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ABSTRACT: A compact two-grids mirror is described. Although analytical calculations and computer simulations are useful it is found that experimental adjustments of the mirror voltage and of the bias divider resistors are needed to achieve the optimum performance. The experimental procedure is given. It is shown that a second-order time-focusing mirror is appropriate for metastable-ion studies with high mass resolution. Large variations of sample voltage can be compensated by the mirror. Thick insulators can be analysed.
Rapid Communications in Mass Spectrometry 04/2005; 5(1):40 - 43. · 2.79 Impact Factor
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Agnès Tempez,
J A Schultz,
S Della-Negra, J Depauw,
D Jacquet,
A Novikov,
Y Lebeyec,
M Pautrat,
M Caroff,
M Ugarov,
H Bensaoula,
M Gonin,
K Fuhrer,
Amina Woods
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ABSTRACT: Secondary ion mass spectrometry (SIMS) for biomolecular analysis is greatly enhanced by the instrumental combination of orthogonal extraction time-of-flight mass spectrometry with massive gold cluster primary ion bombardment. Precursor peptide molecular ion yield enhancements of 1000, and signal-to-noise improvements of up to 20, were measured by comparing SIMS spectra obtained using Au(+) and massive Au(400) (4+) cluster primary ion bombardment of neat films of the neuropeptide fragment dynorphin 1-7. Remarkably low damage cross-sections were also measured from dynorphin 1-7 and gramicidin S during prolonged bombardment with 40 keV Au(400) (4+). For gramicidin S, the molecular ion yield increases slightly as a function of Au(400) (4+) beam fluence up to at least 2 x 10(13) Au(400) (4+)/cm(2). This is in marked contrast to the rapid decrease observed when bombarding with ions such as Au(5) (+) and Au(9) (+). When gramicidin S is impinged with Au(5) (+), the molecular ion yield decreases by a factor of 10 after a fluence of only 8 x 10(12) ions/cm(2). Comparison of these damage cross-sections implies that minimal surface damage occurs during prolonged Au(400) (4+) bombardment. Several practical analytical implications are drawn from these observations.
Rapid Communications in Mass Spectrometry 02/2004; 18(4):371-6. · 2.79 Impact Factor
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ABSTRACT: A sublinear effect in the secondary electron emission from insulating
solids under impacts of gold clusters (Au)n, n = 1-5, with
energy E = 33-11000 keV/atom has been observed experimentally using the
ARAMIS and Tandem accelerators at Orsay. The effect manifests itself in
the decrease of the number of emitted electrons per cluster atom with
the increase of the number of atoms in the cluster and the projectile
energy. We explain this phenomenon by a mechanism of sweeping-out
electrons, which causes a decrease in the number of available electrons
in the solid, after the passage of the forward atoms of the cluster
through the atomic layers from which the electrons can be emitted.
Calculated absolute values of the sublinear effect as well as its
dependencies, based on the theory of secondary electron emission, are in
agreement with the experimental data.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 07/1996; 117:47-54. · 1.21 Impact Factor
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Radiation Effects and Defects in Solids 10/1989; 110(1-2):85-88. · 0.40 Impact Factor
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ABSTRACT: Direct determination of average charge states have been performed with an electrostatic analysis method for carbon ions and carbon cluster (Cn, n=3–10) constituents exiting thin carbon foils. The velocity of the mono and polyatomic projectiles was identical, ranging from 1–4 MeV per atom. The average charge state of carbon cluster constituents is significantly reduced as compared to that of a single carbon projectile at the same velocity, the larger the size of the cluster, the smaller the charge state per cluster atom. This lowering effect decreases when the foil thickness increases.
Phys. Rev. A. 59(6).
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ABSTRACT: Récemment Jungclass et Schmidt ont observé qu'une cible d'acétate d'uranyle bombardée par des produits de fission de 252Cf émet toute une série d'ions agrégats composés de groupements uranyle sans groupements acétate. La question posée est donc de savoir quelle sorte de mécanisme peut exclure la formation de groupements acétate. L'expérience avec des échantillons d'acétate d'uranyle a été recommencée à Orsay avec le spectromètre de masse à haute résolution SuperDEPIL et d'autres instruments. Des expériences avec d'autres types d'acétate ont de plus été réalisées à Darmstadt avec 252Cf, acétate de cobalt (II), manganèse (II), lead (II), calcium et sodium.
http://dx.doi.org/10.1051/jphyscol:1989224.
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ABSTRACT: The objective of this project is the development of the SIMS associated to a new probe of the solid: massive clusters consisting of 100–1000 bismuth or gold atoms. The systematic study of the ionic emission intensities as a function of the mass and energy of these projectiles showed that 100–200 qkeV is sufficient energy for the new probe. It is possible to obtain a time of flight (ToF) spectrum with a single impact. These spectra permit to characterize light molecules (MW∼ a few hundreds) with their fragments and intact molecular ion peaks. To analyze the surface, we propose to obtain cluster beams of 100–150 qkeV with a diameter of 10–100 µm, and to associate measurements of time of flight mass spectrometry with the detection of electron emission in order to locate the impact on the surface. We describe the simulation and the installation, on a 130 kV platform, of our column including a LMIS (Liquid Metal ion Source), lenses and Wien Filter, and of a focusing beam line made of an accelerating gap with its shield and a 130 kV insulator. We shall give the experimental beam specifications obtained with the massive cluster ion source Pegase for bismuth and gold.
Surface and Interface Analysis.
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ABSTRACT: Un spectromètre de masse par temps de vol a été utilisé afin de comparer les processus de désorption d'ions secondaires induits par des ions de quelques MeV, keV et par photons d'un laser pulsé N2. les mesures sont faites avec les mêmes cibles (organiques et inorganiques) dans des conditions expérimentales identiques quelle que soit la sonde de désorption (keV, MeV, laser). Le but de cette expérience est de mesurer les rendements absolus d'émission secondaire et d'observer les différents modes de fragmentation suivant la sonde utilisée. L'utilisation d'un spectromètre de masse par temps de vol combiné avec diverses sondes de désorption-ionisation, peut conduire à une meilleure compréhension des mécanismes de désorption. An experimental comparison is presented concerning secondary ion desorption from insulators by keV and MeV heavy ion and by pulsed laser light. Time of flight mass spectra obtained with these desorption probes turned out to show many similarities /1,2,3/ despite of the quite different energizing processes. Some corresponding data have been published already /1,2,3,4/. The aim of the present work is to measure absolute ion yields and to exhibit the virtually existing differences associated with the three desorption probes. This has an practical aspect, since the combination of the methods could inlarge their capabilities for mass spectrometry but it might also lead to a deeper understanding of the desorption mechanisms. The measurements were made with the same targets under the same experimental conditions whatever the desorption probes (keV, MeV, Laser).
http://dx.doi.org/10.1051/jphyscol:1989212.
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ABSTRACT: A liquid metal ion source (LMIS) has been installed on a pulsed ion gun built at the IPN. The time of flight (TOF) spectra of the pulsed beam were recorded. With the gold source several cluster ions (up to 10 atoms in the cluster) and doubly charged ions were identified in the ion beam TOF spectra. With a second pulsation, single cluster ions can be selected as projectiles for secondary ion TOF mass spectrometry. We have studied the secondary ion emission (SIE) induced by cluster impact from a variety of targets: organic, CsI, metallic. A large enhancement of yield is observed by comparison to single atomic ion impact (e.g. factor of 30 between Au3+ and Au+). The secondary ion yields increase strongly with the number of constituents in the cluster. This effect is not linear. A comparison with other types of clusters and also fission fragments of 252Cf has been performed. The rate of secondary emission stimulated by cluster is similar to SI yield induced by fission fragments.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
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ABSTRACT: C60 molecules accelerated to MeV energies (20 MeV) have been used to induce the desorption-ionization of large biomolecules from solid samples. For a sample consisting of trypsin molecules, the secondary molecular ion emission yield is about two orders of magnitude larger than with MeV atomic ions. This is a consequence of the very high energy density deposited in solids by 20 MeV C60 projectiles that gives rise to a large amount of matter ejected after each impact. Although time-of-flight mass spectra can be recorded within a few seconds, it is more the acquisition of knowledge on mechanistic aspects, in comparison with other particle-induced desorption methods, which is the objective of obtaining these first results with energetic fullerenes.
International Journal of Mass Spectrometry and Ion Processes 164(3):193-200.
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ABSTRACT: Measurement of the H+ secondary ion yield from the surface of solid targets has been used to probe the charge state of fast heavy-ion projectiles at the target surface. Results have been obtained for ion beams of 32S, 40Ar and 84Kr at ≃ 1 MeV/u, and between 0.5 and 1.5 MeV/u for 127I. Increases in the charge state after passage through carbon and Au foils are clearly observed for 84Kr and 127I. The variation of charge state as a function of the thickness of matter traversed is compared with calculated values.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 43(4):484-489. · 1.21 Impact Factor
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ABSTRACT: Heavy gold cluster beams are accelerated to high energy (hundreds of keV/atom) and break up when going through a thin foil. The energy and angular distributions of the constituents are then measured and very well reproduced by a SRIM code calculation, which takes into account atomic interactions only. These distributions do not depend on the number of constituents in the cluster and are found to be the same as those of single gold atoms at the same velocity, in the studied energy range.
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ABSTRACT: It is shown that beams of very heavy gold clusters can be produced by a liquid metal ion source (LMIS). An experimental method is described for defining the LMIS source and the Wien filter parameters that must be set to extract and select large Aun clusters. This method is based on the acceleration of the clusters to high energy (MeV) and on the measurement, after their passage through a thin foil, of their number of constituents and velocity. Only an average mass over charge value is obtained for a given set of source and Wien filter parameters. These parameters can then be used to select heavy Aun cluster beams for applications at low energy (keV) in mass spectrometry.
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K. Baudin,
A. Brunelle,
M. Chabot,
S. Della-Negra, J. Depauw,
D. Gardès,
P. Håkansson,
Y. Le Beyec,
A. Billebaud,
M. Fallavier,
J. Remillieux,
J.C. Poizat,
J.P. Thomas
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ABSTRACT: Energy losses by carbon clusters Cp(p ≤ 8) and fullerene ions C60 in thin carbon foils have been measured in the energy range from 0.3 to 5.65 MeV/atom. A small enhancement in energy loss is obtained for carbon atoms in the clusters relative to single carbon ions at the same velocity. Very large pulse height defects have been observed in the energy response of a silicon detector bombarded by C60 ions with energies ranging from 6 to 30 MeV.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
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ABSTRACT: Fast ions, impinging on solid targets at a few MeV per atom, deposit energy in the material through electronic excitation processes. The relaxation of this energy induces emissions of photons, electrons, ions and neutral species from the target. The detailed study of these ejecta can give insight on the energy deposition and relaxation steps of the ion-solid interaction. Fast polyatomic projectiles allow to deposit very high energy densities (at the surface and in the bulk) well beyond that being possible with any single ion impact. As a result, new and unexpected phenomena are oberved which will be discussed: large non linear emission of ions and cluster ions, very high sputtering yields, production of giant tracks and craters in various irradiated materials including metals. When entering the solid, the atomic constituents of the projectile remain in a close proximity for a certain distance, and the energy density deposited in the overlapping trajectories region is high enough to induce collective effects. Secondary ion emission experiments, performed with various carbon cluster beams delivered by the Tandem accelerator in Orsay, aim to determine this depth of spatial correlation by probing these collective effects inside the solid. The influence of the proximity of the cluster constituents on some of their properties such as their charge state distributions inside the solid has been studied and it has been shown that the mean charge state of the constituents is significantly smaller than when the atoms penetrate the target independently.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
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ABSTRACT: At the Orsay tandem accelerator beams of 32S and 127I at energies of 1 were used to investigate secondary ion emission from Langmuir-Blodgett films deposited on Au. The yields of negative parent ions, dimer and trimer ions were measured for various superposed fatty acid layers as function of primary ion charge state and angle of incidence. By means of TOF mass spectrometry the ejection of intact molecular ions was observed from layers as deep as 200 Å underneath the surface. For grazing primary ion trajectories, the charge state dependence of yields are almost independent of the charge state of the primary ions (PI). The results are in fair agreement with theoretical calculations based on crater formation due to a shock wave expanding from the highly energized zone along the nuclear track.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
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ABSTRACT: A linear time-of-flight mass spectrometer equipped with two acceleration grids and a position sensitive stop detector was used to measure the initial energies and emission angles of H+ ions as a function of the charge state of the incident heavy ion beam. For this purpose, three different targets – a bare gold foil, a bare carbon foil and a thick glycine film deposited on a gold foil – were irradiated by a 127 MeV Iq+ beam (q=17–32) under an angle of incidence of 55° against the surface normal. The measurements were performed at a pressure of about 10−7 mbar. The results are axial, radial and total energy distributions and corresponding mean energies and emission angles. As in previous experiments, the axial energy distribution of H+ measured for the glycine sample is shifted to shorter flight times, i.e. larger energies compared to the distributions obtained with the bare foils. This shift is not charge state dependent. The mean total energy increases with the charge state as 0.14, 0.21 and 0.25 eV per charge unit, respectively, for the gold, carbon and glycine targets. The angular distributions are generally asymmetric; we observed that the H+ ions are ejected preferentially backwards along the line-of-incidence of the primary ions. This effect is much more expressed for the glycine film than for the bare foils. The results are discussed in the frame work of available models of H+ production and desorption.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.
