密封容器中钚材料同位素丰度和年龄的测量

根据相对效率法的原理，利用PC/FRAM分析软件，开展了用高分辨γ谱仪测量密封容器中钚材料的同位素丰度和年龄的实验研究.研究结果表明，同位素丰度和年龄的分析精度随能谱测量精度的提高而提高，如果能谱的测量精度不够，通过PC/FRAM分析得出的钚材料的同位素丰度和年龄有偏低的可能.因此，在能谱测量过程中，建议通过监测某个特征峰的峰面积计数来判定239Pu丰度和年龄的测量精度是否已满足测量要求.Based on the concept of relative detection efficiency, some experiments have been conducted to measure the isotopic abundance and the age of the plutonium material in a sealed container by a high-resolution γ-ray spectrometer. The PC/FRAM software analyzes the spectra. The study shows that the analysis precision of the isotopic abundance and the age will rise as the spectral measurement precision increases, and that If the spectral measurement precision is not enough, the analyzed results by the PC/FRAM software might be lower. Hence, the study suggests that a spectral peak is monitored to show lights on the spectral measurement precision during the process of spectrum acquirement.     

基于钚特征γ谱的核弹头模板技术可行性研究

基于核弹头钚特征γ谱的模板测量技术是深度核裁军核查的重要技术手段之一。 以Monte Carlo数值模拟为手段, 计算假想核弹头γ射线的输运过程, 分析在可能的核查场景中, 通过构建基于特征γ谱子能区计数的相对测量的比对匹配算法, 分析并建立了由成分匹配和结构匹配组成的核弹头模板测量技术, 该方法较好地消除了绝对测量距离误差和时间误差的影响。The nuclear warhead detecting technology based on a template with γ spectrum of Plutonium is an important verification means in the deep irreversible nuclear disarmament. In order to obtain the γ ray spectra, γ ray transportation processing for the hypothesis nuclear warhead model has been simulated. In a possible nuclear disarmament verification case, the template matching algorithm based on the relative counts of the explored γ spectrum of Plutonium in sub energy region is built up, and the template technology of nuclear warhead composed of element matching and structure matching is established. This method could eliminate the effect of the error caused by the detecting distance and time.     

160Tb β-衰变纲图研究

对由160Tb的β-衰变而产生的γ射线利用GeLi和HpGe探测器进行了单谱和γ γ符合谱的测量.根据单谱和γ-γ符合谱的测量结果给出了160Tb的β-衰变纲图.并用绝热对称转动模型对160Dy中转动带与振动带的耦合参数Zγ值进行了计算,得出从振动带到转动带的γ跃迁几率B(E2)值之比不能通过唯一的Zγ值来描述.Tb/β-衰变;衰变纲图;带耦合参数 The γtransitions in 160Tb decay has been studied by γ ray spectroscopy and γ γ coincidence measurements with high efficiency Ge(Li) and HpGe detectors. The β- decay scheme of 160Tb was proposed according to the results of γ ray spectroscopy and γ γ coincidence measurement. The band mixing parameter Zγ for 160Dy is determined and it is observed that the measured γ ray branching ratios do not lead to a unique value of Zγ for 160 Dy.     

Design and gamma sensitivity measurement of a novel dual-emitter vacuum Compton detector

A novel dual-emitter vacuum Compton detector (D-VCD) with higher gamma ray detecting efficiency is proposed. The emitters are made of Ta--Al clad metal. The gamma ray sensitivity is studied by Monte Carlo simulation using the MCNP code. A comparison between calculations and results measured by using the 1.25~MeV gamma ray of Co-60 is also performed. Experimental sensitivities for two sample D-VCDs with the same materials and structures are 1.92×10^ - 20 and 2.02×10^ - 20~C.cm²/MeV separately, which are consistent with the simulation result of 1.98×10^ - 20~C.cm²/MeV and are 4 times higher than that of VCD with a single Fe emitter. According to the simulation results, in a gamma energy range from 0.5 to 3~MeV, the maximum sensitivity variance for the D-VCD is less than 15%, and less than 5% in a range from 1 to 2~MeV in particular. The novel D-VCD is applicable to the detection of intense pulse gamma rays.     

Self-attenuation corrections calculated by LabSOCS Simulations for gamma-spectrometric measurements with HPGe detectors

Simulations from Laboratory Sourceless Object Counting System (LabSOCS) software were used to determine self-attenuation correction factor, which is defined as the efficiency ratio of the sample with the absorbing medium to that of the sample without absorbing medium. The semi-empirical self-attenuation correction formula F(μ) used to correct self-attenuation of a sample was applied. A comparison of the two methods reveals that formula of sample with φ 75 mm× 25 mm and φ75 mm× 10 mm can be, respectively, used in the self-attenuation correction for μ in the ranges of 0 to 0.5 cm^-1 and 0.5 cm^-1 to 2.0 cm^-1, indicating that the semi-empirical formula will not be used when μ has exceeded the interval. The semi-empirical formula value is consistent with the experimental value, within 7.9% accuracy. Therefore, this method is correct and effective. Both of our two methods can accurately produce a relative self-attenuation correction factor when the composition of the sample is known. The self-attenuation correction of a sample with unknown composition can only be carried out using a semi-empirical formula method.     

C/O γ能谱测井新的解析理论和方法

报道了快中子非弹性散射γ能谱测井(C/O γ能谱测井)新的解析理论和方法, 也就是由C/O能谱测井仪在井眼中获取地层的快中子非弹性散射γ射线、 NaI(Tl)探测器测量得到的256道谱, 再由实测非弹谱确定地层中主要元素C, O, Si, Ca和Fe等对非弹γ谱的贡献分额, 利用同一地层F因子相同, 求出C产额与O产额比, C的百分含量与O的百分含量和原子含量比, 及Ca和Si相应比值.A new analyzing theory and method of C/O spectrometry logging is reported. Fast neutron enelastic scattering γ ray spectra(256 channels) were acquired in borehole by NaI(Tl) detector. The enelastic scattering γ ray from major elements C, O, Si, Ca, Fe, etc. have the fractions of mixed enelastic spectrum in formation respectively. Because F factor is the same for identical formation, then the ratio of yield of C to O, the ratio of weight percent of C to O, and the ratio of atoms C to O could be found, and the corresponding ratio of Ca to Si was found.     

Spin polarized current injection and transportation in a double T-shaped organic spintronic device

A double T-shaped device model is constructed to investigate the spin polarized current injection and transportation properties in organic semiconductors.Based on the spin diffusion theory and Ohm’s law and considering the different charge-spin relationship of the special carriers in organic semiconductors,the current spin polarization has been obtained.Effects of the branch current ratio and the polaron proportion on the spin polarized current injection efficiency are studied.From the calculation,it is found that the improvement of the spin polarized current injection efficiency can be obtained by adjusting the branch current ratio;moreover,high polaron proportion in organic semiconductors is beneficial for obtaining high current spin polarization.     

Analysis and applications of a frequency selective surface via a random distribution method

A novel frequency selective surface （FSS） for reducing radar cross section （RCS） is proposed in this paper. This FSS is based on the random distribution method, so it can be called random surface. In this paper, the stacked patches serving as periodic elements are employed for RCS reduction. Previous work has demonstrated the efficiency by utilizing the microstrip patches, especially for the reflectarray. First, the relevant theory of the method is described. Then a sample of a three-layer variable-sized stacked patch random surface with a dimension of 260 mm x 260 mm is simulated, fabricated, and measured in order to demonstrate the validity of the proposed design. For the normal incidence, the 8-dB RCS reduction can be achieved both by the simulation and the measurement in 8 GHz-13 GHz. The oblique incidence of 30° is also investigated, in which the 7-dB RCS reduction can be obtained in a frequency range of 8 GHz-14 GHz.     

Sample indexed spatial orthogonal frequency division multiplexing

Optical spatial modulation(OSM) is a multiple-transmitter technique that can provide higher data rates with low system complexity as compared with single-input single-output systems. Orthogonal frequency division multiplexing(OFDM) is widely implemented to achieve better spectral efficiency in wireless channels. Asymmetrically clipped optical OFDM(O-OFDM) and DC-biased O-OFDM are two well-known O-OFDM techniques suitable for intensity-modulation direct-detection optical systems. In this work, sample indexed spatial OFDM(SIS-OFDM) is proposed to combine OSM and O-OFDM in a novel way and achieve significant performance gain. By assigning time-domain samples of the O-OFDM transmit symbol to different transmitters, SIS-OFDM achieves much better spectral efficiency and reduces computational complexity at the transmitter as compared with previous work that combines OSM with O-OFDM in the frequency domain. We also consider the impact of optical source biasing on overall performance, and the relative performance of imaging receiver(ImR) versus non-imaging receiver(NImR) design for our proposed SIS-OFDM technique. Results indicate that for an Ntx × Nrx multiple-input multiple-output configuration where Ntx = Nrx = 4, SIS-OFDM using ImR can achieve up to 135 dB of signal-to-noise ratio gain over comparable system using a NImR. Also, using Nsc number of O-OFDM subcarriers provides up to Nsc × log2(Ntx) additional bits per symbol of spectral efficiency over techniques that combine OSM and O-OFDM in the frequency domain.     

Measurement of the Gamma Ray Energy in Parapositronium 2γ Decay

Using a silica aerogel sample with oxygen gas introduced as the positronium source,the γ ray energy from the parapositronium 2γ annihilation has been measured as 510998.7(2.5)eV by means of the comparison with the known γ energy 511856.2(2.3)eV of the ¹⁰⁶Ru γ ray.The result,after a revision of the binding energy of positronium,is comparied with the adjusted value of the electron rest mass published in several years ago.     

近距离n, γ混合脉冲辐射场中γ辐射探测技术

n, γ混合脉冲辐射场中, 在近距离、辐射强度低且中子辐射峰值比被测γ辐射峰值强度高的情况下, 传统γ辐射探测技术实施起来面临困难. 对PbWO4和CeF3等近年国内新研制的无机闪烁体进行了系列研究, 使用CeF3分别配光电倍增管和光电管,组合出了对γ辐射灵敏度高, 对中子相对不灵敏, 同时脉冲响应也快的光电探测系统, 应用以此为基础的探测技术在近距离n, γ混合脉冲辐射场中, 可将脉冲γ辐射探测信噪比提高一个量级以上. It is difficult to detect low intensity γ radiation by using traditional γ radiation detection technique in a close distance n, γ commix pulse radiation field with very high intensity neutron radiation. PbWO4 and CeF3 which are newly developed inorganic scintillator in our country have been studied. Photoelectricity detector systemes which have high γ sensitivity and relative insensitive to neutron and fast time response were assembled by using CeF3 and photomultiplier tube. The ratio of signal to noise for γ ray detection can be up to more than 10 times in close distance n, γ commix pulse radiation field by using this detector system.     

带电重粒子激发的γ射线在测定同位素丰度上的应用

本文指出利用带电重粒子冲击原子核时所产生的γ射线来测定同位素丰度的可能性。在有合适的基本设备时,特别是在用一含有标准丰度的样品来作比较测定时,这方法是简便的。这是一种微量或超微量的分析方法。测定锂,硼,碳,氮等轻元素的同位素丰度时适用的核反应及γ射线在第四节中逐项讨论。     

积分中值定理在放射性氙样品γ谱效率刻度技术中的应用

在实验室HPGe探测器测量分析氙气样品过程中需要用到相对方法进行分析, 然而由于放射性氙同位素半衰期较短, 制作相应的标准气体比较难, 给谱仪系统刻度带来困难.针对该问题, 提出使用混合面源模拟刻度四种氙同位素气体源的效率, 并提出将积分中值定理应用到面源刻度实验过程, 大大简化了中间流程, 提高了测量的准确性.利用氙分离纯化系统在高氡环境下采集样品, 获得了天然放射性¹³³Xe气体γ谱, 通过计算得到其活度浓度. 积分中值位置处的混合面源刻度结果和气体源刻度结果一致, 说明本文提出的面源刻度技术及积分中值定理的思想在HPGe 探测器效率刻度测量分析中是有效可行的. 关键词： 面源 无源效率刻度软件 效率刻度     

空气比热容比γ测量值准确度的分析与研究

本文介绍了一种测量空气比热容比γ值的方法。重点分析了测量值的准确度与实验过程中打人气体多少的关系。为准确测量γ值提供了有力依据。     

Experiments on the search for the effect of resonant screening on the probability of Mössbauer absorption of <Superscript>119<Emphasis Type="Italic">m</Emphasis></Superscript>Sn gamma rays

Experiments on the search for the effect of resonant screening on the Mössbauer absorption of ^119m Sn γ rays of energy 23.8 keV emitted by a standard Mössbauer Ca^119m SnO₃ γ source in the resonant SnO₂ absorber of natural isotopic composition are described. Intensities of tin γ rays and X-rays that passed through the absorber were measured with and without a resonant cylindrical screen (which was a black absorber for the 23.8-keV Mössbauer γ line) around the absorber and their ratios were calculated for each radiation separately. No difference beyond the experimental error was found between these ratios measured with the γ source both at rest and when oscillating with a frequency and amplitude enough to completely break the conditions for Mössbauer resonant absorption of 23.8-keV γ rays. The upper limit for the relative decrease, due to the influence of the resonant screen, in the intensities of these γ rays after their passing through the resonant absorber was 0.00030.