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Sample records for improvement rf control

  1. Improved Controls for Fusion RF Systems. Final technical report

    SciTech Connect

    Casey, Jeffrey A.

    2011-11-08

    We have addressed the specific requirements for the integrated systems controlling an array of klystrons used for Lower Hybrid Current Drive (LHCD). The immediate goal for our design was to modernize the transmitter protection system (TPS) for LHCD on the Alcator C-Mod tokamak at the MIT Plasma Science and Fusion Center (MIT-PSFC). Working with the Alcator C-Mod team, we have upgraded the design of these controls to retrofit for improvements in performance and safety, as well as to facilitate the upcoming expansion from 12 to 16 klystrons. The longer range goals to generalize the designs in such a way that they will be of benefit to other programs within the international fusion effort was met by designing a system which was flexible enough to address all the MIT system requirements, and modular enough to adapt to a large variety of other requirements with minimal reconfiguration.

  2. Improvements of Low Level RF Control Systems for J-PARC LINAC 400-MeV Upgrade

    NASA Astrophysics Data System (ADS)

    Fang, Z.; Futatsukawa, K.; Fukui, Y.; Kobayashi, T.; Michizono, S.; Sato, F.; Shinozaki, S.; Chishiro, E.

    The low level RF (LLRF) control systems have been successfully improved for the J-PARC LINAC upgrade. After the installation of 972-MHz high-β acceleration section behind the 324-MHz low-β section beginning in the summer of 2013, the proton beam was successfully accelerated to 400 MeV in January 2014. Many improvements in the LLRF control systems have been carried out to facilitate the operation of the J-PARC LINAC at 400 MeV. The reference 12-MHz signal delay settings for the feedback control systems have been optimized using 12-MHz delay modules. The stability performances of the 972-MHz RF&CLK (Clock) and Mixer&IQ (Mixer & IQ-modulator) boards have been improved using temperature-compensation techniques. By improving the hardware of the feedback control systems, very good stability of the RF systems has been achieved.

  3. Improved RF Isolation Amplifier

    NASA Technical Reports Server (NTRS)

    Stevens, G. L.; Macconnell, J.

    1985-01-01

    Circuit has high reverse isolation and wide bandwidth. Wideband isolation amplifier has low intermodulation distortion and high reverse isolation. Circuit does not require selected or matched components or directional coupling device. Circuit used in applications requiring high reverse isolation such as receiver intermediate-frequency (IF) strips and frequency distribution systems. Also applicable in RF and video signaling.

  4. SNS LINAC RF control system.

    SciTech Connect

    Regan, A. H.; Kwon, S. I.; Prokop, M. S.; Rohlev, T. S.; Thomson, D. W.; Ma, H.

    2002-01-01

    The SNS linac RF control system (RFCS) is currently in development. A system is being installed in a superconducting test stand at Jefferson Laboratory presently. Two systems will soon be installed at Oak Ridge National Laboratory (ORNL) and more are due to be installed early next year. The RF control system provides field control for the entire SNS linac, including an RFQ and 6 DTL cavities at 402.5 MHz as well as three different types of cavities at of 805 MHz: 4 CCL cavities, 36 medium beta superconducting (SRF) cavities, and 45 high beta superconducting cavities. In addition to field control, it provides cavity resonance control, and incorporates high power protect functions. This paper will discuss the RFCS design to date, with emphasis on the challenges of providing a universal digital system for use on each of the individual cavity types. The RF control system hardware has been designed to minimize the amount of changes for all of the applications. Through software/firmware modification and changing a couple of frequency-dependent filters, the same control system design can be used for all five cavity types. The SNS is the first to utilize SRF cavities for a pulsed high-current proton accelerator, thereby making RF control especially challenging.

  5. VERSE-Guided Numerical RF Pulse Design: A Fast Method for Peak RF Power Control

    PubMed Central

    Lee, Daeho; Grissom, William A.; Lustig, Michael; Kerr, Adam B.; Stang, Pascal P.; Pauly, John M.

    2013-01-01

    In parallel excitation, the computational speed of numerical radiofrequency (RF) pulse design methods is critical when subject dependencies and system nonidealities need to be incorporated on-the-fly. One important concern with optimization-based methods is high peak RF power exceeding hardware or safety limits. Hence, online controllability of the peak RF power is essential. Variable-rate selective excitation pulse reshaping is ideally suited to this problem due to its simplicity and low computational cost. In this work, we first improve the fidelity of variable-rate selective excitation implementation for discrete-time waveforms through waveform oversampling such that variable-rate selective excitation can be robustly applied to numerically designed RF pulses. Then, a variable-rate selective excitation-guided numerical RF pulse design is suggested as an online RF pulse design framework, aiming to simultaneously control peak RF power and compensate for off-resonance. PMID:22135085

  6. Linac RF control at transient beamloading

    NASA Astrophysics Data System (ADS)

    Chernogubovsky, M. A.; Sugimoto, M.

    1999-06-01

    Effective RF control design is carried out under electrodynamic property analysis of the transient beam excitation, which gives the basic principle and support method for RF control. The main parameters of the RF system are defined under the directional selective coupling application; the beam dynamics with control characteristics are optimized for operating mode electrodynamics.

  7. Low-level RF control for the AFEL

    SciTech Connect

    Ziomek, C.; Kinross-Wright, J.; Plato, J.

    1994-09-01

    A limiting factor in the performance of the Los Alamos Advanced Free Electron Laser (AFEL) is the stability of the RF accelerating field. A high-performance low-level RF control system has been implemented that uses analog feedback and digital feed forward to regulate the RF field. This low-level RF control system has achieved long-term amplitude and phase stabilities better than {+-}0.25% and {+-}0.33{degree} respectively. In order to improve the RF field stability further, a detailed system analysis and design is proceeding. Subsystem measurements are being used to model the system performance, predict the performance-limiting components, and determine possible improvements. Results to-date, modeling analyses, and suggested future improvements are presented.

  8. RF TECHNIQUES FOR IMPROVED LUMINOSITY IN RHIC.

    SciTech Connect

    BRENNAN,J.M.BLASKIEWICZ,J.BUTLER,J.DELONG,J.FISCHER,W.HAYES,T.

    2004-07-05

    The luminosity of the Relativistic Heavy Ion Collider has improved significantly [1] over the first three physics runs. A number of special rf techniques have been developed to facilitate higher luminosity. The techniques described herein include: an ultra low-noise rf source for the 197 MHz storage rf system, a frequency shift switch-on technique for transferring bunches from the acceleration to the storage system, synchronizing the rings during the energy ramp (including crossing the transition energy) to avoid incidental collisions, installation of dedicated 200 MHZ cavities to provide longitudinal Landau damping on the ramp, and the development of a bunch merging scheme in the Booster to increase the available bunch intensity from the injectors.

  9. Improvements for Omega RF preamplifiers

    NASA Technical Reports Server (NTRS)

    Wright, L.

    1976-01-01

    An improved Omega navigation system preamplifier, which provides both ADF and Omega outputs from a single antenna input, is described. This preamp has tuneable bandpass filtering, zero phase shift at both output ports, adjustable gain at the Omega output, and it receives power via the coaxial cable to the receiver front-end.

  10. Auxiliary coil controls temperature of RF induction heater

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Auxiliary coil controls the temperature of an RF induction furnace that is powered by a relatively unstable RF generator. Manual or servoed adjustments of the relative position of the auxiliary coil, which is placed in close proximity to the RF coil, changes the looseness of the RF coil and hence the corresponding heating effect of its RF field.

  11. Control electronics of the PEP RF system

    SciTech Connect

    Pellegrin, J.L.; Schwarz, H.

    1981-01-01

    The operation of the major components used for controlling the phase and field level of the PEP RF cavities is described. The control electronics of one RF station is composed of several control loops: each cavity has a tuners' servo loop which maintains the frequency constant and also keeps the fields of each cavity balanced; the total gap voltage developed by a pair of cavities is regulated by a gap voltage controller; finally, the phase variation along the amplification chain, the klystron and the cavities are compensated by a phase lock loop. The design criteria of each loop are set forth and the circuit implementation and test results are presented.

  12. Directions for rf-controlled intelligent microvalve

    NASA Astrophysics Data System (ADS)

    Enderling, Stefan; Varadan, Vijay K.; Abbott, Derek

    2001-03-01

    In this paper, we consider the novel concept of a Radio Frequency (RF) controllable microvalve for different medical applications. Wireless communication via a Surface Acoustic Wave Identification-mark (SAW ID-tag) is used to control, drive and locate the microvalve inside the human body. The energy required for these functions is provided by RF pulses, which are transmitted to the valve and back by a reader/transmitter system outside of the body. These RF bursts are converted into Surface Acoustic Waves (SAWs), which propagate along the piezoelectric actuator material of the microvalve. These waves cause deflections, which are employed to open and close the microvalve. We identified five important areas of application of the microvalve in biomedicine: 1) fertility control; 2) artificial venous valves; 3) flow cytometry; 4) drug delivery and 5) DNA mapping.

  13. Rf beam control for the AGS Booster

    SciTech Connect

    Brennan, J.M.

    1994-09-26

    RF beam control systems for hadron synchrotrons have evolved over the past three decades into an essentially standard design. The key difference between hadron and lepton machines is the absence of radiation damping and existence of significant frequency variation in the case of hadrons. Although the motion of the hadron in the potential well of the rf wave is inherently stable it is not strongly damped. Damping must be provided by electronic feedback through the accelerating system. This feedback is typically called the phase loop. The technology of the rf beam control system for the AGS Booster synchrotron is described. First, the overall philosophy of the design is explained in terms of a conventional servo system that regulates the beam horizontal position in the vacuum chamber. The concept of beam transfer functions is fundamental to the mathematics of the design process and is reviewed. The beam transfer functions required for this design are derived from first principles. An overview of the beam signal pick-ups and high level rf equipment is given. The major subsystems, the frequency program, the heterodyne system, and beam feedback loops, are described in detail. Beyond accelerating the beam, the rf system must also synchronize the bunches in the Booster to the buckets in the AGS before transfer. The technical challenge in this process is heightened by the need to accomplish synchronization while the frequency is still changing. Details of the synchronization system are given. This report is intended to serve two purposes. One is to document the hardware and performance of the systems that have been built. The other is to serve as a tutorial vehicle from which the non-expert can not only learn the details of this system but also learn the principles of beam control that have led to the particular design choices made.

  14. Real Time RF Simulator (RTS) and control

    SciTech Connect

    Cancelo, G.; Armiento, C.; Treptow, K.; Vignoni, A.; Zmuda, T.; /Fermilab

    2008-10-01

    The multi-cavity RTS allows LLRF algorithm development and lab testing prior to commissioning with real cavities and cryomodules. The RTS is a valuable tool since it models the functions, errors and disturbances of real RF systems. The advantage of a RTS over an off-line simulator is that it can be implemented on the actual LLRF hardware, on the same FPGA and processor, and run at the same speed of the LLRF control loop. Additionally the RTS can be shared by collaborators who do not have access to RF systems or when the systems are not available to LLRF engineers. The RTS simulator incorporates hardware, firmware and software errors and limitations of a real implementation, which would be hard to identify and time consuming to model in off-line simulations.

  15. Computer control of rf at SLAC

    SciTech Connect

    Schwarz, H.D.

    1985-03-01

    The Stanford Linear Accelerator is presently upgraded for the SLAC Linear Collider project. The energy is to be increased from approximately 31 GeV to 50 GeV. Two electron beams and one positron beam are to be accelerated with high demands on the quality of the beams. The beam specifications are shown. To meet these specifications, all parameters influencing the beams have to be under tight control and continuous surveillance. This task is accomplished by a new computer system implemented at SLAC which has, among many other functions, control over rf accelerating fields. 13 refs., 8 figs., 2 tabs.

  16. Measurements for low level RF control systems

    NASA Astrophysics Data System (ADS)

    Simrock, S. N.

    2007-08-01

    The low level RF control system for the European x-ray free electron laser, which is based on TESLA technology, requires information on a large number of signals and parameters which are either directly measurable as physical signals or must be derived from the physical signals. In most cases, calibrations are required to obtain the desired quantities. The measured signals are used in the real time feedback loops for field and resonance control, and for diagnostic purposes to support automation and exception handling. Good system models and powerful signal processors (including field programmable gate arrays and digital signal processors) combined with fast communication links allow for processing a large number of complex algorithms in real time. Several of these algorithms have been implemented at the free electron laser at Hamburg (FLASH) for evaluation and have increased the availability of the facility for user operation.

  17. RF Control System for the NLC Linacs

    SciTech Connect

    Corredoura, Paul L.

    2000-08-23

    The proposed Next Linear Collider contains a large number of linac RF systems with new requirements for wideband klystron modulation and accurate RF vector detection. The system will be capable of automatically phasing each klystron and compensating for beam loading effects. Accelerator structure alignment is determined by detection of the beam induced dipole modes with a receiver similar to that used for measuring the accelerator RF and is incorporated into the RF system topology. This paper describes the proposed system design, signal processing techniques and includes preliminary test results.

  18. Computer simulation for improving radio frequency (RF) heating uniformity of food products: a review.

    PubMed

    Huang, Zhi; Marra, Francesco; Subbiah, Jeyamkondan; Wang, Shaojin

    2016-11-28

    Radio frequency (RF) heating has great potential for achieving rapid and volumetric heating in foods, providing safe and high quality food products due to deep penetration depth, moisture self-balance effects, and leaving no chemical residues. However, the non-uniform heating problem (usually resulting in hot and cold spots in the heated product) needs to be resolved. The inhomogeneous temperature distribution not only affects the quality of the food but also raises the issue of food safety when the microorganisms or insects may not be controlled in the cold spots. The mathematical modelling for RF heating processes has been extensively studied in a wide variety of agricultural products recently. This paper presents a comprehensive review of recent progresses in computer simulation for RF heating uniformity improvement and the offered solutions to reduce the heating non-uniformity. It provides a brief introduction on the basic principle of RF heating technology, analyzes the applications of numerical simulation, and discusses the factors influencing the RF heating uniformity and the possible methods to improve heating uniformity. Mathematical modelling improves the understanding of RF heating of food and is essential to optimize the RF treatment protocol for pasteurization and disinfestation applications. Recommendations for future research have been proposed to further improve the accuracy of numerical models, by covering both heat and mass transfers in the model, validating these models with sample movement and mixing, and identifying the important model parameters by sensitivity analysis.

  19. Improved chromatic dispersion monitoring using single RF monitoring tone.

    PubMed

    Liu, Andrew; Pendock, Graeme J; Tucker, Rodney S

    2006-05-29

    We demonstrate an improved chromatic dispersion monitoring technique using a single RF monitoring tone. Compared to conventional techniques using a single RF monitoring tone, our proposed technique is able to monitor the sign of the residual dispersion and doubles the monitoring range. Our proposed technique utilizes the RF fading caused by chromatic dispersion and a two-detector dispersion monitor setup, where a dispersion offset is inserted before one of the detectors. The observed monitoring error is less than +/-35 ps/nm over a 1300 ps/nm monitoring range. A small power penalty less than 0.5 dB is observed due to the addition of the RF monitoring tone. Our technique is more than twice as accurate as the conventional technique.

  20. An improved RF circuit for Overhauser magnetometer excitation

    NASA Astrophysics Data System (ADS)

    Zheng, Di; Zhang, Shuang; Guo, Xin; Fu, Haoyang

    2015-08-01

    Overhauser magnetometer is a high-precision device for magnetostatic field measurement, which can be used in a wide variety of purposes: UXO detection, pipeline mapping and other engineering and environmental applications. Traditional proton magnetometer adopts DC polarization, suffering from low polarization efficiency, high power consumption and low signal noise ratio (SNR). Compared with the traditional proton magnetometer, nitroxide free radicals are used for dynamic nuclear polarization (DNP) to enhance nuclear magnetic resonance (NMR). RF excitation is very important for electron resonance in nitrogen oxygen free radical solution, and it is primarily significant for the obtention of high SNR signal and high sensitive field observation. Therefore, RF excitation source plays a crucial role in the development of Overhauser magnetometer. In this paper, an improved design of a RF circuit is discussed. The new RF excitation circuit consists of two parts: Quartz crystal oscillator circuit and RF power amplifier circuit. Simulation and optimization designs for power amplifier circuit based on software ADS are presented. Finally we achieve a continuous and stable sine wave of 60MHz with 1-2.5 W output power, and the second harmonic suppression is close to -20dBc. The improved RF circuit has many merits such as small size, low-power consumption and high efficiency, and it can be applied to Overhauser magnetometer to obtain high sensitive field observation.

  1. Multiband RF pulses with improved performance via convex optimization.

    PubMed

    Shang, Hong; Larson, Peder E Z; Kerr, Adam; Reed, Galen; Sukumar, Subramaniam; Elkhaled, Adam; Gordon, Jeremy W; Ohliger, Michael A; Pauly, John M; Lustig, Michael; Vigneron, Daniel B

    2016-01-01

    Selective RF pulses are commonly designed with the desired profile as a low pass filter frequency response. However, for many MRI and NMR applications, the spectrum is sparse with signals existing at a few discrete resonant frequencies. By specifying a multiband profile and releasing the constraint on "don't-care" regions, the RF pulse performance can be improved to enable a shorter duration, sharper transition, or lower peak B1 amplitude. In this project, a framework for designing multiband RF pulses with improved performance was developed based on the Shinnar-Le Roux (SLR) algorithm and convex optimization. It can create several types of RF pulses with multiband magnitude profiles, arbitrary phase profiles and generalized flip angles. The advantage of this framework with a convex optimization approach is the flexible trade-off of different pulse characteristics. Designs for specialized selective RF pulses for balanced SSFP hyperpolarized (HP) (13)C MRI, a dualband saturation RF pulse for (1)H MR spectroscopy, and a pre-saturation pulse for HP (13)C study were developed and tested.

  2. Multiband RF Pulses with Improved Performance via Convex Optimization

    PubMed Central

    Shang, Hong; Larson, Peder E. Z.; Kerr, Adam; Reed, Galen; Sukumar, Subramaniam; Elkhaled, Adam; Gordon, Jeremy W.; Ohliger, Michael A.; Pauly, John M.; Lustig, Michael; Vigneron, Daniel B.

    2016-01-01

    Selective RF pulses are commonly designed with the desired profile as a low pass filter frequency response. However, for many MRI and NMR applications, the spectrum is sparse with signals existing at a few discrete resonant frequencies. By specifying a multiband profile and releasing the constraint on “don’t-care” regions, the RF pulse performance can be improved to enable a shorter duration, sharper transition, or lower peak B1 amplitude. In this project, a framework for designing multiband RF pulses with improved performance was developed based on the Shinnar-Le Roux (SLR) algorithm and convex optimization. It can create several types of RF pulses with multiband magnitude profiles, arbitrary phase profiles and generalized flip angles. The advantage of this framework with a convex optimization approach is the flexible trade-off of different pulse characteristics. Designs for specialized selective RF pulses for balanced SSFP hyperpolarized (HP) 13C MRI, a dualband saturation RF pulse for 1H MR spectroscopy, and a pre-saturation pulse for HP 13C study were developed and tested. PMID:26754063

  3. The system of RF beam control for electron gun

    NASA Astrophysics Data System (ADS)

    Barnyakov, A. M.; Chernousov, Yu. D.; Ivannikov, V. I.; Levichev, A. E.; Shebolaev, I. V.

    2015-06-01

    The system of RF control of three-electrode electron gun current is described. It consists of a source of microwave signal, coaxial line, coaxial RF switch and RF antenna lead. The system allows one to get the electron beam in the form of bunches with the frequency of the accelerating section to achieve the capture of particles in the acceleration mode close to 100%. The results of calculation and analysis of the elements of the system are presented. Characteristics of the devices are obtained experimentally. The results of using RF control in three-electrode electron gun at electron linear accelerator are described.

  4. Simulations of S-band RF gun with RF beam control

    NASA Astrophysics Data System (ADS)

    Barnyakov, A. M.; Levichev, A. E.; Maltseva, M. V.; Nikiforov, D. A.

    2017-08-01

    The RF gun with RF control is discussed. It is based on the RF triode and two kinds of the cavities. The first cavity is a coaxial cavity with cathode-grid assembly where beam bunches are formed, the second one is an accelerating cavity. The features of such a gun are the following: bunched and relativistic beams in the output of the injector, absence of the back bombarding electrons, low energy spread and short length of the bunches. The scheme of the injector is shown. The electromagnetic field simulation and longitudinal beam dynamics are presented. The possible using of the injector is discussed.

  5. RF Profile Control for Sustained Plasma Regimes

    NASA Astrophysics Data System (ADS)

    Hosea, J.; Bernabei, S.; Leblanc, B.; Majeski, R.; Menard, J.; Ono, M.; Phillips, C. K.; Schilling, G.; Wilson, J. R.

    1999-11-01

    For advancing plasma operation regimes for AT tokamaks and steady state concepts, as well as for forming and sustaining alternate concepts, it is necessary to provide control of the spatial profiles for the important plasma parameters - pressure, current, etc.. RF techniques offer considerable promise for providing this control and should be further developed as rapidly as possible within the well established tokamak program for forming a basis for application to all confinement concepts. Notably, IBW promises to provide internal transport barrier control if the coupling physics can be understood and efficient antenna coupling to the Bernstein wave can be developed. We will review the IBW experience and discuss possible explanations and solutions for the coupling problems encountered. In particular, the competing roles of parametric decay instability and surface mode excitation will be examined in order to elucidate the increase in surface power losses for the larger devices DIII-D and TFTR. Also, issues which need to be understood for employing ICRF and LH techniques to best advantage, such as antenna bombardment and energetic electron excitation, respectively, will be outlined.

  6. Reducing the duration of broadband excitation pulses using optimal control with limited RF amplitude.

    PubMed

    Skinner, Thomas E; Reiss, Timo O; Luy, Burkhard; Khaneja, Navin; Glaser, Steffen J

    2004-03-01

    Combining optimal control theory with a new RF limiting step produces pulses with significantly reduced duration and improved performance for a given maximum RF amplitude compared to previous broadband excitation by optimized pulses (BEBOP). The resulting pulses tolerate variations in RF homogeneity relevant for standard high-resolution NMR probes. Design criteria were transformation of Iz-->Ix over resonance offsets of +/-20kHz and RF variability of +/-5%, with a pulse length of 500 micros and peak RF amplitude equal to 17.5 kHz. Simulations transform Iz to greater than 0.995 Ix, with phase deviations of the final magnetization less than 2 degrees, over ranges of resonance offset and RF variability that exceed the design targets. Experimental performance of the pulse is in excellent agreement with the simulations. Performance tradeoffs for yet shorter pulses or pulses with decreased digitization are also investigated.

  7. rf improvements for Spallation Neutron Source H- ion source.

    PubMed

    Kang, Y W; Fuja, R; Goulding, R H; Hardek, T; Lee, S-W; McCarthy, M P; Piller, M C; Shin, K; Stockli, M P; Welton, R F

    2010-02-01

    The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

  8. An Improved RF Cavity Search for Halo Axions

    SciTech Connect

    Asztalos, S; Bradley, R; Duffy, L; Hagmann, C; Kinion, D; Moltz, D; Rosenberg, L; Sikivie, P; Stoeffl, W; Sullivan, N; Tanner, D; van Bibber, K; Yu, D

    2003-11-11

    The axion is a hypothetical elementary particle and cold dark matter candidate. In this RF cavity experiment, halo axions entering a resonant cavity immersed in a static magnetic field convert into microwave photons, with the resulting photons detected by a low-noise receiver. The ADMX Collaboration presents new limits on the axion-to-photon coupling and local axion dark matter halo mass density from a RF cavity axion search in the axion mass range 1.9-2.3 {micro}eV, broadening the search range to 1.9-3.3 {micro}eV. In addition, we report first results from an improved analysis technique.

  9. RF kicker cavity to increase control in common transport lines

    DOEpatents

    Douglas, David R.; Ament, Lucas J. P.

    2017-04-18

    A method of controlling e-beam transport where electron bunches with different characteristics travel through the same beam pipe. An RF kicker cavity is added at the beginning of the common transport pipe or at various locations along the common transport path to achieve independent control of different bunch types. RF energy is applied by the kicker cavity kicks some portion of the electron bunches, separating the bunches in phase space to allow independent control via optics, or separating bunches into different beam pipes. The RF kicker cavity is operated at a specific frequency to enable kicking of different types of bunches in different directions. The phase of the cavity is set such that the selected type of bunch passes through the cavity when the RF field is at a node, leaving that type of bunch unaffected. Beam optics may be added downstream of the kicker cavity to cause a further separation in phase space.

  10. UNCERTAIN SYSTEM MODELING OF SNS RF CONTROL SYSTEM

    SciTech Connect

    S. KWON; A. REGAN; ET AL

    2001-06-01

    This paper addresses the modeling problem of the linear accelerator RF system for SNS. The cascade of the klystron and the cavity is modeled as a nominal system. In the real world, high voltage power supply ripple, Lorentz Force Detuning, microphonics, cavity RF parameter perturbations, distortions in RF components, and loop time delay imperfection exist inevitably, which must be analyzed. The analysis is based on the accurate modeling of the disturbances and uncertainties. In this paper, a modern control theory is applied for modeling the disturbances, uncertainties, and for analyzing the closed loop system robust performance.

  11. An improved RF cavity search for halo axions

    NASA Astrophysics Data System (ADS)

    Yu, D. B.

    2004-10-01

    The axion is a hypothetical elementary particle and cold dark matter candidate. In this RF cavity experiment, halo axions entering a resonant cavity immersed in a static magnetic field convert into microwave photons, with the resulting photons detected by a low-noise receiver. I present new limits on the axion-to-photon coupling and local axion dark matter halo mass density from a RF cavity axion search in the axion mass range 1.9 2.3 μeV, broadening the search range to 1.9 3.3 μeV. In addition, I report first results from an improved analysis technique, which improves the experiment sensitivity by 13%. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  12. Improved temperature regulation of APS linac RF components.

    SciTech Connect

    Dortwegt, R.

    1998-09-21

    The temperature of the APS S-Band linac's high-power rf components is regulated by water from individual closed-loop deionized (DI) water systems. The rf components are all made of oxygen-free high-conductivity copper and respond quickly to temperature changes. The SLED cavities are especially temperature-sensitive and cause beam energy instabilities when the temperature is not well regulated. Temperature regulation better than {+-} 0.1 F is required to achieve good energy stability. Improvements in the closed-loop water systems have enabled them to achieve a regulation of {+-} 0.05 F over long periods. Regulation philosophy and equipment are discussed and numerical results are presented.

  13. CONTROL SYSTEM ANALYSIS FOR THE PERTURBED LINEAR ACCELERATOR RF SYSTEM

    SciTech Connect

    SUNG-IL KWON; AMY H. REGAN

    2002-04-10

    This paper addresses the modeling problem of the linear accelerator RF system in SNS. Klystrons are modeled as linear parameter varying systems. The effect of the high voltage power supply ripple on the klystron output voltage and the output phase is modeled as an additive disturbance. The cavity is modeled as a linear system and the beam current is modeled as the exogenous disturbance. The output uncertainty of the low level RF system which results from the uncertainties in the RF components and cabling is modeled as multiplicative uncertainty. Also, the feedback loop uncertainty and digital signal processing signal conditioning subsystem uncertainties are lumped together and are modeled as multiplicative uncertainty. Finally, the time delays in the loop are modeled as a lumped time delay. For the perturbed open loop system, the closed loop system performance, and stability are analyzed with the PI feedback controller.

  14. Precise Heater Controller with rf-Biased Josephson Junctions

    NASA Technical Reports Server (NTRS)

    Green, Colin J.; Sergatskov, Dmitri A.; Duncan, R. V.

    2003-01-01

    Paramagnetic susceptibility thermometers used in fundamental physics experiments are capable of measuring temperature changes with a precision of a part in 2 x 10(exp 10). However, heater controllers are only able to control open-loop power dissipation to about a part in 10(exp 5). We used an array of rf-biased Josephson junctions to precisely control the electrical power dissipation in a heater resistor mounted on a thermally isolated cryogenic platform. Theoretically, this method is capable of controlling the electrical power dissipation to better than a part in 10(exp 12). However, this level has not yet been demonstrated experimentally. The experiment consists of a liquid helium cell that also functions as a high-resolution PdMn thermometer, with a heater resistor mounted on it. The cell is thermally connected to a temperature-controlled cooling stage via a weak thermal link. The heater resistor is electrically connected to the array of Josephson junctions using superconducting wire. An rf-biased array of capacitively shunted Josephson junctions drives the voltage across the heater. The quantized voltage across the resistor is Vn = nf(h/2e), where h is Planck's constant, f is the array biasing frequency, e is the charge of an electron, and n is the integer quantum state of the Josephson array. This results in an electrical power dissipation on the cell of Pn = (Vn)(sup 2/R), where R is the heater resistance. The change of the quantum state of the array changes the power dissipated in the heater, which in turn, results in the change of the cell temperature. This temperature change is compared to the expected values based on the known thermal standoff resistance of the cell from the cooling stage. We will present our initial experimental results and discuss future improvements. This work has been funded by the Fundamental Physics Discipline of the Microgravity Science Office of NASA, and supported by a no-cost equipment loan from Sandia National Laboratories.

  15. AN INTERNET RACK MONITOR-CONTROLLER FOR APS LINAC RF ELECTRONICS UPGRADE

    SciTech Connect

    Ma, Hengjie; Smith, Terry; Nassiri, Alireza; Sun, Yine; Doolittle, Lawrence; Ratti, Alex

    2016-06-01

    To support the research and development in APS LINAC area, the existing LINAC rf control performance needs to be much improved, and thus an upgrade of the legacy LINAC rf electronics becomes necessary. The proposed upgrade plan centers on the concept of using a modern, network-attached, rackmount digital electronics platform –Internet Rack Monitor-Controller (or IRMC) to achieve the goal of modernizing the rf electronics at a lower cost. The system model of the envisioned IRMC is basically a 3-tier stack with a high-performance DSP in the mid-layer to perform the core tasks of real-time rf data processing and controls. The Digital Front-End (DFE) attachment layer at bottom bridges the applicationspecific rf front-ends to the DSP. A network communication gateway, together with an embedded event receiver (EVR) in the top layer merges the Internet Rack MonitorController node into the networks of the accelerator controls infrastructure. Although the concept is very much in trend with today’s Internet-of-Things (IoT), this implementation has actually been used in the accelerators for over two decades.

  16. RF control hardware design for CYCIAE-100 cyclotron

    NASA Astrophysics Data System (ADS)

    Yin, Zhiguo; Fu, Xiaoliang; Ji, Bin; Zhao, Zhenlu; Zhang, Tianjue; Li, Pengzhan; Wei, Junyi; Xing, Jiansheng; Wang, Chuan

    2015-11-01

    The Beijing Radioactive Ion-beam Facility project is being constructed by BRIF division of China Institute of Atomic Energy. In this project, a 100 MeV high intensity compact proton cyclotron is built for multiple applications. The first successful beam extraction of CYCIAE-100 cyclotron was done in the middle of 2014. The extracted proton beam energy is 100 MeV and the beam current is more than 20 μA. The RF system of the CYCIAE-100 cyclotron includes two half-wavelength cavities, two 100 kW tetrode amplifiers and power transmission line systems (all above are independent from each other) and two sets of Low Level RF control crates. Each set of LLRF control includes an amplitude control unit, a tuning control unit, a phase control unit, a local Digital Signal Process control unit and an Advanced RISC Machines based EPICS IOC unit. These two identical LLRF control crates share one common reference clock and take advantages of modern digital technologies (e.g. DSP and Direct Digital Synthesizer) to achieve closed loop voltage and phase regulations of the dee-voltage. In the beam commission, the measured dee-voltage stability of RF system is better than 0.1% and phase stability is better than 0.03°. The hardware design of the LLRF system will be reviewed in this paper.

  17. RF Transceivers for Wireless Body Area Network Controllers

    NASA Astrophysics Data System (ADS)

    Eshra, Islam; Allam, Mootaz; Sayed, Alhassan; Benabid, Sorore; Aboushady, Hassan

    2015-11-01

    This paper focuses on the system and circuit level consideration of radio frequency front-end transceivers dedicated to WBAN controllers. We show how highly digitized transceivers employing sigma-delta modulators can achieve the frequency agility required by WBAN controllers. The paper compares the performance and highlights the pros and cons of I/Q transmitters and polar transmitters. For the receiver, different sigma-delta based RF receiver architectures are presented. These architectures are compared with more conventional architectures in terms of their suitability to WBAN controllers.

  18. The Development of the Electrically Controlled High Power RF Switch and Its Application to Active RF Pulse Compression Systems

    SciTech Connect

    Guo, Jiquan

    2008-12-01

    In the past decades, there has been increasing interest in pulsed high power RF sources for building high-gradient high-energy particle accelerators. Passive RF pulse compression systems have been used in many applications to match the available RF sources to the loads requiring higher RF power but a shorter pulse. Theoretically, an active RF pulse compression system has the advantage of higher efficiency and compactness over the passive system. However, the key component for such a system an element capable of switching hundreds of megawatts of RF power in a short time compared to the compressed pulse width is still an open problem. In this dissertation, we present a switch module composed of an active window based on the bulk effects in semiconductor, a circular waveguide three-port network and a movable short plane, with the capability to adjust the S-parameters before and after switching. The RF properties of the switch module were analyzed. We give the scaling laws of the multiple-element switch systems, which allow the expansion of the system to a higher power level. We present a novel overmoded design for the circular waveguide three-port network and the associated circular-to-rectangular mode-converter. We also detail the design and synthesis process of this novel mode-converter. We demonstrate an electrically controlled ultra-fast high power X-band RF active window built with PIN diodes on high resistivity silicon. The window is capable of handling multi-megawatt RF power and can switch in 2-300ns with a 1000A current driver. A low power active pulse compression experiment was carried out with the switch module and a 375ns resonant delay line, obtaining 8 times compression gain with a compression ratio of 20.

  19. Improved antenna pattern recorder provides visual display of RF power

    NASA Technical Reports Server (NTRS)

    Lipin, R., Jr.

    1970-01-01

    Antenna pattern recording system has a discretionary signal level monitor which senses a specified minimum level occurring between sampling intervals. This enables RF power and percent coverage to be calculated more accurately.

  20. Parts control and reliability assurance of RF hybrids

    NASA Astrophysics Data System (ADS)

    Oslica, J. R.

    The paper examines the methods required for properly controlling RF hybrids in order to ensure the achievement and maintenance of the required reliability of these devices. The discussion, based on a case history, encompasses: (1) preliminary part specification (including the vendor design and construction) and procurement; (2) application (in-house control); and (3) the follow-up corrective action program. It is concluded that the application of proper reliability disciplines to the 'front-end' efforts is essential and can greatly enhance device reliability.

  1. Designing RF control subsystems using the VXIbus standard

    SciTech Connect

    Stepp, J.D.; Vong, F.C.; Bridges, J.F.

    1993-08-01

    Various components are being designed to control the RF system of the 7-GeV Advanced Photon Source (APS). The associated control electronics (phase shifters, amplitude modulators, phase detectors, automatic tuning control, and local feedback control) are designed as modular cards with multiple channels for ease of replacement as well as for compact design. Various specifications of the VXIbus are listed and the method used to simplify the design of the control subsystem is shown. A commercial VXI interface board was used to speed the design cycle. Required manpower and actual task times are included. A discussion of the computer architecture and software development of the device drivers which allowed computer control from a VME processor located in a remote crate operating under the Experimental Physics and Industrial Controls Software (EPICS) program is also presented.

  2. High Gradient Operation with the CEBAF Upgrade RF Control System

    SciTech Connect

    J. Hovater; G. Davis; Hai Dong; Alicia Hofler; Lawrence King; John Musson; Tomasz Plawski

    2006-08-16

    The CEBAF Accelerator at Jefferson Lab is presently a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. Energy will be upgraded to 12 GeV with the addition of 10 new high gradient cryomodules (17+ MV/m). The higher gradients pose significant challenges beyond what the present analog low level RF (LLRF) control systems can handle reliably; therefore, a new LLRF control system is needed. A prototype system has been developed incorporating a large FPGA and using digital down and up conversion to minimize the need for analog components. The new system is more flexible and less susceptible to drifts and component nonlinearities. Because resonance control is critical to reach high gradients quickly, the new cryomodules will include a piezoelectric tuner for each cavity, and the LLRF controls must incorporate both feedback and feed-forward methods to achieve optimal resonance control performance. This paper discusses development of the new RF system, system performance for phase and amplitude stability and resonance control under Lorentz detuning measured during recent tests on a prototype cryomodule.

  3. DESIGN OF THE SNS NORMAL CONDUCTING LINAC RF CONTROL SYSTEM

    SciTech Connect

    A. REGAN; ET AL

    2000-08-01

    The Spallation Neutron Source (SNS) is in the process of being, designed for operation in 2004. The SNS is a 1 GeV machine consisting of both a normal-conducting and super-conducting linac as well as a ring and target area The linac front end is a 402.5 MHz RFQ being developed by Lawrence Berkeley Lab. The DTL, being developed at Los Alamos National Laboratory, is also a copper structure operating at 402.5 MHz, with an 805 MHz CCL structure downstream of it. The expected output energy of the DTL is 87 MeV and that of the CCL is 185 MeV. The RF control system under development for the linac is based on the Low Energy Demonstration Accelerator's (LEDA) control system with some new features. This paper will discuss the new design approach and its benefits. Block diagrams and circuit specifics will be addressed. The normal conducting RF control system will be described in detail with reference to the super-conducting control system when appropriate.

  4. Controlling the dipole-dipole interaction using NMR composite rf pulses

    SciTech Connect

    Baudin, Emmanuel

    2014-08-07

    New composite rf pulses are proposed during which the average dipole-dipole interactions within a spin ensemble are controlled, while a global rotation is achieved. The method used to tailor the pulses is based on the average Hamiltonian theory and relies on the geometrical properties of the spin-spin dipolar interaction. I describe several such composite pulses and analyze quantitatively the improvement brought on the control of the NMR dynamics. Numerical simulations show that the magic sandwich pulse sequence, during which the average dipolar field is effectively reversed, is plagued by defects originating from the finite initial and final π/2 rf pulses. A numerical test based on a classical description of nuclear magnetic resonance is used to check that, when these pulses are replaced by magic composite pulses, the efficiency of the magic sandwich is improved.

  5. Multi-platform RF emitter localization using extremum seeking control

    NASA Astrophysics Data System (ADS)

    Al Issa, Huthaifa; Ordóñez, Raúl

    2013-05-01

    In recent years there has been growing interest in Ad-hoc and Wireless Sensor Networks (WSNs) for a variety of indoor applications. Thus, recent developments in communications and RF technology have enabled system concept formulations and designs for low-cost radar systems using state-of-the-art software radio modules. Position-Adaptive radar concepts have been formulated and investigated at the Air Force Research Laboratory (AFRL) within the past few years. Adopting a position-adaptive approach to the design of distributed radar systems shows potential for the development of future radar systems that function under new and challenging environments that contain large clutter discretes and require co-functionality within multi-signal RF environments. In this paper, we present the simulation performance analysis on the application aspect. We apply Extremum Seeking Control (ESC) schemes by using the swarm seeking problem, where the goal is to design a control law for each individual sensor that can minimize the error metric by adapting the sensor positions in real-time based on cross-path loss exponents estimates between sensors, thereby minimizing the unknown estimation error. As a result we achieved source seeking and collision avoidance of the entire group of the sensor positions.

  6. Controlling satellite communication system unwanted emissions in congested RF spectrum

    NASA Astrophysics Data System (ADS)

    Olsen, Donald; Heymann, Roger

    2007-09-01

    The International Telecommunication Union (ITU), a United Nations (UN) agency, is the agency that, under an international treaty, sets radio spectrum usage regulations among member nations. Within the United States of America (USA), the organization that sets regulations, coordinates an application for use, and provides authorization for federal government/agency use of the radio frequency (RF) spectrum is the National Telecommunications and Information Administration (NTIA). In this regard, the NTIA defines which RF spectrum is available for federal government use in the USA, and how it is to be used. The NTIA is a component of the United States (U.S.) Department of Commerce of the federal government. The significance of ITU regulations is that ITU approval is required for U.S. federal government/agency permission to use the RF spectrum outside of U.S. boundaries. All member nations have signed a treaty to do so. U.S. federal regulations for federal use of the RF spectrum are found in the Manual of Regulations and Procedures for Federal Radio Frequency Management, and extracts of the manual are found in what is known as the Table of Frequency Allocations. Nonfederal government and private sector use of the RF spectrum within the U.S. is regulated by the Federal Communications Commission (FCC). There is a need to control "unwanted emissions" (defined to include out-of-band emissions, which are those immediately adjacent to the necessary and allocated bandwidth, plus spurious emissions) to preclude interference to all other authorized users. This paper discusses the causes, effects, and mitigation of unwanted RF emissions to systems in adjacent spectra. Digital modulations are widely used in today's satellite communications. Commercial communications sector standards are covered for the most part worldwide by Digital Video Broadcast - Satellite (DVB-S) and digital satellite news gathering (DSNG) evolutions and the second generation of DVB-S (DVB-S2) standard

  7. Investigation on readout coil design for fluxed locked loop control of HTS rf-SQUID

    NASA Astrophysics Data System (ADS)

    Miyato, Y.; Itozaki, H.

    2017-07-01

    We investigated the readout coil, electro-magnetically coupled with a HTS rf-SQUID for the flux-locked loop control. The design and size of the readout coil affected the SQUID performances. Among the tested combinations of different readout coils with the rf-SQUID, the rectangular coil, which just surrounded the slit in the rf-SQUID, was advantageous for the better performance. We also demonstrated the rf-SQUID operation with the rectangular coils made of the thin flexible print circuit board, which could be put on the rf-SQUID stably.

  8. Real time control of a fast RF impedance matching system

    SciTech Connect

    Rogers, J.H.; Senko, T.; LaRue, P.; Wilson, J.R.; Arnold, W.; Martin, S.; Pivit, E.

    1996-12-31

    A real time control system has been developed to maintain an RF impedance match in the ion cyclotron range of frequencies (ICRF). This system is designed to adjust output parameters with a cycle period of approximately 100 {mu}seconds using commercially available VME based components and a UNIX workstation host. Advanced Ferrite Technologies (AFT) has developed the hybrid tuning system (HTS) which has the capability of tracking a mismatch on the time scale of milliseconds (2.5 MW, 60 MHz) by varying the magnetic field bias of ferrite loaded transmission lines. The control algorithm uses a combination of neural network and fuzzy logic techniques. Initial results of a test facility using a low power prototype are presented. 2 refs., 5 figs.

  9. Active RF Pulse Compression using Electrically Controlled Semiconductor Switches

    SciTech Connect

    Guo, J.; Tantawi, S.G.; /SLAC

    2008-01-30

    In this paper, we will present our recent results on the research of the ultra-fast high power RF switches based on silicon. We have developed a switch module at X-band which can use a silicon window as the switch. The switching is realized by generation of carriers in the bulk silicon. The carriers can be generated electrically or/and optically. The electrically controlled switches use PIN diodes to inject carrier. We have built the PIN diode switches at X-band, with <300ns switching time. The optically controlled switches use powerful lasers to excite carriers. By combining the laser excitation and electrical carrier generation, significant reduction in the required power of both the laser and the electrical driver is expected. High power test is under going.

  10. Using Mini-RF To Improve Accuracy Of Lunar TiO2 Maps

    NASA Astrophysics Data System (ADS)

    Gillis-Davis, J. J.; Bussey, B.; Trang, D.; Carter, L. M.; Williams, K. K.

    2010-12-01

    The Mini-Radio Frequency (Mini-RF) instrument is on board the NASA Lunar Reconnaissance Orbiter, which has been in orbit around the Moon since June 2009. Mini-RF is capable of imaging in two bands, X-band (4.2-cm) and S-band (12.6-cm), at 150 m and 30 m (Zoom Mode) resolution respectively, and with an illumination incidence angle of ~48 degrees. The majority of its observations to date have been obtained in S-Band Zoom Mode. Mini-RF was designed to map the permanently dark areas of the lunar poles and characterize the nature of the deposits. In addition, to aid global analyses of mare composition, Mini-RF has acquired coverage for most of the maria. Mini-RF observations of geologic targets of interest are used to improve TiO2 mapping within the lunar maria. Targets of interest include basalt flows that were estimated to contain high-TiO2 compositions based on Clementine spectral reflectance data but had low-TiO2 compositions as measured by Lunar Prospector neutron spectrometer data (LPNS). Visible and near infrared spectral characteristics of lunar soils are controlled by multiple competing factors. Ilmenite, the principal oxide phase, is dark and spectrally neutral relative to the spectrally red mature lunar mare soils; thus causing soils to become spectrally bluer as ilmenite content increases. However, large uncertainties in ultraviolet-visible (UVVIS) based estimates of TiO2 are revealed when comparing LPNS TiO2 and Clementine UVVIS 415/750 ratio. Prime culprits identified as causing this effect are differential agglutinate formation on high-FeO flows, TiO2 in phases other than ilmenite, and surface contamination by highlands materials. Similar to UVVIS spectra, depolarized radar return is found to anticorrelate with titanium abundance - with higher TiO2 abundance leading to lower radar returns. The source of the titanium affecting the radar return is thought to be ilmenite. The possibility that the radar loss tangent is modulated by other mineralogic

  11. Active RF Pulse Compression Using An Electrically Controlled Semiconductor Switch

    SciTech Connect

    Guo, Jiquan; Tantawi, Sami; /SLAC

    2007-01-10

    First we review the theory of active pulse compression systems using resonant delay lines. Then we describe the design of an electrically controlled semiconductor active switch. The switch comprises an active window and an overmoded waveguide three-port network. The active window is based on a four-inch silicon wafer which has 960 PIN diodes. These are spatially combined in an overmoded waveguide. We describe the philosophy and design methodology for the three-port network and the active window. We then present the results of using this device to compress 11.4 GHz RF signals with high compression ratios. We show how the system can be used with amplifier like sources, in which one can change the phase of the source by manipulating the input to the source. We also show how the active switch can be used to compress a pulse from an oscillator like sources, which is not possible with passive pulse compression systems.

  12. Active RF pulse compression using an electrically controlled semiconductor switch

    NASA Astrophysics Data System (ADS)

    Guo, Jiquan; Tantawi, Sami

    2006-11-01

    First we review the theory of active pulse compression systems using resonant delay lines. Then we describe the design of an electrically controlled semiconductor active switch. The switch comprises an active window and an overmoded waveguide three-port network. The active window is based on a four-inch silicon wafer which has 960 PIN diodes. These are spatially combined in an overmoded waveguide. We describe the philosophy and design methodology for the three-port network and the active window. We then present the results of using this device to compress 11.4 GHz RF signals with high compression ratios. We show how the system can be used with amplifier-like sources, in which one can change the phase of the source by manipulating the input to the source. We also show how the active switch can be used to compress a pulse from an oscillator-like source, which is not possible with passive pulse compression systems.

  13. A non-IQ sampling controller in low level RF system

    NASA Astrophysics Data System (ADS)

    Yin, Cheng-Ke; Dai, Zhi-Min; Liu, Jian-Fei; Zhao, Yu-Bin; Zhang, Tong-Xuan; Fu, Ze-Chuan; Liu, Wei-Qing

    2008-10-01

    This paper describes a non-IQ controller for digital Low Level RF (LLRF) feedback control. Based on this non-IQ sampling method, arbitrary frequency relationship between ADC/DAC sampling clocks and IF signals can be employed. The nonlinearity in digital conversion can be reduced and the system dynamic performance improved. This paper analyzes the nonlinearity in conventional IQ sampling, gives the state variable description of the non-IQ algorithm, presents an implementation and its synchronization, and compares its performances with IQ sampling. Supported by SSRF Project

  14. Low-Level RF Control of Microphonics in Superconducting Spoke-Loaded Cavities

    SciTech Connect

    Conway, Z.A.; Kelly, M.P.; Sharamentov, S.I.; Shepard, K.W.; Davis, G.; Delayen, Jean; Doolittle, Lawrence

    2007-10-01

    This paper presents the results of cw RF frequency control and RF phase-stabilization experiments performed with a piezoelectric fast tuner mechanically coupled to a superconducting, 345 MHz, Ë = 0.5 triple-spoke-loaded cavity operating at 4.2K. The piezoelectric fast tuner damped low-frequency microphonic-noise by an order of magnitude. Two methods of RF phase-stabilization were characterized: overcoupling with negative phase feedback, and also fast mechanical tuner feedback. The Ë = 0.5 triple-spoke-loaded cavity RF field amplitude and phase errors were controlled to ±0.5% and ±30 respectively.

  15. Short range RF communication for jet engine control

    NASA Technical Reports Server (NTRS)

    Sexton, Daniel White (Inventor); Hershey, John Erik (Inventor)

    2007-01-01

    A method transmitting a message over at least one of a plurality of radio frequency (RF) channels of an RF communications network is provided. The method comprises the steps of detecting a presence of jamming pulses in the at least one of the plurality of RF channels. The characteristics of the jamming pulses in the at least one of the plurality of RF channels is determined wherein the determined characteristics define at least interstices between the jamming pulses. The message is transmitted over the at least one of the plurality of RF channels wherein the message is transmitted within the interstices of the jamming pulse determined from the step of determining characteristics of the jamming pulses.

  16. Emittance improvements of cesiated RF-driven H- ion source to enable 60 mA operation of high-energy and high-intensity LINACs by plasma impurity controls

    NASA Astrophysics Data System (ADS)

    Ueno, A.; Ohkoshi, K.; Ikegami, K.; Takagi, A.; Oguri, H.

    2017-08-01

    At the Japan Proton Accelerator Research Complex (J-PARC), the operation of a 400-MeV linear accelerator (LINAC) with an extraction H- ion beam intensity of 60 mA is under investigation. This intensity is 20 % higher than the 50 mA achieved by the J-PARC LINAC and about 50 % higher than those of operating similar LINACs in the world. Recently, the J-PARC cesiated RF-driven H- ion source successfully produces a beam enabling the 60 mA operation. A 66-mA beam with 95%-beam transverse normalized rms emittance of 0.23 πmm.mrad is produced by controlling the impurities of argon, nitrogen and water molecules in the hydrogen plasma and tuning rod-filter-field.

  17. Low-level RF control system issues for an ADTT accelerator

    SciTech Connect

    Ziomek, C.D.; Regan, A.H.; Lynch, M.T.; Bowling, P.S.

    1994-09-01

    The RF control system for a charged-particle accelerator must maintain the correct amplitude and phase of RF field inside the accelerator cavity in the presence of perturbations, noises, and time varying system components. For an accelerator with heavy beam-loading, fluctuations in the beam current cause large perturbations to the RF field amplitude and phase that must be corrected by the RF control system. The ADTT applications require a high-current, heavily beam-loaded, continuous-wave (CW) accelerator. Additional concerns created by the CW operation include system start-up, beam interruption, and fault recovery. Also, the RF control system for an ADTT facility must include sophisticated automation to reduce the operator interaction and support. This paper describes an RF control system design that addresses these various issues by evaluation a combination of feedback and feed forward control techniques. Experience from the high-current Ground Test Accelerator (GTA) is drawn upon for this RF control system design. Comprehensive computer modeling with the Matrix{sub x} software has been used to predict the performance of this RF control system.

  18. Improved steering of the RF field of traveling wave MR with a multimode, coaxial waveguide.

    PubMed

    Andreychenko, A; Kroeze, H; Boer, V O; Lagendijk, J J W; Luijten, P R; van den Berg, C A T

    2014-04-01

    Magnetic resonance imaging of humans at high magnetic field strengths is strongly influenced by the interference of the radiofrequency (RF) electromagnetic field and the body. To minimize this effect, multiple RF sources could be used. A novel setup (called multimode, coaxial waveguide) is proposed that facilitates RF shimming based on the traveling waves. The multimode, coaxial waveguide combines the coaxial waveguide, cylindrical waveguide, high dielectric permittivity lining, and eight radial stub antennas. Each antenna excites multiple waveguide modes. Based on modes orthogonality, a method was devised to decompose an excitation pattern of single stub antenna into waveguide modes. The number of modes present in the excitation pattern of a single stub antenna increased with the higher effective permittivity of the dielectric lining. Thus, RF shimming performance of the setup was improved. An average homogeneity of 10% was demonstrated for a single slice of each principle plane in the human head at 7 T. Traveling wave RF shimming is feasible both in axial and longitudinal directions and is improved with an increased amount of orthogonal waveguide modes. Nevertheless, with the currently available RF amplifiers at 7 T, the performance of the setup is limited to low flip angles. Copyright © 2013 Wiley Periodicals, Inc.

  19. Emittance control and RF bunch compression in the NSRRC photoinjector

    NASA Astrophysics Data System (ADS)

    Lau, W. K.; Hung, S. B.; Lee, A. P.; Chou, C. S.; Huang, N. Y.

    2011-05-01

    The high-brightness photoinjector being constructed at the National Synchrotron Radiation Research Center is for testing new accelerator and light-source concepts. It is the so-called split photoinjector configuration in which a short solenoid magnet is used for emittance compensation. The UV-drive laser pulses are also shaped to produce uniform cylindrical bunches for further reduction of beam emittance. However, limited by the available power from our microwave power system, the nominal accelerating gradient in the S-band booster linac is set at 18 MV/m. A simulation study with PARMELA shows that the linac operating at this gradient fails to freeze the electron beam emittance at low value. A background solenoid magnetic field is applied for beam emittance control in the linac during acceleration. A satisfactory result that meets our preliminary goal has been achieved with the solenoid magnetic field strength at 0.1 T. RF bunch compression as a means to achieve the required beam brightness for high-gain free-electron laser experiments is also examined. The reduction of bunch length to a few hundred femtoseconds can be obtained.

  20. Dual-source RF transmission in cardiac SSFP imaging at 3 T: systematic spatial evaluation of image quality improvement compared to conventional RF transmission.

    PubMed

    Rasper, Michael; Gramer, Bettina M; Settles, Marcus; Laugwitz, Karl-Ludwig; Ibrahim, Tareq; Rummeny, Ernst J; Huber, Armin

    2015-01-01

    The purpose of this investigation was to systematically evaluate the spatial distribution of image quality improvement with dual-source radiofrequency (RF) transmission in cardiac steady-state free precession sequences at 3.0 T. Imaging with and without dual-source RF transmission was performed in 30 patients. Contrast-to-noise ratio for the left ventricular myocardium was significantly higher using dual-source RF transmission, but improvement was not uniformly distributed. The posterior myocardium showed significantly less contrast-to-noise ratio gain than all other cardiac regions. Signal-to-noise ratio increase was higher in the right than in the left ventricle. Subjective image quality was significantly enhanced by parallel RF transmission.

  1. An improved trap design for decoupling multinuclear RF coils.

    PubMed

    Meyerspeer, Martin; Serés Roig, Eulalia; Gruetter, Rolf; Magill, Arthur W

    2014-08-01

    Multinuclear magnetic resonance spectroscopy and imaging require a radiofrequency probe capable of transmitting and receiving at the proton and non-proton frequencies. To minimize coupling between probe elements tuned to different frequencies, LC (inductor-capacitor) traps blocking current at the (1)H frequency can be inserted in non-proton elements. This work compares LC traps with LCC traps, a modified design incorporating an additional capacitor, enabling control of the trap reactance at the low frequency while maintaining (1)H blocking. Losses introduced by both types of trap were analysed using circuit models. Radiofrequency coils incorporating a series of LC and LCC traps were then built and evaluated at the bench. LCC trap performance was then confirmed using (1)H and (13)C measurements in a 7T human scanner. LC and LCC traps both effectively block interaction between non-proton and proton coils at the proton frequency. LCC traps were found to introduce a sensitivity reduction of 5±2%, which was less than half of that caused by LC traps. Sensitivity of non-proton coils is critical. The improved trap design, incorporating one extra capacitor, significantly reduces losses introduced by the trap in the non-proton coil. Copyright © 2013 Wiley Periodicals, Inc.

  2. Active RF Pulse Compression using Electrically Controlled Semiconductor Switches

    SciTech Connect

    Guo Jiquan; Tantawi, Sami

    2006-11-27

    In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer and has achieved a switching time of 300ns. The wafer is inserted into a cylindrical waveguide operating in the TE01 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. The RF energy is stored in a room-temperature, high-Q 375 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has achieved a gain of 8, which is the ratio between output and input power.

  3. Designing Multichannel, Multidimensional, Arbitrary Flip Angle RF Pulses Using an Optimal Control Approach

    PubMed Central

    Xu, Dan; King, Kevin F.; Zhu, Yudong; McKinnon, Graeme C.; Liang, Zhi-Pei

    2009-01-01

    The vast majority of parallel transmission RF pulse designs so far are based on small-tip-angle (STA) approximation of the Bloch equation. These methods can design only excitation pulses with small flip angles (e.g., 30°). The linear class large-tip-angle (LCLTA) method is able to design large-tip-angle parallel transmission pulses through concatenating a sequence of small-excitation pulses when certain k-space trajectories are used. However, both STA and LCLTA are linear approximations of the nonlinear Bloch equation. Therefore, distortions from the ideal magnetization profiles due to the higher order terms can appear in the final magnetization profiles. This issue is addressed in this work by formulating the multidimensional multichannel RF pulse design as an optimal control problem with multiple controls based directly on the Bloch equation. Necessary conditions for the optimal solution are derived and a first-order gradient optimization algorithm is used to iteratively solve the optimal control problem, where an existing pulse is used as an initial “guess.” A systematic design procedure is also presented. Bloch simulation and phantom experimental results using various parallel transmission pulses (excitation, inversion, and refocusing) are shown to illustrate the effectiveness of the optimal control method in improving the spatial localization or homogeneity of the magnetization profiles. PMID:18306407

  4. Fast numerical design of spatial-selective rf pulses in MRI using Krotov and quasi-Newton based optimal control methods.

    PubMed

    Vinding, Mads S; Maximov, Ivan I; Tošner, Zdenĕk; Nielsen, Niels Chr

    2012-08-07

    The use of increasingly strong magnetic fields in magnetic resonance imaging (MRI) improves sensitivity, susceptibility contrast, and spatial or spectral resolution for functional and localized spectroscopic imaging applications. However, along with these benefits come the challenges of increasing static field (B(0)) and rf field (B(1)) inhomogeneities induced by radial field susceptibility differences and poorer dielectric properties of objects in the scanner. Increasing fields also impose the need for rf irradiation at higher frequencies which may lead to elevated patient energy absorption, eventually posing a safety risk. These reasons have motivated the use of multidimensional rf pulses and parallel rf transmission, and their combination with tailoring of rf pulses for fast and low-power rf performance. For the latter application, analytical and approximate solutions are well-established in linear regimes, however, with increasing nonlinearities and constraints on the rf pulses, numerical iterative methods become attractive. Among such procedures, optimal control methods have recently demonstrated great potential. Here, we present a Krotov-based optimal control approach which as compared to earlier approaches provides very fast, monotonic convergence even without educated initial guesses. This is essential for in vivo MRI applications. The method is compared to a second-order gradient ascent method relying on the Broyden-Fletcher-Goldfarb-Shanno (BFGS) quasi-Newton method, and a hybrid scheme Krotov-BFGS is also introduced in this study. These optimal control approaches are demonstrated by the design of a 2D spatial selective rf pulse exciting the letters "JCP" in a water phantom.

  5. Monolithic control components handle 27 W of RF power

    NASA Astrophysics Data System (ADS)

    Shifrin, Mitchell B.; Ayasli, Yalcin; Katzin, Peter J.

    1989-12-01

    This paper describes a general approach to overcoming the voltage limitations of the individual switch FET by effectively combining several FETs in a monolithic series configuration. The operation of this configuration is examined using, as an example, a combination of two FETs that are shunt-mounted to an RF line. The technology described is considered to be appplicable to an arbitrary number of cells in shunt or in series with the RF transmission line. It is shown that such a FET circuit allows the power-handling capability of MMIC GaAs FET switches to be increased by more than an order of magnitude.

  6. Digital low level rf control system with four different intermediate frequencies for the International Linear Collider

    NASA Astrophysics Data System (ADS)

    Wibowo, Sigit Basuki; Matsumoto, Toshihiro; Michizono, Shinichiro; Miura, Takako; Qiu, Feng; Liu, Na

    2017-09-01

    A field programmable gate array-based digital low level rf (LLRF) control system will be used in the International Linear Collider (ILC) in order to satisfy the rf stability requirements. The digital LLRF control system with four different intermediate frequencies has been developed to decrease the required number of analog-to-digital converters in this system. The proof of concept of this technique was demonstrated at the Superconducting RF Test Facility in the High Energy Accelerator Research Organization, Japan. The amplitude and phase stability has fulfilled the ILC requirements.

  7. Rf stability, control and bunch lengthening in electron synchrotron storage rings

    SciTech Connect

    Wachtel, J.M.

    1989-09-01

    A self-consistent theory for nonlinear longitudinal particle motion and rf cavity excitation in a high energy electron storage ring is developed. Coupled first order equations for the motion of an arbitrary number of particles and for the field in several rf cavities are given in the form used in control system theory. Stochastic quantum excitation of synchrotron motion is included, as are the effects of rf control system corrections. Results of computations for double cavity bunch lengthening are given. 11 refs., 4 figs., 1 tab.

  8. RF low-level control for the Linac4 H{sup −} source

    SciTech Connect

    Butterworth, A. Grudiev, A.; Lettry, J.; Paoluzzi, M.; Schmitzer, C.; Nishida, K.

    2015-04-08

    The H{sup −} source for the Linac4 accelerator at CERN uses an RF driven plasma for the production of H{sup −}. The RF is supplied by a 2 MHz RF tube amplifier with a maximum power output of 100 kW and a pulse duration of up to 2 ms. The low-level RF signal generation and measurement system has been developed using standard CERN controls electronics in the VME form factor. The RF frequency and amplitude reference signals are generated using separate arbitrary waveform generator channels. The frequency and amplitude are both freely programmable over the duration of the RF pulse, which allows fine-tuning of the excitation. Measurements of the forward and reverse RF power signals are performed via directional couplers using high-speed digitizers, and permit the estimation of the plasma impedance and deposited power via an equivalent circuit model. The low-level RF hardware and software implementations are described, and experimental results obtained with the Linac4 ion sources in the test stand are presented.

  9. RF low-level control for the Linac4 H- source

    NASA Astrophysics Data System (ADS)

    Butterworth, A.; Grudiev, A.; Lettry, J.; Nishida, K.; Paoluzzi, M.; Schmitzer, C.

    2015-04-01

    The H- source for the Linac4 accelerator at CERN uses an RF driven plasma for the production of H-. The RF is supplied by a 2 MHz RF tube amplifier with a maximum power output of 100 kW and a pulse duration of up to 2 ms. The low-level RF signal generation and measurement system has been developed using standard CERN controls electronics in the VME form factor. The RF frequency and amplitude reference signals are generated using separate arbitrary waveform generator channels. The frequency and amplitude are both freely programmable over the duration of the RF pulse, which allows fine-tuning of the excitation. Measurements of the forward and reverse RF power signals are performed via directional couplers using high-speed digitizers, and permit the estimation of the plasma impedance and deposited power via an equivalent circuit model. The low-level RF hardware and software implementations are described, and experimental results obtained with the Linac4 ion sources in the test stand are presented.

  10. Low power smartdust receiver with novel applications and improvements of an RF power harvesting circuit

    NASA Astrophysics Data System (ADS)

    Salter, Thomas Steven, Jr.

    Smartdust is the evolution of wireless sensor networks to cubic centimeter dimensions or less. Smartdust systems have advantages in cost, flexibility, and rapid deployment that make them ideal for many military, medical, and industrial applications. This work addresses the limitations of prior works of research to provide sufficient lifetime and performance for Smartdust sensor networks through the design, fabrication and testing of a novel low power receiver for use in a Smartdust transceiver. Through the novel optimization of a multi-stage LNA design and novel application of a power matched Villard voltage doubler circuit, a 1.0 V, 1.6 mW low power On-Off Key (OOK) receiver operating at 2.2 GHz is fabricated using 0.13 um CMOS technology. To facilitate data transfer in adverse RF propagation environments (1/r3 loss), the chip receives a 1 Mbps data signal with a sensitivity of -90 dBm while consuming just 1.6 nJ/bit. The receiver operates without the addition of any external passives facilitating its application in Smartdust scale (cm 3) wireless sensor networks. This represents an order of magnitude decrease in power consumption over receiver designs of comparable sensitivity. In an effort to further extend the lifetime of the Smartdust transceiver, RF power harvesting is explored as a power source. The small scale of Smartdust sensor networks poses unique challenges in the design of RF power scavenging systems. To meet these challenges, novel design improvements to an RF power scavenging circuit integrated directly onto CMOS are presented. These improvements include a reduction in the threshold voltage of diode connected MOSFET and sources of circuit parasitics that are unique to integrated circuits. Utilizing these improvements, the voltage necessary to drive Smartdust circuitry (1 V) with a greater than 20% RF to DC conversion efficiency was generated from RF energy levels measured in the environment (66 uW). This represents better than double the RF to DC

  11. Diversity RF receiving system with improved phase-lock characteristics

    NASA Technical Reports Server (NTRS)

    Di Losa, V. J.; Laughlin, C. R., Jr.

    1968-01-01

    Improved diversity receiving system automatically utilizes the combined output from its two independent receiving channels /with cross- polarized receiving antennas/ to increase the reliability of maintaining the requisite phase lock for optimum signal reception. It is adapted for use with AM, PM, or narrow band FM signals.

  12. The integrated optic RF spectrum analyzer

    NASA Technical Reports Server (NTRS)

    Pedinoff, M. E.; Ranganath, T. R.; Joseph, T. R.; Lee, J. Y.

    1981-01-01

    The results of measurements made on a fully integrated optic RF spectrum analyzer (IOSA) are reported. The performance of the device acousto-optic bandwidth, single-tone RF resolution, two-tone RF resolution, single-tone dynamic range, two-tone dynamic range, and single-tone RF response are presented. The device parameters that control device performance are analyzed. These results demonstrate the viability of the IOSA for real time spectrum analysis of pulsed and CW RF signals. Improvements of RF bandwidth resolution can be obtained by the use of larger collimated optical beams which requires larger optical lens elements, and hence, larger crystals.

  13. Transition of RF internal antenna plasma by gas control

    SciTech Connect

    Hamajima, Takafumi; Yamauchi, Toshihiko; Kobayashi, Seiji; Hiruta, Toshihito; Kanno, Yoshinori

    2012-07-11

    The transition between the capacitively coupled plasma (CCP) and the inductively coupled plasma (ICP) was investigated with the internal radio frequency (RF) multi-turn antenna. The transition between them showed the hysteresis curve. The radiation power and the period of the self-pulse mode became small in proportion to the gas pressure. It was found that the ICP transition occurred by decreasing the gas pressure from 400 Pa.

  14. Control of the RF waveform at the chuck of an industrial oxide-etch reactor

    SciTech Connect

    BERRY,LEE; MAYNARD,HELEN; MILLER,PAUL A.; MOORE,TONY; PENDLEY,MICHAEL; RESTA,VICTORIA; SPARKS,DENNIS; YANG,QUINGYUN

    2000-05-04

    Radio frequency (rf) power is applied to the chuck of a high-density plasma reactor in order to extract ions and to control the energy of the ions used for the fabrication of microelectronic devices. In many cases, the temporal shape of the rf waveform largely determines the shape of the spectrum of those extracted ions, thereby strongly affecting feature evolution. Using auxiliary rf circuits the authors successfully made major changes to the rf potential waveform at the chuck of an Applied Materials 5300 HDP Omega reactor without affecting the normal functioning of the reactor's control systems. This work established the practical feasibility of techniques for modifying the ion energy distribution functions of industrial reactors.

  15. Modulation improvements in the 201 MHZ RF generators at LAMPF

    SciTech Connect

    Parsons, W M; Lyles, J T.M.; Harris, H W

    1992-01-01

    Radio-frequency generators, operating at 201 MHz, power the first four stages of the Los Alamos Meson Physics Facility (LAMPF) accelerator. Each generator consists of four stages of seriesconnected, vacuum-tube amplifiers. The modulation scheme for each stage is different. The fist amplifier is a grid-modulated tetrode that produces 500 W peak-power. The second amplifier is a drive-modulated tetrode that produces 5 kill peak-power. The third stage is a grid- and plate-modulated tetrode that produces 130 kill peak-power. The last stage is a plate-modulated triode that produces 2.5 MW peak power. A modernization program has been initiated to improve the reliability of each of these stages. The first two stages of each generator are being replaced with a single, drive-modulated, solid-state amplifier. Specifications for the amplifier design, and requirements for integration into the system are presented. The third stage will be converted to a drive-modulated system using the current tetrode. This modification involves the development of a 17-kV, 15-A switching supply to replace the present plate-modulator. Design requirements for this switching supply are presented. The final stage will remain plate-modulated but will contain a new driver unit for the modulator tube.

  16. RF sputtering for controlling dihydride and monohydride bond densities in amorphous silicon hydride

    DOEpatents

    Jeffery, F.R.; Shanks, H.R.

    1980-08-26

    A process is described for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicone produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous solicone hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

  17. RF pulses for in vivo spectroscopy at high field designed under conditions of limited power using optimal control.

    PubMed

    Matson, Gerald B; Young, Karl; Kaiser, Lana G

    2009-07-01

    Localized in vivo spectroscopy at high magnetic field strength (>3T) is susceptible to localization artifacts such as the chemical shift artifact and the spatial interference artifact for J-coupled spins. This latter artifact results in regions of anomalous phase for J-coupled spins. These artifacts are exacerbated at high magnetic field due to the increased frequency dispersion, coupled with the limited RF pulse bandwidths used for localization. Approaches to minimize these artifacts include increasing the bandwidth of the frequency selective excitation pulses, and the use of frequency selective saturation pulses to suppress the signals in the regions with anomalous phase. The goal of this article is to demonstrate the efficacy of optimal control methods to provide broader bandwidth frequency selective pulses for in vivo spectroscopy in the presence of limited RF power. It is demonstrated by examples that the use of optimal control methods enable the generation of (i) improved bandwidth selective excitation pulses, (ii) more efficient selective inversion pulses to be used for generation of spin echoes, and (iii) improved frequency selective saturation pulses. While optimal control also allows for the generation of frequency selective spin echo pulses, it is argued that it is more efficient to use dual inversion pulses for broadband generation of spin echoes. Finally, the optimal control routines and example RF pulses are made available for downloading.

  18. Control of a small robot using a hybrid optical modulating retro-reflector/RF link

    NASA Astrophysics Data System (ADS)

    Murphy, James L.; Ferraro, Mike S.; Rabinovich, William S.; Goetz, Peter G.; Suite, Michele R.; Uecke, Stanley H.

    2014-06-01

    Tele-operated robots used for Explosive Ordnance Disposal (EOD) are ordinarily controlled using a radio frequency (RF) link. Use of RF links on the battlefield presents several challenges including spectrum allocation and jamming effects (both by the enemy and friendly forces). Several solutions have been attempted including electrical or fiber optic umbilicals and spread spectrum radios with varying degrees of success. Modulating Retro-reflector Free Space Optical (MRR-FSO) communications links avoid these effects entirely but are limited to line of sight operation. We have developed a system consisting of an MRR-FSO link with a tracking optical terminal, a conventional RF link and a deployable pod to provide a relay node bridging the FSO link to the operator and the RF link to the robot. The MRRFSO link provides the capability to operate the robot in the presence of jamming while the RF link allows short range non line of sight operation. The operator uses the MRR-FSO link to drive the robot to a position downrange outside the influence of the jammer or other interference. Once the robot is positioned downrange near the area of operation the pod is deployed. This allows the robot to maneuver freely including venturing beyond line of sight using the short range RF link to maintain communications between the vehicle and pod while the FSO link maintains connectivity between the pod and the operator.

  19. RF-modulated pulsed fiber optic lidar transmitter for improved underwater imaging and communications

    NASA Astrophysics Data System (ADS)

    Kimpel, F.; Chen, Y.; Fouron, J.-L.; Akbulut, M.; Engin, D.; Gupta, S.

    2011-03-01

    We present results on the design, development and initial testing of a fiber-optic based RF-modulated lidar transmitter operating at 532nm, for underwater imaging application in littoral waters. The design implementation is based on using state-of-the-art high-speed FPGAs, thereby producing optical waveforms with arbitrary digital-RF-modulated pulse patterns with carrier frequencies >= 3GHz, with a repetition rate of 0.5-1MHz, and with average powers >=5W (at 532nm). Use of RF-modulated bursts above 500MHz, instead of single optical pulse lidar detection, reduces the effect of volumetric backscatter for underwater imaging application, leading to an improved signal-to-noise-ratio (SNR) and contrast, for a given range. Initial underwater target detection tests conducted at Patuxent River Naval Air Station, MD, in a large water-tank facility, validates the advantages of this hybrid-lidar-radar (HLR) approach for improved underwater imaging, over a wide range of turbidity levels and both white and black targets. The compact, robust and power-efficient fiber laser architecture lends very well to lidar sensor integration on unmanned-underwater-vehicle (UUV) platforms. HLR transmitters can also provide similar advantages in active-sensing situations dominated by continuous backscatter, e.g. underwater communications, imaging through smoke and fire environment, rotor-craft landing in degraded visual environment, and pointing-tracking of active-EO sensors through fog.

  20. Improved nuclear magnetic resonance apparatus having semitoroidal rf coil for use in topical NMR and NMR imaging

    DOEpatents

    Fukushima, E.; Roeder, S.B.W.; Assink, R.A.; Gibson, A.A.V.

    1984-01-01

    An improved nuclear magnetic resonance (NMR) apparatus for use in topical magnetic resonance (TMR) spectroscopy and other remote sensing NMR applications includes a semitoroidal radio frequency (rf) coil. The semitoroidal rf coil produces an effective alternating magnetic field at a distance from the poles of the coil, so as to enable NMR measurements to be taken from selected regions inside an object, particularly including human and other living subjects. The semitoroidal rf coil is relatively insensitive to magnetic interference from metallic objects located behind the coil, thereby rendering the coil particularly suited for use in both conventional and superconducting NMR magnets. The semitoroidal NMR coil can be constructed so that it emits little or no excess rf electric field associated with the rf magnetic field, thus avoiding adverse effects due to dielectric heating of the sample or to any other interaction of the electric field with the sample.

  1. RF Head Coil Design with Improved RF Magnetic Near-Fields Uniformity for Magnetic Resonance Imaging (MRI) Systems

    PubMed Central

    Sohn, Sung-Min; DelaBarre, Lance; Gopinath, Anand; Vaughan, John Thomas

    2015-01-01

    Higher magnetic field strength in magnetic resonance imaging (MRI) systems offers higher signal-to-noise ratio (SNR), contrast, and spatial resolution in MR images. However, the wavelength in ultra-high fields (7 tesla and beyond) becomes shorter than the human body at the Larmor frequency with increasing static magnetic field (B0) of MRI system. At short wavelengths, interference effect appears resulting in non- uniformity of the RF magnetic near-field (B1) over the subject and MR images may have spatially anomalous contrast. The B1 near-field generated by the transverse electromagnetic (TEM) RF coil’s microstrip line element has a maximum near the center of its length and falls off towards both ends. In this study, a double trapezoidal shaped microstrip transmission line element is proposed to obtain uniform B1 field distribution by gradual impedance variation. Two multi-channel RF head coils with uniform and trapezoidal shape elements were built and tested with a phantom at 7T MRI scanner for comparison. The simulation and experimental results show stronger and more uniform B1+ near-field with the trapezoidal shape. PMID:25892746

  2. RF Head Coil Design with Improved RF Magnetic Near-Fields Uniformity for Magnetic Resonance Imaging (MRI) Systems.

    PubMed

    Sohn, Sung-Min; DelaBarre, Lance; Gopinath, Anand; Vaughan, John Thomas

    2014-08-01

    Higher magnetic field strength in magnetic resonance imaging (MRI) systems offers higher signal-to-noise ratio (SNR), contrast, and spatial resolution in MR images. However, the wavelength in ultra-high fields (7 tesla and beyond) becomes shorter than the human body at the Larmor frequency with increasing static magnetic field (B0) of MRI system. At short wavelengths, interference effect appears resulting in non- uniformity of the RF magnetic near-field (B1) over the subject and MR images may have spatially anomalous contrast. The B1 near-field generated by the transverse electromagnetic (TEM) RF coil's microstrip line element has a maximum near the center of its length and falls off towards both ends. In this study, a double trapezoidal shaped microstrip transmission line element is proposed to obtain uniform B1 field distribution by gradual impedance variation. Two multi-channel RF head coils with uniform and trapezoidal shape elements were built and tested with a phantom at 7T MRI scanner for comparison. The simulation and experimental results show stronger and more uniform B1(+) near-field with the trapezoidal shape.

  3. RF beam control system for the Brookhaven Relativistic Heavy Ion Collider, RHIC

    SciTech Connect

    Brennan, J.M.; Campbell, A.; DeLong, J.; Hayes, T.; Onillon, E.; Rose, J.; Vetter, K.

    1998-08-01

    The Relativistic Heavy Ion Collider, RHIC, is two counter-rotating rings with six interaction points. The RF Beam Control system for each ring will control two 28 MHz cavities for acceleration, and five 197 MHz cavities for preserving the 5 ns bunch length during 10 hour beam stores. Digital technology is used extensively in: Direct Digital Synthesis of rf signals and Digital Signal Processing for, the realization of state-variable feedback loops, real-time calculation of rf frequency, and bunch-by-bunch phase measurement of the 120 bunches. DSP technology enables programming the parameters of the feedback loops in order to obtain closed-loop dynamics that are independent of synchrotron frequency.

  4. RF BEAM CONTROL SYSTEM FOR THE BROOKHAVEN RELATIVISTIC HEAVY ION COLLIDER, RHIC

    SciTech Connect

    BRENNAN,J.M.; CAMPBELL,A.; DELONG,J.; HAYES,T.; ONILLON,E.; ROSE,J.; VETTER,K.

    1998-06-22

    The Relativistic Heavy Ion Collider, RHIC, is two counter-rotating rings with six interaction points. The RF Beam Control system for each ring will control two 28 MHz cavities for acceleration, and five 197 MHz cavities for preserving the 5 ns bunch length during 10 hour beam stores. Digital technology is used extensively in: Direct Digital Synthesis of rf signals and Digital Signal Processing for, the realization of state-variable feedback loops, real-time calculation of rf frequency, and bunch-by-bunch phase measurement of the 120 bunches. DSP technology enables programming the parameters of the feedback loops in order to obtain closed-loop dynamics that are independent of synchrotron frequency.

  5. Active control of bright electron beams with RF optics for femtosecond microscopy.

    PubMed

    Williams, J; Zhou, F; Sun, T; Tao, Z; Chang, K; Makino, K; Berz, M; Duxbury, P M; Ruan, C-Y

    2017-07-01

    A frontier challenge in implementing femtosecond electron microscopy is to gain precise optical control of intense beams to mitigate collective space charge effects for significantly improving the throughput. Here, we explore the flexible uses of an RF cavity as a longitudinal lens in a high-intensity beam column for condensing the electron beams both temporally and spectrally, relevant to the design of ultrafast electron microscopy. Through the introduction of a novel atomic grating approach for characterization of electron bunch phase space and control optics, we elucidate the principles for predicting and controlling the phase space dynamics to reach optimal compressions at various electron densities and generating conditions. We provide strategies to identify high-brightness modes, achieving ∼100 fs and ∼1 eV resolutions with 10(6) electrons per bunch, and establish the scaling of performance for different bunch charges. These results benchmark the sensitivity and resolution from the fundamental beam brightness perspective and also validate the adaptive optics concept to enable delicate control of the density-dependent phase space structures to optimize the performance, including delivering ultrashort, monochromatic, high-dose, or coherent electron bunches.

  6. Precision vector control of a superconducting RF cavity driven by an injection locked magnetron

    DOE PAGES

    Chase, Brian; Pasquinelli, Ralph; Cullerton, Ed; ...

    2015-03-01

    The technique presented in this paper enables the regulation of both radio frequency amplitude and phase in narrow band devices such as a Superconducting RF (SRF) cavity driven by constant power output devices i.e. magnetrons [1]. The ability to use low cost high efficiency magnetrons for accelerator RF power systems, with tight vector regulation, presents a substantial cost savings in both construction and operating costs - compared to current RF power system technology. An operating CW system at 2.45 GHz has been experimentally developed. Vector control of an injection locked magnetron has been extensively tested and characterized with a SRFmore » cavity as the load. Amplitude dynamic range of 30 dB, amplitude stability of 0.3% r.m.s, and phase stability of 0.26 degrees r.m.s. has been demonstrated.« less

  7. Precision vector control of a superconducting RF cavity driven by an injection locked magnetron

    SciTech Connect

    Chase, Brian; Pasquinelli, Ralph; Cullerton, Ed; Varghese, Philip

    2015-03-01

    The technique presented in this paper enables the regulation of both radio frequency amplitude and phase in narrow band devices such as a Superconducting RF (SRF) cavity driven by constant power output devices i.e. magnetrons [1]. The ability to use low cost high efficiency magnetrons for accelerator RF power systems, with tight vector regulation, presents a substantial cost savings in both construction and operating costs - compared to current RF power system technology. An operating CW system at 2.45 GHz has been experimentally developed. Vector control of an injection locked magnetron has been extensively tested and characterized with a SRF cavity as the load. Amplitude dynamic range of 30 dB, amplitude stability of 0.3% r.m.s, and phase stability of 0.26 degrees r.m.s. has been demonstrated.

  8. Nano-Resonators for RF-Enabled Networked-Control

    DTIC Science & Technology

    2006-01-01

    Networked Control System As a further embodiment of the NCS environment we consider the application to a velocity estimation problem often... Networked Control System Co-simulation for Co-design,” Proc. American Control Conf. Denver, CO, USA, June, 2003. [12] R.H. Brown and S.C. Schneider

  9. Use of Sensors and RF System Models to Control Inductively Coupled Plasma Sources

    NASA Astrophysics Data System (ADS)

    Berry, Lee A.

    1997-10-01

    Research for the development of plasma sources and processes for new generations of feature and wafer sizes must meet requirements in many dimensions including performance, cost, schedule, and yield. This last requirement is becoming increasingly difficult to meet because the process for submicron features frequently have narrow windows and it is difficult to have the needed tool to tool and wafer to wafer repeatability to consistently hit the window. Data from sensors, in particular post-match rf sensors, can be used to measure and control some of the critical process parameters. This work, in many respects, parallels previous work by Paul Miller on capacitively coupled tools. Three examples utilizing post-match rf sensor data will be presented. First, a common approach to auto-matching is to (separately) use the phase and magnitude of the reflected rf power signal to control two capacitors in the match box. At a minimum, presets must be changed for new processes and auto-matches sometimes fail. By utilizing error signals derived from both pre-and post-match rf sensors, we have developed and tested a new matching algorithm that accommodates a wide range of power and plasma conditions without the need for presets. Second, the same rf data can be used to infer power input to the plasma. Losses in match boxes range from 10-50%, depending on the both the rf system and desired plasma conditions. In addition, because of small, but significant differences in particular tool installation or rf components, there can be differences between the efficiencies of nominally the same tool under identical conditions. Thus machine control based on net power is needed for optimum control. Post-match sensors provide the data needed to separate the loses in the matchbox from power coupled to the plasma. The third use of rf system data is the measurement parameters that can be used to both characterize the tool and to indicate and help diagnose or even predict equipment failures. The

  10. An improved drone tracking control system transponder

    NASA Astrophysics Data System (ADS)

    Miller, James J.; Tannenholz, Philip H.

    A small, compact, and inexpensive method of achieving frequency stability of a solid state LO to +/- 1 MHz in the MD700C-1 drone tracking and control system C-band command and control transponder is described. The methodology for realizing improved RF rejection, local oscillator stability, automatic gain control, and power supply efficiency is discussed. A switching mode regulator and a nonsaturating power supply were designed to operate at 80 percent efficiency to reduce power consumption and heat while operating over a wide voltage range.

  11. FREQUENCY CONTROL OF RF HEATING OF GASEOUS PLASMA

    DOEpatents

    Herold, E.W.

    1962-09-01

    This invention relates to the heating of gaseous plasma by radiofrequency ion-cyclotron resonance heating. The cyclotron resonance frequencies are varied and this invention provides means for automatically controlling the frequency of the radiofrequency to maximize the rate of heating. To this end, a servo-loop is provided to sense the direction of plasma heating with frequency and a control signal is derived to set the center frequency of the radiofrequency energy employed to heat the plasma. (AEC)

  12. Improved analog and RF performances of gate-all-around junctionless MOSFET with drain and source extensions

    NASA Astrophysics Data System (ADS)

    Djeffal, F.; Ferhati, H.; Bentrcia, T.

    2016-02-01

    In this paper, the analytical investigation of a new design including drain and source extensions is presented to assess the electrical behavior of cylindrical gate-all-around junctionless (GAAJ) MOSFET for high performance RF and analog applications. Analytical models for drain current and performance parameters are derived incorporating the effect of two highly doped extension regions. Various analog and RF parameters like transconductance, cut-off frequency, drain current drivability, voltage gain and linearity characteristics have also been investigated. The proposed design shows excellent ability in improving the analog performance and provides a good solution to enhance the RF behavior and linearity of GAAJ MOSFET for low cost and high performance analog/RF applications. The proposed model results have been validated against the data obtained from a commercially available numerical device simulator. Moreover, the developed analytical approaches are easy to be implemented into microelectronic software simulators and therefore allow the study of the GAAJ-based deep submicron circuits.

  13. Improved analog/RF performance of double gate junctionless MOSFET using both gate material engineering and drain/source extensions

    NASA Astrophysics Data System (ADS)

    Chebaki, E.; Djeffal, F.; Ferhati, H.; Bentrcia, T.

    2016-04-01

    In this paper, we propose a new Double Gate Junctionless (DGJ) MOSFET design based on both gate material engineering and drain/source extensions. Analytical models for the long channel device associated to the drain current, analog and radio-frequency (RF) performance parameters are developed incorporating the impact of dual-material gate engineering and two highly doped extension regions on the analog/RF performance of DGJ MOSFET. The transistor performance figures-of-merit (FoM), governing the analog/RF behavior, have also been analyzed. The analog/RF performance is compared between the proposed design and a conventional DGJ MOSFET of similar dimensions, where the proposed device shows excellent ability in improving the analog/RF performance and provides higher drain current and improved figures-of-merit as compared to the conventional DGJ MOSFET. The obtained results have been validated against the data obtained from TCAD software for a wide range of design parameters. Moreover, the developed analytical models are used as mono-objective function to optimize the device analog/RF performance using Genetic Algorithms (GAs). In comparison with the reported numerical data for Inversion-Mode (IM) DG MOSFET, our optimized performance metrics for JL device exhibit enhancement over the reported data for IM device at the same channel length.

  14. Application of extremum seeking for time-varying systems to resonance control of RF cavities

    SciTech Connect

    Scheinker, Alexander

    2016-09-13

    A recently developed form of extremum seeking for time-varying systems is implemented in hardware for the resonance control of radio-frequency cavities without phase measurements. Normal conducting RF cavity resonance control is performed via a slug tuner, while superconducting TESLA-type cavity resonance control is performed via piezo actuators. The controller maintains resonance by minimizing reflected power by utilizing model-independent adaptive feedback. Unlike standard phase-measurement-based resonance control, the presented approach is not sensitive to arbitrary phase shifts of the RF signals due to temperature-dependent cable length or phasemeasurement hardware changes. The phase independence of this method removes common slowly varying drifts and required periodic recalibration of phase-based methods. A general overview of the adaptive controller is presented along with the proof of principle experimental results at room temperature. Lastly, this method allows us to both maintain a cavity at a desired resonance frequency and also to dynamically modify its resonance frequency to track the unknown time-varying frequency of an RF source, thereby maintaining maximal cavity field strength, based only on power-level measurements.

  15. Application of extremum seeking for time-varying systems to resonance control of RF cavities

    DOE PAGES

    Scheinker, Alexander

    2016-09-13

    A recently developed form of extremum seeking for time-varying systems is implemented in hardware for the resonance control of radio-frequency cavities without phase measurements. Normal conducting RF cavity resonance control is performed via a slug tuner, while superconducting TESLA-type cavity resonance control is performed via piezo actuators. The controller maintains resonance by minimizing reflected power by utilizing model-independent adaptive feedback. Unlike standard phase-measurement-based resonance control, the presented approach is not sensitive to arbitrary phase shifts of the RF signals due to temperature-dependent cable length or phasemeasurement hardware changes. The phase independence of this method removes common slowly varying drifts andmore » required periodic recalibration of phase-based methods. A general overview of the adaptive controller is presented along with the proof of principle experimental results at room temperature. Lastly, this method allows us to both maintain a cavity at a desired resonance frequency and also to dynamically modify its resonance frequency to track the unknown time-varying frequency of an RF source, thereby maintaining maximal cavity field strength, based only on power-level measurements.« less

  16. Application of extremum seeking for time-varying systems to resonance control of RF cavities

    SciTech Connect

    Scheinker, Alexander

    2016-09-13

    A recently developed form of extremum seeking for time-varying systems is implemented in hardware for the resonance control of radio-frequency cavities without phase measurements. Normal conducting RF cavity resonance control is performed via a slug tuner, while superconducting TESLA-type cavity resonance control is performed via piezo actuators. The controller maintains resonance by minimizing reflected power by utilizing model-independent adaptive feedback. Unlike standard phase-measurement-based resonance control, the presented approach is not sensitive to arbitrary phase shifts of the RF signals due to temperature-dependent cable length or phasemeasurement hardware changes. The phase independence of this method removes common slowly varying drifts and required periodic recalibration of phase-based methods. A general overview of the adaptive controller is presented along with the proof of principle experimental results at room temperature. Lastly, this method allows us to both maintain a cavity at a desired resonance frequency and also to dynamically modify its resonance frequency to track the unknown time-varying frequency of an RF source, thereby maintaining maximal cavity field strength, based only on power-level measurements.

  17. Interorbit Communication System in Japanese Experiment Module- Control for the RF Energy Radiation to ISS

    NASA Astrophysics Data System (ADS)

    Nagai, Naoki; Yoshihara, Toru; Matsumoto, Hiroyuki; Ijiri, Tatsuya; Wakabyashi, Yasufumi

    2005-12-01

    The JEM Inter orbit Communication System (JEM- ICS) is a part of the Japanese Experiment Module (JEM /KIBO) that is the Japanese experimental facility in the ISS. JEM-ICS is expected to transmit JEM experiment data as much as possible. However certain portion of the antenna viewing angle is interfered by huge ISS structure and the operations time of JEM-ICS is restricted for visiting vehicles and Extravehicular Activity (EVA). Those two aspects need special consideration to avoid hurting flight crew and causing malfunction of hardware such as Orbiter, EMU (Extravehicular Maneuvering / Mobility Unit) and ISS modules. Several safety considerations have been incorporated into JEM-ICS RF radiation design. The system has hardware stoppers to restrict RF radiation angle facing to the ISS module and software masks to avoid direct radiation to the ISS Solar Paddle. JEM-ICS is controlled not to radiate RF during EVA and visiting vehicles' traffic. This paper describes how JAXA designed the JEM-ICS RF radiation to satisfy ISS safety requirements.

  18. A low-level rf control system for a quarter-wave resonator

    NASA Astrophysics Data System (ADS)

    Kim, Jongwon; Hwang, Churlkew

    2012-06-01

    A low-level rf control system was designed and built for an rf deflector, which is a quarter wave resonator, and was designed to deflect a secondary electron beam to measure the bunch length of an ion beam. The deflector has a resonance frequency near 88 MHz, its required phase stability is approximately ±1° and its amplitude stability is less than ±1%. The control system consists of analog input and output components and a digital system based on a field-programmable gate array for signal processing. The system is cost effective, while meeting the stability requirements. Some basic properties of the control system were measured. Then, the capability of the rf control was tested using a mechanical vibrator made of a dielectric rod attached to an audio speaker system, which could induce regulated perturbations in the electric fields of the resonator. The control system was flexible so that its parameters could be easily configured to compensate for the disturbance induced in the resonator.

  19. NSLS-II Digital RF Controller Logic and Applications

    SciTech Connect

    Holub, B.; Gao, F.; Kulpin, J.; Marques, C.; Oliva, J.; Rose, J.; Towne, N.

    2015-05-03

    The National Synchrotron Light Source II (NSLS-II) accelerator consists of the Storage Ring, the Booster Ring and Linac along with their associated cavities. Given the number, types and variety of functions of these cavities, we sought to limit the logic development effort by reuse of parameterized code on one hardware platform. Currently there are six controllers installed in the NSLS-II system. There are two in the Storage ring, two in the Booster ring, one in the Linac and one in the Master Oscillator Distribution system.

  20. The RF beam control system for the Brookhaven AGS synchrotron

    SciTech Connect

    Brennan, J.M.

    1992-09-01

    The new 1.5 GeV Booster synchrotron completes the injector chain for the Relativistic Heavy Ion Collider, RHIC. It enables the AGS to accelerate all heavy ions to 14 GeV/c for collider operation and also in the intensity of the AGS for fixed-target experiments by a factor of four. The ultra-high vacuum enables acceleration of partially stripped ions from the Tandem Van de Graaff to energies sufficient for complete stripping. For high intensities, it accelerates the 200 MeV linac beam in four batches of three bunches per AGS cycle. At 1.5 {times} 10{sup 13} protons per batch, it has the same space charge tune spread as the AGS at 200 MeV. This variety of applications means the Booster must accommodate a very wide range of particle masses and intensities. Since it operates in a Pulse-by-Pulse Modulation mode at 7.5 Hz, the computer controlled functions of time and magnetic field, and the 64 timing triggers of the beam control system take on unique values for each of four PPM users. Beams of {sup 197}Au{sup +33} ions and protons have been accelerated in the same PPM cycle.

  1. The RF beam control system for the Brookhaven AGS synchrotron

    SciTech Connect

    Brennan, J.M.

    1992-01-01

    The new 1.5 GeV Booster synchrotron completes the injector chain for the Relativistic Heavy Ion Collider, RHIC. It enables the AGS to accelerate all heavy ions to 14 GeV/c for collider operation and also in the intensity of the AGS for fixed-target experiments by a factor of four. The ultra-high vacuum enables acceleration of partially stripped ions from the Tandem Van de Graaff to energies sufficient for complete stripping. For high intensities, it accelerates the 200 MeV linac beam in four batches of three bunches per AGS cycle. At 1.5 {times} 10{sup 13} protons per batch, it has the same space charge tune spread as the AGS at 200 MeV. This variety of applications means the Booster must accommodate a very wide range of particle masses and intensities. Since it operates in a Pulse-by-Pulse Modulation mode at 7.5 Hz, the computer controlled functions of time and magnetic field, and the 64 timing triggers of the beam control system take on unique values for each of four PPM users. Beams of {sup 197}Au{sup +33} ions and protons have been accelerated in the same PPM cycle.

  2. GPS Control Segment Improvements

    DTIC Science & Technology

    2015-04-29

    Systems Center GPS Control Segment Improvements Mr. Tim McIntyre GPS Product Support Manager GPS Ops Support and Sustainment Division Peterson...hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and...DATE 29 APR 2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE GPS Control Segment Improvements 5a. CONTRACT

  3. Improving manufacturability of an rf graded channel CMOS process for wireless applications

    NASA Astrophysics Data System (ADS)

    Lamey, Daniel J.; Mackie, Troy; Liang, Han-Bin; Ma, Jun; Robert, Georges; Jasper, Craig; Ngo, David; Papworth, Ken; Cheng, Sunny; Wilcock, Christy; Gurrola, Rosemary; Spears, Edward; Yeung, Bruce

    1998-09-01

    Motorola's Graded Channel CMOS (GCMOS) provides a low cost and highly integrated solution for mixed-mode and RF applications. The GCMOS transistor has demonstrated performance advantages over standard CMOS processes with the same physical gate length. The graded channel, fabricated using lateral diffusion, provides a deep submicron Leff even with a gate length of 0.6 micrometer. The technology is constructed using a process that is fully compatible with standard CMOS manufacturing. However, in order to assure adequate threshold control, the lateral diffusions must be well-behaved. This means that both the channel implant and the source/drain implant must be truly self-aligned, requiring good control of the implants as well as the gate electrode profile. For aggressively designed GCMOS devices, small deviations of the implant beam from normal incidence can lead to unacceptable shifts in threshold. The sources of such error, and current industry standard machine tolerances for each, are discussed. Strategies for ensuring adequate control include a regimen of in-line process monitors, approximate error cancellation of the channel and source/drain implants, and the use of quadrature implants. By using these strategies a manufacturable process has been achieved.

  4. Improved RF performance of travelling wave MR with a high permittivity dielectric lining of the bore.

    PubMed

    Andreychenko, A; Bluemink, J J; Raaijmakers, A J E; Lagendijk, J J W; Luijten, P R; van den Berg, C A T

    2013-09-01

    Application of travelling wave MR to human body imaging is restricted by the limited peak power of the available RF amplifiers. Nevertheless, travelling wave MR advantages like a large field of view excitation and distant location of transmit elements would be desirable for whole body MRI. In this work, improvement of the B1+ efficiency of travelling wave MR is demonstrated. High permittivity dielectric lining placed next to the scanner bore wall effectively reduces attenuation of the travelling wave in the longitudinal direction and at the same time directs the radial power flow toward the load. First, this is shown with an analytical model of a metallic cylindrical waveguide with the dielectric lining next to the wall and loaded with a cylindrical phantom. Simulations and experiments also reveal an increase of B1+ efficiency in the center of the bore for travelling wave MR with a dielectric lining. Phantom experiments show up to a 2-fold gain in B1+ with the dielectric lining. This corresponds to a 4-fold increase in power efficiency of travelling wave MR. In vivo experiments demonstrate an 8-fold signal-to-noise ratio gain with the dielectric lining. Overall, it is shown that dielectric lining is a constructive method to improve efficacy of travelling wave MR.

  5. Computer control of RF-manipulations in the CERN antiproton accumulator

    SciTech Connect

    Johnson, R.; van der Meer, S.; Pedersen, F.; Shering, G.

    1983-08-01

    The CERN antiproton accumulator uses a conventional RF system for bunched beam manipulation within the ring. Several different manipulations are needed, often in close succession, so a fast, reliable and accurate method of switching between them is required. This has led to an unconventional computerized beam control system. For a desired set of beam manipulations, the computer calculates the needed voltage and frequency as functions of time, using a mathematical model of the beam and lattice. These are then loaded into function generators which subsequently operate independently of the computer. The RF system, a dual gap, ferrite loaded cavity driven by a 4CX25000 power tetrode, has three main uses: the stacking process to accumulate the antiprotons, the unstacking process to make the accumulated antiprotons available for extraction, and a variety of test and measurement purposes. Two digital function generators control voltage and frequency in the cavity. The voltage function is logarithmic and is fed into an AVC loop which contains a logarithmic detector and modulator to provide high voltage for stacking and low voltage for unstacking. The frequency function controls a 10 to 30 kHz quadrature VCO which is mixed with the output of a quadrature synthesizer producing an 1840 to 1860 kHz frequency range. RF phase and magnet noise were harmful while manipulating low emittance proton and antiproton bunches. A high-pass phase loop acquires beam cavity phase; adding AC corrections to the frequency program eliminated this problem. The cavity tune is maintained by a tuning loop acting on a DC ferrite base. Schematics are provided.

  6. Two-layer wireless distributed sensor/control network based on RF

    NASA Astrophysics Data System (ADS)

    Feng, Li; Lin, Yuchi; Zhou, Jingjing; Dong, Guimei; Xia, Guisuo

    2006-11-01

    A project of embedded Wireless Distributed Sensor/Control Network (WDSCN) based on RF is presented after analyzing the disadvantages of traditional measure and control system. Because of high-cost and complexity, such wireless techniques as Bluetooth and WiFi can't meet the needs of WDSCN. The two-layer WDSCN is designed based on RF technique, which operates in the ISM free frequency channel with low power and high transmission speed. Also the network is low cost, portable and moveable, integrated with the technologies of computer network, sensor, microprocessor and wireless communications. The two-layer network topology is selected in the system; a simple but efficient self-organization net protocol is designed to fit the periodic data collection, event-driven and store-and-forward. Furthermore, adaptive frequency hopping technique is adopted for anti-jamming apparently. The problems about power reduction and synchronization of data in wireless system are solved efficiently. Based on the discussion above, a measure and control network is set up to control such typical instruments and sensors as temperature sensor and signal converter, collect data, and monitor environmental parameters around. This system works well in different rooms. Experiment results show that the system provides an efficient solution to WDSCN through wireless links, with high efficiency, low power, high stability, flexibility and wide working range.

  7. The amplitude and phase control of the ALS Storage Ring RF System

    SciTech Connect

    Lo, C.C.; Taylor, B.; Baptiste, K.

    1995-03-01

    A 500MHz, 300KW Klystron power amplifier provides RF power to the ALS Storage Ring. In order to accommodate the amplitude and phase changes during beam stacking and decay, which demand continuously varying power levels from the Klystron, four loops are used to keep the system operating properly, with two of those loops dedicated to keeping the two cavity tuners on tune. Description of the control loops and their performance data will be given. Using the modulation anode of the Klystron in the amplitude loop will be discussed.

  8. System control and data acquisition of the two new FWCD RF systems at DIII-D

    SciTech Connect

    Harris, T.E.; Allen, J.C.; Cary, W.P.; Petty, C.C.; Pinsker, R.I.; Ferguson, S.W.

    1995-12-31

    The Fast Wave Current Drive (FWCD) system at DIII-D has increased its available radio frequency (RF) power capabilities with the addition of two new high power transmitters along with their associated transmission line systems. A Sun Sparc-10 workstation, functioning as the FWCD operator console, is being used to control transmitter operating parameters and transmission line tuning parameters, along with acquiring data and making data available for integration into the DIII-D data acquisition system. Labview, a graphical user interface application, is used to manage and control the above processes. This paper will discuss the three primary branches of the FWCD computer control system: transmitter control, transmission line tuning control, and FWCD data acquisition. The main control program developed uses VXI, GPIB, CAMAC, Serial, and Ethernet protocols to blend the three branches together into one cohesive system. The control of the transmitters utilizes VXI technology to communicate with the transmitter`s digital interface. A GPIB network allows for communication with various instruments and CAMAC crate controllers. CAMAC crates are located at each phase-shifter/stub-tuner station and are used to digitize transmission line parameters along with transmission line fault detection during RF transmission. The phase-shifter/stub-tuner stations are located throughout the DIII-D facility and are controlled from the FWCD operator console via the workstation`s Serial port. The Sun workstation has an Ethernet connection allowing for the utilization of the DIII-D data acquisition Open System architecture and of course providing communication with the rest of the world.

  9. System control and data acquisition of the two new FWCD RF systems at DIII-D

    SciTech Connect

    Harris, T.E.; Allen, J.C.; Cary, W.P. Petty, C.C.

    1995-10-01

    The Fast Wave Current Drive (FWCD) system at DIII-D has increased its available radio frequency (RF) power capabilities with the addition of two new high power transmitters along with their associated transmission line systems. A Sun Sparc-10 workstation, functioning as the FWCD operator console, is being used to control transmitter operating parameters and transmission line tuning parameters, along with acquiring data and making data available for integration into the DIII-D data acquisition system. Labview, a graphical user interface application, is used to manage and control the above processes. This paper will discuss the three primary branches of the FWCD computer control system: transmitter control, transmission line tuning control, and FWCD data acquisition. The main control program developed uses VXI, GPIB, CAMAC, Serial, and Ethernet protocols to blend the three branches together into one cohesive system. The control of the transmitters utilizes VXI technology to communicate with the transmitter`s digital interface. A GPIB network allows for communication with various instruments and CAMAC crate controllers. CAMAC crates are located at each phase-shifter/stub-tuner station and are used to digitize transmission line parameters along with transmission line fault detection during RF transmission. The phase-shifter/stub-tuner stations are located through out the DIII-D facility and are controlled from the FWCD operator console via the workstation`s Serial port. The Sun workstation has an Ethernet connection allowing for the utilization of the DIII-D data acquisition {open_quotes}Open System{close_quotes} architecture and of course providing communication with the rest of the world.

  10. On active disturbance rejection based control design for superconducting RF cavities

    NASA Astrophysics Data System (ADS)

    Vincent, John; Morris, Dan; Usher, Nathan; Gao, Zhiqiang; Zhao, Shen; Nicoletti, Achille; Zheng, Qinling

    2011-07-01

    Superconducting RF (SRF) cavities are key components of modern linear particle accelerators. The National Superconducting Cyclotron Laboratory (NSCL) is building a 3 MeV/u re-accelerator (ReA3) using SRF cavities. Lightly loaded SRF cavities have very small bandwidths (high Q) making them very sensitive to mechanical perturbations whether external or self-induced. Additionally, some cavity types exhibit mechanical responses to perturbations that lead to high-order non-stationary transfer functions resulting in very complex control problems. A control system that can adapt to the changing perturbing conditions and transfer functions of these systems would be ideal. This paper describes the application of a control technique known as "Active Disturbance Rejection Control" (ARDC) to this problem.

  11. Improved modeling on the RF behavior of InAs/AlSb HEMTs

    NASA Astrophysics Data System (ADS)

    Guan, He; Lv, Hongliang; Zhang, Yuming; Zhang, Yimen

    2015-12-01

    The leakage current and the impact ionization effect causes a drawback for the performance of InAs/AlSb HEMTs due to the InAs channel with a very narrow band gap of 0.35 eV. In this paper, the conventional HEMT small-signal model was enhanced to characterize the RF behavior for InAs/AlSb HEMTs. The additional gate leakage current induced by the impact ionization was modeled by adding two resistances RGh1 and RGh2 shunting the Cgs-Ri and Cgd-Rj branches, respectively, and the ionized-drain current was characterized by an additional resistance Rmi parallel with the output resistance Rds, meanwhile the influence of the impact ionization on the transconductance was modeled by an additional current source gmi controlled by Vgs. The additional inductance, evaluated as a function of f(ω, R), was introduced to characterize the frequency dependency of impact ionization by using the impact ionization effective rate 1/τi and a new frequency response rate factor n, which guaranteed the enhanced model reliable for a wide frequency range. As a result, the enhanced model achieved good agreement with the measurements of the S-parameters and Y-parameters for a wide frequency range, moreover, the simulated results of the stability factor K, the cutoff frequency fT, the maximum frequency of oscillation fmax, and the unilateral Mason's gain U were estimated to approach the experimental results with a high degree.

  12. An improved hybrid MoM/FDTD technique for MRI RF coils modeling using Huygen's equivalent surface method.

    PubMed

    Li, Bing Keong; Liu, Feng; Weber, Ewald; Padhi, Shantanu; Crozier, Stuart

    2007-01-01

    In this work, an improved hybrid MoM/FDTD algorithm for modeling low to ultra high field MRI RF coil/sample interactions has been proposed. In our previous hybrid MoM/FDTD method, the accuracy of modeling MRI RF coils is generally hindered by two major issues, staircasing errors and rough approximation of the coil current distortions by electromagnetic reflections from sample. In view of this, a Huygen's equivalent surface method has been proposed to effectively bridge MoM and FDTD. In the improved hybrid MoM/FDTD algorithm, staircasing errors are eliminated, and most importantly the complex coil/tissue interactions are explicitly accounted for. The accuracy of the improved hybrid MoM/FDTD method is numerically verified with a well established hybrid Green function/MoM solution and also experimentally underpinned with MR images obtained using a prototype rotary phased array head coil.

  13. Low-level rf control of Spallation Neutron Source: System and characterization

    NASA Astrophysics Data System (ADS)

    Ma, Hengjie; Champion, Mark; Crofford, Mark; Kasemir, Kay-Uwe; Piller, Maurice; Doolittle, Lawrence; Ratti, Alex

    2006-03-01

    The low-level rf control system currently commissioned throughout the Spallation Neutron Source (SNS) LINAC evolved from three design iterations over 1 yr intensive research and development. Its digital hardware implementation is efficient, and has succeeded in achieving a minimum latency of less than 150 ns which is the key for accomplishing an all-digital feedback control for the full bandwidth. The control bandwidth is analyzed in frequency domain and characterized by testing its transient response. The hardware implementation also includes the provision of a time-shared input channel for a superior phase differential measurement between the cavity field and the reference. A companion cosimulation system for the digital hardware was developed to ensure a reliable long-term supportability. A large effort has also been made in the operation software development for the practical issues such as the process automations, cavity filling, beam loading compensation, and the cavity mechanical resonance suppression.

  14. Use of RF Metrology Subsystem for Formation Flying Command & Control Purposes

    NASA Astrophysics Data System (ADS)

    Sougmagne, R.; Andreis, O.; Dellandrea, B.; Mehlen, C.; Alison, B.

    2007-08-01

    The development of the "RF metrology and data-link instrument" for formation flying missions was initiated in 2001 by ESA/CNES for the DARWIN mission in order to define a subsystem able to provide both relative positioning service and inter-vehicle communication data link for formation flying missions. Today, the number of target missions is wide: SIMBOL-X, PEGASE, PROBA-3, XEUS, DARWIN, … THALES ALENIA SPACE is currently developing and manufacturing the first European multi-mission RF metrology and data link instrument (called FFRFS for Formation Flying Radio-Frequency Sensor) in the frame of the FFIORD (Formation Flying In Orbit RF Demonstration) contribution of CNES to the Swedish PRISMA mission: flight models will be delivered in early 2008. The first goal of the FFRFS is to provide relative positioning (accuracy better than 1cm for distance and 1 degree for the line of sight) for formation of 2 to 4 vehicles over a large operational range (3m to 30km). One of its key features is its omni-directional coverage, providing safe conditions during deployment phase or failure recovery situations. Moreover, it offers an omni- directional communication link for the formations allowing inter-vehicle data rate of 12kbps for transmission of telemetry, telecommands or GNC data. These characteristics make the FFRFS the key element of the command & control of a formation flying. The paper presents the outcomes of a study performed under CNES contract on the use of the FFRFS for: Data exchange between vehicles when the formation is established Synchronisation of the on-board time of all the formation's spacecrafts Failure Detection, Isolation and Recovery (FDIR) mainly for the anti-collision aspects. The proposed concepts are illustrated by their application to SIMBOL-X mission, an hard X-ray telescope constituted of 2 satellites flying at 20m distance, currently on study at THALES ALENIA SPACE under CNES phase A contract.

  15. RF transformer

    DOEpatents

    Smith, James L.; Helenberg, Harold W.; Kilsdonk, Dennis J.

    1979-01-01

    There is provided an improved RF transformer having a single-turn secondary of cylindrical shape and a coiled encapsulated primary contained within the secondary. The coil is tapered so that the narrowest separation between the primary and the secondary is at one end of the coil. The encapsulated primary is removable from the secondary so that a variety of different capacity primaries can be utilized with one secondary.

  16. Improvement of radio frequency (RF) heating-assisted alkaline pretreatment on four categories of lignocellulosic biomass.

    PubMed

    Wang, Xiaofei; Taylor, Steven; Wang, Yifen

    2016-10-01

    Pretreatment plays an important role in making the cellulose accessible for enzyme hydrolysis and subsequent conversion because it destroys more or less resistance and recalcitrance of biomass. Radio frequency (RF)-assisted dielectric heating was utilized in the alkaline pretreatment on agricultural residues (corn stover), herbaceous crops (switchgrass), hardwood (sweetgum) and softwood (loblolly pine). Pretreatment was performed at 90 °C with either RF or traditional water bath (WB) heating for 1 h after overnight soaking in NaOH solution (0.2 g NaOH/g Biomass). Pretreated materials were characterized by chemical compositional analysis, enzyme hydrolysis, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The glucan yields of RF-heated four categories of hydrolysates were 89.6, 72.6, 21.7, and 9.9 %. Interestingly, RF heating raised glucan yield on switchgrass and sweetgum but not on corn stover or loblolly pine. The SEM images and FTIR spectra agreed with results of composition analysis and hydrolysis. GC-MS detected some compounds only from RF-heated switchgrass. These compounds were found by other researchers only in high-temperature (150-600 °C) and high-pressure pyrolysis processes.

  17. Phase stable RF transport system

    DOEpatents

    Curtin, Michael T.; Natter, Eckard F.; Denney, Peter M.

    1992-01-01

    An RF transport system delivers a phase-stable RF signal to a load, such as an RF cavity of a charged particle accelerator. A circuit generates a calibration signal at an odd multiple frequency of the RF signal where the calibration signal is superimposed with the RF signal on a common cable that connects the RF signal with the load. Signal isolating diplexers are located at both the RF signal source end and load end of the common cable to enable the calibration to be inserted and extracted from the cable signals without any affect on the RF signal. Any phase shift in the calibration signal during traverse of the common cable is then functionally related to the phase shift in the RF signal. The calibration phase shift is used to control a phase shifter for the RF signal to maintain a stable RF signal at the load.

  18. Control of damping partition numbers in a ring accelerator with rf electromagnetic fields.

    PubMed

    Shimosaki, Yoshito; Tanaka, Hitoshi

    2013-04-12

    A novel scheme to reduce transverse beam emittance in a ring accelerator is proposed by using a pair of coupling cavities as a basic unit to control damping partition numbers. As indicated by Robinson in 1958, a simple rf electromagnetic field (e.g., a TM210 mode by a single coupling cavity) cannot control the damping partition of three eigenoscillation modes in a ring accelerator due to the cancellation between the contributions from the magnetic and electric fields. Based on both analytical and numerical studies, we show that a pair of coupling cavities that satisfy phase and optics matching conditions can overcome this cancellation. The results indicate that the horizontal emittance is reducible to the theoretical limit based on the steady state condition and also, the emittance is reducible below the reduction limit under a nonsteady state by driving the coupling cavities with gated signals.

  19. Improving excitation and inversion accuracy by optimized RF pulse using genetic algorithm.

    PubMed

    Pang, Yong; Shen, Gary X

    2007-05-01

    In this study, a Genetic Algorithm (GA) is introduced to optimize the multidimensional spatial selective RF pulse to reduce the passband and stopband errors of excitation profile while limiting the transition width. This method is also used to diminish the nonlinearity effect of the Bloch equation for large tip angle excitation pulse design. The RF pulse is first designed by the k-space method and then coded into float strings to form an initial population. GA operators are then applied to this population to perform evolution, which is an optimization process. In this process, an evaluation function defined as the sum of the reciprocal of passband and stopband errors is used to assess the fitness value of each individual, so as to find the best individual in current generation. It is possible to optimize the RF pulse after a number of iterations. Simulation results of the Bloch equation show that in a 90 degrees excitation pulse design, compared with the k-space method, a GA-optimized RF pulse can reduce the passband and stopband error by 12% and 3%, respectively, while maintaining the transition width within 2 cm (about 12% of the whole 32 cm FOV). In a 180 degrees inversion pulse design, the passband error can be reduced by 43%, while the transition is also kept at 2 cm in a whole 32 cm FOV.

  20. Influence of Germanium source on dopingless tunnel-FET for improved analog/RF performance

    NASA Astrophysics Data System (ADS)

    Cecil, Kanchan; Singh, Jawar

    2017-01-01

    Dopingless (DL) and junctionless devices have attracted attention due to their simplified fabrication process and low thermal budget requirements. Therefore, in this work, we investigated the influence of low band gap Germanium (Ge) instead of Silicon (Si) as a "Source region" material in dopingless (DL) tunnel field-effect transistor (DLTFET). We observed that the Ge source DLTFET delivers much better performance in comparison to Si DLTFET under various analog/RF figure of merits (FOMs), such as transconductance (gm), transconductance generation factor (TGF) (gm /Id), output conductance (gd), output resistance (RO), intrinsic gain (gmRO), intrinsic gate delay (τ) and RF FOMs, like unity gain frequency (fT), gain bandwidth product (GBW) along with various gate capacitances. These parameters were extracted using 2D TCAD device simulations through small signal ac analysis. Higher ION /IOFF ratio (1014) of Ge source DLTFET can reduce the dynamic as well as static power in digital circuits, while higher transconductance generation factor (gm /Id) ∼ 2287 V-1 can lower the bias power of an amplifier. Similarly, enhanced RF FOMs i.e unity gain frequency (fT) and gain bandwidth product (GBW) in Gigahertz range projects the proposed device preference for RF circuits.

  1. Broadband photonic microwave phase shifter based on controlling two RF modulation sidebands via a Fourier-domain optical processor.

    PubMed

    Yang, J; Chan, E H W; Wang, X; Feng, X; Guan, B

    2015-05-04

    An all-optical photonic microwave phase shifter that can realize a continuous 360° phase shift over a wide frequency range is presented. It is based on the new concept of controlling the amplitude and phase of the two RF modulation sidebands via a Fourier-domain optical processor. The operating frequency range of the phase shifter is largely increased compared to the previously reported Fourier-domain optical processor based phase shifter that uses only one RF modulation sideband. This is due to the extension of the lower RF operating frequency by designing the amplitude and phase of one of the RF modulation sidebands while the other sideband is designed to realize the required RF signal phase shift. The two-sideband amplitude-and-phase-control based photonic microwave phase shifter has a simple structure as it only requires a single laser source, a phase modulator, a Fourier-domain optical processor and a single photodetector. Investigation on the bandwidth limitation problem in the conventional Fourier-domain optical processor based phase shifter is presented. Comparisons between the measured phase shifter output RF amplitude and phase responses with theory, which show excellent agreement, are also presented for the first time. Experimental results demonstrate the full -180° to + 180° phase shift with little RF signal amplitude variation of less than 3 dB and with a phase deviation of less than 4° over a 7.5 GHz to 26.5 GHz frequency range, and the phase shifter exhibits a long term stable performance.

  2. Application of an RF Biased Langmuir Probe to Etch Reactor Chamber Matching, Fault Detection and Process Control

    NASA Astrophysics Data System (ADS)

    Keil, Douglas; Booth, Jean-Paul; Benjamin, Neil; Thorgrimsson, Chris; Brooks, Mitchell; Nagai, Mikio; Albarede, Luc; Kim, Jung

    2008-10-01

    Semiconductor device manufacturing typically occurs in an environment of both increasing equipment costs and per unit sale price shrinkage. Profitability in such a conflicted economic environment depends critically on yield, throughput and cost-of-ownership. This has resulted in increasing interest in improved fault detection, process diagnosis, and advanced process control. Achieving advances in these areas requires an integrated understanding of the basic physical principles driving the processes of interest and the realities of commercial manufacturing. Following this trend, this work examines the usefulness of an RF-biased planar Langmuir probe^1. This method delivers precise real-time (10 Hz) measurements of ion flux and tail weighted electron temperature. However, it is also mechanically non-intrusive, reliable and insensitive to contamination and deposition on the probe. Since the measured parameters are closely related to physical processes occurring at the wafer-plasma interface, significant improvements in process control, chamber matching and fault detection are achieved. Examples illustrating the improvements possible will be given. ^1J.P. Booth, N. St. J. Braithwaite, A. Goodyear and P. Barroy, Rev.Sci.Inst., Vol.71, No.7, July 2000, pgs. 2722-2727.

  3. RF MEMS Switches with SiC Microbridges for Improved Reliability

    NASA Technical Reports Server (NTRS)

    Scardelletti, Maximilian C.; Zorman, Christian A.; Oldham, Daniel R.

    2008-01-01

    Radio frequency (RF) microelectromechanical (MEMS) switches offer superior performance when compared to the traditional semiconductor devices such as PIN diodes or GaAs transistors. MEMS switches have a return loss (RL) better than -25 dB, negligible insertion loss (IL), isolation better than -30 dB, and near zero power consumption. However, RF MEMS switches have several drawbacks the most serious being long-term reliability. The ability for the switch to operate for millions or even billions of cycles is a major concern and must be addressed. MEMS switches are basically grouped in two categories, capacitive and metal-to-metal contact. The capacitive type switch consists of a movable metal bridge spanning a fixed electrode and separated by a narrow air gap and thin insulating material. The metal-to-metal contact type utilizes the same basic design but without the insulating material. After prolonged operation the metal bridges, in most of these switches, begin to sag and eventually fail to actuate. For the metal-to-metal type, the two metal layers may actually fuse together. Also if the switches are not packaged properly or protected from the environment moisture may build up and cause stiction between the top and bottom electrodes rendering them useless. Many MEMS switch designs have been developed and most illustrate fairly good RF characteristics. Nevertheless very few have demonstrated both great RF performance and ability to perform millions/billions of switching cycles. Of these, nearly all are of metal-to-metal type so as the frequency increases RF performance decreases.

  4. Effect of low-frequency ambient magnetic fields on the control unit and RF head of a commercial SQUID magnetometer

    NASA Technical Reports Server (NTRS)

    Marcus, C. M.

    1984-01-01

    The control unit and RF head of the SHE model 330XRFSQUID system are shown to be sensitive to ambient ac magnetic fields below 1 HZ, which cause the appearance of false signals corresponding to a magnetometer signal of 0.000001 phi(0) per gauss of field applied. The control unit shows a sensitivity that is linear with frequency, suggesting that the signal is generated by Faraday induction. In contrast, the RF head response is independent of frequency and shows a strong second-harmonic coversion. This response may be due to the magnetic field sensitivity of the ferrite core inductor in the tuned amplifier of the RF head. These signals induced by ambient fields are a potential source of error in Stanford's Relativity Gyroscope experiment, which uses SQUID's on board a rolling satellite as part of the gyroscope readout system. The extent of the magnetic field sensitivity in these components necessitates the use of additional magnetic shielding aboard the satellite.

  5. Effect of low-frequency ambient magnetic fields on the control unit and RF head of a commercial SQUID magnetometer

    NASA Technical Reports Server (NTRS)

    Marcus, C. M.

    1984-01-01

    The control unit and RF head of the SHE model 330XRFSQUID system are shown to be sensitive to ambient ac magnetic fields below 1 HZ, which cause the appearance of false signals corresponding to a magnetometer signal of 0.000001 phi(0) per gauss of field applied. The control unit shows a sensitivity that is linear with frequency, suggesting that the signal is generated by Faraday induction. In contrast, the RF head response is independent of frequency and shows a strong second-harmonic coversion. This response may be due to the magnetic field sensitivity of the ferrite core inductor in the tuned amplifier of the RF head. These signals induced by ambient fields are a potential source of error in Stanford's Relativity Gyroscope experiment, which uses SQUID's on board a rolling satellite as part of the gyroscope readout system. The extent of the magnetic field sensitivity in these components necessitates the use of additional magnetic shielding aboard the satellite.

  6. Hexagonal gradient scheme with RF spoiling improves spoiling performance for high‐flip‐angle fast gradient echo imaging

    PubMed Central

    Robson, Matthew D.

    2016-01-01

    Purpose To present a framework in which time‐varying gradients are applied with RF spoiling to reduce unwanted signal, particularly at high flip angles. Methods A time‐varying gradient spoiler scheme compatible with RF spoiling is defined, in which spoiler gradients cycle through the vertices of a hexagon, which we call hexagonal spoiling. The method is compared with a traditional constant spoiling gradient both in the transition to and in the steady state. Extended phase graph (EPG) simulations, phantom acquisitions, and in vivo images were used to assess the method. Results Simulations, phantom and in vivo experiments showed that unwanted signal was markedly reduced by employing hexagonal spoiling, both in the transition to and in the steady state. For adipose tissue at 1.5 Tesla, the unwanted signal in the steady state with a 60 ° flip angle was reduced from 22% with constant spoiling to 2% with hexagonal spoiling. Conclusions A time‐varying gradient spoiler scheme that works with RF spoiling, called “hexagonal spoiling,” has been presented and found to offer improved spoiling over the traditional constant spoiling gradient. Magn Reson Med 77:1231–1237, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:27037941

  7. RF noise induced laser perturbation for improving the performance of non-resonant cavity enhanced absorption spectroscopy.

    PubMed

    Ciaffoni, Luca; Couper, John; Hancock, Gus; Peverall, Robert; Robbins, Peter A; Ritchie, Grant A D

    2014-07-14

    We present a novel strategy for suppressing mode structure which often degrades off-axis cavity enhanced absorption spectra. This strategy relies on promoting small, random fluctuations in the optical frequency by perturbing the injection current of the diode laser source with radio frequency (RF) bandwidth-limited white noise. A fast and compact oxygen sensor, constructed from a 764 nm vertical-cavity surface-emitting laser (VCSEL) and an optical cavity with re-entrant configuration, is employed to demonstrate the potential of this scheme for improving the sensitivity and robustness of a field-deployable cavity spectrometer. The RF spectral density of the current noise injected into the VCSEL has been measured, and correlated to the effects on the optical spectral signal-to-noise ratio (SNR) and laser linewidth for a range of re-entrant geometries. A fourfold gain in the SNR has been achieved using the RF noise perturbation for the optimal off-axis alignment, which led to a minimum detectable absorption (MDA) predicted from an Allan variance study as low as 4.3 × 10(-5) at 1 s averaging. For the optically forbidden oxygen transition under investigation, a limit of detection (SNR = 1) of 810 ppm was achieved for a 10 ms acquisition time. This performance level paves the way for a fast, sensitive, in-line oxygen spectrometer that lends itself to a range of applications in respiratory medicine.

  8. Improved manufacturing techniques for RF and laser hardening of missile domes. Phase I. Technical report

    SciTech Connect

    Pawlewicz, W.T.; Mann, I.B.; Martin, P.M.; Hays, D.D.; Graybeal, A.G.

    1982-07-01

    This report summarizes key results and accomplishements during the first year of a Manufacturing Methods and Technology project to adapt an existing Pacific Northwest Laboratory (PNL) optical coating capability developed for high-power fusion-laser applications to the case of rf and laser hardening of plastic missile domes used by the US Army (MICOM). The primary objective of the first year's work was to demonstrate rf hardening of Hellfire and Copperhead 1.06-micron missile domes by use of transparent conductive Indium Tin Oxide (ITO) coatings. The project thus involved adaptation of a coating material and process developed for flat glass components used in fusion lasers to the case of hemispherical or conical heat-sensitive plastic domes used on laser-guided missiles. Specific ITO coating property goals were an electrical sheet resistance of 10 Ohms/square, a coated-dome transmission of 80% or more at 1.06 micron wavelength (compared to 90% for a bare dome), and good adhesion. The sheet resistance goal of 10 Ohms/square was expected to result in an rf attenuation of 30 dB at the frequencies of importance.

  9. A high current gain gate-controlled lateral bipolar junction transistor with 90 nm CMOS technology for future RF SoC applications

    NASA Astrophysics Data System (ADS)

    Chen, Shuo-Mao; Fang, Yean-Kuen; Yeh, Wen-Kuan; Lee, I. C.; Chiang, Yen-Ting

    2008-08-01

    A CMOS-compatible gate-controlled lateral BJT (GC-LBJT) was prepared with a conventional 90 nm CMOS technology for radio frequency system-on-chip (RF SoC) applications. The emitter injection efficiency and the doping profile in P-well were optimized by properly controlling source, drain, and well implants. Consequently, the GC-LBJT with a gate length of 0.15 μm can achieve a current gain over 2000 and 17/19 GHz for the fT/fmax, respectively, which are 1000%, 200%, and 60% improvements in current gain, fT and fmax, respectively as compared to the LBJT reported previously.

  10. MPC improves reformer control

    SciTech Connect

    Jung, C.S.; Noh, K.K.; Yi, S.; Kim, J.S.; Song, H.K.; Hyun, J.C.

    1995-04-01

    A model predictive control strategy was applied to a synthesis gas reformer of Samsung-BP Chemicals in Korea that produces carbon monoxide and hydrogen from naphtha. A strongly endothermic reaction occurs in a catalytic reformer, and reformer outlet temperature is considered to have the most significant effect on product composition. The newly developed reformer is known to be a cost-effective process operating at high reaction temperatures and low steam-to-carbon ratio, but its drawback is temperature control difficulty due to the use of offgas as a part of the fuel. Without smooth control of the reformer outlet temperature, stable operation of the downstream separation units cannot be expected. Therefore, it is a great challenge to apply a model predictive control technique for tight control of reformer outlet temperature. The paper describes model predictive control, the process advanced control project, computer system architecture, analysis of operating condition, control structure, sampling rate, and disturbance estimation.

  11. A software controllable modular RF signal generator with multichannel transmission capabilities

    NASA Astrophysics Data System (ADS)

    Shaw, Z.; Feilner, W.; Esser, B.; Dickens, J. C.; Neuber, A. A.

    2017-09-01

    A software controllable system which generates and transmits user defined RF signals is discussed. The system is implemented with multiple, modular transmitting channels that allow the user to easily replace parts such as amplifiers or antennas. Each channel is comprised of a data pattern generator (DPG), a digital to analog converter (DAC), a power amplifier, and a transmitting antenna. All channels are controlled through a host PC and synchronized through a master clock signal provided to each DAC by an external clock source. Signals to be transmitted are generated through the DPG control software on the PC or can be created by the user in a numerical computing environment. Three experiments are discussed using a two- and four-channel antenna array incorporating Chebyshev tapered TEM horn antennas. Transmitting distinct sets of nonperiodic bipolar impulses through each of the antennas in the array enabled synthesizing a sinusoidal signal of specific frequency in free space. Opposite to the standard phased array approach, each antenna radiates a distinctly different signal rather than the same signal simply phase shifted. The presented approach may be employed as a physical layer of encryption dependent on the position of the receiving antenna.

  12. Time-shaped RF brazing

    NASA Technical Reports Server (NTRS)

    Stein, J. A.; Vannasse, M. A.

    1980-01-01

    One RF generator is controlled from two independent work stations with aid of RF switch and simple control boxes. Brazing may be stopped manually or automatically by external brazing-temperature controller or timer in RF switch housing. Switch is air-operated with water-cooled contacts. If switch loses air pressure, generator stops transmitting power. Time-shared outlet increases utilization and productivity of costly RF generator.

  13. Improving School Access Control

    ERIC Educational Resources Information Center

    National Clearinghouse for Educational Facilities, 2008

    2008-01-01

    Few things are more important for school safety and security than controlling access to buildings and grounds. It is relatively easy to incorporate effective access control measures in new school designs but more difficult in existing schools, where most building and site features cannot be readily altered or reconfigured. The National…

  14. Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

    NASA Astrophysics Data System (ADS)

    Cha, Sungsu; Kim, Yujong; Lee, Byung Cheol; Park, Hyung Dal; Lee, Seung Hyun; Buaphad, Pikad

    2017-05-01

    KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per

  15. Effect of low-frequency ambient magnetic fields on the control unit and rf head of a commercial SQUID magnetometer

    SciTech Connect

    Marcus, C.M.

    1984-09-01

    The control unit and rf head of the SHE model 330X rf SQUID system are shown to be sensitive to ambient ac magnetic fields below 1 Hz, which cause the appearance of false signals corresponding to a magnetometer signal of 10/sup -6/ phi/sub 0/ per gauss of field applied. The control unit shows a sensitivity that is linear with frequency, suggesting that the signal is generated by Faraday induction. In contrast, the rf head response is independent of frequency and shows a strong second-harmonic conversion. This response may be due to the magnetic field sensitivity of the ferrite core inductor in the tuned amplifier of the rf head. These signals induced by ambient fields are a potential source of error in Stanford's Relativity Gyroscope experiment, which uses SQUID's on board a rolling satellite as part of the gyroscope readout system. The extent of the magnetic field sensitivity in these components necessitates the use of additional magnetic shielding aboard the satellite.

  16. Measured performance of the GTA rf systems

    SciTech Connect

    Denney, P.M.; Jachim, S.P.

    1993-06-01

    This paper describes the performance of the RF systems on the Ground Test Accelerator (GTA). The RF system architecture is briefly described. Among the RF performance results presented are RF field flatness and stability, amplitude and phase control resolution, and control system bandwidth and stability. The rejection by the RF systems of beam-induced disturbances, such as transients and noise, are analyzed. The observed responses are also compared to computer-based simulations of the RF systems for validation.

  17. Measured performance of the GTA rf systems

    SciTech Connect

    Denney, P.M.; Jachim, S.P.

    1993-01-01

    This paper describes the performance of the RF systems on the Ground Test Accelerator (GTA). The RF system architecture is briefly described. Among the RF performance results presented are RF field flatness and stability, amplitude and phase control resolution, and control system bandwidth and stability. The rejection by the RF systems of beam-induced disturbances, such as transients and noise, are analyzed. The observed responses are also compared to computer-based simulations of the RF systems for validation.

  18. Shimmed matching pulses: Simultaneous control of rf and static gradients for inhomogeneity correction

    NASA Astrophysics Data System (ADS)

    Franck, John M.; Demas, Vasiliki; Martin, Rachel W.; Bouchard, Louis-S.; Pines, Alexander

    2009-12-01

    Portable NMR systems generally suffer from poor field homogeneity and are therefore used more commonly for imaging and relaxation measurements rather than for spectroscopy. In recent years, various approaches have been proposed to increase the sample volume that is usable for spectroscopy. These include approaches based on manual shimming and those based on clever combinations of modulated radio frequency and gradient fields. However, this volume remains small and, therefore, of limited utility. We present improved pulses designed to correct for inhomogeneous dispersion across wide ranges of frequency offsets without eliminating chemical shift or spatial encoding. This method, based on the adiabatic double passage, combines the relatively larger corrections available from spatially matched rf gradients [C. Meriles et al., J. Magn. Reson. 164, 177 (2003)]. with the adjustable corrections available from time-modulated static field gradients [D. Topgaard et al., Proc. Natl. Acad. Sci. U.S.A. 101, 17576 (2004)]. We explain the origins of these corrections with a theoretical model that simplifies and expedites the design of the pulse waveforms. We also present a generalized method for evaluating and comparing pulses designed for inhomogeneity correction. Experiments validate this method and support simulations that offer new possibilities for significantly enhanced performance in portable environments.

  19. Profile Control by Biased Electrodes in Large Diameter RF Produced Pl asma

    NASA Astrophysics Data System (ADS)

    Shinohara, Shunjiro; Matsuoka, Norikazu; Yoshinaka, Toshiro

    1998-10-01

    Control of the plasma profile has been carried out, using the voltage biasing method in the large diameter (45 cm) RF (radio frequency) produced plasma in the presence of the uniform magnetic field (less than 1200 G). Under the low filling pressure condition of 0.16 mTorr, changing the biasing voltages to the three individual end plates with concentric circular ring shapes, the radial electron density (about 10^10 cm-3) profile could be changed from the hollow to the peaked one. On the contrary, the nearly flat electron temperature (several eV) profile did not change appreciably. The azimuthal rotation velocity measured by the Mach probe, i.e. directional probe, showed the different radial profiles (but nearly uniform along the axis) depending on the biasing voltage. This velocity became slower with the low magnetic field (less than 200 G) or in the higher pressure regime up to 20 mTorr with the higher electron density. The experimental results by other biasing methods will also be presented.

  20. Design and evaluation of a low-level RF control system analog/digital receiver for the ILC main Linacs

    SciTech Connect

    Mavric, Uros; Vidmar, Matjaz; Chase, Brian; /Fermilab

    2008-06-01

    The proposed RF distribution scheme for the two 15 km long ILC LINACs, uses one klystron to feed 26 superconducting RF cavities operating at 1.3 GHz. For a precise control of the vector sum of the signals coming from the SC cavities, the control system needs a high performance, low cost, reliable and modular multichannel receiver. At Fermilab we developed a 96 channel, 1.3 GHz analog/digital receiver for the ILC LINAC LLRF control system. In the paper we present a balanced design approach to the specifications of each receiver section, the design choices made to fulfill the goals and a description of the prototyped system. The design is tested by measuring standard performance parameters, such as noise figure, linearity and temperature sensitivity. Measurements show that the design meets the specifications and it is comparable to other similar systems developed at other laboratories, in terms of performance.

  1. Primary measurement of total ultrasonic power with improved accuracy in rf voltage measurement.

    PubMed

    Dubey, P K; Kumar, Ashok; Kumar, Yudhisther; Gupta, Reeta; Joshi, Deepa

    2010-10-01

    Out of the various existing ultrasonic power measurement techniques, the radiation force balance method using microbalance is most widely used in low power (below 1 W) regime. The major source of uncertainty associated with this technique is the error in ac voltage measurement applied to the transducer for the generation of ultrasonic waves. The sources that deteriorate the ac voltage measurement accuracy include cable length and impedance mismatch. We introduce a new differential peak to peak measurement approach to reduce the ac voltage measurement error. The method holds the average peak amplitude of each polarity. Ultralow offset difference amplifier is used to measure peak to peak voltage. The method is insensitive to the variations in the dc offset of the source. The functionality of this method has been tested and compared with the conventional rf voltage measurement method. The output of this proposed technique is dc, which can be measured with an error of less than 0.1%.

  2. Primary measurement of total ultrasonic power with improved accuracy in rf voltage measurement

    NASA Astrophysics Data System (ADS)

    Dubey, P. K.; Kumar, Ashok; Kumar, Yudhisther; Gupta, Reeta; Joshi, Deepa

    2010-10-01

    Out of the various existing ultrasonic power measurement techniques, the radiation force balance method using microbalance is most widely used in low power (below 1 W) regime. The major source of uncertainty associated with this technique is the error in ac voltage measurement applied to the transducer for the generation of ultrasonic waves. The sources that deteriorate the ac voltage measurement accuracy include cable length and impedance mismatch. We introduce a new differential peak to peak measurement approach to reduce the ac voltage measurement error. The method holds the average peak amplitude of each polarity. Ultralow offset difference amplifier is used to measure peak to peak voltage. The method is insensitive to the variations in the dc offset of the source. The functionality of this method has been tested and compared with the conventional rf voltage measurement method. The output of this proposed technique is dc, which can be measured with an error of less than 0.1%.

  3. Improvement in B1+ Homogeneity and Average Flip Angle Using Dual-Source Parallel RF Excitation for Cardiac MRI in Swine Hearts.

    PubMed

    Schär, Michael; Ding, Haiyan; Herzka, Daniel A

    2015-01-01

    Cardiac MRI may benefit from increased polarization at high magnetic field strength of 3 Tesla but is challenged by increased field inhomogeneity. Initial human studies have shown that the radiofrequency (RF) excitation field (B1+) used for signal excitation in the heart is both inhomogeneous and significantly lower than desired, potentially leading to image artifacts and biased quantitative measures. Recently, multi-channel transmit systems have been introduced allowing localized patient specific RF shimming based on acquired calibration B1+ maps. Some prior human studies have shown lower than desired mean flip angles in the hearts of large patients even after RF shimming. Here, 100 cardiac B1+ map pairs before and after RF shimming were acquired in 55 swine. The mean flip angle and the coefficient of variation (CV) of the flip angle in the heart were determined before and after RF shimming. Mean flip angle, CV, and RF shim values (power ratio and phase difference between the two transmit channels) were tested for correlation with cross sectional body area and the Right-Left/Anterior-Posterior ratio. RF shimming significantly increased the mean flip angle in swine heart from 74.4±6.7% (mean ± standard deviation) to 94.7±4.8% of the desired flip angle and significantly reduced CV from 0.11±0.03 to 0.07±0.02 (p<1e-10 for both). These results compare well with several previous human studies, except that the mean flip angle in the human heart only improved to 89% with RF shimming, possibly because the RF shimming routine does not consider safety constraints in very large patients. Additionally, mean flip angle decreased and CV increased with larger cross sectional body area, however, the RF shimming parameters did not correlate with cross sectional body area. RF shim power ratio correlated weakly with Right-Left/Anterior-Posterior ratio but phase difference did not, further substantiating the need for subject specific cardiac RF shimming.

  4. Improvement in B1+ Homogeneity and Average Flip Angle Using Dual-Source Parallel RF Excitation for Cardiac MRI in Swine Hearts

    PubMed Central

    Schär, Michael; Ding, Haiyan; Herzka, Daniel A.

    2015-01-01

    Cardiac MRI may benefit from increased polarization at high magnetic field strength of 3 Tesla but is challenged by increased field inhomogeneity. Initial human studies have shown that the radiofrequency (RF) excitation field (B1+) used for signal excitation in the heart is both inhomogeneous and significantly lower than desired, potentially leading to image artifacts and biased quantitative measures. Recently, multi-channel transmit systems have been introduced allowing localized patient specific RF shimming based on acquired calibration B1+ maps. Some prior human studies have shown lower than desired mean flip angles in the hearts of large patients even after RF shimming. Here, 100 cardiac B1+ map pairs before and after RF shimming were acquired in 55 swine. The mean flip angle and the coefficient of variation (CV) of the flip angle in the heart were determined before and after RF shimming. Mean flip angle, CV, and RF shim values (power ratio and phase difference between the two transmit channels) were tested for correlation with cross sectional body area and the Right-Left/Anterior-Posterior ratio. RF shimming significantly increased the mean flip angle in swine heart from 74.4±6.7% (mean ± standard deviation) to 94.7±4.8% of the desired flip angle and significantly reduced CV from 0.11±0.03 to 0.07±0.02 (p<<1e-10 for both). These results compare well with several previous human studies, except that the mean flip angle in the human heart only improved to 89% with RF shimming, possibly because the RF shimming routine does not consider safety constraints in very large patients. Additionally, mean flip angle decreased and CV increased with larger cross sectional body area, however, the RF shimming parameters did not correlate with cross sectional body area. RF shim power ratio correlated weakly with Right-Left/Anterior-Posterior ratio but phase difference did not, further substantiating the need for subject specific cardiac RF shimming. PMID:26436658

  5. Improvement of RF performance for AlGaN/GaN HEMT by using a cavity structure

    NASA Astrophysics Data System (ADS)

    Wang, Wen; Yu, Xinxin; Zhou, Jianjun; Chen, Dunjun; Zhang, Kai; Kong, Cen; Lu, Haiyan; Kong, Yuechan; Li, Zhonghui; Chen, Tangsheng

    2016-12-01

    A novel method of improving RF performance for AlGaN/GaN HEMT by introducing a cavity structure under the gate-head of the T-shaped gate is proposed, which can effectively reduce the parasitic gate capacitance. The device with cavity structure presents quite similar DC characteristics with the conventional device without cavity, including a maximum drain current density of 1.16 A/mm, a peak transconductance of 424 mS/mm and a slightly degraded two-terminal breakdown voltage of 29 V. However, in comparison with the device without cavity, the device with cavity presents the significant improvements in small signal characteristics, with the fT increasing from 60 GHz to 84 GHz and the fmax increasing from 93 GHz to 104 GHz.

  6. Recent RF Experiments and Application of RF Waves to Real-Time Control of Safety Factor Profile in JT-60U

    SciTech Connect

    Suzuki, T.; Isayama, A.; Ide, S.; Fujita, T.; Oikawa, T.; Sakata, S.; Sueoka, M.; Hosoyama, H.; Seki, M.

    2005-09-26

    Two topics of applications of RF waves to current profile control in JT-60U are presented; application of lower-hybrid (LH) waves to safety factor profile control and electron cyclotron (EC) waves to neo-classical tearing mode (NTM) control. A real-time control system of safety factor (q) profile was developed. This system, for the first time, enables 1) real time evaluation of q profile using local magnetic pitch angle measurement by motional Stark effect (MSE) diagnostic and 2) control of current drive (CD) location ({rho}CD) by controlling the parallel refractive index N parallel of LH waves through control of phase difference ({delta}{phi}) of LH waves between multi-junction launcher modules. The method for real-time q profile evaluation was newly developed, without time-consuming reconstruction of equilibrium, so that the method requires less computational time. Safety factor profile by the real-time calculation agrees well with that by equilibrium reconstruction with MSE. The control system controls {rho}CD through {delta}{phi} in such a way to decrease the largest residual between the real-time evaluated q profile q(r) and its reference profile qref(r). The real-time control system was applied to a positive shear plasma (q(0){approx}1). The reference q profile was set to monotonic positive shear profile having qref(0)=1.3. The real-time q profile approached to the qref(r) during application of real-time control, and was sustained for 3s, which was limited by the duration of the injected LH power. Temporal evolution of current profile was consistent with relaxation of inductive electric field induced by theoretical LH driven current. An m/n=3/2 NTM that appeared at {beta}N{approx}3 was completely stabilized by ECCD applied to a fully-developed NTM. Precise ECCD at NTM island was essential for the stabilization. ECCD that was applied to resonant rational surface (q=3/2) before an NTM onset suppressed appearance of NTM. In order to keep NTM intensity below a

  7. Active high-power RF switch and pulse compression system

    DOEpatents

    Tantawi, Sami G.; Ruth, Ronald D.; Zolotorev, Max

    1998-01-01

    A high-power RF switching device employs a semiconductor wafer positioned in the third port of a three-port RF device. A controllable source of directed energy, such as a suitable laser or electron beam, is aimed at the semiconductor material. When the source is turned on, the energy incident on the wafer induces an electron-hole plasma layer on the wafer, changing the wafer's dielectric constant, turning the third port into a termination for incident RF signals, and. causing all incident RF signals to be reflected from the surface of the wafer. The propagation constant of RF signals through port 3, therefore, can be changed by controlling the beam. By making the RF coupling to the third port as small as necessary, one can reduce the peak electric field on the unexcited silicon surface for any level of input power from port 1, thereby reducing risk of damaging the wafer by RF with high peak power. The switch is useful to the construction of an improved pulse compression system to boost the peak power of microwave tubes driving linear accelerators. In this application, the high-power RF switch is placed at the coupling iris between the charging waveguide and the resonant storage line of a pulse compression system. This optically controlled high power RF pulse compression system can handle hundreds of Megawatts of power at X-band.

  8. DC characteristics and analog/RF performance of novel polarity control GaAs-Ge based tunnel field effect transistor

    NASA Astrophysics Data System (ADS)

    Nigam, Kaushal; Kondekar, Pravin; Sharma, Dheeraj

    2016-04-01

    In this paper, for the first time, DC characteristics and analog/RF performance of polarity control GaAs-Ge hetero TFET (GaAs-Ge H-TFET) structure have been analysed, using electrically doped dynamically configurable concept. For this, we have considered a hetero structure with two distinctive gates (Control gate and Polarity gate). Polarity gate induces p+ region at the source side and n+ region at the drain side, instead of relying on the abrupt doping profile at the junctions. Therefore, the fabrication process of the proposed device avoids ion-implantation, photo masking and complicated thermal budget. Hence, it shows high immunity against process variations, doping control issues and random dopant fluctuations (RDF). In order to optimize the device performance, interfacing of III-V groups materials with IV group semiconductor is done for hetero-junction. The introduction of hetero-junction and band gap engineering offer higher ION/IOFF ratio (5.1 × 1012), steep sub-threshold slope (18 mV/decade) and significantly change in analog/RF performance. The analog/RF figures of merit are analysed in term of transconductance (gm), output conductance (gds), gate to source capacitance (Cgs), gate to drain capacitance (Cgd), cutoff frequency (fT) and gain bandwidth (GBW) product. The proposed work would be beneficial for low power high frequency applications. The simulation results presented in this paper were carried out by using 2-D ATLAS.

  9. Plasma sweeper to control the coupling of RF power to a magnetically confined plasma

    DOEpatents

    Motley, Robert W.; Glanz, James

    1985-01-01

    A device for coupling RF power (a plasma sweeper) from a phased waveguide array for introducing RF power to a plasma having a magnetic field associated therewith comprises at least one electrode positioned near the plasma and near the phased waveguide array; and a potential source coupled to the electrode for generating a static electric field at the electrode directed into the plasma and having a component substantially perpendicular to the plasma magnetic field such that a non-zero vector cross-product of the electric and magnetic fields exerts a force on the plasma causing the plasma to drift.

  10. The Use of Metal Filled Via Holes for Improving Isolation in LTCC RF and Wireless Multichip Packages

    NASA Technical Reports Server (NTRS)

    Ponchak, George E.; Chun, Donghoon; Yook, Jong-Gwan; Katehi, Linda P. B.

    1999-01-01

    LTCC MCMs (Low Temperature Cofired Ceramic MultiChip Module) for RF and wireless systems often use metal filled via holes to improve isolation between the stripline and microstrip interconnects. In this paper, results from a 3D-FEM electromagnetic characterization of microstrip and stripline interconnects with metal filled via fences for isolation are presented. It is shown that placement of a via hole fence closer than three times the substrate height to the transmission lines increases radiation and coupling. Radiation loss and reflections are increased when a short via fence is used in areas suspected of having high radiation. Also, via posts should not be separated by more than three times the substrate height for low radiation loss, coupling, and suppression of higher order modes in a package.

  11. Improved properties of oxygen and argon RF plasma-activated polyester fabrics loaded with TiO2 nanoparticles.

    PubMed

    Mihailović, Darka; Saponjić, Zoran; Molina, Ricardo; Puac, Nevena; Jovancić, Petar; Nedeljković, Jovan; Radetić, Maja

    2010-06-01

    The potentials of low-pressure capacitively coupled RF oxygen and argon plasmas for the activation of polyester fibers surface that can enhance the deposition of colloidal TiO(2) nanoparticles were discussed. SEM and XPS analysis confirmed the plasma-induced morphological and chemical changes on the surface of polyester fibers. Oxygen and argon plasma pretreated polyester fabrics loaded with TiO(2) nanoparticles provided maximum reduction of Gram-negative bacteria E. coli and UV blocking. The self-cleaning effects tested on blueberry juice stains and photodegradation of methylene blue in aqueous solution proved excellent photocatalytic activity of TiO(2) nanoparticles deposited onto fiber surface. Although both plasmas significantly contributed to overall improvement of properties of such nanocomposite textile material, oxygen plasma treatment, in particular, enhanced the deposition of colloidal TiO(2) nanoparticles and thus ensured superior effects.

  12. Composition control of PZT thin films by varying technological parameters of RF magnetron sputter deposition

    NASA Astrophysics Data System (ADS)

    Pronin, V. P.; Dolgintsev, D. M.; Pronin, I. P.; Senkevich, S. V.; Kaptelov, E. Yu; Sergienko, A. Yu

    2017-07-01

    The article presents the effect of technological parameters of RF magnetron sputtering on the concentration of components of thin-film ferroelectric structures based on lead zirconate titanate PZT in the region of the morphotropic phase boundary. It is shown that by changing the distance from the target to the substrate and the pressure of the working gas mixture Ar + O2, it is possible to vary the composition of the deposited thin layers.

  13. Reconfigurable Antenna Aperture with Optically Controlled GeTe-Based RF Switches

    DTIC Science & Technology

    2015-03-31

    electrical resistivity and OFF state capacitance of GeTe- Based RF Switches under direct optical laser excitation. Our tightly-coupled dipole array...relative to their neighbors. Rapid quench cooling (~100ns) then freezes these atoms into an amorphous solid, locking in a high electrical resistance ...temperature. If the pulse is of appropriately long duration, the structure experiences atomic bond rearrangement and leads to the low resistance phase

  14. Improved optical and electrical properties of rf sputtered Al doped ZnO films on polymer substrates by low-damage processes

    SciTech Connect

    Min, Hyung Seob; Yang, Min Kyu; Lee, Jeon-Kook

    2009-03-15

    Three types of low-damage radio-frequency (rf) magnetron sputtering processes--an interruptive process, a rotating cylindrical holder method, and an off-axis sputtering method--were designed and studied to reduce the film surface temperature during deposition. Low-damage sputtering processes were investigated to improve the resistivity and optical transmittance in the visible range of Al doped ZnO (AZO) thin films deposited on polymer substrates. In the case of the polyethersulfone substrate, AZO films with a resistivity of 1.0x10{sup -3} {omega} cm and an optical transmittance of 75% were obtained by the rotating repeat holder method during rf sputtering.

  15. Characteristics of a high-power RF source of negative hydrogen ions for neutral beam injection into controlled fusion devices

    NASA Astrophysics Data System (ADS)

    Abdrashitov, G. F.; Belchenko, Yu. I.; Gusev, I. A.; Ivanov, A. A.; Kondakov, A. A.; Sanin, A. L.; Sotnikov, O. Z.; Shikhovtsev, I. V.

    2017-01-01

    An injector of hydrogen atoms with an energy of 0.5-1 MeV and equivalent current of up to 1.5 A for purposes of controlled fusion research is currently under design at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. Within this project, a multiple-aperture RF surface-plasma source of negative hydrogen ions is designed. The source design and results of experiments on the generation of a negative ion beam with a current of >1 A in the long-pulse mode are presented.

  16. RF dual-gate-trench LDMOS on InGaAs with improved performance

    NASA Astrophysics Data System (ADS)

    Payal, M.; Singh, Y.

    2017-07-01

    A new power dual-gate-trench LDMOSFET (DGTLDMOS) structure implemented on emerging InGaAs material is proposed. The proposed device consists of two gates out of which one gate is placed horizontally on the surface while other gate is located vertically in a trench. The dual-gate structure of DGTLDMOS creates two channels in p-base which carry current simultaneously from drain to source. This not only enhances the drain current (ID) but also reduces specific on-resistance (Ron,sp) and improves the peak transconductance (gm) resulting higher cut-off frequency (fT) and maximum oscillation frequency (fmax). Another trench filled with Al2O3 is placed in the drift region between gate and drain to enhance reduced-surface-field effect leading to higher breakdown voltage (Vbr) even at increased drift region doping. Based on 2D simulations, it is demonstrate that a DGTLDMOS designed for Vbr of 90 V achieves 2.2 times higher ID, 10 times reduction in Ron,sp, 1.8 times improvement in gm, 2.8 times increase in fT, and 1.8 times improvement in fmax with 3.3 times reduction in cell pitch as compared to the conventional LDMOS.

  17. Improving dust and methane control

    SciTech Connect

    Cecala, A.; Organiscak, J.; Jankowski, R.

    1987-10-01

    The Bureau of Mines has evaluated a number of techniques for controlling dust and methane during the headgate cutout of retreating longwall sections that use antitropal ventilation (headgate to tailgate). Some of these techniques are effective for both methane and dust control, while others are effective for only one or the other. The techniques include the gob curtain, the walkway curtain, stageloader-crusher control and the wing curtain. Each improves the health and safety of workers and is economically feasible in hardware cost, setup cost and maintenance.

  18. Improving dust and methane control

    SciTech Connect

    Cecala, A.; Organiseak, J.; Jankowski, R.

    1987-01-01

    This paper presents a number of techniques for controlling dust and methane during the headgate cutout of retreating longwall sections that use antitropal ventilation (headgate to tailgate). Some of these techniques are effective for both methane and dust control, while others are effective for only one or the other. The techniques include the gob curtain, the walkway curtain, stage-loader-crusher control, and the wing curtain. Each improves the health and safety of workers and is economically feasible in hardware cost, setup cost, and maintenance.

  19. Improving dust and methane control

    SciTech Connect

    Cecala, A.B.; Organiscak, A.; Jankowski, R.A.

    1987-01-01

    This paper evaluates a number of techniques for controlling dust and methane during the headgate cutout of retreating longwall sections that use antitropal ventilation (headgate to tailgate). Some of these techniques are effective for both methane and dust control, while others are effective for only one or the other. The techniques include the gob curtain, the walkway curtain, stageloader-crusher control, and the wing curtain. Each improves the health and safety of workers and is economically feasible in hardware cost, setup cost, and maintenance. By combining various of these techniques, mine operators can substantially reduce the dust and methane concentrations at the shearer and ensure the health and safety of longwall workers.

  20. CONTROL OF THE INJECTED RF BEAM IN THE DIII-D ECH SYSTEM

    SciTech Connect

    K. KAJIWARA; C.B. BAXI; J.L. DOANE; R.E. ELLIS; M.E. FRIEND; M. GREEN; Y.A. GORELOV; J. LOHR; C.P. MOELLER; R.I. PINSKER; D. PONCE; R. PRATER

    2002-08-01

    The DIII-D ECH system includes three launcher assemblies each of which can accommodate the rf beams from two gyrotrons. The launchers use four different designs for the mirrors which focus and direct the beams into the tokamak. The designs use molybdenum brazed to graphite, thin Glidcop or variable thickness Glidcop. A fourth design with laminated Glidcop/stainless steel construction has been operated, but no thermal data are available. All the mirrors operate without active cooling. This paper presents preliminary analyses and measurements of the thermal performance of the three designs for which data have been obtained.

  1. Development of a new RF coil and γ-ray radiation shielding assembly for improved MR image quality in SPECT/MRI

    NASA Astrophysics Data System (ADS)

    Ha, Seunghoon; Hamamura, Mark J.; Roeck, Werner W.; Tugan Muftuler, L.; Nalcioglu, Orhan

    2010-05-01

    Magnetic resonance (MR)-based multimodality imaging systems, such as single-photon emission tomography (SPECT)/magnetic resonance imaging (MRI) or positron emission tomography (PET)/MRI, face many difficulties because of problems with the compatibility of the nuclear detector system with the MR system. However, several studies have reported on the design considerations of MR-compatible nuclear detectors for combined SPECT/MRI. In this study, we developed a new radiofrequency (RF) coil and γ-ray radiation shielding assembly to advance the practical implementation of SPECT/MRI in providing high sensitivity while minimizing the interference between the MRI and SPECT systems. The proposed assembly consists of a three-channel receive-only RF coil and γ-ray radiation shields made of a specialized lead composite powder designed to reduce conductivity and thus minimizing any effect on the magnetic field arising from the induced eddy currents. A conventional birdcage RF coil was also tested for comparison with the proposed RF coil. Quality (Q)-factors were measured using both RF coils without any shielding, with solid lead shielding, and with our composite lead shielding. Signal-to-noise ratios (SNRs) were calculated using 4 T MR images of phantoms both with and without the new γ-ray radiation shields. The Q-factor and SNR measurements demonstrate the improved MRI performance due to the new RF coil/γ-ray radiation shield assembly designed for SPECT/MRI, making it a useful addition to multimodality imaging technology not only for animal studies but also for in vivo study of humans.

  2. Development of a new RF coil and gamma-ray radiation shielding assembly for improved MR image quality in SPECT/MRI.

    PubMed

    Ha, Seunghoon; Hamamura, Mark J; Roeck, Werner W; Muftuler, L Tugan; Nalcioglu, Orhan

    2010-05-07

    Magnetic resonance (MR)-based multimodality imaging systems, such as single-photon emission tomography (SPECT)/magnetic resonance imaging (MRI) or positron emission tomography (PET)/MRI, face many difficulties because of problems with the compatibility of the nuclear detector system with the MR system. However, several studies have reported on the design considerations of MR-compatible nuclear detectors for combined SPECT/MRI. In this study, we developed a new radiofrequency (RF) coil and gamma-ray radiation shielding assembly to advance the practical implementation of SPECT/MRI in providing high sensitivity while minimizing the interference between the MRI and SPECT systems. The proposed assembly consists of a three-channel receive-only RF coil and gamma-ray radiation shields made of a specialized lead composite powder designed to reduce conductivity and thus minimizing any effect on the magnetic field arising from the induced eddy currents. A conventional birdcage RF coil was also tested for comparison with the proposed RF coil. Quality (Q)-factors were measured using both RF coils without any shielding, with solid lead shielding, and with our composite lead shielding. Signal-to-noise ratios (SNRs) were calculated using 4 T MR images of phantoms both with and without the new gamma-ray radiation shields. The Q-factor and SNR measurements demonstrate the improved MRI performance due to the new RF coil/gamma-ray radiation shield assembly designed for SPECT/MRI, making it a useful addition to multimodality imaging technology not only for animal studies but also for in vivo study of humans.

  3. Improved water and lipid suppression for 3D PRESS CSI using RF band selective inversion with gradient dephasing (BASING).

    PubMed

    Star-Lack, J; Nelson, S J; Kurhanewicz, J; Huang, L R; Vigneron, D B

    1997-08-01

    A T1 insensitive solvent suppression technique-band selective inversion with gradient dephasing (BASING)-was developed to suppress water and lipids for 1H magnetic resonance spectroscopy (MRS). BASING, which consists of a frequency selective RF inversion pulse surrounded by spoiler gradient pulses of opposite signs, was used to dephase stopband resonances and minimally impact passband metabolites. Passband phase linearity was achieved with a dual BASING scheme. Using the Shinnar-Le Roux algorithm, a highpass filter was designed to suppress water and rephase the lactate methyl doublet independently of TE, and water/lipid bandstop filters were designed for the brain and prostate. Phantom and in vivo experimental 3D PRESS CSI data were acquired at 1.5 T to compare BASING with CHESS and STIR suppression. With BASING, the measured suppression factor was over 100 times higher than with CHESS or STIR causing baseline distortions to be removed. It was shown that BASING can be incorporated into a variety of sequences to offer improved suppression in the presence of B1 and T1 inhomogeneites.

  4. Investigation of techniques for improving Saturn 5 RF tracking and ranging systems

    NASA Technical Reports Server (NTRS)

    Walsh, J. R., Jr.; Wetherington, R. D.

    1971-01-01

    Results of theoretical analyses of 12 problems are presented and comparisons of theoretical and experimental results are given. The investigations covered were: (1) techniques for improving the Saturn radar altimeter, (2) performance of the phase lock loop of the offset Doppler transponder, (3) signal processing equipment design for an orbital altitude radar return experiment, (4) spectral studies of signals present in the command and communication system (CCS) up-link transmitter, (5) intermodulation in the CCS down-link data demodulators, (6) error rate performance of the CCS transponder command demodulator, (7) flame attenuation effects on telemetry transmissions during Saturn launches, (8) design of a digital television system which converts a standard monochrome picture to a slow-scan picture, (9) methods of obtaining an additional CCS 72-kilobit/sec telemetry channel, (10) computation of the CCS S-band down-link spectra, (11) modeling of portions of the communications systems, and (12) modeling of a telemetry transmitter.

  5. Improving the Th1 cellular efficacy of the lead Yersinia pestis rF1-V subunit vaccine using SA-4-1BBL as a novel adjuvant.

    PubMed

    Dinc, Gunes; Pennington, Jarrod M; Yolcu, Esma S; Lawrenz, Matthew B; Shirwan, Haval

    2014-09-03

    The lead candidate plague subunit vaccine is the recombinant fusion protein rF1-V adjuvanted with alum. While alum generates Th2 regulated robust humoral responses, immune protection against Yersinia pestis has been shown to also involve Th1 driven cellular responses. Therefore, the rF1-V-based subunit vaccine may benefit from an adjuvant system that generates a mixed Th1 and humoral immune response. We herein assessed the efficacy of a novel SA-4-1BBL costimulatory molecule as a Th1 adjuvant to improve cellular responses generated by the rF1-V vaccine. SA-4-1BBL as a single adjuvant had better efficacy than alum in generating CD4(+) and CD8(+) T cells producing TNFα and IFNγ, signature cytokines for Th1 responses. The combination of SA-4-1BBL with alum further increased this Th1 response as compared with the individual adjuvants. Analysis of the humoral response revealed that SA-4-1BBL as a single adjuvant did not generate a significant Ab response against rF1-V, and SA-4-1BBL in combination with alum did not improve Ab titers. However, the combined adjuvants significantly increased the ratio of Th1 regulated IgG2c in C57BL/6 mice to the Th2 regulated IgG1. Finally, a single vaccination with rF1-V adjuvanted with SA-4-1BBL+alum had better protective efficacy than vaccines containing individual adjuvants. Taken together, these results demonstrate that SA-4-1BBL improves the protective efficacy of the alum adjuvanted lead rF1-V subunit vaccine by generating a more balanced Th1 cellular and humoral immune response. As such, this adjuvant platform may prove efficacious not only for the rF1-V vaccine but also against other infections that require both cellular and humoral immune responses for protection. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. RF-Medisys: a radio frequency identification-based electronic medical record system for improving medical information accessibility and services at point of care.

    PubMed

    Ting, Jacky S L; Tsang, Albert H C; Ip, Andrew W H; Ho, George T S

    2011-01-01

    This paper presents an innovative electronic medical records (EMR) system, RF-MediSys, which can perform medical information sharing and retrieval effectively and which is accessible via a 'smart' medical card. With such a system, medical diagnoses and treatment decisions can be significantly improved when compared with the conventional practice of using paper medical records systems. Furthermore, the entire healthcare delivery process, from registration to the dispensing or administration of medicines, can be visualised holistically to facilitate performance review. To examine the feasibility of implementing RF-MediSys and to determine its usefulness to users of the system, a survey was conducted within a multi-disciplinary medical service organisation that operates a network of medical clinics and paramedical service centres throughout Hong Kong Island, the Kowloon Peninsula and the New Territories. Questionnaires were distributed to 300 system users, including nurses, physicians and patients, to collect feedback on the operation and performance of RF-MediSys in comparison with conventional paper-based medical record systems. The response rate to the survey was 67%. Results showed a medium to high level of user satisfaction with the radiofrequency identification (RFID)-based EMR system. In particular, respondents provided high ratings on both 'user-friendliness' and 'system performance'. Findings of the survey highlight the potential of RF-MediSys as a tool to enhance quality of medical services and patient safety.

  7. Low frequency rf current drive

    SciTech Connect

    Hershkowitz, N.

    1992-01-01

    An unshielded antenna for rf heating has been developed and tested during this report period. In addition to design specifications being given, some experimental results are presented utilizing: (1) an unprotected Faraday shield, (2) insulating guard limiters, (3) unshielded antenna experiments, (4) method for detecting small rf driven currents, (5) rf fast wave current drive experiments, (6) alfven wave interactions with electrons, and (7) machine conditioning, impurity generation and density control.

  8. Maintenance and operation procedure, and feedback controls of the J-PARC RF-driven H{sup −} ion source

    SciTech Connect

    Ueno, A. Ohkoshi, K.; Ikegami, K.; Takagi, A.; Yamazaki, S.; Oguri, H.

    2015-04-08

    In order to satisfy the Japan Proton Accelerator Research Complex (J-PARC) second stage requirements of an H{sup −} ion beam of 60mA within normalized emittances of 1.5πmm•mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500μs×25Hz) and a life-time of longer than 1month, the J-PARC cesiated RF-driven H{sup −} ion source was developed by using an internal-antenna developed at the Spallation Neutron Source (SNS). The maintenance and operation procedure to minimize the plasma chamber (PCH) replacement time on the beam line, which is very important to maximize the J-PARC beam time especially for an antenna failure, is presented in this paper. The PCH preserved by filling argon (Ar) gas inside after pre-conditioning including pre-cesiation to produce the required beam at a test-stand successfully produced the required beam on the beam line with slight addition of cesium (Cs). The methods of the feedback controls of a 2MHz-RF-matching, an H{sup −} ion beam intensity and the addition of Cs are also presented. The RF-matching feedback by using two vacuum variable capacitors (VVCs) and RF-frequency shift produced the almost perfect matching with negligibly small reflected RF-power. The H{sup −} ion beam intensity was controlled within errors of ±0.1mA by the RF-power feedback. The amount of Cs was also controlled by remotely opening a Cs-valve to keep the RF-power lower than a settled value.

  9. Enhanced responsivity resonant RF photodetectors.

    PubMed

    Liu, R; Dev, S; Zhong, Y; Lu, R; Streyer, W; Allen, J W; Allen, M S; Wenner, B R; Gong, S; Wasserman, D

    2016-11-14

    The responsivity of room-temperature, semiconductor-based photodetectors consisting of resonant RF circuits coupled to microstrip buslines is investigated. The dependence of the photodetector response on the semiconductor material and RF circuit geometry is presented, as is the detector response as a function of the spatial position of the incident light. We demonstrate significant improvement in detector response by choice of photoconductive material, and for a given material, by positioning our optical signal to overlap with positions of RF field enhancement. Design of RF circuits with strong field enhancement are demonstrated to further improve detector response. The improved detector response demonstrated offers opportunities for applications in RF photonics, materials metrology, or single read-out multiplexed detector arrays.

  10. DESIGN CONSIDERATIONS FOR THE MECHANICAL TUNER OF THE RHIC ELECTRON COOLER RF CAVITY.

    SciTech Connect

    RANK, J.; BEN-ZVI,I.; HAHN,G.; MCINTYRE,G.; DALY,E.; PREBLE,J.

    2005-05-16

    The ECX Project, Brookhaven Lab's predecessor to the RHIC e-Cooler, includes a prototype RF tuner mechanism capable of both coarse and fast tuning. This tuner concept, adapted originally from a DESY design, has longer stroke and significantly higher loads attributable to the very stiff ECX cavity shape. Structural design, kinematics, controls, thermal and RF issues are discussed and certain improvements are proposed.

  11. Control of the optical carrier to sideband ratio in optical double/single sideband modulation by the phase variation of RF signals

    NASA Astrophysics Data System (ADS)

    Feng, Danqi; Sun, Junqiang; Xie, Heng

    2015-10-01

    We propose and experimentally demonstrate a novel approach to realize tunable optical carrier-to-sideband ratio (OCSR) by introducing two radiofrequency (RF) signals with phase difference to drive a Mach-Zehnder modulator. Stimulated Brillouin scattering is adopted to remove the undesirable sideband, converting double sideband (DSB) to single sideband (SSB). By altering RF signal phase difference, wide ranges of OCSR from -23 to 44 dB and -21 to 44 dB are obtained for the DSB and SSB modulation, respectively. The operation frequency bandwidth covers from 5 to 42.3 GHz. The optimum OCSR to maximize the output RF power is also presented for the best transmission behavior. The proposed approach will be vital for optimizing the transmission performance by improving modulation efficiency and receiver sensitivity.

  12. Development of array-type atmospheric-pressure RF plasma generator with electric on-off control for high-throughput numerically controlled processes

    NASA Astrophysics Data System (ADS)

    Takei, H.; Kurio, S.; Matsuyama, S.; Yamauchi, K.; Sano, Y.

    2016-10-01

    An array-type atmospheric-pressure radio-frequency (RF) plasma generator is proposed for high-precision and high-throughput numerically controlled (NC) processes. We propose the use of a metal-oxide-semiconductor field-effect transistor (MOSFET) circuit for direct RF switching to achieve plasma on-off control. We confirmed that this type of circuit works correctly using a MOSFET with a small parasitic capacitance between its source and gate. We examined the design method for the distance between adjacent electrodes, which corresponds to the parasitic capacitance between adjacent electrodes and is very important in the individual on-off control of each electrode. We developed a prototype array-type plasma generator apparatus with 19 electrodes and the same number of MOSFET circuits; we then confirmed that each electrode could control its plasma on-off state individually. We also demonstrated that the thickness uniformity of the surface Si layer of a silicon-on-insulator wafer could be processed to less than 1 nm peak to valley by the NC sacrificial oxidation method using the apparatus.

  13. Effect on plasma and etch-rate uniformity of controlled phase shift between rf voltages applied to powered electrodes in a triode capacitively coupled plasma reactor

    SciTech Connect

    Sung, Dougyong; Jeong, Sangmin; Park, Youngmin; Volynets, Vladimir N.; Ushakov, Andrey G.; Kim, Gon-Ho

    2009-01-15

    The influence of the phase shift between rf voltages applied to the powered electrodes on plasma parameters and etch characteristics was studied in a very high-frequency (VHF) capacitively coupled plasma (CCP) triode reactor. rf voltages at 100 MHz were simultaneously applied to the top and bottom electrodes having a controlled phase shift between them, which could be varied between 0 deg. and 360 deg. Several plasma and process characteristics were measured as a function of the phase shift: (i) radial profiles of plasma-emission intensity, (ii) line-of-sight averaged plasma-emission intensity, and (iii) radial profiles of blanket SiO{sub 2} etching rate over a 300 mm wafer. Radial profiles of plasma emission were obtained using the scanning optical probe. It has been shown that all the measured characteristics strongly depend on the phase shift: (i) plasma-emission intensity is minimal at phase shift equal to 0 deg. and maximal at 180 deg. for all radial positions, while the emission radial profile changes from bell-shaped distribution with considerable nonuniformity at 0 deg. to a much more flattened distribution at 180 deg.; (ii) line-of-sight averaged plasma-emission intensity shows a similar dependence on the phase shift with minimum and maximum at 0 deg. and 180 deg., respectively; and (iii) the etch-rate radial profile at 180 deg. shows a much better uniformity as compared to that at 0 deg. Some of these results can be qualitatively explained by the redistribution of plasma currents that flow between the electrodes and also from the electrodes to the grounded wall with the phase shift. We suggest that the phase-shift effect can be used to improve the plasma and etch-rate spatial uniformity in VHF-CCP triode reactors.

  14. RF System High Power Amplifier Software Conversion at Jefferson Lab

    SciTech Connect

    G. Lahti; H. Dong; T. Seegerger

    2006-10-31

    Jefferson Lab is in the process of converting the RF system from analog RF modules and non-smart high power amplifiers (HPAs) to digital RF modules and smart HPAs. The present analog RF module controls both the RF signal and the non-smart HPA hardware. The new digital RF module will only control the RF signal, so the new HPA must include embedded software. This paper will describe the conversion from a software perspective, including the initial testing, the intermediate mixed system of old and new units, and finally the totally new RF system.

  15. Space Digital Controller for Improved Motor Control

    NASA Astrophysics Data System (ADS)

    Alves-Nunes, Samuel; Daras, Gaetan; Dehez, Bruno; Maillard, Christophe; Bekemans, Marc; Michel, Raymond

    2014-08-01

    Performing digital motor control into space equipment is a new challenge. The new DPC (Digital Programmable Controller) is the first chip that we can use as a micro-controller, allowing us to drive motors with digital control schemes. In this paper, the digital control of hybrid stepper motors is considered. This kind of motor is used for solar array rotation and antenna actuation. New digital control technology brings a lot of advantages, allowing an important reduction of thermal losses inside the motor, and a reduction of thermal constraints on power drive electronic components. The opportunity to drive motors with a digital controller also brings many new functionalities like post-failure torque analysis, micro- vibrations and cogging torque reduction, or electro- mechanical damping of solar array oscillations. To evaluate the performance of the system, Field-Oriented Control (FOC) is implemented on a hybrid stepper motor. A test-bench, made of an active load, has been made to emulate the mechanical behaviour of the solar array, by the use of a torsionally-compliant model. The experimental results show that we can drastically reduce electrical power consumption, compared with the currently used open-loop control scheme.

  16. Improving Control of Two Motor Controllers

    NASA Technical Reports Server (NTRS)

    Toland, Ronald W.

    2004-01-01

    A computer program controls motors that drive translation stages in a metrology system that consists of a pair of two-axis cathetometers. This program is specific to Compumotor Gemini (or equivalent) motors and the Compumotor 6K-series (or equivalent) motor controller. Relative to the software supplied with the controller, this program affords more capabilities and is easier to use. Written as a Virtual Instrument in the LabVIEW software system, the program presents an imitation control panel that the user can manipulate by use of a keyboard and mouse. There are three modes of operation: command, movement, and joystick. In command mode, single commands are sent to the controller for troubleshooting. In movement mode, distance, speed, and/or acceleration commands are sent to the controller. Position readouts from the motors and from position encoders on the translation stages are displayed in marked fields. At any time, the position readouts can be recorded in a file named by the user. In joystick mode, the program yields control of the motors to a joystick. The program sends commands to, and receives data from, the controller via a serial cable connection, using the serial-communication portion of the software supplied with the controller.

  17. Modular multivariable control improves hydrocracking

    SciTech Connect

    Chia, T.L.; Lefkowitz, I.; Tamas, P.D.

    1996-10-01

    Modular multivariable control (MMC), a system of interconnected, single process variable controllers, can be a user-friendly, reliable and cost-effective alternative to centralized, large-scale multivariable control packages. MMC properties and features derive directly from the properties of the coordinated controller which, in turn, is based on internal model control technology. MMC was applied to a hydrocracking unit involving two process variables and three controller outputs. The paper describes modular multivariable control, MMC properties, tuning considerations, application at the DCS level, constraints handling, and process application and results.

  18. Design and test of a resonance control system for suppressing the pump vibration effects for the PEFP 13-MHz RF cavity

    NASA Astrophysics Data System (ADS)

    Li, Ying-Min; Cha, Sung-Su; Jang, Ji-Ho; Kwon, Hyeok-Jung; Song, Young-Gi; Kim, Han-Sung; Seol, Kyung-Tae; Cho, Yong-Sub; Trinh, Tu-Anh

    2013-11-01

    The Proton Engineering Frontier Project developed a 13-MHz pulsed, RF cavity for heavy-ion implanter applications. Typically, slow changes in the room temperature and the mechanical vibrations of the vacuum device may be primary sources of disturbances, and the accelerating cavity of the implanter may not be able to operate at the resonance frequency owing to disturbance effects. We need a voltage-controlled oscillator phased-locked loop circuit to make a control system that could suppress the disturbance effects; thus, the accelerating gradient of the cavity always reached a peak level for a given input power and coupling. An analog-circuit-based RF-frequency-tracking system was developed. Next, we obtained the optimal control parameters for the key control components. Finally, we measured the system performance between an open loop and a closed loop. The key point of the system design is to control the driving frequency that is used to operate the RF source by keeping the phase at around 0 degrees with respect to the resonance peak of the cavity. The experimental results showed that the fluctuations of the control loop error signal were suppressed by about a factor of 10. The presented feedback loop is implemented as a standard proportional controller. The loop p-gain is 120 k.

  19. A Micromechanical RF Channelizer

    NASA Astrophysics Data System (ADS)

    Akgul, Mehmet

    available surface micromachinable materials. For many potential applications, the hot filament CVD method demonstrated in this work is quite enabling, since it provides a much less expensive method than microwave CVD based alternatives for depositing doped CVD diamond over large wafers (e.g., 8") for batch fabrication. The first three methods described so far focus on a single vibrating disk resonator and improve its electrical equivalent modeling, C x/Co, and Q. Once we craft the resonator that meets the challenging design requirements of RF channel-select filters, the last method presents a design hierarchy that achieves the desired filter response with a specific center frequency, bandwidth, and filter termination resistance. The design procedure culminates in specific values for all mechanical geometry variables necessary for the filter layout, such as disk radii, and beam widths; and process design variables such as resonator material thickness and capacitive actuation gap spacing. Finally, the experimental results introduce a 39nm-gap capacitive transducer, voltage-controlled frequency tuning, and a stress relieving coupled array design that enable a 0.09% bandwidth 223.4 MHz channel-select filter with only 2.7dB of in-band insertion loss and 50dB rejection of out-of-band interferers. This amount of rejection is more than 23dB better than previous capacitive-gap transduced filter designs that did not benefit from sub-50nm gaps. It also comes in tandem with a 20dB shape factor of 2.7 realized by a hierarchical mechanical circuit design utilizing 206 micromechanical circuit elements, all contained in an area footprint of only 600mumx420mum. The key to such low insertion loss for this tiny percent bandwidth is Q's>8,800 supplied by polysilicon disk resonators employing for the first time capacitive transducer gaps small enough to generate coupling strengths of C x/Co ˜0.1%, which is a 6.1x improvement over previous efforts. The filter structure utilizes electrical

  20. Metal-insulator transition of valence-controlled VO2 thin film prepared by RF magnetron sputtering using oxygen radical

    NASA Astrophysics Data System (ADS)

    Suetsugu, Takaaki; Shimazu, Yuichi; Tsuchiya, Takashi; Kobayashi, Masaki; Minohara, Makoto; Sakai, Enju; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru

    2016-06-01

    We have prepared b-axis-oriented VO2 thin films by RF magnetron sputtering using oxygen radicals as the reactive gas. The VO2 thin films consist of a mixed-valence V3+/V4+ state formed by oxygen vacancies. The V3+ ratio strongly depends on the film thickness and the oxygen partial pressure of the radical gun during deposition. The lattice constant of the b-axis increases and the metal-insulator transition (MIT) temperature decreases with decreasing V3+ ratio, although the VO2 thin films with a high V3+ ratio of 42% do not exhibit MIT. The bandwidths and spectral weights of V 3d a1g and \\text{e}\\text{g}σ bands at around the Fermi level, which correspond to the insulating phase at 300 K, are smaller in the VO2 thin films with a low V3+ ratio. These results indicate that the control of the mixed-valence V3+/V4+ state is important for the MIT of b-axis-oriented VO2 thin films.

  1. Shape and vibration control of active laminated plates for RF and optical applications

    NASA Astrophysics Data System (ADS)

    Punhani, Amitesh; Washington, Gregory N.

    2006-03-01

    Active shape and vibration control of large structures have long been desired for many practical applications. PVDF being one of the most suitable materials for these applications due to its strong piezoelectric properties and availability in thin sheets has been the focal point of most researchers in this area. Most of the research has been done to find an open loop solution, which would be able to shape the structure as per the desired requirements in an ideal atmosphere. Unmodeled dynamics and external disturbances prevent the open loop (no feedback) solution from achieving the desired shape. This research develops a dynamic model of a laminated plate consisting of two layers of PVDF film joined with a layer of epoxy. The orthotropic properties of PVDF have been modeled and the epoxy layer is considered to be isotropic. A general control model is developed, which would work for most boundary conditions and developed for a simply supported beam with patch actuators. The methodology is then extended for a simply supported laminated plate. This model could be used for real time dynamic disturbance rejection and shape and vibration control of the structure.

  2. Minnesota multiphasic personality inventory-2 restructured form (MMPI-2-RF) scale score differences in bariatric surgery candidates diagnosed with binge eating disorder versus BMI-matched controls.

    PubMed

    Marek, Ryan J; Ben-Porath, Yossef S; Ashton, Kathleen; Heinberg, Leslie J

    2014-04-01

    Binge Eating Disorder (BED) is among the most common psychiatric disorders in bariatric surgery candidates. The Minnesota Multiphasic Personality Inventory-2 Restructured Form (MMPI-2-RF) is a broadband, psychological test that includes measures of emotional and behavioral dysfunction, which have been associated with BED behaviors in bariatric surgery candidates; however these studies have lacked appropriate controls. In the current study, we compared MMPI-2-RF scale scores of bariatric surgery patients diagnosed with BED (BED+) with BMI-matched controls without BED (BED-). Three-hundred and seven BED+ participants (72.64% female and 67.87% Caucasian; mean BMI of 51.36 kg/m(2) [SD = 11.94]) were drawn from a large, database (N = 1304). Three-hundred and seven BED- participants were matched on BMI and demographics (72.64% female, 68.63% Caucasian, and mean BMI of 51.30 kg/m(2) [SD = 11.70]). The BED+ group scored significantly higher on measures of Demoralization, Low Positive Emotions, and Dysfunctional Negative Emotions and scored lower on measures of Antisocial Behaviors, reflecting behavioral constraint. Optimal T-Score cutoffs were below the traditional 65 T score for several MMPI-2-RF scales. MMPI-2-RF externalizing measures also added incrementally to differentiating between the groups beyond the Binge Eating Scale (BES). BED+ individuals produced greater elevations on a number of MMPI-2-RF internalizing scales and externalizing scales. Use of the test in conjunction with a clinical interview and other self-report data can further aid the clinician in guiding patients to appropriate treatment to optimize outcome. Copyright © 2013 Wiley Periodicals, Inc.

  3. RF power recovery feedback circulator

    DOEpatents

    Sharamentov, Sergey I [Bolingbrook, IL

    2011-03-29

    A device and method for improving the efficiency of RF systems having a Reflective Load. In the preferred embodiment, Reflected Energy from a superconducting resonator of a particle accelerator is reintroduced to the resonator after the phase of the Reflected Energy is aligned with the phase of the Supply Energy from a RF Energy Source. In one embodiment, a Circulator is used to transfer Reflected Energy from the Reflective Load into a Phase Adjuster which aligns the phase of the Reflected Energy with that of the Supply Energy. The phase-aligned energy is then combined with the Supply Energy, and reintroduced into the Reflective Load. In systems having a constant phase shift, the Phase Adjuster may be designed to shift the phase of the Reflected Energy by a constant amount using a Phase Shifter. In systems having a variety (variable) phase shifts, a Phase Shifter controlled by a phase feedback loop comprising a Phase Detector and a Feedback Controller to account for the various phase shifts is preferable.

  4. The effects of RF plasma ashing on zinc orthotitanate/potassium silicate thermal control coatings

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Bruckner, Eric J.

    1992-01-01

    Samples of YB-71, a white thermal control coating composed of zinc orthotitanate pigment in a potassium silicate binder, were exposed in air plasma and in oxygen plasma to determine optical property and surface chemistry changes. Results show that YB-71 undergoes a significant reflectance decrease upon exposure to the simulated LEO atomic oxygen environment provided by an air plasma asher. YB-71 samples exposed to the same effective fluence in oxygen plasma, or in a UV screening Faraday cage in air or oxygen, do not undergo as severe reflectance decreases as the samples exposed in the air plasma asher environment. The UV and VUV radiation present in the plasma ashers affects the YB-71 degradation. It is noted that, when using plasma ashers to determine LEO degradation, it is necessary to take into account the sensitivity of the material to the synergistic effects of atomic oxygen and accelerated UV radiation.

  5. Size-controllable synthesis and bandgap modulation of single-layered RF-sputtered bismuth nanoparticles

    PubMed Central

    2014-01-01

    We here report a simple and efficient method to grow single-layer bismuth nanoparticles (BiNPs) with various sizes on glass substrates. Optimal conditions were found to be 200°C and 0.12 W/cm2 at a growth rate of 6 Å/s, with the deposition time around 40 s. Scanning electron microscope (SEM) images were used to calculate the particle size distribution statistics, and high-resolution X-ray diffraction (XRD) patterns were used to examine the chemical interactions between BiNPs and the substrates. By measuring the transmission spectra within the range of 300 to 1,000 nm, we found that the optical bandgap can be modulated from 0.45 to 2.63 eV by controlling the size of these BiNPs. These interesting discoveries offer an insight to explore the dynamic nature of nanoparticles. PMID:24917699

  6. The effects of RF plasma ashing on zinc orthotitanate/potassium silicate thermal control coatings

    NASA Technical Reports Server (NTRS)

    Dever, Joyce A.; Bruckner, Eric J.

    1992-01-01

    Samples of YB-71, a white thermal control coating composed of zinc orthotitanate pigment in a potassium silicate binder, were exposed in air plasma and in oxygen plasma to determine optical property and surface chemistry changes. Results show that YB-71 undergoes a significant reflectance decrease upon exposure to the simulated LEO atomic oxygen environment provided by an air plasma asher. YB-71 samples exposed to the same effective fluence in oxygen plasma, or in a UV screening Faraday cage in air or oxygen, do not undergo as severe reflectance decreases as the samples exposed in the air plasma asher environment. The UV and VUV radiation present in the plasma ashers affects the YB-71 degradation. It is noted that, when using plasma ashers to determine LEO degradation, it is necessary to take into account the sensitivity of the material to the synergistic effects of atomic oxygen and accelerated UV radiation.

  7. RF current profile control studies in the alcator C-mod tokamak

    NASA Astrophysics Data System (ADS)

    Bonoli, P. T.; Porkolab, M.; Wukitch, S. J.; Bernabei, S.; Kaita, R.; Mikkelsen, D.; Phillips, C. K.; Schilling, G.

    1999-09-01

    Time dependent calculations of lower hybrid (LH) current profile control in Alcator C-Mod have been done using the TRANSP [1], FPPRF [2], and LSC [3] codes. Up to 3 MW of LH current drive power was applied in plasmas with high power ICRF minority heating (PICH=1.8-3 MW) and fast current ramp up. Using the experimentally measured temperature profiles, off-axis current generation resulted in nonmonotonic q-profiles with qmin~=1.6. Self-consistent effects of off-axis electron heating by the LH power were also included in the analysis and significant broadening of the electron temperature profile was found with qmin>~2 and a larger shear reversal radius.

  8. Tore Supra LH transmitter upgrade, a new RF driver for the power spectrum

    SciTech Connect

    Berger-By, G.; Achard, J.; Armitano, A.; Bouquey, F.; Corbel, E.; Delpech, L.; Ekedahl, A.; Lombard, G.; Magne, R.; Mollard, P.; Pagano, M.; Prou, M.; Samaille, F.; Volpe, D.; Volpe, R.

    2011-12-23

    New real time tools have been developed for testing new 700kW/3.7GHz/CW klystrons and for the operations on very long plasma shots. After the commissioning of the 18 series tubes on the high power test bed facility, the installation of the first 8 klystrons in the Tore Supra transmitter and the adjustment tests on load, this upgrade work has been materialized during the last 2010 campaign by a successful operation on the Full Active Multijunction (FAM) C3 antenna, with new performances: 3.5MW/40s on plasma. The RF output power control in amplitude and phase has been improved for a better control of the wave spectrum launched into the plasma. The new klystrons have no modulating anode and the high cathode voltage must be adjusted with the RF input power in order to optimize the RF output power with a minimization of the thermal power losses in the collector. A new phase correction, depending on the 3 RF output power ranges used, has been introduced. The improvements made in 2009 and 2010 on the generic phase loop and the procedures used during the real time tests of the RF transfer functions in amplitude and phase are detailed below. All RF measurements systems, RF safety systems and the RF calibration procedures have been revised in order to have the best consistency, reproducibility and with a measurement error against the calorimetry measurement lower than 10%.

  9. LPV Controller Interpolation for Improved Gain-Scheduling Control Performance

    NASA Technical Reports Server (NTRS)

    Wu, Fen; Kim, SungWan

    2002-01-01

    In this paper, a new gain-scheduling control design approach is proposed by combining LPV (linear parameter-varying) control theory with interpolation techniques. The improvement of gain-scheduled controllers can be achieved from local synthesis of Lyapunov functions and continuous construction of a global Lyapunov function by interpolation. It has been shown that this combined LPV control design scheme is capable of improving closed-loop performance derived from local performance improvement. The gain of the LPV controller will also change continuously across parameter space. The advantages of the newly proposed LPV control is demonstrated through a detailed AMB controller design example.

  10. Simplified quantification of labile proton concentration-weighted chemical exchange rate (k(ws) ) with RF saturation time dependent ratiometric analysis (QUESTRA): normalization of relaxation and RF irradiation spillover effects for improved quantitative chemical exchange saturation transfer (CEST) MRI.

    PubMed

    Sun, Phillip Zhe

    2012-04-01

    Chemical exchange saturation transfer MRI is an emerging imaging technique capable of detecting dilute proteins/peptides and microenvironmental properties, with promising in vivo applications. However, chemical exchange saturation transfer MRI contrast is complex, varying not only with the labile proton concentration and exchange rate, but also with experimental conditions such as field strength and radiofrequency (RF) irradiation scheme. Furthermore, the optimal RF irradiation power depends on the exchange rate, which must be estimated in order to optimize the chemical exchange saturation transfer MRI experiments. Although methods including numerical fitting with modified Bloch-McConnell equations, quantification of exchange rate with RF saturation time and power (QUEST and QUESP), have been proposed to address this relationship, they require multiple-parameter non-linear fitting and accurate relaxation measurement. Our work extended the QUEST algorithm with ratiometric analysis (QUESTRA) that normalizes the magnetization transfer ratio at labile and reference frequencies, which effectively eliminates the confounding relaxation and RF spillover effects. Specifically, the QUESTRA contrast approaches its steady state mono-exponentially at a rate determined by the reverse exchange rate (k(ws) ), with little dependence on bulk water T(1) , T(2) , RF power and chemical shift. The proposed algorithm was confirmed numerically, and validated experimentally using a tissue-like phantom of serially titrated pH compartments.

  11. Simplified quantification of labile proton concentration-weighted chemical exchange rate (kws) with RF saturation time dependent ratiometric analysis (QUESTRA) - Normalization of relaxation and RF irradiation spillover effects for improved quantitative chemical exchange saturation transfer (CEST) MRI

    PubMed Central

    Sun, Phillip Zhe

    2012-01-01

    Chemical exchange saturation transfer (CEST) MRI is an emerging imaging technique capable of detecting dilute proteins/peptides and microenvironmental properties, with promising in vivo applications. However, CEST MRI contrast is complex, varying not only with the labile proton concentration and exchange rate, but also with experimental conditions such as field strength and RF irradiation scheme. Furthermore, the optimal RF irradiation power depends on the exchange rate, which must be estimated in order to optimize the CEST MRI experiments. Although methods including numerical fitting with modified Bloch-McConnell equations, quantification of exchange rate with RF saturation time and power (QUEST and QUESP), have been proposed to address this relationship, they require multiple-parameter non-linear fitting and accurate relaxation measurement. Our work here extended the QUEST algorithm with ratiometric analysis (QUESTRA) that normalizes the magnetization transfer ratio (MTR) at labile and reference frequencies, which effectively eliminates the confounding relaxation and RF spillover effects. Specifically, the QUESTRA contrast approaches its steady state mono-exponentially at a rate determined by the reverse exchange rate (kws), with little dependence on bulk water T1, T2, RF power and chemical shift. The proposed algorithm was confirmed numerically, and validated experimentally using a tissue-like phantom of serially titrated pH compartments. PMID:21842497

  12. Patient adherence improves glycemic control.

    PubMed

    Rhee, Mary K; Slocum, Wrenn; Ziemer, David C; Culler, Steven D; Cook, Curtiss B; El-Kebbi, Imad M; Gallina, Daniel L; Barnes, Catherine; Phillips, Lawrence S

    2005-01-01

    The purpose of this study was to assess the influence of appointment keeping and medication adherence on HbA1c. A retrospective evaluation was performed in 1560 patients with type 2 diabetes who presented for a new visit to the Grady Diabetes Clinic between 1991 and 2001 and returned for a follow-up visit and HbA1c after 1 year of care. Appointment keeping was assessed by the number of scheduled intervening visits that were kept, and medication adherence was assessed by the percentage of visits in which self-reported diabetes medication use was as recommended at the preceding visit. The patients had an average age of 55 years, body mass index (BMI) of 32 kg/m2, diabetes duration of 4.6 years, and baseline HbA1c of 9.1%. Ninety percent were African American, and 63% were female. Those who kept more intervening appointments had lower HbA1c levels after 12 months of care (7.6% with 6-7 intervening visits vs 9.7% with 0 intervening visits). Better medication adherence was also associated with lower HbA1c levels after 12 months of care (7.8% with 76%-100% adherence). After adjusting for age, gender, race, BMI, diabetes duration, and diabetes therapy in multivariate linear regression analysis, the benefits of appointment keeping and medication adherence remained significant and contributed independently; the HbA1c was 0.12% lower for every additional intervening appointment that was kept (P = .0001) and 0.34% lower for each quartile of better medication adherence (P = .0009). Keeping more appointments and taking diabetes medications as directed were associated with substantial improvements in HbA1c. Efforts to enhance glycemic outcomes should include emphasis on these simple but critically important aspects of patient adherence.

  13. Improved process control alarm operation.

    PubMed

    Bristol, E H

    2001-01-01

    Alarms are the main connection from the automation to the operator, when addressing process operation outside of its normal function. They are often as much a source of operator overload and consternation as help. Better engineering of the relative role of the operator and automation would materially help overcome the difficulties. Expert systems have been proposed as a solution. But Expert systems are really another form of automation. There remains that aspect of the alarms, which must address our inability to cover and understand a possibly larger domain of the operation not appropriate to traditional controls or present-day automation. Appropriate tools for this domain must support operator discretion and initiative. The paper suggests a set of such general, computer science based, tools requiring only the most basic configuration. They are viewed as implemented on top of those properly detailed alarm displays and interlocks, which reflect the more formal plant operating policies. They include: (a) Various forms of alarm logging and trending; (b) Short, automatically generated, word summaries of alarm activity, which allow low level data to propagate to the highest levels, including: one word and priority summaries; (c) Causal alarm pattern analyses that help the operator to predict or diagnose alarm behavior; (d) Automatic adaptation of alarms and alarm limits to varying process situations; (e) Uniform use of alarm policies to simplify alarm configuration.

  14. A novel RF-insensitive EED utilizing an integrated metal-oxide-semiconductor structure

    NASA Astrophysics Data System (ADS)

    Baginski, Thomas A.; Baginski, Michael E.

    1990-05-01

    The description and characterization of an electroexplosive device (EED) are presented. The structure is designed, using microelectric fabrication techniques, to be inherently immune to radio frequency (RF) radiation and also offers protection against stray signals associated with RF-induced arcing. A detailed discussion of the structure, which includes the fundamental mechanisms of operation, fabrication techniques, the device's frequency response and sensitivity to RF-induced arcing, and its compatibility with present fire control systems, is provided. Preliminary test results of the prototype device are discussed and show a significant improvement in the system's overall EMI immunity. These results include bench and field measurements of the structure's RF response for frequencies of 10-225 MHz and field measurements of the device's sensitivity to RF-induced arcing. The measurements indicate a significant reduction in real power dissipated by an EED employing the structure over an EED employing a conventional bridgewire (20 dB at 90 MHz).

  15. Improved Characteristics of Integrated HTS rf SQUID on Bicrystal SrTiO3 Substrate Resonator Covered with HTS Thin Films in Flip-Chip Geometry

    NASA Astrophysics Data System (ADS)

    Hatsukade, Yoshimi; Takemoto, Makoto; Kurosawa, Ryuichi; Uchida, Yousuke; Tanaka, Saburo

    Integrated high-temperature superconductor (HTS) radio-frequency (rf) superconducting quantum interference devices (SQUIDs) based on a bicrystal SrTiO3 substrate was investigated for application to magnetic contaminant detection. By covering a wide superconducting weak link and/or a slit of the YBa2Cu3O7-x SQUID with HTS thin films in flip-chip geometry, characteristics such as effective area and 1/f noise profile of the SQUID were successfully improved. By installing the covered SQUID in a magnetic contaminant detection system, it was demonstrated that the system can detect a tungsten ball of 15μm in diameter with a signal to noise ratio of about 2.

  16. Feasibility randomised controlled trial of Recovery-focused Cognitive Behavioural Therapy for Older Adults with bipolar disorder (RfCBT-OA): study protocol

    PubMed Central

    Tyler, Elizabeth; Lobban, Fiona; Sutton, Chris; Depp, Colin; Johnson, Sheri; Laidlaw, Ken; Jones, Steven H

    2016-01-01

    Introduction Bipolar disorder is a severe and chronic mental health problem that persists into older adulthood. The number of people living with this condition is set to rise as the UK experiences a rapid ageing of its population. To date, there has been very little research or service development with respect to psychological therapies for this group of people. Methods and analysis A parallel two-arm randomised controlled trial comparing a 14-session, 6-month Recovery-focused Cognitive-Behavioural Therapy for Older Adults with bipolar disorder (RfCBT-OA) plus treatment as usual (TAU) versus TAU alone. Participants will be recruited in the North-West of England via primary and secondary mental health services and through self-referral. The primary objective of the study is to evaluate the feasibility and acceptability of RfCBT-OA; therefore, a formal power calculation is not appropriate. It has been estimated that randomising 25 participants per group will be sufficient to be able to reliably determine the primary feasibility outcomes (eg, recruitment and retention rates), in line with recommendations for sample sizes for feasibility/pilot trials. Participants in both arms will complete assessments at baseline and then every 3 months, over the 12-month follow-up period. We will gain an estimate of the likely effect size of RfCBT-OA on a range of clinical outcomes and estimate parameters needed to determine the appropriate sample size for a definitive, larger trial to evaluate the effectiveness and cost-effectiveness of RfCBT-OA. Data analysis is discussed further in the Analysis section in the main paper. Ethics and dissemination This protocol was approved by the UK National Health Service (NHS) Ethics Committee process (REC ref: 15/NW/0330). The findings of the trial will be disseminated through peer-reviewed journals, national and international conference presentations and local, participating NHS trusts. Trial registration number ISRCTN13875321; Pre

  17. Interactions of release factor RF3 with the translation machinery.

    PubMed

    O'Connor, Michael

    2015-08-01

    The bacterial release factor RF3 is a GTPase that has been implicated in multiple, incompletely understood steps of protein synthesis. This study explores the genetic interaction of RF3 with other components of the translation machinery. RF3 contributes to translation termination by recycling the class I release factors RF1 and RF2 off post-termination ribosomes. RF3 has also been implicated in dissociation of peptidyl-tRNAs from elongating ribosomes and in a post-peptidyltransferase quality control (post-PT QC) mechanism that selectively terminates ribosomes carrying erroneous peptides. A majority of the in vivo studies on RF3 have been carried out in K-12 strains of Escherichia coli which carry a partially defective RF2 protein with an Ala to Thr substitution at position 246. Here, the contribution of the K-12 specific RF2 variant to RF3 activities has been investigated. Strain reconstruction experiments in both E. coli and Salmonella enterica demonstrate that defects in termination and post-PT QC that are associated with RF3 loss, as well as phenotypes uncovered by phenotypic profiling, are all substantially ameliorated when the incompletely active K-12-specific RF2 protein is replaced by a fully active Ala246 RF2. These results indicate that RF3 loss is well tolerated in bacteria with fully active class I release factors, but that many of the previously reported phenotypes for RF3 deletion strains have been compromised by the presence of a partially defective RF2.

  18. Investigation of RF excited CW CO2 waveguide lasers local oscillator - RF excitation

    NASA Technical Reports Server (NTRS)

    Hochuli, U.

    1988-01-01

    A new local oscillator housing was built which seems to have improved laser life. Laser cooling was changed from internal water cooling to the more convenient thermal contact cooling. At the present time, a conclusion can not be made if the 20 percent reduction in power output is the result of poorer cooling or poorer grating alignment. The coupling-starting network was improved from 55 to about 90 percent. It can be adjusted by varying trimmers C sub 1 and C sub 2 to match RF power levels between 10 and 30 W. If the laser admittance changes greatly with laser life rematching will have to be achieved by remote control for space applications. The same holds true if the RF power level has to be changed with a maximum efficiency constraint.

  19. Morphology control of tungsten nanorods grown by glancing angle RF magnetron sputtering under variable argon pressure and flow rate

    NASA Astrophysics Data System (ADS)

    Khedir, Khedir R.; Kannarpady, Ganesh K.; Ishihara, Hidetaka; Woo, Justin; Ryerson, Charles; Biris, Alexandru S.

    2010-09-01

    Morphologically novel tungsten nanorods (WNRs) with the co-existence of two crystalline phases, α-W (thermodynamically stable) and β-W, were fabricated by glancing angle RF magnetron sputtering technique under various Ar pressures and flow rates. For these nanorods, a significant variation in their morphology and surface roughness was observed. These structures could be useful in a wide range of applications such as field emission, robust superhydrophobic coatings, energy, and medicine.

  20. Development of Localized Arc Filament RF Plasma Actuators for High-Speed and High Reynolds Number Flow Control

    DTIC Science & Technology

    2010-01-01

    Previously, these actuators were powered by a high voltage pulsed DC plasma generator with low energy coupling efficiency of 5-10%. In the present work, a...new custom- designed 8-channel pulsed radio frequency (RF) plasma generator has been developed to power up to 8 plasma actuators operated over a wide...the perimeter of a 2.54 cm diameter circular nozzle extension. Both types of actuators coupled approximately the same amount of power to the flow

  1. High-Fidelity Real Gas Model for RF Excited Plasma Flow Control - A Three Dimensional Analysis With Air Chemistry

    DTIC Science & Technology

    2008-05-31

    code for mitigating inert gas flow separation using rf-driven dielectric barrier discharge. In this effort we: (l) develop multi-dimensional first...such detailed plasma kinetics based effort has not been reported before. During the development of this project we have worked in close collaboration... develop multi-dimensional first principles based N2/GŖair chemistry models for the non-equilibrium real gas discharge, and (2) implement it in a finite

  2. Improved Flow-Controlling Vortex Generator

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.; Marner, Wilbur J.; Rohatgi, Naresh K.

    1989-01-01

    Symmetrical tangential streams control flow of radial primary streams. Vortex generator uses small secondary stream of fluid to control normally-larger primary stream. Improved version of vortex generator described in "Variable Control Port for Fluidic Control Device," (NPO-16603). Secondary, or control, flows entering tangentially through diametrically opposite ports set up swirling motion restraining primary flow. Pressure of secondary fluid in relation to primary fluid controlling factor. Like valve, vortex generator varies rate of flow of primary fluid from maximum value down to zero. When properly designed, requires low pressure differential between primary and secondary streams and expends relatively small amount of secondary fluid.

  3. Controlled Temperature Gradient Improves Freezing Alloy

    NASA Technical Reports Server (NTRS)

    Schmidt, Deborah; Alter, Wendy S.; Hamilton, William D.

    1991-01-01

    Controlled gradient of temperature in advancing zone of solidification increases fatigue life of directionally solidified nickel-base superalloy. Improved solidification process eliminates, reduces, or controls microstructure of deleterious brittle phases, including carbides and gamma/gamma prime eutectic. Also reduces microsegregation and makes discrete carbides (if present) become fine and blocky. Expected to improve properties of other alloys, of both directionally-solidified polycrystalline and single-crystal forms.

  4. Recycler barrier RF buckets

    SciTech Connect

    Bhat, C.M.; /Fermilab

    2011-03-01

    The Recycler Ring at Fermilab uses a barrier rf systems for all of its rf manipulations. In this paper, I will give an overview of historical perspective on barrier rf system, the longitudinal beam dynamics issues, aspects of rf linearization to produce long flat bunches and methods used for emittance measurements of the beam in the RR barrier rf buckets. Current rf manipulation schemes used for antiproton beam stacking and longitudinal momentum mining of the RR beam for the Tevatron collider operation are explained along with their importance in spectacular success of the Tevatron luminosity performance.

  5. 14N nuclear quadrupole resonance of p-nitrotoluene using a high-Tc rf SQUID

    NASA Astrophysics Data System (ADS)

    He, D. F.; Tachiki, M.; Itozaki, H.

    2007-03-01

    Using a high-Tc radio-frequency superconducting quantum interference device (rf SQUID), we successfully detected nuclear quadrupole resonance (NQR) at about 887 kHz for 14N in p-nitrotoluene (PNT). A normal metal transformer made of copper wire was used to improve the sensitivity of the high-Tc rf SQUID and pulse-controlled rf switches and cross diodes were inserted in the transformer to reduce the influence of the strong excitation field. The preliminary results for NQR detection using the high-Tc SQUID had a similar signal-to-noise ratio to that of using a low noise preamplifier.

  6. Gyromagnetic RF source for interdisciplinary research.

    PubMed

    Romanchenko, I V; Rostov, V V; Gunin, A V; Konev, V Yu

    2017-02-01

    We demonstrate a source of high power nanosecond RF pulses based on gyromagnetic nonlinear transmission line. The source is designed to explore the exposure of different biological objects to strong RF fields in an air filled rectangular waveguide loaded onto ethanol RF load. The RF pulse amplitude can be varied by 52 dB, reaching a maximum value of nearly 40 kV/cm and decreasing to tens of V/cm. The RF pulse amplitude is controlled by decreasing the incident pulse amplitude from the high voltage driver. The duration of RF pulses lies in the range from 4 to 25 ns and the frequency from 0.6 to 1.0 GHz.

  7. Gyromagnetic RF source for interdisciplinary research

    NASA Astrophysics Data System (ADS)

    Romanchenko, I. V.; Rostov, V. V.; Gunin, A. V.; Konev, V. Yu.

    2017-02-01

    We demonstrate a source of high power nanosecond RF pulses based on gyromagnetic nonlinear transmission line. The source is designed to explore the exposure of different biological objects to strong RF fields in an air filled rectangular waveguide loaded onto ethanol RF load. The RF pulse amplitude can be varied by 52 dB, reaching a maximum value of nearly 40 kV/cm and decreasing to tens of V/cm. The RF pulse amplitude is controlled by decreasing the incident pulse amplitude from the high voltage driver. The duration of RF pulses lies in the range from 4 to 25 ns and the frequency from 0.6 to 1.0 GHz.

  8. Klystron 'efficiency loop' for the ALS storage ring RF system

    SciTech Connect

    Kwiatkowski, Slawomir; Julian, Jim; Baptiste, Kenneth

    2002-05-20

    The recent energy crisis in California has led us to investigate the high power RF systems at the Advanced Light Source (ALS) in order to decrease the energy consumption and power costs. We found the Storage Ring Klystron Power Amplifier system operating as designed but with significant power waste. A simple proportional-integrator (PI) analog loop, which controls the klystron collector beam current, as a function of the output RF power, has been designed and installed. The design considerations, besides efficiency improvement, were to interface to the existing system without major expense. They were to also avoid the klystron cathode power supply filter's resonance in the loop's dynamics, and prevent a conflict with the existing Cavity RF Amplitude Loop dynamics. This efficiency loop will allow us to save up to 700 MW-hours of electrical energy per year and increase the lifetime of the klystron.

  9. 2 MW CW RF load for gyrotrons

    SciTech Connect

    Lawrence Ives, R.; Marsden, David; Mizuhara, Max; Collins, George; Neilson, Jeff; Borchard, Philipp

    2011-07-01

    Final design and assembly are in progress for a 2MW CW RF load for gyrotrons. Such loads are required for testing high power gyrotrons for electron cyclotron heating of fusion plasmas. The research is building on experience with a 1 MW load to increase the power capability, reduce backscattered RF power, and improve the mechanical design. (author)

  10. Conceptual design of data acquisition and control system for two Rf driver based negative ion source for fusion R&D

    NASA Astrophysics Data System (ADS)

    Soni, Jigensh; Yadav, R. K.; Patel, A.; Gahlaut, A.; Mistry, H.; Parmar, K. G.; Mahesh, V.; Parmar, D.; Prajapati, B.; Singh, M. J.; Bandyopadhyay, M.; Bansal, G.; Pandya, K.; Chakraborty, A.

    2013-02-01

    Twin Source - An Inductively coupled two RF driver based 180 kW, 1 MHz negative ion source experimental setup is initiated at IPR, Gandhinagar, under Indian program, with the objective of understanding the physics and technology of multi-driver coupling. Twin Source [1] (TS) also provides an intermediate platform between operational ROBIN [2] [5] and eight RF drivers based Indian test facility -INTF [3]. A twin source experiment requires a central system to provide control, data acquisition and communication interface, referred as TS-CODAC, for which a software architecture similar to ITER CODAC core system has been decided for implementation. The Core System is a software suite for ITER plant system manufacturers to use as a template for the development of their interface with CODAC. The ITER approach, in terms of technology, has been adopted for the TS-CODAC so as to develop necessary expertise for developing and operating a control system based on the ITER guidelines as similar configuration needs to be implemented for the INTF. This cost effective approach will provide an opportunity to evaluate and learn ITER CODAC technology, documentation, information technology and control system processes, on an operational machine. Conceptual design of the TS-CODAC system has been completed. For complete control of the system, approximately 200 Nos. control signals and 152 acquisition signals are needed. In TS-CODAC, control loop time required is within the range of 5ms - 10 ms, therefore for the control system, PLC (Siemens S-7 400) has been chosen as suggested in the ITER slow controller catalog. For the data acquisition, the maximum sampling interval required is 100 micro second, and therefore National Instruments (NI) PXIe system and NI 6259 digitizer cards have been selected as suggested in the ITER fast controller catalog. This paper will present conceptual design of TS -CODAC system based on ITER CODAC Core software and applicable plant system integration processes.

  11. The Murmansk Initiative - RF: Acceptance Testing

    SciTech Connect

    Czajkowski, C.; Wester, D. W.; Dyer, R. S.; Soerlie, A. A.; Moller, B.; Barnes, E.

    2002-02-26

    The Murmansk Initiative-RF (MI) was conceived to provide the Russian Federation (RF) with the capacity to manage low-level liquid radioactive waste (LLRW) and comply with the requirements of the London Convention that prohibit ocean dumping. The trilateral project among Norway, the RF, and the United States of America (U.S.) began in 1994 and was the first to utilize exclusively Russian subcontractors to upgrade and expand an existing LLRW treatment plant on the premises of RTP Atomflot in Murmansk, Russia. The project moved quickly through the design phase. Progress during the construction phase was somewhat slower because of difficulties with acquisition of hardware, inexperience with automated instrumentation and control equipment, and unexpected design changes in the cementation unit. The project advanced into the test-operation phase, which is currently underway, in June 2001. Initial runs with liquid waste have revealed that procedures for unloading spent ion-exchange sorbents could be improved and that sludges formed during removal of alkaline-earth metals should be compacted in order for the facility to operate at its full potential. Resolution of these issues is expected within the next few months.

  12. Tunable RF Cavities Using Orthogonally Biased Ferrite

    SciTech Connect

    Johnson, R.P.; Alsharo'a, M.; Ankenbrandt, C.M.; Entchevitch, I.; Griffin, J.E.; Moretti, A.; Popovic, M.; Tomlin, R.; /Fermilab

    2009-05-01

    Originally conceived as a solution for FFAG applications, a new compact RF cavity design that tunes rapidly over various frequency ranges can be used to upgrade existing machines. The design being developed uses orthogonally biased garnet cores for fast frequency tuning and liquid dielectric to adjust the frequency range and to control the core temperature. We describe measurements of candidate ferrite and dielectric materials. The first use of the new cavity concept will be for improvements to the 8 GeV Fermilab Booster synchrotron.

  13. Playing Action Video Games Improves Visuomotor Control.

    PubMed

    Li, Li; Chen, Rongrong; Chen, Jing

    2016-08-01

    Can playing action video games improve visuomotor control? If so, can these games be used in training people to perform daily visuomotor-control tasks, such as driving? We found that action gamers have better lane-keeping and visuomotor-control skills than do non-action gamers. We then trained non-action gamers with action or nonaction video games. After they played a driving or first-person-shooter video game for 5 or 10 hr, their visuomotor control improved significantly. In contrast, non-action gamers showed no such improvement after they played a nonaction video game. Our model-driven analysis revealed that although different action video games have different effects on the sensorimotor system underlying visuomotor control, action gaming in general improves the responsiveness of the sensorimotor system to input error signals. The findings support a causal link between action gaming (for as little as 5 hr) and enhancement in visuomotor control, and suggest that action video games can be beneficial training tools for driving.

  14. Plasma rotation induced by RF

    SciTech Connect

    Chan, V. S.; Chiu, S. C.; Lin-Liu, Y. R. [General Atomics, P.O. Box 85608, San Diego, California 92186-5698; Omelchenko, Y. A. [General Atomics, P.O. Box 85608, San Diego, California 92186-5698

    1999-09-20

    Plasma rotation has many beneficial effects on tokamak operation including stabilization of MHD and microturbulence to improve the beta limit and confinement. Contrary to present-day tokamaks, neutral beams may not be effective in driving rotation in fusion reactors; hence the investigation of radiofrequency (RF) induced plasma rotation is of great interest and potential importance. This paper reviews the experimental results of RF induced rotation and possible physical mechanisms, suggested by theories, to explain the observations. This subject is only in the infancy of its research and many challenging issues remained to be understood and resolved. (c) 1999 American Institute of Physics.

  15. RF processing

    NASA Astrophysics Data System (ADS)

    Burhans, R. W.

    1982-06-01

    The Loran-C radio frequency processing is discussed. A diagram which generally illustrates the automatic gain control is presented. The augmented differentiator for pulse envelopes adapts conventional communications receiver with wideband AM capability to detect pulse signals such as Loran-C. The circuit enhances reception for surveillance and observation of HF over-the-horizon radar signals or others where time difference estimates between pulse returns are of interest. The high resolution VLF spectrum which receives weak VLF signals by using an HP 3581A wave analyzer detecting signals with a very narrow bandwidth of only 3 Hz is also presented.

  16. Phase modulation in RF tag

    DOEpatents

    Carrender, Curtis Lee; Gilbert, Ronald W.

    2007-02-20

    A radio frequency (RF) communication system employs phase-modulated backscatter signals for RF communication from an RF tag to an interrogator. The interrogator transmits a continuous wave interrogation signal to the RF tag, which based on an information code stored in a memory, phase-modulates the interrogation signal to produce a backscatter response signal that is transmitted back to the interrogator. A phase modulator structure in the RF tag may include a switch coupled between an antenna and a quarter-wavelength stub; and a driver coupled between the memory and a control terminal of the switch. The driver is structured to produce a modulating signal corresponding to the information code, the modulating signal alternately opening and closing the switch to respectively decrease and increase the transmission path taken by the interrogation signal and thereby modulate the phase of the response signal. Alternatively, the phase modulator may include a diode coupled between the antenna and driver. The modulating signal from the driver modulates the capacitance of the diode, which modulates the phase of the response signal reflected by the diode and antenna.

  17. Improving RF Transmit Power and Received Signal Strength in 2.4 GHz ZigBee Based Active RFID System with Embedded Method

    NASA Astrophysics Data System (ADS)

    Po'ad, F. A.; Ismail, W.; Jusoh, J. F.

    2017-08-01

    This paper describes the experiments and analysis conducted on 2.4 GHz embedded active Radio Frequency Identification (RFID) - Wireless Sensor Network (WSN) based system that has been developed for the purposes of location tracking and monitoring in indoor and outdoor environments. Several experiments are conducted to test the effectiveness and performance of the developed system and two of them is by measuring the Radio Frequency (RF) transmitting power and Received Signal Strength (RSS) to prove that the embedded active RFID tag is capable to generate higher transmit power during data transmission and able to provide better RSS reading compared to standalone RFID tag. Experiments are carried out on two RFID tags which are active RFID tag embedded with GPS and GSM (ER2G); and standalone RFID tag communicating with the same active RFID reader. The developed ER2G contributes 12.26 % transmit power and 6.47 % RSS reading higher than standalone RFID tag. The results conclude that the ER2G gives better performance compared to standalone RFID tag and can be used as guidelines for future design improvements.

  18. Improvement of Adaptive Cruise Control Performance

    NASA Astrophysics Data System (ADS)

    Miyata, Shigeharu; Nakagami, Takashi; Kobayashi, Sei; Izumi, Tomoji; Naito, Hisayoshi; Yanou, Akira; Nakamura, Hitomi; Takehara, Shin

    2010-12-01

    This paper describes the Adaptive Cruise Control system (ACC), a system which reduces the driving burden on the driver. The ACC system primarily supports four driving modes on the road and controls the acceleration and deceleration of the vehicle in order to maintain a set speed or to avoid a crash. This paper proposes more accurate methods of detecting the preceding vehicle by radar while cornering, with consideration for the vehicle sideslip angle, and also of controlling the distance between vehicles. By making full use of the proposed identification logic for preceding vehicles and path estimation logic, an improvement in driving stability was achieved.

  19. Compensator improvement for multivariable control systems

    NASA Technical Reports Server (NTRS)

    Mitchell, J. R.; Mcdaniel, W. L., Jr.; Gresham, L. L.

    1977-01-01

    A theory and the associated numerical technique are developed for an iterative design improvement of the compensation for linear, time-invariant control systems with multiple inputs and multiple outputs. A strict constraint algorithm is used in obtaining a solution of the specified constraints of the control design. The result of the research effort is the multiple input, multiple output Compensator Improvement Program (CIP). The objective of the Compensator Improvement Program is to modify in an iterative manner the free parameters of the dynamic compensation matrix so that the system satisfies frequency domain specifications. In this exposition, the underlying principles of the multivariable CIP algorithm are presented and the practical utility of the program is illustrated with space vehicle related examples.

  20. Improved approximations for control augmented structural synthesis

    NASA Technical Reports Server (NTRS)

    Thomas, H. L.; Schmit, L. A.

    1990-01-01

    A methodology for control-augmented structural synthesis is presented for structure-control systems which can be modeled as an assemblage of beam, truss, and nonstructural mass elements augmented by a noncollocated direct output feedback control system. Truss areas, beam cross sectional dimensions, nonstructural masses and rotary inertias, and controller position and velocity gains are treated simultaneously as design variables. The structural mass and a control-system performance index can be minimized simultaneously, with design constraints placed on static stresses and displacements, dynamic harmonic displacements and forces, structural frequencies, and closed-loop eigenvalues and damping ratios. Intermediate design-variable and response-quantity concepts are used to generate new approximations for displacements and actuator forces under harmonic dynamic loads and for system complex eigenvalues. This improves the overall efficiency of the procedure by reducing the number of complete analyses required for convergence. Numerical results which illustrate the effectiveness of the method are given.

  1. Improved approximations for control augmented structural synthesis

    NASA Technical Reports Server (NTRS)

    Thomas, H. L.; Schmit, L. A.

    1990-01-01

    A methodology for control-augmented structural synthesis is presented for structure-control systems which can be modeled as an assemblage of beam, truss, and nonstructural mass elements augmented by a noncollocated direct output feedback control system. Truss areas, beam cross sectional dimensions, nonstructural masses and rotary inertias, and controller position and velocity gains are treated simultaneously as design variables. The structural mass and a control-system performance index can be minimized simultaneously, with design constraints placed on static stresses and displacements, dynamic harmonic displacements and forces, structural frequencies, and closed-loop eigenvalues and damping ratios. Intermediate design-variable and response-quantity concepts are used to generate new approximations for displacements and actuator forces under harmonic dynamic loads and for system complex eigenvalues. This improves the overall efficiency of the procedure by reducing the number of complete analyses required for convergence. Numerical results which illustrate the effectiveness of the method are given.

  2. Improved computed torque control for industrial robots

    NASA Technical Reports Server (NTRS)

    Uebel, Mark; Minis, Ioannis; Cleary, Kevin

    1992-01-01

    The authors examine the computed torque control problem for a robot arm with flexible, geared, joint drive systems which are typical in many industrial robots. The standard computed torque algorithm is not directly applicable to this class of manipulators due to the dynamics introduced by the joint drive systems. The proposed approach overcomes this problem by combining a novel computed torque algorithm with simple torque controllers at each joint of the robot. The control scheme is applied to a seven degree-of-freedom industrial manipulator, and the system performance in standard tasks is evaluated using both dynamic simulation and actual experiments. The results show that the proposed controller leads to improved tracking performance over a conventional PD (proportional plus derivative) controller.

  3. Fabrication of Si/InGaN Heterojunction Solar Cells by RF Sputtering Method: Improved Electrical and Optical Properties of Indium Gallium Nitride (InGaN) Thin Films

    NASA Astrophysics Data System (ADS)

    Jakkala, Pratheesh Kumar

    This dissertation presents a study on the fabrication of Indium Gallium Nitride (InGaN) based heterojunction solar cells using RF magnetron sputtering method. The goal of the study includes improving the electrical, optical and structural properties of InGaN thin films and examining their potential for photovoltaic applications and to reduce the parasitic resistive loses in solar cells. Reactive radio-frequency (RF) magnetron and Direct Current (DC) sputtering are deposition methods for thin films. The characterization techniques include Hall Effect measurement system for electrical properties, UV-Visible Spectroscopy for optical properties, X-Ray Diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDXS) for structural properties and AM 1.5 G irradiance spectrum to measure current-voltage (IV curves) and photovoltaic measurements. Copper Oxide thin films and Beryllium Zinc Oxide thin films are fabricated and their properties are examined for their potential to pair with n-InGaN to form a p-n junction. We conclude Silicon (111) wafer has better electrical properties than RF deposited Copper oxide and BeZnO and used as p-type layer. Aluminum (Al) and Indium Tin Oxide (ITO) are used as back and front metallic contacts respectively. In this study, we present a simple method for optical bandgap tuning of Indium Gallium Nitride (InGaN) thin films by controlling the growth conditions in magnetron RF sputtering. Thin films with different Indium (In) atomic compositions, x = 0.02 to 0.57 are deposited on high temperature aluminosilicate glass and Silicon (111) substrates. Substrate temperature is varied from 35 °C to 450 °C. Total pressure of sputtering gas mixture is kept constant at 12 mTorr but partial pressures of Ar and N2 are varied. Ar partial pressure to total pressure ratio is varied from 0 to 0.75. Optical bandgap values from 1.4 eV to 3.15 eV, absorption coefficient values of ˜ 10 4 /cm to ˜ 7 x 105 /cm and critical film thickness values of 0.04 mum

  4. THE SPALLATION NEUTRON SOURCE CRYOMODULE TEST STAND RF SYSTEM

    SciTech Connect

    Crofford, Mark T; Ball, Jeffrey Allen; Davidson Jr, Taylor L; Hardek, Thomas W; Heidenreich, Dale A; Kasemir, Kay; Kim, Sang-Ho; Kang, Yoon

    2008-01-01

    The Spallation Neutron Source (SNS) has recently commissioned a cryomodule test facility for the repair and testing of the super-conducting radio-frequency (SRF) cavities. This facility utilizes the original 402.5/805 MHz Radio Frequency (RF) Klystron Test Stand as its power source along with dual Low Level RF (LLRF) control systems. One control system is based on the standard SNS Linac LLRF controls with a second system for open-loop only control. The system is designed to allow simultaneous testing of devices in the test cave and other devices which can be tested outside of the enclosure. Initial tests have shown good results; some improvements are yet to be implemented.

  5. Infection prevention and control practitioners: improving engagement.

    PubMed

    Aziz, Ann-Marie

    Every healthcare worker plays a vital part in minimising the risk of cross infection. Infection prevention and control (IPC) practitioners have the skills and competencies to assist organisations in improving engagement among staff and play a vital part in achieving this. IPC practitioners have skills in clinical practice, education, research and leadership, and these skills ensure high-quality care for patients and support strategies for engaging staff. This article highlights how IPC practitioners' skills and competencies are required for preventing infection and improving staff engagement. Engaged staff generate positive outcomes for both patients and staff, which is a welcome result for all healthcare organisations.

  6. Improving infection control in general practice.

    PubMed

    Farrow, S C; Zeuner, D; Hall, C

    1999-03-01

    Infection control measures in the health care setting should protect patients and staff from cross-infection. The prevention of harm is an essential part of good medical practice and failure might result in professional misconduct proceedings by the General Medical Council (GMC) and prosecution under the Health and Safety at Work legislation, as well as civil liability. For a health authority, overall responsibility for public health includes arrangements for the control of communicable diseases and infection in hospital and the community (NHS Management Executive, 1993), a function usually led by the Consultant in Communicable Disease Control (CCDC). This paper describes one district's collaborative approach between public health and GPs to assess and improve local infection control standards.

  7. Rf feedback free electron laser

    DOEpatents

    Brau, C.A.; Swenson, D.A.; Boyd, T.J. Jr.

    1979-11-02

    A free electron laser system and electron beam system for a free electron laser are provided which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

  8. Rf Feedback free electron laser

    DOEpatents

    Brau, Charles A.; Swenson, Donald A.; Boyd, Jr., Thomas J.

    1981-01-01

    A free electron laser system and electron beam system for a free electron laser which use rf feedback to enhance efficiency. Rf energy is extracted from an electron beam by decelerating cavities and returned to accelerating cavities using rf returns such as rf waveguides, rf feedthroughs, etc. This rf energy is added to rf klystron energy to lower the required input energy and thereby enhance energy efficiency of the system.

  9. R&D ERL: Low level RF

    SciTech Connect

    Smith, K.

    2010-01-15

    A superconducting RF (SRF) Energy Recovery Linac (ERL) is currently under development at the Collider-Accelerator Department (C-AD) at Brookhaven National Laboratory (BNL). The major components from an RF perspective are (a) a 5-cell SRF ERL cavity, (b) an SRF photocathode electron gun, and (c) a drive laser for the photocathode gun. Each of these RF subsystems has its own set of RF performance requirements, as well as common requirements for ensuring correct synchronism between them. A low level RF (LLRF) control system is currently under development, which seeks to leverage both technology and experience gained from the recently commissioned RHIC LLRF system upgrade. This note will review the LLRF system requirements and describe the system to be installed at the ERL.

  10. Ventilation equations for improved exothermic process control.

    PubMed

    McKernan, John L; Ellenbecker, Michael J

    2007-04-01

    Exothermic or heated processes create potentially unsafe work environments for an estimated 5-10 million American workers each year. Excessive heat and process contaminants have the potential to cause acute health effects such as heat stroke, and chronic effects such as manganism in welders. Although millions of workers are exposed to exothermic processes, insufficient attention has been given to continuously improving engineering technologies for these processes to provide effective and efficient control. Currently there is no specific occupational standard established by OSHA regarding exposure to heat from exothermic processes, therefore it is important to investigate techniques that can mitigate known and potential adverse occupational health effects. The current understanding of engineering controls for exothermic processes is primarily based on a book chapter written by W. C. L. Hemeon in 1955. Improvements in heat transfer and meteorological theory necessary to design improved process controls have occurred since this time. The research presented involved a review of the physical properties, heat transfer and meteorological theories governing buoyant air flow created by exothermic processes. These properties and theories were used to identify parameters and develop equations required for the determination of buoyant volumetric flow to assist in improving ventilation controls. Goals of this research were to develop and describe a new (i.e. proposed) flow equation, and compare it to currently accepted ones by Hemeon and the American Conference of Governmental Industrial Hygienists (ACGIH). Numerical assessments were conducted to compare solutions from the proposed equations for plume area, mean velocity and flow to those from the ACGIH and Hemeon. Parameters were varied for the dependent variables and solutions from the proposed, ACGIH, and Hemeon equations for plume area, mean velocity and flow were analyzed using a randomized complete block statistical

  11. Improvement of corrosion protection property of Mg-alloy by DLC and Si-DLC coatings with PBII technique and multi-target DC-RF magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Masami, Ikeyama; Setsuo, Nakao; Tsutomu, Sonoda; Junho, Choi

    2009-05-01

    Magnesium alloys have been considered as one of the most promising light weight materials with potential applications for automobile and aircraft components. Their poor corrosion resistance, however, has to date prevented wider usage. Diamond-like carbon (DLC) and silicon-incorporated DLC (Si-DLC) coatings are known to provide a high degree of corrosion protection, and hold accordingly promise for enhancing the corrosion resistance of the magnesium alloys. In this work we have studied the effect of coating conditions of DLC coatings as well as Si incorporation into coating on corrosion resistance, deposited onto AZ91 magnesium alloy substrates by plasma based ion implantation (PBII). The influences of a Ti interlayer beneath the DLC, Si-DLC and Ti incorporated DLC (Ti-DLC) coatings fabricated by multi-target direct-current radio-frequency (DC-RF) magnetron sputtering were also examined on both the adhesion strength and corrosion resistance of the materials. We have also examined the effect of the Si content in the Si-DLC coatings made by magnetron sputtering on the alloys' corrosion resistance. The results of potentiodynamic polarization measurements demonstrate that Si-DLC coating deposited by PBII exhibits the highest corrosion resistance in an aqueous 0.05 M NaCl solution. Although Ti layer is helpful in increasing adhesion between DLC coating and AZ91 substrate, it also influences adversely corrosion protection. The ozone treatment of the magnesium alloy's surface before the formation of coatings has been found to improve both adhesion strength and corrosion resistance.

  12. RF study and 3-D simulations of a side-coupling thermionic RF-gun

    NASA Astrophysics Data System (ADS)

    Rimjaem, S.; Kusoljariyakul, K.; Thongbai, C.

    2014-02-01

    A thermionic RF-gun for generating ultra-short electron bunches was optimized, developed and used as a source at a linac-based THz radiation research laboratory of the Plasma and Beam Physics Research Facility, Chiang Mai University, Thailand. The RF-gun is a π/2-mode standing wave structure, which consists of two S-band accelerating cells and a side-coupling cavity. The 2856 MHz RF wave is supplied from an S-band klystron to the gun through the waveguide input-port at the cylindrical wall of the second cell. A fraction of the RF power is coupled from the second cell to the first one via a side-coupling cavity. Both the waveguide input-port and the side-coupling cavity lead to an asymmetric geometry of the gun. RF properties and electromagnetic field distributions inside the RF-gun were studied and numerically simulated by using computer codes SUPERFISH 7.19 and CST Microwave Studio 2012©. RF characterizations and tunings of the RF-gun were performed to ensure the reliability of the gun operation. The results from 3D simulations and measurements are compared and discussed in this paper. The influence of asymmetric field distributions inside the RF-gun on the electron beam properties was investigated via 3D beam dynamics simulations. A change in the coupling-plane of the side-coupling cavity is suggested to improve the gun performance.

  13. Electrical characterization of rf plasmas

    SciTech Connect

    Miller, P.A.

    1991-08-01

    Radio-frequency (rf) electrical sources are commonly used to generate plasmas for processing of industrial materials and for related experimental work. Published descriptions of such plasmas usually include generator-power measurements, and occasionally include plasma dc-bias measurements. One or both of these quantitites are also used in industrial feedback ccontrol systems for setpoint regulation. Recent work at Sandia an elsewhere with an experimental rf discharge device (the GEC RF Reference Cell'') has shown that power and dc-bias levels are often insufficient information for specifying the state of the plasma. The plasma can have nonlinear electrical characteristics that cause harmonic generation, and the harmonic levels can depend sensitively on the impedance of the external circuitry at harmonic frequencies. Even though the harmonics may be low in amplitude, they can be directly related to large changes in plasma power and to changes in optical emission from the plasma. Consequently, in order for a worker to truly master the plasma-generation process, it is necessary to understand, measure, and control electrical characteristics of the plamsa. In this paper we describe technique that have been developed from work with the Reference Cell for making electrical measurements on rf plasmas, and we describe surprising observations of harmonic behavior. 10 refs., 4 figs.

  14. RF Power and HOM Coupler Tutorial

    SciTech Connect

    Rusnak, B

    2003-10-28

    Radio frequency (RF) couplers are used on superconducting cavities to deliver RF power for creating accelerating fields and to remove unwanted higher-order mode power for reducing emittance growth and cryogenic load. RF couplers in superconducting applications present a number of interdisciplinary design challenges that need to be addressed, since poor performance in these devices can profoundly impact accelerator operations and the overall success of a major facility. This paper will focus on critical design issues for fundamental and higher order mode (HOM) power couplers, highlight a sampling of reliability-related problems observed in couplers, and discuss some design strategies for improving performance.

  15. Improved methodology for generating controlled test atmospheres.

    PubMed

    Miller, R R; Letts, R L; Potts, W J; McKenna, M J

    1980-11-01

    Improved methodology has been developed for generating controlled test atmospheres. Vaporization of volatile liquids is accomplished in a 28 mm (O.D.) glass J-tube in conjunction with a compressed air flameless heat torch, a pressure-sensitive switch, and a positive displacement piston pump. The vaporization system has been very reliable with a variety of test materials in studies ranging from a few days to several months. The J-tube vaporization assembly minimizes the possibility of thermal decomposition of the test material and affords a better margin of safety when vaporizing potentially explosive materials.

  16. Local SAR management by RF shimming: a simulation study with multiple human body models.

    PubMed

    Homann, Hanno; Graesslin, Ingmar; Eggers, Holger; Nehrke, Kay; Vernickel, Peter; Katscher, Ulrich; Dössel, Olaf; Börnert, Peter

    2012-06-01

    Parallel transmission facilitates a relatively direct control of the RF transmit field. This is usually applied to improve the RF field homogeneity but might also allow a reduction of the specific absorption rate (SAR) to increase freedom in sequence design for high-field MRI. However, predicting the local SAR is challenging as it depends not only on the multi-channel drive but also on the individual patient. The potential of RF shimming for SAR management is investigated for a 3 T body coil with eight independent transmit elements, based on Finite-Difference Time-Domain (FDTD) simulations. To address the patient-dependency of the SAR, nine human body models were generated from volunteer MR data and used in the simulations. A novel approach to RF shimming that enforces local SAR constraints is proposed. RF shimming substantially reduced the local SAR, consistently for all volunteers. Using SAR constraints, a further SAR reduction could be achieved with only minor compromises in RF performance. Parallel transmission can become an important tool to control and manage the local SAR in the human body. The practical use of local SAR constraints is feasible with consistent results for a variety of body models.

  17. RF radiation from lightning

    NASA Technical Reports Server (NTRS)

    Levine, D. M.

    1978-01-01

    Radiation from lightning in the RF band from 3-300 MHz were monitored. Radiation in this frequency range is of interest as a potential vehicle for monitoring severe storms and for studying the lightning itself. Simultaneous measurements were made of RF radiation and fast and slow field changes. Continuous analogue recordings with a system having 300 kHz of bandwidth were made together with digital records of selected events (principally return strokes) at greater temporal resolution. The data reveal patterns in the RF radiation for the entire flash which are characteristic of flash type and independent of the frequency of observation. Individual events within the flash also have characteristic RF patterns. Strong radiation occurs during the first return strokes, but delayed about 20 micron sec with respect to the begining of the return stroke; whereas, RF radiation from subsequent return strokes tends to be associated with cloud processes preceding the flash with comparatively little radiation occurring during the return stroke itself.

  18. Implementing New Methods of Laser Marking of Items in the Nuclear Material Control and Accountability System at SSC RF-IPPE: An Automated Laser Marking System

    SciTech Connect

    Regoushevsky, V I; Tambovtsev, S D; Dvukhsherstnov, V G; Efimenko, V F; Ilyantsev, A I; Russ III, G P

    2009-05-18

    For over ten years SSC RF-IPPE, together with the US DOE National Laboratories, has been working on implementing automated control and accountability methods for nuclear materials and other items. Initial efforts to use adhesive bar codes or ones printed (painted) onto metal revealed that these methods were inconvenient and lacked durability under operational conditions. For NM disk applications in critical stands, there is the additional requirement that labels not affect the neutron characteristics of the critical assembly. This is particularly true for the many stainless-steel clad disks containing highly enriched uranium (HEU) and plutonium that are used at SSC RF-IPPE for modeling nuclear power reactors. In search of an alternate method for labeling these disks, we tested several technological options, including laser marking and two-dimensional codes. As a result, the method of laser coloring was chosen in combination with Data Matrix ECC200 symbology. To implement laser marking procedures for the HEU disks and meet all the nuclear material (NM) handling standards and rules, IPPE staff, with U.S. technical and financial support, implemented an automated laser marking system; there are also specially developed procedures for NM movements during laser marking. For the laser marking station, a Zenith 10F system by Telesis Technologies (10 watt Ytterbium Fiber Laser and Merlin software) is used. The presentation includes a flowchart for the automated system and a list of specially developed procedures with comments. Among other things, approaches are discussed for human-factor considerations. To date, markings have been applied to numerous steel-clad HEU disks, and the work continues. In the future this method is expected to be applied to other MC&A items.

  19. A 32-Channel Combined RF and B0 Shim Array for 3T Brain Imaging

    PubMed Central

    Stockmann, Jason P.; Witzel, Thomas; Keil, Boris; Polimeni, Jonathan R.; Mareyam, Azma; LaPierre, Cristen; Setsompop, Kawin; Wald, Lawrence L.

    2016-01-01

    Purpose We add user-controllable direct currents (DC) to the individual elements of a 32-channel radio-frequency (RF) receive array to provide B0 shimming ability while preserving the array’s reception sensitivity and parallel imaging performance. Methods Shim performance using constrained DC current (±2.5A) is simulated for brain arrays ranging from 8 to 128 elements. A 32-channel 3-tesla brain array is realized using inductive chokes to bridge the tuning capacitors on each RF loop. The RF and B0 shimming performance is assessed in bench and imaging measurements. Results The addition of DC currents to the 32-channel RF array is achieved with minimal disruption of the RF performance and/or negative side effects such as conductor heating or mechanical torques. The shimming results agree well with simulations and show performance superior to third-order spherical harmonic (SH) shimming. Imaging tests show the ability to reduce the standard frontal lobe susceptibility-induced fields and improve echo planar imaging geometric distortion. The simulation of 64- and 128-channel brain arrays suggest that even further shimming improvement is possible (equivalent to up to 6th-order SH shim coils). Conclusion Including user-controlled shim currents on the loops of a conventional highly parallel brain array coil is feasible with modest current levels and produces improved B0 shimming performance over standard second-order SH shimming. PMID:25689977

  20. A 32-channel combined RF and B0 shim array for 3T brain imaging.

    PubMed

    Stockmann, Jason P; Witzel, Thomas; Keil, Boris; Polimeni, Jonathan R; Mareyam, Azma; LaPierre, Cristen; Setsompop, Kawin; Wald, Lawrence L

    2016-01-01

    We add user-controllable direct currents (DC) to the individual elements of a 32-channel radio-frequency (RF) receive array to provide B0 shimming ability while preserving the array's reception sensitivity and parallel imaging performance. Shim performance using constrained DC current (± 2.5A) is simulated for brain arrays ranging from 8 to 128 elements. A 32-channel 3-tesla brain array is realized using inductive chokes to bridge the tuning capacitors on each RF loop. The RF and B0 shimming performance is assessed in bench and imaging measurements. The addition of DC currents to the 32-channel RF array is achieved with minimal disruption of the RF performance and/or negative side effects such as conductor heating or mechanical torques. The shimming results agree well with simulations and show performance superior to third-order spherical harmonic (SH) shimming. Imaging tests show the ability to reduce the standard frontal lobe susceptibility-induced fields and improve echo planar imaging geometric distortion. The simulation of 64- and 128-channel brain arrays suggest that even further shimming improvement is possible (equivalent to up to 6th-order SH shim coils). Including user-controlled shim currents on the loops of a conventional highly parallel brain array coil is feasible with modest current levels and produces improved B0 shimming performance over standard second-order SH shimming. © 2015 Wiley Periodicals, Inc.

  1. Flute stabilization due to ponderomotive force created by an rf field with a variable gradient

    SciTech Connect

    Yasaka, Y.; Itatani, R.

    1986-06-30

    An rf-stabilization experiment was performed in the axisymmetric single-mirror device HIEI by controlling the radial-gradient scale length of the rf field with the aid of an azimuthally phased antenna array. The flute stability depends sensitively on the scale length of the perpendicular rf electric field, which shows that rf stabilization is caused by the ponderomotive force for ions.

  2. Microfluidic stretchable RF electronics.

    PubMed

    Cheng, Shi; Wu, Zhigang

    2010-12-07

    Stretchable electronics is a revolutionary technology that will potentially create a world of radically different electronic devices and systems that open up an entirely new spectrum of possibilities. This article proposes a microfluidic based solution for stretchable radio frequency (RF) electronics, using hybrid integration of active circuits assembled on flex foils and liquid alloy passive structures embedded in elastic substrates, e.g. polydimethylsiloxane (PDMS). This concept was employed to implement a 900 MHz stretchable RF radiation sensor, consisting of a large area elastic antenna and a cluster of conventional rigid components for RF power detection. The integrated radiation sensor except the power supply was fully embedded in a thin elastomeric substrate. Good electrical performance of the standalone stretchable antenna as well as the RF power detection sub-module was verified by experiments. The sensor successfully detected the RF radiation over 5 m distance in the system demonstration. Experiments on two-dimensional (2D) stretching up to 15%, folding and twisting of the demonstrated sensor were also carried out. Despite the integrated device was severely deformed, no failure in RF radiation sensing was observed in the tests. This technique illuminates a promising route of realizing stretchable and foldable large area integrated RF electronics that are of great interest to a variety of applications like wearable computing, health monitoring, medical diagnostics, and curvilinear electronics.

  3. Reciprocal light-dark transcriptional control of nif and rbc expression and light-dependent posttranslational control of nitrogenase activity in Synechococcus sp. strain RF-1.

    PubMed

    Chow, T J; Tabita, F R

    1994-10-01

    Synechococcus sp. strain RF-1 exhibits a circadian rhythm of N2 fixation when cells are grown under a light-dark cycle, with nitrogenase activity observed only during the dark period. This dark-dependent activity correlated with nif gene transcription in strain RF-1. By using antibodies against dinitrogenase reductase (the Fe protein of the nitrogenase complex), it was found that there was a distinct shift in the mobility of this protein on sodium dodecyl sulfate gels during the light-dark cycle. The Fe protein was present only when cells were incubated in the dark. Upon illumination, there was a conversion of all Fe protein to a modified form, after which it rapidly disappeared from extracts. These studies indicated that all nitrogenase activity present during the dark cycle resulted from de novo synthesis of nitrogenase. Upon entering the light phase, cells appeared to quickly degrade the modified form of Fe protein, perhaps as a result of activating or inducing a protease. By contrast, transcription of the rbcL gene, which encodes the catalytic subunit of the key enzyme of CO2 fixation (a light-dependent process), was enhanced in the light.

  4. Improvement of the SOFIA secondary mirror controller

    NASA Astrophysics Data System (ADS)

    Reinacher, Andreas; Onillon, Emmanuel; Roeser, Hans-Peter

    2010-07-01

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a 2.5m infrared telescope build into a Boeing 747SP. During observations the telescope will not only be subject to aircraft vibrations and maneuver loads - by opening a large door to give the observatory an unhindered view of the sky, there will also be aerodynamic and aeroacoustic disturbances. A critical factor in the overall telescope performance is the SOFIA Secondary Mirror Assembly. The 35cm silicon carbide mirror is mounted on the Secondary Mirror Mechanism, which has five degrees-of-freedom (rotation about line of sight is blocked) and consists of two parts: The slow moving base for focusing and centering, and on top of that the Tilt Chop Mechanism (TCM) for chopping with a frequency of up to 20Hz and a chop throw of up to 10arcmin. A new controller for the TCM is introduced in this paper in order to meet the stringent performance requirements for the chopper. A state space controller is chosen that combines a feedback path for steady state behavior with a model-based feed forward controller for improved settling time performance. The paper explains the modeling of the TCM via a grey box model approach optimized with system identification data and compares simulated with measured data. Then the structure of the controller is explained and Matlab/Simulink simulations are presented. The simulation results are compared to measurements taken with the real system on ground and finally flight test results with open and closed door are discussed.

  5. RF waveguide phase-directed power combiners

    DOEpatents

    Nantista, Christopher D.; Dolgashev, Valery A.; Tantawi, Sami G.

    2017-05-02

    High power RF phase-directed power combiners include magic H hybrid and/or superhybrid circuits oriented in orthogonal H-planes and connected using E-plane bends and/or twists to produce compact 3D waveguide circuits, including 8.times.8 and 16.times.16 combiners. Using phase control at the input ports, RF power can be directed to a single output port, enabling fast switching between output ports for applications such as multi-angle radiation therapy.

  6. Recent Advancements of RF Guns

    NASA Astrophysics Data System (ADS)

    Faillace, Luigi

    High-brightness, high-current electron beams are the main requirement for fourth generation light sources such as free-electron lasers (FELs), energy recovery Linacs (ERLs) and high-energy linear colliders. The most successful device for producing such beams is the Radio-Frequency (RF) photoinjector that has been undergoing a constant evolution over the past nearly 30 years towards the production of ever-lower beam emittances and higher currents. The on-going progress in the technology of higher quality materials as well as the enhanced quality of laser pulse shaping have allowed huge improvements in the generation of higher-quality electron beams. Here, it is presented an overview of recent advancements and future perspectives of RF photoinjectors for a fifth generation light source.

  7. Improved Topology Control Algorithm for MANETs

    NASA Astrophysics Data System (ADS)

    Hamad, Hatem

    2008-06-01

    A mobile wireless ad hoc network is formed dynamically without a need for a pre-existing infrastructure. Frequent Topology changes leads to more processing and hence more power consumption. Reducing power consumption during node's life time is a challenging task. Adaptive Self-Configuring sEnsor Networks Topologies (ASCENT) is a topology control technique for reducing the power consumption during the node lifetime. In ASCENT, each node assesses its connectivity and adapts its participation in the multi-hop network topology based on the operating region. In this paper, I study some of the problems in ASCENT algorithm and propose a modified state diagram, which adaptively adjusts the states of individual nodes, to reduce redundancy. This helps to achieve the optimum number of Active nodes in the network. I implement the modified state diagram, and simulation results highlight that the improved ASCENT state diagram is able to achieve better performance than the original ASCENT algorithm.

  8. Improving Symptom Control in Early Parkinson's Disease

    PubMed Central

    Hauser, Robert A.

    2009-01-01

    Motor symptoms in Parkinson's disease (PD) are caused by a severe loss of pigmented dopamine-producing nigro-striatal neurons. Symptomatic therapies provide benefit for motor features by restoring dopamine receptor stimulation. Studies have demonstrated that delaying the introduction of dopaminergic medical therapy is associated with a rapid decline in quality of life. Nonmotor symptoms, such as depression, are common in early PD and also affect quality of life. Therefore, dopaminergic therapy should typically be initiated at, or shortly following, diagnosis. Monamine oxidase-B inhibitors provide mild symptomatic benefit, have excellent side effect profiles, and may improve long-term outcomes, making them an important first-line treatment option. Dopamine agonists (DAs) provide moderate symptomatic benefit but are associated with more side effects than levodopa. However, they delay the development of motor complications by delaying the need for levodopa. Levodopa (LD) is the most efficacious medication, but its chronic use is associated with the development of motor complications that can be difficult to resolve. Younger patients are more likely to develop levodopa-induced motor complications and they are therefore often treated with a DA before levodopa is added. For older patients, levodopa provides good motor benefit with a relatively low-risk of motor complications. Using levodopa with a dopa-decarboxylase inhibitor lessens adverse effects, and further adding a catechol-O-methyl transferase inhibitor can improve symptom control. PMID:21180628

  9. The upgraded rf system for the AGS and high intensity proton beams

    SciTech Connect

    Brennan, J.M.

    1995-05-01

    The AGS has been upgraded over the past three years to produce a record beam intensity of 6 {times} 10{sup 13} protons per pulse for the fixed-target physics program. The major elements of the upgrade are: the new 1.5 GeV Booster synchrotron, the main magnet power supply, a high frequency longitudinal dilution cavity, a feedback damper for transverse instabilities, a fast gamma transition jump system, and a new high-power rf system. The new rf system and its role in achieving the high intensity goal are the subjects of this report. The rf system is heavily beam loaded, with 7 Amps of rf current in the beam and a peak power of 0.75 MW delivered to the beam by ten cavities. As an example of the scale of beam loading, at one point in the acceleration cycle the cavities are operated at 1.5 kV/gap; whereas, were it not for the new power amplifiers, the beam-induced voltage on the cavities would be over 25 kV/gap. The upgraded rf system, comprising: new power amplifiers, wide band rf feedback, improved cavities, and new low-level beam control electronics, is described. Results of measurements with beam, which characterize the system`s performance, are presented. A typical high intensity acceleration cycle is described with emphasis on the key challenges of beam loading.

  10. Pregnant women models analyzed for RF exposure and temperature increase in 3T RF shimmed birdcages.

    PubMed

    Murbach, Manuel; Neufeld, Esra; Samaras, Theodoros; Córcoles, Juan; Robb, Fraser J; Kainz, Wolfgang; Kuster, Niels

    2017-05-01

    MRI is increasingly used to scan pregnant patients. We investigated the effect of 3 Tesla (T) two-port radiofrequency (RF) shimming in anatomical pregnant women models. RF shimming improves B1(+) uniformity, but may at the same time significantly alter the induced current distribution and result in large changes in both the level and location of the absorbed RF energy. In this study, we evaluated the electrothermal exposure of pregnant women in the third, seventh, and ninth month of gestation at various imaging landmarks in RF body coils, including modes with RF shimming. Although RF shimmed configurations may lower the local RF exposure for the mother, they can increase the thermal load on the fetus. In worst-case configurations, whole-body exposure and local peak temperatures-up to 40.8°C-are equal in fetus and mother. Two-port RF shimming can significantly increase the fetal exposure in pregnant women, requiring further research to derive a very robust safety management. For the time being, restriction to the CP mode, which reduces fetal SAR exposure compared with linear-horizontal polarization modes, may be advisable. Results from this study do not support scanning pregnant patients above the normal operating mode. Magn Reson Med 77:2048-2056, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

  11. Non-targeted metabolomics analysis of cardiac Muscle Ring Finger-1 (MuRF1), MuRF2, and MuRF3 in vivo reveals novel and redundant metabolic changes.

    PubMed

    Banerjee, Ranjan; He, Jun; Spaniel, Carolyn; Quintana, Megan T; Wang, Zhongjing; Bain, James; Newgard, Christopher B; Muehlbauer, Michael J; Willis, Monte S

    2015-04-01

    The muscle-specific ubiquitin ligases MuRF1, MuRF2, MuRF3 have been reported to have overlapping substrate specificities, interacting with each other as well as proteins involved in metabolism and cardiac function. In the heart, all three MuRF family proteins have proven critical to cardiac responses to ischemia and heart failure. The non-targeted metabolomics analysis of MuRF1-/-, MuRF2-/-, and MuRF3-/- hearts was initiated to investigate the hypothesis that MuRF1, MuRF2, and MuRF3 have a similarly altered metabolome, representing alterations in overlapping metabolic processes. Ventricular tissue was flash frozen and quantitatively analyzed by GC/MS using a library built upon the Fiehn GC/MS Metabolomics RTL Library. Non-targeted metabolomic analysis identified significant differences (via VIP statistical analysis) in taurine, myoinositol, and stearic acid for the three MuRF-/- phenotypes relative to their matched controls. Moreover, pathway enrichment analysis demonstrated that MuRF1-/- had significant changes in metabolite(s) involved in taurine metabolism and primary acid biosynthesis while MuRF2-/- had changes associated with ascorbic acid/aldarate metabolism (via VIP and t-test analysis vs. sibling-matched wildtype controls). By identifying the functional metabolic consequences of MuRF1, MuRF2, and MuRF3 in the intact heart, non-targeted metabolomics analysis discovered common pathways functionally affected by cardiac MuRF family proteins in vivo. These novel metabolomics findings will aid in guiding the molecular studies delineating the mechanisms that MuRF family proteins regulate metabolic pathways. Understanding these mechanism is an important key to understanding MuRF family proteins' protective effects on the heart during cardiac disease.

  12. Non-targeted metabolomics analysis of cardiac Muscle Ring Finger-1 (MuRF1), MuRF2, and MuRF3 in vivo reveals novel and redundant metabolic changes

    PubMed Central

    Banerjee, Ranjan; He, Jun; Spaniel, Carolyn; Quintana, Megan T.; Wang, Zhongjing; Bain, James; Newgard, Christopher B.; Muehlbauer, Michael J.; Willis, Monte S.

    2017-01-01

    The muscle-specific ubiquitin ligases MuRF1, MuRF2, MuRF3 have been reported to have overlapping substrate specificities, interacting with each other as well as proteins involved in metabolism and cardiac function. In the heart, all three MuRF family proteins have proven critical to cardiac responses to ischemia and heart failure. The non-targeted metabolomics analysis of MuRF1-/-, MuRF2-/-, and MuRF3-/- hearts was initiated to investigate the hypothesis that MuRF1, MuRF2, and MuRF3 have a similarly altered metabolome, representing alterations in overlapping metabolic processes. Ventricular tissue was flash frozen and quantitatively analyzed by GC/MS using a library built upon the Fiehn GC/MS Metabolomics RTL Library. Non-targeted metabolomic analysis identified significant differences (via VIP statistical analysis) in taurine, myoinositol, and stearic acid for the three MuRF-/- phenotypes relative to their matched controls. Moreover, pathway enrichment analysis demonstrated that MuRF1-/- had significant changes in metabolite(s) involved in taurine metabolism and primary acid biosynthesis while MuRF2-/- had changes associated with ascorbic acid/aldarate metabolism (via VIP and t-test analysis vs. sibling-matched wildtype controls). By identifying the functional metabolic consequences of MuRF1, MuRF2, and MuRF3 in the intact heart, non-targeted metabolomics analysis discovered common pathways functionally affected by cardiac MuRF family proteins in vivo. These novel metabolomics findings will aid in guiding the molecular studies delineating the mechanisms that MuRF family proteins regulate metabolic pathways. Understanding these mechanism is an important key to understanding MuRF family proteins' protective effects on the heart during cardiac disease. PMID:28325996

  13. Rf power sources

    SciTech Connect

    Allen, M.A.

    1988-05-01

    This paper covers RF power sources for accelerator applications. The approach has been with particular customers in mind. These customers are high energy physicists who use accelerators as experimental tools in the study of the nucleus of the atom, and synchrotron light sources derived from electron or positron storage rings. This paper is confined to electron-positron linear accelerators since the RF sources have always defined what is possible to achieve with these accelerators. 11 refs., 13 figs.

  14. Microbunching and RF Compression

    SciTech Connect

    Venturini, M.; Migliorati, M.; Ronsivalle, C.; Ferrario, M.; Vaccarezza, C.

    2010-05-23

    Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.

  15. The RF Design of an HOM Polarized RF Gun for the ILC

    SciTech Connect

    Wang, J.W.; Clendenin, J.E.; Colby, E.R.; Miller, R.A.; Lewellen, J.W.; /Argonne

    2006-11-15

    The ILC requires a polarized electron beam. While a highly polarized beam can be produced by a GaAs-type cathode in a DC gun of the type currently in use at SLAC, JLAB and elsewhere, the ILC injector system can be simplified and made more efficient if a GaAs-type cathode can be combined with a low emittance RF gun. Since this type of cathode is known to be extremely sensitive to vacuum contamination including back bombardment by electrons and ions, any successful polarized RF gun must have a significantly improved operating vacuum compared to existing RF guns. We present a new RF design for an L-Band normal conducting (NC) RF gun for the ILC polarized electron source. This design incorporates a higher order mode (HOM) structure, whose chief virtue in this application is an improved conductance for vacuum pumping on the cathode. Computer simulation models have been used to optimize the RF parameters with two principal goals: first to minimize the required RF power; second to reduce the peak surface field relative to the field at the cathode in order to suppress field emitted electron bombardment. The beam properties have been simulated initially using PARMELA. Vacuum and other practical issues for implementing this design are discussed.

  16. Timing control improves seabed survey data quality

    SciTech Connect

    Green, R.

    1996-04-01

    Seateam has completed development of and field-proven the Dolphin data acquisition and timing system for high-density surveys offshore. The Dolphin project was initiated to improve quality control of survey sensor data and ensure time synchronization, thus leading to faster turnaround of seabed terrain information. Data received from survey sensors is asynchronous, so the system must provide for data correlation. This includes establishment of data latency, i.e., the time difference between data creation and timing of the message at first-byte arrival at the recording system. Until recently, asynchronous data from multiple sensors was collected by a single computer, regardless of whether it had additional intelligent or non-intelligent serial cards. This computer was fully responsible for time stamping all incoming data, plus associated storage and distribution. Though this initially sufficed and is still applicable to low-density data, increasingly larger data volumes required an associated boost in the capability to time stamp data prior to eventual correction.

  17. Improving conveyor efficiency by controlling fugitive material

    SciTech Connect

    Goldbeck, L.J.

    1996-11-01

    The conveyor belt has been identified as one of the major sources of what call DURT-fugitive material that escapes from bulk handling systems. This presentation is focused on ways to dramatically improve belt conveyor designs to control DURT. This information can`t be found in any of the computer design software currently used to guide engineers. It is the result of the author`s examination of DURT-generating conveyors all over the world, in all types of industries. The solution to conveyor DURT starts with the client--the people who will live with the conveyor and its fugitive material on a daily basis. Too often the client specifies the tonnage he expects the conveyor to deliver but does not include in the same specification a target for cleanliness. Until these specifications list a quantitative amount of belt carryback permissible and the amount of spillage allowed to leak out at the transfer points--and until design and engineering firms are held accountable for these performance levels--belt conveyors will continue to be a major source of DURT. This paper examines a typical conveyor transfer point and reviews a number of items that are seldom given more than a cursory look at the design stage, but which can contribute heavily to fugitive material problems.

  18. Station to instrumented aircraft L-band telemetry system and RF signal controller for spacecraft simulations and station calibration

    NASA Technical Reports Server (NTRS)

    Scaffidi, C. A.; Stocklin, F. J.; Feldman, M. B.

    1971-01-01

    An L-band telemetry system designed to provide the capability of near-real-time processing of calibration data is described. The system also provides the capability of performing computerized spacecraft simulations, with the aircraft as a data source, and evaluating the network response. The salient characteristics of a telemetry analysis and simulation program (TASP) are discussed, together with the results of TASP testing. The results of the L-band system testing have successfully demonstrated the capability of near-real-time processing of telemetry test data, the control of the ground-received signal to within + or - 0.5 db, and the computer generation of test signals.

  19. VERSE-guided parallel RF excitations using dynamic field correction.

    PubMed

    Çavuşoğlu, Mustafa; Mooiweer, Ronald; Pruessmann, Klaas P; Malik, Shaihan J

    2017-02-17

    In parallel RF pulse design, peak RF magnitudes and specific absorption rate levels are critical concerns in the hardware and safety limits. The variable rate selective excitation (VERSE) method is an efficient technique to limit the peak RF power by applying a local-only RF and gradient waveform reshaping while retaining the on-resonance profile. The accuracy of the excitation performed by the VERSEd RF and gradient waveforms strictly depends on the performance of the employed hardware. Any deviation from the nominal gradient fields as a result of frequency dependent system imperfections violates the VERSE condition similarly to off-resonance effects, leading to significant excitation errors and the RF pulse not converging to the targeted peak RF power. Moreover, for iterative VERSE-guided RF pulse design (i.e. reVERSE), the k-space trajectory actually changes at every iteration, which is assumed to be constant. In this work, we show both theoretically and experimentally the effect of gradient system imperfections on iteratively VERSEd parallel RF excitations. In order to improve the excitation accuracy besides limiting the RF power below certain thresholds, we propose to integrate gradient field monitoring or gradient impulse response function (GIRF) estimations of the actual gradient fields into the RF pulse design problem. A third-order dynamic field camera comprising a set of NMR field sensors and GIRFs was used to measure or estimate the actual gradient waveforms that are involved in the VERSE algorithm respectively. The deviating and variable k-space is counteracted at each iteration of the VERSE-guided iterative RF pulse design. The proposed approaches are demonstrated for accelerated multiple-channel spatially selective RF pulses, and highly improved experimental performance was achieved at both 3 T and 7 T.

  20. Controlling the object phase for g-factor reduction in phase-Constrained parallel MRI using spatially selective RF pulses.

    PubMed

    Kettinger, Adam O; Kannengiesser, Stephan A R; Breuer, Felix A; Vidnyanszky, Zoltan; Blaimer, Martin

    2017-09-01

    Parallel imaging generally entails a reduction in the signal-to-noise ratio of the final image. Phase-constrained methods aim to improve reconstruction quality by using symmetry properties of k-space. Noise amplification in phase-constrained reconstruction depends heavily on the object background phase. The purpose of this work is to present a new approach of using tailored radiofrequency pulses to optimize the object phase distribution in order to maximize the benefit of phase-constrained reconstruction, and to minimize the noise amplification. Intrinsic object phase and coil sensitivity profiles are measured in a prescan. Optimal phase distribution is computed to maximize signal-to-noise ratio in the given setup. Tailored radiofrequency pulses are designed to introduce the optimal phase map in the following accelerated acquisitions, subsequently reconstructed by phase-constrained methods. The potential of the method is demonstrated in vivo with in-plane accelerated (8x) and simultaneous multislice (3x) acquisitions. Mean g-factors are reduced by up to a factor of 2 compared with conventional techniques when an appropriate phase-constrained reconstruction is applied to phase-optimized acquisitions, enhancing the signal-to-noise ratio of the final images and the visibility of small details. Combining phase-constrained reconstruction and phase optimization by tailored radiofrequency pulses can provide notable improvement in the signal-to-noise ratio and reconstruction quality of accelerated MRI. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  1. Controlled surface modification of Ti-40Nb implant alloy by electrochemically assisted inductively coupled RF plasma oxidation.

    PubMed

    Göttlicher, Markus; Rohnke, Marcus; Helth, Arne; Leichtweiß, Thomas; Gemming, Thomas; Gebert, Annett; Eckert, Jürgen; Janek, Jürgen

    2013-11-01

    Low temperature metal oxidation induced by plasma in the absence of liquid electrolytes can be useful for the surface preparation of orthopedic devices since residues from these may be harmful and need to be removed before implantation. In this study the oxidation of Ti-40Nb for biomedical application was achieved by employing an inductively coupled radio frequency oxygen plasma. The correlation between the growth mode of the surface oxide and the electric conductivity ratio of the plasma and the oxide phase were studied by varying the sample temperature, oxygen gas pressure and additional bias potential. The plasma treated samples were characterised by confocal laser microscopy, SEM, EBSD, XPS, TEM and ToF-SIMS. The surface energy was determined by contact angle measurements using the Owens-Wendt-Rabel-Kaelble method. Well adhering oxide layers consisting of TiO2 and Nb2O5 with thicknesses between 50 and 150 nm were obtained. Surface roughness values and microstructure indicate that the growth mode of the oxide can be well controlled by the sample temperature and oxygen gas pressure. At temperatures above 450°C a migration of Ti ions towards the surface controls the growth process. A bias potential higher than +50 V causes rough and defective surfaces with high surface energies. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Control of electron energy distribution by the power balance of the combined inductively and capacitively coupled RF plasmas

    NASA Astrophysics Data System (ADS)

    Kim, Jin Seok; Lee, Ho-Jun; Lee, Hae June

    2016-09-01

    The control of electron energy probability function (EEPF) is important to control discharge characteristics in materials processing. For example, O radical density increases by changing the EEPF in O2 plasma, which provides high etching efficiency. The effect of the power balance between the capacitively coupled plasma (CCP) and the inductively coupled plasma (ICP) on the EEPF in Ar and O2 plasmas is investigated with a 1d3v (one-dimensional space and three-dimensional velocity domain) particle-in-cell (PIC) simulation for the combined inductively and capacitively coupled plasmas. The combined effects of the transverse electromagnetic and the longitudinal electrostatic fields are solved in PIC simulation at the same time. In a pressure range of a few mTorr, high energy electrons (>5 eV) are heated by the capacitive power in the sheath while low energy electrons (<5 eV) are heated by the inductive power in the bulk region. The EEPF has bi-Maxwellian distribution when the CCP power is dominant, but it changes to Maxwellian-like distribution with increasing inductive power. Finally, the EEPF changes to Druyvesteyn-like distribution when the inductive power is dominant.

  3. RF Wave Propagation and Scattering in Tokamaks

    NASA Astrophysics Data System (ADS)

    Horton, Wendell; Goniche, Marc; Arefiev, Alex; Peysson, Yves; Ekedahl, Annika; InstituteFusion Studies Collaboration; IRFM CEA Collaboration

    2016-10-01

    The propagation, scattering and absorption of the lower hybrid and electron cyclotron RF waves used to control fusion plasmas is reviewed. Drift wave turbulence driven by the steep ion and electron temperature gradients in H-mode divertor tokamaks produces strong scattering of the RF waves used for heating and plasma currents drive Both the 3-5GHz lower-hybrid (LH) and the 170GHZ electron cyclotron (EC) waves experience scattering and diffraction as propagating through the statistically complex density of the plasma. Ray equations are used to calculate the spread of the rays and the associated change in the parallel phase, polarization and group velocity of the RF waves in the propagation through the fusion plasma. A Fokker Planck equation for the phase space of the RF plasmons is one method to describe the spread of the RF wave power in the complex geometry of a divertor tokamak using the ray tracing codes. The evolution of the electron distribution function from the resonant electron-wave interactions is summarized for several scenarios. The resulting X-ray spectrum is broaden giving better agreement with the measured X-ray spectrum than that calculated in the absence of the turbulent scattering of the RF waves. M. Goniche et al., and Tore Supra Team, Phys. Plasmas 21, 2014.

  4. Efficient high-resolution RF pulse design applied to simultaneous multi-slice excitation

    NASA Astrophysics Data System (ADS)

    Aigner, Christoph Stefan; Clason, Christian; Rund, Armin; Stollberger, Rudolf

    2016-02-01

    RF pulse design via optimal control is typically based on gradient and quasi-Newton approaches and therefore suffers from slow convergence. We present a flexible and highly efficient method that uses exact second-order information within a globally convergent trust-region CG-Newton method to yield an improved convergence rate. The approach is applied to the design of RF pulses for single- and simultaneous multi-slice (SMS) excitation and validated using phantom and in vivo experiments on a 3 T scanner using a modified gradient echo sequence.

  5. Simulation and analysis of rf feedback systems on the SLC damping rings

    SciTech Connect

    Minty, M.; Himel, T.; Krejcik, P.; Siemann, R.H.; Tighe, R.

    1993-09-01

    The rf system of the SLC Damping Rings has evolved since tighter tolerances on beam stability are encountered as beam intensities are increased. There are now many feedback systems controlling the phase and amplitude of the rf, the phase of the beam, and the tune of the cavity. The bandwidths of the feedback loops range from several MHz to compensate for beam loading to a few Hz for the cavity tuners. To improve our understanding of the interaction of these loops and verify the expected behavior, we have simulated their behavior using computer models. A description of the models and the first results are discussed.

  6. Residual stress improvement of platinum thin film in Au/Pt/Ti/p-GaAs ohmic contact by RF sputtering power

    NASA Astrophysics Data System (ADS)

    Parvizian, M.; Rahimi-Ashtari, F.; Goodarzi, A.; Sabrloui, B.; Sabaghzade, J.; Zabihi, M. S.

    2012-11-01

    This work seeks to characterize residual stress and microstructure of platinum thin film in Au/Pt/Ti/p-GaAs ohmic contact. Platinum thin films are deposited on p-GaAs (1 0 0) wafer and SiO2 via patterned area on it by a RF sputtering deposition system while different deposition powers are considered. Evolution of residual stress, roughness and grain size of the films by changing the deposition power are studied. The residual stress is measured by substrate curvature method, and the microstructure of the films is considered by SEM and AFM analysis. AFM analyze shows that Pt layer roughness dramatically increases from 2.2 nm to 8.7 nm on SiO2 substrate and from 1.05 nm to 5 nm on GaAs substrate when power increases from 150 W to 300 W. Also SEM images show that grain size increases on either GaAs or SiO2 substrates and step coverage deteriorates by increasing the deposition power. Pt layer stress measurement shows that there is a minimum and suitable point at 200 W for GaAs substrate. Also it is observed that the platinum stress changes from tensile to compressive for SiO2 substrate when RF deposition power increases from 200 W to 250 W.

  7. The effect of realistic surface coefficients on the electron dynamics and process control in simulations of capacitive RF plasmas

    NASA Astrophysics Data System (ADS)

    Daksha, Manaswi; Berger, Birk; Schulze, Julian; Derzsi, Aranka; Korolov, Ihor; Donko, Zoltan; Wilczek, Sebastian; Mussenbrock, Thomas

    2016-09-01

    In most PIC simulations of capacitively coupled plasmas (CCPs), only an ion induced constant secondary electron emission coefficient, γ, is used, which is usually guessed to be 0.1. Similarly, a constant electron reflection coefficient, ρ, is typically used and assumed to be 0 - 0.2. Here, we utilize an ion and atom induced energy-dependent γ for ``dirty'' and ``clean'' surfaces in a single frequency 13.56 MHz CCP. Its effects on electron heating mode transitions are analyzed as a function of pressure. By utilizing the same energy-dependent γ, its effects on the separate control of the ion flux and mean ion energy are studied for a dual frequency (df) CCP with frequencies of 2 and 27 MHz. The results are compared to multiple simulations with constant γ and significant differences are found. Finally, ρ is varied in a single frequency CCP and its effects on plasma parameters such as the sheath width and electron density are studied. Strong effects of using different reflection probabilities at both electrodes on the discharge symmetry are found. A df CCP is modeled to understand the coupling between the electrical asymmetry effect (EAE) and a discharge asymmetry induced by different electron reflection coefficients for the two electrodes.

  8. Effects of the wall boundary conditions of a showerhead plasma reactor on the uniformity control of RF plasma deposition

    NASA Astrophysics Data System (ADS)

    Kim, Ho Jun; Lee, Hae June

    2017-08-01

    Technical difficulties hinder the formation of uniform deposition profiles near the electrode edge during a deposition in a showerhead capacitively coupled plasma (CCP) reactor. The discharge structure, gas flow, and radial distribution of the source gas outward from the electrode edge are subject to change significantly, which in turn affects the spatial distributions of the radical fluxes toward the electrode. To control the local non-uniformity of deposition profiles in the SiH4/NH3/N2/He CCP discharges for a hydrogenated silicon nitride (SiNxHy) film, the effects of the reactor components―including the sidewall boundary condition, electrode spacing, and showerhead design―were investigated using an axisymmetric fluid model. When the sidewall is electrically grounded, the deposition rate profiles of the SiNxHy film remain consistently convex (in which the deposition rate at the reactor center is locally much higher than that near the electrode edge), regardless of electrode spacing. However, when the sidewall surface is dielectric, the deposition rate profile can be transformed between a convex and a concave shape (in which the deposition rate at the reactor center is locally much lower than that near the electrode edge) by varying electrode spacing. The showerhead design also enables the modification of edge deposition profiles by redistribution of the local depletion rate of radicals. The simulation results agree very well with the experimental measurement.

  9. Low frequency rf current drive. Annual progress report

    SciTech Connect

    Hershkowitz, N.

    1992-12-31

    An unshielded antenna for rf heating has been developed and tested during this report period. In addition to design specifications being given, some experimental results are presented utilizing: (1) an unprotected Faraday shield, (2) insulating guard limiters, (3) unshielded antenna experiments, (4) method for detecting small rf driven currents, (5) rf fast wave current drive experiments, (6) alfven wave interactions with electrons, and (7) machine conditioning, impurity generation and density control.

  10. Remotely controlled steerable sheath improves result and procedural parameters of atrial fibrillation ablation with magnetic navigation

    PubMed Central

    Errahmouni, Abdelkarim; Latcu, Decebal Gabriel; Bun, Sok-Sithikun; Rijo, Nicolas; Dugourd, Céline; Saoudi, Nadir

    2015-01-01

    Aims The magnetic navigation (MN) system may be coupled with a new advancement system that fully controls both the catheter and a robotic deflectable sheath (RSh) or with a fixed-curve sheath and a catheter-only advancement system (CAS). We aimed to compare these approaches for atrial fibrillation (AF) ablation. Methods and results Atrial fibrillation ablation patients (45, 23 paroxysmal and 22 persistent) performed with MN–RSh (RSh group) were compared with a control group (37, 18 paroxysmal and19 persistent) performed with MN–CAS (CAS group). Setup duration was measured from the procedure's start to operator transfer to control room. Ablation step duration was defined as the time from the beginning of the first radiofrequency (RF) pulse to the end of the last one and was separately acquired for the left and the right pulmonary vein (PV) pairs. Clinical characteristics, left atrial size, and AF-type distribution were similar between the groups. Setup duration as well as mapping times was also similar. Ablation step duration for the left PVs was similar, but was shorter for the right PVs in RSh group (46 ± 9 vs. 63 ± 12 min, P < 0.0001). Radiofrequency delivery time (34 ± 9 vs. 40 ± 11 min, P = 0.007) and procedure duration (227 ± 36 vs. 254 ± 62 min, P = 0.01) were shorter in RSh group. No complication occurred in RSh group. During follow-up, there were five recurrences (11%) in RSh group and 11 (29%) in CAS group (P = 0.027). Conclusion The use of the RSh for AF ablation with MN is safe and improves outcome. Right PV isolation is faster, RF delivery time and procedure time are reduced. PMID:25662989

  11. RF Gun Optimization Study

    SciTech Connect

    A. S. Hofler; P. Evtushenko; M. Krasilnikov

    2007-08-01

    Injector gun design is an iterative process where the designer optimizes a few nonlinearly interdependent beam parameters to achieve the required beam quality for a particle accelerator. Few tools exist to automate the optimization process and thoroughly explore the parameter space. The challenging beam requirements of new accelerator applications such as light sources and electron cooling devices drive the development of RF and SRF photo injectors. RF and SRF gun design is further complicated because the bunches are space charge dominated and require additional emittance compensation. A genetic algorithm has been successfully used to optimize DC photo injector designs for Cornell* and Jefferson Lab**, and we propose studying how the genetic algorithm techniques can be applied to the design of RF and SRF gun injectors. In this paper, we report on the initial phase of the study where we model and optimize gun designs that have been benchmarked with beam measurements and simulation.

  12. Virtual Prototyping of RF Weapons

    NASA Astrophysics Data System (ADS)

    Cartwright, Keith

    2002-08-01

    We are attempting to perform virtual prototyping of RF systems, from pulse power through to antennas, with the ICEPIC (Improved Concurrent Electromagnetic Particle-in-Cell) HPC software that we have developed over the past several years with funding from AFOSR. This code simulates from first principles (Maxwell's equations and Lorenz's force law) the electrodynamics and charged particle dynamics of the RF-producing part of the system. Such simulations require major computational resources. In the past, we have simulated GigaWatt-class sources that have already been built in the laboratory including the relativistic klystron oscillator (RKO) and the magnetically insulated line oscillator (MILO). Our simulations have uncovered undesirable features of these sources, and have led us to suggest ways to improve them. We are now taking the next step in our evolution towards true virtual prototyping. We have begun to simulate the relativistic magnetron before it is been built at our lab. The details of the device that will eventually be built, including the geometric structure and the externally generated magnetic field distribution, will be based on our simulations. In this paper, we present results from ICEPIC simulations that lead to the improvement of the RKO and MILO as well as predicted characteristics the relativistic magnetron that we plan to build in the fall of 2002.

  13. Multi-Physics Analysis of the Fermilab Booster RF Cavity

    SciTech Connect

    Awida, M.; Reid, J.; Yakovlev, V.; Lebedev, V.; Khabiboulline, T.; Champion, M.; /Fermilab

    2012-05-14

    After about 40 years of operation the RF accelerating cavities in Fermilab Booster need an upgrade to improve their reliability and to increase the repetition rate in order to support a future experimental program. An increase in the repetition rate from 7 to 15 Hz entails increasing the power dissipation in the RF cavities, their ferrite loaded tuners, and HOM dampers. The increased duty factor requires careful modelling for the RF heating effects in the cavity. A multi-physic analysis investigating both the RF and thermal properties of Booster cavity under various operating conditions is presented in this paper.

  14. Rf2a and rf2b transcription factors

    DOEpatents

    Beachy, Roger N.; Petruccelli, Silvana; Dai, Shunhong

    2007-10-02

    A method of activating the rice tungro bacilliform virus (RTBV) promoter in vivo is disclosed. The RTBV promoter is activated by exposure to at least one protein selected from the group consisting of Rf2a and Rf2b.

  15. Rotorcraft flying qualities improvement using advanced control

    NASA Technical Reports Server (NTRS)

    Walker, D.; Postlethwaite, I.; Howitt, J.; Foster, N.

    1993-01-01

    We report on recent experience gained when a multivariable helicopter flight control law was tested on the Large Motion Simulator (LMS) at DRA Bedford. This was part of a study into the application of multivariable control theory to the design of full-authority flight control systems for high-performance helicopters. In this paper, we present some of the results that were obtained during the piloted simulation trial and from subsequent off-line simulation and analysis. The performance provided by the control law led to level 1 handling quality ratings for almost all of the mission task elements assessed, both during the real-time and off-line analysis.

  16. High voltage RF feedthrough bushing

    DOEpatents

    Grotz, Glenn F.

    1984-01-01

    Described is a multi-element, high voltage radio frequency bushing for trmitting RF energy to an antenna located in a vacuum container. The bushing includes a center conductor of complex geometrical shape, an outer coaxial shield conductor, and a thin-walled hollow truncated cone insulator disposed between central and outer conductors. The shape of the center conductor, which includes a reverse curvature portion formed of a radially inwardly directed shoulder and a convex portion, controls the uniformity of the axial surface gradient on the insulator cone. The outer shield has a first substantially cylindrical portion and a second radially inwardly extending truncated cone portion.

  17. Improvements and new features for the diagnostics and control system of the ECH system on DIII-D

    NASA Astrophysics Data System (ADS)

    Torrezan, A. C.; Ponce, D.; Gorelov, Y. A.; Cengher, M.; Lohr, J.; Ellis, R. A.

    2016-10-01

    In this work we discuss improvements and new features for the diagnostics and controls of the electron cyclotron heating (ECH) system on the DIII-D tokamak. As for diagnostics, a new mapping system to measure the power density on a gyrotron collector, which should not exceed 500 W/cm2, has been designed and assembled. The new mapping system was designed to enable the test of new depressed collector gyrotrons that requires more RTD channels and for easier servicing and expansion compared with a previous system. First results from this diagnostic will be presented. As for controls, obsolete timing generators and auxiliary circuitry are being replaced by a more flexible approach using a FPGA. Besides being a simple replacement, the FPGA design will also add new features to the ECH control system such as an attempt to restart RF generation after RF loss or the recovery of selected interlocks. Upgrades made to the ECH launchers and issues found in the last experimental campaign as well as planned improvements will also be described. Work supported by US DOE under DE-FC02-04ER54698 and DE-AC02-09CH11466.

  18. Technology development of RF MEMS switches on printed circuit boards

    NASA Astrophysics Data System (ADS)

    Chang, Hung-Pin

    Today, some engineers have shifted their focus on the micro-electro-mechanical system (MEMS) to pursue better technological advancements. Recent development in RF MEMS technologies have lead to superior switch characteristics, i.e., very low insertion loss, very low power requirements, and high isolation comparing to the conventional semiconductor devices. This success has promised the potential of MEMS to revolutionize RF and microwave system implementation for the next generation of communication applications. However, RF MEMS switches integrated monolithically with various RF functional components on the same substrate to create multifunctional and reconfigurable complete communication systems remains to be a challenge research topic due to the concerns of the high cost of packaging process and the high cost of RF matching requirements in module board implementation. Furthermore, the fabrication of most RF MEMS switches requires thickness control and surface planarization of wide metal lines prior to deposition of a metal membrane bridge, which poses a major challenge to manufacturability. To ease the fabrication of RF MEMS switches and to facilitate their integration with other RF components such as antennas, phase delay lines, tunable filters, it is imperative to develop a manufacturable RF MEMS switch technology on a common substrate housing all essential RF components. Development of a novel RF MEMS technology to build a RF MEMS switch and provide a system-level packaging on microwave laminated printed circuit boards (PCBs) are proposed in this dissertation. Two key processes, high-density inductively coupled plasma chemical vapor deposition (HDICP CVD) for low temperature dielectric deposition, and compressive molding planarization (COMP) for the temporary sacrificial polymer planarization have been developed for fabricating RF MEMS switches on PCBs. Several membrane-type capacitive switches have been fabricated showing excellent RF performance and dynamic

  19. A geometrically adjustable 16-channel transmit/receive transmission line array for improved RF efficiency and parallel imaging performance at 7 Tesla.

    PubMed

    Adriany, Gregor; Van de Moortele, Pierre-Francois; Ritter, Johannes; Moeller, Steen; Auerbach, Edward J; Akgün, Can; Snyder, Carl J; Vaughan, Thomas; Uğurbil, Kâmil

    2008-03-01

    A novel geometrically adjustable transceiver array system is presented. A key feature of the geometrically adjustable array was the introduction of decoupling capacitors that allow for automatic change in capacitance dependent on neighboring resonant element distance. The 16-element head array version of such an adjustable coil based on transmission line technology was compared to fixed geometry transmission line arrays (TLAs) of various sizes at 7T. The focus of this comparison was on parallel imaging performance, RF transmit efficiency, and signal-to-noise ratio (SNR). Significant gains in parallel imaging performance and SNR were observed for the new coil and attributed to its adjustability and to the design of the individual elements with a three-sided ground plane. (c) 2008 Wiley-Liss, Inc.

  20. Rf system considerations for a large hadron collider

    SciTech Connect

    Raka, E.

    1988-01-01

    In this paper, we shall discuss how we arrive at a particular choice of voltage and frequency; the type of acceleration structure that would be suitable for obtaining the required voltage and resonant impedance; static beam loading including a simplified beam stability criterion involving the beam current and total rf system shunt impedance; the basic principle of rf phase and frequency control loops; and the effect of rf noise and its interaction with these loops. Finally, we shall consider the need for and design of rf systems to damp independently coherent oscillations of individual bunches or groups of bunches. 30 refs., 17 figs., 2 tabs.

  1. Iron-control additives improve acidizing

    SciTech Connect

    Walker, M.; Dill, W. ); Besler, M. )

    1989-07-24

    Iron sulfide and sulfur precipitation in sour wells can be controlled with iron-sequestering agents and sulfide modifiers. Oil production has been routinely increased in sour wells where precipitation of iron sulfide and elemental sulfur has been brought under control. Production increases have been especially noteworthy on wells that had a history of rapid production decline after acid stimulation. Twenty-fold production increases have been recorded. Key to the production increase has been to increase permeability with: Iron chelating agents that control precipitation of iron sulfide. A sulfide modifier that reduces precipitation of solids in the presence of excessive amounts of hydrogen sulfide and prevents precipitation of elemental sulfur.

  2. AC/RF Superconductivity

    SciTech Connect

    Ciovati, Gianluigi

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  3. RF shielded connectors

    NASA Technical Reports Server (NTRS)

    Fisher, A.; Clatterbuck, C.

    1974-01-01

    Gap, where cable joins connector housing, is shielded effectively by composite RF shielding made from suitable potting resin material (fumed silica, thixotropic prepolymer composition), conductive coating (silver-filled, flexible, polyurethane resin), and protective jacket (wax coated housing formed around another wax form having contours shaped to match configuration).

  4. Oxide Films RF Applications

    DTIC Science & Technology

    2006-06-01

    AUTHOR(S) 5d. PROJECT NUMBER SKOWRONSKI , Marek 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING...Report Title: Oxide Films RF applications University: Carnegie Mellon University PIs: M. Skowronski & P. Salvador Agency: Office of Naval Research Award

  5. Planetary camera control improves microfiche production

    NASA Technical Reports Server (NTRS)

    Chesterton, W. L.; Lewis, E. B.

    1965-01-01

    Microfiche is prepared using an automatic control system for a planetary camera. The system provides blank end-of-row exposures and signals card completion so the legend of the next card may by photographed.

  6. Improvement on fuzzy controller design techniques

    NASA Technical Reports Server (NTRS)

    Wang, Paul P.

    1993-01-01

    This paper addresses three main issues, which are somewhat interrelated. The first issue deals with the classification or types of fuzzy controllers. Careful examination of the fuzzy controllers designed by various engineers reveals distinctive classes of fuzzy controllers. Classification is believed to be helpful from different perspectives. The second issue deals with the design according to specifications, experiments related to the tuning of fuzzy controllers, according to the specification, will be discussed. General design procedure, hopefully, can be outlined in order to ease the burden of a design engineer. The third issue deals with the simplicity and limitation of the rule-based IF-THEN logical statements. The methodology of fuzzy-constraint network is proposed here as an alternative to the design practice at present. It is our belief that predicate calculus and the first order logic possess much more expressive power.

  7. Advanced Synthesis of Spinnable MWCNT Forests by RF-Induction Heating Enhanced CVD Process

    NASA Astrophysics Data System (ADS)

    Zakhidov, Anvar; Holmes, William; UTD Solarno Team; Solarno UTD Team

    2015-03-01

    We demonstrate here an advanced method to effectively grow tall multi-wall carbon nanotubes (MWCNT) vertically oriented forests which are highly spinnable. Heating of the Fe catalyst is achieved extremely fast by RF induction heating using coils outside the quartz tube. This method and the new apparatus designed and presented in this paper allow separate control over the temperature of the substrate and the temperature of the incoming gases. In addition to temperature control, the fast T-ramping of the substrate preserves the catalyst nanoclusters from Ostwald ripening and other growth quenching effects such as carbon overgrowth of the catalyst. We show that the parametric sweet spot or bell curve of substrate spinnability can be increased significantly with this improved RF-CVD method. The catalyst nanoclusters also show a wide band of density arrangements that very positively effect spinnability and the drawing ratio. Drawing ratios can vary from 2 meters to 12 meters of sheets drawn from only 1cm of forest. RF-CVD method allows to grow fast (in several minuts) higher CNT forests at higher temperature of synthesis up to 800 K, and obtain dry-spinable CNTs, Characterization results of the samples created in the newRF-CVD system will be presented and compared to previous CNT sheet samples by conventional three-zone resistive heating CVD to measure the extent of property improvements of the CNT sheets and forests. Specifics of the experimental system will be addressed in detail and future property improvements and applications explored.

  8. Improved internal control for molecular diagnosis assays.

    PubMed

    Vinayagamoorthy, T; Maryanski, Danielle; Vinayagamoorthy, Dilanthi; Hay, Katie S L; Yo, Jacob; Carter, Mark; Wiegel, Joseph

    2015-01-01

    The two principal determining steps in molecular diagnosis are the amplification and the identification steps. Accuracy of DNA amplification is primarily determined by the annealing sequence of the PCR primer to the analyte DNA. Accuracy for identification is determined either by the annealing region of a labelled probe for the real time PCR analysis, or the annealing of a sequencing primer for DNA sequencing analysis, that binds to the respective analyte (amplicon). Presently, housekeeping genes (Beta globin, GAPDH) are used in molecular diagnosis to verify that the PCR conditions are optimum, and are thus known as amplification controls [1-4]. Although these genes have been useful as amplification controls, they lack the true definition of an internal control because the primers and annealing conditions are not identical to the analyte being assayed. This may result in a false negative report [5]. The IC-Code platform technology described here provides a true internal control where the internal control and analyte share identical PCR primers annealing sequences for the amplification step and identical sequencing primer annealing sequence for the identification step. •The analyte and internal control have the same PCR and sequencing annealing sequences.•This method assures for little or no false negatives and false positives due to the method's design of using identical annealing conditions for the internal control and analyte, and by using DNA sequencing analysis for the identification step of the analyte, respectively.•This method also allows for a set lower limit of detection to be used by varying the amount of internal control used in the assay.

  9. Demonstration of multispectral target locator using collocated RF antenna/LWIR joint sensor system and datacube

    NASA Astrophysics Data System (ADS)

    Jang, Woo-Yong; Park, James; Kakas, George; Noyola, Michael

    2016-10-01

    Recently, we configured RF antennas and a LWIR camera connected to an actuator system to form a collocated sensor system. We also developed a GUI which directly controls both RF and IR systems, azimuth motion, as well as performs post-processing for data integration and location finding. RF range data and LWIR images were collected simultaneously by using our configured sensor system as azimuth was varied from 0 to 70°. Series of collected RF data was transformed into a single 2-D radar image showing range profile of targets against azimuth. For LWIR, data was aligned into a single panoramic image as a function of azimuth by incorporating shift parameters observed in the measurements. Both RF/IR images were then arranged into a 3-D datacube, having azimuth as a common domain, and this datacube directly provided locational information of targets. For demonstration, we successfully located objects such as a corner reflector and a blackbody source under a dark background. In addition, we highlight some additional features available in our sensor system including target classification using both Euclidean and SVM based multi-classifier techniques, and tracking capability for region of interest on moving targets. Future work would be to improve the current system for outdoor measurement to locate distant targets.

  10. Rebuilding Habitat and Shoreline Resilience through Improved Flood Control Project

    EPA Pesticide Factsheets

    Information about the SFBWQP Rebuilding Habitat and Shoreline Resilience through Improved Flood Control Project, part of an EPA competitive grant program to improve SF Bay water quality focused on restoring impaired waters and enhancing aquatic resources.

  11. RF generated atmospheric pressure plasmas and applications

    NASA Astrophysics Data System (ADS)

    Park, Jaeyoung; Herrmann, Hans W.; Henins, Ivars; Gautier, Donald C.

    2001-10-01

    RF generated atmospheric pressure plasma sources have been developed for various materials applications. They operate with rf power and produce a α-mode capacitive discharge that is stable, steady-state, non-thermal, and volumetric. The plasma parameters of this source have been measured: electron densities of 10^11 cm-3 and electron temperatures of 2 eV by using neutral bremsstrahlung emission. Localized electron heating near the sheath boundary has been observed and is related to the discharge stability and α to γ mode (or arcing) transition using 1D fluid model. The discharge stability improves with increase in rf frequency. The electrode surface property such as the secondary electron emission coefficient also plays a significant role in determining α to γ mode transition. For example, a stable α-mode air discharge is produced using 100 MHz rf power with the use of a boron nitride cover on one of the electrodes. In comparison, an air discharge becomes unstable at a lower rf frequency (e.g. 13.56 MHz) or with an alumina cover. Similar results were obtained with various feedgas such as steam, CO_2, and hydrocarbon containing gases. Further characterization of this high frequency source is under progress. For its applications, we have successfully demonstrated the effective neutralization of actual chemical warfare agents such as VX, GD and HD. In addition, significant progresses have been made in the area of etching of organic and metal film etching, and production of novel materials.

  12. Investigation of Microscopic Materials Limitations of Superconducting RF Cavities

    SciTech Connect

    Anlage, Steven

    2014-07-23

    The high-field performance of SRF cavities is often limited by breakdown events below the intrinsic limiting surface fields of Nb, and there is abundant evidence that these breakdown events are localized in space inside the cavity. Also, there is a lack of detailed understanding of the causal links between surface treatments and ultimate RF performance at low temperatures. An understanding of these links would provide a clear roadmap for improvement of SRF cavity performance, and establish a cause-and-effect ‘RF materials science’ of Nb. We propose two specific microscopic approaches to addressing these issues. First is a spatially-resolved local microwave-microscope probe that operates at SRF frequencies and temperatures to discover the microscopic origins of breakdown, and produce quantitative measurements of RF critical fields of coatings and films. Second, RF Laser Scanning Microscopy (LSM) has allowed visualization of RF current flow and sources of nonlinear RF response in superconducting devices with micro-meter spatial resolution. The LSM will be used in conjunction with surface preparation and characterization techniques to create definitive links between physical and chemical processing steps and ultimate cryogenic microwave performance. We propose to develop RF laser scanning microscopy of small-sample Nb pieces to establish surface-processing / RF performance relations through measurement of RF current distributions on micron-length scales and low temperatures.

  13. RF BREAKDOWN STUDIES USING PRESSURIZED CAVITIES

    SciTech Connect

    Johnson, Rolland

    2014-09-21

    Many present and future particle accelerators are limited by the maximum electric gradient and peak surface fields that can be realized in RF cavities. Despite considerable effort, a comprehensive theory of RF breakdown has not been achieved and mitigation techniques to improve practical maximum accelerating gradients have had only limited success. Part of the problem is that RF breakdown in an evacuated cavity involves a complex mixture of effects, which include the geometry, metallurgy, and surface preparation of the accelerating structures and the make-up and pressure of the residual gas in which plasmas form. Studies showed that high gradients can be achieved quickly in 805 MHz RF cavities pressurized with dense hydrogen gas, as needed for muon cooling channels, without the need for long conditioning times, even in the presence of strong external magnetic fields. This positive result was expected because the dense gas can practically eliminate dark currents and multipacting. In this project we used this high pressure technique to suppress effects of residual vacuum and geometry that are found in evacuated cavities in order to isolate and study the role of the metallic surfaces in RF cavity breakdown as a function of magnetic field, frequency, and surface preparation. One of the interesting and useful outcomes of this project was the unanticipated collaborations with LANL and Fermilab that led to new insights as to the operation of evacuated normal-conducting RF cavities in high external magnetic fields. Other accomplishments included: (1) RF breakdown experiments to test the effects of SF6 dopant in H2 and He gases with Sn, Al, and Cu electrodes were carried out in an 805 MHz cavity and compared to calculations and computer simulations. The heavy corrosion caused by the SF6 components led to the suggestion that a small admixture of oxygen, instead of SF6, to the hydrogen would allow the same advantages without the corrosion in a practical muon beam line. (2) A

  14. Magnetic Bearing Controller Improvements for High Speed Flywheel System

    NASA Technical Reports Server (NTRS)

    Dever, Timothy P.; Brown, Gerald V.; Jansen, Ralph H.; Kascak, Peter E.; Provenza, Andrew J.

    2003-01-01

    A magnetic bearing control system for a high-speed flywheel system is described. The flywheel utilizes a five axis active magnetic bearing system, using eddy current sensors for position feedback to the bearing controller. Magnetic bearing controller features designed to improve flywheel operation and testing are described. Operational improvements include feed forward control to compensate for rotor imbalance, moving notch filtering to compensate for synchronous and harmonic rotational noise, and fixed notching to prevent rotor bending mode excitation. Testing improvements include adding safe gain, bearing current hold, bearing current zero, and excitation input features. Performance and testing improvements provided by these features are measured and discussed.

  15. Feedback field control improves the precision of T2 * quantification at 7 T.

    PubMed

    Wyss, Michael; Duerst, Yolanda; Nanz, Daniel; Kasper, Lars; Wilm, Bertram Jakob; Dietrich, Benjamin Emmanuel; Gross, Simon; Schmid, Thomas; Brunner, David Otto; Pruessmann, Klaas Paul

    2017-10-01

    T2 * mapping offers access to a number of important structural and physiological tissue parameters. It is robust against RF field variations and overall signal scaling. However, T2 * measurement is highly sensitive to magnetic field errors, including perturbations caused by breathing motion at high baseline field. The goal of this work is to assess this issue in T2 * mapping of the brain and to study the benefit of field stabilization by feedback field control. T2 * quantification in the brain was investigated by phantom and in vivo measurements at 7 T. Repeated measurements were made with and without feedback field control using NMR field sensing and dynamic third-order shim actuation. The precision and reliability of T2 * quantification was assessed by studying variation across repeated measurements as well as fitting errors. Breathing effects were found to introduce significant error in T2 * mapping results. Field control mitigates this problem substantially. In a phantom it virtually eliminates the effects of emulated breathing fluctuations in the head. In vivo it enhances the structural fidelity of T2 * maps and reduces fitting residuals along with standard deviation. In conclusion, feedback field control improves the fidelity of T2 * mapping in the presence of field perturbations. It is an effective means of countering bulk susceptibility effects of breathing and hence holds particular promise for efforts to leverage high field for T2 * studies in vivo. Copyright © 2017 John Wiley & Sons, Ltd.

  16. Training Attentional Control Improves Cognitive and Motor Task Performance.

    PubMed

    Ducrocq, Emmanuel; Wilson, Mark; Vine, Sam; Derakshan, Nazanin

    2016-10-01

    Attentional control is a necessary function for the regulation of goal-directed behavior. In three experiments we investigated whether training inhibitory control using a visual search task could improve task-specific measures of attentional control and performance. In Experiment 1 results revealed that training elicited a near-transfer effect, improving performance on a cognitive (antisaccade) task assessing inhibitory control. In Experiment 2 an initial far-transfer effect of training was observed on an index of attentional control validated for tennis. The principal aim of Experiment 3 was to expand on these findings by assessing objective gaze measures of inhibitory control during the performance of a tennis task. Training improved inhibitory control and performance when pressure was elevated, confirming the mechanisms by which cognitive anxiety impacts performance. These results suggest that attentional control training can improve inhibition and reduce taskspecific distractibility with promise of transfer to more efficient sporting performance in competitive contexts.

  17. 48 CFR 970.0370 - Management Controls and Improvements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... SUPPLEMENTARY REGULATIONS DOE MANAGEMENT AND OPERATING CONTRACTS Improper Business Practices and Personal Conflicts of Interest 970.0370 Management Controls and Improvements. ... 48 Federal Acquisition Regulations System 5 2011-10-01 2011-10-01 false Management Controls and...

  18. 48 CFR 970.0370 - Management Controls and Improvements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... SUPPLEMENTARY REGULATIONS DOE MANAGEMENT AND OPERATING CONTRACTS Improper Business Practices and Personal Conflicts of Interest 970.0370 Management Controls and Improvements. ... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false Management Controls and...

  19. 48 CFR 970.0370 - Management Controls and Improvements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... SUPPLEMENTARY REGULATIONS DOE MANAGEMENT AND OPERATING CONTRACTS Improper Business Practices and Personal Conflicts of Interest 970.0370 Management Controls and Improvements. ... 48 Federal Acquisition Regulations System 5 2013-10-01 2013-10-01 false Management Controls and...

  20. 48 CFR 970.0370 - Management Controls and Improvements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... SUPPLEMENTARY REGULATIONS DOE MANAGEMENT AND OPERATING CONTRACTS Improper Business Practices and Personal Conflicts of Interest 970.0370 Management Controls and Improvements. ... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Management Controls...

  1. 48 CFR 970.0370 - Management Controls and Improvements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... SUPPLEMENTARY REGULATIONS DOE MANAGEMENT AND OPERATING CONTRACTS Improper Business Practices and Personal Conflicts of Interest 970.0370 Management Controls and Improvements. ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Management Controls...

  2. A Metamaterial-Inspired Approach to RF Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Fowler, Clayton; Zhou, Jiangfeng

    2016-03-01

    We demonstrate an RF energy harvesting rectenna design based on a metamaterial perfect absorber (MPA). With the embedded Schottky diodes, the rectenna converts captured RF energy to DC currents. The Fabry-Perot cavity resonance of the MPA greatly improves the amount of energy captured and hence improves the rectification efficiency. Furthermore, the FP resonance exhibits a high Q-factor and significantly increases the voltage across the Schottky diodes. This leads to a factor of 16 improvement of RF-DC conversion efficiency at ambient intensity level.

  3. A Metamaterial-Inspired Approach to RF Energy Harvesting

    NASA Astrophysics Data System (ADS)

    Fowler, Clayton; Zhou, Jiangfeng

    We demonstrate an RF energy harvesting rectenna design based on a metamaterial perfect absorber (MPA). With the embedded Schottky diodes, the rectenna converts captured RF energy to DC currents. The Fabry-Perot cavity resonance of the MPA greatly improves the amount of energy captured and hence improves the rectification efficiency. Furthermore, the FP resonance exhibits high Q-factor and significantly increases the voltage across the Schottky diodes. This leads to a factor of 16 improvement of RF-DC conversion efficiency at ambient intensity level.

  4. Air Traffic Control Improvement Using Prioritized CSMA

    NASA Technical Reports Server (NTRS)

    Robinson, Daryl C.

    2001-01-01

    Version 7 simulations of the industry-standard network simulation software "OPNET" are presented of two applications of the Aeronautical Telecommunications Network (ATN), Controller Pilot Data Link Communications (CPDLC) and Automatic Dependent Surveillance-Broadcast mode (ADS-B), over VHF Data Link mode 2 (VDL-2). Communication is modeled for air traffic between just three cities. All aircraft are assumed to have the same equipage. The simulation involves Air Traffic Control (ATC) ground stations and 105 aircraft taking off, flying realistic free-flight trajectories, and landing in a 24-hr period. All communication is modeled as unreliable. Collision-less, prioritized carrier sense multiple access (CSMA) is successfully tested. The statistics presented include latency, queue length, and packet loss. This research may show that a communications system simpler than the currently accepted standard envisioned may not only suffice, but also surpass performance of the standard at a lower cost of deployment.

  5. Computer control improves ethylene plant operation

    SciTech Connect

    Whitehead, B.D.; Parnis, M.

    1987-11-01

    ICIA Australia ordered a turnkey 250,000-tpy ethylene plant to be built at the Botany site, Sydney, Australia. Following a feasibility study, an additional order was placed for a process computer system for advanced process control and optimization. This article gives a broad outline of the process computer tasks, how the tasks were implemented, what problems were met, what lessons were learned and what results were achieved.

  6. Amide proton transfer imaging with improved robustness to magnetic field inhomogeneity and magnetization transfer asymmetry using Saturation with Frequency Alternating RF Irradiation (SAFARI)

    PubMed Central

    Scheidegger, Rachel; Vinogradov, Elena; Alsop, David C

    2011-01-01

    Amide proton transfer (APT) imaging has shown promise as an indicator of tissue pH and as a marker for brain tumors. Sources of error in APT measurements include direct water saturation, and magnetization transfer (MT) from membranes and macromolecules. These are typically suppressed by post-processing asymmetry analysis. However, this approach is strongly dependent on B0 homogeneity and can introduce additional errors due to intrinsic MT asymmetry, aliphatic proton features opposite the amide peak, and radiation damping-induced asymmetry. Although several methods exist to correct for B0 inhomogeneity, they tremendously increase scan times and do not address errors induced by asymmetry of the z-spectrum. In this paper, a novel saturation scheme - saturation with frequency alternating RF irradiation (SAFARI) - is proposed in combination with a new magnetization transfer ratio (MTR) parameter designed to generate APT images insensitive to direct water saturation and MT, even in the presence of B0 inhomogeneity. The feasibility of the SAFARI technique is demonstrated in phantoms and in the human brain. Experimental results show that SAFARI successfully removes direct water saturation and MT contamination from APT images. It is insensitive to B0 offsets up to 180Hz without using additional B0 correction, thereby dramatically reducing scanning time. PMID:21608029

  7. A Two-Frequency RF Photocathode Gun

    SciTech Connect

    Dowell, D.

    2004-11-05

    In this paper we resurrect an idea originally proposed by Serafini[1] in 1992 for an RF photocathode gun capable of operating simultaneously at the fundamental frequency and a higher frequency harmonic. Driving the gun at two frequencies with the proper field ratio and relative phase produces a beam with essentially no rf emittance and a linear longitudinal phase space distribution. Such a gun allows a completely new range of operating parameters for controlling space charge emittance growth. In addition, the linear longitudinal phase space distribution aids in bunch compression. This paper will compare results of simulations for the two-frequency gun with the standard rf gun, and the unique properties of the two-frequency gun will be discussed.

  8. VHF Injector Pumping Slot RF Shielding Effectiveness

    SciTech Connect

    Staples, John

    2007-08-08

    The effectiveness of the shielding of the pumping slots is calculated for two radial depths of the slots with Mafia-2 and compared to a simple recipe that calculates the RF attenuation in a slot. CBP Technical Note 378 describes the pumping configuration of the 100 MHz VHF photoinjector. The cavity is surrounded by 36 slots, 4.9 cm wide, separated by bars, also 4.9 cm wide. The radial depth of the bars controls the attenuation of the RF from the cavity proper to the annular plenum outside the bars where the getter pumps are located. This note describes calculations of the level of RF fields in the plenum for two different values of the radial depth of the bars and two different values of the spacing between the outer dimension of the bars and the outer plenum wall.

  9. Short radius drilling system improves directional control

    SciTech Connect

    Leazer, C.

    1995-08-01

    Horizontal drilling capabilities and applications have been dramatically increased with development of Becfield Drilling Services` Short Radius Horizontal Drilling System utilizing the Articulated Downhole Drilling Motor (ADM). The system gives precise directional control, predictability , and reliability not previously available in short-radius operations. Because of the unique, patented design of the ADM, the short-radius system can be rotated during lateral drilling operations. This is a significant development in short-radius horizontal drilling technology. This paper reviews the design and operation of this equipment.

  10. RF Gun Optimization Study

    SciTech Connect

    Alicia Hofler; Pavel Evtushenko

    2007-07-03

    Injector gun design is an iterative process where the designer optimizes a few nonlinearly interdependent beam parameters to achieve the required beam quality for a particle accelerator. Few tools exist to automate the optimization process and thoroughly explore the parameter space. The challenging beam requirements of new accelerator applications such as light sources and electron cooling devices drive the development of RF and SRF photo injectors. A genetic algorithm (GA) has been successfully used to optimize DC photo injector designs at Cornell University [1] and Jefferson Lab [2]. We propose to apply GA techniques to the design of RF and SRF gun injectors. In this paper, we report on the initial phase of the study where we model and optimize a system that has been benchmarked with beam measurements and simulation.

  11. Improving vehicle productivity through better contamination control

    SciTech Connect

    Chaplin, J.

    1986-01-01

    A method of relating OEM filtration cost to oil cleanliness and the resulting effect on the realiability on mature mobile equipment hydraulic systems is investigated. A rational for determining the fluid cleanliness to achieve minimum mean time between failure and guidelines for assessing the cost of improved filtration to meet that objective are presented. The purpose of this paper is to review specific portions of recent studies relating to vehicle reliability as affected by hydraulic component/system failure. In these studies fluid cleanliness was measured using the proposed ISO 4406 solid contaminant code and reliability measured as average time between breakdowns. A relationship between specific levels of fluid contamination and system reliability was established. It then followed that if that relationship could be demonstrated, system cleanliness levels could be selected by the OEM with reasonable confidence that extended mean time between failure (MTBF) would result from the choice.

  12. LANSCE 201.25 MHz drift tube linac RF power status

    SciTech Connect

    Lyles, J.T.M.; Friedrichs, C.C., Jr.

    1996-09-01

    The Los Alamos Neutron Science Center linac provides high power proton beams for neutron science, tritium target development, nuclear physics, material science, isotope production, and weapons research. Number of simultaneous beam users places heavy demands on the RF powerplant, espcially the 201.25 MHz power amplifiers (PA) driving four drift tube linac cavities. Designed nearly 30 years ago, these amplifiers have operated at up to 3 Megawatts with duty factors of 12%. The number of power tubes, age of cooling and control subsystems, tube manufacturing problems, and operation near maximum PA tube ratings have all affected system reliability. By monitoring final power amplifier plate dissipation and tube vcauum, improved operating procedures have raised RF system reliability above 95% for operation periods in 1993-95. Higher beam current for a proposed Long Pulse Spallation Source (LPSS) cannot be delivered simultaneously with other beams at high duty factor, however. Plans are underway to develop a new final power amplifier which can use low-level RF modulations for amplitude control. With only a few power tubes, the system will deliver high peak power and duty factor, with improved DC to RF efficiency, and a simplified cooling system.

  13. Rf systems for RHIC

    SciTech Connect

    Rose, J.; Brodowski, J.; Connolly, R.; Deng, D.P.; Kwiatkowski, S.; Pirkl, W.; Ratti, A.

    1995-05-01

    The RHIC rf systems must capture the injected beam, accelerate it through transition to top energy, shorten the bunches prior to rebucketing, and store the beam for 10 hours in the presence of strong intra-beam scattering. These different functions are met by three independent systems. An accelerating system at 26.7 Mhz (h = 342), a storage system at 196.1 MHz (h = 2508), and a wideband system for the damping of injection efforts.

  14. RF Pulsed Heating

    SciTech Connect

    Pritzkau, David P.

    2002-01-03

    RF pulsed heating is a process by which a metal is heated from magnetic fields on its surface due to high-power pulsed RF. When the thermal stresses induced are larger than the elastic limit, microcracks and surface roughening will occur due to cyclic fatigue. Pulsed heating limits the maximum magnetic field on the surface and through it the maximum achievable accelerating gradient in a normal conducting accelerator structure. An experiment using circularly cylindrical cavities operating in the TE{sub 011} mode at a resonant frequency of 11.424 GHz is designed to study pulsed heating on OFE copper, a material commonly used in normal conducting accelerator structures. The high-power pulsed RF is supplied by an X-band klystron capable of outputting 50 MW, 1.5 {micro}s pulses. The test pieces of the cavity are designed to be removable to allow testing of different materials with different surface preparations. A diagnostic tool is developed to measure the temperature rise in the cavity utilizing the dynamic Q change of the resonant mode due to heating. The diagnostic consists of simultaneously exciting a TE{sub 012} mode to steady-state in the cavity at 18 GHz and measuring the change in reflected power as the cavity is heated from high-power pulsed RF. Two experimental runs were completed. One run was executed at a calculated temperature rise of 120 K for 56 x 10{sup 6} pulses. The second run was executed at a calculated temperature rise of 82 K for 86 x 10{sup 6} pulses. Scanning electron microscope pictures show extensive damage occurring in the region of maximum temperature rise on the surface of the test pieces.

  15. Active shear flow control for improved combustion

    NASA Astrophysics Data System (ADS)

    Gutmark, E.; Parr, T. P.; Hanson-Parr, D. M.; Schadow, K. C.

    1990-01-01

    The acoustical and fluid dynamic facets of an excited premixed flame were studied experimentally to evaluate possibilities for development of a stabilizing closed-loop control system. The flame was analyzed as a nonlinear system which includes different subcomponents: acoustics, fluid dynamics, and chemical reaction. Identification of the acoustical and fluid dynamics subsystems is done by analyzing the transfer function, which was obtained by driving the system with both white-noise and a frequency-sweeping sine-wave. The features obtained by this analysis are compared to results of flow visualization and hot-wire flow-field and spectral measurements. The acoustical subsystem is determined by the resonant acoustic modes of the settling chamber. These modes are subsequently filtered and amplified by the flow shear layer, whose instability characteristics are dominated by the preferred mode frequency.

  16. Implementing Controlled Composition to Improve Vocabulary Mastery of EFL Students

    ERIC Educational Resources Information Center

    Juriah

    2015-01-01

    The purposes of this study was to know how (1) Controlled composition teaching techniques implemented by the English teacher at SDN 027 Samarinda to improve vocabulary mastery, and (2) Controlled composition teaching techniques improves vocabulary mastery of the sixth grade students of SDN 027 Samarinda. This research used a Classroom Action…

  17. Improving Corrosion Prevention and Control in the Army

    DTIC Science & Technology

    2012-03-01

    Improving Corrosion Prevention and Control in the Army by Lieutenant Colonel Adalberto Morales United States Army Logistics...From - To) 4. TITLE AND SUBTITLE Improving Corrosion Prevention and Control in the Army 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...14. ABSTRACT The Army spends approximately 2.4 billion of dollars annually in corrosion prevention and corrective maintenance of tactical wheeled

  18. Design of an Electrically Automated RF Transceiver Head Coil in MRI

    PubMed Central

    Sohn, Sung-Min; DelaBarre, Lance; Gopinath, Anand; Vaughan, John Thomas

    2015-01-01

    Magnetic resonance imaging (MRI) is a widely used nonionizing and noninvasive diagnostic instrument to produce detailed images of the human body. The radio-frequency (RF) coil is an essential part of MRI hardware as an RF front-end. RF coils transmit RF energy to the subject and receive the returning MR signal. This paper presents an MRI-compatible hardware design of the new automatic frequency tuning and impedance matching system. The system automatically corrects the detuned and mismatched condition that occurs due to loading effects caused by the variable subjects (i.e., different human heads or torsos). An eight-channel RF transceiver head coil with the automatic system has been fabricated and tested at 7 Tesla (T) MRI system. The automatic frequency tuning and impedance matching system uses digitally controlled capacitor arrays with real-time feedback control capability. The hardware design is not only compatible with current MRI scanners in all aspects but also it operates the tuning and matching function rapidly and accurately. The experimental results show that the automatic function increases return losses from 8.4 dB to 23.7 dB (maximum difference) and from 12.7 dB to 19.6 dB (minimum difference) among eight channels within 550 ms. The reflected RF power decrease from 23.1 % to 1.5 % (maximum difference) and from 5.3 % to 1.1 % (minimum difference). Therefore, these results improve signal-to-noise ratio (SNR) in MR images with phantoms. PMID:25361512

  19. Design of an Electrically Automated RF Transceiver Head Coil in MRI.

    PubMed

    Sohn, Sung-Min; DelaBarre, Lance; Gopinath, Anand; Vaughan, John Thomas

    2015-10-01

    Magnetic resonance imaging (MRI) is a widely used nonionizing and noninvasive diagnostic instrument to produce detailed images of the human body. The radio-frequency (RF) coil is an essential part of MRI hardware as an RF front-end. RF coils transmit RF energy to the subject and receive the returning MR signal. This paper presents an MRI-compatible hardware design of the new automatic frequency tuning and impedance matching system. The system automatically corrects the detuned and mismatched condition that occurs due to loading effects caused by the variable subjects (i.e., different human heads or torsos). An eight-channel RF transceiver head coil with the automatic system has been fabricated and tested at 7 Tesla (T) MRI system. The automatic frequency tuning and impedance matching system uses digitally controlled capacitor arrays with real-time feedback control capability. The hardware design is not only compatible with current MRI scanners in all aspects but also it operates the tuning and matching function rapidly and accurately. The experimental results show that the automatic function increases return losses from 8.4 dB to 23.7 dB (maximum difference) and from 12.7 dB to 19.6 dB (minimum difference) among eight channels within 550 ms . The reflected RF power decrease from 23.1% to 1.5% (maximum difference) and from 5.3% to 1.1% (minimum difference). Therefore, these results improve signal-to-noise ratio (SNR) in MR images with phantoms.

  20. Improved control strategies correct main fractionator operating problems

    SciTech Connect

    Golden, S.W.

    1995-08-21

    Heat and mass balance control of refinery main fractionators can be improved through simple process design changes. Metering flows of internal reflux streams improves unit operability and controllability. Modifying the process system design to measure small internal reflux flow is another inexpensive way to control main fractionators. Three case histories show how simple design changes in refinery main fractionators can solve advanced control problems, thus changing product yields and improving refinery economics. The three cases are a delayed coker, a crude unit, and a FCC unit.

  1. Programmable RF System for RF System-on-Chip

    NASA Astrophysics Data System (ADS)

    Ryu, Jee-Youl; Kim, Sung-Woo; Lee, Dong-Hyun; Park, Seung-Hun; Lee, Jung-Hoon; Ha, Deock-Ho; Kim, Seung-Un

    This paper proposes a new automatic programmable radio frequency (RF) system for a System-on-Chip (SoC) transceiver. We built a 5-GHz low noise amplifier (LNA) with an on-chip programmable RF system using 0.18-(m SiGe technology. This system is extremely useful for today's RF IC devices in a complete RF transceiver environment. The programmable RF system helps it to provide DC output voltages, hence, making the compensation network automatic. The programmable RF system automatically adjusts performance of 5-GHz low noise amplifier with the processor in the SoC transceiver when the LNA goes out of the normal range of operation. The ACN compensates abnormal operation due to the unusual thermal variation or unusual process variation.

  2. An improved auto-tuning scheme for PI controllers.

    PubMed

    Mudi, Rajani K; Dey, Chanchal; Lee, Tsu-Tian

    2008-01-01

    Ziegler-Nichols tuned PI and PID controllers are usually found to provide poor performances for high-order and nonlinear systems. In this study, an improved auto-tuning scheme is presented for Ziegler-Nichols tuned PI controllers (ZNPICs). With a view to improving the transient response, the proportional and integral gains of the proposed controller are continuously modified based on the current process trend. The proposed controller is tested for a number of high-order linear and nonlinear dead-time processes under both set-point change and load disturbance. It exhibits significantly improved performance compared to ZNPIC, and Refined Ziegler-Nichols tuned PI controller (RZNPIC). Robustness of the proposed scheme is established by varying the controller parameters as well as the dead-time of the process under control.

  3. Improved LTVMPC design for steering control of autonomous vehicle

    NASA Astrophysics Data System (ADS)

    Velhal, Shridhar; Thomas, Susy

    2017-01-01

    An improved linear time varying model predictive control for steering control of autonomous vehicle running on slippery road is presented. Control strategy is designed such that the vehicle will follow the predefined trajectory with highest possible entry speed. In linear time varying model predictive control, nonlinear vehicle model is successively linearized at each sampling instant. This linear time varying model is used to design MPC which will predict the future horizon. By incorporating predicted input horizon in each successive linearization the effectiveness of controller has been improved. The tracking performance using steering with front wheel and braking at four wheels are presented to illustrate the effectiveness of the proposed method.

  4. NQR detection of explosive simulants using RF atomic magnetometers

    NASA Astrophysics Data System (ADS)

    Monti, Mark C.; Alexson, Dimitri A.; Okamitsu, Jeffrey K.

    2016-05-01

    Nuclear Quadrupole Resonance (NQR) is a highly selective spectroscopic method that can be used to detect and identify a number of chemicals of interest to the defense, national security, and law enforcement community. In the past, there have been several documented attempts to utilize NQR to detect nitrogen bearing explosives using induction sensors to detect the NQR RF signatures. We present here our work on the NQR detection of explosive simulants using optically pumped RF atomic magnetometers. RF atomic magnetometers can provide an order of magnitude (or more) improvement in sensitivity versus induction sensors and can enable mitigation of RF interference, which has classically has been a problem for conventional NQR using induction sensors. We present the theory of operation of optically pumped RF atomic magnetometers along with the result of laboratory work on the detection of explosive simulant material. An outline of ongoing work will also be presented along with a path for a fieldable detection system.

  5. RF wave propagation and scattering in turbulent tokamak plasmas

    SciTech Connect

    Horton, W. Michoski, C.; Peysson, Y.; Decker, J.

    2015-12-10

    Drift wave turbulence driven by the steep electron and ion temperature gradients in H-mode divertor tokamaks produce scattering of the RF waves used for heating and current drive. The X-ray emission spectra produced by the fast electrons require the turbulence broaden RF wave spectrum. Both the 5 GHz Lower Hybrid waves and the 170 GHz electron cyclotron [EC] RF waves experience scattering and diffraction by the electron density fluctuations. With strong LHCD there are bifurcations in the coupled turbulent transport dynamics giving improved steady-state confinement states. The stochastic scattering of the RF rays makes the prediction of the distribution of the rays and the associated particle heating a statistical problem. Thus, we introduce a Fokker-Planck equation for the probably density of the RF rays. The general frame work of the coupled system of coupled high frequency current driving rays with the low-frequency turbulent transport determines the profiles of the plasma density and temperatures.

  6. Upgrade of the cryogenic CERN RF test facility

    SciTech Connect

    Pirotte, O.; Benda, V.; Brunner, O.; Inglese, V.; Maesen, P.; Vullierme, B.; Koettig, T.

    2014-01-29

    With the large number of superconducting radiofrequency (RF) cryomodules to be tested for the former LEP and the present LHC accelerator a RF test facility was erected early in the 1990’s in the largest cryogenic test facility at CERN located at Point 18. This facility consisted of four vertical test stands for single cavities and originally one and then two horizontal test benches for RF cryomodules operating at 4.5 K in saturated helium. CERN is presently working on the upgrade of its accelerator infrastructure, which requires new superconducting cavities operating below 2 K in saturated superfluid helium. Consequently, the RF test facility has been renewed in order to allow efficient cavity and cryomodule tests in superfluid helium and to improve its thermal performances. The new RF test facility is described and its performances are presented.

  7. Progress on a cryogenically cooled RF gun polarized electron source

    SciTech Connect

    Fliller, R.P., III; Edwards, H.; /Fermilab

    2006-08-01

    RF guns have proven useful in multiple accelerator applications. An RF gun capable of producing polarized electrons is an attractive electron source for the ILC or an electron-ion collider. Producing such a gun has proven elusive. The NEA GaAs photocathode needed for polarized electron production is damaged by the vacuum environment in an RF gun. Electron and ion back bombardment can also damage the cathode. These problems must be mitigated before producing an RF gun polarized electron source. In this paper we report continuing efforts to improve the vacuum environment in a normal conducting RF gun by cooling it with liquid nitrogen after a high temperature vacuum bake out. We also report on a design of a cathode preparation chamber to produce bulk GaAs photocathodes for testing in such a gun. Future directions are also discussed.

  8. Simulation study on control of spill structure of slow extracted beam from a medical synchrotron with feed-forward and feedback using a fast quadruple magnet and RF-knockout system

    NASA Astrophysics Data System (ADS)

    Muraoka, Ryo; Nakanishi, Tetsuya

    2017-02-01

    A feedback control of the spill structure for the slow beam extraction from the medical synchrotron using a fast quadruple and radio frequency (RF)-knockout (QAR method) is studied to obtain the designed spill structure. In addition the feed-forward control is used so that the feedback control is performed effectively. In this extraction method, the spill of several ms are extracted continuously with an interval time of less than 1 ms. Beam simulation showed that a flat spill structure was effectively obtained with feed-forward and feedback control system as well as a step-wise structure which is useful for the shortening of an irradiation time in a spot scanning operation. The effect of current ripples from main quadruple magnet's power supplies could be also reduced with the feedback control application.

  9. Mechanism of Translation Termination: RF1 Dissociation Follows Dissociation of RF3 from the Ribosome.

    PubMed

    Shi, Xinying; Joseph, Simpson

    2016-11-15

    Release factors 1 and 2 (RF1 and RF2, respectively) bind to ribosomes that have a stop codon in the A site and catalyze the release of the newly synthesized protein. Following peptide release, the dissociation of RF1 and RF2 from the ribosome is accelerated by release factor 3 (RF3). The mechanism for RF3-promoted dissociation of RF1 and RF2 is unclear. It was previously proposed that RF3 hydrolyzes GTP and dissociates from the ribosome after RF1 dissociation. Here we monitored directly the dissociation kinetics of RF1 and RF3 using Förster resonance energy transfer-based assays. In contrast to the previous model, our data show that RF3 hydrolyzes GTP and dissociates from the ribosome before RF1 dissociation. We propose that RF3 stabilizes the ratcheted state of the ribosome, which consequently accelerates the dissociation of RF1 and RF2.

  10. Studies of RF sheaths and diagnostics on IShTAR

    NASA Astrophysics Data System (ADS)

    Crombé, K.; Devaux, S.; D'Inca, R.; Faudot, E.; Faugel, H.; Fünfgelder, H.; Heuraux, S.; Jacquot, J.; Louche, F.; Moritz, J.; Ochoukov, R.; Tripsky, M.; Van Eester, D.; Wauters, T.; Noterdaeme, J.-M.

    2015-12-01

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a linear magnetised plasma test facility for RF sheaths studies at the Max-Planck-Institut für Plasmaphysik in Garching. In contrast to a tokamak, a test stand provides more liberty to impose the parameters and gives better access for the instrumentation and antennas. The project will support the development of diagnostic methods for characterising RF sheaths and validate and improve theoretical predictions. The cylindrical vacuum vessel has a diameter of 1 m and is 1.1 m long. The plasma is created by an external cylindrical plasma source equipped with a helical antenna that has been designed to excite the m=1 helicon mode. In inductive mode, plasma densities and electron temperatures have been characterised with a planar Langmuir probe as a function of gas pressure and input RF power. A 2D array of RF compensated Langmuir probes and a spectrometer are planned. A single strap RF antenna has been designed; the plasma-facing surface is aligned to the cylindrical plasma to ease the modelling. The probes will allow direct measurements of plasma density profiles in front of the RF antenna, and thus a detailed study of the density modifications induced by RF sheaths, which influences the coupling. The RF antenna frequency has been chosen to study different plasma wave interactions: the accessible plasma density range includes an evanescent and propagative behaviour of slow or fast waves, and allows the study of the effect of the lower hybrid resonance layer.

  11. Booster Synchrotron RF System Upgrade for SPEAR3

    SciTech Connect

    Park, Sanghyun; Corbett, Jeff; /SLAC

    2012-07-06

    Recent progress at the SPEAR3 includes the increase in stored current from 100 mA to 200 mA and top-off injection to allow beamlines to stay open during injection. Presently the booster injects 3.0 GeV beam to SPEAR3 three times a day. The stored beam decays to about 150 mA between the injections. The growing user demands are to increase the stored current to the design value of 500 mA, and to maintain it at a constant value within a percent or so. To achieve this goal the booster must inject once every few minutes. For improved injection efficiency, all RF systems at the linac, booster and SPEAR3 need to be phase-locked. The present booster RF system is basically a copy of the SPEAR2 RF system with 358.5 MHz and 40 kW peak RF power driving a 5-cell RF cavity for 1.0 MV gap voltage. These requirements entail a booster RF system upgrade to a scaled down version of the SPEAR3 RF system of 476.3 MHz with 1.2 MW cw klystron output power capabilities. We will analyze each subsystem option for their merits within budgetary and geometric space constraints. A substantial portion of the system will come from the decommissioned PEP-II RF stations.

  12. Control methods to improve non-linear HVAC system operations

    NASA Astrophysics Data System (ADS)

    Phalak, Kaustubh Pradeep

    The change of weather conditions and occupancy schedules makes heating ventilating and air-conditioning (HVAC) systems heavily dynamic. The mass and thermal inertia, nonlinear characteristics and interactions in HVAC systems make the control more complicated. As a result, some conventional control methods often cannot provide desired control performance under variable operating conditions. The purpose of this study is to develop control methods to improve the control performance of HVAC systems. This study focuses on optimizing the airflow-pressure control method of air side economizers, identifying robust building pressurization controls, developing a control method to control outdoor air and building pressure in absence of flow and pressure sensors, stabilizing the cooling coil valve operation and, return fan speed control. The improvements can be achieved by identifying and selecting a method with relatively linear performance characteristics out of the available options, applying fans rather than dampers to control building pressure, and improving the controller's stability range using cascade control method. A steady state nonlinear network model, for an air handling unit (AHU), air distribution system and conditioned space, is applied to analyze the system control performance of air-side economizers and building pressurization. The study shows that traditional controls with completely interlinked outdoor air, recirculated air, relief air dampers have the best control performance. The decoupled relief damper control may result in negative building static pressure at lower outdoor airflow ratio and excessively positive building static pressure at higher outdoor airflow ratio. On the other hand, return fan speed control has a better controllability on building pressurization. In absence of flow and pressure sensors fixed interlinked damper and linear return fan speed tracking control can maintain constant outside air ratio and positive building pressure. The

  13. Limitation of linear colliders from transverse rf deflections

    SciTech Connect

    Seeman, J.T.

    1987-01-01

    Offaxis beam trajectories in a linear collider produce transverse wakefield and chromatic effects which cause emittance enlargement. One cause for non-centered trajectories in the accelerating structures is radial rf fields which produce transverse deflections. Static deflections can be compensated by static dipole magnetic fields. However, fluctuations of the rf fields cause variations in the deflections which must be managed or limited. Given the level of fluctuation of the phase and amplitude of an rf system, a limit on the allowable rf deflection can be calculated. Parameters, such as the beam emittance, lattice design, rf wavelength and the initial and final beam energies, influence the tolerances. Two tolerances are calculated: (1) one assumes that the wakefields are completely controlled, and that chromatic effects are the only enlarging mechanism (optimistic), and (2) the other assumes the limit is due to transverse wakefields without the aid of Landau damping (pessimistic).

  14. RF Communications Laboratory Renewal

    DTIC Science & Technology

    1987-04-08

    January, 1967, required placing steel beams in the lab building roof to withstand the 10,000 ft. -lb. torque rating of the positioner. All proposed...intBilUjr.™w«l«niw»r^MWMMUlPIWMMUIl»UfMM TWTWfTWTWI! SOUTH DAKOTA STATE UNIVERSITY Box 2220 Brooklngs, SO 57007-0194 Department of Electrical ...sampling and vector voltmeters, slotted lines, an rf bridge, a Q meter, octave directional couplers, f>tc. The EE Dept. also has a Hybrid

  15. RF impedance measurement calibration

    SciTech Connect

    Matthews, P.J.; Song, J.J.

    1993-02-12

    The intent of this note is not to explain all of the available calibration methods in detail. Instead, we will focus on the calibration methods of interest for RF impedance coupling measurements and attempt to explain: (1). The standards and measurements necessary for the various calibration techniques. (2). The advantages and disadvantages of each technique. (3). The mathematical manipulations that need to be applied to the measured standards and devices. (4). An outline of the steps needed for writing a calibration routine that operated from a remote computer. For further details of the various techniques presented in this note, the reader should consult the references.

  16. RF Modal Quantity Gaging

    NASA Technical Reports Server (NTRS)

    Vanleuven, K.

    1989-01-01

    The primary objective is to provide a concept of a radio frequency (RF) modal resonance technique which is being investigated as a method for gaging the quantities of subcritical cryogenic propellants in metallic tanks. Of special interest are the potential applications of the technique to microgravity propellant gaging situations. The results of concept testing using cryogenic oxygen, hydrogen, and nitrogen, as well as paraffin simulations of microgravity fluid orientations, are reported. These test results were positive and showed that the gaging concept was viable.

  17. Tomcat-Projects_RF

    SciTech Connect

    Warrant, Marilyn M.; Garcia, Rudy J.; Zhang, Pengchu; Arms, Robert M.; Herzer, John A.; Conrad, Gregory N.; Brabson, John M.

    2004-09-15

    Tomcat-Projects_RF is a software package for analyzing sensor data obtained from a database and displaying the results with Java Servlet Pages (JSP). SQL Views into the dataset are tailored for personnel having different roles in monitoring the items in a storage facility. For example, an inspector, a host treaty compliance officer, a system engineer and software developers were the users identified that would need to access data at different levels of detail, The analysis provides a high level status of the storage facility and allows the user to go deeper into the data details if the user desires.

  18. RF current sensor

    DOEpatents

    Moore, James A.; Sparks, Dennis O.

    1998-11-10

    An RF sensor having a novel current sensing probe and a voltage sensing probe to measure voltage and current. The current sensor is disposed in a transmission line to link all of the flux generated by the flowing current in order to obtain an accurate measurement. The voltage sensor is a flat plate which operates as a capacitive plate to sense voltage on a center conductor of the transmission line, in which the measured voltage is obtained across a resistance leg of a R-C differentiator circuit formed by the characteristic impedance of a connecting transmission line and a capacitance of the plate, which is positioned proximal to the center conductor.

  19. Versatile Low Level RF System For Linear Accelerators

    SciTech Connect

    Potter, James M.

    2011-06-01

    The Low Level RF (LLRF) system is the source of all of the rf signals required for an rf linear accelerator. These signals are amplified to drive accelerator and buncher cavities. It can even provide the synchronizing signal for the rf power for a synchrotron. The use of Direct Digital Synthesis (DDS) techniques results in a versatile system that can provide multiple coherent signals at the same or different frequencies with adjustable amplitudes and phase relations. Pulsing the DDS allows rf switching with an essentially infinite on/off ratio. The LLRF system includes a versatile phase detector that allows phase-locking the rf frequency to a cavity at any phase angle over the full 360 deg. range. With the use of stepper motor driven slug tuners multiple cavity resonant frequencies can be phase locked to the rf source frequency. No external phase shifters are required and there is no feedback loop phase setup required. All that is needed is to turn the frequency feedback on. The use of Digital Signal Processing (DSP) allows amplitude and phase control over the entire rf pulse. This paper describes the basic principles of a LLRF system that has been used for both proton accelerators and electron accelerators, including multiple tank accelerators, sub-harmonic and fundamental bunchers, and synchrotrons.

  20. Improved Process control of wood waste fired boilers

    SciTech Connect

    Process Control Solutions, Inc.

    2004-01-30

    This project's principal aim was the conceptual and feasibility stage development of improved process control methods for wood-waste-fired water-tube boilers operating in industrial manufacturing applications (primarily pulp and paper). The specific objectives put forth in the original project proposal were as follows: (1) fully characterize the wood-waste boiler control inter-relationships and constraints through data collection and analysis; (2) design an improved control architecture; (3) develop and test an appropriate control and optimization algorithm; and (4) develop and test a procedure for reproducing the approach and deriving the benefits on similar pulp and paper wood-waste boilers. Detailed tasks were developed supporting these objectives.

  1. Ion source with external RF antenna

    DOEpatents

    Leung, Ka-Ngo; Ji, Qing; Wilde, Stephen

    2005-12-13

    A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source.

  2. SIMULATION STUDY AND INITIAL TEST OF THESNS RING RF SYSTEM

    SciTech Connect

    Zhang, Yan; Ma, Hengjie; Holmes, Jeffrey A; Champion, Mark; Chu, Paul; Cousineau, Sarah M; Hardek, Thomas W; Plum, Michael A; Danilov, Viatcheslav; Piller, Chip

    2008-01-01

    The rfsimulator code was developed for the study of the Spallation Neutron Source (SNS) dual-harmonic ring RF control. It uses time-domain solvers to compute beam-cavity interactions and FFT methods to simulate the time responses of the linear RF system. The important elements of the system considered in the model include beam loading, dynamic cavity detuning, circuit bandwidth, loop delay, proportional-integral controller for feedback and adaptive feed forward, stochastic noise, width-in-turn loop parameter change, beam current fluctuation, and bunch leakage. As the beam power increases, beam loss in the ring goes up and thus precise control of the bunching RF phase and amplitude is required to limit beam loss. The code will help in the development of a functional RF control and in achieving the goal of minimizing beam loss in the accumulator ring.

  3. The MUCOOL RF Program

    SciTech Connect

    Norem, J.; Bross, A.; Moretti, A.; Norris, B.; Qian, Z.; Torun, Y.; Rimmer, R.; Li, D.; Virostek, S.; Zisman, M.; Sandstrom, R.; /Geneva U.

    2006-06-26

    Efficient muon cooling requires high RF gradients in the presence of high (3T) solenoidal fields. The Muon Ionization Cooling Experiment (MICE) also requires that the x-ray production from these cavities is low, in order to minimize backgrounds in the particle detectors that must be located near the cavities. These cavities require thin Be windows to ensure the highest fields on the beam axis. In order to develop these cavities, the MUCOOL RF Program was started about 6 years ago. Initial measurements were made on a six-cell cavity and a single-cell pillbox, both operating at 805 MHz. We have now begun measurements of a 201 MHz pillbox cavity. This program has led to new techniques to look at dark currents, a new model for breakdown and a general model of cavity performance based on surface damage. The experimental program includes studies of thin Be windows, conditioning, dark current production from different materials, magnetic-field effects and breakdown.

  4. RF Design of the LCLS Gun

    SciTech Connect

    Limborg-Deprey, C

    2010-12-13

    Final dimensions for the LCLS RF gun are described. This gun, referred to as the LCLS gun, is a modified version of the UCLA/BNL/SLAC 1.6 cell S-Band RF gun [1], referred to as the prototype gun. The changes include a larger mode separation (15 MHz for the LCLS gun vs. 3.5 MHz for the prototype gun), a larger radius at the iris between the 2 cells, a reduced surface field on the curvature of the iris between the two cells, Z power coupling, increased cooling channels for operation at 120 Hz, dual rf feed, deformation tuning of the full cell, and field probes in both cells. Temporal shaping of the klystron pulse, to reduce the average power dissipated in the gun, has also been adopted. By increasing the mode separation, the amplitude of the 0-mode electric field on the cathode decreases from 10% of the peak on axis field for the prototype gun to less than 3% for the LCLS gun for the steady state fields. Beam performance is improved as shown by the PARMELA simulations. The gun should be designed to accept a future load lock system. Modifications follow the recommendations of our RF review committee [2]. Files and reference documents are compiled in Section IV.

  5. RF system considerations for large high-duty-factor linacs

    SciTech Connect

    Lynch, M.T.; Ziomek, C.D.; Tallerico, P.J.; Regan, A.H.; Eaton, L.; Lawrence, G.

    1994-09-01

    RF systems are often a major cost item for linacs, but this is especially true for large high-duty-factor linacs (up to and including CW) such as the Accelerator for Production of Tritium (APT) or the Accelerator for Transmutation of nuclear Waste (ATW). In addition, the high energy and high average beam current of these machines (approximately 1 GeV, 100--200 mA) leads to a need for excellent control of the accelerating fields in order to minimize the possibility of beam loss in the accelerator and the resulting activation. This paper will address the key considerations and limitations in the design of the RF system. These considerations impact the design of both the high power RF components and the RF controls. As might be expected, the two concerns sometimes lead to conflicting design requirements. For example minimum RF operating costs lead to a desire for operation near saturation of the high power RF generators in order to maximize the operating efficiency. Optimal control of the RF fields leads to a desire for maximum overdrive capability in those same generators in order to respond quickly to disturbances of the accelerator fields.

  6. Genetic improvement of tomato by targeted control of fruit softening.

    PubMed

    Uluisik, Selman; Chapman, Natalie H; Smith, Rebecca; Poole, Mervin; Adams, Gary; Gillis, Richard B; Besong, Tabot M D; Sheldon, Judith; Stiegelmeyer, Suzy; Perez, Laura; Samsulrizal, Nurul; Wang, Duoduo; Fisk, Ian D; Yang, Ni; Baxter, Charles; Rickett, Daniel; Fray, Rupert; Blanco-Ulate, Barbara; Powell, Ann L T; Harding, Stephen E; Craigon, Jim; Rose, Jocelyn K C; Fich, Eric A; Sun, Li; Domozych, David S; Fraser, Paul D; Tucker, Gregory A; Grierson, Don; Seymour, Graham B

    2016-09-01

    Controlling the rate of softening to extend shelf life was a key target for researchers engineering genetically modified (GM) tomatoes in the 1990s, but only modest improvements were achieved. Hybrids grown nowadays contain 'non-ripening mutations' that slow ripening and improve shelf life, but adversely affect flavor and color. We report substantial, targeted control of tomato softening, without affecting other aspects of ripening, by silencing a gene encoding a pectate lyase.

  7. Effects of RF inhomogeneity at 3.0T on ramped RF excitation: application to 3D time-of-flight MR angiography of the intracranial arteries.

    PubMed

    Eissa, Amir M; Wilman, Alan H

    2007-03-01

    To demonstrate the effects of inherent RF inhomogeneity on ramped RF excitation at 3.0T, and to introduce a simple correction for improving visualization of distal intracranial arteries in three-dimensional time-of-flight MR angiography (3D-TOF-MRA). At 3.0T, the effects of RF inhomogeneity arising from RF interference were demonstrated for ramped RF excitation in intracranial 3D-TOF-MRA. Computer simulations and experiments on phantoms and eight normal volunteers were performed. Four different ramp shapes were tested as a possible means of countering the reduced RF field that affects the distal intracranial arteries. RF destructive interference alters the ramp pulse shape, which is problematic for vessels that proceed from the center to the edge of the brain. Increasing the ramp pulse slope was shown to be an effective yet simple correction to counter the falling-off of the RF field toward the periphery of the head. With this approach, circle-of-Willis 3D-TOF-MRA studies had improved distal visibility. Ramped RF excitation is severely affected by RF interference at 3.0T, which makes the ramp profile suboptimal for distal intracranial blood vessels. A simple correction of the ramp slope can make a marked improvement.

  8. Rf power systems for the national synchrotron light source

    SciTech Connect

    Dickinson, T.; Rheaume, R.H.

    1981-01-01

    The booster synchrotron and the two storage rings at the NSLS are provided with rf power systems of 3 kW, 50 kW, and 500 kW nominal output power, all at 53 MHz. This power is supplied by grounded grid tetrode amplifiers designed for television broadcast service. These amplifiers and associated power supplies, control and interlock systems, rf controls, and computer interface are described.

  9. Alternative RF coupling configurations for H- ion sources

    NASA Astrophysics Data System (ADS)

    Briefi, S.; Gutmann, P.; Fantz, U.

    2015-04-01

    RF heated sources for negative hydrogen ions both for fusion and accelerators require very high RF powers in order to achieve the required H- current what poses high demands on the RF generators and the RF circuit. Therefore it is highly desirable to improve the RF efficiency of the sources. This could be achieved by applying different RF coupling concepts than the currently used inductive coupling via a helical antenna, namely Helicon coupling or coupling via a planar ICP antenna enhanced with ferrites. In order to investigate the feasibility of these concepts, two small laboratory experiments have been set up. The PlanICE experiment, where the enhanced inductive coupling is going to be investigated, is currently under assembly. At the CHARLIE experiment systematic measurements concerning Helicon coupling in hydrogen and deuterium are carried out. The investigations show that a prominent feature of Helicon discharges occurs: the so-called low-field peak. This is a local improvement of the coupling efficiency at a magnetic field strength of a few mT which results in an increased electron density and dissociation degree. The full Helicon mode has not been achieved yet due to the limited available RF power and magnetic field strength but it might be sufficient for the application of the coupling concept to ion sources to operate the discharge in the low-field-peak region.

  10. Benefits of Improved HP Turbine Active Clearance Control

    NASA Technical Reports Server (NTRS)

    Ruiz, Rafael; Albers, Bob; Sak, Wojciech; Seitzer, Ken; Steinetz, Bruce M.

    2007-01-01

    As part of the NASA Propulsion 21 program, GE Aircraft Engines was contracted to develop an improved high pressure turbine(HPT) active clearance control (ACC) system. The system is envisioned to minimize blade tip clearances to improve HPT efficiency throughout the engine operation range simultaneously reducing fuel consumption and emissions.

  11. Modulator considerations for the SNS RF system

    SciTech Connect

    Tallerico, P.J.; Reass, W.A.

    1998-12-31

    The Spallation Neutron Source (SNS) is an intense neutron source for neutron scattering experiments. The project is in the research stage, with construction funding beginning next year. The SNS is comprised of an ion source, a 1,000 MeV, H{sup {minus}} linear accelerator, an accumulator ring, a neutron producing target, and experimental area to utilize the scattering of the neutrons. The linear accelerator is RF driven, and the peak beam current is 27 mA and the beam duty factor is 5.84%. The peak RF power required is 104 MW, and the H{sup {minus}} beam pulse length is 0.97 ms at a 60 Hz repetition rate. The RF pulses must be about 0.1 ms longer than the beam pulses, due to the Q of the accelerating cavities, and the time required to establish control of the cavity fields. The modulators for the klystrons in this accelerator are discussed in this paper. The SNS is designed to be expandable, so the beam power can be doubled or even quadrupled in the future. One of the double-power options is to double the beam pulse length and duty factor. The authors are specifying the klystrons to operate in this twice-duty-factor mode, and the modulator also should be expandable to 2 ms pulses at 60 Hz. Due to the long pulse length and low RF frequency of 805 MHz, the klystron power is specified at 2.5 MW peak, and the RF system will have 56 klystrons at 805 MHz, and three 1.25 MW peak power klystrons at 402.5 MHz for the low energy portion of the accelerator. The low frequency modulators are conventional floating-deck modulation anode control systems.

  12. NSLS-II RF BEAM POSITION MONITOR

    SciTech Connect

    Vetter, K.; Della Penna, A. J.; DeLong, J.; Kosciuk, B.; Mead, J.; Pinayev, I.; Singh, O.; Tian, Y.; Ha, K.; Portmann, G.; Sebek J.

    2011-03-28

    An internal R&D program has been undertaken at BNL to develop a sub-micron RF Beam Position Monitor (BPM) for the NSLS-II 3rd generation light source that is currently under construction. The BPM R&D program started in August 2009. Successful beam tests were conducted 15 months from the start of the program. The NSLS-II RF BPM has been designed to meet all requirements for the NSLS-II Injection system and Storage Ring. Housing of the RF BPM's in +-0.1 C thermally controlled racks provide sub-micron stabilization without active correction. An active pilot-tone has been incorporated to aid long-term (8hr min) stabilization to 200nm RMS. The development of a sub-micron BPM for the NSLS-II has successfully demonstrated performance and stability. Pilot Tone calibration combiner and RF synthesizer has been implemented and algorithm development is underway. The program is currently on schedule to start production development of 60 Injection BPM's starting in the Fall of 2011. The production of {approx}250 Storage Ring BPM's will overlap the Injection schedule.

  13. Superconductor Digital-RF Receiver Systems

    NASA Astrophysics Data System (ADS)

    Mukhanov, Oleg A.; Kirichenko, Dmitri; Vernik, Igor V.; Filippov, Timur V.; Kirichenko, Alexander; Webber, Robert; Dotsenko, Vladimir; Talalaevskii, Andrei; Tang, Jia Cao; Sahu, Anubhav; Shevchenko, Pavel; Miller, Robert; Kaplan, Steven B.; Sarwana, Saad; Gupta, Deepnarayan

    Digital superconductor electronics has been experiencing rapid maturation with the emergence of smaller-scale, lower-cost communications applications which became the major technology drivers. These applications are primarily in the area of wireless communications, radar, and surveillance as well as in imaging and sensor systems. In these areas, the fundamental advantages of superconductivity translate into system benefits through novel Digital-RF architectures with direct digitization of wide band, high frequency radio frequency (RF) signals. At the same time the availability of relatively small 4K cryocoolers has lowered the foremost market barrier for cryogenically-cooled digital electronic systems. Recently, we have achieved a major breakthrough in the development, demonstration, and successful delivery of the cryocooled superconductor digital-RF receivers directly digitizing signals in a broad range from kilohertz to gigahertz. These essentially hybrid-technology systems combine a variety of superconductor and semiconductor technologies packaged with two-stage commercial cryocoolers: cryogenic Nb mixed-signal and digital circuits based on Rapid Single Flux Quantum (RSFQ) technology, room-temperature amplifiers, FPGA processing and control circuitry. The demonstrated cryocooled digital-RF systems are the world's first and fastest directly digitizing receivers operating with live satellite signals in X-band and performing signal acquisition in HF to L-band at ˜30GHz clock frequencies.

  14. Controlled release fertilizer improves quality of container longleaf pine seedlings

    Treesearch

    R. Kasten Dumroese; Jeff Parkhurst; James P. Barnett

    2005-01-01

    In an operational trial, increasing the amount of nitrogen (N) applied to container longleaf pine seedlings by incorporating controlled release fertilizer (CRF) into the media improved seedling growth and quality. Compared with control seedlings that received 40 mg N, seedlings receiving 66 mg N through CRF supplemented with liquid fertilizer had needles that were 4 in...

  15. Perpendicular cultivation for improved weed control in organic peanut production

    USDA-ARS?s Scientific Manuscript database

    Intensive cultivation in organic peanut is partially effective, but in-row weed control remains problematic. In an attempt to improve in-row weed control, trials were conducted to determine the feasibility of early-season cultivation perpendicular to row direction using a tine weeder when integrate...

  16. The process of managerial control in quality improvement initiatives.

    PubMed

    Slovensky, D J; Fottler, M D

    1994-11-01

    The fundamental intent of strategic management is to position an organization with in its market to exploit organizational competencies and strengths to gain competitive advantage. Competitive advantage may be achieved through such strategies as low cost, high quality, or unique services or products. For health care organizations accredited by the Joint Commission on Accreditation of Healthcare Organizations, continually improving both processes and outcomes of organizational performance--quality improvement--in all operational areas of the organization is a mandated strategy. Defining and measuring quality and controlling the quality improvement strategy remain problematic. The article discusses the nature and processes of managerial control, some potential measures of quality, and related information needs.

  17. RF MEMS Based Reconfigurable Antennas

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.

    2004-01-01

    The presentation will first of all address the advantages of RF MEMS circuit in antenna applications and also the need for electronically reconfigurable antennas. Next, discuss some of the recent examples of RF MEMS based reconfigurable microstrip antennas. Finally, conclude the talk with a summary of MEMS antenna performance.

  18. NSLS-II RF SYSTEMS

    SciTech Connect

    Rose, J.; Gash, W.; Holub, B.; Kawashima, Y.; Ma, H.; Towne, N.; Yeddulla, M.

    2011-03-28

    The NSLS-II is a new third generation light source being constructed at Brookhaven Lab. The storage ring is optimized for low emittance by use of damping wigglers to reduce the emittance to below 1 nm-rad. The RF systems are designed to provide stable beam through tight RF phase and amplitude stability requirements.

  19. Rf and space-charge induced emittances in laser-driven rf guns

    SciTech Connect

    Kim, Kwang-Je; Chen, Yu-Jiuan

    1988-10-01

    Laser-driven rf electron guns are potential sources of high-current, low-emittance, short bunch-length electron beams, which are required for many advanced accelerator applications, such as free-electron lasers and injectors for high-energy machines. In such guns the design of which was pioneered at Los Alamos National Laboratory and which is currently being developed at several other laboratories, a high-power laser beam illuminates a photo-cathode surface placed on an end wall of an rf cavity. The main advantages of this type of gun are that the time structure of the electron beam is controlled by the laser, eliminating the need for bunchers, and that the electric field in rf cavities can be made very strong, so that the effects due to space-charge repulsion can be minimized. In this paper, we present an approximate but simple analysis for the transverse and longitudinal emittances in rf guns that takes into account both the time variation of the rf field and the space-charge effect. The results are compared and found to agree well with those from simulation. 7 refs., 6 figs.

  20. System studies of rf current drive for MST

    SciTech Connect

    Anderson, J. K.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Hendries, E. R.; Seltzman, A. H.; Thomas, M. A.; Diem, S.; Harvey, R. W.; Kaufman, M. C.

    2011-12-23

    Two rf schemes are being studied on the MST reversed field pinch for their potential in current profile control experiments. MHD modeling has shown that a substantial externally-driven off axis parallel current can improve stability of the dominant core tearing modes. A radially localized axisymmetric population of fast electrons has been observed by SXR emission during LH injection (100kW at 800MHz), and is consistent with CQL3D modeling which predicts a small driven current. Computational work suggests that doubling the input power will statistically improve the LH-induced SXR signal to background ratio, and that about 2MW of injected power (an order of magnitude increase) will drive enough current for stabilization of tearing modes. Additionally, a 1 MW 5.5 GHz electron Bernstein wave (EBW) experiment is under construction, which utilizes a very simple and compact antenna compatible with the demands of the RFP. EBW allows access to electron cyclotron heating and current drive in the overdense plasma. Coupling of the external electromagnetic wave to the EBW has been demonstrated, and initial tests at {approx}100kW power have produced a small, localized xray flux consistent with rf heating and high diffusivity of fast electrons. Computational work is currently underway to answer the very important questions of how much power is required, and what level of electron diffusivity is tolerable, to generate a consequential amount of EBW current.

  1. Similarity law for rf breakdown

    NASA Astrophysics Data System (ADS)

    Lisovskiy, V.; Booth, J.-P.; Landry, K.; Douai, D.; Cassagne, V.; Yegorenkov, V.

    2008-04-01

    This paper demonstrates that the similarity law for the rf gas breakdown has the form Urf=ψ(p·L,L/R,f·L)(where Urf is the rf breakdown voltage, p is the gas pressure, L and R are the length and diameter of the discharge tube, respectively, f is the frequency of the rf electric field). It means that two rf breakdown curves registered for narrow inter-electrode gaps or in geometrically similar tubes and depicted in the Urf(p·L) graph will coincide only when the condition f·L=const is met. This similarity law follows from the rf gas breakdown equation and it is well supported by the results of measurements.

  2. Wrist Resistance Training Improves Motor Control And Strength.

    PubMed

    Chu, Edward; Kim, You-Sin; Hill, Genevieve; Kim, Yoon Hyuk; Kim, Chang Kook; Shim, Jae Kun

    2017-07-28

    The aim of the present study was to investigate the effects of a 6-week direction specific resistance training program on isometric torque control and isokinetic torque strength of the wrist joint. Nineteen subjects were randomly assigned to either the wrist training group (n=9) or the control group (n=10). The training group performed wrist exercises in six directions (flexion, extension, pronation, supination, radial deviation, and ulnar deviation) while the control group did not. Data were collected on the isometric torque control, one-repetition maximum (1-RM) strength, and isokinetic maximum torque (angular velocity of 60°/s wrist movements) before and after six weeks of resistance training and at two-week intervals during training. The training group showed significant decreases in isometric torque control error in all six directions after 2 weeks of resistance training, while the control group did not show significant increase or decrease. After 4 weeks of training, the training group showed significant increases in maximum strength in all six directions as assessed by 1-RM strength and isokinetic strength tests, while the control group did not show any statistically significant changes. This study shows that motor control significantly improves within the first two weeks of resistance training, while the wrist strength significantly improves within the first four weeks of resistance training. Based on the findings of this study, coaches and trainers should consider wrist resistance training to improve athletes' muscular strength and control of the wrist muscles.

  3. Dual Feed RF Gun Design for the LCLS

    SciTech Connect

    Xiao, L.; Boyce, R.F.; Dowell, D.H.; Li, Z.; Limborg-Deprey, C.; Schmerge, J.F.; /SLAC

    2005-05-23

    In order to remove the dipole field introduced by the coupler in existing S-band BNL/SLAC/UCLA 1.6 cell RF gun, a dual feed design for the LCLS RF gun is proposed together with several significant changes. The improvements include adopting z-coupling instead of {theta}-coupling, modifying the iris dimensions and profile to increase 0- and {pi}-mode separation from 3.4 to 15MHz and reduce the surface field on the iris, incorporating racetrack cavity shape to minimize the quadrupole field, increasing cooling for operation at 120Hz and other small changes to improve performance and diagnostic capabilities. The 3D gun structure had been modeled with the parallel finite element complex eigensolver Omega3p to provide the desired RF parameters and to generate the gun cavity dimensions needed for fabrication. In this paper the RF gun design will be presented.

  4. A Single Switcher Combined Series Parallel Hybrid Envelope Tracking Amplifier for Wideband RF Power Amplifier Applications.

    PubMed

    Anabtawi, Nijad; Ferzli, Rony; Harmanani, Haidar M

    2016-05-01

    In this paper, an improved architecture for RF power amplifier envelope tracking supply modulator is presented. It consists of a single switched mode supply regulator and one linear regulator. The switched mode supply regulator has two outputs, one of which is used in conjunction with the linear regulator to provide a wideband, high efficiency power supply to the RF amplifier, whereas the second output provides a band limited high efficiency supply to the linear regulator. The design offers improved power efficiency, reduced system complexity and area savings since the dual output switched mode regulator requires one inductor and a simple control loop. The design was implemented in 14nm CMOS process and validated with simulations. The supply modulator achieves a peak efficiency of 74% with a 6 dB PAPR 20MHz LTE signal at 29dBm output power.

  5. A Single Switcher Combined Series Parallel Hybrid Envelope Tracking Amplifier for Wideband RF Power Amplifier Applications

    PubMed Central

    Anabtawi, Nijad; Ferzli, Rony; Harmanani, Haidar M.

    2017-01-01

    In this paper, an improved architecture for RF power amplifier envelope tracking supply modulator is presented. It consists of a single switched mode supply regulator and one linear regulator. The switched mode supply regulator has two outputs, one of which is used in conjunction with the linear regulator to provide a wideband, high efficiency power supply to the RF amplifier, whereas the second output provides a band limited high efficiency supply to the linear regulator. The design offers improved power efficiency, reduced system complexity and area savings since the dual output switched mode regulator requires one inductor and a simple control loop. The design was implemented in 14nm CMOS process and validated with simulations. The supply modulator achieves a peak efficiency of 74% with a 6 dB PAPR 20MHz LTE signal at 29dBm output power. PMID:28919658

  6. Studies on human eRF3-PABP interaction reveal the influence of eRF3a N-terminal glycin repeat on eRF3-PABP binding affinity and the lower affinity of eRF3a 12-GGC allele involved in cancer susceptibility

    PubMed Central

    Jerbi, Soumaya; Jolles, Béatrice; Bouceba, Tahar; Jean-Jean, Olivier

    2016-01-01

    ABSTRACT The eukaryotic release factor 3 (eRF3) has been involved in the control of mRNA degradation through its association with the cytoplasmic Poly(A) Binding Protein, PABP. In mammals, eRF3 N-terminal domain contains two overlapping PAM2 motifs which specifically recognize the MLLE domain of PABP. In humans, eRF3a/GSPT1 gene contains a stable GGC repeat encoding a repeat of glycine residues in eRF3a N-terminus. There are five known eRF3a/GSPT1 alleles in the human population, encoding 7, 9, 10, 11 and 12 glycines. Several studies have reported that the presence of eRF3a 12-GGC allele is correlated with an increased risk of cancer development. Using surface plasmon resonance, we have studied the interaction of the various allelic forms of eRF3a with PABP alone or poly(A)-bound PABP. We found that the N-terminal glycine repeat of eRF3a influences eRF3a-PABP interaction and that eRF3a 12-GGC allele has a decreased binding affinity for PABP. Our comparative analysis on eRF3a alleles suggests that the presence of eRF3a 12-GGC allele could modify the coupling between translation termination and mRNA deadenylation. PMID:26818177

  7. Reduction of Ag-Si electrical contact resistance by selective RF heating

    NASA Astrophysics Data System (ADS)

    de Wijs, W.-J. A.; Ljevar, S.; van de Sande, M. J.; de With, G.

    2016-06-01

    Fast and selective inductive heating of pre-sintered silver lines on silicon as present in solar cells using 27 MHz radio-frequency inductive fields is shown. IR measurements of silicon substrates show that above 450 °C the heating rate of the samples increases sharply, indicating that both the silver and the silicon are heated. By moving the substrate with respect to the RF antenna and modulation of the RF field, silicon wafers were heated reproducibly above 450 °C with heating rates in excess of 200 °C s-1. Furthermore, selective heating of lines of pre-sintered silver paste was shown below the 450 °C threshold on silicon substrates. The orientation of the silver tracks relative to the RF antenna appeared to be crucial for homogeneity of heating. Transmission line measurements show a clear effect on contact formation between the silver lines and the silicon substrate. To lower the contact resistance sufficiently for industrial feasibility, a high temperature difference between the Si substrate and the Ag tracks is required. The present RF heating process does not match the time scale needed for contact formation between silver and silicon sufficiently, but the significantly improved process control achieved shows promise for applications requiring fast heating and cooling rates.

  8. Gyrokinetic Calculations of Microinstabilities and Transport During RF H-Modes on Alcator C-Mod

    SciTech Connect

    M.H. Redi; C. Fiore; P. Bonoli; C. Bourdelle; R. Budny; W.D. Dorland; D. Ernst; G. Hammett; D. Mikkelsen; J. Rice; S. Wukitch

    2002-06-18

    Physics understanding for the experimental improvement of particle and energy confinement is being advanced through massively parallel calculations of microturbulence for simulated plasma conditions. The ultimate goal, an experimentally validated, global, non-local, fully nonlinear calculation of plasma microturbulence is still not within reach, but extraordinary progress has been achieved in understanding microturbulence, driving forces and the plasma response in recent years. In this paper we discuss gyrokinetic simulations of plasma turbulence being carried out to examine a reproducible, H-mode, RF heated experiment on the Alcator CMOD tokamak3, which exhibits an internal transport barrier (ITB). This off axis RF case represents the early phase of a very interesting dual frequency RF experiment, which shows density control with central RF heating later in the discharge. The ITB exhibits steep, spontaneous density peaking: a reduction in particle transport occurring without a central particle source. Since the central temperature is maintained while the central density is increasing, this also suggests a thermal transport barrier exists. TRANSP analysis shows that ceff drops inside the ITB. Sawtooth heat pulse analysis also shows a localized thermal transport barrier. For this ICRF EDA H-mode, the minority resonance is at r/a * 0.5 on the high field side. There is a normal shear profile, with q monotonic.

  9. Robert R. Wilson Prize Talk: RF Superconductivity - Technology of Choice

    NASA Astrophysics Data System (ADS)

    Edwards, Helen

    2003-04-01

    In 1992, Bjoern Wiik, soon to become Director of DESY, organized an international effort dedicated to a dramatic improvement in performance and cost of accelerating structures based on RF superconductivity. In this paper I will discuss the degree to which this goal has been achieved and the accompanying technology advances. Today, RF superconductivity is the technology of choice for high duty factor, high beam brightness applications and a serious competitor for use in a linear collider.

  10. Improved Smith predictor control for fast steering mirror system

    NASA Astrophysics Data System (ADS)

    Cao, Zheng; Chen, Jing; Deng, Chao; Mao, Yao; Li, Zhijun

    2017-06-01

    In this paper, a novel Smith predictor control strategy improved by a high bandwidth inner loop for fast steering mirror (FSM) tracking control system based on a charge-coupled device (CCD) and rate sensor is proposed. A high bandwidth velocity closed-loop constructed by a fiber-optic gyroscope is utilized to provide a robust controlled plant for the Smith predictor controller. Usually, due to the mechanical resonances and time delay induced by a low CCD sampling rate, the tracking performance of FSM system is insufficient when suffering uncertain input command. Therefore, the Smith predictor control, which is famous for its delay-free characteristic and suitable for regulating systems with an excessively long time delay, is recommended to compensate for the CCD time delay. However, the classical Smith predictor is sensitive to plant parameter variations, which could deteriorate the stability of the control system. Thus, in order to make a robust Smith predictor, a cascaded dual closed-loop including a high bandwidth velocity inner loop is introduced to reduce the influence of plant parameter variations. The low sensitivity to parameter variation of this method shows the significant improvement of the conventional Smith predictor control. Simultaneously, the analysis of tracking accuracy and the bandwidth of the FSM system is also presented. A series of comparative experimental results demonstrate that the tracking performance of the FSM control system can be effectively improved by the proposed approach.

  11. rf-driven ion sources for industrial applications (invited) (abstract)

    SciTech Connect

    Leung, Ka-Ngo

    2008-02-15

    The Plasma and Ion Source Technology Group at the Lawrence Berkeley National Laboratory have been developing rf-driven ion sources for the last two decades. These sources are being used to generate both positive and negative ion beams. Some of these sources are operating in particle accelerators such as the Spallation Neutron Source (SNS) at Oak Ridge, while others are being employed in various industrial ion beam systems. There are four areas where the rf-driven ion sources are commonly used in industry. (1) In semiconductor manufacturing, rf-driven sources have found important applications in plasma etching, ion beam implantation, and ion beam lithography. (2) In material analysis and surface modification, miniature rf-ion sources can be found in focused ion beam systems. They can provide ion beams of essentially any element in the Periodic Table. The newly developed combined rf ion-electron beam unit improves greatly the performance of the secondary ion mass spectrometry tool. (3) For neutron production, rf ion source is a major component of compact, high flux D-D, D-T, or T-T neutron generators. These neutron sources are now being employed in boron neutron capture therapy (BNCT) as well as in neutron imaging and material interrogation. (4) Large area rf-driven ion source will be used in an industrial design neutral beam diagnostic system for probing fusion plasmas. Such sources can be easily scaled to provide large ion beam current for future fusion reactor applications.

  12. Basic Study on the Generation of RF Plasmas in Premixed Oxy-combustion with Methane

    NASA Astrophysics Data System (ADS)

    Osaka, Yugo; Kobayashi, Noriyuki; Razzak, M. A.; Ohno, Noriyasu; Takamura, Shuichi; Uesugi, Yoshihiko

    Oxy-combustion generates a high temperature field (above 3000 K), which is applied to next generation power plants and high temperature industrial technologies because of N2 free processes. However, the combustion temperature is so high that the furnace wall may be fatally damaged. In addition, it is very difficult to control the heat flux and chemical species' concentrations because of rapid chemical reactions. We have developed a new method for controlling the flame by electromagnetic force on this field. In this paper, we experimentally investigated the power coupling between the premixed oxy-combustion with methane and radio frequency (RF) power through the induction coil. By optimizing the power coupling, we observed that the flame can absorb RF power up to 1.5 kW. Spectroscopic measurements also showed an increase in the emission intensity from OH radicals in the flame, indicating improved combustibility.

  13. An improved PID switching control strategy for type 1 diabetes.

    PubMed

    Marchetti, Gianni; Barolo, Massimiliano; Jovanovic, Lois; Zisser, Howard; Seborg, Dale E

    2006-01-01

    In order for an "artificial pancreas" to become a reality for ambulatory use, a practical closed-loop control strategy must be developed and critically evaluated. In this paper, an improved PID control strategy for blood glucose control is proposed and evaluated in silico using a physiologic model of Hovorka et al. The key features of the proposed control strategy are: (i) a switching strategy for initiating PID control after a meal and insulin bolus; (ii) a novel time-varying setpoint trajectory, (iii) noise and derivative filters to reduce sensitivity to sensor noise, and (iv) a systematic controller tuning strategy. Simulation results demonstrate that the proposed control strategy compares favorably to alternatives for realistic conditions that include meal challenges, incorrect carbohydrate meal estimates, changes in insulin sensitivity, and measurement noise.

  14. An improved PID switching control strategy for type 1 diabetes.

    PubMed

    Marchetti, Gianni; Barolo, Massimiliano; Jovanovic, Lois; Zisser, Howard; Seborg, Dale E

    2008-03-01

    In order for an "artificial pancreas" to become a reality for ambulatory use, a practical closed-loop control strategy must be developed and validated. In this paper, an improved PID control strategy for blood glucose control is proposed and critically evaluated in silico using a physiologic model of Hovorka et al. [1]. The key features of the proposed control strategy are: 1) a switching strategy for initiating PID control after a meal and insulin bolus; 2) a novel time-varying setpoint trajectory; 3) noise and derivative filters to reduce sensitivity to sensor noise; and 4) a practical controller tuning strategy. Simulation results demonstrate that proposed control strategy compares favorably to alternatives for realistic conditions that include meal challenges, incorrect carbohydrate meal estimates, changes in insulin sensitivity, and measurement noise.

  15. Velocity control for improving flow through a bottleneck

    NASA Astrophysics Data System (ADS)

    Yamamoto, Hiroki; Yanagisawa, Daichi; Nishinari, Katsuhiro

    2017-04-01

    A bottleneck can largely deteriorate the flow, such as a traffic light or an on-ramp at a road. To alleviate bottleneck situations, one of the important strategies is to control input rate to suit the state of the road. In this study, we propose an effective velocity control of traveling particles, in which the particle velocity depends on the state of a bottleneck. To analyze our method, we modify the totally asymmetric simple exclusion process (TASEP) and introduce a slow-to-start rule, which we refer to as controlled TASEP in the present paper. Flow improvement is verified in numerical simulations and theoretical analyses by using controlled TASEP.

  16. COMPARISON OF RF CAVITY TRANSPORT MODELS FOR BBU SIMULATIONS

    SciTech Connect

    Ilkyoung Shin,Byung Yunn,Todd Satogata,Shahid Ahmed

    2011-03-01

    The transverse focusing effect in RF cavities plays a considerable role in beam dynamics for low-energy beamline sections and can contribute to beam breakup (BBU) instability. The purpose of this analysis is to examine RF cavity models in simulation codes which will be used for BBU experiments at Jefferson Lab and improve BBU simulation results. We review two RF cavity models in the simulation codes elegant and TDBBU (a BBU simulation code developed at Jefferson Lab). elegant can include the Rosenzweig-Serafini (R-S) model for the RF focusing effect. Whereas TDBBU uses a model from the code TRANSPORT which considers the adiabatic damping effect, but not the RF focusing effect. Quantitative comparisons are discussed for the CEBAF beamline. We also compare the R-S model with the results from numerical simulations for a CEBAF-type 5-cell superconducting cavity to validate the use of the R-S model as an improved low-energy RF cavity transport model in TDBBU. We have implemented the R-S model in TDBBU. It will improve BBU simulation results to be more matched with analytic calculations and experimental results.

  17. Spectroscopy of {sup 257}Rf

    SciTech Connect

    Qian, J.; Heinz, A.; Winkler, R.; Khoo, T. L.; Janssens, R. V. F.; Peterson, D.; Seweryniak, D.; Ahmad, I.; Back, B. B.; Carpenter, M. P.; Greene, J. P.; Jiang, C. L.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; Robinson, A.; Savard, G.; Scott, R.; Vondrasek, R.; Wang, X.

    2009-06-15

    The isotope {sup 257}Rf was produced in the fusion-evaporation reaction {sup 208}Pb({sup 50}Ti,n){sup 257}Rf. Reaction products were separated and identified by mass. Delayed spectroscopy of {sup 257}Rf and its decay products was performed. A partial decay scheme with configuration assignments is proposed based on {alpha} hindrance factors. The excitation energy of the 1/2{sup +}[620] configuration in {sup 253}No is proposed. The energy of this 1/2{sup +} state in a series of N=151 isotones increases with nuclear charge, reflecting an increase in the N=152 gap. This gap is deduced to grow substantially from 850 to 1400 keV between Z=94 and 102. An isomeric state in {sup 257}Rf, with a half-life of 160{sub -31}{sup +42} {mu}s, was discovered by detecting internal conversion electrons followed by {alpha} decay. It is interpreted as a three-quasiparticle high-K isomer. A second group of internal conversion electrons, with a half-life of 4.1{sub -1.3}{sup +2.4} s, followed by {alpha} decay, was also observed. These events might originate from the decay of excited states in {sup 257}Lr, populated by electron-capture decay of {sup 257}Rf. Fission of {sup 257}Rf was unambiguously detected, with a branching ratio of b{sub Rf}{sup SF}=0.02{+-}0.01.

  18. Use of controlled vocabularies to improve biomedical information retrieval tasks.

    PubMed

    Pasche, Emilie; Gobeill, Julien; Vishnyakova, Dina; Ruch, Patrick; Lovis, Christian

    2013-01-01

    The high heterogeneity of biomedical vocabulary is a major obstacle for information retrieval in large biomedical collections. Therefore, using biomedical controlled vocabularies is crucial for managing these contents. We investigate the impact of query expansion based on controlled vocabularies to improve the effectiveness of two search engines. Our strategy relies on the enrichment of users' queries with additional terms, directly derived from such vocabularies applied to infectious diseases and chemical patents. We observed that query expansion based on pathogen names resulted in improvements of the top-precision of our first search engine, while the normalization of diseases degraded the top-precision. The expansion of chemical entities, which was performed on the second search engine, positively affected the mean average precision. We have shown that query expansion of some types of biomedical entities has a great potential to improve search effectiveness; therefore a fine-tuning of query expansion strategies could help improving the performances of search engines.

  19. Design of RF system for CYCIAE-230 superconducting cyclotron

    NASA Astrophysics Data System (ADS)

    Yin, Zhiguo; Ji, Bin; Fu, Xiaoliang; Cao, Xuelong; Zhao, Zhenlu; Zhang, Tinajue

    2017-05-01

    The CYCIAE230 is a low-current, compact superconducting cyclotron designed for proton therapy. The Radio Frequency system consists of four RF cavities and applies second harmonic to accelerate beams. The driving power for the cavity system is estimated to be approximately 150 kW. The LLRF controller is a self-made device developed and tested at low power using a small-scale cavity model. In this paper, the resonator systems of an S.C. cyclotron in history are reviewed. Contrary to those RF systems, the cavities of the CYCIAE230 cyclotron connect two opposite dees. Two high-power RF windows are included in the system. Each window carries approximately 75 kW RF power from the driver to the cavities. Thus, the RF system for the CY-CIAE230 cyclotron is operated in driven push-pull mode. The two-way amplifier-coupler-cavity systems are operated with approximately the same amount of RF power but 180° out of phase compared with each other. The design, as well as the technical advantage and limitations of this operating mode, of the CYCIAE230 cyclotron RF system is analyzed.

  20. Improved confinement in ELM-suppressed high-density H-modes at the ITER field via modification of the plasma boundary with Lower Hybrid RF

    NASA Astrophysics Data System (ADS)

    Terry, J. L.

    2014-10-01

    Injecting Lower Hybrid (LH) power into Alcator C-Mod's high-density H-mode plasmas has enhanced global confinement by increasing pedestal temperature gradients, modifying edge rotation, and decreasing edge and SOL turbulence. These new experiments indicate that edge LHRF can be used as a tool to increase confinement via direct modification of boundary quantities. Ray-tracing modeling and accessibility calculations for the LH waves indicate that the LH waves do not penetrate to regions inside the top of the pedestal and are not driving current in these plasmas; instead the LH power modifies the boundary conditions. When moderate amounts of LH power (PLH/Ptot = 20%) are applied to high-density EDA H-modes (neo = 3.5×1020 m-3) , we observe the following effects: edge/SOL fluctuation power decreases by roughly an order of magnitude; pedestal temperature gradients are increased; global energy confinement time and H-factor increase by 30-40% (H98 from 0.7 to 1.0); co-current core and pedestal rotation velocities increase; power to the (outer) divertor target increases promptly with an increment that is roughly 1/2 of the injected LH power, qualitatively consistent with the inaccessibility of the LH waves; and the central frequency of the edge-localized Quasi-Coherent Mode down-shifts and becomes much more coherent. These H-mode confinement improvements brought about by the edge LHRF are the result of changes in the pedestal (e.g. changes in rotation/shear and increased pedestal temperature gradients), with no substantial change in peaking of core density or temperature profiles. There is not perfect correlation with edge turbulence suppression, indicating that the turbulence decrease may be a necessary, but not sufficient, condition for the pedestal and confinement improvements. Supported by US DoE Awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  1. Effects of Response Preparation on Developmental Improvements in Inhibitory Control

    PubMed Central

    Ordaz, Sarah; Stephanie, Davis; Luna, Beatriz

    2010-01-01

    Studies in adults indicate that response preparation is crucial to inhibitory control, but it remains unclear whether preparation contributes to improvements in inhibitory control over the course of childhood and adolescence. In order to assess the role of response preparation in developmental improvements in inhibitory control, we parametrically manipulated the duration of the instruction period in an antisaccade (AS) task given to participants ages 8 to 31 years. Regressions showing a protracted development of AS performance were consistent with existing research, and two novel findings emerged. First, all participants showed improved performance with increased preparation time, indicating that response preparation is crucial to inhibitory control at all stages of development. Preparatory processes did not deteriorate at even the longest preparatory period, indicating that the youngest participants were able to sustain preparation at even the longest interval. Second, developmental trajectories did not differ for different preparatory period lengths, highlighting that the processes supporting response preparation continue to mature in tandem with improvements in AS performance. Our findings suggest that developmental improvements are not simply due to an inhibitory system that is faster to engage but may also reflect qualitative changes in the processes engaged during the preparatory period. PMID:20347061

  2. RUGGED CERAMIC WINDOW FOR RF APPLICATIONS

    SciTech Connect

    MIKE NEUBAUER

    2012-11-01

    High-current RF cavities that are needed for many accelerator applications are often limited by the power transmission capability of the pressure barriers (windows) that separate the cavity from the power source. Most efforts to improve RF window design have focused on alumina ceramic, the most popular historical choice, and have not taken advantage of new materials. Alternative window materials have been investigated using a novel Merit Factor comparison and likely candidates have been tested for the material properties which will enable construction in the self-matched window configuration. Window assemblies have also been modeled and fabricated using compressed window techniques which have proven to increase the power handling capability of waveguide windows. Candidate materials have been chosen to be used in fabricating a window for high power testing at Thomas Jefferson National Accelerator Facility.

  3. Rugged Ceramic Window for RF Applications

    SciTech Connect

    Neubauer, Michael; Johnson, Rolland P.; Rimmer, Robert; Elliot, Tom; Stirbet, Mircea

    2009-05-04

    High-current RF cavities that are needed for many accelerator applications are often limited by the power transmission capability of the pressure barriers (windows) that separate the cavity from the power source. Most efforts to improve RF window design have focused on alumina ceramic, the most popular historical choice, and have not taken advantage of new materials. Alternative window materials have been investigated using a novel Merit Factor comparison and likely candidates have been tested for the material properties which will enable construction in the self-matched window configuration. Window assemblies have also been modeled and fabricated using compressed window techniques which have proven to increase the power handling capability of waveguide windows. Candidate materials have been chosen to be used in fabricating a window for high power testing at Thomas Jefferson National Accelerator Facility.

  4. ILC RF System R and D

    SciTech Connect

    Adolphsen, Chris; /SLAC

    2012-07-03

    The Linac Group at SLAC is actively pursuing a broad range of R&D to improve the reliability and reduce the cost of the L-band (1.3 GHz) rf system proposed for the ILC linacs. Current activities include the long-term evaluation of a 120 kV Marx Modulator driving a 10 MW Multi-Beam Klystron, design of a second-generation Marx Modulator, testing of a sheet-beam gun and beam transport system for a klystron, construction of an rf distribution system with remotely-adjustable power tapoffs, and development of a system to combine the power from many klystrons in low-loss circular waveguide where it would be tapped-off periodically to power groups of cavities. This paper surveys progress during the past few years.

  5. Air Force Internal Control Systems: A Proposal for Improvement.

    DTIC Science & Technology

    1986-09-01

    structured interview was especially appreciated. Particularly helpful was the guidance offered by Mrs. Rosie Kellison and her associates in the Cost... h ) Include recognition of noteworthy accomplishments, particularly when management improvements in one program or activity may be applicable...34Objective and Standards of Internal Control--AFLC," B , 35:11 (2 May 1983). 23. Calnan, William H . Internal Controls. Standards. and Implementation. Idea

  6. An improved adaptive control for repetitive motion of robots

    NASA Technical Reports Server (NTRS)

    Pourboghrat, F.

    1989-01-01

    An adaptive control algorithm is proposed for a class of nonlinear systems, such as robotic manipulators, which is capable of improving its performance in repetitive motions. When the task is repeated, the error between the desired trajectory and that of the system is guaranteed to decrease. The design is based on the combination of a direct adaptive control and a learning process. This method does not require any knowledge of the dynamic parameters of the system.

  7. Impact of HVAC control improvements on supermarket humidity levels

    SciTech Connect

    Khattar, M.; Henderson, H.I. Jr.

    1999-07-01

    This paper presents field-monitored data from two supermarkets where the impact of implementing minor HVAC control improvements was evaluated. The control improvements were intended to increase the dehumidification capacity of the HVAC system and lower space humidity levels. Direct digital control (DDC) was installed at each store to monitor system performance and implement the control improvements. At the first test store, a 33,400 ft{sup 2} (3,104 m{sup 2}) supermarket near Minneapolis, a conventional 50 ton (176 kW) split system conditioned the sales area. At the second store, a 50,000 ft{sup 2} (4,647 m{sup 2}{minus}) supermarket near Indianapolis, three rooftop units (RTUs) with a total capacity of 98 tons (344 kW) conditioned the store. The results from both supermarkets confirm the impact that supply airflow and part-load control of evaporator coil temperatures can have on dehumidification performance. Seemingly minor control adjustments can often have a big impact on the performance of supermarket HVAC systems. Even enhanced dehumidification technologies, such as heat pipe-assisted evaporator coils, can benefit from minor system tuning.

  8. RF tuning element

    NASA Technical Reports Server (NTRS)

    McGrath, William R. (Inventor); Lubecke, Victor M. (Inventor)

    1992-01-01

    A device for tuning a circuit includes a substrate, a transmission line on the substrate that includes first and second conductors coupled to a circuit to be tuned, and a movable short-circuit for varying the impedance the transmission line presents to the circuit to be tuned. The movable short-circuit includes a dielectric layer disposed atop the transmission line and a distributed shorting element in the form of a conductive member that is configured to be slid along at least a portion of the transmission line atop the dielectric layer. The conductive member is configured to span the first and second conductors of the transmission line and to define at least a first opening that spans the two conductors so that the conductive member includes first and second sections separated by the first opening. The first and second sections of the conductive member combine with the first and second conductors of the transmission line to form first and second low impedance sections of transmission line, and the opening combines with the first and second conductors of the transmission line and the dielectric layer to form a first high impedance section of transmission line intermediate the first and second low impedance sections. Each of the first low impedance section and the first high impedance section have a length along the transmission line of approximately one-quarter wavelength, thus providing a periodic variation of transmission line impedance. That enhances reflection of rf power.

  9. DESIGN OF A DC/RF PHOTOELECTRON GUN.

    SciTech Connect

    YU,D.NEWSHAM,Y.SMIRONOV,A.YU,J.SMEDLEY,J.SRINIVASAN RAU,T.LEWELLEN,J.ZHOLENTS,A.

    2003-05-12

    An integrated dc/rf photoelectron gun produces a low-emittance beam by first rapidly accelerating electrons at a high gradient during a short ({approx}1 ns), high-voltage pulse, and then injecting the electrons into an rf cavity for subsequent acceleration. Simulations show that significant improvement of the emittance appears when a high field ({approx} 0.5-1 GV/m) is applied to the cathode surface. An adjustable dc gap ({le} 1 mm) which can be integrated with an rf cavity is designed for initial testing at the Injector Test Stand at Argonne National Laboratory using an existing 70-kV pulse generator. Plans for additional experiments of an integrated dc/rf gun with a 250-kV pulse generator are being made.

  10. Development and applications of Krotov method of global control improvement

    SciTech Connect

    Rasina, Irina V.; Trushkova, Ekaterina A.; Baturina, Olga V.; Bulatov, Alexander V.; Guseva, Irina S.

    2016-06-08

    This is a survey of works on main properties, application and development of the Krotov method of global control improvement very popular among researchers of modern problems in quantum physics and quantum chemistry, applying actively optimal control methods. The survey includes a brief description of the method in comparison with well known gradient method demonstrating such its serious advantage as absence of tuning parameters; investigations aimed to make its special version for the quantum system well defined and more effective; and generalization for wide classes of control systems, including the systems of heterogeneous structure.

  11. Improving the sensitivity of negative controls in ancient DNA extractions.

    PubMed

    Xu, Zhi; Zhang, Fan; Xu, Bosong; Tan, Jingze; Li, Shilin; Jin, Li

    2009-04-01

    Much attention has been paid on ancient DNA (aDNA) studies, and negative control was used as one of the stringent quality assurance criteria in order to detect potential contamination. However, the results of some aDNA studies showed the evidence of contamination despite their negative controls failed to do so. Using lambda DNA to mock extraneous contaminating DNA, our study showed that aDNA had a property of improving the efficiency of extraction including contaminating DNA, while negative controls had low sensitivity to detect contamination. To circumvent this problem, carrier DNA such as poly(dA) is suggested to be introduced into aDNA extraction.

  12. Experience with the PEP-II RF System at High Beam Currents

    SciTech Connect

    Corredoura, Paul L.

    2000-07-06

    The PEP-II Factory Low-Level RF System (LLRF) is a fully programmable VXI based design running under an EPICS control environment. Several RF feedback loops are used to control longitudinal coupled-bunch modes driven by the accelerating mode of the RF cavities. This paper updates the performance of the LLRF system as beam currents reach design levels. Modifications which enhance the stability, diagnostics, and overall operational performance are described. Recent data from high current operation is included.

  13. Mixed application MMIC technologies - Progress in combining RF, digital and photonic circuits

    NASA Technical Reports Server (NTRS)

    Swirhun, S.; Bendett, M.; Sokolov, V.; Bauhahn, P.; Sullivan, C.; Mactaggart, R.; Mukherjee, S.; Hibbs-Brenner, M.; Mondal, J.

    1991-01-01

    Approaches for future 'mixed application' monolithic integrated circuits (ICs) employing optical receive/transmit, RF amplification and modulation and digital control functions are discussed. We focus on compatibility of the photonic component fabrication with conventional RF and digital IC technologies. Recent progress at Honeywell in integrating several parts of the desired RF/digital/photonic circuit integration suite required for construction of a future millimeter-wave optically-controlled phased-array element are illustrated.

  14. Unbalanced field RF electron gun

    DOEpatents

    Hofler, Alicia

    2013-11-12

    A design for an RF electron gun having a gun cavity utilizing an unbalanced electric field arrangement. Essentially, the electric field in the first (partial) cell has higher field strength than the electric field in the second (full) cell of the electron gun. The accompanying method discloses the use of the unbalanced field arrangement in the operation of an RF electron gun in order to accelerate an electron beam.

  15. Beam screen cryogenic control improvements for the LHC run 2

    NASA Astrophysics Data System (ADS)

    Bradu, B.; Rogez, E.; Blanco-Viñuela, E.; Ferlin, G.; Tovar-Gonzalez, A.

    2017-02-01

    This paper presents the improvements made on the cryogenic control system for the LHC beam screens. The regulation objective is to maintain an acceptable temperature range around 20 K which simultaneously ensures a good LHC beam vacuum and limits cryogenic heat loads. In total, through the 27 km of the LHC machine, there are 485 regulation loops affected by beam disturbances. Due to the increase of the LHC performance during Run 2, standard PID controllers cannot keeps the temperature transients of the beam screens within desired limits. Several alternative control techniques have been studied and validated using dynamic simulation and then deployed on the LHC cryogenic control system in 2015. The main contribution is the addition of a feed-forward control in order to compensate the beam effects on the beam screen temperature based on the main beam parameters of the machine in real time.

  16. Improvements and applications of entrainment control for nonlinear dynamical systems.

    PubMed

    Liu, Fang; Song, Qiang; Cao, Jinde

    2008-12-01

    This paper improves the existing entrainment control approaches and develops unified schemes to chaos control and generalized (lag, anticipated, and complete) synchronization of nonlinear dynamical systems. By introducing impulsive effects to the open-loop control method, we completely remove its restrictions on goal dynamics and initial conditions, and derive a sufficient condition to estimate the upper bound of impulsive intervals to ensure the global asymptotic stability. We then propose two effective ways to implement the entrainment strategy which combine open-loop and closed-loop control, and we prove that the feedback gains can be chosen according to a lower bound or be tuned with an adaptive control law. Numerical examples are given to verify the theoretical results and to illustrate their applications.

  17. Concepts for a short wavelength rf gun

    NASA Astrophysics Data System (ADS)

    Kuzikov, S. V.; Shchelkunov, S.; Vikharev, A. A.

    2017-03-01

    Three concepts of an rf gun to be operated at 0.1-10 mm wavelengths are considered. In all the concepts, the rf system exploits an accelerating traveling wave. In comparison with a classical decimeter standing-wave rf gun, we analyze the advantages of new concepts, available rf sources, and achievable beam parameters.

  18. Improved pointing at trackable targets by integrating control valve signals

    NASA Technical Reports Server (NTRS)

    Stone, R. W.; Laverty, C. R.; Colby, M. J.

    1982-01-01

    A compact, low-cost add-on electronic module has been developed for the STRAP III control system to improve pointing at trackable targets. The module provides peak-to-peak limit cycle excursions of + or - 5 arcseconds while tracking a +3 magnitude or brighter star. This is achieved without using rate-integrating gyroscopes, thus reducing payload length, weight, cost, and preparation time. This module has flown successfully five times. In May 1981, it improved the performance of a two-startracker attitude control system with TV camera and joystick control which pointed at a nontrackable target. This paper describes the operation of the module, how it alters the ordinary STRAP III operation, and how it was developed using an analog-computer-based rocket flight simulator.

  19. RF Sputtering for preparing substantially pure amorphous silicon monohydride

    DOEpatents

    Jeffrey, Frank R.; Shanks, Howard R.

    1982-10-12

    A process for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicon produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous silicon hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

  20. RF assisted Glow Discharge Condition experiment for SST-1 Tokamak

    NASA Astrophysics Data System (ADS)

    Raval, Dilip; Khan, Ziauddin; George, Siju; Dhanani, Kalpeshkumar R.; Paravastu, Yuvakiran; Semwal, Pratibha; Thankey, Prashant; Shoaib Khan, Mohammad; Kakati, Bharat; Pradhan, Subrata

    2017-04-01

    Impurity control reduces the radiation loss from plasma and hence enhances the plasma operation. Oxygen and water vapors are the most common impurities in tokamak devices. Water vapour can be reduced with extensive baking while in order to have a significant reduction in oxygen it is necessary to use glow discharge condition (GDC). RF assisted glow discharge cleaning system will be implemented to remove low z impurities at PFC installed SST-1 vacuum vessel. A RF assisted Glow discharge conditioning is studied at laboratory to find the optimum operating parameters in a view to implement at SST-1 tokamak. Helium is used as a fuel gas in the present experiment. It is observed that the ultimate impurity level is reduced significantly below to the accepted level for plasma operation after RF assisted GDC. The experimental findings of RF assisted Glow discharge conditioning is discussed in details in this paper.

  1. Timing and low-level rf system for an x-ray laser

    NASA Astrophysics Data System (ADS)

    Otake, Yuji; Maesaka, Hirokazu; Matsubara, Shinich; Hosoda, Naoyasu; Ohshima, Takashi

    2016-02-01

    An x-ray free-electron laser (XFEL), SACLA, designed to open up new science, was constructed for generating coherent x rays with a peak power of more than 10 GW and a very short pulse of below 30 fs. This feature demands a very highly short-term temporal stability of less than 50 fs to the acceleration rf field of SACLA. For this reason, we developed a timing and low-level rf (LLRF) system for SACLA based on that of the SPring8 compact SASE source (SCSS) test accelerator for verifying the feasibility of an XFEL. The performance of the system using the in-phase and quadrature rf manipulation method was improved from SCSS's system. Since the facility length of SACLA is 700 m, which is 10 times longer than that of the SCSS test accelerator, a phase-stabilized optical-fiber system designed to transmit time standard rf signals with low loss was also developed and deployed. This optical-fiber system equips fiber optical-length feedback control in order to mitigate environmental effects, such as temperature and humidity changes. On the other hand, the demanded maximum rf temporal stability is less than 50 fs, which is almost 10 times smaller than that of the SCSS test accelerator. Hence, reducing electric noise and increasing the temperature stability around timing and LLRF instruments were necessary and realized with a very low-noise power supply and a hemathermal 19-inch enclosure. The short-term temporal performance of the timing LLRF system finally attained a temporal stability of less than 13.6 fs in rms measured by a beam arrival-time measurement. This stability greatly helps to achieve the stable x-ray lasing of SACLA for routine operation during user experiments.

  2. Improving active space telescope wavefront control using predictive thermal modeling

    NASA Astrophysics Data System (ADS)

    Gersh-Range, Jessica; Perrin, Marshall D.

    2015-01-01

    Active control algorithms for space telescopes are less mature than those for large ground telescopes due to differences in the wavefront control problems. Active wavefront control for space telescopes at L2, such as the James Webb Space Telescope (JWST), requires weighing control costs against the benefits of correcting wavefront perturbations that are a predictable byproduct of the observing schedule, which is known and determined in advance. To improve the control algorithms for these telescopes, we have developed a model that calculates the temperature and wavefront evolution during a hypothetical mission, assuming the dominant wavefront perturbations are due to changes in the spacecraft attitude with respect to the sun. Using this model, we show that the wavefront can be controlled passively by introducing scheduling constraints that limit the allowable attitudes for an observation based on the observation duration and the mean telescope temperature. We also describe the implementation of a predictive controller designed to prevent the wavefront error (WFE) from exceeding a desired threshold. This controller outperforms simpler algorithms even with substantial model error, achieving a lower WFE without requiring significantly more corrections. Consequently, predictive wavefront control based on known spacecraft attitude plans is a promising approach for JWST and other future active space observatories.

  3. Improved Continuous-Time Higher Harmonic Control Using Hinfinity Methods

    NASA Astrophysics Data System (ADS)

    Fan, Frank H.

    The helicopter is a versatile aircraft that can take-off and land vertically, hover efficiently, and maneuver in confined space. This versatility is enabled by the main rotor, which also causes undesired harmonic vibration during operation. This unwanted vibration has a negative impact on the practicality of the helicopter and also increases its operational cost. Passive control techniques have been applied to helicopter vibration suppression, but these methods are generally heavy and are not robust to changes in operating conditions. Feedback control offers the advantages of robustness and potentially higher performance over passive control techniques, and amongst the various feedback schemes, Shaw's higher harmonic control algorithm has been shown to be an effective method for attenuating harmonic disturbance in helicopters. In this thesis, the higher harmonic disturbance algorithm is further developed to achieve improved performance. One goal in this thesis is to determine the importance of periodicity in the helicopter rotor dynamics for control synthesis. Based on the analysis of wind tunnel data and simulation results, we conclude the helicopter rotor can be modeled reasonably well as linear and time-invariant for control design purposes. Modeling the helicopter rotor as linear time-invariant allows us to apply linear control theory concepts to the higher harmonic control problem. Another goal in this thesis is to find the limits of performance in harmonic disturbance rejection. To achieve this goal, we first define the metrics to measure the performance of the controller in terms of response speed and robustness to changes in the plant dynamics. The performance metrics are incorporated into an Hinfinity control problem. For a given plant, the resulting Hinfinity controller achieves the maximum performance, thus allowing us to identify the performance limitation in harmonic disturbance rejection. However, the Hinfinity controllers are of high order, and may

  4. Lithography focus/exposure control and corrections to improve CDU

    NASA Astrophysics Data System (ADS)

    Kim, Young Ki; Yelverton, Mark; Lee, Joungchel; Cheng, Jerry; Wei, Hong; Kim, Jeong Soo; Gutjahr, Karsten; Gao, Jie; Karur-Shanmugam, Ram; Herrera, Pedro; Huang, Kevin; Volkovich, Roie; Pierson, Bill

    2013-04-01

    As leading edge lithography moves to advanced nodes which requires better critical dimension (CD) control ability within wafer. Current methods generally make exposure corrections by field via factory automation or by sub-recipe to improve CD uniformity. KLA-Tencor has developed a method to provide CD uniformity (CDU) control using a generated Focus/Exposure (F/E) model from a representative process. Exposure corrections by each field can be applied back to the scanner so as to improve CD uniformity through the factory automation. CDU improvement can be observed either at after lithography or after etch metrology steps. In addition to corrections, the graphic K-T Analyzer interface also facilitates the focus/exposure monitoring at the extreme wafer edge. This paper will explain the KT CDFE method and the application in production environment. Run to run focus/exposure monitoring will be carried out both on monitoring and production wafers to control the wafer process and/or scanner fleet. CDU improvement opportunities will be considered as well.

  5. Improved diabetes control in the elderly delays global cognitive decline.

    PubMed

    Luchsinger, J A; Palmas, W; Teresi, J A; Silver, S; Kong, J; Eimicke, J P; Weinstock, R S; Shea, S

    2011-06-01

    To examine whether improved diabetes control is related to better cognitive outcomes. Randomized control trial. A randomized trial of telemedicine vs. usual care in elderly persons with type 2 diabetes. Participants were 2169 persons 55 years and older with type 2 diabetes from New York City and Upstate New York. The diabetes case management intervention was implemented by a diabetes nurse, via a telemedicine unit in the participant's home, and in coordination with the primary care physician. Hemoglobin A1c (HbA1c), systolic blood pressure (SBP), and low density lipoprotein cholesterol (LDL), were measured at a baseline visit and at up to 5 annual follow-up visits. Global cognition was measured at those visits with the Comprehensive Assessment and Referral Evaluation (CARE). In mixed models the intervention was related to slower global cognitive decline in the intervention group (p = 0.01). Improvements in HbA1c (p = 0.03), but not SBP or LDL, mediated the effect of the intervention on cognitive decline. Improved diabetes control in the elderly following existing guidelines through a telemedicine intervention was associated with less global cognitive decline. The main mediator of this effect seemed to be improvements in HbA1c.

  6. Improved satellite attitude control using a disturbance compensator

    NASA Astrophysics Data System (ADS)

    Yamashita, Toshiaki; Ogura, Naoto; Kurii, Toshihiro; Hashimoto, Tatsuaki

    2004-07-01

    An attitude control algorithm using a disturbance compensator has been developed for three-axis-controlled satellites with flexible appendages. It consists of a compensator to stabilize the system (e.g., PD control), a filter to prevent excitation of the neglected higher flexible-mode vibration (e.g., a low-pass filter), and a compensator to suppress the effect of disturbances on the satellite attitude. This disturbance compensator can be designed in the frequency-domain in terms of the robust model matching design method, and also, in the time-domain in terms of the observer/estimator approach. The designed compensator can easily be implemented for a conventional attitude control system. Theoretically, the disturbance compensator makes it possible to assure arbitrarily low sensitivity over any frequency range for disturbances due not only to the environment but also to structural flexibility with keeping the control performance for reference inputs. Thus, the control algorithm can improve the control performance of satellites with the flexible structures. It is applied for the attitude control system of the Japanese VLBI satellite, "HALCA", launched on February 12, 1997.

  7. [Bi]:[Te] Control, Structural and Thermoelectric Properties of Flexible Bi x Te y Thin Films Prepared by RF Magnetron Sputtering at Different Sputtering Pressures

    NASA Astrophysics Data System (ADS)

    Nuthongkum, Pilaipon; Sakdanuphab, Rachsak; Horprathum, Mati; Sakulkalavek, Aparporn

    2017-07-01

    In this work, flexible Bi x Te y thin films were prepared by radio frequency (RF) magnetron sputtering using a Bi2Te3 target on polyimide substrate. The effects of sputtering pressures, which ranged between 0.6 Pa and 1.6 Pa on the [Bi]:[Te] ratio, and structural and thermoelectric properties were investigated. The [Bi]:[Te] ratio of thin film was determined by energy-dispersive spectrometry (EDS). The EDS spectra show the variation of the [Bi]:[Te] ratio as the sputtering pressure is varied. The film deposited at 1.4 Pa almost has a stoichiometric composition. The selective films with different [Bi]:[Te] ratios and sputtering pressures were characterized by their surface morphologies, crystal and chemical structures by field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD) and Raman spectroscopy, respectively. Electrical transport properties, including carrier concentration and mobility, were measured by Hall effect measurements. Seebeck coefficients and electrical conductivities were simultaneously measured by a direct current four-terminal method (ZEM-3). The XRD and Raman spectroscopy results show a difference in microstructure between BiTe and Bi2Te3 depending on the [Bi]:[Te] ratio. Electrical conductivity and Seebeck coefficient are related to the crystal and chemical structures. The maximum power factor of the Bi2Te3 thin film is 9.5 × 10-4 W/K2 m at room temperature, and it increases to 12.0 × 10-4 W/K2 m at 195°C.

  8. Photonic generation and independent steering of multiple RF signals for software defined radars.

    PubMed

    Ghelfi, Paolo; Laghezza, Francesco; Scotti, Filippo; Serafino, Giovanni; Pinna, Sergio; Bogoni, Antonella

    2013-09-23

    As the improvement of radar systems claims for digital approaches, photonics is becoming a solution for software defined high frequency and high stability signal generation. We report on our recent activities on the photonic generation of flexible wideband RF signals, extending the proposed architecture to the independent optical beamforming of multiple signals. The scheme has been tested generating two wideband signals at 10 GHz and 40 GHz, and controlling their independent delays at two antenna elements. Thanks to the multiple functionalities, the proposed scheme allows to improve the effectiveness of the photonic approach, reducing its cost and allowing flexibility, extremely wide bandwidth, and high stability.

  9. Enhanced IGCC regulatory control and coordinated plant-wide control strategies for improving power ramp rates

    SciTech Connect

    Mahapatra, P.; Zitney, S.

    2012-01-01

    As part of ongoing R&D activities at the National Energy Technology Laboratory’s (NETL) Advanced Virtual Energy Simulation Training & Research (AVESTAR™) Center, this paper highlights strategies for enhancing low-level regulatory control and system-wide coordinated control strategies implemented in a high-fidelity dynamic simulator for an Integrated Gasification Combined Cycle (IGCC) power plant with carbon capture. The underlying IGCC plant dynamic model contains 20 major process areas, each of which is tightly integrated with the rest of the power plant, making individual functionally-independent processes prone to routine disturbances. Single-loop feedback control although adequate to meet the primary control objective for most processes, does not take into account in advance the effect of these disturbances, making the entire power plant undergo large offshoots and/or oscillations before the feedback action has an opportunity to impact control performance. In this paper, controller enhancements ranging from retuning feedback control loops, multiplicative feed-forward control and other control techniques such as split-range control, feedback trim and dynamic compensation, applicable on various subsections of the integrated IGCC plant, have been highlighted and improvements in control responses have been given. Compared to using classical feedback-based control structure, the enhanced IGCC regulatory control architecture reduces plant settling time and peak offshoots, achieves faster disturbance rejection, and promotes higher power ramp-rates. In addition, improvements in IGCC coordinated plant-wide control strategies for “Gasifier-Lead”, “GT-Lead” and “Plantwide” operation modes have been proposed and their responses compared. The paper is concluded with a brief discussion on the potential IGCC controller improvements resulting from using advanced process control, including model predictive control (MPC), as a supervisory control layer.

  10. Instrumentation and control improvements at Experimental Breeder Reactor II

    SciTech Connect

    Christensen, L.J.; Planchon, H.P.

    1993-03-01

    The purpose of this paper is to describe instrumentation and control (I&C) system improvements at Experimental Breeder Reactor 11 (EBR-11). The improvements are focused on three objectives; to keep the reactor and balance of plant (BOP) I&C systems at a high level of reliability, to provide diagnostic systems that can provide accurate information needed for analysis of fuel performance, and to provide systems that will be prototypic of I&C systems of the next generation of liquid metal reactor (LMR) plants.

  11. Instrumentation and control improvements at Experimental Breeder Reactor II

    SciTech Connect

    Christensen, L.J.; Planchon, H.P.

    1993-01-01

    The purpose of this paper is to describe instrumentation and control (I C) system improvements at Experimental Breeder Reactor 11 (EBR-11). The improvements are focused on three objectives; to keep the reactor and balance of plant (BOP) I C systems at a high level of reliability, to provide diagnostic systems that can provide accurate information needed for analysis of fuel performance, and to provide systems that will be prototypic of I C systems of the next generation of liquid metal reactor (LMR) plants.

  12. Control systems improvements in a precision coordinate measuring machine

    NASA Astrophysics Data System (ADS)

    Douglass, S. S.; Babelay, E. F., Jr.; Igou, R. E.; Woodard, L. M.; Green, W. L.

    1981-09-01

    A conventional, manually driven Moore No. 3 coordinate measuring machine at the Oak Ridge Y-12 Plant is being upgraded to provide a continuous-path numerical control capability and simultaneously serve as a vehicle for testing new machine slide-control concepts. Besides new lead screw drive motors, an NC machine control unit, and a closed-loop servo system, the machine has also been equipped with vibration isolation, air-bearing slideways, and laser interferometric position feedback. The present conventional slide servo system will be replaced with a digital servo system wherein various feedback and compensation techniques can be realized through the use of a high speed, dedicated digital processor. The improvements to data are described with emphasis on identification and compensation of the slide control systems.

  13. Tune-control improvements on the rapid-cycling synchrotron

    SciTech Connect

    Potts, C.; Faber, M.; Gunderson, G.; Knott, M.; Voss, D.

    1981-01-01

    The as-built lattice of the Rapid-Cycling Synchrotron (RCS) had two sets of correction sextupoles and two sets of quadrupoles energized by dc power supplies to control the tune and the tune tilt. With this method of powering these magnets, adjustment of tune conditions during the accelerating cycle as needed was not possible. A set of dynamically programmable power supplies has been built and operated to provide the required chromaticity adjustment. The short accelerating time (16.7 ms) of the RCS and the inductance of the magnets dictated large transistor amplifier power supplies. The required time resolution and waveform flexibility indicated the desirability of computer control. Both the amplifiers and controls are described, along with resulting improvements in the beam performance. A set of octupole magnets and programmable power supplies with similar dynamic qualities have been constructed and installed to control the anticipated high-intensity transverse instability. This system will be operational in the spring of 1981.

  14. Improving a pharmaceutical purchasing and inventory control system.

    PubMed

    Rubin, H; Keller, D D

    1983-01-01

    A method by which a pharmacy department improved its purchasing and inventory control system is described. System changes to the computerized inventory control system included implementation of a formulary, affiliation with a group purchasing association, and transfer of specified purchasing and inventory control functions to the technical staff of the purchasing department. Pharmacy maintained the decision-making authority over all vendors and dosage forms of drug products. Optimal results were achieved when the purchasing department's pharmacy buyer position was staffed with an employee who had previous experience as a clerical worker in the pharmacy. The authors state that this system has proved to be an effective, cost efficient method of purchasing and inventory control of pharmaceuticals in their hospital.

  15. RF gun emittance correction using unsymmetrical RF cavities

    NASA Astrophysics Data System (ADS)

    Serafini, L.; Rivolta, R.; Terzoli, L.; Pagani, C.

    1992-07-01

    The beam dynamics in RF guns is characterized by an optimum injection phase which minimizes the RF-field-induced emittance blowup: such a condition corresponds to a vanishing first order term in the phase dependence of the exit transverse momentum. Away from the optimum phase, a sharp increase of the emittance is found. In this paper we analyze the possibility of compensating for both the first and second order terms, in order to recover the minimum emittance value even at phases different from the optimum one. Our scheme is based on the use of an unsymmetrical RF cavity, added downstream of the gun cavity and fully uncoupled from it, in order to be independently phased. At the exit of this cavity the minimum emittance value can be recovered, the injection phase being a free parameter to be independently optimized. In this way higher injection phases can be exploited, where the longitudinal rms emittance displays a minimum, and long bunches extracted from the gun can be magnetically compressed more efficiently, achieving a significant beam brightness increase with respect to conventionally optimized RF guns. An analytical study of the beam dynamics inside the unsymmetrical RF cavity is presented, together with the results of some numerical simulations performed with the PIC code ITACA [L. Serafini and C. Pagani, Proc. 1st EPAC, Rome, June 1988 (Word Scientific) p. 866].

  16. Plasma Aerodynamic Control Effectors for Improved Wind Turbine Performance

    SciTech Connect

    Mehul P. Patel; Srikanth Vasudevan; Robert C. Nelson; Thomas C. Corke

    2008-08-01

    Orbital Research Inc is developing an innovative Plasma Aerodynamic Control Effectors (PACE) technology for improved performance of wind turbines. The PACE system is aimed towards the design of "smart" rotor blades to enhance energy capture and reduce aerodynamic loading and noise using flow-control. The PACE system will provide ability to change aerodynamic loads and pitch distribution across the wind turbine blade without any moving surfaces. Additional benefits of the PACE system include reduced blade structure weight and complexity that should translate into a substantially reduced initial cost. During the Phase I program, the ORI-UND Team demonstrated (proof-of-concept) performance improvements on select rotor blade designs using PACE concepts. Control of both 2-D and 3-D flows were demonstrated. An analytical study was conducted to estimate control requirements for the PACE system to maintain control during wind gusts. Finally, independent laboratory experiments were conducted to identify promising dielectric materials for the plasma actuator, and to examine environmental effects (water and dust) on the plasma actuator operation. The proposed PACE system will be capable of capturing additional energy, and reducing aerodynamic loading and noise on wind turbines. Supplementary benefits from the PACE system include reduced blade structure weight and complexity that translates into reduced initial capital costs.

  17. Techniques for improving transients in learning control systems

    NASA Technical Reports Server (NTRS)

    Chang, C.-K.; Longman, Richard W.; Phan, Minh

    1992-01-01

    A discrete modern control formulation is used to study the nature of the transient behavior of the learning process during repetitions. Several alternative learning control schemes are developed to improve the transient performance. These include a new method using an alternating sign on the learning gain, which is very effective in limiting peak transients and also very useful in multiple-input, multiple-output systems. Other methods include learning at an increasing number of points progressing with time, or an increasing number of points of increasing density.

  18. Improved Stabilization Method for Lurie Networked Control Systems

    PubMed Central

    Zeng, Hong-Bing; Xiao, Shen-Ping; Yu, Fei

    2014-01-01

    The problem of stabilization of Lurie networked control systems (NCSs) is investigated in this paper. The network-induced delays in NCSs are assumed to be time-varying and bounded. By utilizing a reciprocally convex technique to consider the relationship between the network-induced delay and its varying interval, a new absolute stability condition is derived in terms of linear matrix inequalities (LMIs). Based on the obtained condition, an improved cone complementary linearisation (CCL) iteration algorithm is presented to design a state feedback controller. The effectiveness of the proposed method is verified by a numerical example. PMID:24892090

  19. A photocathode RF gun for x-ray FEL

    SciTech Connect

    Wang, X.J.; Batchelor, K.; Ben-Zvi, I.

    1995-12-31

    A 1.6 cell photocathode RF gun was developed by a BNL/SLAC/UCLA collaboration for X-ray FEL and other applications. The objective of the collaboration is to develop a cost effective and more reliable photocathode RF gun based on the operational experience of the original BNL gun. The new photocathode RF gun is cable of producing 1 mm-mrad normalized rms emittance photocurrent with a peak current of 100 A. The half-cell length of the new RF gun was lengthened to reduce the peak field on the cavity surface, the side-coupled scheme for cavity and waveguide coupling was replaced by a symmetrized coupling to the full-cell. The cavity aperture was increased to improve the coupling between two cells and for flat beam application. The experimental results of cold testing the RF gun will be presented. We will also present an injector design based on the new photocathode RF gun and emittance compensation technique.

  20. Studies of RF sheaths and diagnostics on IShTAR

    SciTech Connect

    Crombé, K.; D’Inca, R.; Faugel, H.; Fünfgelder, H.; Jacquot, J.; Ochoukov, R.; Louche, F.; Tripsky, M.; Van Eester, D.; Wauters, T.

    2015-12-10

    IShTAR (Ion cyclotron Sheath Test ARrangement) is a linear magnetised plasma test facility for RF sheaths studies at the Max-Planck-Institut für Plasmaphysik in Garching. In contrast to a tokamak, a test stand provides more liberty to impose the parameters and gives better access for the instrumentation and antennas. The project will support the development of diagnostic methods for characterising RF sheaths and validate and improve theoretical predictions. The cylindrical vacuum vessel has a diameter of 1 m and is 1.1 m long. The plasma is created by an external cylindrical plasma source equipped with a helical antenna that has been designed to excite the m=1 helicon mode. In inductive mode, plasma densities and electron temperatures have been characterised with a planar Langmuir probe as a function of gas pressure and input RF power. A 2D array of RF compensated Langmuir probes and a spectrometer are planned. A single strap RF antenna has been designed; the plasma-facing surface is aligned to the cylindrical plasma to ease the modelling. The probes will allow direct measurements of plasma density profiles in front of the RF antenna, and thus a detailed study of the density modifications induced by RF sheaths, which influences the coupling. The RF antenna frequency has been chosen to study different plasma wave interactions: the accessible plasma density range includes an evanescent and propagative behaviour of slow or fast waves, and allows the study of the effect of the lower hybrid resonance layer.

  1. Controlled architecture for improved macromolecular memory within polymer networks.

    PubMed

    DiPasquale, Stephen A; Byrne, Mark E

    2016-08-01

    This brief review analyzes recent developments in the field of living/controlled polymerization and the potential of this technique for creating imprinted polymers with highly structured architecture with macromolecular memory. As a result, it is possible to engineer polymers at the molecular level with increased homogeneity relating to enhanced template binding and transport. Only recently has living/controlled polymerization been exploited to decrease heterogeneity and substantially improve the efficiency of the imprinting process for both highly and weakly crosslinked imprinted polymers. Living polymerization can be utilized to create imprinted networks that are vastly more efficient than similar polymers produced using conventional free radical polymerization, and these improvements increase the role that macromolecular memory can play in the design and engineering of new drug delivery and sensing platforms.

  2. Spontaneous respiratory modulation improves cardiovascular control in essential hypertension.

    PubMed

    Pinheiro, Carlos Hermano da Justa; Medeiros, Renato Antônio Ribeiro; Pinheiro, Denise Gonçalves Moura; Marinho, Maria de Jesus Ferreira

    2007-06-01

    Recent studies show that controlled breathing improves baroreflex and heart rate variability and lowers blood pressure in hypertensive patients. To evaluate the effects of slow breathing training on cardiorespiratory system modulation of patients (n=10, men and women, ages ranging from 45 to 60) with essential hypertension seen in an outpatient setting. According to the study design, each patient was used as his/her own control, and data were collected before and after the intervention. The following parameters were assessed: heart rate variability (HRV), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), respirometry, chest expansion measurement, and statistical data analysis. Respiratory training was performed in 30-minute sessions held twice a week over one month using slow breathing exercises. Our results were as follows: a reduction in SBP, DPB, and MAP (p < 0.05 vs control); an increase in heart rate variability, as evidenced by greater RR interval variation and SDNN index; a decline in respiratory rate (p < 0.01 vs control); and an increase in tidal volume (p < 0.01 vs control) and thoracic expansibility (p < 0.01 vs control). Respiratory retraining using the slow breathing technique appears to be a useful adjunctive for cardiorespiratory control in hypertensive patients.

  3. Variable power combiner for RF mode shimming in 7-T MR imaging.

    PubMed

    Yazdanbakhsh, Pedram; Solbach, Klaus; Bitz, Andreas K

    2012-09-01

    This contribution discusses the utilization of RF power in an MRI system with RF mode shimming which enables the superposition of circularly polarized modes of a transmit RF coil array driven by a Butler matrix. Since the required power for the individual modes can vary widely, mode-shimming can result in a significant underutilization of the total available RF power. A variable power combiner (VPC) is proposed to improve the power utilization: it can be realized as a reconfiguration of the MRI transmit system by the inclusion of one additional matrix network which receives the power from all transmit amplifiers at its input ports and provides any desired (combined) power distribution at its output ports by controlling the phase and amplitude of the amplifiers' input signals. The power distribution at the output ports of the VPC is then fed into the "mode" ports of the coil array Butler matrix in order to superimpose the spatial modes at the highest achievable power utilization. The VPC configuration is compared to the standard configuration of the transmit chain of our MRI system with 8 transmit channels and 16 coils. In realistic scenarios, improved power utilization was achieved from 17% to 60% and from 14% to 55% for an elliptical phantom and a region of interest in the abdomen, respectively, and an increase of the power utilization of 1 dB for a region of interest in the upper leg. In general, it is found that the VPC allows significant improvement in power utilization when the shimming solution demands only a few modes to be energized, while the technique can yield loss in power utilization in cases with many modes required at high power level.

  4. Controls Over Army Deployable Disbursing System Payments Need Improvement

    DTIC Science & Technology

    2011-08-17

    Controls Over Army Deployable Disbursing System Payments Need Improvement Report No. D-2011-101 August 17, 2011 Report...DRIVE ARLINGTON VIRGINIA 22202-4704 August 17, 20 ll MEMORANDUM FOR UNDER SECRETARY OF DEFENSE (COMPTROLLER)/ CHI EF FINANCIAL OFFICER, DOD...We appreciate the comtes ies extended to the staff. Please direct questions to me at (703) 60 1-5868 (DSN 664-5868). p~ Q . ;n~ Patricia A. Marsh

  5. Improved Controller for a Three-Axis Piezoelectric Stage

    NASA Technical Reports Server (NTRS)

    Rao, Shanti; Palmer, Dean

    2009-01-01

    An improved closed-loop controller has been built for a three-axis piezoelectric positioning stage. The stage can be any of a number of commercially available or custom-made units that are used for precise three-axis positioning of optics in astronomical instruments and could be used for precise positioning in diverse fields of endeavor that include adaptive optics, fabrication of semiconductors, and nanotechnology.

  6. The control algorithm improving performance of electric load simulator

    NASA Astrophysics Data System (ADS)

    Guo, Chenxia; Yang, Ruifeng; Zhang, Peng; Fu, Mengyao

    2017-01-01

    In order to improve dynamic performance and signal tracking accuracy of electric load simulator, the influence of the moment of inertia, stiffness, friction, gaps and other factors on the system performance were analyzed on the basis of researching the working principle of load simulator in this paper. The PID controller based on Wavelet Neural Network was used to achieve the friction nonlinear compensation, while the gap inverse model was used to compensate the gap nonlinear. The compensation results were simulated by MATLAB software. It was shown that the follow-up performance of sine response curve of the system became better after compensating, the track error was significantly reduced, the accuracy was improved greatly and the system dynamic performance was improved.

  7. Combination of Epstein-Barr virus scaffold (BdRF1/VCA-p40) and small capsid protein (BFRF3/VCA-p18) into a single molecule for improved serodiagnosis of acute and malignant EBV-driven disease.

    PubMed

    Fachiroh, Jajah; Stevens, Servi J C; Haryana, Sofia M; Middeldorp, Jaap M

    2010-10-01

    Current single Epstein-Barr virus (EBV) markers fail to reach 100% sensitivity for serodiagnosis of acute and malignant diseases associated with EBV infection. Previous study had identified immunodominant epitopes of VCA-p40 and VCA-p18, and indicated that these two VCA antigens may have diagnostic value for EBV-related diseases. A recombinant protein of the full-length BdRF1 fused to the immunodominant domain of BFRF3 as 6-his tagged protein in Escherichia coli was developed. The recombinant protein was extracted in 8M urea solution and purified by metal-affinity chromatography yielding a 55 kDa product (VCA-p40+18). VCA-p40+18 blot-strips examined for IgM reactivity in infectious mononucleosis samples yielded 100% sensitivity and specificity, with improved reactivity compared with IgM/VCA-p18-ELISAs. A recent study described a synthetic peptide-based IgA/[EBNA1+VCA-p18]-ELISA (IgA/EBV-ELISA), with a sensitivity of 90% for diagnosing nasopharyngeal carcinoma. Immunoblot analysis of biopsy-confirmed nasopharyngeal carcinoma cases with low or negative IgA/EBV-ELISA showed 100% IgG reactivity to VCA-p40 and VCA-p18 proteins. Evaluation of VCA-p40+18 as an additional marker for screening and diagnosis of nasopharyngeal carcinoma was carried out. The data showed positive IgA/VCA-p40+18 reactivity by ELISA for 63.6% (14 of 22) nasopharyngeal carcinoma samples that were missed by peptide-based IgA/EBV-ELISA, suggested VCA-p40+18 as an improved marker for nasopharyngeal carcinoma serodiagnosis. The VCA-p40+18 may be combined with an EBNA1 synthetic peptide as an antigen mixture in one or separate IgA ELISA for improved nasopharyngeal carcinoma serodiagnosis. Copyright (c) 2010 Elsevier B.V. All rights reserved.

  8. Design of 250-MW CW RF system for APT

    SciTech Connect

    Rees, D.

    1997-09-01

    The design for the RF systems for the APT (Accelerator Production of Tritium) proton linac will be presented. The linac produces a continuous beam power of 130 MW at 1300 MeV with the installed capability to produce up to a 170 MW beam at 1700 MeV. The linac is comprised of a 350 MHz RFQ to 7 MeV followed in sequence by a 700 MHz coupled-cavity drift tube linac, coupled-cavity linac, and superconducting (SC) linac to 1700 MeV. At the 1700 MeV, 100 mA level the linac requires 213 MW of continuous-wave (CW) RF power. This power will be supplied by klystrons with a nominal output power of 1.0 MW. 237 kystrons are required with all but three of these klystrons operating at 700 MHz. The klystron count includes redundancy provisions that will be described which allow the RF systems to meet an operational availability in excess of 95 percent. The approach to achieve this redundancy will be presented for both the normal conducting (NC) and SC accelerators. Because of the large amount of CW RF power required for the APT linac, efficiency is very important to minimize operating cost. Operation and the RF system design, including in-progress advanced technology developments which improve efficiency, will be discussed. RF system performance will also be predicted. Because of the simultaneous pressures to increase RF system reliability, reduce tunnel envelope, and minimize RF system cost, the design of the RF vacuum windows has become an important issue. The power from a klystron will be divided into four equal parts to minimize the stress on the RF vacuum windows. Even with this reduction, the RF power level at the window is at the upper boundary of the power levels employed at other CW accelerator facilities. The design of a 350 MHz, coaxial vacuum window will be presented as well as test results and high power conditioning profiles. The transmission of 950 kW, CW, power through this window has been demonstrated with only minimal high power conditioning.

  9. Mutation at tyrosine in AMLRY (GILRY like) motif of yeast eRF1 on nonsense codons suppression and binding affinity to eRF3.

    PubMed

    Akhmaloka; Susilowati, Prima Endang; Subandi; Madayanti, Fida

    2008-04-21

    Termination translation in Saccharomyces cerevisiae is controlled by two interacting polypeptide chain release factors, eRF1 and eRF3. Two regions in human eRF1, position at 281-305 and position at 411-415, were proposed to be involved on the interaction to eRF3. In this study we have constructed and characterized yeast eRF1 mutant at position 410 (correspond to 415 human eRF1) from tyrosine to serine residue resulting eRF1(Y410S). The mutations did not affect the viability and temperature sensitivity of the cell. The stop codons suppression of the mutant was analyzed in vivo using PGK-stop codon-LACZ gene fusion and showed that the suppression of the mutant was significantly increased in all of codon terminations. The suppression on UAG codon was the highest increased among the stop codons by comparing the suppression of the wild type respectively. In vitro interaction between eRF1 (mutant and wild type) to eRF3 were carried out using eRF1-(His)6 and eRF1(Y410S)-(His)6 expressed in Escherichia coli and indigenous Saccharomyces cerevisiae eRF3. The results showed that the binding affinity of eRF1(Y410S) to eRF3 was decreased up to 20% of the wild type binding affinity. Computer modeling analysis using Swiss-Prot and Amber version 9.0 programs revealed that the overall structure of eRF1(Y410S) has no significant different with the wild type. However, substitution of tyrosine to serine triggered the structural change on the other motif of C-terminal domain of eRF1. The data suggested that increasing stop codon suppression and decreasing of the binding affinity of eRF1(Y410S) were probably due to the slight modification on the structure of the C-terminal domain.

  10. An improved auto-tuning scheme for PID controllers.

    PubMed

    Dey, Chanchal; Mudi, Rajani K

    2009-10-01

    An improved auto-tuning scheme is proposed for Ziegler-Nichols (ZN) tuned PID controllers (ZNPIDs), which usually provide excessively large overshoots, not tolerable in most of the situations, for high-order and nonlinear processes. To overcome this limitation ZNPIDs are upgraded by some easily interpretable heuristic rules through an online gain modifying factor defined on the instantaneous process states. This study is an extension of our earlier work [Mudi RK., Dey C. Lee TT. An improved auto-tuning scheme for PI controllers. ISA Trans 2008; 47: 45-52] to ZNPIDs, thereby making the scheme suitable for a wide range of processes and more generalized too. The proposed augmented ZNPID (AZNPID) is tested on various high-order linear and nonlinear dead-time processes with improved performance over ZNPID, refined ZNPID (RZNPID), and other schemes reported in the literature. Stability issues are addressed for linear processes. Robust performance of AZNPID is observed while changing its tunable parameters as well as the process dead-time. The proposed scheme is also implemented on a real time servo-based position control system.

  11. Traffic improvement and transportation pollution control in Xiamen

    SciTech Connect

    Dongxing Yuan; Zilin, Wu

    1996-12-31

    in this paper, the urban traffic improvement and transportation control in Xiamen are highlighted. Xiamen is a port city and an economical special zone of China. As the economy grows, the transportation is developing dramatically and becoming the key for further economic development. The air quality is threatened by the rapid growth of the vehicles in the city. The most urgent task in improving urban traffic is to establish a sound traffic system. The municipal government takes great effort to improve the traffic condition, as well as to reduce green house gases and protect air environment. Some management and technical measures are carried out. Those management measures are mainly as follows: (1) systematic planning of the city arrangement and city functional division, and integrated planning of the urban roads system, (2) putting great emphasis on tail gas monitoring and management, and (3) establishing optimized utilization of motor vehicles. Those included in the main technical measures are (1) making the roads clear, (2) enlarging traffic capacity, and (3) developing the public transport. The most urgent task in improving urban traffic is to establish a sound traffic system. The city municipal government and Transportation Management Bureau plan to make a series of reforms to improve the urban traffic condition, such as building high quality road around the city, reducing the number of one way roads and replacing gasoline buses with electric buses. An optimized traffic system of Xiamen, taking public transport as the main means, is the key to meet the needs of both traffic improvement and urban transportation pollution control.

  12. Improving inferior vena cava filter retrieval rates with the define, measure, analyze, improve, control methodology.

    PubMed

    Sutphin, Patrick D; Reis, Stephen P; McKune, Angie; Ravanzo, Maria; Kalva, Sanjeeva P; Pillai, Anil K

    2015-04-01

    To design a sustainable process to improve optional inferior vena cava (IVC) filter retrieval rates based on the Define, Measure, Analyze, Improve, Control (DMAIC) methodology of the Six Sigma process improvement paradigm. DMAIC, an acronym for Define, Measure, Analyze, Improve, and Control, was employed to design and implement a quality improvement project to increase IVC filter retrieval rates at a tertiary academic hospital. Retrievable IVC filters were placed in 139 patients over a 2-year period. The baseline IVC filter retrieval rate (n = 51) was reviewed through a retrospective analysis, and two strategies were devised to improve the filter retrieval rate: (a) mailing of letters to clinicians and patients for patients who had filters placed within 8 months of implementation of the project (n = 43) and (b) a prospective automated scheduling of a clinic visit at 4 weeks after filter placement for all new patients (n = 45). The effectiveness of these strategies was assessed by measuring the filter retrieval rates and estimated increase in revenue to interventional radiology. IVC filter retrieval rates increased from a baseline of 8% to 40% with the mailing of letters and to 52% with the automated scheduling of a clinic visit 4 weeks after IVC filter placement. The estimated revenue per 100 IVC filters placed increased from $2,249 to $10,518 with the mailing of letters and to $17,022 with the automated scheduling of a clinic visit. Using the DMAIC methodology, a simple and sustainable quality improvement intervention was devised that markedly improved IVC filter retrieval rates in eligible patients. Copyright © 2015 SIR. Published by Elsevier Inc. All rights reserved.

  13. Additive manufacturing of RF absorbers

    NASA Astrophysics Data System (ADS)

    Mills, Matthew S.

    The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

  14. A New RF System for the CEBAF Normal Conducting Cavities

    SciTech Connect

    Curt Hovater; Hai Dong; Alicia Hofler; George Lahti; John Musson; Tomasz Plawski

    2004-08-01

    The CEBAF Accelerator at Jefferson Lab is a 6 GeV five pass electron accelerator consisting of two superconducting linacs joined by independent magnetic transport arcs. CEBAF also has numerous normal conducting cavities for beam conditioning in the injector and for RF extraction to the experimental halls. The RF systems that presently control these cavities are becoming expensive to maintain, therefore a replacement RF control system is now being developed. For the new RF system, cavity field control is maintained digitally using an FPGA which contains the feedback algorithm. The system incorporates digital down conversion, using quadrature under-sampling at an IF frequency of 70 MHz. The VXI bus-crate was chosen as the operating platform because of its excellent RFI/EMI properties and its compatibility with the EPICS control system. The normal conducting cavities operate at both the 1497 MHz accelerating frequency and the sub-harmonic frequency of 499 MHz. To accommodate this, the ne w design will use different receiver-transmitter daughter cards for each frequency. This paper discusses the development of the new RF system and reports on initial results.

  15. A generalized slab-wise framework for parallel transmit multiband RF pulse design

    PubMed Central

    Wu, Xiaoping; Schmitter, Sebastian; Auerbach, Edward J.; Uğurbil, Kâmil; de Moortele, Pierre-François Van

    2015-01-01

    Purpose We propose a new slab-wise framework to design parallel transmit multi-band pulses for volumetric simultaneous multi-slice imaging with a large field of view along the slice direction (FOVs). Theory and Methods The slab-wise framework divides FOVs into a few contiguous slabs and optimizes pulses for each slab. Effects of relevant design parameters including slab number and transmit B1 (B1+) mapping slice placement were investigated for human brain imaging by designing pulses with global or local SAR control based on electromagnetic simulations of a 7T head RF array. Pulse design using in-vivo B1+ maps was demonstrated and evaluated with Bloch simulations. Results RF performance with respect to SAR reduction or B1+ homogenization across the entire human brain improved with increasing slabs; however, this improvement was non-linear and leveled off at ~12 slabs when the slab thickness reduced to ~12 mm. The impact of using different slice placements for B1+ mapping was small. Conclusion Compared to slice-wise approaches where each of the many imaging slices requires both B1+ mapping and pulse optimization, the proposed slab-wise design framework is shown to attain comparable RF performance while drastically reducing the number of required pulses; therefore, it can be used to increase time efficiency for B1+ mapping, pulse calculation and sequence preparation. PMID:25994797

  16. Modular open RF architecture: extending VICTORY to RF systems

    NASA Astrophysics Data System (ADS)

    Melber, Adam; Dirner, Jason; Johnson, Michael

    2015-05-01

    Radio frequency products spanning multiple functions have become increasingly critical to the warfighter. Military use of the electromagnetic spectrum now includes communications, electronic warfare (EW), intelligence, and mission command systems. Due to the urgent needs of counterinsurgency operations, various quick reaction capabilities (QRCs) have been fielded to enhance warfighter capability. Although these QRCs were highly successfully in their respective missions, they were designed independently resulting in significant challenges when integrated on a common platform. This paper discusses how the Modular Open RF Architecture (MORA) addresses these challenges by defining an open architecture for multifunction missions that decomposes monolithic radio systems into high-level components with welldefined functions and interfaces. The functional decomposition maximizes hardware sharing while minimizing added complexity and cost due to modularization. MORA achieves significant size, weight and power (SWaP) savings by allowing hardware such as power amplifiers and antennas to be shared across systems. By separating signal conditioning from the processing that implements the actual radio application, MORA exposes previously inaccessible architecture points, providing system integrators with the flexibility to insert third-party capabilities to address technical challenges and emerging requirements. MORA leverages the Vehicular Integration for Command, Control, Communication, Computers, Intelligence, Surveillance, and Reconnaissance (C4ISR)/EW Interoperability (VICTORY) framework. This paper concludes by discussing how MORA, VICTORY and other standards such as OpenVPX are being leveraged by the U.S. Army Research, Development, and Engineering Command (RDECOM) Communications Electronics Research, Development, and Engineering Center (CERDEC) to define a converged architecture enabling rapid technology insertion, interoperability and reduced SWaP.

  17. New and future strategies to improve asthma control in children.

    PubMed

    Anderson, William C; Szefler, Stanley J

    2015-10-01

    Symptomatic asthma in childhood has lifelong effects on lung function and disease severity, emphasizing the need for improved pediatric asthma control. Control of pediatric risk and impairment domains can be achieved through increased medication adherence or new therapeutic strategies. Developing electronic monitoring device technology with reminders might be a key noninvasive resource to address poor adherence in children and adolescents in a clinical setting. In patients who have persistently poor control despite optimal medication compliance, newly emerging pharmaceuticals, including inhaled therapies and biologics, might be key to their treatment. However, barriers exist to their development in the pediatric population, and insights must be drawn from adult studies, which has its own unique limitations. Biomarkers to direct the use of such potentially expensive therapies to those patients most likely to benefit are imperative. In this review the current literature regarding strategies to improve pediatric asthma control is addressed with the goal of exploring the potential and pitfalls of strategies that might be available in the near future.

  18. Tune control improvements on the rapid cycling synchrotron

    SciTech Connect

    Potts, C.; Faber, M.; Gunderson, G.; Knott, M.; Voss, D.

    1981-06-01

    The as-built lattice of the Rapid Cycling Synchrotron (RCS) had two sets of correction sextupoles and two sets of quadrupoles energized by dc power supplies to control the tune and the tune tilt. With this method of powering these magnets, adjustment of tune conditions during the accelerating cycle as needed was not possible. A set of dynamically programmable power supplies has been built and operated to provide the required chromaticity adjustment. The short accelerating time (16.7 ms) of the RCS and the inductance of the magnets dictated large transistor amplifier power supplies. The required time resolution and waveform flexibility indicated the desirability of computer control. Both the amplifiers and controls are described, along with resulting improvements in the beam performance. 5 refs.

  19. RF Testing Of Microwave Integrated Circuits

    NASA Technical Reports Server (NTRS)

    Romanofsky, R. R.; Ponchak, G. E.; Shalkhauser, K. A.; Bhasin, K. B.

    1988-01-01

    Fixtures and techniques are undergoing development. Four test fixtures and two advanced techniques developed in continuing efforts to improve RF characterization of MMIC's. Finline/waveguide test fixture developed to test submodules of 30-GHz monolithic receiver. Universal commercially-manufactured coaxial test fixture modified to enable characterization of various microwave solid-state devices in frequency range of 26.5 to 40 GHz. Probe/waveguide fixture is compact, simple, and designed for non destructive testing of large number of MMIC's. Nondestructive-testing fixture includes cosine-tapered ridge, to match impedance wavequide to microstrip. Advanced technique is microwave-wafer probing. Second advanced technique is electro-optical sampling.

  20. RF Circuit Simulation of the JET ITER-like ICRH Antenna

    SciTech Connect

    Evrard, M.; Durodie, F.; Lamalle, P.U.

    2005-09-26

    In support of the development of a suitable matching algorithm, a RF circuit simulation of the complete JET ICRH antenna has been implemented in a Matlab/Simulink environment. The circuit model allows studying the time evolution of the capacitor positions under control of error signals computed from measurable RF quantities by proposed matching algorithms. The effect of arcs and their 'visibility' on the measured RF signals is also examined.

  1. Team-Based Care and Improved Blood Pressure Control

    PubMed Central

    Proia, Krista K.; Thota, Anilkrishna B.; Njie, Gibril J.; Finnie, Ramona K.C.; Hopkins, David P.; Mukhtar, Qaiser; Pronk, Nicolaas P.; Zeigler, Donald; Kottke, Thomas E.; Rask, Kimberly J.; Lackland, Daniel T.; Brooks, Joy F.; Braun, Lynne T.; Cooksey, Tonya

    2015-01-01

    Context Uncontrolled hypertension remains a widely prevalent cardiovascular risk factor in the U.S. team-based care, established by adding new staff or changing the roles of existing staff such as nurses and pharmacists to work with a primary care provider and the patient. Team-based care has the potential to improve the quality of hypertension management. The goal of this Community Guide systematic review was to examine the effectiveness of team-based care in improving blood pressure (BP) outcomes. Evidence acquisition An existing systematic review (search period, January 1980–July 2003) assessing team-based care for BP control was supplemented with a Community Guide update (January 2003–May 2012). For the Community Guide update, two reviewers independently abstracted data and assessed quality of eligible studies. Evidence synthesis Twenty-eight studies in the prior review (1980–2003) and an additional 52 studies from the Community Guide update (2003–2012) qualified for inclusion. Results from both bodies of evidence suggest that team-based care is effective in improving BP outcomes. From the update, the proportion of patients with controlled BP improved (median increase=12 percentage points); systolic BP decreased (median reduction=5.4 mmHg); and diastolic BP also decreased (median reduction=1.8 mmHg). Conclusions Team-based care increased the proportion of people with controlled BP and reduced both systolic and diastolic BP, especially when pharmacists and nurses were part of the team. Findings are applicable to a range of U.S. settings and population groups. Implementation of this multidisciplinary approach will require health system–level organizational changes and could be an important element of the medical home. PMID:24933494

  2. Position control of nonlinear hydraulic system using an improved PSO based PID controller

    NASA Astrophysics Data System (ADS)

    Ye, Yi; Yin, Chen-Bo; Gong, Yue; Zhou, Jun-jing

    2017-01-01

    This paper addresses the position control of valve-controlled cylinder system employed in hydraulic excavator. Nonlinearities such as dead zone, saturation, discharge coefficient and friction existed in the system are highlighted during the mathematical modeling. On this basis, simulation model is established and then validated against experiments. Aim for achieving excellent position control performances, an improved particle swarm optimization (PSO) algorithm is presented to search for the optimal proportional-integral-derivative (PID) controller gains for the nonlinear hydraulic system. The proposed algorithm is a hybrid based on the standard PSO algorithm but with the addition of selection and crossover operators from genetic algorithm in order to enhance the searching efficiency. Furthermore, a nonlinear decreasing scheme for the inertia weight of the improved PSO algorithm is adopted to balance global exploration and local exploration abilities of particles. Then a co-simulation platform combining the simulation model with the improved PSO tuning based PID controller is developed. Comparisons of the improved PSO, standard PSO and Phase Margin (PM) tuning methods are carried out with three position references as step signal, ramp signal and sinusoidal wave using the co-simulation platform. The results demonstrated that the improved PSO algorithm can perform well in PID control for positioning of nonlinear hydraulic system.

  3. Cryogenic vacuumm RF feedthrough device

    DOEpatents

    Wu, Genfa; Phillips, Harry Lawrence

    2008-12-30

    A cryogenic vacuum rf feedthrough device comprising: 1) a probe for insertion into a particle beam; 2) a coaxial cable comprising an inner conductor and an outer conductor, a dielectric/insulating layer surrounding the inner conductor, the latter being connected to the probe for the transmission of higher mode rf energy from the probe; and 3) a high thermal conductivity stub attached to the coaxial dielectric about and in thermal contact with the inner conductor which high thermal conductivity stub transmits heat generated in the vicinity of the probe efficiently and radially from the area of the probe and inner conductor all while maintaining useful rf transmission line characteristics between the inner and outer coaxial conductors.

  4. Ion bombardment in RF photoguns

    SciTech Connect

    Pozdeyev,E.; Kayran, D.; Litvinenko, V. N.

    2009-05-04

    A linac-ring eRHIC design requires a high-intensity CW source of polarized electrons. An SRF gun is viable option that can deliver the required beam. Numerical simulations presented elsewhere have shown that ion bombardment can occur in an RF gun, possibly limiting lifetime of a NEA GaAs cathode. In this paper, we analytically solve the equations of motion of ions in an RF gun using the ponderomotive potential of the Rf field. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper discusses possible mitigation techniques that can reduce the rate of ion bombardment.

  5. Klystron equalization for RF feedback

    SciTech Connect

    Corredoura, P.

    1993-01-01

    The next generation of colliding beam storage rings support higher luminosities by significantly increasing the number of bunches and decreasing the spacing between respective bunches. The heavy beam loading requires large RF cavity detuning which drives several lower coupled bunch modes very strongly. One technique which has proven to be very successful in reducing the coupled bunch mode driving impedance is RF feedback around the klystron-cavity combination. The gain and bandwidth of the feedback loop is limited by the group delay around the feedback loop. Existing klystrons on the world market have not been optimized for this application and contribute a large portion of the total loop group delay. This paper describes a technique to reduce klystron group delay by adding an equalizing filter to the klystron RF drive. Such a filter was built and tested on a 500 kill klystron as part of the on going PEP-II R D effort here at SLAC.

  6. Klystron equalization for RF feedback

    SciTech Connect

    Corredoura, P.

    1993-01-01

    The next generation of colliding beam storage rings support higher luminosities by significantly increasing the number of bunches and decreasing the spacing between respective bunches. The heavy beam loading requires large RF cavity detuning which drives several lower coupled bunch modes very strongly. One technique which has proven to be very successful in reducing the coupled bunch mode driving impedance is RF feedback around the klystron-cavity combination. The gain and bandwidth of the feedback loop is limited by the group delay around the feedback loop. Existing klystrons on the world market have not been optimized for this application and contribute a large portion of the total loop group delay. This paper describes a technique to reduce klystron group delay by adding an equalizing filter to the klystron RF drive. Such a filter was built and tested on a 500 kill klystron as part of the on going PEP-II R&D effort here at SLAC.

  7. Ion extraction from a saddle antenna RF surface plasma source

    SciTech Connect

    Dudnikov, V. Johnson, R. P.; Han, B.; Murray, S.; Pennisi, T.; Piller, C.; Santana, M.; Stockli, M.; Welton, R.; Breitschopf, J.; Dudnikova, G.

    2015-04-08

    Existing RF Surface Plasma Sources (SPS) for accelerators have specific efficiencies for H{sup +} and H{sup −} ion generation around 3 to 5 mA/cm{sup 2} per kW, where about 50 kW of RF power is typically needed for 50 mA beam current production. The Saddle Antenna (SA) SPS described here was developed to improve H{sup −} ion production efficiency and SPS reliability and availability. At low RF power, the efficiency of positive ion generation in the plasma has been improved to 200 mA/cm{sup 2} per kW of RF power at 13.56 MHz. Initial cesiation of the SPS was performed by heating cesium chromate cartridges by discharge as was done in the very first versions of the SPS. A small oven to decompose cesium compounds and alloys was developed and tested. After cesiation, the current of negative ions to the collector was increased from 1 mA to 10 mA with RF power ∼1.5 kW in the plasma (6 mm diameter emission aperture) and up to 30 mA with ∼4 kW RF power in the plasma and 250 Gauss longitudinal magnetic field. The ratio of electron current to negative ion current was improved from 30 to 2. Stable generation of H{sup −} beam without intensity degradation was demonstrated in the AlN discharge chamber for a long time at high discharge power in an RF SPS with an external antenna. Continuous wave (CW) operation of the SA SPS has been tested on the small test stand. The general design of the CW SA SPS is based on the pulsed version. Some modifications were made to improve the cooling and cesiation stability. The extracted collector current can be increased significantly by optimizing the longitudinal magnetic field in the discharge chamber. CW operation with negative ion extraction was tested with RF power up to 1.8 kW from the generator (∼1.2 kW in the plasma) with production up to Ic=7 mA. Long term operation was tested with 1.2 kW from the RF generator (∼0.8 kW in the plasma) with production of Ic=5 mA, Iex ∼15 mA (Uex=8 kV, Uc=14 kV)

  8. Improving wind turbine array efficiency through active flow control

    NASA Astrophysics Data System (ADS)

    Velarde, John-Michael; Wang, Guannan; Shea, Patrick; Glauser, Mark; Castillo, Luciano

    2013-11-01

    We attempted to demonstrate the capability of instrumenting three wind turbine blades with an air delivery system that provided active flow control in an effort to improve turbine performance in the presence of the wake turbulence that is inherent in a turbine array. Presently, turbines are being designed for set conditions, such as steady incoming wind and a set velocity profile, however conditions can be drastically different in the field - thus causing poor performance from the turbines. The blades were instrumented with pressure transducers which measured the suction surface pressure; the sensor setup was such that three unique blade configurations existed: spanwise sensors, chord-wise sensors, and a reference sensor. The compressed air was delivered through a rotary union connected to the turbine hub with tubing attached to the suction side of the blades. The primary purpose of this test was to demonstrate the ability to deliver air to a rotating frame for active flow control. We collected data under three test conditions using an open-section wind tunnel, courtesy of Texas Tech University: static with no flow control, rotation with no flow control, and rotation with active flow control.

  9. Improved automatic tuning of PID controller for stable processes.

    PubMed

    Kumar Padhy, Prabin; Majhi, Somanath

    2009-10-01

    This paper presents an improved automatic tuning method for stable processes using a modified relay in the presence of static load disturbances and measurement noise. The modified relay consists of a standard relay in series with a PI controller of unity proportional gain. The integral time constant of the PI controller of the modified relay is chosen so as to ensure a minimum loop phase margin of 30( composite function). A limit cycle is then obtained using the modified relay. Hereafter, the PID controller is designed using the limit cycle output data. The derivative time constant is obtained by maintaining the above mentioned loop phase margin. Minimizing the distance of Nyquist curve of the loop transfer function from the imaginary axis of the complex plane gives the proportional gain. The integral time constant of the PID controller is set equal to the integral time constant of the PI controller of the modified relay. The effectiveness of the proposed technique is verified by simulation results.

  10. Compact superconducting rf-dipole cavity designs for deflecting and crabbing applications

    SciTech Connect

    De Silva, Subashini; Delayen, Jean R.; Castilla, Alejandro

    2013-06-01

    Over the years the superconducting parallel-bar design has evolved into an rf-dipole cavity with improved properties. The new rf-dipole design is considered for a number of deflecting and crabbing applications. Some of those applications are the 499 MHz rf separator system for the Jefferson Lab 12 GeV upgrade, the 400 MHz crabbing cavity system for the proposed LHC high luminosity upgrade, and the 750 MHz crabbing cavity for the medium energy electron-ion collider in Jefferson Lab. In this paper we present the optimized rf design in terms of rf performance including rf properties, higher order modes (HOM) properties, multipacting and multipole expansion for the above mentioned applications.

  11. Improved rate control for electron-beam evaporation and evaluation of optical performance improvements.

    PubMed

    Gevelber, Michael; Xu, Bing; Smith, Douglas

    2006-03-01

    A new deposition-rate-control and electron-beam-gun (e-gun) strategy was developed that significantly reduces the growth-rate variations for e-beam-deposited SiO2 coatings. The resulting improvements in optical performance are evaluated for multilayer bandpass filters. The adverse effect of uneven silica-source depletion on coating spectral performances during long deposition runs is discussed.

  12. Regional Joint-Integrated Air and Missile Defense (RF-IAMD): An Operational Level Integrated Air and Missile Defense (IAMD) Command and Control (C2) Organization

    DTIC Science & Technology

    2015-05-15

    currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) (15-05-2015) 2. REPORT TYPE...CONTRACT NUMBER Operational Level Integrated Air and Missile Defense (IAMD) Command and Control (C2) Organization 5b. GRANT NUMBER 5c. PROGRAM...Defense (RJ-IAMD): An Operational Level Integrated Air and Missile Defense (IAMD) Command and Control (C2) Organization By Arthur Q. Bruggeman

  13. Liquid Metal Droplet and Micro Corrugated Diaphragm RF-MEMS for reconfigurable RF filters

    NASA Astrophysics Data System (ADS)

    Irshad, Wasim

    Widely Tunable RF Filters that are small, cost-effective and offer ultra low power consumption are extremely desirable. Indeed, such filters would allow drastic simplification of RF front-ends in countless applications from cell phones to satellites in space by replacing switched-array of static acoustic filters and YIG filters respectively. Switched array of acoustic filters are de facto means of channel selection in mobile applications such as cell phones. SAW and BAW filters satisfy most criteria needed by mobile applications such as low cost, size and power consumption. However, the trade-off is a significant loss of 3-4 dB in modern cell phone RF front-end. This leads to need for power-hungry amplifiers and short battery life. It is a necessary trade-off since there are no better alternatives. These devices are in mm scale and consume mW. YIG filters dominate applications where size or power is not a constraint but demand excellent RF performance like low loss and high tuning ratio. These devices are measured in inches and require several watts to operate. Clearly, a tunable RF filter technology that would combine the cost, size and power consumption benefits of acoustic filters with excellent RF performance of YIG filters would be extremely desirable and imminently useful. The objective of this dissertation is to develop such a technology based upon RF-MEMS Evanescent-mode cavity filter. Two highly novel RF-MEMS devices have been developed over the course of this PhD to address the unique MEMS needs of this technology. The first part of the dissertation is dedicated to introducing the fundamental concepts of tunable cavity resonators and filters. This includes the physics behind it, key performance metrics and what they depend on and requirements of the MEMS tuners. Initial gap control and MEMS attachment method are identified as potential hurdles towards achieving very high RF performance. Simple and elegant solutions to both these issues are discussed in

  14. Application of controlling instruments for improvements in cow sire selection.

    PubMed

    König, S; Lessner, S; Simianer, H

    2007-04-01

    National estimated breeding values of bulls from 1998 through 2006 from 12 different German artificial insemination (AI) organizations were used to determine the differences in expected and realized selection intensities for cow sire selection, considering the total merit index as well as subindexes for production, conformation, somatic cell count, fertility, and functional herd life. The expected selection intensity was derived from a Gaussian distribution and from the replacement rate describing the percentage of bulls graduated as cow sires from the total amount of progeny-tested young bulls within the AI organization and by birth year. Realized selection intensities for all indexes were derived from the selection differential of cow sires, defined as the deviation of the average index of selected cow sires from the average index of the total number of progeny-tested young bulls. A low replacement rate of cow sires was associated with relatively high realized selection intensities for the total merit, production, and conformation indexes, but was not related to the somatic cell count, fertility, and functional herd life indexes. The controlling value, defined as the ratio of realized to expected selection intensities, indicates the effectiveness of cow sire selection for different traits. Low controlling values (i.e., low realized selection intensities in combination with moderate or high expected selection intensities) suggest improvements in the step of cow sire selection, especially when discussing the total merit index. Analysis of variance revealed significant differences in expected selection intensities, realized selection intensities, and controlling values for the total merit, production, and conformation indexes between AI organizations and birth years of bulls. Artificial insemination organizations applying well-defined breeding policies (e.g., high controlling values for the total merit index) were successful in the national competition when

  15. Quality-control analytical methods: continuous quality improvement.

    PubMed

    Venti, Eden M

    2006-01-01

    It is vital that all compounding pharmacies have a continuous quality improvement program in place by way of standard operating procedures to assure that patients receive high-quality preparations. The program should take into consideration any federal and state regulatory requirements, as well as professional association expectations. Quality control measurements and regular review of those measurements are the foundations of a good quality plan. All pharmacy personnel should be aware of the importance of reporting potential internal quality concerns or problems and should be encouraged to do so without fear of repercussions. Ideally, an error-free compounding pracitice would be the goal. Since this is not practical, quality issues should not be viewed as problems, but as opportunities to improve compounding practices by correcting, before they become pervasive, the processes used in the preparation of prescriptions.

  16. Human eye visual hyperacuity: Controlled diffraction for image resolution improvement

    NASA Astrophysics Data System (ADS)

    Lagunas, A.; Domínguez, O.; Martinez-Conde, S.; Macknik, S. L.; Del-Río, C.

    2017-09-01

    The Human Visual System appears to be using a low number of sensors for image capturing, and furthermore, regarding the physical dimensions of cones—photoreceptors responsible for the sharp central vision—we may realize that these sensors are of a relatively small size and area. Nonetheless, the human eye is capable of resolving fine details thanks to visual hyperacuity and presents an impressive sensitivity and dynamic range when set against conventional digital cameras of similar characteristics. This article is based on the hypothesis that the human eye may be benefiting from diffraction to improve both image resolution and acquisition process. The developed method involves the introduction of a controlled diffraction pattern at an initial stage that enables the use of a limited number of sensors for capturing the image and makes possible a subsequent post-processing to improve the final image resolution.

  17. Localization of RF Breakdown in Copper RF Structure by the Use of Acoustic Sensors

    SciTech Connect

    Le Pimpec, F.

    2004-12-03

    X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer damage due to Radio Frequency (RF) breakdown when processed to high gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage. Acoustic sensors attached to an accelerator structure can detect both normal and breakdown RF pulses. Using an array of acoustic sensors, we have been able to pinpoint both the cell and azimuth location of individual breakdown events. This allows studies of breakdown in time and in space, so that underlying causes can be determined. This technique provided a significant understanding of breakdown in the structure input coupler.

  18. Negative ion source with external RF antenna

    DOEpatents

    Leung, Ka-Ngo; Hahto, Sami K.; Hahto, Sari T.

    2007-02-13

    A radio frequency (RF) driven plasma ion source has an external RF antenna, i.e. the RF antenna is positioned outside the plasma generating chamber rather than inside. The RF antenna is typically formed of a small diameter metal tube coated with an insulator. An external RF antenna assembly is used to mount the external RF antenna to the ion source. The RF antenna tubing is wound around the external RF antenna assembly to form a coil. The external RF antenna assembly is formed of a material, e.g. quartz, which is essentially transparent to the RF waves. The external RF antenna assembly is attached to and forms a part of the plasma source chamber so that the RF waves emitted by the RF antenna enter into the inside of the plasma chamber and ionize a gas contained therein. The plasma ion source is typically a multi-cusp ion source. A converter can be included in the ion source to produce negative ions.

  19. Surface Analysis of OFE-Copper X-Band Accelerating Structures and Possible Correlation to RF Breakdown Events

    SciTech Connect

    Harvey, S

    2003-10-08

    X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer vacuum surface damage caused by radio frequency (RF) breakdown, when processed to high electric-field gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage. RF reflected wave analysis and acoustic sensor pickup have provided breakdowns localization in RF structures. Particle contaminations found following clean autopsy of four RF-processed travelling wave structures, have been catalogued and analyzed. Their influence on RF breakdown, as well as that of several other material-based properties, will be discussed.

  20. DASHBOARDS & CONTROL CHARTS EXPERIENCES IN IMPROVING SAFETY AT HANFORD WASHINGTON

    SciTech Connect

    PREVETTE, S.S.

    2006-02-27

    The aim of this paper is to demonstrate the integration of safety methodology, quality tools, leadership, and teamwork at Hanford and their significant positive impact on safe performance of work. Dashboards, Leading Indicators, Control charts, Pareto Charts, Dr. W. Edward Deming's Red Bead Experiment, and Dr. Deming's System of Profound Knowledge have been the principal tools and theory of an integrated management system. Coupled with involved leadership and teamwork, they have led to significant improvements in worker safety and protection, and environmental restoration at one of the nation's largest nuclear cleanup sites.

  1. Improvement of Targeting Efficiency in Chaos Control Using Clustering

    NASA Astrophysics Data System (ADS)

    Sutcu, Y.; Iplikci, S.; Denizhan, Y.

    2002-09-01

    In this paper an improved version of the previously presented ECR (Extended Control Regions) targeting method is proposed, where the system data is first pre-processed and subdivided into clusters, and then one artificial neural network is assigned to each such cluster. Furthermore, an analytical criterion for determining the region of the current system state during targeting is introduced, whereas in the original ECR method the region information was hidden in the neural networks. Simulation results on several chaotic systems show that this modified version of the ECR method reduces the average reaching time and in general also the training time of the neural networks.

  2. Improving Advanced Inverter Control Convergence in Distribution Power Flow

    SciTech Connect

    Nagarajan, Adarsh; Palmintier, Bryan; Ding, Fei; Mather, Barry; Baggu, Murali

    2016-11-21

    Simulation of modern distribution system powerflow increasingly requires capturing the impact of advanced PV inverter voltage regulation on powerflow. With Volt/var control, the inverter adjusts its reactive power flow as a function of the point of common coupling (PCC) voltage. Similarly, Volt/watt control curtails active power production as a function of PCC voltage. However, with larger systems and higher penetrations of PV, this active/reactive power flow itself can cause significant changes to the PCC voltage potentially introducing oscillations that slow the convergence of system simulations. Improper treatment of these advanced inverter functions could potentially lead to incorrect results. This paper explores a simple approach to speed such convergence by blending in the previous iteration's reactive power estimate to dampen these oscillations. Results with a single large (5MW) PV system and with multiple 500kW advanced inverters show dramatic improvements using this approach.

  3. An improved force feedback control algorithm for active tendons.

    PubMed

    Guo, Tieneng; Liu, Zhifeng; Cai, Ligang

    2012-01-01

    An active tendon, consisting of a displacement actuator and a co-located force sensor, has been adopted by many studies to suppress the vibration of large space flexible structures. The damping, provided by the force feedback control algorithm in these studies, is small and can increase, especially for tendons with low axial stiffness. This study introduces an improved force feedback algorithm, which is based on the idea of velocity feedback. The algorithm provides a large damping ratio for space flexible structures and does not require a structure model. The effectiveness of the algorithm is demonstrated on a structure similar to JPL-MPI. The results show that large damping can be achieved for the vibration control of large space structures.

  4. Improved Position Sensor for Feedback Control of Levitation

    NASA Technical Reports Server (NTRS)

    Hyers, Robert; Savage, Larry; Rogers, Jan

    2004-01-01

    An improved optoelectronic apparatus has been developed to provide the position feedback needed for controlling the levitation subsystem of a containerless-processing system. As explained, the advantage of this apparatus over prior optoelectronic apparatuses that have served this purpose stems from the use of an incandescent lamp, instead of a laser, to illuminate the levitated object. In containerless processing, a small object to be processed is levitated (e.g., by use of a microwave, low-frequency electromagnetic, electrostatic, or acoustic field) so that it is not in contact with the wall of the processing chamber or with any other solid object during processing. In the case of electrostatic or low-frequency electromagnetic levitation, real-time measurement of the displacement of the levitated object from its nominal levitation position along the vertical axis (and, in some cases, along one or two horizontal axes) is needed for feedback control of the levitating field.

  5. Measure Up Pressure Down: Provider Toolkit to Improve Hypertension Control.

    PubMed

    Torres, Jennifer

    2016-05-01

    Hypertension is one of the most important risk factors for heart disease, stroke, kidney failure, and diabetes complications. Nearly one in three Americans adults has high blood pressure, and the cost associated with treating this condition is staggering. The Measure Up Pressure Down: Provider Toolkit to Improve Hypertension Control is a resource developed by the American Medical Group Foundation in partnership with the American Medical Group Association. The goal of this toolkit is to mobilize health care practitioners to work together through team-based approaches to achieve an 80% control rate of high blood pressure among their patient population. The toolkit can be used by health educators, clinic administrators, physicians, students, and other clinic staff as a step-by-step resource for developing the infrastructure needed to better identify and treat individuals with high blood pressure or other chronic conditions.

  6. An Improved Force Feedback Control Algorithm for Active Tendons

    PubMed Central

    Guo, Tieneng; Liu, Zhifeng; Cai, Ligang

    2012-01-01

    An active tendon, consisting of a displacement actuator and a co-located force sensor, has been adopted by many studies to suppress the vibration of large space flexible structures. The damping, provided by the force feedback control algorithm in these studies, is small and can increase, especially for tendons with low axial stiffness. This study introduces an improved force feedback algorithm, which is based on the idea of velocity feedback. The algorithm provides a large damping ratio for space flexible structures and does not require a structure model. The effectiveness of the algorithm is demonstrated on a structure similar to JPL-MPI. The results show that large damping can be achieved for the vibration control of large space structures. PMID:23112660

  7. Metformin and ageing: improving ageing outcomes beyond glycaemic control.

    PubMed

    Valencia, Willy Marcos; Palacio, Ana; Tamariz, Leonardo; Florez, Hermes

    2017-08-02

    In a world where the population is ageing, there is growing interest and demand for research evaluating strategies that address the ageing process. After 60 years of successful use of metformin in our pharmaceutical armamentarium, we are learning that, beyond improving glycaemic control, metformin may have additional mechanisms and pathways of action that need further study. Although, metformin's effect on clinical ageing outcomes may still be considered speculative, the findings from studies into cellular and animal models and from observational and pilot human studies support the existence of beneficial effects on ageing. At present, progress for human research, using randomised clinical trials to evaluate metformin's clinical impact, has just started. Here, we present a review on the ageing process and the mechanisms involved, and the role that metformin may have to counter these. We go on to discuss the upcoming large randomised clinical trials that may provide insight on the use of metformin for ageing outcomes beyond glycaemic control.

  8. Silicon ohmic lateral-contact MEMS switch for RF applications

    NASA Astrophysics Data System (ADS)

    Rogozhin, A.; Miakonkikh, A.; Tatarintsev, A.; Lebedev, K.; Kalnov, V.; Rudenko, K.; Lukichev, V.

    2016-12-01

    Application variety and huge potential market of RF MEMS switches guarantee relentless research interest to the field. There are lots of different types of MEMS switches. Direct contact MEMS switches are simplifier for integration than capacitive MEMS switches. Lateral technology considerably simplifies the formation process. The objective of this research is to estimate characteristics of the simple direct-contact lateral MEMS switch and to understand the improvement directions. The MEMS switches were fabricated on the SOI wafers by e-beam lithography, dry etching and wet HF-etching. E-beam lithography and dry etching were used to form the cantilever and electrodes on the buried oxide layer. The structure with two control electrodes was used. IV characteristics were measured by Keithley 4200-SCS. The distance between cantilever and control electrodes was 100 nm. From the obtained IV characteristics it is clear that the devices switches at about 60 V. High control voltage could be explained by the large distance between cantilever and control electrode, and high rigidity of the cantilever. Following simulation in COMSOL Multiphysics showed that the control voltage could be decreased to 20-30 V by adding of spring element to the cantilever and device geometry modification.

  9. Development of an RF Conditioning System for Charged-Particle Accelerators

    SciTech Connect

    Kang, Yoon W; Howlader, Mostofa; Shajedul Hasan, Dr. S. M.

    2008-01-01

    Charged-particle accelerators use various vacuum windows on their accelerating radio-frequency (RF) cavities to throughput very high RF power. Before being placed on the cavities, the windows should be cleaned, baked, and fully RF conditioned to prevent a poor vacuum from outgassing, as well as other forms of contamination. An example is the coaxial fundamental power coupler (FPC) with an annular alumina ceramic window for each of the 81 superconducting RF cavities in the Spallation Neutron Source (SNS) linear accelerator. The FPCs needed to be tested up to 650-kW peak in a traveling wave and 2.6 MW with standing wave peaks in 1.3 and 60 pulses/s at 805 MHz. In this paper, an Experimental-Physics-and-Industrial-Control-System-based RF conditioning system for the SNS RF test facility is presented. This paper summarizes the hardware and software design strategies, provides the results obtained, and describes the future research scope.

  10. Converging Redundant Sensor Network Information for Improved Building Control

    SciTech Connect

    Dale Tiller; D. Phil; Gregor Henze; Xin Guo

    2007-09-30

    This project investigated the development and application of sensor networks to enhance building energy management and security. Commercial, industrial and residential buildings often incorporate systems used to determine occupancy, but current sensor technology and control algorithms limit the effectiveness of these systems. For example, most of these systems rely on single monitoring points to detect occupancy, when more than one monitoring point could improve system performance. Phase I of the project focused on instrumentation and data collection. During the initial project phase, a new occupancy detection system was developed, commissioned and installed in a sample of private offices and open-plan office workstations. Data acquisition systems were developed and deployed to collect data on space occupancy profiles. Phase II of the project demonstrated that a network of several sensors provides a more accurate measure of occupancy than is possible using systems based on single monitoring points. This phase also established that analysis algorithms could be applied to the sensor network data stream to improve the accuracy of system performance in energy management and security applications. In Phase III of the project, the sensor network from Phase I was complemented by a control strategy developed based on the results from the first two project phases: this controller was implemented in a small sample of work areas, and applied to lighting control. Two additional technologies were developed in the course of completing the project. A prototype web-based display that portrays the current status of each detector in a sensor network monitoring building occupancy was designed and implemented. A new capability that enables occupancy sensors in a sensor network to dynamically set the 'time delay' interval based on ongoing occupant behavior in the space was also designed and implemented.

  11. Improving Hypertension Control and Patient Engagement Using Digital Tools.

    PubMed

    Milani, Richard V; Lavie, Carl J; Bober, Robert M; Milani, Alexander R; Ventura, Hector O

    2017-01-01

    Hypertension is present in 30% of the adult US population and is a major contributor to cardiovascular disease. The established office-based approach yields only 50% blood pressure control rates and low levels of patient engagement. Available home technology now provides accurate, reliable data that can be transmitted directly to the electronic medical record. We evaluated blood pressure control in 156 patients with uncontrolled hypertension enrolled into a home-based digital-medicine blood pressure program and compared them with 400 patients (matched to age, sex, body mass index, and blood pressure) in a usual-care group after 90 days. Digital-medicine patients completed questionnaires online, were asked to submit at least one blood pressure reading/week, and received medication management and lifestyle recommendations via a clinical pharmacist and a health coach. Blood pressure units were commercially available that transmitted data directly to the electronic medical record. Digital-medicine patients averaged 4.2 blood pressure readings per week. At 90 days, 71% of digital-medicine vs 31% of usual-care patients had achieved target blood pressure control. Mean decrease in systolic/diastolic blood pressure was 14/5 mm Hg in digital medicine, vs 4/2 mm Hg in usual care (P < .001). Excess sodium consumption decreased from 32% to 8% in the digital-medicine group (P = .004). Mean patient activation increased from 41.9 to 44.1 (P = .008), and the percentage of patients with low patient activation decreased from 15% to 6% (P = .03) in the digital-medicine group. A digital hypertension program is feasible and associated with significant improvement in blood pressure control rates and lifestyle change. Utilization of a virtual health intervention using connected devices improves patient activation and is well accepted by patients.

  12. [Plan to improve malaria control towards its elimination in Mesoamerica].

    PubMed

    Rodríguez, Mario Henry; Betanzos-Reyes, Angel Francisco

    2011-01-01

    To develop a plan to strengthen the control of malaria towards its elimination. In 2009, under the coordination of the National Public HealthInstitute ofMexico, atransdisciplinary equipment of technical and operative experts was conformed to carry out a situational analysis of malaria and control programs and for the selection of effective practices of intervention that would be incorporated to the plan, within the framework of an exercise in Theory of Change. Criteria for thestratificationof thelocalities, based ontheirtransmission characteristics were established. The structural and operative limitations of the control programs were identified. A plan of interventions was elaborated to improve the coverage of epidemiological surveillance, anti-malaria interventions and opportune diagnosis and treatment of cases. The plan delineates progressive phases of implementation: reorganization, intensification of interventions and evaluation of elimination feasibility. The adoption of a regional strategic plan will provide guidance and administrative elements to conform a system that coordinates the activities of the national control programs and facilitate the elimination of malaria in the region.

  13. Improved Sensitivity Relations in State Constrained Optimal Control

    SciTech Connect

    Bettiol, Piernicola; Frankowska, Hélène; Vinter, Richard B.

    2015-04-15

    Sensitivity relations in optimal control provide an interpretation of the costate trajectory and the Hamiltonian, evaluated along an optimal trajectory, in terms of gradients of the value function. While sensitivity relations are a straightforward consequence of standard transversality conditions for state constraint free optimal control problems formulated in terms of control-dependent differential equations with smooth data, their verification for problems with either pathwise state constraints, nonsmooth data, or for problems where the dynamic constraint takes the form of a differential inclusion, requires careful analysis. In this paper we establish validity of both ‘full’ and ‘partial’ sensitivity relations for an adjoint state of the maximum principle, for optimal control problems with pathwise state constraints, where the underlying control system is described by a differential inclusion. The partial sensitivity relation interprets the costate in terms of partial Clarke subgradients of the value function with respect to the state variable, while the full sensitivity relation interprets the couple, comprising the costate and Hamiltonian, as the Clarke subgradient of the value function with respect to both time and state variables. These relations are distinct because, for nonsmooth data, the partial Clarke subdifferential does not coincide with the projection of the (full) Clarke subdifferential on the relevant coordinate space. We show for the first time (even for problems without state constraints) that a costate trajectory can be chosen to satisfy the partial and full sensitivity relations simultaneously. The partial sensitivity relation in this paper is new for state constraint problems, while the full sensitivity relation improves on earlier results in the literature (for optimal control problems formulated in terms of Lipschitz continuous multifunctions), because a less restrictive inward pointing hypothesis is invoked in the proof, and because

  14. Inspiratory resistive loading improves cycling capacity: a placebo controlled trial

    PubMed Central

    Gething, A; Williams, M; Davies, B

    2004-01-01

    Background: Respiratory muscle training has been shown to improve both its strength and endurance. The effect of these improvements on whole-body exercise performance remains controversial. Objective: To assess the effect of a 10 week inspiratory resistive loading (IRL) intervention on respiratory muscle performance and whole-body exercise endurance. Methods: Fifteen apparently healthy subjects (10 men, 5 women) were randomly allocated to one of three groups. One group underwent IRL set at 80% of maximum inspiratory pressure with ever decreasing work/rest ratios until task failure, for three days a week for 10 weeks (IRL group). A second placebo group performed the same training procedure but with a minimal resistance (PLA group). IRL and placebo training were performed at rest. The remaining five control subjects performed no IRL during the 10 week study period (CON group). Cycling endurance capacity at 75% V·O2peak was measured before and after the intervention. Results: After the 10 week IRL intervention, respiratory muscle strength (maximum inspiratory pressure) and endurance (sum of sustained maximum inspiratory pressure) had significantly improved (by 34% and 38% respectively). An increase in diaphragm thickness was also observed. These improvements translated into a 36% increase in cycling time to exhaustion at 75% V·O2peak. During cycling trials, heart rate, ventilation, and rating of perceived exertion were attenuated in the IRL group. No changes were observed for the PLA or CON group either in the time to exhaustion or cardiorespiratory response to the same intensity of exercise. Conclusion: Ten weeks of IRL attenuated the heart rate, ventilatory, and perceptual response to constant workload exercise, and improved the cycling time to exhaustion. Familiarisation was not a factor and the placebo effect was minimal. PMID:15562168

  15. Systematic uncertainties in RF-based measurement of superconducting cavity quality factors

    DOE PAGES

    Holzbauer, J. P.; Pischalnikov, Yu.; Sergatskov, D. A.; ...

    2016-05-10

    Q0 determinations based on RF power measurements are subject to at least three potentially large systematic effects that have not been previously appreciated. Here, instrumental factors that can systematically bias RF based measurements of Q0 are quantified and steps that can be taken to improve the determination of Q0 are discussed.

  16. Systematic uncertainties in RF-based measurement of superconducting cavity quality factors

    SciTech Connect

    Holzbauer, J. P.; Pischalnikov, Yu.; Sergatskov, D. A.; Schappert, W.; Smith, S.

    2016-05-10

    Q0 determinations based on RF power measurements are subject to at least three potentially large systematic effects that have not been previously appreciated. Here, instrumental factors that can systematically bias RF based measurements of Q0 are quantified and steps that can be taken to improve the determination of Q0 are discussed.

  17. Systematic uncertainties in RF-based measurement of superconducting cavity quality factors

    SciTech Connect

    Holzbauer, J. P.; Pischalnikov, Yu.; Sergatskov, D. A.; Schappert, W.; Smith, S.

    2016-05-10

    Q0 determinations based on RF power measurements are subject to at least three potentially large systematic effects that have not been previously appreciated. Here, instrumental factors that can systematically bias RF based measurements of Q0 are quantified and steps that can be taken to improve the determination of Q0 are discussed.

  18. Does Self-Control Training Improve Self-Control? A Meta-Analysis.

    PubMed

    Friese, Malte; Frankenbach, Julius; Job, Veronika; Loschelder, David D

    2017-08-01

    Self-control is positively associated with a host of beneficial outcomes. Therefore, psychological interventions that reliably improve self-control are of great societal value. A prominent idea suggests that training self-control by repeatedly overriding dominant responses should lead to broad improvements in self-control over time. Here, we conducted a random-effects meta-analysis based on robust variance estimation of the published and unpublished literature on self-control training effects. Results based on 33 studies and 158 effect sizes revealed a small-to-medium effect of g = 0.30, confidence interval (CI95) [0.17, 0.42]. Moderator analyses found that training effects tended to be larger for (a) self-control stamina rather than strength, (b) studies with inactive compared to active control groups, (c) males than females, and (d) when proponents of the strength model of self-control were (co)authors of a study. Bias-correction techniques suggested the presence of small-study effects and/or publication bias and arrived at smaller effect size estimates (range: gcorrected = .13 to .24). The mechanisms underlying the effect are poorly understood. There is not enough evidence to conclude that the repeated control of dominant responses is the critical element driving training effects.

  19. High-Power Rf Load

    DOEpatents

    Tantawi, Sami G.; Vlieks, Arnold E.

    1998-09-01

    A compact high-power RF load comprises a series of very low Q resonators, or chokes [16], in a circular waveguide [10]. The sequence of chokes absorb the RF power gradually in a short distance while keeping the bandwidth relatively wide. A polarizer [12] at the input end of the load is provided to convert incoming TE.sub.10 mode signals to circularly polarized TE.sub.11 mode signals. Because the load operates in the circularly polarized mode, the energy is uniformly and efficiently absorbed and the load is more compact than a rectangular load. Using these techniques, a load having a bandwidth of 500 MHz can be produced with an average power dissipation level of 1.5 kW at X-band, and a peak power dissipation of 100 MW. The load can be made from common lossy materials, such as stainless steel, and is less than 15 cm in length. These techniques can also produce loads for use as an alternative to ordinary waveguide loads in small and medium RF accelerators, in radar systems, and in other microwave applications. The design is easily scalable to other RF frequencies and adaptable to the use of other lossy materials.

  20. RF spectrometers for heterodyne receivers

    NASA Technical Reports Server (NTRS)

    Buhl, D.; Mumma, M. J.

    1980-01-01

    Several types of spectrometers developed for radio astronomy receivers which utilize RF filters, multiple oscillators and mixers, digital autocorrelators and acoustic/optic devices are considered. The RF spectrometer developed at GSFC to provide wide bandwidths (greater than 1 GHz) as well as high resolution (5MHz) is described. The 128 channel filter bank is divided into high and low resolution sections. The high resolution section is tunable by providing a second mixer ahead of the filter bank. This is necessary because infrared receivers which use gas lasers as local oscillators are only tunable to specific laser frequencies. To compensate for astronomical Doppler shifts and molecule frequency differences a second local oscillator and mixer is needed. A diagram of the RF section of the filter bank is shown. The RF spectrometer is shown to be the best means of achieving ultra-wide bandwidths for infrared heterodyne receivers. For high resolution with a large number of channels, the acousto/optical spectrometer is the principle instrument, particularly for balloon or space flight applications.

  1. Breakdown-Resistant RF Connectors for Vacuum

    NASA Technical Reports Server (NTRS)

    Caro, Edward R.; Bonazza, Walter J.

    1987-01-01

    Resilient inserts compensate for insulation shrinkage. Coaxial-cable connector for radio-frequency (RF) energy resists electrical breakdown in vacuum. Used on RF equipment in vacuum chambers as well as in spaceborne radar and communication gear.

  2. Automatic calorimetry system monitors RF power

    NASA Technical Reports Server (NTRS)

    Harness, B. W.; Heiberger, E. C.

    1969-01-01

    Calorimetry system monitors the average power dissipated in a high power RF transmitter. Sensors measure the change in temperature and the flow rate of the coolant, while a multiplier computes the power dissipated in the RF load.

  3. Combination radiofrequency (RF) ablation and IV liposomal heat shock protein suppression: Reduced tumor growth and increased animal endpoint survival in a small animal tumor model

    PubMed Central

    Yang, Wei; Ahmed, Muneeb; Tasawwar, Beenish; Levchenko, Tatynana; Sawant, Rupa R.; Torchilin, Vladimir; Goldberg, S. Nahum

    2012-01-01

    Background To investigate the effect of IV liposomal quercetin (a known down-regulator of heat shock proteins) alone and with liposomal doxorubicin on tumor growth and end-point survival when combined with radiofrequency (RF) tumor ablation in a rat tumor model. Methods Solitary subcutaneous R3230 mammary adenocarcinoma tumors (1.3–1.5 cm) were implanted in 48 female Fischer rats. Initially, 32 tumors (n=8, each group) were randomized into four experimental groups: (a) conventional monopolar RF alone (70°C for 5 min), (b) IV liposomal quercetin alone (1 mg/kg), (c) IV liposomal quercetin followed 24hr later with RF, and (d) no treatment. Next, 16 additional tumors were randomized into two groups (n=8, each) that received a combined RF and liposomal doxorubicin (15 min post-RF, 8 mg/kg) either with or without liposomal quercetin. Kaplan-Meier survival analysis was performed using a tumor diameter of 3.0 cm as the defined survival endpoint. Results Differences in endpoint survival and tumor doubling time among the groups were highly significant (P<0.001). Endpoint survivals were 12.5±2.2 days for the control group, 16.6±2.9 days for tumors treated with RF alone, 15.5±2.1days for tumors treated with liposomal quercetin alone, and 22.0±3.9 days with combined RF and quercetin. Additionally, combination quercetin/RF/doxorubicin therapy resulted in the longest survival (48.3±20.4 days), followed by RF/doxorubicin (29.9±3.8 days). Conclusions IV liposomal quercetin in combination with RF ablation reduces tumor growth rates and improves animal endpoint survival. Further increases in endpoint survival can be seen by adding an additional anti-tumor adjuvant agent liposomal doxorubicin. This suggests that targeting several post-ablation processes with multi-drug nanotherapies can increase overall ablation efficacy. PMID:22230341

  4. Combination radiofrequency (RF) ablation and IV liposomal heat shock protein suppression: reduced tumor growth and increased animal endpoint survival in a small animal tumor model.

    PubMed

    Yang, Wei; Ahmed, Muneeb; Tasawwar, Beenish; Levchenko, Tatynana; Sawant, Rupa R; Torchilin, Vladimir; Goldberg, S Nahum

    2012-06-10

    To investigate the effect of IV liposomal quercetin (a known down-regulator of heat shock proteins) alone and with liposomal doxorubicin on tumor growth and end-point survival when combined with radiofrequency (RF) tumor ablation in a rat tumor model. Solitary subcutaneous R3230 mammary adenocarcinoma tumors (1.3-1.5 cm) were implanted in 48 female Fischer rats. Initially, 32 tumors (n=8, each group) were randomized into four experimental groups: (a) conventional monopolar RF alone (70°C for 5 min), (b) IV liposomal quercetin alone (1 mg/kg), (c) IV liposomal quercetin followed 24hr later with RF, and (d) no treatment. Next, 16 additional tumors were randomized into two groups (n=8, each) that received a combined RF and liposomal doxorubicin (15 min post-RF, 8 mg/kg) either with or without liposomal quercetin. Kaplan-Meier survival analysis was performed using a tumor diameter of 3.0 cm as the defined survival endpoint. Differences in endpoint survival and tumor doubling time among the groups were highly significant (P<0.001). Endpoint survivals were 12.5±2.2 days for the control group, 16.6±2.9 days for tumors treated with RF alone, 15.5±2.1 days for tumors treated with liposomal quercetin alone, and 22.0±3.9 days with combined RF and quercetin. Additionally, combination quercetin/RF/doxorubicin therapy resulted in the longest survival (48.3±20.4 days), followed by RF/doxorubicin (29.9±3.8 days). IV liposomal quercetin in combination with RF ablation reduces tumor growth rates and improves animal endpoint survival. Further increases in endpoint survival can be seen by adding an additional anti-tumor adjuvant agent liposomal doxorubicin. This suggests that targeting several post-ablation processes with multi-drug nanotherapies can increase overall ablation efficacy. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. RF-MEMS for future mobile applications: experimental verification of a reconfigurable 8-bit power attenuator up to 110 GHz

    NASA Astrophysics Data System (ADS)

    Iannacci, J.; Tschoban, C.

    2017-04-01

    RF-MEMS technology is proposed as a key enabling solution for realising the high-performance and highly reconfigurable passive components that future communication standards will demand. In this work, we present, test and discuss a novel design concept for an 8-bit reconfigurable power attenuator, manufactured using the RF-MEMS technology available at the CMM-FBK, in Italy. The device features electrostatically controlled MEMS ohmic switches in order to select/deselect the resistive loads (both in series and shunt configuration) that attenuate the RF signal, and comprises eight cascaded stages (i.e. 8-bit), thus implementing 256 different network configurations. The fabricated samples are measured (S-parameters) from 10 MHz to 110 GHz in a wide range of different configurations, and modelled/simulated with Ansys HFSS. The device exhibits attenuation levels (S21) in the range from  ‑10 dB to  ‑60 dB, up to 110 GHz. In particular, S21 shows flatness from 15 dB down to 3–5 dB and from 10 MHz to 50 GHz, as well as fewer linear traces up to 110 GHz. A comprehensive discussion is developed regarding the voltage standing wave ratio, which is employed as a quality indicator for the attenuation levels. The margins of improvement at design level which are needed to overcome the limitations of the presented RF-MEMS device are also discussed.

  6. Single-chip fully integrated direct-modulation CMOS RF transmitters for short-range wireless applications.

    PubMed

    El-Desouki, Munir M; Qasim, Syed Manzoor; BenSaleh, Mohammed; Deen, M Jamal

    2013-08-02

    Ultra-low power radio frequency (RF) transceivers used in short-range application such as wireless sensor networks (WSNs) require efficient, reliable and fully integrated transmitter architectures with minimal building blocks. This paper presents the design, implementation and performance evaluation of single-chip, fully integrated 2.4 GHz and 433 MHz RF transmitters using direct-modulation power voltage-controlled oscillators (PVCOs) in addition to a 2.0 GHz phase-locked loop (PLL) based transmitter. All three RF transmitters have been fabricated in a standard mixed-signal CMOS 0.18 µm technology. Measurement results of the 2.4 GHz transmitter show an improvement in drain efficiency from 27% to 36%. The 2.4 GHz and 433 MHz transmitters deliver an output power of 8 dBm with a phase noise of -122 dBc/Hz at 1 MHz offset, while drawing 15.4 mA of current and an output power of 6.5 dBm with a phase noise of -120 dBc/Hz at 1 MHz offset, while drawing 20.8 mA of current from 1.5 V power supplies, respectively. The PLL transmitter delivers an output power of 9 mW with a locking range of 128 MHz and consumes 26 mA from 1.8 V power supply. The experimental results demonstrate that the RF transmitters can be efficiently used in low power WSN applications.

  7. Control of Phase in Tin Sulfide Thin Films Produced via RF-Sputtering of SnS2 Target with Post-deposition Annealing

    NASA Astrophysics Data System (ADS)

    Banai, R. E.; Cordell, J. C.; Lindwall, G.; Tanen, N. J.; Shang, S.-L.; Nasr, J. R.; Liu, Z.-K.; Brownson, J. R. S.; Horn, M. W.

    2016-01-01

    Tin (II) Monosulfide (SnS) has become an interesting new material for thin film photovoltaics. SnS-based devices have achieved limited success in improved solar cell efficiency. While annealing is a typical post-deposition treatment used to improve thin film quality, sulfur volatility is an issue, despite strong Sn-S bonds in tin sulfide compounds. Annealing of sulfur-rich sputtered tin sulfide thin films in a vacuum environment has not been previously reported. In the present work, we investigated the optoelectronic properties, crystallographic phase, and morphology of annealed, sputtered tin sulfide thin films. Specifically, we studied the phase change and improvement in material quality as a result of post-deposition heat treatments. Tin sulfide thin films were sputtered with and without substrate heating. These samples were then annealed between 300°C and 500°C under moderate vacuum (<1 × 10-4 Pa) in the deposition chamber to find the optimal annealing process for producing α-SnS. Significantly improved crystallinity and morphology were seen in sulfur-rich thin films annealed at 400-500°C for 60 min. Annealed films had resistivity in the range of 30-300 Ω-cm. Experimental observations were confirmed by calculated phase diagrams, which show that annealing around 400°C at low pressure is optimal to obtain a phase-pure α-SnS film from an amorphous SnS2 film.

  8. [Improvement of routine works and quality control in mycobacterial laboratory].

    PubMed

    Suzuki, Katsuhiro; Higuchi, Takeshi

    2007-03-01

    Many new methods have been introduced into routine laboratory works in microbiology since 1990. Molecular biology, in particular, opened a new era and promoted a technician's skill much. PCR and hybridization technique have been ordinary one in many laboratories. Since old techniques such as smear and culture are still needed, amount of routine works is increasing gradually. Thus, improving efficiency and keeping quality of routine works are becoming more and more important issues. This symposium focused on such points, and four skilled technicians around Japan presented their own tips. 1. Coexistence of M. tuberculosis and M. avium complex (MAC) in the MGIT culture system: Yasushi WATANABE (Clinical Laboratory Division, NHO Nishi-Niigata Chuo National Hospital). Sputum samples of some tuberculosis patients yielded only MAC in the MGIT culture system. Such co-infected cases presented problems to mislead proper treatment and infection control. The detection rate of MAC was significantly high, and the growth speed of MAC was significantly rapid in the MGIT culture system, compared to those of M. tuberculosis. Additionally, M. tuberculosis was not detected with even more quantity than MAC in the small amount of mixed samples. Higher sensitivity and growth speed of MAC are the important characteristics of the MGIT system. 2. Internal quality control with ordinary examination results: Akio AONO (Department of Clinical Examination, Double-Barred Cross Hospital, Japan Anti-Tuberculosis Association). Our laboratory utilizes ordinary examination results as the internal quality control for specimen pretreatment, culture, and drug susceptibility testing. The contamination rate of MGIT culture system is useful for the evaluation of the decontamination process. It was 6.3% on average in our laboratory in 2005. The number of drug resistant strains is also useful to assess the performance of drug susceptibility testing. The incidence of each anti-tuberculosis drug resistance

  9. Condensing economizers for thermal efficiency improvements and emissions control

    SciTech Connect

    Heaphy, J.P.; Carbonara, J.; Litzke, W.; Butcher, T.A.

    1993-12-31

    Flue gas condensing economizers improve the thermal efficiency of boilers by recovering sensible heat and water vapor latent heat from flue gas exhaust. In addition to improving thermal efficiency, condensing economizers also have the potential to act as control devices for emissions of particulates, SO{sub x}, and air toxics. Both Consolidated Edison of New York and Brookhaven National LaborAtory are currently working on condensing economizer technology with an emphasis on developing their potential for emissions control. Con Edison is currently conducting a condensing economizer demonstration at their oil-fired 74th Street Station in New York. Since installing this equipment in February of 1992 a heat rate improvement of 800 Btu/kWh has been seen. At another location, Ravenswood Station, a two stage condensing economizer has been installed in a pilot test. In this advanced configuration -the ``Integrated Flue Gas Treatment or IFGT system- two heat exchanger sections are installed and sprays of water with and without SO{sub 2} sorbents are included. Detailed studies of the removal of particulates, SO{sub 2}, SO{sub 3}, and selected air toxics have been done for a variety of operating conditions. Removal efficiencies for SO{sub 2} have been over 98% and for SO{sub 3} over 65%. Brookhaven National Laboratory`s studies involve predicting and enhancing particulate capture in condensing economizers with an emphasis on small, coal-fired applications. This work is funded by the Pittsburgh Energy Technology Center of the Department of Energy. Flyash capture efficiencies as high as 97% have been achieved to date with a single stage economizer.

  10. RF Reference Switch for Spaceflight Radiometer Calibration

    NASA Technical Reports Server (NTRS)

    Knuble, Joseph

    2013-01-01

    The goal of this technology is to provide improved calibration and measurement sensitivity to the Soil Moisture Active Passive Mission (SMAP) radiometer. While RF switches have been used in the past to calibrate microwave radiometers, the switch used on SMAP employs several techniques uniquely tailored to the instrument requirements and passive remote-sensing in general to improve radiometer performance. Measurement error and sensitivity are improved by employing techniques to reduce thermal gradients within the device, reduce insertion loss during antenna observations, increase insertion loss temporal stability, and increase rejection of radar and RFI (radio-frequency interference) signals during calibration. The two legs of the single-pole double-throw reference switch employ three PIN diodes per leg in a parallel-shunt configuration to minimize insertion loss and increase stability while exceeding rejection requirements at 1,413 MHz. The high-speed packaged diodes are selected to minimize junction capacitance and resistance while ensuring the parallel devices have very similar I-V curves. Switch rejection is improved by adding high-impedance quarter-wave tapers before and after the diodes, along with replacing the ground via of one diode per leg with an open circuit stub. Errors due to thermal gradients in the switch are reduced by embedding the 50-ohm reference load within the switch, along with using a 0.25-in. (approximately equal to 0.6-cm) aluminum prebacked substrate. Previous spaceflight microwave radiometers did not embed the reference load and thermocouple directly within the calibration switch. In doing so, the SMAP switch reduces error caused by thermal gradients between the load and switch. Thermal issues are further reduced by moving the custom, highspeed regulated driver circuit to a physically separate PWB (printed wiring board). Regarding RF performance, previous spaceflight reference switches have not employed high-impedance tapers to improve

  11. Spatial domain method for the design of RF pulses in multicoil parallel excitation.

    PubMed

    Grissom, William; Yip, Chun-yu; Zhang, Zhenghui; Stenger, V Andrew; Fessler, Jeffrey A; Noll, Douglas C

    2006-09-01

    Parallel excitation has been introduced as a means of accelerating multidimensional, spatially-selective excitation using multiple transmit coils, each driven by a unique RF pulse. Previous approaches to RF pulse design in parallel excitation were either formulated in the frequency domain or restricted to echo-planar trajectories, or both. This paper presents an approach that is formulated as a quadratic optimization problem in the spatial domain and allows the use of arbitrary k-space trajectories. Compared to frequency domain approaches, the new design method has some important advantages. It allows for the specification of a region of interest (ROI), which improves excitation accuracy at high speedup factors. It allows for magnetic field inhomogeneity compensation during excitation. Regularization may be used to control integrated and peak pulse power. The effects of Bloch equation nonlinearity on the large-tip-angle excitation error of RF pulses designed with the method are investigated, and the utility of Tikhonov regularization in mitigating this error is demonstrated. Copyright (c) 2006 Wiley-Liss, Inc.

  12. Review of pulsed rf power generation

    SciTech Connect

    Lavine, T.L.

    1992-04-01

    I am going to talk about pulsed high-power rf generation for normal-conducting electron and positron linacs suitable for applications to high-energy physics in the Next Linear Collider, or NLC. The talk will cover some basic rf system design issues, klystrons and other microwave power sources, rf pulse-compression devices, and test facilities for system-integration studies.

  13. RF digital-to-analog converter

    DOEpatents

    Conway, P.H.; Yu, D.U.L.

    1995-02-28

    A digital-to-analog converter is disclosed for producing an RF output signal proportional to a digital input word of N bits from an RF reference input, N being an integer greater or equal to 2. The converter comprises a plurality of power splitters, power combiners and a plurality of mixers or RF switches connected in a predetermined configuration. 18 figs.

  14. RF digital-to-analog converter

    DOEpatents

    Conway, Patrick H.; Yu, David U. L.

    1995-01-01

    A digital-to analogue converter for producing an RF output signal proportional to a digital input word of N bits from an RF reference input, N being an integer greater or equal to 2. The converter comprises a plurality of power splitters, power combiners and a plurality of mixers or RF switches connected in a predetermined configuration.

  15. High-brightness rf linear accelerators

    SciTech Connect

    Jameson, R.A.

    1986-01-01

    The issue of high brightness and its ramifications in linacs driven by radio-frequency fields is discussed. A history of the RF linacs is reviewed briefly. Some current applications are then examined that are driving progress in RF linacs. The physics affecting the brightness of RF linacs is then discussed, followed by the economic feasibility of higher brightness machines. (LEW)

  16. 75 FR 18238 - United States Section; Final Environmental Impact Statement, Flood Control Improvements and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-09

    ..., Flood Control Improvements and Partial Levee Relocation, United States Section, International Boundary and Water Commission (USIBWC) Presidio Flood Control Project (FCP), Presidio, TX AGENCY: United States... potential consequences of each action alternative in reference to flood control improvements. Following the...

  17. Improving labeling efficiency in automatic quality control of MRSI data.

    PubMed

    Pedrosa de Barros, Nuno; McKinley, Richard; Wiest, Roland; Slotboom, Johannes

    2017-02-07

    To improve the efficiency of the labeling task in automatic quality control of MR spectroscopy imaging data. 28'432 short and long echo time (TE) spectra (1.5 tesla; point resolved spectroscopy (PRESS); repetition time (TR)= 1,500 ms) from 18 different brain tumor patients were labeled by two experts as either accept or reject, depending on their quality. For each spectrum, 47 signal features were extracted. The data was then used to run several simulations and test an active learning approach using uncertainty sampling. The performance of the classifiers was evaluated as a function of the number of patients in the training set, number of spectra in the training set, and a parameter α used to control the level of classification uncertainty required for a new spectrum to be selected for labeling. The results showed that the proposed strategy allows reductions of up to 72.97% for short TE and 62.09% for long TE in the amount of data that needs to be labeled, without significant impact in classification accuracy. Further reductions are possible with significant but minimal impact in performance. Active learning using uncertainty sampling is an effective way to increase the labeling efficiency for training automatic quality control classifiers. Magn Reson Med, 2017. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

  18. Reducing mass peak instability caused by the phase changes of RF and AC signals in a rectilinear ion-trap analyzer

    NASA Astrophysics Data System (ADS)

    Lu, Xinqiong; Ni, Kai; Yu, Quan; Xu, Wenchao; Qian, Xiang; Wang, Xiaohao

    2017-03-01

    For an ion trap with resonance ejection, peak intensity and peak position of the acquired mass spectra are affected by the phase difference between the radio frequency (RF) and auxiliary alternating current (AC) potentials. To ensure measurement stability, RF and AC phase-locking is commonly used in commercial ion trap mass spectrometers. In this study, a compact electronic control system was developed to accurately regulate the RF and AC phases and was employed in a photoionization rectilinear ion trap (RIT) mass spectrometer. We found that the phase-locking method was defective in multicomponent analysis because the optimal RF and AC phase difference was usually different for different m/z peaks. After studying and characterizing the relationship between the peaks and the RF and AC phases, a correction method based on data processing was used to improve the peaks' stability and accuracy. The results show that the fluctuations of both peak intensity and peak position were significantly reduced and that the instrument presented satisfying reproducibility and quantitative ability.

  19. Influences of the RF power ratio on the optical and electrical properties of GZO thin films by DC coupled RF magnetron sputtering at room temperature

    NASA Astrophysics Data System (ADS)

    Peng, Shou; Yao, Tingting; Yang, Yong; Zhang, Kuanxiang; Jiang, Jiwen; Jin, Kewu; Li, Gang; Cao, Xin; Xu, Genbao; Wang, Yun

    2016-12-01

    Ga-doped zinc oxide (GZO) thin films were deposited by closed field unbalanced DC coupled RF magnetron sputtering system at room temperature. The RF sputtering power ratio was adjusted from 0% to 100%. The crystal structure, surface morphology, transmittance and electrical resistivity of GZO films mainly influenced by RF sputtering power ratio were investigated by X-ray diffractometer, scanning electronic microscope, ultraviolet-visible spectrophotometer and Hall effect measurement. The research results indicate that the increasing RF power ratio can effectively reduce the discharge voltage of system and increase the ionizing rate of particles. Meanwhile, the higher RF power ratio can increase the carrier mobility in GZO thin film and improve the optical and electrical properties of GZO thin film significantly. Within the optimal discharge voltage window, the film deposits at 80% RF power ratio exhibits the lowest resistivity of 2.6×10-4 Ω cm. We obtain the GZO film with the best average optical transmittance is approximately 84% in the visible wavelength. With the increasing RF power ratio, the densification of GZO film is enhanced. The densification of GZO film is decrease when the RF power ratio is 100%.

  20. Dynamics of the L {yields} H transition, VH-mode evolution, edge localized modes and R.F. driven confinement control in tokamaks

    SciTech Connect

    Diamond, P.H.; Lebedev, V.B.; Liang, Y.M.; Gruzinov, A.V.; Gruzinov, I.; Medvedev, M.; Carreras, B.A.; Newman, D.E.; Charlton, L.; Sidikman, K.L.

    1995-02-01

    Several novel theoretical results related to L {yields} H transition physics, VH-mode evolution, Edge Localized Modes and active confinement control are presented. Critical issues are identified, results are discussed and important unresolved questions are listed. The basic physics is discussed in the contexts of current experiments and of ITER.