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- Qian, Li-Bing, et al.
(författare)
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Transmission of electrons through the conical glass capillary with the grounded conducting outer surface
- 2017
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 66:12
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Tidskriftsartikel (refereegranskat)abstract
- The transmission of 1.5 keV-electrons through a conical glass capillary is reported. This study aims to understand the so-called guiding effect for the negatively charged particles (e.g. electrons). The guiding mechanism is understood quite well with positively charged particles in particular highly charged ions, but not clear with electrons, i. e., even the basic scheme mediated by the existence of negative charge patches to guide the electrons is still somewhat controversial.. The study of the charging-up dynamics causing the electrons transport inside the capillary will shed light on this issue. In order to perform this, a data acquisition system has been setup to follow the time evolution of the two-dimensional angular distribution of the transmitted electrons. The electrons are detected by the multi-channel plate (MCP) detector with a phosphor screen. The image from the phosphor screen is recorded by a charge-coupled device camera. The timing signals for the detected events are extracted from the back stack of the MCP detector and recorded by the data acquisition system, synchronized with the acquired images. The electron beam has a size of 0.5 mm x 0.5 mm and a divergence of less than 0.35.. The inner diameter of the straight part of the capillary is 1.2 mm and the exit diameter is 225 mu m. A small conducting aperture of 0.3 mm in diameter is placed at the entrance of the capillary. Two-dimensional angular distribution of the transmitted electrons through conical glass capillary and its time evolution are measured. The results show that the transmission rate decreases and reaches to a constant value for the completely discharged glass capillary with time going by. The centroid of the angular distribution moves to an asymptotic value while the width remains unchanged. These transmission characteristics are different from those indicated in our previous work (2016 Acta Phys: Si n: 65 204103). The difference originates from the different manipulations of the capillary outer surface. A conducting layer is coated on the outer surface of the capillary and grounded in this work. This isolates various discharge/charge channels and forms a new stable discharge channel. The transmission rate as a function of the tilt angle shows that the allowed transmission occurs at the tilt angle limited by the geometrical factors, i. e., the geometrical opening angle given by the aspect ratio as well as the beam divergence. The transmission characteristics suggest that most likely there are formed no negative patches to facilitate the electron transmission through the glass capillary at this selected beam energy. It is different from that of highly charged ions, where the formation of the charge patches prohibits the close collisions between the following ions and guides them out of the capillary.
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| 2. |
- Wan, Cheng-Liang, et al.
(författare)
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Dynamics of slow electrons transmitting through straight glass capillary and tapered glass capillary
- 2016
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Ingår i: Wuli xuebao. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 65:20
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Tidskriftsartikel (refereegranskat)abstract
- It has been found that the transmission rate of the electrons through insulating capillaries as a function of time/incident charge is not the same as that of the ions. The question arises that by using the electrons, if the negative charge patches can be formed to facilitate the transmission of the following electrons, thereby substantiating that the so-called guiding effect works also for electrons. This study aims to observe the time evolutions of the transmission of electrons through a straight glass tube and a tapered glass capillary. This will reveal the details of how and (or) if the negative charge patches can be formed when the electrons transport through them. In this work, a set of MCP/phosphor two-dimensional detection system based on Labview platform is developed to obtain the time evolution of the angular distribution of the transmitted electrons. The pulsed electron beams are obtained to test our detection system. The time evolution of the angular profile of 1.5 keV electrons transmitting through the glass tube/capillary is observed. The transmitted electrons are observed on the detector for a very short time and disappear for a time and then appear again for both the glass tube and tapered glass capillary, leading to an oscillation. The positive charge patches are formed in the insulating glass tube and tapered glass capillary since the secondary electron emission coefficient for the incident energy is larger than 1. It is due to the fact that fast discharge of the deposited charge leads to the increase of the transmission rate, while the fast blocking of the incident electrons due to the deposited positive charge leads to the decrease of the transmission rate. The geometrical configuration of the taper glass capillary tends to make the secondary electrons deposited at the exit part to form the negative patches that facilitate the transmission of electrons. This suggests that if the stable transmission needs to be reached for producing the electron micro-beam by using tapered glass capillaries, the steps must be taken to have the proper grounding and shielding of the glass capillaries and tubes. Our results show a difference in transmission through the insulating capillary between electrons and highly charged ions.
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| 3. |
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社会企业家 : 影响经济、社会与文化的新力量
- 2016
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- 其一，本书提供一个全新的理论视角，在系统梳理和反思社会创业的理论和实践基础上，从社会—经济—文化三维视角审视了社会创业，建立了基于三维学科知识体系的价值观，该探索性的研究丰富了社会创业研究的理论元。三维视角建构的社会创业价值方法，推崇社会企业应当兼顾商业、人文和社会价值，并具体运用于评价不同类型社会创业的内在价值和外在价值，社会企业和社会创业要规划一个完整的价值创造战略，推动和驱使企业创造社会和人文效益，并由此形成良性互动，创造更好的经济价值。其二，本书汇集了来自9个国家的23位具有不同背景的研究人员的最新研究成果。书中的论文结合商业、社会和人类发展需要，从不同背景出发探讨经济、政治、文化等议题，涉及不同国家和区域的情况。对于社会创业，探讨范围包括人口稀少的地区或城区、社会创业教育、旨在卫生保健事业的社会创业、社会创业融资、社会创业如何建立和完善共享价值观等，所有这些都是从社会属性和社会结构层面寻找社会创业的理念，从这个意义上而言，这是一本拓展社会创业研究领域的著作。其三，社会创业的实践推动着理论的发展。社会创业在全球实践的兴盛可追溯到穆罕默德·尤努斯于1976年创立的格莱珉银行，通过他们非凡而卓有成效的努力，促进了社会最贫困阶层的经济和社会发展，2006年穆罕默德·尤努斯和孟加拉乡村银行被授予诺贝尔和平奖。在理论领域，社会创业的学术论文和专著从2000年后呈几何级数增长，主要集中在六个研究主题： 社会创业的变革性影响(Eikenberry & Kluver, 2004; Fowler, 2000)，社会创新架构(Austin et al． , 2006)，社会创业（社会性创业）的界定及定义 (Mair & Marti, 2006; Peredo & McLean, 2006; Thompson, 2002; Weerawardena & Mort, 2006; Dees, 2006; Alex Nicholls, 2006), 社会创业和缓解贫困(Fowler, 2000; Seelos & Mair, 2005), 社会企业家的动力和价值观 (Hemingway & Maclagan, 2004; Alex Nicholls, 2006, 2015; Anders Lundstrom, 2010), 以及社会创业组织的启动类型和启动模式(De Leeuw, 1999)。这些研究的时间相对较早，目前国内学者从不同研究主题各有介绍。作为系统梳理社会创业理论和案例的主要著作者，安德斯·伦德斯特罗姆教授在理论和实践领域均具有国际性影响力和声誉。伦德斯特罗姆教授1994年就成立了小企业研究瑞典基金会和国际研究网络经济增长创新研究(IPREG)； 1996 年他设立了企业创业研究国际奖，这是一个为全世界的学者设立的独特奖项； 作为国际小企业署(ICSB)的前任主席，先后组织了三次以企业创业、小企业以及企业创新为主题的世界性会议。本书是安德斯·伦德斯特罗姆教授在社会创业领域的最新著作，也是这个领域比较具有代表性的著作。
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