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This chapter (Quadrupole Inductively Coupled Plasma‐Mass Spectrometry) is a contribution to the Geostandards and Geoanalytical Research Handbook of Rock and Mineral Analysis – an online textbook that is a fully revised and updated edition of Handbook of the Silicate Rock Analysis (P. J. Potts, 1987, Blackie, Glasgow). Chapter 7 (from Section 2 of the handbook dealing with techniques for the determination of major and trace elements) describes both the history of ICP‐MS, including development of the plasma sampling interface and the operation of modern ICP‐MS instrumentation. Given their central importance to ICP‐MS operation, ion extraction through the sampling interface, ion transmission, ion separation (with a particular focus on the quadrupole mass filter) and counting are given particular attention. Discussion of the analytical characteristics of ICP‐MS particularly focusses on spectroscopic interferences (and their mitigation). Finally, an overview of geochemical analysis by ICP‐MS considers drift correction, calibration strategies, and laser ablation microsampling. [ABSTRACT FROM AUTHOR]

Methotrexate (MTX) is a therapeutic drug that is widely used in clinic for treatment of a variety of cancers. However, MTX has limited selectivity and serious cytotoxicity, at the same time, there are problems such as narrow therapeutic window and large individual variability in metabolism and excretion of MTX. Therefore, blood concentration monitoring is required for MTX administration in clinical practice. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has the advantages of strong specificity, good separation characteristics, high sensitivity and fast detection speed, which has become the internationally recognized “gold standard” for blood concentration monitoring of drugs. In this study, an isotope dilution mass spectrometry method was developed for accurate measurement of MTX in serum by the house-made QLIT-6610MD quadrupole-linear ion trap liquid chromatography-mass spectrometer. Unlike the traditional triple quadrupole QqQ tandem mass spectrometer, the quadrupole-linear ion trap (Q-LIT) mass spectrometer adopts the quadrupole-linear ion trap direct axial coupling design, i.e., a single linear ion trap is used to replace the QqQ tandem mass spectrometer’s back-end fragmentation cell and the quadrupole, and no other components are installed between the quadrupole and linear ion trap, which greatly streamlines the quality and efficiency of the mass spectrometer while ensuring the original performance of the instrument. With this unique configuration, the QLIT-6610MD instrument uses a simultaneous fragmentation and accumulation technique, which remarkedly reduces matrix-induced interferences and effectively reduces space charge effects. Serum samples were pretreated with methanol to precipitate proteins and the supernatants were measured by QLIT-6610MD spectrometer. The linear correlation coefficient (R2＞0.999 0) is obtained for MTX in the range of 10-5 000 μg/L. The limit of quantification is 10 μg/L. The precision of the quality control is better than 6.94%, and the recoveries of spiked serum samples are 86.39%-97.84% with a coefficient of variation less than 8.04%. We used the QLIT-6610MD and AB QTRAP 6500+ liquid chromatography-mass spectrometers to analyze 70 clinical serum samples for comparison of the performance of the house-made instrument by means of Pearson’s coefficient and BLand-ALtman method. The results showed that the QLIT-6610MD mass spectrometry achieves a similar level of performance to AB ATRAP 6500+ instrument, and provides a new domestic instrument option for clinical mass spectrometry. In addition, this study explores the possibility applying the multi-stage fragmentation technique (MSn) to determine MTX in serum, gaining fundamental data for future studies.

Methotrexate (MTX) is a therapeutic drug that is widely used in clinic for treatment of a variety of cancers. However, MTX has limited selectivity and serious cytotoxicity, at the same time, there are problems such as narrow therapeutic window and large individual variability in metabolism and excretion of MTX. Therefore, blood concentration monitoring is required for MTX administration in clinical practice. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has the advantages of strong specificity, good separation characteristics, high sensitivity and fast detection peed, which has become the internationally recognized “ gold standard” for blood concentration monitoring of drugs. In this study, an isotope dilution mass spectrometry method was developed for accurate measurement of MTX in serum by the house-made QLIT-6610MD quadrupole-linear ion trap liquid chromatography-mass spectrometer. Unlike the traditional triple quadrupole QqQ tandem mass spectrometer, the quadrupole-linear ion trap (Q-LIT) mass spectrometer adopts the quadrupolelinear ion trap direct axial coupling design, i.e., a single linear ion trap is used to replace the QqQ tandem mass spectrometer’s back-end fragmentation cell and the quadrupole, and no other components are installed between the quadrupole and linear ion trap, which greatly streamlines the quality and efficiency of the mass spectrometer while ensuring the original performance of the instrument. With this unique configuration, the QLIT-6610MD instrument uses a simultaneous fragmentation and accumulation technique, which remarkedly reduces matrix-induced interferences and effectively reduces space charge effects. Serum samples were pretreated with methanol to precipitate proteins and the supernatants were measured by QLIT-6610MD spectrometer. The linear correlation coefficient (R²>0.999 0) is obtained for MTX in the range of 10-5 000 μg/L. The limit of quantification is 10 μg/L. The precision of the quality control is better than 6.94%, and the recoveries of spiked serum samples are 86.39%-97.84% with a coefficient of variation less than 8.04%. We used the QLIT-6610MD and AB QTRAP 6500+ liquid chromatography-mass spectrometers to analyze 70 clinical serum samples for comparison of the performance of the house-made instrument by means of Pearson’s coefficient and BLand-ALtman method. The results showed that the QLIT-6610MD mass spectrometry achieves a similar level of performance to AB ATRAP 6500+ instrument, and provides a new domestic instrument option for clinical mass spectrometry. In addition, this study explores the possibility applying the multi-stage fragmentation technique (MSn) to determine MTX in serum, gaining fundamental data for future studies. [ABSTRACT FROM AUTHOR]

This work suggests to optimize the geometry of a quadrupole magnet by means of a genetic algorithm adapted to solve multi-objective optimization problems. To that end, a non-domination sorting genetic algorithm known as NSGA-III is used. The optimization objectives are chosen such that a high magnetic field quality in the aperture of the magnet is guaranteed, while simultaneously the magnet design remains cost-efficient. The field quality is computed using a magnetostatic finite element model of the quadrupole, the results of which are post-processed and integrated into the optimization algorithm. An extensive analysis of the optimization results is performed, including Pareto front movements and identification of best designs. [ABSTRACT FROM AUTHOR]

This study investigates the transmission contour (shape of the mass peak) through the numerical simulation of ion trajectories in a quadrupole field with small spatial harmonics. The impact of the octupole component on the field is examined, demonstrating a possibility of achieving a resolving power of 5000 with a 2% octupole component and a negative constant component on a pair of electrodes of a smaller radius. A stability diagram near the working apex is significantly affected by the octupole field. The data from the previous experiment qualitatively validated the simulation results. [ABSTRACT FROM AUTHOR]

Quadrupole mass spectrometers are widely used, and voltage scanning is their traditional working mode. By fixing the scanning voltage frequency and changing the value of the RF voltage, ions with different mass numbers can reach the detector in sequence, achieving ion selection. When analyzing high-mass molecules, several kilovolts of scanning voltage are required, which is not conducive to the miniaturization and safety of the instrument. By selecting the frequency of the scanning RF power supply and fixing the value of the RF power supply voltage, ion selection can be achieved by changing the frequency of the RF power supply, enabling miniaturized mass spectrometry analysis of high-mass molecules. In this paper, a high-speed gallium nitride driver circuit for frequency scanning mass spectrometry analysis is designed. The NCP51820 high-speed gate driver and INN650D140A gallium nitride MOS tube are selected to form a full-bridge driver, realizing a quadrupole rectangular wave RF power supply. The system has a maximum withstand voltage of 650 V and a frequency range of 400 K–4 MHz, allowing for scanning measurements of mass numbers ranging from 3 to 606 amu. [ABSTRACT FROM AUTHOR]

The demand for accurate mass spectrometry measurement in the field of clinical diagnosis is increasing. In the face of foreign monopoly, our team has developed new technologies and new methods for the selective enrichment of trace targets in complex matrices by ion traps, and has developed a quadrupole-linear ion trap (quadrupole-linear ion trap, Q-LIT) tandem mass spectrometer with independent intellectual property rights and a liquid chromatography tandem mass spectrometry system (model QLIT-6610MD), which have obtained a medical device registration certificate in China. In this study, a home-built Q-LIT liquid chromatography-tandem mass spectrometer QLIT-6610MD was developed to measure vancomycin in serum with high accuracy . After protein precipitation and liquid-liquid extraction, the samples were analyzed by QLIT-6610MD. The endogenous substances in the samples did not interfere with the quantification. The results showed that vancomycin has a good linear relationship of signal intensity vs. concentration in the range of 1.56-50.0 mg/L with the linear correlation coefficient (R2)≥0.99, and the limit of detection and limit of quantitation are 0.19 and 1.56 mg/L, respectively. Intra-day and inter-day precisions are 1.62%-3.82% and 2.07%-5.07%, respectively. The recoveries of vancomycin in serum samples are 95.97%-97.74%. The coefficient of variability (CV) of matrix effect normalization factor is less than 7.60%, CV of sample stability is better than 4.26%, and CV of long interval sample analysis is better than 2.13%. The method was verified by the determination of low, medium and high quality controls, and the results were all within the range of target values. QLIT-6610MD, AB API4000 and YS EXACT 9900MD were used to determine 42 real clinical serum samples. The correlation and consistency of the data were analyzed by Deming regression, Bland-Altman analysis and Pearson correlation analysis. The results showed good consistency among the results obtained by the three spectrometers, indicating that the data of three instruments are comparable, which prove that the home-made QLIT-6610MD can reach the quantitative accuracy of triple quadrupole-mass spectrometer. The instrument can effectively reduce the interference of matrix ions and enhance the capture efficiency of target ions, based on quadrupole-linear ion trap tandem mass spectrometric technique. QLIT-6610MD has great potential to provide a new instrumentation solution for real-time clinical analysis in the future.

A prototype of a type A quadrupole magnet has been designed and manufactured for the 3 GeV storage ring of Siam Photon Source II, the second synchrotron light source in Thailand. The required quadrupole gradient is 51 T/m with the magnet effective length being 162 mm. Magnet modeling and magnetic field calculation were performed using Radia and Opera-3D. The bore radius of the magnet is 16 mm. The magnet will be operated at the excitation of 5544 A-turns. A mechanical analysis of the magnet structure was performed in SOLIDWORKS and ANSYS, where the maximum deformation of 0.003 mm was found at the magnet poles, and the first-mode natural frequency was higher than 100 Hz. The magnet yoke is made of AISI 1006 low-carbon steel with a fabrication tolerance of ±0.020 mm. Magnet coils are water-cooled and made of high-purity copper. The temperature rise of the coils was below 3.0 °C at the maximum excitation of 6664 A-turns, which is 20% above the operating point. Magnetic field measurement was carried out using the Hall probe technique. The measured magnetic field and coil temperature of the prototype show good agreement with the calculations.

To protect the antenna systems of modern aircraft, radio-transparent dielectric fairings are widely used. At low flight speeds, when designing and evaluating the characteristics of the fairing-antenna, it is assumed that the dielectric constant is a constant value and does not depend on the aircraft's flight speed. As the flight speed increases, as a result of aerodynamic heating of the fairing, its dielectric permeability changes, which leads to errors in the processing of received signals. Currently, to take into account the effect of dielectric coatings heating when designing antenna systems, the temperature of the fairing wall is averaged over its thickness. This method during maneuvering and at high flight speeds leads to large errors in determining the characteristics of the fairing antenna since the nature of the temperature distribution along the thickness of the fairing wall is not taken into account. A new approach to the analysis of dielectric layers with their uneven heating along the thickness is proposed. The obtained results make it possible to adjust the signal processing algorithms with analog and digital matrices, as a result of taking into account the emerging heat flows affecting the fairing of the aviation antenna, which leads to the improvement of the characteristics of the antenna systems.

Although a quadruple mass analyzer and an ion trap mass analyzer have complementary analytical features, they usually have different geometries, operational modes, and electronic control systems. As a continuous effort to extend its coverage, both quadrupole and ion trap operation modes were realized on a "brick" miniature mass spectrometer with a single mass analyzer. In the quadrupole operation mode, low-mass ions ranging from 31 to 502 Th can be analyzed. On the other hand, the ion trap mode can be utilized to cover ions with higher mass to charge ratios (up to 922 Th), as well as performing tandem mass spectrometry. To realize the multiplexing of both operation modes, a printed circuit board (PCB)-based multi-electrode quadrupole–ion trap mass analyzer was designed and integrated in the system. To cover both volatile and non-volatile molecules, two ionization sources were also implemented, including a nano electrospray ionization source and an in-vacuum plasma ionization source. Performances of the instrument operated in these two modes were characterized, such as mass resolution, sensitivity, and mass range. Results demonstrate that the combination of the quadrupole and ion trap operation modes can provide new capabilities when solving analytical problems. [ABSTRACT FROM AUTHOR]

A major challenge in modern mass spectrometry (MS) is achieving high mass resolving power and accuracy for precision analyses in high mass‐to‐charge (m/z) regions. To advance the capability of MS for increasingly demanding applications, understanding limitations of state‐of‐the‐art techniques and their status in applied sciences is essential. This review summarizes important instruments in high‐resolution mass spectrometry (HRMS) and related advances to extend their working range to high m/z regions. It starts with an overview of HRMS techniques that provide adequate performance for macromolecular analysis, including Fourier‐transform, time‐of‐flight (TOF), quadrupole‐TOF, and related data‐processing techniques. Methodologies and applications of HRMS for characterizing macromolecules in biochemistry and material sciences are summarized, such as top‐down proteomics, native MS, drug discovery, structural virology, and polymer analyses. [ABSTRACT FROM AUTHOR]

The development of methods for calculating the physical and instrument characteristics of mass spectrometers based on correct physical and mathematical theories that allow us to design and calculate devices with improved analytical capabilities is an urgent task of corpuscular optics and scientific instrumentation. Currently, quadrupole electrostatic systems are widely used. These are primarily quadrupole lenses, quadrupole aberration correctors, quadrupole traps and quadrupole mass spectrometers. The quadrupole mass analyzer refers to the so-called antiresonance mass spectrometers, in which a part of the ions, when a beam of ions moves through an electric field having both a constant and a time-varying component, passes a field with a limited amplitude of vibrations, while the amplitude of vibrations of the other part of the ions increases indefinitely with time, and drop out of the bundle. Since the nature of the motion of charged particles depends on the mass-to-charge ratio, such an electric field can work as a mass filter, that is, pass through itself only ions having a certain value of the mass-to-charge ratio. Quadrupole systems with complex electrode geometries are usually used to create quadrupole fields, which makes their practical implementation difficult. Therefore, the development and research of quadrupole systems with a fairly simple geometry of electrodes, the fields of which can be described analytically, is quite relevant. Using a simple analytical formula for the potential and its derivatives, which accurately describes the electrostatic potential of a quadrupole field, it is possible to accurately calculate the stability regions of quadrupole ion traps when additional radio frequency fields are applied. [ABSTRACT FROM AUTHOR]

This technical document explores the issue of aerodynamic heating on dielectric fairings used to protect antenna systems on aircraft. The heating of the fairing can lead to errors in signal processing. The document proposes a new approach to analyzing dielectric layers with uneven heating, which can improve antenna system characteristics. It discusses mathematical equations and experimental results related to the determination of wave arrival angles in a two-element antenna array. The research provides insights into the effects of various factors on the accuracy of determining the arrival of electromagnetic waves, with implications for the design of radome-antenna systems for moving objects and space communication and navigation systems. The document also provides contact information and research interests for four individuals in the field of telecommunications and information technologies. [Extracted from the article]

The mass analyzer based on quadrupole field theory, including quadrupole and ion trap, control and screen ions by a non-magnetic, alternating electric field, which was the first proposed by Professor Paul in 1953. Since the birth of quadrupole, ion trap and other related mass spectrometry technologies have been developed relatively maturely, which have made a significant impact and contribution to mass spectrometry. This paper deduced and interpretd the complete physical and mathematical formulae of the design and generation process of the quadrupole field. The process of obtaining the potential distribution of the quadrupole field, the obtaining process of boundary conditions such as electrode shape and voltage on the electrode, and the process of deducing the quadrupole structure and ion trap structure according to the potential distribution of the quadrupole field were discussed. In the above processes, for the purpose of binding ions, a general potential (Prof. Paul called it “allgemeinste potential” in German) distribution equation was obtained by introducing a simple harmonic motion model. And then, according to the basic laws of electromagnetic field and Maxwell’s equation, the condition of zero electric field divergence was introduced. Based on this, through the discussion of the two simplest solutions and boundary conditions, the structure and field distribution equations of the quadrupole and the ion trap were obtained, respectively. This content was an important supplement to the elaboration on the theory of quadrupole field mass spectrometry, which was helpful for a deeper understanding of basic principles of quadrupole field. At the same time, this paper provided a potential mass analyzer design method. Firstly, the design began with the conception of the state of ion motion, and then a force that could control the movement of ions according to the idea was found. Secondly, combined with the basic laws of electromagnetic fields, the general equation and its limiting conditions for the potential distribution that could form this force were obtained. Thirdly, according to the easy-to-operate settings in practice, the boundary conditions of the field (such as electrode shape, electrode voltage, etc.) were obtained, and the intermediate variables in the general equation were replaced with these operable physical parameters. At last, according to the potential distribution equation, the ion motion equation was calculated, and the mathematical relationship between the mass-to-charge ratio and the controllable physical parameters was found. And finally, a mass analysis method for controlling and separating ions was obtained. This kind of design method has important reference significance for theoretical research and original innovation research related to mass spectrometry.

Numerous experiments have shown that the loads applied to Nb3Sn strands and cables can reduce their critical current. Experiments, performed on uniaxially loaded strands, allowed to define clear laws to describe the evolution of the critical surface as a function of the applied current, field, temperature and strain. It is, however, still unclear how these laws can be applied to superconducting magnets. The present paper proposes a methodology to estimate the critical current and temperature margin reduction on superconducting magnets due to stress on the superconducting material. The methodology is tested on the MQXF magnets, a quadrupole developed for the High Luminosity LHC project, and successfully validated by comparing computed strain with data from strain gauge measurements. Results suggested that, because of the stresses arising in winding during assembly, cool-down and powering, the current limit of the magnet is lower than the expected short sample limit, and that the most critical region does not coincide with the peak field location.

The results of synthesis and electromagnetic calculation of a hybrid quadrupole lens for a proton linear accelerator of the DARIA compact neutron source are presented. The lens includes a permanent magnet quadrupole with a fixed magnetic field gradient and an auxiliary electromagnetic quadrupole excited by a pulsed current. The permanent magnet quadrupole is made of a radiation resistant rare-earth magnet and the electromagnetic quadrupole is designed to compensate for permanent magnet magnetization losses resulting from radiation degradation as neutron fluence accumulates during accelerator operation. A hybrid quadrupole lens can be applied for fast adjustment of the focusing channel as well as for transporting the accelerated ion beams with different ion mass-to-charge ratios. [ABSTRACT FROM AUTHOR]

A prototype of a type A quadrupole magnet has been designed and manufactured for the 3 GeV storage ring of Siam Photon Source II, the second synchrotron light source in Thailand. The required quadrupole gradient is 51 T/m with the magnet effective length being 162 mm. Magnet modeling and magnetic field calculation were performed using Radia and Opera-3D. The bore radius of the magnet is 16 mm. The magnet will be operated at the excitation of 5544 A-turns. A mechanical analysis of the magnet structure was performed in SOLIDWORKS and ANSYS, where the maximum deformation of 0.003 mm was found at the magnet poles, and the first-mode natural frequency was higher than 100 Hz. The magnet yoke is made of AISI 1006 low-carbon steel with a fabrication tolerance of ±0.020 mm. Magnet coils are water-cooled and made of high-purity copper. The temperature rise of the coils was below 3.0 °C at the maximum excitation of 6664 A-turns, which is 20% above the operating point. Magnetic field measurement was carried out using the Hall probe technique. The measured magnetic field and coil temperature of the prototype show good agreement with the calculations. [ABSTRACT FROM AUTHOR]

To meet the requirements of miniaturization and low power consumption of portable instruments, a set of lower computer control system of portable quadrupole mass spectrometry was designed. The new control system was developed based on Xilinx spartan-6 series field programmable gate array (FPGA) platform. A single FPGA chip was used to replace the cumbersome architecture of traditional multiple chip combinations. The original W5500\MCU\DSP\DDR and other functional chips on the main control circuit board were removed, and the scanning, control, acquisition, storage, data processing, high-speed transmission and other functions realized by these chips were integrated into the same FPGA chip. The control system mainly communicated with the lower computer through the upper computer. The lower computer controlled the DAC voltage to scan the quadrupole, and at the same time linked the 16 bit ADC to collect data. The collected data was processed by some columns of algorithms, and then a large amount of data was accumulated and compressed, stored in the chip. Finally, the whole spectrum data was integrated according to the frame format and uploaded to the upper computer for displaying. The lower computer control system also integrated tuning control, feedback control, high voltage control and other functional modules. The difficulty in the design of the whole system lied in the high utilization of chip resources, which required a reasonable allocation of various chip resources and a balance in performance, speed and area. Compared with the existing miniaturized quadrupole mass spectrometry control system, the new control system not only saved the chip cost on the premise of unchanged function and performance, but also saved about 2.7 W in the power consumption of the master hardware board, which was about 37% of the power consumption of the original board, and reduced about 20 cm2 in the area of the master hardware board, which was about 10% of the area of the original board. The performance of the portable quadrupole mass spectrometer lower computer control system was fully verified by the 25 volatile organic compounds (VOCs) mixed standard test experiment, and was successfully applied in the portable quadrupole mass spectrometer. This design has high technology portability and practical value for similar miniaturized instruments. At this stage of the design, it is not possible to integrate all the functions of the instrument and realize a real single-chip lower computer control system, and the integrated functional modules need to be further optimized. Under the demand of miniaturization and low power consumption of portable instruments, the concept and design of integration will go further and further, and will slowly and truly achieve simple substitution for cumbersome, single substitution for combination, so as to make the concept of portability to the extreme and obtain the maximum value with the least consumption.

Vitamin D deficiency and insufficiency is a global health issue that afflicts people of different age groups all over the world. As a reliable indicator for the evaluation of vitamin D, 25OHD is usually determined by LC-MS/MS. The tandem mass spectrometry based on ion trap has the characteristics of simple structure and high sensitivity. However, there are some problems such as narrow linear range and space charge effect, which limit its analysis of trace substances in complex matrix samples. In this study, the device and technology of a new quadrupole linear ion trap mass spectrometry was used to reduce the space charge interference of trace or ultra trace target ions by high abundance impurity ions in complex matrices. For the first time, isotope dilution mass spectrometry for accurate measurement of serum 25OHD was established by QLIT-6610MD, which is quadrupole-linear ion trap tandem mass spectrometer, and was independently developed by Technology Innovation Center of Mass Spectrometry for State Market Regulation, Center for Advanced Measurement Science, National Institute of Metrology. Serum samples were precipitated with methanol, extracted with n-hexane, dried with liquid nitrogen, redissolved in the initial mobile phase, and determined by QLIT-6610MD. The matrix-matched standard curve was used for quantification. The linear ranges of 25OHD2 and 25OHD3 were in the range of 0.78-50 μg/L and 1.56-100 μg/L with R2>0.999 9, respectively. The detection and quantification limits of 25OHD2 and 25OHD3 were 0.06, 0.12 μg/L and 0.02, 0.06 μg/L, respectively. The precision of quality control was better than 4.06%. The recoveries ranged from 99.25% to 108.38%, and the coefficients of variation were all less than 5.1%. After the method confirmation, the quantitative results of clinical samples were compared with triple quadrupole tandem mass spectrometry. 50 Clinical serum samples were measured and compared by QLIT-6610MD, AB 4500MD and YS EXACT 9900MD. The correlation and consistency of the data were analyzed by Pearson and Bland-Altman. The correlation coefficient of the three groups data was R≥0.998 0, P

The mass analyzer based on quadrupole field theory, including quadrupole and ion trap, control and screen ions by a non-magnetic, alternating electric field, which was the first proposed by Professor Paul in 1953. Since the birth of quadrupole, ion trap and other related mass spectrometry technologies have been developed relatively maturely, which have made a significant impact and contribution to mass spectrometry. This paper deduced and interpretd the complete physical and mathematical formulae of the design and generation process of the quadrupole field. The process of obtaining the potential distribution of the quadrupole field, the obtaining process of boundary conditions such as electrode shape and voltage on the electrode, and the process of deducing the quadrupole structure and ion trap structure according to the potential distribution of the quadrupole field were discussed. In the above processes, for the purpose of binding ions, a general potential (Prof. Paul called it “allgemeinste potential” in German) distribution equation was obtained by introducing a simple harmonic motion model. And then, according to the basic laws of electromagnetic field and Maxwell’s equation, the condition of zero electric field divergence was introduced. Based on this, through the discussion of the two simplest solutions and boundary conditions, the structure and field distribution equations of the quadrupole and the ion trap were obtained, respectively. This content was an important supplement to the elaboration on the theory of quadrupole field mass spectrometry, which was helpful for a deeper understanding of basic principles of quadrupole field. At the same time, this paper provided a potential mass analyzer design method. Firstly, the design began with the conception of the state of ion motion, and then a force that could control the movement of ions according to the idea was found. Secondly, combined with the basic laws of electromagnetic fields, the general equation and its limiting conditions for the potential distribution that could form this force were obtained. Thirdly, according to the easy-to-operate settings in practice, the boundary conditions of the field (such as electrode shape, electrode voltage, etc.) were obtained, and the intermediate variables in the general equation were replaced with these operable physical parameters. At last, according to the potential distribution equation, the ion motion equation was calculated, and the mathematical relationship between the masstocharge ratio and the controllable physical parameters was found. And finally, a mass analysis method for controlling and separating ions was obtained. This kind of design method has important reference significance for theoretical research and original innovation research related to mass spectrometry. [ABSTRACT FROM AUTHOR]

A quadrupolar compound Pyr‐BA with two pyrrole‐type nitrogen atoms doped externally was prepared in this work. In high contrast with other π ionic radicals, its cationic radical Pyr‐BA⋅+ undergoes unusual symmetry‐broken charge separation (SB‐CS), generating the mixed valence complex of Pyr‐BA+1−q⋅⋅⋅Pyr‐BA+1+q, where q is the degree of charge transfer. Variable‐temperature (VT) single‐crystal analysis, absorption and EPR experiments all confirmed that aggregation and lower temperature would help to facilitate this SB‐CS process. Gibbs energy calculations and gauge‐including magnetically induced current simulation both validate that, for Pyr‐BA⋅+, SB‐CS behavior is more favorable than the conventional dimerization mode. To the best of our knowledge, this is the first study that shows solid single‐crystal evidence for spontaneous SB‐CS between identical ionic radicals. Such a unique phenomenon is of great significance both in terms of fundamental aspects and uncharted material science. [ABSTRACT FROM AUTHOR]

To meet the requirements of miniaturization and low power consumption of portable instruments, a set of lower computer control system of portable quadrupole mass spectrometry was designed. The new control system was developed based on Xilinx spartan-6 series field programmable gate array (FPGA) platform. A single FPGA chip was used to replace the cumbersome architecture of traditional multiple chip combinations. The original W5500\MCU\DSP\DDR and other functional chips on the main control circuit board were removed, and the scanning, control, acquisition, storage, data processing, high-speed transmission and other functions realized by these chips were integrated into the same FPGA chip. The control system mainly communicated with the lower computer through the upper computer. The lower computer controlled the DAC voltage to scan the quadrupole, and at the same time linked the 16 bit ADC to collect data. The collected data was processed by some columns of algorithms, and then a large amount of data was accumulated and compressed, stored in the chip. Finally, the whole spectrum data was integrated according to the frame format and uploaded to the upper computer for displaying. The lower computer control system also integrated tuning control, feedback control, high voltage control and other functional modules. The difficulty in the design of the whole system lied in the high utilization of chip resources, which required a reasonable allocation of various chip resources and a balance in performance, speed and area. Compared with the existing miniaturized quadrupole mass spectrometry control system, the new control system not only saved the chip cost on the premise of unchanged function and performance, but also saved about 2.7 W in the power consumption of the master hardware board, which was about 37% of the power consumption of the original board, and reduced about 20 cm² in the area of the master hardware board, which was about 10% of the area of the original board. The performance of the portable quadrupole mass spectrometer lower computer control system was fully verified by the 25 volatile organic compounds (VOCs) mixed standard test experiment, and was successfully applied in the portable quadrupole mass spectrometer. This design has high technology portability and practical value for similar miniaturized instruments. At this stage of the design, it is not possible to integrate all the functions of the instrument and realize a real single-chip lower computer control system, and the integrated functional modules need to be further optimized. Under the demand of miniaturization and low power consumption of portable instruments, the concept and design of integration will go further and further, and will slowly and truly achieve simple substitution for cumbersome, single substitution for combination, so as to make the concept of portability to the extreme and obtain the maximum value with the least consumption. [ABSTRACT FROM AUTHOR]

Vitamin D deficiency and insufficiency is a global health issue that afflicts people of different age groups all over the world. As a reliable indicator for the evaluation of vitamin D, 25OHD is usually determined by LC-MS/MS. The tandem mass spectrometry based on ion trap has the characteristics of simple structure and high sensitivity. However, there are some problems such as narrow linear range and space charge effect, which limit its analysis of trace substances in complex matrix samples. In this study, the device and technology of a new quadrupole linear ion trap mass spectrometry was used to reduce the space charge interference of trace or ultra trace target ions by high abundance impurity ions in complex matrices. For the first time, isotope dilution mass spectrometry for accurate measurement of serum 25OHD was established by QLIT-6610 MD, which is quadrupole-linear ion trap tandem mass spectrometer, and was independently developed by Technology Innovation Center of Mass Spectrometry for State Market Regulation, Center for Advanced Measurement Science, National Institute of Metrology. Serum samples were precipitated with methanol, extracted with n-hexane, dried with liquid nitrogen, redissolved in the initial mobile phase, and determined by QLIT-6610 MD. The matrix-matched standard curve was used for quantification. The linear ranges of 25OHD2 and 25OHD3 were in the range of 0.78-50 μg/L and 1.56-100 μg/L with R²＞0.999 9, respectively. The detection and quantification limits of 25OHD2 and 25OHD3 were 0.06, 0.12 μg/L and 0.02, 0.06 μg/L, respectively. The precision of quality control was better than 4.06%. The recoveries ranged from 99.25% to 108.38%, and the coefficients of variation were all less than 5.1%. After the method confirmation, the quantitative results of clinical samples were compared with triple quadrupole tandem mass spectrometry. 50 Clinical serum samples were measured and compared by QLIT-6610 MD, AB 4500 MD and YS EXACT 9900 MD. The correlation and consistency of the data were analyzed by Pearson and Bland-Altman. The correlation coefficient of the three groups data was R≥0.998 0, P＜0.01, and the results of Bland-Altman analysis showed good consistency, indicating that the results measured by the three instruments were consistent, which meant that QLIT-6610 MD can meet the needs of clinical diagnosis. QLIT-6610 MD achieved the same level of triple quadrupole mass spectrometry to determine the concentration of 25OHD in serum. It can not only become a new choice for clinical mass spectrometry, but also lay a foundation for the development of domestic mass spectrometer. Based on the direct axial coupling technology of quadrupole and linear ion trap, QLIT-6610 MD can greatly reduce the interference of matrix ions and make the ion trap detect target ions more effectively. This technology has a strong potential to further improve the measurement accuracy of trace or ultra trace targets in complex matrices. In the future, it can be applied to mass spectrometry monitoring scenarios that needs to meet the requirements of high accuracy, high sensitivity, on-site speed and low cost at the same time. [ABSTRACT FROM AUTHOR]

Manipulating radiation patterns is challenging, especially at low frequencies. In this paper, we demonstrate that acoustic metamaterials arranged as an array of quadrupoles remarkably improve the directionality of acoustic radiation at low frequencies, compared with previous metamaterials arranged as monopole and dipole structures. The directivity of the acoustic radiation can be adjusted by changing the characteristic parameter and the symmetry of the structure, which provides a flexible method of adjusting radiation directions. The directionality can be further improved by constructing a linear array. Our work establishes acoustic radiation control via quadrupolar metamaterials. [ABSTRACT FROM AUTHOR]

In this paper, we have proposed a graphene-based tunable plasmonic sensor in the far-infrared region. Our structure consists of patterned graphene disks on a SiO 2 gap dielectric structure. On a SiO 2 substrate, a monolayer of graphene is placed. On top of that, with a gap dielectric structure, graphene is disk patterned, forming a 2D metastructure. At the resonance wavelength where the dominating electric dipole due to plasmonic resonance is suppressed, the scattering is enhanced due to the magnetic dipole and magnetic quadrupole. The parameter tuning of the proposed device can tune this scattering. We have shown a dominating tunable magnetic quadrupolar scattering at some geometrical parameters. Moreover, graphene has a tunable chemical potential, allowing us to tune the resonance wavelength up to 30 µm. We have shown two tuning schemes to this range with the advantage of a double graphene structure. Along with the interplay of the multipole analysis of these plasmonic resonances, we have shown practical application to sensing. A chemical solvent sensor for detecting hazardous solvents like benzene and nitrobenzene has been proposed, considering the experimental dispersion of these compounds. The chemical solvent sensor has shown a maximum sensitivity of 1307.716 nm/RIU. We also have shown a potential application for high-sensitivity sensing where the refractive index changes only a fraction compared to the base parameter of the air environment, reporting a maximum sensitivity of 4830.95 nm/RIU. [ABSTRACT FROM AUTHOR]

Although a quadruple mass analyzer and an ion trap mass analyzer have complementary analytical features, they usually have different geometries, operational modes, and electronic control systems. As a continuous effort to extend its coverage, both quadrupole and ion trap operation modes were realized on a “brick” miniature mass spectrometer with a single mass analyzer. In the quadrupole operation mode, low-mass ions ranging from 31 to 502 Th can be analyzed. On the other hand, the ion trap mode can be utilized to cover ions with higher mass to charge ratios (up to 922 Th), as well as performing tandem mass spectrometry. To realize the multiplexing of both operation modes, a printed circuit board (PCB)-based multi-electrode quadrupole–ion trap mass analyzer was designed and integrated in the system. To cover both volatile and non-volatile molecules, two ionization sources were also implemented, including a nano electrospray ionization source and an in-vacuum plasma ionization source. Performances of the instrument operated in these two modes were characterized, such as mass resolution, sensitivity, and mass range. Results demonstrate that the combination of the quadrupole and ion trap operation modes can provide new capabilities when solving analytical problems.

The LHC accelerator research program (LARP), in collaboration with CERN and under the scope of the high luminosity upgrade of the Large Hadron Collider, is in the prototyping stage in the development of a 150 mm aperture high-field Nb3Sn quadrupole magnet called MQXF. This magnet is mechanically supported using a shell-based support structure, which has been extensively demonstrated on several R&D models within LARP, as well as in the more recent short (1.2 m magnetic length) MQXF model program. The MQXFA magnets are each 4.2 m magnetic length, and the first mechanical long model, MQXFA1M (using aluminum surrogate coils), and MQXFAP1 prototype magnet (the first prototype with Nb3Sn coils) have been assembled at the LBNL. In this paper, we summarize the tooling and the assembly processes, and discuss the mechanical performance of these first two assemblies, comparing strain gauge data with finite element model analysis, as well as the near-term plans for the long MQXF magnet program.

In the present article, frequency-domain formulations of quadrupole corrections are derived in a computationally efficient form for the Ffowcs Williams and Hawkings (FW-H) equation with permeable control surfaces. Quadrupole corrections effectively reduce spurious noise associated with hydrodynamic fluctuations passing across integral surfaces, originally derived for Formulation 1A of Farassat in the time domain. When a corresponding frequency-domain formulation is sought, however, difficulty arises as its Green's function is written in a convective form and different from that of Formulation 1A. First, the mathematical framework of the convective FW-H equation is shown to be equivalent to Formulation 1A by applying a simple Galilean transformation for rectilinear motion. Then, a frequency-domain formulation is derived via a Fourier transform applied directly to the time-domain quadrupole correction forms. The results of the derived formulation agree precisely with the time-domain solutions, in the verification study of vortex convection, as well as non-uniform entropy convection, in which spurious noise can be effectively removed by the present quadrupole correction integrals. [ABSTRACT FROM AUTHOR]

Understanding degradation mechanisms of organic photovoltaics (OPVs) is a critical prerequisite for improving device stability. Herein, the effect of molecular structure on the photostability of non‐fullerene acceptors (NFAs) is studied by changing end‐group substitution of ITIC derivatives: ITIC, ITIC‐2F, and ITIC‐DM. Using an assay of in situ spectroscopy techniques and molecular simulations, the photodegradation product of ITIC and the rate of product formation are identified, which correlates excellently to reported device stability, with ITIC‐2F being the most stable and ITIC‐DM the least. The choice of acceptor is found to affect both the donor polymer (PBDB‐T) photostability and the morphological stability of the bulk heterojunction blend. Molecular simulations reveal that NFA end‐group substitution strongly modulates the electron distribution within the molecule and thus its quadrupole moment. Compared to unsubstituted‐ITIC, end‐group fluorination results in a stronger, and demethylation a weaker, molecular quadrupole moment. This influences the intermolecular interactions between NFAs and between the NFA and the polymer, which in turn affects the photostability and morphological stability. This hypothesis is further tested on two other high quadrupole acceptors, Y6 and IEICO‐4F, which both show impressive photostability. The strong correlation observed between NFA quadrupole moment and photostability opens a new synthetic direction for photostable organic photovoltaic materials. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a millimeter-wave printed quadrupole antenna is proposed. It consists of two symmetric printed dipoles that make the quadrupole radiating power omnidirectionally. Such an arrangement eliminates the influence of the ground as reflector. Simulation results show that the quadrupole antenna exhibits a broad impedance bandwidth and an enhanced gain compared to conventional dipoles. More interestingly, the configuration of the quadrupole includes an integrated feed network, making the design compact. Next, a novel omnidirectional array was designed, simulated, fabricated, and measured, exhibiting enhanced features like compactness, broad bandwidth, high gain, high efficiency, low cross-polarization, low cross-polarization level, low cost, and low profile.

In the framework of the Hi-Lumi LHC Project, CERN and U.S. LARP are jointly developing MQXF, a 150-mm aperture high-field Nb3Sn quadrupole for the upgrade of the inner triplet of the low-beta interaction regions. The magnet is supported by a shell-based structure, providing the preload by means of bladder-key technology and differential thermal contraction of the various components. Two short models have been produced using the same cross section currently considered for the final magnet. The structures were preliminarily tested replacing the superconducting coils with blocks of aluminum. This procedure allows for model validation and calibration, and also to set performance goals for the real magnet. Strain gauges were used to monitor the behavior of the structure during assembly, cool down and also excitation in the case of the magnets. The various structures differ for the shell partitioning strategies adopted and for the presence of thick or thin laminations. This paper presents the results obtained and discusses the mechanical performance of all the short models produced up to now.

The Large Hadron Collider Luminosity upgrade (HiLumi) program requires new low-β triplet quadrupole magnets, called MQXF, in the interaction region to increase the LHC peak and integrated luminosity. The MQXF magnets, designed and fabricated in collaboration between CERN and the U.S. LARP, will all have the same cross section. The MQXF long model, referred as MQXFA, is a quadrupole using the Nb3Sn superconducting technology with 150 mm aperture and a 4.2 m magnetic length and is the first long prototype of the final MQXF design. The MQXFA magnet is based on the previous LARP HQ and MQXFS designs. In this paper, we present the baseline design of the MQXFA structure with detailed three-dimensional (3-D) numerical analysis. A detailed tolerance analysis of the baseline case has been performed by using a 3-D finite element model, which allows fast computation of structures modeled with actual tolerances. Tolerance sensitivity of each component is discussed to verify the actual tolerances to be achieved by vendors. Tolerance stack-up analysis is presented in the end of this paper.

Miniature ion trap mass spectrometer enables mass-to-charge ratio analysis of ions via quadrupole field in a low vacuum environment. It plays an important role in on-site detection due to its portability and specificity. In order to gain a deeper understanding of the analysis mechanism of miniature ion trap mass spectrometers, a quadrupole MS ion trajectory numerical simulation model (QITNS) is established in this paper for ions trajectory calculation under the action of quadrupole field, exciting field and neutral gas molecule collision. Compared with the existing methods, the model in this paper is simpler and more direct, which effectively explored the effects of dipole excitation and quadrupole excitation on ion manipulation under high background pressure. The simulation results demonstrate that high RF amplitude, low auxiliary AC amplitude and quadrupole excitation can effectively improve the isolation resolution. Besides, it clarified the difference between the analysis mechanism of ion trap mass spectrometers under high background pressure (above 13.332 Pa) and absolute vacuum conditions. The relevant results are consistent with the conclusions of previous experiments and other theories, proving the applicability and accuracy of the proposed calculation model and solution method. This research bears the guiding significance for further understanding the mechanism of quadrupole mass spectrometry as well as designing and developing miniature mass spectrometers. [Display omitted] • A simple numerical model is proposed for quadrupole mass spectrometry by directly coupling resonance and attenuation terms. • The model can elucidate the key factors for improving the resolution of the ion trap mass spectrometer. • It can also elucidate the ion manipulation rules under high background pressure conditions for miniaturized ion trap. [ABSTRACT FROM AUTHOR]

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This paper introduces an alternative generalization of the static solution with quadrupole moment, the q -metric, that describes a deformed compact object in the presence of the external fields characterized by multipole moments. In addition, we also examine the impact of the external fields up to quadrupole on the circular geodesics and the interplay of these two quadrupoles on the place of the innermost stable circular orbit (ISCO) in the equatorial plane. [ABSTRACT FROM AUTHOR]

In preparation for the high-luminosity upgrade of the Large Hadron Collider (LHC), the LHC Accelerator Research Program (LARP) in collaboration with CERN is pursuing the development of MQXF: a 150-mm-aperture high-field Nb3Sn quadrupole magnet. The development phase starts with the fabrication and test of several short models (1.2-m magnetic length) and will continue with the development of several long prototypes. All of them are mechanically supported using a shell-based support structure, which has been extensively demonstrated on several RD models within LARP. The first short model MQXFS-AT has been assembled at LBNL with coils fabricated by LARP and CERN. In this paper, we summarize the assembly process and show how it relies strongly on experience acquired during the LARP 120-mm-aperture HQ magnet series. We present comparison between strain gauges data and finite-element model analysis. Finally, we present the implication of the MQXFS-AT experience on the design of the long prototype support structure.

The last‐passage (LP) Monte Carlo algorithms for the charge density on an L‐shaped conducting surface are further developed by deriving a quadrupole LP Green's function on the L‐shaped flat surface. To demonstrate the algorithm, charge densities on an L‐shaped conductor are computed in 3D space and it is found that these results agree very well with the ones from the Given‐Hwang's original last‐passage algorithm on a flat surface. Compared with the Given‐Hwang's LP algorithm, the quadrupole LP one is very suitable for charge density near the L‐shaped edge boundary. [ABSTRACT FROM AUTHOR]

Manipulating radiation patterns is challenging, especially at low frequencies. In this paper, we demonstrate that acoustic metamaterials arranged as an array of quadrupoles remarkably improve the directionality of acoustic radiation at low frequencies, compared with previous metamaterials arranged as monopole and dipole structures. The directivity of the acoustic radiation can be adjusted by changing the characteristic parameter and the symmetry of the structure, which provides a flexible method of adjusting radiation directions. The directionality can be further improved by constructing a linear array. Our work establishes acoustic radiation control via quadrupolar metamaterials.

Mass spectrometry (MS) is one of the most widely used analytical techniques in many fields. Recent developments in chemical and biological researches have drawn much attention to the measurement of substances with low abundances in samples. Continuous efforts have been made consequently to further improve the sensitivity of MS. Modifications on the mass analyzers of mass spectrometers offer a direct, universal and practical way to obtain higher sensitivity. This review provides a comprehensive overview of the latest developments in mass analyzers for the improvement of mass spectrometers’ sensitivity, including quadrupole, ion trap, time-of-flight (TOF) and Fourier transform ion cyclotron (FT-ICR), as well as different combinations of these mass analyzers. The advantages and limitations of different mass analyzers and their combinations are compared and discussed. This review provides guidance to the selection of suitable mass spectrometers in chemical and biological analytical applications. It is also beneficial to the development of novel mass spectrometers.

We critically evaluate the current status of portable mass spectrometry (pMS), particularly where this aligns with ambient ionization. Assessing the field of pMS can be quite subjective, especially in relation to the portable aspects of design, deployment, and operation. In this review, we discuss what it means to be portable and introduce a set of criteria by which pMS and ambient ionization sources can be assessed. Moreover, we consider the recent literature in terms of the most popular and significant advances in portable instrumentation for ambient ionization and miniature mass spectrometers. Finally, emerging trends and exciting future prospects are discussed and some recommendations are offered.

In this article, a novel substrate integrated waveguide power divider is proposed to feed antenna array elements in series. This feed network inherently provides uniform output power to eight quadrupole antennas. More importantly, it leads to a compact configuration since the feed network can be integrated inside the elements without increasing the array size. Its design procedure is first discussed. Next, the series feed network was used to feed a novel compact omnidirectional antenna array. Targeting the fifth-generation (5G) 26 GHz millimeter-wave (mm-wave) band, the simulated results showed that the proposed array exhibits a broad impedance bandwidth of 4.15 GHz and a high gain of 13.6 dBi. A prototype was fabricated and measured, exhibiting a measured impedance bandwidth of 6.72 GHz and a gain of 12.3 dBi. Its attractive features indicate that the proposed antenna array is well suitable for millimeter-wave wireless communication systems. [ABSTRACT FROM AUTHOR]