Zr^(4+)共掺对Cs_(2)LaLiBr_(6):Ce晶体的中子/伽马甄别性能的影响

中子探测技术广泛用于国土安全、核材料安全检测以及高能物理等领域,由于3He资源紧缺,近年来急需开发出能够同时甄别中子/伽马的新型闪烁晶体,Cs_(2)LaLiBr_(6):Ce(CLLB:Ce)晶体具有良好的中子/伽马甄别能力、优异的能量分辨率以及高的光输出,但其中子/伽马甄别性能有待进一步提高。本研究采用垂直布里奇曼法成功生长了Zr^(4+)共掺杂的CLLB:Ce晶体。通过不同表征手段研究了Zr^(4+)共掺杂CLLB:Ce晶体的结构和组分,结果表明Zr^(4+)成功掺入基质材料且对基质晶体结构不产生明显的影响,Zr^(4+)共掺杂后没有产生新的发光中心,紫外衰减时间约为27.0 ns,仍具有较快的荧光衰减。Zr^(4+)共掺杂CLLB:Ce晶体的品质因子(Figure of Merit,FOM)从1.2提高到1.5,表明其中子/伽马甄别能力得到改善。结合热稳定性和闪烁衰减时间,探讨了衰减时间对FOM的影响机制,Zr^(4+)共掺杂可以抑制浅电子陷阱和Vk中心,减少电子捕获和脱陷过程,使Ce^(3+)直接捕获的概率大大增加,从而表现出更快的衰减速率。本研究显示,Zr^(4+)共掺杂CLLB:Ce晶体在中子/伽马探测领域具有潜在的应用前景。

Optimization of Generator Based on Gaussian Process Regression Model with Conditional Likelihood Lower Bound Search

The noise that comes from finite element simulation often causes the model to fall into the local optimal solution and over fitting during optimization of generator.Thus,this paper proposes a Gaussian Process Regression(GPR)model based on Conditional Likelihood Lower Bound Search(CLLBS)to optimize the design of the generator,which can filter the noise in the data and search for global optimization by combining the Conditional Likelihood Lower Bound Search method.Taking the efficiency optimization of 15 kW Permanent Magnet Synchronous Motor as an example.Firstly,this method uses the elementary effect analysis to choose the sensitive variables,combining the evolutionary algorithm to design the super Latin cube sampling plan;Then the generator-converter system is simulated by establishing a co-simulation platform to obtain data.A Gaussian process regression model combing the method of the conditional likelihood lower bound search is established,which combined the chi-square test to optimize the accuracy of the model globally.Secondly,after the model reaches the accuracy,the Pareto frontier is obtained through the NSGA-II algorithm by considering the maximum output torque as a constraint.Last,the constrained optimization is transformed into an unconstrained optimizing problem by introducing maximum constrained improvement expectation(CEI)optimization method based on the re-interpolation model,which cross-validated the optimization results of the Gaussian process regression model.The above method increase the efficiency of generator by 0.76%and 0.5%respectively;And this method can be used for rapid modeling and multi-objective optimization of generator systems.

Conceptual design of a Cs2LiLaBr6 scintillator‑based neutron total cross section spectrometer on the back‑n beam line at CSNS

To reduce the experimental uncertainty in the 235 U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section(FAST) spectrometer has been designed based on a Cs2Li La Br6(CLLB) scintillator considering the γ-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and γ-rays was evaluated with different 6Li/7 Li abundance ratios using Geant4. The neutron-γdiscrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs,and light readout modes. A cubic 6Li-enriched( > 90%) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the Φ 50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-γ discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.

1英寸Cs_(2)LiLaBr_(6)∶Ce闪烁晶体的生长及性能研究

Cs_(2)LiLaBr_(6)∶Ce(CLLB∶Ce)晶体n/γ双读出闪烁性能优异,其实用化瓶颈在于大尺寸、高光学质量晶体的生长。本研究采用非化学计量比配比,避开CLLB∶Ce非一致熔融组分区域,通过改进研制坩埚下降法晶体生长炉,并优化温度场和降低坩埚下降速度等晶体生长工艺,从而克服组分过冷,保持生长界面稳定,得到了直径1英寸(1英寸=2.54 cm)的CLLB∶Ce晶体毛坯,等径透明部分长度达40 mm,单晶比例由52%提高至79%,可见光区光学透过率达到70%以上。在^(137)Cs激发下能量分辨率达3.7%,在^(252)Cf激发下晶体的品质因子达到1.42,可以很好地甄别中子和γ射线。

全人源抗人干扰素α1b基因工程抗体与抗原的结合表位鉴定

目的鉴定抗原人干扰素α1b(huIFN-α1b)与1株全人源抗体蛋白AIFNa1IgG1的结合表位。方法从正常人分离纯化淋巴细胞并抽提mRNA进行CDNA合成,以CDNA为模板通过PCR扩增得到huIFN-α1b基因,通过重叠延伸PCR法构建huIFN-α1b蛋白29-35位氨基酸残基缺失突变体及点突变体,野生型和突变基因与载体pET30a连接构建重组表达载体,将以上重组表达载体转化大肠杆菌表达宿主E.coli Rosseta(DE3),诱导表达后的huIFN-α1b蛋白及突变体通过Western blot分析其与全人源抗huIFN-α1b基因工程抗体蛋白的结合活性。结果 huIFN-α1b蛋白在E.coli Rosseta(DE3)细胞中成功表达,Western-blot分析表明野生型huIFN-α1b蛋白与抗体结合,29-35位氨基酸缺失与抗体失去结合活性,其中27位的Ser,33位的Asp,34位的Arg,35的His,36位的Asp突变为Gly后,抗体与huIFN-α1b的结合可减弱到不可检测的水平。结论 huIFN-α1b蛋白29-35位氨基酸形成的表位是与抗体AIFNa1IgG1结合的重要表位。