Magnetic Sector Research Articles

Position-dependent microchannel plate gain correction in Rosetta's ROSINA/DFMS mass spectrometer

Mass spectrometers that rely on microchannel plate (MCP) detectors age when they are used intensively. The ageing process is due to a reduction of the MCP gain as ions repeatedly bombard the MCP, leading to a reduction of the secondary electron yield of an impacting ion and to a reduction of the electron amplification within the MCP pores. MCP gain therefore is both time- and position-dependent. This is particularly true for the Double Focusing Mass Spectrometer DFMS, part of the ROSINA instrument, embarked on the European Space Agency's Rosetta spacecraft that studied comet 67P/Churyumov-Gerasimenko continuously for over more than 2 years. A position-dependent gain correction technique is developed here. A detailed assessment of the technique demonstrates that improper treatment of this position-dependent gain can lead to misleading results and false conclusions, especially regarding less abundant species whose mass peak signature overlaps with peaks of abundant species. The correction technique presented here avoids such problems, especially in the situation where detector ageing is significant and uneven across the detector. It is also able to explain why all recorded mass peaks have a nearly symmetric double Gaussian shape, despite the strong variations in the position-dependent gain.

Beam optics of upgraded high energy heavy ion microbeam in Lanzhou

In order to expand applications of the Lanzhou microbeam the resent improvements were introduced in its slits, lens system and target chamber. In this study a beam optics of the new system was calculated for the 12C+6 ion beam of 966 MeV. To compensate a negative influence of a sector magnet dispersion on the beam dynamics an excitation of the magnetic quadrupole between two bending dipoles was determined. By varying parameters of the final triplet of magnetic quadrupole lenses a set of the microbeam systems with a stigmatic focusing were obtained. The best two of them were selected applying an optimization for a beam collimation by object and divergence slits. Simulation of the beam dynamics after the collimation allowed to determine the slit sizes that provide the highest current in the 1 µm probe on the target for these microbeam systems.Additionally, to improve the beam parameters at the microbeam entrance and then match the system parameters with this beam, the approach of an automatic probe-forming system is proposed. It is aimed at providing the highest possible resolution of the microbeam for the different beam varieties from a cyclotron.

Contributions to the Interpretation of Mass Spectrum of Hexaethoxydisiloxane Linked scans and M+1, M+2 isotopic effects

The aim of this article is the study of the fragmentation reactions of hexaethoxydisiloxane initiated by electronic impact in the ionization chamber of a double focusing mass spectrometer. The initiation center of fragmentation reactions is established by quantum calculations. The daughter ions of hexaethoxydisiloxane molecular ion are obtained by linked scan B/E. The primary fragmentation ions with the masses 341, 297, 296 and 269 were obtained experimentally by B/E linked scan by radical induced fragmentation reactions. The eliminations of neutral fragments such as hydrogen, acetaldehyde, ethylene and water from the primary ions and the obtained ions by consecutive elimination reactions were emphasized experimentally by the B/E(1-E)1/2 linked scan by charge induced reactions.

A comparison between the two lobes of comet 67P/Churyumov–Gerasimenko based on D/H ratios in H2O measured with the Rosetta/ROSINA DFMS

ABSTRACT The nucleus of the Jupiter-family comet 67P/Churyumov–Gerasimenko was discovered to be bi-lobate in shape when the European Space Agency spacecraft Rosetta first approached it in 2014 July. The bi-lobate structure of the cometary nucleus has led to much discussion regarding the possible manner of its formation and on how the composition of each lobe might compare with that of the other. During its two-year-long mission from 2014 to 2016, Rosetta remained in close proximity to 67P/Churyumov–Gerasimenko, studying its coma and nucleus in situ. Based on lobe-specific measurements of HDO and H2O performed with the ROSINA Double Focusing Mass Spectrometer (DFMS) on board Rosetta, the deuterium-to-hydrogen (D/H) ratios in water from the two lobes can be compared. No appreciable difference was observed, suggesting that both lobes formed in the same region and are homogeneous in their D/H ratios.

The surface distributions of the production of the major volatile species, H2O, CO2, CO and O2, from the nucleus of comet 67P/Churyumov-Gerasimenko throughout the Rosetta Mission as measured by the ROSINA double focusing mass spectrometer

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) suite of instruments operated throughout the over two years of the Rosetta mission operations in the vicinity of comet 67P/Churyumov-Gerasimenko. It measured gas densities and composition throughout the comet's atmosphere, or coma. Here we present two-years' worth of measurements of the relative densities of the four major volatile species in the coma of the comet, H2O, CO2, CO and O2, by one of the ROSINA sub-systems called the Double Focusing Mass Spectrometer (DFMS). The absolute total gas densities were provided by the Comet Pressure Sensor (COPS), another ROSINA sub-system. DFMS is a very high mass resolution and high sensitivity mass spectrometer able to resolve at a tiny fraction of an atomic mass unit. We have analyzed the combined DFMS and COPS measurements using an inversion scheme based on spherical harmonics that solves for the distribution of potential surface activity of each species as the comet rotates, changing solar illumination, over short time intervals and as the comet changes distance from the sun and orientation of its spin axis over long time intervals. We also use the surface boundary conditions derived from the inversion scheme to simulate the whole coma with our fully kinetic Direct Simulation Monte Carlo model and calculate the production rates of the four major species throughout the mission. We compare the derived production rates with revised remote sensing observations by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) as well as with published observations from the Microwave Instrument for the Rosetta Orbiter (MIRO). Finally we use the variation of the surface production of the major species to calculate the total mass loss over the mission and, for different estimates of the dust/gas ratio, calculate the variation of surface loss all over the nucleus.

Direct ion content measurements in a non-sputtering magnetron discharge

In present contribution we report the first direct measurements of ion fluxes in a non-sputtering magnetron discharge (NSMD) with Al cathode in Ar/O2 mixtures. The diagnostic unit comprising three-electrode electrostatic lens ion extractor, magnetic sector mass-analyzer, and a vacuum electron multiplier was calibrated and then used to record the time-resolved ion counts of Al+ and Ar+ both in NSMD and arc regimes. The results clearly indicate that in NSMD the dominant species are Ar ions while Al ion signal is lower than the sensitivity limit due to noise level, in contrast to the arc discharge. The capabilities of the diagnostics setup and its sensitivity limits are discussed.

The magnetic toroidal sector as a broad-band electron–positron pair spectrometer I. lepton trajectories

We report an analysis of electron-optical properties of a toroidal magnetic sector spectrometer and examine parameters for its implementation in a relativistic heavy-ion storage ring like HESR. For studies of free-free pair production in heavy-ion atom collisions this spectrometer exhibits very high efficiencies for coincident $e^+e^-$ pair spectroscopy over a wide range of momenta of emitted lepton pairs. The high coincidence efficiency of the spectrometer is the key for stringent tests of theoretical predictions for the coincident positron- and electron- emission characteristics and for the phase space correlation of lepton vector momenta in free-free pair production.

Effects of fertilizer types and water quality on carbon dioxide emissions from soil in wheat-maize rotations

The use of fertilizers as addition inputs in agricultural systems can increase the yield of wheat and maize, while also stimulating the emission of carbon dioxide from soil that the main man-made greenhouse gas. Our objectives focused on the impact of different types of synthetic fertilizers and water quality. The purposes were to determine the feasibility of using wasted water for irrigation and to relate CO2 fluxes to the yield of maize and wheat, as well as to select the best fertilizer type with low CO2 emission and high yield. The experiment consisted of a double factors test focusing on four forms of fertilizer (urea, amine and slow release fertilizer) and the quality of water (reclaimed water and underground water). The results showed that the reclaimed water was not significant on the CO2 discharge rate, the maize-wheat yield or the soil properties in 2014 or 2015; however, the CO2 emission increased slightly in 2015. Focusing on fertilizer treatments, the reclaimed water & amine fertilizer treatment (CAF) that had higher cumulative CO2 emissions was 32.75 t·ha−1 in 2014 and 33.86 t·ha−1 in 2015. According to the ratio CO2/Y, the slow released fertilizer that reduces CO2 emissions and keeps the yield high is the preferred choice.

The formation of NeH+ in static vacuum mass spectrometers and re-determination of 21Ne/20Ne of air

Abstract Air-derived neon is used for routine calibration of magnetic sector mass spectrometers, principally for determining sensitivity and mass discrimination for Ne isotope determinations. The commonly accepted 21Ne/20Ne ratio of air (0.002959 ± 0.000022; Eberhardt et al. (1965) does not take account of the contribution of 20NeH+ at m/z = 21. Honda et al. (2015) and Wielandt and Storey (2019) have recently re-determined the 21Ne/20Neair by resolving 20NeH+ from 21Ne+. The 21Ne/20Neair values of the two studies differ by 1.8%, beyond the uncertainty of the measurements (±

CHO-Bearing Molecules in Comet 67P/Churyumov-Gerasimenko

In 2004, the Rosetta spacecraft was sent to comet 67P/Churyumov-Gerasimenko for the first ever long-term investigation of a comet. After its arrival in 2014, the spacecraft spent more than 2 years in immediate proximity to the comet. During these 2 years, the ROSINA Double Focusing Mass Spectrometer (DFMS) onboard Rosetta discovered a coma with an unexpectedly complex chemical composition that included many oxygenated molecules. Determining the exact cometary composition is an essential first step to understanding of the organic rich chemistry in star forming regions and protoplanetary disks that are ultimately conserved in cometary ices. In this study, a joint approach of laboratory calibration and space data analysis was used to perform a detailed identification and quantification of CHO compounds in the coma of 67P/Churyumov-Gerasimenko. The goal was to derive the CHO compound abundances relative to water for masses up to 100 u. For this study, the May 2015 postequinox period represents the best bulk abundances of comet 67P/Churyumov-Gerasimenko. A wide variety of CHO compounds were discovered, and their bulk abundances were derived. Finally, these results are compared to abundances of CHO-bearing molecules in other comets, obtained mostly from ground-based observations and modeling.

Self-Supplied Liquid Injection Field Desorption/Ionization Ion Source for an Orthogonal Time-of-Flight Instrument.

A new implementation of a dedicated ion source for field ionization (FI), field desorption (FD), and liquid injection field desorption/ionization (LIFDI) for the JEOL AccuTOF GC series of orthogonal-acceleration time-of-flight instruments is presented. In contrast to existing implementations, this third-party LIFDI probe and source combination does not require the exchange of the entire ion source comprising ion source block and lens stack to switch from electron ionization (EI) to LIFDI. Rather, the methods may be swapped conveniently by only exchanging the ion source block for a mechanical probe guide and inserting the LIFDI probe in place of the standard direct insertion probe (DIP) via the vacuum lock. Further, this LIFDI setup does not require any changes of the electronics or software of the AccuTOF mass spectrometer because it is self-supplied in terms of power supply, observation optics, and computer control. The setup offers advanced FI/FD/LIFDI control features such as emission-controlled emitter heating current and emitter flash baking during elongated runs as required for gas chromatography-FI-mass spectrometry (MS). The LIFDI source and probe and its operation are reported in detail. FI spectra of the volatile analytes toluene, heptane, and pentafluoroiodobenzene are presented. LIFDI operation is demonstrated for the analysis of the saturated hydrocarbon dotriacontane and the low-mass hydrocarbon polymers polystyrene 484 and polystyrene 1050. Further, the air-sensitive 2nd-generation Hoveyda-Grubbs catalyst is analyzed by LIFDI-MS. For comparison with long-established LIFDI instrumentation, some of the spectra obtained with the new setup are also compared with those from a double-focusing magnetic sector instrument.

A magnetic spectrometer for electron‐positron pair spectroscopy in storage rings

We report an analysis of electron‐optical properties of a toroidal magnetic sector spectrometer and examine parameters for its implementation in a relativistic heavy‐ion storage ring, for example the High Energy Storage ring (HESR) at the future Facility for Antiproton and Ion Research (FAIR) facility. For studies of free–free pair production in heavy‐ion atom collisions, this spectrometer exhibits very high efficiencies for coincident e+–e− pair spectroscopy over a wide range of momenta of emitted lepton pairs. The high coincidence efficiency of the spectrometer is the key for stringent tests of theoretical predictions for the phase space correlation of lepton vector momenta in free–free pair production.

VGAM: Compact and Low‐Power Mass Spectrometer‐Based Instrumentation for Volcanic Gas Monitoring

AbstractCompact mass spectrometers (MSs) can provide simultaneous multispecies analysis with high sensitivity and precision. For volcanic gas monitoring in situ, instrumental mass spectrometry requires reliability and ruggedness combined with low power usage and portability. The Volcanic Gas Analytical Monitor (VGAM) is capable of quantitative molecular analysis of a variety of atmospheric and volcanic gases in a single sensor by ion trap mass spectrometry. These gases include H2, He, H2O, N2, O2, Ar, NO, N2O, CO, CO2, H2S, SO, SO2, and CH4. Unlike previous field instruments using magnetic sector and quadrupole MSs with vacuums backed by compact turbomolecular pumps, the VGAM uses a low‐power autoresonant ion trap MS and nonevaporable getter‐ion pumped vacuum that operates at only 25‐W total power, which is often the power requirement for just the MS. Ratiometric mass spectral response is combined with total pressure measurements to report absolute partial pressures. Data are generated in real time and are recorded to internal flash memory. Relatively low power (<1 W) data telemetry to remote sites is possible. Analysis of volcanic plumes, fumaroles, and solfatara fields is accomplished by direct inlet of gases, after trapping as much excess water vapor in both the external and internal foreline as possible. We report herein on the VGAM autorun and postprocessing procedures, initial calibration results for CO2, and the results of a brief field deployment at Sulfur Banks solfatara field, Kilauea Volcano, Hawaii.

Fuelling Development? The Rise of New Development Finance in Korea’s Overseas Energy Cooperation with Southeast Asia

‘Aid world’ has undergone critical changes and reforms to reconfigure the relationship between the role of private sector instruments and broadly defined development cooperation. Against the backdrop of the global/Euro financial crisis, development cooperation has become increasingly susceptible to financial instruments, logic, and actors. Such deepening of the financialisation–development nexus has been linked to the rise of the beyond aid agenda and the new and innovative development financing at its heart. Using the case of Korea’s energy development cooperation with Southeast Asia, our analysis shows how the keen take on the beyond aid agenda has further advanced the Korean government’s position on the utility of aid to pursue ‘national interests’ and ‘co-prosperity’. Also, our findings indicate that the Korean government mobilises both aid and other public finance to serve the national interests of (corporate) capital accumulation in the name of development.

Multi-analyte method for the analysis of legacy and alternative brominated and chlorinated flame retardants in food products of animal origin using gas chromatography - magnetic sector high resolution mass spectrometry

An analytical method was developed and validated for the analysis of 32 halogenated flame retardants (HFRs), including 13 polybrominated diphenyl ethers (PBDEs), 9 dechlorane-related compounds (DRCs) and 10 of the so-called alternative BFRs in food samples of animal origin. Gas chromatography (GC) coupled with magnetic sector high resolution mass spectrometry (HRMS) was used for the instrumental analysis. Intralaboratory validation of the developed method was performed in terms of recovery, repeatability, linear calibration ranges, instrumental and method limits of quantitation (i-LOQ and m-LOQ). Where possible, trueness was verified by the analysis of reference materials (RMs). For analytes with available isotopically labeled surrogates, recoveries in the range of 70–120% and repeatability rates below 20% were observed, while for compounds quantitated using absolute calibration the values of recovery ranged from 59 to 153% and the repeatability in terms of RSDs was in the range of 1–26%. The values measured for the four analyzed RMs agreed with the provided consensus values, revealing that the recovery of reference concentrations for compounds with assigned consensus values was in 72–119% range. The elaborated method met the sensitivity criteria according to the Commission Recommendation, 2014/118/EU on the monitoring of BFRs in food products. The developed method was successfully applied for the analysis of numerous food samples. The analyses revealed ubiquitous presence of PBDEs and the majority of DRCs in the analyzed samples, while alternative BFRs were detected only occasionally.

Conjugate Ionosphere‐Magnetosphere Observations of a Sub‐Alfvénic Compressional Intermediate‐m Wave: A Case Study Using EKB Radar and Van Allen Probes

AbstractA Pc5 wave was simultaneously observed in the ionosphere by EKB radar and in the magnetosphere by both Van Allen Probe spacecraft within a substorm activity. The wave was located in the nightside, in 1.5‐ to 3‐hr magnetic local time sector, and in the region corresponding to the magnetic shells with maximal distances 4.6–7.8 Earth's radii. As it was found using both the radar and spacecraft data, the wave had frequency of about 1.8 mHz and azimuthal wave number m≈−10; that is, the wave was westward propagating. The EKB radar data revealed the equatorward wave propagating in the ionosphere, which corresponded to the earthward propagation in the magnetosphere. Furthermore, the field‐aligned magnetic component was approximately 2 times larger than both transverse components and accompanied by antiphase pressure oscillations; that is, the wave is compressional and diamagnetic. According to both radar and spacecraft measurements, among two transverse magnetic components, the dominant one was the poloidal. The wave was possibly driven by substorm‐injected energetic protons registered by the spacecraft: the proton fluxes were modulated with the wave frequency at energies of about 90 keV, which corresponded to the energy of the drift wave‐particle resonance. The wave frequency was much lower than the minimal frequency of the field line resonance calculated using the spacecraft data. We conclude that the wave is not the Alfvén mode, but some kind of compressional wave, for example, the drift‐compressional mode.

GC-MS ANALYSIS, HPTLC FINGERPRINT PROFILE AND DPPH FREE RADICAL SCAVENGING ASSAY OF METHANOL EXTRACT OF MARTYNIA ANNUA LINN SEEDS

Objective: To investigate the photochemical constituents present in methanol extract of martynia annua seeds using Gas Chromatography-Mass Spectroscopy(GC-MS), High-Performance Thin–Layer Chromatography(HPTLC) analysis and study antioxidant activity.
 Methods: Methanol extract of Martynia annua seeds were subjected to GC-MS and HPTLC analysis. HPTLC analysis was carried out using GAMAG system with a linomate5 applicator, system mobile phase (Toluene: Chloroform: Ethanol (4:4:1 V/V/V)), two different volume of extract was applied 2 µl and 5 µl. GC-MS analysis was carried out on JEOL GC MATE ΙΙ, column HP 5 MS and Quadruple double focusing mass analyzer. Antioxidant activity was determined by DPPH assay.
 Results: GC-MS analysis provided 17 peaks indicating the presence of seventeen different phytochemicals in methanol extract of martynia annua seeds. HPTLC fingerprint showed 6 peaks at both size 2 µl and 5 µl at 254 nm whereas 4 peaks, 9 peaks were detected at 366 nm for 2 µl and 5 µl respectively. After derivatization with 10 % methanolic sulphuric acid, 8 peaks, 11 peaks were detected for 2 µl and 5 µl respectively when the derivatized plate was scanned at 540 nm. DPPH free radical scavenging result showed EC50 value of 44.1±1.1 µg/ml.
 Conclusion: The GC-MS analysis showed the presence of fatty acids, ester, aldehydes and ketones whereas in HPTLC different peaks at different UV-lights before and after derivatization were observed. Maximum percentage inhibition using DPPH assay was found 74 at concentration of 50 µg/ml.

Green's theorem in seismic imaging across the scales

Abstract. The earthquake seismology and seismic exploration communities have developed a variety of seismic imaging methods for passive- and active-source data. Despite the seemingly different approaches and underlying principles, many of those methods are based in some way or another on Green's theorem. The aim of this paper is to discuss a variety of imaging methods in a systematic way, using a specific form of Green's theorem (the homogeneous Green's function representation) as a common starting point. The imaging methods we cover are time-reversal acoustics, seismic interferometry, back propagation, source–receiver redatuming and imaging by double focusing. We review classical approaches and discuss recent developments that fully account for multiple scattering, using the Marchenko method. We briefly indicate new applications for monitoring and forecasting of responses to induced seismic sources, which are discussed in detail in a companion paper.

Round‐robin test of medium‐energy ion scattering for quantitative depth profiling of ultrathin HfO2/SiO2/Si films

Medium‐energy ion scattering (MEIS) has been used for quantitative depth profiling with single atomic layer resolution to determine the composition, thickness, and interface structure of ultrathin films and nanoparticles. To assure the consistency of the MEIS analysis, an international round‐robin test (RRT) with nominally 1‐, 3‐, 5‐, and 7‐nm thick HfO2 films was conducted among 12 institutions. The measurements were performed at each participating laboratory under their own conditions, and the collected data were analyzed. For the data analysis, the Moliere potential, the stopping and range of ions in matter (SRIM) 95 and new fitted electronic stopping power and the Chu straggling were used. For analyzing the MEIS data from the magnetic sector and electrostatic analyzers, the neutralization corrections of Marion and Young for 100‐keV H+ and He+ ions and of Armstrong for 400‐ to 500‐keV He+ ions were used. The standard deviations were 5.3% for the composition, 15.3% for the thickness, and 13.3% for the Hf content, and they were improved to 7.3%, 4.5%, and 7.0% by using refitted electronic stopping powers based on the experimental data. Hence, this study suggests that correct electronic stopping powers are critical for quantitative MEIS analysis.

Momentum dispersion and mass resolution of magnetic sector instruments for surface analysis

The momentum‐dependent dispersion of ion trajectories in a homogeneous magnetic sector field is derived by a trigonometric method. Contrary to the often used transfer matrix technique, the results are not restricted to small momentum differences. Based on the results of the trigonometric evaluation, an expression for the mass resolution of a magnetic sector for an entering ion beam is derived and extensively discussed. An example for high‐resolution magnetic mass spectrometry is presented.