Search

Improved focal plane array detector systems are described which can provide improved readout speeds, random addressing and even be employed to simultaneously measure position, intensity and energy. This latter capability promises to rekindle interests in Laue techniques. Simulations of three varieties of foil mask spectrometer in both on- and off-axis configurations indicate that systems of stacked silicon detectors can provide energy measurements within 1% of the true value based on the use of single `foils' and ∼10000 photons. An eight-detector hybrid design can provide energy coverage from 4 to 60 keV. Energy resolution can be improved by increased integration time or higher flux experiments. An off-axis spectrometer design in which the angle between the incident beam and the detector system is 45° results in a shift in the optimum energy response of the spectrometer system. In the case of a 200 µm-thick silicon absorber, the energy optimum shifts from 8.7 keV to 10.3 keV as the angle of incidence goes from 0 to 45°. These new designs make better use of incident photons, lower the impact of source flicker through simultaneous rather than sequential collection of intensities, and improve the energy range relative to previously reported systems. [ABSTRACT FROM AUTHOR]

Spatial aperture coding is a technique used to improve throughput without sacrificing resolution both in optical spectroscopy and sector mass spectrometry (MS). Previous work demonstrated that aperture coding combined with a position-sensitive array detector in a miniature cycloidal mass spectrometer was successful in providing high-throughput, high-resolution measurements. However, due to poor alignment and field nonuniformities, reconstruction artifacts were present. Recently, significant progress was made in eliminating most of the reconstruction artifacts with improved field uniformity and alignment. However, artifacts as large as 1/3 of the main peak were still observed at low mass (<17 u). Such artifacts will reduce accuracy in identification and quantification of analytes, reducing the impact of the throughput advantage gained by using a coded aperture. The artifacts were hypothesized to be a result of a mass dependent in curvature of ions in the ion source. Ions with higher mass (m/z > 17 u) and a larger curvature did not pass through all slits in the coded aperture. Therefore, when reconstructing with a system response derived from the aperture image from a higher mass m/z = 32 u ion, reconstruction artifacts appeared for m/z < 17 u. In this work, two methods were implemented to significantly reduce the presence of artifacts in reconstructed data. First, we modified the reconstruction algorithm to incorporate a mass-dependent system response function across the mass range (10–110 u). This method reduced the size of the artifacts by 82%. Second, to validate the hypothesis that the mass-dependent system response function was a result of differences in curvature of ions in the ion source, we modified the design of the ion source by shifting the coded aperture slits relative to the center of the ionization volume. This method resulted in ions of all masses passing through all slits in the coded aperture, a constant system response function across the entire mass range. Artifacts were reduced by 94%. [ABSTRACT FROM AUTHOR]

Recent advances in the miniaturization and optimization of Raman spectroscopic techniques provide the promise of handheld instruments that can be used to quickly and routinely identify and characterize naturally occurring crystalline compounds. For these reasons, we are building a database of Raman spectra that may be used to identify and characterize minerals and inorganic gem materials. The RRUFF project is the largest, most comprehensive research study of minerals ever undertaken. Samples of all known minerals are being subjected to X-ray diffraction to obtain cell parameters, constrain the symmetry, and provide identification. When required, crystal structures are also being determined. This is especially necessary when variations in site occupancies can affect the Raman spectral behavior. Electron-microprobe analysis is being conducted on each sample to obtain an empirical formula. Fragments of the characterized samples are oriented for Raman spectroscopy in the directions necessary to measure symmetry effects of orientation. These fragments are glued onto titanium pins and polished to ensure the highest-quality spectra. The Raman spectrum of a mineral is analogous to its diffraction pattern, inasmuch as it provides a unique "fingerprint" of the mineral, influenced by the crystal structure and the bond strengths of the constituent arrangement of atoms. Therefore, a complete library of spectra is essential to the accurate identification of unknown samples. Also under investigation is how well a mature Raman database can be used to estimate chemical composition, site occupancy, and order-disorder, as well as to determine the orientation of the sample. At the time of writing this abstract, the database contains about 1,700 minerals in various stages of examination. Most of the major rock-forming minerals are present. About 25 samples are being added to the project each week. The data are freely available via the Internet at http://rruff.info. [ABSTRACT FROM AUTHOR]

Describes an experiment in the determination of the C60 to C70 ration in fullerene soot with the use of high performance liquid chromatography. Description of the setup; Resulting chromatogram.

A number of important breakthroughs have occurred in recent years that allow Raman spectroscopy to be considered as a routine but powerful analytical tool for identifying and characterizing natural crystalline compounds. The long-standing limitation in sensitivity and the detection limit capabilities of conventional Raman have now dropped to the levels of parts per million and lower. These developments have resulted from a combination of technological advances in optical components, sources, and detector technology. Advanced technologies developed for fiber-optic telecommunication are now being applied to implement an entirely new generation of miniature spectrometers. Optical systems for entire spectrometers can be built in volumes of cubic millimeters. New approaches for optical component fabrication, mounting, and alignment have been developed that yield highly robust systems capable of providing exceedingly high levels of performance. Performance considerations and design "trade-offs" include resolution, excitation, wavelength, sensitivity, size, and weight. A new generation of handheld Raman spectroscopic instrumentation is currently being introduced that will find application in diverse fields such as process control, product quality control, medical diagnostics, and environmental analysis, as well as in the analysis of gems and minerals. The use of Raman spectra to assist in the nondestructive identification of gems, however, requires a credible database as well as appropriate search algorithms. Such a database is currently being developed by the RRUFF project as a public domain asset (http://rruff.info), sponsored by Mike Scott. [ABSTRACT FROM AUTHOR]

Mass spectrometers are essential instruments for in situ analysis of planetary materials. Ideally, a space flight mass spectrometer would have a mass range from ∼10 u to at least 500 u to enable analysis of organic molecules to aid in searching for the requirements for life; capability for high precision isotope ratios of carbon, nitrogen, oxygen, sulfur, and noble gases to understand solar system evolution and functioning; and ability to resolve isobaric interferences at low m/z such as CO and N 2 to study planetary atmospheres. Despite the considerable progress in flight mass spectrometry since the 1970s, no single flight mass spectrometer has all these ideal characteristics. In this paper, we present a proof-of-concept super-resolution coded aperture cycloidal miniature mass spectrometer (SR-CAMMS) for planetary science. Design considerations and preliminary results are presented including: a mass range of 10–260 u with resolution of 0.5 u or better; the ability to resolve the isobaric interference between CO and N 2 at m/z = 28 u using sampling-super resolution; and the ability to acquire isotope ratios with Poisson statistics limited precision. Thus, the instrument met all design considerations except mass range, which was expected to be 10–500 u; reasons for this discrepancy are discussed in the paper. [Display omitted] • Super-resolution coded aperture miniature mass spectrometer: (SR-CAMMS). • Combines cycloidal mass analyzers, coded apertures, super-resolution, array detectors. • SR-CAMMS demonstrates mass range of 10–270 with 0.5 u or better resolution. • SR-CAMMS demonstrates isobaric separation of N 2 and CO using super-resolution. • SR-CAMMS demonstrates Poisson statistics limited isotope ratio precision with N 2. [ABSTRACT FROM AUTHOR]

Rationale Methods Results Conclusions Higher resolution in fieldable mass spectrometers (MS) is desirable in space flight applications to enable resolving isobaric interferences at m/z < 60 u. Resolution in portable cycloidal MS coupled with array detectors could be improved by reducing the slit width and/or by reducing the width of the detector pixels. However, these solutions are expensive and can result in reduced sensitivity. In this paper, we demonstrate high‐resolution spectral reconstruction in a cycloidal coded aperture miniature mass spectrometer (C‐CAMMS) without changing the slit or detector pixel sizes using a class of signal processing techniques called super‐resolution (SR).We developed an SR reconstruction algorithm using a sampling SR approach whereby a set of spatially shifted low‐resolution measurements are reconstructed into a higher‐resolution spectrum. This algorithm was applied to experimental data collected using the C‐CAMMS prototype. It was then applied to synthetic data with additive noise, system response variation, and spatial shift nonuniformity to investigate the source of reconstruction artifacts in the experimental data.Experimental results using two ½ pixel shifted spectra resulted in a resolution of ¾ pixel full width at half maximum (FWHM) at m/z = 28 u. This resolution is equivalent to 0.013 u, six times better than the resolution previously published at m/z = 28 for N2+ using C‐CAMMS. However, the reconstructed spectra exhibited some artifacts. The results of the synthetic data study indicate that the artifacts are most likely caused by the system response variation.This paper demonstrates super‐resolution spectral reconstruction in C‐CAMMS without changing the slit or detector pixel sizes using a sampling SR approach. With improvements, this technique could be used to resolve isobaric interferences in a portable cycloidal MS for space flight applications. [ABSTRACT FROM AUTHOR]

With the advent of technologies such as ion array detectors and high energy permanent magnet materials, there is renewed interest in the unique focusing properties of the cycloidal mass analyzer and its ability to enable small, high‐resolution, and high‐sensitivity instruments. However, most literature dealing with the design of cycloidal mass analyzers assumes a single channel detector because at the time of those publications, compatible multichannel detectors were not available. This manuscript introduces and discusses considerations and a procedure for designing cycloidal mass analyzers coupled with focal plane ion array detectors. To arrive at a set of relevant design considerations, we first review the unique focusing properties of the cycloidal mass analyzer and then present calculations detailing how the dimensions and position of the focal plane array detector relative to the ion source determine the possible mass ranges and resolutions of a cycloidal mass analyzer. We present derivations and calculations used to determine the volume of homogeneous electric and magnetic fields needed to contain the ion trajectories and explore the relationship between electric and magnetic field homogeneity on resolving power using finite element analysis (FEA) simulations. A set of equations relating the electric field homogeneity to the geometry of the electric sector electrodes was developed by fitting homogeneity values from 78 different FEA models. Finally, a sequence of steps is suggested for designing a cycloidal mass analyzer employing an array detector. [ABSTRACT FROM AUTHOR]

The article examines the impact of array detectors on Raman spectroscopy. The defining characteristics of detectors are presented. The improvements in lasers, optics, and detectors have contributed to the evolution of Raman spectroscopy. Array detectors have resulted in greatly reduced measurement times due to their extreme sensitivity and low noise. The sensitivity of modern array detectors has enabled Raman spectroscopy to be used to detect compounds at part per million concentrations and to perform Raman analyses.

This article reviews current mass spectra (MS) detector technology and provides a glimpse of what scientists hope future detectors will be capable of. The technology of MS can be divided into three processes: ion generation, ion separation, and ion detection. Ion generation and separation have received significant and focused attention. The first prevalent MS ionization source, the electron impact source, has given way to a variety of other specialized ionization sources, for example, spark source, thermal ionization, chemical ionization, fast-atom bombardment, secondary ion, and glow discharge. Ion detection technology, by contrast, has received less attention. Traditional analog and electron multiplier detectors have been used for decades. Advances in this technology have occurred, but they have been incremental rather than revolutionary. Very few new detection approaches have been devised. In addition, detector technology is often given brief or no mention in MS texts and reviews. Thus, it has remained an area of rather understated importance, despite the fundamental need to better understand ions.

Characterizes the Focal Plane Camera (FPC) fitted to a Mattauch-Herzog geometry mass spectograph. Components of FPC; Limitation of detection by the instrument with glow discharge source; Weakness of FPC limitingsensitivity and baseline resolution; Period for data acquisition of images.

Forensic science is critical to the administration of justice. The discipline of forensic science is remarkably complex and includes methodologies ranging from DNA analysis to chemical composition to pattern recognition. Many forensic practices developed under the auspices of law enforcement and were vetted primarily by the legal system rather than being subjected to scientific scrutiny and empirical testing. Beginning in the 1990s, exonerations based on DNA-related methods revealed problems with some forensic disciplines, leading to calls for major reforms. This process generated a National Academy of Science report in 2009 that was highly critical of many forensic practices and eventually led to the establishment of the National Commission for Forensic Science (NCFS) in 2013. The NCFS was a deliberative body that catalyzed communication between nonforensic scientists, forensic scientists, and other stakeholders in the legal community. In 2017, despite continuing problems with forensic science, the Department of Justice terminated the NCFS. Just when forensic science needs the most support, it is getting the least. We urge the larger scientific community to come to the aid of our forensic colleagues by advocating for urgently needed research, testing, and financial support. [ABSTRACT FROM AUTHOR]

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer’s compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified.ᅟ [ABSTRACT FROM AUTHOR]

Simple techniques are described for construction of a discharge channel, and spark gap trigger electrode for a traveling-wave excited molecular hydrogen laser. [ABSTRACT FROM AUTHOR]

A fourth-generation focal plane camera containing 1696 Faraday-strip detectors was fitted to a Mattauch-Herzog mass spectrograph and characterized for its performance with inductively coupled plasma ionization. The camera provides limits of detection in the single to tens of ng L−1range for most elements and has a linear dynamic range of at least nine orders of magnitude. Isotope-ratio precision better than 0.02% has also been achieved with this device, and this fourth-generation system features the broadest simultaneous mass range obtainable to date with this family of focal plane camera detectors. [ABSTRACT FROM AUTHOR]

An ambient desorption/ionization (ADI) source, known as the flowing atmospheric pressure afterglow (FAPA), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) equipped with a focal plane camera (FPC) array detector. The FAPA ionization source enables direct mass spectral analysis of solids, liquids, and gases through either positive or negative ionization modes. In either case, spectra are generally simple with dominant peaks being the molecular ions or protonated molecular ions. Use of the FAPA source with the MHMS allows the FPC detector to be characterized for the determination of molecular species, whereas previously only atomic mass spectrometry (MS) has been demonstrated. Furthermore, the FPC is shown to be sensitive to negative ions without the need to change any detector parameters. The analysis of solid, liquid, and gaseous samples through positive and negative ionization is demonstrated with detection limits (1–25 fmol/s, ∼0.3–10 pg of analyte per mL of helium) surpassing those obtained with the FAPA source coupled to a time-of-flight mass analyzer. [Copyright &y& Elsevier]

A 512-channel Faraday-strip array detector has been developed and fitted to a Mattauch-Herzog geometry mass spectrograph for the simultaneous acquisition of multiple mass-to-charge values. Several advantages are realized by using simultaneous detection methods, including higher duty cycles, removal of correlated noise, and multianalyte transient analyses independent of spectral skew. The news 512-channel version offers narrower, more closely spaced pixels, providing improved spectral peak sampling and resolution. En addition, the electronics in the amplification stage of the new detector array incorporate a sample-and-hold feature that enables truly simultaneous interrogation of all 512 channels. While sensitivity and linear dynamic range remain impressive for this Faraday-based detector system, limits of detection and isotope ratio data have suffered slightly from leaky p-n junctions produced during the manufacture of the semiconductor-based amplification and readout stages. This paper describes the new 512-channel detector array, the current dominant noise sources, and the figures of merit for the device as pertaining to inductively coupled plasma ionization. [ABSTRACT FROM AUTHOR]

An ambient mass spectrometry ionization source based on an atmospheric-pressure flowing afterglow has been coupled to a Mattauch-Herzog mass spectrograph capable of simultaneous acquisition of a range of mass-to-charge values by means of a Faraday-strip array detector. The flowing afterglow was used as the ionization pathway for species produced by hydride generation. This ionization strategy circumvents problems, such as discharge instabilities or memory effects, induced by introducing the gaseous sample into the discharge. The generated spectra show both atomic and molecular peaks; calibration curves were calculated for both peak types with limits of detection for arsenic below 10 ppb. This study demonstrates the ability to use an ambient mass spectrometry source, commonly used for molecular analyses, for the detection of gas phase elemental species with the possibilty of performing speciation by coupling with a separation technique. [ABSTRACT FROM AUTHOR]

In mass spectrometry, several advantages can be derived when multiple mass-to-charge values are detected simultaneously and continuously. One such advantage is an improved duty cycle, which leads to superior limits of detection, better precision, shorter analysis times, and reduced sample sizes. A second advantage is the ability to reduce correlated noise by taking the ratio of two or more simultaneously collected signals, enabling greatly enhanced isotope ratio data. A final advantage is the elimination of spectral skew, leading to more accurate transient signal analysis. Here, these advantages are demonstrated by means of a novel Faraday-strip array detector coupled to a Mattauch-Herzog mass spectrograph. The same system is used to monitor elemental fractionation phenomena in laser ablation inductively coupled plasma mass spectrometry. [ABSTRACT FROM AUTHOR]

A second-generation Faraday-strip array detector has been coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph, thereby offering simultaneous acquisition of a range of mass-to-charge ratios. The second-generation device incorporates narrower, more closely spaced collectors than the earlier system. Furthermore, the new camera can acquire signal on all collectors at a frequency greater than 2 kHz and has the ability to independently adjust the gain level of each collector. Each collector can also be reset independently. With these improvements, limits of detection in the hundreds of picograms per liter for metals in solution have been obtained. Some additional features, such as a broader linear dynamic range (over 7 orders of magnitude), greater resolving power (up to 600), and improved isotope ratio accuracy were attained. In addition, isotope ratio precision as low as 0.018% RSD was achieved. [ABSTRACT FROM AUTHOR]

Abstract: An electrothermal vaporization (ETV) system useful for the analysis of solutions and slurries has been coupled with a sector-field inductively coupled plasma mass spectrometer (ICP–MS) equipped with an array detector. The ability of this instrument to record the transient signals produced for a number of analytes in ETV–ICP–MS is demonstrated. Detection limits for Mn, Fe, Co, Ni, Cu, Zn and Ga are in the range of 4–60 pg μL−1 for aqueous solutions and in the low μg g−1 range for the analysis of 10 mg mL−1 slurries of Al2O3 powders. The dynamic ranges measured for Fe, Cu and Ga spanned 3–5 orders of magnitude when the detector was operated in the low-gain mode and appear to be limited by the ETV system. Trace amounts of Fe, Cu and Ga could be directly determined in Al2O3 powders at the 2–270 μg g−1 level without the use of thermochemical reagents. The results well agree with literature values for Fe and Cu, whereas deviations of 50% at the 90 μg g−1 level for Ga were found. [Copyright &y& Elsevier]

The use of a separation step, such as liquid chromatography, prior to inductively coupled plasma mass spectrometry (ICP-MS) has become a common tool for highly selective and sensitive analyses. This type of coupling has several benefits including the ability to perform speciation analysis or to remove isobaric interferences. Several limitations of conventional instruments result from the necessity to scan or pulse the mass spectrometer to obtain a complete mass spectrum. When the instrument is operated in such a non-continuous manner, duty cycle is reduced, resulting in poorer absolute limits of detection. Additionally, with scanning instruments, spectral skew can be introduced into the measurement, limiting quantitation accuracy. To address these shortcomings, a high-performance liquid chromatograph has been coupled to an ICP-MS capable of continuous sample introduction and simultaneous multimass detection. These features have been realized with a novel detector array, the focal plane camera. Instrument performance has been tested for both speciation analysis and for the elimination of isobaric interferences. Absolute limits of detection in the sub picogram to tens of picograms regime are obtainable, while the added mass dimension introduced by simultaneous detection dramatically increases chromatographic peak capacity. [ABSTRACT FROM AUTHOR]

The use of laser ablation (LA) as a sample-introduction method for inductively coupled plasma mass spectrometry (ICP-MS) creates a powerful tool for trace elemental analysis. With this type of instrument, high analyte spatial resolution is possible in three dimensions with ng/g limits of detection and minimal sample consumption. Here, simultaneous detection is used to eliminate the correlated noise that plagues the ablation process. This benefit allows analyses to be performed with single laser pulses, resulting in improved depth resolution, even less sample consumption, and improved measurement precision. The new instrument includes an LA sample-introduction system coupled to an ICP ionization source and a Mattauch-Herzog mass spectrograph (MHMS) fitted with a novel array detector. With this instrument, absolute limits of detection are in the tens to hundreds of fg regime and isotope-ratio precision is better than 0.02% RSD with a one-hour integration period. Finally, depth-profile analysis has been performed with a depth resolution of 5 nm per ablation event. [Copyright &y& Elsevier]

A novel charge-sensitive detector array, termed the focal plane camera (FPC), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) with an inductively coupled plasma ionization source. The FPC employs an array of gold Faraday cups, each with its own charge-integrating circuit that allows the simultaneous detection of several m/z ratios. The ion-sampling interface of the MHMS has been redesigned to provide better heat transfer away from the sampler and skimmer cones and to reduce the negative effects of turbulent gas flows around the plasma. The instrument has produced limits of detection in the tens to hundreds of parts per quadrillion regime and isotope ratio accuracy and precision of 5% error and 0.007% RSD, respectively. Limits of detection with the FPC are comparable to those obtained with a single-channel secondary electron multiplier (SEM). However, the isotope ratio accuracy and precision are better with the FPC than when the SEM is employed. The dynamic range has been shown to be linear over 7 orders of magnitude. [ABSTRACT FROM AUTHOR]

A study focusing on the ability to utilize isotopic analysis of Pb used in small arms projectiles from varying geographic origin was undertaken using the GV Instruments Isoprobe multicollector inductively coupled plasma mass spectrometer. With the exception of two classes of ammunition, these samples were able to be distinguished from one another. Also, following rigorous normalization and mass bias correction, these data were compared to data collected by geochemists in localities corresponding to projectile manufacture. This comparison was successful when projectiles in certain economically isolated countries were analyzed. Pb isotopic analysis with MC-ICPMS is shown to be useful as a tool for distinguishing between ammunition of various manufacturing origins. [ABSTRACT FROM AUTHOR]

The improvised explosive triacetone triperoxide (TATP) was synthesized and characterized by 1H-nuclear magnetic resonance (NMR), 13C-NMR, Raman and infrared (IR) spectroscopy. Triacetone triperoxide was subsequently analyzed by ion mobility spectrometry (IMS) in positive ion mode, and detected as a cluster of three peaks with a drift time of the most intense peak at 13.06 ms. Triacetone triperoxide was then analyzed after dissolution in toluene, where a dramatic increase in peak intensity was observed, at a flight time of 12.56 ms (K0=2.71 cm2 V−1 s−1). Triacetone triperoxide was subsequently analyzed by coupling the ion mobility spectrometer to a triple quadrupole mass spectrometer, where a single peak at m/z of 223 atomic mass units identified the species present in the ion mobility spectra as being triacetone triperoxide. [Copyright &y& Elsevier]

Studies the crystal structure of synthetic kosmochlor, NaCrSi[sub2]O[sub6], using single crystal X-ray diffraction at high pressure. Experimental methods; Results; Discussion.

Examines the structural characterization of dimethyldiselenoarsinate anion. Synthesis of arsenic-selenium solution species by reacting equimolar sodium selenite and sodium dimethylarsinate; Human metabolism of arsenite; Formation of monoselenosphosphate for selenoprotein biosynthesis.

We report a new synthesis of the seleno-bis (S-glutathionyl) arsinium anion, [(GS)2AsSe]−. An aqueous solution of bis-glutathionylarsenous acid, (GS)2As&z.sbnd;OH, prepared from stoichiometric glutathione and arsenite, was reacted in situ with a solution of sodium hydrogen selenide, prepared from elemental selenium and sodium borohydride. Analysis of the arsenic and selenium K-edge X-ray absorption spectra indicated virtually quantitative formation of [(GS)2AsSe]−, with As&z.sbnd;Se and As&z.sbnd;S distances of 2.31 and 2.25 A˚, respectively, and the concentrated sample allowed a definitive X-ray spectroscopic characterization. Size-exclusion chromatography was used to separate [(GS)2AsSe]− from residual borate in the reaction mixture. [Copyright &y& Elsevier]

This work demonstrates a novel approach to mass spectrometry using the "virtual-slit" created by the small, localized volume from which ions are generated by localized ionization techniques such as laser ionization of particles and surfaces, and spark ionization. That is, the volume in which the ions are generated creates a localized source of ions in much the same way as a slit that allows only ions from a specific cross sectional area to pass. As demonstrated in this work, the unique perfect focusing properties of a cycloidal mass analyzer can enable the localized ionization volume to function as a virtual-slit. In this manuscript, we provide a proof-of-concept (POC) demonstration of a virtual-slit cycloidal mass spectrometer (VS-CMS) consisting of a cycloidal mass analyzer, a laser ionization source, and an ion array detector. The laser is used to ionize either bulk or thin film samples of Cu, Ti, Ni, and Cr. Results indicate that the width of the peaks at the detector is the same as the laser spot size, validating the concept of virtual-slit focusing. Furthermore, the Ti and Cu ablated with each laser pulse is estimated at 60 and 140 fg, respectively, indicating that a very low detection limit is possible given the ability of the cycloidal mass analyzer to collect ions generated by laser ionization that have wide energy and angular dispersions. The VS-CMS concept has the potential to enable development of fieldable instruments for chemical, elemental, and isotopic analysis of organic and inorganic samples, that are relatively small compared to currently used laser ionization time-of-flight and laser ablation inductively coupled plasma mass spectrometers. [Display omitted] • First demonstration of a "virtual-slit" cycloidal mass analyzer (VS-CMS). • Virtual-slit focusing: ionization region size equals peak width on array detector. • Perfect focusing cycloidal mass analyzer enables virtual slit focusing. • VS-CMS proof of concept demonstrates isotope ratios and sensitivity to <100 fg. • VS-CMS can enable development of portable instruments for isotope ratio analysis. [ABSTRACT FROM AUTHOR]

This work compares the coded aperture imaging performance of thermionic filament and carbon nanotube (CNT) field emitter-based electron sources in cycloidal-coded aperture mass spectrometers. The use of spatially coded apertures in mass spectrometry enables miniaturization by improving throughput without sacrificing resolution. CNT-based electron ionization sources for mass spectrometers provide several potential benefits over conventional thermionic emitters, including low voltage and low power consumption, room temperature operation, long lifetime, and ability to emit electrons in a pulsed mode. However, spatiotemporal variation in electron emission from CNTs is a major disadvantage. In this study, electron emission stability and spatiotemporal stability of the coded aperture image were compared for coded aperture cycloidal mass analyzers with either a CNT-based ion source or a thermionic filament-based ion source. We found that the thermionic filament-based ion source produced a significantly more stable coded aperture image than the CNT based ion source. The aperture image fluctuations in the CNT-based source are likely a result of adsorption and desorption of molecules on the CNT surface that cause local work function changes and induce spatiotemporal variation in electron emission and subsequent ion generation. Image 1 • Aperture coding improves performance; enables miniaturization of mass spectrometers. • Higher electron emission variation from carbon nanotubes over thermionic filaments. • Adsorption and desorption of gases cause work function changes in carbon nanotubes. • Thermionic filament-based ion sources produce a more stable coded aperture image. [ABSTRACT FROM AUTHOR]