from −1.7 to +25 eV at a preset frequency, and the energy spread of the electron beam at 15 nA is 100 meV or better. Ions are orthogonally extracted into the analyzer at a frequency of up to 80 kHz while maintaining an upper m/z-limit of at least 300 and a mass resolving power of ∼1000. A complete REC mass spectrum, which includes an effective yield versus electron energy curve for each negative ion formed from the compound being analyzed, typically takes several days to produce with a quadrupole or magnetic sector mass spectrometer. With the EM TOF described in this work, three-dimensional negative ion electron capture spectra are recorded in an interval on the order of only 1 s and displayed in real time. This new analytical capability could make it possible to ...

Quantitative Elemental Analysis for Rhodium and Palladium in Minerals by Time-of-Flight Resonance Ionization Mass Spectrometry

Abstract: Results are presented for the trace analysis of Pd and Rh by time-of-flight-resonance ionization mass spectrometry (TOF-RIMS). The spectrometer, developed at the Advanced Mineral Technology Laboratory (Ontario, Canada), is based on a commercial laser-induced mass analyzer with upgrades that include independent laser ablation and ionization sources and pulsed ion optics to minimize noise caused by primary ion formation. The schemes presented for Rh and particularly for Pd detection are simpler than others reported in the literature. The experimental laser fluences were found to be in reasonable agreement with theoretical estimates. The TOF-RIMS measurements were quantified on the basis of calibration curves derived using reference samples covering 3 orders of magnitude in concentration. Minimum detection limits of ∼15 parts per billion were found for both metals, with a precision of ∼±15%. Samples from sulfide, iron oxide, and silicate minerals were also examined. The results are in excellent agreement wit...

Electric sector time-of-flight mass spectrometer with adjustable ion optical elements

Abstract: The invention provides apparatus and methods for performing time-of-flight (TOF) mass spectrometry. A TOF mass spectrometer of the present invention comprises one or more ion focusing electric sectors. At least one of the electric sectors is associated with an ion optical element. The ion optical elements comprise at least one adjustable electrode, such that the adjustable electrode is able to modify the potential experienced by an ion entering or exiting the electric sector with which it is associated.

Quantitative depth profile analysis by direct current glow discharge time of flight mass spectrometry

Abstract: Three operation modes, based on the “absolute sensitivity factor” concept, were studied in a simple laboratory-made glow discharge ion source coupled to a time of flight mass spectrometer for depth profile quantification of conductive zinc coatings. In method 1 voltage and pressure are fixed, in method 2 constant voltage and electrical current are used and method 3 resorts to using fixed electrical current and pressure. For qualitative depth profiling of steels with a coating of galfan, slightly better results were obtained using method 1. In quantitative depth profiling studies with the GD-TOFMS system, good correlation for absolute sensitivity factors was obtained when a calibration for signal intensities of analytes versus the product “sputtering rates × elemental concentrations” was tried using homogeneous reference materials of different matrices. Therefore, conversion of the experimental emission intensities obtained from the qualitative profiles into elemental concentrations and of erosion times into depths was investigated. In this vein, quantitative profiles have resulted when using the three methods investigated for galfan, electroplated ZnNi and a galvanized coating containing lead. Method 3 provided, in general terms, slightly better results than method 1 for the three coatings, while method 2 proved to be less reliable for in-depth quantitative results.

Simultaneous measurements of the ultrasonic wave velocity and thickness of a solid plate made from one side of the plate

Abstract: A new method is proposed for the simultaneous measurement of the ultrasonic wave velocity and the thickness of a solid plate with access from only one side. A line-contact transmitter and a line-contact receiver were placed on the same side of the specimen, and the times of flight were measured for varying distance between the transducers. The ultrasonic wave velocity and the thickness of the specimen can be simultaneously determined from the relationship between the time of flight and the ultrasonic beam path. A least-squares fitting routine was employed to increase the accuracy of the measurements. Experimental results for several specimens of different materials as well as different thicknesses show good agreement with those measured by conventional methods.

Photon time-of-flight distributions through turbid media directly measured with single-photon avalanche diodes

Abstract: We present measurements of photon time-of-flight distributions for a 9-ps, 532-nm laser pulse traveling through Intralipid suspensions and compare the measurements with the results of Monte Carlo simulations that yield the corresponding temporal point-spread function. We show that to obtain satisfactory agreement of experiments and simulation results, one must assume a quadratic dependence of the scattering coefficient on the Intralipid concentration.

Compact very high resolution time-of-flight mass spectrometer

Abstract: The invention relates to a compact time-of-flight mass spectrometer which enables very accurate mass determinations. The invention consists of a method of producing a high resolution by means of a long flight path, where the ion beam repeatedly sweeps a figure of eight in two opposed cylindrical capacitors, each of 254.56°, and the linear ion beam paths between the cylindrical capacitors are extended virtually by a change in potential so as to cause a time focusing with respect to an initial energy spread.

Time-of-flight mass spectrometer system

Abstract: An ion beam supplied from a source is modulated so the ions at a constant flux is deflected by different amounts during two different types of deflection time periods according to a binary sequence, in order to encode the ion beam with phase information of the sequence. The binary sequence is such that ions released during two consecutive time periods of the same type overlap before reaching a detector, thereby increasing the duty cycle. The detector output signal is demodulated using the phase information of the binary sequence to recover an ion mass spectrum.