32 research outputs found
High current carbon nanotube cathode for miniature high power THz source application
No full textThis RG 100/05 (SEP) is a supplement fund to support the A*STAR SERG grant 042
101 0080 entitled “High Current Carbon Nanotube (CNT) Cathode for Miniature High
Power THz sources” (Jan 2005 –Jan 2008), where the PI is Asst Professor Ang Lay Kee,
Ricky.
For coherent radiation at THz frequency using Smith-Purcell based free electron laser
(SP-FEL), a high current electron beam is required
High current carbon nanotube cathode for miniature high power THz source application
No full textThis RG 100/05 (SEP) is a supplement fund to support the A*STAR SERG grant 042
101 0080 entitled “High Current Carbon Nanotube (CNT) Cathode for Miniature High
Power THz sources” (Jan 2005 –Jan 2008), where the PI is Asst Professor Ang Lay Kee,
Ricky.
For coherent radiation at THz frequency using Smith-Purcell based free electron laser
(SP-FEL), a high current electron beam is required
Multi-dimensional theory of space-charge-limited current : quantum, short-pulse and transition
No full textThe interaction of the intense charged particles in a vacuum gap has remained an area of considerable interest to accelerator physics, sheath physics, high current diodes, high power microwave sources, vacuum micro- and nano-electronics. Previously, most of the developments of space-charge-limited (SCL) flows are focused on one-dimensional (1D) classical models and the multi-dimensional SCL flows (especially for 3D features) are relatively undeveloped. The classical Child-Langmuir law, which predicts the maximum space-charge-limiting current that can be transported across a 1D planar gap under steady-state condition, is one of the most important considerations used in various types of high current diodes, triodes and multi-stage acceleration gaps. This thesis presents recent advances in the theories of multi-dimensional SCL flows in various operating regimes such as quantum, short pulse and transition from field emission.DOCTOR OF PHILOSOPHY (EEE
Multi-dimentional theory of space-charge-limited current : quantum, short-pulse and transition
No full textThis thesis presents recent advances in the theories of multi-dimensional space-charge-limited (SCL) flows in various operating regimes such as quantum, short pulse and transition from field emission.Doctor of Philosophy (EEE
Modeling of field emission from a sharp tip
No full textThe interaction of the charged particles in a vacuum gap has essentially remained an area that is worth exploring in domains of accelerator physics, sheath physics, high current diodes, microwaves sources, and vacuum microelectronics including nano-electronics. Most of the theoretical developments focused on one dimensional (1D) classical models and they have extended to simple geometries or shapes.
Recently, two dimensional (2D) models are developed and build upon, and had extended to multi-dimensional models, but they are simple of geometries instead of complex geometries.
In this Final Year Project (FYP) report presents the existing knowledge and understanding the behavior of the field emission in the transition from field emission to space charge limited (SCL) regime using a sharp tip model. In the transition region, the electron particles are emitted due to the field emission and both the trajectories of the emitted electrons are tracked using the classical Newtonian physics.Bachelor of Engineerin
Modeling of electron emission : its physics and novel applications
No full textThis thesis provides a deeper understanding of the physics behind the process of various electron emission mechanisms such as thermionic emission, photoemission,
field emission and secondary electron emission, and explores its novel applications. The first topic is focused on the formulation of a nonequilibrium model to clarify the electron photo-field emission mechanism for an ultrafast laser excitation on a metallic surface under a dc biased voltage. The second topic is to study the reduction of shot noise for field emission including the effects of quantum partitioning, Coulomb repulsion and quantum correlation effects. The third topic is to use a statistical model to explain the occurrence of multipactor discharge due to secondary electron emission, and its high power absorption in a dielectric-loaded accelerating structure. For applications, we have proposed a new technique for low-temperature refrigeration
based on thermal-field electron emission in a crossed-field gap.DOCTOR OF PHILOSOPHY (EEE
Optimization and comparison of argon plasma-induced quantum well intermixing using RIE and ICP
No full textIn this project, a novel quantum well intermixing (QWI) technique using inductively-coupled (ICP) and reactive-ion etcher (RIE) Argon plasma exposure has been developed.Master of Engineerin
Modeling of field emission : protrusive surface at high current regime
No full textThis report presents a two dimensional model for field emission from a sharp cathode in high current regime. The trajectories of the electrons emitted from various points on the cathode are determined. The continuity equation is used to determine the charge density in the cathode-anode gap. The space charge field at the apex of the cathode is calculated from this charge distribution. At high current, the space charge strength is high. This leads to a reduction in the surface electric field at the cathode. The reduced surface electric field called the Poisson Electric Field, FP, determines the Poisson current density, JP. For the Fowler Nordheim plots, a "turn over" region in the high Field Emitted Vacuum Space Charge limit is predicted. The report also presents the effect of varying the cathode work function phi, the height to width ratio (h/w) on the Laplace (without space charge) and Poisson (with space charge) current densities. The sharper the emitter, higher is the field at which turn over occurs. This turn over region is not noted in past experiments – possible reasons are noted. Possible ways to extend the analysis to three dimensions are given.Bachelor of Engineerin
Modeling of short-pulse child-langmuir law
No full textThis report concentrates on the development of ID short-pulse space-charge-limiting
(SCL) models for the classical, weakly relativistic and quantum regimes. Here, we are interested in the electron flows in the planar configuration at the space-charge limit. The effects of the finite pulse length of a SCL electron pulse emitted from a planar diode for a wide range of applied voltage, gap spacing, and pulse duration have been investigated. The results from the analytical short-pulse models in the classical and relativistic regimes are consistent with particle-in-cell (PIC) simulations. The transit time of the electron flows across a gap in various regimes (classical, relativistic, quantum) has also been formulated in analytical form. In addition, ID short-pulse models of classical and relativistic SCL law in a drift space is developed. And a selfconsistent model of transition from field emission to short-pulse classical CL law is also presented.MASTER OF ENGINEERING (EEE
Converting thermal energy to electricity using nanomaterials
No full textThermionic electron emission is a key phenomenon utilized in a variety of applications, from display communications, space propulsion to direct energy conversion. Thermionic converters are an interesting option for lightweight and long-life power generators due to a number of compelling advantages, including all solid construction, no moving parts, and waste heat rejection at high temperature. New class of very high temperature compatible materials, like Carbon nanotubes (CNTs) are currently being investigated for their performance as thermionic emitter cathodes for possible thermionic applications due to their long life time, their ability to be produced in aligned arrays, and their nanoscale tip geometry based on their diameter.
In this project an experiment is conducted to test with field emission system by using nanostructure materials i.e. Carbon Nanotubes, Nano Zinc Oxide (ZnO); and obtain the corresponding current-temperature data to look into potential therminioic application of these films. For the conventional emitters a very high temperature in the excess of 1000K is required to obtain a significant emission current. Due to the limitation of the heater provided in the project, a highest temperature of 573K will be applied to the test sample. For the field emission to occur, electric fields will be provided in the same time. The results indicated a general consistency of the field emission and thermionic emission from the same films. The potential for the thermionic energy conversion based on these films is presented. The Field Emission System base on the LABVIEW language is used to control measure and process monitoring of the field emission test.Bachelor of Engineerin
