一种提高相对论返波管功率容量的方法

 对相对论返波管实验中射频击穿现象进行了分析和数值模拟研究,发现谐振反射器和慢波结构的局部场增强诱导了场致电子发射,引起了金属表面的射频击穿,通过研究分析,提出采用分布反馈式谐振反射器,并采用梯形倒角非均匀慢波结构替换正弦慢波结构的方法来抑制射频击穿。数值模拟研究表明,在微波功率2 GW时,改进后的反射器最大场强由1.4 MV/cm降低为570 kV/cm,慢波结构表面最大电场由1.1 MV/cm降低到780 kV/cm。改进后的结构在二极管电压765 kV时获得了微波功率2.2 GW、脉宽45 ns的实验结果,微波功率和脉宽得到显著提升。     

Novel high-voltage self-adaptive power device based on interface charge＊

This paper presents a novel high-voltage lateral double diffused metal-oxide semiconductor （LDMOS） with self- adaptive interface charge （SAC） layer and its physical model of the vertical interface electric field. The SAC can be self-adaptive to collect high concentration dynamic inversion holes, which effectively enhance the electric field of dielectric buried layer （EI） and increase breakdown voltage （BV）. The BV and EI of SAC LDMOS increase to 612 V and 600 V/tim from 204 V and 90.7 V/ttm of the conventional silicon-on-insulator, respectively. Moreover, enhancement factors of r/which present the enhanced ability of interface charge on EI are defined and analysed.     

Ultra-low on-resistance high voltage (>600 V) SOI MOSFET with a reduced cell pitch

A low specific on-resistance (R S,on) silicon-on-insulator (SOI) trench MOSFET (metal-oxide-semiconductor-field-effect-transistor) with a reduced cell pitch is proposed.The lateral MOSFET features multiple trenches:two oxide trenches in the drift region and a trench gate extended to the buried oxide (BOX) (SOI MT MOSFET).Firstly,the oxide trenches increase the average electric field strength along the x direction due to lower permittivity of oxide compared with that of Si;secondly,the oxide trenches cause multiple-directional depletion,which improves the electric field distribution and enhances the reduced surface field (RESURF) effect in the SOI layer.Both of them result in a high breakdown voltage (BV).Thirdly,the oxide trenches cause the drift region to be folded in the vertical direction,leading to a shortened cell pitch and a reduced R S,on.Fourthly,the trench gate extended to the BOX further reduces R S,on,owing to the electron accumulation layer.The BV of the MT MOSFET increases from 309 V for a conventional SOI lateral double diffused metal-oxide semiconductor (LDMOS) to 632 V at the same half cell pitch of 21.5 μm,and R S,on decreases from 419 m · cm 2 to 36.6 m · cm 2.The proposed structure can also help to dramatically reduce the cell pitch at the same breakdown voltage.     

Research on high-voltage 4H-SiC P-i-N diode with planar edge junction termination techniques

The planar edge termination techniques of junction termination extension (JTE) and offset field plates and field-limiting rings for the 4H-SiC P-i-N diode were investigated and optimized by using a two-dimensional device simulator ISE-TCAD10.0. By experimental verification, a good consistency between simulation and experiment can be observed. The results show that the reverse breakdown voltage for the 4H-SiC P-i-N diode with optimized JTE edge termination can accomplish near ideal breakdown voltage and much lower leakage current. The breakdown voltage can be near 1650 V, which achieves more than 90 percent of ideal parallel plane junction breakdown voltage and the leakage current density can be near 3 × 10-5 A/cm2.     

Analysis of statistical nature of electrical breakdown time delay in nitrogen at 6.6 mbar pressure in presence of positive ions and N(4S) atoms

On the basis of the mean value of electrical breakdown time delay and the standard deviation of electrical breakdown time delay σ dependence on the afterglow period τ, the mechanisms which dominantly influence to breakdown initiation in nitrogen were separated. It was shown that the positive ions formed in mutual collision of long‐lived metastable molecules have a dominant role in breakdown initiation for τ values up to 70 ms. The metastable molecules were derived from previous breakdown and discharge. In this case σ ≪ t_d and the total time delay t_d is approximately equal to formative time t_f which decreases in value with the increase of overvoltage. When positive ions have a dominant role in the breakdown initiation the Gaussian distribution describes data of t_d ≈ t_f very well. For τ > 1 s, N (⁴S) atoms formed in previous breakdown and discharge, have a dominant role in the breakdown initiation. Then, σ ≈ and Laue's distribution, which is valid for statistical time delay t_s, describes t_d data very well (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

激光诱导击穿光谱实验装置的参数优化研究

为了使激光诱导击穿光谱(LIBS)实验装置中的多个关键参数达到最优化设置,以便更好地服务于煤质分析,实验中对这些参数与煤粉等离子体中待测元素发射谱线信噪比间的关系进行了详细研究,并根据信噪比大小来进行最优化参数的选择.实验结果表明,对于本LIBS实验装置,其最优化参数设置是将激光脉冲能量设为120 mJ·Pulse-1...     

强直流场介质表面次级电子倍增效应的数值模拟研究

通过粒子模拟方法,实现了强直流场下介质表面击穿过程中次级电子倍增效应的数值模拟.具体研究了强直流场场强、介质表面光滑度和次级电子产生率等对次级电子倍增的影响,以及倾斜直流场和外加磁场对次级电子倍增的抑制.结果表明,选择次级电子产生率较低的介质材料和倾斜强直流场可以有效降低次级电子倍增效应的强度,而外加磁场必须超过一定值时才可以有效降低次级电子倍增强度. 关键词： 次级电子倍增 强直流场 介质表面击穿 数值模拟     

Quantitative analysis of cement powder by laser induced breakdown spectroscopy

Determination of elemental composition of cement powder plays an important role in the cement and construction industries. In the present paper, Laser induced breakdown spectroscopy (LIBS) is used for measuring the concentration of cement ingredient. Cement powder samples are pressed into pellets. Laser pulses are focused on the surface of pellets. A microplasma is formed in the front of samples. The plasma emission contains information about the elemental composition of the samples. By assumption of local thermodynamic equilibrium (LTE) and using several standard cement samples, a calibration curve is prepared for each element. The major and minor elements of cement such as Ca, Si, K, Mg, Al, Na, Ti, Mn and Sr are qualitatively and quantitatively determined. For verification of LTE conditions, plasma parameters such as plasma electron temperature and electron density are computed. According to the obtained results, the LIBS technique could be a suitable method for determination of elemental composition in the cement production industries.     

激光诱导击穿光谱数据特征自动提取方法研究

根据激光诱导击穿光谱(LIBS)展宽主要为非线性Lorentz函数模型,利用Levenberg-Marquardt(L-M)算法对该理论模型中的待定参数进行优化估值,扣除了光谱信号中的连续背景,校正和还原了峰位和峰强,并对拟合数据点自动提取方法进行了分析;以MatrixVB与VB混合编程相结合,实现了基于L-M算法的L...     

土壤重金属铬元素的激光诱导击穿光谱定量分析研究

利用Nd ∶YAG脉冲激光器(波长:1064 nm)作为光源,在实验室自然大气环境下诱导产生土壤激光等离子体,通过等离子体原子发射光谱法定量分析了国家标准土壤样品中元素Cr的含量.实验上研究了在最佳实验条件下土壤中Cr的LIBS分析谱线,测定了Cr元素的定标曲线.实验结果表明,Cr元素浓度在(60—400)×10^-6范围内,元素含量与光谱线强度之间有较好的线性关系;元素Cr浓度分析测量的相对标准偏差(RSD)为7.89%,定量分析结果与标准值的相对偏差为5.3%,Cr元素的检测限为1 关键词： 土壤污染 定量分析 激光诱导击穿光谱 定标曲线