^60Coγ射线在Au／Al界面剂量分布测量及其蒙特卡罗模拟

研究了高原子序数材料金与铝交界时^60Coγ射线入射产生的剂量深度分布。用电离室测量了Au/Al界面剂量梯度分布，并且用蒙特卡罗方法对界面附近的剂量梯度分布进行了计算，得到了与实验符合较好的结果。采用的实验覆试及理论模拟方法为研究γ射线剂量增强提供了手段。     

γ射线外照射条件下体模红骨髓剂量及剂量深度分布的蒙特卡罗计算

用蒙特卡罗方法,对0.025、0.05、0.11、0.30、0.661、1.25、3.0和6.OMeV等八种能量的平行宽束γ射线沿垂直于体模中心轴线方向的旋转照射,位于体模躯干下端离体模中心轴线的距离分别为50、100和200cm的1.25MeVγ点源对体模正面照射,1.25MeV平行宽束γ射线对体模正面、背面和侧面方向的垂直照射,以及当体模处于年龄为22.5小时的落下灰γ辐射场中时,计算了体模的红骨髓平均剂量D_m、干细胞活存率计权等效剂量D_(sw)和组织吸收剂量的深度分布。计算结果,除低能(<0.05MeV)γ射线和近距离(距体模中心2m以内)点源照射条件之外,D_m和D_(sw)在2％以内相符。对于在落下灰γ辐射场中测量人体红骨髓平均剂量的仪器,可用1.25MeVγ射线平行宽束旋转照射条件进行刻度。     

^60Coγ射线在界面附近金中的剂量分布

设计了一种多层平行板金电离室，应用测量法测量了＾６０Ｃｏγ射线在金与低原子序数材料交界时界面及金中的剂量分布。     

γ 射线在硅界面附近的剂量分布

研究了金、钨等多种材料与硅交界时６０Ｃｏγ射线在界面硅一侧产生的深度剂量分布。将该分布与均匀硅材料中的平衡剂量比较,发现在界面附近具有明显的剂量梯度分布。特别在金等高原子序数材料与硅交界的情况下,硅界面的剂量有显著增强现象。以康普顿散射、光电、俄歇效应和次级电子的输运机制为基础,用半径验电子输运方程对界面附近的剂量梯度分布进行了计算,得到了与实验符合较好的结果。     

医用加速器X-射线射野剂量分布的蒙特卡罗模拟与实验测量

用电离室测量及蒙特卡罗方法计算水模体中瓦里安6 MV X-射线射野的百分深度剂量和射野离轴比,对测量和计算结果进行比较和分析。结果表明:10 cm×10 cm射野百分深度剂量在0-20 cm深度范围内,按2 mm/2%标准,?≤1的通过率为96.47%,按3 mm/3%标准,?≤1的通过率为99.23%;射野离轴比按2 mm/2%标准,?≤1的通过率为97.56%,按3 mm/3%标准,?≤1的通过率为99.42%;10 cm×10 cm射野深度剂量中的电子线份额为5.3%,40 cm×40 cm射野深度剂量中的电子线份额为15.2%。通过电离室测量和蒙特卡罗计算的方法能够确定X-射线射野的剂量分布特性。     

~(60)Coγ辐照加工产品剂量分布的蒙特卡罗模拟

对上海金鹏源(SHJPY)~(60)Coγ辐照装置进行数学建模,运用蒙特卡罗方法(MCNP),模拟计算辐照装置在装载0.1g/cm3的均匀产品情况下的剂量分布,软件模拟计算结果的统计误差控制在5%以内,模拟计算结果与实际0.1g/cm3产品剂量分布测试结果比较,发现偏差的绝对值在15%(多数在8%以下)以内,模拟计算与测量数据基本吻合,计算结果可以反应产品吸收剂量的分布规律。     

^60Co远程治疗机剂量场分布的蒙特卡罗计算

基于^60Co放射源的远程治疗机是常用的放疗设备。对治疗机的靶区做精确的剂量计算有助于确保放疗质量。现今放疗设备剂量分布的计算基本是以半经验解析方法为主，而半经验解析方法的适用范围是有限的，用蒙特卡罗方法可很好地克服以上缺陷，因此有必要对蒙特卡罗方法在放射医学领域中的应用作进一步研究，建立一种更为准确和实用的剂量场分布的计算方法。     

γ射线透过率的蒙特卡罗模拟

为验证MCNP程序进行γ射线透过率模拟的准确性,利用MCNP程序模拟了能量分别为2、5、8、10 MeV的γ射线穿过不同厚度的铅和铁后的透过率值。模拟结果表明,利用MCNP程序进行γ射线透过率模拟,与按射线衰减规律的计算值相符。     

60Co γ射线辐照营养霜临界剂量研究

对辐照营养霜的氧化还原电位、超微弱发光、色泽三刺激值以及理化指标进行了分析,认为辐照营养霜的临界剂量为8kGy。     

用蒙特卡罗方法计算^60Co集装箱检测大厅辐射场剂量分布及其散？…

本文应用蒙特卡罗方法计算了无模拟检测物才有模拟检测物情况下＾６０Ｃｏ集装箱检测大厅内的辐射剂量率分布。首先将无模拟检测物条件下的计算结果与实验测量数据对照,验证了所设物理模型的合理性。然后,用两种厚度的聚乙烯板和铁板作模拟检测物进行了系统的计算。通过对计算结果的分析,讨论了模拟检测物对厅内辐射剂量率的影响。结果表明,＾６０Ｃｏ集装箱检测系统的辐射安全性良好。     

X射线不同方向入射界面产生剂量增强的模拟研究

为了研究X射线入射方向对界面剂量增强的影响,通过建立一个典型的金/硅界面结构模型,采用MCNP蒙卡计算程序计算50keV能量X射线以不同的方向入射界面时在规定的区域内产生的能量沉积,进而得到剂量增强系数.     

Thermodynamic properties at the kinetic freeze-out in the Au+Au and Cu+Cu collisions at the RHIC using the Tsallis distribution

The thermodynamic properties of charged particles,such as the energy density,pressure,entropy density,particle density,and squared speed of sound at the kinetic freeze-out in the Au+Au collisions from the relativistic heavy ion collider(RHIC)beam energy scan program(√sNN=7.7-200 GeV)and in the Cu+Cu collisions at √sNN=62.4,200 GeV are studied using the thermodynamically consistent Tsallis distribution.The energy density,pressure,and particle density decrease monotonically with the collision energy for the same collision centrality;These properties also decrease monotonically from the central to peripheral collisions at the same collision energy.While the scaled energy density e/T4 and scaled entropy density s/T3 demonstrate the opposite trend with the collision energy for the same collision centrality.There is a correlation between e/T4 and s/T3 at the same centrality.In addition,the squared speed of sound was calculated to determine that all the collision energies share nearly the same value at different collision centralities.     

Si/SiO2系统的总剂量辐射损伤及辐射感生界面态的能级分布

对比了目前常用的三种用54HC电路制作工艺制作的MOS电容的总剂量辐射实验结果,并从微观氧化物电荷、界面态的感生变化及其界面态的能量分布变化等角度,研究了在不同制作工艺条件下,54HC电路Si/SiO2系统总剂量辐射损伤特性.     

Determining the shear properties of the PyC/SiC interface for a model TRISO fuel

The fracture behavior of TRISO-coated fuel particles is dependent on the shear strength of the interface between the inner pyrolytic carbon (PyC) and silicon carbide coatings. This study evaluates the interfacial shear properties and the crack extension mechanism for TRISO-coated model tubes using a push-out technique. The interfacial debond shear strength was found to increase with increasing sample thickness and finally approached a constant value. The intrinsic interfacial debond shear strength of ∼280 MPa was estimated. After the layer is debonded, the applied load is primarily transferred by interfacial friction. A non-linear shear-lag model predicts that the residual clamping stress at the interface is ∼350 MPa, and the coefficient of friction is ∼0.23, yielding a frictional stress of ∼80 MPa. These relatively high values are attributed to the interfacial roughness. Of importance in these findings is that this unusually high interfacial strength could allow significant loads to be transferred between the inner PyC and SiC in application, potentially leading to failure of the SiC layer.     

Gate/Geant4-based Monte Carlo simulation for calculation of dose distribution of 400 MeV/u carbon ion beam and fragments in water

The applications of carbon ion beam in tumor therapy have attracted more attention in recent years.Monte Carlo simulation is an important approach to obtain accurate radiotherapy parameters. In this work, a400 Me V/u carbon ion beam incident on water phantom was simulated with Gate/Geant4 tools. In methods, the authors set up a carbon ion beam source according to the experiment parameters of Haettner, defined the geometries and materials, set up the physics processes, and designed the means of information collection. In results,the authors obtained the longitudinal dose distribution, the lateral dose distribution, and the relative uncertainty of dose. The dose contributions of all kinds of fragments were calculated detailedly and compared with the Francis results. This work is helpful for people's understanding of the dose distributions produced by carbon ion beam and fragments in water. The simulation method is also significative for radiotherapy treatment planning of carbon ion beam, and it is easy to extend. For obtaining a special result, we may change the particle energy, particle type,target material, target geometry, physics process, detector,etc.