Temperature of intermediate mass fragments in simulated 40Ca + 40Ca reactions around the Fermi energies by AMD model

The primary fragments in ~(40)Ca +~(40)Ca reactions at 35,50,80,100,140,and 300 MeV/u were simulated using the antisymmetrized molecular dynamics model,in the phase space at t=300 fm/c with a coalescence radius R_c=5 fm.The standard Gogny interactions g0,g0 as,and gOass were adopted in simulating the collisions at an impact parameter of b=0 fm.It was found,using an isobaric yield ratio method,that temperature of the primary fragment depends on the incident energy and hardness of the interaction potential.The temperature obtained in this work agrees with the results by the self-consistent fitting method.     

An improved thermometer for intermediate-mass fragments

An improved thermometer (TIB) is proposed for intermediate-mass fragments via the difference between isobaric yield ratios. The residual free energy of three isobars is replaced by that of the binding energy. The measured fragments in the 140A MeV 40, 48Ca+ 9Be (181Ta) and 58, 64Ni+ 9Be (181Ta) reactions are analyzed to obtain TIB ranging from 0.6 to 3.5 MeV. TIB is suggested to be a direct determination of temperature avoiding the fit-ting procedure.     

Heavy-ion fusion cross-section data for systems with compound atomic mass between 18 and 80

Fusion cross-section data are presented as a function of center-of-mass energy for different reactions involving light and medium-light heavy-ion systems with compound atomic mass number between 18 and 80. The systems range from ⁶Li + ¹²C to ⁴⁰Ca + ⁴⁰Ca. The data are given for the region starting from slightly below the Coulomb barrier energy to about six to seven times its value, if they are available. This compilation is primarily to facilitate theoretical interpretation of experimental results. It also serves to give researchers an overview of the range and status of the data. Literature published up to June 1983 has been surveyed.     

Systematic investigation of spectroscopic factors from (d,p) reactions for deuteron nuclear data evaluation

Spectroscopic factors for the (d,p) reactions on ¹²C, ²⁷Al, ⁴⁰Ca, and ⁵⁸Ni for incident deuteron energies up to 100 MeV were extracted systematically by fitting theoretical distorted wave Born approximation calculations to the existing experimental data. The extracted spectroscopic factors show similar incident energy dependence for all the target nuclei. An empirical expression describing the energy dependence has been deduced and implemented in a computational code system developed specially for deuteron-induced reactions. The calculation with the code system reproduces the measured ²⁷Al(d,p)²⁸Al cross sections in the incident energy range from the threshold to 20 MeV and the measured double-differential cross sections for (d,xp) reactions on ¹²C and ⁵⁸Ni at 56 and 100 MeV fairly well.     

~(40)K-~(40)Ca法的初步研究

报道了样品中钾、钙化学分离和纯化,以及质谱测定流程的建立。测试了国家球团矿标样W7220和W7107、国家40K-40Ar法标准矿物黑云母(ZBH-25)和角闪石(ZBJ)的钾钙含量,以及国际二级钙标样Tachiti和国家钾含量标样的钙和钾同位素比值。实测结果与相应的标称值在误差范围内一致。在此基础上,用实验所得的两组黑云母和角闪石的(40Ca/42Ca) 和 (40K/42Ca)数据,构筑了40K-40Ca法等时线年龄为(133.532.1)Ma, 此与标称值年龄132.7Ma在误差范围内一致。而所得的初始值(40Ca/42Ca)i为151.4160.003, 相应的xCa 值为+26.5,示踪了该矿物组合的原岩具有陆源性质,为固体地球化学的研究提出了新的判据。     

钙钛锆石的自蔓延高温合成与热力学分析

基于自蔓延高温合成法,采用Fe₂O₃、CrO₃和Ca(NO₃)₂为氧化剂,Ti为还原剂制备了钙钛锆石。共设计了4个体系,计算了各体系的绝热温度,测量了各体系的实际燃烧温度,并探索了Ca(NO₃)₂为氧化剂时,TiO₂与Ti摩尔比（TiO₂∶Ti）对燃烧温度的影响。结果显示,所有体系均能自持发生,但以Fe₂O₃和CrO₃为氧化剂时,产物的主要物相为烧绿石(Ca₂Ti₂O₆)、Zr₅Ti₇O₂₄、钙钛矿(CaTiO₃)及少量TiO₂,以Ca(NO₃)₂为氧化剂时,各体系的主要物相均为钙钛锆石(CaZrTi₂O₇)、CaTiO₃及少量TiO₂。同时,以Ca(NO₃)₂为氧化剂时,随TiO₂∶Ti的降低,燃烧温度和绝热温度均逐渐升高。     

Consistent calculations of (n,x) and (n,xγ) cross sections for 40CA En = 1–20 MeV

Cross sections for neutron interaction with ⁴⁰Ca, with emphasis on production of gamma rays, are calculated and compared with experiment. Various nuclear models are applied judiciously for the calculation. The Hauser-Feshbach theory for binary reactions is here extended to include tertiary reactions, which are important for ⁴⁰Ca from 10 to 20 MeV. To conserve angular momentum, we included continuum-level spins and parities in the gamma-ray-production calculation. An extensive measurement of gamma-ray-production cross sections, which became available after all model parameters were fixed, confirms the predictability of the models, particularly in the high-energy range, where tertiary reactions contribute significantly. Recommended values of the total neutron cross section are presented graphically in detail and other cross sections in overview.     

充气飞行时间探测方法分析

本工作涉及充气飞行时间探测器的工作原理和实验测量结果。在不同能量(64、48和33MeV)下，利用充气飞行时间探测方法对同量异位素³⁶S和³⁶Cl进行鉴别，并与用传统的ΔE－E方法在相同能量下的鉴别结果进行比较。实验结果表明，在入射能量较高（E_i＞40MeV）时，ΔE－E法的鉴别能力比充气飞行时间法的稍好些；在E_i＜40MeV时，充气飞行时间法的鉴别能力比ΔE－E法的好，入射能量为20～40MeV时，充气飞行时间法能明显将³⁶S和³⁶Cl区分出来。     

载钯硅藻土吸氕/氘动力学同位素效应

恒温等容条件下,通过p-t曲线测量,研究在223~393K范围内载钯硅藻土(Pd/K)吸氕、氘动力学特性。应用反应速率分析方法计算了反应速率常数,得到了Pd/K吸氕、氘反应活化能。动力学计算结果显示:在整个温度范围内,载钯硅藻土与氕、氘反应明显分为两个温度段。低温段(223~313K),载钯硅藻土吸氕、氘反应速率常数随温度升高而增大且吸氕反应速率大于吸氘反应速率,吸氕、氘反应活化能分别为19.5、19.2kJ/mol;高温段(313~393K),载钯硅藻土吸氕、氘反应速率则随温度升高而减小,氕、氘反应活化能分别为:-18.6、-12.1kJ/mol。测试结果表明,载钯硅藻土吸氕、氘反应存在显著的动力学同位素效应且同位素效应依赖于温度的变化。     

Deuterium implantation in graphite

A study has been made of deuterium ion implantation in polycrystalline graphite over the temperature range 100 K to 450 K. Deuterium depth profiles are obtained using a method based on observing the energy spectra of the tritons and protons from D-D reactions initiated with a 200 keV probing deuteron beam. In marked contrast to the low adsorption for gaseous hydrogen previously reported, graphite is found here to retain large concentrations of implanted deuterium with atomic loadings exceeding unity in the deeper regions of a cold target. The amount of deuterium retained continues to decrease with increasing temperature until at 150°C the retention has fallen to approximately half that at −160°C. No evidence is found for a layer of surface deuterium of the type seen in metals such as copper. Scanning electron micrographs of irradiated areas show no observable surface deformation for doses of up to 2.4 × 10¹⁹ deuterons/cm².     

A nuclear density probe:isobaric yield ratio difference

We report our recent progress on the nuclear symmetry energy probe,which is called the isobaric yield ratio difference(IBD),and its application in neutron density determination in experiments.The results obtained by the IBD,from which the isobaric yields in the measured 140 A MeV ~(40.48)Ca + ~9Be and ~(58.64)Ni + ~9Be reactions,and the calculated 80 A MeV ~(38-52)Ca +~(12)C reactions by using a modified statistical abrasion-ablation model,show the sensitivity of the IBD to the density differences between reactions.     

Plasma-assisted ammonia synthesis in a packed-bed dielectric barrier discharge reactor: roles of dielectric constant and thermal conductivity of packing materials

In this article, plasma-assisted NH₃ synthesis directly from N₂ and H₂ over packing materials with different dielectric constants (BaTiO₃, TiO₂ and SiO₂) and thermal conductivities (BeO, AlN and Al₂O₃) at room temperature and atmospheric pressure is reported. The higher dielectric constant and thermal conductivity of packing material are found to be the key parameters in enhancing the NH₃ synthesis performance. The NH₃ concentration of 1344 ppm is achieved in the presence of BaTiO₃, which is 106% higher than that of SiO₂, at the specific input energy (SIE) of 5.4 kJ·l⁻¹. The presence of materials with higher dielectric constant, i.e. BaTiO3 and TiO₂ in this work, would contribute to the increase of electron energy and energy injected to plasma, which is conductive to the generation of chemically active species by electron-impact reactions. Therefore, the employment of packing materials with higher dielectric constant has proved to be beneficial for NH₃ synthesis. Compared to that of Al₂O₃, the presence of BeO and AlN yields 31.0% and 16.9% improvement in NH₃ concentration, respectively, at the SIE of 5.4 kJ·l⁻¹. The results of IR imaging show that the addition of BeO decreases the surface temperature of the packed region by 20.5% to 70.3°C and results in an extension of entropy increment compared to that of Al₂O₃, at the SIE of 5.4 kJ·l⁻¹. The results indicate that the presence of materials with higher thermal conductivity is beneficial for NH₃ synthesis, which has been confirmed by the lower surface temperature and higher entropy increment of the packed region. In addition, when SIE is higher than the optimal value, further increasing SIE would lead to the decrease of energy efficiency, which would be related to the exacerbation in reverse reaction of NH₃ formation reactions.     

Comparison of 41Ca analysis on 0.5 MV and 5 MV-AMS systems

A comparative study was made between the compact AMS system at the PSI/ETH Laboratory of Ion Beam Physics in Zurich with 0.5 MV terminal voltage and the 5 MV-AMS system at the Scottish Universities Environmental Research Centre (SUERC), Glasgow. Overall 34 urinary samples with ⁴¹Ca/⁴⁰Ca ratios in the range from 4 × 10^?11 to 3 × 10^?10 were processed to CaF₂ and aliquots of the same material were measured on both instruments.Measurements on the compact AMS system were performed in charge state 3+ achieving a transmission of 4% at 1.7 MeV beam energy. Under these conditions a suppression of the interference ⁴¹K is virtually impossible. However, samples with an excess of potassium can be identified by a shift of the ⁴¹Ca/⁴¹K peak in the ΔE ? E histogram of the gas ionization detector employed and a criterion for data rejection can be defined. An overall precision of ～4% and a ⁴¹Ca/⁴⁰Ca background level of 5 × 10^?12 have been reached.For studies with higher demands on the detection limit AMS systems like the one at SUERC are attractive: in charge state 5+ and using a gas stripper beam energy of 27 MeV, a transmission of 5%, a ⁴¹K suppression factor of ～500 and a ⁴¹Ca/⁴⁰Ca background level of 3 × 10^?14 are achieved.We demonstrate that both systems are well suited for large-scale ⁴¹Ca biomedical applications.     

The energy dependence of proton-induced degradation in AlGaN/GaN high electron mobility transistors

The effects of proton irradiation at various energies are reported for AlGaN/GaN high electron mobility transistors (HEMTs). The devices exhibit little degradation when irradiated with 15-, 40-, and 105-MeV protons at fluences up to 10/sup 13/ cm/sup -2/, and the damage completely recovers after annealing at room temperature. For 1.8-MeV proton irradiation, the drain saturation current decreases 10.6% and the maximum transconductance decreases 6.1% at a fluence of 10/sup 12/ cm/sup -2/. The greater degradation measured at the lowest proton energy considered here is caused by the much larger nonionizing energy loss of the 1.8-MeV protons.     

大尺寸BGO晶体的温度特性研究

锦屏深地核天体物理（JUNA）实验项目将在中国锦屏深地实验室开展恒星平稳氦燃烧阶段关键的(α,γ)和(α,n)反应以及恒星平稳氢燃烧阶段关键的(p,γ)和(p,α)反应的直接测量。该项目计划研制一套锗酸铋（BGO）探测器阵列用于(α,γ)和(p,γ)反应的γ射线探测。由于BGO晶体的光产额对温度敏感,温度的变化会导致γ能谱峰位的漂移和能量分辨率的变化。本文使用制冷系统对尺寸为6 cm×8 cm×25 cm的BGO晶体进行降温,利用¹³⁷Cs源测量了其γ能谱峰位和能量分辨率,对BGO探测器性能随温度的变化关系进行了研究。结果表明：在-20～22.1 ℃温度区间内,BGO探测器的γ能谱峰位与温度呈良好的线性关系,能量分辨率随温度的降低而提高。     

Accelerated Leach Tests of SRL-165 High-Level Waste Glass in Deionized Water

Accelerated short-term leach tests in a laboratory are neccessary in order to estimate, with reasonable accuracy, the long-term leaching behavior of high-level waste glass. In the present study, static leach tests of an SRL-165 high-level waste glass were carried out in deionized water at two different glass-surface-area to solution-volume ratios (SA/V-ratio), namely 0.85 and 0.079 cm^?1 at 90°C, and 0.85 cm^?1 at 40°C.

First, an equation was examined which related Si-concentrations with time, temperature and SA/V-ratio under the present static conditions. The parameter determined at 90°C, 0.85 cm^?1 can be used to calculate the Si-concentration at 40°C, 0.85 cm^?1. Second, at the low SA/V- ratio of 0.079 cm^?1, the concentrations of Ca and Mg in the leachates peaked and then decreased a little. The equation used above does not explain the variation of the concentrations of Ca and Mg at a low SA/V-ratio. The precipitation of Ca and Mg onto the glass surface is probably caused by the adsorption efficiency of the surface layer or the formation of crystalline materials at the low SA/V-ratio of 0.079 cm^?1. Third, the in-depth profiles of some elements obtained by secondary ion mass spectroscopy (SIMS) were qualitatively in agreement with the results of solution analyses. This indicates the particular usefulness of SIMS for analyzing leaching behavior of the glass in in-situ burial studies where solution analyses are often impractical.     

Total cross sections for the 40Ca(n,p) and (n, α) reactions between 2.7 and 5.5 MeV

Measurements have been made of the ⁴⁰Ca(n,p), ⁴⁰Ca(n,α), ⁴⁰Ca(n,n′) ⁴⁰Ca(3.35) cross sections in the energy range 2.7–5.5 MeV. Neutron flux measurements are made using the associated particle technique. The data are compared to previous data and the recent Hauser-Feshbach calculations made by Fu (1979).     

The Spectral Emission Characteristics of Laser Induced Plasma on Tea Samples

Laser induced breakdown spectroscopy(LIBS) provides a useful technique for food security as well as determining nutrition contents.In this paper,optical emission studies of laser induced plasma on commercial tea samples were carried out.The spectral intensities of Mg,Mn,Ca,Al,C and CN vibration bands varying with laser energy and the detection delay time of an intensified charge coupled device were studied.In addition,the relative concentrations of six microelements,i.e.,Mg,Mn,Ca,Al,Na and K,were analyzed semi-quantitatively as well as H,for four kinds of tea samples.Moreover,the plasma parameters were explored,including electron temperature and electron number density.The electron temperature and electron number density were around 11000 K and 10~(17) cm~(-3),respectively.The results show that it is reasonable to consider the LIBS technique as a new method for analyzing the compositions of tea leaf samples.     

适用于研究低能裂变碎片电荷分布的探测器装置

为研究²⁵²Cf自发裂变碎片电荷分布，建立了由屏栅电离室和ΔE-E粒子望远镜构成的探测器系统。在该系统中，将薄的屏栅电离室作为碎片的ΔE探测器，E探测器是金硅面垒半导体探测器。通过分析实验测量的4参数关联数据，得到了²⁵²Cf自发裂变碎片质量数、动能及碎片在气体ΔE探测器中的能量沉积分布等物理量。用多高斯（multi-Gaussian）分布函数对ΔE探测器的能量响应函数进行最小二乘法拟合，得到了在固定质量数A^*_L和动能条件下轻碎片的电荷分布。结果表明：该探测器系统的电荷分辨能力Z/ΔZ约为40∶1；建立起来的测量技术可用于测定²³⁵U(n,f)和²³⁹Pu(n,f)反应碎片的电荷分布。     

能量色散X荧光法测定茶叶中的微量元素

本文介绍了用国产能量色散ｘ射线荧光仪同时测定茶叶中的Ｃａ、Ｍｎ、Ｆｅ、Ｃｕ和Ｚｎ的分析方法。该方法采用将茶叶样品高温灰化，以Ｙ为内标，用ｘ射线荧光分析仪测定微量元素的含量取得了很好的结果。