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本文描述了为GC/MS用的EI/CI组合离子源的特性和结构。当化学电离室中反应气体压强为1托时,离子源内其它部分压强不超过7×10~(-5)托。在电子轰击型工作时与单独专用的EI源一样灵敏,对于空气给出相同的离子流。 相似文献
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基于磁质谱离子光学成像聚焦原理对其离子光学系统、离子源和质量分析器的物理参数及几何结构尺寸进行优化,研制了新型小型磁偏转质谱计,其质量为4.3 kg,体积为(220×164×162) mm3,功耗为25 W。对质谱计的质量范围、灵敏度、分辨能力、最小可检漏率和稳定性等性能指标开展实验研究。结果表明,该质谱计的质量范围为1~134 u,大通道和小通道50%峰高处的分辨能力分别为56和13,对氩气、氮气和氦气的灵敏度分别为1.63×10-4、1.17×10-4、2.3×10-5 A/Pa,最小可检漏率为1.24×10-10 Pa·m3/s,仪器在3.5 h内的稳定性为2.5%。 相似文献
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柴油车的尿素通过混合器热解为NH3与NOx反应,NH3在混合器中分布均匀的差异影响了NOx的转化效率与NH3泄漏。试验选取了不同混合器进行WHTC瞬态循环与WHSC稳态循环试验。结果表明:SCR的NOx转化效率与转化速率随混合器流场均匀性的提升而提高,且流场均匀性能高的混合器对抑制NH3泄漏更有效果。3#混合器的瞬态与稳态循环NOx比排放为0.186g·(kW·h)-1与0.041g·(kW·h)-1,NH3泄漏为0.254×10-6与0.068×10-6;2#混合器的瞬态与稳态循环NOx比排放分别为0.346 g·(kW·h)-1与0.063 g·(kW·h)-1,NH3泄漏为2.944×10-6与2.254×10-6。 相似文献
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本研究联合三重四极杆电感耦合等离子体质谱(ICP-QQQ-MS)和多接收电感耦合等离子体质谱(MC-ICP-MS),快速准确地测量浓缩铀材料中铀同位素丰度比值、230Th/234U和231Pa/235U原子物质的量比值,并诊断铀年龄。结果表明,Neptune XT型MC-ICP-MS和Agilent 8800型ICP-QQQ-MS对233U丰度的有效检测限分别为3×10-9和6×10-10,适用于233U丰度高于6×10-8和样品量充足的样品,对10-7量级233U/235U同位素丰度比的测量精密度达到1.0%(2σ)和4.8%(2σ)。采用GBW04240作为外标校正质量分馏效应,建立了基于ICP-QQQ-MS的10-5量级原子物质的量比值的230Th/234... 相似文献
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采用超音速火焰喷涂技术制备CoCrAlSiY合金涂层,研究了该涂层的微观结构、力学性能,以及在不同载荷(2,5,8 N)下的摩擦磨损性能。结果表明:CoCrAlSiY合金涂层主要由CoCr2O4、CoAl和α-Al2O3相组成,各物相分布均匀,涂层致密;涂层的硬度为(7.41±0.16) GPa,与其他同类合金涂层硬度相近;在2,5,8 N载荷下摩擦磨损时,CoCrAlSiY合金涂层的平均摩擦因数分别为0.33,0.24,0.22,对应的磨损率分别为3.52×10-5,4.85×10-5,5.58×10-5 mm3·N-1·m-1;低载荷(2 N)下的磨损机制主要是黏着磨损和磨粒磨损,高载荷(5,8 N)下涂层发生脆性断裂而大块剥落;在摩擦磨损过程中涂层表面形成氧化物,特别是在5 N和8 N载荷下,磨损表面出现大量α-Al2O3 相似文献
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将Nafion和石墨烯及纳米金复合后修饰在玻碳电极上制成修饰电极,用于尿酸电化学行为的研究。在pH 5.8的磷酸盐缓冲溶液中,该修饰电极对尿酸具有良好的电催化作用,尿酸浓度在2.0×10-7 ~2.0×10-5 mol/L范围内与其氧化峰电流呈较好的线性关系,相关系数为0.9843,检出限为1.0×10-8 mol/L。方法用于实际样品的测定,加标回收率为96.8~103.2%,RSD为2.7~3.3%。 相似文献
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电子轰击源垂直加速式飞行时间质谱仪的研制 总被引:6,自引:3,他引:3
介绍了自制的电子轰击离子源(electron ionization, EI)垂直加速式飞行时间质谱仪(orthogonal acceleration time-of-flight mass spectrometer, Oa-TOF MS)的原理,结构以及初步的实验结果。搭建了电子轰击源垂直加速式飞行时间质谱仪,并得到室内空气成分谱图。结果表明,仪器分辨率优于2 000(full width at half maximum,FWHM),质量精度优于4×10-5,可以用于气体成分的快速定性分析。 相似文献
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宽带无线光相干通信通过信道均衡来抑制大气湍流产生的码间串扰。以湍流环境下的中频信号作为样本,分别采用反向传播(BP)神经网络和长短期记忆(LSTM)神经网络进行训练,将训练达到稳定的网络模型作为信道均衡器,以均衡器输出的中频信号作为系统性能评价指标并与自适应光学波前畸变校正算法进行比较。仿真结果表明,智能信道均衡算法对于系统误码率的改善优于自适应光学波前畸变校正算法。实验结果表明:采用BP神经网络信道均衡技术、LSTM神经网络信道均衡技术,以及波前畸变校正技术后,中频信号直方图的峰值分别位于0.49、0.38、0.38 V,相应的系统误码率分别为3.79×10-5、1.64×10-4和8.48×10-2。智能信道均衡技术相比于波前畸变校正技术对于中频信号幅值随机起伏和误码率都有明显改善。 相似文献
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A. S. Metel S. N. Grigoriev Yu. A. Melnik V. P. Bolbukov 《Instruments and Experimental Techniques》2012,55(2):288-293
In order to increase the equivalent current of a fast neutral atom beam the cold hollow cathode of the beam source is bombarded
with electrons extracted from the plasma produced in the vacuum chamber and accelerated in the sheath between the plasma emitter
of the source and its emissive grid. The cold cathode bombardment by accelerated electrons raises its electron emission current
by an order of magnitude and as a result voltage U
c
between the anode and the cathode of the source diminishes more than two times. This allows of increasing several times the
beam equivalent current or decreasing the working gas pressure. A slight decrease in the U
c
with increasing the accelerating voltage U at an overall cutoff of the electrons from the chamber reveals the influence of secondary electrons emitted by the grid.
Measurement of the beam current is discussed. 相似文献
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B. K. Kondrat’ev A. V. Turchin V. I. Turchin 《Instruments and Experimental Techniques》2008,51(4):567-573
The results of use of a cold hollow cathode with a multipole magnetic field in a duoplasmatron-type ion source are described. The operating parameters of a duoplasmatron with the developed cathode and a duoplasmatron with a cold hollow two-cylinder cathode are compared. It is shown that the use of a cathode with a multipole magnetic field offers additional possibilities of reducing the operating gas pressure in an ion source and contributes to an increase in both the current and the phase density of the ion-beam current at the output of a charged-particle source and to a decrease in the phase volume of this beam. 相似文献
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A gas-discharge source of oxygen ions is described. The source contains an anode and a hollow cold cathode with one extracting grid (extractor) placed at the opposite end to the anode. The hollow cathode has three multicast magnetic systems of permanent polarity. The first system is placed inside the cathode near the anode, the second system is situated outside the cathode opposite to the first one, and the third system is placed below the second one near the extractor surface. Like poles of the first and second magnetic systems are directed towards each other. The second and third systems have poles of similar orientations. Using this source, a beam of oxygen ions with a current density of up to 0.5 mA/cm2 and nonuniformity of <5% was obtained across a 200-mm-diameter area at a distance of 120 mm from the face of the ion source. The source offers the following optimum performance characteristics: a discharge current of 0.4–1.2 A, oxygen flow rate of 9–12 cm3/min, and extracting voltage of 400–600 V. No limitations were revealed on the service life of a source operating in optimal modes. 相似文献
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S. FUJITA T. R. C. WELLS W. USHIO H. SATO M. M. EL‐GOMATI 《Journal of microscopy》2010,239(3):215-222
Even though the Schottky emitter is a high‐brightness source of choice for electron beam systems, its angular current intensity is substantially lower than that of thermionic cathodes, rendering the emitter impractical for applications that require high beam current. In this study, two strategies were attempted to enhance its angular intensity, and their experimental results are reported. The first scheme is to employ a higher extraction field for increasing the brightness. However, the tip shape transformation was found to induce undesirably elevated emission from the facet edges at high fields. The second scheme exploits the fact that the angular intensity is proportional to the square of the electron gun focal length [ Fujita, S. & Shimoyama, H. (2005) Theory of cathode trajectory characterization by canonical mapping transformation. J. Electron Microsc. 54 , 331–343], which can be increased by scaling‐up the emitter tip radius. A high angular current intensity (JΩ∼ 1.5 mA sr−1) was obtained from a scaled‐up emitter. Preliminary performance tests were conducted on an electron probe‐forming column by substituting the new emitter for the original tungsten filament gun. The beam current up to a few microamperes was achieved with submicron spatial resolution. 相似文献
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The time response of a scintillator-light guide-photomultiplier combination was measured with a time-constant of 3 ns. Single detected electrons were recognizable at the output of the photomultiplier. The distribution of the number of photoelectrons produced by one detected electron and the pulse-height distribution of the photomultiplier output pulses were analysed. Statistical noise computed from these distributions was compared with the noise produced by the dark current of the photomultiplier. 相似文献
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A plasma ferroelectric cathode is used to form electron beams with a high pulse charge and a high charge in an electron bunch in an rf electron gun of a 10-cm wavelength range. The design of the cathode is described, and the results of calculations of the densities of the cathode-emitted and the gun-outputted currents are presented. The operation of the cathode in the rf gun was studied experimentally: the electron energy, the pulse current, and the transverse emittance of the beam were measured. The electron beam obtained at the output of the single-resonator gun had a pulse current of up to 10 A, a pulse duration of 60 ns, and an electron energy of ?500 keV. The normalized beam emittance was 40 mm mrad. 相似文献
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Abdel Salam FW el-Khabeary H Ahmed MM Abdel Reheem AM 《The Review of scientific instruments》2011,82(3):033304
In this work, an improved form of a saddle field ion source has been designed and constructed. It consists of four anode rods made from copper and two copper cathode discs. The two cathode discs are placed symmetrically on both sides of the four anode rods. The electrical discharge and output ion beam characteristics were measured at different pressures using argon gas. The optimum distance between each two anode rods was determined. Also the optimum distance between the four anode rods and any cathode disc was obtained. It was found that the optimum distance between each two anode rods equal to 6 mm, while the optimum distance between the four anode rods and any cathode disc equal to 16 mm, where a stable discharge current and maximum output ion beam current can be obtained. The effect of negative extraction voltage applied to both the extractor electrode and Faraday cup on the output ion beam current was studied. The sputter yield of copper and aluminum targets using argon ions of different energies was determined. 相似文献
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An extractor gauge type electron bombardment ion source using carbon fiber bundles as field electron emitters is described. The cold cathode permits operation of the ionizer within a liquid He cooled cryopump. The high pumping speed for all molecules (except helium) together with its low background pressure make this ion source a very promising detector for crossed molecular beam scattering experiments. 相似文献