高纯锗探测器的广泛应用和自主研制进展

以目前国际上极为活跃开展的暗物质探测、无中微子双 衰变研究为例,评述了高纯锗探测器的重要性及其广泛的应用前景。介绍了己开展的高纯锗单晶、探测器制备的关键技术研究进展:合作单位已研制出了用于高纯锗单晶材料制备的区熔炉、单晶炉;并制备出直径为20  50 cm、纯度为12N(< 41011  atoms/cm3)、位错< 5000 atoms/cm2 的锗单晶;掌握了高纯锗探测器(平面型、同轴型)制备的关键技术,用进口高纯锗单晶材料制备出的同轴型高纯锗探测器对射线的能量分辨率及探测效率均达到进口产品指标,使用自制的12N 高纯锗单晶材料己制备出平面型高纯锗探测器。呼吁加速高纯锗研制的自主创新步伐,尽早实现其国产化目标。The article reviews importance and wide applications of HPGe detector, especially the application on the dark matter search experiment and double beta decay experiment. The research progress on the Highpurity germanium single crystal and HPGe detector in China has been introduced. The cooperation partner developed new type zone-refining furnace and single crystal furnace. The ultra-purity germanium single crystal with 20~50 cm, purity up to 12N(net impurity concentration is less than 41011 atoms/cm3), and dislocation less than 5 000 /cm3 was prepared. The key technologies for preparing planar and coaxial HPGe detector were mastered. The coaxial detector, which has been made of imported ultra-purity germanium single crystal has excellent energy resolution and efficiency as the imported commercial detector. The planar detector using selfmade germanium single crystal was also successfully manufactured. The research group appeals for speeding up the pace of independent innovation on the high-purity germanium, and achieving the high-purity germanium localization as soon as possible.     

暗物质理论研究进展

评述了天体物理中暗物质的发现以及标准模型所面临的问题,综述了解决这些问题及标准模型之外可能出现的新物理与暗物质的联系。介绍了暗物质粒子选择条件和可能的暗物质粒子的候选者;对圆柱形暗物质表面密度与星系和星系团暗物质晕的晕核半径的关系进行了讨论,与其他模型进行了比较,得出暗物质晕的特征半径r_*的暗物质表面密度分布不是一个普适量;并叙述了近几年暗物质研究中提出的新理论模型-Hidden dark matter,最后叙述了中国暗物质实验探测研究的进展,2016年底DAMPE的第一批数据有可能给出;中国锦屏地下实验室（CJPL）的CDEX和PandaX合作组的第一期实验没有发现暗物质粒子存在的信号,期待他们下期的实验。A review of the evidence of the dark matter found in universe and the problems faced by the standard model. To address these issues as well as the possible relationship between the new physics beyond the standard model and dark matter, and given the selection condition of dark matter and possible candidates of the weakly-interacting massive particles (WIMPs). The correlation between the column surface density and the halo core radius of the dark matter halos of galaxies and cluster of galaxies is discussed, and the other models are compared. We find that the surface density within the halo characteristic radius r* is not an universal quantity; The new model (hidden dark matter)proposed in the study of dark matter is described. At last, the research progress of dark matter experiment in China is commented. At the end of 2016, the first batch of DAMPE data may be given;No significant excess events of WIMPS were found in the first stage of both the CDEX and PandaX experiments located in the China Jinping Underground Laboratory(CJPL). Look forward to their the next stage of these experiments in CJPL.     

连续小波变换高光谱数据的土壤有机质含量反演模型构建

土壤有机质含量是反映土壤肥力的重要指标,对其进行动态监测是实施精准农业的重要措施。近年来,众多学者尝试采用土壤近地传感(proximal soil sensing),尤其是近地高光谱技术,在田间和实验室获取不同形态土壤的高光谱数据,不断引入新方法建立适用于不同地域和不同土壤类型的有机质含量的反演模型。该研究在实验室内利用ASD FS3采集了土壤高光谱数据,采用“重铬酸钾-外加热法”测得了土壤有机质含量;分析了土壤原始光谱反射率(R)与有机质含量的相关性,选取R2>0.15的敏感波段的反射率;利用CWT对土壤原始光谱反射率(R)、光谱反射率的连续统去除(CR)进行不同尺度的分解,分析小波系数与土壤有机质含量的相关性,选取R2>0.3的敏感波段的小波系数;利用R选取的波段信息和R-CWT,CR-CWT的选取的小波系数,分别建立偏最小二乘回归(PLSR)、BP神经网络(BPNN)、支持向量机回归(SVMR)三种不同的土壤有机质含量反演模型。结果表明：相比R与土壤有机质含量的决定系数R2,R-CWT,CR-CWT变换后得到的小波系数与土壤有机质含量的决定系数R2分别提高了0.15和0.2左右;CR-CWT-SVMR的模型效果最为显著,预测集的R2和RMSE分别为0.83,4.02,RPD值为2.48,具有较高的估测精度,能够全面稳定地估算土壤有机质含量;CR-CWT-PLSR的模型精度与CR-CWT-BPNN,CR-CWT-SVMR相比虽有一定差距,但是其计算量要明显小于非线性的BPNN和SVMR方法,具有模型简单、运算速度快等特点,对开发与设计田间传感器具有较大的应用价值。     

Constraining WIMP magnetic moment from CDMS II experiment

We consider a degenerate or a nearly degenerate dark matter sector where a sizable magnetic moment of a (almost) Dirac type neutral dark matter candidate N is anticipated. Then, due to soft photon exchange, the cross-section in direct detection of N   can be enhanced at low Q²$Q^2$ region. We discuss the implication of this type of models in view of the recent CDMS II report.     

A complete calculation for direct detection of Wino dark matter

In the anomaly-mediated supersymmetry (SUSY) breaking scenario, neutral gaugino of SUL₍₂₎$\mathit{SU}{(2)}_L$ multiplet, Wino, can be the lightest SUSY particle and become a candidate for dark matter. We calculated scattering cross section of Wino dark matter with nucleon, which is responsible for direct detection of the dark matter, on the assumption that the SUSY particles and the heavier Higgs bosons have masses of the order of the gravitino mass in the SUSY standard model. In such a case, the Wino–nucleon coupling is generated by loop processes. We have included two-loop contribution to Wino–gluon interaction in the calculation, since it is one of the leading contributions to the Wino–nucleon coupling. It was found that the spin-independent scattering cross section with proton is ^{10−(46–48)} cm²${10}^{-(46\text{–}48)}{\text{cm}}^2$. While it is almost independent of the Wino mass, the result is quite sensitive to the Higgs boson mass due to the accidental cancellation.     

颗粒气体团簇行为实验研究

颗粒体系由于非弹性碰撞和摩擦等内秉的能量耗散特性,由宏观粒子形成的颗粒气体体系经常会有局部凝聚现象,这是颗粒气体体系与分子气体体系的最大区别之一.理解和预测这一现象的发生将有助于人们对远离平衡态体系的复杂现象,如有序结构、斑图和团簇形成的认知.这种局部凝聚现象可以类比于分子气体中亚稳分解形成的液滴,将气液相分离用于解释和寻求局部凝聚现象的此模型得到了分子动力学模拟的校验.但是实验的校验却由于宏观粒子运动受重力作用的影响难以在实验室中实现.作为实践十号卫星的前期实验,本文利用国家微重力实验室落塔装置,以水平激振装有不同尺寸和数目的颗粒样品,在短时微重力条件下,成功观察到颗粒气体团簇的形成;并将实验结果与颗粒气体类范德瓦耳斯气体分子相分离模型对比,由形成团簇样品的颗粒数密度条件,来实验确定了所选颗粒的恢复系数,得到直径为0.5 mm的钛珠颗粒的恢复系数在0.6—0.8之间,直径为1 mm的钛珠颗粒的恢复系数约为0.8,直径为2.5 mm的钛珠颗粒的恢复系数应大于0.8.     

高温辐射场作用下的原子过程

等离子体中辐射能量密度与物质能量密度的比值是区分等离子体原子过程性质的重要参量. 根据这个参量, 等离子体中的原子过程可分为碰撞占优和辐射占优两种典型类型. 数值模拟发现碰撞占优和辐射占优的原子过程有不同的性质: 碰撞占优的等离子体能够很快达到LTE状态; 辐射占优等离子体的束缚电子温度、电离度和自由电子温度存在不同的弛豫时间尺度, 存在某种形式的准平衡状态.     

成分无序颗粒体系中切向力的分布

采用离散元模拟研究成分无序颗粒体系中切向力的几率分布.将切向力分为主切向力和次切向力分别进行统计,结果表明主切向力与次切向力服从不同的分布.随着缺陷率的增加,主切向力由近似的正态分布变为双峰状的分布,最后变为单峰状的分布;而次切向力总是指数型分布.通过理论计算和模拟讨论了切向力分布,说明缺陷率较大的成分无序体系与结构无序体系有类似的力分布规律.