A relativistic magnetron with a coupling channel as the external resonator

We present the results of the first demonstration experiments on a twofold increase in the output power of a relativistic magnetron with a waveguide coupling channel between opposite cavities of the anode assembly, which contains a specially arranged H-tee and discharge gap. Switching of the gap leads to the formation and extraction of microwave pulses with increased power and short duration from the H-tee.     

Spectral characteristics of a relativistic magnetron with coupled cavities

The spectral characteristics of a relativistic microwave magnetron with cavities coupled via an external waveguide channel have been experimentally studied. It is shown that the output microwave radiation with a stable narrow spectrum and improved energy characteristics can be obtained with properly adjusted coupling in the system.     

A relativistic magnetron with cavities coupled via a waveguide slit array

The distributed output of electromagnetic energy from a relativistic magnetron has been experimentally studied with the aim of obtaining directed coherent radiation. A specific feature of the modified microwave generator was the presence of an external coupling channel with a waveguide slit array. The influence of the coupling channel on the spectral and spatial characteristics of output radiation is determined.     

Effect of external signal on the output power of an oscillator with electron feedback

The effect of an external single-frequency harmonic signal on the output power of an oscillator with electron feedback has been studied by analytical and numerical methods. It is established that an increase in the input signal power leads to sharp growth in the output power of the nonautonomous oscillator. Physical processes that take place in the electron beam with virtual cathode under the action of an external harmonic signal, which leads to velocity modulation in the electron beam entering the interaction space, have been analyzed. The obtained results well agree with the data of previous experimental investigations of the signal gain in a low-voltage vircator.     

On the possibility of mechanical tuning of a periodic-pulse relativistic magnetron

A method for the mechanical tuning of a periodic-pulse relativistic magnetron is described. The method, based on using an anode unit with the cavity edge lids having variable internal radius, allows the oscillation frequency to be varied within 8% without a significant loss in the output power.     

连续Nd:YAG激光器输出功率稳定性研究

本文介绍一种用两套LiNbO3晶体作电光调制器,高稳定硅光电二极管作光反馈控制信号的激光稳功率仪串联使用来稳定Nd:YAG激光器输出功率的方法。对于输出功率为5瓦左右,本身输出功率稳定度为10%/小时的Nd:YAG激光器,其输出光束经稳功率系统后,其稳定度为0.2/小时。     

Hysteresis and process stability in reactive high power impulse magnetron sputtering of metal oxides

In the further development of reactive sputter deposition, strategies which allow for stabilization of the transition zone between the metallic and compound modes, elimination of the process hysteresis, and increase of the deposition rate, are of particular interest. In this study, the hysteresis behavior and the characteristics of the transition zone during reactive high power impulse magnetron sputtering (HiPIMS) of Al and Ce targets in an Ar-O₂ atmosphere as a function of the pulsing frequency and the pumping speed are investigated. Comparison with reactive direct current magnetron sputtering (DCMS) reveals that HiPIMS allows for elimination/suppression of the hysteresis and a smoother transition from the metallic to the compound sputtering mode. For the experimental conditions employed in the present study, optimum behavior with respect to the hysteresis width is obtained at frequency values between 2 and 4 kHz, while HiPIMS processes with values below or above this range resemble the DCMS behavior. Al-O films are deposited using both HiPIMS and DCMS. Analysis of the film properties shows that elimination/suppression of the hysteresis in HiPIMS facilitates the growth of stoichiometric and transparent Al₂O₃ at relatively high deposition rates over a wider range of experimental conditions as compared to DCMS.     

Laser with a nonlinear mirror: application for improving the output power stability of a cw laser

We put forward a new method for improving the output power stability of a cw laser. The basic idea is to replace the output mirror of a laser with a nonlinear mirror that is formed by a dispersive nonlinear Fabry-Perot étalon. Based on the semiclassical dynamic model for this system, first we derive the static conditions for this laser operating with stabilized output power, then we study the dynamic responses of output power to gain fluctuations. Both static and dynamic results show that, compared with normal lasers, the output power stability of our laser can be improved significantly when the output power fluctuations are caused by the fluctuations of the gain. The improvement of the output power can be explained by the fact that there exists an optical servoloop in this laser that is produced by the nonlinear mirror.     

Effect of material constants on power output in piezoelectric vibration-based generators

A possible power output estimation based on material constants in piezoelectric vibration-based generators is proposed. A modified equivalent circuit model of the generator was built and was validated by the measurement results in the generator fabricated using potassium sodium niobate-based and lead zirconate titanate (PZT) ceramics. Subsequently, generators with the same structure using other PZT-based and bismuth-layered structure ferroelectrics ceramics were fabricated and tested. The power outputs of these generators were expressed as a linear functions of the term composed of electromechanical coupling coefficients k(sys)(2) and mechanical quality factors Q*(m) of the generator. The relationship between device constants (k(sys)(2) and Q*(m)) and material constants (k(31)(2) and Q(m)) was clarified. Estimation of the power output using material constants is demonstrated and the appropriate piezoelectric material for the generator is suggested.     

Effect of sputtering power on the physical properties of dc magnetron sputtered copper oxide thin films

Cuprous oxide films were deposited on glass substrates using dc magnetron sputtering technique by sputtering of pure copper target in a mixture of argon and oxygen atmosphere under various sputtering powers in the range 0.38–1.50 W cm⁻². The influence of sputtering power on the structural, electrical and optical properties was systematically studied. The films were polycrystalline in nature with cubic structure. The films formed at sputtering powers ≤0.76 W cm⁻² exhibited mixed phase of Cu₂O and CuO while those formed at 1.08 W cm⁻² were single phase Cu₂O. The single-phase Cu₂O films formed at a sputtering power of 1.08 W cm⁻² showed electrical resistivity of 46 Ω cm, Hall mobility of 5.7 cm² V⁻¹ s⁻¹ and optical band gap of 2.04 eV.     

Effect of rf power on the properties of rf magnetron sputtered ZnO:Al thin films

Aluminum doped zinc oxide ZnO:Al thin films were prepared using rf magnetron sputtering. The preparation was performed at room temperature and low pressure with varying rf power between P = 50 W and P = 500 W. Structural, electrical and optical film properties were studied depending on rf power. Special attention was paid to correlations among film structure, sheet resistance and optical transmission. Films with largest crystallite size exhibited highest optical transmission, but not lowest electrical resistivity. An explanation for this finding was sought in terms of the amount of Al atoms incorporated in the films and the places they occupy, parameters which are in turn related to rf power.     

A study on the microstructure and property development of d.c. magnetron co-sputtered ternary titanium aluminium nitride coatings Part II Effect of magnetron discharge power

Advanced ternary (Ti,Al)N coatings were produced by reactive magnetron co-sputtering technique with separate titanium and aluminium targets at a 30° magnetron configuration. The aluminium magnetron discharge power was adjusted from 0 to 6.0 W/cm² to investigate the effect of magnetron discharge power on the microstructure and property development of the coatings. It was found that increasing the aluminium magnetron discharge power caused the deposition rate and the aluminium content to increase, and the grain size and surface roughness of the coatings to decrease substantially. Tighter packing of the grain columns occurred and the microstructure changed from a porous zone 1 to a densified zone T structure, resulting in a continuous increase of the coating hardness. The major texture component of the coatings changed from the (111) to (200) orientations. The (101) orientations of the AlN structure also developed. It was found that the microstructure and hardness enhancement of the coatings was associated with an increased formation of the TiAlN and AlN phases and a densified, fine grain structure at higher magnetron discharge powers.     

水中爆炸对围岩增耦的实验研究

为研究水中爆炸对围岩的增耦,在一个直径1.6 m的水泥砂浆半球体装置上,将其中心预留的直径0.3 m的腔室内注水和置入水泥砂浆芯体,对比性地进行了一系列的1.00 gTNT(2,4,6-三硝基甲苯)当量的填实和空腔爆炸实验.水泥砂浆球表运动测量数据表明,与水泥砂浆中的空腔解耦相比,水中空腔爆炸的解耦效果较差,尤其水腔中爆炸可大大增强爆炸能量的耦合.可以推断,水下爆炸会明显增强围岩中的爆炸应力波强度,近水域中的空中爆炸也可能会增强围岩中的爆炸能耦合,因而相对于围岩和堤坝中同距离、同药量的爆炸来讲,所引起的破坏危险更大.     

A relativistic version of the principle of virtual power

A relativistic version of the principle of virtual power in continuum mechanics is proposed which involves only arbitrary finite virtual velocity fields (and not infinitesimal variations) and accommodates thermodynamically irreversible processes. Along with the motion equations of the relativistic continuum, it provides the energy equation in the presence of dissipative processes such as heat conduction and viscosity in the purely thermomechanical case and the Joule effect and hysteresis in the case of the electrodynamics of continua with interactions.     

Control of the gas laser output power

The paper considers the influence of a transverse magnetic field on the positive column of a glow discharge on the example of the gas discharge laser. The magnetic field was created using a developed system consisting of several electromagnets and an equalizing device for a greater uniformity of the field. It is shown that as a result of application of the magnetic system charged particles in the discharge gap are shifted to the walls of the discharge tube, which reduces the efficiency of the laser and decreases its output power. Thus, changing the current through the electromagnets the output power of the laser can be varied. The inertia of the impact of the magnetic field on the plasma in the discharge gap was of the order of one millisecond.     

衬底温度对低功率直流磁控溅射ZnO薄膜特性的影响

采用低功率直流反应磁控溅射法,在Si衬底上成功制备出了具有高c轴择优取向的ZnO薄膜,利用X射线衍射仪、荧光分光光度计研究了沉积温度对ZnO薄膜微观结构及光致发光特性的影响.结果表明,合适的衬底温度有利于提高ZnO薄膜结晶质量;在室温下测量样品的光致发光谱(PL),观察到波长位于440nm左右和485nm左右的蓝色发光峰及527nm左右微弱的绿光峰,随衬底温度升高,样品的PL谱中蓝光强度都明显增大,低功率溅射对其蓝光发射具有很重要的影响.综合分析得出440nm左右的蓝光发射应与Zni有关,485nm附近的蓝光发射是由于氧空位形成的深施主能级上电子跃迁到价带顶的结果,而527nm左右的较弱的绿光发射主要来源于导带底到氧错位缺陷能级的跃迁.生长温度主要是通过改变薄膜中缺陷种类及浓度而影响着ZnO薄膜的发光特性的.