共查询到18条相似文献,搜索用时 171 毫秒
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大发射电流密度Ir—Ce合金阴极的研究 总被引:1,自引:1,他引:0
制作了一种发民流密度较大的铱-铈两相合金阴极。在1773K时,阴极零场发射电流密度为6.75A/cm^2,有效逸出功为2.73eV;在1823K时,观察到最大发射电流密度超过21.2A/cm^2。同时简介了阴极制作工艺和抗中毒情况以及未来的改进发展方向。 相似文献
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重点研究了粉末冶金法制备Ir-Ce(铱-铈)合金阴极过程中压制压力和烧结温度对发射性能的影响,建立起了一套稳定的制备工艺。试验得到Ir-Ce掺W阴极在1753K时的发射电流密度达12.4A/cm2,电流密度保持为1.7A/cm2,发射试验稳定达150h。从机理上验证了它是一种高温大发射电流的发射体。试验还表明Ir-Ce阴极具有良好的抗中毒能力。作为应用研究,测量了该阴极在热阴极微波电子枪中的发射性能,微波腔场强约10MV/m,工作温度1913K,零场发射电流密度为10A/cm2,最大发射电流密度达21A/cm2,在2020K时计算零场发射电流密度可达42A/cm2。 相似文献
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介绍了适用于强流离子源的间热式大面积六硼化镧中空阴极。在15cm双潘宁离子湖泊 上放电特性研究表明,该阴极性能良好,能可靠工作,使用过程中多次暴露于大气中,发射性能并未变坏,加热功率为1.45kW,LaB6发射电流密度为20A/cm^2,放电电流400A,脉冲宽度30ms,放电波形重复性很好。使用100h后,发射体尺寸无明显变化。 相似文献
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^239Pu,^241Am,^99Tc和^137Cs在高压实缓冲材料中的扩散系数 总被引:2,自引:0,他引:2
本文从物质的一维非稳态扩散规律出发,在常温,纯氮条件下,测定了^239Pu,^241Am,^99Tc和^137Cs在作为高放废物深地质处置库缓冲材料的高压实钠质膨润土中的扩散系数,90d的实验测定结果表明,在膨润土的干密度为1.9g/cm^3时,^239Pu,^241Am扩散系数为在10^-15m^2/s,^99Tc约为10^-13m^2/s,而^137Cs约为10^-12m^2/s,都随缓冲材料 相似文献
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该研究跟踪国际先进水平,首次在我国进行折流板环形脉冲柱应用研究。采用5cm柱径,板间距2cm,开孔率25%,正弦脉冲波。水力学性能研究结果表明,液泛通量高达2.7cm/s,可采用V_c(1-X)+V_d/x=V_0(1-x_e) ̄(KX)关联分散相存留分数。其K值为4.5一6,大于零,为Ⅱ型柱;U传质结果表明,理论级当量高度为70cm,当在振幅a=2cm,频率f=1.5s ̄(-1)的脉冲条件下操作时,其理论级当量高度将降至50cm。同脉冲筛板柱的对比试验结果表明,其传质性能优于脉冲筛板柱。与相同工艺条件下的串级结果对比,在a=2cm,f=1.5s ̄(-1)条件下,200cm的萃取柱可达4个理论级。 相似文献
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氮酮是目前应用最好的药物皮肤渗透促渗剂之一。用^3H-Azone作示踪剂,研究了透皮吸收后,Azone能迅速透过皮肤进入血液循环,分布到各脏器中。体外法测定表明,它的平衡渗透率为1.00μg/h.cm^2,在8g内总渗透率为0.70%。Azone透皮吸收后,在大鼠血液中的浓度先上升,在2h时达最大;然后下降,峰值浓度为2.70μg/ml,到24h时仍高达1.6μg/ml。由此证明Azone在皮肤上 相似文献
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报道了山西广播电视卫星地球站环境影响的评价工作。电磁辐射环境现状调查结果表明,评价区环境电磁辐射最高值为4.725*10^-5μW/cm^2,属正常环境水平;发射天线对地面环境电磁辐射贡献最大为3.02*10^-6μW/cm^2;高功放室对工作岗位电磁辐射贡献最大为3.16μW/cm^2;同时,计算了天线前方建筑物的允许建筑高度。 相似文献
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《等离子体科学和技术》2016,18(9):918-923
Plasma source is the most important part of the laboratory plasma platform for fundamental plasma experimental research. Barium oxide coated cathode plasma source is well recognized as an effective technique due to its high electron emission current. An indirectly heated oxide coated cathode plasma source has been constructed on a linear magnetized plasma device. The electron emission current density can reach 2 A/cm 2 to 6 A/cm 2 in pulsed mode within pulse length 5–20 ms. A 10 cm diameter, 2 m long plasma column with density 10 18 m −3 to 10 19 m 3 and electron temperature Te ≈ 3–7 eV is produced. The spatial uniformity of the emission ability is less than 4% and the discharge reproducibility is better than 97%. With a wide range of the plasma parameters, this kind of plasma source provides great flexibility for many basic plasma investigations. The detail of construction and initial characterization of oxide coated cathode are described in this paper. 相似文献
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The experimental progress of laser-driven Cs3Sb photocathodes is reported. The cathodes prepared in an UHV system can be used to generate short-pulsed, high-brightness electron beams. Emission properties are tested under a 50–200 ns pulsed Xe+ laser illumination. The quantum efficiency in the range of 2–5.6% and current density of 108 A/cm2 are obtained. A brightness of 1.85 × 109 A/m2 rad2 is also measured. Mass analysis and other methods have been used for investigating the plasma formation when laser intensity rises above the “break-down” threshold. The current density increases rapidly during the plasma electron emission, but the pulse width of the emission is enlarged, and the brightness is limited. It is observed that the plasma is just composed of cesium and antimony atoms from the cathode rather than adsorbed residual gases. 相似文献
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Numerical calculation and fluid simulation methods were used to obtain the plasma characteristics in the discharge region of the LIPS-300 ion thruster’s 20 A emission current hollow cathode and to verify the structural design of the emitter.The results of the two methods indicated that the highest plasma density and electron temperature,which improved significantly in the orifice region,were located in the discharge region of the hollow cathode.The magnitude of plasma density was about 10~(21)m~(-3)in the emitter and orifice regions,as obtained by numerical calculations,but decreased exponentially in the plume region with the distance from the orifice exit.Meanwhile,compared to the emitter region,the electron temperature and current improved by about 36%in the orifice region.The hollow cathode performance test results were in good agreement with the numerical calculation results,which proved that that the structural design of the emitter and the orifice met the requirements of a 20 A emission current.The numerical calculation method can be used to estimate plasma characteristics in the preliminary design stage of hollow cathodes. 相似文献
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Zhiwei HUA 《等离子体科学和技术》2022,24(7):74010
Emitter overheating is by far the greatest problem limiting the performance of novel C12A7 hollow cathodes. To explore the failure operating point and degradation mechanism of the C12A7 hollow cathode, microscopic analyses of a degraded electride emitter after 10 h of thermal electron emission are presented in this paper. The morphology and composition variation of overheated electride emitters by scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction indicate the melting and decomposition of electride of the surface layer. The monitored temperature of the electride emitter during the C12A7 hollow cathode operation shows that to avoid overheating the electride emitter, the average current density allowed should be about 64 mA mm−2 for the C12A7 hollow cathode in its current configuration. Experimental results of the heaterless C12A7 hollow cathode demonstrate that xenon (Xe) ion bombardment can remove the insulating layer and restore the thermionic emission capability for less degraded emitters. Based on experimental results and microscopic characterization, the depletion and degradation mechanisms of electride emitters during the hollow cathode operation are discussed. 相似文献
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研究了用电沉积方法从90Sr母液中分离医用90Y的工艺条件。以0.1 mol/L pH 2.5的(NH4)2SO4溶液为电沉积底液,以铂为阳极,铂或不锈钢为阴极,控制阴极电流密度0.5A/cm2,电沉积50min,90Y在阴极沉积率大于95%。阴极上的90Y用0.1~0.5mol/L的热硝酸洗脱后再次电沉积。二次电沉积后90Y/Sr90的分离系数大于8×105,洗脱收率大于70%。铂丝阴极上的90Y可用200~400μL 0.1~0.5mol/L的热硝酸洗脱,制成用于标记药物的90Y溶液;沉积有90Y的不锈钢阴极经热处理后,制成心血管放射性支架或医用敷帖片,其90Y的日浸出率分别小于1%和0.1%。残液中的90Sr经放置一段时间(20天)后,可用来再次分离90Y。 相似文献
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Trace radioactive impurities found in all semiconductor devices induce soft errors in semiconductor memories by ?-particle emission. Data taken on 16K d-RAMs which have been fast neutron irradiated to fluences from 1013 to 1016 n/cm2 show that soft errors in these devices can be significantly reduced while maintaining acceptable device operation. Reduction in soft error rate by factors as high as 80 are observed following irradiation and thermal annealing. The effect on device parameters is discussed as well as the defects responsible for this beneficial radiation processing. Estimates of the soft error rate improvement to be expected on higher density memory devices (64K and 256K d-RAMs) will also be presented. 相似文献
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Two experimental techniques have been used to quantify the atomic oxygen density in the case of hot air plasma generated by a microwave (MW) resonant cavity. The latter operates at a frequency of 2.45 GHz inside a cell of gas conditioning at a pressure of 600 mbar, an injected air flow of 12 L/min and an input MW power of 1 kW. The first technique is based on the standard two photon absorption laser induced fluorescence (TALIF) using xenon for calibration but applied for the first time in the present post discharge hot air plasma column having a temperature of about 4500 K near the axis of the nozzle. The second diagnostic technique is an actinometry method based on optical emission spectroscopy (OES). In this case, we compared the spectra intensities of a specific atomic oxygen line (844 nm) and the closest wavelength xenon line (823 nm). The two lines need to be collected under absolutely the same spectroscopic parameters. The xenon emission is due to the addition of a small proportion of xenon (1% Xe) of this chemically inert gas inside the air while a further small quantity of H2 (2%) is also added in the mixture in order to collect OH(A¬X) and NH(A-X) spectra without noise. The latter molecular spectra are required to estimate gas and excitation temperatures. Optical emission spectroscopy measurements, at for instance the position z=12 mm on the axis plasma column that leads to a gas measured temperature equal to 3500 K, an excitation temperature of about 9500 K and an atomic oxygen density 2.09×1017± 0.2×1017 cm −3 . This is in very good agreement with the TALIF measurement, which is equal to 2.0×1017 cm −3 . 相似文献