四极离子阱阱内离子解离技术的研究进展

准确高效的离子解离技术对串联质谱分析方法具有非常重要的影响。四极离子阱可以存储离子，实现离子选择存储或逐出并进行多级质谱分析，适合各种解离技术在阱内的实施。由于生物质谱分析等研究工作对分子结构鉴定的需求，研究人员陆续开发了一系列阱内离子解离技术，推动了相关仪器与应用的发展。本文在离子阱几何结构和阱内离子运动规律的基础上，对是否依赖背景气体碰撞的两类阱内离子解离技术进行综述。其中，将依赖于背景气体碰撞的解离技术分为基于共振激发和非共振激发两类，归纳了每种解离技术的实施过程、解离特点及应用，并对各种解离技术存在的问题以及未来的研究方向进行总结。     

Nuclear quadrupole double resonance spectrometer with magnetic property measurement system direct current superconducting quantum interference device detector and automatic tuning

A new nuclear quadrupole double resonance spectrometer based on a commercial superconducting quantum interference device (SQUID) setup (a Magnetic Property Measurement System (MPMS) from Quantum Design) is described. The experiment involves the indirect detection of pure quadrupole resonances (PQR) of a dilute spin system via the direct SQUID detected NMR of an abundant spin system. The experiment is conducted at low (3-20 K) temperatures and the magnetic field is cycled between a high (5.5 T) polarizing field, to an intermediate (0.1 T) detection field, to zero field where the sample is irradiated with a modulated search RF and back to the detection field. Loss of the NMR signal indicates the detection of a PQR. The RF circuit used for both the NMR and zero field irradiation is digitally controlled. Use of the External Device Control allows for the complete automation of the system. Test measurements on diphenyl ether are in good agreement with previously reported results. Pure (17)O quadrupole resonances were detected for spin systems with concentrations as low as 120 μM.     

An ultralow noise current amplifier based on superconducting quantum interference device for high sensitivity applications

An integrated ultrahigh sensitive current amplifier based on a niobium dc superconducting quantum interference device (SQUID) has been developed. The sensor design is based on a multiturn signal coil coupled to a suitable SQUID magnetometer. The signal coil consists of 60 square niobium turns tightly coupled to a superconducting flux transformer of a SQUID magnetometer. The primary coil (pick-up coil) of the flux transformer has been suitably designed in order to accommodate the multiturn input coil. It has a side length of 10 mm and a width of 2.4 mm. In such a way we have obtained a signal current to magnetic flux transfer coefficient (current sensitivity) as low as 62 nA∕Φ(0). The sensor has been characterized in liquid helium by using a direct coupling low noise readout electronic and a standard modulated electronic in flux locked loop configuration for the noise measurements. Beside the circuit complexity, the sensor has exhibited a smooth and free resonance voltage-flux characteristic guaranteeing a reliable and a stable working operation. Considering a SQUID magnetic flux noise of S(Φ)(1∕2) = 1.8 μΦ(0)∕Hz(1∕2) at T = 4.2 K, a current noise as low as 110 fA∕Hz(1∕2) is obtained. Such a value is about a factor two less than the noise of other SQUIDs of the same category. As an application, Nyquist noise measurements of integrated test resistors using the current sensing noise thermometer technique are reported. Due to its high performance such a sensor can be employed in all applications requiring an extremely current sensitivity like the readout of the gravitational wave detectors and the current sensing noise thermometry.     

四极杆线性离子阱系统和预存干涉波的傅里叶逆变换技术

本文在回顾四极杆线性离子阱结构和原理的基础上,阐释了线性离子阱的电子系统和串联质谱的核心技术原理,介绍了预存干涉波的傅里叶逆变换技术在四极杆线性离子阱中的应用,特别是用于选择母离子。四极杆线性离子阱的加工精度要求适中、成本低、电路设计和控制(包括射频和直流)相对容易,使其在研发方面具有较大优势。线性离子阱特有的MS^n、碰撞冷却、较高的灵敏度和分辨率,以及选择性的离子储存和激发能力都使其拥有广阔的应用前景。预存干涉波的傅里叶逆变换技术的应用使得母离子被特异性驻留,而非母离子通过共振被甩出,提高了线性离子阱的分析能力。     

Determination of dioxins/furans and PCBs by quadrupole ion-trap gas chromatography-mass spectrometry

The versatility and sensitivity of the quadrupole ion trap tandem mass spectrometer has been applied to the determination of polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibenzofurans (PCDFs), and of polychlorinated biphenyls (PCBs). A brief introduction to the theory of ion confinement in a quadrupole ion trap permits discussion of ion trajectory stability, mass-selective ion ejection, the frequencies of ion motion, and the role of resonant excitation of ion motion. The tandem mass spectrometric examination of PCDDs and PCDFs eluting and co-eluting from a gas chromatographic column is described. Illustrative examples are given of the analysis of field samples containing PCDDs and PCDFs. A comparison is presented of the performance of each of a quadrupole ion trap tandem mass spectrometer, a triple stage quadrupole mass spectrometer, and a sector instrument of relatively high mass resolution for the determination of PCDDs and PCDFs. This comparison is made with respect to instrument tuning, calibration plots, detection limits, ion signals at low concentration, relative response factors, ionization cross-sections, and the examination of field samples. The application of quadrupole ion trap tandem mass spectrometry to the examination of PCBs is focused upon those PCB congeners that have the greatest toxicity. 39 congeners of the total of 209 PCB congeners have been identified as having the greatest toxicities. Chemical ionization has been used for the determination of co-eluting congeners #77 and #110 where the toxicity of the former is much greater than that of the latter. An analytical protocol, based on the variation of molecular ion fragmentation according to the degree (or absence) of chlorine ortho-substitution, has been proposed for distinguishing between toxic and nontoxic PCB congeners.     

Quadrupole ion traps

The extraordinary story of the three‐dimensional radiofrequency quadrupole ion trap, accompanied by a seemingly unintelligible theoretical treatment, is told in some detail because of the quite considerable degree of commercial success that quadrupole technology has achieved. The quadrupole ion trap, often used in conjunction with a quadrupole mass filter, remained a laboratory curiosity until 1979 when, at the American Society for Mass Spectrometry Conference in Seattle, George Stafford, Jr., of Finnigan Corp., learned of the Masters' study of Allison Armitage of a combined quadrupole ion trap/quadrupole mass filter instrument for the observation of electron impact and chemical ionization mass spectra of simple compounds eluting from a gas chromatograph. Stafford developed subsequently the mass‐selective axial instability method for obtaining mass spectra from the quadrupole ion trap alone and, in 1983, Finnigan Corp. announced the first commercial quadrupole ion trap instrument as a detector for a gas chromatograph. In 1987, confinement of ions generated externally to the ion trap was demonstrated and, soon after, the new technique of electrospray ionization was shown to be compatible with the ion trap. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:961–989, 2009     

Compact cryogenic system with mechanical cryocoolers for antihydrogen synthesis

We have developed a compact cryogenic system which cools a vacuum chamber housing multi-ring trap electrodes (MRTs) of an antihydrogen synthesis trap using mechanical cryocoolers to achieve background pressure less than 10(-12) Torr. The vacuum chamber and the cryocoolers are thermally connected by copper strips of 99.9999% in purity. All components are installed within a diametric gap between the MRT of phi108 mm and a magnet bore of phi160 mm. An adjusting mechanism is prepared to align the MRT axis to the magnet axis. The vacuum chamber was successfully cooled down to 4.0 K after 14 h of cooling with heat load of 0.8 W.     

Electrostatic ion trap and Fourier transform measurements for high-resolution mass spectrometry

We report on the development of an electrostatic ion trap for high-resolution mass spectrometry. The trap works on purely electrostatic fields and hence trapping and storing of ions is not mass restrictive, unlike other techniques based on Penning, Paul, or radio frequency quadrupole ion traps. It allows simultaneous trapping and studying of multiple mass species over a large mass range. Mass spectra were recorded in "dispersive" and "self-bunching" modes of ions. Storage lifetimes of about 100 ms and mass resolving power of about 20,000 could be achieved from the fifth harmonic Fourier transform spectrum of Xe ions recorded in the self-bunching mode.     

A high-current plasma emitter of electrons based on a glow discharge with a multirod electrostatic trap

Pulsed electron guns that produce 170-mm-diameter beams with currents of up to 700 A, electron energies of 300 keV, and a pulse width of ～200 μs at a gas pressure of ～0.01 Pa are experimentally studied. Glow-discharge plasma with electron confinement in an electrostatic trap is used as the electron emitter. The trap is formed by a hexagonal prism that consists of 204 cathode rods, which are 5 mm in diameter, 200 mm in length and are spaced by 1.5 mm, as well as 780 cathode rods, which are 5 mm in diameter and 98 mm in length, the spacing between their axes amounting to 15 mm. The latter rods are inside the former system of rods. The plasma emitter fills the hexagonal prism, which is free of rods, at the trap center with a distance of 280 mm between opposite sides and a height of ～200 mm between the emissive grid connected to the anode and the trap bottom covered with 23-mm-diameter cathode disks. All the cathode rods and disks are insulated from one another and connected to the discharge power supply through TVO-2 430-Ω resistors. The current limitation in the circuit of each cathode element by a value of ～2 A at a pulse width of ～5 ms of the glow-discharge current of up to 1 kA fully excludes its glow-to-arc transitions and allows production of continuous pulsed electron beams with an energy capacity of up to 40 kJ and a uniform distribution of the current density over its cross-sectional area of ～0.025 m².     

Pantechnik new superconducting ion source: PantechniK Indian Superconducting Ion Source

The new ECR ion source PantechniK Indian Superconducting Ion Source (PKISIS) was recently commissioned at Pantechnik. Three superconducting coils generate the axial magnetic field configuration, while the radial magnetic field is done with the multi-layer permanent magnets. Special care was devoted to the design of the hexapolar structure, allowing a maximum magnetic field of 1.32 T at the wall of the 82 mm diameter plasma chamber. The three superconducting coils using low temperature superconducting wires are cooled by a single double stage cryo-cooler (4.2 K). Cryogen-free technology is used, providing reliability and easy maintenance at low cost. The maximum installed RF power (18.0 GHz) is of 2 kW. Metallic beams can be produced with an oven (T(max) = 1400 °C) installed with an angle of 5° with respect to the source axis or a sputtering system, mounted on the axis of the source. The beam extraction system is constituted of three electrodes in accel-decel configuration. The new source of Pantechnik is conceived for reaching optimum performances at 18 GHz RF frequencies. PKISIS magnetic fields are 2.1 T axial B(inj) and 1.32 T radial field in the wall, variable B(min) with an independent coil and a large and opened extraction region. Moreover, PKISIS integrates modern design concepts, like RF direct injection (2 kW availability), dc-bias moving disk, out-of-axis oven and axial sputtering facility for metal beams. Finally, PKISIS is also conceived in order to operate in a high-voltage platform with minor power consumption.     

离子阱质谱仪小型化的最新研究进展

为适应科技发展的需要，质谱议的小型化已成为目前分析仪器发展的一个重要趋势，其中离子阱质谱仪的小型化取得了举世瞩目的成果。离子阱的小型化是通过应用小型真空泵、小型真空系统及较低的射频电压和简化阱结构（从双曲线离子阱到圆柱型离子阱再到矩形离子阱）来实现的。和其他形式的Paul离子阱一样，在外部离子注入模式下，圆柱形离子阱具有较低的捕获效率和较低的储存容量（对于商业尺寸的离子阱只能存储大约500个离子），尤其是在低射频电压工作条件下，阱尺寸减小时更是如此。为克服这些缺点，出现了一种新的离子阱质量分析器一矩形离子阱质量分析器。本文介绍了离子阱质量分析器的小型化原理，对其最新研究进展进行了评述。     

Development of an x-ray diffraction camera used in magnetic fields up to 10 T

A high-field x-ray diffraction (HF-XRD) camera was developed to observe structural changes of magnetic materials in magnetic fields up to 10 T. The instrument mainly consists of a Debye-Scherrer-type camera with a diameter of 80.1 mm, a 10-T cryocooled superconducting magnet with a 100-mm room-temperature bore, an x-ray source, a power supply, and a chiller for the x-ray source. An x-ray detector (image plate) in the HF-XRD camera can be taken out and inserted into the magnet without changing the sample position. The performance of the instrument was tested by measuring the HF-XRD for silicon and ferromagnetic MnBi powders. A change of x-ray diffraction pattern was observed due to the magnetic orientation of MnBi, showing that the instrument is useful for studying field-induced orientation processes and structural properties of field-controlled materials.     

Low noise measurement system for determination of the critical currents in superconducting tapes by a pulse method

Steady state measurements of the high critical currents in superconducting composite wires and tapes might be burdened with some errors. The origin of the errors is mainly associated with the Joule heat generated at current leads contacts, which at high transport currents can considerably increase temperature of an investigated sample wire. To avoid this unwanted heating phenomenon pulsed current methods are widely used. A waveform of the current pulse is usually shaped by means of a series RLC circuit with the subcritical dumping condition. Measurement results (i.e., a value of current peak, its time derivative, and a voltage drop along a superconducting sample) are recorded by means of a 4-channels, 12-bit resolution, 50 ns sampling time, digital recorder. Very low noise, broadband, voltage preamplifiers, based on rf bipolar transistors, were designed and fabricated. From the data, current-voltage characteristics are plotted and then the critical currents of investigated tapes are determined. Presented in the work our home-made, low noise, measurement setup allows to obtain a current pulse of about 4000 A at duration time of several milliseconds.     

Experimental setup for laser spectroscopy of molecules in a high magnetic field

An experimental setup to measure the effects of a high magnetic field on the structure and decay dynamics of molecules is designed and constructed. A vacuum chamber is mounted in the bore of a superconducting magnet. A molecular beam passes in the chamber. Pulsed laser light excites the molecules in the field. The parent or fragment ions are extracted by an electric field parallel to the magnetic field. They are detected by a microchannel plate. Their mass and charge are determined by the time-of-flight method. The performance of the setup was examined using resonance-enhanced two-photon ionization through the X(2)?Π-A(2)Σ(+) transition of nitric oxide (NO) molecules. The ions were detected with sufficient mass resolution to discriminate the species in a field of up to 10 T. This is the first experiment to succeed in the mass-selective detection of ions by the time-of-flight method in a high magnetic field. By measuring NO(+) ion current as a function of the laser frequency, the X(2)Π-A(2)?Σ(+) rotational transition lines, separated clearly from the background noise, were observed in fields of up to 10 T. From the relative strengths of the transition lines, the ion detection efficiency was determined as a function of the magnetic field strength. This setup was shown to be applicable in a field higher than 10 T. The Landau levels of molecules were successfully observed to demonstrate the setup.     

用Pro/E实现对离子阱的结构仿

简述了三维四极离子阱的基本结构和工作原理。探讨了用Pro/E设计三维四极离子阱基本结构模型的一种简要方法,用参数方程建立基准辅助双曲线,得到了三维四极离子阱的一般实体模型图。     

Superconducting helically wound magnet for the free-electron laser

Theoretical and experimental studies conducted by the Stanford Free Electron Laser group have resulted in the first operation of a free-electron laser amplifier and free-electron laser oscillator. Two superconducting helically wound periodic magnetics have been constructed for use with the laser. In this paper we present a discussion of design considerations and test results for the two magnets. The tests included measurement of the magnitude and the variation of the transverse magnetic field with radius in the bore of the magnets, the critical current, and the intensity, angular distribution, and spectrum of the spontaneous radiation emitted by electrons moving through the field.