Showing papers on "Time of flight published in 2016"

Time-of-Flight Measurements of Single-Electron Wave Packets in Quantum Hall Edge States.

Abstract: We report time-of-flight measurements on electrons traveling in quantum Hall edge states. Hot-electron wave packets are emitted one per cycle into edge states formed along a depleted sample boundary. The electron arrival time is detected by driving a detector barrier with a square wave that acts as a shutter. By adding an extra path using a deflection barrier, we measure a delay in the arrival time, from which the edge-state velocity v is deduced. We find that v follows 1/B dependence, in good agreement with the E[over →]×B[over →] drift. The edge potential is estimated from the energy dependence of v using a harmonic approximation.

A high-resolution time-of-flight chemical ionization mass spectrometerutilizing hydronium ions (H 3 O + ToF-CIMS) for measurements ofvolatile organic compounds in the atmosphere

Abstract: . Proton transfer reactions between hydronium ions (H3O+) and volatile organic compounds (VOCs) provide a fast and highly sensitive technique for VOC measurements, leading to extensive use of proton-transfer-reaction mass spectrometry (PTR-MS) in atmospheric research. Based on the same ionization approach, we describe the development of a high-resolution time-of-flight chemical ionization mass spectrometer (ToF-CIMS) utilizing H3O+ as the reagent ion. The new H3O+ ToF-CIMS has sensitivities of 100–1000 cps ppb−1 (ion counts per second per part-per-billion mixing ratio of VOC) and detection limits of 20–600 ppt at 3σ for a 1 s integration time for simultaneous measurements of many VOC species of atmospheric relevance. The ToF analyzer with mass resolution (m∕Δm) of up to 6000 allows the separation of isobaric masses, as shown in previous studies using similar ToF-MS. While radio frequency (RF)-only quadrupole ion guides provide better overall ion transmission than ion lens system, low-mass cutoff of RF-only quadrupole causes H3O+ ions to be transmitted less efficiently than heavier masses, which leads to unusual humidity dependence of reagent ions and difficulty obtaining a humidity-independent parameter for normalization. The humidity dependence of the instrument was characterized for various VOC species and the behaviors for different species can be explained by compound-specific properties that affect the ion chemistry (e.g., proton affinity and dipole moment). The new H3O+ ToF-CIMS was successfully deployed on the NOAA WP-3D research aircraft for the SONGNEX campaign in spring of 2015. The measured mixing ratios of several aromatics from the H3O+ ToF-CIMS agreed within ±10 % with independent gas chromatography measurements from whole air samples. Initial results from the SONGNEX measurements demonstrate that the H3O+ ToF-CIMS data set will be valuable for the identification and characterization of emissions from various sources, investigation of secondary formation of many photochemical organic products and therefore the chemical evolution of gas-phase organic carbon in the atmosphere.

Multiscale Investigation of Silicon Anode Li Insertion Mechanisms by Time-of-Flight Secondary Ion Mass Spectrometer Imaging Performed on an In Situ Focused Ion Beam Cross Section

Abstract: Considering its specific capacity, silicon is one of the most promising materials to replace graphite in lithium ion batteries anodes. However, its rapid capacity fading prevents its use in current batteries. Understanding lithiation and degradation mechanisms of silicon is important for improving its cyclability. In this work a novel approach is developed by using a focused ion beam implemented in the analysis chamber of a state-of-the-art time of flight secondary ion mass spectrometer. Detailed mapping of elements distribution, including lithium, inside a silicon particle or in the entire depth of the electrode, can thus be performed. During the first lithiation, a core–shell mechanism is observed and its evolution upon electrochemical cycling was examined. This mechanism is observed for all particles in the electrode, independently of their position. Cross analysis with Auger spectroscopy allowed Li concentration in the entire shell to be quantified. Fast lithiation paths getting through the pure silic...

Time-of-flight electron energy loss spectroscopy using TM110 deflection cavities

Abstract: We demonstrate the use of two TM110 resonant cavities to generate ultrashort electron pulses and subsequently measure electron energy losses in a time-of-flight type of setup. The method utilizes two synchronized microwave cavities separated by a drift space of 1.45 m. The setup has an energy resolution of 12 ± 2 eV FWHM at 30 keV, with an upper limit for the temporal resolution of 2.7 ± 0.4 ps. Both the time and energy resolution are currently limited by the brightness of the tungsten filament electron gun used. Through simulations, it is shown that an energy resolution of 0.95 eV and a temporal resolution of 110 fs can be achieved using an electron gun with a higher brightness. With this, a new method is provided for time-resolved electron spectroscopy without the need for elaborate laser setups or expensive magnetic spectrometers.

Synthesis and characterization of P δ-layer in SiO2 by monolayer doping.

Abstract: Achieving the required control of dopant distribution and selectivity for nanostructured semiconducting building block is a key issue for a large variety of applications. A promising strategy is monolayer doping (MLD), which consists in the creation of a well-ordered monolayer of dopant-containing molecules bonded to the surface of the substrate. In this work, we synthesize a P δ-layer embedded in a SiO2 matrix by MLD. Using a multi-technique approach based on time of flight secondary ion mass spectrometry (ToF-SIMS) and Rutherford backscattering spectrometry (RBS) analyses, we characterize the tuning of P dose as a function of the processing time and temperature. We found the proper conditions for a full grafting of the molecules, reaching a maximal dose of 8.3 × 10(14) atoms/cm(2). Moreover, using 1D rate equation model, we model P diffusion in SiO2 after annealing and we extract a P diffusivity in SiO2 of 1.5 × 10(17) cm(2) s(-1).

High-precision time of flight measurement systems

Abstract: A system and method is disclosed for measuring time of flight to an object. A transmitter transmits an electromagnetic signal and provides a reference signal corresponding to the electromagnetic signal. A receiver receives the electromagnetic signal and provides a response signal corresponding to the received electromagnetic signal. A detection circuit is configured to determine a time of flight between the transmitter and the receiver based upon the reference signal and the response signal.

Isotope identification capabilities using time resolved prompt gamma emission from epithermal neutrons

Abstract: We present a concept of integrated measurements for isotope identification which takes advantage of the time structure of spallation neutron sources for time resolved γ spectroscopy. Time resolved Prompt Gamma Activation Analysis (T-PGAA) consists in the measurement of gamma energy spectrum induced by the radioactive capture as a function of incident neutron Time Of Flight (TOF), directly related with the energy of incident neutrons. The potential of the proposed concept was explored on INES (Italian Neutron Experimental Station) at the ISIS spallation neutron source (U.K.). Through this new technique we show an increase in the sensitivity to specific elements of archaeometric relevance, through incident neutron energy selection in prompt γ spectra for multicomponent samples. Results on a standard bronze sample are presented.

An improvement of isochronous mass spectrometry: Velocity measurements using two time-of-flight detectors

Abstract: Isochronous mass spectrometry (IMS) in storage rings is a powerful tool for mass measurements of exotic nuclei with very short half-lives down to several tens of microseconds, using a multicomponent secondary beam separated in-flight without cooling. However, the inevitable momentum spread of secondary ions limits the precision of nuclear masses determined by using IMS. Therefore, the momentum measurement in addition to the revolution period of stored ions is crucial to reduce the influence of the momentum spread on the standard deviation of the revolution period, which would lead to a much improved mass resolving power of IMS. One of the proposals to upgrade IMS is that the velocity of secondary ions could be directly measured by using two time-of-flight (double TOF) detectors installed in a straight section of a storage ring. In this paper, we outline the principle of IMS with double TOF detectors and the method to correct the momentum spread of stored ions.

A high-resolution time-of-flight energy analyzer for femtosecond electron pulses at 30 keV

Abstract: We report a time-of-flight spectrometer for electron pulses at up to 30 keV, which is a suitable energy for atomic-resolution femtosecond investigations via time-resolved electron diffraction, microscopy, and energy loss spectroscopy. For realistic femtosecond beams without apertures, the instrument's energy resolution is ∼0.5 eV (full width at half maximum) or 2 × 10(-5) at a throughput of 50%-90%. We demonstrate the analyzer's versatility by three first applications, namely, femtosecond electron pulse metrology via optical streaking, in situ drift correction in laser-microwave synchronization for electron pulse compression, and time-resolved electron energy loss spectroscopy of aluminum, showing the instrument's capability of tracking plasmonic loss peak positions with few-meV accuracy.

High performance diagnostics for Time-Of-Flight and X ray measurements in laser produced plasmas, based on fast diamond detectors

Abstract: The paper reports about the use of single-crystal Chemical Vapour Deposited (CVD) diamonds as radiation detectors in laser-matter interaction experiments on the ABC laser in ENEA-Frascati. The detectors have been designed and realized by University of Tor Vergata-Rome. The interdigital configuration and the new design of the bias-tee voltage supply units guarantee a fast time response. The detectors are sensitive to soft-X photons and to particles. A remarkable immunity to electromagnetic noise, associated with the laser-target interaction, makes them especially useful for the measurements of the time of flight of fast particles. A novel diamond assembly has been tested in plasmas generated by the ABC laser in the nanosecond regime at intensities I=1013÷14 W/cm2, where contributions from X rays, fast electrons and ions could be observed. © 2016 IOP Publishing Ltd and Sissa Medialab srl.

Time-of-flight detection of ultra-cold atoms using resonant frequency modulation imaging

Abstract: Resonant frequency modulation imaging is used to detect free falling ultra-cold atoms. A theoretical comparison of fluorescence imaging (FI) and frequency modulation imaging (FMI) is made, indicating that for low optical depth clouds, FMI accomplished a higher signal-to-noise ratio under conditions necessary for a 200 μm spatially resolved atom interferometer. A 750 ms time-of-flight measurement reveals near atom shot-noise limited number measurements of 2×106 Bose-condensed Rb87 atoms. The detection system is applied to high precision spinor BEC based atom interferometer.

A novel double-focusing time-of-flight mass spectrometer for absolute recoil ion cross sections measurements.

Abstract: In this work, the inclusion of an Einzel-like lens inside the time-of-flight drift tube of a standard mass spectrometer coupled to a gas cell—to study ionization of atoms and molecules by electron impact—is described. Both this lens and a conical collimator are responsible for further focalization of the ions and charged molecular fragments inside the spectrometer, allowing a much better resolution at the time-of-flight spectra, leading to a separation of a single mass-to-charge unit up to 100 a.m.u. The procedure to obtain the overall absolute efficiency of the spectrometer and micro-channel plate detector is also discussed.

State-of-the-Art Three-Dimensional Chemical Characterization of Solid Oxide Fuel Cell Using Focused Ion Beam Time-of-Flight Secondary Ion Mass Spectrometry Tomography

Abstract: In this paper the potential of time-of-flight secondary ion mass spectroscopy combined with focused ion beam technology to characterize the composition of a solid oxide fuel cell (SOFC) in three-dimension is demonstrated. The very high sensitivity of this method allows even very small amounts of elements/compounds to be detected and localized. Therefore, interlayer diffusion of elements between porous electrodes and presence of pollutants can be analyzed with a spatial resolution of the order of 100 nm. However, proper element recognition and mass interference still remain important issues. Here, we present a complete elemental analysis of the SOFC as well as techniques that help to validate the reliability of obtained results. A discussion on origins of probable artifacts is provided.

Laser intensity effects in carrier‑envelope phase‑tagged time of flight‑photoemission electron microscopy

Abstract: A time of flight-photoemission electron microscope is combined with a single-shot stereographic above-threshold ionization phase meter for studying attosecond control of electrons in tailored plasmonic nanostructures spatially and energetically via a carrier-envelope phase tagging technique. First carrier-envelope phase-resolved measurements of gold nanoparticles on gold plane and surface roughness from a gold film show an apparent carrier-envelope phase modulation with a period of π. This modulation is found to originate from an intensity dependence of the photoelectron spectra and the carrier-envelope phase measurement rather than from an intrinsic carrier-envelope phase dependence, which is confirmed by simulations. This useful finding suggests that intensity tagging should be considered for phase tagging experiments on plasmonic nanostructures with low carrier-envelope phase sensitivity in order to correct for the intensity-related carrier-envelope phase artifact.

Dipolar dissociation dynamics in electron collisions with carbon monoxide

Abstract: Dipolar dissociation processes in the electron collisions with carbon monoxide have been studied using time of flight (TOF) mass spectroscopy in combination with the highly differential velocity slice imaging (VSI) technique. By probing ion-pair states, both positive and/or negative ions may be detected. The ion yield curve of negative ions provides the threshold energy for the ion-pair production. On the other hand, the kinetic energy distributions and angular distributions of the fragment anion provide detailed dynamics of the dipolar dissociation process. Two ion-pair states have been identified based on angular distribution measurements using the VSI technique.

Axial spatial distribution focusing: improving MALDI-TOF/RTOF mass spectrometric performance for high-energy collision-induced dissociation of biomolecules

Abstract: The matrix-assisted laser desorption/ionization (MALDI) technique is a soft ionization method known to be particularly well suited for the analysis of large and/or fragile molecules.1 Since its discovery in the late 1980s,2,3 this technique has been coupled to several mass-analyzing systems4–7 but has been extensively used in combination with time-of-flight (TOF) analyzers due to the pulsed nature of lasers. MALDI mass spectrometry has been used to analyze a wide range of biomolecules and in particular lipids, peptides and oligosaccharides.8–10 Valuable information, when dealing with the structural elucidation of these biomolecules, can be obtained through sequencing experiments where precursor ions generated in the ion source of the mass spectrometer are isolated using a Bradbury-Nielsen11 ion gate for example, and then fragmented. The spectra resulting from the fragmentation processes have been called tandem (MS/MS), post-source decay (PSD) and laser-induced-dissociation (LID) spectra. Experiments in which the precursor ions undergo collisions with a neutral gas, such as helium or argon, give rise to collision-induced dissociation (CID) spectra. Such PSD/LID and CID MS/MS experiments can be performed in most MALDI-TOF/RTOF mass spectrometers, depending on the instrumental parameters and setup. The fragmentation process in mass spectrometry has been studied extensively12,13 and these investigations are ongoing. Importantly, the fragmentation of biomolecules in most MALDI instruments is induced mainly by the excess of internal energy of the precursor ions obtained during the desorption/ionization event.14–16 The excess of internal energy is usually obtained from the use of a UV laser during the initial desorption/ionization steps.17 Cotter et al.18 described a mass spectrometer capable of generating high-energy (HE) CID (20 keV lab collision energy) MALDI-MS/MS spectra. This mass spectrometer was equipped with a high-vacuum ion generation chamber, and a collision cell followed by an ion selector prior to a curved field reflectron (CFR). In 2006, Belgacem et al.19 described a very similar mass spectrometer where the collision cell was placed, this time, after the ion selector (or ion gate). Such a configuration proved to be more efficient for the production of HE-CID ions in product ion spectra. This was believed to be because the metastable ions formed in the source are more likely to undergo HE-CID if the collisions occur later in their metastable decay life-time and thus further away from the ion source. Using the aforementioned MALDI mass spectrometer, it is possible to generate MS/MS spectra with very high-energy collisions when employing helium as a collision gas (these spectra will be referred to as CID spectra). Similarly, MS/MS spectra can be obtained without gas in the collision chamber and, in that case, they can simply be described as PSD mass spectra.15 The CID spectra generated in this device19 do have some advantages. These include, but are not limited to, the observation of side-chain fragmentation, charge-remote fragmentation, and cross-ring cleavage when studying the three mentioned compound classes. On its own, the use of CID is not enough to generate significant yields of product ions. Abundant CID spectra can only be obtained if sufficient energy is transferred to the analytes during the desorption/ionization event. This is generally achieved by increasing the laser energy deposited onto the sample.14 However, this increase in deposited laser energy results in a significant loss of mass resolution for both the precursor and the product ions. The reduction in mass resolution has led to the development of axial spatial distribution focusing (ASDF)20 in order to achieve mass resolution in MS/MS similar to that normally seen for MS and, furthermore, be independent of the increased laser fluence. The MALDI process results in a plume of material expanding from the sample surface in which the ions are formed during the first tens of nanoseconds. The resultant ions have typical velocities of a few hundred metres per second and trajectories largely normal to the sample surface. Within the plume, there are distributions of velocity and position, which depend on the characteristics of the sample and the laser. These distributions can be resolved into components in two directions, as shown in Fig.​Fig.1(A):1(A): the radial direction parallel to the sample surface and the axial direction normal to the sample surface and also parallel to the ion optical axis. The axial velocity distribution is dependent on the type of matrix and the laser wavelength while the radial velocity distribution is affected by the sample topography and angle of incidence of the laser. The spatial distributions depend on the laser beam diameter in the radial direction and the sample depth as well as laser pulse length in the axial direction. Figure 1 (A) Simplified view representing the various ion distributions in a MALDI source of a mass spectrometer. (B) Schematic and simplified view of the MALDI TOF/ReTOF instrument equipped with an ASDF cell: 1 XY sample stage. 2 Source and ion optics. 3 Nd:YAG ... In terms of their effect on the performance of the mass spectrometer, the radial distributions are responsible for the sensitivity while the axial distributions produce a spread in the time of flight of ions and ultimately determine the mass resolution. Most, but crucially not all, of these distributions are compensated for by the ion source design. All the radial distributions are controlled by electrostatic lenses in the ion optics. The axial velocity distribution is controlled by the pulsed extraction.21 However, there is no method of controlling the effect of the axial spatial distribution (that is to say the differences in initial position) of the ions. This is known22 to be because pulsed extraction can compensate for either the velocity distribution or the spatial distribution but not both simultaneously. When the laser fluence is close to the threshold for MALDI ions, the axial spatial distribution can be very small so that its contribution to the time-of-flight spread is also small and high mass resolution is achieved. However, when the laser fluence is increased, as is the case for MS/MS, it is the authors' assertion that the size of the initial axial spatial distribution increases to the point where it dominates the spread in the time of flight and results in low mass resolution. Since the axial spatial distribution cannot be corrected in the ion source, an additional step is required downstream during the flight of the ions that acts on the axial spatial distribution without disturbing the effect of the pulsed extraction on the axial velocity distribution. This is the function of the ASDF cell and its location is determined by three factors. First, the spatial distribution of the ions along the flight path due to the initial axial spatial distribution has to be very much larger than that due to the initial velocity distribution. Secondly, the ASDF must be carried out in the field-free region where the precursor and product ions are still moving together. Finally, because applying an electrostatic field modifies the ion energies, the ASDF should be after all (or the vast majority) of the product ions have been formed, whether by PSD or CID. The location which satisfies these criteria is just in front of the reflectron, as shown schematically in Fig.​Fig.11(B). The ASDF cell, item 7 in the inset of Fig.​Fig.1(B),1(B), consists of two high transmission grids spaced 12.5 mm apart where a fast high-voltage pulse can be applied to the grid 1 closest to the ion source and the exit grid 2 is at ground potential. Initially, grid 1 is at 0 V until the precursor (and product) ions of interest, already selected by the ion gate, enter the ASDF cell. At that time, the high-voltage pulse is applied to the first grid and an axial electrostatic field is produced. The result is pulse bunching of the ions such that the spatial distribution is focused just after the exit of the cell. Because the axial spatial distribution in the ASDF cell is predominantly due to the initial spatial distribution in the ion source, the initial spatial distribution is focused while the axial velocity distribution is largely unaffected. Typically, the ASDF focal length is 50 to 80 mm depending on the m/z values of the product ions. This range is effectively matched to the transfer characteristics of the curved field reflectron so that the net effect is a narrow time distribution at the detector for both the initial axial velocity and the spatial distributions. The result is high mass resolution for MS/MS and this is largely independent of laser fluence. In this paper, the effectiveness of ASDF in combination with the CFR will be demonstrated by the results of fragmentation of a variety of biomolecules by PSD and CID.

A tandem time–of–flight spectrometer for negative–ion/positive–ion coincidence measurements with soft x-ray excitation

Abstract: We present a newly constructed spectrometer for negative–ion/positive–ion coincidence spectroscopy of gaseous samples. The instrument consists of two time–of–flight ion spectrometers and a magnetic momentum filter for deflection of electrons. The instrument can measure double and triple coincidences between mass–resolved negative and positive ions with high detection efficiency. First results include identification of several negative–ion/positive–ion coincidence channels following inner-shell photoexcitation of sulfur hexafluoride (SF6).

Time-of-flight MeV-SIMS with beam induced secondary electron trigger

Abstract: A new Time-of-flight MeV Secondary Ion Mass Spectrometry (MeV-SIMS) setup was developed to be used with a capillary microprobe for molecular imaging with heavy primary ions at MeV energies. Due to the low output current of the ion collimating capillary a Time-of-flight (ToF) measurement method with high duty cycle is necessary. Secondary electrons from the sample surface and transmitted ions were studied as start signals. They enable measurements with a continuous primary beam and unpulsed ToF spectrometer. Tests with various primary ion beams and sample types have shown that a secondary electron signal is obtained from 30% to 40% of incident MeV particles. This provides a ToF start signal with considerably better time resolution than the one obtained from transmitted primary ions detected in a radiation hard gas ionization detector. Beam induced secondary electrons therefore allow for MeV-SIMS measurements with reasonable mass resolution at primary ion beam currents in the low fA range.

Excitation function of the alpha particle induced nuclear reactions on enriched 116Cd, production of the theranostic isotope 117mSn

Abstract: 117mSn is one of the radioisotopes can be beneficially produced through alpha particle irradiation. The targets were prepared by deposition of 116Cd metal onto high purity 12 μm thick Cu backing. The average deposited thickness was 21.9 μm. The beam energy was thoroughly measured by Time of Flight (TOF) methods and proved to be 51.2 MeV. For the experiment the well-established stacked foil technique was used. In addition to the Cd targets, Ti foils were also inserted into the stacks for energy and intensity monitoring. The Cu backings were also used for monitoring and as recoil catcher of the reaction products from the cadmium layer. The activities of the irradiated foils were measured with HPGe detector for gamma-ray spectrometry and cross section values were determined. As a result excitation functions for the formation of 117mSn, 117m,gIn, 116mIn, 115mIn and 115m,gCd from enriched 116Cd were deduced and compared with the available literature data and with the results of the nuclear reaction model code calculations EMPIRE 3.2 and TALYS 1.8. Yield curves were also deduced for the measured nuclear reactions and compared with the literature.

Time of flight mass spectrometer

Abstract: A time of flight (TOF) mass spectrometer including an ion source and a detector separated by an ion flight path is disclosed A tilt correction device 42 is located along a portion of said flight path and includes tilt correction electrodes arranged to generate at least one dipole electric field which is configured to tilt an isochronous plane 14 of ions produced by the ion source so as to correct a previous angular misalignment between the isochronous plane 14 and the planar surface 32 of the detector The voltages applied to the tilt correction electrodes may be modified in use so as to improve a measure of the alignment between the isochronous plane and the planar surface of the ion detector The tilt correction device is preferably a multipole device which includes four or more poles (see Figs 2 & 3) and is located relatively close to planar surface of the detector

Study of a prototype module of a precision time-of-flight detector for particle identification at low momentum

Abstract: In this thesis, Time Of internally Reflected Cherenkov light detector (TORCH), proposed for the LHCb Upgrade to perform three-sigma separation between kaon and pion up to 10 GeV/c, was studied. TORCH is designed to add significant particle identification capability to the existing LHCb system based on two gas Ring Imaging Cherenkov detectors. TORCH would be placed at 10 m from the interaction point, where the flight time difference between a primary pion and kaon is 37.5 ps. TORCH will give a pion-kaon separation of three sigma at 10 GeV/c from the flight time using the Cherenkov photons generated by the charged particle in a 1 cm-thick quartz plate. In order to calculate accurately the flight time in a busy LHCb environment, Cherenkov angle and photon detection time information, as well as the momentum information from the tracking detector are included in the analysis. For the required TORCH performance, the flight time difference must be measured with a resolution of better than 70 ps for a single Cherenkov photon. In order to demonstrate the required performance, the intrinsic time resolution of the photon detector and electronics jitter have been investigated, firstly with commercially available Micro-Channel Plate Photo Multiplier Tubes (MCP-PMT) and electronics, then custom-made Multi-Channel MCP-PMT with custom-made electronics, which are designed for the TORCH RD The Multi-Channel MCP-PMT has been developed in collaboration with industry. For the custom electronics, NINO, an ASIC chip developed for the Time of Flight detector of the ALICE experiment was used as well as the HPTDC ASIC chip, which is being used by the ATLAS, CMS and ALICE experiments. Important characteristics such as the linearity and time walk have been carefully analysed and a method to correct biases introduced by those characteristics has been developed. TORCH optics must propagate the Cherenkov photons to the photocathode of the Multichannel MCPMT with minimum loss. On the other hand, spectra of photons reaching the photocathode should not be too wide in order to limit the chromatic error. All the optical components have been tested with a stand-alone system and results are compared with simulation studies. A small scale TORCH prototype has been constructed to test the system with a charged-particle beam and results are being analysed.

Dipolar dissociation dynamics in electron collisions with carbon monoxide

Abstract: Dipolar dissociation processes in the electron collisions with carbon monoxide have been studied using time of flight (TOF) mass spectroscopy in combination with the highly differential velocity slice imaging (VSI) technique. Probing ion-pair states both positive and/or negative ions may be detected. The ion yield curve of negative ions provides the threshold energy for the ion-pair production. On the other hand, the kinetic energy distributions and angular distributions of the fragment anion provide detailed dynamics of the dipolar dissociation process. Two ion-pair states have been identified based on angular distribution measurements using VSI technique.

Precision timing calorimeter for high energy physics

Abstract: Scintillator based calorimeter technology is studied with the aim to achieve particle detection with a time resolution on the order of a few 10 ps for photons and electrons at energies of a few GeV and above. We present results from a prototype of a 1.4×1.4×11.4 cm 3 sampling calorimeter cell consisting of tungsten absorber plates and Cerium-doped Lutetium Yttrium Orthosilicate (LYSO) crystal scintillator plates. The LYSO plates are read out with wave lengths shifting fibers which are optically coupled to fast photo detectors on both ends of the fibers. The measurements with electrons were performed at the Fermilab Test Beam Facility (FTBF) and the CERN SPS H2 test beam. In addition to the baseline setup plastic scintillation counter and a MCP-PMT were used as trigger and as a reference for a time of flight measurement (TOF). We also present measurements with a fast laser to further characterize the response of the prototype and the photo sensors. All data were recorded using a DRS4 fast sampling digitizer. These measurements are part of an R&D program whose aim is to demonstrate the feasibility of building a large scale electromagnetic calorimeter with a time resolution on the order of 10 ps, to be used in high energy physics experiments.

Time-of-flight mass spectrometer

Abstract: PROBLEM TO BE SOLVED: To provide a time-of-flight mass spectrometer (TOF-MS) capable of performing mass spectrometry of a sample at a high throughput.SOLUTION: A TOF-MS includes: an acceleration part for accelerating an ion; a detector for detecting an event of arrival of the ion after acceleration; and an analyzing part for performing mass spectrometry of a sample on the basis of a time of flight of the ion. A first structure of the detector includes an MCP, a dynode, and an anode. In the first structure, the potential of the dynode is set at a potential higher than that of an output face of the MCP. The anode is disposed at an intermediate position between the MCP and the dynode, or on the dynode side with respect to the intermediate position. The anode has plural apertures and is set at a potential higher than that of the dynode.SELECTED DRAWING: Figure 2

Bayesian Integration and Classification of Composition C-4 Plastic Explosives Based on Time-of-Flight-Secondary Ion Mass Spectrometry and Laser Ablation-Inductively Coupled Plasma Mass Spectrometry

Abstract: Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) were used for characterization and identification of unique signatures from a series of 18 Composition C-4 plastic explosives. The samples were obtained from various commercial and military sources around the country. Positive and negative ion TOF-SIMS data were acquired directly from the C-4 residue on Si surfaces, where the positive ion mass spectra obtained were consistent with the major composition of organic additives, and the negative ion mass spectra were more consistent with explosive content in the C-4 samples. Each series of mass spectra was subjected to partial least squares-discriminant analysis (PLS-DA), a multivariate statistical analysis approach which serves to first find the areas of maximum variance within different classes of C-4 and subsequently to classify unknown samples based on correlations between the unknown data set and the original data set (often...

Design, simulations and test of a Time-of-Flight spectrometer for mass measurement of exotic beams from SPIRAL1/SPIRAL2 and γ-ray spectroscopy of N=Z nuclei close to $^{100}$Sn

Abstract: The new generation of nuclear facilities calls for new technological developments to produce, accelerate, manipulate and analyse exotic nuclei. The main topic of this thesis work was the simulation, design and test of a Multi-Reflection Time-of-Flight Mass spectrometer (MR-ToFMS) for fast mass separation and fast mass measurement of radioactive ions in the installations S3 and DESIR at SPIRAL2. Such a device could separate isobaric nuclei and provide SPIRAL2 with high purity beams. Also, its mass measurement capabilities would help to determine binding energies of exotic and superheavy nuclei with a high precision. This apparatus has been simulated with the SIMION 8.1 software and designed accordingly. First offline tests have been performed with a stable ion source at LPC Caen. In addition a low-aberration electrostatic deflector has been simulated and designed to operate with this MR-ToF-MS without spoiling its performances. This work also describes the analysis and results of the first online tests of a FEBIAD-type ion source intended to provide SPIRAL1 and SPIRAL2 radioactive beams of competitive intensities. Finally, we describe the analysis of a nuclear physics experiment, including the calibration of the different detectors and the gamma-spectroscopy of nuclei in the vicinity of the doubly magic 100Sn.