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Collisional effects on characteristics of asymmetric radio-frequency sheaths
碰撞对非对称射频鞘层特性的影响

Lu Yan,Wang You-Nian,
芦岩
,王友年

物理学报 , 2004,
Abstract: For most reactive radio frequency plasma etching processing, the plasma sheaths near two electrodes are asymmetric due to the powered electrode area being smaller than the grounded electrode area. Taking collisional effects of ions with neutrals in the sheaths into account, a self consistent dynamic model is proposed here to describe the characteristics of radio frequency sheaths. Numerical results show the collisional effects on some physical quantities, such as instantaneous voltages on the electrodes, instantaneous thicknesses of the electron sheathes, spatial distributions of the ion density and the electric field in the sheaths, and instantaneous voltage difference between two electrodes.
Ion energy distribution functions behind the sheaths of magnetized and non magnetized radio frequency discharges  [PDF]
Jan Trieschmann,Mohammed Shihab,Daniel Szeremley,Abd Elfattah Elgendy,Sara Gallian,Denis Eremin,Ralf Peter Brinkmann,Thomas Mussenbrock
Physics , 2012, DOI: 10.1088/0022-3727/46/8/084016
Abstract: The effect of a magnetic field on the characteristics of capacitively coupled radio frequency discharges is investigated and found to be substantial. A one-dimensional particle-in-cell simulation shows that geometrically symmetric discharges can be asymmetrized by applying a spatially inhomogeneous magnetic field. This effect is similar to the recently discovered electrical asymmetry effect. Both effects act independently, they can work in the same direction or compensate each other. Also the ion energy distribution functions at the electrodes are strongly affected by the magnetic field, although only indirectly. The field influences not the dynamics of the sheath itself but rather its operating conditions, i.e., the ion flux through it and voltage drop across it. To support this interpretation, the particle-in-cell results are compared with the outcome of the recently proposed ensemble-in-spacetime algorithm. Although that scheme resolves only the sheath and neglects magnetization, it is able to reproduce the ion energy distribution functions with very good accuracy, regardless of whether the discharge is magnetized or not.
Applicability of new radio technologies for advanced UMTS networks  [PDF]
A. Dekorsy,M. Schacht,S. Brueck,G. Fischer
Advances in Radio Science : Kleinheubacher Berichte , 2004,
Abstract: An expanded effort is under the way to support the evolution of UMTS (Universal Mobile Telecommunication System). Apart from delivering high data rates, future UMTS releases will also require to provide high network performance in terms of system capacity, low radiated power, and high coverage. Well promising performance-enhancing technologies are smart antennas as well as multiuser detection. Although these new radio technologies have recently been subject to intense research, main UMTS network integration aspects with their specific constraints have been neglected in many cases. Especially the interaction with UMTS radio resource control being required to meet Quality of Service (QoS) constraints has to be included to assess the applicability of these technologies for UMTS. In this paper, we study the interaction of beamforming concepts as well as multiuser detection with load and power control. We also work out UMTS specific constraints like signal-to-interference-plus-noise ratio (SINR) operating points, pilot power pollution or channel estimation, all strongly limiting network performance. Results are shown for capacity gains and power reduction for all beamforming concepts of interest as well as linear multiuser detection schemes. The results show that fix as well as user-specific beamforming significantly improves network performance gains in downlink. In uplink multiuser detection indicates fairly modest system capacity gains, while it reduces tremendously mobile station power.
A radio-frequency sheath model for complex waveforms  [PDF]
Miles M. Turner,Pascal Chabert
Physics , 2012,
Abstract: Plasma sheaths driven by radio-frequency voltages occur frequently, in contexts ranging from plasma processing applications to magnetically confined fusion experiments. These sheaths are crucial because they dominantly affect impedance, power absorption, ion acceleration and sometimes the stability of the nearby plasma. An analytical understanding of sheath behavior is therefore important, both intrinsically and as an element in more elaborate theoretical structures. In practice, these radio-frequency sheaths are commonly excited by highly anharmonic waveforms, but no analytical model exists for this general case. In this letter we present a mathematically simple sheath model that can be solved for essentially arbitrary excitation waveforms. We show that this model is in good agreement with earlier models for single frequency excitation, and we show by example how to develop a solution for a complex wave form. This solution is in good agreement with simulation data. This simple and accurate model is likely to have wide application.
The radio-frequency quadrupole  [PDF]
Maurizio Vretenar
Physics , 2013, DOI: 10.5170/CERN-2013-001.207
Abstract: Radio-frequency quadrupole (RFQ) linear accelerators appeared on the accelerator scene in the late 1970s and have since revolutionized the domain of low-energy proton and ion acceleration. The RFQ makes the reliable production of unprecedented ion beam intensities possible within a compact radio-frequency (RF) resonator which concentrates the three main functions of the low-energy linac section: focusing, bunching and accelerating. Its sophisticated electrode structure and strict beam dynamics and RF requirements, however, impose severe constraints on the mechanical and RF layout, making the construction of RFQs particularly challenging. This lecture will introduce the main beam optics, RF and mechanical features of a RFQ emphasizing how these three aspects are interrelated and how they contribute to the final performance of the RFQ.
Radio Frequency Interference  [PDF]
R D Ekers,J F Bell
Physics , 2000,
Abstract: We describe the nature of the interference challenges facing radio astronomy in the next decade. These challenges will not be solved by regulation only, negotiation and mitigation will become vital. There is no silver bullet for mitigating against interference. A successful mitigation approach is most likely to be a hierarchical or progressive approach throughout the telescope and signal conditioning and processing systems. We summarise some of the approaches, including adaptive systems.
Radio Frequency Interference Mitigation at the WSRT  [PDF]
P. A. Fridman,W. A. Baan,R. P. Millenaar
Physics , 2010, DOI: 10.1086/422350
Abstract: The sensitivity of radio astronomical stations is often limited by man-made radio frequency interference (RFI) due to a variety of terrestrial activities. An RFI mitigation subsystem (RFIMS) based on real-time digital signalprocessing is proposed here for the Westerbork Synthesis Radio Telescope based on a powerful field programmable gate array processor. In this system the radio astronomy signals polluted by RFI are "cleaned" with the RFIMS before routine back-end correlation processing takes place. The high temporal and frequency resolution of RFIMS allows the detection and excision of RFI better than do standard radio telescope back-end configurations.
Radio Frequency Identifiers: What are the Possibilities?  [PDF]
Ahmed Elmorshidy
Computer Science , 2010,
Abstract: This paper defines the components of radio frequency identifiers (RFID). It also explores the different areas and sectors where RFID can be beneficial. The paper discusses the uses and advantages of RFID in deference, consumer packaged goods (CPG), healthcare, logistics, manufacturing, and retail.
Radio-frequency power generation  [PDF]
Richard G. Carter
Physics , 2013, DOI: 10.5170/CERN-2013-001.45
Abstract: This paper reviews the main types of radio-frequency power amplifiers which are, or may be, used for high-power hadron accelerators. It covers tetrodes, inductive output tubes, klystrons and magnetrons with power outputs greater than 10 kW continuous wave or 100 kW pulsed at frequencies from 50 MHz to 30 GHz. Factors affecting the satisfactory operation of amplifiers include cooling, matching and protection circuits are discussed. The paper concludes with a summary of the state of the art for the different technologies.
Radio Frequency Association of Efimov Trimers  [PDF]
Thomas Lompe,Timo B. Ottenstein,Friedhelm Serwane,Andre N. Wenz,Gerhard Zürn,Selim Jochim
Physics , 2010, DOI: 10.1126/science.1193148
Abstract: The quantum-mechanical three-body problem is one of the fundamental challenges of few-body physics. When the two-body interactions become resonant, an infinite series of universal three-body bound states is predicted to occur, whose properties are determined by the strength of the two-body interactions. We report on the association and direct observation of a trimer state consisting of three distinguishable fermions using radio-frequency (RF) spectroscopy. The measurements of its binding energy are consistent with theoretical predictions which include non-universal corrections.
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