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A compact X-band backward traveling-wave accelerating structure

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Nuclear Science and Techniques 2024年第5期35卷 13-29页

作者： Xian-Cai Lin Hao Zha Jia-Ru Shi Qiang Gao Fang-Jun Hu Qing-Zhu Li Huai-Bi Chen Department of Engineering Physics Tsinghua UniversityBeijing 100084China key laboratory of particle and radiation imaging(Tsinghua University) Ministry of EducationBeijing 100084China

Very high-energy electrons(VHEEs)are potential candidates for FLASH radiotherapy for deep-seated *** proposed a compact VHEE facility based on an X-band high-gradient high-power *** this study,we investigated and realized the first X-band backward traveling-wave(BTW)accelerating structure as the buncher for a VHEE facility.A method for calculating the parameters of single cell from the field distribution was introduced to simplify the design of the BTW ***-domain circuit equations were applied to calculate the transient beam parameters of the buncher in the unsteady state.A prototype of the BTW structure with a thermionic cathode-diode electron gun was designed,fabricated,and tested at high power at the Tsinghua X-band high-power test *** structure successfully operated with 5-MW microwave pulses from the pulse compressor and outputted electron bunches with an energy of 8 MeV and a pulsed current of 108 mA.

关键词： Backward traveling-wave accelerating structure Equivalent circuit model High-power test Very high-energy electron radiotherapy

Analyzing the surface passivity effect of germanium oxynitride:a comprehensive approach through first principles simulation and interface state density

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Nuclear Science and Techniques 2024年第5期35卷 74-84页

作者： Sheng-Jie Du Xiu-Xia Li Yang Tian Yuan-Yuan Liu Ke Jia Zhong-Zheng Tang Jian-Ping Cheng Zhi Deng Yu-Lan Li Zheng-Cao Li Sha-Sha Lv College of Nuclear Science and Technology Joint laboratory of Jinping Ultra‑Low radiation Background Measurement of Ministry of Ecology and Environment key laboratory of Beam Technology of Ministry of Education Beijing Normal UniversityBeijing Normal UniversityBeijing 100875China Joint Research Center Nuctech Company LimitedBeijing 100084China Department of Engineering Physics Key Laboratory of Particle&Radiation Imaging of Ministry of EducationTsinghua UniversityBeijing 100084China key laboratory of Advanced Materials(MOE) School of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

High-purity germanium(HPGe)detectors,which are used for direct dark matter detection,have the advantages of a low threshold and excellent energy *** surface passivation of HPGe has become crucial for achieving an extremely low energy *** this study,first-principles simulations,passivation film preparation,and metal oxide semiconductor(MOS)capacitor characterization were combined to study surface *** calculations of the energy band structure of the -H,-OH,and -NH_(2) passivation groups on the surface of Ge were performed,and the interface state density and potential with five different passivation groups with N/O atomic ratios were accurately analyzed to obtain a stable surface *** on the theoretical calculation results,the surface passivation layers of the Ge_(2)ON_(2) film were prepared via magnetron sputtering in accordance with the optimum atomic ratio *** microstructure,C-V,and I-V electrical properties of the layers,and the passivation effect of the Al/Ge_(2)ON_(2)/Ge MOS were characterized to test the interface state *** mean interface state density obtained by the Terman method was 8.4×10^(11) cm^(-2) eV^(-1).The processing of germanium oxynitrogen passivation films is expected to be used in direct dark matter detection of the HPGe detector surface passivation technology to reduce the detector leakage currents.

关键词： Surface passivation High purity germanium detector Germanium nitrogen oxide Interface state density

Finesse measurement for high-power optical enhancement cavity

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Chinese Physics B 2024年第1期33卷 414-421页

作者：陆心怡柳兴田其立王焕汪嘉俊颜立新 Department of Engineering Physics Tsinghua UniversityBeijing 100084China key laboratory of particle&radiation imaging Ministry of EducationBeijing 100084China

Finesse is a critical parameter for describing the characteristics of an optical enhancement cavity(OEC). This paper first presents a review of finesse measurement techniques, including a comparative analysis of the advantages, disadvantages, and potential limitations of several main methods from both theoretical and practical perspectives. A variant of the existing method called the free spectral range(FSR) modulation method is proposed and compared with three other finesse measurement methods, i.e., the fast-switching cavity ring-down(CRD) method, the rapidly swept-frequency(SF) CRD method, and the ringing effect method. A high-power OEC platform with a high finesse of approximately 16000 is built and measured with the four methods. The performance of these methods is compared, and the results show that the FSR modulation method and the fast-switching CRD method are more suitable and accurate than the other two methods for high-finesse OEC measurements. The CRD method and the ringing effect method can be implemented in open loop using simple equipment and are easy to perform. Additionally, recommendations for selecting finesse measurement methods under different conditions are proposed, which benefit the development of OEC and its applications.

关键词： optical enhancement cavity finesse measurement cavity ring-down ringing effect

Research on a Monte Carlo global variance reduction method based on an automatic importance sampling method

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Nuclear Science and Techniques 2024年第5期35卷 200-215页

作者： Yi-Sheng Hao Zhen Wu Shen-Shen Gao Rui Qiu Hui Zhang Jun-Li Li Department of Engineering Physics Tsinghua UniversityBeijing 100084China key laboratory of particle and radiation imaging of Ministry of Education Beijing 100084China Nuctech Company Limited Beijing 100084China

Global variance reduction is a bottleneck in Monte Carlo shielding *** global variance reduction problem requires that the statistical error of the entire space is *** study proposed a grid-AIS method for the global variance reduction problem based on the AIS method,which was implemented in the Monte Carlo program *** proposed method was validated using the VENUS-Ⅲ international benchmark problem and a self-shielding calculation *** results from the VENUS-Ⅲ benchmark problem showed that the grid-AIS method achieved a significant reduction in the variance of the statistical errors of the MESH grids,decreasing from 1.08×10^(-2) to 3.84×10^(-3),representing a 64.00% *** demonstrates that the grid-AIS method is effective in addressing global *** results of the selfshielding calculation demonstrate that the grid-AIS method produced accurate computational ***,the grid-AIS method exhibited a computational efficiency approximately one order of magnitude higher than that of the AIS method and approximately two orders of magnitude higher than that of the conventional Monte Carlo method.

关键词： Monte Carlo Global variance reduction Reactor shielding Automatic importance sampling

Normalized glandular dose coefficients for digital breast tomosynthesis using detailed Chinese breast models

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Nuclear Science and Techniques 2024年第5期35卷 42-59页

作者： Jia-Hao Wang Rui Qiu An-Kang Hu Ye-Qi Liu Zhen Wu Hui Zhang Jun-Li Li Department of Engineering Physics Tsinghua UniversityBeijing 100084China key laboratory of particle and radiation imaging Ministry of EducationTsinghua UniversityBeijing 100084China Joint Institute of Tsinghua University Nuctech Company Limited BeijingBeijing 100084China

The rise in breast cancer diagnoses among Chinese women has necessitated the use of X-ray breast screening,which carries a radiation *** study aimed to provide a dosimetry protocol for the Chinese female population to replace the traditional standard that utilizes simplified breast models,for the accurate estimation of the mean glandular dose of a patient undergoing digital breast tomosynthesis(DBT).The first set of detailed Chinese female breast models and representative breast parameters was *** backscatter radiation and computational efficiency,we improved the combination of these models and the Chinese reference adult female whole-body voxel *** acquisition for four commercial DBT systems that are widely employed in China was simulated using the Monte Carlo method to obtain the normalized glandular dose coefficients of DBT(D_(gN)^(DBT))and the glandular depth dose(D_(g)^(dep)(z))for different breast characteristics and X-ray *** calculated a series of D_(gN)^(DBT) values for breasts with different percentage mass glandularities(5%,25%,50%,75%,and 100%)and compressed breast thicknesses(2,3,4,5,6,and 7 cm)at various tube potentials(25,28,30,32,35,and 49 kV)and target/filter combinations(W/Rh,W/Al,Mo/Mo,Rh/Rh,and Rh/Ag).The parameter dependence of the breast characteristics and beam conditions on D_(gN)^(DBT) in detailed breast models was *** D_(gN)^(DBT) results were 14.6-51.0%lower than those of the traditional dosimetry standard in *** difference in D_(gN)^(DBT) was mainly due to a decrease in the depth of the main energy deposition area caused by the glandular distribution along the depth *** results obtained in this study may be used to improve breast dosimetry in China and provide more detailed information on risk assessment during DBT.

关键词： Digital breast tomosynthesis Normalized glandular dose coefficients Detailed breast model Monte Carlo simulation

Broadband high-efficiency plasmonic metalens with negative dispersion characteristic

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Photonics Research 2024年第4期12卷 813-820页

作者： YONG-QIANG LIU YONG ZHU HONGCHENG YIN JINHAI SUN YAN WANG YONGXING CHE National key laboratory of Scattering and radiation Beijing 100854China

Controlling the dispersion characteristic of metasurfaces(or metalenses) along a broad bandwidth is of great importance to develop high-performance broadband metadevices. Different from traditional lenses that rely on the material refractive index along the light trajectory, metasurfaces or metalenses provide a new regime of dispersion control via a sub-wavelength metastructure, which is known as negative chromatic ***, broadband metalenses design with high-performance focusing especially with a reduced device dimension is a significant challenge in society. Here, we design, fabricate, and demonstrate a broadband highperformance diffractive-type plasmonic metalens based on a circular split-ring resonator metasurface with a relative working bandwidth of 28.6%. The metalens thickness is only 0.09λ0(λ0is at the central wavelength),which is much thinner than previous broadband all-dielectric metalenses. The full-wave simulation results show that both high transmissive efficiency above 80%(the maximum is even above 90%) and high average focusing efficiency above 45%(the maximum is 56%) are achieved within the entire working bandwidth of 9–12 ***, an average high numerical aperture of 0.7(NA = 0.7) of high-efficiency microwave metalens is obtained in the simulations. The broadband high-performance metalens is also fabricated and experimental measurements verify its much higher average focusing efficiency of 55%(the maximum is above 65% within the broad bandwidth) and a moderate high NA of 0.6. The proposed plasmonic metalens can facilitate the development of wavelength-dependent broadband diffractive devices and is also meaningful to further studies on arbitrary dispersion control in diffractive optics based on plasmonic metasurfaces.

关键词： resonator dispersion high

Optimized online filter stack spectrometer for ultrashort X-ray pulses

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Nuclear Science and Techniques 2024年第5期35卷 85-98页

作者： Jia-Xing Wen Ge Ma Ming-Hai Yu Yu-Chi Wu Yong-Hong Yan Shao-Yi Wang Huai-Zhong Gao Lu-Shan Wang Yu-Gang Zhou Qiang Li Yue Yang Fang Tan Xiao-Hui Zhang Jie Zhang Wen-Bo Mo Jing-Qin Su Wei-Min Zhou Yu-Qiu Gu Ming Zeng Zong-Qing Zhao Science and Technology on Plasma Physics laboratory Laser Fusion Research CenterCAEPMianyang 621900China Department of Engineering Physics Tsinghua UniversityBeijing 100084China key laboratory of particle and radiation imaging(Tsinghua University) Ministry of EducationBeijing 100084China School of Information Engineering Southwest University of Science and TechnologyMianyang 621010China

Currently,with the advent of high-repetition-rate laser-plasma experiments,the demand for online diagnosis for the X-ray spectrum is increasing because the laser-plasma-generated X-ray spectrum is very important for characterizing electron dynamics and *** this study,scintillators and silicon PIN(P-type–intrinsic-N-type semiconductor)diodes were used to construct a wideband online filter stack *** X-ray sensor and filter arrangement was optimized using a genetic algorithm to minimize the condition number of the response ***,the unfolding error was significantly reduced based on numerical *** detector responses were quantitatively calibrated by irradiating the scintillator and PIN diode with various nuclides and comparing the measuredγ-ray peaks.A prototype 15-channel spectrometer was developed by integrating an X-ray detector with front-and back-end *** prototype spectrometer could record X-ray pulse signals at a repetition rate of 1 ***,an optimized spectrometer was employed to record the real-time spectra of laser-driven bremsstrahlung *** optimized spectrometer offers a compact solution for spectrum diagnostics of ultrashort X-ray pulses,exhibiting improved accuracy in terms of spectrum measurements and repetition rates,and could be widely used in next-generation high-repetition-rate high-power laser facilities.

关键词： Filter stack spectrometer Laser plasma diagnostics X-ray diagnostics Scintillator PIN diode

Hydrophobic long-chain two-dimensional perovskite scintillators for underwater X-ray imaging

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Rare Metals 2024年第1期43卷 175-185页

作者： Jin-Xiao Zheng Zi-An Zhou Tiao Feng Hui Li Cheng-Hua Sun NüWang Yang Tian Yong Zhao Shu-Yun Zhou key laboratory of Photochemical Conversion and Optoelectronic Materials Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China laboratory of Bioinspired Smart Interfacial Science and Technology of the Ministry of Education Beijing Key Laboratory of Bioinspired Energy Materials and DevicesSchool of ChemistryBeijing Advanced Innovation Center for Biomedical EngineeringBeihang UniversityBeijing 100191China Department of Engineering Physics Tsinghua University and Key Laboratory of Particle and Radiation Imaging Ministry of EducationTsinghua UniversityBeijing 100084China e-mail:yangt@***

The underwater X-ray imaging technology development is significant to subaqueous target reconnaissance/detection/identification, subfluvial archaeology,submerged resource exploration, etc. As the core of X-ray imaging detection, the scintillator has been plagued by inherent moisture absorption and decomposition, and strict requirements for seamless packaging and ***, we designed a manganese-doped two-dimensional(2D) perovskite scintillator modified by hydrophobic longchain organic amine through the combination of component and doping engineering. The modified perovskites show high water repellency that can be used as an underwater X-ray scintillator. X-ray images of aquatic organisms or other objects with a high spatial resolution of10 lp·mm^(-1) at a big view field(32 mm × 32 mm) were obtained by scintillation screen. This hydrophobic perovskite scintillator based on molecular design is of great promise in underwater X-ray nondestructive testing technology development.

关键词： Two-dimensional perovskite Hydrophobic Scintillators Underwater X-ray imaging Underwater nondestructive testing technology

Protein lysine crotonylation in cellular processions and disease associations

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Genes & Diseases 2024年第5期11卷 219-235页

作者： Hongling Zhao Yang Han Pingkun Zhou Hua Guan Shanshan Gao Beijing key laboratory for Radiobiology Beijing Institute of Radiation MedicineBeijing 100850China

Protein lysine crotonylation(Kcr)is one conserved form of posttranslational modifications of proteins,which plays an important role in a series of cellular physiological and pathological *** e-amino groups are the primary sites of such modification,resulting in four-carbon planar lysine crotonylation that is structurally and functionally distinct from the acetylation of these *** levels of Kcr modifications have been identified on both histone and non-histone *** present review offers an update on the research progression regarding protein Kcr modifications in biomedical contexts and provides a discussion of the mechanisms whereby Kcr modification governs a range of biological *** addition,given the importance of protein Kcr modification in disease onset and progression,the potential viability of Kcr regulators as therapeutic targets is elucidated.

关键词： Cell biology Disease Lysine crotonylation Posttranslational modification Therapeutic target