Magnetic Sector Research Articles

Isotopic composition of CO2in the coma of 67P/Churyumov-Gerasimenko measured with ROSINA/DFMS

Measurements of isotopic abundances in cometary ices are key to understanding and reconstructing the history and origin of material in the solar system. Comets are considered the most pristine material in the solar system. Isotopic fractionation (enrichment of an isotope in a molecule compared to the initial abundance) is sensitive to environmental conditions at the time of comet formation. Therefore, measurements of cometary isotope ratios can provide information on the composition, density, temperature, and radiation during formation of the molecules, during the chemical evolution from the presolar cloud to the protosolar nebula, and the protoplanetary disk before accretion in solid bodies. Most isotopic abundances of 12 C/ 13 C and 16 O/ 18 O in comets to date are in agreement with terrestrial abundances. Prior to the Rosetta mission, measurements of 12 C/ 13 C in comets were only available for HCN, CN, and C 2 and for 16 O/ 18 O in H 2 O. Measurements of 12 C/ 13 C in comets were only available from ground based observations and remote sensing, while 16 O/ 18 O in H 2 O had also been measured in-situ. To date, no measurements of the CO 2 isotopologues in comets were available. This paper presents the first measurements of the CO 2 isotopologues in the coma of 67P/Churyumov-Gerasimenko (67P). Methods. We analyzed measurements taken by the Double Focusing Mass Spectrometer (DFMS) of the ROSINA experiment on board the ESA spacecraft Rosetta in the coma of 67P. The CO 2 isotopologues results for 67P are: 12 C/ 13 C = 84 ± 4, 16 O/ 18 O = 494 ± 8, and 13 C 16 O 2 / 12 C 18 O 16 O = 5.87 ± 0.07. The oxygen isotopic ratio is within error bars compatible with terrestrial abundances but not with solar wind measurements. Conclusions. The carbon isotopic ratio and the combined carbon and oxygen isotopic ratio are slightly (14%) enriched in 13 C, within 1σ uncertainty, compared to solar wind abundances and solar abundances. The small fractionation of 12 C/ 13 C in CO 2 is probably compatible with an origin of the material in comets from the native cloud.

Quantifying Short-Chain Chlorinated Paraffin Congener Groups.

Accurate quantification of short-chain chlorinated paraffins (SCCPs) poses an exceptional challenge to analytical chemists. SCCPs are complex mixtures of chlorinated alkanes with variable chain length and chlorination level; congeners with a fixed chain length (n) and number of chlorines (m) are referred to as a "congener group" CnClm. Recently, we resolved individual CnClm by mathematically deconvolving soft ionization high-resolution mass spectra of SCCP mixtures. Here we extend the method to quantifying CnClm by introducing CnClm specific response factors (RFs) that are calculated from 17 SCCP chain-length standards with a single carbon chain length and variable chlorination level. The signal pattern of each standard is measured on APCI-QTOF-MS. RFs of each CnClm are obtained by pairwise optimization of the normal distribution's fit to the signal patterns of the 17 chain-length standards. The method was verified by quantifying SCCP technical mixtures and spiked environmental samples with accuracies of 82-123% and 76-109%, respectively. The absolute differences between calculated and manufacturer-reported chlorination degrees were -0.9 to 1.0%Cl for SCCP mixtures of 49-71%Cl. The quantification method has been replicated with ECNI magnetic sector MS and ECNI-Q-Orbitrap-MS. CnClm concentrations determined with the three instruments were highly correlated (R2 > 0.90) with each other.

Solid phase microextraction and gas chromatography coupled to magnetic sector high resolution mass spectrometry for the ultra-trace determination of contaminants in surface water

With the aim of monitoring water quality according to the regulations established by the European Union it would be necessary to implement analytical methodologies capable of simultaneously determining a broad range of organic pollutants at ultra-trace levels, allowing for increased sample throughput. In addition, the high number of samples to be analyzed requires a particular focus on setting up fully automated analytical methodologies. In view of that, this study is aimed at the development of a complete automated procedure for the ultra-trace determination of certain pesticides, polycyclic aromatic hydrocarbons (PAHs), brominated diphenyl ethers (BDEs) and polychlorinated biphenyls (PCBs) in surface waters. The proposed method is based on an on-line combination of solid phase microextraction (SPME) and gas chromatography coupled to double-focusing magnetic sector high resolution mass spectrometry (GC–HRMS). SPME as well as GC–HRMS conditions were optimized to achieve maximum extraction efficiency and sensitivity, which was reinforced by using multiple ion detection (MID) as acquisition mode. Using only 19mL of water and with minimum sample manipulation, the method allowed for the determination of 53 compounds exhibiting good linearity (R2>0.99), recoveries between 84 and 118% and relative standard deviation (RSD) values <20% for intra-day and inter-day precision. In addition, the method provides quantification limits (LOQs) between 0.1–50ngL−1, lower than the Environmental Quality Standards (EQS) fixed by Directive 2013/39/EC. Finally, the method was successfully applied to determine target contaminants in Almería surface water compartments, detecting dioxin-like PCBs, BDEs and some pesticides.

Quantitative imaging of deuterated metabolic tracers in biological tissues with nanoscale secondary ion mass spectrometry

In the field of secondary ion mass spectrometry at nanometer scale (NanoSIMS), configuration of parallel detectors to routinely measure isotope ratios in sub-100nm domains brings classical stable isotope tracer studies from the whole tissue level down to the suborganelle level. Over the past decade, the marriage of stable isotope tracers with NanoSIMS has been applied to a range of fundamental biological questions that were largely inaccessible by other means. Although multiplexed measurement of different stable isotope tracers is feasible, in practice there remains a gap in the current analytical capacity to efficiently measure stable isotopes commonly utilized in tracer studies. One such example is the measurement of deuterated tracers. The most obvious approach to measuring deuterium/hydrogen isotope ratios is at mass 2/1. However, the radius of the magnetic sector limits concomitant measurement of other masses critical to multiplexed exploration of biological samples. Here we determine the experimental parameters to measure deuterated tracers in biological samples using the C2H− polyatomic ion species (C2D−/C2H−) while operating the NanoSIMS at a reduced Mass Resolving Power of 14,000. Through control of the sputtering parameters, we demonstrate that there is an analytical window during which the C2D−/C2H− isotope ratio can be measured with sufficient precision for biological studies where the degree of D-labeling is typically well above natural abundance. We provide validation of this method by comparing the C2D measurement of D-water labeling in the murine small intestine relative to measurements of native D/H conducted in the same analytical fields. Additional proof-of-concept demonstrations include measurement of D-water, D-glucose, and D-thymidine in biological specimens. Therefore, this study provides a practical template for deuterium-based tracer studies in biological systems.

Co-Registered In Situ Secondary Electron and Mass Spectral Imaging on the Helium Ion Microscope Demonstrated Using Lithium Titanate and Magnesium Oxide Nanoparticles.

The development of a high resolution elemental imaging platform combining coregistered secondary ion mass spectrometry and high resolution secondary electron imaging is reported. The basic instrument setup and operation are discussed and in situ image correlation is demonstrated on a lithium titanate and magnesium oxide nanoparticle mixture. The instrument uses both helium and neon ion beams generated by a gas field ion source to irradiate the sample. Both secondary electrons and secondary ions may be detected. Secondary ion mass spectrometry (SIMS) is performed using an in-house developed double focusing magnetic sector spectrometer with parallel detection. Spatial resolutions of 10 nm have been obtained in SIMS mode. Both the secondary electron and SIMS image data are very surface sensitive and have approximately the same information depth. While the spatial resolutions are approximately a factor of 10 different, switching between the different images modes may be done in situ and extremely rapidly, allowing for simple imaging of the same region of interest and excellent coregistration of data sets. The ability to correlate mass spectral images on the 10 nm scale with secondary electron images on the nanometer scale in situ has the potential to provide a step change in our understanding of nanoscale phenomena in fields from materials science to life science.

Instrumentation and Method Development for On-Site Analysis of Helium Isotopes.

Helium isotope determination may be useful in measuring volcanic activity and issuing earlier warnings of possible eruptions. A method is presented for measuring the 3He/4He ratio in a gas sample using a multiturn time-of-flight mass spectrometer "infiTOF". In contrast to conventional waveform averaging, peaks are determined by counting ion pulses from each time-of-flight trigger. Samples were also measured by conventional magnetic-sector mass spectrometry for comparison. Magnetic sector results were used to designate a standard for infiTOF measurement and to calculate a ratio for each sample measured by infiTOF. Mass assignment error for ultrapure 3He+ standard was 4.30 × 10-5 Da. Mass assignment error of 4He2+ and 3He+ for sample cylinders was 3.00 × 10-8 Da and 2.25 × 10-4 Da, respectively. Abundance ratios determined by infiTOF were found to be within 2% of the abundance ratios determined by magnetic-sector mass spectrometry. Mass drift was <50 × 10-6 Da over 10 h. Sample flow rate was not found to affect the results as long as the reference sample was analyzed under the same conditions. Results indicate that the infiTOF system may be a viable tool for measuring helium isotopes, which may eventually lead to earlier warnings of volcanic activity.

Magnetic system of a superconducting separated-sector cyclotron for hadron therapy

The development of a cyclotron magnetic system based on superconducting sector magnets is discussed. The cyclotron is conceived as a booster accelerator of a source of 12С6+ ions with energy of 400MeV/nucleon for the purposes of hadron therapy. The results of preliminary investigations aimed at developing such a facility have been reported in our previous papers. In this paper, we consider various configurations of the booster’s magnetic system for various field levels. We also analyze the effects of the positions and shapes of superconducting coils on the magnetic field and select the optimum configuration for the cyclotron’s magnetic system.

Organics in comet 67P – a first comparative analysis of mass spectra from ROSINA–DFMS, COSAC and Ptolemy

The ESA Rosetta spacecraft followed comet 67P at a close distance for more than 2 yr. In addition, it deployed the lander Philae on to the surface of the comet. The (surface) composition of the comet is of great interest to understand the origin and evolution of comets. By combining measurements made on the comet itself and in the coma, we probe the nature of this surface material and compare it to remote sensing observations. We compare data from the double focusing mass spectrometer (DFMS) of the ROSINA experiment on ESA's Rosetta mission and previously published data from the two mass spectrometers COSAC (COmetary Sampling And Composition) and Ptolemy on the lander. The mass spectra of all three instruments show very similar patterns of mainly CHO-bearing molecules that sublimate at temperatures of 275 K. The DFMS data also show a great variety of CH-, CHN-, CHS-, CHO2- and CHNO-bearing saturated and unsaturated species. Methyl isocyanate, propanal and glycol aldehyde suggested by the earlier analysis of the measured COSAC spectrum could not be confirmed. The presence of polyoxymethylene in the Ptolemy spectrum was found to be unlikely. However, the signature of the aromatic compound toluene was identified in DFMS and Ptolemy data. Comparison with remote sensing instruments confirms the complex nature of the organics on the surface of 67P, which is much more diverse than anticipated.

The nano-fractal structured tungsten oxides films with high thermal stability prepared by the deposition of size-selected W clusters

Size-selected W − clusters (n = 1650) were deposited on the highly ordered pyrolytic graphite surface at room temperature under high vacuum conditions by utilizing a magnetron sputtering source and a magnet sector field. Moreover, geometrical structure and surface chemical states of deposited clusters were analyzed by in situ scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy, respectively. The formation of 2-D islands (lateral size ~150 nm) with multiple dendritic arms was observed by STM, and the structure of the individual W1650 clusters survived within the dendritic arms. To study the thermal stability of the nano-fractal structure under the atmospheric conditions, the sample was brought to the ambient air conditions and sequentially post-annealed at 200, 300, and 500 °C in the air. The nano-fractal structure was maintained after the 1st post-annealing process at 200 °C for 1 h in the air, and the subsequent 2nd post-annealing at 300 °C (for 1 h, in the air) also did not induce any noticeable change in the topological structure of the sample. The topological changes were observed only after the further post-annealing at a higher temperature (at 500 °C, 1 h) in the air. We show high potential use of these nano-structured films of tungsten oxides in ambient conditions.

A new negative and positive gas ion source for isotope ratio mass spectrometry.

The goal of this research was to construct an effective gas ion source for isotope ratio mass spectrometry, which generates sufficiently strong and stable ion beams for multiple isotope ratio analysis of sulfur and oxygen from readily available gases such as SO2 , CO2 , CO, O2 and chlorine from CH3 Cl gas. By means of a 60° sector mass spectrometer equipped with a new type of sensitive ion source and with a dual-inlet system and triple collector assembly, we have measured 34 S/32 S and challenging 36 S/32 S isotope ratios using positive sulfur ions generated from SO2 gas. The new ion source differs from the Nier-type ones by the electron beam being replaced with a tungsten filament. The obtained isotope signals of 32 S+ , 34 S+ and 36 S+ were from 1 to 5V (depending on the pressure of admitted gas) on high-ohm resistors of 200MΩ, 5 GΩ and 500 GΩ, respectively. The variable 33 S peak was not recorded as useful due to interference from H32 S+ ions. Although the ionizing electrons in the new ion source have significant energy dispersion the obtained peak profiles are flat-topped and they lead to good resolving power for the mass spectrometer (M/∆M≈100). The achieved precision of δ34 S and δ36 S determination was better than ±0.01 and ±0.1‰, respectively. The determination of 37 Cl/35 Cl in a volatile organic compound CH2 Cl2 was easily achieved on Cl- negative ions with a precision of ±0.005‰. The new ion source has great potential in the quantitative analysis of gases on positive ion mass spectra as well as, in the case of gases with high electron affinity such as CH3 Cl, CH3 Br, SF6 , SiF4 , on negative ones. It usefulness was demonstrated on an example of multiple sulfur isotope analysis and 37 Cl/35 Cl ratio determination with great precision. A negative ion source of this type will probably be useful in a more complicated instruments used in SIMS or AMS. Copyright © 2017 John Wiley & Sons, Ltd.

On-line double focusing of atenolol and metoprolol in human urine using capillary electrophoresis with the aid of β-cyclodextrin

A maneuverable and sensitive on-line double focusing technique combined field amplified sample stacking (FASS) with micelle to solvent stacking (MSS) with the aid of β-cyelodextrin (β-CD) is developed to detect the contents of AT and ME in human urine by capillary electrophoresis (CE) with UV detector. Small amount of β-CD not only increase the critical micelle concentration (CMC) of SDS, but also strengthen the interaction between SDS and the aimed compound by forming inclusion complexes. The result indicates that the addition of β-CD affords 5.5- and 3.5-fold improvements for atenolol (AT) and metoprolol (ME) in sensitivity than that of in the absence of β-CD in the double focusing system, respectively. Under the optimal conditions, about 200-fold improvement in sensitivity for analytes is achieved compared with conventional CE method. The limits of detection (LODs) at a signal-to-noise of 3 (S/N = 3) of the two β-blockers can be reached 3.3 and 3.7 ng mL−1 respectively, which are lower than minimum required performance levels (MRPLs) set by the World Anti Doping Agency. The relative standard deviations (RSDs) of peak areas of intra-day and inter-day are 3.51–3.38% and 2.34–4.28% (n = 6), respectively. AT and ME in urine without special pretreatment and additional instrument are analyzed. The recoveries are 82–98% with RSDs less than 2.0%.

Evidence for depletion of heavy silicon isotopes at comet 67P/Churyumov-Gerasimenko

Context. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) was designed to measure the composition of the gas in the coma of comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta mission. In addition to the volatiles, ROSINA measured refractories sputtered off the comet by the interaction of solar wind protons with the surface of the comet. Aims. The origin of different solar system materials is still heavily debated. Isotopic ratios can be used to distinguish between different reservoirs and investigate processes occurring during the formation of the solar system. Methods. ROSINA consisted of two mass spectrometers and a pressure sensor. In the ROSINA Double Focusing Mass Spectrometer (DFMS), the neutral gas of cometary origin was ionized and then deflected in an electric and a magnetic field that separated the ions based on their mass-to-charge ratio. The DFMS had a high mass resolution, dynamic range, and sensitivity that allowed detection of rare species and the known major volatiles. Results. We measured the relative abundance of all three stable silicon isotopes with the ROSINA instrument on board the Rosetta spacecraft. Furthermore, we measured $^{13}$C/$^{12}$C in C$_2$H$_4$, C$_2$H$_5$, and CO. The DFMS in situ measurements indicate that the average silicon isotopic composition shows depletion in the heavy isotopes $^{29}$Si and $^{30}$Si with respect to $^{28}$Si and solar abundances, while $^{13}$C to $^{12}$C is analytically indistinguishable from bulk planetary and meteorite compositions. Although the origin of the deficiency of the heavy silicon isotopes cannot be explained unambiguously, we discuss mechanisms that could have contributed to the measured depletion of the isotopes $^{29}$Si and $^{30}$Si.

Determination of kinetic energy release from metastable peak widths: An investigation of the instrument-dependence

The kinetic energy that is released upon bond rupture is often represented as T1/2. A value that is derived from the FWHM of a fragment peak by the use of two different conversion formulas. The choice of formula depends on whether the peak is recorded by scanning a magnetic sector or an electrostatic analyzer. We have conducted a systematic variation of the possible scan configurations of two different double focusing instruments in two countries. We have found that a double focusing mass spectrometer in normal geometry gives rise to T1/2 values that are 1.4 times larger when analyzing peaks that are obtained from magnet scans compared to the peaks that are obtained by scanning an electrostatic analyzer. The E scans (MIKE experiments) give rise to the same values for both of the employed mass spectrometers. The results are explained in terms of energy defocusing when the reactions take place too far away from the focal points and show that only the E scans T1/2 values can be compared from instrument to instrument.

The heterogeneous coma of comet 67P/Churyumov-Gerasimenko as seen by ROSINA: H2O, CO2, and CO from September 2014 to February 2016

Context.The ESA Rosetta mission has been investigating the environment of comet 67P/Churyumov-Gerasimenko (67P) since August 2014. Among the experiments on board the spacecraft, the ROSINA experiment (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) includes two mass spectrometers to analyse the composition of neutrals and ions and a COmet Pressure Sensor (COPS) to monitor the density and velocity of neutrals in the coma.Aims.We study heterogeneities in the coma during three periods starting in October 2014 (summer in the northern hemisphere) and ending in February 2016 (end of winter in the northern hemisphere). We provide a detailed description of the main volatiles dynamics (H2O, CO2, CO) and their abundance ratios.Methods.We analysed and compared the data of the Reflectron-type Time-Of-Flight (RTOF) mass spectrometer with data from both the Double Focusing Mass Spectrometer (DFMS) and COPS during the comet escort phase. This comparison has demonstrated that the observations performed with each ROSINA sensor are indeed consistent. Furthermore, we used a Direct Simulation Monte Carlo (DSMC) model to compare modelled densitites with in situ detections.Results.Our analysis shows how the active regions of the main volatiles evolve with the seasons with a variability mostly driven by the illumination conditions; this is the case except for an unexpected dichotomy suggesting the presence of a dust layer containing water deposited in the northern hemisphere during previous perihelions hiding the presence of CO2. The influence of various parameters is investigated in detail: distance to the comet, heliocentric distance, longitude and latitude of sub-satellite point, local time, and phase angle.

Regular Consumption of a Functional Symbiotic Yogurt Increases Calcium Absorption in Young Adult Women

We investigated the effect of daily consumption of a yogurt containing prebiotic fiber and probiotics (functional yogurt) compared to a common yogurt (control), on calcium absorption in adult women (21–33 years; n=30) using a cross‐over design. Each yogurt was consumed during 3 weeks separated by a 3 week wash‐out period. Calcium absorption was measured at the end of each yogurt‐consumption period, using an oral isotope tracer (42Ca) administered along with a standard breakfast meal. Recovery of 42‐‐‐‐‐‐‐Ca in urine was measured in complete collections at 4h, 24h, and 36h post‐dosing using magnetic sector thermal ionization mass spectrometry. Bone mass, PTH and vitamin D status were evaluated at baseline. Bone mineral content (BMC) and density (BMD) at total body (TB), lumbar spine (LS), femoral neck (FN) and trochanter (TR) were measured by dual energy X‐ray absorptiometry. Serum 25(OH)D and intact PTH were determined by chemiluminescent assays. Temporal changes in urinary 42‐‐‐‐‐‐‐Ca recovery were analyzed by repeated‐measures ANOVA. Comparison between treatments at each time point was evaluated by paired t test. Relationships between variables were examined by correlation analysis. Average Z scores of bone measurements were adequate, 0.59 (TBBMC), 0.49 (TBBMD), 0.05 (LSBMD), 0.99 (FNBMD), −0.54 (TRBMD) although TRBMD and LSBMD Z scores were lower than −1 in 30% and 7% of the women, respectively. Serum 25(OH)D was 37.9 ± 9.9 ng/mL indicating vitamin D sufficiency. As expected, urinary 42‐‐‐‐‐‐‐Ca recovery increased over time for each type of yogurt (P&lt;0.01). There were no significant differences by yogurt type at 4h or 24h but at 36h, 42‐‐‐‐‐‐‐Ca recovery in urine was 37% higher after consumption of the functional yogurt compared to the control yogurt (P=0.05). Urinary recovery of 42‐‐‐‐‐‐‐Ca was not related to vitamin D, PTH or bone mass measurements. These results suggest that the functional yogurt tested increased calcium absorption possibly by passive processes in the distal small intestine or in the colon.Support or Funding InformationCooperativa Nacional de Productores de Leche (CONAPROLE), Uruguay

Mass spectroscopy of the ion flux produced during inductively coupled plasma nitriding process

Ion fluxes on the surface of sample embedded in inductively coupled plasma have been studied in conditions typical for titanium alloy nitriding: total pressure 0.44 Pa, Ar/N2 = 70%/30%, and RF power 1500 W. The gas composition was independently monitored by the quadrupole analyser. The ion fluxes were sampled using a specially designed electrostatic extractor and then analysed with a magnetic sector mass-separator. The extractor design allowed us to apply a bias voltage to the plasma facing electrode thus imitating interaction of ions with the surface during the plasma processing. The ion fluxes of Ar+, , and N+ on the surface were measured. The mass spectroscopy diagnostics unit is suitable for extensive ion content studies in the plasma technology facilities.

A questionnaire measuring staff perceptions of Lean adoption in healthcare: development and psychometric testing

BackgroundDuring the past decade, the concept of Lean has spread rapidly within the healthcare sector, but there is a lack of instruments that can measure staff’s perceptions of Lean adoption. Thus, the aim of the present study was to develop a questionnaire measuring Lean in healthcare, based on Liker’s description of Lean, by adapting an existing instrument developed for the service sector.MethodsA mixed-method design was used. Initially, items from the service sector instrument were categorized according to Liker’s 14 principles describing Lean within four domains: philosophy, processes, people and partners and problem-solving. Items were lacking for three of Liker’s principles and were therefore developed de novo. Think-aloud interviews were conducted with 12 healthcare staff from different professions to contextualize and examine the face validity of the questionnaire prototype. Thereafter, the adjusted questionnaire’s psychometric properties were assessed on the basis of a cross-sectional survey among 386 staff working in primary care.ResultsThe think-aloud interviews led to adjustments in the questionnaire to better suit a healthcare context, and the number of items was reduced. Confirmatory factor analysis of the adjusted questionnaire showed a generally acceptable correspondence with Liker’s description of Lean. Internal consistency, measured using Cronbach’s alpha, for the factors in Liker’s description of Lean was 0.60 for the factor people and partners, and over 0.70 for the three other factors. Test-retest reliability measured by the intra-class correlation coefficient ranged from 0.77 to 0.88 for the four factors.ConclusionsWe designed a questionnaire capturing staff’s perceptions of Lean adoption in healthcare on the basis of Liker’s description. This Lean in Healthcare Questionnaire (LiHcQ) showed generally acceptable psychometric properties, which supports its usability for measuring Lean adoption in healthcare. We suggest that further research focus on verifying the usability of LiHcQ in other healthcare settings, and on adjusting the instrument if needed.

Coded Apertures in Mass Spectrometry.

The use of coded apertures in mass spectrometry can break the trade-off between throughput and resolution that has historically plagued conventional instruments. Despite their very early stage of development, coded apertures have been shown to increase throughput by more than one order of magnitude, with no loss in resolution in a simple 90-degree magnetic sector. This enhanced throughput can increase the signal level with respect to the underlying noise, thereby significantly improving sensitivity to low concentrations of analyte. Simultaneous resolution can be maintained, preventing any decrease in selectivity. Both one- and two-dimensional (2D) codes have been demonstrated. A 2D code can provide increased measurement diversity and therefore improved numerical conditioning of the mass spectrum that is reconstructed from the coded signal. This review discusses the state of development, the applications where coding is expected to provide added value, and the various instrument modifications necessary to implement coded apertures in mass spectrometers.

LA-Q-ICP-MS apatite U/Pb geochronology using common Pb in plagioclase: Examples from layered mafic intrusions

Apatite geochronology is a versatile method for providing medium temperature history constraints of magmatic and metamorphic rocks. The LA-ICP-MS technique is widely applied to U/Pb geochronology using various minerals. Apatite U/Pb geochronology, in contrast to e.g., zircon, is compromised by variable amounts of common Pb incorporated into the crystal during growth. Magmatic apatite often shows a sufficient spread in data to obtain a precise and accurate lower intercept age. If this is not the case, the initial Pb isotopic composition needs to be estimated to obtain accurate and precise age information from apatite. Two approaches are common, one being the estimation of common Pb from a Pb evolution model and the other being the measurement of a coexisting mineral phase that tends to incorporate Pb but not U, e.g., feldspar. Most recent studies applying LA-ICP-MS to the analysis of Pb isotopes in feldspar utilize either multicollector or magnetic sector mass spectrometers. In this study we first evaluate the application of quadrupole mass spectrometry for apatite U/Pb geochronology combined with Pb isotopic measurements in feldspar and compare the results with modeled initial Pb isotopic compositions. The resulting age information is accurate and precise despite using plagioclase rather than K-feldspar, as is normally used, to define initial Pb isotope compositions. We apply this method to apatite-bearing gabbroic rocks from layered intrusions (Bushveld, Bjerkreim-Sokndal, Hasvik, and Skaergaard) ranging in age from ca. 2 Ga to ca. 55 Ma and generate metamorphic/cooling ages generally consistent with the known geologic history of these intrusions.

Energy-spread measurement of triple-pulse electron beams based on the magnetic dispersion principle

The method of energy dispersion in magnetic field is used to analyze the energy spread of the triple-pulse electron beam generated by the Dragon-II linear induction accelerator. A sector magnet is applied for energy analysis of the electron beam, with a bending radius of 300 mm and a deflection angle of 90°. For each pulse, the time-resolved and integral images of the electron position at the output port of beam-bending line are recorded by a streak camera and a CCD camera, respectively. Experimental results demonstrate an energy spread of less than ±2.0% for the electron pulses. The cavity voltage waveforms obtained by different detectors are also analyzed for comparison.