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A machine learning approach to TCAD model calibration for MOSFET

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Nuclear Science and Techniques 2023年第12期34卷 133-145页

作者： Bai‑chuan Wang chuan‑xiang tang Meng‑Tong Qiu Wei Chen Tan Wang Jing‑Yan Xu Li‑Li Ding Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China State Key Laboratory of Intense Pulsed Radiation Simulation and Effect Xi’an 710024China

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 ***, 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.

关键词： Machine learning Radiation effects Surrogate model TCAD model calibration

Design, fabrication, and testing of low-group-velocity S-band traveling-wave accelerating structure

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Nuclear Science and Techniques 2022年第11期33卷 133-143页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Liu-Yuan Zhou Yi-Fan Liang Jian Gao Qiang Gao Huai-Bi Chen chuan-xiang tang Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

To implement the Tsinghua Thomson Scattering X-ray Source upgrade plan and the Very Compact Inverse Compton Scattering Gamma-ray Source (VIGAS) program, a new 1.5-m traveling-wave accelerating structure was designed to replace the old 3-m SLAC-type structure with the aim of increasing the accelerating gradient from15 to 30 MV/m. The new type of structure works in the 3π/4 mode with a comparatively low group velocity varying from 0.007c to 0.003c to increase the accelerating gradient at a given power. An elliptical iris was employed to reduce the surface field enhancement. The filling process of the low-group-velocity structure was analyzed using a circuit model. After fabrication, the structure was precisely tuned using the non-contact tuning method, followed by detailed low-power radiofrequency measurements. The structure was first installed and utilized at a beamline for the terahertz experiment at Tsinghua University. After 120 h of conditioning, it is now operating at a gradient of 24.2 MV/m and a 20.7-MW input power, with the klystron operating at its full power. It is expected to generate an accelerating gradient of 30 MV/m when the klystron power is upgraded to 30 MW in the near future.

关键词： Traveling-wave accelerating structure Cavity optimization Tuning method High-power test

Fabrication,tuning,and high-gradient testing of an X-band traveling-wave accelerating structure for VIGAS

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Nuclear Science and Techniques 2022年第8期33卷 77-88页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Qiang Gao Jia-Yang Liu Liu-Yuan Zhou Jian Gao Huai-Bi Chen chuan-xiang tang Department of Engineering Physics Tsinghua UniversityBeijing 100084China Key Laboratory of Particle and Radiation Imaging(Tsinghua University) Ministry of EducationBeijing 100084China

X-band high-gradient linear accelerators are a challenging and attractive technology for compact electron linear-accelerator *** Very Compact Inverse Compton Scattering Gamma-ray Source(VIGAS)program at Tsinghua University will utilize X-band high-gradient accelerating structures to boost the electron beam from 50 to 350 MeV over a short distance.A constant-impedance traveling-wave structure consisting of 72 cells working in the 2π/3 mode was designed and fabricated for this *** tuning and detailed measurements were successfully applied to the *** 180 h of conditioning in the Tsinghua high-power test stand,the structure reached a target gradient of 80 MV/*** breakdown rate versus gradient of this structure was measured and analyzed.

关键词： Traveling-wave accelerating structure X-band high gradient Tuning method High-power test

Beam and image experiment of beam deflection electron gun for distributed X-ray sources

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Nuclear Science and Techniques 2019年第3期30卷 127-138页

作者： Cheng-Jun Tan chuan-xiang tang Wen-Hui Huang Qing-Xiu Jin Ying-Chao Du Qun Luo Pei-Dong Wu Dong-Hai Liu Lu-Ming Zhang Cong Xu Accelerator Laboratory Department of Engineering PhysicsTsinghua University Key Laboratory of Particle and Radiation Imaging Ministry of Education Tsinghua University Nuctech Company Limited

Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray *** electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.

关键词： Beam deflection electron gun X-ray imaging Distributed X-ray sources Stationary CT

Influence of Film Thickness on Nanofabrication of Graphene Oxide

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Nanomanufacturing and Metrology 2024年第2期7卷 13-25页

作者： chuan tang Lei Chen Linmao Qian Tribology Research Institute The State Key Laboratory of Rail Vehicle SystemSchool of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu 610031China

Nanofabrication of two-dimensional materials through mechanical machining is normally influenced by not only process parameters such as load and velocity but also intrinsic properties such as strength and ***,we examined the effects of graphene oxide(GO)film thickness on nanofabrication on the plane surfaces and at the step edges using scanning probe microscope *** material removal of GO initiates at the load above a critical value,which strongly depends on film thickness and *** the increase in film thickness,the critical load decreases monotonically on the plane surfaces but increases gradually at the step ***,the critical load for the GO monolayer at the step edges is at least 25 times lower than that on the plane surfaces,and the gap decreases to around 3 times when GO thickness increases to four ***,mechanical nanofabrication initiating from the GO step edge allows producing various nanopatterns under extremely low loads around 1 ***,the GO nanostructures are deoxidized by annealing at 800°C in high-purity argon to restore their highly functionalized conjugated structures,which are supported by X-ray diffraction and Raman *** work provides a novel approach to fabricating graphene-like nanostructures by deoxidizing GO after nanofabrication,which holds significant potential for applications in graphene-based devices.

关键词： Graphene oxide Nanofabrication Film thickness step edge Nanopattern Deoxidized treatment

Beam dynamics optimization of very-high-frequency gun photoinjector

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Nuclear Science and Techniques 2022年第9期33卷 80-92页

作者： Han Chen Lian-Min Zheng Bin Gao Zi-Zheng Li Ying-Chao Du Ren-Kai Li Wen-Hui Huang chuan-xiang tang Duan Gu Zheng Qi Meng Zhang Hai-Xiao Deng Qiang Gu Dong Wang Department of Engineering Physics Tsinghua UniversityBeijing 100084China Chinese Academy of Sciences Shanghai Institute of Applied PhysicsShanghai 201800China Chinese Academy of Sciences Shanghai Advanced Research InstituteShanghai 201210China

Very-high-frequency(VHF)gun photoinjectors,capable of producing high-brightness and high-repetitionrate electron bunches,are some of the best electron sources for driving MHz-class repetition-rate free-electron *** this study,the beam dynamics optimization of a VHF gun photoinjector for Shanghai HIgh Repetition Rate X-ray Free Electron Laser and Extreme Light Facility(SHINE)is systematically demonstrated using a genetic *** the inclusion of the solenoid geometry as an optimization variable into the genetic algorithm,the optimum projected normalized emittance for 100 pC bunches with bunch length of 1 mm rms is reduced to 0.1 mm mrad for 100%of the particles and 0.075 mm mrad for 95%of the particles,proving that sub-100 nm emittance can be achieved in the SHINE injector using a single-cell Tsinghua University(THU)VHF *** emittance fulfills the requirements not only of SHINE and Linac Coherent Light Source(LCLS)-II but also of LCLS-II-High Energy(LCLS-II-HE).We demonstrate that the optimal emittance in the VHF gun injector is reduced via the optimization of the solenoid geometry,thereby reducing solenoid spherical *** the inclusion of high-order(H.O.)energy spread among the optimization objectives,the *** spread can be reduced by a factor of nearly six using a high-harmonic cavity despite a 38%emittance ***,the beam dynamics in the SHINE main accelerator show that reducing the *** spread in the injector is of great significance to improving compression efficiency and reducing bunch current spike.

关键词： VHF gun photoinjector Multi-objective optimization Emittance High-order energy spread

Lysogenic phage therapy towards emerging contaminant bioremediation

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Science China Technological Sciences 2024年第10期67卷 3129-3131页

作者： tang xiang ZHOU ShunGui Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation College of Resources and EnvironmentFujian Agriculture and Forestry University

Emerging contaminants often arise as by-products of technological advances,(bio)transformation products, or replacements for previously regulated chemicals. Once released into the environment, they present a significant threat to human health within the One Health framework. Among various strategies for contaminant remediation, microbial-based initiatives are particularly promising for the removal and remediation of emerging contaminants due to their environmentally friendly characteristics, such as minimal chemical use and reduced energy consumption.

关键词： BACTERIA GENES

Intelligent responsive self-assembled micro-nanocapsules: Used to delay gel gelation time

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Petroleum Science 2024年第4期21卷 2433-2443页

作者： chuan-Hong Kang Ji-xiang Guo Dong-Tao Fei Wyclif Kiyingi Unconventional Petroleum Research Institute China University of Petroleum

In the application of polymer gels to profile control and water shutoff,the gelation time will directly determine whether the gel can "go further" in the formation,but the most of the methods for delaying gel gelation time are complicated or have low *** is an urgent need for an effective method for delaying gel gelation time with intelligent *** by the slow-release effect of drug capsules,this paper uses the self-assembly effect of gas-phase hydrophobic SiO2in aqueous solution as a capsule to prepare an intelligent responsive self-assembled *** capsule slowly releases the cross-linking agent under the stimulation of external conditions such as temperature and pH value,thus delaying gel gelation *** the pH value is 2 and the concentration of gas-phase hydrophobic SiO2particles is 10%,the gelation time of the capsule gel system at 30,60,90,and 120℃ is12.5,13.2,15.2,and 21.1 times longer than that of the gel system without containing capsule,*** with other methods,the yield stress of the gel without containing capsules was 78 Pa,and the yield stress after the addition of capsules was 322 *** intelligent responsive self-assembled micronanocapsules prepared by gas-phase hydrophobic silica nanoparticles can not only delay the gel gelation time,but also increase the gel *** slow release of cross-linking agent from capsule provides an effective method for prolongating the gelation time of polymer gels.

关键词： Profile control and water shutoff Polymer gel Delayed gelation time Intelligent response Self-assembled Micro-nanocapsules

Nutrient enrichment driven by canopy rainfall redistribution:Mechanism,quantification,and pattern

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Science China Earth Sciences 2024年第5期67卷 1529-1544页

作者： chuan YUAN Xiaoping YUE Yafeng ZHANG Yu ZHANG Yanting HU Qiang tang Li GUO Shuai WANG Xingwu DUAN Wenhua xiang Xiaohua WEI Xiaoyan LI College of Forestry and Biotechnology Zhejiang A&F UniversityHangzhou 311300China Chongqing Jinfo Mountain Karst Ecosystem National Observation and Research Station School of Geographical SciencesSouthwest UniversityChongqing 400715China Shapotou Desert Research and Experiment Station Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China School of Geographical Sciences Hebei Normal UniversityShijiazhuang 050024China Faculty of Life Science and Technology Central South University of Forestry and TechnologyChangsha 410004China State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu 610065China State Key Laboratory of Earth Surface Processes and Resource Ecology Faculty of Geographical ScienceBeijing Normal UniversityBeijing 100875China Yunnan Key Laboratory of Soil Erosion Prevention and Green Development Institute of International Rivers and Eco-securityYunnan UniversityKunming 650091China Department of Earth Environmental and Geographic SciencesUniversity of British Columbia(Okanagan)KelownaBritish Columbia V1V 1V7Canada

Vegetation canopies intercept and redistribute rainfall into throughfall and stemflow,which transfer substantial amounts of elements into the soil,influencing soil microbial community,plant survival,and plant community *** advancements in ecohydrological research,the implication of nutrient enrichment resulting from this redistribution of rainfall by canopies remains largely *** address this gap,we conducted a systematic review of 1020 papers published between 2000 and 2022,gathering data on nutrient concentration and enrichment for critical ions(including K^(+),Na^(+),Ca^(2+),Mg^(2+),NH_(4)^(+),Cl^(-),NO_(3)^(-)and SO_(4)^(2-))from the Web of Science and Chinese Knowledge Infrastructure *** aimed to synthesize the mechanisms,quantify the enrichments,and identify global patterns of nutrient enrichment in stemflow and throughfall across climate zones,and vegetation types and *** results of this study indicate that stemflow exhibits,on average,2.1times greater ion concentration(6.13 mg L^(-1))compared to *** particular,among the investigated ions,SO_(4)^(2-)(12.45and 6.32 mg L^(-1))for stemflow and throughfall,respectively,and Cl^(-)(9.21 and 4.81 mg L^(-1))exhibit the highest concentrations in both rainfall redistribution components,while K^(+)(13.7 and 5.8)and Mg^(2+)(5.6 and 2.8)have the highest enrichment *** climate zones,throughfall and stemflow show the lowest ion concentrations but the highest enrichment factors in extremely humid *** the temperature gradient,ion concentrations are the highest in cold climates with no clear patterns observed for enrichment factors with increasing *** addition,shrubs,conifers,mixed forests,and artificial ecosystems demonstrate enrichment factors 1.1 to 3.0 times greater than those of trees,broad-leaved plants,pure forests,and natural *** findings emphasize the need for increased attentions to artificial ecosystems,such as urban

关键词： Ecohydrology Rainfall redistribution Nutrients transport Enrichment characteristics Climate zones