Well-type phoswich counter for low-flux X-ray/γ-ray detection

Phoswich counters that can detect low-flux hard-X-ray/γ-ray from localized sources are described. The counter consists of a small inorganic scintillator with a fast decay time (the detection part) glued to the interior bottom surface of a well-shaped block of another inorganic scintillator with a slow decay time (the shielding part). The first model counter was built by using a new scintillator, gadolinium silicate (GSO), in the decision part and CsI(Tl) in the shielding part. A detector system consisting of 64 such phoswich counters (total area ~740 cm²) was flown onboard a balloon, setting a limit to the ⁵⁷Co line flux from SN 1987A, at ~10^-4 cm^-2 s The sensitivity for continuum flux was around a few ×10 ^-6 cm^-2 s^-1 keV^-1 between 100 and 200 keV. In the second model, CsI(Tl) was replaced by bismuth germanate (BGO), and radioactive contaminations in GSO were reduced. Improvements are planned to reach a sensitivity (3σ) around 5×10^-7 cm^-1 s^-1 keV^-1 for the continuum     

Operando FT-IR study on basicity improvement of Ni(Mg,Al)O hydrotalcite-derived catalysts promoted by glow plasma discharge

CO₂ adsorption on the surface of hydrotalcite-derived mixed oxide catalysts was investigated under low pressure glow discharge plasma in operando conditions via FT-IR spectroscopy. Nickel catalysts were promoted with various transition metal species (Ce, Fe, La, Zr) to influence their physico-chemical properties. Fe and Zr species were successfully incorporated into hydrotalcite brucite layers. After calcination formed a single phase with Ni(Mg, Al)O mixed oxide, while La and Ce species formed separate phases. This had a consequence in the distribution of surface basic sites as well as in the affinity to CO produced upon CO₂ dissociation in plasma. Plasma treatment activated the surface of prepared materials and changed their properties via the generation of strong basic sites associated with low coordinated surface oxygen anions. Moreover, the CO₂ adsorption capacity of prepared materials increased after plasma treatment.     

Mechanism of high growth rate for diamond-like carbon films synthesized by helicon wave plasma chemical vapor deposition

A high growth rate fabrication of diamond-like carbon(DLC)films at room temperature was achieved by helicon wave plasma chemical vapor deposition(HWP-CVD)using Ar/CH_4gas mixtures.The microstructure and morphology of the films were characterized by Raman spectroscopy and scanning electron microscopy.The diagnosis of plasma excited by a helicon wave was measured by optical emission spectroscopy and a Langmuir probe.The mechanism of high growth rate fabrication for DLC films by HWP-CVD has been discussed.The growth rate of the DLC films reaches a maximum value of 54μm h~(-1)at the CH_4flow rate of 85 sccm,which is attributed to the higher plasma density during the helicon wave plasma discharge.The CH and H_αradicals play an important role in the growth of DLC films.The results show that the H_αradicals are beneficial to the formation and stabilization of C=C bond from sp~2to sp~3.     

Large conductivity enhancement in polycrystalline 12CaO · 7Al2O3 thin films induced by extrusion of clathrated O ions by hot Au implantation and ultraviolet light illumination

Large enhancement in electrical conductivity from <10⁻¹⁰ S cm⁻¹ to 4 × 10⁻² S cm⁻¹ was achieved in polycrystalline 12CaO · 7Al₂O₃ (p-C12A7) thin films by hot Au⁺ implantation at 600 °C and subsequent ultraviolet (UV) light illumination. Although the as-implanted films were transparent and insulating, the subsequent UV-light illumination induced persistent electronic conduction and coloration. A good correlation was found between the concentration of photo-induced F⁺-like centers (a cage trapping an electron) and calculated displacements per atom, indicating that the hot Au⁺ implantation extruded free O²⁻ ions from the cages in the p-C12A7 films by kick-out effects and left electrons in the cages. These results suggest that H⁻ ions are formed by the Au⁺ implantation through the decomposition of preexisting OH⁻ ions. Subsequent UV-light illumination produced F⁺-like centers via photoionization of the H⁻ ions, which leads to the electronic conduction and coloration.     

PIXE measurements of Kr-sputtered TiN coatings

Titanium nitride films of 30–300 nm thickness deposited via dc magnetron sputtering were irradiated with 150–700 keV Kr ions at fluences up to 2.1 × 10¹⁷ cm⁻². These films were then scanned with a well-collimated 400 keV proton beam and the X-ray yield of Ti was measured both in and outside the Kr beam spot. This procedure results in a precision determination of the average film thickness (± 1% in the case of tens of nm films). The PIXE results are found to be consistent with RBS data of the same specimens. Sputtering yields were determined from the variation of X-ray yields assuming unchanged Ti/N stoichiometry in the implanted area. For thick TiN films (d₀ > 100 nm) the sputtering yields are in good agreement with predictions of the collisional cascade model by Sigmund. In contrast, sputtering of thin layers (d₀ = 30 nm) depended sensitively on the ion energy, being a factor of 2 higher at 150 keV than at 500 keV.     

基于MnO2共沉淀的海水中234Th的分析方法

利用室内模拟MnO₂共沉淀和直接β计数分析海水中²³⁴Th。实验中对模拟条件进行了优化,结果表明：共沉淀滤膜选择混合膜时,实验流程空白计数率稳定在(0.50±0.04)min^-1;共沉淀前若酸化,会破坏海水中U和CO₃^2-络合作用,导致U-Th分离效果减弱;共沉淀时最佳pH=10.0;海水中添加碳酸盐能明显降低海水中U的共沉淀效率;增大沉淀剂的用量,会一定程度改善U-Th的分离效果,每升海水中加入1.2mg KMnO₄和3.0mg MnCl₂·4H₂O时最佳。本实验方法已经将模拟条件的结论结合实际情况应用到东海天然海水中²³⁴Th的分析,该方法的全程回收率为（36.0±5.2)%(n=3)。     

Structural evolution in Fe ion implanted Si upon thermal annealing

We have performed high-dose Fe ion implantation into Si and characterized ion-beam-induced microstructures as well as annealing-induced ones using transmission electron microscopy (TEM) and grazing-incidence X-ray diffraction (GIXRD). Single crystals of Si(1 0 0) substrate were irradiated at 623 K with 120 keV Fe⁺ ions to a fluence of 4 × 10¹⁷ cm⁻². The irradiated samples were then annealed in a vacuum furnace at temperatures ranging from 773 K to 1073 K. Cross-sectional TEM observations and GIXRD measurements revealed that a layered structure is formed in the as-implanted specimen with ε-FeSi, β-FeSi₂ and damaged Si, as component layers. A continuous β-FeSi₂ layer was formed on the topmost layer of the Si substrate after thermal annealing.     

Dissociation of fast HeH ions at glancing angle scattering from a crystal surface

Scattered H⁺ fragments resulting from glancing angle incidence of MeV HeH⁺ ions on the clean (001) surface of a SnTe crystal are distributed on an ellipse in the E-φ plane, where the angle φ is measured in the plane parallel to the surface and E is the energy of the fragment. The kinetic energies released upon dissociation derived from the diameters of the ellipses are smaller than those calculated from the explosion of fully ionized fragments.

Based on a simplified model, we have simulated the dissociative scattering of HeH⁺ ions at the surface, where the dissociation takes place via excitation of HeH⁺ ions and the charges of fragments change along the trajectory. It is concluded from the simulation that the cross section for dissociation in HeH⁺-electron collisions is of the order of 10⁻¹⁶ cm².     

铀铌合金表面热氧化膜结构研究

采用X射线光电谱分析技术、结合Ar离子枪溅射,研究了大气环境、不同温度(室温、100、200和300℃)条件下铀铌合金样品表面氧化膜结构的变化情况。实验结果表明:随温度升高,氧化膜厚度增大,氧化膜结构发生明显变化。不同温度热氧化处理后,铀铌合金初始表面Nb主要以Nb2O5形式存在,在Nb2O5与金属Nb之间,总存在一定厚度的NbO及少量其他价态氧化物NbOx(0x1,1x2)的混合层。室温～200℃热氧化合金样品表面铀均以含间隙氧的UO2+x(P型)存在,其U4f7/2结合能较UO2低约0.7eV。室温条件下,氧化膜成分主要为UO2;100、200℃热氧化后,氧化膜中除UO2外,还含有少量P型UO2+x,其U4f5/2卫星峰的结合能为396.6eV。300℃热氧化后的合金样品表面为铀的高价氧化物(U3O8或UOx,2x3),U4f特征峰的结合能分别为381.8和392.2eV;氧化层为UO2和金属铀的混合物。热氧化过程中,温度对铀氧化的影响较对Nb的明显得多。     

α-C_xN_y:H_(1-x-y)薄膜的制备和光学性能分析

采用外置式电容耦合低压等离子体化学气相沉积法,以高纯CH4/N2/H2作为反应气体,制备非晶α-CxNy:H1-x-y薄膜。研究了薄膜沉积速率和入射功率之间的关系,随着功率增大,薄膜沉积速率先增大后减小;SEM图像表明薄膜无层状、柱状结构;AFM图像表明薄膜粗糙度在0.2～0.3nm之间;傅里叶红外光谱(FTIR)显示了薄膜的成键情况;紫外-可见-近红外光谱表明,随着入射功率的增大,薄膜的光学带隙逐渐减小。     

A neutronic experiment to support the design of an Indian TBM shield module for ITER

A shield module is associated with an Indian Test Blanket Module (TBM) in ITER to limit the radiation doses in port inter-space areas. The shield module is made of stainless steel plates and water channels. It is identified as an important component for radiation protection because of its radiation exposure control functionality. The radiation protection classification leads to more assurance of the component design. In order to validate and verify the design of the shield module, a neutronic laboratory-scale experiment is designed and executed. The experiment is planned by considering the irradiation under a neutron source of 14 MeV and yields of 10 10 ns ⁻¹. The reference neutron spectrum of the ITER TBM shield module has been achieved through optimization of the neutron source spectrum by a combination of steel and lead materials. The neutron spectrum and flux are measured using a multiple foil activation technique and neutron dose-rate meter LB 6411 (He-3 proton recoil counter with polyethylene), respectively. The neutronic design simulation is assessed using MCNP5 and FENDL 2.1 cross-section data. The paper covers neutronic design, irradiation and the outcome of the experiment in detail.     

High energy oxygen ion induced modifications in lead based perovskite thin films

The lead based ferroelectric PbZr_0.53Ti_0.47O₃ (PZT), (Pb_0.90La_0.10)TiO₃ (PLT10) and (Pb_0.80La_0.20)TiO₃ (PLT20) thin films, prepared by pulsed laser ablation technique, were studied for their response to the 70 MeV oxygen ion irradiation. The dielectric analysis, capacitance–voltage (C–V) and DC leakage current measurements were performed before and after the irradiation to high-energy oxygen ions. The irradiation produced considerable changes in the dielectric, C–V, leakage characteristics and induced some amount of amorphization. The PZT films showed partial recrystallization after a thermal annealing at 400 °C for 10 min. The phase transition temperature [T_c] of PLT20 increased from 115 °C to 120 °C. The DC conductivity measurements showed a shift in the onset of non-linear conduction region. The current density decreased by two orders of magnitude after irradiation. After annealing the irradiated films at a temperature of 400 °C for 10 min, the films partially regained the dielectric and electrical properties. The results are discussed in terms of the irradiation-induced amorphization, the pinning of the ferroelectric domains by trapped charges and the thermal annealing of the defects generated during the irradiation.     

Isomer separation of Cu and Cu with a resonance ionization laser ion source

Radioactive copper isotopes were ionized with the resonance ionization laser ion source (RILIS) at the on-line isotope separator ISOLDE (CERN). Using the different hyperfine structure in the 3d¹⁰ 4s  ²S_1/2 – 3d¹⁰ 4p  ²P⁰_1/2 transition the low- and high-spin isomers of ⁷⁰Cu were selectively enhanced by tuning the laser wavelength. The light was provided by a narrow-bandwidth dye laser pumped by copper vapor lasers (CVL) and frequency doubled in a BBO crystal. The ground state to isomeric state intensity ratio could be varied by a factor of 30, allowing to assign gamma transitions unambiguously to the decay of the individual isomers. It is shown that the method can also be used to determine magnetic moments. In a first experiment for the 1⁺ ground state of ⁷⁰Cu a magnetic moment of (+)1.8(3) μ_N and for the high-spin isomer of ⁷⁰Cu a magnetic moment of (±)1.2(3) μ_N could be deduced.     

Charge state dependence of L-shell X-ray production cross sections of 28Ni, 29Cu, 30Zn, 31Ga and 32Ge by 12 MeV O ions

L-shell X-ray production cross sections of elements from Z₂=28 to 32 were measured. A 12 MeV incident oxygen beam, with and without K-shell vacancies, was used to make a charge state dependence analysis. Simultaneous measurements were made of both scattered particles and X-rays from the ultra-clean foils that had been made sufficiently thin to reach the single-collision regime. Target L-shell to projectile K-shell electron capture for hydrogen-like (q=Z₁ − 1) and fully stripped (q=Z₁) oxygen ions were then extracted. The measurements are compared with the predictions of the ECPSSR theory using a single-hole fluorescence yield. In general and contrast to the first Born calculations, this theory gives reasonable agreement with the data for oxygen ions without K vacancies. However, the ECPSSR still significantly overpredicts the data for oxygen ions with K vacancies.     

Superconductivity in MgB2 films synthesized by ablation from high-power ion beam

MgB₂ thin films with T_c = 19 K were fabricated by the ion ablation technique utilizing a high-energy pulsed ion beam. A target remains pure MgB₂ after ablation, proving the excellent capability of ablation by the high-power ion beam. Chemical compositions of the deposited material, however, may vary with positions of the substrates from the beam axis. X-ray diffraction patterns exhibit only (0 0 1) and (0 0 2) peaks, which indicate a c-axis orientation of the films. Scanning electron microscopy images show a possible growth of single crystals with hexagonal shape and 1 μm size.     

Fe-Al/Al2O3涂层表面氧化膜的掠入射X射线衍射研究

本文采用掠入射X射线衍射（GXRD）α-2θ扫描模式,进行了掠入射角α为0.1°～5°范围内Fe-Al/Al₂O₃阻氚涂层表面氧化膜的X射线衍射实验。结果表明,随α的增加,表面氧化膜中Al₂O₃相与Fe₃Al相对应的衍射峰强度绝对值增强;α的增加加深了分析区域的深度,引起Al₂O₃相的相对含量下降,导致Al₂O₃相对衍射峰强度降低。对Fe-Al/ Al₂O₃涂层表面氧化膜的掠入射X射线衍射而言,较佳的掠入射角是0.25°,此时对应Al₂O₃相的衍射峰相对强度最高。经比对PDF卡片,表面氧化膜相结构为暂态γ-Al₂O₃（200）。在此基础上建立了GXRD分析Fe-Al/ Al₂O₃涂层表面亚微米氧化膜的相结构组成的快速无损检测方法。     

Release of nitrogen from SiOxNy films during RBS measurement

We have found that nitrogen atoms are released very rapidly from ultrathin SiO_xN_y films (2.6 nm) during RBS measurement with 500 keV He⁺ ions. The release behavior strongly depends on the preparation technique of the SiO_xN_y films. There is no release from the film prepared by thermal nitridation of SiO₂, while 80% of the nitrogen atoms are released from the film prepared by plasma nitridation at a fluence of 1×10¹⁶ cm⁻². The release cross-section for plasma SiO_xN_y films is of the order of 10⁻¹⁶ cm². This large cross-section cannot be explained by a simple recoil mechanism. The nitrogen release is also observed under irradiation with 5–10 keV electrons though the cross-section is of the order of 10⁻¹⁹ cm². These findings suggest that the observed nitrogen release is an electronic excitation induced process.     

Aqueous corrosion of lanthanum aluminosilicate glasses: influence of inorganic anions

In order to confine specific long-life actinides, originating from high-level nuclear wastes, lanthanum aluminosilicate glasses are considered. The aqueous corrosion behavior of these glasses is studied under static conditions (T=96 °C, duration between one and six months, glass surface area/leachate volume, S/V=0.3, 50 and 500 cm⁻¹) by means of solution analysis (ICP-MS and spectrophotometry) and solid analysis (X-ray photoelectron spectroscopy and Rutherford backscattering spectrometry). Tests performed at high S/V ratio lead to silicon releases of 10⁻³ mol l⁻¹ while lanthanum releases reach 10^−4.5 mol l⁻¹. Phosphate anions are found to modify the dissolution, as an amorphous lanthanide phosphate is evidenced at the glass surface after the corrosion experiment. The lanthanide releases decrease in presence of phosphate, but the matrix dissolution process is not reduced.     

甲醛肟在Purex流程铀钚分离中的应用

为了进一步优化Purex流程,研究了甲醛肟（FO）的硝酸水溶液对30%TBP/煤油中Pu(Ⅳ)的还原反萃取行为,考察了FO浓度、两相接触时间、两相相比、反萃液硝酸浓度、NO₃^-浓度、有机相U浓度和温度对Pu(Ⅳ)的还原反萃的影响。结果表明：延长两相接触时间能显著提高Pu(Ⅳ)的反萃率,增加甲醛肟的浓度、降低反萃液酸度、降低NO₃^-浓度、增加有机相U浓度和升高温度也对Pu(Ⅳ)的反萃率有一定的提高。采用16级逆流反萃取实验（还原反萃段12级,补充萃取段4级）,模拟Purex流程1B槽U/Pu分离工艺,在相比（1BF∶1BX∶1BS）为4∶1∶1的条件下,U和Pu 的回收率均大于99.99%;铀中去钚的分离因子SF(Pu/U)＝1.0×10⁴;钚中去铀的分离因子SF(U/Pu)＝8.3×10⁴。FO作为新型络合 还原反萃取剂,可有效实现铀钚分离。     

双探头WIZARD22470型伽马计数仪定量性能研究

伽马计数仪是对微量放射性精确测量的主要仪器之一,仪器性能的准确性、实验操作的规范性与实验结果的可靠性、真实性密切相关.为了在使用之前对仪器性能进行系统研究,本研究利用三种正电子核素18 F、68 Ga和89 Zr对双探头WIZARD22470型伽马计数仪进行双探头探测效率、伽马计数检测限、检测稳定性,以及与放射性测量线...