Mass Balance in Near-Cathode Plasma and Initiation of Quick-Moving Cathode Spots

The explosive model of a quick-moving cathode spot [2], [3] allows us to describe many experimental facts qualitatively. However, some details of the model need further physical explanation, in particular because of the analysis of the latest experimental data [4]. Estimations given in this paper show it is possible to include in the framework of the explosive model mass balance in the plasma ball and explain the fact of the appearance of a new spot at the periphery of an old one observed in experiments [9], [10]. From the physical point of view, solution of this question is connected in the paper with the presence of oxide film on the cathode surface. Besides, it is shown that the discrepancy in erosion, observed in experiments [2], [4], can be connected with the difference in the thickness of oxide film.     

Anode and Cathode Spots in High-Voltage Nanosecond-Pulse Discharge Initiated by Runaway Electrons in Air

We report the experimental results with nanosecond-pulse discharges formed in the air gap between a fiat electrode and a sharp electrode. The appearance of anode and cathode spots on the electrodes is studied experimentally. It is considered that bright spots on the fiat cathode with positive polarity of the sharp electrode are formed due to the explosive electron emission on the cathode and the dynamic displacement current in the gap. It is also shown that with negative polarity of the sharp electrode, bright spots on the flat anode are formed after changing the polarity of the flat electrode due to the discharge oscillatory mode. Under these conditions, the explosive electron emission firstly forms on the sharp cathode. With negative polarity of the sharp electrode of the subnanosecond-pulse pulser, the runaway electron beam current is measured behind the anode foil with a time resolution of no more than 100ps.     

On the Nature and the Motion of Arc Cathode Spots in UHV

Cathode spot types and spot motion of arcs in ultra high vacuum have been investigated with large area cathodes that consisted of two adjacent pieces of Mo and Cu. Arc currents were 20–60 A dc and 8–20 kA pulse (duration about 1 ms). Two spot types occured with different velocities and surface erosion: Type 1 spots are typical for surfaces covered by oxides or thick adsorption layers, whereas clean surfaces show only type 2 spots. During arc-conditioning both types exist simultaneously in a complex mutual dependence. Type 1 spots react weakly on the cathode material, while type 2 spots burn preferentially on Cu and at the boundary line between Mo and Cu. The motion of type 1 spots is determined by the expanding spot plasma, whereas type 2 spots show a step-by step motion, determined by explosions in the arc craters. Generally a spontaneous formation of type 2 spots beneath the arc plasma takes place only with contaminated surfaces (probably by a transition from type 1 to type 2 spots). Thus a breakdown between plasma and cathode surface requires the presence of contaminations. The observed effects occur in low current dc-arcs as well as in high current pulse arcs. They are discussed for different spot models.     

The Analytical Wavefunctions of SU(3) Limit in the Interacting Boson Model

A projection method to calculate the physical states from intrinsic states is put forward. Using this projection method, the physical states of the ground state band in the interacting boson model (IBM) SU(3) limit are calculated. The wave functions are expressed in terms of the building blocks of the IBM wave functions.     

质子-中子相互作用玻色子模型SU(3)算法与简单应用

质子-中子相互作用玻色子模型(简称IBM-2)具有很好的壳模型微观基础,是描述中重质量偶偶核结构的标准模型之一.对比早期建立在弱耦合U(5)基底的NPBOS算法,本文介绍基于弱耦合SU(3)基底求解IBM-2模型哈密顿量的新算法结构,通过举例典型相互作用项在SU(3)基底下矩阵元说明如何利用SU(3)群代数技术求解IB...     

改进碳纳米管电接触及粘贴性能的一体式冷阴极制作

在阴极玻璃面板上研发了一种新型的一体式冷阴极.印刷的银浆被烧结后用于形成银底电极.制备了薄层底电极浆料,其中含有大量碳纳米管.将薄层底电极浆料印刷在银底电极表面,然后再将普通碳纳米管浆料制作在烘烤的薄层底电极浆料上.利用高纯度氩气作为保护气体,在烧结炉中对这两种浆料同时进行烧结.烧结后的薄层底电极将和银底电极相互融合在一起,碳纳米管层则覆盖于薄层底电极的表面.同一阴极像素中制作了两个碳纳米管发射极.备用碳纳米管发射极的存在,有利于延长整体显示器的使用寿命.利用薄层底电极作为碳纳米管层和银底电极之间的中间层,能够有效改善碳纳米管的粘贴性能,同时增强二者之间的可靠欧姆接触.利用碳纳米管作为阴极制作了一体式冷阴极场发射显示器.该显示器具有良好的发光图像质量以及更好的场发射特性.与普通碳纳米管阴极场发射显示器相比,一体式冷阴极场发射显示器能够将开启场强从2.11 V/μm减小到1.68 V/μm;将最大场发射电流从905 μA提高到1 866.2 μA;数值为367 μA场发射电流的电流波动不超过4.5％.该一体式冷阴极场发射显示器已经以稳定的发光亮度而连续运行10余天.     

Energy Level Statistics of SO(5) Limit of Super-symmetry U(6/4) in Interacting Boson-Fermion Model

We study the energy level statistics of the SO(5) limit of super-symmetry U(6/4) in odd-A nucleus using the interacting boson-fermion model. The nearest neighbor spacing distribution (NSD) and the spectral rigidity (△3)are investigated, and the factors that affect the properties of level statistics are also discussed. The results show that the boson number N is a dominant factor. If N is small, both the interaction strengths of subgroups SOB(5) and SOBF(5)and the spin play important roles in the energy level statistics, however, along with the increase of N, the statistics distribution would tend to be in Poisson form.     

Energy Staggering in Ground Bands of ~(232)Th and ~(236,238)U Nuclei Using the Interacting Vector Boson Model

The△I = 2 and △I = 4 staggering parameters of transition energies Eγfor normally deformed positive parity ground bands in232 Th and236,238 U nuclei are studied in framework of the symplectic extension of the interacting vector boson model. The model parameters are obtained from the fitting procedure between the calculated excitation energies and the corresponding experimental ones. The staggering parameters represent the finite difference approximations to higher order derivatives dnEγ/d Inof the γ-ray transition energies in a△I = 2 and △I = 4 bands, which yielding multipoint formulae. The first order derivative(two-point formula) provides us with information about the dynamical moment of inertia. The staggering oscillation for the fourth order derivative(five-point formula) is about 0.5 Ke V and is even larger than that in superdeformed bands. The quite similarity in dynamical moments of inertia of the isotopes236,238 U up to high spin states indicate that the phenomenon of identical bands is not restricted to superdeformed bands.     

The Interacting Boson Model of Dipole-Octupole Strong Correlations in SU(3) Limit for Positive Parity States

Within the framework of the Usdpf(16) interacting boson model (IBM), the effects of strong correlations of the dipole (p--boson) and the octupole (f--boson) degree of freedom on the positive-parity states of even-even nuclei in SU(3) limit are discussed. It is shown that configurations of an even number of many p- and f-bosons can not only be incorporated into the usual low-lying collective rotational bands, such as the ground state band, β- and γ-vibrational bands, but also naturally form the Kπ＝ 1+, 3+ rotational bands, etc. These results are similar to that of Usdg (15)-IBM and in agreement well with the experimental data of the 176 72 Hf 104 nucleus. Besides, several intraband E2 transition probabilities are given, which are consistent with that of Usd(6)-IBM.     

铂同位素的研究——费米子动力学对称模型和相互作用玻色子模型的比较

利用费米子动力学对称性模型(FDSM)系统研究了偶偶核铂的同位素,其跃迁可以很好地由对相互作用+四极相互作用来描述,计算了铂(^190—196Pt)同位素的能级、电四极矩、旋磁比、同质异能移和同位素移动,结果表明理论值与实验值符合的很好.计算结果还与相互作用玻色子模型(IBM)的结果进行了比较.计算结果表明即使在FDSM中质子–中子耦合系统(SO^π(8)×SP^ν(6))形式上不包括SO(6)动力学对称性,但¹⁹⁶Pt附近确实存在精确的等效SO(6)动力学对称性     

Study of Platinum Isotopes: A Comparison of the Fermion Dynamical Symmetry Model and the Interacting Boson Model

The systematics of the even platinum isotopes are described within the framework of the Fermion Dynamical Symmetry Model. By using a pairing—plus—quadrupole type interactions, we show that the transitional behavior of these isotopes can be effectively accounted for. Good agreement is obtained between theory and data for energy levels, B(E₂) values, electric quadrupole moments, gyromagnetic factors, and the isomer shifts and isotope shifts for ^190—196Pt. The Calculations are also compared with various results obtained from the Interacting Boson Model. Consequently, our numerical calculation show that a very accurate effective SO(6) dynamical sysmmetry exists around ¹⁹⁶Pt, even though the proton-neutron coupled system (SO^π(8)×SP^ν(6)) does not formally contain such a dynamical symmetry in the fermion dynamical symmetry model. Implications of this effective dynamical symmetry are discussed.     

非弹性度和集团数在高能极限下的行为

在胶子相互作用模型基础上作了两点改进,把所有部分子的相互作用(qq,qg,gg)都包括进来,并考虑部分子分布函数随能量标度的演化.在没有区分软硬过程的贡献及部分子分布函数的具体形式下,导出了非弹性度和集团数在高能极限下的行为.     

铕(Ⅲ)-苯甲酸衍生物配位化合物中Eu(Ⅲ)离子格位

以 2 ,3 二甲氧基苯甲酸 (2 ,3 HDMOBA)和 4 甲基苯甲酸 (p HMBA)为配体 ,合成了新的稀土配合物Eu(2 ,3 DMOBA) 3 和Eu(p MBA) 3 。在 77K下测定了高分辨激发光谱和时间分辨谱。配合物Eu(2 ,3 DMOBA) 3中Eu(Ⅲ )离子格位只有一种 ,配合物Eu(p MBA) 3 中确有化学环境类似的多种类型的Eu(Ⅲ )离子。     

High-Resolution Infrared Spectrum of CD(3)CN: Analysis of the Interacting nu(3) and nu(6) Bands and Evaluation of the A(0) Constant

The infrared spectrum in the range 900-1230 cm(-1) including the fundamental bands nu(3) and nu(6) of CD(3)CN has been studied. The resolution attained was 0.0025 cm(-1) in the measurement on the Bruker 120 HR Fourier spectrometer in Oulu. About 4000 lines were assigned in the nu(6) band. For the weak nu(3) band, which has not been observed earlier directly, we were able to assign 206 lines in three subbands K=8-10. These lines become detectable due to the strong nu(3)/nu(6) Coriolis resonance. There is also an l(1,-2) resonance between nu(3) and nu(6), which made it possible to obtain a value 2.647721(50) cm(-1) for the axial rotational constant A(0), when D(0)(K) from force field calculations was applied. Different types of resonances with the overtone 3nu(8) and the combinations nu(4)+nu(8) and nu(7)+nu(8) were observed. A fit with a standard deviation of 0.0019 cm(-1) was attained by using a model of 10 different resonances. Copyright 2001 Academic Press.     

白光LED用红色荧光粉α-Gd2(MoO4)3:Eu的制备及其发光性能研究

以Gd2O3,MoO3,Eu2O3为原料,采用传统的高温固相反应方法制备了一种新的白光LED用红色荧光粉材料α相Gd2(MoO4)3:Eu.利用XRD,SEM,激发和发射光谱对其进行了研究.分析了助熔剂和激 .活剂对样品的晶体结构,表面形貌和发光性能的影响.结果表明这种荧光粉可以被近紫外光(395 nm)和蓝光(465 nm)有效激发,发射峰值位于613 nm(Eu3 离子的5D0→7F2跃迁)的红光,激发波长与目前广泛使用的蓝光和紫外光LED芯片相符合.因此,三价Eu离子激活的α相Gd2(MoO4)3是一种可能应用在白光LED上的红色荧光粉材料.     

On the Higher Order Effects of A Consistent Q Framework in the sd Interacting Boson Model

By utilizing the 1/N expansion technique(ONET),the analytical expressions of low-lying energy spectrum,the deformation parameter and the reduced matrix elements of E2 transitions to the order of 1/N are systematically given for a consistent Q framework in the sd interacting boson model.It is shown that it is important to consider the angular momentum projection in the intrinsic state formalism.     

多孔硅-导电聚酯材料复合发光器的光学特性研究

poly-4-dicyanomethylene-4H-cyclopenta[2,1-b:3,4-b]dithiophene monolayer(PCDM)是一种导电,低导带聚酯材料。如果在多孔硅纳米结构中附上一层以自组方式生成的PCDM单分子层,就可以制成能够产生稳定电致发光的器件。发光器的结构是金／PCDM／多孔硅／硅／铝,发光器的电致发光,在白天可用肉眼观察到。有很宽的发光波长,几乎覆盖了整个可见光区域且峰值位于650nm,发光器的面积为1cm^2,启动正向电压在14－30V,电流约300mA。经长时间测试,发光器的稳定性很好,在空气中放置3个月,在输入功率不变的情况下,发光强度也不发生变化,当施以反向电压时,样品仍可以发光而且稳定性较高,在250h内I－V未发生明显变化,扫描电镜图像显示PCDM覆盖的表面要比多孔硅表面平整,而PCDM分子有可能进入到多孔硅纳米孔径当中去,起到了提高发光器稳定性和延长其寿命的作用。