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recoil polarimetry in meson photoproduction at MAMI

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Chinese Physics C 2009年第12期33卷 1373-1376页

作者： M.H. Sikora D.I. Glazier D.P. Watts University of Edinburgh King’s Buildings Edinburgh EH9 3JZ United Kingdom

The nucleon excitation spectrum remains poorly known, with the masses, widths, EM couplings and even existence of many states not well established. A program of experiments using meson photoproduction off the nucleon is being carried out to improve this situation. A new large acceptance recoil polarimeter has been developed by the Edinburgh group for use in such reactions with the Crystal Ball at MAMI. This work summarizes the procedure used to measure recoil polarization with the new device and presents some preliminary results for the double polarization observable Cx in the reaction γp→pπ, compared to the current partial wave analysis.

关键词： polarimeter meson photoproduction polarization observable recoil

Propagation of positive, negative, and recoil leaders in upward lightning flashes

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Earth and Planetary Physics 2019年第2期3卷 102-110页

作者： XiuShu Qie ShanFeng Yuan HongBo Zhang RuBin Jiang ZhiJun Wu MingYuan Liu ZhuLing Sun YunJiao Pu JinLiang Li Abhay Srivastava ZiLong Ma GaoPeng Lu Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO) Institute of Atmospheric Science Chinese Academy of Sciences Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of information Science & Technology College of Earth and Planetary Science University of Chinese Academy of Sciences Fujian Meteorological Service Center Fujian Meteorological Bureau

Leader propagation is a fundamental issue in lightning physics. The propagation characteristics of positive leaders and negative leaders are summarized and compared based on data from high-speed camera and electromagnetic field in rocket-triggered lightning and tower-initiated lightning discharges; available channel base current data recorded in rocket-triggered lightning are also used. The negative leaders propagate in a stepped fashion accompanied by many branches. The stems ahead of the negative leader tip determine the manner and direction of the leader propagation, and even the branching and winding of the lightning channel. The impulsive current, electromagnetic field, and related optical images suggest that the positive leader may develop in a step-like fashion at its initial stage of triggered lightning. However, the stepping processes of the positive leader are obviously different from those of the negative leader. Tower-initiated lightning revealed that the most conspicuous characteristics of the stepwise positive leader involve the intermittent brush-like corona zone in front of the leader tip and the luminosity enhancement of the channel behind the tip. In rockettriggered lightning flashes, the charge transferred during an individual step for the negative leader was nearly an order greater than for the positive counterpart. The successive streamers ahead of the leader tip are essential for both negative and positive leader propagation, and the stems could be formed from one or more streamers in the previous negative streamer zone with the main leader channel dim. High-resolution observation of tower lightning also revealed a new type of bidirectional recoil leader, with polarity contrary to the traditional one, traversing in negative channels associated with tower-initiated and rocket-triggered lightning.

关键词： lightning propagation negative leader positive leader recoil leader

ELASTIC recoil DETECTION ANALYSIS OF LIGHT ELEMENTS IN THIN FILMS USING 35 MeV^(35) Cl^(6+) BEAM

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Nuclear Science and Techniques 1992年第3期3卷 175-181页

作者：杨熙宏韦伦存李认兴于金祥梁斌任晓棠王兆江洪秀花张利春 Peking University Beijing 100871 China

In this paper, an elastic recoil detection analysis method is described using 35 MeV 35Cl as incident ions. This method can determine and profile simultaneously H, D, He, C and O or in the other case, H, C, N and O. The depth resolution for the elements heavier than He is better than 20 nm. It has been applied to study the Co/Si and TiN thin films, and the depth profiles of He implanted in monocrystal silicon.

关键词： Elastic recoil detection analysis Depth Resolution Mass resolution He implantation profile Co/Si and TiN thin films

CALCULATION AND OPTIMIZATION OF EXPERIMENTAL PARAMETERS IN ELASTIC recoil DETECTION (ERD)

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Nuclear Science and Techniques 1990年第Z1期1卷 93-98页

作者：任孟眉封爱国朱沛然刘家瑞李大万 Institute of Physics Acadcmia Sinica Beijing 100080 China Central Institute of Nationalities Beijing 100081 China

Elastic recoil detection (ERD) proposed for the analysis of light elements in a heavier matrix is an appropriate method for its specialities. Optimization of experimental parameters in ERD such as scattering geometry and incident beam energy is very important when using a small accelerator with energy lower than 10 MeV. In this paper a computer program ERDAl is developed for the purpose, and is proved to be useful for practical handling of ERD experiments.

关键词： Elastic recoil detection Maximum detectable depth Depth resolution

Calculation and analysis of the number of return photons from sodium laser beacon excited by the long pulse laser with circular polarization

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Chinese Physics B 2014年第12期23卷 240-248页

作者：刘向远钱仙妹李玉杰饶瑞中 Key Laboratory of Atmospheric Composition and Optical Radiation Anhui Institute of Optics and Fine MechanicsChinese Academy of Sciences College of Materials and Chemical Engineering West Anhui University

The number of return photons from sodium laser beacon（SLB） greatly suffers down-pumping, recoil, and geomagnetic field when the long pulse laser with circular polarization interacts with sodium atoms in the mesosphere. Considering recoil and down-pumping effects on the number of return photons from SLB, the spontaneous radiation rates are obtained by numerical computations and fittings. Furthermore, combining with the geomagnetic field effects, a new expression is achieved for calculating the number of return photons. By using this expression and considering the stochastic distribution of laser intensity in the mesosphere under different turbulence models for atmosphere, the number of return photons excited by the narrow-band single mode laser and that by the narrow-band three-mode laser are respectively calculated. The results show that the narrow-band three-mode laser with a specific spectrum structure has a higher spontaneous radiation rate and more return photons than a narrow-band single mode laser. Of note, the effect of the atmospheric turbulence on the number of return photons is remarkable. Calculation results indicate that the number of return photons under the HV5/7 model for atmospheric turbulence is much higher than that under the Greenwood and Mod HV models.

关键词： sodium laser beacon spontaneous radiation rates the number of return photons down-pumping recoil geomagnetic field

Research on momentum transfer in simple railgun

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Defence Technology（防务技术） 2019年第5期15卷 735-740页

作者： Yingtao Xu Bo Tang Baoming Li The National Key Laboratory of Transient Physics Nanjing University of Science and Technology

In this paper,the momentum conservation equation in the longitudinal direction for simple railgun was deduced.Then,a three-dimensional model was established and the finite element method was utilized to simulate the problem.Based on the simulation,some results such as the surface force on the electromagnetic field,the electromagnetic force on the conductor in the longitudinal direction were obtained.Besides,the surface force density on different longitudinal section of railgun was analyzed and discussed in details.The results showed that the momentum of the railgun system was conserved when the surface force of the electromagnetic field was contained.Moreover,large amount of longitudinal force was transmitted to the breech by the electromagnetic field in the form of surface force.The exact position and distribution of recoil were related to the current input device.

关键词： Railgun Momentum conservation recoil Surface force

Complex experimental analysis of rifle-shooter interaction

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Defence Technology（防务技术） 2017年第5期13卷 346-352页

作者： Michal Taraszewski Janusz Ewertowski Warsaw University of Technology Faculty of Production EngineeringDepartment of Mechanics and Armament Technologyul.Narbutta 8502-524 WarszawaPoland

In this study, a complex analysis of a man-weapon interaction based on experimental effort is presented.The attention is focused on how a shooter can influence on a rifle, opposite to generally considered in literature rifle's impact on a shooter. It is shown, based on the kbk AKM weapon, that each support point of the rifle has an substantial impact on the system. It is said that identifying human reactions on weapon may let to describe gun movement and thus may be applied to weapon accuracy determination.

关键词： Rifle-shooter interaction Man-weapon forces Muzzle climb Firearm recoil Accuracy

Rigid body dynamics modeling, experimental characterization, and performance analysis of a howitzer

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Defence Technology（防务技术） 2016年第6期12卷 480-489页

作者： Nachiketa TIWARI Mukund PATIL Ravi SHANKAR Abhishek SARASWAT Rituraj DWIVEDI Department of Mechanical Engineering Indian Institute of Technology Ordnance Factory Kanpur India

A large caliber howitzer is a complex and cumbersome assembly. Understanding its dynamics and performance attributes' sensitivity to changes in its design parameters can be a very time-consuming and expensive exercise, as such an effort requires highly sophisticated test rigs and platforms. However, the need of such an understanding is crucially important for system designers, users, and evaluators. Some of the key performance attributes of such a system are its vertical jump, forward motion, recoil displacement, and force transmitted to ground through tires and trail after the gun has been fired. In this work, we have developed a rigid body dynamics model for a representative howitzer system, and used relatively simple experimental procedures to estimate its principal design parameters. Such procedures can help in obviating the need of expensive experimental rigs, especially in early stages of the design cycle. These parameters were subsequently incorporated into our simulation model,which was then used to predict gun performance. Finally, we conducted several sensitivity studies to understand the influence of changes in various design parameters on system performance. Their results provide useful insights in our understanding of the functioning of the overall system.

关键词： Howitzer gun CAD modeling Dynamic simulation recoil assembly parameters Sensitivity analysis

Investigation of enhancement in planar fast neutron detector efficiency with stacked structure using Geant4

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Nuclear Science and Techniques 2017年第11期28卷 154-163页

作者： Shivang Tripathi Chandrakant Upadhyay C. P. Nagaraj K. Devan A. Venkatesan K. Madhusoodanan Homi Bhabha National Institute AnushaktinagarMumbai 400094 India Indira Gandhi Centre for Atomic Research Kalpakkam 603102 India

Geant4 based Monte Carlo study has been carried out to assess the improvement in efficiency of the planar structure of Silicon Carbide(SiC)-based semiconductor fast neutron detector with the stacked structure. A proton recoil detector was simulated, which consists of hydrogenous converter, i.e., high-density polyethylene(HDPE) for generating recoil protons by means of neutron elastic scattering(n, p) reaction and semiconductor material SiC, for generating a detectable electrical signal upon transport of recoil protons through it. SiC is considered in order to overcome the various factors associated with conventional Si-based devices such as operability in a harsh radiation environment, as often encountered in nuclear facilities. Converter layer thickness is optimized by considering 10~9 neutron events of different monoenergetic neutron sources as well as ^(241)Am-Be neutron spectrum. It is found that the optimized thickness for neutron energy range of 1–10 MeV is ~400 μm. However, the efficiency of fast neutron detection is estimated to be only 0.112%,which is considered very low for meaningful and reliable detection of neutrons. To overcome this problem, a stacked juxtaposition of converter layer between SiC layers has been analyzed in order to achieve high efficiency. It is noted that a tenfold efficiency improvement has been obtained—1.04% for 10 layers stacked configuration vis-à-vis 0.112% of single converter layer detector. Further simulation of the stacked detector with respect to variable converter thickness has been performed to achieve the efficiency as high as ~3.85% with up to 50 stacks.

关键词： Geant4 Fast neutron detector Silicon carbide recoil proton Stacked detector