基于脉冲分组的光剂量监控新算法

精确控制脉冲激光加工光剂量是保证加工产品工艺和质量的关键。在对现有的光剂量控制算法进行分析后,提出了基于脉冲分组的光剂量监控新算法,有效提高了光剂量监测精度和反馈控制速度。设计了光剂量监控系统,实现了脉冲激光加工光剂量实时监测及反馈控制。与Ophir公司的StarLab激光能量测量系统相比,500个激光脉冲以内的总能量测量,本系统测量误差不超过±0.1 5%。对一套脉冲最大重复频率为10 kHz、单脉冲最大能量为5 mJ、恒压工作下最大能量波动为±10%的脉冲激光加工系统光剂量进行了监控实验。在本系统的监控下,可将日标光剂量为150 mJ/mm~2以内的加工光剂量控制精度和重复精度分别控制在0.90%和0.100mJ/mm~2以内,同时将光剂量反馈控制速度提高了4倍。     

三维数值仿真研究锗硅异质结双极晶体管总剂量效应

为探索锗硅异质结双极晶体管(SiGe HBT)总剂量效应的损伤机理,采用半导体器件三维模拟工具(TCAD),建立电离辐照总剂量效应损伤模型,分析比较电离辐射在SiGe HBT不同氧化层结构的不同位置引入陷阱电荷缺陷后,器件正向Gummel特性和反向Gummel特性的退化特征,获得SiGe HBT总剂量效应损伤规律,并与⁶⁰Coγ辐照实验进行对比.结果表明:总剂量辐照在SiGe HBT器件中引入的氧化物陷阱正电荷主要在pn结附近的Si/SiO₂界面处产生影响,引起pn结耗尽区的变化,带来载流子复合增加,最终导致基极电流增大、增益下降;其中EB Spacer氧化层中产生的陷阱电荷主要影响正向Gummel特性,而LOCOS隔离氧化层中的陷阱电荷则是造成反向Gummel特性退化的主要因素.通过数值模拟分析获得的SiGe HBT总剂量效应损伤规律与不同偏置下⁶⁰Coγ辐照实验的结论符合得较好.     

Determination and pharmacokinetics of [6]-gingerol in mouse plasma by liquid chromatography-tandem mass spectrometry

This study describes the development of a rapid and sensitive high‐performance liquid chromatography–electrospray ionization tandem mass spectrometry (LC‐MS/MS) assay for the quantification of [6]‐gingerol in mouse plasma and application to a pharmacokinetic study after dose ranging in mice. The assay involved a protein precipitation step with acetonitrile and an isocratic elution using a mobile phase consisting of acetonitrile and water containing 0.1% formic acid (80:20 v/v). The multiple reaction monitoring was based on the transition of m/z = 277.2 → 177.1 for [6]‐gingerol and 294.2 → 137.1 for nonivamide (internal standard). The assay was validated to demonstrate the specificity, linearity, recovery, accuracy, precision and stability. The calibration curves were linear over the wide concentration range of 10–10,000 ng/mL (r ≥ 0.9988). The lower limit of quantification was 10 ng/mL using a small volume of mouse plasma (20 μL). The method was successfully applied to a pharmacokinetic study in mice after intravenous injection of [6]‐gingerol at 1.5, 3 and 6 mg/kg doses. The pharmacokinetics of [6]‐gingerol were linear over the dose range studied as demonstrated by the linear increase in area under the concentration‐time curve (AUC_inf) with no significant change in the systemic clearance (Cl_s), volume of distribution (V_ss) and elimination half‐life (t_1/2) as a function of dose. Copyright © 2011 John Wiley & Sons, Ltd.     

CMOS电路总剂量效应最劣偏置甄别

采用电路分析和解析建模方法研究了CMOS电路中甄别总剂量效应最劣辐照与测试偏置的问题。通过引入小规模模拟电路和数字电路的例子进行具体分析,获取了不同电路的最劣偏置情况。对于数字电路,引入了敏感因子的概念用于定量计算不同辐照与测试偏置组合下电路的总剂量效应敏感程度。利用实测数据或电路仿真结果对甄别结果进行了一一验证,得到相一致的结论,证明了该研究思路的正确性。     

全息光栅制作中光栅掩模形状随曝光量及干涉场条纹对比度的变化规律

为了在光栅制作中对光栅掩模占宽比及槽深加以控制,结合光刻胶在显影过程中的非线性特性,建立了光栅掩模槽形演化的数学模型,由此分析和模拟曝光量、条纹对比度对光栅槽形的影响。结果表明:在显影条件确定时,光栅掩模占宽比随光刻胶曝光量的增大而减小,条纹对比度减小,则不仅使光栅占宽比减小,同时也是使光栅槽深减小的主要原因,这样做的前提是预先通过实验和计算确定出一个曝光量上限Ec。该方法能够反映光栅掩模形状的演化规律,为全息光栅参数预测和工艺控制提供依据。     

Evaluation and prediction of the degradation of space Si solar cells induced by a low-earth-orbit radiation environment

Space-graded silicon solar cells are evaluated by 1 MeV and 2 MeV electron-irradiation. The mean degradation of the maximum power (P_max) is presented and analyzed. The degradation at both electron energies has been correlated with the displacement damage dose (D_d). A good linearity between the electron D_d and the mean P_max degradation is obtained. The concept of D_d has also been used to predict the Si solar cell response in a low-earth-orbit (Altitude 799 km, Inclination 99^o) radiation environment, considering the shielded effect of a 120 μ m-thick silica coverglass on reducing the radiation. Compared with the on-orbit data from a Si solar array of a Chinese satellite (duration from April 2007 to July 2010), a good match can be found between the on-orbit data and the predicted results using D_d methodology, indicating the method is appropriate for evaluating the radiation damage of the solar cells, and also to provide a new technique for studying radiation effects on the optoelectronic detectors used in many high energy physics applications, where harsh radiation environments produce damage in optoelectronic device materials.     

Monte Carlo simulation of glandular dose in a dedicated breast CT system

A dedicated breast CT system (DBCT) is a new method for breast cancer detection proposed in recent years. In this paper, the glandular dose in the DBCT is simulated using the Monte Carlo method. The phantom shape is half ellipsoid, and a series of phantoms with different sizes, shapes and compositions were constructed. In order to optimize the spectra, monoenergy X-ray beams of 5-80 keV were used in simulation. The dose distribution of a breast phantom was studied: a higher energy beam generated more uniform distribution, and the outer parts got more dose than the inner parts. For polyenergtic spectra, four spectra of Al filters with different thicknesses were simulated, and the polyenergtic glandular dose was calculated as a spectral weighted combination of the monoenergetic dose.     

Analytical and statistical calculation of gamma dose rate for the accident of losing the shield for Tehran Research Reactor

In this paper we study the analytical and statistical results of estimating the gamma dose rate at pool access floor in TRR when the core shield accidentally decreases to some non-permitted levels. Due to the risk of experimental techniques, we use the analytical and statistical methods. In normal conditions (no risk),the discrepancies between experiment and two methods are justified and it is found that for such problems we have to normalize these methods to experimental results as follows: the analytical method by factor 0.13 and MCNP by 1.7.     

Two-dimensional particle-in-cell plasma source ion implantation of a prolate spheroid target

A two-dimensional particle-in-cell simulation is used to study the time-dependent evolution of the sheath surrounding a prolate spheroid target during a high voltage pulse in plasma source ion implantation. Our study shows that the potential contour lines pack more closely in the plasma sheath near the vertex of the major axis, i.e. where a thinner sheath is formed, and a non-uniform total ion dose distribution is incident along the surface of the prolate spheroid target due to the focusing of ions by the potential structure. Ion focusing takes place not only at the vertex of the major axis, where dense potential contour lines exist, but also at the vertex of the minor axis, where sparse contour lines exist. This results in two peaks of the received ion dose, locating at the vertices of the major and minor axes of the prolate spheroid target, and an ion dose valley, staying always between the vertices, rather than at the vertex of the minor axis.     

Radiochromic gel dosemeter for three-dimensional dosimetry

A gel dosemeter in which ionising radiation causes a colour change was produced by modifying an existing Fricke gel system. This allows a more convenient preparation procedure and gives a better quality dosimetric system for three-dimensional (3-D) dose measurements. The role of three active components of the Ferrous sulphate Xylenol orange Gelatin (FXG) gel dosemeter is quantified with special consideration of their effect on system sensitivity and stability. The optimal composition was found to be 0.5 mM ferrous sulphate, 0.1 mM xylenol orange and 25 mM sulphuric acid. The dose response is linear in the range 0.1–30 Gy. The FXG sensitivity, derived from the gradient of the dose response curve, was found to be ΔA=0.084 cm⁻¹ Gy⁻¹, where A is the optical absorption coefficient at a wavelength of 585 nm, with reproducibility and 24 h stability of better than 5%.