IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)最新文献

{"title":"Advance in dispenser cathodes materials of high emission property","authors":"Chunying Shen, T. Qiu, Xiaoyun Li, Xiaomeng Gao","doi":"10.1109/IVESC.2004.1414194","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414194","url":null,"abstract":"More and more attention has been paid to cathode materials at home and abroad which are the key parts of microwave tubes. The recent advances in porous tungsten matrix with high emission density, impregnant composition and surface properties are presented.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133500043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Field emission of uniform carbon cone arrays grown on porous silicon substrate","authors":"Qiang-sheng Wang, Junjie Li, Zongli Wang, C. Shi, Haijun Li, C. Gu","doi":"10.1109/IVESC.2004.1414222","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414222","url":null,"abstract":"Uniform carbon cones arrays with average height of 1/spl mu/m were grown on porous silicon substrate using the hot filament chemical vapor deposition (HFCVD). Raman spectroscopy was used to characterize as-prepared carbon cones, which are composed of D peak (/spl sim/1352cm/sup -1/), G peak (-1601cm/sup -1/) and a broad peak at /spl sim/1475cm/sup -1/ attributed to hydrogenated carbon (a-C:H). It was found that both the immersion of porous silicon substrate in Fe/sub 2/(SO/sub 4/)/sub 3/ aqueous solution and the applied voltage in the deposition are vital to the growth of the carbon cones. Furthermore, the field emission properties of the as-prepared carbon cone arrays were studied, which shows an excellent field emission property. The threshold field is 2.2 V//spl mu/m, emission current of more than 80 /spl mu/A could be obtained as applied electric field is 3.4 V//spl mu/m. The internal-tip mechanism has been proposed for cone arrays in order to account for the observed field emission.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129373520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Field electron emission of nano-structure carbon based thin films","authors":"Binglin Zhang, N. Yao, Zhanling Lu, Zhiqin Fan, Yongmei Zhao, Xinyue Zhang, Lan Zhang, Hueizhong Ma","doi":"10.1109/IVESC.2004.1414241","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414241","url":null,"abstract":"Nano-crystalline fullerene-like film, nano-crystalline graphitic film and nano structure amorphous carbon film were prepared by microwave plasma chemical vapor deposition (MPCVD). The nano-structure and surface morphology of the deposited films were identified by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman scattering and scanning electron microscope (SEM). The field electron emission characteristics of the films were studied by a testing method of diode structure in a vacuum chamber. The deposited nano-structure carbon based thin films and phosphor coated indium tin oxide (ITO) film were used to be cathode and anode, respectively. At the initial measurement, a very low turn-on field of 0.6V//spl mu/m was obtained for the three kinds of nano-structure carbon based materials. After cycling of voltage up and down several times, the turn-on field went up to more than 1.0 V//spl mu/m, and the current density decreased. In this paper, we suggest a theoretical model to discuss the field electron emission mechanism for the nano-structure carbon based thin films, and explain the emission characteristics. The surface local states, the bond dangling of carbon atoms and adsorbates on the surface of the films were considered in the theoretical model.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116176413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characteristics of scandate-type cathode with sub-micron structure Sc/sub 2/O/sub 3/ doped tungsten bodies","authors":"Haiqing Yuan, X. Gu, Kexin Pan, Yiman Wang, W. Liu, Ke Zhang, Jingshu Wang, Meili Zhou, Ji Li","doi":"10.1109/IVESC.2004.1414170","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414170","url":null,"abstract":"Development and improvement of scandate-type cathode have been continuously in progress in last decade and recent years. Required by some new devices such as high power microwave sources, cathodes with current density of up to 100A/cm/sup 2/ at low pulse durations and relevant lifetime are being developed. Scandate type cathode has shown the emission capability of approaching to 100A/cm/sup 2/ or even more. Uniformization in emission, robustness in real environment and reproducibility in manufacturing process may be the major problems for their practical use. Based on previous study, we further developed the Scandia doping technique and cathode fabrication process. Cathodes with sub-micron structure Sc/sub 2/O/sub 3/ doped porous tungsten bodies have been successfully fabricated. Repeatable high emission properties were also verified for different batches of cathodes.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"245 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122116567","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of polishing of stainless steel substrates on field emission properties of carbon nanotubes films","authors":"Zhiqin Fan, Zhanling Lu, Shi'e Yang, N. Yao, L. Cheng, Binlin Zhang","doi":"10.1109/IVESC.2004.1414216","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414216","url":null,"abstract":"Carbon nanotubes (CNTs) were synthesized from methane and hydrogen gas mixture directly on stainless steel plates by microwave plasma chemical vapor deposition (MPCVD). By pretreatment of the substrates such as mechanically polishing, we found the polishing can lower the turn-on field and improve the emission current density. The current density of the un-pretreated sample attains 2.9mA/cm/sup 2/, but the polished sample attains 5.5 mA/cm/sup 2/, at the electric field of 7.5 V//spl mu/m.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125519109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Application of neural network to design of TWT","authors":"Liu Wei, Li Shi, Shen Bin, Yin He-jun","doi":"10.1109/IVESC.2004.1414271","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414271","url":null,"abstract":"In this paper, the method of back-propagation network in the computer code MATLAB is used to simulate data, which be applied to the design of traveling-wave tube. Compared with the quadratic interpolation, the simulation result according by the BP network was closer to the effect on dispersion in the test.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"146 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130196158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Synthesis and field emission of high pure AlN nanowires","authors":"Y. Ma, K. Huo, Y. Hu, Z. Hu, Y. Chen","doi":"10.1109/IVESC.2004.1414215","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414215","url":null,"abstract":"Ever since Spindt field emitter arrays were invented, great efforts have been devoted to explore novel electron sources for better and more reliable performance. In addition to carbon series (diamond films, diamond-like carbon films, carbon nanotubes, and etc.), the one-dimensional (1D) nanostructures of group III nitrides, GaN, AlN, InN and their alloys, are expected to be a kind of promising candidates due to the combination of 1D geometries, small or even negative electron affinity (NEA) and adjustable bandgap which is beneficial for field emission. Our recent study did indicate the good field emission properties of AlN nanowires prepared by the extended vapor-liquid-solid growth (Wu et al., 2003). Herein we report a improved method to fabricate pure AlN nanowires. The white AlN nanowires were produced by the reaction of Al powder and carbon-coated Ni nanoparticles at 1400/spl deg/C and collected from the down-stream of the reaction tube. The products were well characterized by TEM, SEM, XRD and Raman spectrum. The field emission properties of AlN nanowires were measured in a vacuum chamber at a base pressure of /spl sim/1/spl times/10/sup -7/ Torr. The emission current-voltage (I-V) curve were repeatedly measured by a Keithley system for different distances (D) between the sample and anode. The I-V curve qualitatively follow the conventional Fowler-Nordheim behavior according to the straight line plot of log (J/E/sup 2/) versus I/E. The field emission mechanism is also discussed.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129162076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"NanoPhysics of electron dynamics near surfaces in high power microwave devices and systems","authors":"N. Luhmann, G. Caryotakis, J. Heritage, R. Umstadd","doi":"10.1109/IVESC.2004.1413955","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1413955","url":null,"abstract":"Recently, a consortium comprising the above indicated universities have been awarded a five year Multidisciplinary University Research Initiative (MURI) program aimed at providing a fundamental understanding of RF breakdown phenomena and developing novel, high current density cathodes. The start date is June 1, 2004 and this talk will focus on both the initial activities and long term directions. The above goals will be accomplished by addressing two underlying issues: \"pulse shortening\" caused by RF breakdown and the lack of suitable, robust high current density cathodes. RF breakdown is a phenomenon that is poorly understood with respect to both the \"nano-physics\" of its inception as well as the techniques to minimize its effects. Understanding it and preventing it require coordinated experimental and simulation programs. The cathodes required for so-called high power microwave (HPM) sources must provide in excess of 100 A/cm and conventional thermionic cathode technology falls short of that current density by about a factor of 5. Cathode studies will employ laser deposition techniques will the goal of achieving up to 200 A/cm emission from oxide and scandate based thermionic cathodes at relevant lifetimes. Both advanced field emitter array (FEA) and carbon nanotube (CNT) based field emitter arrays will also be developed, along with integrated active control elements, for higher current density cathodes. We will employ two kinds of nanotube structures for this purpose: high-density vertically aligned nanotube towers and gated individual nanotube field emitters. We will develop triode-like gated individual nanotube field emitters by performing controlled synthesis to grow individual vertical nanotubes at desired sites. To investigate the RF breakdown issue, we will implement a comprehensive experimental and computational program. RF breakdown experiments will be conducted in a resonant single-cell cavity, configured as a \"windowtron\" and fed directly by a 50-MW X-band SLAC klystron. This experimental arrangement was used in a previous MURI and was found to be much more effective than an earlier method of inserting the cavity in a resonant ring to provide the required sustained power. Computational studies will include computer modeling of the breakdown dynamics in the actual cavity geometry using a newly developed parallel processing version of MAGIC 3D. To gain clearer insight into the physics of RF breakdown, a microscopic model will be developed.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"2015 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127765972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A review of oxide cathode research in IECAS","authors":"X. Liao, X.X. Wang, Q. Zhao, M. Meng","doi":"10.1109/IVESC.2004.1414151","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414151","url":null,"abstract":"Summary form only given. Oxide cathode is invented, developed and applied in vacuum electronic devices over 100 years. This paper presents a review for the research results of the emission mechanisms, characteristics and applications of the oxide cathode in IECAS, which includes a dynamical surface emission center theory, a high reliable and long lifetime oxide cathode, as well as a low temperature' and large emission current oxide cathode. The characteristics of these cathodes, such as, DC and PC emission, evaporations, resistance to poisoning and lifetime, are discussed. These cathodes have been wildly applied in communication secondary planet TWT, high power wide pulse klystrons and high operating ratio TWT, which shows that good characteristics for the emission and lifetime can been reached.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117185796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Field emission from metal covered by film of polymer insulator","authors":"A. Ionov, E. O. Popov, A. Pashkevich, V. Svetlichnyi, M. Nikolaeva","doi":"10.1109/IVESC.2004.1414142","DOIUrl":"https://doi.org/10.1109/IVESC.2004.1414142","url":null,"abstract":"Summary form only given. We obtained a low-threshold field emission from polished surface of metallic electrode which was covered by thin film of non-conjugated polymers such as: i) imide/siloxane copolymer; ii) aryl-polycarbonate; iii) Nylon 66. The films were prepared by deposition of a solution on the polished Mo or Nb electrodes. Then films were heated in air at a constant temperature to remove the major part of the polymer solvent. Field emission measurements were carried out in vacuum chamber at pressure of about 4 /spl times/ 10/sup -6/ Torr in construction with accelerating grid. We obtained a stable field emission at 4 kV/mm. However, for initial activation of the cathode, the threshold field should be 2.5-3 times more than 4 kV/mm. We observed a homogeneous fluorescence from the phosphorus glass anode with current-voltage characteristic corresponds to Fowler-Nordheim law at small electric fields but at high electric fields, there is deviation to smallest values of current. The field emission from polished metals we did not observe up to 25 kV/mm. Topography of the polymer film surfaces was analysed by an atomic force microscope before and after action of threshold field. Initially, polymers had smooth surfaces but after a threshold field emission, the surfaces were modified very strong: spikes were formed up to 400 nm high and its density was about 10 cm. Apart from conducting organic polymer such as poly (3-octylthiophene) where polymer bulk material emits electrons itself (I. Musa et al., 1998) in our case, there are two critical parameters where field emission effect exists: i) critical film thickness depending from polymer (about or less one micron) and ii) critical temperature of heat treatment for polymer film. We consider that polymer accepts the charge from metallic cathode due to relatively large effect of electrification (J. Lowell and A. C. Rose-Innes, 1980). Under the action of external electric field, the soft polymer surface was modified and polymer's needles emit electrons. We also discuss small electron affinity and field emission time stability. It should be also noted that there is correlation between field emission effect and conductivity effect that is spontaneously arisen when thin polymer films were placed between two metallic electrodes. For example, the imide/siloxane copolymer films exhibit high conductivity and supercurrents being placed between two normal metals and superconductors correspondingly (A. N. Ionov et al. 2003). There, it was also confirmed that the conductivity occurs through many channels orientated perpendicular to the polymer surfaces and connecting the two metallic electrodes. The cross-section of the conductive channels grows with increasing current as well as number of conductive path. The smallest observed value of the cross-section was less than 10/sup -10/ cm/sup 2/.","PeriodicalId":340787,"journal":{"name":"IVESC 2004. The 5th International Vacuum Electron Sources Conference Proceedings (IEEE Cat. No.04EX839)","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124425671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}