相对论全腔轴向提取磁控管阳极释气数值模拟研究

相对论电子轰击阳极产生二次电子和释气以及释气电离产生的击穿现象是限制全腔轴向提取透明阴极磁控管（TCMAC）工作性能的一个重要因素。本研究对TCMAC中轰击产生的阳极二次电子以及释气电离现象进行了物理建模以及三维数值模拟研究,考察了其对TCMAC运行性能的影响。初步计算结果表明,二次电子发射与阳极释气对TCMAC工作都有一定影响,释气后电离产生的正离子数大于系统中电子数时,会导致TCMAC击穿。     

相对论磁控管透明阴极技术作用机理研究

透明阴极技术对相对论磁控管振荡启动过程具有显著影响,但其加速启动过程的作用机理仍有待深入研究。对采用扇形单元透明阴极的L波段相对论磁控管进行数值模拟,分析了场分布模式和带电粒子空间运动规律,发现透明阴极与实心阴极在磁控管振荡启动过程的差异。可见透明阴极带来的静电场角向分量与外加轴向磁场引起的洛伦兹力,对初始工作状态的电子具有向阳极加速漂移的作用。采用透明阴极的相对论磁控管的电子轮辐外缘更贴近阳极,群聚电子在轴向上具有随距离连续变化的速度分布,使得电子与高频电磁场的能量交换更加充分。对扇形阴极单元的个数与张角组合的匹配效果进行了模拟,给出了磁控管振荡建立阶段静电场角向分量对阴极电子发射与漂移运动的作用规律。透明阴极的设计需要与磁控管慢波结构相匹配,以得到最优化的工作状态。     

活性氧捕获材料的研究进展

生命从呼吸中获得氧气, 氧气再进一步在线粒体中将糖类等氧化得到能量, 提供给生命过程使用. 然而在氧化过程中, 会生成高度活泼的活性氧. 当体内控制失衡的时候, 它的浓度会大大增加, 发生氧化应激, 对机体产生不可逆的破坏, 引起衰老、肿瘤、心血管以及神经性疾病等. 抵抗活性氧的核心物质是抗氧化物, 它的存在使氧化应激受到控制, 从而保护机体免遭伤害. 本文对国内外近年来在活性氧自由基捕获方面的研究进行系统的综述, 通过梳理, 提出研究的金字塔型三级结构. 设计抗氧化物大分子与无机纳米粒子复合的纳米杂化自由基捕获器可以一方面解决无机纳米粒子的毒性问题, 另一方面还可以赋予纳米粒子额外的功能. 期待这篇综述文章能为改性纳米粒子捕捉活性氧提供一些有益思路, 为功能高分子材料与杂化纳米技术在生物医学领域的探索提供借鉴.     

相对论磁控管的实验研究

简要分析了相对论磁控管的主要特点与问题,编制了谐振系统数值计算程序,通过数值计算与冷测,对不同阴极尺寸与输出结构的磁控管进行了研究,清晰地描述了磁控管的振荡模式与简并现象。制作了A6型相对论磁控管并进行了热测实验,研究了输出功率与工作磁场的关系,经过大量优化工作,在S波段获得了380MW的微波辐射。     

大口径等离子体电极普克尔盒电光开关研究

设计建造了通光口径为240mm×240mm等离子体电极普克尔盒,在KDP的两侧用磁控阴极放电产生了覆盖全口径的等离子体电极。用仿真线成形,产生了电压幅值10kV,脉冲上升时间50ns,脉宽500ns,顶部电压波动＜±2%的矩形开关脉冲。测得电光开关的光学特性为全口径静态透过率85.8%,静态消光比132,开关效率97.6%,开关上升时间95ns。     

Laccase bound to cryogel functionalized with phenylalanine for the decolorization of textile dyes

In this study, amino acid functionalized poly(2-hydroxyethyl methacrylate-N-methacrylolyl-l-phenylalanine) [PHEMAPA] cryogel discs were prepared. In this respect, phenylalanine containing N-methacryloyl-(L)-phenylalanine methyl ester (MAPA) was polymerized with 2-hydroxyethyl methacrylate (HEMA) without requirement of any activation step. Laccase bound poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-phenylalanine) [Lac-PHEMAPA] cryogel discs were applied for decolorization of Reactive Blue-247 (RB-247). The ability of Lac-PHEMAPA cryogel discs on dye decolorization was found to be as 90% in 2 h and even more within 4h. The decolorization activities of 86% and 73% were observed at relatively low (4°C) and high (60°C) temperatures, respectively. The effect of dye concentration on dye decolorization and 100% decolorization activity was achieved in dye concentration between 50–300 ppm. Lac-PHEMAPA cryogel discs maintained 80% of its decolorization activity after six cycles. Consequently, the PHEMAPA cryogel discs are promising materials for immobilizing laccase. The Lac-PHEMAPA has a rapid dye decolorization in a broad range of temperature. The preparation is furthermore very stable and activity is preserved during storage.     

Structural and electrical properties of SrTiO3 thin films as insulator of metal-ferroelectric-insulator-semiconductor （MFIS） structures

SrTiO₃ (STO) thin films were deposited on p-Si(100) substrates at various substrate temperatures from 300℃ to 700℃ by radio frequency (RF) magnetron sputtering technique. Their structure and electrical properties were investigated. It was found that the transition from amorphous phase to polycrystalline phase occurred at the substrate temperatures 300--400℃. Their crystallinity became better when the substrate temperatures further increased. The dielectric and leakage current measurements were carried out by using the Si/STO/Pt metal--insulator--semiconductor (MIS) structures at room temperature. It was found that the fixed charge density decreased and both the interface trap density and the dielectric constant increased when the substrate temperatures were increased. The leakage current mechanisms for STO MIS structures with STO films prepared at 700℃ followed the space charge limited current (SCLC) under the low applied electric field and the Poole--Frenkel emission under the high one. In addition, the resistivity for films prepared at 700℃ was higher than 10¹¹\Omega \cdot cm under the voltage lower than 10V (corresponding to the electric field of 1.54\times 10³kV\cdotcm^-1). It suggested that the STO films prepared at 700℃ were suitable for acting as the insulator of metal--ferroelectric--insulator--semiconductor (MFIS) structures.     

Deposition of MgO films by pulsed mid-frequency magnetron sputtering

MgO films were deposited by pulsed mid-frequency magnetron sputtering from metallic targets in the mixture of Ar and O₂ gas. The surface morphology, crystalline structure, and optical properties were characterized by using atomic force microscopy (AFM), X-ray diffraction (XRD), and spectroscopic ellipsometry, respectively. The secondary electron emission coefficients of MgO films were measured by using a self-made apparatus in He gas. A pronounced hysteresis phenomenon of target voltage, current, and deposition rate with increasing and decreasing O₂ flow rate was observed. The structure of films deposited at a metallic mode changes from Mg phase to the mixed Mg and MgO phase, and the films have a very rough surface. All the films deposited at oxide mode have high transparency and smooth surface, and show (2 2 0) preferred orientation growth. The refractive index and extinction coefficient at a wavelength of 670 nm for MgO films deposited at oxide mode with a O₂ flow rate of 3 sccm are 1.698 and 1.16×10⁻⁴, respectively. The secondary emission coefficient at a E/p of 57.8 V/(cm Torr) for MgO films deposited at a O₂ flow rate of 3 sccm is 0.16, which is higher than that of MgO films deposited by e-beam evaporation.     

铁磁超导态/绝缘层/自旋三重态p波超导体结的直流Josephson电流

由Bogoliubov-de Gennes方程得到铁磁超导共存态(FS)的自洽方程，利用推广的Furusaki-Tsukada的电流公式计算了铁磁超导态/绝缘层/自旋三重态p波超导体(FS/I/p)结的直流Josephson电流随结的温度、相位差以及FS中磁交换能、结界面的势垒散射强度的变化关系.研究表明：FS中磁交换能、结界面的势垒散射均抑制FS/I/p结的直流Josephson电流.当自旋三重态超导体具有p_x波配对势时，自旋三重态超导体结的直流Josephson电流随结两侧相位差的振荡周期是π. 关键词： 铁磁超导态 自旋三重态超导体 p波超导体 直流Josephson电流     

Spectroscopic system for controlling gas flow and impurity content during magnetron deposition of films

An automated system for controlling oxygen flow in vacuum-plasma magnetron deposition of oxides with simultaneous monitoring of gas impurities in a vacuum chamber is proposed. Features of using compact spectrometers in such a system are considered. The precision of controlling the flow of metal and oxygen particles during deposition of Ti and Al oxides is determined. The sensitivity to impurity content is estimated. The effect of sputtered metal and type of coating (metal or oxide) on the sensitivity to impurities of air, water vapor, and oil in the vacuum chamber is found. __________ Translated from Zhurnal Prikladnoi Spektroskopii Vol. 74, No. 3, pp. 412–416, May–June, 2007.