Simulation of gamma minitype reference radiation for calibration of personal dosimeter

An investigation using Monte Carlo simulation on a minitype reference radiation(MRR) for the calibration of gamma personal dosimeters is reported. The distributions of dose rate and scattering gamma spectrum are the main simulation objects with the variable physical structures of MRR and the dosimeters as parameters that are to be calibrated. Further, the influences on the reference radiation caused by these parameters are analyzed in detail.This work provides a theoretical basis for better understanding of MRR used for calibration of gamma personal dosimeters. This analysis can help in the development of a calibration technology for such tools based on MRR.

Radiation Cross Calibration Based on GF-1 Side Swing Angle

Radiation cross-calibration is an effective method to check and verify theaccuracy and stability of sensor measurements. Satellites with high radiation accuracy areused to calibrate satellites with low radiation accuracy. In order to ensure the reliability ofthe radiation cross-calibration method, we propose to obtain the gain and offset of theGaoFen-1 satellite by linear regression after the radiation cross-calibration of the satellitewith low precision and compare with the official coefficient. Finally, we get therelationship between the error in radiation cross-calibration results and side swing angle.The linear correction coefficients of each band are: 0.618, 0.625, 0.512 and 0.474. Theresults show that after the method is corrected by the linear correction coefficient, theerror caused by the side swing angle during the cross-calibration of the orbital radiation isreduced. The accuracy of radiation cross-calibration is improved, the frequency ofcalibration is improved and the requirements of remote sensing applications in the newera are adapted.

A machine learning approach to TCAD model calibration for MOSFET

Machine learning-based surrogate models have significant advantages in terms of computing efficiency. In this paper, we present a pilot study on fast calibration using machine learning techniques. Technology computer-aided design(TCAD) is a powerful simulation tool for electronic devices. This simulation tool has been widely used in the research of radiation effects.However, calibration of TCAD models is time-consuming. In this study, we introduce a fast calibration approach for TCAD model calibration of metal–oxide–semiconductor field-effect transistors(MOSFETs). This approach utilized a machine learning-based surrogate model that was several orders of magnitude faster than the original TCAD simulation. The desired calibration results were obtained within several seconds. In this study, a fundamental model containing 26 parameters is introduced to represent the typical structure of a MOSFET. Classifications were developed to improve the efficiency of the training sample generation. Feature selection techniques were employed to identify important parameters. A surrogate model consisting of a classifier and a regressor was built. A calibration procedure based on the surrogate model was proposed and tested with three calibration goals. Our work demonstrates the feasibility of machine learning-based fast model calibrations for MOSFET. In addition, this study shows that these machine learning techniques learn patterns and correlations from data instead of employing domain expertise. This indicates that machine learning could be an alternative research approach to complement classical physics-based research.

The Study of In-Orbit Calibration Accuracy of NOAA Satellite Infrared Sounder and Its Effect on Temperature Profile Retrievals

The calibration accuracy of High Resolution Infrared Radiation Sounder Mod. 2 (HIRS / 2) on NOAA-10 satellite is analyzed in this paper. The non-linear effect in the linear calibration curve induces a deviation of 1.5 degrees (k) of brightness temperature in the tenth channel (8.3 um, water vapor absorption) of the HIRS/2 and the non-linear effect affects the other channels to a different extent. Based on analyzing non- linearity in two-point calibration curve, a tri-point calibration equation is given. A numerical test of effects of the linear and non-linear calibration models on the accuracy of atmospheric temperature retrievals is carried out.

Feasibility study on determining the conventional true value of gamma-ray air kerma in a minitype reference radiation

A minitype reference radiation(MRR) with dimensions of only 1 m × 1 m × 1 m has been developed for the in situ calibration of photon dosimeters.The present work conducts a feasibility study on determining the conventional true value of gamma-ray air kerma at the point of test in the MRR.Owing to its smaller dimensions,the scattered gamma-rays in the MRR are expected to induce a non-negligible interference with the radiation field compared with conditions in the standard reference radiation stipulated by ISO4037-1 or GB/T12162.1.A gamma-ray spectrometer was employed to obtain the spectra of scattered gamma-rays within the MRR,and the feature components of the spectra were extracted by principal component analysis to characterize the interference of a dosimeter probe in the radiation field.A prediction model of the CAK at the point of test was built by least squares support vector machine based on the feature component data obtained from nine sample dosimeters under five different dose rates.The mean prediction error of the CAK prediction model was within ±4.5%,and the maximum prediction error was about ±10%.

Main Features of a Complete Ultrasonic Measurement Model: Formal Aspects of Modeling of Both Transducers Radiation and Ultrasonic Flaws Responses

This paper aims at describing the theoretical fundamentals of a reciprocity-based ultrasonic measurement model. This complete inspection simulation can be decomposed in two modeling steps, one dedicated to transducer radiation and one to flaw scattering and echo synthesis. The physical meaning of the input/output signals used in these two modeling tools is defined and the theoretical principles of both field calculation and echo computation models are then detailed. The influence on the modeling results of some changes in the simulated configuration (as the incident angle) or some input signal parameters (like the frequency) are studied: it is thus theoretically established that the simulated results can be compared between each other in terms of amplitude for numerous applications when changing some inspection parameters in the simulation but that a calibration for echo calculation is generally required.

Estimation of Thermal Imaging System Operating Range Based on Background Radiation

Traditional operating range prediction methods assume that the atmospheric radiances in a target path and a background path are equal. But they are different in a real-world environment. To solve this problem,the influence of atmospheric radiance on operating range prediction is analyzed in this paper. Range estimation model in thermal imaging based on background radiation（ REBR） is proposed. Infrared image radiometric calibration is used to calculate the background radiation of a system entrance pupil. The result shows that,compared with traditional operating range prediction methods,the REBR method is more suitable for the actual atmospheric transmission process and the physical process of infrared imaging.

Variation in patient dose due to differences in calibration and dosimetry protocols

For precise and accurate patient dose delivery,the dosimetry system must be calibrated properly according to the recommendations of standard dosimetry protocols such as TG-51 and TRS-398. However, the dosimetry protocol followed by a calibration laboratory is usually different from the protocols that are followed by different clinics, which may result in variations in the patient dose.Our prime objective in this study was to investigate the effect of the two protocols on dosimetry measurements.Dose measurements were performed for a Co-60 teletherapy unit and a high-energy Varian linear accelerator with 6 and 15 MV photon and 6, 9, 12, and 15 MeV electron beams, following the recommendations and procedures of the AAPM TG-51 and IAEA TRS-398 dosimetry protocols. The dosimetry systems used for this study were calibrated in a Co-60 radiation beam at the Secondary Standard Dosimetry Laboratory(SSDL) PINSTECH,Pakistan, following the IAEA TRS-398 protocol. The ratio of the measured absorbed doses to water in clinical setting,D_w(TG-51/TRS-398), was 0.999 and 0.997 for 6 and15 MV photon beams,whereas these ratios were 1.013,1.009, 1.003, and 1.000 for 6, 9, 12, and 15 MeV electron beams, respectively. This difference in the absorbed dosesto-water D_w ratio may be attributed mainly due to beam quality(K_Q) and ion recombination correction factor.

On-Site Calibration Method of Dosimeter Based on X-Ray Source

The real-time monitoring of environmental radiation dose for nuclear fa-cilities is an important part of safety, in order to guarantee the accuracy of the monitoring results regular calibration is necessary. Around nuclear facilities there are so many environmental dosimeters installed dispers-edly, because of its huge quantity, widely distributed, and in real-time monitoring state;it will cost lots of manpower and finance if it were tak-en to calibrate on standard laboratory;what’s more it will make the en-vironment out of control. To solve the problem of the measurement ac-curacy of the stationary gamma radiation dosimeter, an on-site calibra-tion method is proposed. The radioactive source is X-ray spectrum, and the dose reference instrument which has been calibrated by the national standard laboratory is a high pressure ionization. On-site calibration is divided into two parts;firstly the energy response experiment of dosim-eter for high and low energy is done in the laboratory, and the energy response curve is obtained combining with Monte Carlo simulation;sec-ondly experiment is carried out in the field of the measuring dosimeter, and the substitution method to calibrate the dosimeter is used;finally the calibration coefficient is gotten through energy curve correction. In order to verify the accuracy of on-site calibration method, the calibrated dosimeter is test in the standard laboratory and the error is 3.4%. The re-sult shows that the on-site calibration method using X-ray is feasible, and it can improves the accuracy of the measurement results of the stationary γ-ray instrument;what’s more important is that it has great reference value for the radiation safety management and radiation environment evaluation.

用于定标海表测温辐射计的镓黑体辐射源

设计了镓黑体对海表测温辐射计进行定标。首先,介绍了该黑体的结构与工作原理,对黑体发射率进行仿真,并开展发射率的测量实验,讨论其不确定度的来源。然后,开展了电加热和水浴加热下镓的相变复现实验,讨论电加热功率对镓相变复现的影响。最后,通过红外海面温度自主辐射计实验对该黑体进行验证。结果表明:该黑体基于蒙特卡罗软件仿真的发射率优于0.9988,实验测得的黑体辐射源发射率结果与仿真结果较为吻合,测量重复性(标准偏差)达0.1%;相变温度坪台的复现性均优于±0.03 K;相变温坪附近时,红外海面温度自主辐射计和FLUKE 1524测温仪测得的黑体腔附近温度的数据差值均在±0.15 K以内。设计的镓黑体可以应用到海表测温辐射计进行校准,为发展自主知识产权的海表测温设备提供校准源。

基于光辐射强度的日盲紫外放电检测结果一致性校准方法

随着紫外放电检测技术的广泛应用,为解决不同型号日盲紫外成像仪的检测结果缺乏一致性和可比性的问题,该文基于MODTRAN模型分析了温度、湿度、气压和检测距离等不同因素对日盲紫外波段光辐射的大气传输过程的影响特性,建立了紫外检测辐射传输模型,搭建了辐射计量一致性校准平台,提出了紫外检测结果一致性校准方法。利用该方法建立了3台不同型号紫外成像仪的检测结果一致性校准公式,可将紫外成像仪测得的光斑面积换算为检测目标产生的光辐射强度。使用3台紫外成像仪对棒-板模型电晕放电和氘灯光源进行紫外放电检测,由一致性校准公式所得检测目标的光辐射强度计算值的相对标准偏差均小于0.1,验证了一致性校准方法的普适性。

基于距离修正的小目标中波红外光谱辐射测温方法

对高速运动的远距离空间目标而言,温度是表征其工作状态与性能的重要参数之一。准确获取目标的温度对判别其运动状态和预测其态势发展等具有重要的参考价值。目前常用的面目标或点目标的处理方法,在小目标的辐射特性测量中将不再适用,而光谱探测增加了目标在波长维度的可分辨信息,可以准确获取目标能量随波长的分布情况,为目标温度的反演提供了可能,极具应用潜力。无狭缝光谱仪可以降低对空间目标的跟踪和稳定精度的要求,具有结构简单、帧频高和响应速度快等特点,在天文观测和航天器观测等方面具有较高的应用价值。对目标红外辐射特性测量的光谱定标模型进行了分析,确定了红外探测器像元线性响应模型中的主要参数。为了减小成像距离对测温精度的影响,提出了一种基于距离修正的目标温度反演模型,提高了测温精度,符合实际工程实践应用中的精度需求,对红外辐射光谱测温具有一定的指导意义。

月球直射辐照度仪同光轴装调及传递定标

采用激光水平仪与平面反射镜相结合的方式,在实验室模拟月球对追踪相机与探测镜头进行同光轴装调,避免未同光轴导致测试不到信号或者信号太小造成数据不准确的问题,实验结果显示实验室同光轴装调误差在±0.03°以内。为保证仪器定标系数的准确性,采用已溯源于国家计量基准的标准灯传递定标微光灯的方式,利用激光测距仪与激光水平仪、平面反射镜相结合的方式保证传递定标精度,解决了直接使用标准灯定标带来的探测器非线性响应误差和长定标距离误差的难题。为地基对月观测仪器建立高精度的月球辐射模型提供了一种思路与解决方法。

卫星微波高层探测通道定标精度评估

全球/区域数值预报同化系统所需要的重要资料来源之一是卫星微波遥感的亮温数据。微波遥感仪器的高层大气(平流层中上部)探测通道亮温的定标精度,受多种因素影响,存在一定的偏差。由于高层大气高精度探测资料相对比较匮乏,因此对微波遥感的高层大气亮温的精度检验评估成为重要研究内容。本文对在轨运行的微波温度遥感器AMSU-A、ATMS和FY-3D MWTS-2在2020年观测数据进行了定标精度检验评估,综合使用了三种评估方法进行了较为全面的分析,即基于掩星资料、再分析资料的辐射传输模拟比较和同类仪器交叉定标比较。三种检验评估方法从不同角度揭示了各仪器高层大气探测通道观测资料的误差特征,分析了对比误差的可能来源。三种评估方案给出的高层通道亮温的偏差存在差异,但基本结果变化趋势是一致的,即高层通道相比中低层通道,存在较大的噪音。除了交叉定标方法,其它两种方法都检验出了高层资料偏差的季节变化;整体而言,AMSU-A表现要优于MWTS-2和ATMS。本研究评估的高层亮温偏差的时间、空间变化特征可为微波高层大气资料的同化、气候应用提供参考。

In-Orbit Calibration Uncertainty of the Microwave Radiation Imager on board Fengyun-3C

This study evaluates the in-orbit calibration uncertainty(CU)for the microwave radiation imager(MWRI)on board the Chinese polar-orbiting meteorological satellite Fengyun-3 C(FY-3 C).Uncertainty analysis of the MWRI provides a direct link to the calibration system of the sensor and quantifies the calibration confidence based on the prelaunch and postlaunch measurements.The unique design of the sensor makes the uncertainty in the calibration of the sensor highly correlate to the uncertainty in the brightness temperature(TB)measured at the hot view,while the cold view has negligible impacts on the calibration confidence.Lack of knowledge on the emission of the hot-load reflector hampers the MWRI calibration accuracy significantly in the descending passes of the orbits when the hotload reflector is heated nonuniformly by the solar illumination.Radiance contamination originating from the satellite and in-orbit environments could enter the primary reflector via the hot view and further impinge on the CU,especially at the 10.65-GHz channels where the main-beam width is much broader than that of higher-frequency channels.The monthly-mean CU is lower than 2 K at all channels,depending on the observed earth scenes and in-orbit environments,and the month-to-month variation of CU is also noticed for all channels.Due to the uncertainty in the emissive hot-load reflector,CU in the descending passes is generally larger than that in the ascending orbits.Moreover,up to 1-K CU difference between the ocean and land scenes is found for the 10.65-GHz channels,while this difference is less than 0.1 K at the 89-GHz channels.

黑体涂层宽温区红外光谱发射率特性研究(内封面文章)

为了研究高发射率黑体涂层的宽温区红外辐射特性,基于两种发射率测量装置测量了应用于不同温度场景的JSC-3和GR两种涂层宽温区3~14μm内的光谱发射率。其中JSC-3和GR涂层的测量温度范围分别是室温~1000℃和室温~150℃。分析了两种涂层光谱发射率与温度之间的关系以及不同角度下方向光谱发射率的变化。实验结果表明:宽温区内JSC-3和GR涂层在8~14μm的光谱发射率分别优于0.96和0.97,且光谱发射率保持稳定,变化量分别小于0.01和0.003。两种涂层在0°~30°内的方向光谱发射率均具有较好的一致性,变化量均小于0.005。最后利用积分球反射法得到了两种涂层在室温下3~14μm内的连续光谱发射率数据,实现了两种涂层在宽温区宽波段内的光谱发射率数据覆盖。

全国标准级测氡仪的统一校准及低浓度测量比对

为了提升国内氡计量能力,组织了全国11家已建标实验室的标准级测氡仪开展统一校准。在校准的基础上,开展了低浓度测量比对,分析参比实验室在低浓度水平处进行量值传递的可行性。统一校准在700~3000 Bq/m^(3)氡浓度量级进行,氡浓度参考值可溯源至氡活度基准装置,不确定度为1.6%(k=2)。各标准级测氡仪的体积活度响应范围为0.93~1.02,不确定度范围为2.2%~3.6%(k=2)。低浓度比对在100~400 Bq/m^(3)氡浓度量级进行,大部分标准级测氡仪的|E_(n)|值小于1,通过优化量传的策略,标准级测氡仪在100 Bq/m^(3)以上开展量值传递是可行的;但在100 Bq/m^(3)或以下浓度量级开展量值传递,各参比实验室仍需提升测量能力及氡浓度调控能力。

智能激光3D投影空间目标辐射照度校准技术

由于激光3D投影系统的光路复杂,且受空间目标的形状和大小的影响,导致在特定空间内难以取得理想的投影效果,使得投影目标与实际投影点之间存在较大的偏差,因此,提出一种辐射照度校准方法。分别利用矩形、圆形两种不同形状的辐射面和敏感面搭建辐射照度测量仪,得到4种不同辐射照度测量结果;利用斯忒藩-玻尔兹曼全辐射定律,对测量结果校准,进而完成对智能激光3D投影空间目标辐射照度的校准。实验结果表明,所提方法辐射照度校准结果与实际结果基本一致,且辐射照度校准误差保持在6 W·m^(2)以内。

逐像元自适应增益成像系统的星上辐射定标方法

逐像元自适应增益成像系统通过在每个像元的电子链路中集成四档不同容积的积分电容,可以在确保高信噪比的前提下实现大动态范围的遥感成像需求。此成像系统在发射前测试时,由于甚低增益(ULG)的动态范围过大而实验室积分球能量有限,只能通过与低增益(LG)的比例系数递推来间接对ULG后半量程的输出特性标定;星载太阳定标器反射能量过大会导致高增益(HG)和中增益(MG)输出饱和也无法直接测定辐射定标系数,只可通过比例系数推定。提出一种星上增益比例系数测定的方案,分别利用四档增益的输出作为特征对实验图像分类,将不同成像目标的输出码值作为多个定标能级,利用最小二乘法线性拟合相邻增益输出后得到相邻增益的比例系数。此方案验证了实验室增益比例系数测定结果,同时在外场成像实验中用该方法计算得到的比例系数用于相邻两档增益中较低增益图像反演较高增益图像,结果与实际较高增益图像对比归一化均方误差大部分小于0.01、两图像结构相关系数基本在90%左右、数据相关系数达到90%。证明该方法测定的相邻两增益比例相关系数有较高准确性,在星上辐射定标时用于高增益辐射定标系数的递推求取有极大的可行性,解决了星上不能直接对HG、MG辐射定标的问题。

基于优先级融合算法的高精度黑体温控研究

为优化红外成像光谱仪探测性能,提出了一种具有用户自定义指标和温控精度达到1.0 mK的优先级融合控制算法(Priority fusion algorithm,PFA),该算法将基础PID、模糊PID和自抗扰控制算法与BP神经网络算法相融合,能够实现高性能黑体温控。通过Simulink仿真实验,仿真结果表明,与传统算法相比,PFA算法的超调量从3.606%下降到0.101%,响应时间从64 min下降到14.4 min,温度控制精度达到1.0 mK。同时搭建了黑体辐射定标平台,物理实验结果与理论模拟结果基本一致。该模型为高精度温控黑体在空间遥感领域的实际应用奠定理论基础,在温控领域具有重大意义。