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1

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

Microsoft Academic Search

Ceralink Inc. developed FastFuse, a rapid, new, energy saving process for lamination of glass and composites using radio frequency (RF) heating technology. The Inventions and Innovations program supported the technical and commercial research and development needed to elevate the innovation from bench scale to a self-supporting technology with significant potential for growth. The attached report provides an overview of the

Shawn M. Allan; Patricia M. Strickland; Holly S. Shulman

2009-01-01

2

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

Ceralink Inc. developed FastFuse™, a rapid, new, energy saving process for lamination of glass and composites using radio frequency (RF) heating technology. The Inventions and Innovations program supported the technical and commercial research and development needed to elevate the innovation from bench scale to a self-supporting technology with significant potential for growth. The attached report provides an overview of the technical and commerical progress achieved for FastFuse™ during the course of the project. FastFuse™ has the potential to revolutionize the laminate manufacturing industries by replacing energy intensive, multi-step processes with an energy efficient, single-step process that allows higher throughput. FastFuse™ transmits RF energy directly into the interlayer to generate heat, eliminating the need to directly heat glass layers and the surrounding enclosures, such as autoclaves or vacuum systems. FastFuse™ offers lower start-up and energy costs (up to 90% or more reduction in energy costs), and faster cycles times (less than 5 minutes). FastFuse™ is compatible with EVA, TPU, and PVB interlayers, and has been demonstrated for glass, plastics, and multi-material structures such as photovoltaics and transparent armor.

Shawn M. Allan; Patricia M. Strickland; Holly S. Shulman

2009-11-11

3

Radio-frequency and microwave energies, magnetic and electric fields  

NASA Technical Reports Server (NTRS)

The biological effects of radio frequency, including microwave, radiation are considered. Effects on body temperature, the eye, reproductive systems, internal organs, blood cells, the cardiovascular system, and the central nervous system are included. Generalized effects of electric and magnetic fields are also discussed. Experimentation with animals and clinical studies on humans are cited, and possible mechanisms of the effects observed are suggested.

Michaelson, S. M.

1975-01-01

4

Radio frequency detection assembly and method for detecting radio frequencies  

DOEpatents

A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

Cown, Steven H. (Rigby, ID); Derr, Kurt Warren (Idaho Falls, ID)

2010-03-16

5

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination identifying castable molds for

Allan, Shawn M.

2012-02-27

6

Energy Saving Glass Lamination via Selective Radio Frequency Heating  

SciTech Connect

This project focused on advancing radio-frequency (RF) lamination technology closer to commercial implementation, in order to reduce the energy intensity of glass lamination by up to 90%. Lamination comprises a wide range of products including autoglass, architectural safety and innovative design glass, transparent armor (e.g. bullet proof glass), smart glass, mirrors, and encapsulation of photovoltaics. Lamination is also the fastest growing segment of glass manufacturing, with photovoltaics, architectural needs, and an anticipated transition to laminated side windows in vehicles. The state-of-the-art for glass lamination is to use autoclaves, which apply heat and uniform gas pressure to bond the laminates over the course of 1 to 18 hours. Laminates consist of layers of glass or other materials bonded with vinyl or urethane interlayers. In autoclaving, significant heat energy is lost heating the chamber, pressurized air, glass racks, and the glass. In RF lamination, the heat is generated directly in the vinyl interlayer, causing it to heat and melt quickly, in just 1 to 10 minutes, without significantly heating the glass or the equipment. The main purpose of this project was to provide evidence that low energy, rapid RF lamination quality met the same standards as conventionally autoclaved windows. The development of concepts for laminating curved glass with RF lamination was a major goal. Other primary goals included developing a stronger understanding of the lamination product markets described above, and to refine the potential benefits of commercial implementation. The scope of the project was to complete implementation concept studies in preparation for continuation into advanced development, pilot studies, and commercial implementation. The project consisted of 6 main tasks. The first dealt with lamination with poly-vinyl butyral (PVB) interlayers, which prior work had shown difficulties in achieving good quality laminates, working with Pilkington North America. The second task dealt with a study of current lamination processes in the various laminate industries, and development of concepts for integrating RF lamination into new or existing processes. The third task explored the use of a non-destructive technique for analyzing laminate adhesion with the University of Illinois at Urbana-Champaign. The fourth task focused on developing concepts for curved glass lamination using RF lamination. The fifth and sixth tasks together comprised an analysis of laminate product markets, ranking for applicability and commercialization potential, and the development of commercialization strategies for those products. In addition, throughout the project as new experimental data and conventional process data were obtained, the benefits analysis of RF lamination was refined. The goals of the project described above were achieved, positioning RF lamination for the next stage growth envisioned in the original Industrial Grand Challenge proposal. Working with Pilkington North America, lamination of flat autoglass with PVB was achieved, meeting all 16 stringent industry tests. In particular, PVB laminates made with RF lamination passed environmental tests including the high temperature, 120 ���°C bake test, without significant formation of bubbles (defects). The adhesion of PVB to glass was measured using the pummel method. Adhesion values ranging from 1 to 7 out of 10 were obtained. The significant process parameters affecting the environmental and adhesion performance were identified through a designed experiment. Pre-lamination process variables including PVB storage humidity and the de-airing process (vacuum or nip rolling) were significant, as well as the level of pressure applied to the laminate during the RF process. Analysis of manufacturing with RF lamination equipment, based on the processes developed indicated that 3 RF presses could replace a typical auto-industry autoclave to achieve equal or greater throughput with possibly less capital cost and smaller footprint. Concepts for curved lamination id

Allan, Shawn M.; Baranova, Inessa; Poley, Joseph; Reis, Henrique

2012-02-27

7

Stabilized radio frequency quadrupole  

DOEpatents

A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

Lancaster, Henry D. (Orinda, CA); Fugitt, Jock A. (Berkeley, CA); Howard, Donald R. (Danville, CA)

1984-01-01

8

Impact of Mobile Transmitter Sources on Radio Frequency Wireless Energy Harvesting  

E-print Network

1 Impact of Mobile Transmitter Sources on Radio Frequency Wireless Energy Harvesting Antonio Organization, Tata Consultancy Services, India. Abstract--Wireless energy harvesting sensor networks consti battery resource, but are able to re-charge themselves through directed electromagnetic energy transfer

Sanyal, Sugata

9

Optimized Trigger for Ultra-High-Energy Cosmic-Ray and Neutrino Observations with the Low Frequency Radio Array  

E-print Network

When an ultra-high energy neutrino or cosmic ray strikes the Lunar surface a radio-frequency pulse is emitted. We plan to use the LOFAR radio telescope to detect these pulses. In this work we propose an e?cient trigger implementation for LOFAR optimized for the observation of short radio pulses.

Singh, K; Scholten, O; Anderson, J M; van Ardenne, A; Arts, M; Avruch, M; Asgekar, A; Bell, M; Bennema, P; Bentum, M; Bernadi, G; Best, P; Boonstra, A -J; Bregman, J; van de Brink, R; Broekema, C; Brouw, W; Brueggen, M; Buitink, S; Butcher, H; van Cappellen, W; Ciardi, B; Coolen, A; Damstra, S; Dettmar, R; van Diepen, G; Dijkstra, K; Donker, P; Doorduin, A; Drost, M; van Duin, A; Eisloeffel, J; Falcke, H; Garrett, M; Gerbers, M; Griessmeier, J; Grit, T; Gruppen, P; Gunst, A; van Haarlem, M; Hoeft, M; Holties, H; Horandel, J; Horneffer, L A; Huijgen, A; James, C; de Jong, A; Kant, D; Kooistra, E; Koopman, Y; Koopmans, L; Kuper, G; Lambropoulos, P; van Leeuwen, J; Loose, M; Maat, P; Mallary, C; McFadden, R; Meulman, H; Mol, J -D; Morawietz, J; Mulder, E; Munk, H; Nieuwenhuis, L; Nijboer, R; Norden, M; Noordam, J; Overeem, R; Paas, H; Pandey, V N; Pandey-Pommier, M; Pizzo, R; Polatidis, A; Reich, W; de Reijer, J; Renting, A; Riemers, P; Roettgering, H; Romein, J; Roosjen, J; Ruiter, M; Schoenmakers, A; Schoonderbeek, G; Sluman, J; Smirnov, O; Stappers, B; Steinmetz, M; Stiepel, H; Stuurwold, K; Tagger, M; Tang, Y; ter Veen, S; Vermeulen, R; de Vos, M; Vogt, C; van der Wal, E; Weggemans, H; Wijnholds, S; Wise, M; Wucknitz, O; Yattawatta, S; van Zwieten, J

2011-01-01

10

Energy harvesting of radio frequency and vibration energy to enable wireless sensor monitoring of civil infrastructure  

NASA Astrophysics Data System (ADS)

To power distributed wireless sensor networks on bridges, traditional power cables or battery replacement are excessively expensive or infeasible. This project develops two power harvesting technologies. First, a novel parametric frequency-increased generator (PFIG) is developed. The fabricated PFIG harvests the non-periodic and unprecedentedly low frequency (DC to 30 Hz) and low acceleration (0.55-9.8 m/s2) mechanical energy available on bridges with an average power > 2 ?W. Prototype power conversion and storage electronics were designed and the harvester system was used to charge a capacitor from arbitrary bridge-like vibrations. Second, an RF scavenger operating at medium and shortwave frequencies has been designed and tested. Power scavenging at MHz frequencies allows for lower antenna directivities, reducing sensitivity to antenna positioning. Furthermore, ambient RF signals at these frequencies have higher power levels away from cities and residential areas compared to the UHF and SHF bands utilized for cellular communication systems. An RF power scavenger operating at 1 MHz along with power management and storage circuitry has been demonstrated. It powers a LED at a distance of 10 km from AM radio stations.

Galchev, Tzeno; McCullagh, James; Peterson, Rebecca L.; Najafi, Khalil; Mortazawi, Amir

2011-04-01

11

Thermal chondroplasty: effect of bipolar and monopolar radio frequency energy  

NASA Astrophysics Data System (ADS)

Cartilage fibrillation is commonly associated with injury and long-term degeneration. Contouring the articular surface with radiofrequency energy (RFE) may stabilize the surface, and improve clinical function, but subchondral bone injury has been reported in some patients. The purpose of this research was to document the effects of bipolar and monopolar RFE on articular cartilage. Bipolar RFE and monopolar RFE treatment of abraded bovine cartilage was investigated in an in vitro model. Bipolar RFE caused greater chondrocyte death than monopolar RFE, (bipolar RFE: 1700-mm; monopolar RFE: 800-mm) (p<0.05). Both bipolar RFE and monopolar RFE contoured the articular surface but the depth of chondrocyte death raised concerns regarding the clinical application of RFE. Further work investigated the arthroscopic application of bipolar RFE and monopolar RFE on human chondromalacic cartilage in vitro. Both devices smoothed the fibrillated surface, but bipolar RFE caused increased depth of chondrocyte death compared to monopolar RFE (bipolar RFE 2100-mm; monopolar RFE 620-mm (p<0.05). Fluoroptic thermometry has demonstrated cartilage matrix temperatures exceeding 70° C 2-mm below the articular surface during the application of bipolar RFE. The clinical use of the bipolar RFE systems available to date will likely result in unacceptable chondrocyte death and subchondral injury. While RFE demonstrates some promise for the management of cartilage injury, further work must be completed to define the parameters for its application.

Edwards, Ryland B.; Lu, Yan; Cole, Brian J.; Markel, Mark D.

2001-06-01

12

Radio frequency strain monitor  

NASA Technical Reports Server (NTRS)

A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.

Heyman, Joseph S. (Inventor); Rogowski, Robert S. (Inventor); Holben, Jr., Milford S. (Inventor)

1989-01-01

13

LOW-FREQUENCY RADIO OBSERVATIONS OF PICOFLARE CATEGORY ENERGY RELEASES IN THE SOLAR ATMOSPHERE  

SciTech Connect

We report low-frequency (80 MHz) radio observations of circularly polarized non-thermal type I radio bursts ({sup n}oise storms{sup )} in the solar corona whose estimated energy is {approx}10{sup 21} erg. These are the weakest energy release events reported to date in the solar atmosphere. The plot of the distribution of the number of bursts (dN) versus their corresponding peak flux density in the range S to S+dS shows a power-law behavior, i.e., dN {proportional_to} S {sup {gamma}} dS. The power-law index {gamma} is in the range -2.2 to -2.7 for the events reported in the present work. The present results provide independent observational evidence for the existence of picoflare category energy releases in the solar atmosphere which are yet to be explored.

Ramesh, R.; Sasikumar Raja, K.; Kathiravan, C.; Satya Narayanan, A., E-mail: ramesh@iiap.res.in [Indian Institute of Astrophysics, Bangalore 560 034 (India)

2013-01-10

14

Superconducting Radio-Frequency Cavities  

NASA Astrophysics Data System (ADS)

Superconducting cavities have been operating routinely in a variety of accelerators with a range of demanding applications. With the success of completed projects, niobium cavities have become an enabling technology, offering upgrade paths for existing facilities and pushing frontier accelerators for nuclear physics, high-energy physics, materials science, and the life sciences. With continued progress in basic understanding of radio-frequency superconductivity, the performance of cavities has steadily improved to approach theoretical capabilities.

Padamsee, Hasan S.

2014-10-01

15

Development of Equipment to Separate Nonthermal and Thermal Effects of Radio Frequency Energy on Microorganisms  

SciTech Connect

A radio frequency (RF) dielectric heater has been developed for isolating thermal and nonthermal effects of RF energy on microorganisms in liquid foods. The modified heater enables the simultaneous application of RF energy and removal of thermal energy from the liquids. A double-pipe heat exchanger is an integral part of the heater. The outer pipe is made of Teflon. The inner pipe is made of stainless steel that is grounded in the RF circuit. Liquid food flows through the annular region between the two concentric pipes. Cooling water flows through the stainless steel pipe. The food in the annular region absorbs the RF energy. Concurrently, the cooling water flowing in the inner pipe removes the thermal energy from the food, thus controlling the temperature.

D.J. Geveke; M. Kozempel; C. Brunkhorst

1999-11-01

16

Radio frequency coaxial feedthrough  

DOEpatents

An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

Owens, Thomas L. (Kingston, TN)

1989-01-17

17

Investigation of effect of excitation frequency on electron energy distribution functions in low pressure radio frequency bounded plasmas  

SciTech Connect

Particle in cell (PIC) simulations are employed to investigate the effect of excitation frequency {omega} on electron energy distribution functions (EEDFs) in a low pressure radio frequency (rf) discharge. The discharge is maintained over a length of 0.10 m, bounded by two infinite parallel plates, with the coherent heating field localized at the center of the discharge over a distance of 0.05 m and applied perpendicularly along the y and z directions. On varying the excitation frequency f (={omega}/2{pi}) in the range 0.01-50 MHz, it is observed that for f {<=} 5 MHz the EEDF shows a trend toward a convex (Druyvesteyn-like) distribution. For f > 5 MHz, the distribution resembles more like a Maxwellian with the familiar break energy visible in most of the distributions. A prominent ''hot tail'' is observed at f{>=} 20 MHz and the temperature of the tail is seen to decrease with further increase in frequency (e.g., at 30 MHz and 50 MHz). The mechanism for the generation of the ''hot tail'' is considered to be due to preferential transit time heating of energetic electrons as a function of {omega}, in the antenna heating field. There exists an optimum frequency for which high energy electrons are maximally heated. The occurrence of the Druyvesteyn-like distributions at lower {omega} may be explained by a balance between the heating of the electrons in the effective electric field and elastic cooling due to electron neutral collision frequency {nu}{sub en}; the transition being dictated by {omega} {approx} 2{pi}{nu}{sub en}.

Bhattacharjee, Sudeep [Space plasma, Power and Propulsion, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Department of Physics, Indian Institute of Technology, Kanpur 208 016 (India); Lafleur, Trevor; Charles, Christine; Boswell, Rod [Space plasma, Power and Propulsion, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2011-07-15

18

Low Frequency Radio Experiment (LORE)  

NASA Astrophysics Data System (ADS)

High temporal and frequency resolution observations of solar generated disturbances below 15 MHz in the near-Sun region and at Sun-Earth distances in conjunction with optical and high energy observations of Sun are essential to understand the structure and evolution of eruptions, such as, flares, coronal mass ejections (CMEs), and their associated solar wind disturbances at heights above the photosphere and their consequences in the interplanetary medium. This talk presents a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii below 30 MHz. The LORE, although not part of Aditya-L1 mission, can be complimentary to planned Aditya-L1 coronagraph and its other on-board payloads as well as synergistic to ground based observations, which are routinely carried out by Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and it is particularly suitable for providing data on the detailed time and frequency structure of fast drifting Type-III and slow drifting Type-II radio bursts with unprecedented time and frequency resolution as well as goniopolarimetry, made possible with better designed antennas and state-of-art electronics, employing FPGAs and an intelligent data management system. This would enable wide ranging studies such as studies of nonlinear plasma processes, CME in-situ radio emission, CME driven phenomena, interplanetary CME driven shocks, ICMEs driven by decelerating IP shocks and space weather effects of Solar Wind interaction regions. The talk will highlight the science objectives as well as the proposed technical design features.

Manoharan, Periasamy K.; Joshi, Bhal Chandra; Naidu, Arun Kumar

19

Tailoring electron energy distribution functions through energy confinement in dual radio-frequency driven atmospheric pressure plasmas  

SciTech Connect

A multi-scale numerical model based on hydrodynamic equations with semi-kinetic treatment of electrons is used to investigate the influence of dual frequency excitation on the effective electron energy distribution function (EEDF) in a radio-frequency driven atmospheric pressure plasma. It is found that variations of power density, voltage ratio, and phase relationship provide separate control over the electron density and the mean electron energy. This is exploited to directly influence both the phase dependent and time averaged effective EEDF. This enables tailoring the EEDF for enhanced control of non-equilibrium plasma chemical kinetics at ambient pressure and temperature.

O'Neill, C.; Waskoenig, J. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Gans, T. [Centre for Plasma Physics, School of Maths and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)

2012-10-08

20

High power radio frequency attenuation device  

DOEpatents

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

Kerns, Quentin A. (Bloomingdale, IL); Miller, Harold W. (Winfield, IL)

1984-01-01

21

Radio Frequency Identification  

NSDL National Science Digital Library

A wealth of information about RFID is available at this site (1), ranging from background material to case studies. A discussion highlighting the myriad of uses for RFID is included. Transponder News (2) offers several articles that explore the technology in greater detail. Two in particular look at current and future trends, while others are editorial essays and technical notes. Pacific Northwest National Laboratory (3) is involved in the development of advanced tags for RFID systems. The project's homepage outlines current research efforts for three different types of radio frequency tags, which are being designed for varying degrees of sophistication and functionality. While RFID technology can be very useful, the fact that information about items is collected remotely raises concerns about privacy and security. This issue is addressed in a research paper from the Massachusetts Institute of Technology (4). The authors review current RFID systems and their operation, and then propose a number of security mechanisms that could reduce the risk associated with their use. A paper presented at the 2002 European Wireless Conference (5) compares the performance of RFID systems that use ultra-high frequency (UHF) communications to those that use microwave communications. It is argued that although microwave-based devices, such as Bluetooth, are suitable for worldwide operation, systems that communicate in the UHF range have greater range and less interference. The introduction of RFID smart tags in goods is discussed in this article (6). Now that these tags are cheap enough to be attached to thousands of items, stores will be able to track goods as they are transferred from storehouses to retail shelves, thereby minimizing the possibility of loss or theft. RFID technology has found another use in the war with Iraq. An article from May 20, 2003 (7) describes wristbands embedded with an RFID chip. The status and position of a wounded soldier who is wearing such a wristband can be monitored while he or she is recovering at a medical facility. For additional updates on the development of RFID technology, RFID News (8) maintains current news about emerging standards, innovative applications, and general issues.

Leske, Cavin.

22

SITE TECHNOLOGY CAPSULE: IITRI RADIO FREQUENCY HEATING TECHNOLOGY  

EPA Science Inventory

Radio frequency heating (RFH) technologies use electromagnetic energy in the radio frequency (RF) band to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. Contaminants are removed from in situ soils and transfe...

23

Ion energy distribution functions in magnetized and non magnetized radio frequency discharges  

E-print Network

The effect of a spatially inhomogeneous static magnetic field on the characteristics of capacitively coupled radio frequency discharges is investigated, with a focus on the sheath dynamics and the energy distribution functions (IEDFs) of the ions impinging the electrodes. Numerical studies are performed with two different kinetic algorithms. The first is a Particle-in-Cell (PIC) code which takes into account the entire discharge; the second is the novel Ensemble-in-Spacetime scheme (EST) which resolves only the sheath. When EST is fed with the sheath voltage and ion flux calculated by PIC, excellent agreement of the IEDFs is found: the applied magnetic field predominantly influences the plasma bulk, i.e., the electron density and the ion flux to the walls; the dynamics of the sheath itself is only indirectly affected. It is concluded that EST may be used as an efficient postprocessing tool to obtain the IEDFs in cases where only simplified (i.e., global or fluiddynamic) information is available.

Trieschmann, Jan; Szeremley, Daniel; Elgendy, Abd Elfattah; Gallian, Sara; Eremin, Denis; Brinkmann, Ralf Peter; Mussenbrock, Thomas

2012-01-01

24

Energy spectra of meteor trails in the radio-frequency range  

Microsoft Academic Search

The paper presents a method for calculating the energy spectra of radio waves scattered by an ensemble of meteor trails formed in a given region of space over a given period of time. Astronomical and atmospheric factors are taken into account as well as instrumentation characteristics. Experiments have been carried out that confirm the calculations in terms of both absolute

V. I. Boikov; T. V. Kazakova; A. V. Karpov; M. M. Katsevman

1990-01-01

25

Very low frequency radio astronomy  

NASA Astrophysics Data System (ADS)

Very low frequency (VLF) radio astronomy covers the frequency range below about 30 MHz (or the wavelength range above 10 m). This is the last window of the electromagnetic spectrum never to have been observed with spatial resolution. This is a range over which the Earth's ionosphere transmits either poorly or not at all. In this paper, we describe some means to observe this frequency range and we review what can be expected from exploring the astrophysics of the universe at very low radio frequencies. We present the scientific case for a large array to be set up on the far side of the Moon. This would open an entirely new field of remote probing of astrophysical plasmas in the Universe.

Bougeret, J.-L.

26

Digital Channelizing Radio Frequency Receiver  

Microsoft Academic Search

HYPRES is developing a class of digital receivers featuring direct digitization at radio frequency (RF). Such a receiver consists of a wideband analog-to-digital converter (ADC) modulator and multiple digital channelizer units to extract different frequency bands-of-interest within the broad digitized spectrum. The single-bit oversampled data, from either a lowpass delta or bandpass delta-sigma modulator, are applied to one or more

Deepnarayan Gupta; Timur V. Filippov; Alexander F. Kirichenko; Dmitri E. Kirichenko; Igor V. Vernik; Anubhav Sahu; Saad Sarwana; Pavel Shevchenko; Andrei Talalaevskii; Oleg A. Mukhanov

2007-01-01

27

Radio Frequency Interference and the National Radio Astronomy Observatory  

NASA Astrophysics Data System (ADS)

Radio frequency interference (RFI) and radio astronomy have been closely linked since the emergence of radio astronomy as a scientific discipline in the 1930s. Even before the official establishment of the National Radio Astronomy Observatory, protection against contemporary and future radio noise levels was seen as crucial to ensure success of any new observatory. My talk will examine the various local, regional, national, and international efforts enacted to protect NRAO and other American radio astronomy sites from RFI.

Smith, Sierra

2014-01-01

28

Radio frequency power load and associated method  

NASA Technical Reports Server (NTRS)

A radio frequency power load and associated method. A radio frequency power load apparatus includes a container and a fluid having an ion source therein, the fluid being contained in the container. Two conductors are immersed in the fluid. A radio frequency transmission system includes a radio frequency transmitter, a radio frequency amplifier connected to the transmitter and a radio frequency power load apparatus connected to the amplifier. The apparatus includes a fluid having an ion source therein, and two conductors immersed in the fluid. A method of dissipating power generated by a radio frequency transmission system includes the steps of: immersing two conductors of a radio frequency power load apparatus in a fluid having an ion source therein; and connecting the apparatus to an amplifier of the transmission system.

Sims, III, William Herbert (Inventor); Chavers, Donald Gregory (Inventor); Richeson, James J. (Inventor)

2010-01-01

29

Tracing Ghost Cavities with Low Frequency Radio Observations  

E-print Network

We present X-ray and multi-frequency radio observations of the central radio sources in several X-ray cavity systems. We show that targeted radio observations are key to determining if the lobes are being actively fed by the central AGN. Low frequency observations provide a unique way to study both the lifecycle of the central radio source as well as its energy input into the ICM over several outburst episodes.

Tracy Clarke; Elizabeth Blanton; Craig Sarazin; Namir Kassim; Loren Anderson; Henrique Schmitt; Gopal-Krishna; Doris Neumann

2006-12-20

30

Radio frequency coaxial feedthrough device  

DOEpatents

A radio frequency coaxial vacuum feedthrough is provided which utilizes a cylindrical ceramic vacuum break formed of an alumina ceramic. The cylinder is coaxially disposed and brazed between tapered coaxial conductors to form a vacuum sealed connection between a pressurized upstream coaxial transmission line and a utilization device located within a vacuum container. The feedthrough provides 50 ohm matched impedance RF feedthrough up to about 500 MHz at power levels in the multimegawatt range.

Owens, Thomas L. (Kingston, TN); Baity, Frederick W. (Oak Ridge, TN); Hoffman, Daniel J. (Oak Ridge, TN); Whealton, John H. (Oak Ridge, TN)

1987-01-01

31

Low Radio Frequency Picosatellite Missions  

NASA Astrophysics Data System (ADS)

The dramatic advances in cubesat and other picosatellite capabilities are opening the door for scientifically important observations at low radio frequencies. Because simple antennas are effective at low frequencies, and receiver technology allows low mass and low power instruments, these observations are an ideal match for very small spacecraft. A workshop on cubesat missions for low frequency radio astronomy was held at the Kiss Institute for Space Sciences, Caltech, to explore mission concepts involving one up to hundreds of picosatellites. One result from this workshop was that there are opportunities for viable missions throughout this large range. For example, the sky-integrated spectral signature of highly redshifted neutral hydrogen from the dark ages and cosmic dawn epochs can be measured by a single antenna on a single spacecraft. There are challenging issues of calibration, foreground removal, and RF interference that need to be solved, but the basic concept is appealingly simple. At the other extreme, imaging of angular structure in the high-redshift hydrogen signal will require an interferometer array with a very large number of antennas. In this case the primary requirement is a sufficiently low individual spacecraft mass that hundreds can be launched affordably. The technical challenges for large arrays are long-term relative station keeping and high downlink data rates. Missions using several to a few tens of picosatellites can image and track bright sources such as solar and planetary radio bursts, and will provide essential validation of technologies needed for much larger arrays.This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Jones, Dayton L.

2014-06-01

32

Intelligent Radio Frequency (RF) Monitoring  

E-print Network

? Intelligent Radio Frequency (RF) Monitoring ? 2009 Armstrong International, Inc. www.armstronginternational.com 2 ?Expect many enjoyable experiences!? David M. Armstrong Present Process Challenges ? Identifying a failure ? Procedure... day Weeks a Year 52 week Total Hours 8760 hr/hr *Max Flow Thru is Calculated Using a 7/64" Orifice @ 200 psig for Each Application Listed Above & Blow 1 Hour 1 Day 1 Week 1 Month 3 Months 1 Year Drip 97 2,328 16,296 69,840 209,520 849,720 Tracer...

Kimbrough, B.

33

Radio-Frequency Strain Monitor  

NASA Technical Reports Server (NTRS)

Radio-frequency (RF) strain monitor developed to measure lengths of objects. RF waveguide or cable bonded to structure monitored. Propagation of RF signal along waveguide results in phase shift proportional to length of path traveled. Impedance mismatches placed in RF cable at nodes of structure. Records mismatches and detects overall length of line and lengths of intervals between nodes. Used to detect changes in elements of large structure with single cable. Monitor has potential for many applications, including monitoring stability of such large structures as aircraft, bridges, and buildings in Earthquake zones.

Heyman, Joseph S.; Rogowski, Robert S.; Holben, Milford S., Jr.

1988-01-01

34

Coping with Radio Frequency Interference  

NASA Astrophysics Data System (ADS)

The radio spectrum is a finite resource, on which humanity makes many demands. And pressure on it is ever increasing with the development of new technology and ideas for radio services. After all, we all benefit from wifi and cell phones. Radio astronomers have a small percentage of the spectrum allocated to them at octave intervals in the metre-centimetre bands, and at important frequencies, such as that of the 21cm line of HI. Signals from other services, as well as from our own poorly-engineered equipment, sometimes contaminate our bands: these signals constitute RFI. These may totally obliterate the astronomical signal, or, in the case of CLOUDSAT, may be capable of completely destroying a receiver, which introduces us to the new possibility of 'destructive interference'. A geo-stationary satellite can block access to a piece of sky from one site. Good equipment design eliminates self-inflicted interference, while physical separation often provides adequate practical mitigation at many frequencies. However, new observatories end up being located in the West Australian desert or Antarctica. In future they may be on the back side of the Moon. But there is no Earth-bound protection via physical separation against satellite signals. Some mitigation can be achieved by frequent data dumps and the excision of RFI, or by real-time detection and blanking of the receiver, or by more sophisticated algoriths. Astronomers of necessity aim to achieve mitigation via coordination, at the local level, and by participating in spectrum management at the national and international levels. This involves them spending a lot of time in Geneva at the International Telegraphic Union protecting their access to spectrum, and access to clean spectrum from the L3 point and the far side of the Moon.

Lewis, B. M.

2009-01-01

35

Treatment of Severe (Stage III and IV) Chronic Pressure Ulcers Using Pulsed Radio Frequency Energy in a Quadriplegic Patient  

PubMed Central

Objective: To report an adjuvant treatment to basic wound care of stage III and IV pressure ulcers in a patient with quadriplegia. Methods: Pulsed radio frequency energy was used as an adjunct to basic wound care of 3 large, long-standing (6 years) stage III and IV pressure ulcers that were unresponsive to conventional therapy in a 59-year-old man with quadriplegia. Results: The ulcers (on right foot, left heel, and sacrum) markedly decreased in size (16.7, 28.5, and 13.1 mm2 per day, respectively). The ulcer on the right foot healed within 4 weeks, the left heel ulcer reduced in size by 95% at 7 months, and the large sacral ulcer healed to closure in 11 months. Conclusion: Pulsed radio frequency energy treatment with basic wound care, if administered early in the course of pressure ulcer therapy, might avoid the lengthy hospitalizations and repeated surgical procedures necessary for treatment of uncontrolled ulcers, reducing the overall cost of treatment and improving the quality of life for chronically ill or injured patients. PMID:19008935

Porreca, Eugene G.; Giordano-Jablon, Gina M.

2008-01-01

36

SITE TECHNOLOGY CAPSULE: IITRI RADIO FREQUENCY HEATING TECHNOLOGY  

EPA Science Inventory

Radio frequency heating (RFH) technologies use electromagnetic energy in the radio frequency i(RF) band to heat soil in-situ, thereby potentially enhancing the performances of standard soil vapor extraction (SVE) technologies. ontaminants are removed from in situ soils and transf...

37

DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - KAI TECHNOLOGIES, INC.  

EPA Science Inventory

Radio frequency heating (RFH) is a process that uses electromagnetic energy in the radio frequency (RF) band to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. An RFH system developed by KAI Technologies, I...

38

IN SITU AND SOIL DECONTAMINATION BY RADIO FREQUENCY HEATING  

EPA Science Inventory

In situ radio frequency heating is performed by applying electromagnetic energy in the radio frequency band to an array of electrodes placed in bore holes drilled through the contaminated soil. he process removes organic contaminants from large volumes of soil by volatilization, ...

39

A radio frequency coaxial feedthrough  

DOEpatents

An improved radio frequency coaxial transmission line vacuum feedthrough is provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflection from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits the voltage and power handling capabilities of a feedthrough.

Owens, T.L.

1987-12-07

40

Method and apparatus for radio frequency ceramic sintering  

DOEpatents

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

Hoffman, Daniel J. (Oak Ridge, TN); Kimrey, Jr., Harold D. (Knoxville, TN)

1993-01-01

41

Method and apparatus for radio frequency ceramic sintering  

DOEpatents

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents. 6 figures.

Hoffman, D.J.; Kimrey, H.D. Jr.

1993-11-30

42

Introduction to special section on Mitigation of Radio Frequency Interference in Radio Astronomy  

E-print Network

Introduction to special section on Mitigation of Radio Frequency Interference in Radio Astronomy presented at the Workshop on the Mitigation of Radio Frequency Interference in Radio Astronomy (RFI2004), Introduction to special section on Mitigation of Radio Frequency Interference in Radio Astronomy, Radio Sci

Ellingson, Steven W.

43

Radio Frequency Identification iny integrated circuits equipped with radio an-  

E-print Network

checkout lines. Yet, despite the technology's current widespread use andsignificantfuturepotential their knowledge orconsent.TypicalofthiscoverageisaWiredNewsarticle that erroneously reported clothing giant Benetton's plans "to weave radio frequency ID chips into its garments to track its clothes worldwide."1

Han, Richard Y.

44

Numerical modelling of a radio-frequency micro ion thruster  

E-print Network

A simple performance model is developed for an inductively-coupled radio-frequency micro ion thruster. Methods of particle and energy balance are utilized for modeling the chamber plasma discharge. A transformer model is ...

Tsay, Michael Meng-Tsuan

2006-01-01

45

Integrally formed radio frequency quadrupole  

DOEpatents

An improved radio frequency quadrupole (10) is provided having an elongate housing (11) with an elongate central axis (12) and top, bottom and two side walls (13a-d) symmetrically disposed about the axis, and vanes (14a-d) formed integrally with the walls (13a-d), the vanes (14a-d) each having a cross-section at right angles to the central axis (12) which tapers inwardly toward the axis to form electrode tips (15a-d) spaced from each other by predetermined distances. Each of the four walls (13a-d), and the vanes (14a-d) integral therewith, is a separate structural element having a central lengthwise plane (16) passing through the tip of the vane, the walls (13a-d) having flat mounting surfaces (17, 18) at right angles to and parallel to the control plane (16), respectively, which are butted together to position the walls and vane tips relative to each other.

Abbott, Steven R. (Concord, CA)

1989-01-01

46

Design and development of a radio frequency quadrupole linac postaccelerator for the Variable Energy Cyclotron Center rare ion beam project  

NASA Astrophysics Data System (ADS)

A four-rod type heavy-ion radio frequency quadrupole (RFQ) linac has been designed, constructed, and tested for the rare ion beam (RIB) facility project at VECC. Designed for cw operation, this RFQ is the first postaccelerator in the RIB beam line. It will accelerate A /q?14 heavy ions coming from the ion source to the energy of around 100 keV/u for subsequent acceleration in a number of Interdigital H-Linac. Operating at a resonance frequency of 37.83 MHz, maximum intervane voltage of around 54 kV will be needed to achieve the final energy over a vane length of 3.12 m for a power loss of 35 kW. In the first beam tests, transmission efficiency of about 90% was measured at the QQ focus after the RFQ for O5+ beam. In this article the design of the RFQ including the effect of vane modulation on the rf characteristics and results of beam tests will be presented.

Dechoudhury, S.; Naik, V.; Mondal, M.; Chatterjee, A.; Pandey, H. K.; Mandi, T. K.; Bandyopadhyay, A.; Karmakar, P.; Bhattacharjee, S.; Chouhan, P. S.; Ali, S.; Srivastava, S. C. L.; Chakrabarti, A.

2010-02-01

47

Design and development of a radio frequency quadrupole linac postaccelerator for the Variable Energy Cyclotron Center rare ion beam project.  

PubMed

A four-rod type heavy-ion radio frequency quadrupole (RFQ) linac has been designed, constructed, and tested for the rare ion beam (RIB) facility project at VECC. Designed for cw operation, this RFQ is the first postaccelerator in the RIB beam line. It will accelerate A/q < or = 14 heavy ions coming from the ion source to the energy of around 100 keV/u for subsequent acceleration in a number of Interdigital H-Linac. Operating at a resonance frequency of 37.83 MHz, maximum intervane voltage of around 54 kV will be needed to achieve the final energy over a vane length of 3.12 m for a power loss of 35 kW. In the first beam tests, transmission efficiency of about 90% was measured at the QQ focus after the RFQ for O(5+) beam. In this article the design of the RFQ including the effect of vane modulation on the rf characteristics and results of beam tests will be presented. PMID:20192486

Dechoudhury, S; Naik, V; Mondal, M; Chatterjee, A; Pandey, H K; Mandi, T K; Bandyopadhyay, A; Karmakar, P; Bhattacharjee, S; Chouhan, P S; Ali, S; Srivastava, S C L; Chakrabarti, A

2010-02-01

48

DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - IIT RESEARCH INSTITUTE  

EPA Science Inventory

Radio frequency heating (RFH) is a process that uses electromagnetic energy generated by radio waves to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. An RFH system developed by the IIT Research Institute ...

49

High-power radio-frequency attenuation device  

DOEpatents

A resistor device for attenuating radio frequency power includes a radio frequency conductor connected to a series of fins formed of high relative magnetic permeability material. The fins are dimensional to accommodate the skin depth of the current conduction therethrough, as well as an inner heat conducting portion where current does not travel. Thermal connections for air or water cooling are provided for the inner heat conducting portions of each fin. Also disclosed is a resistor device to selectively alternate unwanted radio frequency energy in a resonant cavity.

Kerns, Q.A.; Miller, H.W.

1981-12-30

50

A power amplifier tube used to amplify weak microwave energy (provided by a radio-frequency exciter) to a high power level for  

E-print Network

Klystron · A power amplifier tube used to amplify weak microwave energy (provided by a radio are characterized by high peak power, small size, efficient operation, and low operating voltage.efficient operation- frequency exciter) to a high power level for a radar transmitter.a radar transmitter. · A klystron

Cruz-Pol, Sandra L.

51

Multi-mode radio frequency device  

DOEpatents

A transponder device having multiple modes of operation, such as an active mode and a passive mode, wherein the modes of operation are selected in response to the strength of a received radio frequency signal. A communication system is also provided having a transceiver configured to transmit a radio frequency signal and to receive a responsive signal, and a transponder configured to operate in a plurality of modes and to activate modes of operation in response to the radio frequency signal. Ideally, each mode of operation is activated and deactivated independent of the other modes, although two or more modes may be concurrently operational.

Gilbert, Ronald W. (Morgan Hill, CA); Carrender, Curtis Lee (Morgan Hill, CA); Anderson, Gordon A. (Benton City, WA); Steele, Kerry D. (Kennewick, WA)

2007-02-13

52

NASA Radio Frequency Spectrum Management Manual  

NASA Technical Reports Server (NTRS)

The Radio Frequency (RF) Spectrum Management Manual sets forth procedures and guidelines for the management requirements for controlling the use of radio frequencies by the National Aeronautics and Space Administration. It is applicable to NASA Headquarters and field installations. NASA Management Instruction 1102.3 assigns the authority for management of radio frequencies for the National Aeronautics and Space Administration to the Associate Administrator for Space Operations, NASA Headquarters. This manual is issued in loose-leaf form and will be revised by page changes.

1989-01-01

53

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false External radio frequency power amplifiers. 2.815 Section...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...AND REGULATIONS Marketing of Radio-frequency Devices § 2.815 External...

2013-10-01

54

47 CFR 2.815 - External radio frequency power amplifiers.  

Code of Federal Regulations, 2012 CFR

... External radio frequency power amplifiers. 2.815 Section 2.815 ...External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power amplifier is any device which,...

2012-10-01

55

Plasma sheath model and ion energy distribution for all radio frequencies Theodoros Panagopoulos and Demetre J. Economoua)  

E-print Network

amenable to analysis since, in both cases, the sheath can be described as a dc sheath; actually a series electropositive glow discharge were studied with a model that is valid for arbitrary radio frequencies rf transit time i is a critical parameter for describing the sheath dynamics. © 1999 American Institute

Economou, Demetre J.

56

Security approaches for Radio Frequency Identification systems  

E-print Network

In this thesis, I explore the challenges related to the security of the Electronic Product Code (EPC) class of Radio Frequency Identification (RFID) tags and associated data. RFID systems can be used to improve supply chain ...

Foley, Joseph Timothy, 1976-

2007-01-01

57

Measurements of metastable atom density using energies and densities of energetic "fast" electrons detected in the electron energy distribution function associated with the afterglow plasma produced by a radio frequency inductively coupled plasma helium d.  

E-print Network

??In this work, electron density, electron temperature, electron energy distribution function (EEDF), and metastable atom density in the afterglow of low-pressure (50 mTorr) helium radio-frequency… (more)

Blessington, Jon C.

2007-01-01

58

Gap length effect on electron energy distribution in capacitive radio frequency discharges  

SciTech Connect

A study on the dependence of electron energy distribution function (EEDF) on discharge gap size in capacitive rf discharges was conducted. The evolution of the EEDF over a gap size range from 2.5 to 7 cm in 65 mTorr Ar discharges was investigated both experimentally and theoretically. The measured EEDFs exhibited typical bi-Maxwellian forms with low energy electron groups. A significant depletion in the low energy portion of the bi-Maxwellian was found with decreasing gap size. The results show that electron heating by bulk electric fields, which is the main heating process of the low-energy electrons, is greatly enhanced as the gap size decreases, resulting in the abrupt change of the EEDF. The calculated EEDFs based on nonlocal kinetic theory are in good agreement with the experiments.

You, S. J.; Kim, S. S.; Kim, Jung-Hyung; Seong, Dae-Jin; Shin, Yong-Hyeon; Chang, H. Y. [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon 305-306 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2007-11-26

59

Power Supplies and Radio Frequency Department at Culham  

E-print Network

Power Supplies and Radio Frequency Department at Culham Culham Centre for Fusion Energy #12;WeMW 800tonne flywheel-driven generators, high current and high voltage DC switches in pulsed supplies frequency generators. We have an ongoing need for power electrical engineers and technicians across a range

60

An overview of the Low Energy Demonstration Accelerator (LEDA) project RF (radio frequency) systems  

SciTech Connect

Successful operation of the Accelerator Production of Tritium (APT) plant will require that accelerator downtime be kept to an absolute minimum. Over 230 separate 1 MW RF systems are expected to be used in the APT plant, making the efficiency and reliability of these systems two of the most critical factors in plant operation. The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for APT. The design of the RF systems used in LEDA has been driven by the need for high efficiency and extremely high system reliability. The authors present details of the high voltage power supply and transmitter systems as well as detailed descriptions of the waveguide layout between the klystrons and the accelerating cavities. The first stage of LEDA operations will use four 1.2 MW klystrons to test the RFQ and supply power to one test stand. The RFQ will serve as a power combiner for multiple RF systems. They present some of the unique challenges expected in the use of this concept.

Bradley, J. III; Cummings, K.; Lynch, M.; Rees, D.; Roybal, W.; Tallerico, P. [Los Alamos National Lab., NM (United States); Toole, L. [Savannah River Site, SC (United States)

1997-05-12

61

The characteristics of atmospheric radio frequency discharges with frequency increasing at a constant power density  

SciTech Connect

A computational model is used to investigate the characteristics of atmospheric radio frequency discharges by increasing frequency from 20 to 100 MHz at a constant power density. The simulation results show that increasing frequency can effectively enhance electron density before the transition frequency but after it the ignition is quenched then the electron density decreases. However this simulation also indicates the maximum time-averaged electron energy reduces monotonically with the excitation frequency increasing at a constant power density.

Zhang Yuantao; Li Qingquan; Lou Jie; Li Qingmin [School of Electrical Engineering, Shandong University, Jinan, Shandong Province 250061 (China)

2010-10-04

62

Monitoring Radio Frequency Interference in Southwest Virginia  

NASA Astrophysics Data System (ADS)

The radio signals received from astronomical objects are extremely weak. Because of this, radio sources are easily shrouded by interference from devices such as satellites and cell phone towers. Radio astronomy is very susceptible to this radio frequency interference (RFI). Possibly even worse than complete veiling, weaker interfering signals can contaminate the data collected by radio telescopes, possibly leading astronomers to mistaken interpretations. To help promote student awareness of the connection between radio astronomy and RFI, an inquiry-based science curriculum was developed to allow high school students to determine RFI levels in their communities. The Quiet Skies Project_the result of a collaboration between the National Aeronautics and Space Administration (NASA), the National Science Foundation (NSF), and the National Radio Astronomy Observatory (NRAO)_encourages students to collect and analyze RFI data and develop conclusions as a team. Because the project focuses on electromagnetic radiation, it is appropriate for physics, physical science, chemistry, or general science classes. My class-about 50 students from 15 southwest Virginia high schools-participated in the Quiet Skies Project and were pioneers in the use of the beta version of the Quiet Skies Detector (QSD), which is used to detect RFI. Students have been involved with the project since 2005 and have collected and shared data with NRAO. In analyzing the data they have noted some trends in RFI in Southwest Virginia.

Rapp, Steve

2010-01-01

63

Radio-frequency measurements of coherent transition and cherenkov radiation: implications for high-energy neutrino detection  

PubMed

We report on measurements of (11-18)-cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultrahigh-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultrahigh-energy neutrinos. PMID:11138159

Gorham; Saltzberg; Schoessow; Gai; Power; Konecny; Conde

2000-12-01

64

Radio-Frequency Measurements of Coherent Transition and Cherenkov Radiation: Implications for High-Energy Neutrino Detection  

E-print Network

We report on measurements of 11-18 cm wavelength radio emission from interactions of 15.2 MeV pulsed electron bunches at the Argonne Wakefield Accelerator. The electrons were observed both in a configuration where they produced primarily transition radiation from an aluminum foil, and in a configuration designed for the electrons to produce Cherenkov radiation in a silica sand target. Our aim was to emulate the large electron excess expected to develop during an electromagnetic cascade initiated by an ultra high-energy particle. Such charge asymmetries are predicted to produce strong coherent radio pulses, which are the basis for several experiments to detect high-energy neutrinos from the showers they induce in Antarctic ice and in the lunar regolith. We detected coherent emission which we attribute both to transition and possibly Cherenkov radiation at different levels depending on the experimental conditions. We discuss implications for experiments relying on radio emission for detection of electromagnetic cascades produced by ultra high-energy neutrinos.

Peter Gorham; David Saltzberg; Paul Schoessow; Wei Gai; John G. Power; Richard Konecny; M. E. Conde

2000-04-05

65

Radio Frequency (RF) strain monitor  

NASA Technical Reports Server (NTRS)

This invention relates to an apparatus for measuring strain in a structure. In particular, the invention detects strain in parts per million to over ten percent along an entire length (or other dimension) of a structure measuring a few millimeters to several kilometers. By using a propagation path bonded to the structure, the invention is not limited by the signal attenuation characteristics of the structure and thus frequencies in the megahertz to gigahertz range may be used to detect strain in part per million to over ten percent with high precision.

Heyman, Joseph S. (inventor); Rogowski, Robert S. (inventor); Holben, Milford S., Jr. (inventor)

1988-01-01

66

Radio Frequency Identification: Beyond the myths  

Microsoft Academic Search

Abstract: Radio Frequency Identification (RFID) is one of the most promising,information system technologies for the health care industry today andin the future. Many experts and researchers consider that RFID should improve the tracking of patients, medical personnel, drugs, and equipment, decrease medical errors, provide positive identification of patients and

S. Bureau; B. S. Prabhu; R. Gadh

67

Privacy debate centers on radio frequency identification  

Microsoft Academic Search

The emergence of radio frequency identification (RFID) has brought with it a plethora of privacy concerns and experts are questioning whether the hoopla surrounding RFID is justified. Using RFID should trigger the same privacy concerns as other commonly used technology such as credit cards, cell phones, and the Internet. RFID's potential to revolutionize the retail industry by maximizing suppliers' ability

B. J. Alfonsi

2004-01-01

68

Commissioning of helium injector for coupled radio frequency quadrupole and separated function radio frequency quadrupole accelerator.  

PubMed

A project to study a new type of acceleration structure has been launched at Peking University, in which a traditional radio frequency quadrupole (RFQ) and a separated function radio frequency quadrupole are coupled in one cavity to accelerate the He+ beam. A helium injector for this project is developed. The injector consists of a 2.45 GHz permanent magnet electron cyclotron resonance ion source and a 1.16 m long low energy beam transport (LEBT). The commissioning of this injector was carried out and an onsite test was held in June 2013. A 14 mA He+ beam with the energy of 30 keV has been delivered to the end of the LEBT, where a diaphragm with the diameter of 7 mm is located. The position of the diaphragm corresponds to the entrance of the RFQ electrodes. The beam emittance and fraction were measured after the 7 mm diaphragm. Its rms emittance is about 0.14 ??mm?mrad and the fraction of He+ is about 99%. PMID:24593446

Peng, Shixiang; Chen, Jia; Ren, Haitao; Zhao, Jie; Xu, Yuan; Zhang, Tao; Zhang, Ailing; Xia, Wenlong; Gao, Shuli; Wang, Zhi; Luo, Yuting; Guo, Zhiyu; Chen, Jia'er

2014-02-01

69

High Energy Astrophysics: Radio Galaxies Geoffrey V. Bicknell Radio Galaxies  

E-print Network

High Energy Astrophysics: Radio Galaxies © Geoffrey V. Bicknell Radio Galaxies 1 Fanaroff Laing #12;High Energy Astrophysics: Radio Galaxies 2/56 The prototype FR 2 radio galaxy, Cygnus A Energy Astrophysics: Radio Galaxies 3/56 Cygnus A at 850 microns. Only the hot spots and core are visible

Bicknell, Geoff

70

Low Frequency Radio Signals from Sprite Streamers  

NASA Astrophysics Data System (ADS)

Sprites are mesospheric discharges that carry significant electrical currents and produce radio signals observed typically in the extremely low (ELF) to very low (VLF) frequency bands [Cummer et al., GRL, 25, 1281, 1998]. Recently, Low-Frequency (LF) radio observations of sprite-producing lightning discharges have shown the existence of consecutive broadband pulses exhibiting EM radiation that spans in the LF range, and it has been suggested that this LF radio signals may stem from non-luminous relativistic electron beams above thunderstorms [Fullekrug et al., JGR, 115, A00E09, 2010]. In this talk, we present the first theoretical estimates of the radio signals produced by individual sprite streamers using simulation results from a plasma fluid model. It is demonstrated that the spectral content of the radiation produced by sprite streamers is a function of the air density N and the lightning-induced quasi-static ambient electric field E in the regions of space where the sprite streamers are propagating. We demonstrate that the exponential growth of the current in sprite streamers at 75 km would be preferentially associated with electromagnetic radiation in the frequency range from 0 and up to ˜3 kHz, whereas the growth of the streamer current at 40 km could produce radiation with frequencies up to ˜300 kHz, consistently with the scaling of atmospheric air density [Kosar et al., JGR, 117, A08328, 2012]. We further conjecture that the periodic branching of streamers may lead to a radiation spectrum enhancement in the VLF to LF range. The present study shows that sprite streamers could be responsible for at least part of the LF radiation associated with sprite-producing lightning discharges that was detected recently by Fullekrug et al. [2010].

Qin, J.; Celestin, S. J.; Pasko, V. P.

2013-12-01

71

Radio frequency (RF) heated supersonic flow laboratory  

SciTech Connect

A unique supersonic flow apparatus which employs an inductively-coupled, radio frequency (RF) torch to supply high enthalpy source gas to the nozzle inlet is described. The main features of this system are the plasma tube, a cooled nozzle assembly, and a combustion/expansion chamber with a heat exchanger. A description of these components with current test data is presented. In addition, a discussion of anticipated experiments utilizing this system is included.

Wantuck, P.; Watanabe, H.

1990-01-01

72

Joint Time-Frequency Spectrum Sensing for Cognitive Radio  

E-print Network

Joint Time-Frequency Spectrum Sensing for Cognitive Radio Wael Guib`ene and Aawatif Hayar EURECOM-frequency plane. Index Terms--Cognitive radio, sensing algorithm, Wigner Ville distribution , algebraic detector, joint time frequency detection. I. INTRODUCTION Cognitive Radio (CR) as introduced by Mitola [1

Paris-Sud XI, Université de

73

Radio frequency assisted chemical vapor infiltration  

SciTech Connect

A process for the rapid densification of carbon/carbon composites has been developed. The method makes use of the direct radio frequency heating of three dimensional carbon preforms to establish inverted thermal gradients. Rapid densification from the inside-out, of 2.5 cm. diameter parts, in as little as 30 hours was demonstrated. A simple model is used to predict the initial thermal gradients and is compared to experimental measurements. The results are discussed in terms of frequency, part dimension and radiative heat loss.

Devlin, D.J.; Barbero, R.S.; Siebein, K.N. [Los Alamos National Lab., NM (United States). Materials Science and Technology Div.

1996-06-01

74

Radio frequency interference at QUASAR Network Observatories  

NASA Astrophysics Data System (ADS)

Different sources of radio frequency interference (RFI) at Quasar-network observatories and their affect on VLBIsessions are discussed. For example, the stronger of them registered last time are UMTS mobile phone base stations which were built not far from Quasar-network observatories location. These stations emit signals near 2100MHz and produce RFI of critical level. To control RFI level regular spectral measurements of the intermediate frequency signals at the outputs of the receivers are conducted. As a result, real spread of RFI sources, including DORIS, have to be taken into account in planning of VLBI observation sessions and especially it is concerned VLBI 2010 project realization.

Ilin, Gennadii

2011-07-01

75

Radio-frequency scanning tunnelling microscopy.  

PubMed

The scanning tunnelling microscope (STM) relies on localized electron tunnelling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical systems--ranging from semiconductors to superconductors to atomic and molecular nanosystems. A severe limitation in scanning tunnelling microscopy is the low temporal resolution, originating from the diminished high-frequency response of the tunnel current readout circuitry. Here we overcome this limitation by measuring the reflection from a resonant inductor-capacitor circuit in which the tunnel junction is embedded, and demonstrate electronic bandwidths as high as 10 MHz. This approximately 100-fold bandwidth improvement on the state of the art translates into fast surface topography as well as delicate measurements in mesoscopic electronics and mechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM have allowed us to perform thermometry at the nanometre scale. Furthermore, we have detected high-frequency mechanical motion with a sensitivity approaching approximately 15 fm Hz(-1/2). This sensitivity is on par with the highest available from nanoscale optical and electrical displacement detection techniques, and the radio-frequency STM is expected to be capable of quantum-limited position measurements. PMID:17972882

Kemiktarak, U; Ndukum, T; Schwab, K C; Ekinci, K L

2007-11-01

76

Experimental measurement of the electron energy distribution function in the radio frequency electron cyclotron resonance inductive discharge.  

PubMed

Recently, the existence of electron cyclotron resonance (ECR) in a weakly magnetized inductively coupled plasma (MICP) has been evidenced [ChinWook Chung et al., Phys. Rev. Lett. 80, 095002 (2002)]. The distinctive feature of the ECR effect in the MICP is efficacious heating of low-energy electrons. In the present paper, electron heating characteristics in the MICP have been investigated by observing electron energy distribution function dependencies on various external parameters such as gas pressure, driving frequency, and rf power (electron density). It is found that the ECR effect on electron heating becomes enhanced with decreasing pressure or increasing driving frequency. The ECR heating becomes weak at high rf power due to the electron-electron collisions. PMID:14995724

Chung, ChinWook; Kim, S S; Chang, H Y

2004-01-01

77

Wideband versatile radio-frequency spectrum analyzer.  

PubMed

Operation of a wideband, versatile optical spectrum analyzer for radio-frequency (RF) signals is demonstrated. The device is based on spectral hole burning (SHB). The demonstration features 2.3-GHz instantaneous bandwidth, 500-kHz resolution, and a 32-dB dynamic range. A true RF signal, transferred to the optical carrier with the help of a Mach-Zehnder modulator, is analyzed with optical carrier suppression and zooming capabilities. This is to the authors' knowledge the largest instantaneous bandwidth ever demonstrated for a SHB-based processor in rare-earth-doped crystals. PMID:12659254

Lavielle, V; Lorgeré, I; Le Gouët, J L; Tonda, S; Dolfi, D

2003-03-15

78

Radio-Frequency Spectroscopy of Ultracold Fermions  

E-print Network

Radio-frequency techniques were used to study ultracold fermions. We observed the absence of mean-field "clock" shifts, the dominant source of systematic error in current atomic clocks based on bosonic atoms. This is a direct consequence of fermionic antisymmetry. Resonance shifts proportional to interaction strengths were observed in a three-level system. However, in the strongly interacting regime, these shifts became very small, reflecting the quantum unitarity limit and many-body effects. This insight into an interacting Fermi gas is relevant for the quest to observe superfluidity in this system.

S. Gupta; Z. Hadzibabic; M. W. Zwierlein; C. A. Stan; K. Dieckmann; C. H. Schunck; E. G. M. van Kempen; B. J. Verhaar; W. Ketterle

2003-07-10

79

Low Frequency Radio Observations of GRS1915+105 with GMRT  

E-print Network

We present the first detailed low frequency radio measurements of the galactic microquasar GRS1915+105 with GMRT. Simultaneous observations were carried out at 610 and 244 MHz. Our data does not show any signature of spectral turn over even at low radio frequency of 244 MHz. We propose that while the radio emission at high radio frequencies could predominantly come from compact jets, the emission at lower frequency originates in the lobes at the end of the jet which acts like a reservoir of low energy electrons.

C. H. Ishwara-Chandra; A. Pramesh Rao; Mamta Pandey; R. K. Manchanda; Philippe Durouchoux

2005-12-02

80

Optical generation of radio-frequency power  

SciTech Connect

An optical technique for high-power radio-frequency (RF) signal generation is described. The technique uses a unique photodetector based on a traveling-wave design driven by an appropriately modulated light source. The traveling-wave photodetector (TWPD) exhibits simultaneously a theoretical quantum efficiency approaching 100 % and a very large electrical bandwidth. Additionally, it is capable of dissipating the high-power levels required for the RF generation technique. The modulated light source is formed by either the beating together of two lasers or by the direct modulation of a light source. A system example is given which predicts RF power levels of 100`s of mW`s at millimeter wave frequencies with a theoretical ``wall-plug`` efficiency approaching 34%.

Hietala, V.M.; Vawter, G.A.; Brennan, T.M.; Hammons, B.E.; Meyer, W.J.

1994-11-01

81

Updates on IceCube's Radio Frequency extension  

Microsoft Academic Search

A variety of radio frequency (RF) detectors were deployed in the Antarctic ice as an enhancement to the optically-based IceCube Neutrino Observatory, and as a step towards a large-scale high-energy neutrino detector. This RF addition includes a set of 5 deep-deployed (300m-1400m) digitizing detectors, a shallow array (˜35m) of transient detectors and a set of transmitters. All Are sensitive to

Hagar Landsman

2011-01-01

82

Radio Frequency Mass Gauging of Propellants  

NASA Technical Reports Server (NTRS)

A combined experimental and computer simulation effort was conducted to measure radio frequency (RF) tank resonance modes in a dewar partially filled with liquid oxygen, and compare the measurements with numerical simulations. The goal of the effort was to demonstrate that computer simulations of a tank's electromagnetic eigenmodes can be used to accurately predict ground-based measurements, thereby providing a computational tool for predicting tank modes in a low-gravity environment. Matching the measured resonant frequencies of several tank modes with computer simulations can be used to gauge the amount of liquid in a tank, thus providing a possible method to gauge cryogenic propellant tanks in low-gravity. Using a handheld RF spectrum analyzer and a small antenna in a 46 liter capacity dewar for experimental measurements, we have verified that the four lowest transverse magnetic eigenmodes can be accurately predicted as a function of liquid oxygen fill level using computer simulations. The input to the computer simulations consisted of tank dimensions, and the dielectric constant of the fluid. Without using any adjustable parameters, the calculated and measured frequencies agree such that the liquid oxygen fill level was gauged to within 2 percent full scale uncertainty. These results demonstrate the utility of using electromagnetic simulations to form the basis of an RF mass gauging technology with the power to simulate tank resonance frequencies from arbitrary fluid configurations.

Zimmerli, Gregory A.; Vaden, Karl R.; Herlacher, Michael D.; Buchanan, David A.; VanDresar, Neil T.

2007-01-01

83

The Current Status of Low Frequency Radio Astronomy from Space  

Microsoft Academic Search

Ground-based radio astronomy is severely limited by the Earth's ionosphere. Below 15 -- 20 MHz, space-based radio observations are superior or even mandatory. Three different areas of astronomical research manifest themselves at low radio frequencies: solar, planetary, and galactic-extragalactic. Space-based observations of solar phenomena at low frequencies are a natural extension of high-frequency ground-based observations that have been carried out

M. L. Kaiser; K. W. Weiler

2000-01-01

84

Imaging interplanetary CMEs at radio frequency from solar polar orbit  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) represent a great concentration of mass and energy input into the lower corona. They have come to be recognized as the major driver of physical conditions change in the Sun-Earth system. Consequently, observations of CMEs are important for understanding and ultimately predicting space weather conditions. This paper discusses a proposed mission, the Solar Polar Orbit Radio Telescope (SPORT) mission, which will observe the propagation of interplanetary CMEs to distances of near 0.35 AU from the Sun. The orbit of SPORT is an elliptical solar polar orbit. The inclination angle between the orbit and ecliptic plane should be about 90°. The main payload on board SPORT will be an imaging radiometer working at the meter wavelength band (radio telescope), which can follow the propagation of interplanetary CMEs. The images that are obtained by the radio telescope embody the brightness temperature of the objectives. Due to the very large size required for the antenna aperture of the radio telescope, we adopt interferometric imaging technology to reduce it. Interferometric imaging technology is based on indirect spatial frequency domain measurements plus Fourier transformation. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind ion instrument, an energetic particle detector, a magnetometer, a wave detector and a solar radio burst spectrometer.

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Liu, Hao; Yan, Jingye; Wang, Chi; Wang, Chuanbing; Wang, Shui

2011-09-01

85

Hybrid optical radio frequency airborne communications  

NASA Astrophysics Data System (ADS)

Optical RF Communications Adjunct Program flight test results provide validation of the theoretical models and hybrid optical radio frequency (RF) airborne system concepts developed by the Defense Advanced Research Projects Agency and the U.S. Air Force Research Laboratory. Theoretical models of the free-space optical communications (FSOC), RF, and network components accurately predict the flight test results under a wide range of day and night operating conditions. The FSOC system, including the adaptive optics and optical modem, can operate under high turbulence conditions. The RF and network mechanisms of Layer 2 retransmission and failover provide increased reliability, reducing end-to-end packet error rates. Overall the test results show that stable, long-range FSOC is possible and practical for near-term operations.

Bagley, Zachary C.; Hughes, David H.; Juarez, Juan C.; Kolodzy, Paul; Martin, Todd; Northcott, Malcolm; Pike, H. Alan; Plasson, Ned D.; Stadler, Brian; Stotts, Larry B.; Young, David W.

2012-05-01

86

An improved integrally formed radio frequency quadrupole  

DOEpatents

An improved radio frequency quadrupole is provided having an elongate housing with an elongate central axis and top, bottom and two side walls symmetrically disposed about the axis, and vanes formed integrally with the walls, the vanes each having a cross-section at right angles to the central axis which tapers inwardly toward the axis to form electrode tips spaced from each other by predetermined distances. Each of the four walls, and the vanes integral therewith, is a separate structural element having a central lengthwise plane passing through the tip of the vane, the walls having flat mounting surfaces at right angles to and parallel to the control plane, respectively, which are butted together to position the walls and vane tips relative to each other. 4 figs.

Abbott, S.R.

1987-10-05

87

Low Frequency Radio Emissions: Remote Sensing of the Energetic Heliosphere  

NASA Astrophysics Data System (ADS)

Low frequency radio emissions (below about 50 MHz) are tracers of energetic plasma instabilities. Their observation provides us with a unique proxy for instable energetic electron populations. In the solar wind, two types of emissions can be monitored: Type II and Type III radio bursts. The former are related to interplanetary shocks, while the latter are linked to energetic electron beams going out from the solar corona. The magnetized planets are also producing low frequency radio emissions linked to the auroral activity, and thus to the interaction between the planet and the solar wind. These radio emission are non-thermal emissions. They are very powerful (Jupiter is as intense as the Sun in this frequency range). Furthermore, the low frequency radio instrumentation in space has the advantage to be quasi-isotropic. The antenna systems have no intrinsic directivity. However, goniopolarimetric inversions have been developed to derive the observed radio waves parameters (assuming we see a single source at a given time). Hence, the low frequency radio systems can monitor the whole sky at once and provide direction of arrival for each event. We will present the various emission mechanisms involved for the low frequency radio emissions in the solar system, the various propagation effects along the wave path and the radio instrumentation necessary to derived all relevant wave parameters. We will discuss how these radio emissions can be used in a space weather perspective. We will finally overview the possible future steps in terms of instrumentation for this frequency range.

Cecconi, Baptiste

2014-05-01

88

Polarimetric Observations at Low Radio Frequencies  

NASA Astrophysics Data System (ADS)

Magnetic fields play a fundamental role in the evolution of astrophysical systems. These fields can be studied through wide-field spectropolarimetry, which allows for faint polarised signals to be detected at relatively low radio frequencies. An interferometric polarisation mode has recently become available at the Giant Metrewave Radio Telescope (GMRT). A detailed analysis of the GMRT's instrumental response is presented. The findings are used to create a polarisation pipeline, which in combination with rotation measure (RM) Synthesis is used for the detection of extended linearly polarised emission at 610 MHz. A number of compact sources are detected and their Faraday depth and polarisation fraction are reported. New holography observations of the GMRT's primary beam are presented. Instantaneous off-axis polarisation is substantial and scales with the Stokes I beam. The developed beam models are used to reduce direction-dependent instrumental polarisation, and the Stokes I beam is shown to deviate from circular symmetry. A new technique for electric vector polarisation angle calibration is developed that removes the need for known sources on the sky, eliminates ionospheric effects, and avoids a flaw in current methods which could erroneously yield multiple Faraday components for sources that are well-parameterised by a single RM. A sample of nine galaxies from two Southern Compact Groups are then presented, with constraints being placed on the polarised fraction, RM, spectral index, star formation rate, companion sources, and hydrodynamical state. One galaxy has a displaced peak of radio emission that is extended beyond the disk in comparison to the near-IR disk - suggesting the radio disturbance may be a consequence of ram pressure stripping. Linear polarisation is detected from the core of NGC 7552 at 610 MHz, while another three galaxies ESO 0353-G036, NGC 7590, and NGC 7599 are found to be unpolarised. An analysis of additional extended sources allows for an FR-I and an FR-II radio source to be morphologically classified. Finally, spatial spectral variations are identified in the youngest known Galactic supernova remnant G1.9+0.3, with flatter spectra in the NW and SE. Models of cosmic ray acceleration at oblique shocks suggest the variation is most consistent with an ambient B field perpendicular to the axis of bilateral symmetry. For the first time, the presence of polarised emission is detected. There is increased ordering of the B field in the NW and strong Faraday depolarisation must also be present. An intrinsically radially-oriented field could be provided by a systematic gradient in RM of 140 rad m-2 from N to S and can also explain the depolarisation. Such a gradient may be caused by an anisotropic regular magnetic field within the remnant or in an intervening Faraday screen.

Farnes, J. S.

2012-06-01

89

Circuits and passive components for radio-frequency power conversion  

E-print Network

This thesis focuses on developing technology for high efficiency power converters operating at very high frequencies. The work in the thesis involves two aspects of such converters: rf (radio-frequency) power circuit design ...

Han, Yehui, Ph. D. Massachusetts Institute of Technology

2010-01-01

90

Radio Frequency Identification for Educational Gaming using Mobile Devices  

Microsoft Academic Search

Radio Frequency Identification (RFID) is a location determination technology that has been receiving a lot of commercial attention in recent times, especially in the areas of asset tracking and supply chain management. The technology makes use of radio frequency communication to transfer data between the two key components of an RFID system, the tag and the reader. Location based gaming,

Kevin Curran; Martin Porter

2009-01-01

91

CITY OF PRINCE GEORGE: RADIO FREQUENCY TREATMENT OF PARTIALLY  

E-print Network

#12;CITY OF PRINCE GEORGE: RADIO FREQUENCY TREATMENT OF PARTIALLY DIGESTED/DEWATERED BIOSOLIDS/DEWATERED BIOSOLIDS FINAL REPORT SUMMARY The City of Prince George recently proposed to investigate the possibility of applying radio frequency (RF) technology to partially digested/dewatered biosolids from domestic wastewater

92

Radio-frequency scanning tunnelling microscopy U. Kemiktarak1  

E-print Network

LETTERS Radio-frequency scanning tunnelling microscopy U. Kemiktarak1 , T. Ndukum3 , K. C. Schwab3-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical measurementsinmesoscopicelectronicsandmechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM

93

Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)  

E-print Network

Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Kurt Alexander Polzin;Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD) Prepared by: Kurt Alexander Polzin Dr. Michael R. LaPointe Dissertation Reader #12;c Copyright by Kurt Alexander Polzin, 2006. All

Choueiri, Edgar

94

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope  

E-print Network

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope Stephen M. White Array (LOFAR) will be a radio astronomy interferometric array operating in the approximate fre­ quency of high solar activity the Sun will be a prominent (and highly variable) feature of the low­frequency sky

White, Stephen

95

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope  

E-print Network

Solar radioastronomy with the LOFAR (LOw Frequency ARray) radio telescope Stephen M. Whitea, Namir, USA bRemote Sensing Div., Naval Research Lab., Washington D.C., USA ABSTRACT The Low Frequency Array (LOFAR) will be a radio astronomy interferometric array operating in the approximate fre- quency range 10

96

Investigations of the output energy deviation and other parameters during commissioning of the four-rod radio frequency quadrupole at the Fermi National Accelerator Laboratory  

NASA Astrophysics Data System (ADS)

After 30 years of operation, the Cockcroft-Walton based injector at the Fermi National Accelerator Laboratory has been replaced by a new beam line including a dimpled magnetron 35 keV source in combination with a 750 keV four-rod radio frequency quadrupole (RFQ). The new injector is followed by the existing drift tube linac. Prior to installation, a test beam line was built which included the magnetron source and the four-rod RFQ with a number of beam measurement instrumentation. The first beam test with the RFQ showed an output energy deviation greater than 2.5%. Other problems also showed up which led to investigations of the output energy, power consumption and transmission properties using rf simulations which were complemented with additional beam measurements. The sources of this deviation and the mechanical modifications of the RFQ to solve this matter will be presented in this paper. Meanwhile, the nominal output energy of 750 keV has been confirmed and the new injector with the four-rod RFQ is in full operation.

Schmidt, J. S.; Koubek, B.; Schempp, A.; Tan, C. Y.; Bollinger, D. S.; Duel, K. L.; Karns, P. R.; Pellico, W. A.; Scarpine, V. E.; Schupbach, B. A.; Kurennoy, S. S.

2014-03-01

97

Radio Frequency Plasma Applications for Space Propulsion  

SciTech Connect

Recent developments in solid-state radio frequency (RF) power technologies allow for the practical consideration of RF heated plasmas for space propulsion. These technologies permit the use of any electrical power source, de-couple the power and propellant sources, and allow for the effcient use of both the propellant mass and power. Effcient use of the propellant is obtained by expelling the rocket exhaust at the highest possible velocity, which can be orders of magnitude higher than those achieved in chemical rockets. Handling the hot plasma exhaust requires the use of magnetic nozzles, and the basic physics of ion detachment from the magnetic #12;eld is discussed. The plasma can be generated by RF using helicon waves to heat electrons. Further direct heating of the ions helps to reduce the line radiation losses, and the magnetic geometry is tailored to allow ion cyclotron resonance heating. RF #12;eld and ion trajectory calculations are presented to give a reasonably self-consistent picture of the ion acceleration process.

Baity, F.W., Jr.; Barber, G.C.; Carter, M.D.; Chang-Diaz, F.R.; Goulding, R.H.; Ilin, A.V.; Jaeger, E.F.; Sparks, D.O.; Squire, J.P.

1999-09-13

98

Extending the ICRF to Higher Radio Frequencies  

NASA Technical Reports Server (NTRS)

The ICRF forms the basis for all astrometry including use as the inertial coordinate system for navigating deep space missions. This frame was defined using S/X-band observations over the past 20+ years. In January 2002, the VLBA approved our proposal for observing time to extend the ICRF to K-band (24 GHz) and Q-band (43 GHz). The first step will be observations at K- and Q-bands on a subset of ICRF sources. Eventually, K- and Q-band multi-epoch observations will be used to estimate positions, flux density and source structure for a large fraction of the current S/X-band ICRF source list. This work will benefit the radio astronomy community by extending the VLBA calibrator list at these bands. In the longer term, we would also like to extend the ICRF to Ka-band (32 GHz). A celestial reference frame will be needed at this frequency to support deep space navigation. A navigation demonstration is being considered for NASA's Mars 2005 mission. The initial K- and Q-band work will serve to identify candidate sources at Ka-band for use with that mission.

Jacobs, C. S.; Jones, D. L.; Lanyi, G. E.; Lowe, S. T.; Naudet, C. J.; Resch, G. M.; Steppe, J. A.; Zhang, L. D.; Ulvestad, J. S.; Taylor, G. B.

2002-01-01

99

Radio-frequency plasma spraying of ceramics  

SciTech Connect

This study was aimed at developing a novel spraying process using a radio-frequency (rf) plasma. Experiments of Al{sub 2}O{sub 3} and ZrO{sub 2} {minus} 8 wt% Y{sub 2}O{sub 3} spraying showed that the initial powder size was the most important parameter for depositing dense coatings. The optimum powder sizes of Al{sub 2}O{sub 3} and ZrO{sub 2} {minus} 8 wt% Y{sub 2}O{sub 3} were considered to be around 100 and 80 {mu}m, respectively. The use of such large-size powders compared with those used by conventional dc plasma spraying made it possible to deposit adherent ceramics coatings of 150 to 300 {mu}m on as-rolled SS304 substrates. It was also shown that low particle velocity of about 10 m/s, which is peculiar to rf plasma spraying, was sufficient for particle deformation, though it imposed a severe limitation on the substrate position. These experimental results prove that rf plasma spraying is an effective process and a strong candidate to open new fields of spraying applications.

Okada, T.; Hamatani, H.; Yoshida, T. (Dept. of Metallurgy and Materials Science, Faculty of Engineering, The Univ. of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113 (JP))

1989-11-01

100

Adaptive radio frequency interference mitigation for HF surface wave radar  

Microsoft Academic Search

The paper analyses the characteristics of radio frequency interference (RFI) in HF surface wave radar (HFSWR) which adopt the linear frequency modulated interrupted continuous wave (FMICW). RFI will influence all the range cells including all the positive and negative frequency, and that the negative frequency range cells contain only the interference information. Based on the above characteristics, we introduce and

Wan Xianrong; Wen Biyang; Ke Hengyu

2004-01-01

101

47 CFR 2.805 - Operation of radio frequency products prior to equipment authorization.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Operation of radio frequency products prior to equipment authorization...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...AND REGULATIONS Marketing of Radio-frequency Devices § 2.805 Operation of...

2013-10-01

102

47 CFR 15.204 - External radio frequency power amplifiers and antenna modifications.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false External radio frequency power amplifiers and antenna modifications...COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.204 External radio frequency power amplifiers and antenna...

2013-10-01

103

78 FR 13893 - Certain Radio Frequency Identification (“RFID”) Products and Components Thereof; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION [Docket No. 2941] Certain Radio Frequency Identification (``RFID'') Products...received a complaint entitled Certain Radio Frequency Identification (``RFID'') Products...States after importation of certain radio frequency identification (``RFID'')...

2013-03-01

104

47 CFR 2.803 - Marketing of radio frequency devices prior to equipment authorization.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 false Marketing of radio frequency devices prior to equipment authorization...COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO TREATY MATTERS...AND REGULATIONS Marketing of Radio-frequency Devices § 2.803 Marketing of...

2012-10-01

105

47 CFR 15.204 - External radio frequency power amplifiers and antenna modifications.  

Code of Federal Regulations, 2012 CFR

...false External radio frequency power amplifiers and antenna modifications. 15.204...204 External radio frequency power amplifiers and antenna modifications. ...any external radio frequency power amplifier or amplifier kit intended for use...

2012-10-01

106

Energy fluxes in a radio-frequency magnetron discharge for the deposition of superhard cubic boron nitride coatings  

SciTech Connect

Energy flux measurements by a calorimetric probe in a rf-magnetron plasma used for the deposition of super-hard c-BN coatings are presented and discussed. Argon as working gas is used for sputtering a h-BN target. Adding a certain amount of N{sub 2} is essential for the formation of stoichiometric BN films, since a lack of nitrogen will lead to boron rich films. Subsequently, the contributions of different plasma species, surface reactions, and film growth to the resulting variation of the substrate temperature in dependence on nitrogen admixture are estimated and discussed. In addition, SRIM simulations are performed to estimate the energy influx by sputtered neutral atoms. The influence of magnetron target power and oxygen admixture (for comparison with nitrogen) to the process gas on the total energy flux is determined and discussed qualitatively, too. The results indicate that variation of the energy influx due to additional nitrogen flow, which causes a decrease of electron and ion densities, electron temperature and plasma potential, is negligible, while the admixture of oxygen leads to a drastic increase of the energy influx. The typical hysteresis effect which can be observed during magnetron sputtering in oxygen containing gas mixtures has also been confirmed in the energy influx measurements for the investigated system. However, the underlying mechanism is not understood yet, and will be addressed in further investigations.

Bornholdt, S.; Kersten, H. [Christian-Albrechts-University Kiel, Institute of Experimental and Applied Physics, D-24098 Kiel (Germany); Ye, J.; Ulrich, S. [Karlsruhe Institute of Technology, Institute for Applied Materials-Applied Materials Physics (IAM-AWP), D-76344 Eggenstein-Leopoldshafen (Germany)

2012-12-15

107

Antarctic Radio Frequency Albedo and Implications for Cosmic Ray Reconstruction  

E-print Network

From an elevation of ~38 km, the balloon-borne ANtarctic Impulsive Transient Antenna (ANITA) is designed to detect the up-coming radio frequency (RF) signal resulting from a sub-surface neutrino-nucleon collision. Although no neutrinos have been discovered thus far, ANITA is nevertheless the only experiment to self-trigger on radio frequency emissions from cosmic-ray induced atmospheric air showers. In the majority of those cases, down-coming RF signals are observed via their reflection from the Antarctic ice sheet and back up to the ANITA interferometer. Estimating the energy scale of the incident cosmic rays therefore requires an estimate of the fractional power reflected at the air-ice interface. Similarly, inferring the energy of neutrinos interacting in-ice from observations of the upwards-directed signal refracting out to ANITA also requires consideration of signal coherence across the interface. By comparing the direct Solar RF signal intensity measured with ANITA to the surface-reflected Solar signal ...

Besson, D Z; Sullivan, M; Allison, P; Barwick, S W; Baughman, B M; Beatty, J J; Belov, K; Bevan, S; Binns, W R; Chen, C; Chen, P; Clem, J M; Connolly, A; De Marco, D; Dowkontt, P F; DuVernois, M; Goldstein, D; Gorham, P W; Grashorn, E W; Hill, B; Hoover, S; Huang, M; Israel, M H; Javaid, A; Kowalski, J; Learned, J; Liewer, K M; Matsuno, S; Mercurio, B C; Miki, C; Mottram, M; Nam, J; Naudet, C J; Nichol, R J; Palladino, K; Romero-Wolf, A; Ruckman, L; Saltzberg, D; Seckel, D; Shang, R Y; Stockham, M; Varner, G S; Vieregg, A G; Wang, Y

2013-01-01

108

Radio frequency analog electronics based on carbon nanotube transistors  

E-print Network

Radio frequency analog electronics based on carbon nanotube transistors Coskun Kocabas*, Hoon band with power gains as high as 14 dB. As a demon- stration, we fabricated nanotube transistor radios technologies. The invention of the transistor in 1947 represents the birth of the solid state electronics age

Rogers, John A.

109

Adaptive radio frequency interference mitigation for HF surface wave radar  

Microsoft Academic Search

The paper analyses the characteristics of radio frequency interference (RFI) in HF surface wave radar (HF-SWR) which adopts\\u000a the linear frequency modulated interrupted continuous wave (FMICW). RFI will influence all the range cells including all the\\u000a positive frequency and negative frequency, and the negative frequency range cells contain only the interference information.\\u000a Based on the above characteristics, we introduce and

Wan Xian-rong; Ke Heng-yu; Cheng Feng

2005-01-01

110

Radio frequency overview of the high explosive radio telemetry project  

SciTech Connect

High explosive radio telemetry (HERT) is a project that is being developed jointly by Los Alamos National Laboratory and AlliedSignal Federal Manufacturing and Technologies. The ultimate goal is to develop a small, modular telemetry system capable of high-speed detection of explosive events, with an accuracy on the order of 10 nanoseconds. The reliable telemetry of this data, from a high-speed missile trajectory, is a very challenging opportunity. All captured data must be transmitted in less than 20 microseconds of time duration. This requires a high bits/Hertz microwave telemetry modulation code to insure transmission of the data with the limited time interval available.

Bracht, R. [Los Alamos National Lab., NM (United States); Dimsdle, J.; Rich, D.; Smith, F. [AlliedSignal Federal Manufacturing and Technologies, Kansas City, MO (United States)

1998-12-31

111

RFIDSim : a discrete event simulator for Radio Frequency Identification systems  

E-print Network

This thesis presents RFIDSim, a discrete event process-oriented simulator designed to model Radio Frequency Identification (RFID) communication. The simulator focuses on the discovery and identification process of passive ...

Yu, Kenneth Kwan-Wai, 1979-

2003-01-01

112

Radio-frequency spectroscopy of ultracold atomic Fermi gases  

E-print Network

This thesis presents experiments investigating the phase diagram of ultracold atomic Fermi gases using radio-frequency spectroscopy. The tunability of many experimental parameters including the temperature, the interparticle ...

Schirotzek, Andre

2010-01-01

113

Radio frequency identification (RFID) applications in semiconductor manufacturing  

E-print Network

Radio frequency identification (RFID) has an enormous potential impact within the semiconductor supply chain, especially within semiconductor manufacturing. The end benefit of RFID will be in the mass serialization, and ...

Cassett, David Ian, 1971-

2004-01-01

114

Radio Frequency (RF) Trap for Confinement of Antimatter Plasmas Using Rotating Wall Electric Fields  

NASA Technical Reports Server (NTRS)

Perturbations associated with a rotating wall electric field enable the confinement of ions for periods approaching weeks. This steady state confinement is a result of a radio frequency manipulation of the ions. Using state-of-the-art techniques it is shown that radio frequency energy can produce useable manipulation of the ion cloud (matter or antimatter) for use in containment experiments. The current research focuses on the improvement of confinement systems capable of containing and transporting antimatter.

Sims, William Herbert, III; Pearson, J. Boise

2004-01-01

115

Visible and Controllable RFID Tags Radio frequency identification (RFID) tags containing  

E-print Network

;Introduction and Motivation Since its invention in the early 20th century, radio frequency identification (RFIDVisible and Controllable RFID Tags Abstract Radio frequency identification (RFID) tags containing

Greenberg, Saul

116

An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland  

E-print Network

We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

Avva, J; Miki, C; Saltzberg, D; Vieregg, A G

2014-01-01

117

An in situ measurement of the radio-frequency attenuation in ice at Summit Station, Greenland  

E-print Network

We report an in situ measurement of the electric field attenuation length at radio frequencies for the bulk ice at Summit Station, Greenland, made by broadcasting radio-frequency signals vertically through the ice and measuring the relative power in the return ground bounce signal. We find the depth-averaged field attenuation length to be 947 +92/-85 meters at 75 MHz. While this measurement has clear radioglaciological applications, the radio clarity of the ice also has implications for the detection of ultra-high energy (UHE) astrophysical particles via their radio emission in dielectric media such as ice. The measured attenuation length at Summit Station is comparable to previously measured radio-frequency attenuation lengths at candidate particle detector sites around the world, and strengthens the case for Summit Station as the most promising northern site for UHE neutrino detection.

J. Avva; J. M. Kovac; C. Miki; D. Saltzberg; A. G. Vieregg

2014-09-18

118

Unveiling the nature of the unidentified gamma-ray sources: blazar counterparts at low radio frequencies  

NASA Astrophysics Data System (ADS)

About one third of the gamma-ray sources detected by Fermi have still no firmly established counterpart at lower energies. Here we propose a new approach to find candidate counterparts for the unidentified gamma-ray sources (UGSs) based on the 325 MHz radio survey performed with Westerbork Synthesis Radio Telescope (WSRT) in the northern hemisphere. First we investigate the low-frequency radio properties of blazars, the largest known population of gamma-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO VLA Sky survey (NVSS). We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in literature to look for infrared and optical counterparts of the gamma-ray blazar candidates selected with the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research we identify 23 new gamma-ray blazar candidates out of 32 UGSs investigated. I will also present the first analysis of very low frequency radio emission of blazars based on the recent Very Large Array Low-Frequency Sky Survey (VLSS) at 74 MHz. I show that blazars present radio flat spectra when evaluated at 74 MHz, about an order of magnitude in frequency lower than previous analyses. The implications of these findings in the contest of the blazars - radio galaxies connection will be discussed.

Massaro, Francesco; D'Abrusco, R.; Giroletti, M.; Paggi, A.; Masetti, N.; Tosti, G.

2014-07-01

119

Searching for Low-Frequency Radio Transients from Supernovae  

NASA Astrophysics Data System (ADS)

Supernovae events may be accompanied by prompt emission of a low-frequency electromagnetic transient. These transient events are created by the interaction of a shock wave of charged particles created by SN core-collapse with a stars ambient magnetic field. Such events can be detected in low-frequency radio array. Here we discuss an ongoing search for such events using two radio arrays: the Long Wavelength Array (LWA) and Eight-meter-wavelength Transient Array (ETA).

Tsai-Wei, Jr.; Cutchin, Sean; Kothari, Manthan; Schmitt, Christian; Kavic, Michael; Simonetti, John

2011-10-01

120

Optical constants and dispersion energy parameters of NiO thin films prepared by radio frequency magnetron sputtering technique  

NASA Astrophysics Data System (ADS)

In this paper, we report on rf power induced change in the structural and optical properties of nickel oxide (NiO) thin films deposited onto glass substrates by rf magnetron sputtering technique. The crystallinity of the film was found to increase with increasing rf power and the deposited film belong to cubic phase. The maximum optical transmittance of 95% was observed for the film deposited at 100 W. The slight shift in transmission threshold towards higher wavelength region with increasing rf power revealed the systematic reduction in optical energy band gap (3.93 to 3.12 eV) of the films. The dispersion curve of the refractive index shows an anomalous dispersion in the absorption region and a normal dispersion in the transparent region. It was observed that the dispersion data obeyed the single oscillator of the Wemple-Didomenico model, from which the dispersion parameters, dielectric constants, relaxation time, and optical non-linear susceptibility were evaluated. We have made an attempt to discuss and correlate these results with the light of possible mechanisms underlying the phenomena.

Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.

2013-09-01

121

Radio-frequency quadrupole: A new linear accelerator  

NASA Astrophysics Data System (ADS)

The radio frequency quadrupole (RFQ) linear accelerator is discussed. In the RFQ, the use of RF electric fields for radial focusing, combined with special programming of the bunching, allows high current dc beams to be captured and accelerated with only small beam loss and low radial emittance growth. Advantages of the RFQ linac include a low injection energy (20 to 50 keV for protons) and a final energy high enough so the beam can be further accelerated with high efficiency in a Wideroee or Alvarez linac. The beam dynamics parameters of three RFQ systems are described. These are the final design for the prototype test of the Fusion Materials Irradiation Test accelerator, the final design for the prototype test of the Pion Generator for Medical Irradiations, and an improved low velocity linac for heavy ion fusion.

Stokes, R. H.; Wangler, T. P.; Crandall, K. R.

122

RADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR  

E-print Network

-yet unmatched flight performance and increasingly understood muscular and nervous systems [2]. AdditionallyRADIO-CONTROLLED CYBORG BEETLES: A RADIO-FREQUENCY SYSTEM FOR INSECT NEURAL FLIGHT CONTROL H. Sato1 were accomplished by optic lobe stimulation while muscular stimulation of either right or left basalar

Maharbiz, Michel

123

Multi-dimensional ultra-high frequency passive radio frequency identification tag antenna designs  

E-print Network

In this thesis, we present the design, simulation, and empirical evaluation of two novel multi-dimensional ultra-high frequency (UHF) passive radio frequency identification (RFID) tag antennas, the Albano-Dipole antenna ...

Delichatsios, Stefanie Alkistis

2006-01-01

124

The Current Status of Low Frequency Radio Astronomy from Space  

NASA Astrophysics Data System (ADS)

Ground-based radio astronomy is severely limited by the Earth's ionosphere. Below 15 -- 20 MHz, space-based radio observations are superior or even mandatory. Three different areas of astronomical research manifest themselves at low radio frequencies: solar, planetary, and galactic-extragalactic. Space-based observations of solar phenomena at low frequencies are a natural extension of high-frequency ground-based observations that have been carried out since the beginnings of radio astronomy. Measurements of known solar phenomena such as Types II and III bursts have been extended from the few solar radii altitude range reachable by ground-based techniques out to 1 AU and beyond. These space-based solar measurements have become critical in our developing an understanding of ``space weather." In contrast, non-thermal planetary radio emissions are almost exclusively a space radio astronomy phenomenon. With the exception of two components of Jupiter's complex radio spectrum, the magnetospheric and Auroral radio emissions of Earth, Jupiter, Saturn, Uranus, and Neptune have all been discovered by space radio astronomy techniques. For astrophysical applications, the lack of angular resolution from space at low frequencies has thwarted progress such that most areas still remain to be fully exploited. Results to date have only included overall cosmic background spectra and extremely crude (~1 steradian resolution) ``maps." In this overview we will briefly summarize the current status of science in the three areas of research and outline some future concepts for low-frequency, space-based instruments for solar, planetary, and astrophysical problems.

Kaiser, M. L.; Weiler, K. W.

125

Microcalorimetry of dust particles in a radio-frequency plasma  

NASA Astrophysics Data System (ADS)

The internal temperature of rhodamine B-dyed dust particles (2rp=1.2 ?m) immersed in radio-frequency (rf) plasmas has been measured for various plasma conditions. For this purpose, the dye has been excited with an argon-ion laser and the fluorescent emission of the particles has been recorded with an optical multichannel analyzer system. The temperature has been determined after comparison with calibration curves. In argon, the particle temperature increases with rf power and is independent of pressure. In oxygen, an increase with rf power is observed, too. However, the energy flux towards the particles includes also heating by atom recombination (association) and exothermic combustion reactions. These temperature measurements have been compared with calculations based on the thermal balance, where measurements of gas temperature, electron density, and electron temperature have been used. A good agreement between theory and experiment has been found.

Swinkels, G. H. P. M.; Kersten, H.; Deutsch, H.; Kroesen, G. M. W.

2000-08-01

126

Transvaginal Radio Frequency Treatment of the Endopelvic Fascia: A Prospective Evaluation for the Treatment of Genuine Stress Urinary Incontinence  

Microsoft Academic Search

PurposeWe evaluate the safety and efficacy of a new treatment modality for genuine stress urinary incontinence which was a transvaginal radio frequency applicator to deliver radio frequency energy to the endopelvic fascia. The purported mechanism of effect for this therapy is shrinkage of the collagenated tissue which composes the endopelvic fascia that supports the bladder neck and proximal urethra, thus

ROGER R. DMOCHOWSKI; MARK AVON; JAMES ROSS; JAY M. COOPER; RICHARD KAPLAN; BEVERLY LOVE; NEERAJ KOHLI; DAVID ALBALA; BRUCE SHINGLETON

2003-01-01

127

Spectrum Sensing in Cognitive Radios Based on Multiple Cyclic Frequencies  

Microsoft Academic Search

Cognitive radios sense the radio spectrum in order to find unused frequency\\u000abands and use them in an agile manner. Transmission by the primary user must be\\u000adetected reliably even in the low signal-to-noise ratio (SNR) regime and in the\\u000aface of shadowing and fading. Communication signals are typically\\u000acyclostationary, and have many periodic statistical properties related to the\\u000asymbol

Jarmo Lundén; Visa Koivunen; Anu Huttunenand; H. Vincent Poor

2007-01-01

128

Cosmic Radio-Frequency Radiation Near One Megacycle  

Microsoft Academic Search

Observations of cosmic radio-frequency radiation on frequencies of 2130 kc\\/sec, 1435 kc\\/sec, 900 kc\\/sec, and 520 kc\\/sec have been made, using a method of recording which effectively reduces interference from atmospherics. At these frequencies, the intensity of the radiation is approximately 10 - watt per square metre per cycle per second** per steradian. The ionospheric effects associated with observations near

Grote Reber; G. R. Ellis

1956-01-01

129

Radio frequency dc-dc power conversion  

E-print Network

THIS THESIS addresses the development of system architectures and circuit topologies for dc-dc power conversion at very high frequencies. The systems architectures that are developed are structured to overcome limitations ...

Rivas, Juan, 1976-

2007-01-01

130

Radio frequency interference measurements in Indonesia. A survey to establish a radio astronomy observatory  

NASA Astrophysics Data System (ADS)

We report the first measurements of radio frequency spectrum occupancy performed at sites aimed to host the future radio astronomy observatory in Indonesia. The survey is intended to obtain the radio frequency interference (RFI) environment in a spectral range from low frequency 10 MHz up to 8 GHz. The measurements permit the identification of the spectral occupancy over those selected sites in reference to the allocated radio spectrum in Indonesia. The sites are in close proximity to Australia, the future host of Square Kilometre Array (SKA) at low frequency. Therefore, the survey was deliberately made to approximately adhere the SKA protocol for RFI measurements, but with lower sensitivity. The RFI environment at Bosscha Observatory in Lembang was also measured for comparison. Within the sensitivity limit of the measurement equipment, it is found that a location called Fatumonas in the surrounding of Mount Timau in West Timor has very low level of RFI, with a total spectrum occupancy in this measured frequency range being about 1 %, mostly found at low frequency below 20 MHz. More detailed measurements as well as a strategy for a radio quiet zone must be implemented in the near future.

Hidayat, Taufiq; Munir, Achmad; Dermawan, Budi; Jaelani, Anton Timur; Léon, Stéphane; Nugroho, Dading Hadi; Suksmono, Andriyan Bayu; Mahasena, Putra; Premadi, Premana Wardayanti; Herdiwijaya, Dhani; Kunjaya, Chatief; Dupe, Zadrach Ledoufij; Brahmantyo, Budi; Mandey, Denny; Yusuf, Muhammad; Tri Wulandari, Hesti Retno; Arief, Falahuddin; Irfan, Muhammad; Puri Jatmiko, Agus Triono; Akbar, Evan Irawan; Sianturi, Hery Leo; Tanesib, Jehunias Leonidas; Warsito, Ali; Utama, Judhistira Aria

2014-02-01

131

Black phosphorus radio-frequency transistors.  

PubMed

Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin films offer a moderate bandgap of around 0.3 eV and high carrier mobility, which lead to transistors with decent on-off ratios and high on-state current densities. Here, we demonstrate the gigahertz frequency operation of BP field-effect transistors for the first time. The BP transistors demonstrated here show respectable current saturation with an on-off ratio that exceeds 2 × 10(3). We achieved a current density in excess of 270 mA/mm and DC transconductance above 180 mS/mm for hole conduction. Using standard high frequency characterization techniques, we measured a short-circuit current-gain cutoff frequency fT of 12 GHz and a maximum oscillation frequency fmax of 20 GHz in 300 nm channel length devices. BP devices may offer advantages over graphene transistors for high frequency electronics in terms of voltage and power gain due to the good current saturation properties arising from their finite bandgap, thus can be considered as a promising candidate for the future high performance thin film electronics technology for operation in the multi-GHz frequency range and beyond. PMID:25347787

Wang, Han; Wang, Xiaomu; Xia, Fengnian; Wang, Luhao; Jiang, Hao; Xia, Qiangfei; Chin, Matthew L; Dubey, Madan; Han, Shu-Jen

2014-11-12

132

Dual radio frequency plasma source: Understanding via electrical asymmetry effect  

SciTech Connect

On the basis of the global model, the influences of driving voltage and frequency on electron heating in geometrically symmetrical dual capacitively coupled radio frequency plasma have been investigated. Consistent with the experimental and simulation results, non-monotonic behavior of dc self bias and plasma heating with increasing high frequency is observed. In addition to the local maxima of plasma parameters for the integer values of the ratio between the frequencies ({xi}), ourstudies also predict local maxima for odd integer values of 2{xi} as a consequence of the electrical asymmetry effect produced by dual frequency voltage sources.

Bora, B. [Departamento de Plasma Termonuclear, Comision Chilena de Energia Nuclear (CCHEN), Casilla 188-D, Santiago (Chile); Departamento de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Bhuyan, H.; Favre, M.; Wyndham, E. [Departamento de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Wong, C. S. [Plasma Technology Research Centre, Physics Department, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia)

2013-04-21

133

Low-frequency radio navigation system  

NASA Technical Reports Server (NTRS)

A method of continuous wave navigation using four transmitters operating at sufficiently low frequencies to assure essentially pure groundwave operation is described. The transmitters are keyed to transmit constant bursts (1/4 sec) in a time-multiplexed pattern with phase modulation of at least one transmitter for identification of the transmitters and with the ability to identify the absolute phase of the modulated transmitter and the ability to modulate low rate data for transmission. The transmitters are optimally positioned to provide groundwave coverage over a service region of about 50 by 50 km for the frequencies selected in the range of 200 to 500 kHz, but their locations are not critical because of the beneficial effect of overdetermination of position of a receiver made possible by the fourth transmitter. Four frequencies are used, at least two of which are selected to provide optimal resolution. All transmitters are synchronized to an average phase as received by a monitor receiver.

Wallis, D. E. (inventor)

1983-01-01

134

A Radio-Frequency-over-Fiber link for large-array radio astronomy applications  

NASA Astrophysics Data System (ADS)

A prototype 425-850 MHz Radio-Frequency-over-Fiber (RFoF) link for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is presented. The design is based on a directly modulated Fabry-Perot (FP) laser, operating at ambient temperature, and a single-mode fiber. The dynamic performance, gain stability, and phase stability of the RFoF link are characterized. Tests on a two-element interferometer built at the Dominion Radio Astrophysical Observatory for CHIME prototyping demonstrate that RFoF can be successfully used as a cost-effective solution for analog signal transport on the CHIME telescope and other large-array radio astronomy applications.

Mena, J.; Bandura, K.; Cliche, J.-F.; Dobbs, M.; Gilbert, A.; Tang, Q. Y.

2013-10-01

135

The solar elongation distribution of low-frequency radio bursts  

NASA Technical Reports Server (NTRS)

Over 500 days of low-frequency (less than 1 MHz) radio observations from the IMP-6 spacecraft have been accumulated to produce a two-dimensional map (frequency vs elongation) of solar type III burst occurrences. This map indicates that most solar bursts in this frequency range are observed at the second harmonic of the plasma frequency, rather than the fundamental. The map also shows that the solar wind electron density varies as an inverse power of heliocentric distance, with the exponent somewhat less than 2 to perhaps 3 or higher.

Kaiser, M. L.

1975-01-01

136

Simulation study on radio frequency safety of electric explosive device  

NASA Astrophysics Data System (ADS)

Radio frequency (RF) is a great danger to the electric explosive device (EED) of typical ordnance. This paper introduced the RF firing mechanism of the EED and the measuring method of its RF impedance. Through the professional antenna simulation software CST, a dipole antenna model of the EED was set up, the gain coefficient of the antenna model was obtained, and the RF power penetrating into the EED was calculated. The multi-frequency analysis of the emulation indicates that in the certain frequency range of 0.5-2 GHz, the gain coefficient of the antenna model increases as the frequency does.

Yang, Peijie; Tan, Zhiliang; Liu, Chaoyang; Du, Zhide

2013-03-01

137

Systems and methods for determining radio frequency interference  

NASA Technical Reports Server (NTRS)

The presence, frequency and amplitude of radio frequency interference superimposed on communication links originating from a terrestrial region and including a relay in a geostationary spacecraft are determined by pointing a narrow beam antenna on the satellite at the terrestrial region. The level of noise radiated from the region to the antenna is measured at a terrestrial station that is usually remote from the region. Calibrating radio signals having a plurality of predetermined EIRP's (Effective Isotropic Radiated Power) and frequencies in the spectrum are transmitted from the region through the spacecraft narrow beam antenna back to the station. At the station, the levels of the received calibrating signals are separately measured for each of the frequency bands and EIRP's.

Johannsen, K. G.; Sabaroff, S.; Henry, V. F. (inventors)

1978-01-01

138

Controlled radio frequency vessel sealing system for surgical applications  

NASA Astrophysics Data System (ADS)

A radio frequency tissue welding system has been developed for occlusion of vessels during surgery. The system is designed to replace commonly used mechanical clip and suture ligation techniques. Other energy based ligation techniques are limited to use on small structures (energy delivery consisting of a high heat cycle, a low heat cycle and a cooling cycle. The generator output is also voltage limited and delivers high current in order to remodel the collagen in approximately 5 seconds with no sticking or charring. The vessel sealing system was compared to other energy based ligation techniques including ultrasonic sealing and other bipolar systems. The pressure required to burst the vessel was used for comparison. Average burst pressures on 3 - 7 mm arteries were 126 +/- 154 mmHg, 607 +/- 314 mmHg, and 913 +/- 304 mmHg for ultrasonic, standard bipolar, and vessel sealing, respectively. Histologic evaluation showed vessel wall fusion and minimal thermal damage to adjacent tissues for the vessel sealing system.

Kennedy, Jenifer S.; Buysse, Steve; Chandler, James; Eggleston, Jeff; Taylor, Kenneth D.; Thomsen, Sharon L.

1998-04-01

139

A tunable EBG absorber for radio-frequency power imaging  

Microsoft Academic Search

Absorption characteristics of a tunable electromagnetic band-gap (EBG) absorber are analyzed, which is designed to capture 2d radio-frequency (RF) power distributions incident on the absorber surface. The EBG absorber has lumped resistors interconnecting the mushroom-type surface patches to absorb the incident RF power at the resonance frequency where the EBG structure exhibits a high-impedance feature. The absorbed RF power distribution

Satoshi Yagitani; Keigo Katsuda; Ryo Tanaka; Masayuki Nojima; Yoshiyuki Yoshimura; Hirokazu Sugiura

2011-01-01

140

Computer simulations of ions in radio-frequency traps  

NASA Technical Reports Server (NTRS)

The motion of ions in a trapped-ion frequency standard affects the stability of the standard. In order to study the motion and structures of large ion clouds in a radio-frequency (RF) trap, a computer simulation of the system that incorporates the effect of thermal excitation of the ions was developed. Results are presented from the simulation for cloud sizes up to 512 ions, emphasizing cloud structures in the low-temperature regime.

Williams, A.; Prestage, J. D.; Maleki, L.; Djomehri, J.; Harabetian, E.

1990-01-01

141

29. View of typical radio frequency monitor group electronic tubetype ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

29. View of typical radio frequency monitor group electronic tube-type cabinet. System is water-cooled with antenna assist. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

142

Fabrication of the APS storage ring radio frequency accelerating cavities  

Microsoft Academic Search

Specification, heat treatment, strength, and fatigue life of the Advanced Photon Source (APS) Storage Ring 352-MHz radio frequency (RF) accelerating cavity copper is discussed. Heat transfer studies, including finite element analysis, and configuration of water cooling is described. Requirements for and techniques of machining are considered. Braze and electron beam joint designs are compared. Vacuum considerations during fabrication are discussed

K. Primdahl; J. Bridges; F. DePaola; R. Kustom; D. Snee

1993-01-01

143

Radio frequency telemetry system for sensors and actuators  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote powering/receiving device. Such technology has many applications, but is especially useful in the biomedical area.

Simons, Rainee N. (Inventor); Miranda, Felix A. (Inventor)

2003-01-01

144

Radio Frequency Telemetry System for Sensors and Actuators  

NASA Technical Reports Server (NTRS)

The present invention discloses and teaches apparatus for combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote poweringheceiving device. Such technology has many applications, but is especially useful in the biomedical area.

Simons, Rainee N. (Inventor); Miranda, Felix A. (Inventor)

2003-01-01

145

Authentication of Radio Frequency Identification Devices Using Electronic Characteristics  

ERIC Educational Resources Information Center

Radio frequency identification (RFID) tags are low-cost devices that are used to uniquely identify the objects to which they are attached. Due to the low cost and size that is driving the technology, a tag has limited computational capabilities and resources. This limitation makes the implementation of conventional security protocols to prevent…

Chinnappa Gounder Periaswamy, Senthilkumar

2010-01-01

146

75. Transmitter building no. 102, view of typical radio frequency ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

75. Transmitter building no. 102, view of typical radio frequency switching group for lower antenna A & B and upper antenna A & B and MIP/MWOC automated interface cabinet. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

147

Radio frequency and infrared drying of sized textile warp yarns  

SciTech Connect

Drying sized textile warp yarns without contacting the warp is easily accomplished by either radio frequency or infrared techniques. Although the process is more expensive than conventional drying, the substantial savings accrued during subsequent weaving and finishing of the cloth can help keep the US textile industry competitive and support electrical load. 5 refs., 8 figs., 14 tabs.

Ruddick, H.G. (West Point Foundry and Machine Co., GA (USA))

1990-11-01

148

Low-frequency radio maps and spectra of supernova remnants  

NASA Technical Reports Server (NTRS)

Low-frequency radio maps of 18 supernova remnants have been constructed from observations made at the Arecibo Observatory. The integrated flux densities have been combined with others in the literature to show that most of the sources have simple power-law spectra. None of the sources show features which would suggest changes in the spectrum spatially across the given source.

Dickel, J. R.; Denoyer, L. K.

1975-01-01

149

Image transmission in tactical radio frequency shared network propagation environments  

Microsoft Academic Search

The need to transmit images across tactical radio frequency (rf) links has been identified in army digitization applications. For example, military doctrine requires that tactical functions like identification of battlefield entities as potential targets and battle damage assessment be performed by the soldier. Currently, a key input to these processes is imagery. Therefore, the quality and timeliness of the image

Kent H. White; Kerry A. Wagner; Scott O'Hanian

1997-01-01

150

Radio frequency identification and food retailing in the UK  

Microsoft Academic Search

Purpose – This paper aims to offer an outline of the characteristics of radio frequency identification (RFID) technology and briefly discusses some of its perceived benefits and challenges for food retailers in the UK. Design\\/methodology\\/approach – The paper draws material largely from trade and practitioner sources and illustrates general themes with specific retail examples. Findings – The paper suggests that

Peter Jones; Colin Clarke-Hill; Daphne Comfort; David Hillier; Peter Shears

2005-01-01

151

Radio-frequency quadrupole: General properties and specific applications  

NASA Astrophysics Data System (ADS)

The general properties of radio frequency quadrupole accelerators are reviewed and beam dynamics simulation results are presented for their use in a variety of accelerating systems. The low-beta sections of the Fusion Materials Irradiation Test Accelerator, a 200 MHz proton linear accelerator, and a xenon accelerator for heavy ion fusion are included.

Stokes, R. H.; Crandall, K. R.; Hamm, R. W.; Humphry, F. J.; Jameson, R. A.; Knapp, E. A.; Potter, J. M.; Rodenz, G. W.; Stovall, J. E.; Swenson, D. A.

1980-07-01

152

INNOVATIVE TECHNOLOGY EVALUATION REPORT: RADIO FREQUENCY HEATING, KAI TECHNOLOGIES, INC.  

EPA Science Inventory

A demonstration of KAI Technologies in-situ radio frequency heating system for soil treatment was conducted from January 1994 to July 1994 at Kelly Air Force Base in San Antonio, Texas. This demonstration was conducted as a joint effort between the USEPA and the USAF. The technol...

153

INNOVATIVE TECHNOLOGY EVALUATION REPORT: RADIO FREQUENCY HEATING, KAI TECHNOLOGIES, INC.  

EPA Science Inventory

A demonstration of KAI Technologies in-situ radio frequency heating system for soil treatment was conducted from January 1994 to July 1994 at Kelly Air Force Base in San Antonio, Texas. his demonstration was conducted as a joint effort between the USEPA and the USAF. he technolog...

154

DETECTION OF TRANSIENT IN RADIO FREQUENCY FINGERPRINTING USING SIGNAL PHASE  

E-print Network

of the transient can be delayed. In addition, the performance of the Bayesian Step Change Detector mayDETECTION OF TRANSIENT IN RADIO FREQUENCY FINGERPRINTING USING SIGNAL PHASE Jeyanthi Hall Michel wireless devices. It es- sentially involves the detection of the transient signal and the extraction

Barbeau, Michel

155

Celestial Reference Frame Realizations at Multiple Radio Frequency Bands  

NASA Astrophysics Data System (ADS)

The International Celestial Reference Frame (ICRF) was adopted by the IAU in 1997 based on VLBI measurements at S/X - band (2.3/8.4 GHz) and complemented by HIPPARC OS measurements at optical frequencies. At that time, the IAU encouraged the astrometric community to extend the ICRF to additional frequency bands. In response, VLBI measurements have been made at 24, 32, and 43 GHz. Meanwhile, the 8.4 GHz work has been greatly improved with the release of the ICRF - 2 in 2009. This paper will discuss the programmatic and scientific motivations for extending the ICRF to these higher radio bands. Results to date will be summarized including evidence that these new high frequency frames are rapidly approaching the accuracy of the 8.4 GHz ICRF - 2. We will discuss the current limiting errors and prospects for the future accuracy of radio reference frames. In particular, we will discuss using multiple radio frames to characterize t he frequency dependent systematic noise floor from extended source morphology and core shift. Finally, given the potential of the Gaia optical mission for state - of - the - art astrometry, we will discuss simulations which show the potential for a radio - optical frame tie at the 10 - 15 ?as level of precision (1 - sigma). The research described in this paper was done under contract with NASA. Government sponsorship acknowledged. ©2012 California Institute of Technology.

Jacobs, Chris

2012-08-01

156

Radio frequency power sensor based on MEMS technology  

Microsoft Academic Search

We present the first measurement results of a power sensor for radio frequency (rf) signals (50 kHz - 40 GHz) with almost no dissipation during the measurement. This sensor is, therefore, a 'through' power sensor, that means that the rf signal is available during the measurement of its power. The power detection has been realized by measuring capacitively the movement

Luis J. Fernandez; Eelke Visser; Javier Sesé; Remco Wiegerink; Jaap Flokstra; Henri Jansen; Miko Elwenspoek

2003-01-01

157

Fabrication of the APS Storage Ring radio frequency accelerating cavities  

SciTech Connect

Specification, heat treatment, strength, and fatigue life of the Advanced Photon Source (APS) Storage Ring 352-MHz radio frequency (RF) accelerating cavity copper is discussed. Heat transfer studies, including finite element analysis, and configuration of water cooling is described. Requirements for and techniques of machining are considered. Braze and electron beam joint designs are compared. Vacuum considerations during fabrication are discussed.

Primdahl, K.; Bridges, J.; DePaola, F.; Kustom, R. [Argonne National Lab., IL (US); Snee, D. [Fermi National Accelerator Lab., Batavia, IL (US)

1993-07-01

158

Radio frequency arraying method for receivers  

NASA Technical Reports Server (NTRS)

A method and apparatus for increasing the signal to noise ratio of a receiving facility for coherent frequency reception by arraying receiving systems using separate antennas for each, or one antenna for all systems are presented. One system is operated with a carrier tracking loop to provide a first local oscillator frequency for the first and all other systems arrayed, with individual tracking loops in all other systems operated at IF for tracking out any phase differences due to separate group delays using an adjustable phase shifter for a second reference to compensate for different group delays in the antenna and low noise amplifier of each of the other systems. The second IF output of all systems is summed into the first system. This technique may also be used when two systems are arrayed to an antenna designed for circular or linear polarization diversity reception to effectively provide the same signal to noise ratio for both polarized signal transmission channels that would result from matched polarization. An arrangement adapted to high rate telemetry reception is disclosed. With additional components, the same arrangement is adapted to provide low rate telemetry reception as well.

Brockman, M. H.; Easterling, M. F. (inventors)

1980-01-01

159

LOFAR: A new radio telescope for low frequency radio observations: Science and project status  

E-print Network

LOFAR, the Low Frequency Array, is a large radio telescope consisting about 100 soccer field sized antenna stations spread over a region of 400 km in diameter. It will operate in the frequency range from ~10 to 240 MHz, with a resolution at 240 MHz of better than an arcsecond. Its superb sensitivity will allow for a broad range of astrophysical studies. In this contribution we first discuss four major areas of astrophysical research in which LOFAR will undoubtedly make important contributions: reionisation, distant galaxies and AGNs, transient radio sources and cosmic rays. Subsequently, we will discuss the technical concept of the instrument and the status of the LOFAR project

H. Rottgering; A. G. de Bruyn; R. P. Fender; J. Kuijpers; M. P. van Haarlem; M. Johnston-Hollitt; G. K Miley

2003-07-11

160

Radio Frequency Spectra of 388 Bright 74 MHz Sources  

E-print Network

As a service to the community, we have compiled radio frequency spectra from the literature for all sources within the VLA Low Frequency Sky Survey (VLSS) that are brighter than 15 Jy at 74 MHz. Over 160 references were used to maximize the amount of spectral data used in the compilation of the spectra, while also taking care to determine the corrections needed to put the flux densities from all reference on the same absolute flux density scale. With the new VLSS data, we are able to vastly improve upon previous efforts to compile spectra of bright radio sources to frequencies below 100 MHz because (1) the VLSS flux densities are more reliable than those from some previous low frequency surveys and (2) the VLSS covers a much larger area of the sky (declination >-30 deg.) than many other low frequency surveys (e.g., the 8C survey). In this paper, we discuss how the spectra were constructed and how parameters quantifying the shapes of the spectra were derived. Both the spectra and the shape parameters are made available here to assist in the calibration of observations made with current and future low frequency radio facilities.

J. F. Helmboldt; N. E. Kassim; A. S. Cohen; W. M. Lane; T. J. Lazio

2007-07-23

161

Exploring the magnetized cosmic web through low frequency radio emission  

E-print Network

Recent improvements in the capabilities of low frequency radio telescopes provide a unique opportunity to study thermal and non-thermal properties of the cosmic web. We argue that the diffuse, polarized emission from giant radio relics traces structure formation shock waves and illuminates the large-scale magnetic field. To show this, we model the population of shock-accelerated relativistic electrons in high-resolution cosmological simulations of galaxy clusters and calculate the resulting radio synchrotron emission. We find that individual shock waves correspond to localized peaks in the radio surface brightness map which enables us to measure Mach numbers for these shocks. We show that the luminosities and number counts of the relics strongly depend on the magnetic field properties, the cluster mass and dynamical state. By suitably combining different cluster data, including Faraday rotation measures, we are able to constrain some macroscopic parameters of the plasma at the structure formation shocks, such as models of turbulence. We also predict upper limits for the properties of the warm-hot intergalactic medium, such as its temperature and density. We predict that the current generation of radio telescopes (LOFAR, GMRT, MWA, LWA) have the potential to discover a substantially larger sample of radio relics, with multiple relics expected for each violently merging cluster. Future experiments (SKA) should enable us to further probe the macroscopic parameters of plasma physics in clusters.

N. Battaglia; C. Pfrommer; J. L. Sievers; J. R. Bond; T. A. Ensslin

2008-06-19

162

Monitoring Radio Frequency Interference: The Quiet Skies Project  

NASA Astrophysics Data System (ADS)

The Quiet Skies Project is a result of the Research Experience for Teacher (RET) program during the summer of 2004. Teachers were involved in discovering the relationship between radio frequency interference (RFI) and radio astronomy observations. S. Rapp participated in astronomy observations with the Green Bank Telescope in order to characterize RFI issues at radio observatories and worked closely with the Green Bank Interference Protection Group. This work included such tasks as mitigation of locally-generated RFI from power poles and running radiation propagation studies for transmitters within the National Radio Quiet Zone. A curriculum was created to allow high school students to participate in a research effort to determine RFI levels in their communities. The aim of the project is to promote student awareness of radio astronomy and radio frequency interference through an inquiry-based science curriculum. It is hoped that the project will go national by 2007. A prototype RFI detector was created and tested at four wavelengths; 850, 900, 1425, and 1675 MHz. High school students used a beta version of the RFI detector to explore the occurrence of RFI at their schools and in their communities. The student goals of the Quiet Skies Project are to: Measure interference levels at their schools and in their communities; Reduce and transmit their data to an NRAO data base; Use online spectrum allocation data, and local information to determine possible causes of interference in their area; Analyze the complex trade-offs between radio astronomy's need for quiet skies, and other commercial, and non-commercial uses of the spectrum and share their insights with others. This work was funded by the NSF-RET program and a grant from the NASA-IDEAS program

Rapp, S.; Gear, C.; Maddalena, R. J.; Heatherly, S. A.

2004-12-01

163

A simple, tunable, and highly sensitive radio-frequency sensor  

PubMed Central

We report a radio frequency (RF) sensor that exploits tunable attenuators and phase shifters to achieve high-sensitivity and broad band frequency tunability. Three frequency bands are combined to enable sensor operations from ?20?MHz to ?38?GHz. The effective quality factor (Qeff) of the sensor is as high as ?3.8?×?106 with 200??l of water samples. We also demonstrate the measurement of 2-proponal-water-solution permittivity at 0.01 mole concentration level from ?1?GHz to ?10?GHz. Methanol-water solution and de-ionized water are used to calibrate the RF sensor for the quantitative measurements. PMID:24023393

Cui, Yan; Sun, Jiwei; He, Yuxi; Wang, Zheng; Wang, Pingshan

2013-01-01

164

Transurethral radio frequency ablation of the prostate  

NASA Astrophysics Data System (ADS)

Since 1993, radiofrequency ablation of the prostate has been studied as a potential treatment for symptomatic bladder outlet obstruction due to benign prostatic hyperplasia. Two transurethral radiofrequency delivery systems have been developed to the point of undergoing initial human clinical trials. The TUNATM system involves focal interstitial radiofrequency energy application, while the TURAPYTM system involves a circumferential application of radiofrequency energy to the prostatic urethra via a simple delivery catheter. Experimental studies in animal models and human prostate tissue have demonstrated the nature of radiofrequency induced tissue heating and thermal injury. Observed thermal effects are relatively focused, with steep temperature gradients occurring over a few millimeters from the radiofrequency emission source. This allows precise and focused tissue treatment with little or no danger of injury to surrounding structures. Early human clinical experience in the treatment of benign prostatic hyperplasia has demonstrated efficacy in the relief of voiding symptoms and safety and minimal morbidity associated with this technology. The existing operative approaches are relatively simple. Ongoing development of more versatile delivery systems for radiofrequency ablation of the prostate is expected. Results from larger clinical trials with longer term followup will eventually allow adequate assessment of the role of radiofrequency ablation in the surgical management of benign prostatic hyperplasia.

Kabalin, John N.

1996-05-01

165

Low Frequency Radio Astronomical Antennas for the Lunar Environment  

NASA Astrophysics Data System (ADS)

Low radio frequencies (? MHz) represent the last of the relatively unexplored wavebands in the electromagnetic spectrum for astrophysics. Such observations are very challenging from the surface of the Earth because of an abundance of human-made radio interference (e.g., FM bands, TV channels) and because of ionospheric refraction. The lunar farside presents a unique opportunity to fully open this cosmic window because of the demonstrated radio-quiet environment. The ultimate science goal of a lunar farside low frequency telescope is to explore a new frontier in cosmology, the so-called Dark Ages. This era occurs between Recombination (at z 1100) when the universe first becomes transparent (producing what we observe today as the CMB) and Reionization when the first stars and galaxies form (at z 10-20). During the Dark Ages, the universe was unlit by any star and the only detectable signal is likely to arise from neutral hydrogen absorption against the CMB (from the collapse of the first structures). Observing this absorption signal would be a powerful probe of fundamental cosmology. During the Dark Ages (z 20 - 150), when the 21-cm (1.4 GHz) neutral hydrogen line is redshifted into the low frequency radio band (10-30 MHz, 10-30 m), the absorption signal has the potential to be the richest of all cosmological data sets. In this poster, we will discuss the opportunities and options for low frequency radio antennas in both lunar orbit and on the lunar surface. We are investigating a novel concept to deploy a large number of low-mass antennas deposited on sheets of polyimide film. We will also describe results of laboratory vacuum testing at U. Colorado on polyimide film cycled between -150 C and 100 C, and exposed to far-ultraviolet light, with conditions like those on the lunar surface.

Burns, Jack O.; Lazio, J.; ROLSS DALI Teams

2009-01-01

166

Superconducting Radio Frequency Technology: An Overview  

SciTech Connect

Superconducting RF cavities are becoming more often the choice for larger scale particle accelerator projects such as linear colliders, energy recovery linacs, free electron lasers or storage rings. Among the many advantages compared to normal conducting copper structures, the superconducting devices dissipate less rf power, permit higher accelerating gradients in CW operation and provide better quality particle beams. In most cases these accelerating cavities are fabricated from high purity bulk niobium, which has superior superconducting properties such as critical temperature and critical magnetic field when compared to other superconducting materials. Research during the last decade has shown, that the metallurgical properties--purity, grain structure, mechanical properties and oxidation behavior--have significant influence on the performance of these accelerating devices. This contribution attempts to give a short overview of the superconducting RF technology with emphasis on the importance of the material properties of the high purity niobium.

Peter Kneisel

2003-06-01

167

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION*  

E-print Network

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION* R. Agustsson- picosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron beam will be presented. INTRODUCTION Some of the most compelling and demanding applications in high-energy electron beam

Brookhaven National Laboratory

168

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION*  

E-print Network

NORMAL CONDUCTING RADIO FREQUENCY X-BAND DEFLECTING CAVITY FABRICATION AND VALIDATION* R. Agustsson of the sub- picosecond ultra-relativistic electron beams. The device is optimized for the 100 MeV electron will be presented. INTRODUCTION Some of the most compelling and demanding applications in high-energy electron beam

Brookhaven National Laboratory

169

Development of structural materials exhibiting dielectric and magnetic loss at radio frequencies  

Microsoft Academic Search

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The reduction of radio frequency (RF) return from military assets has been of critical interest for the last twenty years. New materials are required that not only provide a reduction in specular and travelling wave RF energy, but also

J. R. Jr. Duke; P. G. Apen; M. Hoisington

1996-01-01

170

A Graphical Approach to Radio Frequency Quadrupole Design  

E-print Network

The design of a radio frequency quadrupole, an important section of all ion accelerators, and the calculation of its beam dynamics properties can be achieved using the existing computational tools. These programs, originally designed in 1980s, show effects of aging in their user interfaces and in their output. The authors believe there is room for improvement in both design techniques using a graphical approach and in the amount of analytical calculations before going into CPU burning finite element analysis techniques. Additionally an emphasis on the graphical method of controlling the evolution of the relevant parameters using the drag-to-change paradigm is bound to be beneficial to the designer. A computer code, named DEMIRCI, has been written in C++ to demonstrate these ideas. This tool has been used in the design of Turkish Atomic Energy Authority (TAEK)'s 1.5 MeV proton beamline at Saraykoy Nuclear Research and Training Center (SANAEM). DEMIRCI starts with a simple analytical model, calculates the RFQ b...

Turemen, G; Yasatekin, B

2014-01-01

171

Radio-frequency plasma transducer for use in harsh environments.  

PubMed

We describe a compact transducer used to generate and modulate low-intensity radio-frequency atmospheric pressure plasma (RF-APP) for high temperature gap measurement and generation of air-coupled ultrasound. The new transducer consists of a quarter-wave transmission line where the ground return path is a coaxial solenoid winding. The RF-APP is initiated at the open end of the transmission line and stabilized by passive negative feedback between the electrical impedance of the plasma and the energy stored in the solenoid. The electrical impedance of the plasma was measured at the lower-voltage source end of the transducer, eliminating the need to measure kilovolt-level voltages near the discharge. We describe the use of a 7 MHz RF-APP prototype as a harsh-environment clearance sensor to demonstrate the suitability of plasma discharges for a common nondestructive inspection application. Clearance measurements of 0-5 mm were performed on a rotating calibration target with a measurement precision of 0.1 mm and a 20 kHz sampling rate. PMID:17979443

May, Andrew; Andarawis, Emad

2007-10-01

172

Analyzing Radio-Frequency Coverage for the ISS  

NASA Technical Reports Server (NTRS)

The Interactive Coverage Analysis Tool (iCAT) is an interactive desktop computer program serving to (1) support planning of coverage, and management of usage of frequencies, of current and proposed radio communication systems on and near the International Space Station (ISS) and (2) enable definition of requirements for development of future such systems. The iCAT can also be used in design trade studies for other (both outer-space and terrestrial) communication systems. A user can enter the parameters of a communication-system link budget in a table in a worksheet. The nominal (onaxis) link values for the bit-to-noise-energy ratio, received isotropic power (RIP), carrier-to-noise ratio (C/N), power flux density (PFD), and link margin of the system are calculated and displayed in the table. Plots of field gradients for the RIP, C/N, PFD, and link margin are constructed in an ISS coordinate system, at a specified link range, for both the forward and return link parameters, and are displayed in worksheets. The forward and reverse link antenna gain patterns are also constructed and displayed. Line-of-sight (LOS) obstructions can be both incorporated into the gradient plots and displayed on separate plots.

Bolen, Steven M.; Sham, Catherine C.

2007-01-01

173

Radio-frequency plasma transducer for use in harsh environments  

SciTech Connect

We describe a compact transducer used to generate and modulate low-intensity radio-frequency atmospheric pressure plasma (RF-APP) for high temperature gap measurement and generation of air-coupled ultrasound. The new transducer consists of a quarter-wave transmission line where the ground return path is a coaxial solenoid winding. The RF-APP is initiated at the open end of the transmission line and stabilized by passive negative feedback between the electrical impedance of the plasma and the energy stored in the solenoid. The electrical impedance of the plasma was measured at the lower-voltage source end of the transducer, eliminating the need to measure kilovolt-level voltages near the discharge. We describe the use of a 7 MHz RF-APP prototype as a harsh-environment clearance sensor to demonstrate the suitability of plasma discharges for a common nondestructive inspection application. Clearance measurements of 0-5 mm were performed on a rotating calibration target with a measurement precision of 0.1 mm and a 20 kHz sampling rate.

May, Andrew; Andarawis, Emad [GE Global Research, 1 Research Circle, Niskayuna, New York 12309 (United States)

2007-10-15

174

Dowsing can be interfered with by radio frequency radiation.  

PubMed

The soil radiation, watercourses and ores have been located for centuries by sensitive persons, dowsers. An ideomotoric explanation of the dowsing reaction, with no physical interaction, has been accepted. Our present re-analyses of some such results have shown, that there could be a physical phenomenon connecting the human reactions in field experiments, where the test subjects walked or were sitting in a slow-moving car, with the windows covered, and a dowsing rod in their hands was recorded. The correlations between the reaction points by test subjects in the moving car and the points by walking along the same path were highly significant. The correlation was not seen in all test locations. The distance between the test location and the radio tower, and the incidence angle of the transmitted radio wave, possibly had an effect on results. We hypothesize that the experiments carried out in the 20th century were interfered with by man-made radio frequency radiation, mainly FM radio and TV broadcasting, as test subjects' bodies absorbed the radio waves and unconscious hand movement reactions took place following the standing waves or intensity variations due to multipath propagation. PMID:22365422

Huttunen, Paavo; Niinimaa, Ahti; Myllylä, Risto

2012-04-01

175

Controller design issues in the feedback control of radio frequency plasma processing reactors  

E-print Network

Controller design issues in the feedback control of radio frequency plasma processing reactors the potential for improving the reliability and performance of radio frequency rf plasma processing reactors feedback control of inductively coupled plasma processing reactors for polysilicon etching and

Kushner, Mark

176

Radio frequency analog electronics based on carbon nanotube transistors  

PubMed Central

The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into circuits is challenging because of difficulties in controlling the geometries, spatial positions, and electronic properties of individual tubes. We have implemented solutions to some of these challenges to yield radio frequency (RF) SWNT analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. As a demonstration, we fabricated nanotube transistor radios, in which SWNT devices provide all of the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. These results represent important first steps to practical implementation of SWNTs in high-speed analog circuits. Comparison studies indicate certain performance advantages over silicon and capabilities that complement those in existing compound semiconductor technologies. PMID:18227509

Kocabas, Coskun; Kim, Hoon-sik; Banks, Tony; Rogers, John A.; Pesetski, Aaron A.; Baumgardner, James E.; Krishnaswamy, S. V.; Zhang, Hong

2008-01-01

177

Predictions for high-frequency radio surveys of extragalactic sources  

E-print Network

We present detailed predictions of the contributions of the various source populations to the counts at frequencies of tens of GHz. New evolutionary models are worked out for flat-spectrum radio quasars, BL Lac objects, and steep-spectrum sources. Source populations characterized by spectra peaking at high radio frequencies, such as extreme GPS sources, ADAF/ADIOS sources and early phases of gamma-ray burst afterglows are also dealt with. The counts of different populations of star-forming galaxies (normal spirals, starbursts, high-z galaxies detected by SCUBA and MAMBO surveys, interpreted as proto-spheroidal galaxies) are estimated taking into account both synchrotron and free-free emission, and dust re-radiation. Our analysis is completed by updated counts of Sunyaev-Zeldovich effects in clusters of galaxies and by a preliminary estimate of galactic-scale Sunyaev-Zeldovich signals associated to proto-galactic plasma.

Gianfranco De Zotti; Roberto Ricci; Dino Mesa; Laura Silva; Pasquale Mazzotta; Luigi Toffolatti; Joaquin Gonzalez-Nuevo

2004-10-28

178

Radio frequency communication system utilizing radiating transmission lines  

DOEpatents

A radio communication system for use in tunnels, mines, buildings or other shielded locations in which a pair of radiating transmission lines (30), (31) extend through such location in spaced coextensive relation to each other. Each transmission line (30), (31) has at least one unidirectional amplifier (32), (33) interposed therein with the sense of the unidirectional amplifier (32) of one transmission line (30) being opposite to the sense of the unidirectional amplifier (33) of the other transmission line (31). Each of the amplifiers (32), (33) has a gain which is less than the coupling loss between the transmission lines (30), (31). Two or more mobile transceivers (35) in the location served by the system are coupled to the transmission lines (30), (31) by electromagnetic wave propagation in space in order to communicate directly with each other at a given radio frequency within the frequency range of the system.

Struven, Warren C. (San Carlos, CA)

1984-01-01

179

Hermetic aluminum radio frequency interconnection and method for making  

Microsoft Academic Search

The present invention provides a light-weight, hermetic coaxial radio-frequency (RF) interconnection having an electrically conductive outer housing made of aluminum or an aluminum alloy, a central electrical conductor made of ferrous or non-ferrous material, and a cylinder of dielectric material comprising a low-melting-temperature, high-thermal-expansion aluminophosphate glass composition for hermetically sealing between the aluminum-alloy outer housing and the ferrous or non-ferrous

R. D. Kilgo; L. Kovacic; R. K. Brow

2000-01-01

180

Terahertz bandwidth integrated radio frequency spectrum analyzer via nonlinear optics  

E-print Network

We report an integrated all-optical radio frequency spectrum analyzer based on a ~ 4cm long doped silica glass waveguide, with a bandwidth greater than 2.5 THz. We use this device to characterize the intensity power spectrum of ultrahigh repetition rate mode-locked lasers at repetition rates up to 400 GHz, and observe dynamic noise related behavior not observable with other techniques.

Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Clerici, Matteo; Caspani, Lucia; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Moss, David J

2014-01-01

181

Tunable (LSMO) Ferromagnetic Thin Films for Radio Frequency Applications  

Microsoft Academic Search

In this letter, an original work in tunable (La,Sr)MnO3 (LSMO) ferromagnetic thin film materials for radio frequency applications is presented. 400 nm thick LSMO thin film is formed by the chemical solution deposition on the top of indium tin oxide (ITO)\\/SiO2\\/Si heterostructure. Interdigitated capacitor structures are used to study the behavior of LSMO thin film materials when a dc electrostatic

M. Al Ahmad; Young Taek Lee; Chae Il Cheon; Eui-Jung Yun; R. Plana

2009-01-01

182

CARS spectroscopy of radio-frequency discharge plasma in hydrogen  

Microsoft Academic Search

The population of the vibrational and rotational levels of hydrogen is studied by the narrow-and broadband CARS spectroscopy in capacitive and inductive-capacitive radio-frequency discharge plasmas. Computational codes are developed to analyze and process CARS spectra of hydrogen obtained under conditions of disturbance of thermodynamic equilibrium over internal degrees of freedom of molecules. To interpret the measurement results, a model is

V. A. Shakhatov; O. A. Gordeev

2007-01-01

183

CARS spectroscopy of radio-frequency discharge plasma in hydrogen  

Microsoft Academic Search

The population of the vibrational and rotational levels of hydrogen is studied by the narrow-and broadband CARS spectroscopy\\u000a in capacitive and inductive-capacitive radio-frequency discharge plasmas. Computational codes are developed to analyze and\\u000a process CARS spectra of hydrogen obtained under conditions of disturbance of thermodynamic equilibrium over internal degrees\\u000a of freedom of molecules. To interpret the measurement results, a model is

V. A. Shakhatov; O. A. Gordeev

2007-01-01

184

Longitudinal capture in the radio-frequency-quadrupole structure  

SciTech Connect

The radio-frequency-quadrupole (RFQ) linac structure not only can attain easily transverse focusing in the low-beta region, but also can obtain very high capture efficiency because of its low beta-lambda and low-particle rigidity. An optimization study of the zero space-charge longitudinal capture in an RFQ linac that yields configurations with large capture efficiency is described.

Inagaki, S.

1980-03-01

185

Perforated-Layer Implementation Of Radio-Frequency Lenses  

NASA Technical Reports Server (NTRS)

Luneberg-type radio-frequency dielectric lenses made of stacked perforated circular dielectric sheets, according to proposal. Perforation pattern designed to achieve required spatial variation of permittivity. Consists of round holes distributed across face of each sheet in "Swiss-cheese" pattern, plus straight or curved slots that break up outer parts into petals in "daisy-wheel" pattern. Holes and slots made by numerically controlled machining.

Dolgin, Benjamin P.

1996-01-01

186

Spectral Occupancy at VHF: Implications for Frequency-Agile Cognitive Radios  

E-print Network

Spectral Occupancy at VHF: Implications for Frequency-Agile Cognitive Radios Steven W. Ellingson Blacksburg, VA 24061 Email: ellingson@vt.edu Abstract-- Frequency-agile cognitive radio is a potential solu. I. INTRODUCTION Frequency-agile cognitive radio is a potential solution to the problem

Ellingson, Steven W.

187

Imaging interplanetary CMEs at radio frequency from solar polar orbit  

Microsoft Academic Search

Coronal mass ejections (CMEs) represent a great concentration of mass and energy input into the lower corona. They have come to be recognized as the major driver of physical conditions change in the Sun–Earth system. Consequently, observations of CMEs are important for understanding and ultimately predicting space weather conditions. This paper discusses a proposed mission, the Solar Polar Orbit Radio

Ji Wu; Weiying Sun; Jianhua Zheng; Cheng Zhang; Hao Liu; Jingye Yan; Chi Wang; Chuanbing Wang; Shui Wang

2011-01-01

188

Imaging Interplanetary CMEs at Radio Frequency From Solar Polar Orbit  

NASA Astrophysics Data System (ADS)

Coronal mass ejections (CMEs) are violent discharges of plasma and magnetic fields from the Sun's corona. They have come to be recognized as the major driver of physical conditions in the Sun-Earth system. Consequently, the detection of CMEs is important for un-derstanding and ultimately predicting space weather conditions. The Solar Polar Orbit Radio Telescope (SPORT) is a proposed mission to observe the propagation of interplanetary CMEs from solar polar orbit. The main payload (radio telescope) on board SPORT will be an in-terferometric imaging radiometer working at the meter wavelength band, which will follow the propagation of interplanetary CMEs from a distance of a few solar radii to near 1 AU from solar polar orbit. The SPORT spacecraft will also be equipped with a set of optical and in situ measurement instruments such as a EUV solar telescope, a solar wind plasma experiment, a solar wind ion composition instrument, an energetic particle detector, a wave detector, a mag-netometer and an interplanetary radio burst tracker. In this paper, we first describe the current shortage of interplanetary CME observations. Next, the scientific motivation and objectives of SPORT are introduced. We discuss the basic specifications of the main radio telescope of SPORT with reference to the radio emission mechanisms and the radio frequency band to be observed. Finally, we discuss the key technologies of the SPORT mission, including the con-ceptual design of the main telescope, the image retrieval algorithm and the solar polar orbit injection. Other payloads and their respective observation objectives are also briefly discussed. Key words: Interplanetary CMEs; Interferometric imaging; Solar polar orbit; Radiometer.

Wu, Ji; Sun, Weiying; Zheng, Jianhua; Zhang, Cheng; Wang, Chi; Wang, C. B.; Wang, S.

189

Development of a superconducting radio frequency photoelectron injector  

NASA Astrophysics Data System (ADS)

A superconducting radio frequency (RF) photoelectron injector (SRF gun) is under development at the Research Center Dresden-Rossendorf. This project aims mainly at replacing the present thermionic gun of the superconducting electron linac ELBE. Thereby the beam quality is greatly improved. Especially, the normalized transverse emittance can be reduced by up to one order of magnitude depending on the operating conditions. The length of the electron bunches will be shortened by about two orders of magnitude making the present bunchers in the injection beam line dispensable. The maximum obtainable bunch charge of the present thermionic gun amounts to 80 pC. The SRF gun is designed to deliver also higher bunch charge values up to 2.5 nC. Therefore, this gun can be used also for advanced facilities such as energy recovery linacs (ERLs) and soft X-ray FELs. The SRF gun is designed as a 3{1}/{2} cell cavity structure with three cells basically TESLA cells supplemented by a newly developed gun cell and a choke filter. The exit energy is projected to be 9.5 MeV. In this paper, we present a description of the design of the SRF gun with special emphasis on the physical and technical problems arising from the necessity of integrating a photocathode into the superconducting cavity structure. Preparation, transfer, cooling and alignment of the photocathode are discussed. In designing the SRF gun cryostat for most components wherever possible the technical solutions were adapted from the ELBE cryostat in some cases with major modifications. As concerns the status of the project the design is finished, most parts are manufactured and the gun is being assembled. Some of the key components are tested in special test arrangements such as cavity warm tuning, cathode cooling, the mechanical behavior of the tuners and the effectiveness of the magnetic screening of the cavity.

Arnold, A.; Büttig, H.; Janssen, D.; Kamps, T.; Klemz, G.; Lehmann, W. D.; Lehnert, U.; Lipka, D.; Marhauser, F.; Michel, P.; Möller, K.; Murcek, P.; Schneider, Ch.; Schurig, R.; Staufenbiel, F.; Stephan, J.; Teichert, J.; Volkov, V.; Will, I.; Xiang, R.

2007-07-01

190

The radio-frequency design of an iris-type coupler for the CPHS radio-frequency quadrupole  

NASA Astrophysics Data System (ADS)

The Compact Pulsed Hadron Source (CPHS) project is a university-based proton accelerator platform (13 MeV, 16 kW, 50 mA peak current, 0.5 ms pulse width at 50 Hz) for multi-disciplinary neutron and proton applications. The CPHS linac consists of a 3 MeV radio-frequency quadrupole (RFQ) linac and a 13 MeV drift tube linac (DTL). Both the RFQ and DTL share a 325 MHz, 2.1 MW klystron source. A single iris-type radio-frequency (RF) coupler is used to feed 537 kW of RF power to the RFQ cavity. Three-dimensional electromagnetic models of the ridge-loaded tapered waveguide (RLWG) and the coupler-cavity system are presented, and the design process and results of the RLWG and iris plate are described in detail.

Xiong, Zheng-Feng; Zheng, Shu-Xin; Xing, Qing-Zi; Guan, Xia-Ling

2012-01-01

191

Optical frequency comb technology for ultra-broadband radio-frequency photonics  

E-print Network

The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology, covering a myriad of applications, from molecular spectroscopy to laser ranging and optical communications. However, the ideal characteristics of an optical frequency comb are application dependent. In this review, the different techniques for the generation and processing of high-repetition-rate (>10 GHz) optical frequency combs with technologies compatible with optical communication equipment are covered. Particular emphasis is put on the benefits and prospects of this technology in the general field of radio-frequency photonics, including applications in high-performance microwave photonic filtering, ultra-broadband coherent communications, and radio-frequency arbitrary waveform generation.

Torres-Company, Victor

2014-01-01

192

The highest frequency detection of a radio relic: 16 GHz AMI observations of the `Sausage' cluster  

NASA Astrophysics Data System (ADS)

We observed the cluster CIZA J2242.8+5301 with the Arcminute Microkelvin Imager at 16 GHz and present the first high radio-frequency detection of diffuse, non-thermal cluster emission. This cluster hosts a variety of bright, extended, steep-spectrum synchrotron-emitting radio sources, associated with the intracluster medium, called radio relics. Most notably, the northern, Mpc-wide, narrow relic provides strong evidence for diffusive shock acceleration in clusters. We detect a puzzling, flat-spectrum, diffuse extension of the southern relic, which is not visible in the lower radio-frequency maps. The northern radio relic is unequivocally detected and measures an integrated flux of 1.2 ± 0.3 mJy. While the low-frequency (<2 GHz) spectrum of the northern relic is well represented by a power law, it clearly steepens towards 16 GHz. This result is inconsistent with diffusive shock acceleration predictions of ageing plasma behind a uniform shock front. The steepening could be caused by an inhomogeneous medium with temperature/density gradients or by lower acceleration efficiencies of high energy electrons. Further modelling is necessary to explain the observed spectrum.

Stroe, Andra; Rumsey, Clare; Harwood, Jeremy J.; van Weeren, Reinout J.; Röttgering, Huub J. A.; Saunders, Richard D. E.; Sobral, David; Perrott, Yvette C.; Schammel, Michel P.

2014-06-01

193

RFID Transponders' Radio Frequency Emissions in Aircraft Communication and Navigation Radio Bands  

NASA Technical Reports Server (NTRS)

Radiated emissions in aircraft communication and navigation bands are measured from several active radio frequency identification (RFID) tags. The individual tags are different in design and operations. They may also operate in different frequency bands. The process for measuring the emissions is discussed, and includes tag interrogation, reverberation chamber testing, and instrument settings selection. The measurement results are described and compared against aircraft emission limits. In addition, interference path loss for the cargo bays of passenger aircraft is measured. Cargo bay path loss is more appropriate for RFID tags than passenger cabin path loss. The path loss data are reported for several aircraft radio systems on a Boeing 747 and an Airbus A320.

Nguyen, Truong X.; Ely, Jay J.; Williams, Reuben A.; Koppen, Sandra V.; Salud, Maria Theresa P.

2006-01-01

194

Ross Ice Shelf in situ radio-frequency ice attenuation  

E-print Network

We have measured the in situ average electric field attenuation length for radio-frequency signals broadcast vertically through the Ross Ice Shelf. We chose a location, Moore Embayment, south of Minna Bluff, known for its high reflectivity at the ice-sea interface. We confirmed specular reflection and used the return pulses to measure the average attenuation length from 75-1250 MHz over the round-trip distance of 1155 m. We find the average electric field attenuation length to vary from 500 m at 75 MHz to 300 m at 1250 MHz, with an experimental uncertainty of 55 to 15 m. We discuss the implications for neutrino telescopes that use the radio technique and include the Ross Ice Shelf as part of their sensitive volume.

Barrella, Taylor; Saltzberg, David

2010-01-01

195

A very low frequency radio astronomy observatory on the Moon  

NASA Technical Reports Server (NTRS)

Because of terrestrial ionospheric absorption, very little is known of the radio sky beyond 10 m wavelength. An extremely simple, low cost very low frequency radio telescope is proposed, consisting of a large array of short wires laid on the lunar surface, each wire equipped with an amplifier and a digitizer, and connected to a common computer. The telescope could do simultaneous multifrequency observations of much of the visible sky with high resolution in the 10 to 100 m wavelength range, and with lower resolution in the 100 to 1000 m range. It would explore structure and spectra of galactic and extragalactic point sources, objects, and clouds, and would produce detailed quasi-three-dimensional mapping of interstellar matter within several thousand parsecs of the Sun.

Douglas, James N.; Smith, Harlan J.

1988-01-01

196

Ross Ice Shelf in situ radio-frequency ice attenuation  

E-print Network

We have measured the in situ average electric field attenuation length for radio-frequency signals broadcast vertically through the Ross Ice Shelf. We chose a location, Moore Embayment, south of Minna Bluff, known for its high reflectivity at the ice-sea interface. We confirmed specular reflection and used the return pulses to measure the average attenuation length from 75-1250 MHz over the round-trip distance of 1155 m. We find the average electric field attenuation length to vary from 500 m at 75 MHz to 300 m at 1250 MHz, with an experimental uncertainty of 55 to 15 m. We discuss the implications for neutrino telescopes that use the radio technique and include the Ross Ice Shelf as part of their sensitive volume.

Taylor Barrella; Steven Barwick; David Saltzberg

2010-11-02

197

Radio frequency needle hyperthermia of normal and cancerous animal tissue  

NASA Astrophysics Data System (ADS)

Capacitative radio frequency (RF) was met with little success when used to treat human cancer. Conductive rf needle hyperthermia (RFNH) is used successfully for human tissue ablation in neurosurgery, cardiology, and recently in urology. RFNH ablates tissue by causing thermal damage limited to the vicinity of the rf needle. We conducted a series of studies to evaluate the effect of RFNH on cancerous and normal tissue. RFNH was applied to normal porcine livers during open surgery. Liver function tests were elevated two days post treatment, then returned to normal. Pigs were sequentially sacrificed. RFNH induced lesions were found to be maximal in size on days 2 - 4 post treatment and later became smaller as liver regenerated. Phase 2 included mice bearing two subcutaneous murine bladder tumors (MBT2). The rf needle was inserted into both tumors of each mouse, but rf current was applied to one tumor only. Energies of 3 to 7.5 watts were applied for 30 seconds to 5 minutes using a 0.02 inch needle. Mice were sacrificed 0, 1, and 3 days after treatment. Necrotic lesions 0.5 - 1.2 cm in diameter were found within the treated tumors. In phase 3, mice bearing a single 8 - 18 mm subcutaneous tumor were treated by RFNH aiming for complete tumor destruction. All control mice died of huge tumors within 31 days. Treated mice were alive with no signs of tumor when sacrificed 60 days after treatment. In phase 3 RFNH is capable of complete tumor eradication with little damage to surrounding normal tissue. It may have clinical applications for percutaneous endoscopic and laparoscopic treatment of tumors.

Shalhav, Arieh; Ramon, J.; Goldwasser, Benad; Nativ, Ofer; Cherniack, Ramy; Zajdel, Liliana

1994-12-01

198

H- radio frequency source development at the Spallation Neutron Source.  

PubMed

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ?38 mA peak current in the linac and an availability of ?90%. H(-) beam pulses (?1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ?60 kW) of a copper antenna that has been encased with a thickness of ?0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ?99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ?75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance?installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ?100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence. PMID:22380234

Welton, R F; Dudnikov, V G; Gawne, K R; Han, B X; Murray, S N; Pennisi, T R; Roseberry, R T; Santana, M; Stockli, M P; Turvey, M W

2012-02-01

199

H- radio frequency source development at the Spallation Neutron Sourcea)  

NASA Astrophysics Data System (ADS)

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ˜38 mA peak current in the linac and an availability of ˜90%. H- beam pulses (˜1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ˜60 kW) of a copper antenna that has been encased with a thickness of ˜0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ˜99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ˜75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance/installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ˜100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

Welton, R. F.; Dudnikov, V. G.; Gawne, K. R.; Han, B. X.; Murray, S. N.; Pennisi, T. R.; Roseberry, R. T.; Santana, M.; Stockli, M. P.; Turvey, M. W.

2012-02-01

200

Power absorption in electrically asymmetric dual frequency capacitive radio frequency discharges  

SciTech Connect

The symmetry of capacitive radio frequency discharges can be controlled via the electrical asymmetry effect by driving one electrode with a fundamental frequency and its second harmonic. In such electrically asymmetric discharges, the mean ion energies at both electrodes are controlled separately from the ion flux by tuning the phase angle {theta} between the harmonics at fixed voltage amplitudes. Here, the question why the ion flux is nearly independent of {theta} is answered by investigating the power absorbed by the electrons P{sub e} as a function of {theta} and time experimentally, by a particle in cell simulation, and an analytical model. The dynamics of P{sub e} is understood by the model and is found to be strongly affected by the choice of {theta}. However, on time average, P{sub e} is nearly constant, independently of {theta}. Thus, the ion flux remains approximately constant. In addition, it is shown that the absolute value of the individual voltages across the powered and grounded electrode sheath vary linearly with the dc self-bias. However, their sum remains constant. This yields, in combination with the constancy of the ion flux, a constant power absorbed by the ions and, in conclusion, a total power absorption that is independent of {theta}.

Schuengel, E.; Czarnetzki, U. [Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Schulze, J. [Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44780 Bochum (Germany); Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary); Donko, Z. [Research Institute for Solid State Physics and Optics, Hungarian Academy of Sciences, P.O. Box 49, 1525 Budapest (Hungary)

2011-01-15

201

Comparative Study of Frequency Agile Data Transmission Schemes for Cognitive Radio Transceivers  

E-print Network

Comparative Study of Frequency Agile Data Transmission Schemes for Cognitive Radio Transceivers agile data transmission schemes employed by cognitive radio transceivers for use in dynamic spectrum requirements and conditions1 are known as cognitive radios [4]. With re- cent developments in cognitive radio

Kansas, University of

202

Faraday accelerator with radio-frequency assisted discharge (FARAD)  

NASA Astrophysics Data System (ADS)

A new electrodeless accelerator concept, called Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD), that relies on an RF-assisted discharge to produce a plasma, an applied magnetic field to guide the plasma into the acceleration region, and an induced current sheet to accelerate the plasma, is presented. The presence of a preionized plasma allows for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts. A proof-of-concept experiment, supported by optical and probe diagnostics, was constructed and used to demonstrate the main features of the FARAD and to gain physical insight into the low-voltage, low-energy current sheet formation and acceleration processes. Magnetic field data indicate that the peak sheet velocity in this unoptimized configuration operating at a pulse energy of 78.5 J is 12 km/s. It is found that changes in the background gas pressure and applied field affect the initial preionized plasma distribution which, in turn, affects the sheet's initial location, relative magnetic impermeability and subsequent velocity history. The results of the experimental investigation motivated further theoretical and numerical investigations of pulsed inductive plasma acceleration. A model consisting of a set of coupled circuit equations and a one-dimensional momentum equation was nondimensionalized leading to the identification of several scaling parameters. Numerical analysis revealed the benefits of underdamped current waveforms and led to an efficiency maximization criterion that requires matching the external circuit's natural period to the acceleration timescale. Predictions of the model were compared to experimental measurements and were found to be in good qualitative agreement and reasonable quantitative agreement for most quantities. A set of design rules aimed at producing a high-performance FARAD thruster are derived using the modeling results and physical insights. The rules concern the optimization of each of the major processes in FARAD: plasma acceleration, current sheet formation, applied field generation, and mass injection and preionization, and are cast as specific prescriptions for the dynamic impedance, inductance change, circuit damping, plasma collisionality (or magnetization), magnetic field strength and topology, and intra-pulse sequencing.

Polzin, Kurt Alexander

203

High-resolution radio study of SNR IC443 at low radio frequencies  

E-print Network

We investigated in detail the morphology at low radio frequencies of the supernova remnant IC443 and accurately established its radio continuum spectral properties. We used the VLA in multiple configurations to produce high resolution radio images of IC443 at 74 and 330 MHz. The changes with position in the radio spectral index were correlated with data in near infrared from 2MASS, in gamma-rays from VERITAS, and with the molecular 12^CO line emission. The new image at 74 MHz has HPBW=35", rms=30 mJy/beam and at 330 MHz HPBW= 17" and rms=1.7 mJy/beam. The integrated flux densities for the whole SNR are S_74MHz=470+/-51 Jy and S_330MHz=248+/-15 Jy. For the pulsar wind nebula associated with the compact source CXOUJ061705.3+222127, we calculated S_330MHz=0.23+/-0.05 Jy, S_1420MHz=0.20+/-0.04 Jy, and alpha~0.0. Substantial variations are observed in spectral index between 74 and 330 MHz across IC443. The flattest spectral components (-0.25< alpha<-0.05) coincide with the brightest parts of the SNR along th...

Castelletti, G; Clarke, T; Kassim, N E

2011-01-01

204

Radio-frequency ablation electrode displacement elastography: A phantom study  

PubMed Central

This article describes the evaluation of a novel method of tissue displacement for use in the elastographic visualization of radio-frequency (rf) ablation-induced lesions. The method involves use of the radio-frequency ablation electrode as a displacement device, which provides localized compression in the region of interest. This displacement mechanism offers the advantage of easyin vivo implementation since problems such as excessive lateral and elevational displacements present when using external compression are reduced with this approach. The method was tested on a single-inclusion tissue-mimicking phantom containing a radio-frequency ablation electrode rigidly attached to the inclusion center. Full-frame rf echo signals were acquired from the phantom before and after electrode displacements ranging from 0.05 to 0.2 mm. One-dimensional cross-correlation analysis between pre-and postcompression signals was used to measure tissue displacements, and strains were determined by computing the gradient of the displacement. The strain contrast, contrast-to-noise ratio, and signal-to-noise ratio were estimated from the resulting strain images. Comparisons are drawn between the elastographically measured dimensions and those known a priori for the single-inclusion phantom. Electrode displacement elastography was found to slightly underestimate the inclusion dimensions. The method was also tested on a second tissue-mimicking phantom and on in vitro rf-ablated lesions in canine liver tissue. The results validate previous in vivo findings that electrode displacement elastography is an effective method for monitoring rf ablation. PMID:18649476

Bharat, Shyam; Varghese, Tomy; Madsen, Ernest L.; Zagzebski, James A.

2008-01-01

205

Occupational exposure to radio-frequency electromagnetic fields  

SciTech Connect

The paper considers occupational exposure to radio-frequency (RF) electromagnetic (EM) fields in industrial processes in near-field situations where electric and magnetic field strengths are monitored to assess the health hazard. Plastic materials are joined by an RF machine whose electrodes are not shielded and which may produce high level RF fields in the immediate vicinity, exceeding the ANSI standard. A physiotherapist may be exposed to high E and H fields using RF shortwave therapy, the maintenance personnel in FM/TV broadcast towers are subject to intense RF fields, and induction heating equipment used for forging, annealing and brazing can expose operators' hands to magnetic fields.

Mild, K.H.

1980-01-01

206

Moving target indication in the presence of radio frequency interference  

NASA Astrophysics Data System (ADS)

Moving target indication (MTI) is greatly complicated by the presence of radio frequency interference (RFI) which 'rings' the MTI filter causing false alarms. This effect is particularly important in radars with a limited number of coherent bursts on target. A subclutter RFI processing (SRP) technique has been developed to allow effective MTI processing in the presence of impulsive RFI. This technique does not have the sensitivity gap characteristic of conventional 'RFI detectors'. Thus, RFI induced false alarms can be effectively eliminating while still maintaining useful subclutter target visibility. The SRP technique has been analyzed by Monte Carlo simulation and by experiments conducted with recorded coherent radar signals.

Fong, E.; Walker, J. A.; Bath, W. G.

207

Towards optimization of probe placement for radio-frequency ablation.  

PubMed

We present a model for the optimal placement of mono- and bipolar probes in radio-frequency (RF) ablation. The model is based on a numerical computation of the probe's electric potential and of the steady state of the heat distribution during RF ablation. The optimization is performed by minimizing a temperature based objective functional under these constraining equations. The paper discusses the discretization and implementation of the approach. Finally, applications of the optimization to artificial data and a comparison to a real RF ablation are presented. PMID:17354926

Altrogge, Inga; Kröger, Tim; Preusser, Tobias; Büskens, Christof; Pereira, Philippe L; Schmidt, Diethard; Weihusen, Andreas; Peitgen, Heinz-Otto

2006-01-01

208

Plasma plume propagation characteristics of pulsed radio frequency plasma jet  

SciTech Connect

A 4 cm long helium cold atmospheric pressure plasma jet with pulsed radio frequency (rf) excitation was obtained by a copper electrode inside a quartz tube. The plasma bullet propagation characteristics common to the microseconds direct current pulse and kilohertz plasma jet is not observed in this case. The space-, time-, and wavelength-resolved optical emission profiles suggest the pulsed rf plasma channel out of the tube was strengthened by ions and metastables with longer life time than the rf period, and the plasma propagation was actually an illumination of the plasma channel caused by energetic electrons accelerated along the channel.

Liu, J. H.; Liu, X. Y.; Hu, K.; Liu, D. W.; Lu, X. P. [Advanced Electromagnetic Engineering and Technology Laboratory, Huazhong University of Science and Technology, WuHan, HuBei 430074 (China); Iza, F.; Kong, M. G. [Department of Electronic and Electrical Engineering, Loughborough University, Leicestershire LE11 3TU (United Kingdom)

2011-04-11

209

Primary lung cancer: treatment with radio-frequency thermal ablation.  

PubMed

Primary lung cancer is the most frequently diagnosed malignancy in the world and the leading cause of death from cancer [1]. When the initial diagnosis is made, most cases are inoperable or the patients' condition does not permit surgical interventions [2]. For patients with inoperable lung cancer, percutaneous radio-frequency thermal ablation (RFA) under CT guidance represents an alternative and minimally invasive treatment. It can also be applied in combination with radiation therapy and chemotherapy. We report three cases treated by percutaneous CT-guided RF ablation, from which two had post-operative recurrent tumor and one was inoperable. PMID:14666377

Thanos, L; Mylona, S; Pomoni, M; Kalioras, V; Zoganas, L; Batakis, N

2004-05-01

210

Development of a radio frequency surface contour mapping system  

SciTech Connect

A radio-frequency based system is being developed for imaging the top surface of the contents of vessels used in coal processes including lockhoppers, gasifiers, and mixing chambers. The system will be designed to image a minimum of 25 pixels with a depth resolution of {+-}1 inch over ranges of 4 to 30 feet. The system must tolerate harsh environments as found in coal gasifiers with temperatures up to 1800 F and pressures up to 600 psig. The system will provide both a visual readout of the contour of the upper surface of a vessel`s contents via a computer monitor and a data interface to the process control system.

Buttermore, W.H.; Weber, W.H.; Straszheim

1994-10-01

211

Plasma sheath thickness in radio-frequency discharges  

NASA Astrophysics Data System (ADS)

The radio-frequency glow discharges of several kinds of gases were examined to measure the ion sheath thickness at the cathode electrode. At intermediate gas pressures around 0.05- 0.5 Torr, the sheath thickness d depends on the pressure P in the expression P1/2d=K0 for almost all of the discharges examined. It was also pointed out that the constant K0 value decreased linearly against a mass of the predominant ion in the plasma. The discrepancy between the sheath thickness measured in this work and by theoretical solution was discussed for the argon discharge.

Mutsukura, Nobuki; Kobayashi, Kenji; Machi, Yoshio

1990-09-01

212

Detection of NMR signals with a radio-frequency atomic magnetometer I.M. Savukov 1  

E-print Network

Detection of NMR signals with a radio-frequency atomic magnetometer I.M. Savukov 1 , S.J. Seltzer of proton NMR signals with a radio-frequency (rf) atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic

Romalis, Mike

213

Practical Frequency Synchronization Scheme in an Open Software Radio TD-SCDMA System  

Microsoft Academic Search

This paper concerns how to achieve the initial frequency acquisition and frequency tracking in an open software radio TD-SCDMA platform, which consists of several common PCs and universal software radio peripheral. In this proposal, at the stage of frequency acquisition, the frequency difference between the base station and the terminal can be reduced step by step, by adjusting the size

Lin Huang; Hanwen Cao; Kan Zheng; G. Decarreau

2007-01-01

214

arXiv:astro-ph/0309647v123Sep2003 Hydra A at Low Radio Frequencies  

E-print Network

arXiv:astro-ph/0309647v123Sep2003 Hydra A at Low Radio Frequencies W.M. Lane Naval Research Lab present new, low-frequency images of the powerful FR I radio galaxy Hydra A (3C 218). Images were made: galaxies 1. Introduction Hydra A (3C 218) is a high luminosity Fanaroff- Riley type I (FR I) radio galaxy

Taylor, Greg

215

Vandermonde-subspace Frequency Division Multiplexing for Two-Tiered Cognitive Radio  

E-print Network

Vandermonde-subspace Frequency Division Multiplexing for Two-Tiered Cognitive Radio Networks--Vandermonde-subspace frequency division multi- plexing (VFDM) is an overlay spectrum sharing technique for cognitive radio. VFDM/Hz over cognitive radio systems based on unused band detection. We also present some key design parameters

Paris-Sud XI, Université de

216

Jupiter's low-frequency radio spectrum from Cassini\\/Radio and Plasma Wave Science (RPWS) absolute flux density measurements  

Microsoft Academic Search

We apply the calibration method developed by Dulk et al. [2001] to the data from the Cassini\\/Radio and Plasma Wave Science (RPWS) High-Frequency Receiver in order to derive flux density measurements of six components of the Jovian low-frequency radio spectrum over the full frequency range of the instrument (3.5 kHz to 16.1 MHz). The estimated accuracy is better than 50%,

P. Zarka; B. Cecconi; W. S. Kurth

2004-01-01

217

Radio Frequency Station - Beam Dynamics Interaction in Circular Accelerators  

SciTech Connect

The longitudinal beam dynamics in circular accelerators is mainly defined by the interaction of the beam current with the accelerating Radio Frequency (RF) stations. For stable operation, Low Level RF (LLRF) feedback systems are employed to reduce coherent instabilities and regulate the accelerating voltage. The LLRF system design has implications for the dynamics and stability of the closed-loop RF systems as well as for the particle beam, and is very sensitive to the operating range of accelerator currents and energies. Stability of the RF loop and the beam are necessary conditions for reliable machine operation. This dissertation describes theoretical formalisms and models that determine the longitudinal beam dynamics based on the LLRF implementation, time domain simulations that capture the dynamic behavior of the RF station-beam interaction, and measurements from the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC) that validate the models and simulations. These models and simulations are structured to capture the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They also provide the opportunity to study diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven instabilities and single bunch longitudinal emittance growth. Coupled-bunch instabilities and RF station power were the performance limiting effects for PEP-II. The sensitivity of the instabilities to individual LLRF parameters, the effectiveness of alternative operational algorithms, and the possible tradeoffs between RF loop and beam stability were studied. New algorithms were implemented, with significant performance improvement leading to a world record current during the last PEP-II run of 3212 mA for the Low Energy Ring. Longitudinal beam emittance growth due to RF noise is a major concern for LHC. Simulations studies and measurements were conducted that clearly show the correlation between RF noise and longitudinal bunch emittance, identify the major LLRF noise contributions, and determine the RF component dominating this effect. With these results, LHC upgrades and alternative algorithms are evaluated to reduce longitudinal emittance growth during operations. The applications of this work are described with regard to future machines and analysis of new technical implementations, as well as to possible future work which would continue the directions of this dissertation.

Mastoridis, Themistoklis; /Stanford U., Elect. Eng. Dept. /SLAC

2011-03-01

218

The electrical asymmetry effect in capacitively coupled radio-frequency discharges  

NASA Astrophysics Data System (ADS)

We present an analytical model to describe capacitively coupled radio-frequency (CCRF) discharges and the electrical asymmetry effect (EAE) based on the non-linearity of the boundary sheaths. The model describes various discharge types, e.g. single and multi-frequency as well as geometrically symmetric and asymmetric discharges. It yields simple analytical expressions for important plasma parameters such as the dc self-bias, the uncompensated charge in both sheaths, the discharge current and the power dissipated to electrons. Based on the model results the EAE is understood. This effect allows control of the symmetry of CCRF discharges driven by multiple consecutive harmonics of a fundamental frequency electrically by tuning the individual phase shifts between the driving frequencies. This novel class of capacitive radio-frequency (RF) discharges has various advantages: (i) A variable dc self-bias can be generated as a function of the phase shifts between the driving frequencies. In this way, the symmetry of the sheaths in geometrically symmetric discharges can be broken and controlled for the first time. (ii) Almost ideal separate control of ion energy and flux at the electrodes can be realized in contrast to classical dual-frequency discharges driven by two substantially different frequencies. (iii) Non-linear self-excited plasma series resonance oscillations of the RF current can be switched on and off electrically even in geometrically symmetric discharges. Here, the basics of the EAE are introduced and its main applications are discussed based on experimental, simulation, and modeling results.

Czarnetzki, U.; Schulze, J.; Schüngel, E.; Donkó, Z.

2011-04-01

219

Nonlinear frequency coupling in dual radio-frequency driven atmospheric pressure plasmas  

SciTech Connect

Plasma ionization, and associated mode transitions, in dual radio-frequency driven atmospheric pressure plasmas are governed through nonlinear frequency coupling in the dynamics of the plasma boundary sheath. Ionization in low-power mode is determined by the nonlinear coupling of electron heating and the momentary local plasma density. Ionization in high-power mode is driven by electron avalanches during phases of transient high electric fields within the boundary sheath. The transition between these distinctly different modes is controlled by the total voltage of both frequency components.

Waskoenig, J.; Gans, T. [Centre for Plasma Physics, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

2010-05-03

220

Hermetic aluminum radio frequency interconnection and method for making  

SciTech Connect

The present invention provides a light-weight, hermetic coaxial radio-frequency (RF) interconnection having an electrically conductive outer housing made of aluminum or an aluminum alloy, a central electrical conductor made of ferrous or non-ferrous material, and a cylinder of dielectric material comprising a low-melting-temperature, high-thermal-expansion aluminophosphate glass composition for hermetically sealing between the aluminum-alloy outer housing and the ferrous or non-ferrous center conductor. The entire RF interconnection assembly is made permanently hermetic by thermally fusing the center conductor, glass, and housing concurrently by bringing the glass to the melt point by way of exposure to an atmospheric temperature sufficient to melt the glass, less than 540 C, but that does not melt the center conductor or the outer aluminum or aluminum alloy housing. The composition of the glass used is controlled to provide a suitable low dielectric constant so that an appropriate electrical characteristic impedance, for example 50 ohms, can be achieved for an electrical interconnection that performs well at high radio frequencies and also provides an interconnection maintaining a relatively small physical size.

Kilgo, R.D.; Kovacic, L.; Brow, R.K.

2000-03-14

221

Microminiature radio frequency transmitter for communication and tracking applications  

NASA Astrophysics Data System (ADS)

A micro-miniature radio frequency (rf) transmitter has been developed and demonstrated by the Oak Ridge National Laboratory. The objective of the rf transmitter development was to maximize the transmission distance while drastically shrinking the overall transmitter size, including antenna. Based on analysis and testing, an application-specific integrated circuit (ASIC) with a 16-GHz gallium arsenide (GaAs) oscillator and integrated on-chip antenna was designed and fabricated using microwave monolithic integrated circuit (MMIC) technology. Details of the development and the results of various field tests are discussed. The rf transmitter is applicable to covert surveillance and tracking scenarios due to its small size of 2.2 multiplied by 2.2 mm, including the antenna. Additionally, the 16-GHz frequency is well above the operational range of consumer-grade radio scanners, providing a degree of protection from unauthorized interception. Variations of the transmitter design have been demonstrated for tracking and tagging beacons, transmission of digital data, and transmission of real-time analog video from a surveillance camera. Preliminary laboratory measurements indicate adaptability to direct-sequence spread-spectrum transmission, providing a low probability of intercept and/or detection. Concepts related to law enforcement applications are presented.

Crutcher, Richard I.; Emery, Mike S.; Falter, Kelly G.; Nowlin, C. H.; Rochelle, Jim M.; Clonts, Lloyd G.

1997-02-01

222

Hermetic aluminum radio frequency interconnection and method for making  

DOEpatents

The present invention provides a light-weight, hermetic coaxial radio-frequency (RF) interconnection having an electrically conductive outer housing made of aluminum or an aluminum alloy, a central electrical conductor made of ferrous or non-ferrous material, and a cylinder of dielectric material comprising a low-melting-temperature, high-thermal-expansion aluminophosphate glass composition for hermetically sealing between the aluminum-alloy outer housing and the ferrous or non-ferrous center conductor. The entire RF interconnection assembly is made permanently hermetic by thermally fusing the center conductor, glass, and housing concurrently by bringing the glass to the melt point by way of exposure to an atmospheric temperature sufficient to melt the glass, less than 540.degree. C., but that does not melt the center conductor or the outer aluminum or aluminum alloy housing. The composition of the glass used is controlled to provide a suitable low dielectric constant so that an appropriate electrical characteristic impedance, for example 50 ohms, can be achieved for an electrical interconnection that performs well at high radio frequencies and also provides an interconnection maintaining a relatively small physical size.

Kilgo, Riley D. (Albuquerque, NM); Kovacic, Larry (Albuquerque, NM); Brow, Richard K. (Rolla, MO)

2000-01-01

223

Radio-Frequency Spectroscopy of a Strongly Interacting Two-Dimensional Fermi Gas  

SciTech Connect

We realize and study a strongly interacting two-component atomic Fermi gas confined to two dimensions in an optical lattice. Using radio-frequency spectroscopy we measure the interaction energy of the strongly interacting gas. We observe the confinement-induced Feshbach resonance on the attractive side of the 3D Feshbach resonance and find the existence of confinement-induced molecules in very good agreement with theoretical predictions.

Froehlich, Bernd; Feld, Michael; Vogt, Enrico; Koschorreck, Marco; Koehl, Michael [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB30HE (United Kingdom); Zwerger, Wilhelm [Technische Universitaet Muenchen, Physik Department, James-Franck-Strasse, 85748 Garching (Germany)

2011-03-11

224

Design and characterization of a radio-frequency dc/dc power converter  

E-print Network

The use of radio-frequency (RF) amplifier topologies in dc/dc power converters allows the operating frequency to be increased by more than two orders of magnitude over the frequency of conventional converters. This enables ...

Jackson, David A. (David Alexander)

2005-01-01

225

New synchronization method of arbitrary different radio frequencies in accelerators  

NASA Astrophysics Data System (ADS)

In electron accelerator facilities, radio frequencies for a linac accelerator and a circular accelerator including a booster synchrotron ring and a storage ring are completely different. In order to improve the beam transmission efficiency from a linac to a circular accelerator, and to make the beam intensity constant, both rf's are generally synchronized. This method is well known and uses a common subharmonic frequency of around 10 MHz. The rf's used are generated by using a frequency multiplier from the common frequency, and they are continuously generated. We paid attention to the fact that the electron beam from a linac accelerator is always pulsed, and the rf of the linac requires only a moment during beam emission and acceleration. Taking this fact into account, we invented a new synchronization method for the rf's of both the linac and the circular accelerators. The new method is explained by describing a concrete example at the synchrotron radiation facility, SPring-8 (Super Photon ring 8 GeV). A 2856 MHz rf for the linac is generated by 508.58 MHz rf of the storage ring for a short duration of about 290 ?s. Thus, the phase difference between the two rf's is automatically fixed. This method can be applied to any combination of arbitrary different rf's.

Kawashima, Y.; Asaka, T.; Takashima, T.

2001-08-01

226

High frequency energy measurements  

SciTech Connect

High-frequency (> 100 MHz) energy measurements present special problems to the experimenter. Environment or available electronics often limit the applicability of a given detector type. The physical properties of many detectors are frequency dependent and in some cases, the physical effect employed can be frequency dependent. State-of-the-art measurements generally involve a detection scheme in association with high-speed electronics and a method of data recording. Events can be single or repetitive shot requiring real time, sampling, or digitizing data recording. Potential modification of the pulse by the detector and the associated electronics should not be overlooked. This presentation will review typical applications, methods of choosing a detector, and high-speed detectors. Special considerations and limitations of some applications and devices will be described.

Stotlar, S.C.

1981-01-01

227

analysis and design of metal-surface mounted radio frequency identification (RFID) transponders  

Microsoft Academic Search

With the development of the radio frequency integrated circuit (RFIC), contactless radio frequency identification (RFID) technology, as one of the fastest growing sectors of automatic identification procedures (Auto-ID), gains broad application in tracking assets in supply chain management. However, one of the largest challenges for the RFID industry is that the ultra high frequency (UHF) RFID transponder doesn't function well

Sanyi Zhan

2008-01-01

228

High Q radio frequency circuits employing a superconductive layer on a thermally matched aggregate metallic substrate  

Microsoft Academic Search

High Q radio frequency circuits such as reference cavity resonators for frequency standards and coupled cavity circuits for linear accelerators are disclosed. Such circuits comprise a radio frequency wave supporting structure formed by a superconductive layer deposited upon or otherwise formed on a metallic substrate member. The substrate is matched to the coefficient of linear thermal expansion of the superconductive

1969-01-01

229

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance  

E-print Network

Subfemtotesla radio-frequency atomic magnetometer for detection of nuclear quadrupole resonance S 20 November 2006 A radio-frequency tunable atomic magnetometer is developed for detection of nuclearHz 14 N NQR frequency of ammonium nitrate. A potential application of the magnetometer is detection

Romalis, Mike

230

Controlling the electromagnetically induced transparency frequency tuning range by radio-frequency field  

NASA Astrophysics Data System (ADS)

The Electromagnetically Induced Transparency (EIT) is associated with a ? three-level system and the spectral position of EIT window can be changed by varying the frequency of the coupling field, however, at large detuning the EIT will evolve into a dispersion-like feature and transparency property of EIT become less obvious. In this paper, it is shown that we can perform EIT frequency tuning by a radio-frequency (rf) field. In the cascade quasic-? four-level system, the absorption profile of probe field is calculated by solving the equations of motion of the density matrix. It is shown that the Autler-Townes doublet originates from the rf-field induced dynamic Stark effect and the spectral position of EIT window is determined by the frequency detuning of the coupling field. When the frequency detuning of the coupling field is half of the rf Rabi frequency, the EIT feature remain its absorptive profile. The frequency tuning rang of EIT is determined by the rf Rabi frequency, and can be explained using a dressed-state analysis. Therefore, frequency tuning range of EIT can be controlled by the rf Rabi frequency.

Zhang, Lianshui; Zhuang, Zhonghong; Wang, Jian; Feng, Xiaomin; Yang, Lijun

2008-01-01

231

Very low frequency radio astronomy from lunar orbit  

NASA Astrophysics Data System (ADS)

This paper discusses the use of very low frequency aperture synthesis as a probe of astrophysical phenomena. Specifically, the science achievable with the Lunar Observer Radio Astronomy Experiment (LORAE) is discussed. The density distribution and the degree of turbulence of the galactic plasma can be determined from its effect on background radio sources. These same absorption phenomena can be used to determine magnetic field strengths within astrophysical plasmas. Detection of unabsorbed synchrotron emission can provide information on the relativistic plasma component. The detection of new pulsars may prove feasible because of their steep spectra. Observations of planets in the solar system will be used to study their interaction with the solar wind. VLF studies of the sun will provide new information on the outer layers of its atmosphere and magnetic field as well as provide insight on the propagation of MHD disturbances through the corona. The plasma in the earth's magnetic field can be observed in detail and as a function of time. This will prove invaluable in understanding auroral phenomena end reconnection events.

Duric, Nebojsa

232

Radio transmitter energy recovery system  

SciTech Connect

An am transmitter includes an rf signal generator and a switching-type rf signal amplifier. The rf amplifier output depends upon the energizing voltage applied thereacross, so it acts as a modulator. The energizing voltage is produced by a high -power audio amplifier which includes a pulse-width modulator driving a high-power audio switch. The switch terminals are coupled in series with an audio-frequency filter, energizing terminals of the rf amplifier and a source of direct energizing potential, for varying the voltage across the rf amplifier at an audio rate in response to the duty cycle of the width-modulated pulses for audio modulating the rf carrier. In order to reduce modulation distortion at low duty cycles resulting from the finite turn-on and turn-off time of the audio switch, an offset voltage generator is coupled to the filter by a diode. Energy stored in inductive components of the filter cause a voltage pulse during each turn-off of the audio switch. The voltage pulse is coupled to the offset voltage generator by the diode, and the voltage at the filter is maintained at the offset voltage while current flows in the offset voltage generator and the inductors lose energy. The offset generator includes a capacitor for storing energy resulting from the current flow in the inductor. A dc to ac inverter is coupled to the capacitor and generates alternating voltage. The ac is rectified and a pulsating direct current is coupled to the energizing source for recovering the energy in the inductive pulse.

Wolf, R.E.

1982-03-09

233

Radio frequency heating of ceramic windows in fusion applications  

SciTech Connect

Ceramic windows will be used as material barriers for radio frequency plasma heating in fusion reactors. This report examines the theory behind rf heating phenomena. Heating calculations are presented for various window materials, thicknesses, wavelengths, and power densities. The most pertinent material properties are loss tangent, thermal conductivity, dielectric constant, strength, and radiation resistance. Calculations indicate that among candidate materials, beryllium oxide offers the most promise because of its large thermal conductivity and relatively low loss tangent and dielectric constant. On the other hand, beryllia is susceptible to neutron damage, and this may adversely affect its electrical properties. Another promising candidate is sapphire, particularly at lower temperatures where the thermal conductivity is high. Fused silica suffers from low thermal conductivity and large positive temperature coefficient for loss tangent, but it may be useful under some conditions. In summary, calculations of heating can lead to elimination of some candidate materials and selection of others for further study.

Fowler, J.D. Jr.

1981-11-01

234

Superconducting radio-frequency modules test faciilty operating experience  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service Fermilab SRF R&D needs. The first stage of the project has been successfully completed, which allows for distribution of cryogens for a single cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at MDB results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J.; /Fermilab

2007-07-01

235

Superconducting Radio-Frequency Modules Test Facility Operating Experience  

NASA Astrophysics Data System (ADS)

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R&D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service the SRF R&D needs. The project's first stage has been successfully completed, which allows for distribution of cryogens for a single-cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at Meson Detector Building (MDB) results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J.

2008-03-01

236

SUPERCONDUCTING RADIO-FREQUENCY MODULES TEST FACILITY OPERATING EXPERIENCE  

SciTech Connect

Fermilab is heavily engaged and making strong technical contributions to the superconducting radio-frequency research and development program (SRF R and D). Four major SRF test areas are being constructed to enable vertical and horizontal cavity testing, as well as cryomodule testing. The existing Fermilab cryogenic infrastructure has been modified to service the SRF R and D needs. The project's first stage has been successfully completed, which allows for distribution of cryogens for a single-cavity cryomodule using the existing Cryogenic Test Facility (CTF) that houses three Tevatron satellite refrigerators. The cooling capacity available for cryomodule testing at Meson Detector Building (MDB) results from the liquefaction capacity of the CTF cryogenic system. The cryogenic system for a single 9-cell cryomodule is currently operational. The paper describes the status, challenges and operational experience of the initial phase of the project.

Soyars, W.; Bossert, R.; Darve, C.; Degraff, B.; Klebaner, A.; Martinez, A.; Pei, L.; Theilacker, J. [Fermi National Accelerator Laboratory Batavia, IL, 60510 (United States)

2008-03-16

237

NbN thin films for superconducting radio frequency cavities  

NASA Astrophysics Data System (ADS)

NbN thin films have the potential to be incorporated into radio frequency cavities in a multilayer coating to overcome the fundamental field gradient limit of 50 MV m-1 for the bulk niobium based technology that is currently implemented in particle accelerators. In addition to having a larger critical field value than bulk niobium, NbN films develop smoother surfaces which are optimal for cavity performance and lead to fewer losses. Here, we present a study on the correlation of film deposition parameters, surface morphology, microstructure, transport properties and superconducting properties of NbN thin films. We have achieved films with bulk-like lattice parameters and superconducting transition temperatures. These NbN films have a lower surface roughness than similarly grown niobium films of comparable thickness. The potential application of NbN thin films in accelerator cavities is discussed.

Roach, W. M.; Skuza, J. R.; Beringer, D. B.; Li, Z.; Clavero, C.; Lukaszew, R. A.

2012-12-01

238

Energy Efficient Transmissions In MIMO Cognitive Radio Networks  

E-print Network

Energy Efficient Transmissions In MIMO Cognitive Radio Networks Liqun Fu The Institute of Network@ie.cuhk.edu.hk Abstract-In this paper, we consider energy efficient transmis sions for MIMO cognitive radio networks. Index Terms-Cognitive radio networks, MIMO, Energy efficiency. I. INTRODUCTION Cognitive radio, which

Huang, Jianwei

239

Stabilization of Fundamental-Frequency Microwave Oscillators for Radio-Relay Systems (Panel)  

Microsoft Academic Search

Frequency tolerances for microwave communications are presently under study within the International Telecommunications Union (ITU). This is being carried out in preparation for the World Administrative Radio Conference, 1979 (WAKC-79), which will revise the existing Radio Regulations. The International Radio Consultative Committee (CCIR) will hold in the Autumn of 1978, its Special Preparatory Meeting (SPM) for the WARC-79. So far,

F. Ivanek

1978-01-01

240

A new Main Injector radio frequency system for 2.3 MW Project X operations  

SciTech Connect

For Project X Fermilab Main Injector will be required to provide up to 2.3 MW to a neutrino production target at energies between 60 and 120 GeV. To accomplish the above power levels 3 times the current beam intensity will need to be accelerated. In addition the injection energy of Main Injector will need to be as low as 6 GeV. The current 30 year old Main Injector radio frequency system will not be able to provide the required power and a new system will be required. The specifications of the new system will be described.

Dey, J.; Kourbanis, I.; /Fermilab

2011-03-01

241

Latitudinal beaming of Jupiter's low frequency radio emissions  

NASA Technical Reports Server (NTRS)

By comparing RAE-1 and IMP-6 satellite measurements of Jupiter's radio emission near 1MHz with recent Voyager-1 and 2 observations in the same frequency range, the properties of the low frequency radiation pattern over a 10 deg range of latitudes with respect to the Jovian rotation equator can be studied. These observations, which cover a wider latitudinal range than is possible from the earth, are consistent with many aspects of earlier ground-based measurements used to infer a sharp beaming pattern for the decameter wavelength emissions. Marked, systematic changes are found in the statistical occurrence probability distributions with system 3 central meridian longitude as the jovigraphic latitude of the observer changes over this range. Simultaneous observations by the two Voyager spacecraft suggest that the instantaneous beam width may be no more than a few degrees at times. The new hectometer-wave results can be interpreted in terms of a narrow, curved sheet at a fixed magnetic latitude into which the emission is beamed to escape the planet.

Alexander, J. K.; Desch, M. D.; Kaiser, M. L.; Thieman, J. R.

1979-01-01

242

Enhancement of electromagnetic propagation through complex media for Radio Frequency Identification  

E-print Network

In this thesis, I present and examine the fundamental limitations involved in Radio Frequency Identification (RFID) as well as provide a means to improve reader-tag communication in ultra high frequency RFID systems. The ...

Marti, Uttara P

2005-01-01

243

Chapter 7: Radio-Frequency Wave Physics in the FTU  

SciTech Connect

This chapter reports the main physics results obtained with three radio-frequency-injection systems. The frequency of 8 GHz for the lower hybrid (LH) current drive (CD) (LHCD) system was chosen to explore CD at high density: full CD has been demonstrated for central densities up to 1.4 x 10{sup 20} m{sup -3} at 0.5 MA with an applied power up to 2.0 MW. The Frascati Tokamak Upgrade (FTU) database shows CD efficiencies from 0.1 to 0.3 x 10{sup 20} AW{sup -1} m{sup -2}. In combined experiments with electron cyclotron (EC) waves (140 GHz, up to 1.2 MW), a suprathermal absorption by the fast electron tail generated by LHCD has been observed in both downshifted and upshifted interaction regimes, with the resulting electron cyclotron current drive (ECCD) ranging from 20 to 100 kA, depending on experimental conditions. With pure EC resonance heating, the narrowness of the radial power deposition profile has been exploited, resulting in strong local electron heating. Results in high-density regimes are also presented. The third system (433 MHz, 0.5 MW) is the first to test ion Bernstein wave (IBW) coupling with a waveguide antenna. The experiment operates at high frequency, avoiding the occurrence of nonlinear phenomena at the edge. Improved confinement regimes resulting in a central peaking of the pressure profiles have been achieved with P{sub IBW} up to 0.4 MW. Modeling and experimental results are summarized.

Granucci, G. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Airoldi, A. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Barbato, E. [Associazione EURATOM-ENEA sulla Fusione (Italy); Bruschi, A. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Cardinali, A. [Associazione EURATOM-ENEA sulla Fusione (Italy); Castaldo, C. [Associazione EURATOM-ENEA sulla Fusione (Italy); Cesario, R. [Associazione EURATOM-ENEA sulla Fusione (Italy); Cirant, S. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Esposito, B. [Associazione EURATOM-ENEA sulla Fusione (Italy); Farina, D. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Gandini, F. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Giruzzi, G. [Association EURATOM-CEA sur la Fusion (France); Gormezano, C. [Associazione EURATOM-ENEA sulla Fusione (Italy); Leigheb, M. [Associazione EURATOM-ENEA sulla Fusione (Italy); Marinucci, M. [Associazione EURATOM-ENEA sulla Fusione (Italy); Mirizzi, F. [Associazione EURATOM-ENEA sulla Fusione (Italy); Nowak, S. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Panaccione, L. [Associazione EURATOM-ENEA sulla Fusione (Italy); Pericoli-Ridolfini, V. [Associazione EURATOM-ENEA sulla Fusione (Italy); Podda, S. [Associazione EURATOM-ENEA sulla Fusione (Italy); Ramponi, G. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Ravera, G.L. [Associazione EURATOM-ENEA sulla Fusione (Italy); Saveliev, A.N. [A. F. Ioffe Physico-Technical Institute (Russian Federation); Simonetto, A. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Sozzi, C. [Associazione EURATOM-ENEA-CNR sulla Fusione (Italy); Tuccillo, A.A. [Associazione EURATOM-ENEA sulla Fusione (Italy); Zonca, F. [Associazione EURATOM-ENEA sulla Fusione (Italy)

2004-05-15

244

Charge dynamics in capacitively coupled radio frequency discharges  

NASA Astrophysics Data System (ADS)

In a capacitively coupled radio frequency (CCRF) discharge the number of positive and negative charges lost to each electrode must balance within one RF period to ensure a constant total uncompensated charge in the discharge, Qtot, on time average. This balance is the result of a compensation of electron and ion fluxes at each electrode within one RF period. Although Qtot is constant on temporal average, it is time dependent on time scales shorter than one RF period, since it results from a balance of the typically constant ion flux and the strongly time dependent electron flux at each electrode. Nevertheless, Qtot is assumed to be constant in various models. Here the dynamics of Qtot is investigated in a geometrically symmetric CCRF discharge operated in argon at 13.56 and 27.12 MHz with variable phase shift ? between the driving voltages by a PIC simulation and an analytical model. Via the electrical asymmetry effect (EAE) a variable dc self-bias is generated as a function of ?. It is found that Qtot is not temporally constant within the low frequency period, but fluctuates by about 10% around its time average value. This modulation is understood by an analytical model. It is demonstrated that this charge dynamics leads to a phase shift of the dc self-bias not captured by models neglecting the charge dynamics. This dynamics is not restricted to dual frequency discharges. It is a general phenomenon in all CCRF discharges and can generally be described by the model introduced here. Finally, Qtot is split into the uncompensated charges in each sheath. The sheath charge dynamics and the self-excitation of non-linear plasma series resonance oscillations of the RF current via the EAE at low pressures of a few pascals are discussed.

Schulze, J.; Schüngel, E.; Donkó, Z.; Czarnetzki, U.

2010-06-01

245

Room temperature femtotesla radio-frequency atomic magnetometer W. Chalupczak,1  

E-print Network

Room temperature femtotesla radio-frequency atomic magnetometer W. Chalupczak,1 R. M. Godun,1 S online 12 June 2012) A radio-frequency tunable atomic magnetometer with a sensitivity of about 1 fT/Hz1/2 in a range of 10�500 kHz is demonstrated. The magnetometer is operated in the orientation configuration

246

47 CFR 2.803 - Marketing of radio frequency products prior to equipment authorization.  

Code of Federal Regulations, 2013 CFR

...Marketing of radio frequency products prior to equipment authorization...Marketing of radio frequency products prior to equipment authorization...includes sale or lease, or offering for sale or lease...selling or leasing or offering for sale or lease...1) Activities under product development and...

2013-10-01

247

Nonlinear Exothermic Contributions to RadioFrequency Bonding of Adhesives 1  

E-print Network

Nonlinear Exothermic Contributions to Radio­Frequency Bonding of Adhesives 1 H.T. Banks 2 S and Department of Mathematics, Box 8205, North Car­ olina State University, Raleigh, NC 27695­8205. 3 Lord This work describes an effort to model the radio­frequency curing of epoxy adhesives in bonding

248

Exascale Real-Time Radio Frequency Interference Mitigation  

NASA Astrophysics Data System (ADS)

Radio Frequency Interference (RFI) mitigation is extremely important to take advantage of the vastly improved bandwidth, sensitivity, and field-of-view of exascale telescopes. For current instruments, RFI mitigation is typically done offline, and in some cases (partially) manually. At the same time, it is clear that due to the high bandwidth requirements, RFI mitigation will have to be done automatically, and in real-time, for exascale instruments. In general, real-time RFI mitigation will be less precise than offline approaches. Due to memory constraints, there is much less data to work with, typically only in the order of one second or less, as opposed to the entire observation. In addition, we can record only limited statistics of the past. Moreover, we will typically have only few frequency channels locally available at each compute core. Finally, the amount of processing that can be spent on RFI mitigation is extremely limited due to computing and power constraints. Nevertheless, there are potential benefits as well, which include the possibility of working on higher time and frequency resolutions before any integration is done, leading to more accurate results. Most importantly, we can remove RFI before beam forming, which combines data from all receivers. The RFI that is present in the data streams from the separate receivers is also combined, effectively taking the union of all RFI. Thus, the RFI from all receivers pollutes all beams. Therefore, it is essential to do real-time RFI mitigation before the beam former. This is particularly important for pulsar surveys, for instance. modes. Although our techniques are generic, we describe how we implemented real-time RFI mitigation for one of the SKA pathfinders: The Low Frequency Array (LOFAR). The RFI mitigation algorithms and operations we introduce here are extremely fast, and the computational requirements scale linearly in the number of samples and frequency channels. We evaluate the quality of the algorithms with real LOFAR pulsar observations. By comparing the signal-to-noise ratios of the folded pulse profiles, we can quantitatively compare the impact of real-time RFI mitigation, and compare different algorithms.

van Nieuwpoort, Rob; Lofar Team

2014-04-01

249

The driving frequency effects on the atmospheric pressure corona jet plasmas from low frequency to radio frequency  

SciTech Connect

Lately, the atmospheric pressure jet type corona plasma, which has been typically driven by dc to low frequency (LF: several tens of kHz), is often generated by using radio frequency of 13.56 MHz. Yet, the relationship between the plasma and its driving frequency has seldom been investigated. Hence, in this study, dependence of the atmospheric pressure corona plasma characteristics on the driving frequency was explored experimentally from LF to rf (5 kHz-13.56 MHz). The plasmas generated by the driving frequency under 2 MHz were cylindrical shape of several tens of millimeters long while the 13.56 MHz plasma is spherical and a few millimeters long. As the driving frequency was increased, the plasma length became shortened. At the lower driving frequencies (below 2 MHz), the plasmas existed as positive streamer and negative glow for each half period of the applied voltage, but the discharge was more continuous in time for the 13.56 MHz plasma. It was inferred from the measured I-V curves that the higher driving frequency induced higher discharge currents, and the gas temperature was increased as the driving frequency was increased.

Kim, Dan Bee [Division of Physical Metrology, Korea Research Institute of Standards and Science, 209 Gajeongno, Yuseong-gu, Daejeon 305-340 (Korea, Republic of); Jung, H.; Gweon, B.; Rhee, J. K.; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Moon, S. Y. [LG Electronics Advanced Research Institute, 16 Woomyeon-Dong, Seocho-Gu, Seoul 137-724 (Korea, Republic of)

2011-04-15

250

A THz source by up-converting radio frequency with plasma waveguide  

NASA Astrophysics Data System (ADS)

The discharged frequency of a radio frequency (rf) cavity is independent of its charging source frequency and defined only by its geometry. If the dimension of a cavity could be effectively changed during its discharging state, it will emit electromagnetic energy at a different frequency than its charging source frequency. By treating the plasma as a conductor wall, we simulated the process to generate a tunable terahertz (THz) source by putting a hollow conductor wall in an rf cavity. We found that the rf energy trapped inside the "plasma wall" will be effectively converted to a higher frequency electromagnetic wave, whose parameters are determined by the radius, thickness, and density of the wall. Computer simulations have been used to study this process in detail. The study confirms that THz could emit from a discharged rf cavity by properly setting the plasma parameters. It has a great potential to develop a table-top THz source with the technology. Besides, the source will have tunability in phase, amplitude, pulse length, and frequency, which was very desired in many applications and hard to realize.

Wang, Lanfa; Wang, Faya

2014-11-01

251

From T.H. Lee, The Design of CMOS Radio-Frequency Integrated Circuits A Nonlinear History of Radio 1998 Cambridge University Press Page 1 of 34  

E-print Network

From T.H. Lee, The Design of CMOS Radio-Frequency Integrated Circuits A Nonlinear History of Radio ©1998 Cambridge University Press Page 1 of 34 A Nonlinear History of Radio 1.0 Introduction Integrated history of radio touches briefly on just some of the main stories, and provides pointers to the literature

Lee, Thomas H.

252

Manufacture of radio frequency micromachined switches with annealing.  

PubMed

The fabrication and characterization of a radio frequency (RF) micromachined switch with annealing were presented. The structure of the RF switch consists of a membrane, coplanar waveguide (CPW) lines, and eight springs. The RF switch is manufactured using the complementary metal oxide semiconductor (CMOS) process. The switch requires a post-process to release the membrane and springs. The post-process uses a wet etching to remove the sacrificial silicon dioxide layer, and to obtain the suspended structures of the switch. In order to improve the residual stress of the switch, an annealing process is applied to the switch, and the membrane obtains an excellent flatness. The finite element method (FEM) software CoventorWare is utilized to simulate the stress and displacement of the RF switch. Experimental results show that the RF switch has an insertion loss of 0.9 dB at 35 GHz and an isolation of 21 dB at 39 GHz. The actuation voltage of the switch is 14 V. PMID:24445415

Lin, Cheng-Yang; Dai, Ching-Liang

2013-01-01

253

Radio-frequency measurement of an asymmetric single electron transistor  

NASA Astrophysics Data System (ADS)

Since the invention of the radio-frequency single-electron transistor (RF-SET) by Schoelkopf et al.,[1] most measurements have focused on the symmetric single electron transistor. It has been shown, however, that the symmetric SET has a rather low measurement efficiency in its normal working regime.[2][3] Recently, it has been pointed out that an asymmetric SET can be considerably more efficient than a symmetric SET as a quantum amplifier. In this case the measurement efficiency of the asymmetric SET becomes similar to that of the quantum point contact (QPC) detector which can approach the quantum limit. We investigate the asymmetric SET by fabricating Al/AlOx SETs with junction areas 40x40 nm^2 and 40x80nm^2 and total resistance of about 25k?. The results of RF and DC characterization of such asymmetric SETs will be discussed. [1] R. J. Schoelkopf, P. Wahlgren, A. A. Kozhevnikov, P. Delsing, D. E. Prober, Science, 280, 1242 (1998). [2] A. N. Korotkov, Phys. Rev. B, 63, 085312 (2001); 63, 115403 (2001). [3] D. Mozyrsky, I. Martin, and M. B. Hastings, Phys. Rev. Lett., 92, 018303 (2004). [4] S. A. Gurvitz and G. P. Berman, Phys. Rev. B, 72 , 073303(2005).

Ji, Zhongqing; Xue, Weiwei; Rimberg, A. J.

2007-03-01

254

Image transmission in tactical radio frequency shared network propagation environments  

NASA Astrophysics Data System (ADS)

The need to transmit images across tactical radio frequency (rf) links has been identified in army digitization applications. For example, military doctrine requires that tactical functions like identification of battlefield entities as potential targets and battle damage assessment be performed by the soldier. Currently, a key input to these processes is imagery. Therefore, the quality and timeliness of the image directly impact tactical performance. The military is investigating the employment of remote sensors and advanced communications systems to meet this requirement as part of its digitization effort. Army communications systems exist that partially meet this requirement. However, many existing solutions employ these legacy systems in the context of a point-to-point communications architecture. Solutions to the problem of transmitting images across a rf network have not been fully explored. The term network implies that the rf transmission media is common to and shared by multiple subscribers. It is a suite of capabilities that collectively manage media access and information transfer for its subscribers thus providing substantial improvements in effectiveness, efficiency, and robustness. This paper discusses the challenges of transmitting images using one army legacy communications system in a tactical rf network, presents a conceptual framework for attacking the problem, and discusses one solution.

White, Kent H.; Wagner, Kerry A.; O'Hanian, Scott

1997-06-01

255

Radio-Frequency Current Drive in DIII-D  

SciTech Connect

Two methods of radio-frequency (rf) current drive that are well suited to controlling and sustaining the current profile in burning plasma experiments have been studied in the DIII-D tokamak. Fast-wave current drive (FWCD) gave centrally peaked current densities that increased linearly with central electron temperature. While high harmonic absorption of the fast waves on energetic beam ions could reduce the available power for current drive, FWCD figures of merit as high as {gamma}{sub FW} = 0.5 x 10{sup 19} A/m{sup 2}.W were still achieved. Electron cyclotron current drive (ECCD) was shown to be localized to the region of power deposition, with a current drive efficiency that decreased as the magnetic well depth increased. The detrimental effect of the magnetic well could be mitigated by raising the electron beta. ECCD figures of merit as high as {gamma}{sub EC} = 0.5 x 10{sup 19} A/m{sup 2}.W were measured for central deposition. The experimental FWCD and ECCD were both extensively tested against theoretical models and were found to be in excellent agreement. Validation of these predictive models of rf current drive aids in scenario development for next-step tokamaks.

Petty, C.C. [General Atomics (United States)

2005-10-15

256

The Stabiliy of Radio-Frequency Plasma Treated Polydimethylsiloxane Surface  

PubMed Central

Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in micro-fluidic systems. To transform the hydrophobic PDMS surface to hydrophilic it has been treated with radio frequency (RF) air plasma at 150, 300 and 500 mtorr pressure for up to 30 minutes. Following the surface treatment, the PDMS specimens were stored in air, deionized water or 0.14 M NaCl solution at 4 °C, 20 °C, and 70 °C. The change in the hydrophilicity (wettability) of the PDMS surfaces has been followed by contact angle measurements and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) Spectroscopy as a function of time. As an effect of the RF plasma treatment the contact angles measured on PDMS surfaces dropped from 113±4 degrees to 9±3 degrees. The chamber pressure and the treatment time had no or negligible effect on the results. However, the PDMS surface gradually lost its hydrophilic properties in time. The rate of this process is influenced by the difference in the dielectric constants of the PDMS and its ambient environment. It has been the smallest at low temperatures in deionized water and largest at high temperatures in air. Apparently, the OH groups generated on the PDMS surface during the plasma treatment tend towards a more hydrophilic/less hydrophobic environment during the relaxation processes. The correlation between FTIR–ATR spectral information and contact angle data supports this interpretation. PMID:17279784

Chen, I-Jane

2008-01-01

257

Operating a radio-frequency plasma source on water vapor.  

PubMed

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires n(i) approximately = n(e), where n(i) is the positive ion density. But in the electronegative water plasma, quasineutrality requires n(i+) = n(i-) + n(e). The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production. PMID:19725651

Nguyen, Sonca V T; Foster, John E; Gallimore, Alec D

2009-08-01

258

Operating a radio-frequency plasma source on water vapor  

SciTech Connect

A magnetically enhanced radio-frequency (rf) plasma source operating on water vapor has an extensive list of potential applications. In this work, the use of a rf plasma source to dissociate water vapor for hydrogen production is investigated. This paper describes a rf plasma source operated on water vapor and characterizes its plasma properties using a Langmuir probe, a residual gas analyzer, and a spectrometer. The plasma source operated first on argon and then on water vapor at operating pressures just over 300 mtorr. Argon and water vapor plasma number densities differ significantly. In the electropositive argon plasma, quasineutrality requires n{sub i}{approx_equal}n{sub e}, where n{sub i} is the positive ion density. But in the electronegative water plasma, quasineutrality requires n{sub i+}=n{sub i-}+n{sub e}. The positive ion density and electron density of the water vapor plasma are approximately one and two orders of magnitude lower, respectively, than those of argon plasma. These results suggest that attachment and dissociative attachment are present in electronegative water vapor plasma. The electron temperature for this water vapor plasma source is between 1.5 and 4 eV. Without an applied axial magnetic field, hydrogen production increases linearly with rf power. With an axial magnetic field, hydrogen production jumps to a maximum value at 500 W and then saturates with rf power. The presence of the applied axial magnetic field is therefore shown to enhance hydrogen production.

Nguyen, Sonca V. T.; Gallimore, Alec D. [Plasmadynamics and Electric Propulsion Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States); Foster, John E. [Plasma Science and Technology Laboratory, University of Michigan, Ann Arbor, Michigan 48108 (United States)

2009-08-15

259

Method of making radio frequency ion source antenna  

DOEpatents

In the method, the radio frequency (RF) antenna is made by providing a clean coil made of copper tubing or other metal conductor, which is coated with a tacky organic binder, and then with a powdered glass frit, as by sprinkling the frit uniformly over the binder. The coil is then heated internally in an inert gas atmosphere, preferably by passing an electrical heating current along the coil. Initially, the coil is internally heated to about 200.degree. C. to boil off the water from the binder, and then to about 750.degree. C.-850.degree. C. to melt the glass frit, while also burning off the organic binder. The melted frit forms a molten glass coating on the metal coil, which is then cooled to solidify the glass, so that the metal coil is covered with a thin continuous homogeneous impervious glass coating of substantially uniform thickness. The glass coating affords complete electrical insulation and complete dielectric protection for the metal coil of the RF antenna, to withstand voltage breakdown and to prevent sputtering, while also doubling the plasma generating efficiency of the RF antenna, when energized with RF power in the vacuum chamber of an ion source for a particle accelerator or the like. The glass frit preferably contains apprxoimately 45% lead oxide.

Ehlers, Kenneth W. (Alamo, CA); Leung, Ka-Ngo (Hercules, CA)

1988-01-01

260

Correlation of Fermi Photons with High-frequency Radio Giant Pulses from the Crab Pulsar  

NASA Astrophysics Data System (ADS)

To constrain the giant pulse (GP) emission mechanism and test the model of Lyutikov for GP emission, we have carried out a campaign of simultaneous observations of the Crab pulsar at ?-ray (Fermi) and radio (Green Bank Telescope) wavelengths. Over 10 hr of simultaneous observations we obtained a sample of 2.1 × 104 GPs, observed at a radio frequency of 9 GHz, and 77 Fermi photons, with energies between 100 MeV and 5 GeV. The majority of GPs came from the interpulse (IP) phase window. We found no change in the GP generation rate within 10-120 s windows at lags of up to ±40 minutes of observed ?-ray photons. The 95% upper limit for a ?-ray flux enhancement in pulsed emission phase window around all GPs is four times the average pulsed ?-ray flux from the Crab. For the subset of IP GPs, the enhancement upper limit, within the IP emission window, is 12 times the average pulsed ?-ray flux. These results suggest that GPs, at least high-frequency IP GPs, are due to changes in coherence of radio emission rather than an overall increase in the magnetospheric particle density.

Bilous, A. V.; Kondratiev, V. I.; McLaughlin, M. A.; Ransom, S. M.; Lyutikov, M.; Mickaliger, M.; Langston, G. I.

2011-02-01

261

Study of the change of electron temperature inside magnetic island caused by localized radio frequency heating  

SciTech Connect

The change in the electron temperature inside magnetic island caused by localized radio frequency (rf) heating is studied numerically by solving the two-dimensional energy transport equation, to investigate the dependence of the temperature change on the location and width of the rf power deposition along the minor radius and the helical angle, the island width, and the ratio between the parallel and the perpendicular heat conductivity. Based on obtained numerical results, suggestions for optimizing the island stabilization by localized rf heating are made.

Yang, J.; Zhu, S. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Center for Magnetic Fusion Theory, Chinese Academy of Sciences, Hefei 230031 (China); Yu, Q. [Max-Planck-Institute fuer Plasmaphysik, EURATOM Association, Garching 85748 (Germany); Zhuang, G. [College of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China)

2010-05-15

262

Radio Frequency Generation of an Electron Plasma in a Malmberg-Penning Trap  

SciTech Connect

The generation of an electron plasma via low-power Radio Frequency (RF) excitation has been observed in the Malmberg-Penning trap ELTRAP under ultra-high vacuum conditions. The process is sensitive to the RF parameters as well as to the trapping length. The electron heating mechanism necessary to reach the ionization energy of the residual gas has been modeled with the use of a simple one-dimensional iterative map, whose properties show a behavior similar to that of the Fermi acceleration map.

Paroli, B. [INFN Sezione di Milano and Dipartimento di Fisica, Universita degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Dipartimento di Energia, Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano (Italy); De Luca, F.; Pozzoli, R.; Rome, M. [INFN Sezione di Milano and Dipartimento di Fisica, Universita degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy); Maero, G. [Dipartimento di Fisica, Universita degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)

2010-06-16

263

Tuning the work function of graphene by nitrogen plasma treatment with different radio-frequency powers  

NASA Astrophysics Data System (ADS)

Graphene prepared by the chemical vapor deposition method was treated with nitrogen plasma under different radio-frequency (rf) power conditions in order to experimentally study the change in the work function. Control of the rf power could change the work function of graphene from 4.91 eV to 4.37 eV. It is shown that the increased rf power may lead to the increased number of graphitic nitrogen, increasing the electron concentration, and shifting the Fermi level to higher energy. The ability to controllably tune the work function of graphene is essential for optimizing the efficiency of optoelectronic and electronic devices.

Zeng, Jian-Jhou; Lin, Yow-Jon

2014-06-01

264

High-energy neutrinos from radio galaxies  

E-print Network

The IceCube experiment has recently reported the first observation of high-energy cosmic neutrinos. Their origin is still unknown. In this paper, we investigate the possibility that they originate in active galaxies. We show that hadronic interactions (pp) in the generally less powerful, more frequent, FR-I radio galaxies are one of the candidate source classes being able to accommodate the observation while the more powerful, less frequent, class of FR-II radio galaxies has too low of a column depths to explain the signal.

Tjus, J Becker; Halzen, F; Kheirandish, A; Saba, S M

2014-01-01

265

A radio detector system for ultra high energy cosmic showers  

Microsoft Academic Search

A passive radio detection system is proposed for the detection and study of ultra high energy cosmic rays (UHECR) showers and meteors. TV and FM radio signals reflected by ionization clouds produced by meteors are clearly detectable. This technique known as radio meteor scatter is well established. UHECRs produces in principle similar ionization trails. A radio detection station operating at

Denis Oliveira Damazio; Helio Takai

2003-01-01

266

Energy Efficient Transmissions in MIMO Cognitive Radio Networks  

E-print Network

Energy Efficient Transmissions in MIMO Cognitive Radio Networks Liqun Fu The Institute of Network@ie.cuhk.edu.hk Abstract--In this paper, we consider energy efficient transmis- sions for MIMO cognitive radio networks on the traffic load of the secondary system. Index Terms--Cognitive radio networks, MIMO, Energy- efficiency. I

Huang, Jianwei

267

Radio Frequency Characteristics of Printed Meander Inductors and Interdigital Capacitors  

NASA Astrophysics Data System (ADS)

Radio frequency (RF) characterizations of printed silver ink inductors manufactured at low (150 °C) and high (850 °C) temperatures and interdigital capacitors manufactured at high (850 °C) temperatures were carried out in the 500 MHz to 6 GHz range. The S-parameter responses of the components were measured with a probe station and an Agilent 8510C network analyzer. Electrical parameters such as inductance, capacitance, and a quality factor were estimated from experimental results and numerical calculation. Component parameters are dependent on physical dimensions and material properties. The components were created in a 4 ×4 mm2 area with line widths/gaps of 500/500, 250/250, and 200/200 µm. Windings in the coils varied from 2 to 5 turns and finger counts in the capacitors, from 5 to 11 within the defined area and line widths. As a result, low-T-cured (150 °C) silver ink meander line inductors achieved 8 to 18 nH inductances at 1 and 2 GHz with a quality value of 10-25. High-T-cured (850 °C) silver ink meander line inductors had 6-15 nH inductances and quality values were around 100, indicating a conductivity challenge with low-T-cured inks. Interdigital capacitors with 1 to 4 pF capacitances and sufficient quality values were created. A low-loss BaTiO3 coating was printed over the interdigital capacitors; they exhibited suitable electrical characteristics to allow decreasing the physical size of the component.

Myllymaki, Sami; Teirikangas, Merja; Nelo, Mikko; Tulppo, Joel; Soboci?ski, Maciej; Juuti, Jari; Jantunen, Heli; Sloma, Marcin; Jakubowska, Malgorzata

2013-05-01

268

Scattering of radio frequency waves by blobs in tokamak plasmasa)  

NASA Astrophysics Data System (ADS)

The density fluctuations and blobs present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction, reflection, diffraction, and coupling to other plasma waves. This, in turn, affects the spectrum of the RF waves and the electromagnetic power that reaches the core of the plasma. The usual geometric optics analysis of RF scattering by density blobs accounts for only refractive effects. It is valid when the amplitude of the fluctuations is small, of the order of 10%, compared to the background density. In experiments, density fluctuations with much larger amplitudes are routinely observed, so that a more general treatment of the scattering process is needed. In this paper, a full-wave model for the scattering of RF waves by a blob is developed. The full-wave approach extends the range of validity well beyond that of geometric optics; however, it is theoretically and computationally much more challenging. The theoretical procedure, although similar to that followed for the Mie solution of Maxwell's equations, is generalized to plasmas in a magnetic field. Besides diffraction and reflection, the model includes coupling to a different plasma wave than the one imposed by the external antenna structure. In the model, it is assumed that the RF waves interact with a spherical blob. The plasma inside and around the blob is cold, homogeneous, and imbedded in a uniform magnetic field. After formulating the complete analytical theory, the effect of the blob on short wavelength electron cyclotron waves and longer wavelength lower hybrid waves is studied numerically.

Ram, Abhay K.; Hizanidis, Kyriakos; Kominis, Yannis

2013-05-01

269

Radio-Frequency Plasma Cleaning of a Penning Malmberg Trap  

NASA Technical Reports Server (NTRS)

Radio-frequency-generated plasma has been demonstrated to be a promising means of cleaning the interior surfaces of a Penning-Malmberg trap that is used in experiments on the confinement of antimatter. {Such a trap was reported in Modified Penning-Malmberg Trap for Storing Antiprotons (MFS-31780), NASA Tech Briefs, Vol. 29, No. 3 (March 2005), page 66.} Cleaning of the interior surfaces is necessary to minimize numbers of contaminant atoms and molecules, which reduce confinement times by engaging in matter/antimatter-annihilation reactions with confined antimatter particles. A modified Penning-Malmberg trap like the one described in the cited prior article includes several collinear ring electrodes (some of which are segmented) inside a tubular vacuum chamber, as illustrated in Figure 1. During operation of the trap, a small cloud of charged antiparticles (e.g., antiprotons or positrons) is confined to a spheroidal central region by means of a magnetic field in combination with DC and radiofrequency (RF) electric fields applied via the electrodes. In the present developmental method of cleaning by use of RF-generated plasma, one evacuates the vacuum chamber, backfills the chamber with hydrogen at a suitable low pressure, and uses an RF-signal generator and baluns to apply RF voltages to the ring electrodes. Each ring is excited in the polarity opposite that of the adjacent ring. The electric field generated by the RF signal creates a discharge in the low-pressure gas. The RF power and gas pressure are adjusted so that the plasma generated in the discharge (see Figure 2) physically and chemically attacks any solid, liquid, and gaseous contaminant layers on the electrode surfaces. The products of the physical and chemical cleaning reactions are gaseous and are removed by the vacuum pumps.

Sims, William Herbert, III; Martin, James; Pearson, J. Boise; Lewis, Raymond

2005-01-01

270

Scattering of radio frequency waves by blobs in tokamak plasmas  

SciTech Connect

The density fluctuations and blobs present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction, reflection, diffraction, and coupling to other plasma waves. This, in turn, affects the spectrum of the RF waves and the electromagnetic power that reaches the core of the plasma. The usual geometric optics analysis of RF scattering by density blobs accounts for only refractive effects. It is valid when the amplitude of the fluctuations is small, of the order of 10%, compared to the background density. In experiments, density fluctuations with much larger amplitudes are routinely observed, so that a more general treatment of the scattering process is needed. In this paper, a full-wave model for the scattering of RF waves by a blob is developed. The full-wave approach extends the range of validity well beyond that of geometric optics; however, it is theoretically and computationally much more challenging. The theoretical procedure, although similar to that followed for the Mie solution of Maxwell's equations, is generalized to plasmas in a magnetic field. Besides diffraction and reflection, the model includes coupling to a different plasma wave than the one imposed by the external antenna structure. In the model, it is assumed that the RF waves interact with a spherical blob. The plasma inside and around the blob is cold, homogeneous, and imbedded in a uniform magnetic field. After formulating the complete analytical theory, the effect of the blob on short wavelength electron cyclotron waves and longer wavelength lower hybrid waves is studied numerically.

Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hizanidis, Kyriakos; Kominis, Yannis [School of Electrical and Computer Engineering, National Technical University of Athens, Association EURATOM-Hellenic Republic, Athens, GR-15773 (Greece)] [School of Electrical and Computer Engineering, National Technical University of Athens, Association EURATOM-Hellenic Republic, Athens, GR-15773 (Greece)

2013-05-15

271

Analytical model for the radio-frequency sheath.  

PubMed

A simple analytical model for the planar radio-frequency (rf) sheath in capacitive discharges is developed that is based on the assumptions of a step profile for the electron front, charge exchange collisions with constant cross sections, negligible ionization within the sheath, and negligible ion dynamics. The continuity, momentum conservation, and Poisson equations are combined in a single integro-differential equation for the square of the ion drift velocity, the so called sheath equation. Starting from the kinetic Boltzmann equation, special attention is paid to the derivation and the validity of the approximate fluid equation for momentum balance. The integrals in the sheath equation appear in the screening function which considers the relative contribution of the temporal mean of the electron density to the space charge in the sheath. It is shown that the screening function is quite insensitive to variations of the effective sheath parameters. The two parameters defining the solution are the ratios of the maximum sheath extension to the ion mean free path and the Debye length, respectively. A simple general analytic expression for the screening function is introduced. By means of this expression approximate analytical solutions are obtained for the collisionless as well as the highly collisional case that compare well with the exact numerical solution. A simple transition formula allows application to all degrees of collisionality. In addition, the solutions are used to calculate all static and dynamic quantities of the sheath, e.g., the ion density, fields, and currents. Further, the rf Child-Langmuir laws for the collisionless as well as the collisional case are derived. An essential part of the model is the a priori knowledge of the wave form of the sheath voltage. This wave form is derived on the basis of a cubic charge-voltage relation for individual sheaths, considering both sheaths and the self-consistent self-bias in a discharge with arbitrary symmetry. The externally applied rf voltage is assumed to be sinusoidal, although the model can be extended to arbitrary wave forms, e.g., for dual-frequency discharges. The model calculates explicitly the cubic correction parameter in the charge-voltage relation for the case of highly asymmetric discharges. It is shown that the cubic correction is generally moderate but more pronounced in the collisionless case. The analytical results are compared to experimental data from the literature obtained by laser electric field measurements of the mean and dynamic fields in the capacitive sheath for various gases and pressures. Very good agreement is found throughout. PMID:24483571

Czarnetzki, Uwe

2013-12-01

272

Energy and composition sensitivity of geosynchrotron radio emission from EAS  

E-print Network

We analyse the sensitivity of geosynchrotron radio emission from inclined extensive air showers to the energy and mass of primary cosmic rays. We demonstrate that radio emission measurements at suitable lateral distances can infer both the number of electrons and positrons in the shower maximum and the atmospheric depth of the maximum on a shower-to-shower basis. Alternatively, measurements at a fixed lateral distance but in two different observing frequency bands yield comparable information. An RMS error of 5% in the determination of the number of electrons and positrons at shower maximum can be achieved. Through the determination of these quantities, geosynchrotron radiation provides access to the energy and mass of primary cosmic rays on a shower-to-shower basis.

T. Huege; R. Ulrich; R. Engel

2007-07-25

273

Radio-frequency single-electron transistor: Toward the shot-noise limit A. Aassime,a)  

E-print Network

to a few kHz. With the invention of the radio-frequency SET rf-SET ,5 the SET was made fast and veryRadio-frequency single-electron transistor: Toward the shot-noise limit A. Aassime,a) D. Gunnarsson is embedded. We measured the charge sensitivity of this radio-frequency single-electron transistor to be 3

274

Calculation of frequency and spatial separation regulations for fixed service receiving stations and radio facilities of other services  

Microsoft Academic Search

In the process of transmission of fixed service radio links it is important to provide the required frequency and spatial separation between fixed service receiving stations and radio facilities of other services operating in the same frequency band as fixed service stations. According to radio regulations, the frequency bands assigned to the fixed service are in most cases also used

A. K. Meteisky; V. I. Mordachev; V. M. Kozel

2001-01-01

275

Radio Frequency Field Calculations for Plasma Heating Simulations in VASIMR  

NASA Astrophysics Data System (ADS)

(VASIMR)1 is plasma heating by ion-cyclotron RF heating (ICRF). Mathematical simulation helps to design an ICRF antenna, i.e. make maximal absorption of RF power into the plasma in the resonance area. Another goal of a particle simulation is design of a magnetic nozzle and optimize the performance of VASIMR2. field in the plasma, 2) ion density and velocity, 3) ion-cyclotron radio-frequency electromagnetic field. The assumptions of quasineutral and collisionless plasma are based on the range of operating VASIMR parameters. Carlo simulations for systems of million of particles in a reasonable time and without the need for a powerful supercomputer. The particle to grid weighting method is used for calculating the ion density, which is used for recalculation of the electric potential and RF field. dimensional problem to a weighted sum over two-dimensional solutions. Absorption is introduced in the cold plasma model by adding an imaginary collision frequency to the RF driven frequency, which is equivalent to adding an imaginary particle mass in the dielectric tensor elements. static and RF fields using the VASIMR code2. The VASIMR and EMIR codes are then iterated to estimate the ICRF effects on the plasma density. The iteration is performed by calculating the RF fields with the EMIR code, and using these fields to follow nonlinear ion trajectories with the VASIMR code on the gyro-frequency time scale. The ion trajectories are used to generate RF power absorption values and a density input for the next EMIR calculation. The codes are iterated until the density profile becomes reasonably stable, then the collisional absorption parameter in the EMIR code is adjusted and the iteration is continued until the power deposited by the RF system matches the power absorbed by the ion trajectories in a global sense. electric field. The solved algebraic system of equations is represented by ill-conditioned 18-diagonal matrix with complex elements. Since early development of the EMIR code, the frontal method direct solver was used. That solver requires large CPU time and RAM, which both are proportional to Nr Nz2, for a grid of the size Nr x Nz. These requirements make almost impossible to use existent EMIR solver on PC to obtain RF fields with good accuracy. system. The suggested iterative method is Modified Incomplete Cholesky Preconditioned Conjugate Gradient Squared solver4. The solver involves a couple of the control parameters, which let a user tune the code to make iterations converge as fast as possible for a particular grid. Since the iterative solver does not require large RAM, and works much faster than the direct solver, the new algorithm lets us resolve RF fields on a PC with required accuracy. REFERENCES 1. Chang Díaz F.R., "Research Status of The Variable Specific Impulse Magnetoplasma Rocket", Proc. 39th Annual Meeting of the Division of Plasma Physics (Pittsburgh, PA, 1997), Bulletin of APS, 42 2057. 2. Ilin A.V., Chang Díaz F.R., Squire J.P. and Carter M.D. "Monte Carlo Particle Dynamics in a Variable Specific Impulse Magnetoplasma Rocket", (Proceedings of Open Systems' 98), Transactions of Fusion Technology, 35 330 - 334 (1999). 3. Jaeger E.F., Batchelor D.B., Weitzner H. and Whealton J.H. "ICRF Wave Propagation And Absorption in Tokamak And Mirror Magnetic Fields - A Full-wave Calculation", Computer Physics Com., 40 33 - 64 (1986). 4. Ilin, A. V., Bagheri, B., Scott, L. R., Briggs, J. M., and McCammon, J. A. "Parallelization of Poisson-Boltzmann and Brownian Dynamics calculation", Parallel Computing in Computational Chemistry, ACB Books, Washington D.C., (1995) 170-185.

Ilin, A. V.; Díaz, F. R. Chang; Squire, J. P.; Carter, M. D.

2002-01-01

276

Radio Frequency Phototube, Optical Clock and Precise Measurements in Nuclear Physics  

E-print Network

Recently a new experimental program of novel systematic studies of light hypernuclei using pionic decay was established at JLab (Study of Light Hypernuclei by Pionic Decay at JLab, JLab Experiment PR-08-012). The highlights of the proposed program include high precision measurements of binding energies of hypernuclei by using a high resolution pion spectrometer, HpiS. The average values of binding energies will be determined within an accuracy of ~10 keV or better. Therefore, the crucial point of this program is an absolute calibration of the HpiS with accuracy 10E-4 or better. The merging of continuous wave laser-based precision optical-frequency metrology with mode-locked ultrafast lasers has led to precision control of the visible frequency spectrum produced by mode-locked lasers. Such a phase-controlled mode-locked laser forms the foundation of an optical clock or femtosecond optical frequency comb (OFC) generator, with a regular comb of sharp lines with well defined frequencies. Combination of this technique with a recently developed radio frequency (RF) phototube results in a new tool for precision time measurement. We are proposing a new time-of-flight (TOF) system based on an RF phototube and OFC technique. The proposed TOF system achieves 10 fs instability level and opens new possibilities for precise measurements in nuclear physics such as an absolute calibration of magnetic spectrometers within accuracy 10E-4 - 10E-5.

Amur Margaryan

2009-10-16

277

Coupling effects in inductive discharges with radio frequency substrate biasing  

SciTech Connect

Low pressure inductively coupled plasmas (ICP) operated in neon at 27.12 MHz with capacitive substrate biasing (CCP) at 13.56 MHz are investigated by phase resolved optical emission spectroscopy, voltage, and current measurements. Three coupling mechanisms are found potentially limiting the separate control of ion energy and flux: (i) Sheath heating due to the substrate biasing affects the electron dynamics even at high ratios of ICP to CCP power. At fixed CCP power, (ii) the substrate sheath voltage and (iii) the amplitude as well as frequency of plasma series resonance oscillations of the RF current are affected by the ICP power.

Schulze, J.; Schuengel, E.; Czarnetzki, U.

2012-01-09

278

Coupling effects in inductive discharges with radio frequency substrate biasing  

NASA Astrophysics Data System (ADS)

Low pressure inductively coupled plasmas (ICP) operated in neon at 27.12 MHz with capacitive substrate biasing (CCP) at 13.56 MHz are investigated by phase resolved optical emission spectroscopy, voltage, and current measurements. Three coupling mechanisms are found potentially limiting the separate control of ion energy and flux: (i) Sheath heating due to the substrate biasing affects the electron dynamics even at high ratios of ICP to CCP power. At fixed CCP power, (ii) the substrate sheath voltage and (iii) the amplitude as well as frequency of plasma series resonance oscillations of the RF current are affected by the ICP power.

Schulze, J.; Schüngel, E.; Czarnetzki, U.

2012-01-01

279

2010 Raj JainCSE574sWashington University in St. Louis Radio FrequencyRadio Frequency  

E-print Network

openers use RFID Implants in human, horses, fishes, animals Animal ID Standards ISO 11784 and 11785 use, Radio receiver, radio modulator, control logic, memory and a power system Power Source: Passive Tags. Designed to be implanted in humans. Identify patients. Semi-passive RFIDs used in E-Z Pass toll collection

Jain, Raj

280

Review of radio-frequency, nonlinear effects on the ionosphere  

SciTech Connect

Modification of the ionosphere by high power radio waves in the megahertz band has been intensively investigated over the past two decades. This research has yielded advances in aeronomy, geophysics, and plasma physics with applications to radio communication and has provided a fruitful interaction of radio theorists and experimentalists. There being almost no linear effects of powerful radio waves on the ionosphere, we concentrate on the nonlinear effects. To put the subject in perspective we trace its history beginning in the early 1930s and highlight the important events up to the late 1960s. We then shift to a phenomenological approach and deal in order with ohmic heating, parametric instabilities, self-focusing and kilometer-scale irregularities, meter-scale irregularities, and a collection of recently discovered effects. We conclude with the observation that stronger international cooperation would benefit this research, and describe a list of promising, difficult challenges.

Gordon, W.E.; Duncan, L.M.

1983-01-01

281

Radio Frequency Spectroscopy Of a Quasi-Two-Dimensional Fermi Gas  

NASA Astrophysics Data System (ADS)

This dissertation presents the first experiments on radio frequency (rf) spectroscopy of a quasi-two dimensional strongly interacting ultracold atomic Fermi gas. A 50-50 mixture of spin-up and spin-down atoms is confined in a series of pancake-shaped traps produced using an optical standing-wave. To make the system quasi-two dimensional, I adjust the Fermi energy in the weakly confined direction to be comparable to the harmonic oscillator energy level spacing in the tightly confined direction. For a perfectly two dimensional system, at low enough temperature, spin-up and spin-down atoms should form dimers in the ground state of the tightly confined direction. However, in our quasi-two dimensional system I find that the simple dimer theory does not agree with the measured radio-frequency spectra. Instead, the data can be explained by polaron to polaron transitions, which is a many-body effect. Here, a polaron is a spin-down impurity surrounded by a cloud of particle-hole pairs in a spin-up Fermi sea. With this unique strongly interacting quasi-two dimensional system, I am able to study the interplay between confinement induced two-body pairing and many-body physics in confined mesoscopic systems of several hundred atoms, which has not been previously explored and offers new challenges for predictions.

Zhang, Yingyi

282

Supplying the Power Requirements to a Sensor Network Using Radio Frequency Power Transfer  

PubMed Central

Wireless power transmission is a method of supplying power to small electronic devices when there is no wired connection. One way to increase the range of these systems is to use a directional transmitting antenna, the problem with this approach is that power can only be transmitted through a narrow beam and directly forward, requiring the transmitter to always be aligned with the sensor node position. The work outlined in this article describes the design and testing of an autonomous radio frequency power transfer system that is capable of rotating the base transmitter to track the position of sensor nodes and transferring power to that sensor node. The system's base station monitors the node's energy levels and forms a charge queue to plan charging order and maintain energy levels of the nodes. Results show a radio frequency harvesting circuit with a measured S11 value of ?31.5 dB and a conversion efficiency of 39.1%. Simulation and experimentation verified the level of power transfer and efficiency. The results of this work show a small network of three nodes with different storage types powered by a central base node. PMID:23012506

Percy, Steven; Knight, Chris; Cooray, Francis; Smart, Ken

2012-01-01

283

Multi-frequency radio observations of a solar eclipse  

Microsoft Academic Search

The main results of radio observations of the Feb. 16, 1980 eclipse carried out in Yunnan are summarized. The authors have found: The radius of the radio sun in solar maximum year amounts to 1.007, 1.013, 1.040, 1.067 and 1.090 R_sun; at 0.86 cm, 2.0 cm, 3.2 cm, 8.2 cm and 21 cm respectively. The flux density spectra of the

Q.-J. Fu; S.-C. Ji; X.-H. Luo; Z.-M. Gao; X.-M. Mun

1983-01-01

284

Low Frequency Radio Transients in the Galactic Center  

Microsoft Academic Search

We report the detection of a new radio transient source, GCRT J1746-2757, located only 1.1 degrees north of the Galactic center. Consistent with other radio transients toward the Galactic center, this source brightened and faded on a time scale of a few months. No X-ray counterpart was detected, but upper limits suggest that GCRT J1746-2757 may have been a \\

S. D. Hyman; A. L. Bartleson; T. J. W. Lazio; N. E. Kassim

2001-01-01

285

Preliminary analysis of investigation Radio Frequency Interference (RFI) profile analysis at Universiti Teknologi MARA  

Microsoft Academic Search

In this paper, we have identified some important Radio Frequency Interference (RFI) sources that can potentially be a problem for any future radio astronomical observations in Universiti Teknologi MARA (UiTM) and possibly in Malaysia as a whole. Analysis is done by classifying and characterizing the strength of the sources' RFI profiles. Comparison of the RFI profiles between the indoor (Faculty

Z. S. Hamidi; Z. Z. Abidin; Z. A. Ibrahim; N. N. M. Shariff; Ungku Ferwani Salwa Ungku Ibrahim; R. Umar

2011-01-01

286

Monolithic Multichannel GSa\\/s Transient Waveform Recorder for Measuring Radio Emissions from High Energy Particle Cascades  

Microsoft Academic Search

A number of particle astrophysics initiatives to exploit radio emission from high energy particle cascades require high- frequency sampling of antenna array signals. Nyquist-limited sampling of GHz frequency radio signals for an antenna array may be accomplished by commercially available test units. However, these technologies are incompatible with the size, power and cost constraints of long-duration balloon or satellite flight.

Gary S. Varner; Peter Gorham; Jing Cao

287

Collisionless electron heating by radio frequency bias in low gas pressure inductive discharge  

SciTech Connect

We show experimental observations of collisionless electron heating by the combinations of the capacitive radio frequency (RF) bias power and the inductive power in low argon gas pressure RF biased inductively coupled plasma (ICP). With small RF bias powers in the ICP, the electron energy distribution (EED) evolved from bi-Maxwellian distribution to Maxwellian distribution by enhanced plasma bulk heating and the collisionless sheath heating was weak. In the capacitive RF bias dominant regime, however, high energy electrons by the RF bias were heated on the EEDs in the presence of the ICP. The collisionless heating mechanism of the high energy electrons transited from collisionless inductive heating to capacitive coupled collisionless heating by the electron bounce resonance in the RF biased ICP.

Lee, Hyo-Chang; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

2012-12-10

288

Collisionless electron heating by radio frequency bias in low gas pressure inductive discharge  

NASA Astrophysics Data System (ADS)

We show experimental observations of collisionless electron heating by the combinations of the capacitive radio frequency (RF) bias power and the inductive power in low argon gas pressure RF biased inductively coupled plasma (ICP). With small RF bias powers in the ICP, the electron energy distribution (EED) evolved from bi-Maxwellian distribution to Maxwellian distribution by enhanced plasma bulk heating and the collisionless sheath heating was weak. In the capacitive RF bias dominant regime, however, high energy electrons by the RF bias were heated on the EEDs in the presence of the ICP. The collisionless heating mechanism of the high energy electrons transited from collisionless inductive heating to capacitive coupled collisionless heating by the electron bounce resonance in the RF biased ICP.

Lee, Hyo-Chang; Chung, Chin-Wook

2012-12-01

289

Sleep EEG alterations: effects of pulsed magnetic fields versus pulse-modulated radio frequency electromagnetic fields.  

PubMed

Studies have repeatedly shown that electroencephalographic power during sleep is enhanced in the spindle frequency range following radio frequency electromagnetic field exposures pulse-modulated with fundamental frequency components of 2, 8, 14 or 217 Hz and combinations of these. However, signals used in previous studies also had significant harmonic components above 20 Hz. The current study aimed: (i) to determine if modulation components above 20 Hz, in combination with radio frequency, are necessary to alter the electroencephalogram; and (ii) to test the demodulation hypothesis, if the same effects occur after magnetic field exposure with the same pulse sequence used in the pulse-modulated radio frequency exposure. In a randomized double-blind crossover design, 25 young healthy men were exposed at weekly intervals to three different conditions for 30 min before sleep. Cognitive tasks were also performed during exposure. The conditions were a 2-Hz pulse-modulated radio frequency field, a 2-Hz pulsed magnetic field, and sham. Radio frequency exposure increased electroencephalogram power in the spindle frequency range. Furthermore, delta and theta activity (non-rapid eye movement sleep), and alpha and delta activity (rapid eye movement sleep) were affected following both exposure conditions. No effect on sleep architecture and no clear impact of exposure on cognition was observed. These results demonstrate that both pulse-modulated radio frequency and pulsed magnetic fields affect brain physiology, and the presence of significant frequency components above 20 Hz are not fundamental for these effects to occur. Because responses were not identical for all exposures, the study does not support the hypothesis that effects of radio frequency exposure are based on demodulation of the signal only. PMID:22724534

Schmid, Marc R; Murbach, Manuel; Lustenberger, Caroline; Maire, Micheline; Kuster, Niels; Achermann, Peter; Loughran, Sarah P

2012-12-01

290

Radio-Frequency Conversion and Synthesis (for a 115mW GPS Receiver)  

E-print Network

at the antenna (PS -130dBm, PN -110dBm) · Large processing gain (GPS data bit, Tb = 20ms; C/A code chip, Tc 1Radio-Frequency Conversion and Synthesis (for a 115mW GPS Receiver) Arvin Shahani Stanford University #12;Overview · GPS Overview · Frequency Conversion · Frequency Synthesis · Conclusion #12;GPS

Lee, Thomas H.

291

Extending the ICRF to Higher Radio Frequencies: 24 and 43 GHz Astrometry  

NASA Technical Reports Server (NTRS)

We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-band) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.

Jacobs, Christopher S.; Charlot, Patrick; Fomalont, Ed B.; Gordon, David; Lanyi, Gabor E.; Ma, Chopo; Naudet, Charles J.; Sovers, Ojars J.; Zhang, Li-Wei D.

2004-01-01

292

Extending the ICRF to Higher Radio Frequencies: Imaging and Source Structure  

NASA Technical Reports Server (NTRS)

We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-braid) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.

Boboltz, David A.; Fey, Alan L.; Charlot, Patrick; Fomalont, Edward B.; Lanyi, Gabor E.; Zhang, Li-Wei

2004-01-01

293

Encoding, application and association of radio frequency identification tags on high speed manufacturing lines  

E-print Network

One of the entry points of radio frequency identification technology in supply chain applications is at the manufacturing line, after production, as packaged goods leave for the next link of the network of suppliers, ...

Fonseca, Herbert Moreti, 1973-

2004-01-01

294

REGENERATION AND REACTIVATION OF CARBON ADSORBENTS BY RADIO FREQUENCY INDUCTION HEATING  

EPA Science Inventory

1. Electrical Properties of Adsorbents: We measured the electric permittivity of four commercially available carbon adsorbents (supplied by Wesvaco Inc) over the radio frequency range (1 to 40 MHz). Westvaco is by far the largest volume supplier of activated carbon...

295

The Universe at Low Radio Frequencies ASP Conference Series, Vol. XXX , 2000  

E-print Network

The Universe at Low Radio Frequencies ASP Conference Series, Vol. XXX , 2000 A. Pramesh Rao et al.3% to 16.8%. Deep red CCD images do not reveal any optical object with a brightness and/or position typical

Roy, Alan

296

Integrating Radio Frequency Identification (RFID) data with Electronic Data Interchange (EDI) business processes  

E-print Network

Radio Frequency Identification (RFID) technology, an important component in the enterprise IT infrastructure, must be integrated into the legacy IT system. This thesis studies how RFID technology can be integrated into the ...

Chen, Yan (Yan Henry), 1976-

2005-01-01

297

A systems approach to the evaluation of Radio Frequency Identification (RFID) in the defense industry  

E-print Network

Radio Frequency Identification (RFID) is a wireless technology with possible applications in the supply chain. RFID tags' fast read rates, non-line-of-sight identification and large storage capacity may revolutionize supply ...

Shah, Ronak R

2005-01-01

298

A Dedicated Search for Low Frequency Radio Transient Astrophysical Events using ETA  

E-print Network

Frequency Radio Transients, Eight-meter-wavelength Transient Array, Crab Giant Pulses, Gamma Ray Bursts-annihilation of primordial black holes (PBHs), gamma ray bursts (GRBs), and supernovae are expected to produce single

Ellingson, Steven W.

299

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation protection program. This report supersedes USAFOEHL Report 80-42, 'A practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

300

Base-level management of radio-frequency radiation-protection program. Final report  

SciTech Connect

AFOEHL developed this report to assist the base-level aerospace medical team manage their radio-frequency radiation-protection program. This report supersedes USAFOEHL Report 80-42, 'A Practical R-F Guide for BEES.'

Rademacher, S.E.; Montgomery, N.D.

1989-04-01

301

Potential health effects of video display terminals and radio frequency heaters and sealers  

NASA Astrophysics Data System (ADS)

Video display terminals and radio frequency heaters and sealers have wide industrial applications. Both of these technologies involve the use of nonionizing radiation. Radiation leakages from these devices and their potential health effects are investigated.

302

Radio Frequency Identification of Katrina Hurricane Victims Rajit Gadh and B.S. Prabhu  

E-print Network

1 Radio Frequency Identification of Katrina Hurricane Victims Rajit Gadh and B.S. Prabhu Recently of the hurricane Katrina. Motivated by the interest generated by this news, in what follows we comment

California at Los Angeles, University of

303

Use of Radio Frequency Identification for Targeted Advertising: A Collaborative Filtering Approach Using Bayesian Networks  

E-print Network

This article discusses a potential application of radio frequency identification (RFID) and collaborative filtering for targeted advertising in grocery stores. Every day hundreds of items in grocery stores are marked down ...

Cinicioglu, Esma N.; Shenoy, Prakash P.; Kocabasoglu, Canan

2007-07-01

304

Computer simulation of a novel technique for Radio-Frequency Ablation of ventricular arrhythmias  

E-print Network

Ventricular Tachycardia (VT) is a rapid arrhythmia, most commonly due to reentrant electrical activity in the heart. A common treatment for VT is Radio-Frequency Ablation (RFA), which is minimally invasive, but requires ...

Rosbury, Tamara S

2006-01-01

305

POTENTIAL HUMAN STUDY POPULATIONS FOR NON-IONIZING (RADIO FREQUENCY) RADIATION HEALTH EFFECTS  

EPA Science Inventory

This research project was initiated to identify potential human populations for future epidemiological studies of the health effects of radio frequency radiation. Through a literature search and contacts with various groups and organizations, numerous occupations and applications...

306

Measurement of radio-frequency magnetic fluctuations in the VTF magnetic reconnection experiment  

E-print Network

In this thesis work, I designed, fabricated, and calibrated, a radio-frequency magnetic probe, subsequently used to measure magnetic turbulance in the reconnecting plasmas of the Versatile Toroidal Facility (VTF). Reconnecting ...

Whitney, John Peter, 1982-

2004-01-01

307

Wideband Waveform Optimization with Energy Detector Receiver in Cognitive Radio  

E-print Network

Wideband Waveform Optimization with Energy Detector Receiver in Cognitive Radio Zhen Hu Department investigates the transmitted waveform optimization issues for wideband cognitive radio with energy detector receiver. The motivation is to provide a cheap cognitive radio network with simple and cheap cognitive

Qiu, Robert Caiming

308

Radio Observations of Explosive Energy Releases on the Sun  

NASA Technical Reports Server (NTRS)

This chapter is devoted to a discussion of the radio observations of explosive energy releases (normal flares and small-scale energy releases) on the Sun. Radio imaging observations of solar flares and coronal transients and the relationship of radio phenomena with those observed in hard and soft X-rays and underlying physics are discussed.

Kundu, Mukul R.; White, S. M.

2003-01-01

309

IS THE OBSERVED HIGH-FREQUENCY RADIO LUMINOSITY DISTRIBUTION OF QSOs BIMODAL?  

SciTech Connect

The distribution of QSO radio luminosities has long been debated in the literature. Some argue that it is a bimodal distribution, implying that there are two separate QSO populations (normally referred to as 'radio-loud' and 'radio-quiet'), while others claim it forms a more continuous distribution characteristic of a single population. We use deep observations at 20 GHz to investigate whether the distribution is bimodal at high radio frequencies. Carrying out this study at high radio frequencies has an advantage over previous studies as the radio emission comes predominantly from the core of the active galactic nucleus, and hence probes the most recent activity. Studies carried out at lower frequencies are dominated by the large-scale lobes where the emission is built up over longer timescales (10{sup 7}-10{sup 8} yr), thereby confusing the sample. Our sample comprises 874 X-ray-selected QSOs that were observed as part of the 6dF Galaxy Survey. Of these, 40% were detected down to a 3{sigma} detection limit of 0.2-0.5 mJy. No evidence of bimodality is seen in either the 20 GHz luminosity distribution or in the distribution of the R{sub 20} parameter: the ratio of the radio to optical luminosities traditionally used to classify objects as being either radio-loud or radio-quiet. Previous results have claimed that at low radio luminosities, star formation processes can dominate the radio emission observed in QSOs. We attempt to investigate these claims by stacking the undetected sources at 20 GHz and discuss the limitations in carrying out this analysis. However, if the radio emission was solely due to star formation processes, we calculate that this corresponds to star formation rates ranging from {approx}10 M{sub Sun} yr{sup -1} to {approx}2300 M{sub Sun} yr{sup -1}.

Mahony, Elizabeth K.; Sadler, Elaine M.; Croom, Scott M.; Murphy, Tara [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Ekers, Ronald D.; Feain, Ilana J., E-mail: emahony@physics.usyd.edu.au [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

2012-07-20

310

FORTE observations of lightning radio-frequency signatures: Capabilities and basic results  

Microsoft Academic Search

The FORTE satellite, launched on August 29, 1997, carries both radio-frequency-receiver and optical (imaging and photometric) payloads for the study of lightning. The radio-frequency (RF) data for the first 7 months of operation are described, both to illustrate the satellite{close_quote}s capabilities and to explain the basic statistical findings so far. FORTE{close_quote}s multichannel RF trigger system represents a significant advance in

Abram R. Jacobson; Stephen O. Knox; Robert Franz; Donald C. Enemark

1999-01-01

311

Investigation of inherent radio frequency oscillation and minor switching in amorphous chalcogenide semiconductors  

E-print Network

INVESTIGATION OF INHERENT RADIO FREQUENCY OSCILLATION AND MINOR SWITCHING IN AMORPHOUS CHALCOGENIDE SEMICONDUCTORS A Thesis by ROBERT WAYNE GILL JR. Submitted to the Graduate College of Texas AAM University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE August 1971 Major Subject: Electrical Engineering INVESTIGATION OF INHERENT RADIO FREQUENCY OSCILLATION AND MINOR SWITCHING IN AMORPHOUS CHALCOGENIDE SEMICONDUCTORS A Thesis by ROBERT WAYNE GILL JR...

Gill, Robert Wayne

2012-06-07

312

Radio-frequency tag with optoelectronic interface for distributed wireless chemical and biological sensor applications  

Microsoft Academic Search

A battery-free, wireless optical chemical sensor with integral contactless power and data link is demonstrated. The chemical sensor and its optoelectronic interface form an integral part of a radio-frequency tag which we have developed specifically for use as a wireless chemical and biological sensor, and which is compatible with the International Standards Organisation ISO15693 radio-frequency identification (RFID) protocol. The chemical

Ivana Murkovi? Steinberg; Matthew D. Steinberg

2009-01-01

313

High-frequency radio-wave ablation of osteoid osteoma in the lumbar spine  

Microsoft Academic Search

The authors report on the first known application in the spine of percutaneous ablation of osteoid osteoma using radio-frequency\\u000a waves. The technique involves a CT-guided biopsy of the lesion followed by introduction of a 1-mm probe connected to a radio-frequency\\u000a lesion generator. The procedure was performed on an outpatient basis and the patient experienced immediate relief of his symptoms.\\u000a No

O. L. Osti; R. Sebben

1998-01-01

314

Emergency and operational low and medium frequency band radio communications system for underground mines  

SciTech Connect

This paper reports on a minewide low- and medium-frequency radio system has been developed and installed in coal and metalliferous mines. The radio system established reliable emergency communications between mine personnel on the surface, in working areas, or traveling in designated escapeway. The system also provides operational communications to improve coordination among working groups in the underground mining complex. The radio system utilizes two robust radio signal transmission modes to establish underground radio coverage areas. The seam transmission mode occurs when layers of coal, trona, potash, quartzite, or gilsonite are surrounded by more electrically conductive sediment layers. The layering forms a natural waveguide for transmission of medium-frequency (MF) band (300 to 23 000 kHz) radio signals. The conductor transmission line mode waveguide occurs when electrical conductors, such as ac power distribution cable, conveyor belt structures, steel pipe, and rail are in place in mine passageways. The conductor transmission waveguide attenuation rate is lowest in the low-frequency and (30 to 300 kHz). Safety is inherent in the system design since robust radio signal transmission modes are likely to survive events such as rock falls, fire, or explosion. Since the conductor utilities are necessary parts of the underground mine infrastructure, transmission line installation and maintenance cost can be avoided in the radio system.

Stolarczyk, L.G. (Stolar, Inc., Raton, NM (US))

1991-07-01

315

Encoding many channels in the same frequency through radio vorticity: first experimental test  

E-print Network

We have shown experimentally that it is possible to propagate and use the properties of twisted non-monochromatic incoherent radio waves to simultaneously transmit to infinity more radio channels on the same frequency band by encoding them in different orbital angular momentum states. This novel radio technique allows the implementation of, at least in principle, an infinite number of channels on one and the same frequency, even without using polarization or dense coding techniques. An optimal combination of all these physical properties and techniques represents a solution for the problem of radio band congestion. Our experimental findings show that the vorticity of each twisted electromagnetic wave is preserved after the propagation, paving the way for entirely new paradigms in radio communication protocols.

Tamburini, Fabrizio; Sponselli, Anna; Romanato, Filippo; Thidé, Bo; Bianchini, Antonio; Palmieri, Luca; Someda, Carlo G

2011-01-01

316

Indication of radio frequency interference (RFI) sources for solar burst monitoring in Malaysia  

NASA Astrophysics Data System (ADS)

Apart of monitoring the Sun project, the Radio Frequency Interference (RFI) surveying in the region of (1-1200) MHz has been conducted. The main objective of this surveying is to test and qualify the potential of monitoring a continuous radio emission of Solar in Malaysia. This work is also an initiative of International Space Weather Initiative (ISWI) project where Malaysia is one of the country that participate a e-Callisto Spectrometer network in order to study the behavior of Solar radio burst in frequency of (45-800) MHz region which will be install in this October. Detail results will indicate the potential of monitoring a solar in Malaysia.

Hamidi, Z. S.; Abidin, Z. Z.; Ibrahim, Z. A.; Shariff, N. N. M.

2012-06-01

317

Secular decrease of the radio emission flux density of Cassiopeia A at the 38-MHz frequency  

NASA Astrophysics Data System (ADS)

The radio emission flux density of Cassiopeia A relative to Cygnus A was measured with the DKR-1000 radio telescope in 1987, 1988, and 1991. The mean rate of the secular flux-density decline at the 7.9-m wavelength during 1956-1991 is determined, on the basis of earlier published data, to be 0.70 +/- 0.19 percent/yr. This value is half that extrapolated to the 38-MHz frequency, which was obtained from frequency dependences of the secular decrease rate for Cassiopeia A radio emission.

Vinyajkin, E. N.; Volodin, A. G.; Koval'Chuk, O. M.

1992-09-01

318

Progress in ultra high energy neutrino experiments using radio techniques  

SciTech Connect

Studying the source of Ultra High Energy Cosmic Ray (UHECR) can provide important clues on the understanding of UHE particle physics, astrophysics, and other extremely energetic phenomena in the universe. However, charged CR particles are deflected by magnetic fields and can not point back to the source. Furthermore, UHECR charged particles above the Greisen-Zatsepin-Kuzmin (GZK) cutoff (about 5 Multiplication-Sign 10{sup 19} eV) suffer severe energy loss due to the interaction with the Cosmic Microwave Background Radiation (CMBR). Consequently almost all the information carried by CR particles about their origin is lost. Neutrinos, which are neutral particles and have extremely weak interactions with other materials can arrive at the earth without deflection and absorption. Therefore UHE neutrinos can be traced back to the place where they are produced. Due to their weak interaction and ultra high energies (thus extremely low flux) the detection of UHE neutrinos requires a large collecting area and massive amounts of material. Cherenkov detection at radio frequency, which has long attenuation lengths and can travel freely in natural dense medium (ice, rock and salt et al), can fulfill the detection requirement. Many UHE neutrino experiments are being performed by radio techniques using natural ice, lunar, and salt as detection mediums. These experiments have obtained much data about radio production, propagation and detection, and the upper limit of UHE neutrino flux.

Liu Jiali [Physics department, Kunming University, Kunming, 650214 (China); Tiedt, Douglas [Physics department, South Dakota School of Mines and Technology, Rapid City, SD, 57701-3995 (United States)

2013-05-23

319

Spatial distribution of the plasma parameters in a radio-frequency driven negative ion sourcea)  

NASA Astrophysics Data System (ADS)

Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure.

Todorov, D.; Tarnev, Kh.; Paunska, Ts.; Lishev, St.; Shivarova, A.

2014-02-01

320

Spatial distribution of the plasma parameters in a radio-frequency driven negative ion source.  

PubMed

Results from initial stage of modeling of the SPIDER source of negative hydrogen/deuterium ions currently under development in Consorzio RFX (Padova) regarding ITER are presented. A 2D model developed within the fluid plasma theory for low-pressure discharges (free-fall regime maintenance) is applied to the gas-discharge conditions planned and required for the SPIDER source: gas pressure of 0.3 Pa and radio-frequency (rf) power of 100 kW absorbed in a single driver. The results are for the spatial distribution of the plasma characteristics (charged particle densities, electron temperature and electron energy flux, plasma potential, and dc electric field) with conclusions for the role of the electron energy flux in the formation of the discharge structure. PMID:24593544

Todorov, D; Tarnev, Kh; Paunska, Ts; Lishev, St; Shivarova, A

2014-02-01

321

Laboratory performance of the BEAR (Beam Experiment Aboard Rocket) RFQ (radio-frequency quadrupole)  

SciTech Connect

The BEAR (Beam Experiment Aboard Rocket) accelerator will be part of an experiment to demonstrate the operation of an ion accelerator in space and to characterize the exoatmospheric propagation of a neutral particle beam. The RFQ (radio-frequency quadrupole) has been designed to produce a 25-mA H/sup /minus// beam with an emittance of 0.01 cm-mrad (rms normalized) at an energy of 1 MeV. Because of the rigors of spaceflight, the accelerator design has been constrained by factors not normally applicable to conventional terrestrial accelerators. These factors and the mechanical features are described in a companion paper in these proceedings. The design techniques developed for BEAR would be applicable whenever, rugged, lightweight, or power-efficient systems are required. The BEAR RFQ has been operated under power with beam in the laboratory. This paper details of measured beam transport, emittance, and energy spectra. 6 refs., 4 figs.

O'Shea, P.G.; Schrage, D.L.; Young, L.M.; Zaugg, T.J.; Lynch, M.T.; McKenna, K.F.; Hansborough, L.D.

1988-01-01

322

Calibrating CHIME, A New Radio Interferometer to Probe Dark Energy  

E-print Network

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a transit interferometer currently being built at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC, Canada. We will use CHIME to map neutral hydrogen in the frequency range 400 -- 800\\,MHz over half of the sky, producing a measurement of baryon acoustic oscillations (BAO) at redshifts between 0.8 -- 2.5 to probe dark energy. We have deployed a pathfinder version of CHIME that will yield constraints on the BAO power spectrum and provide a test-bed for our calibration scheme. I will discuss the CHIME calibration requirements and describe instrumentation we are developing to meet these requirements.

Newburgh, Laura B; Amiri, Mandana; Bandura, Kevin; Bond, J Richard; Connor, Liam; Cliche, Jean-François; Davis, Greg; Deng, Meiling; Denman, Nolan; Dobbs, Matt; Fandino, Mateus; Fong, Heather; Gibbs, Kenneth; Gilbert, Adam; Griffin, Elizabeth; Halpern, Mark; Hanna, David; Hincks, Adam D; Hinshaw, Gary; Höfer, Carolin; Klages, Peter; Landecker, Tom; Masui, Kiyoshi; Parra, Juan Mena; Pen, Ue-Li; Peterson, Jeff; Recnik, Andre; Shaw, J Richard; Sigurdson, Kris; Sitwell, Michael; Smecher, Graeme; Smegal, Rick; Vanderlinde, Keith; Wiebe, Don

2014-01-01

323

Calibrating CHIME: a new radio interferometer to probe dark energy  

NASA Astrophysics Data System (ADS)

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a transit interferometer currently being built at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, BC, Canada. We will use CHIME to map neutral hydrogen in the frequency range 400 { 800MHz over half of the sky, producing a measurement of baryon acoustic oscillations (BAO) at redshifts between 0.8 { 2.5 to probe dark energy. We have deployed a pathfinder version of CHIME that will yield constraints on the BAO power spectrum and provide a test-bed for our calibration scheme. I will discuss the CHIME calibration requirements and describe instrumentation we are developing to meet these requirements.

Newburgh, Laura B.; Addison, Graeme E.; Amiri, Mandana; Bandura, Kevin; Bond, J. Richard; Connor, Liam; Cliche, Jean-François; Davis, Greg; Deng, Meiling; Denman, Nolan; Dobbs, Matt; Fandino, Mateus; Fong, Heather; Gibbs, Kenneth; Gilbert, Adam; Griffin, Elizabeth; Halpern, Mark; Hanna, David; Hincks, Adam D.; Hinshaw, Gary; Höfer, Carolin; Klages, Peter; Landecker, Tom; Masui, Kiyoshi; Parra, Juan Mena; Pen, Ue-Li; Peterson, Jeff; Recnik, Andre; Shaw, J. Richard; Sigurdson, Kris; Sitwell, Micheal; Smecher, Graeme; Smegal, Rick; Vanderlinde, Keith; Wiebe, Don

2014-07-01

324

Endotoxin removal by radio frequency gas plasma (glow discharge)  

NASA Astrophysics Data System (ADS)

Contaminants remaining on implantable medical devices, even following sterilization, include dangerous fever-causing residues of the outer lipopolysaccharide-rich membranes of Gram-negative bacteria such as the common gut microorganism E. coli. The conventional method for endotoxin removal is by Food & Drug Administration (FDA)-recommended dry-heat depyrogenation at 250°C for at least 45 minutes, an excessively time-consuming high-temperature technique not suitable for low-melting or heat-distortable biomaterials. This investigation evaluated the mechanism by which E. coli endotoxin contamination can be eliminated from surfaces during ambient temperature single 3-minute to cumulative 15-minute exposures to radio-frequency glow discharge (RFGD)-generated residual room air plasmas activated at 0.1-0.2 torr in a 35MHz electrodeless chamber. The main analytical technique for retained pyrogenic bio-activity was the Kinetic Chromogenic Limulus Amebocyte Lysate (LAL) Assay, sufficiently sensitive to document compliance with FDA-required Endotoxin Unit (EU) titers less than 20 EU per medical device by optical detection of enzymatic color development corresponding to < 0.5 EU/ml in sterile water extracts of each device. The main analytical technique for identification of chemical compositions, amounts, and changes during sequential reference Endotoxin additions and subsequent RFGD-treatment removals from infrared (IR)-transparent germanium (Ge) prisms was Multiple Attenuated Internal Reflection (MAIR) infrared spectroscopy sensitive to even monolayer amounts of retained bio-contaminant. KimaxRTM 60 mm x 15 mm and 50mm x 15mm laboratory glass dishes and germanium internal reflection prisms were inoculated with E. coli bacterial endotoxin water suspensions at increments of 0.005, 0.05, 0.5, and 5 EU, and characterized by MAIR-IR spectroscopy of the dried residues on the Ge prisms and LAL Assay of sterile water extracts from both glass and Ge specimens. The Ge prism MAIR-IR measurements were repeated after employing 3-minute RFGD treatments sequentially for more than 10 cycles to observe removal of deposited matter that correlated with diminished EU titers. The results showed that 5 cycles, for a total exposure time of 15 minutes to low-temperature gas plasma, was sufficient to reduce endotoxin titers to below 0.05 EU/ml, and correlated with concurrent reduction of major endotoxin reference standard absorption bands at 3391 cm-1, 2887 cm-1, 1646 cm -1 1342 cm-1, and 1103 cm-1 to less than 0.05 Absorbance Units. Band depletion varied from 15% to 40% per 3-minute cycle of RFGD exposure, based on peak-to-peak analyses. In some cases, 100% of all applied biomass was removed within 5 sequential 3-minute RFGD cycles. The lipid ester absorption band expected at 1725 cm-1 was not detectable until after the first RFGD cycle, suggesting an unmasking of the actual bacterial endotoxin membrane induced within the gas plasma environment. Future work must determine the applicability of this low-temperature, quick depyrogenation process to medical devices of more complicated geometry than the flat surfaces tested here.

Poon, Angela

325

Self-consistent modeling of radio-frequency plasma generation in stellarators  

SciTech Connect

A self-consistent model of radio-frequency (RF) plasma generation in stellarators in the ion cyclotron frequency range is described. The model includes equations for the particle and energy balance and boundary conditions for Maxwell’s equations. The equation of charged particle balance takes into account the influx of particles due to ionization and their loss via diffusion and convection. The equation of electron energy balance takes into account the RF heating power source, as well as energy losses due to the excitation and electron-impact ionization of gas atoms, energy exchange via Coulomb collisions, and plasma heat conduction. The deposited RF power is calculated by solving the boundary problem for Maxwell’s equations. When describing the dissipation of the energy of the RF field, collisional absorption and Landau damping are taken into account. At each time step, Maxwell’s equations are solved for the current profiles of the plasma density and plasma temperature. The calculations are performed for a cylindrical plasma. The plasma is assumed to be axisymmetric and homogeneous along the plasma column. The system of balance equations is solved using the Crank-Nicholson scheme. Maxwell’s equations are solved in a one-dimensional approximation by using the Fourier transformation along the azimuthal and longitudinal coordinates. Results of simulations of RF plasma generation in the Uragan-2M stellarator by using a frame antenna operating at frequencies lower than the ion cyclotron frequency are presented. The calculations show that the slow wave generated by the antenna is efficiently absorbed at the periphery of the plasma column, due to which only a small fraction of the input power reaches the confinement region. As a result, the temperature on the axis of the plasma column remains low, whereas at the periphery it is substantially higher. This leads to strong absorption of the RF field at the periphery via the Landau mechanism.

Moiseenko, V. E., E-mail: moiseenk@ipp.kharkov.ua; Stadnik, Yu. S., E-mail: stadnikys@kipt.kharkov.ua [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine); Lysoivan, A. I., E-mail: a.lyssoivan@fz-juelich.de [Royal Military Academy, EURATOM-Belgian State Association, Laboratory for Plasma Physics (Belgium); Korovin, V. B. [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)] [National Academy of Sciences of Ukraine, National Science Center Kharkov Institute of Physics and Technology (Ukraine)

2013-11-15

326

Low-Frequency Radio Observations of X-Ray Ghost Bubbles in A2597: A History of Radio Activity in the Core  

Microsoft Academic Search

A previous analysis of the Chandra X-ray image of the center of the cooling core cluster A2597 showed two ``ghost holes'' in the X-ray emission to the west and northeast of the central radio galaxy PKS 2322-123. Previous radio observations did not detect any radio emission coming from the interior of the X-ray holes. We present new low-frequency radio observations

T. E. Clarke; C. L. Sarazin; E. L. Blanton; D. M. Neumann; N. E. Kassim

2005-01-01

327

2006 Raj JainCSE574sWashington University in St. Louis Radio FrequencyRadio Frequency  

E-print Network

door openers use RFID ! Implants in human, horses, fishes, animals Animal ID Standards ISO 11784, radio modulator, control logic, memory and a power system ! Power Source: " Passive Tags: Powered. Designed to be implanted in humans. Identify patients. " Semi-passive RFIDs used in E-Z Pass toll

Jain, Raj

328

Radio frequency polyphase filter design in 0.13-?m CMOS for wireless communications  

Microsoft Academic Search

Polyphase filters are an efficient solution for high image rejection and great accuracy quadrature generation in radio frequency (RF) receivers. Analytical modeling of passive polyphase filter suitable for RF front-end applications operating in 2.4 GHz frequency band is dealt with. This analytical analysis has been used to calibrate the optimal values of passive components in order to obtain the maximum

F. Haddad; R. Bouchakour; W. Rahajandraibe; L. Zaid; O. Frioui

2007-01-01

329

A low-power CMOS integrated circuit for field-powered radio frequency identification tags  

Microsoft Academic Search

Cheap, compact radio frequency identification (RFID) tags will make a wide range of new applications cost-effective. Minimum cost can be achieved only in a passive tag (that acquires operating power from the interrogating RF field). A compact tag form factor demands a small tag antenna, that in turn demands either external components or a high-frequency RF carrier for effective tag

D. Friedman; H. Heinreich; D.-W. Duan

1997-01-01

330

Frequency planning and system design of wide-area coverage cellular radio systems  

Microsoft Academic Search

A cellular-based approach to frequency planning and system design in wide-area-coverage radio systems is presented. The basic cellular theory is described; appropriate frequency allocation methods are discussed; and performance planning criteria are detailed with respect to ESKOM's experience in VHF and UHF systems. The use of computerized propagation prediction tools in the design process is discussed

A. R. Johnson

1992-01-01

331

Comparison of Pulsed Sinusoid Radio Frequency Interference Detection Algorithms Using Time and  

E-print Network

Comparison of Pulsed Sinusoid Radio Frequency Interference Detection Algorithms Using Time (ROC) for pulsed sinusoid RFI. Downlink data bandwidth is one of the major design factors-11]. RFI is often localized in time and frequency, relative to the integration times and pre

Ruf, Christopher

332

HEATING THE HOT ATMOSPHERES OF GALAXY GROUPS AND CLUSTERS WITH CAVITIES: THE RELATIONSHIP BETWEEN JET POWER AND LOW-FREQUENCY RADIO EMISSION  

SciTech Connect

We present scaling relations between jet power and radio power measured using the Giant Metrewave Radio Telescope (GMRT), Chandra, and XMM-Newton, for a sample of nine galaxy groups combined with the BIrzan et al. sample of clusters. Cavity power is used as a proxy for mechanical jet power. Radio power is measured at 235 MHz and 1.4 GHz, and the integrated 10 MHz-10 GHz radio luminosity is estimated from the GMRT 610-235 MHz spectral index. The use of consistently analyzed, high-resolution low-frequency radio data from a single observatory makes the radio powers for the groups more reliable than those used by previous studies, and the combined sample covers 6-7 decades in radio power and 5 decades in cavity power. We find a relation of the form P{sub jet}{proportional_to} L{approx}0.7{sub radio} for integrated radio luminosity, with a total scatter of {sigma}{sub Lrad} = 0.63 and an intrinsic scatter of {sigma}{sub i,Lrad} = 0.59. A similar relation is found for 235 MHz power, but a slightly flatter relation with greater scatter is found for 1.4 GHz power, suggesting that low-frequency or broadband radio measurements are superior jet power indicators. We find our low-frequency relations to be in good agreement with previous observational results. Comparison with jet models shows reasonable agreement, which may be improved if radio sources have a significant low-energy electron population. We consider possible factors that could bias our results or render them more uncertain, and find that correcting for such factors in those groups we are able to study in detail leads to a flattening of the P{sub jet}:L{sub radio} relation.

O'Sullivan, E.; Raychaudhury, S.; Ponman, T. J. [School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT (United Kingdom); Giacintucci, S.; David, L. P.; Gitti, M.; Vrtilek, J. M., E-mail: ejos@star.sr.bham.ac.uk [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-07-01

333

High power water load for microwave and millimeter-wave radio frequency sources  

DOEpatents

A high power water load for microwave and millimeter wave radio frequency sources has a front wall including an input port for the application of RF power, a cylindrical dissipation cavity lined with a dissipating material having a thickness which varies with depth, and a rear wall including a rotating reflector for the reflection of wave energy inside the cylindrical cavity. The dissipation cavity includes a water jacket for removal of heat generated by the absorptive material coating the dissipation cavity, and this absorptive material has a thickness which is greater near the front wall than near the rear wall. Waves entering the cavity reflect from the rotating reflector, impinging and reflecting multiple times on the absorptive coating of the dissipation cavity, dissipating equal amounts of power on each internal reflection.

Ives, R. Lawrence (Saratoga, CA); Mizuhara, Yosuke M. (Palo Alto, CA); Schumacher, Richard V. (Sunnyvale, CA); Pendleton, Rand P. (Saratoga, CA)

1999-01-01

334

Strong Meissner screening change in superconducting radio frequency cavities due to mild baking  

NASA Astrophysics Data System (ADS)

We investigate "hot" regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-?SR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth ?L=23±2 nm. In contrast, a cutout sample from the 120 ?C baked cavity shows a much larger ? >100 nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions.

Romanenko, A.; Grassellino, A.; Barkov, F.; Suter, A.; Salman, Z.; Prokscha, T.

2014-02-01

335

Strong Meissner screening change in superconducting radio frequency cavities due to mild baking  

E-print Network

We investigate "hot" regions with anomalous high field dissipation in bulk niobium superconducting radio frequency cavities for particle accelerators by using low energy muon spin rotation (LE-$\\mu$SR) on corresponding cavity cutouts. We demonstrate that superconducting properties at the hot region are well described by the non-local Pippard/BCS model for niobium in the clean limit with a London penetration depth $\\lambda_\\mathrm{L} = 23 \\pm 2$ nm. In contrast, a cutout sample from the 120$^\\circ$C baked cavity shows a much larger $\\lambda > 100$ nm and a depth dependent mean free path, likely due to gradient in vacancy concentration. We suggest that these vacancies can efficiently trap hydrogen and hence prevent the formation of hydrides responsible for rf losses in hot regions.

Romanenko, A; Barkov, F; Suter, A; Salman, Z; Prokscha, T

2013-01-01

336

Design of high power radio frequency radial combiner for proton accelerator.  

PubMed

A simplified design method has been proposed for systematic design of novel radio frequency (rf) power combiner and divider, incorporating radial slab-line structure, without using isolation resistor and external tuning mechanism. Due to low insertion loss, high power capability, and rigid mechanical configuration, this structure is advantageous for modern solid state rf power source used for feeding rf energy to superconducting accelerating structures. Analysis, based on equivalent circuit and radial transmission line approximation, provides simple design formula for calculating combiner parameters. Based on this method, novel 8-way and 16-way power combiners, with power handling capability of 4 kW, have been designed, as part of high power solid state rf amplifier development. Detailed experiments showed good performance in accordance with theory. PMID:19191467

Jain, Akhilesh; Sharma, Deepak Kumar; Gupta, Alok Kumar; Hannurkar, P R

2009-01-01

337

A Conceptual Design of Radio Frequency Quadrupole for TAC Proton Linac  

E-print Network

The conceptual beam dynamics design of 352.2 MHz Radio-Frequency Quadrupole (RFQ) of Turkish Accelerator Center (TAC) project which accelerates continuous wave (CW) proton beam with 30 mA current from 50 keV to 3 MeV kinetic energy has been performed in this study. Also, it includes error analysis of the RFQ in which some fluctuations have been introduced to input beam parameters to see how the output beam parameters are affected, two-dimensional (2-D) and three-dimensional (3-D) electromagnetic structural design of the RFQ to obtain optimum cavity paramaters that agree with the ones of the beam dynamics. The beam dynamics and error analysis of the RFQ have been done by using LIDOS.RFQ. Electromagnetic design parameters were obtained by using SUPERFISH on 2-D cavity geometry and CST Microwave Studio on 3-D cavity geometry.

Kisoglu, H F; Yilmaz, M

2014-01-01

338

Radio Frequency Noise Effects on the CERN Large Hadron Collider Beam Diffusion  

SciTech Connect

Radio frequency (rf) accelerating system noise can have a detrimental impact on the Large Hadron Collider (LHC) performance through longitudinal motion and longitudinal emittance growth. A theoretical formalism has been developed to relate the beam and rf station dynamics with the bunch length growth. Measurements were conducted at LHC to determine the performance limiting rf components and validate the formalism through studies of the beam diffusion dependence on rf noise. As a result, a noise threshold was established for acceptable performance which provides the foundation for beam diffusion estimates for higher energies and intensities. Measurements were also conducted to determine the low level rf noise spectrum and its major contributions, as well as to validate models and simulations of this system.

Mastoridis, T.; Baudrenghien, P.; Butterworth, A.; Molendijk, J.; /CERN; Rivetta, C.; Fox, J.D.; /SLAC

2012-04-30

339

Radio-frequency excitation of single molecules by scanning tunnelling microscopy  

NASA Astrophysics Data System (ADS)

We have upgraded a low-temperature scanning tunnelling microscope (STM) with a radio-frequency (RF) modulation system to extend STM spectroscopy to the range of low energy excitations (<1 meV). We studied single molecules of a stable hydrocarbon π-radical weakly physisorbed on Au(111). At 5 K thermal excitation of the adsorbed molecules is inhibited due to the lack of short-wavelength phonons of the substrate. We demonstrate resonant excitation of mechanical modes of single molecules by RF tunnelling at 115 MHz, which induces structural changes in the molecule ranging from controlled diffusion and modification of bond angles to bond breaking as the ultimate climax (resonance catastrophe). Our results pave the way towards RF-STM-based spectroscopy and controlled manipulation of molecular nanostructures on a surface.

Müllegger, Stefan; Das, Amal K.; Mayr, Karlheinz; Koch, Reinhold

2014-04-01

340

Radio-frequency excitation of single molecules by scanning tunnelling microscopy.  

PubMed

We have upgraded a low-temperature scanning tunnelling microscope (STM) with a radio-frequency (RF) modulation system to extend STM spectroscopy to the range of low energy excitations (<1 meV). We studied single molecules of a stable hydrocarbon ?-radical weakly physisorbed on Au(111). At 5 K thermal excitation of the adsorbed molecules is inhibited due to the lack of short-wavelength phonons of the substrate. We demonstrate resonant excitation of mechanical modes of single molecules by RF tunnelling at 115 MHz, which induces structural changes in the molecule ranging from controlled diffusion and modification of bond angles to bond breaking as the ultimate climax (resonance catastrophe). Our results pave the way towards RF-STM-based spectroscopy and controlled manipulation of molecular nanostructures on a surface. PMID:24594655

Müllegger, Stefan; Das, Amal K; Mayr, Karlheinz; Koch, Reinhold

2014-04-01

341

Dielectric properties of salmon ( Oncorhynchus keta) and sturgeon ( Acipenser transmontanus) caviar at radio frequency (RF) and microwave (MW) pasteurization frequencies  

Microsoft Academic Search

Radio frequency (RF) and microwave (MW) heating provide an important advantage of more rapid heat penetration in pasteurization processes for heat labile high value foods, which to date, have only been pasteurized by conductive heating. The objectives of this work were to determine the dielectric constant, loss factor and power penetration depth for salmon (0.8% and 2.3% total salt) and

Murad Al-Holy; Yifen Wang; Juming Tang; Barbara Rasco

2005-01-01

342

Radio-frequency-driven dipole-dipole interactions in spatially separated volumes  

NASA Astrophysics Data System (ADS)

Radio-frequency (rf) fields in the MHz range are used to induce resonant energy transfer between cold Rydberg atoms in spatially separated volumes. After laser preparation of the Rydberg atoms, dipole-dipole coupling excites the 49s atoms in one cylinder to the 49p state while the 41d atoms in the second cylinder are transferred down to the 42p state. The energy exchanged between the atoms in this process is 33GHz . An external rf field brings this energy transfer into resonance. The strength of the interaction has been investigated as a function of amplitude (0-1V/cm) and frequency (1-30MHz) of the rf field and as a function of a static-field offset. Multiphoton transitions up to fifth order as well as selection rules prohibiting the process at certain fields have been observed. The width of the resonances has been reduced compared to earlier results by switching off external magnetic fields of the magneto-optical trap, making sub-MHz spectroscopy possible. All features are well reproduced by theoretical calculations taking the strong ac Stark shift due to the rf field into account.

Tauschinsky, Atreju; van Ditzhuijzen, C. S. E.; Noordam, L. D.; van den Heuvell, H. B. Van Linden

2008-12-01

343

Observation of solar radio bursts using swept-frequency radiospectrograph in 20-40 MHz Band  

NASA Astrophysics Data System (ADS)

A new station for the observation of solar decametric radio bursts has been developed at Miyagi Vocational Training College in Tsukidate, Miyagi, Japan. Using the swept frequency radiospectrograph covering a frequency range from 20 MHz to 40 MHz within 200 msec, with bandwidth of 30 KHz, the radio outbursts from the sun have been currently monitored with colored dynamic spectrum display. After July 1982, successful observations provide the data which include all types of solar radio bursts such as type I, II, III, IV and V in the decametric wavelength range. In addition to these typical radio bursts, rising tone bursts with fast drift rate followed by strong type III bursts and a series of bursts repeating rising and falling tone bursts with slow drift rate have been observed.

Aoyama, Takashi; Oya, Hiroshi

344

Limits on low frequency radio emission from southern exoplanets with the Murchison Widefield Array  

E-print Network

We present the results of a survey for low frequency radio emission from 17 known exoplanetary systems with the Murchison Widefield Array. This sample includes 13 systems that have not previously been targeted with radio observations. We detected no radio emission at 154 MHz, and put 3 sigma upper limits in the range 15.2-112.5 mJy on this emission. We also searched for circularly polarised emission and made no detections, obtaining 3 sigma upper limits in the range 3.4-49.9 mJy. These are comparable with the best low frequency radio limits in the existing literature and translate to luminosity limits of between 1.2 x 10^14 W and 1.4 x 10^17 W if the emission is assumed to be 100% circularly polarised. These are the first results from a larger program to systematically search for exoplanetary emission with the MWA.

Murphy, Tara; Kaplan, David L; Gaensler, B M; Offringa, Andre R; Lenc, Emil; Hurley-Walker, Natasha

2014-01-01

345

Dynamic link\\/frequency selection in multi-hop cognitive radio networks for delay sensitive applications  

Microsoft Academic Search

Regarding the dynamic nature of cognitive radio networks and the delay of the central decision algorithms due to collecting necessary information in a multi-hop wireless network, distributed resource allocation algorithms are of crucial importance. In this paper we propose a new distributed resource allocation algorithm that properly selects link\\/frequency in a multi-hop cognitive radio network for delay sensitive applications. This

Behrouz Jashni; A. A. Tadaion; Farid Ashtiani

2010-01-01

346

Plasma production using microwave and radio frequency sources  

SciTech Connect

The initial breakdown of neutral fill gas is an important issue for stellarators where ionization of the neutral gas prefill is necessary before other auxiliary power can be coupled to the system. Microwaves with frequencies at the fundamental electron cyclotron resonance can be used for this purpose because they couple to electrons through linear wave-particle interactions. In addition, microwave applications at twice the electron cyclotron frequency typically have a strong enough nonlinear coupling to initiate breakdown with reasonable agreement between theory and experiment. Nonlinear couplings at higher harmonics are progressively weaker, and the possibilities of using the third harmonic are discussed. A difficulty can arise when microwave sources are used for plasma production because it is often too expensive to support the frequency ranges needed to obtain breakdown at arbitrary static magnetic field values. Thus, devices that rely exclusively on microwave sources to obtain target plasmas may be limited in their operational range by their microwave source frequencies. Alternatively, rf sources possessing a broad band of tunable frequencies are often available in the megahertz frequency range. The use of these types of power sources to produce target plasmas could add to the operational limits of many devices. Waves with frequencies of a few megahertz have been used to produce plasmas at the Institute of Physics and Technology at Kharkov (KFTI) for many years. The technique and mechanism by which the neutral gas is broken down in the very early phases of these discharges are presented.

Carter, M.D.

1989-01-01

347

A review of organizations influencing radio frequency allocations to deep space research  

NASA Technical Reports Server (NTRS)

The charters and functions of various national and international scientific organizations were examined to identify those which have a direct or indirect influence on the allocation of radio frequencies for use in deep space research. Those organizations identified as having the ability to influence frequency allocations are described. A brief description of each organization is provided, and the members who are influential specifically in frequency allocations are listed. The interrelations between the organizations and how they influence allocations are explained.

1976-01-01

348

Radio-Frequency Inverters With Transmission-Line Input Networks  

E-print Network

A soft-switching inverter topology (the Class Phi ) is presented which draws dc source current through a transmission line or a lumped-network approximation of a distributed line. By aligning the inverter switching frequency ...

Phinney, Joshua W.

349

Health aspects of radio-frequency radiation accidents. Part II: A proposed protocol for assessment of health effects in radio-frequency radiation accidents  

SciTech Connect

A protocol is proposed for the assessment of health effects following a radio-frequency radiation accident. The protocol is intended to ensure uniform recording of exposure and medical data. This should meet the requirements of the individuals exposed as well as contributing to scientific knowledge. Difficult aspects about the collection of exposure and medical data are discussed and the need to consider the feelings of the exposed individual(s) is emphasized.

Hocking, B.; Joyner, K.

1988-01-01

350

Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory  

NASA Astrophysics Data System (ADS)

The Rosse Solar-Terrestrial Observatory (RSTO; http://www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53°05'38.9?, 7°55'12.7?) in 2010 to study solar radio bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy in Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range of 10 - 870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range of 10 - 400 MHz are obtained with four sweeps per second over 600 channels. Here, we describe the RSTO solar radio spectrometer set-up, and present dynamic spectra of samples of type II, III and IV radio bursts. In particular, we describe the fine-scale structure observed in type II bursts, including band splitting and rapidly varying herringbone features.

Zucca, P.; Carley, E. P.; McCauley, J.; Gallagher, P. T.; Monstein, C.; McAteer, R. T. J.

2012-10-01

351

Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma  

SciTech Connect

Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H. [Facultad de Fisica, Pontificia Universidad Catolica de Chile, Ave. Vicuna Mackenna 4860, Santiago 22 (Chile); Kakati, M. [Thermal Plasma Processed Materials Laboratory, Centre of Plasma Physics, Institute for Plasma Research, Sonapur 782 402, Assam (India)

2011-10-15

352

Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma  

NASA Astrophysics Data System (ADS)

Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.; Kakati, M.

2011-10-01

353

Numerical analysis of radio-frequency sheath-plasma interactions in the ion cyclotron range of frequencies  

SciTech Connect

A new finite element numerical scheme for analyzing self-consistent radio-frequency (RF) sheath-plasma interaction problems in the ion cyclotron range of frequencies is applied to various problems represented by simplified models for the tokamak scrape-off layer. The present code incorporates a modified boundary condition, which is called a sheath boundary condition, that couples the radio-frequency waves and sheaths at the material boundaries by treating the sheath as a thin vacuum layer. A series of numerical analyses in one- and two-dimensional domains show several important physical properties, such as the existence of multiple roots, hysteresis effects, presence and characteristics of the sheath-plasma waves, and the phase shift of a reflected slow wave, some of which are newly identified by introducing a spatially varying plasma density and background magnetic field.

Kohno, H. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Myra, J. R.; D'Ippolito, D. A. [Lodestar Research Corporation, 2400 Central Avenue P-5, Boulder, Colorado 80301 (United States)

2012-01-15

354

Detection of NMR signals with a radio-frequency atomic magnetometer  

E-print Network

We demonstrate detection of proton NMR signals with a radio frequency atomic magnetometer tuned to the NMR frequency of 62 kHz. High-frequency operation of the atomic magnetometer makes it relatively insensitive to ambient magnetic field noise. We obtain magnetic field sensitivity of 7 fT/Hz$^{1/2}$ using only a thin aluminum shield. We also derive an expression for the fundamental sensitivity limit of a surface inductive pick-up coil as a function of frequency and find that an atomic rf magnetometer is intrinsically more sensitive than a coil of comparable size for frequencies below about 50 MHz.

Savukov, I M; Seltzer, S J

2006-01-01

355

The electrical asymmetry effect in geometrically asymmetric capacitive radio frequency plasmas  

NASA Astrophysics Data System (ADS)

The electrical asymmetry effect (EAE) allows an almost ideal separate control of the mean ion energy, , and flux, ?i, at the electrodes in capacitive radio frequency discharges with identical electrode areas driven at two consecutive harmonics with adjustable phase shift, ?. In such geometrically symmetric discharges, a DC self bias is generated as a function of ?. Consequently, can be controlled separately from ?i by adjusting the phase shift. Here, we systematically study the EAE in low pressure dual-frequency discharges with different electrode areas operated in argon at 13.56 MHz and 27.12 MHz by experiments, kinetic simulations, and analytical modeling. We find that the functional dependence of the DC self bias on ? is similar, but its absolute value is strongly affected by the electrode area ratio. Consequently, the ion energy distributions change and can be controlled by adjusting ?, but its control range is different at both electrodes and determined by the area ratio. Under distinct conditions, the geometric asymmetry can be compensated electrically. In contrast to geometrically symmetric discharges, we find the ratio of the maximum sheath voltages to remain constant as a function of ? at low pressures and ?i to depend on ? at the smaller electrode. These observations are understood by the model. Finally, we study the self-excitation of non-linear plasma series resonance oscillations and its effect on the electron heating.

Schüngel, E.; Eremin, D.; Schulze, J.; Mussenbrock, T.; Czarnetzki, U.

2012-09-01

356

Radio astronomy with the European Lunar Lander: Opening up the last unexplored frequency regime  

NASA Astrophysics Data System (ADS)

The Moon is a unique location in our solar system and provides important information regarding the exposure to free space that is essential for future human space exploration to mars and beyond. The active broadband (100 kHz-100 MHz) tripole antenna now envisaged to be placed on the European Lunar Lander located at the Lunar South Pole allows for sensitive measurements of the exosphere and ionosphere, and their interaction with the Earths magnetosphere, solar particles, wind and CMEs and studies of radio communication on the Moon, that are essential for future lunar human and science exploration. In addition, the Lunar South Pole provides an excellent opportunity for radio astronomy. Placing a single radio antenna in an eternally dark crater or behind a mountain at the South (or North) pole would potentially provide perfect shielding from man-made radio interference (RFI), absence of ionospheric distortions, and high temperature and antenna gain stability that allows detection of the 21 cm wave emission from pristine hydrogen formed after the Big Bang and into the period where the first stars formed. A detection of the 21 cm line from the Moon at these frequencies would allow for the first time a clue on the distribution and evolution on mass in the early universe between the Epoch of Recombination and Epoch of Reionization (EoR). Next to providing a cosmological breakthrough, a single lunar radio antenna would allow for studies of the effect of solar flares and coronal mass ejections (CMEs) on the solar wind at distances close to Earth (space weather) and would open up the study of low frequency radio events (flares and pulses) from planets such as Jupiter and Saturn, which are known to emit bright (kJy-MJy) radio emission below 30 MHz (Jester and Falcke, 2009). Finally, a single radio antenna on the lunar lander would pave the way for a future large lunar radio interferometer; not only will it demonstrate the possibilities for lunar radio science and open up the last unexplored radio regime, but it will also allow a determination of the limitations of lunar radio science by measuring the local radio background noise.

Klein Wolt, Marc; Aminaei, Amin; Zarka, Philippe; Schrader, Jan-Rutger; Boonstra, Albert-Jan; Falcke, Heino

2012-12-01

357

Ionospheric irregularities causing scintillation of GHz frequency radio signals  

NASA Technical Reports Server (NTRS)

Consideration of the recently observed phenomenon of scintillation of satellite signals at GHz frequency range. Based on the scintillation data and results from in situ measurements, several ionospheric irregularity models with different power spectra are studied. Scintillation index is computed for the various models and compared with observed results. Both magnitude and frequency dependence of the scintillation index are investigated. It is found that a thick irregularity slab of the order of 200 km with an electron density fluctuation of about 20 per cent of its background value and with a nonmonotonic power spectrum may account for the maximum observed values of the scintillation index as well as its frequency dependence. Some future observations and measurements are suggested.

Wernik, A. W.; Liu, C. H.

1974-01-01

358

Theory study on a photonic-assisted radio frequency phase shifter with direct current voltage control  

NASA Astrophysics Data System (ADS)

A photonic-assisted radio frequency phase shifter with direct current voltage control is proposed using a polymer-based integrated Mach—Zehnder modulator. A closed-form expression of radio frequency (RF) signal power and phase is given. Theoretical calculation reveals that by carefully setting the bias voltages, RF signal power variation lower than 1-dB and phase accuracy less than 3° can be achieved and are not degraded by perturbation of modulation index once the bias voltage drift is kept within −3% ~ 3%.

Li, Jing; Ning, Ti-Gang; Pei, Li; Jian, Wei; You, Hai-Dong; Wen, Xiao-Dong; Chen, Hong-Yao; Zhang, Chan; Zheng, Jing-Jing

2014-10-01

359

Single shot time stamping of ultrabright radio frequency compressed electron pulses  

NASA Astrophysics Data System (ADS)

We demonstrate a method of time-stamping Radio Frequency compressed electron bunches for Ultrafast Electron Diffraction experiments in the sub-pC regime. We use an in-situ ultra-stable photo-triggered streak camera to directly track the time of arrival of each electron pulse and correct for the timing jitter in the radio frequency synchronization. We show that we can correct for timing jitter down to 30 fs root-mean-square with minimal distortion to the diffraction patterns, and performed a proof-of-principle experiment by measuring the ultrafast electron-phonon coupling dynamics of silicon.

Gao, M.; Jiang, Y.; Kassier, G. H.; Dwayne Miller, R. J.

2013-07-01

360

Single shot time stamping of ultrabright radio frequency compressed electron pulses  

SciTech Connect

We demonstrate a method of time-stamping Radio Frequency compressed electron bunches for Ultrafast Electron Diffraction experiments in the sub-pC regime. We use an in-situ ultra-stable photo-triggered streak camera to directly track the time of arrival of each electron pulse and correct for the timing jitter in the radio frequency synchronization. We show that we can correct for timing jitter down to 30 fs root-mean-square with minimal distortion to the diffraction patterns, and performed a proof-of-principle experiment by measuring the ultrafast electron-phonon coupling dynamics of silicon.

Gao, M.; Dwayne Miller, R. J. [Department of Chemistry and Physics, University of Toronto, Toronto, ON. M5S 3H6 (Canada); Max Planck Research Department for Structural Dynamics, Department of Physics, Center for Free Electron Laser Science, University of Hamburg, DESY, D-22607 Hamburg (Germany); Jiang, Y.; Kassier, G. H. [Max Planck Research Department for Structural Dynamics, Department of Physics, Center for Free Electron Laser Science, University of Hamburg, DESY, D-22607 Hamburg (Germany)

2013-07-15

361

Frequency Dependence of Pulse Width for 150 Radio Normal Pulsars  

NASA Astrophysics Data System (ADS)

The frequency dependence of the pulse width is studied for 150 normal pulsars, mostly selected from the European Pulsar Network, for which the 10% multifrequency pulse widths can be well fit with the Thorsett relationship W 10 = A?? + W 10, min. The relative fraction of pulse width change between 0.4 GHz and 4.85 GHz, ? = (W 4.85 – W 0.4)/W 0.4, is calculated in terms of the best-fit relationship for each pulsar. It is found that 81 pulsars (54%) have ? < –10% (group A), showing considerable profile narrowing at high frequencies, 40 pulsars (27%) have –10% <=? <= 10% (group B), meaning a marginal change in pulse width, and 29 pulsars (19%) have ? > 10% (group C), showing a remarkable profile broadening at high frequencies. The fractions of the group-A and group-C pulsars suggest that the profile narrowing phenomenon at high frequencies is more common than the profile broadening phenomenon, but a large fraction of the group-B and group-C pulsars (a total of 46%) is also revealed. The group-C pulsars, together with a portion of group-B pulsars with slight pulse broadening, can hardly be explained using the conventional radius-to-frequency mapping, which only applies to the profile narrowing phenomenon. Based on a recent version of the fan beam model, a type of broadband emission model, we propose that the diverse frequency dependence of pulse width is a consequence of different types of distribution of emission spectra across the emission region. The geometrical effect predicting a link between the emission beam shrinkage and spectrum steepening is tested but disfavored.

Chen, J. L.; Wang, H. G.

2014-11-01

362

The modification of a radio frequency Cockcroft Walton generator  

E-print Network

-Naiton penerator, 17 The $M ko exciter had to satisfy the requf. resents that it be vsriblo in frequency ao as co pornN optitun aiiysnonc of tho r f crsnsfoneer, anal thee it deliver tho required driving power of approximately a$ watts to tho r~f anplifier...-Naiton penerator, 17 The $M ko exciter had to satisfy the requf. resents that it be vsriblo in frequency ao as co pornN optitun aiiysnonc of tho r f crsnsfoneer, anal thee it deliver tho required driving power of approximately a$ watts to tho r~f anplifier...

Holt, Joseph Marion

2012-06-07

363

Radio frequency circuits for wireless receiver front-ends  

E-print Network

. This can be hard to do, especially at RF frequencies where lead inductance and capacitance make short and open circuits di?cult to obtain. Active devices, such as transistors and tunnel diode, very often can not be connected in stable short or open circuit.... This can be hard to do, especially at RF frequencies where lead inductance and capacitance make short and open circuits di?cult to obtain. Active devices, such as transistors and tunnel diode, very often can not be connected in stable short or open circuit...

Xin, Chunyu

2005-11-01

364

Radio frequency linear accelerators for NDT applications: Basic overview of RF linacs  

SciTech Connect

High energy X-ray radiography can be an important part of a quality control program. In this article the author will present an overview of the technology found in a typical high energy X-ray source, the radio frequency (RF) linear accelerator. In NDT, linacs are used primarily for the inspection of thick sections of materials. Linacs are also used in applications such as high energy computed tomography of specimens greater than 1 m thick and cargo container inspection. Recent developments in reliable portable linacs are opening up other applications such as field inspection of pipelines, ships, bridges, and other civil infrastructure. The replacement of isotopes (such as Co-60) by the linac is an area for growth in the future. The shorter exposure times, improved image capabilities, and greatly reduced regulatory requirements of the linac make a persuasive argument for the replacement of isotopes with a portable linac. The linacs discussed here are those with X-ray energies from 1 to 20 MeV intended for use in NDT applications. The discussion will be in very broad terms; it will be impossible to discuss every variation in linac design. In addition, some topics have been necessarily simplified to increase the comprehensibility for a wider audience.

Hansen, H.J. [L and W Research, Inc., Wallingford, CT (United States)

1998-02-01

365

Introduction The rapid growth of wireless systems at radio frequencies  

E-print Network

) typically represent the device in 1D or 2D. When solved, the system of equations results in a Jacobian matrix of size (2H+1)N x (2H+1)N ­­ indeed a potentially huge numerical problem (typical N in 2D is more requirements for communications systems necessitate accurate analysis of harmonic content with frequency dif

Dutton, Robert W.

366

Introduction The rapid growth of wireless systems at radio frequencies  

E-print Network

the DC compo- nent. Those nodes (or grid) typically represent the device in 1D or 2D. When solved numerical problem (typical N in 2D is more than 3000, and H can easily e xceed 100). The effi- cient requirements for communications systems necessitate accurate analysis of harmonic content with frequency dif

Dutton, Robert W.

367

RADIO-FREQUENCY BACKSCATTER OF ARTIFICIAL ELECTRON CLOUDS  

Microsoft Academic Search

Backscatter and forward-scatter reflection properties of chemically ; created electron clouds were measured throughout the HF spectrum. The ; measurements included radar cross sections, signal fading characteristics, and ; frequency-time-dependence. These quantities led to certain conclusions regarding ; the cloud model that describes in general the chemical releases. The model so ; presented appears to be a limited coherent type

Philip B. Gallagher; R. A. Barnes

1963-01-01

368

Electromagnetic compatibility between radio links and frequency agile radars  

Microsoft Academic Search

Some recent advances in radar technology, such as pulse compression techniques, frequency agility and other sophisticated electronic counter counter measures, together with the constant escalation in peak output powers, have resulted in the advent of a new generation of high performance radars. The increased capabilities of modern radars, however, almost invariably correspond also to an increased occupation and pollution of

E. Chiarucci; R. Esposito

1975-01-01

369

Leveraging Multiple Heterogeneous Radios for Energy-efficient Routing  

E-print Network

to be accumulated so that a high-power/high-rate radio can save energy in comparison to communicating via a low the goal is to save energy while keeping delay within some acceptable bound. Formally, let us assume efficiency than these lower-power radios due to their higher bit rates, the larger idle costs make them less

Kravets, Robin

370

Motivation and possibilities of affordable low-frequency radio interferometry in space  

E-print Network

The motivation to build spaceborne interferometric arrays for low-frequency radio astronomy is widely recognised because frequencies below the ionospheric cutoff are inaccessible for ground-based radio telescopes. We discuss the theoretical possibilities to use low-frequency spacecraft arrays to detect signals from magnetized extrasolar planets, including earthlike ones. A major uncertainty that prohibits us from knowing if it is possible to detect exoplanet cyclotron maser signals is the incomplete knowledge of the properties of the interstellar plasma. We also present some ideas of how to construct efficient and affordable space-based radio telescopes. We discuss two possibilities, a log-periodic antenna in the spin plane and a two-spacecraft concept where one spacecraft holds a large parabolic wire mesh reflector and the other one contains the receiver. In the latter case, the effective area could be of the order of 1 km$^2$. The purpose of the paper is to stress once more the importance of spaceborne low-frequency measurements by bringing in the intriguing possibility of detecting earthlike exoplanet radio emissions and to demonstrate that building even very large low-frequency antennas in space is not necessarily too expensive.

P. Janhunen; A. Olsson; R. Karlsson; J. -M. Griessmeier

2003-05-23

371

Interpreting the low-frequency radio spectra of starburst galaxies: a pudding of Strömgren spheres  

NASA Astrophysics Data System (ADS)

The low-frequency radio emission of starburst galaxies is informative, but it can be absorbed in several ways. Most importantly, starburst galaxies are home to many H II regions, whose free-free absorption blocks low-frequency radio waves. These H II regions are discrete objects, but most multiwavelength models of starbursts assume a uniform medium of ionized gas, if they include the absorption at all. I calculate the effective absorption coefficient of H II regions in starbursts, which is ultimately a cross-section times the density of H II regions. The cross-sections are calculated by assuming that H II regions are Strömgren spheres. The coefficient asymptotes to a constant value at low frequencies, because H II regions partially cover the starburst and are buried part way into the starburst's synchrotron-emitting material. Considering Strömgren spheres around either OB stars or Super Star Clusters, I demonstrate the method by fitting to the low-frequency radio spectrum of M82. I discuss implications of the results for synchrotron spectrum shape, H II region pressure and free-free emission as a star formation rate indicator. However, these results are preliminary and could be affected by systematics. I argue that there is no volume-filling warm ionized medium in starbursts and that H II regions may be the most important absorption process down to ˜10 MHz. Future data at low and high radio frequency will improve our knowledge of the ionized gas.

Lacki, Brian C.

2013-06-01

372

Radio emission of RRAT-pulsars at a frequency of 111 MHz  

NASA Astrophysics Data System (ADS)

We will report about our resalts concerning the observations of a number of Rotating Radio Transient (RRAT) pulsars .These observations have been carried out at Large Phased Array of P.N. Lebedev Physical Institute at 111 MHz during 2010-2013 years. RRAT- pulsars were first discovered in archive Parkes Multibeam Pulsar Survey [1,2]and Arecibo Pulsar Survey[3] at higher frequency 1400 MHz and some pulsars were discovered at frequency of 350 MHz with Green Bank Telescope[4]. A characteristic feature of these pulsars is sporadic radio emission in rare active phase and no radio emission for a long time making it difficult to find periodicity .Fast Folding Algorithm processing of observations at 111 MHz shows that even in passive phase RRAT-pulsars generate weak radio emission with the period corresponding to the period of sporadic radio pulses observed in the active phase. The flux density of the radio emission of these pulsars in passive phase is rather small even at low frequency 111 MHz, that greatly complicates its registration at high frequencies since flux density of the RRAT- pulsars decreases with increasing frequency.\\ ?nterline{References}\\ 1.McLaughlin M.A., Lyne A.G., Lorimer D.R. et al., 2006, Nature,439,817. 2.Keane E.F., Ludovici D.A., Eatough E.P. et al., 2010, MNRAS,401,1057. 3.Deneva J.S., Cordes J.M., McLaughlin M.A. et al., 2009,ApJ,703,2259. 4.Keane E.F.,McLaughlin M.A., Bull.Astr.Soc.India, 2011,39,1.

Losovsky, Boris; Dmitry Dumsky, Mr/.

373

Nonlinear nonresonant forces by radio-frequency waves in plasmas  

SciTech Connect

Nonresonant forces by applied rf waves in plasmas are analyzed. Along the background dc magnetic field, the force arises from the gradient of the ponderomotive potential. Only when the dc magnetic field is straight, however, is this parallel force completely consistent with that from the single particle picture, where the ponderomotive force depends on the gradients of rf fields only. Across the dc magnetic field, besides the ponderomotive force from the particle picture, additional Reynolds stress and polarization stress contribute to the total force. For waves with frequency much lower than the cyclotron frequency, the perpendicular forces from the particle and fluid pictures can have opposite signs. In plasmas with a symmetry angle (e.g., toroidal systems), nonresonant forces cannot drive net flow or current in the flux surface, but the radial force may influence macroscopic behavior of plasma. Moreover, nonresonant forces may drive flow or current in linear plasmas or in a localized region of toroidal plasmas.

Gao Zhe; Fisch, Nathaniel J.; Qin, Hong; Myra, J. R. [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Lodestar Research Corporation, Boulder, Colorado 80301 (United States)

2007-08-15

374

Low Frequency Radio Observations of X-ray Ghost Bubbles in Abell 2597: A History of Radio Activity in the Core  

Microsoft Academic Search

A previous analysis of the Chandra X-ray image of the center of the cooling\\u000acore cluster Abell 2597 showed two ``ghost holes'' in the X-ray emission to the\\u000awest and northeast of the central radio galaxy PKS 2322-123. Previous radio\\u000aobservations did not detect any radio emission coming from the interior of the\\u000aX-ray holes. We present new low frequency

T. E. Clarke; C. L. Sarazin; E. L. Blanton; D. M. Neumann; N. E. Kassim

2005-01-01

375

Mission Assessment of the Faraday Accelerator with Radio-frequency Assisted Discharge (FARAD)  

NASA Technical Reports Server (NTRS)

Pulsed inductive thrusters have typically been considered for future, high-power, missions requiring nuclear electric propulsion. These high-power systems, while promising equivalent or improved performance over state-of-the-art propulsion systems, presently have no planned missions for which they are well suited. The ability to efficiently operate an inductive thruster at lower energy and power levels may provide inductive thrusters near term applicability and mission pull. The Faraday Accelerator with Radio-frequency Assisted Discharge concept demonstrated potential for a high-efficiency, low-energy pulsed inductive thruster. The added benefits of energy recapture and/or pulse compression are shown to enhance the performance of the pulsed inductive propulsion system, yielding a system that con compete with and potentially outperform current state-of-the-art electric propulsion technologies. These enhancements lead to mission-level benefits associated with the use of a pulsed inductive thruster. Analyses of low-power near to mid-term missions and higher power far-term missions are undertaken to compare the performance of pulsed inductive thrusters with that delivered by state-of-the-art and development-level electric propulsion systems.

Dankanich, John W.; Polzin, Kurt A.

2008-01-01

376

Design and analysis of a radio frequency extractor in an S-band relativistic klystron amplifier  

SciTech Connect

A radio frequency (RF) extractor converts the energy of a strongly modulated intense relativistic electron beam (IREB) into the energy of high power microwave in relativistic klystron amplifier (RKA). In the aim of efficiently extracting the energy of the modulated IREB, a RF extractor with all round coupling structure is proposed. Due to the all round structure, the operating transverse magnetic mode can be established easily and its resonant property can be investigated with an approach of group delay time. Furthermore, the external quality factor can be low enough. The design and analysis of the extractor applied in an S-band RKA are carried out, and the performance of the extractor is validated with three-dimensional (3D) particle-in-cell simulations. The extraction efficiency reaches 27% in the simulation with a totally 3D model of the whole RKA. The primary experiments are also carried out and the results show that the RF extractor with the external quality factor of 7.9 extracted 22% of the beam power and transformed it into the high power microwave. Better results are expected after the parasitic mode between the input and middle cavities is suppressed.

Zhang Zehai; Zhang Jun; Shu Ting; Qi Zumin [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha, Hunan 410073 (China)

2012-09-15

377

Effect of Addition of Nitrogen to a Capacitively Radio-Frequency Hydrogen Discharge  

NASA Astrophysics Data System (ADS)

A hybrid PIC/MC model is developed in this work for H2-xN2 capacitively coupled radio-frequency (CCRF) discharges in which we take into account 43 kinds of collisions reaction processes between charged particles (e-, H+3, H+2, H+, N+2, N+) and ground-state molecules (H2, N2). In addition, the mean energies and densities of electrons and ions (H+3, H+2, H+), and electric field distributions in the H2-N2 CCRF discharge are simulated by this model. Furthermore, the effects of addition of a variable percentage of nitrogen (0-30%) into the H2 discharge on the plasma processes and discharge characteristics are studied. It is shown that by increasing the percentage of nitrogen added to the system, the RF sheath thickness will narrow, the sheath electric field will be enhanced, and the mean energy of hydrogen ions impacting the electrodes will be increased. Because the electron impact ionization and dissociative ionization rates increase when N2 is added to the system, the electron mean density will increase while the electron mean energy and hydrogen ion density near the electrodes will decrease. This work aims to provide a theoretical basis for experimental studies and technological developments with regard to H2-N2 CCRF plasmas.

Zhang, Lianzhu; Yao, Fubao; Zhao, Guoming; Hao, Yingying; Sun, Qian

2014-03-01

378

A COMBINED LOW-RADIO FREQUENCY/X-RAY STUDY OF GALAXY GROUPS. I. GIANT METREWAVE RADIO TELESCOPE OBSERVATIONS AT 235 MHz AND 610 MHz  

SciTech Connect

We present new Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz of 18 X-ray bright galaxy groups. These observations are part of an extended project, presented here and in future papers, which combines low-frequency radio and X-ray data to investigate the interaction between central active galactic nuclei (AGNs) and the intra-group medium (IGM). The radio images show a very diverse population of group-central radio sources, varying widely in size, power, morphology, and spectral index. Comparison of the radio images with Chandra and XMM-Newton X-ray images shows that groups with significant substructure in the X-ray band and marginal radio emission at {approx}>1 GHz host low-frequency radio structures that correlate with substructures in IGM. Radio-filled X-ray cavities, the most evident form of AGN/IGM interaction in our sample, are found in half of the systems and are typically associated with small, low-, or mid-power double radio sources. Two systems, NGC5044 and NGC4636, possess multiple cavities, which are isotropically distributed around the group center, possibly due to group weather. In other systems the radio/X-ray correlations are less evident. However, the AGN/IGM interaction can manifest itself through the effects of the high-pressure medium on the morphology, spectral properties, and evolution of the radio-emitting plasma. In particular, the IGM can confine fading radio lobes in old/dying radio galaxies and prevent them from dissipating quickly. Evidence for radio emission produced by former outbursts that co-exist with current activity is found in six groups of the sample.

Giacintucci, Simona [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); O'Sullivan, Ewan; Vrtilek, Jan; David, Laurence P.; Mazzotta, Pasquale; Gitti, Myriam; Jones, Christine; Forman, William R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Raychaudhury, Somak; Ponman, Trevor [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Venturi, Tiziana [INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129, Bologna (Italy); Athreya, Ramana M. [IISER, Pune, Maharashtra 411 008 (India); Clarke, Tracy E. [Naval Research Laboratory, 4555 Overlook Avenue SW, Code 7213, Washington, DC 20375 (United States); Murgia, Matteo [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (Italy); Ishwara-Chandra, C. H., E-mail: simona@astro.umd.edu [National Centre for Radio Astrophysics, TIFR, Post Bag No. 3, Ganeshkhind, Pune 411 007 (India)

2011-05-10

379

Radio frequency CD by LH waves in the reversed field experiment  

SciTech Connect

We present a feasibility study for the active control of the poloidal current density profile in the RFX (reversed field pinch) experiment using radio frequency in the range of lower hybrid waves. The main goal of the rf current drive is to reduce the magnetic fluctuations and the magnetic stochasticity, so as to improve the energy confinement. The compelling constraints of accessibility and damping of the slow waves due to the present and extrapolated RFX plasma parameters are investigated; they have been used to fix the frequency ({approx_equal}1.3 GHz) and the best n{sub parallel} values ({approx_equal}8), and therefore the antenna size (Grill). A modified version of the FELICE code, which takes into account the strong shear of the magnetic field of the RFP plasmas, has been developed and used to estimate the antenna-plasma coupling: the reflected power for the proposed antenna is found to be less than 30% for a quite wide range of plasma parameters. In order to estimate the current drive profile and efficiency a one dimensional Fokker-Planck code has been used: an additional crucial contribution to the driven current is due to the enhancement of the plasma conductivity as consequence of the suprathermal electron population increase. Although the total estimated CD efficiency is promising, the rf-power required to drive the current necessary to produce a significant reduction of the magnetic fluctuations is found to be in the MW range.

Bilato, R. [Consorzio RFX, Corso Stati Uniti 4, 35127 Padova (Italy); Istituto Nazionale di Fisica della Materia, Padova (Italy); Brambilla, M. [Maz Planck Institute fuer Plasmaphysik, EURATOM Ass., D-85748 Garching (Germany)

1999-09-20

380

A Low-Frequency Distributed Aperture Array for Radio Astronomy in Space  

NASA Astrophysics Data System (ADS)

The frequency band below 30 MHz is one of the last unexplored bands in radio astronomy. This band is well suited for studying the early cosmos at high hydrogen redshifts, the so-called dark ages, extragalactic surveys, (extra) solar planetary bursts, and high energy particle physics. In addition, space research such as space weather tomography, are also areas of scientific interest. Due to ionospheric scintillation (below 30MHz) and its opaqueness (below 15MHz), earth-bound radio astronomy observations in these bands are either severely limited in sensitivity and spatial resolution or entirely impossible. A radio telescope in space obviously would not be hampered by the Earth's ionosphere. In the past, several (limited) studies have been conducted to explore possibilities for such an array in space. These studies considered aperture synthesis arrays in space, at the back-side of the Moon, or a satellite constellation operating in a coherent mode. In 2009 an ESA project, Distributed Aperture Array for Radio Astronomy in Space (DARIS), set out to investigate the space-based radio telescope concept. The focus of this feasibility study is on a moderate size three-dimensional satellite constellation operating as a coherent large aperture synthesis array. This aperture synthesis array would consist of 5 to 50 antennas (satellites) having a maximum separation of 100 km. This study considers the main aspects of such a distributed system in more detail than previous studies. This conference contribution aims at presenting an overview of the DARIS project and at discussing the main results. The project selected extra-galactic surveys and the search for transient radio sources as the best suited science cases within the DARIS concept, and it investigated the scientific and technical requirements for such an array. Several antenna concepts were considered and simulated. An active antenna dipole array concept would be well suited, and a moderate 5 m tip-tip antenna system would lead to a sky noise limited system. Multiple digital signal processing scenarios were considered. Ultimately, although a distributed signal processing approach would be fa-vorable in terms of reliability and scalability, for complexity reasons the project has chosen to have several (5 to 50) identical receiving nodes, and one centralized processing node i.e. the correlator. Analysis has shown that with current technologies, one MHz bandwidth can be processed with full duty cycle. The limiting factor is the inter-satellite link bandwidth. Several deployment locations, such as Moon orbit, Earth-Moon L2, and dynamic Solar orbits were investigated. Each of those locations has its pro's and con's such as interference levels from the Earth (which drive the number of sampling bits), relative speed-vectors of the satellite nodes (influencing maximum correlator integration times, and the need for orbit maintenance), and achievable down-link bandwidth to Earth. Two preferred deployment location were selected: Moon orbit and dynamic Solar orbit. The main advantage of the Moon orbit is that the syn-thetic aperture is filled more rapidly, making it more suitable for transient science than the dynamic Solar orbit. The project also studied the relation between the three-dimensional satellite configuration, the deployment location and the quality of the sky maps. The conclusion is that for the science cases under consideration, sufficient independent aperture sampling points can be obtained in a 1 MHz limited band (with 1 kHz channels) by using bandwidth synthesis. It is expected that, as a result, up to about one million astronomical sources can be detected in a five year duration mission.

Boonstra, Albert-Jan; Saks, Noah; Falcke, Heino; Klein-Wolt, Marc; Bentum, Ark; Thilak Rajan, Raj; Wijnholds, Ir. Stefan J.; Arts, Michel; van-T Klooster, Kees; Belien, Frederik

381

Low-power radio-frequency capacitively coupled plasma in air: an alternative spectral source?  

Microsoft Academic Search

The low power radio frequency capacitively coupled plasma sustained in air at atmospheric pressure is described with the aim of using it as spectral source for atomic emission spectroscopy of pneumatically nebulized liquid samples and the direct analysis of non-conductive solid samples. The plasma was generated at a frequency of 13.56 MHz, absorbed RF powers of 20-70 W and air

Sorin Anghel; Alpar Simon; Tiberiu Frentiu; Emil A. Cordos

2000-01-01

382

Source location of the smooth high-frequency radio emissions from Uranus  

NASA Technical Reports Server (NTRS)

The source location of the smooth high-frequency radio emissions from Uranus has been determined. Specifically, by fitting the signal dropouts which occurred as Voyager traversed the hollow center of the emission pattern to a symmetrical cone centered on the source magnetic field direction at the cyclotron frequency, a southern-hemisphere (nightside) source was found at approximately 56 deg S, 219 deg W. The half-angle for the hollow portion of the emission pattern was found to be 13 deg.

Farrell, W. M.; Calvert, W.

1989-01-01

383

Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver  

Microsoft Academic Search

We present goniopolarimetric (also known as direction finding) results of the Saturn kilometric radiation (SKR), using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver data. Tools to retrieve the characteristics of the SKR sources have been developed that allow us to measure their 3-D location and beaming angle relative to the magnetic field in the source and,

B. Cecconi; L. Lamy; P. Zarka; R. Prangé; W. S. Kurth; P. Louarn

2009-01-01

384

Radio Frequency Identification Technology and the Risk Society: A Preliminary Review and Critique for Justice Studies  

Microsoft Academic Search

Radio Frequency Identification (RFID) technology promises to revolutionize the way in which citizens interact with society, guaranteeing heightened security and increased protection speculatively critiques the soundness of this logic, especially mindful of the risk society thesis. Relevant historical background on RFID is provided, several notable applications in the corporate and governmental sectors are delineated, and the ethical and

Brian Sellers

2009-01-01

385

Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators: An undergraduate experiment  

E-print Network

Understanding Pound-Drever-Hall locking using voltage controlled radio-frequency oscillators controlled oscillator to a cavity resonance at 800 MHz using the Pound-Drever-Hall method. This technique of microwave oscillators, and adapted to the optical domain by Drever et al.2 In brief, the source

Le Roy, Robert J.

386

Method for Automated Monitoring of Hand Hygiene Adherence without Radio-Frequency Identification  

PubMed Central

Many efforts to automatically measure hand hygiene activity depend on radio-frequency identification equipment or similar technology that can be expensive to install. We have developed a method for automatically tracking the use of hand hygiene dispensers before healthcare workers enter (or after they exit) patient rooms that is easily and quickly deployed without permanent hardware. PMID:20973724

Polgreen, Philip M.; Hlady, Christopher S.; Severson, Monica A.; Segre, Alberto M.; Herman, Ted

2011-01-01

387

New optical and radio frequency angular tropospheric refraction models for deep space applications  

NASA Technical Reports Server (NTRS)

The development of angular tropospheric refraction models for optical and radio frequency usage is presented. The models are compact analytic functions, finite over the entire domain of elevation angle, and accurate over large ranges of pressure, temperature, and relative humidity. Additionally, FORTRAN subroutines for each of the models are included.

Berman, A. L.; Rockwell, S. T.

1976-01-01

388

High-rate chemical vapor deposition of nanocrystalline silicon carbide films by radio frequency thermal plasma  

E-print Network

thermal plasma F. Liao a , S. Park a , J.M. Larson b , M.R. Zachariah a , S.L. Girshick a,* a Department were deposited by radio frequency thermal plasma chemical vapor deposition (CVD) at rates up to several; Nanomaterials; Silicon carbide; Thermal plasmas; Thin films; Si tetrachlorine precursor Silicon carbide has

Zachariah, Michael R.

389

A radio frequency tracing experiment of bedload transport in a small braided mountain stream  

Microsoft Academic Search

Radio frequency identification technology is used for monitoring the displacement of coarse particles in streams since the beginning of the 2000s. Passive integrated transponders (PIT tags) are small, cheap and long-lasting electronic tags that can be programmed with their own identification code. Initially used in environmental research for animal tracking, they have been deployed successfully in a variety of fluvial

F. Liebault; M. Chapuis; H. Bellot; M. Deschatres

2009-01-01

390

Intelligent tire monitor system of aerial vehicles based on radio frequency technology  

Microsoft Academic Search

A low power consuming intelligent monitor system of tire based on radio frequency technology is designed in this paper. The low consuming power unit, the measurement unit, the agreement of timestamp and the protocol of chain layers are presented in details. The main program flow charts of the measuring terminal and host terminal are given. he tire is the only

Kai-rui Zhao; Shicheng Xu; Qing Ye; Yan Li

2011-01-01

391

IMPROVED TECHNIQUE FOR MONITORING ELECTROCARDIOGRAMS DURING EXPOSURE TO RADIO-FREQUENCY RADIATION  

EPA Science Inventory

Studies were conducted which examined the effects of radio frequency (RF) radiation on heart rate (HR), deep body temperature (TEMP), and electrocardiographic (ECG) waveform parameters in anesthetized rats. One group of animals was exposed to two power levels of continuous wave R...

392

Low-power radio frequency circuit architectures for portable wireless communications  

Microsoft Academic Search

Ultra-low-power implementations of radio-frequency integrated circuits are benefiting from rapid improvements in integrated circuit technology, circuit architecture techniques and wireless system innovations. Some of the key technological developments driving this field are discussed, in addition to new approaches for the realization of next generation wireless circuits and systems that dissipate very little dc power

Lawrence E. Larson

1998-01-01

393

A Low Power Radio Telemetry Achieving Very High Data Rates at Biocompatible Frequencies  

Microsoft Academic Search

This papers reports a solution for a low power, high data rate telemetry, intended to be used in capsule endoscopy. The system is taking advantage of the small absorption of radio waves of low frequencies, around 120 MHz, to allow a telemetry up to a million bit per second of raw data, while keeping the power consumption to 6 mW.

D. Turgis; R. Puers

2007-01-01

394

Radio frequency (rf) plasma spheroidized HA powders: powder characterization and spark plasma sintering behavior  

Microsoft Academic Search

The present study describes the synthesis of spheroidized hydroxyapatite (HA) powders using a radio frequency (rf) inductively coupled plasma (ICP) torch. The spheroidized powders were consolidated through a spark plasma sintering (SPS) system. The microstructure and crystallographic phases in the synthesized powders were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD) and Raman spectrometry. Results

J. L. Xu; K. A. Khor; Y. W. Gu; R. Kumar; P. Cheang

2005-01-01

395

A Two-Dimensional Model of Chemical Vapor Infiltration With Radio Frequency Heating  

E-print Network

vapor infiltration (CVI) has emerged as one of the leading techniques for the fabrication of fiber was developed and used to simulate chemical vapor infil- tration of fiber-reinforced composite materials-consistently the power absorbed by the preform from a radio frequency induction coil. The model equations were solved

Economou, Demetre J.

396

Radio frequency identification in retailing and privacy and public policy issues  

Microsoft Academic Search

Outlines the characteristics of Radio Frequency Identification (RFID) technology and shows the growth of retail interest in the technology’s introduction in the UK. Discusses privacy and public policy issues that are associated with RFID. Concludes that retailers have to address a series of privacy and public liberties, associated with RFID.

Peter Jones; Colin Clarke-Hill; Daphne Comfort; David Hillier; Peter Shears

2004-01-01

397

Epidemiological studies of radio-frequency radiation: current status and areas of concern  

Microsoft Academic Search

These comments deal with the possible impact on human populations of intense sources of radio-frequency radiation, and not the much lower level of the usual sources of such radiation associated, for example with household appliances. These intense sources were developed and extensively used first in World War II (1940–1945). Much of the health evaluation has been done by, and for,

John R. Goldsmith

1996-01-01

398

Fast simulation of nonlinear radio frequency ultrasound images in inhomogeneous nonlinear media: CREANUIS  

E-print Network

Fast simulation of nonlinear radio frequency ultrasound images in inhomogeneous nonlinear media et traitement de l'image pour la sant´e, 7 avenue Jean Capelle, Bat Blaise Pascal, 69621 Villeurbanne, Nantes, France 91 #12;The simulation of ultrasound images is usually based on two main strategies: either

Paris-Sud XI, Université de

399

A radio frequency identification-based quality evaluation system design for the wine industry  

Microsoft Academic Search

In the wine industry, how to evaluate the quality of wine in objective ways has been a thorny problem. The invention of radio frequency identification (RFID) has provided an effective tool to manage wine production. This article reports on the design and the use of an RFID-based quality evaluation system to monitor the whole supply chain of wine. With the

Lixing Wang; S. K. Kowk; W. H. Ip

2012-01-01

400

A radio frequency identification-based quality evaluation system design for the wine industry  

Microsoft Academic Search

In the wine industry, how to evaluate the quality of wine in objective ways has been a thorny problem. The invention of radio frequency identification (RFID) has provided an effective tool to manage wine production. This article reports on the design and the use of an RFID-based quality evaluation system to monitor the whole supply chain of wine. With the

Lixing Wang; S. K. Kowk; W. H. Ip

2011-01-01

401

Design, Fabrication and Testing of Two Dimensional Radio-Frequency Metamaterials.  

National Technical Information Service (NTIS)

This project focused on radio frequency (RF) metamaterials (MTM) structures using two different methods: wet etching copper (Cu) on insulating glass reinforced epoxy resin (FR4) and silver nano-particle ink printed SRR meta-atoms on photo paper (Ag on pap...

R. P. Krones

2014-01-01

402

PHOTONIC SYNTHESIS AND HARDWARE CORRELATIONS OF ULTRABROADBAND RADIO-FREQUENCY WAVEFORMS AND POWER  

E-print Network

PHOTONIC SYNTHESIS AND HARDWARE CORRELATIONS OF ULTRABROADBAND RADIO-FREQUENCY WAVEFORMS AND POWER Jiang and F.S. Toong. Many thanks to Hsiao-Kuan Yuan and my other friends from Purdue who always love ..........................................18 3.1.3 Equalized RF Waveforms............................................23 3.2 Power Spectra

Purdue University

403

Pulsed Discharge Effects on Bacteria Inactivation in Low-Pressure Radio-Frequency Oxygen Plasma  

Microsoft Academic Search

The sporicidal effects of low-pressure radio frequency (RF) discharges in oxygen, produced by the application of continuous and pulsed RF power, were evaluated. For all cases, the survival curves showed a biphasic evolution. The maximum efficiency for bacteria sterilization was obtained when the RF power was injected in the continuous wave mode, while in the pulsed mode the lowest treatment

Dragos Vicoveanu; Yasunori Ohtsu; Hiroharu Fujita

2008-01-01

404

An Electron Bunch Compression Scheme for a Superconducting Radio Frequency Linear Accelerator Driven Light Source  

Microsoft Academic Search

We describe an electron bunch compression scheme suitable for use in a light source driven by a superconducting radio frequency (SRF) linac. The key feature is the use of a recirculating linac to perform the initial bunch compression. Phasing of the second pass beam through the linac is chosen to de-chirp the electron bunch prior to acceleration to the final

C. Tennant; S. V. Benson; D. Douglas; P. Evtushenko; R. A. Legg

2011-01-01

405

Quasilinear theory of collisionless electron heating in radio frequency gas discharges  

E-print Network

to be a collisionless one rather than the conven- tional Joule heating dominant for higher pressures. The problemQuasilinear theory of collisionless electron heating in radio frequency gas discharges Yu. M. Aliev heating of rf discharges is treated for characteristic scale lengths of the heating field much shorter

Kaganovich, Igor

406

Stochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a)  

E-print Network

the mean-free-path is small as compared to and to colli- sional Joule heating. In region B, L, electrons plasma boundary at x L. But contrary to the Joule heating, this hybrid heating is nonlocal: the placeStochastic electron heating in bounded radio-frequency plasmas I. D. Kaganovich,a) V. I. Kolobov

Kaganovich, Igor

407

Ultrasound radio-frequency time series for finding malignant breast lesions  

E-print Network

to augment the Breast Imaging-Reporting and Data System (BI-RADS). Breast ultrasound is used as a supplement 050 051 052 053 Ultrasound radio-frequency time series for finding malignant breast lesions Anonymous-based solutions for breast lesion characterization to reduce the patient recall rate after mammography screening

de Freitas, Nando

408

A radio frequency controlled microvalve for biomedical applications  

NASA Astrophysics Data System (ADS)

In this paper we propose the use of a RF controlled microvalve for implementation on a PZT substrate for biomedical applications. Such device has a huge range of applications such as parallel mixing of photo-lithographically defined nanolitre volumes, flow control in pneumatically driven microfluidic systems and lab-on-chip applications. The microvalve makes use of direct actuation mechanisms at the microscale level to allow its use in vivo applications. A number of acoustic propagation modes are investigated and their suitability for biomedical applications, in terms of the required displacement, device size and operation frequency. A theoretical model of the Surface Acoustic Wave (SAW) device is presented and its use in micro-valve application was evaluated using ANSYS tools. Furthermore, the wireless aspect of the device is considered through combining the RF antenna with the microvalve simulation by assuming a high carrier frequency with a small peak-to-peak signal. A new microvalve structure which uses a parallel type piezoelectric bimorph actuator was designed and simulated using ANSYS tools. Then, further optimization of the device was carried out to achieve a better coupling between electrical signal and mechanical actuation within the SAW device.

Dissanayake, Don W.; Tikka, Ajay C.; Al-Sarawi, Said F.; Abbott, Derek

2007-01-01

409

A new simplified high radio frequency power amplifier  

SciTech Connect

In order to simplify a present standard high rf power amplifier of ion cyclotron range of frequency plasma heating system, a new amplifier arrangement composed of a tetrode with a grounded cathode and a field effect transistor (FET) switching circuit providing an input rf power is proposed. The FET switching circuit is so small that it can be installed close to the tetrode in one cubicle. It might be called a single tube high rf power amplifier. A test amplifier composed of the tetrode (8F76R) and the FET (2SK-1310) switching circuit is constructed. The maximum output rf power of 8.5 kW was stably obtained at 70 MHz. The feasibility of the single tube high rf power amplifier was experimentally proved.

Ogawa, Y.; Okutsu, H.; Kobayashi, N.; Hayakawa, A. [Advanced System Design and Engineering Department, Toshiba Corporation, Shinsugita-cho 8, Isogo-ku, Yokohama-shi 235-8523 (Japan)

2004-10-01

410

Efficient use of the Earth exploration-satellite service radio frequency allocation in 8025-8400 MHz  

Microsoft Academic Search

The radio frequency spectrum (9 kHz-275 GHz) is a limited finite resource for which many radio services compete. Most of the 525 radio frequency bands are shared by two or more of the 30 recognized services. Worldwide, except for some individual country differences, in the 8025-8400 MHz range, often referred to as the X-band, the Earth exploration-satellite service (EESS) shares

David F. McGinnis Jr.; Wayne A. Whyte Jr.; Edward M. Davison

2005-01-01

411

Variable Temperature Rate Studies for the Reaction H3O+ Measured with a Coaxial Molecular Beam Radio Frequency Ring  

E-print Network

Beam Radio Frequency Ring Electrode Ion Trap Mark A. Smith,*,,,§ Bing Yuan, and Andrei Sanov+ are determined using a coaxial molecular beam radio frequency ring electrode ion trap (CoMB-RET). The H3O association reaction at 300 K using the Canterbury selected ion flow tube (SIFT) system in 1996,4 and the rate

Sanov, Andrei

412

Challenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components  

E-print Network

and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave componentsChallenges and opportunities for multi-functional oxide thin films for voltage tunable radio frequency/microwave components Guru Subramanyam, M. W. Cole, Nian X. Sun, Thottam S. Kalkur, Nick M

Chen, Long-Qing

413

Extraction of negative ions from pulsed electronegative inductively coupled plasmas having a radio-frequency substrate bias  

E-print Network

Extraction of negative ions from pulsed electronegative inductively coupled plasmas having a radio ions into features. By modulating power in inductively coupled plasmas ICPs , the plasma potential coupled plasmas ICPs powered at radio frequency rf where the carrier frequency the power is square wave

Kushner, Mark

414

IITRI RADIO FREQUENCY HEATING TECHNOLOGY - INNOVATIVE TECHNOLOGY EVALUATION REPORT  

EPA Science Inventory

IITRI's patented in situ RFH technology enhances the removal of volatile and semi-volatile organics by soil vapor extraction (SVE). Electromagnetic energy heats the soil resulting in increased contaminant vapor pressures and potentially higher soil permeability. RFH heats soil us...

415

Radio-frequency-quadrupole linac in a heavy ion fusion driver system  

SciTech Connect

A new type of linear accelerator, the radio-frequency quadrupole (RFQ) linac, is being developed for the acceleration of low-velocity ions. The RFQ accelerator can be adapted to any high-current applications. A recent experimental test carried out at the Los Alamos Scienific Laboratory (LASL) has demonstrated the outstandig properties of RFQ systems. The test linac accepts a 30-mA proton beam of 100-keV energy and focuses, bunches, and accelerates the beam to an energy to 640 keV. This ia done in a length of 1.1 m, with a transmission efficiency of 87% and with a radial emittance growth of less than 60%. The proven capability of the RFQ linac, when extended to heavy ion acceleration, should provide an ideal technique for use in the low-velocity portion of a heavy-ion linac for inertial-confinement fusion. A specific concept for such an RFQ-based system is described.

Hansborough, L.D.; Stokes, R.; Swenson, D.A.; Wangler, T.P.

1980-01-01

416

Radio Frequency Plasma Discharge Lamps for Use as Stable Calibration Light Sources  

NASA Technical Reports Server (NTRS)

Stable high radiance in visible and near-ultraviolet wavelengths is desirable for radiometric calibration sources. In this work, newly available electrodeless radio-frequency (RF) driven plasma light sources were combined with research grade, low-noise power supplies and coupled to an integrating sphere to produce a uniform radiance source. The stock light sources consist of a 28 VDC power supply, RF driver, and a resonant RF cavity. The RF cavity includes a small bulb with a fill gas that is ionized by the electric field and emits light. This assembly is known as the emitter. The RF driver supplies a source of RF energy to the emitter. In commercial form, embedded electronics within the RF driver perform a continual optimization routine to maximize energy transfer to the emitter. This optimization routine continually varies the light output sinusoidally by approximately 2% over a several-second period. Modifying to eliminate this optimization eliminates the sinusoidal variation but allows the output to slowly drift over time. This drift can be minimized by allowing sufficient warm-up time to achieve thermal equilibrium. It was also found that supplying the RF driver with a low-noise source of DC electrical power improves the stability of the lamp output. Finally, coupling the light into an integrating sphere reduces the effect of spatial fluctuations, and decreases noise at the output port of the sphere.

McAndrew, Brendan; Cooper, John; Arecchi, Angelo; McKee, Greg; Durell, Christopher

2012-01-01

417

Development of structural materials exhibiting dielectric and magnetic loss at radio frequencies  

SciTech Connect

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The reduction of radio frequency (RF) return from military assets has been of critical interest for the last twenty years. New materials are required that not only provide a reduction in specular and travelling wave RF energy, but also function mechanically in primary structural applications. Typical radar attenuating material (RAM) is structurally parasitic and its utilization decreases the vehicle range by adding significant weight. New conducting and semiconducting polymers have demonstrated potential for RF absorption and can be incorporated into newly developed isotropic structural foams developed from laser target technology at LANL to absorb RF energy. Successful implementation of this technology will lead to broad-band absorbers, light-weight absorbers and radar-absorbing structures (RAS) that can be applied to existing aircraft or integrated into new designs. These new materials also show a high potential to be developed into {open_quotes}smart{close_quotes} structures, i.e., structures that adapt to the threat environment and optimize their absorption.

Duke, J.R. Jr.; Apen, P.G.; Hoisington, M.

1996-10-01

418

Characterization of nonthermal Ne-N{sub 2} mixture radio frequency discharge  

SciTech Connect

This paper deals with optical emission spectroscopic studies of low pressure (p=0.1{yields}0.5 mbar) Ne-N{sub 2} capacitively coupled radio frequency (rf) plasma that can be used for plasma nitriding, etc. It reports the methods to calculate the electron temperature (T{sub e}) in nonthermal plasmas. Since, the selected Ne I lines, used to calculate electron temperature, are found in corona balance; therefore, it allows us to use modified Boltzmann technique to calculate electron temperature. Langmuir probe is also used to calculate electron temperature and electron energy distribution functions (EEDFs). The measurements are worked out for different discharge parameters like neon percentage, filling pressure and RF power. It is found that electron temperature increases with the increase in neon percentage and decreases with the increase in pressure, whereas excitation temperature (T{sub exc}) increases with power, neon percentage, and decreases with pressure. It is also observed that electron temperature measured by Langmuir probe technique is slightly greater than the one measured via modified Boltzmann plot method. The tails of the EEDFs gain height and extend toward the higher energy with the increase in neon percentage in the mixture.

Rehman, N. U.; Zakaullah, M. [Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); Khan, F. U. [Department of Physics, Gomal University, 29050 D.I. Khan (Pakistan); Naseer, S. [Department of Physics, Peshawar University, 25120 Peshawar (Pakistan)

2008-12-15

419

Matching an H- beam into a radio frequency quadrupole at Rutherford Appleton Laboratorya)  

NASA Astrophysics Data System (ADS)

A major component of work being carried out to upgrade the ISIS spallation neutron source at Rutherford Appleton Laboratory (RAL) is the Front End Test Stand (FETS). FETS is aimed at improving the luminosity of the linac, and consists of a Penning ion source, Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ), and Medium Energy Beam Transport (MEBT). It may serve as a first part of the accelerator chain providing a 60 mA, 3 MeV H- beam up to a 10% duty cycle. The current output of the source and the transmission of the LEBT are reasonable, but there are issues with the alignment to provide a centred beam matched into the acceptance of the RFQ. Improvements have been made to the post acceleration to address this problem. Measurements with a collimated beam have been performed to understand the behaviour of the solenoids and steerer magnets. Comparing these results with simulations proved that, besides possible mechanical imperfections of the ion source and post acceleration assembly, agreement can only be achieved if the magnetic fields are distorted.

Gabor, C.; Back, J. J.; Faircloth, D. C.; Lawrie, S. R.; Letchford, A. P.

2014-02-01

420

Polychrest: a development system for radio-frequency-coupled implants.  

PubMed

Inductively-coupled neurological prosthetic implants may employ RF coils of unusual design (for example 'square' spiral inductors printed in thick-film ink on both sides of the alumina substrate) for which published empirical design equations are hard or impossible to find. 'Polychrest' enables the rapid experimental generation of ad hoc design data for RF-coupled energy-transfer systems, leading quickly to a working model which can be thoroughly studied and understood. PMID:3713145

Donaldson, P E

1986-04-01

421

Faraday Acceleration with Radio-Frequency Assisted Discharge  

Microsoft Academic Search

Abstract A new electrodeless accelerator concept that relies on an RF-assisted discharge, an applied magnetic ?eld, and electromagnetic acceleration using an inductive coil is presented. The presence of a preionized plasma allows for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts. A proof-of-concept experiment, supported by optical and probe diagnostics,

Edgar Y. Choueiri; Kurt A. Polzin

2006-01-01

422

Electromagnetic and mechanical design of gridded radio-frequency cavity windows  

SciTech Connect

Electromagnetic, thermal and structural analyses of radio-frequency (RF) cavities were performed as part of a developmental RF cavity program for muon cooling. RF cavities are necessary to provide longitudinal focusing of the muons and to compensate for their energy loss. Closing the cavity ends by electrically conducting windows reduces the power requirement and increases the on-axis electric field for a given maximum surface electric field. Many factors must be considered in the design of RF cavity windows. RF heating can cause the windows to deform in the axial direction of the cavity. The resulting thermal stresses in the window must be maintained below the yield stress of the window material. The out-of-plane deflection must be small enough so that the consequent frequency shift is tolerable. For example, for an 805 MHz cavity, the out-of-plane deflection must be kept below 25 microns to prevent the frequency of the cavity from shifting more than 10 kHz. In addition, the window design should yield smooth electric and magnetic fields, terminate field leakage beyond the window, and minimize beam scattering. In the present thesis, gridded-tube window designs were considered because of their high structural integrity. As a starting point in the analysis, a cylindrical pillbox cavity was considered as a benchmark problem. Analytical and finite element solutions were obtained for the electric and magnetic fields, power loss density, and temperature profile. Excellent agreement was obtained between the analytical and finite element results. The finite element method was then used to study a variety of gridded-tube windows. It was found that cooling of the gridded-tube windows by passing helium gas inside the tubes significantly reduces the out-of-plane deflection and the thermal stresses. Certain tube geometries and grid patterns were found to satisfy all of the design requirements.

Alsharoa, Mohammad M.; /IIT, Chicago /Fermilab

2004-12-01

423

Process for preparing superconducting films by radio-frequency generated aerosol-plasma deposition in atmosphere  

SciTech Connect

This patent describes a process for coating a layer of superconductive material with a thickness of from about 0.1 to about 500 microns onto a substrate at a deposition rate of from about 0.01 to about 10 microns per minute per 335 square centimeters of substrate surface. It comprises: providing a solution comprised of an yttrium compound, a barium compound, and a copper compound; subjecting the solution to ultrasonic sound waves at a frequency in excess of 20,000 hertz; providing a radio frequency plasma reactor; generating a hot plasma within the radio frequency reactor; contacting the aerosol with the hot plasma gas within the plasma reactor while subjecting the aerosol to a substantially atmospheric pressure of from about 600 to about 1,000 millimeters of mercury and to a radio frequency alternating current at a frequency of from about 100 kilohertz to about 30 megahertz, thereby forming a vapor; providing a substrate disposed outside of the plasma reactor; providing a substrate holder in contact with the substrate; electrically grounding the substrate holder; and contacting the vapor with the substrate; thereby forming a superconductive film in the as deposited state.

Snyder, R.L.; Wang, X.; Zhong, H.

1992-10-20

424

Low-frequency study of two giant radio galaxies: 3C 35 and 3C 223  

NASA Astrophysics Data System (ADS)

Aims: Radio galaxies with a projected linear size ?1 Mpc are classified as giant radio sources. According to the current interpretation these are old sources which have evolved in a low-density ambient medium. Because radiative losses are negligible at low frequency, extending spectral aging studies in this frequency range will allow us to determine the zero-age electron spectrum injected and then to improve the estimate of the synchrotron age of the source. Methods: We present Very Large Array images at 74 MHz and 327 MHz of two giant radio sources: 3C 35 and 3C 223. We performed a spectral study using 74, 327, 608 and 1400 GHz images. The spectral shape is estimated in different positions along the source. Results: The radio spectrum follows a power-law in the hotspots, while in the inner region of the lobe the shape of the spectrum shows a curvature at high frequencies. This steepening agrees with synchrotron aging of the emitting relativistic electrons. In order to estimate the synchrotron age of the sources, the spectra were fitted with a synchrotron model of emission. They show that 3C 35 is an old source of 143 ± 20 Myr, while 3C 223 is a younger source of 72 ± 4 Myr.

Orrù, E.; Murgia, M.; Feretti, L.; Govoni, F.; Giovannini, G.; Lane, W.; Kassim, N.; Paladino, R.

2010-06-01

425

Frequency dependence of the evolution of the radio emission of the supernova remnant Cas A  

NASA Astrophysics Data System (ADS)

Many-year measurements of the radio flux of the young supernova remnant Cassiopeia A relative to the radio galaxy Cygnus A were continued at 290 and 151.5 MHz. The new data are used together with previously published observations carried out at decameter, meter, centimeter, and millimeter wavelengths to derive the frequency dependence of the secular variation of the radio flux density of Cas A: . The observed slowing of the secular variations with decreasing frequency at decameter wavelengths can be explained by a decrease in the optical depth of a remnant HII zone around Cas A with time due to recombination of hydrogen atoms. The new derived frequency dependence for the rate of the secular decrease, absolute and relative measurements of the radio flux density of Cas A carried out over the last 25 years, and the absolute spectrum of Cyg A are used to construct the spectrum of Cas A in the range 5-250 000 MHz predicted for epoch 2015.5.

Vinyaikin, E. N.

2014-09-01

426

Relations among low ionosphere parameters and high frequency radio wave absorption  

NASA Technical Reports Server (NTRS)

Charged particle conductivities measured in the very low ionosphere at White Sands Missile Range, New Mexico, and Wallops Island, Virginia, are compared with atmospheric parameters and high frequency radio wave absorption measurements. Charged particle densities are derived from the conductivity data. Between 33 and 58 km, positive conductivity correlated well with neutral atmospheric temperature, with temperature coefficients as large as 4.6%/deg K. Good correlations were also found between HF radio wave absorption and negative conductivity at altitudes as low as 53 km, indicating that the day-to-day absorption variations were principally due to variations in electron loss rate.

Cipriano, J. P.

1973-01-01

427

Study of Ultra-High Energy Cosmic Rays from Extensive Air Showers Radio Emission  

NASA Astrophysics Data System (ADS)

The study of cosmic rays with the help of radio detection from extensive air showers may be an alternative to traditional detecting methods, which use a large area array installed with hundreds and thousands of scintillation detectors for charged particles, or the detectors of measuring the emission produced by relativistic particles of EAS in the optical wavelengths. Processes that lead to the emission of electromagnetic radiation are well known and calculations show that the air shower radio emission depends on the processes of development of the electromagnetic cascade, i.e. related with the longitudinal development of the shower, with the magnetic field near sea level etc. In this regard, there is a question to establish the correlation between characteristics of EAS both longitudinal and lateral development and radio emission parameters observed when air shower particles pass through the atmosphere. For this purpose, in Yakutsk, radio array for detecting air shower radio emission was established. The array consists of the antenna field on which crossed antennas are installed; antennas oriented E - W and N - S. Radio emission measurements are conducted at frequency 32 MHz, free from industrial noise. In 2008 - 2013 years, Yakutsk array has measured several seasons of registration of EAS events, including showers with energies above 10 (19) eV. In the course of the data analysis the following results were obtained: a) lateral distribution of the radio signal plotted as a function of distance from the shower axis ; b) a correlation between the amplitude of the radio signal with the energy of the shower, which is determined by measuring the fluxes of charged particles , muons and EAS Cerenkov radiation (energy balance method); c) we made evaluation of the depth of maximum development of the shower using form of radio emission LDF measured in ultra-high energy showers; g) a comparison of the Yakutsk array data with data from other arrays.

Petrov, Igor; Kozlov, Vladimir; Petrov, Zim; Knurenko, Stanislav; Pravdin, Mikhail

428

A new approach to multi-frequency synthesis in radio interferometry  

E-print Network

We present a new approach to multi-frequency synthesis in radio astronomy. Using Bayesian inference techniques, the new technique estimates the sky brightness and the spectral index simultaneously. In principle, the bandwidth of a wide-band observation can be fully exploited for sensitivity and resolution, currently only limited by higher order effects like spectral curvature. Employing this new approach, we further present a multi-frequency extension to the imaging algorithm RESOLVE. In simulations, this new algorithm outperforms current multi-frequency imaging techniques like MS-MF-CLEAN.

Junklewitz, H; Enßlin, T

2014-01-01

429

Response of radio frequency superconducting quantum interference devices to electromagnetic interference  

SciTech Connect

A number of applications of high-temperature superconductor radio frequency superconducting quantum interference devices (rf SQUIDs) require a certain immunity of these sensors against electromagnetic interference (EMI). We have investigated effects of electromagnetic radiation in the high-frequency and ultrahigh-frequency range on various types of rf SQUIDs. It has been found that EMI of sufficient field strength reduces the voltage versus flux transfer function, and thus increases the flux noise of the SQUIDs. SQUIDs with a wire wound tank circuit coil have been found to be more sensitive to EMI than SQUIDs integrated into a superconducting microstrip resonator. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Mueck, M.; Dechert, J.; Gail, J.; Kreutzbruck, M.; Schoene, S.; Weidl, R. [Institut fuer Angewandte Physik, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany)] [Institut fuer Angewandte Physik, Justus-Liebig-Universitaet Giessen, Heinrich-Buff-Ring 16, 35392 Giessen (Germany)

1995-09-01

430

Radio frequency discharge with control of plasma potential distribution.  

PubMed

A RF discharge plasma generator with additional electrodes for independent control of plasma potential distribution is proposed. With positive biasing of this ring electrode relative end flanges and longitudinal magnetic field a confinement of fast electrons in the discharge will be improved for reliable triggering of pulsed RF discharge at low gas density and rate of ion generation will be enhanced. In the proposed discharge combination, the electron energy is enhanced by RF field and the fast electron confinement is improved by enhanced positive plasma potential which improves the efficiency of plasma generation significantly. This combination creates a synergetic effect with a significantly improving the plasma generation performance at low gas density. The discharge parameters can be optimized for enhance plasma generation with acceptable electrode sputtering. PMID:22380229

Dudnikov, Vadim; Dudnikov, A

2012-02-01

431

Thermocatalytic treatment of biomass tar model compounds via radio frequency.  

PubMed

A new effective RF tar thermocatalytic treatment process with low energy intensive has been proposed to remove tar from biomass gasification. Toluene and naphthalene as biomass tar model compounds were removed via both thermal and catalytic treatment over a wide temperature range from 850 °C to 1200 °C and 450 °C to 900 °C, respectively at residence time of 0-0.7 s. Thermal characteristics of the new technique are also described in this paper. This study clearly clarified that toluene was much easier to be removed than naphthalene. Soot was found as the final product of thermal treatment of the tar model and completely removed during catalytic treatment. Radical reactions generated by RF non-thermal effect improve the tar removal. The study showed that Y-zeolite has better catalytic activity compared to dolomite on toluene and naphthalene removal due to its acidic nature and large surface area, even at lower reaction temperature of about 550 °C. PMID:23567671

Anis, Samsudin; Zainal, Z A; Bakar, M Z A

2013-05-01

432

Slow Radio-Frequency Processing of Large Oil Shale Volumes to Produce Petroleum-Like Shale Oil  

SciTech Connect

A process is proposed to convert oil shale by radio frequency heating over a period of months to years to create a product similar to natural petroleum. Electrodes would be placed in drill holes, either vertical or horizontal, and a radio frequency chosen so that the penetration depth of the radio waves is of the order of tens to hundreds of meters. A combination of excess volume production and overburden compaction drives the oil and gas from the shale into the drill holes, where it is pumped to the surface. Electrical energy for the process could be provided initially by excess regional capacity, especially off-peak power, which would generate {approx}3 x 10{sup 5} bbl/day of synthetic crude oil, depending on shale grade. The electricity cost, using conservative efficiency assumptions, is $4.70 to $6.30/bbl, depending on grade and heating rate. At steady state, co-produced gas can generate more than half the electric power needed for the process, with the fraction depending on oil shale grade. This would increase production to 7.3 x 10{sup 5} bbl/day for 104 l/Mg shale and 1.6 x 10{sup 6} bbl/day for 146 l/Mg shale using a combination of off-peak power and power from co-produced gas.

Burnham, A K

2003-08-20

433

Unveiling the Nature of the Unidentified Gamma-Ray Sources. III. Gamma-Ray Blazar-like Counterparts at Low Radio Frequencies  

NASA Astrophysics Data System (ADS)

About one-third of the ?-ray sources listed in the second Fermi Large Area Telescope catalog (2FGL) have no firmly established counterpart at lower energies and so are classified as unidentified gamma-ray sources (UGSs). Here, we propose a new approach to find candidate counterparts for the UGSs based on the 325 MHz radio survey performed with the Westerbork Synthesis Radio Telescope in the northern hemisphere. First, we investigate the low-frequency radio properties of blazars, the largest known population of ?-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO Very Large Array Sky Survey. We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in the literature to look for infrared and optical counterparts of the ?-ray blazar candidates selected using the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research, we identify 23 new ?-ray blazar candidates out of the 32 UGSs investigated. Comparison with previous results on the UGSs is also presented. Finally, we speculate on the advantages of using low-frequency radio observations to associate UGSs and to search for ?-ray pulsar candidates.

Massaro, F.; D'Abrusco, R.; Giroletti, M.; Paggi, A.; Masetti, N.; Tosti, G.; Nori, M.; Funk, S.

2013-07-01

434

NASA's Radio Frequency Bolt Monitor: A Lifetime of Spinoffs  

NASA Technical Reports Server (NTRS)

This story begins in the 1970s, when Dr. Joseph Heyman, a young scientist at NASA s Langley Research Center, was asked to support the investigation of a wind tunnel accident at a sister center. Although the work was outside of his physics background, it sparked a research focus that guided his lengthy NASA career and would earn him a slew of accolades, including NASA s highest award medals for Exceptional Leadership, Exceptional Achievement, and Exceptional Service; the coveted Silver Snoopy Astronaut Award for Space Shuttle Return to Flight; and the Arthur Fleming Award for being one of the Top Ten Federal Scientists in Government Service. He won 30 additional NASA awards, including the Agency s Invention of the Year and the Agency s highest award for technology transfer, and was the only person to ever win 4 R&D 100 Awards. Back in 1973, though, Heyman was a young civil servant with a background in physics who was asked to sit on an accident review panel. The panel met at Ames Research Center, in Moffet Field, California, and after considerable investigation, concluded that a high-pressure pebble heater used for heating gas had failed, due to improperly tightened bolts in a 1,000-pound gate valve control section. The accident showered the facility with incendiary ceramic spheres and nearly a ton of metal, but, luckily, caused no injuries. Heyman returned to Langley and began work on a solution. He developed an ultrasonic device that would measure bolt elongation, as opposed to torque, the factor typically measured in testing bolt preload or tension. Torque measurement can lead to load errors, with miscalculations as high as 80 percent that can be passed over during installation. Bolt stretch, however, is nearly always accurate to 1 percent or better. Within 1 month, he had an acoustic resonance solution that accurately determined bolt elongation. He assumed his work on this project had ended, but it was actually the start of nearly 15 years of work perfecting, improving, inventing, and modifying the "bolt monitor", all the while, filing numerous patents, presenting papers, and holding demonstrations as the technology matured. Industry engineers challenged Heyman s inventiveness, and reminded the physicist that most bolts are not perfect resonators, and that early devices required that the bolt have reasonably flat and parallel faces. The U.S. Geological Survey asked NASA for help in determining the load in mine roof bolts, which are 8- to 10-feet-long and rough cut. To solve that problem, Heyman modified the original device to operate at a lower frequency and to generate propagation modes that could be used to "lock" the instrument on a particular mode. Further work in this vein led to the development of the Pulsed Phase Locked Loop (P2L2) that worked on the mine bolts. The next set of problems involved high-strength bolts with head markings. For this solution, Heyman invented a modified P2L2 that tracked a specific phase point in the measurement wave. This class of instrumentation, well suited to measuring small changes in acoustic velocity, won the NASA "Invention of the Year" award in 1982. Other scientists and engineers have continued the evolution of this technology both inside NASA and outside of the Agency. Within NASA, the technology has been improved for medical applications, with a particular focus on intercranial pressure (ICP) monitoring.

2005-01-01

435

A space-based radio frequency transient event classifier  

SciTech Connect

The Department of Energy is currently investigating economical and reliable techniques for space-based nuclear weapon treaty verification. Nuclear weapon detonations produce RF transients that are signatures of illegal nuclear weapons tests. However, there are many other sources of RF signals, both natural and man-made. Direct digitization of RF signals requires rates of 300 MSamples per second and produces 10{sup 13} samples per day of data to analyze. it is impractical to store and downlink all digitized RF data from such a satellite without a prohibitively expensive increase in the number and capacities of ground stations. Reliable and robust data processing and information extraction must be performed onboard the spacecraft in order to reduce downlinked data to a reasonable volume. The FORTE (Fast On-Orbit Recording of Transient Events) satellite records RF transients in space. These transients will be classified onboard the spacecraft with an Event Classifier specialized hardware that performs signal preprocessing and neural network classification. The authors describe the Event Classifier requirements, scientific constraints, design and implementation.

Moore, K.R.; Blain, C.P.; Caffrey, M.P.; Franz, R.C.; Henneke, K.M.; Jones, R.G.

1998-03-01

436

New Antennas and Methods for the Low Frequency Stellar and Planetary Radio Astronomy  

NASA Astrophysics Data System (ADS)

According to the special Program of the National Academy of Sciences of Ukraine, creation of the new giant Ukrainian radio telescope (GURT) was started a few years ago on the UTR-2 radio telescope observatory. The main goal is to reach maximum band at the lowest frequencies (10-70 MHz), effective area (step-by-step up to 100,000 sq.m), and high interference immunity for resolving many astrophysical tasks when the sensitivity is less limited by the confusion effects. These tasks include stellar radio astronomy (the Sun, solar wind, flare stars, pulsars, transients) and planetary one (Jupiter, planetary lightnings, Earth ionosphere, the Moon, exoplanets). This array should be complementary to the LOFAR, E-LOFAR systems. The first stages of the GURT (6 x 25 cross dipole active elements) and broad-band digital registration of the impulsive and sporadic events were tested in comparison with the existing largest decameter array UTR-2.

Konovalenko, A. A.; Falkovich, I. S.; Rucker, H. O.; Lecacheux, A.; Zarka, Ph.; Koliadin, V. L.; Zakharenko, V. V.; Stanislavsky, A. A.; Melnik, V. N.; Litvinenko, G. V.; Gridin, A. A.; Bubnov, I. N.; Kalinichenko, N. N.; Reznik, A. P.; Sidorchuk, M. A.; Stepkin, S. V.; Mukha, D. V.; Nikolajenko, V. S.; Karlsson, R.; Thide, B.

437

SiOx Ink-Repellent Layer Deposited by Radio Frequency (RF) Plasmas in Continuous Wave and Pulse Mode  

NASA Astrophysics Data System (ADS)

Low surface energy layers, proposed application for non-water printing in computer to plate (CTP) technology, are deposited in both continuous wave and pulse radio frequency (13.56 MHz) plasma with hexamethyldisiloxane (HMDSO) as precursor. It is found that the plasma mode dominates the polymer growth rate and the surface composition. Derived from the spectra of X-ray photoelectron spectroscopy (XPS) and combined with printable test it is concluded that concentration of Si in coatings plays an important role for the ink printability and the ink does not adhere on the surface with high silicon concentration.

Chen, Qiang; Fu, Yabo; Pang, Hua; Zhang, Yuefei; Zhang, Guangqiu

2007-12-01

438

First Demonstration of Electron Beam Generation and Characterization with an All Superconducting Radio-frequency (SRF) Photoinjector  

SciTech Connect

In preparation for a high brightness, high average current electron source for the energy-recovery linac BERLinPro an all superconducting radio-frequency photoinjector is now in operation at Helmholtz-Zentrum Berlin. The aim of this experiment is beam demonstration with a high brightness electron source able to generate sub-ps pulse length electron bunches from a superconducting (SC) cathode film made of Pb coated on the backwall of a Nb SRF cavity. This paper describes the setup of the experiment and first results from beam measurements.

Kamps, T; Barday, R; Jankowiak, A; Knobloch, J; Kugeler, O; Matveenko, A N; Neumann, A; Quast, T; Rudolph, J; Schubert, S G; Volker, J; Kneisel, P; Nietubyc, R; Sekutowicz, J K; Smedley, J; Volkov, V; Weinberg, G

2011-09-01

439

First Spectroscopic Imaging Observations of the Sun at Low Radio Frequencies with the Murchison Widefield Array Prototype  

NASA Astrophysics Data System (ADS)

We present the first spectroscopic images of solar radio transients from the prototype for the Murchison Widefield Array, observed on 2010 March 27. Our observations span the instantaneous frequency band 170.9- 201.6 MHz. Though our observing period is characterized as a period of "low" to "medium" activity, one broadband emission feature and numerous short-lived, narrowband, non-thermal emission features are evident. Our data represent a significant advance in low radio frequency solar imaging, enabling us to follow the spatial, spectral, and temporal evolution of events simultaneously and in unprecedented detail. The rich variety of features seen here reaffirms the coronal diagnostic capability of low radio frequency emission and provides an early glimpse of the nature of radio observations that will become available as the next generation of low-frequency radio interferometers come online over the next few years.

Oberoi, Divya; Matthews, Lynn D.; Cairns, Iver H.; Emrich, David; Lobzin, Vasili; Lonsdale, Colin J.; Morgan, Edward H.; Prabu, T.; Vedantham, Harish; Wayth, Randall B.; Williams, Andrew; Williams, Christopher; White, Stephen M.; Allen, G.; Arcus, Wayne; Barnes, David; Benkevitch, Leonid; Bernardi, Gianni; Bowman, Judd D.; Briggs, Frank H.; Bunton, John D.; Burns, Steve; Cappallo, Roger C.; Clark, M. A.; Corey, Brian E.; Dawson, M.; DeBoer, David; De Gans, A.; deSouza, Ludi; Derome, Mark; Edgar, R. G.; Elton, T.; Goeke, Robert; Gopalakrishna, M. R.; Greenhill, Lincoln J.; Hazelton, Bryna; Herne, David; Hewitt, Jacqueline N.; Kamini, P. A.; Kaplan, David L.; Kasper, Justin C.; Kennedy, Rachel; Kincaid, Barton B.; Kocz, Jonathan; Koeing, R.; Kowald, Errol; Lynch, Mervyn J.; Madhavi, S.; McWhirter, Stephen R.; Mitchell, Daniel A.; Morales, Miguel F.; Ng, A.; Ord, Stephen M.; Pathikulangara, Joseph; Rogers, Alan E. E.; Roshi, Anish; Salah, Joseph E.; Sault, Robert J.; Schinckel, Antony; Udaya Shankar, N.; Srivani, K. S.; Stevens, Jamie; Subrahmanyan, Ravi; Thakkar, D.; Tingay, Steven J.; Tuthill, J.; Vaccarella, Annino; Waterson, Mark; Webster, Rachel L.; Whitney, Alan R.

2011-02-01

440

Laser nitriding for niobium superconducting radio-frequency accelerator cavities  

SciTech Connect

Particle accelerators are a key tool for scientific research ranging from fundamental studies of matter to analytical studies at light sources. Cost-forperformance is critical, both in terms of initial capital outlay and ongoing operating expense, especially for electricity. It depends on the niobium superconducting radiofrequency (SRF) accelerator cavities at the heart of most of these machines. Presently Nb SRF cavities operate near 1.9 K, well (and expensively) below the 4.2 K atmospheric boiling point of liquid He. Transforming the 40 nm thick active interior surface layer from Nb to delta NbN (Tc = 17 K instead of 9.2 K) appears to be a promising approach. Traditional furnace nitriding appears to have not been successful for this. Further, exposing a complete SRF cavity to the time-temperature history required for nitriding risks mechanical distortion. Gas laser nitriding instead has been applied successfully to other metals [P.Schaaf, Prog. Mat. Sci. 47 (2002) 1]. The beam dimensions and thermal diffusion length permit modeling in one dimension to predict the time course of the surface temperature for a range of per-pulse energy densities. As with the earlier work, we chose conditions just sufficient for boiling as a reference point. We used a Spectra Physics HIPPO nanosecond laser (l = 1064 nm, Emax= 0.392 mJ, beam spot@ 34 microns, PRF =15 – 30 kHz) to obtain an incident fluence of 1.73 - 2.15 J/cm2 for each laser pulse at the target. The target was a 50 mm diameter SRF-grade Nb disk maintained in a nitrogen atmosphere at a pressure of 550 – 625 torr and rotated at a constant speed of 9 rpm. The materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and x-ray diffraction (XRD). The SEM images show a sharp transition with fluence from a smooth, undulating topography to significant roughening, interpreted here as the onset of ablation. EPMA measurements of N/Nb atom ratio as a function of depth found a constant value to depths greater than the SRF active layer thickness. Certain irradiation conditions resulted in values consistent with formation of delta NbN. Under certain irradiation conditions, XRD data were consistent only with delta NbN on top of Nb metal. Funding: authored by Jefferson Science Associates LLC under US DOE Contract De-AC05-06OR23177. We are indebted to Prof. P. Schaaf (Goettingen) for the simulation code and helpful discussions.

Senthilraja Singaravelu, John Klopf, Gwyn Williams, Michael Kelley

2010-10-01

441

Radio Diagnostics of Flare Energy Release Arnold O. Benz  

E-print Network

for radio diagnostics. 1 Introduction A major issue of solar physics in the past three decades is the way resistor in an electric circuit. On the contrary, the release of electromagnetic energy occurs at least

442

Radio-frequency spectroscopic measurement for pairing gap in an ultracold Fermi gas  

NASA Astrophysics Data System (ADS)

The study of ultracold Fermi gases has exploded a variety of experimental and theoretical research since the achievement of degenerate quantum gases in the lab, which expands the research range over atomic physics, condensed matter physics, astrophysics and particle physics. Using the Feshbach resonance, one can tune the attractive two-body interaction from weak to strong and thereby make a smooth crossover from the BCS superfluid of cooper pairs to the Bose Einstein condensate of bound molecules. In this crossover regime, the pairing effect plays a significant role in interpreting the interaction mechanism. Whenever the localized or delocalized pairing occurs at sufficiently low temperature, the single-particle energy will shift with respect to free atoms, due to the two-body or many-body interaction. Measuring the pairing gap can improve the understanding of the thermodynamics and hydrodynamics of the phase transition from the pseudogap to the superfluid, which will make an analogue to the high-temperature superconductivity in condensed matter. In this work, we will give a brief introduction to a novel radio-frequency (RF) spectroscopic measurement for pairing gap in an ultracold Fermi gas, which is currently widely used on the ultracold atomic table in the lab. In different interaction regimes of the BEC-BCS crossover, ultracold atoms are excited with a RF pulse and the characteristic behavior can be extracted from the spectrum.

Jiang, KaiJun; Luo, Hua; Li, Kai; Zhang, DongFang; Gao, TianYou; Peng, ShiGuo

2013-03-01

443

Intrinsic noise measurement of an ultra-sensitive radio-frequency single electron transistor  

NASA Astrophysics Data System (ADS)

The radio-frequency single electron transistor (rf-SET) has been the focus of intense interest since its invention in 1998[1]. Using cryogenic ultra-thin film evaporation techniques [2] and an improved on-chip superconducting matching network [3], we have consistently fabricated rf-SETs with charge sensitivity of 1.7--5?e/?Hz and uncoupled energy sensitivity 1.1--5. Using our 1GHz resonant circuit, intrinsic noise in the SET arising from a dc voltage bias was measured in the white noise limit. We measured the offset charge dependence of the intrinsic noise in the vicinity of the Josephson-quasiparticle and double Josephson-quasiparticle transport cycles. In regions for which the offset charge and resistance noise are strongly suppressed, we can determine the SET shot noise in the sup-gap regime. We discuss the effects of correlations between charge carriers on the measured Fano factor. [1] R.J.Schoelkopf et al., Science 280,1238 (1998); [2] N.A.Court et al., Cond-mat 0706.4150 (2007); [3] W.W.Xue et al., Appl.Phys.Lett. 91, 093511 (2007).

Xue, W. W.; Ji, Z.; Pan, Feng; Rimberg, A. J.

2008-03-01

444

First-principles calculations of niobium hydride formation in superconducting radio-frequency cavities  

SciTech Connect

Niobium hydride is suspected to be a major contributor to degradation of the quality factor of niobium superconducting radio-frequency (SRF) cavities. In this study, we connect the fundamental properties of hydrogen in niobium to SRF cavity performance and processing. We modeled several of the niobium hydride phases relevant to SRF cavities and present their thermodynamic, electronic, and geometric properties determined from calculations based on density-functional theory. We find that the absorption of hydrogen from the gas phase into niobium is exothermic and hydrogen becomes somewhat anionic. The absorption of hydrogen by niobium lattice vacancies is strongly preferred over absorption into interstitial sites. A single vacancy can accommodate six hydrogen atoms in the symmetrically equivalent lowest-energy sites and additional hydrogen in the nearby interstitial sites affected by the strain field: this indicates that a vacancy can serve as a nucleation center for hydride phase formation. Small hydride precipitates may then occur near lattice vacancies upon cooling. Vacancy clusters and extended defects should also be enriched in hydrogen, potentially resulting in extended hydride phase regions upon cooling. We also assess the phase changes in the niobium-hydrogen system based on charge transfer between niobium and hydrogen, the strain field associated with interstitial hydrogen, and the geometry of the hydride phases. The results of this study stress the importance of not only the hydrogen content in niobium, but also the recovery state of niobium for the performance of SRF cavities.

Ford, Denise C.; Cooley, Lance D.; Seidman, David N.

2013-09-01

445

Multipurpose neutron generators based on the radio frequency quadrupole linear accelerator  

NASA Astrophysics Data System (ADS)

Neutron generators based on the Radio Frequency Quadrupole accelerator are now used for a variety of applications. These compact linear accelerators can produce from 108 to more than 1013 neutrons/second using either proton or deuteron beams to bombard beryllium targets. They exhibit long lifetimes at full output, as there is little target or beam degradation. Since they do not use radioactive materials, licensing requirements are less stringent than for isotopic sources or tritium sealed tube generators. The light weight and compact size of these robust systems make them transportable. The low divergence output beam from the RFQ also allows use of a remote target, which can reduce the seize of the shielding and moderator. The RFQ linac can be designed with a wide range of output beam energy and used with other targets such as lithium and deuterium to produce a neutron spectrum tailored to a specific application. These pulsed systems are well-suited for applications requiring a high peak neutron flux, including activation analysis of very short-lived reaction products. They can replace conventional sources in non-destructive testing applications such as thermal or fast neutron radiography, and can also be used for cancer therapy.

Hamm, Robert W.

2000-12-01

446

Proton beam studies with a 1.25 MeV, cw radio frequency quadrupole linac  

SciTech Connect

A high-current, cw linear accelerator has been proposed as a spallation neutron source driver for tritium production. Key features of this accelerator are high current (100 mA), low emittance-growth beam propagation, cw operation, high efficiency, and minimal maintenance downtime. A 268 MHz, cw radio frequency quadrupole (RFQ) LINAC section and klystrode based rf system were obtained from the Chalk River Laboratories and were previously installed at LANL to support systems development and advanced studies in support of cw, proton accelerators. A variation of the Low Energy Demonstration Accelerator (LEDA) proton injector, modified to operate at 50 keV, was mated to the RFQ and was operated to support advance developments for the Accelerator Production of Tritium (APT) program. High current, proton beam studies were completed which focused on the details of injector-RFQ integration, development of beam diagnostics, development of operations procedures, and personnel and equipment safety systems integration. This development led to acceleration of up to 100 mA proton beam.

Bolme, G.O.; Hardek, T.W.; Hansborough, L.D. [and others

1998-12-31

447

Performance report on the ground test accelerator radio-frequency quadrupole  

SciTech Connect

The Ground Test Accelerator (GTA) uses a radio-frequency quadrupole (RFQ) to bunch and accelerate a 35 keV input beam to a final energy of 2.5 MeV. Most measured parameters of the GTA RFQ agreed with simulated predictions. The relative shape of the transmission versus the vane-voltage relationship and the Courant-Snyder (CS) parameters of the output beam`s transverse and longitudinal phase spaces agreed well with predictions. However, the transmission of the RFQ was significantly lower than expected. Improved simulation studies included image charges and multipole effects in the RFQ. Most of the predicted properties of the RFQ, such as input matched-beam conditions and output-beam shapes were unaffected by these additional effects. However, the comparison of measured with predicted absolute values of transmitted beam was much improved by the inclusion of these effects in the simulations. The comparison implied a value for the input emittance that is consistent with measurements.

Sander, O.R.; Atkins, W.H.; Bolme, G.O.; Brown, S.; Cole, R.; Connolly, R.; Gilpatrick, J.D.; Garnett, R.; Guy, F.W.; Ingalls, W.B. [and others

1994-09-01

448

Charging and discharging in ion implanted dielectric films used for capacitive radio frequency microelectromechanical systems switch  

NASA Astrophysics Data System (ADS)

In this work, metal-insulator-semiconductor (MIS) capacitor structure was used to investigate the dielectric charging and discharging in the capacitive radio frequency microelectromechanical switches. The insulator in MIS structure is silicon nitride films (SiN), which were deposited by either low pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD) processes. Phosphorus or boron ions were implanted into dielectric layer in order to introduce impurity energy levels into the band gap of SiN. The relaxation processes of the injected charges in SiN were changed due to the ion implantation, which led to the change in relaxation time of the trapped charges. In our experiments, the space charges were introduced by stressing the sample electrically with dc biasing. The effects of implantation process on charge accumulation and dissipation in the dielectric are studied by capacitance-voltage (C-V) measurement qualitatively and quantitatively. The experimental results show that the charging and discharging behavior of the ion implanted silicon nitride films deposited by LPCVD is quite different from the one deposited by PECVD. The charge accumulation in the dielectric film can be reduced by ion implantation with proper dielectric deposition method.

Li, Gang; San, Haisheng; Chen, Xu-yuan

2009-06-01

449

Detection of Traveling Ionospheric Disturbances by Medium Frequency Doppler Sounding Using AM Radio Transmissions  

NASA Astrophysics Data System (ADS)

Nighttime traveling ionosphere disturbances (TIDs) propagating in the lower F region of the ionosphere were detected from time variations in the Doppler shifts of commercial AM radio broadcast stations. Three separately deployed receivers, components of the Intercepted Signals for Ionospheric Science (ISIS) Array software radio instrumentation network, recorded signals from two radio stations during eleven nights in March-April, 2012. Combining these measurements established that variations in the frequencies of the received signals, with amplitudes up to a few tenths of a Hertz, resulted from Doppler shifts produced by the ionosphere. At times, TIDs were detected as large amplitude variations in the Doppler shift with approximately 40-minute period correlated across the array. For one study interval, 0000-0400 UT on April 13, 2012, simultaneous GPS-TEC, digisonde, and superDARN coherent backscatter radar measurements confirmed the detection of TIDs with the same period. Detection of the AM signals at widely spaced receivers allowed the phase velocity and wavelength of the TIDs to be inferred, with some limitations due to differing reflection heights for the different frequencies. These measurements will be compared to phase velocities and wavelengths determined from combining an array of GPS receivers; discrepancies due to the altitude sensitivity of the techniques or other effects will be discussed. These results demonstrate that AM radio signals can be used for detection of nighttime TIDs.

Chilcote, M. A.; Labelle, J. W.; Lind, F. D.; Coster, A. J.; Galkin, I. A.; Miller, E.; Weatherwax, A. T.

2013-12-01

450

Plasma Parameters of SRF Cavities for Radio-Frequency Discharge Processing  

NASA Astrophysics Data System (ADS)

Superconducting radio frequency (SRF) cavities of bulk Niobium are accelerating field-generating components of particle accelerators. Cavities are designed to support TM modes at a resonant frequency, which usually serve as their identifier. RF plasma surface modification dry-etching technology as an alternative to the currently existing wet etching technology requires a different RF coupling regime. The choice of power generator frequency greatly affects the field and plasma parameters distribution over the cavity. These are adjusted by a coaxial centerline antenna to provide for optimum level of plasma sheath uniformity. In the search for best etching conditions, we are opting for radio frequency (13.56 MHz, 100 MHz) and microwave frequency plasma (2.45 GHz) in Ar/Cl2 gas mixture. We have developed five optical probes for simultaneous spectroscopic measurements of the plasma properties at five points inside the cavity. The electron temperature and density measurement at the same set of points will be also measured with a Langmuir probe. The measurement of plasma parameters at different pressure and power for the chosen frequency set with varying chlorine content will be presented.

Upadhyay, Janardan; Popovic, Svetozar; Vuskovic, Lepsha; Valente-Feliciano, Anne-Marie; Phillips, Larry

2012-10-01