Emittance and brightness measurements in a proton electron cyclotron resonance ion source

A new method has been developed for measuring the emittance and brightness of a proton beam extracted from an electron cyclotron resonance (ECR) ion source located inside a solenoidal magnetic field, in which the envelope of the extracted beam undergoes amplitude modulation with axial distance. The mathematical framework of the method is presented. Experimental procedures are described and results are discussed based on applying this method to the TRIUMF ECR ion source to examine the variation of the extracted beam emittance and brightness with the geometry of the extraction electrode system.     

A capillary-based supersonic jet inlet system for resonance-enhanced laser ionization mass spectrometry: principle and first on-line process analytical applications

A new supersonic jet inlet system for resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS), based on a fused-silica capillary with an integral nozzle has been developed. The new jet inlet system generates a supersonic molecular beam that originates in the center of the ion source of the time-of-flight mass spectrometer. Because of the design of the inlet system, high spatial overlap of sample and laser beam (i.e., increased detection sensitivity) and excellent jet beam qualities are achieved with good adiabatic cooling properties of analyte molecules (i.e., considerably enhanced optical selectivity of the REMPI process). Furthermore, the inlet is very robust and chemically inert and contains no moving parts. As a result of these properties, the new inlet is perfectly suited for field applications of jet-REMPI. A first field application of a mobile supersonic jet-REMPI mass spectrometer equipped with the novel inlet technique is reported; namely, the concentration of monochlorobenzene, which is an indicator for the formation and emission of toxic polychlorinated dibenzo-p-dioxins/furans, PCDD/F) was measured on-line in the flue gas of a waste incineration plant.     

High-resolution broadband N2 coherent anti-Stokes Raman spectroscopy: comparison of measurements for conventional and modeless broadband dye lasers

We have performed high-resolution N2 coherent anti-Stokes Raman spectroscopy (CARS) measurements using a modeless dye laser (MDL) as the Stokes beam source to determine the effects of a reduction in mode noise on the accuracy and precision of the method. These results are compared with previous research that employed a conventional broadband dye laser (CBDL) as the Stokes beam source. A new spectral-fitting procedure was developed to avoid starting-point bias in the least-squares fitting results, which possibly had altered the previous measurements. Single-shot measurements of pressure were performed in a static-pressure vessel over the range of 0.1-4.0 atm to examine the pressure sensitivity of the technique. The precision of these measurements is a measure of the baseline noise level of the system, which sets the detection limit for flow-field pressure fluctuations. Centerline measurements of pressure and temperature in an underexpanded jet (Mj = 1.85) were also used to determine the performance of the technique in a compressible flow field. Our study represents the first known application, to our knowledge, of a MDL CARS system in a low-temperature, low-pressure supersonic environment. Improvements in accuracy for mean single-shot measurements and increased precision were found for pressure vessel conditions above 1.0 atm. For subatmospheric pressure vessel conditions (0.1-1.0 atm) and the underexpanded jet measurements, there was a decrease in accuracy and precision compared with the CBDL results. A comparison with the CBDL study is included, along with a discussion of the MDL system behavior.     

一种测量薄膜磁性的表面磁光克尔效应装置

介绍表面磁光克尔效应谱（SMOKE）的一种新方案。通过适当分光并测量信号束和参考束的光强比，可以明显改善由于激光的光强不稳造成的误差，还使得随机偏振激光器也能用于SMOKE装置。同时该方案中没有采用信号调制，因此对探测器等硬件要求很低。实验结果表明，采用光强稳定度为5％的普通国产He－Ne随机偏振激光器，其测量灵敏度能够达到目前国际上通常用于超薄膜磁性测量的SMOKE的同类水平。     

Cyclotron resonance maser operating in a nonresonant electron bunching regime

A new scheme of the cyclotron resonance maser (CRM) based on the phenomenon of electron bunching in a nonresonant wave field is proposed. In this scheme, the electron-wave interaction space is divided into two regions due to magnetic field profiling. In the first (input) region, the magnetic field is such that the working traveling wave is relatively far from the resonance with electrons. It is established that, under certain conditions, the motion of electrons in a nonresonant wave field is accompanied by their effective bunching without significant changes in the energy. In the second (output) region, the magnetic field is close to the resonance and the bunched electron beam effectively radiates at the working wave frequency. Thus, the regular electrodynamic system features an electron-wave interaction of the klystron type with spatially separated processes of the electron bunching and wave emission. The proposed scheme can be used for increasing the efficiency of CRMs with various configurations. It is especially advantageous in CRMs with frequency multiplication, where the electron bunching in a low-frequency nonresonant wave field is accompanied by wave emission at a multiple frequency.     

激光-分子束-表面散射装置的研制

介绍了自行设计和加工的激光-分子束-表面散射装置，并对超高真空转动密封结构作了详细描述。差分泵浦的超音速分子束对准样品中心，射入超高真空主室。样品架安放在主室中央，四极质谱检测器可绕样品转动，用来测量表面散射分子的平动能及角分布。三个石英窗口作为激光窗口，可用LIF或MPI方法来测量表面散射分子的内能态分布，也可用于研究表面光化学。最后给出了分子束发散角及室温时CH2I2在Ag（110）表面用308um激光光解碎片碘的TOF谱的测量结果。     

A Simulator for Producing of High Flux Atomic Oxygen Beam by Using ECR Plasma Source

In order to study the atomic oxygen corrosion of spacecraft materials in low earth orbit environment, an atomic oxygen simulator was established. In the simulator, a 2.45 GHz microwave source with maximum power of 600 W was launched into the circular cavity to generate ECR (electron cyclotron resonance) plasma. The oxygen ion beam moved onto a negatively biased Mo plate under the condition of symmetry magnetic mirror field confine, then was neutralized and reflected to form oxygen atom beam. The properties of plasma density, electron temperature, plasma space potential and ion incident energy were characterized. The atomic oxygen beam flux was calibrated by measuring the mass loss rate of Kapton during the atomic oxygen exposure. The test results show that the atomic oxygen beam with flux of 1016-1017 atoms-cm-2·s-1 and energy of 5-30 eV and a cross section of φ80 mm could be obtained under the operating pressure of 10-1-10-3 Pa. Such a high flux source can provide accelerated simulation tests of mater     

Oriented growth of magnetite along the carbon nanotubes via covalently bonded method in a simple solvothermal system

A new type of CNTs/magnetite hybrid material was prepared via covalently bonded method in a simple solvothermal system using FeCl₃ as iron source, ethylene glycol as the reducing agent, and 4-aminophenoxyphthalonitrile-grafted CNTs as templates. The magnetite nanoparticles, with the diameters of 70-80 nm, were self-assembled along the CNTs. The FTIR, UV-vis and DSC revealed that a stable covalent bond between nitriles group and iron ion promoted the oriented growth of magnetite nanoparticles along the CNTs, resulting in good dispersibility and solution storage stability. The magnetic properties measurements indicated that a higher saturated magnetization (70.7 emu g⁻¹) existed in the CNTs/magnetite hybrid material, which further enhanced the electromagnetic properties. The magnetic loss was caused mainly by natural resonance, which is in good agreement with the Kittel equation results. The novel electromagnetic hybrid material is believed to have potential applications in the microwave absorbing performances.     

Design and investigation of gas cluster ion accelerator

A gas cluster ion accelerator with energies up to 20 keV is described. Parameters of the main components of the equipment were determined. It was demonstrated that a pulse regime of the accelerator can be realized with a relatively low (500 l/sec) pumping speed of the cluster ion source. Conditions for stable cluster beam generation were found. In pulse mode ion clusters appear in the accelerated beam in the first stages of ion beam evolution. A model describing the behavior of the ion beam in the pulse regime is suggested. To analyze the beam mass composition two systems were constructed: a magnetic mass-separation system and a time-of-flight system. Cluster ions Ar_n⁺ with number of atoms/charge n ≥ 500 were detected in the beam by using deflection in a homogeneous magnetic field. Clusters up to 3000 atoms/charge were detected by using time-of-flight measurements.     

The fault current limiting characteristics of a flux-lock type high-Tc superconducting fault current limiter using series resonance

We analyzed the fault current limiting characteristics of a flux-lock type high-T_c superconducting fault current limiter (HTSC-FCL) using series resonance between capacitor for series resonance and magnetic field coil which was installed in coil 3. The capacitor for the series resonance in the flux-lock type HTSC-FCL was inserted in series with the magnetic field coil to apply enough magnetic field into HTSC element, which resulted in higher resistance of HTSC element.However, the impedance of the flux-lock type HTSC-FCL has started to decrease since the current of coil 3 exceeded one of coil 2 after a fault accident. The decrease in the impedance of the FCL causes the line current to increase and, if continues, the capacitor for the series resonance to be destructed. To avoid this operation, the flux-lock type HTSC-FCL requires an additional device such as fault current interrupter or control circuit for magnetic field.This paper investigated the parameter range where the operation as mentioned above for the designed flux-lock type HTSC-FCL using series resonance occurred from the experimental results. In the design of the flux-lock type HTSC-FCL, the some methods to avoid the continuous increase of the line current were suggested and confirmed by the experiments that the suggested methods were available to prevent the continuous increase of the line current after a fault happened.     

Influence of annealing and rinsing on magnetic and photocatalytic properties of TiO2

Samples of TiO₂, calcined at 100 °C (type 1) and 200 °C (type 2), have been prepared without and with water rinsing. The crystallite sizes determined by XRD method were smaller than 15 nm for both types of samples. Magnetic resonance spectra of the obtained samples have been studied in 230-300 K temperature range. Before rinsing no magnetic spectra were observed but after rinsing the magnetic response appeared in form of a resonance line centered at g_eff ∼ 2.54 with linewidth ΔH_pp ∼ 460 G in type 1 samples and g_eff ∼ 2.26 with linewidth ΔH_pp ∼ 220 G in type 2 samples. The integrated intensity of the observed spectrum was two times greater in the type 1 sample. The resonance line could be attributed to the localized magnetic moments in the correlated spin system formed during rinsing. The rinsing resulted also in higher photocatalytic properties under UV-VIS irradiation. It is suggested that the number of oxygen vacancies increases after rinsing and as they are involved in the formation of low oxidation states of titanium ions, they could be responsible for the appearance of the observed magnetic properties.     

横向磁场中机械载荷作用梁式薄板的非线性主共振

研究了磁场环境中受机械载荷作用梁式薄板的非线性主共振问题。在给出薄板的非线性电磁弹性耦合运动基本方程及电磁力表达式的基础上，得到了横向稳恒磁场和机械载荷共同作用下梁式薄板的振动方程。应用伽辽金积分法，并进行无量纲化处理，进一步导出了相应的非线性振动微分方程。采用平均法对主共振问题进行了求解，得到了稳态运动下的幅频响应方程。通过算例给出了几种情况下的幅频响应曲线图和时间历程图，分析了板厚和磁场对系统振动的影响。     

Prony methods in NMR spectroscopy

The Prony method and a modified Prony method (MPM), developed to improve the performance of this technique at low signal-to-noise ratio, are described and applied to analysis of magnetic resonance spectroscopy (MRS) signals. Furthermore, the way in which results from MPM can be used as prior information in a Bayesian model is also described. First, analysis on simulated data is used to establish the methods' limits of reliability. Their performance with respect to peak identification and quantification of nuclear magnetic resonance parameters are then assayed on real data. Results of application of the methods to ¹H-MRS signals from cultured cells are discussed and compared with those deriving from application of fast Fourier transform. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 565–571, 1997     

均匀场聚焦带状注速调管电子光学系统的研究

本文系统地阐述了均匀场聚焦带状电子注的传输理论,设计了柱面阴极皮尔斯电子枪,模拟显示轨迹的层流性较好;设计了产生均匀磁场的磁聚焦结构,在1 m长的距离内,成功地实现了X波段100 MW带状电子注的稳定传输,电子注通过率达到100%;同时设计了收集极新型结构,给出了电子注在收集极内的发散情况。     

Generating Bessel beams by use of localized modes

We propose a novel method for generating both propagating and evanescent Bessel beams. To generate propagating Bessel beams we propose using a pair of distributed Bragg reflectors (DBRs) with a resonant point source on one side of the system. Those modes that couple with the localized modes supported by the DBR system will be selectively transmitted. This is used to produce a single narrow band of transmission in kappa space that, combined with the circular symmetry of the system, yields a propagating Bessel beam. We present numerical simulations showing that a propagating Bessel beam with central spot size of approximately 0.5lambda0 can be maintained for a distance in excess of 3000lambda0. To generate evanescent Bessel beams we propose using transmission of a resonant point source through a thin film. A transmission resonance is produced as a result of the multiple scattering occurring between the interfaces. This narrow resonance combined with the circular symmetry of the system corresponds to an evanescent Bessel beam. Because propagating modes are also transmitted, although the evanescent transmission resonance is many orders of magnitude greater than the transmission for the propagating modes, within a certain distance the propagating modes swamp the exponentially decaying evanescent ones. Thus there is only a certain regime in which evanescent Bessel beams dominate. However, within this regime the central spot size of the beam can be made significantly smaller than the wavelength of light used. Thus evanescent Bessel beams may have technical application, in high-density recording for example. We present numerical simulations showing that with a simple glass thin film an evanescent Bessel beam with central spot size of approximately 0.34lambda0 can be maintained for a distance of 0.14lambda0. By choice of different material parameters, the central spot size can be made smaller still.     

一种超支化聚酯的合成及反应动力学

以等物质的量比的间苯二甲酸（A2型单体）和三羟甲基丙烷（B3型单体）为原料,采用熔融聚合工艺制备了一种具有芳香-脂肪骨架的新型超支化聚酯（HBPE）。利用红外光谱、核磁共振、凝胶渗透色谱和热分析等手段对HBPE进行了表征。同时对合成HBPE的反应动力学进行了研究,建立了适合该体系的反应动力学方程,实验结果与理论研究符合...     

A new method for determining the efficiency of laser radiation conversion into 13.5 ± 0.3 nm radiation in laser-plasma extreme ultraviolet sources

We have studied extreme ultraviolet (EUV) emission from a laser-plasma source employing a supersonic xenon jet as the target. The output EUV energy has been determined as a function of the laser pulse energy for the supersonic xenon jet in comparison to the solid metal (Cu, Mo, Ta) targets. Based on these results, a new method for determining the efficiency of laser radiation conversion into EUV radiation is proposed, which ensures unambiguous characterization of the properties of various targets. Ways to optimize the xenon jet source are discussed.     

Features of a Silver-Beam Magnetic Resonance Apparatus as a Frequency Standard

Silver has two stable isotopes Ag107 and Ag109 with nearly equal populations (51.35 percent and 48.65 percent). A microwave magnetic resonance apparatus employing a silver beam and simultaneous magnetic resonance of both isotopes was built and a so-called superposition line was measured. The possibility of using such an apparatus as a frequency standard is discussed.     

平行导线间轴向运动导电梁主-内联合共振EI北大核心CSCD

研究轴向运动导电梁在平行导线产生的磁场环境中的主-内联合共振问题。基于电磁场基本理论和哈密顿原理,导出轴向运动梁在外激励和磁场共同作用下的非线性振动方程。针对一端夹支一端铰支的导电梁,采用多尺度法求解方程,得到非线性方程的近似解析解和幅频响应方程,并对稳态解的稳定性进行了分析。通过算例,得到系统前两阶幅值随频率调谐参数、外激励力、轴向速度、电流强度等参数的变化规律。结果表明:系统发生主-内联合共振时一阶和二阶响应都被激发,且存在不同的多解区域;一阶和二阶幅值的稳态解个数在几个多解区域同步变化,其个数取决于外激励力、运动速度和电流强度值。     

Physical origin of the frequency shifts in cesium beam frequency standards-related environmental sensitivity

When observed in a cesium beam frequency standard, the hyperfine transition frequency of the atoms differs slightly from the invariant transition frequency of the unperturbed atoms at rest. The various physical and technical origins of the frequency offsets are stated. They relate to fundamental physical effects, to the method of probing the atomic resonance and to the frequency control of the slaved oscillator. The variation of the frequency offsets under a change of the value of the internal operating characteristics is considered. The sensitivity to a change of the magnetic induction, the microwave power and the temperature is given. A comparison is made of the sensitivity of cesium beam frequency standards of the commercially available type, making use of magnetic state selection, and of devices under study in which the state preparation and detection is accomplished optically. The pathways between the external stimuli and the physical origin of the frequency offsets are specified.