Studies on the mechanisms of powerful terahertz radiations from laser plasmas

A survey on the mechanisms of powerful terahertz (THz) radiation from laser plasmas is presented.Firstly,an analytical model is described,showing that a transverse net current formed in a plasma can be converted into THz radiations at the plasma oscillation frequency.This theory is applied to explain THz generation in a gas driven by two-color laser pulses.It is also applied to THz generation in a tenuous plasma driven by a chirped laser pulse,a few-cycle laser pulse,a DC/AC bias electric field.These are well verified by particle-in-cell simulations,demonstrating that THz radiations produced in these approaches are nearly single-cycles and linear polarized.In the chirped laser scheme and the few-cycle laser scheme,THz radiations with the peak field strength of tens of MV/cm and the peak power of gigawatt can be achieved with the incident laser intensity less than 10 17 W/cm 2.     

Multi-modal calculations of prompt fission neutrons from 238U（n,f） at low induced energy

Properties of prompt fission neutrons from ²³⁸U(n, f) are calculated for incident neutron energies below 6 MeV using the multi-modal model, including the prompt fission neutron spectrum, the average prompt fission neutron multiplicity, and the prompt fission neutron multiplicity as a function of the fission fragment mass υ(A) (usually named “sawtooth” data) The three most dominant fission modes are taken into account. The model parameters are determined on the basis of experimental fission fragment data. The predicted results are in good agreement with the experimental data.     

Determination of the time resolution for neutron scintillation detectors by multi-coincidence measurement

Based on the multi-coincidence measurement, the time resolution of three liquid scintillation detectors (BC501A) were determined strictly by solving the coincidence equations, where the influence from electronics estimated by self coincidence measurement as well as the background had been considered. The result of this work agreed well with the result that was deduced from the traditional method, and it will be helpful to analyze the energy resolution of neutron time of flight spectra measured by using such detectors at CIAE (China Institute of Atomic Energy).     

近场强度分布对线性相位反演算法复原效果的影响

利用数值仿真的方法详细的分析了近场强度分布对线性相位反演算法复原效果的影响.对近场强度分布分别为倾斜、环形和高斯随机型的情况下的复原结果与光强均匀时的复原结果进行对比,结果表明像倾斜型这种大部分为奇函数的近场强度分布对复原效果的影响比较恶劣;而像环形、随机型这样的偶函数或大部分为偶函数的近场强度分布对复原效果的影响则不...     

用于光纤法布里-珀罗传感器腔长互相关解调的光楔的数学模型研究

光楔是实现光纤法布里-珀罗(F-P)传感器互相关解调的重要光学元件.根据互相关解调的原理分析了造成光楔和光纤F-P传感器F-P腔的反射光相位不同的因素,进而建立了光楔的干涉光强的数学模型,在此基础上对具有不同反射率的光楔的干涉光强进行了数值仿真,和相同反射率的光纤F-P传感器F-P腔的干涉光强对比之后建立了光楔的简化数...     

Transmission-mode GaN photocathode based on graded Al_xGa_(1-x)N buffer layer

We create a GaN photocathode based on graded Alx Ga1-x N buffer layers to overcome the influence of buffer-emission layer interface on the photoemission of transmission-mode GaN photocathodes.A gateshaped spectral response with a 260-nm starting wavelength and a 375-nm cut-off wavelength is obtained.Average quantum efficiency is 15% and short wavelength responses are almost equivalent to long wavelength ones.The fitted interface recombination velocity is 5×104 cm/s,with negligible magnitude,proving that the design of the graded buffer layers is efficient in obtaining good interface quality between the buffer and the emission layer.     

相对论和非相对论理论模型研究奇异核的性质

采用相对论和非相对论理论模型可描述奇异核的性质 .相对论平均场理论预言了2 6,2 7,2 8P存在一个质子晕 ,而27,28,29S存在两个质子晕 .最近 ,MSU的最新的实验发现了2 6,2 7,2 8P核存在一个质子晕.采用相对论 Hartree- Fock理论研究了 Fock项和矢量介子对奇异核性质的贡献,研究表明交换项和矢量介子对非常丰中子核性质的影响非常不同于对稳定线附近核性质的影响.同时,采用形变的Hartree- Fock- Bogoliubov理论研究了某些轻核同位素链的性质和形变.     

聚乙烯吡咯烷酮中纳米邻苯二甲酸铽络合物的不寻常荧光特性

本文以聚乙烯吡咯烷酮为基质制得了纳米邻苯二甲酸铽络合物并对其荧光光谱进行了研究 ,结果表明聚乙烯吡咯烷酮中纳米邻苯二甲酸铽络合物主要荧光发射峰的相对强度及峰的半高宽有明显变化 ,并且主峰附近分化出两个峰。     

V型原子与光场拉曼相互作用传送未知原子态

未知量子态从一个地方到另一个地方的隐形传送在量子信息领域中有非常重要的作用,提出了一种利用简并V型三能级原子与振幅很大的单模相干态腔场的拉曼相互作用来传送未知原子态的方案。     

二（2,4,4—三甲基戊基）膦酸稀土配合物的振动光谱

测定了二（２，４，４－三甲基戊基）膦酸（ＢＴＭＰＰＡ）及其稀土配合物Ｌｎ（ＢＴＭＰＰ）３在４０００～５０ｃｍ＾－１光谱区内的ＦＴ－ＩＲ光谱和部分配合物的激光拉曼光谱，对其谱带进行了经验归属。发现稀土氧键具有较高的离子键特性。由Ｌｎ－Ｏ伸缩振动频率值算出其近似力常数约８ｍ ｄｙｎ／ｎｍ。