4H-SiC肖特基二极管γ射线探测器的模型与分析

 在研究反偏压4H-SiC肖特基二极管作为g射线探测器工作机理的基础上建立了数值模型,模拟了不同偏压和辐照剂量率下探测器的暗电流、工作电流和灵敏度。模拟结果表明:探测器的灵敏度随反向偏压的增加而上升;对于Au/SiC肖特基二极管,有源区掺杂数密度为2.2×10¹⁵ cm^-3时,0 V偏压下探测器的灵敏度为13.9×10^-9 C/Gy,100 V偏压下为24.5×10^-9 C/Gy。计算结果与实验数据符合得较好。     

光纤光栅的压力传感特性研究

对聚合物封装的光纤光栅的压力敏感特性进行了实验研究,在10MPa的压力范围内,光纤光栅中心波长的相对变化与外界压力成良好的线性关系,由于聚合物基底的带动作用,两种不同聚合物封装的光纤光栅的压力灵敏度分别为-3.96×10^-5/MPa和-6.28×10^-5/MPa,提高为裸光栅的20倍和31.7倍。     

宽带腔增强吸收光谱技术应用于痕量气体探测及气溶胶消光系数测量

基于氙灯的非相干宽带腔增强吸收光谱系统, 并将其应用于痕量气体及气溶胶消光系数的测量. 该系统的探测灵敏度通过测量NO₂在520—560 nm波长范围内的吸收得到验证, 最小可探测灵敏度为1.8× 10^-7cm^-1 (1σ, 0.12 s积分时间, 50次平均), 对应的NO₂探测极限～33 nmol/mol. 结合标准气溶胶粒子发生系统, 测量了不同浓度的单分散硫酸铵气溶胶粒子在532 nm波长处的消光系数, 得到粒径为600 nm的硫酸铵气溶胶的消光截面为1.12× 10^-8cm², 与文献报道值1.167× 10^-8cm²相一致, 验证了气溶胶测量的可行性和准确性.     

硅的低温电学性质

本文在20°—300°K研究了室温载流子浓度2×10¹²—1×10²⁰cm^-3含硼或磷(砷)Si的电学性质。对一些p-Si样品用弱场横向磁阻法及杂质激活能法进行了补偿度的测定,并进行了比较。从霍尔系数与温度关系的分析指出,对于较纯样品,硼受主能级的电离能为0.045eV,磷施主能级为0.045eV,在载流子浓度为10¹⁸—10¹⁹cm^-3时发现了费米简并,对载流子浓度为2×10¹⁷—1×10¹⁸cm^-3的p-Si及5×10¹⁷—4×10¹⁸cm^-3的n-Si观察到了杂质电导行为。从霍尔系数与电导率计算了非本征的霍尔迁移率。在100°—300°K间,晶格散射迁移率μ满足关系式AT^-a,其中A=2.1×10⁹,α=2.7(对空穴);或A=1.2×10⁸,α=2.0(对电子)。另外,根据我们的材料(载流子浓度在5×10¹¹—5×10²⁰cm^-3间),分别建立了一条电阻率与载流子浓度及电阻率与迁移率的关系曲线,以提供制备材料时参考之用。     

110keV质子辐照对温控涂层性质的影响

实验研究了1.0×10¹¹—1.0×10¹⁷p/cm²通量范围内110keV质子辐照引起的温控涂层热光性能的变化. 实验表明, 在1.0×10¹¹p/cm²通量辐照下6种温控涂层材料的相对光反射率基本没有变化,当辐射通量在1.0×10¹²—1.0×10¹⁶p/cm²范围变化时,某些低吸收率的温控涂层的太阳吸收率随着辐射通量增加先变小而后又增大.这一特性对于制备更低太阳吸收率的温控涂层具有应用价值.     

电子通量对ZnO/K2SiO3热控涂层光学性能的影响

 研究了电子通量对ZnO/K₂SiO₃热控涂层光学性能的影响。分别采用通量为5×10¹¹/cm²·s，8×10¹¹/cm²·s，1×10¹²/cm²·s 和5×10¹²/cm²·s的电子对试样进行辐照。电子辐照下涂层的光学性能发生了退化，并且发现了退化涂层在空气中的“漂白”现象。分析了ZnO/K₂SiO₃热控涂层光学性能的退化机制，同时讨论了电子通量对太阳光谱吸收系数的影响。实验结果发现，在5×10¹¹～1×10¹²/cm²·s的电子通量范围内，电子通量对ZnO/K₂SiO³热控涂层光学性能的影响相同。因此在这个电子通量范围内，采用加速地面试验来模拟空间的电子辐照效应是有效的。     

Cl/HN3/I2全气相化学激光体系的化学动力学模拟计算

 对Cl/HN₃/I₂产生NCl(a)/I激光的过程进行了化学动力学计算，主要考察了Cl,HN₃和I₂的初始粒子数密度及其配比对小信号增益系数的影响。结果发现,当温度为400K, 初始Cl粒子数密度为1×10¹⁵，1×10¹⁶和1×10¹⁷cm^-3时,小信号增益系数分别达到1.6×10^-4,1.1×10^-3和1.1×10^-2cm^-1，获得最佳小信号增益系数的HN₃和I₂的初始粒子数密度分别为初始Cl粒子数密度的1～2倍和2%～4%。同时，对Cl，HN₃和I₂配比对小信号增益系数和增益持续时间的影响进行了讨论。     

基于沉淀工艺制作四脚氧化锌纳米材料场致发射阴极的研究

采用沉淀法制备四脚氧化锌纳米材料场致发射阴极，将阴极和荧光屏封装起来抽真空并对屏施加电压，测试阴极的发射电流和荧光屏的发光亮度.利用沉淀法制备出面积为(13×15) cm²的阴极，测试结果表明，硅酸钾体积百分比在50×10^-3—83×10^-3范围，硝酸钡浓度在50×10^-4—77×10^-4 M范围，四脚氧化锌的浓度在82×10^-4—12×10^{-3相似文献}   

中子衍射仪的构造与性能

本文描述了一台中子衍射仪,并检验了这台仪器的性能和精确度。在采用NaCl单晶体作单色器,选择中子波长为1.06埃时,仪器的分辨率△λ/λ=0.026单色中子束强度为3×10⁶中子/分。利用这台衍射仪测量了NaCl单晶体样品和α-Fe多晶样品的中子衍射图。     

克里奇中间体CH2OO与CF3CF=CF2反应的动力学研究

本文使用OH激光诱导荧光方法研究了结构最简单的克里奇中间体CH₂OO和CF₃CF=CF₂的反应动力学. 在压强为10 Torr条件下,测量了温度在283,298,308和318 K的反应速率常数,分别为(1.45±0.14)×10^-13,(1.18±0.11)×10^-13,(1.11±0.08)×10^-13和(1.04±0.08)×10^-13 cm³·molecule^-1·s^-1. 根据阿伦尼乌斯方程,获得该反应的活化能为(-1.66±0.21) kcal/mol. 在6.3∽70 torr压力范围内,未观察到该反应的速率常数存在压力相关.     

Improved sensitivity in the search for a parity-violating energy difference in the vibrational spectrum of the enantiomers of CHFClBr

The theoretical prediction that enantiomers of chiral molecules have different spectra because of parity violation associated with neutral currents in the weak interaction has been experimentally looked for. Last searches of a frequency difference in the vibrational spectrum of the enantiomers of CHFClBr obtained with our infrared saturation spectrometer is presented. The frequencies of a saturation resonance of separated enantiomers of CHFClBr have been compared at a 5×10^-14 level. A residual pressure shift probably induced by uncontrolled impurities of the samples has been observed and found to limit our experimental sensitivity. Finally no parity violating frequency difference is observed within the present sensitivity of 2.5×10^-13. A new experimental scheme is proposed which should let the parity violation effect observable. Received 22 January 2002 Published online 19 July 2002     

High resolution ethylene absorption spectrum between 6035 and 6210 cm-1

A two-channel photo-acoustic spectrometer (PA spectrometer) with a near infrared diode laser was used for taking measurements of a high resolution ethylene absorption spectrum. A semiconductor TEC-100 laser with an outer resonator generates a continuous single-frequency radiation in the range 6030–6300 cm^-1. A newly designed model of photo-acoustic detector (PAD) in the form of a ring type resonator provides for measurement of weak absorption cross-section equal to 4×10^-23 cm²/mol at a laser radiation power of 3 mW. The PAD threshold sensitivity is 2×10^-9 cm^-1 Hz^-1/2 W, when the signal to noise ratio equals to 1. The ethylene absorption spectrum within the range 6035–6210 cm^-1 was measured for the first time with a spectral resolution of 10 MHz. The reported line centre positions have an uncertainty of ± 0.0005 cm^-1. The precise measurements of ethylene absorption cross-sections were carried out using the mixture of high purity ethylene and broadening gas (nitrogen) at the mixture ratio 1:50–1:200. Measurements were carried out at a mixture pressure of about 4.2 kPa. PACS 42.62.Fi; 42.55.Px     

LED-based Fourier-transform spectroscopy of H2 18O in the range 15000–15700 cm−1

The spectrum of H₂ ¹⁸O in the range 15000–15700 cm^?1 has been recorded for the first time on a Fourier-transform spectrometer using a high-brightness light-emitting diode as a radiation source. The measurements have been conducted at room temperature with a resolution of 0.05 cm^?1. A threshold sensitivity in absorption of 2 × 10^?7 cm^?1 has been achieved due to both the use of a light-emitting diode and optimization of the multipass cell with a base length of 60 cm, which ensured a 19.2-m length of the absorbing layer. A high signal-to-noise ratio (S/N = 2000–10000) made it possible to record about 670 water-vapor lines with intensities of 1.0 × 10^?26–2.2 × 10^–24 cm/mol at 296 K. The energies of 265 vibrational-rotational levels of the H₂ ¹⁸O molecule are determined and attributed to seven vibrational states, namely, (033), (113), (212), (231), (311), (330), and (410).     

ΔT-window neutron spectrometer

A high resolution neutron spectrometer making use of a ΔT-window filter for the analyser and time-of-flight technique for analysing incident neutron energy has been designed. The spectrometer will provide a continuously variable energy resolution ΔE from 40–50μeV at ∼ 5230μeV. The range of energy transfer allowed is −1450μeV to +2950μeV and the range of wavevector transferQ allowed is 0·82–3·06 ?⁻¹. Depending on the resolution used, the counting rates are expected to vary from 28–60 × 10³ counts/hr if one assumes 10% isotropic elastic scattering from the sample.     

A three‐crystal spectrometer for high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy and X‐ray emission spectroscopy at SSRF

A Johann‐type spectrometer for the study of high‐energy resolution fluorescence‐detected X‐ray absorption spectroscopy, X‐ray emission spectroscopy and resonant inelastic X‐ray scattering has been developed at BL14W1 X‐ray absorption fine structure spectroscopy beamline of Shanghai Synchrotron Radiation Facility. The spectrometer consists of three crystal analyzers mounted on a vertical motion stage. The instrument is scanned vertically and covers the Bragg angle range of 71.5–88°. The energy resolution of the spectrometer ranges from sub‐eV to a few eV. The spectrometer has a solid angle of about 1.87 × 0^?3 of 4π sr, and the overall photons acquired by the detector could be 10⁵ counts per second for the standard sample. The performances of the spectrometer are illustrated by the three experiments that are difficult to perform with the conventional absorption or emission spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

在有机染料溶液中简并的四波混频作用和位相复共轭

本文研究了近共振吸收增强的有机染料溶液中简并的四波混频作用和位相复共轭特性。由直接位相复共轭得到了高质量的再现象。再现象分辨率为6条线/毫米。对于浓度为2.5×10^-5克分子若丹明6G酒精溶液,得到非线性反射率达10％。 关键词：     

C2H2 Overtones Near 12300 cm-1 Revisited with a Very Sensitive Cavity Ring-down Spectrometer

利用单模连续的钛宝石激光器, 构建了一台光腔衰荡光谱仪, 其可探测的最小吸收可达1.8×10^-10/cm. 该光谱仪被用来记录C₂H₂分子在12240～12350 cm^-1的泛频光谱. 与在同一波段测量的已报到的CRDS和激光腔内吸收光谱仪结果比较,本测量同时具有更好的灵敏度和精度. 由此,获得了乙炔分子在12290.12、12311.82和12350.61 cm^-1附近高泛频谱带更准确的振转参数     

Doppler-limited spectra of the ν3 vibration of 12CH4 and 13CH4

The tetrahedral splittings in the P and R branches of the ν₃ band of natural methane have been examined with Doppler-limited resolution using a difference-frequency spectrometer. The spectra obtained by this difference-frequency mixer are compared to recent high-resolution grating spectrometer studies of ¹²CH₄ and enriched ¹³CH₄. The resolution, selectivity and precision are improved over the conventional methods. The mixing spectrometer utilizes tunable, narrow linewidth infrared radiation generated in the nonlinear optical crystal, LiNbO₃ as the beat frequency between a CW argon ion and a tunable dye laser. This spectrometer covers the 2.2 to 4.2 μm infrared spectrum with an instrumental resolution of 5 × 10^?4 cm^?1 and continuous scans up to ～1 cm^?1 and with ir power ～1 μW.     

A modified electron bombardment type ion source for the study of solids

A modified electron bombardment type ion source suitable for use with mass spectrometer is described. Ion formation occurs throughout a relatively large volume in the ionisation box, since no magnetic field is used to collimate the ionising electrons. A sensitivity of 2 × 10⁻⁵ amp/torr is obtained for an ion extraction energy of 2 keV and 200 mass resolution. Trajectory tracing has been used to study the operation of the ion source. Capability of the ion source to analyse solid samples in microgram quantity was tested by studying evaporation of BaO from tungsten.     

NOISE AND SENSITIVITY IN POLYSILICON PIEZORESISTIVE CANTILEVERS

Piezoresistive cantilevers with dimensions of 200×50×1.8μm³ have been fabricated from polycrystalline silicon using reactive ion etching (RIE) and back etching processes. Full Wheatstone bridges have been designed symmetrically on-chip, with two resistors placed on the cantilevers and two resistors on the substrate. The differential measurements of the two cantilevers can reduce the thermal shift of the signal in the system and the external noise in the laboratory. The characteristics of the fabricated cantilevers have been analysed by measuring the noise and the sensitivity. The measured noise spectra show that the 1/f noise is the dominant noise source at low frequencies. With the linear relation between 1/f noise and bias voltages, the Hooge factor (α) was calculated to be 0.0067. The 1/f noise was explained in terms of a lattice scattering model, which occurs in the depletion region of the grains. The displacement sensitivity of the cantilevers ((ΔR)/Rz^-1) was calculated to be 1×10^-6nm^-1 by measuring the resistance change and the vertical deflection of the cantilever. The gauge factor of the piezoresistive cantilever was calculated to be 19. At a 3 V bias voltage and 1000 Hz measurement bandwidth, 1 nm of minimum detectable deflection has been obtained.