22Na次级束的产生与应用

在日本东京大学核研究中心的放射性离子束分离器上,利用逆运动学反应¹H(²²Ne,²²Na)n产生了²²Na次级束。经分离器电磁系统的分离提纯后,获得了能量为（78.3±1.0） MeV的²²Na次级束。实验靶站处次级束的强度达2.5×10⁵ s^-1,其中²²Na的纯度好于90%。²²Na次级束已应用于与核天体物理Ne丰度异常问题相关的²²Na+α共振散射实验研究。     

Determination of sulphur and copper depth distribution in patina layers using nuclear reaction techniques

A method for Cu and S profiling in patina layers was developed by applying a combination of nuclear reaction analysis (NRA) and Rutherford backscattering spectroscopy (RBS). The copper profiling was performed by using the 1327 keV γ-ray deexciting the third excited state to the ground state of ⁶³Cu produced by the reaction ⁶³Cu(p,p^′γ)⁶³Cu. For the determination of sulphur the 2230 keV γ-ray was used deexciting the first excited state to the ground state of ³²S formed through the reaction ³²S(p,p^′γ)³²S, which exhibits three sharp resonances at projectile energies 3.094, 3.195 and 3.379 MeV. The relevant cross-sections were measured in the energy range between 3.0 and 3.7 MeV in steps of 20 keV at 125° to the incident proton beam direction. The technique was tested using artificially produced and natural copper patina layers. Supporting information on the depth distribution of the constituent elements of the patina samples was obtained by p-RBS (E_p: 1.5 MeV, θ: 160°).     

离散纵标输运计算方法在压水堆核电厂41Ar活化源项分析中的应用

压水堆核电厂功率运行期间,反应堆压力容器外的环形空腔空气中所含的⁴⁰Ar被中子活化,形成具有放射性的⁴¹Ar。文章采用二维离散纵标输运计算程序DORT分析了反应堆堆腔区域的中子注量率分布情况,采用NJOY评价核数据处理程序,根据DORT分析得到的通量作为权重通量,利用基础评价核数据库ENDF/B-Ⅶ.0制作⁴⁰Ar中子俘获反应的微观截面,在此基础上,分析了百万千瓦级压水堆核电厂每台机组反应堆堆腔空气中⁴⁰Ar中子活化生成⁴¹Ar的生成率以及电厂⁴¹Ar的环境排放源项。文章给出的⁴¹Ar源项分析方法可作为压水堆核电厂设计中确定⁴¹Ar源项的最佳估算值的参考。     

Cobalt cross sections for 14 MeV neutrons

14 MeV cross sections for the reactions ⁵⁹Co(n,2n) ^58m+gCo, ⁵⁹Co(n,p) ⁵⁹Fe and ⁵⁹Co(n,) ⁵⁶Mn were measured relative to the ⁵⁶Fe(n,p) ⁵⁶Mn reaction employing the activation technique. Accuracies of about 1% were achieved for the (n,) reaction and 2% for the others. The isomeric cross section ratio was measured for the ⁵⁹Co(n,2n) reactions.

Nuclear reactions – ⁵⁹Co(n,2n) ^58m+gCo, ⁵⁹Co(n,p) ⁵⁹Fe, ⁵⁹Co(n,) ⁵⁶Mn, E_n = 14.3, 14.7 MeV: measured activation cross sections relative to ⁵⁶Fe(n,p) ⁵⁶Mn.

⁵⁹Co(n,2n) ^58m,gCo, E_n = 14.3 MeV; measured isomeric cross section ratio. Natural targets. Ge, NaI and 4πβ detectors.     

正电子致电离截面实验中束流强度的在线测量

本文采用HPGe探测器实时收集了正电子碰撞厚Ti靶伴随产生的湮灭光子,并结合HPGe探测器对放置在碰撞点处²²Na标准源产生的511 keV湮灭光子的探测效率刻度值,得到了8~9.5 keV正电子引起Ti原子内壳层电离截面实验中正电子束流强度的实时测量结果。结果表明,在实验测量的38 h内,基于²²Na标准源慢正电子束流装置产生的正电子束流强度不稳定,随时间的变化有着不同程度的衰减,且存在小幅度波动现象。因此,低能正电子致原子内壳层电离截面实验中应采用在线法获取慢正电子束流强度。     

Investigations of lattice location and mobility of carbon in GaAs using the channeling technique

In order to get information about the lattice location and the mobility of ¹²C in GaAs wafers, the channeling technique in combination with nuclear reaction analysis (NRA) is a powerful method. The targets were implanted with ¹²C ions (2.6 × 10¹³−2.6 × 10¹⁵cm⁻²) at energies between 60 and 3000 keV. This corresponds to implantation depths of about 0.1 to 3 μm. Using the nuclear reaction ¹²C(d, p)¹³C a depth distribution of the implanted carbon is obtained. The relationship between the concentration of ¹⁴C in random and along the 100 and 110 axial directions gives information about the substitutional lattice location of carbon within the GaAs crystal. In addition, we measured lattice defect depth distributions with a 1.5 MeV ⁴He⁺ beam before and after thermal annealing at temperatures up to 600°C.     

The Mn/H and B/H thermal absorption cross-section ratios

Measurements have been made of the Mn/H and B/H thermal absorption cross-section ratios. Values of 40.07 ± 0.39 and 2324 ± 20 were obtained for these ratios, respectively. Taking the H 2200 m s⁻¹ cross section as 332.55 ± 0.69 mbarn, these ratios give values of 13.32 ± 0.13 and 773 ± 7 barn for the 2200 m s⁻¹ neutron cross sections of Mn and natural B, respectively.     

Measurements of the (n, np+d) activation cross sections with 13.4–14.9 MeV neutrons using a fusion neutronics source/JAERI

The activation cross sections for 20 (n, np+d) reactions were measured in the energy range between 13.4 and 14.9 MeV by the activation method. The mass-separated isotopes of ⁸⁷Sr, ^95,100Mo, ¹⁰⁴Ru, ¹⁰⁶Pd, ^113,116Cd, ^118,119,120Sn, ^123,128,130Te, ^184,186W, and ^189,190Os were irradiated. The 16 cross sections, excepting those for ¹¹⁸Sn, ¹²⁸Te and ^184,186W, were obtained for the first time. The d–T neutron source of the fusion neutronics source (FNS) at the Japan Atomic Energy Research Institute (JAERI) was used for irradiation. All cross section values were determined relative to that of the ²⁷Al (n, ) ²⁴Na reaction (ENDF/B-VI). To measure weakly induced activities, an efficiency calibration technique with a well-type HPGe detector was applied. The present results were compared with the comprehensive evaluated data in the JENDL-3.3, the JENDL-Activation File, the ENDF/B-VI and the FENDL/A-2.0. Most of the data in the JENDL-3.3 and the JENDL-Activation File were in good agreement with the present result. However, relative to our values, 13 of the 20 evaluated data in FENDL/A-2.0 were overestimated more than 2 times or underestimated by less than one tenth.     

低本底高分辨测量技术在16N衰变的出射α粒子测量中的应用

¹⁶N的β延迟α衰变能谱在Ec.m.≈12 MeV处有一低能峰,该α峰的形状和高度可用于约束12C(α,γ)16O反应截面的E1部分,对其进行测量具有重要意义。本工作尝试采用重离子注入法对其进行测量,在兰州重离子加速器国家实验室RIBLL1放射性束流线上产生了16N放射性束流并将其注入到双面硅微条探测器(DSSD)中,利用DSSD对其β延迟α能谱进行了测量。通过选用薄的DSSD探测器、DSSD正反面能量符合关系以及DSSD点火数约束等方法,显著减小了16N衰变产生的电子对α能谱测量的干扰,将α能谱的测量阈值降低到800 keV左右,成功观测到了Ec.m.≈12 MeV处的低能峰。该方法为间接研究12C(α,γ)16O反应率开辟了一条新的实验方法。     

Radiation damage factor for ion-implanted silicon detectorsirradiated with heavy ions

Ion-implanted silicon detectors were irradiated with 18-150 MeV ¹⁶O, 20 MeV ⁴⁰Ar, and 53 MeV ¹¹⁰Xe. A linear increase of the leakage current was observed as a function of the particle fluence up to 2.2×10⁸ cm^-2. Extracted damage factors are proportional to the averaged nuclear stopping power over five orders of magnitude covering heavy ions studied in the present work and also protons of 25-800 MeV energies     

Some remarks on the neutron elastic—And inelastic—Scattering cross sections of palladium

The cross sections for the elastic-scattering of 5.9, 7.1 and 8 MeV neutrons from elemental Pd were measured at 40 scattering angles distributed between ≈15 and 160°. The inelastic-scattering cross sections for the excitation of Pd levels at energies of 260–560 keV were measured with high resolution at the same energies, and at a scattering angle of 80°. The experimental results were combined with lower-energy values previously obtained by this group to provide a comprehensive data base extending from near the inelastic-scattering threshold to 8 MeV. That data base was interpreted in terms of a coupled-channels model, including the inelastic excitation of one- and two-phonon vibrational levels of the even isotopes of Pd. It was concluded that the Pd inelastic-scattering cross sections, at the low energies of interest in assessment of fast-fission-reactor performance are large (≈50% greater than given in widely-used evaluated fission-product data files). They primarily involve compound-nucleus processes, with only a small direct-reaction component attributable to the excitation of the one-phonon 2⁺ vibrational levels of the even isotopes of Pd.     

Measurement of the cross sections for the reactions Cr(n,2n)Cr, Zn(n,2n)Zn, Y(n,2n)Y and Zr(n,2n)Zr from 13.5 to 14.8 MeV

Cross section measurements for the reactions ⁵²Cr(n,2n)⁵¹Cr, ⁶⁶Zn(n,2n)⁶⁵Zn, ⁸⁹Y(n,2n)⁸⁸Y and ⁹⁶Zr(n,2n)⁹⁵Zr were carried out in the neutron energy range 13.47–14.79 MeV applying the activation technique. Neutrons were produced via the T(d,n)⁴He reaction, making use of the variation of neutron energy with the emission angle. The neutron fluences incident on the samples were determined relative to the well-evaluated cross section for the reaction ⁹³Nb(n,2n)^92mNb.

The induced γ-ray activities of the irradiated Zn, Zr and Y₂O₃ samples and their monitor foils were measured by means of a calibrated Ge(Li) γ-ray detector at the KFI, Debrecen. At the IRK, Vienna, relative γ-ray measurements using a high-purity Ge detector were combined with integral γ-ray counting by means of a NaI(TI) well-type detector on the Cr, Zn and Zr foils of highest activity and on some Nb monitor foils; integral γ-ray counting only was applied in the case of the Y₂O₃ samples. All necessary corrections were taken into account.

The results are compared to the corresponding results of cross section measurements published in the literature. The uncertainties obtained in this work are considerably smaller in most cases than the uncertainties given by other authors.     

中子俘获反应截面在线测量技术研究

利用γ全吸收型4π BaF₂探测装置,对中子俘获反应截面进行了在线测量。基于HI-13串列加速器提供的脉冲化质子束,通过⁷Li(p,n) ⁷Be反应产生中子,构建了keV能区中子源实验条件,经屏蔽准直后的中子轰击样品,应用4π BaF₂装置在线测量(n,γ)反应复合核退激时释放的瞬发γ射线级联,测量了Au、C、Nb、空白等样品。通过计算⁹³Nb(n,γ)⁹⁴Nb和¹⁹⁷Au(n,γ)¹⁹⁸Au两个反应的截面数据比值并与文献数据比对,检验了4π BaF₂探测装置和(n,γ)反应截面在线测量技术,为在中国散裂中子源（CSNS）上顺利开展(n,γ)反应截面数据测量工作提供了技术支持。     

RBS studies of the lattice damage caused by 1 Me V Si implantation into Al0.3Ga0.7As/GaAs superlattices at elevated temperature

The lattice damage accumulation in GaAs and Al_0.3Ga_0.7As/GaAs superlattices by 1 MeV Si⁺irradiation at room temperature and 350°C has been studied. For irradiations at 350°C, at lower doses the samples were almost defect-free after irradiation, while a large density of accumulated defects was induced at a higher dose. The critical dose above which the damage accumulation is more efficient is estimated to be 2 × 10¹⁵ + Si/cm² for GaAs, and is 5 × 10¹⁵ Si/cm² for Al_0.8Ga_0.7As/GaAs superlattice for implantation with 1.0 MeV Si ions at 350°C. The damage accumulation rate for 1 MeV Si ion implantation in Al_0.3Ga_0.7As/GaAs superlattice is less than that in GaAs.     

Positron emission yields for encapsulated Na sources

We have measured the total γ-activity and the emitted positron yields from two commercial ²²Na sources ( 5 mCi and 70 mCi). For the weaker source, we find good agreement between the number of positrons expected (based on γ-yield measurements) and those observed, after estimating the effect of positron absorption in the Ti window of the source capsule. The yield of positrons from the stronger source is a factor of two lower than expected. Reasons for the discrepancy are discussed.     

keV能区中子注量率测量初级标准装置研制

由于大多数中子探测器在keV能区处于共振能区,截面数据无法精确已知,无法作为中子注量率测量初级标准装置。⁶Li在keV能区的截面精确已知,本文以此设计了一种包含⁶LiF转换体的硅半导体探测器系统（LiF-SSD探测器）,建立了keV能区中子参考辐射场中子注量率测量初级标准装置。利用SRIM和TRIM程序估算了LiF-SSD探测器的计数率;基于Geant4开发了探测器响应计算程序,给出了中子能量为27.4 keV的探测器脉冲幅度计算谱;利用⁴⁵Sc(p,n)-⁴⁵Ti反应,测量了27.4 keV中子能量点的探测器脉冲幅度谱,测量结果与理论计算谱符合较好。     

北京市气溶胶放射性核素分析(2013—2016)

利用中国锦屏地下实验室(CJPL)低本底γ谱仪对北京地区近4年34组气溶胶样品中长寿命放射性核素进行研究。发现气溶胶样品中含有²³⁸U、²²⁶Ra、²¹⁰Pb、²³²Th、²²⁸Ra、 ⁴⁰K、⁷Be、¹³⁷Cs,其活度浓度均值分别为17.47 μBq·m^-3、21.19 μBq·m^-3、2.39 mBq·m^-3、11.12 μBq·m^-3、14.43 μBq·m^-3、226.64 μBq·m^-3、6.98 mBq·m^-3、2.36 μBq·m^-3,且均在本底范围之内。同时,放射性核素活度浓度与环境参数存在相关性,⁷Be、⁴⁰K、¹³⁷Cs、²²⁶Ra均与季节负相关,²¹⁰Pb与季节正相关;⁴⁰K与空气质量指数(AQI)正相关。     

γ射线闪烁体探测器响应函数模型研究

建立了一种可用于γ射线能谱分析的CsI(Tl)闪烁体探测器响应函数(DRF)模型,并对0.05~1.5 MeVγ射线能谱进行了拟合。描述γ射线能谱特征的每个函数均是基于对射线作用机制的分析,采用权重最小二乘法实现了22 Na、60 Co、137 Cs、238Pu实验能谱的拟合,并同时得到了函数中与射线能量相关的非线性参数。最后利用该DRF模型对CsI(Tl)探测器测量152 Eu源的γ射线能谱进行了拟合,结果表明,此DRF模型可较好地应用于γ射线能谱的分析。     

Charged-particle activation methods for the analysis of carbon and oxygen in high-purity gallium

Methods for the instrumental analysis of C and O at trace level in high-purity gallium were developed. The ¹²C (d, n)¹³N and ¹⁶O(t, n)¹⁸F reactions were used between 2.5 and 3.5 MeV, allowing analyses down to tens of ppb/weight. The ¹⁶O(p, )¹³N reaction at 15 MeV was also used; in this case ¹³N has to be separated radiochemically.     

Mechanism of irradiation assisted stress corrosion crack initiation in thermally sensitized 304 stainless steel

Thermally sensitized 304 stainless steels, irradiated up to 1.2 × 10²¹ n/cm² (E > 1 MeV), were slow-strain-rate-tensile tested in 290 °C water containing 0.2 ppm dissolved oxygen (DO), followed by scanning and transmission electron microscopic examinations, to study mechanism of irradiation-assisted-stress-corrosion-crack (IASCC) initiation. Intergranular (IG) cracking behaviors changed at a border fluence (around 1 × 10²⁰ n/cm²), above which deformation twinning were predominant and deformation localization occurred earlier with increasing fluence. The crack initiation sites tended to link to the deformation bands, indicating that the crack initiation may be brought about by the deformation bands interacted with grain boundaries. Thus the border fluence is equivalent to the IASCC threshold fluence for the sensitized material, although the terminology of IASCC is originally given to the non-sensitized materials without microstructural definition. The IASCC threshold fluence was found to change with irradiation conditions. Changes in IASCC susceptibility and IASCC threshold fluence with fluence and DO were further discussed.