Laser-assisted Simulation of Dose Rate Effects of Wide Band Gap Semiconductor Devices

Laser-assisted simulation technique has played a crucial role in the investigation of dose rate effects of silicon-based devices and integrated circuits,due to its exceptional advantages in terms of flexibility,safety,convenience,and precision.In recent years,wide band gap materials,known for their strong bonding and high ionization energy,have gained increasing attention from researchers and hold significant promise for extensive applications in specialized environments.Consequently,there is a growing need for comprehensive research on the dose rate effects of wide band gap materials.In response to this need,the use of laser-assisted simulation technology has emerged as a promising approach,offering an effective means to assess the efficacy of investigating these materials and devices.This paper focused on investigating the feasibility of laser-assisted simulation to study the dose rate effects of wide band gap semiconductor devices.Theoretical conversion factors for laser-assisted simulation of dose rate effects of GaN-based and SiC-based devices were been provided.Moreover,to validate the accuracy of the conversion factors,pulsed laser and dose rate experiments were conducted on GaN-based and SiC-based PIN diodes.The results demonstrate that pulsed laser radiation andγ-ray radiation can produce highly similar photocurrent responses in GaN-based and SiC-based PIN diodes,with correlation coefficients of 0.98 and 0.974,respectively.This finding reaffirms the effectiveness of laser-assisted simulation technology,making it a valuable complement in studying the dose rate effects of wide band gap semiconductor devices.

Dose rate effects on shape memory epoxy resin during 1 Me V electron irradiation in air

The effects of 1 Me V electron irradiation in air at a fixed accumulated dose and dose rates of 393.8,196.9,78.8,and 39.4 Gy s^(-1)on a shape memory epoxy(SMEP)resin were studied.Under low-dose-rate irradiation,accelerated degradation of the shape memory performance was observed;specifically,the shape recovery ratio decreased exponentially with increasing irradiation time(that is,with decreasing dose rate).In addition,the glass transition temperature of the SMEP,as measured by dynamic mechanical analysis,decreased overall with decreasing dose rate.The dose rate effects of 1 Me V electron irradiation on the SMEP were confirmed by structural analysis using electron paramagnetic resonance(EPR)spectroscopy and Fourier transform infrared(FTIR)spectroscopy.The EPR spectra showed that the concentration of free radicals increased exponentially with increasing irradiation time.Moreover,the FTIR spectra showed higher intensities of the peaks at 1660 and 1720 cm^(-1),which are attributed to stretching vibrations of amide C=O and ketone/acid C=O,at lower dose rates.The intensities of the IR peaks at 1660 and 1720 cm^(-1) increased exponentially with increasing irradiation time,and the relative intensity of the IR peak at 2926 cm^(-1)decreased exponentially with increasing irradiation time.The solid-state13 C nuclear magnetic resonance(NMR)spectra of the SMEP before and after 1 Me V electron irradiation at a dose of 1970 k Gy and a dose rate of 78.8 Gy s^(-1) indicated damage to the CH_(2)–N groups and aliphatic isopropanol segment.This result is consistent with the detection of nitrogenous free radicals,a phenoxy-type free radical,and several types of pyrolytic carbon radicals by EPR.During the subsequent propagation process,the free radicals produced at lower dose rates were more likely to react with oxygen,which was present at higher concentrations,and form the more destructive peroxy free radicals and oxidation products such as acids,amides,and ketones.The increase in peroxy free radicals at lower dose rates was thought to accelerate the degradation of the macroscopic performance of the SMEP.

Study of the dose rate effect of 180 nm nMOSFETs

Radiation induced offstate leakage in the shallow trench isolation regions of SIMC 0.18 μm nMOSFETs is studied as a function of dose rate. A ＂true＂ dose rate effect （TDRE） is observed. Increased damage is observed at low dose rate （LDR） than at high dose rate （HDR） when annealing is taken into account. A new method of simulating radiation induced degradation in shallow trench isolation （STI） is presented. A comparison of radiation induced offstate leakage current in test nMOSFETs between total dose irradiation experiments and simulation results exhibits excellent agreement. The investigation results imply that the enhancement of the leakage current may be worse for the dose rate encountered in the environment of space.

Dose-rate effects of low-dropout voltage regulator at various biases

A low-dropout voltage regulator,LM2941,was irradiated by ^(60)Coγ-rays at various dose rates and biases for investigating the total dose and dose rate effects.The radiation responses show that the key electrical parameters, including its output and dropout voltage,and the maximum output current,are sensitive to total dose and dose rates, and are significantly degraded at low dose rate and zero bias.The integrated circuits damage change with the dose rates and biases,and the dose-rate effects are relative to its electric field.

Effects of total dose irradiation on the threshold voltage of H-gate SOI NMOS devices

This work researched the impact of total dose irradiation on the threshold voltage of N-type metal oxide semiconductor field effect transistors(nMOSFETs) in silicon-on-insulator(SOI) technology.Using the subthreshold separation technology,the factor causing the threshold voltage shift was divided into two parts:trapped oxide charges and interface states,the effects of which are presented under irradiation.Furthermore,by analyzing the data,the threshold voltage shows a negative shift at first and then turns to positive shift when irradiation dose is lower.Additionally,the influence of the dose rate effects on threshold voltage is discussed.The research results show that the threshold voltage shift is more significant in low dose rate conditions,even for a low dose of100 krad(Si).The degeneration value of threshold voltage is 23.4%and 58.0%for the front-gate and the back-gate at the low dose rate,respectively.

Energy spectrum measurement and dose rate estimation of natural neutrons in Tibet region

In this work, natural neutron spectra at nine sites in Tibet region were measured using a multi-sphere neutron spectrometer. The altitude-dependence of the spectra total fluence rate and ambient dose equivalent rate were analyzed. From the normalized natural neutron spectra at different altitudes, the spectrum fractions for neutrons of greater than 0.1 MeV do not differ obviously, while those of the thermal neutrons differ greatly from each other. The total fluence rate, effective dose rate and the ambient dose equivalent rate varied with the altitude according to an exponential law.

抗结核固定剂量复合剂对初治活动性肺结核患者病灶吸收效果的影响

目的探讨抗结核固定剂量复合剂对初治活动性肺结核患者病灶吸收效果的影响。方法便利选取2021年2月—2023年1月福州结核病防治院收治的初治活动性肺结核患者64例为研究对象,按照随机数表法分为两组。对照组(32例)给予常规抗结核药物治疗,观察组(32例)实施抗结核固定剂量复合剂治疗。对比两组治疗总有效率、痰菌阴转率、病灶吸收情况、不良反应。结果观察组总有效率为93.75%,高于对照组的75.00%,差异有统计学意义(χ^(2)=4.267,P<0.05)。观察组第2、5、6个月的痰菌阴转率均高于对照组,差异有统计学意义(P均<0.05)。治疗第2、6个月,两组患者病灶吸收情况相比,差异无统计学意义(P>0.05)。两组不良反应发生率相比,差异无统计学意义(P>0.05)。结论在初治活动性肺结核患者中应用抗结核固定剂量复合剂治疗效果显著,能够增强病灶吸收率,提高痰菌阴转率。

双极晶体管空间辐射效应的研究进展

双极晶体管具有电流驱动能力强、噪声低、线性度高等优点,已成为航天飞行器中常用的电子元器件。然而,在空间辐射环境下服役时,双极晶体管容易发生性能退化,进而危及航天设备的运行。因此,本文综述了双极晶体管在空间辐射环境中产生的损伤效应,主要包含电离损伤效应、位移损伤效应以及电离/位移损伤协同效应,并分析了双极晶体管的性能退化规律以及损伤机理,从而为双极晶体管的抗辐射研究提供一定的参考。

器件瞬态剂量率效应脉冲激光试验技术及应用

针对抗瞬态辐射对宽剂量率范围、弱电磁干扰、精细测量等瞬态剂量率效应试验评估需求,开展激光瞬态剂量率效应的激光注入控制及定量模拟试验技术研究,研究脉冲激光与“强光一号”加速器剂量率等效试验机制,结合激光辐照过程中的能量传输模型进行激光有效能量计算,给出激光能量和γ射线剂量率的定量关系,形成直径为3 cm、均匀度达90%的大尺寸高均匀度试验辐照光斑,及等效剂量率大于1.2×10^(12) rad·s^(-1)的激光定量模拟瞬态剂量率效应试验能力。对多款不同类型器件开展了激光和“强光一号”加速器对比试验证明了该技术的有效性,可为抗核辐射发展提供便捷、精细、充分的激光试验技术支持。

A retrospective analysis of the safety and efficacy of low dose tacrolimus (FK506) for living donor liver transplant recipients

We sought to evaluate the efficacy and effects of low-dose tacrolimus （FK506） to recipients with living donor liver transplantation （LDLT）. A total of 66 patients who underwent LDLT between 2001 and 2007 were enrolled in this study. According to different doses of tacrolimus, the recipients were randomly divided into two groups： the low-dose tacrolimus group （group A） and the normal-dose tacrolimus group （group B）. The blood concentration of tacrolimus and its side effects including infection, hyperglycemia, hypertension, high blood creatinine and jaundice were monitored once a week at the perioperative period, and once a month thereafter. Besides, the survival rates of the recipients were analyzed at the 1and 3-year time point after operation. Among these patients, no significant acute rejection was detected after LDLT. The incidences of infection, hyperglycemia, liver dysfunction and renal impairment in group A were markedly lower than those in group B. However, no significant differences were detected in the incidence of hypertension between the two groups. Moreover, the recipients in each group had a similar survival rate according to the results of 1and 3-year follow-up. The incidence of side effects that associated with tacrolimus positively correlated with tacrolimus blood concentration. In conclusion, long-term and low-dose administration of tacrolimus is a safe and effective treatment for LDLT recipients.

Radiological characterization of building materials used in Malaysia and assessment of external and internal doses

In this study, the activity concentrations of ^(226)Ra,^(232)Th,^(222)Rn, and ^(40)K, emanation fractions(P),equilibrium equivalent concentration(EEC), and mass exhalation rates(E_m) of radon released from building materials used in Malaysia were studied using gamma-ray spectrometer with HPGe detector. Radiological parameters[activity concentration index(ACI), indoor air-absorbed dose rate(D_(in)), annual effective dose(AED_(in)) from external and internal(E_(Rn)), soft tissues(H_(ST)) and lung(H_L), and effective dose equivalent(H_(eff))] were estimated to evaluate radiological hazards due to the use of these building materials: sand, cement, gravel, bricks, tiles, fly ash, white cement, and ceramic raw materials. The measured P, EEC,and E_m vary from 10 to 30%, 0.9 to 22 Bq m^(-3), and 33 to 674 mBq h^(-1) kg^(-1), respectively, while the calculated ACI and AED_(in) vary from 0.1 ± 0.01 to 2.1 ± 0.1 and 0.1 ± 0.01 to 2.4 ± 0.6 mSv y^(-1), respectively. On the other hand, the internal annual effective dose ranges from 0.1 to 1.4 mSv y^(-1). The estimated radiological risk parameters were below the recommended maximum values, and radiological hazards associated with building materials under investigation are therefore negligible.

新疆伊犁盆地南缘天然放射性水平评价

本文根据新疆伊犁盆地南缘1∶2.5万地面γ能谱测量中的铀、钍、钾含量数据,对新疆伊犁盆地南缘地表介质的天然放射性进行了研究和评价。测量结果显示,该地区地表介质中放射性核素^(238)U、^(232)Th和^(40)K的比活度,分别为6.14~2584.64 Bq/kg、2.86~105.63 Bq/kg、11.58~2190.83 Bq/kg。γ射线空气吸收剂量率均值为75.56 nGy/h,低于全国(81.50 nGy/h)和世界(80.00 nGy/h)的平均值;内、外照射指数和年有效剂量都在国家限量标准控制范围内。研究区局部放射性水平相对偏高,与含铀地层露头受自然动力和人类活动等作用下铀元素扩散有关;由于含铀地层露头规模有限,其对放射性环境的影响具有强度小、范围小、不均匀特征。

Integrating Test Data and ATBM Simulations into Dose Propagation Uncertainty Formulation for Bone Fracture Risk Assessment

We consider the problem of assessing bone fracture risk for a subject hit by a blunt impact projectile. We aim at constructing a framework for integrating test data and Advanced Total Body Model (ATBM) simulations into the risk assessment. The ATBM is a finite element model managed by the Joint Non-Lethal Weapons Directorate for the purpose of assessing the risk of injury caused by blunt impacts from non-lethal weapons. In ATBM simulations, the quantity that determines arm bone fracture is the calculated maximum strain in the bone. The main obstacle to accurate prediction is that the calculated strain is incompatible with the measured strain. The fracture strain measured in bending tests of real bones is affected by random inhomogeneity in bones and uncertainty in measurement gauge attachment location/orientation. In contrast, the strain calculated in ATBM simulations is based on the assumption that all bones are perfectly elastic with homogeneous material properties and no measurement uncertainty. To connect test data and ATBM simulations in a proper and meaningful setting, we introduce the concept of elasticity-homogenized strain. We interpret test data in terms of the homogenized strain, and build an empirical dose-injury model with the homogenized strain as the input dose for predicting injury. The maximum strain calculated by ATBM has randomness due to uncertainty in specifications of ATBM setup parameters. The dose propagation uncertainty formulation accommodates this uncertainty efficiently by simply updating the shape parameters in the dose-injury model, avoiding the high computational cost of sampling this uncertainty via multiple ATBM runs.

SiGe HBT瞬时剂量率效应实验及仿真研究

锗硅异质结双极晶体管(SiGe Heterojunction Bipolar Transistor,SiGe HBT)由于其优异的温度和频率特性,在航空航天等极端环境中具有良好的使用前景,其辐射效应得到了广泛关注。针对KT9041 SiGe HBT进行了瞬时γ射线及脉冲激光辐照实验,获得其瞬时剂量率效应(Transient Dose Rate Effect,TDRE)响应。实验结果表明,SiGe HBT收集极在辐照下会产生明显的光电流脉冲,并且存在着饱和阈值的现象。此外,在脉冲激光辐照实验中还进行了SiGe HBT总剂量效应与瞬时剂量率效应的协同效应研究。发现SiGe HBT在经过总剂量辐照后其产生的光电流幅值会变大。为了分析实验中观察到的现象,应用TCAD建立了KT9041 SiGe HBT的仿真模型,并进行了瞬时γ射线辐照以及总剂量效应仿真研究。仿真发现,SiGe HBT收集极光电流出现的饱和现象是由示波器端口50Ω匹配电阻所造成的。而总剂量效应导致的光电流幅值变大则是由于总剂量效应会在SiGe HBT收集极电极处的Si/SiO2界面引入正电荷缺陷,正电荷缺陷产生的局部电场会对自由电子产生吸引作用,导致更多的自由电子被收集极收集,从而产生幅值更大的光电流。

水中浸没γ外照射剂量率转换系数计算方法研究

采用蒙特卡罗软件建立点源球壳模型,快速计算得到能量在10 keV~10 MeV区间的30种单能γ射线在水中的有效作用距离;采用蒙卡软件程序的F6卡、F4卡结合FM4卡、*F8卡三种方法,计算得到参考人在水中浸没外照射条件下的单能γ射线和19种核素的放射性活度浓度-剂量率转换系数。计算结果表明,分别与采用MIRD模型的美国能源署FGR 12报告、FGR 15报告和采用体素模型的ICRP 144相比,相对偏差均在±10%以内,计算方法和结果可为工程上快速计算提供借鉴参考。

基于GIS的某流域土壤放射性分布特征和健康风险评价

土壤中天然放射性核素含量调查是土壤污染防治的基础。选取广东省珠江流域某水系,基于GIS技术和放化方法,应用γ辐射剂量率、等效镭比活度、外照射指数和年有效剂量率指标评价了土壤环境放射性水平,最后应用地累积指数法、单因子指数法和内梅罗综合指数法进行了土壤放射性健康风险评价。结果表明:1)研究区土壤中放射性核素^(238)U、^(226)Ra、^(232)Th、^(40)K、^(137)Cs和^(210)Pb含量均值分别为73.31、68.62、103.48、535.12、0.74、60.75 Bq kg(干),与全省范围水平总体水平相当。2)研究区土壤中放射性核素238 U、232 Th、226 Ra、40 K、137 Cs、210 Pb的背景值和异常阈值分别为(27.50,111.55)、(40.46,134.7)、(26.98,103.95)、(232.61,904.00)、(0.43,0.7)、(25.14,98.35)Bq kg(干)。3)土壤环境放射性水平指标D、Raeq、Hex和AEDR的均值分别为(118.68±54.26)nGy h、(257.8±122.91)Bq kg、0.70±0.33、(145.55±66.54)μSv a。4)地累积指数法和单因子指数法测算研究区土壤中放射性核素污染等级均为轻度污染,但内梅罗综合指数法测算结果偏高,污染等级为重度污染。

广西某铀矿山周围土壤和大米放射性调查及评价

在调查研究2016—2021年广西地区某铀矿山附近土壤中的^(238)U、^(226)Ra及种植大米中的^(238)U、^(226)Ra、^(210)Po、^(210)Pb等放射性核素活度浓度的基础上,对其进行了评价。Spearman秩相关系数分析显示,在2016—2021年铀矿山周围土壤和大米中的^(238)U、^(226)Ra、^(210)Po、^(210)Pb等没有显著变化,大部分采样点土壤污染程度属于无污染到中污染。待积有效剂量率依^(210)Po、^(210)Pb、^(226)Ra、^(238)U顺序降低,USEPA健康风险模型计算结果显示健康总风险低于不可接受值。

脉冲式低剂量率放疗在复发食管癌再程放疗中的疗效观察及耐受性分析

目的探讨脉冲式低剂量率放疗在复发食管癌再程放疗中的疗效及耐受性。方法选取2018年1月~2019年12月扬州大学附属医院肿瘤科收治的食管癌患者80例,所有患者既往均接受过胸部放疗且出现照射野内复发,采用简单随机抽样法将其分为两组:试验组和对照组,每组各40例。试验组患者采用脉冲式低剂量率放疗,对照组患者采用常规调强放疗。观察两组患者的疗效及耐受性。结果试验组患者的客观缓解率更高(80%vs 40%,P=0.010),常见不良反应发生率更低(5%vs 30%,P=0.037),晚期中重度放射性损伤发生率更低(30%vs 75%,P=0.004),急性放射性损伤发生率更低(25%vs 65%,P=0.011),1年生存率更高(85%vs 45%,P=0.008);虽然2年生存率差异无统计学意义(25%vs 5%,P=0.077),但试验组仍然高于对照组。结论脉冲式低剂量率放疗具有显著的临床疗效,且对邻近器官有很好的保护作用,带来的不良反应较小,是复发食管癌患者再程放疗的一种更优的选择。

不同剂量辛伐他汀治疗高脂血症的效果分析

目的:分析不同剂量辛伐他汀治疗高脂血症的临床效果。方法:选取江苏省泗洪医院2020年5月—2021年5月收治的高脂血症患者80例为研究对象,使用随机数字表法分为研究组和对照组,各40例。研究组采取剂量为40 mg/d的辛伐他汀治疗,对照组采取剂量为20 mg/d的辛伐他汀治疗。比较两组血脂指标、临床疗效、不良反应。结果:治疗后,两组血脂指标均较治疗前改善,研究组甘油三酯、总胆固醇及低密度脂蛋白胆固醇水平均低于对照组,高密度脂蛋白胆固醇水平高于对照组,差异有统计学意义(P<0.001);研究组治疗总有效率高于对照组,差异有统计学意义(P=0.025);研究组不良反应总发生率低于对照组,差异有统计学意义(P=0.048)。结论:选用大剂量辛伐他汀治疗高脂血症,能够有效调节患者的血脂水平,获得较好的治疗效果,改善血脂指标,降低不良反应发生率。

Method of simulation of low dose rate for total dose effect in 0.18 μm CMOS technology

Three methods for simulating low dose rate irradiation are presented and experimentally verified by using 0.18 μm CMOS transistors.The results show that it is the best way to use a series of high dose rate irradiations, with 100 °C annealing steps in-between irradiation steps, to simulate a continuous low dose rate irradiation.This approach can reduce the low dose rate testing time by as much as a factor of 45 with respect to the actual 0.5 rad（Si）/s dose rate irradiation.The procedure also provides detailed information on the behavior of the test devices in a low dose rate environment.