A Hadamard transform electron ionization time-of-flight mass spectrometer

We describe the first Hadamard transform time-of-flight mass spectrometer (HT-TOFMS) that incorporates an electron (impact) ionization source. This implementation was realized in an existent TOF instrument using commercially available components and simple modifications to the ion source. In the present apparatus, a Hadamard mask is expressed by modulating the ion generation process within the ion source; thus, the present approach differs from previous designs that use external electrostatic devices to modulate a continuous ion stream. The present implementation may be operated in conventional TOF mode at 12.5 kHz and in HT-TOF mode at 20-40 MHz. In Hadamard mode the design can operate using any circulant simplex code, allowing the operator much flexibility for optimizing resolution and mass range and for eliminating nonstochastic fluctuations, e.g., encoding errors and signal hum. We demonstrate typical performance of the HT-TOFMS in standard and reflectron geometries using sequences of three constructions and of varied length, generating HT-TOF mass spectra of molecules that match conventional reference spectra. The auxiliary material includes an electrical schematic for the floating high-speed encoding amplifier, which is also of use in other high-speed electrostatic optics applications, and a list of 537 validated vectors comprising the first row of each circulant simplex sequence (S(n)=3-8219) derived using maximal shift register (n=2(m)-1), quadratic residue (n=4m-3), and twin prime constructions [n=p(p+2)].     

A shock tube with a high-repetition-rate time-of-flight mass spectrometer for investigations of complex reaction systems

A conventional membrane-type stainless steel shock tube has been coupled to a high-repetition-rate time-of-flight mass spectrometer (HRR-TOF-MS) to be used to study complex reaction systems such as the formation of pollutants in combustion processes or formation of nanoparticles from metal containing organic compounds. Opposed to other TOF-MS shock tubes, our instrument is equipped with a modular sampling unit that allows to sample with or without a skimmer. The skimmer unit can be mounted or removed in less than 10 min. Thus, it is possible to adjust the sampling procedure, namely, the mass flux into the ionization chamber of the HRR-TOF-MS, to the experimental situation imposed by species-specific ionization cross sections and vapor pressures. The whole sampling section was optimized with respect to a minimal distance between the nozzle tip inside the shock tube and the ion source inside the TOF-MS. The design of the apparatus is presented and the influence of the skimmer on the measured spectra is demonstrated by comparing data from both operation modes for conditions typical for chemical kinetics experiments. The well-studied thermal decomposition of acetylene has been used as a test system to validate the new setup against kinetics mechanisms reported in literature.     

A hardware and software system for the laser time-of-flight mass spectrometer

The hardware and software system for a laser time-of-flight mass spectrometer is based on the double-level principle. At the upper level, the personal computer automatically controls online recording and processing of mass spectra with the highest priority. The monitoring and stabilization functions are fulfilled by controllers of the second control level. The exchange between the controllers and personal computer takes place in the periods between mass-spectrum recording and processing. The use of the hardware and software system has made it possible (i) to form short mass peaks with a half-height duration of up to 10 ns, (ii) to decrease a scatter of relative sensitivity coefficients from two or three down to one order of magnitude, and (iii) to increase a dynamic range of the recorded mass spectra up to 1?1 × 10⁹.     

A time-of-flight mass spectrometer for detecting a point of air leakage from a spacecraft module

The possibility of using a time-of-flight mass spectrometer for determining a point of air leakage from a spacecraft module is discussed. A procedure for carrying out ground experiments in a vacuum chamber is proposed for artificial simulation of the composition of the intrinsic external atmosphere of the spaccraft. The described mass spectrometer is capable of detecting leakages of small-concentration gas flows with a high level of confidence.     

飞行时间质谱仪国内研究状况及发展趋势

本文介绍飞行时间质谱仪的发展历史,对近二十年来国内飞行时间质谱仪的研制状况做较全面的概述。最后结合国内情况,介绍飞行时间质谱仪为适应不同应用领域研究对象的需要,目前主要的两个发展方向,一个是发展超高分辨、高灵敏度的高档仪器,另一个是发展小型台式仪器。     

Automated correction of ion trajectories in a time-of-flight mass spectrometer with an axially symmetric electrostatic field

The possibility of controlling the trajectories of ion beams in a time-of-flight mass analyzer with an axially symmetric electric field is considered. It is shown that a double grid installed at the input of the mass analyzer can change the coordinates of ions entering the mass analyzer, thereby leading to an increase in the analyzer transmission efficiency and, as a result, in its sensitivity.     

A time-of-flight mass spectrometer for monitoring the inhalational anesthesia concentration in the real-time mode

The use of a medical mass spectrometer for measuring the concentration of the gas mixture components in the breathing circuit of an inhalational anesthesia machine in the real-time mode is described. The resolution of the mass spectrometer is M/ΔM = 200, and the detection threshold in terms of the partial pressure of the analyzed gases is 2 × 10^?12 mbar. The mass spectrometer is capable of measuring the volumetric content of CO₂, O₂, and inhalational anesthetic sevoflurane. The respiratory coefficient (CO₂/O₂) was measured during anesthesia to estimate the patient’s stress reaction to a surgical injury.     

Shock tube/time-of-flight mass spectrometer for high temperature kinetic studies

A shock tube (ST) with online, time-of-flight mass spectrometric (TOF-MS) detection has been constructed for the study of elementary reactions at high temperature. The ST and TOF-MS are coupled by a differentially pumped molecular beam sampling interface, which ensures that the samples entering the TOF-MS are not contaminated by gases drawn from the cold end wall thermal boundary layer in the ST. Additionally, the interface allows a large range of postshock pressures to be used in the shock tube while maintaining high vacuum in the TOF-MS. The apparatus and the details of the sampling system are described along with an analysis in which cooling of the sampled gases and minimization of thermal boundary layer effects are discussed. The accuracy of kinetic measurements made with the apparatus has been tested by investigating the thermal unimolecular dissociation of cyclohexene to ethylene and 1,3-butadiene, a well characterized reaction for which considerable literature data that are in good agreement exist. The experiments were performed at nominal reflected shock wave pressures of 600 and 1300 Torr, and temperatures ranging from 1260 to 1430 K. The rate coefficients obtained are compared with the earlier shock tube studies and are found to be in very good agreement. As expected no significant difference is observed in the rate constant between pressures of 600 and 1300 Torr.     

Shock tube coupled to the time-of-flight mass spectrometer via a molecular beam sampling system

A method for continuous mass spectrometric analysis of high-temperature reacting gas mixtures is described. The apparatus consists of a unique combination of three devices: the shock tube, the time-of-flight mass spectrometer, and the supersonic molecular beam. The driven section of the shock tube constitutes the reservoir of a supersonic molecular beam by which gas is continuously extracted from the reaction zone and introduced through a two-stage high-capacity vacuum system into the ionization region of the mass spectrometer. The shock tube and the mass spectrometer are coupled at right angles to one another. This configuration avoids excessive pressure buildup in the mass spectrometer system. The apparatus has an estimated mass resolution of 100 amu, a frequency range of 10-100 kHz, and can be operated over a wide range of shock conditions during the complete high-temperature pulse.     

A hyperboloid mass spectrometer with a monopolar ion trap

A hyperboloid mass spectrometer with an analyzer utilizing a three-dimensional ion trap bounded by the planez=0 is described. Potential distribution in a monopolar trap is numerically simulated and the influence of distortion function ΔU(z, r) on the trajectories of charged particles is investigated. Mass peaks for various operating modes of the analyzer are calculated. An experimental mass spectrometer with a monopolar ion trap has been investigated. Spectra of the residual atmosphere and of that with tetrachloromethane CCI₄ puffed into the vacuum chamber have been measured. The resolution obtained isR _0.5=1.2×10³.     

A differential time-of-flight spectrometer of very slow neutrons

A time-of-flight spectrometer of neutrons with energies of 0.05–2.50 μeV is described. This spectrometer has been tested by measuring the total and differential neutron cross sections for a number of materials—aluminum, copper, silicon, zirconium, polyethylene, ⁶LiF, and fluoropolymers—that are essential for experiments in physics of ultracold neutrons.     

The possibilities of a mass spectrometer equipped with a Llewellyn inlet system in the analysis of air and water samples

The design of a multimembrane inlet system, in which the method proposed by Llewellyn for enriching gases (through the addition of volatile organic components and certain other gases) for purposes of chromatography/mass spectrometry is described. A mechanism that enables one to obtain an enrichment effect of 10⁶ for a considerable group of compounds in the process of analyzing air and water samples, supplied to the mass spectrometer through the proposed inlet system, is considered. The results are given from the experimental verification of the inlet system operating as part of a portable magnetic mass spectrometer.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 101–104.Original Russian Text Copyright © 2004 by Kogan, Victorova, Victorov.     

高分辨率旋转光栅光谱仪的设计

针对光栅光谱仪中高分辨率与宽光谱难以同时满足的问题,设计了一款基于旋转光栅的Czerny-Turner（C-T型）光路结构的高分辨率宽光谱拉曼光谱仪,激发波长为532 nm,光谱范围为80～3000 $ {\mathrm{c}\mathrm{m}}^{-1} $,分辨率为1.2 $ {\mathrm{c}\mathrm{m}}^{-1} $。将光谱范围分为低（80～1450 $ {\mathrm{c}\mathrm{m}}^{-1} $）、中（855～2225 $ {\mathrm{c}\mathrm{m}}^{-1} $）、高（1630～3000 $ {\mathrm{c}\mathrm{m}}^{-1} $）3个波段,以优化中波段为主,对全波段进行了优化。通过微调光栅的旋转角度,确保低、中、高波段均位于CCD的有效像面上。该光谱仪成像系统的点列图、均方根图和调制传递函数图均符合设计要求。     

高分辨率电喷雾电离飞行时间质谱仪测定大豆磷脂中的磷脂酰胆碱

首次实现了国内用自制高分辨率电喷雾电离飞行时间质谱仪(ESI-TOF-MS)检测大豆磷脂中的磷脂酰胆碱(PC),共检测出了52种磷脂酰胆碱.实验证明,高分辨率ESI-TOF-MS具有定性速度快、灵敏度高、精确度好的优点,是目前磷脂检测的最为有效的工具.     

A time-of-flight measurement system for the HADES wide-aperture dielectron spectrometer

The HADES spectrometer and a time-of-flight detector based on long-sized (50–250 cm) scintillation counters are described. The detector is designed for identification of electrons, pions, and protons with momenta of 0.1–1.5 GeV/c at a flight distance of 220–250 cm. The operating conditions are analyzed, and the requirements to the detector and counter design are formulated. The design of the counters and their arrangement in the spectrometer are considered. The results of experimental studies of such characteristics of long counters as the light attenuation length in a scintillator and temporal and spatial resolutions, dependeing on the location of the point of the particle’s hit on the counter, are presented. Analysis of the data has shown that the main factor determining the spatial resolution of long counters is the quality of the polishing of the side faces of the scintillators, which determines the effective (averaged over the scintillator side surfaces) coefficient of total internal reflectionR. It is shown that, forR>-0.99, it is quite possible to achieve temporal and spatial resolutions of 100 ns and 2–3 cm, respectively, for scintillators with a length of up to 250 cm and a cross section of 1–20 cm². Foreign and Russian photomultipliers were used in the counters.     

An integrated ion trap and time-of-flight mass spectrometer for chemical and photo- reaction dynamics studies

We demonstrate the integration of a linear quadrupole trap with a simple time-of-flight mass spectrometer with medium-mass resolution (m/Δm ～ 50) geared towards the demands of atomic, molecular, and chemical physics experiments. By utilizing a novel radial ion extraction scheme from the linear quadrupole trap into the mass analyzer, a device with large trap capacity and high optical access is realized without sacrificing mass resolution. This provides the ability to address trapped ions with laser light and facilitates interactions with neutral background gases prior to analyzing the trapped ions. Here, we describe the construction and implementation of the device as well as present representative ToF spectra. We conclude by demonstrating the flexibility of the device with proof-of-principle experiments that include the observation of molecular-ion photodissociation and the measurement of trapped-ion chemical reaction rates.     

A time-of-flight backscattering spectrometer at the Spallation Neutron Source, BASIS

We describe the design and current performance of the backscattering silicon spectrometer (BASIS), a time-of-flight backscattering spectrometer built at the spallation neutron source (SNS) of the Oak Ridge National Laboratory (ORNL). BASIS is the first silicon-based backscattering spectrometer installed at a spallation neutron source. In addition to high intensity, it offers a high-energy resolution of about 3.5 μeV and a large and variable energy transfer range. These ensure an excellent overlap with the dynamic ranges accessible at other inelastic spectrometers at the SNS.     

A cryosystem for cooling samples in a secondary-ion mass spectrometer with a static analyzer

A cryogenic system for cooling samples in an IMS-4F secondary-ion mass spectrometer with a static analyzer is described. The cryogenic system allows maintenance of the sample temperature with an accuracy of ±1 K in a temperature range of 60–420 K by combining heating and cooling (by using liquid helium or nitrogen). The effect of the sample temperature (300 and 110 K) on the secondary-ion mass spectra of Si and GaAs samples is considered.     

Combining high mass resolution and velocity imaging in a time-of-flight ion spectrometer using pulsed fields and an electrostatic lens

We describe a momentum resolving time-of-flight ion mass spectrometer that combines a high mass resolution, a velocity focusing condition for improved momentum resolution, and field-free conditions in the source region for high resolution electron detection. It is used in electron-ion coincidence experiments to record multiple ionic fragments produced in breakup reactions of small to medium sized molecules, such as F(3)SiCH(2)CH(2)Si(CH(3))(3). These breakup reactions are caused by soft x rays or intense laser fields. The ion spectrometer uses pulsed extraction fields, an electrostatic lens, and a delay line detector to resolve the position. Additionally, we describe a simple analytical method for calculating the momentum from the measured hit position and the time of flight of the ions.