Mode control in a high-gain relativistic klystron amplifier

Middle cavities between the input and output cavity can be used to decrease the required input RF power for the relativistic klystron amplifier.Meanwhile higher modes,which affect the working mode,are also easy to excite in a device with more middle cavities.In order for the positive feedback process for higher modes to be excited,a special measure is taken to increase the threshold current for such modes.Higher modes' excitation will be avoided when the threshold current is significantly larger than the beam current.So a high-gain S-band relativistic klystron amplifier is designed for the beam of current 5 kA and beam voltage 600 kV.Particle in cell simulations show that the gain is 1.6×105 with the input RF power of 6.8 kW,and that the output RF power reaches 1.1 GW.     

Ultraviolet light emissions from N2 microplasma electrically induced by metal-insulator-semiconductor devices

Various metal-insulator-semiconductor (MIS) devices in the form of Au/SiO_x(x<2)/Si, Au/AlO_y(y<1.5)/Si, Au/SiO_x/ZnO and Au/AlO_y/ZnO have been fabricated. For each device, once a sufficiently high positive voltage is applied on the Au electrode, the same ultraviolet (UV) emission with a spectrum featuring several specific peaks is detected. Interestingly, such UV emissions related to the MIS devices originate from the external N₂ microplasma. It is believed that at the high enough positive voltages the highly energetic electrons emitted out of the Au electrode activate the air to generate the N₂ microplasma.     

Temperature dependence of symmetric and asymmetric structured Au stripe waveguides

The thermal effects on pigtailed 22-nm-thick, 5-μm-wide and 1-cm-long Au stripe long-range surface plasmon polariton (LRSPP) waveguides, embedded in polymer/polymer layers and in polymer/silica layers, are theoretically and experimentally demonstrated. The polymer and silica cladding layers have thermo-optic coefficients of opposite signs. As the temperature varies the Au stripe LRSPP waveguide embedded in the polymer/polymer layers retains its symmetry in the refractive index, but that embedded in the polymer/silica layers becomes asymmetric in the refractive index. The thermal sensitivity in the optical output power of the symmetric structure is smaller than 0.02 dB/°C but the sensitivity of the asymmetric structure is ∼ 0.3 dB/°C. These structures open up potential applications of the LRSPP waveguides for temperature independent/dependent photonic devices.     

Experimental study of Love-wave immunosensors based on ZnO/LiTaO3 structures

Experimental study of Love-mode immunosensors based on structures of ZnO/36°YX-LiTaO₃ is presented, in which the ZnO films with c-axis (0 0 2) orientation have been successfully grown on the 36°YX-LiTaO₃ substrates by RF magnetron sputtering technique. Then the Love-mode immunosensors based on the ZnO/36°YX-LiTaO₃ structures and monitoring antibody-antigen immunoreactions in aqueous solutions in real time are fabricated. The experimental results show that the optimal thickness of ZnO layers is about 1.20 μm in the structures deposited on 36°YX-LiTaO₃ substrates, which is much less than that of SiO₂ overlayers about 6 μm. The antibody-antigen immunoreaction experiments also show that the frequency shifts of the sensors with 1.33 μm ZnO films are proportional to the concentration of antigen in solution as the concentration range less than 100 μg/ml.     

原子漏斗及其应用

文章简单介绍了磁、光原子漏斗的基本原理，详细综述了各种原子漏斗方案及其实验结果．这些漏斗方案主要包括采用红失谐高斯光束、蓝失谐消逝波光场和空心光束串联而成的光学原子漏斗，采用载流导线的静磁原子漏斗以及采用磁光凝胶构成的磁光原子漏斗．文章最后还简单介绍了原子漏斗在原子光学领域中的潜在应用．     

Synthesis of poly(N‐9‐ethylcarbazole‐exo‐norbornene‐5,6‐dicarboximide) for hole‐transporting layer in hybrid organic light‐emitting devices

We synthesized new polynorbornene dicarboximide (PCaNI) functionalized with hole‐transporting carbazole moieties and its copolymer (PCaNA) by ring‐opening metathesis polymerization (ROMP), where the PCaNA was further reacted with 3‐amino‐triethoxysilane to prepare PCaNI/silica hybrid. We also investigated the feasibility of PCaNI and PCaNI/silica hybrid (PCaSi) as a hole‐transporting material for hybrid organic light emitting devices (HOLEDs). To improve the performance of the PCaNI‐based HOLEDs, N,N′‐diphenyl‐N,N′‐(3‐methylphenyl)‐[1,1′‐biphenyl]‐4‐4′‐diamine (TPD) was also introduced into the PCaNI matrix. Results showed that PCaNI exhibited high glass transition temperature (～260 °C) and high optical transparency in the visible region. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of PCaNI were measured as 5.6 and 2.2 eV, while the TPD‐doped PCaNI showed 5.7 eV (HOMO) and 2.6 eV (LUMO). The PCaNI/silica hybrid nanolayers showed excellent solvent resistance due to the formation of covalent bonds between ITO and PCaNI. The HOLEDs with PCaNI/TPD or PCaSi/TPD hybrid nanolayers exhibited relatively higher luminance (～10,000 cd/m²), lower operating voltage (～6.5 V at 300 cd/m²), and higher current efficiency (～2.7 cd/A). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Impedance measurement technique for quantum systems

The impedance measurement technique consists in that the phase-dependent (parametric) inductance of the system is probed by the classical tank circuit via measuring the voltage. The notion of the parametric inductance for the impedance measurement technique is revisited for the case when a quantum system is probed. Measurement of the quantum state of the system of superconducting circuits (qubits) is studied theoretically. It is shown that the result of the measurement is defined by the partial energy levels population in the qubits and by its derivative.     

An approach to the Gummel map by vector extrapolation methods

The numerical approximation of nonlinear partial differential equations requires the computation of large nonlinear systems, that are typically solved by iterative schemes. At each step of the iterative process, a large and sparse linear system has to be solved, and the amount of time elapsed per step grows with the dimensions of the problem. As a consequence, the convergence rate may become very slow, requiring massive cpu-time to compute the solution. In all such cases, it is important to improve the rate of convergence of the iterative scheme. This can be achieved, for instance, by vector extrapolation methods. In this work, we apply some vector extrapolation methods to the electronic device simulation to improve the rate of convergence of the family of Gummel decoupling algorithms. Furthermore, a different approach to the topological ε-algorithm is proposed and preliminary results are presented.