三种铁电阴极材料电子发射性能试验研究

本文采用锆钛酸铅、钛酸铋钠和钛酸钡三种不同铁电阴极材料,进行了电子发射试验,测定了电子发射电流密度,并对其在电子发射试验时的波形进行了分析讨论.结果认为:锆钛酸铅材料的电子发射电流密度略优于其他两种材料,但从无铅化角度来讲,钛酸钡与钛酸铋钠材料将有望取代现有的锆钛酸铅铁电阴极材料.     

阴极寿命的电流加速试验方法机理及结果

阴极寿命的加速试验一般采用温度加速寿命试验方法，有关电流加速寿命试验方法的文献不多。在研制氧化执分散型氧化物阴极时，分析了大电流密度对阴极的影响；为了避免测试用二极管阳极蒸发物对阴极的影响，采用了模拟电子枪发射系统的电子枪模拟管，并分析了这种测量管测试结果与标准二极管测试结果之间的关系。     

阴极寿命的电流加速试验方法机理及结果

阴极寿命的加速试验一般采用温度加速寿命试验方法，有关电流加速寿命试验方法的文献不多，在研制氧化钪分散型氧化物阴极时，分析了大电流密度对阴极的影响；为了避免测试用二极管阳极蒸发物对阴极的影响，采用了模拟电子枪发射系统的电子枪模拟管，并分析了这种测量管测试结果与标准二极管测试结果之间的关系。     

铁电阴极几何参数对二极管电子发射的影响

主要讨论了触发电场的脉宽和阴极几何参数对铁电二极管电子发射的影响,通过对不同脉宽激励下的电子发射试验发现触发脉冲的最佳工作宽度范围是150-250ns。对不同几何参数铁电阴极片在正脉冲激励下的电子发射研究指出:一般实验条件下(触发电压小于4kV/mm),触发梯度电场相同时,阴极越厚,条栅电极越细密,发射电流密度越大;极化反转发射中前沿发射方式和后沿发射方式可以共时存在。     

四针状氧化锌纳米材料的发射稳定性研究

采用四针状氧化锌纳米材料作为阴极发射体制作了真空场发射二极管，观察其阴极发射电流的稳定性。在实验过程中，阴极发射电流的波动幅度在2％以下，说明四针状氧化锌纳米发射体具有较好的发射稳定性。     

喷雾干燥纳米氧化钪粒子掺杂含钪扩散阴极的发射特性

采用喷雾干燥法制备氧化钪掺杂钨粉。用这种钨粉制作基体并浸渍铝酸钡、钙,研制了大电流密度含钪扩散阴极。分别在平板二极管和电子枪内研究了阴极的脉冲与直流发射性能以及寿命,并对高直流电流密度下的电子冷却效应和温度补偿进行了探讨。结果表明,阴极在二极管结构内,温度为950℃时,空间电荷限制区偏离点脉冲电流密度可达到122 A/cm~2,直流电流密度可达到60 A/cm~2以上。在初始直流载荷20 A/cm~2的条件下进行寿命试验,电流逐步上升至30 A/cm~2,连续工作2000 h,提升电流密度至40 A/cm~2后,继续稳定工作达3000 h以上。在电子枪内,初始脉冲电流58 A/cm~2时的欠热特性膝点温度仅为900℃,阴极在50 A/cm~2的电流密度下稳定工作1000 h,并仍在继续。上述结果表明,所研制的阴极优于当前所用的其他各类热阴极,工艺可控,具有在太赫兹领域等新型连续波微波真空电子器件内实际应用的能力。     

铁电阴极材料电子发射机理实验研究(英文)

作为一种新型功能材料,为获得更高的电子发射电流密度和更好的电子束品质,对于铁电电子发射机理的探讨,一直方兴未艾.针对采用锆钛酸铅、钛酸钡和钛酸铋钠这3种不同铁电阴极材料,进行了电子发射实验,并着重对样品电子发射前后的宏微观变化进行了对比分析.认为不同种类的铁电材料遵循不同的电子发射机理,等离子体在发射过程中起着重要作用.对于钛酸钡材料,电子发射以等离子体致电子发射为主;对于钛酸铋钠材料,电子发射以快极化反转电子发射为主;而对于锆钛酸铅材料,2种机理作用兼而有之.     

自封闭低电压真空微电子二极管阵列研究

对真空微电子二极管阵列的结构及其制造工艺技术进行了研究，重点集中在该类器件的核心，即场致发射尖锥阵列的制造及自封闭真空空腔形成技术的研究。采用不同的阴极发射尖锥材料，在优化的几何结构和工艺条件下研制成功了性能良好的自封闭低电压真空微电子二极管阵列，在Ｕ≤５Ｖ条件下，对Ｍｏ锥和Ｔｉ锥分别获得３．７μＡ每尖锥和９．５μＡ每尖锥的发射电流。同时对真空微电子二极管阵列的结构参数与电流－电压特性间的关系，影     

自封闭低电压真空微电子二极管阵列研究

对真空微电子二极管阵列的结构及其制造工艺技术进行了研究，重点集中在该类器件的核心，即场致发射尖锥阵列的制造及自封闭真空空腔形成技术的研究。采用不同的阴极发射尖锥材料，在优化的几何结构和工艺条件下研制成功了性能良好的自封闭低电压真空微电子二极管阵列，在U≤5V条件下，对Mo锥和Ti锥分别获得3．7μA每尖锥和9．5μA每尖锥的发射电流。同时对真空微电子二极管阵列的结构参数与电流-电压特性间的关系，影响场发射特性的各种因素进行了分析讨论。     

离子发动机空心阴极寿命预测

为验证空心阴极的寿命,本文根据空心阴极LaB6发射体的损耗特点,采用数学建模方法对空心阴极的寿命进行了预测.预测结果表明兰州物理研究所研制的空心阴极工作在额定状态下(发射电流5.00 A),其寿命可达到40000 h以上.3500 h寿命试验后空心阴极解剖分析结果初步验证了预测模型的正确性.     

缺位型强电流铁电阴极材料的研究

采用一种新型的缺位型铁电陶瓷作为阴极材料 ,获得了 1 87A/cm2 的强电流发射密度。通过缺位型与非缺位型材料的发射电流的对比 ,从理论上分析了缺位对于电子发射的影响 ,从材料学角度出发 ,总结出提高发射电流密度的三种有效方法 :即增强阴极表面半导体性 ,增大内偏置电场和增大材料的介电常数     

Electron emission in a flat cathode-curved anode system in the space-charge-limited current regime

The process of electron emission in a vacuum diode with curved cathode in the space-charge-limited current regime has been theoretically studied. The space charge density, electric field, and velocity field distributions in the interelectrode gap are determined by means of expansion with respect to a small parameter representing the ratio of the characteristic transverse and longitudinal scales. Based on these results, the current density distribution over the cathode surface is analytically described. The analytical results are compared to the data of numerical calculations available in the literature.     

Current passage in a vacuum diode with field-and laser-controlled ferroelectric cathode

We present the results of experimental investigation of a planar vacuum diode with field-and laser-controlled ferroelectric cathode based on prepolarized ceramics of the TsTS-23 (TsTS-19) grade. The diode current passes when the spontaneous polarization vector is oriented both toward the anode and in the opposite direction. It is established that an increase in the laser power density on the ceramic surface leads to a decrease in the diode current pulse duration. The maximum currents achieved in a field-controlled diode exceed the Langmuir current values by two to three orders of magnitude. The current pulse characteristics are determined by the mutual orientation of the polarization vector and the control electric field.     

Singularity in the current density distribution at the boundary of emitting region on a flat cathode surface

The process of electron emission from the boundary of regions with infinite and zero emissivity on a flat cathode surface of a vacuum diode in the space-charge-limited current regime has been theoretically studied. The space charge density, electric field, and velocity field distributions in the interelectrode gap are determined using self-similar solutions of the equations of motion of charged particles. It is established that a singularity, where the emission current density tends to infinity according to a power law, appears at the boundary. From this special point, electrons are emitted at an angle of 103° relative to the electrode surface.     

Dense plasma formation on the surface of a ferroelectric cathode

An enhanced electron emission mode of the ferroelectric plasma cathode operation is reported. The enhanced emission is achieved due to the generation of dense plasma (10¹⁹-10²⁰ m⁻³). This plasma is formed by a flashover which is initiated by charged particles. These particles are attracted to the ferroelectric surface by a driving electric field and are released during its decay. Generation of an electron beam with current amplitude ?2.5 kA is demonstrated in a diode under an accelerating voltage of 150-300 kV and pulse duration of 300 ns.     

Long-lived explosive-emission cathode for high-power microwave radiation generators

The operation of cold explosive-emission cathodes having a current density of ∼10⁴ A/cm², fabricated using various materials, was investigated under a large number of switching cycles. The cathode voltage was ∼500 kV, the maximum current ∼5 kA, and the pulse duration ∼20 ns. It is shown that when the number of switchings is small (⩽10³ pulses), cathodes having similar geometry exhibit similar emission properties. For most of the materials studied, as the number of switching cycles increases (⩾10³ pulses), the current rise time increases (as far as the pulse duration) and the maximum vacuum diode current decreases. When a graphite cathode was used, the maximum current remained unchanged up to 10⁸ switching cycles. The mass removed from the cathode was determined for various materials. The results were used to achieve continuous operation of a relativistic 3 cm backward-wave tube having an output power of 350–400MW and an almost constant power level during 10⁸ pulses at a repetition frequency of 100–150 Hz. Pis’ma Zh. Tekh. Fiz. 25, 84–94 (November 26, 1999)     

Protecting the anode foil of a high-current electron accelerator against arc-discharge damage

The mechanism of anode foil damage during the extraction of a high-power pulsed electron beam from a high-current diode has been experimentally studied on a TEU-500 electron accelerator [1]. It is established that the breakage of the anode foil is caused by the appearance of cathode spots on its surface, the intense electron emission from these spots during positive voltage pulses (postpulses following the main negative pulse of accelerating voltage), and the formation of arc discharge in the interelectrode gap. The improvement of diode matching to the pulse-forming line of the accelerator and the use of an auxiliary electrode (anode) forming additional vacuum discharge gap (crowbar) with the cathode practically excludes the anode foil breakage by arc discharge and significantly increases the working life of the foil (up to ∼10⁵ electron beam pulses).