An analogue front-end ASIC prototype designed for PMT signal readout

The Water Cherenkov Detector Array(WCDA) is one of the core detectors in the Large High Altitude Air Shower Observatory(LHAASO),and it consists of 3600 photomultiplier tubes(PMTs).Both high resolution time and charge measurement are required over a large dynamic range from 1 photoelectron(P.E.) to 4000 P.E.The prototype of an analogue front-end Application Specific Integrated Circuit(ASIC) fabricated using Global Foundry 0.35 μm CMOS technology is designed to read out the PMT signal in the WCDA.This ASIC employs leading edge discrimination and an(RC)~4 shaping structure.Combined with the following Time-to-Digital Converter(TDC) and Analog-to-Digital Converter(ADC),both the arrival time and charge of the PMT signal can be measured.Initial test results indicate that time resolution is better than 350 ps and charge resolution is better than 10% at 1 P.E.and better than 1% with large input signals(300 P.E.to 4000 P.E.).Besides,this ASIC has a good channel-to-channel isolation of more than 84 dB and the temperature dependency of charge measurement is less than 5% in the range 0-50°C.     

Microwave photonic crystal on the slot transmission line with a ferroelectric film

A microwave electrically tunable photonic crystal based on a periodically width-modulated slot transmission line with a ferroelectric film is investigated for the first time. The dispersion and transmission characteristics of electromagnetic waves propagating in such a structure are calculated. The electric control over photonic crystal characteristics is simulated.     

利用地磁场综合模型CM4分析中国大陆地区地磁场变化

第四代地磁场综合模型CM4是迄今为止将地磁场的内源场和外源场分离得最为彻底的数学模型.利用该模型结合Taylor多项式模型,基于1960—2000年期间中国大陆地区的实测数据,计算并分析了以10a为间隔的内源场和外源场的变化情况,通过将1960—1990年的所有磁异常点归算至2000年以分析地壳磁异常场的总体分布趋势.结果显示:地磁北向分量X的内源场强度总体呈逐年减弱的趋势,从1960年到2000年共下降了约750nT,外源场强度总体呈先增强后减弱的趋势,共下降了约32nT;地磁东向分量Y的内源场强度总体呈先减弱后增强的趋势,1960—2000年期间共上升了约40nT,外源场强度总体呈先减弱后增强再减弱的趋势,共上升了约3.8nT;地磁垂直分量Z的内源场变化趋势与Y分量类似,共上升了约600nT,外源场总体呈先减弱后增强的趋势,共上升了约4.6nT.对于地壳磁异常场,X分量、Z分量、地磁总强度F和地磁水平分量H在中国大陆地区都为负异常分布,X分量和H分量的负异常强度随经度增加而减弱,Z分量和F分量则相反;Y分量和磁偏角D的分布较为类似,在中国的中西部大部分地区为正异常,强度随经度增加而减弱,磁倾角I主要以负异常为主,负异常强度随经度增加而增强.     

SiC纳米棒的紫外发光研究

采用聚硅氮烷前驱体在高温常压下热裂解的方法制备了3C-SiC纳米棒,在室温下观察到来自纳米棒的378 nm（33?eV） 强紫外发射. 利用扫描电子显微镜、透射电子显微镜、高分辨透射电子显微镜和X射线衍射对样品的形貌和结构进行表征,观察到在该结构中存在类似6H-SiC结构的三层堆垛层错. 利用室温荧光光谱和室温荧光衰减曲线研究了强紫外发射的产生机理,紫外发射来源于3C-SiC纳米棒中的三层堆垛层错的发光. 关键词： 碳化硅 纳米棒 光致发光     

碳掺杂硼氮纳米管电子场发射的第一性原理研究

对闭口硼氮纳米管（BNNT）顶层掺碳体系,运用第一性原理研究了电子场发射性能.结果表明,掺碳的BNNT体系电子结构变化显著;外电场愈强,体系态密度向低能端移动幅度愈大,且最高占据分子轨道（HOMO）/最低未占据分子轨道（LUMO）能隙愈小.体系态密度和局域态密度,HOMO和LUMO及其能隙分析一致表明,各种碳掺杂体系中C_eqBNNT的场发射性能最佳. 关键词： 硼氮纳米管 碳掺杂 第一性原理     

Muon Motion Induced by a Superintense Laser in Muon‐Catalyzed Fusion

Considering the mixture after muon‐catalyzed fusion (μ CF) reaction as overdense plasma, we study muon motion in the plasma produced by a superintense linearly polarized femtosecond laser pulse. Muon drift along the propagation of laser radiation remains after the end of the laser pulse. At the peak laser intensity of 10²¹W/cm², muon goes from the skin layer into field‐free matter at short time which is much less than the pulse duration, before the laser pulse reaches its maximum. Besides, the influence of the laser on other particles in the plasma is less. Hence, this work can avoid muon sticking to alpha (α) effectively and reduce muon‐loss probability in μ CF. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

氮掺杂及水分子吸附碳纳米管电子场发射第一性原理研究

对闭口碳纳米管(CNT)顶端分层掺氮及吸附不同数目水分子体系,运用第一性原理研究了有电场存在时的电子场发射性能.结果表明：掺氮并吸附水分子的CNT结构稳定;外电场愈强、水分子数愈多,体系态密度(DOS)向低能端移动幅度愈大且最高分子占据轨道(HOMO)/最低分子空轨道(LUMO)能隙愈小.吸附能,DOS/LDOS,HOMO/LUMO及其能隙分析一致表明,第三层氮掺杂CNT吸附不同数目水分子体系的场发射性能最佳. 关键词： 氮掺杂 水吸附 密度泛函理论 电子场发射     

LUND面积定律产生子在R值测量中的应用

对Lund弦碎裂模型强子化面积定律严格求解,得到e⁺e^－湮没产生少体初始强子态的遍举分布.基于面积定律的新产生子LUARLW在2—5GeV能区的模拟结果与BES数据的多种谱分布符合很好,用于BES上强子产生总截面测量的强子探测效率的估计.     

波长调制吸收光谱技术的燃气轮机燃烧室温度组分二维分布测量方法

可调半导体激光光谱技术(TDLAS)可实现温度、组分浓度等多参数同时测量,具有体积小、响应速度快、环境适应性高等优点,逐渐成为燃烧流场诊断的主要手段之一.TDLAS光谱测量常采用直接吸收技术和波长调制技术,其中强度归一化的波长调制技术,适合存在振动、湍流等致光束偏转效应和强辐射本底等恶劣应用环境条件的燃气轮机流场参数测...     

General M-lumps,T-breathers,and hybrid solutions to (2+1)-dimensional generalized KDKK equation

A special transformation is introduced and thereby leads to the N-soliton solution of the(2+1)-dimensional generalized Konopelchenko-Dubrovsky-Kaup-Kupershmidt(KDKK) equation.Then,by employing the long wave limit and imposing complex conjugate constraints to the related solitons,various localized interaction solutions are constructed,including the general M-lumps,T-breathers,and hybrid wave solutions.Dynamical behaviors of these solutions are investigated analytically and graphically.The solutions obtained are very helpful in studying the interaction phenomena of nonlinear localized waves.Therefore,we hope these results can provide some theoretical guidance to the experts in oceanography,atmospheric science,and weather forecasting.