•He detection by LIBS method was investigated in He containing Be coatings.•At optimized conditions, 2.8 % of He was confidently detectable with LOD 0.7 %•There was an upper limit of 20 mbar Ar ...background pressure for reliable He detection.•He detection was limited due to the He line broadening and increased noise.•Very high excitation energy of He atom complicates the application of CF-LIBS.
Laser Induced Breakdown Spectroscopy (LIBS) method is considered to be a promising tool for analyzing the retention of hydrogen isotopes (D and T) and helium (He) on the first walls and divertor regions of future fusion reactors. Helium will be produced in DT reactions but could also be used in the initial non-nuclear phases of DEMO concepts. The present study investigates the He detection by LIBS method in the Be coatings simulating the deposits on the divertor plasma-facing components of JET while the results are also relevant for He detection in the deposits of other wall materials. The study was carried out in a vacuum vessel filled with 2–40 mbar argon background gas. It was shown that 2.8 at. % of He was confidently detectable by LIBS at optimized measurement conditions and the estimated limit of detection at used experimental conditions is approximately 0.7 at. %. The intensity of the He emission line at 587.56 nm was the strongest at the center of the laser-induced plasma plume. The He line intensity increased with the pressure of Ar gas but the broadening of the He line and the increase of the background emission and noise set an upper limit to the Ar background pressure usable for He detection. The application of the calibration-free LIBS procedure resulted in the overestimation of the He/Be ratio by several orders of magnitude. The overestimation can be explained by the deviation of LIBS plasma from the local thermodynamic equilibrium, which is caused by the very high excitation energy of He atoms.
► SiN film hydrogen permeability at 400°C was determined as P=1×10−17molH2/msPa0.5. ► We presumably report the first quantitative data on H permeation through SiN. ► Permeation reduction factor of ...2000 was achieved with only 500nm thick SiN layer. ► High SiN barrier efficiency was found only when H is incorporated in SiN forming strong bonds. ► SiN containing ∼7at.% H is ∼100 times less permeable than the film without H.
Amorphous silicon nitride films, 500 and 700nm thick, were deposited on Eurofer substrates by applying reactive radio-frequency magnetron sputtering from pure Si targets in an argon/nitrogen atmosphere. The hydrogen permeation through such double-layered, 40mm diameter membranes at 400°C and 1bar upstream pressure involved the use of a conventional technique with enhanced sensitivity. The extremely high barrier efficiency for these films with respect to hydrogen, expressed as a permeation-reduction factor in excess of 2000, was only achieved with films containing 6–7at.% of hydrogen. The achieved permeation-reduction factor at 400°C corresponds to the permeability of silicon nitride, which is as low as P=1×10−17molH2/msPa0.5. The hydrogen concentration was determined with an Elastic Recoil Detection Analysis, which indicated that this high concentration represents only the strongly bound hydrogen that is not mobile at this low temperature, but impedes the mobility of the diffusive hydrogen. A silicon nitride film with a low hydrogen content is a far less efficient barrier, which supports the role of the strongly bound hydrogen.
Particle induced X-ray emission (PIXE) at microprobe of Jožef Stefan Institute is used to measure two-dimensional quantitative elemental maps of biological tissue. To improve chemical and biological ...understanding of the processes in vivo, supplementary information about chemical bonding and/or molecular distributions could be obtained by heavy-ion induced molecular desorption and a corresponding mass spectroscopy with Time-Of-Flight (TOF) mass spectrometer. As the method combines the use of heavy focused ions in MeV energy range and TOF Secondary Ion Mass Spectrometry, it is denoted as MeV SIMS.
At Jožef Stefan Institute, we constructed a linear TOF spectrometer and mount it to our multipurpose nuclear microprobe. A beam of 8MeV 35Cl7+ could be focused to a diameter of better than 3μm×3μm and pulsed by electrostatic deflection at the high-energy side of accelerator. TOF mass spectrometer incorporates an 1m long drift tube and a double stack microchannel plate (MCP) as a stop detector positioned at the end of the drift path. Secondary ions are focused at MCP using electrostatic cylindrical einzel lens.
Time of flight spectra are currently acquired with a single-hit time-to-digital converter. Pulsed ion beam produces a shower of secondary ions that are ejected from positively biased target and accelerated towards MCP. We start our time measurement simultaneously with the start of the beam pulse. Signal of the first ion hitting MCP is used to stop the time measurement. Standard pulses proportional to the time of flight are produced with time to analog converter (TAC) and fed into analog-to-digital converter to obtain a time histogram. To enable efficient detection of desorbed fragments with higher molecular masses, which are of particular interest, we recently implemented a state-of art Field Programmable Gate Array (FPGA)-based multi-hit TOF acquisition. To test the system we used focused 8MeV 35Cl7+ ion beam with pulse length of 180ns. Mass resolution of measured SIMS spectra, dominantly determined by the duration of the beam pulse, is in good agreement with resolution estimated from pulse length. With improved high-voltage switching ability that will enable beam pulses with duration of 50ns, a mass resolution of better than 500 is anticipated.
A new TOF telescope has been constructed for thin film and surface analysis. The timing system consists of two electrostatic mirror type detectors of Busch design. The detection efficiency of timing ...stations for very light ions was significantly improved using DLC (diamond like carbon) foils coated with LiF instead of the conventionally used carbon foils. Ion energy is measured by a 300mm2 ULTRA ion-implanted silicon detector. For the ERDA measurements with heavy and energetic ion beams, a time-of-flight (TOF) spectrometer is positioned at 37.5°. Spectrometer can be easily moved to 120° backward angle for time-of-flight RBS analysis with low energy beam of light ions. Positioning and fine adjustments of sample orientation are performed with a motorized sample stage. The same spectrometer can be also installed at the ion microprobe scattering chamber for 3D elemental imaging.
In the Elastic Recoil Detection Analysis (ERDA) and Heavy Ion Rutherford Backscattering Spectrometry (HIRBS), silicon surface barrier (SSB) detectors as well as other types of Si charged particle ...detectors are conventionally used for measuring ion energy due to their simplicity and ease of use. Energy resolution of such detectors is a limiting factor for both, mass and depth resolution in the experiment. In the present work we have studied performance of the commercially available F series ORTEC SSB detector designed in particular for heavy ion spectroscopy (BF-023-300-60). Detector energy and mass resolution were measured for a wide range of ion masses (7Li, 16O, 28Si, 35Cl and 81Br) and energies (2–20MeV). Obtained results were compared with the already published data for a standard A series ORTEC SSB detector (BA-017-100-100) and gas ionization chambers. Possible application of the F series SSB detector in time-of-flight ERDA (TOF-ERDA) spectrometer was discussed.
Megaelectronvolt-Secondary Ion Mass Spectrometry (MeV-SIMS) is an emerging Ion Beam Analysis technique for molecular speciation and submicron imaging. Various setups have been constructed in the ...recent years. Still a systematic investigation on the dependence of MeV-SIMS yields on different ion beam parameters is missing. A reliable measurement method of the beam current down to the attoampere range is needed for this investigation. Therefore, a new detector has been added to the MeV-SIMS setup at the Ruđer Bošković Institute (RBI), which measures the current directly using a Si PIN-diode. In this work, we present the constructed system, its characteristics, and results of the first yield measurements. These measurements have already identified important factors that have to be considered while constructing a MeV SIMS setup.
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•First application of MeV SIMS to determine deposition order of blue ballpoint pens.•Each pen contains combination of dyes and pigments giving different mass spectra.•Molecular ...imaging was performed with the micron lateral resolution.•MeV SIMS detects surface molecules revealing deposition order of intercepting lines.•Technique is non-destructive so samples can be reused for other measurements.
Secondary Ion Mass Spectrometry using MeV ion excitation was utilised for the analysis of optically indistinguishable intersecting ballpoint pen lines on paper. It was demonstrated that the technique was able to identify different colorants (dyes and synthetic organic pigments) with high efficiency and in a single measurement. The analysis of ink-ink intersections was performed using the Time-of-Flight mass spectrometer for MeV Secondary Ion Mass Spectrometry. This technique is attached to the heavy ion microprobe at the accelerator facility, and employs focused 8 MeV Si4+ ions for the surface analysis. Molecular imaging allowed for successful identification of sequence deposition order of otherwise optically indistinguishable intersecting lines.
Thin films of nonstoichiometric silicon oxide (SiO x with x < 2) have been studied extensively during the past few decades because of their importance in many electronic and optoelectronic ...applications, and particular attention has been paid to models that can better describe their global structure. Herein, we present a detailed study of SiO x films deposited on silicon(111) and silica substrates using the low-pressure chemical vapor deposition (LPCVD) method by thermal oxidation of silane in an oxygen atmosphere at a temperature of 570 °C. The oxygen and silane flows in the reactor were varied to obtain films with different values of oxygen content x. Ellipsometry and m-line measurements were used to determine the complex refractive index of the deposited films. The oxygen contents in the films were measured by infrared spectroscopy, energy-dispersive X-ray spectroscopy (EDX), and time-of-flight elastic recoil detection analysis (TOF-ERDA). The oxygen contents in the films were also estimated from the measured values of the complex refractive indices using Bruggeman’s effective-medium aproximation (EMA). All of the results were in good agreement, except for those obtained from infrared spectroscopy, which corresponded to systematically higher oxygen contents. This effect was interpreted as being due to an inhomogeneous distribution of oxygen atoms in the films (phase separation). This issue was confirmed by X-ray photoelectron spectroscopy (XPS) analysis of the Si 2p core levels, which showed an almost-complete phase separation of the silicon-rich oxides into amorphous silicon and silicon dioxide, indicating that the mixture model is the most appropriate for the present films.
Molecular imaging of cannabis leaf tissue with MeV-SIMS method Jenčič, Boštjan; Jeromel, Luka; Ogrinc Potočnik, Nina ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
03/2016, Volume:
371
Journal Article
Peer reviewed
To broaden our analytical capabilities with molecular imaging in addition to the existing elemental imaging with micro-PIXE, a linear Time-Of-Flight mass spectrometer for MeV Secondary Ion Mass ...Spectrometry (MeV-SIMS) was constructed and added to the existing nuclear microprobe at the Jožef Stefan Institute. We measured absolute molecular yields and damage cross-section of reference materials, without significant alteration of the fragile biological samples during the duration of measurements in the mapping mode. We explored the analytical capability of the MeV-SIMS technique for chemical mapping of the plant tissue of medicinal cannabis leaves. A series of hand-cut plant tissue slices were prepared by standard shock-freezing and freeze-drying protocol and deposited on the Si wafer. We show the measured MeV-SIMS spectra showing a series of peaks in the mass area of cannabinoids, as well as their corresponding maps. The indicated molecular distributions at masses of 345.5u and 359.4u may be attributed to the protonated THCA and THCA-C4 acids, and show enhancement in the areas with opened trichome morphology.
Imaging Mass Spectroscopy (IMS) is a unique research tool providing localization and identification of a wide range of biomolecules as essential data to understand biochemical processes in living ...organisms. Secondary Ion Mass Spectrometry with high-energy heavy ions (MeV-SIMS) is emerging as a promising IMS technique for chemical imaging of biological tissue.
We measured the molecular mass spatial distributions in leaves of khat (Catha edulis). Khat is a natural drug plant, native to eastern Africa and the Arabian Peninsula. In these countries, fresh leaves are being chewed by significant part of population. It was reported that 80% of the adult population in Yemen chew the khat leaves. The main stimulating effects of khat are induced by a monoamine alkaloid called cathinone. During leaf ageing, cathinone is further metabolised to cathine and norephedrine. Earlier studies identified the alkaloids in khat, however little is known on their spatial distribution, reflecting the biosynthesis and accumulation in the tissue.
Chemical mapping of alkaloids on cross-sections of khat leaves by MeV-SIMS was done at JSI by a pulsed 5.8MeV 35Cl6+ beam, focused to a diameter of 15μm, using a linear time-of-flight (TOF) spectrometer with a mass resolution of 500. In addition, measurements of MeV-SIMS mass spectra were performed at Kyoto University by a continuous broad beam of 6MeV 63Cu4+ ions at an orthogonal TOF spectrometer with a high mass resolution of 11,000. Sections of leaves were analysed and mass spectra obtained at both MeV-SIMS setups were compared. Tissue-level distributions of detected alkaloids are presented and discussed.
