SYNCHROTRON RADIATION, FREE ELECTRON LASER, APPLICATION OF NUCLEAR TECHNOLOGY, ETC. Design of a multi-cusp ion source for proton therapy

NASA Astrophysics Data System (ADS)

Wu, Xiao-Bing; Huang, Tao; Ouyang, Hua-Fu; Zhang, Hua-Shun; Gong, Ke-Yun

2010-12-01

The permanent magnets of the discharge chamber in a multi-cusp proton source are studied and designed. The three electrode extraction system is adopted and simulated. A method to extract different amounts of current while keeping the beam emittance unchanged is proposed.

Development of a compact filament-discharge multi-cusp H- ion source.

PubMed

Jia, XianLu; Zhang, TianJue; Zheng, Xia; Qin, JiuChang

2012-02-01

A 14 MeV medical cyclotron with the external ion source has been designed and is being constructed at China Institute of Atomic Energy. The H(-) ion will be accelerated by this machine and the proton beam will be extracted by carbon strippers in dual opposite direction. The compact multi-cusp H(-) ion source has been developed for the cyclotron. The 79.5 mm long ion source is 48 mm in diameter, which is consisting of a special shape filament, ten columns of permanent magnets providing a multi-cusp field, and a three-electrode extraction system. So far, the 3 mA∕25 keV H(-) beam with an emittance of 0.3 π mm mrad has been obtained from the ion source. The paper gives the design details and the beam test results. Further experimental study is under way and an extracted beam of 5 mA is expected.

Improvements to the internal and external antenna H(-) ion sources at the Spallation Neutron Source.

PubMed

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

2014-02-01

The Spallation Neutron Source (SNS), a large scale neutron production facility, routinely operates with 30-40 mA peak current in the linac. Recent measurements have shown that our RF-driven internal antenna, Cs-enhanced, multi-cusp ion sources injects ∼55 mA of H(-) beam current (∼1 ms, 60 Hz) at 65-kV into a Radio Frequency Quadrupole (RFQ) accelerator through a closely coupled electrostatic Low-Energy Beam Transport system. Over the last several years a decrease in RFQ transmission and issues with internal antennas has stimulated source development at the SNS both for the internal and external antenna ion sources. This report discusses progress in improving internal antenna reliability, H(-) yield improvements which resulted from modifications to the outlet aperture assembly (applicable to both internal and external antenna sources) and studies made of the long standing problem of beam persistence with the external antenna source. The current status of the external antenna ion source will also be presented.

Low energy spread ion source with a coaxial magnetic filter

DOEpatents

Leung, Ka-Ngo; Lee, Yung-Hee Yvette

2000-01-01

Multicusp ion sources are capable of producing ions with low axial energy spread which are necessary in applications such as ion projection lithography (IPL) and radioactive ion beam production. The addition of a radially extending magnetic filter consisting of a pair of permanent magnets to the multicusp source reduces the energy spread considerably due to the improvement in the uniformity of the axial plasma potential distribution in the discharge region. A coaxial multicusp ion source designed to further reduce the energy spread utilizes a cylindrical magnetic filter to achieve a more uniform axial plasma potential distribution. The coaxial magnetic filter divides the source chamber into an outer annular discharge region in which the plasma is produced and a coaxial inner ion extraction region into which the ions radially diffuse but from which ionizing electrons are excluded. The energy spread in the coaxial source has been measured to be 0.6 eV. Unlike other ion sources, the coaxial source has the capability of adjusting the radial plasma potential distribution and therefore the transverse ion temperature (or beam emittance).

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

PubMed

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

2012-02-01

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

Challenges/issues of NIS used in particle accelerator facilities

NASA Astrophysics Data System (ADS)

Faircloth, Dan

2013-09-01

High current, high duty cycle negative ion sources are an essential component of many high power particle accelerators. This talk gives an overview of the state-of-the-art sources used around the world. Volume, surface and charge exchange negative ion production processes are detailed. Cesiated magnetron and Penning surface plasma sources are discussed along with surface converter sources. Multicusp volume sources with filament and LaB6 cathodes are described before moving onto RF inductively coupled volume sources with internal and external antennas. The major challenges facing accelerator facilities are detailed. Beam current, source lifetime and reliability are the most pressing. The pros and cons of each source technology is discussed along with their development programs. The uncertainties and unknowns common to these sources are discussed. The dynamics of cesium surface coverage and the causes of source variability are still unknown. Minimizing beam emittance is essential to maximizing the transport of high current beams; space charge effects are very important. The basic physics of negative ion production is still not well understood, theoretical and experimental programs continue to improve this, but there are still many mysteries to be solved.

Planned Experiments on the Princeton Advanced Test Stand

NASA Astrophysics Data System (ADS)

Stepanov, A.; Gilson, E. P.; Grisham, L.; Kaganovich, I.; Davidson, R. C.

2010-11-01

The Princeton Advanced Test Stand (PATS) device is an experimental facility based on the STS-100 high voltage test stand transferred from LBNL. It consists of a multicusp RF ion source, a pulsed extraction system capable of forming high-perveance 100keV ion beams, and a large six-foot-long vacuum with convenient access for beam diagnostics. This results in a flexible system for studying high perveance ion beams relevant to NDCX-I/II, including experiments on beam neutralization by ferroelectric plasma sources (FEPS) being developed at PPPL. Research on PATS will concern the basic physics of beam-plasma interactions, such as the effects of volume neutralization on beam emittance, as well as optimizing technology of the FEPS. PATS combines the advantage of an ion beam source and a large-volume plasma source in a chamber with ample access for diagnostics, resulting in a robust setup for investigating and improving relevant aspects of neutralized drift. There are also plans for running the ion source with strongly electro-negative gases such as chlorine, making it possible to extract positive or negative ion beams.

Effect of high energy electrons on H⁻ production and destruction in a high current DC negative ion source for cyclotron.

PubMed

Onai, M; Etoh, H; Aoki, Y; Shibata, T; Mattei, S; Fujita, S; Hatayama, A; Lettry, J

2016-02-01

Recently, a filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In this study, numerical modeling of the filament arc-discharge source plasma has been done with kinetic modeling of electrons in the ion source plasmas by the multi-cusp arc-discharge code and zero dimensional rate equations for hydrogen molecules and negative ions. In this paper, main focus is placed on the effects of the arc-discharge power on the electron energy distribution function and the resultant H(-) production. The modelling results reasonably explains the dependence of the H(-) extraction current on the arc-discharge power in the experiments.

Ion source and beam guiding studies for an API neutron generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sy, A.; Ji, Q.; Persaud, A.

2013-04-19

Recently developed neutron imaging methods require high neutron yields for fast imaging times and small beam widths for good imaging resolution. For ion sources with low current density to be viable for these types of imaging methods, large extraction apertures and beam focusing must be used. We present recent work on the optimization of a Penning-type ion source for neutron generator applications. Two multi-cusp magnet configurations have been tested and are shown to increase the extracted ion current density over operation without multi-cusp magnetic fields. The use of multi-cusp magnetic confinement and gold electrode surfaces have resulted in increased ionmore » current density, up to 2.2 mA/cm{sup 2}. Passive beam focusing using tapered dielectric capillaries has been explored due to its potential for beam compression without the cost and complexity issues associated with active focusing elements. Initial results from first experiments indicate the possibility of beam compression. Further work is required to evaluate the viability of such focusing methods for associated particle imaging (API) systems.« less

Numerical modeling of the SNS H{sup −} ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veitzer, Seth A.; Beckwith, Kristian R. C.; Kundrapu, Madhusudhan

Ion source rf antennas that produce H- ions can fail when plasma heating causes ablation of the insulating coating due to small structural defects such as cracks. Reducing antenna failures that reduce the operating capabilities of the Spallation Neutron Source (SNS) accelerator is one of the top priorities of the SNS H- Source Program at ORNL. Numerical modeling of ion sources can provide techniques for optimizing design in order to reduce antenna failures. There are a number of difficulties in developing accurate models of rf inductive plasmas. First, a large range of spatial and temporal scales must be resolved inmore » order to accurately capture the physics of plasma motion, including the Debye length, rf frequencies on the order of tens of MHz, simulation time scales of many hundreds of rf periods, large device sizes on tens of cm, and ion motions that are thousands of times slower than electrons. This results in large simulation domains with many computational cells for solving plasma and electromagnetic equations, short time steps, and long-duration simulations. In order to reduce the computational requirements, one can develop implicit models for both fields and particle motions (e.g. divergence-preserving ADI methods), various electrostatic models, or magnetohydrodynamic models. We have performed simulations using all three of these methods and have found that fluid models have the greatest potential for giving accurate solutions while still being fast enough to perform long timescale simulations in a reasonable amount of time. We have implemented a number of fluid models with electromagnetics using the simulation tool USim and applied them to modeling the SNS H- ion source. We found that a reduced, single-fluid MHD model with an imposed magnetic field due to the rf antenna current and the confining multi-cusp field generated increased bulk plasma velocities of > 200 m/s in the region of the antenna where ablation is often observed in the SNS source. We report here on comparisons of simulated plasma parameters and code performance using more accurate physical models, such as two-temperature extended MHD models, for both a related benchmark system describing a inductively coupled plasma reactor, and for the SNS ion source. We also present results from scaling studies for mesh generation and solvers in the USim simulation code.« less

Ion Source Development at the SNS

NASA Astrophysics Data System (ADS)

Welton, R. F.; Stockli, M. P.; Murray, S. N.; Carr, J.; Carmichael, J.; Goulding, R. H.; Baity, F. W.

2007-08-01

The US Spallation Neutron Source (SNS) has recently begun producing neutrons and is currently on track to becoming a world-leading facility for material science based on neutron scattering. The facility is comprised of an H- ion source, a linear accelerator, an accumulator ring, a liquid-Hg target and a suite of neutron scattering instruments. Over the next several years the average H- current from the ion source will be increased in order to meet the baseline facility requirement of providing 1.4 MW of beam-power to the target and the SNS power upgrade power requirement of 2+ MW on target. Meeting the latter goal will require H- currents of 70-100 mA with an RMS emittance of 0.20-0.35 π mm mrad and a ˜7% duty-factor. To date, the RF-driven-multicusp SNS ion source has only been able to demonstrate sustained operation at 33 mA of beam current at a ˜7% duty-factor. This report details our efforts to develop variations of the current ion source which can meet these requirements. Designs and experimental results are presented for helicon plasma drivers, high-power external antennas, glow-discharge plasma guns and advanced Cs systems.

Microwave electron cyclotron electron resonance (ECR) ion source with a large, uniformly distributed, axially symmetric, ECR plasma volume

DOEpatents

Alton, Gerald D.

1996-01-01

An electron cyclotron resonance (ECR) ion source includes a primary mirror coil disposed coaxially around a vacuum vessel in which a plasma is induced and introducing a solenoidal ECR-producing field throughout the length of the vacuum vessel. Radial plasma confinement is provided by a multi-cusp, multi-polar permanent magnet array disposed azimuthally around the vessel and within the primary mirror coil. Axial confinement is provided either by multi-cusp permanent magnets at the opposite axial ends of the vessel, or by secondary mirror coils disposed on opposite sides of the primary coil.

Effect of high energy electrons on H{sup −} production and destruction in a high current DC negative ion source for cyclotron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onai, M., E-mail: onai@ppl.appi.keio.ac.jp; Fujita, S.; Hatayama, A.

2016-02-15

Recently, a filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In this study, numerical modeling of the filament arc-discharge source plasma has been done with kinetic modeling of electrons in the ion source plasmas by the multi-cusp arc-discharge code and zero dimensional rate equations for hydrogen molecules and negative ions. In this paper, main focus is placed on the effects of the arc-discharge power on the electron energy distribution function and the resultant H{sup −} production. The modelling results reasonably explains the dependence of the H{sup −} extraction current on the arc-discharge powermore » in the experiments.« less

Numerical Analysis of Plasma Transport in Tandem Volume Magnetic Multicusp Ion Sources

DTIC Science & Technology

1992-03-01

the results of the model are qualitatively correct. Boltzmann Equation, Ion Sources, Plasma Simulation, Electron Temperature, Plasma Density, Ion Temperature, Hydrogen Ions, Magnetic Filters, Hydrogen Plasma Chemistry .

Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

NASA Astrophysics Data System (ADS)

Dechana, A.; Thamboon, P.; Boonyawan, D.

2014-10-01

A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al2O3 layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al2O3 films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed.

Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber.

PubMed

Dechana, A; Thamboon, P; Boonyawan, D

2014-10-01

A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al2O3 layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al2O3 films-analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques-will be discussed.

A continuously self regenerating high-flux neutron-generator facility

NASA Astrophysics Data System (ADS)

Rogers, A. M.; Becker, T. A.; Bernstein, L. A.; van Bibber, K.; Bleuel, D. L.; Chen, A. X.; Daub, B. H.; Goldblum, B. L.; Firestone, R. B.; Leung, K.-N.; Renne, P. R.; Waltz, C.

2013-10-01

A facility based on a next-generation, high-flux D-D neutron generator (HFNG) is being constructed at UC Berkeley. The current generator, designed around two RF-driven multicusp deuterium ion sources, is capable of producing a neutron output of >1011 n/s. A specially designed titanium-coated copper target located between the ion sources accelerates D+ ions up to 150 keV, generating 2.45 MeV neutrons through the d(d,3He)n fusion reaction. Deuterium in the target is self loaded and regenerating through ion implantation, enabling stable and continuous long-term operation. The proposed science program is focused on pioneering advances in the 40Ar/39Ar dating technique for geochronology, new nuclear data measurements, basic nuclear science research including statistical model studies of radiative-strength functions and level densities, and education. An overview of the facility and its unique capabilities as well as first measurements from the HFNG commissioning will be presented. Work supported by NSF Grant No. EAR-0960138, U.S. DOE LBL Contract No. DE-AC02-05CH11231, and U.S. DOE LLNL Contract No. DE-AC52-07NA27344.

Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dechana, A.; Thamboon, P.; Boonyawan, D., E-mail: dheerawan.b@cmu.ac.th

A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides highmore » flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al{sub 2}O{sub 3} layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al{sub 2}O{sub 3} films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed.« less

Design of the central region for axial injection in the VINCY cyclotron

NASA Astrophysics Data System (ADS)

Milinković, Ljiljana; Toprek, Dragan

1996-02-01

This paper describes the design of the central region for h = 1, h = 2 and h = 4 modes of acceleration in the VINCY cyclotron. The result which is worth reported in that the central region is unique and compatible with the three above mentioned harmonic modes of operation. Only one spiral type inflector will be used. The central region is designed to operate with two external ion sources: (a) an ECR ion source with the maximum extraction voltage of 25 kV for heavy ions, and (b) a multicusp ion source with the maximum extraction voltage of 30 kV for H - and D - ions. Heavy ions will be accelerated by the second and fourth harmonics, D - ions by the second harmonic and H - ions by the first harmonic of the RF field. The central region is equipped with an axial injection system. The electric field distribution in the inflector and in the four acceleration gaps has been numerically calculated from an electric potential map produced by the program RELAX3D. The geometry of the central region has been tested with the computations of orbits carried out by means of the computer code CYCLONE. The optical properties of the spiral inflector and the central region were studied by using the programs CASINO and CYCLONE respectively. We have also made an effort to minimize the inflector fringe field using the RELAX3D program.

mA beam acceleration efforts on 100 MeV H- cyclotron at CIAE

NASA Astrophysics Data System (ADS)

Zhang, Tianjue; An, Shizhong; Lv, Yinlong; Ge, Tao; Jia, Xianlu; Ji, Bin; Yin, Zhiguo; Pan, Gaofeng; Cao, Lei; Guan, Fengping; Yang, Jianjun; Li, Zhenguo; Zhao, Zhenlu; Wu, Longcheng; Zhang, He; Wang, Jingfeng; Zhang, Yiwang; Liu, Jingyuan; Li, Shiqiang; Lu, Xiaotong; Liu, Zhenwei; Li, Yaoqian; Guo, Juanjuan; Cao, Xuelong; Guan, Leilei; Wang, Fei; Wang, Yang; Yang, Guang; Zhang, Suping; Hou, Shigang; Wang, Feng

2017-09-01

Various technologies for high current compact H- cyclotron have been developed at CIAE since 1990s. A 375 μA proton beam was extracted from a 30 MeV compact H- cyclotron CYCIAE-30 at the end of 1994. A central region model cyclotron CYCIAE-CRM was developed for the design verification of a 100 MeV high current compact H- cyclotron CYCIAE-100. It is also a 10 MeV proton machine as a prototype for PET application. A 430 μA beam was achieved in 2009. The first beam was extracted from the CYCIAE-100 cyclotron on July 4, 2014, the operation stability has been improved and beam current has been increased gradually. A 1.1 mA proton beam was measured on the internal target in July 2016. The effort for an increasing of proton beam has continued till now. In this paper, the effort on several aspects for mA beam development will be presented, including the multi-cusp source, buncher, matching from the energy of the injected beam, vertical beam line and central region, beam loading of the RF system and instrumentation for beam diagnostics etc.

Characterization of Boron Contamination in Fluorine Implantation using Boron Trifluoride as a Source Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmeide, Matthias; Kondratenko, Serguei

2011-01-07

Fluorine implantation process purity was considered on different types of high current implanters. It was found that implanters equipped with an indirectly heated cathode ion source show an enhanced deep boron contamination compared to a high current implanter using a cold RF-driven multicusp ion source when boron trifluoride is used for fluorine implantations. This contamination is directly related to the source technology and thus, should be considered potentially for any implanter design using hot cathode/hot filament ion source, independently of the manufacturer.The boron contamination results from the generation of double charged boron ions in the arc chamber and the subsequentmore » charge exchange reaction to single charged boron ions taking place between the arc chamber and the extraction electrode. The generation of the double charged boron ions depends mostly on the source parameters, whereas the pressure in the region between the arc chamber and the extraction electrode is mostly responsible for the charge exchange from double charged to single charged ions. The apparent mass covers a wide range, starting at mass 11. A portion of boron ions with energies of (19/11) times higher than fluorine energy has the same magnetic rigidity as fluorine beam and cannot be separated by the analyzer magnet. The earlier described charge exchange effects between the extraction electrode and the entrance to the analyzer magnet, however, generates boron beam with a higher magnetic rigidity compared to fluorine beam and cannot cause boron contamination after mass-separation.The energetic boron contamination was studied as a function of the ion source parameters, such as gas flow, arc voltage, and source magnet settings, as well as analyzing magnet aperture resolution. This allows process optimization reducing boron contamination to the level acceptable for device performance.« less

The R&D progress of 4 MW EAST-NBI high current ion source.

PubMed

Xie, Yahong; Hu, Chundong; Liu, Sheng; Xu, Yongjian; Liang, Lizhen; Xie, Yuanlai; Sheng, Peng; Jiang, Caichao; Liu, Zhimin

2014-02-01

A high current ion source, which consists of the multi-cusp bucket plasma generator and tetrode accelerator with multi-slot apertures, is developed and tested for the Experimental Advanced Superconducting Tokamak neutral beam injector. Three ion sources are tested on the test bed with arc power of 80 kW, beam voltage of 80 keV, and beam power of 4 MW. The arc regulation technology with Langmuir probes is employed for the long pulse operation of ion source, and the long pulse beam of 50 keV @ 15.5 A @ 100 s and 80 keV @ 52A @ 1s are extracted, respectively.

High-Flux Neutron Generator Facility for Geochronology and Nuclear Physics Research

NASA Astrophysics Data System (ADS)

Waltz, Cory; HFNG Collaboration

2015-04-01

A facility based on a next-generation, high-flux D-D neutron generator (HFNG) is being commissioned at UC Berkeley. The generator is designed to produce monoenergetic 2.45 MeV neutrons at outputs exceeding 1011 n/s. The HFNG is designed around two RF-driven multi-cusp ion sources that straddle a titanium-coated copper target. D + ions, accelerated up to 150 keV from the ion sources, self-load the target and drive neutron generation through the d(d,n)3 He fusion reaction. A well-integrated cooling system is capable of handling beam power reaching 120 kW impinging on the target. The unique design of the HFNG target permits experimental samples to be placed inside the target volume, allowing the samples to receive the highest neutron flux (1011 cm-2 s-1) possible from the generator. In addition, external beams of neutrons will be available simultaneously, ranging from thermal to 2.45 MeV. Achieving the highest neutron yields required carefully designed schemes to mitigate back-streaming of high energy electrons liberated from the cathode target by deuteron bombardment. The proposed science program is focused on pioneering advances in the 40 Ar/39 Ar dating technique for geochronology, new nuclear data measurements, basic nuclear science, and education. An end goal is to become a user facility for researchers. This work is supported by NSF Grant No. EAR-0960138, U.S. DOE LBNL Contract No. DE-AC02-05CH11231, U.S. DOE LLNL Contract No. DE-AC52-07NA27344, and UC Office of the President Award 12-LR-238745.

Positive and negative ion beam merging system for neutral beam production

DOEpatents

Leung, Ka-Ngo; Reijonen, Jani

2005-12-13

The positive and negative ion beam merging system extracts positive and negative ions of the same species and of the same energy from two separate ion sources. The positive and negative ions from both sources pass through a bending magnetic field region between the pole faces of an electromagnet. Since the positive and negative ions come from mirror image positions on opposite sides of a beam axis, and the positive and negative ions are identical, the trajectories will be symmetrical and the positive and negative ion beams will merge into a single neutral beam as they leave the pole face of the electromagnet. The ion sources are preferably multicusp plasma ion sources. The ion sources may include a multi-aperture extraction system for increasing ion current from the sources.

Effects on H(-) production in a multicusp ion source by mixture of H2 with H2O, NH3, CH4, N2H4, and SF6

NASA Technical Reports Server (NTRS)

Orient, O. J.; Chutjian, A.; Leung, K. N.

1987-01-01

Effects of H(-) production in a multicusp ion source are measured by separately mixing with hydrogen small amounts (0.33-10 percent) of water, ammonia, methane, and hydrazine these are molecules which produce large amounts of H(-) via dissociative attachment (DA) resonances at higher electron energies. The mixing was done in a separate reservoir, with careful measurement of individual pressures. Experimental enhancements of 1.4 and less were observed, whereas calculated enhancements, using accurate DA cross sections for ground-state H2, should have produced factors of 1.5, 3.0, 1.3, and 2.4 enhancements for water, ammonia methane, and hydrazine, respectively, at a mean electron energy of 1.0 eV in the extraction region. The difference is accounted for by including, in the enhancement calculation, vibrationally and rotationally excited H2 molecules, with v-double prime = 5-11, and J-double prime = 0-5, and the large DA cross sections for the excited H2 (v-double prime, J-double prime). The relative populations of H2 (v-double prime, J-double prime) thus obtained are found to be substantially smaller than those predicted by theoretical calculations. The effect on H(-) current was also studied by mixing small amounts of SF6 with H2. A 1.5 percent mixture was found to reduce the H(-) output by one half.

Method and source for producing a high concentration of positively charged molecular hydrogen or deuterium ions

DOEpatents

Ehlers, Kenneth W.; Leung, Ka-Ngo

1988-01-01

A high concentration of positive molecular ions of hydrogen or deuterium gas is extracted from a positive ion source having a short path length of extracted ions, relative to the mean free path of the gas molecules, to minimize the production of other ion species by collision between the positive ions and gas molecules. The ion source has arrays of permanent magnets to produce a multi-cusp magnetic field in regions remote from the plasma grid and the electron emitters, for largely confining the plasma to the space therebetween. The ion source has a chamber which is short in length, relative to its transverse dimensions, and the electron emitters are at an even shorter distance from the plasma grid, which contains one or more extraction apertures.

Analysis of the spatial non-uniformity of negative ion production in surface-produced negative ion sources

NASA Astrophysics Data System (ADS)

Fujita, S.; Yamamoto, T.; Yoshida, M.; Onai, M.; Kojima, A.; Hatayama, A.; Kashiwagi, M.

2017-08-01

In order to improve the uniformity of the negative ion production, the KEIO-MARC code has been applied to the QST's JT60SA negative ion source in three different magnetic configurations (i) MC-PGMF (Multi-Cusp and PG Magnetic Filter), (ii) TNT-MF (TeNT Magnetic Filter) and (iii) MTNT-MF (Modified TeNT Magnetic Filter). From the results, we have confirmed that the electron rotation inside the negative ion source is an essential element in order to obtain a uniform production of the negative ions. By adding extra tent magnets on the longitudinal sides, the electron rotation has been enhanced, and a uniform production of negative ions has been realized.

Production of N[sup +] ions from a multicusp ion beam apparatus

DOEpatents

Kango Leung; Kunkel, W.B.; Walther, S.R.

1993-03-30

A method of generating a high purity (at least 98%) N[sup +] ion beam using a multicusp ion source having a chamber formed by a cylindrical chamber wall surrounded by a plurality of magnets, a filament centrally disposed in said chamber, a plasma electrode having an extraction orifice at one end of the chamber, a magnetic filter having two parallel magnets spaced from said plasma electrode and dividing the chamber into arc discharge and extraction regions. The method includes ionizing nitrogen gas in the arc discharge region of the chamber, maintaining the chamber wall at a positive voltage relative to the filament and at a magnitude for an optimum percentage of N[sup +] ions in the extracted ion beams, disposing a hot liner within the chamber and near the chamber wall to limit recombination of N[sup +] ions into the N[sub 2][sup +] ions, spacing the magnets of the magnetic filter from each other for optimum percentage of N[sup 3] ions in the extracted ion beams, and maintaining a relatively low pressure downstream of the extraction orifice and of a magnitude (preferably within the range of 3-8[times]10[sup [minus]4] torr) for an optimum percentage of N[sup +] ions in the extracted ion beam.

On the evolutionary advantage of multi-cusped teeth

PubMed Central

Bush, Mark B.; Barani, Amir; Lawn, Brian R.

2016-01-01

A hallmark of mammalian evolution is a progressive complexity in postcanine tooth morphology. However, the driving force for this complexity remains unclear: whether to expand the versatility in diet source, or to bolster tooth structural integrity. In this study, we take a quantitative approach to this question by examining the roles of number, position and height of multiple cusps in determining sustainable bite forces. Our approach is to use an extended finite-element methodology with due provision for step-by-step growth of an embedded crack to determine how fracture progresses with increasing occlusal load. We argue that multi-cusp postcanine teeth are well configured to withstand high bite forces provided that multiple cusps are contacted simultaneously to share the load. However, contact on a single near-wall cusp diminishes the strength. Location of the load points and cusp height, rather than cusp number or radius, are principal governing factors. Given these findings, we conclude that while complex tooth structures can enhance durability, increases in cusp number are more likely to be driven by the demands of food manipulation. Structural integrity of complex teeth is maintained when individual cusps remain sufficiently distant from the side walls and do not become excessively tall relative to tooth width. PMID:27558851

Status of ion sources at National Institute of Radiological Sciences.

PubMed

Kitagawa, A; Fujita, T; Goto, A; Hattori, T; Hamano, T; Hojo, S; Honma, T; Imaseki, H; Katagiri, K; Muramatsu, M; Sakamoto, Y; Sekiguchi, M; Suda, M; Sugiura, A; Suya, N

2012-02-01

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ion radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.

Status of ion sources at National Institute of Radiological Sciencesa)

NASA Astrophysics Data System (ADS)

Kitagawa, A.; Fujita, T.; Goto, A.; Hattori, T.; Hamano, T.; Hojo, S.; Honma, T.; Imaseki, H.; Katagiri, K.; Muramatsu, M.; Sakamoto, Y.; Sekiguchi, M.; Suda, M.; Sugiura, A.; Suya, N.

2012-02-01

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ion radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.

Progress in the development of an H{sup −} ion source for cyclotrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Etoh, H., E-mail: Hrh-Etoh@shi.co.jp; Aoki, Y.; Mitsubori, H.

2015-04-08

A multi-cusp DC H{sup −} ion source has been developed for cyclotrons in medical use. Beam optics of the H{sup −} ion beam is studied using a 2D beam trajectory code. The simulation results are compared with the experimental results obtained in the Mark I source, which has produced up to 16 mA H{sup −} ion beams. The optimum extraction voltages show good agreement between the calculation and the experimental results. A new ion source, Mark II source, is designed to achieve the next goal of producing an H{sup −} beam of 20 mA. The magnetic field configurations and the plasma electrodemore » design are optimized for Cs-seeded operation. Primary electron trajectory simulation shows that primary electrons are confined well and the magnetic filter prevents the primary electrons from entering into the extraction region.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitagawa, A.; Fujita, T.; Goto, A.

The National Institute of Radiological Sciences (NIRS) maintains various ion accelerators in order to study the effects of radiation of the human body and medical uses of radiation. Two electrostatic tandem accelerators and three cyclotrons delivered by commercial companies have offered various life science tools; these include proton-induced x-ray emission analysis (PIXE), micro beam irradiation, neutron exposure, and radioisotope tracers and probes. A duoplasmatron, a multicusp ion source, a penning ion source (PIG), and an electron cyclotron resonance ion source (ECRIS) are in operation for these purposes. The Heavy-Ion Medical Accelerator in Chiba (HIMAC) is an accelerator complex for heavy-ionmore » radiotherapy, fully developed by NIRS. HIMAC is utilized not only for daily treatment with the carbon beam but also for fundamental experiments. Several ECRISs and a PIG at HIMAC satisfy various research and clinical requirements.« less

Production of N.sup.+ ions from a multicusp ion beam apparatus

DOEpatents

Leung, Ka-Ngo; Kunkel, Wulf B.; Walther, Steven R.

1993-01-01

A method of generating a high purity (at least 98%) N.sup.+ ion beam using a multicusp ion source (10) having a chamber (11) formed by a cylindrical chamber wall (12) surrounded by a plurality of magnets (13), a filament (57) centrally disposed in said chamber, a plasma electrode (36) having an extraction orifice (41) at one end of the chamber, a magnetic filter having two parallel magnets (21, 22) spaced from said plasma electrode (36) and dividing the chamber (11) into arc discharge and extraction regions. The method includes ionizing nitrogen gas in the arc discharge region of the chamber (11), maintaining the chamber wall (12) at a positive voltage relative to the filament (57) and at a magnitude for an optimum percentage of N.sup.+ ions in the extracted ion beams, disposing a hot liner (45) within the chamber and near the chamber wall (12) to limit recombination of N.sup.+ ions into the N.sub.2.sup.+ ions, spacing the magnets (21, 22) of the magnetic filter from each other for optimum percentage of N.sup.3 ions in the extracted ion beams, and maintaining a relatively low pressure downstream of the extraction orifice and of a magnitude (preferably within the range of 3-8.times.10.sup.-4 torr) for an optimum percentage of N.sup.+ ions in the extracted ion beam.

Effects of magnetic field strength in the discharge channel on the performance of a multi-cusped field thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Peng; Liu, Hui; Gao, Yuanyuan

The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field strength in the discharge channel were investigated. Four thrusters with different outer diameters of the magnet rings were designed to change the magnetic field strength in the discharge channel. It is found that increasing the magnetic field strength could restrain the radial cross-field electron current and decrease the radial width of main ionization region, which gives rise to the reduction of propellant utilization and thruster performance. The test results in different anode voltage conditions indicate that both the thrust and anode efficiency are higher for the weakermore » magnetic field in the discharge channel.« less

Compact electron beam focusing column

NASA Astrophysics Data System (ADS)

Persaud, Arun; Leung, Ka-Ngo; Reijonen, Jani

2001-12-01

A novel design for an electron beam focusing column has been developed at LBNL. The design is based on a low-energy spread multicusp plasma source which is used as a cathode for electron beam production. The focusing column is 10 mm in length. The electron beam is focused by means of electrostatic fields. The column is designed for a maximum voltage of 50 kV. Simulations of the electron trajectories have been performed by using the 2D simulation code IGUN and EGUN. The electron temperature has also been incorporated into the simulations. The electron beam simulations, column design and fabrication will be discussed in this presentation.

A 1D ion species model for an RF driven negative ion source

NASA Astrophysics Data System (ADS)

Turner, I.; Holmes, A. J. T.

2017-08-01

A one-dimensional model for an RF driven negative ion source has been developed based on an inductive discharge. The RF source differs from traditional filament and arc ion sources because there are no primary electrons present, and is simply composed of an antenna region (driver) and a main plasma discharge region. However the model does still make use of the classical plasma transport equations for particle energy and flow, which have previously worked well for modelling DC driven sources. The model has been developed primarily to model the Small Negative Ion Facility (SNIF) ion source at CCFE, but may be easily adapted to model other RF sources. Currently the model considers the hydrogen ion species, and provides a detailed description of the plasma parameters along the source axis, i.e. plasma temperature, density and potential, as well as current densities and species fluxes. The inputs to the model are currently the RF power, the magnetic filter field and the source gas pressure. Results from the model are presented and where possible compared to existing experimental data from SNIF, with varying RF power, source pressure.

Ion source and injection line for high intensity medical cyclotron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jia, XianLu, E-mail: jiaxl@ciae.ac.cn; Guan, Fengping; Yao, Hongjuan

2014-02-15

A 14 MeV high intensity compact cyclotron, CYCIAE-14, was built at China Institute of Atomic Energy (CIAE). An injection system based on the external H− ion source was used on CYCIAE-14 so as to provide high intensity beam, while most positron emission tomography cyclotrons adopt internal ion source. A beam intensity of 100 μA/14 MeV was extracted from the cyclotron with a small multi-cusp H− ion source (CIAE-CH-I type) and a short injection line, which the H− ion source of 3 mA/25 keV H− beam with emittance of 0.3π mm mrad and the injection line of with only 1.2 m from themore » extraction of ion source to the medial plane of the cyclotron. To increase the extracted beam intensity of the cyclotron, a new ion source (CIAE-CH-II type) of 9.1 mA was used, with maximum of 500 μA was achieved from the cyclotron. The design and test results of the ion source and injection line optimized for high intensity acceleration will be given in this paper.« less

High brightness--multiple beamlets source for patterned X-ray production

DOEpatents

Leung, Ka-Ngo [Hercules, CA; Ji, Qing [Albany, CA; Barletta, William A [Oakland, CA; Jiang, Ximan [El Cerrito, CA; Ji, Lili [Albany, CA

2009-10-27

Techniques for controllably directing beamlets to a target substrate are disclosed. The beamlets may be either positive ions or electrons. It has been shown that beamlets may be produced with a diameter of 1 .mu.m, with inter-aperture spacings of 12 .mu.m. An array of such beamlets, may be used for maskless lithography. By step-wise movement of the beamlets relative to the target substrate, individual devices may be directly e-beam written. Ion beams may be directly written as well. Due to the high brightness of the beamlets from extraction from a multicusp source, exposure times for lithographic exposure are thought to be minimized. Alternatively, the beamlets may be electrons striking a high Z material for X-ray production, thereafter collimated to provide patterned X-ray exposures such as those used in CAT scans. Such a device may be used for remote detection of explosives.

High current DC negative ion source for cyclotron.

PubMed

Etoh, H; Onai, M; Aoki, Y; Mitsubori, H; Arakawa, Y; Sakuraba, J; Kato, T; Mitsumoto, T; Hiasa, T; Yajima, S; Shibata, T; Hatayama, A; Okumura, Y

2016-02-01

A filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In Cs-free operation, continuous H(-) beam of 10 mA and D(-) beam of 3.3 mA were obtained stably at an arc-discharge power of 3 kW and 2.4 kW, respectively. In Cs-seeded operation, H(-) beam current reached 22 mA at a lower arc power of 2.6 kW with less co-extracted electron current. The optimum gas flow rate, which gives the highest H(-) current, was 15 sccm in the Cs-free operation, while it decreased to 4 sccm in the Cs-seeded operation. The relationship between H(-) production and the design/operating parameters has been also investigated by a numerical study with KEIO-MARC code, which gives a reasonable explanation to the experimental results of the H(-) current dependence on the arc power.

The effects of magnetic field in plume region on the performance of multi-cusped field thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Peng, E-mail: hupengemail@126.com; Liu, Hui, E-mail: thruster@126.com; Yu, Daren

2015-10-15

The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field in the plume region were investigated. Five magnetic field shielding rings were separately mounted near the exit of discharge channel to decrease the strength of magnetic field in the plume region in different levels, while the magnetic field in the upstream was well maintained. The test results show that the electron current increases with the decrease of magnetic field strength in the plume region, which gives rise to higher propellant utilization and lower current utilization. On the other hand, the stronger magnetic field in the plume regionmore » improves the performance at low voltages (high current mode) while lower magnetic field improves the performance at high voltages (low current mode). This work can provide some optimal design ideas of the magnetic strength in the plume region to improve the performance of thruster.« less

Radio Frequency Plasma Discharge Lamps for Use as Stable Calibration Light Sources

NASA Technical Reports Server (NTRS)

McAndrew, Brendan; Cooper, John; Arecchi, Angelo; McKee, Greg; Durell, Christopher

2012-01-01

Stable high radiance in visible and near-ultraviolet wavelengths is desirable for radiometric calibration sources. In this work, newly available electrodeless radio-frequency (RF) driven plasma light sources were combined with research grade, low-noise power supplies and coupled to an integrating sphere to produce a uniform radiance source. The stock light sources consist of a 28 VDC power supply, RF driver, and a resonant RF cavity. The RF cavity includes a small bulb with a fill gas that is ionized by the electric field and emits light. This assembly is known as the emitter. The RF driver supplies a source of RF energy to the emitter. In commercial form, embedded electronics within the RF driver perform a continual optimization routine to maximize energy transfer to the emitter. This optimization routine continually varies the light output sinusoidally by approximately 2% over a several-second period. Modifying to eliminate this optimization eliminates the sinusoidal variation but allows the output to slowly drift over time. This drift can be minimized by allowing sufficient warm-up time to achieve thermal equilibrium. It was also found that supplying the RF driver with a low-noise source of DC electrical power improves the stability of the lamp output. Finally, coupling the light into an integrating sphere reduces the effect of spatial fluctuations, and decreases noise at the output port of the sphere.

System integration of RF based negative ion experimental facility at IPR

NASA Astrophysics Data System (ADS)

Bansal, G.; Bandyopadhyay, M.; Singh, M. J.; Gahlaut, A.; Soni, J.; Pandya, K.; Parmar, K. G.; Sonara, J.; Chakraborty, A.

2010-02-01

The setting up of RF based negative ion experimental facility shall witness the beginning of experiments on the negative ion source fusion applications in India. A 1 MHz RF generator shall launch 100 kW RF power into a single driver on the plasma source to produce a plasma of density ~5 × 1012 cm-3. The source can deliver a negative ion beam of ~10 A with a current density of ~30 mA/cm2 and accelerated to 35 kV through an electrostatic ion accelerator. The experimental system is similar to a RF based negative ion source, BATMAN, presently operating at IPP. The subsystems for source operation are designed and procured principally from indigenous resources, keeping the IPP configuration as a base line. The operation of negative ion source is supported by many subsystems e.g. vacuum pumping system with gate valves, cooling water system, gas feed system, cesium delivery system, RF generator, high voltage power supplies, data acquisition and control system, and different diagnostics. The first experiments of negative ion source are expected to start at IPR from the middle of 2009.

A NEW THERMIONIC RF ELECTRON GUN FOR SYNCHROTRON LIGHT SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kutsaev, Sergey; Agustsson, R.; Hartzell, J

A thermionic RF gun is a compact and efficient source of electrons used in many practical applications. RadiaBeam Systems and the Advanced Photon Source at Argonne National Laboratory collaborate in developing of a reliable and robust thermionic RF gun for synchrotron light sources which would offer substantial improvements over existing thermionic RF guns and allow stable operation with up to 1A of beam peak current at a 100 Hz pulse repetition rate and a 1.5 μs RF pulse length. In this paper, we discuss the electromagnetic and engineering design of the cavity and report the progress towards high power testsmore » of the cathode assembly of the new gun.« less

RF synchronized short pulse laser ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuwa, Yasuhiro, E-mail: fuwa@kyticr.kuicr.kyoto-u.ac.jp; Iwashita, Yoshihisa; Tongu, Hiromu

A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at themore » exit of RF resonator by a probe.« less

Compact Power Conditioning and RF Systems for a High Power RF Source

DTIC Science & Technology

2008-12-01

RF systems have increasing potential for application by the Army. High power RF, or high power microwave ( HPM ), systems can disrupt or disable...that are small, lightweight, portable, and use an independent energy source. The resulting system will be able to produce HPM from a compact package...The consortium was formed to advance the technology of the components required for a compact HPM source with the final goal of full system

Evaluation of power transfer efficiency for a high power inductively coupled radio-frequency hydrogen ion source

NASA Astrophysics Data System (ADS)

Jain, P.; Recchia, M.; Cavenago, M.; Fantz, U.; Gaio, E.; Kraus, W.; Maistrello, A.; Veltri, P.

2018-04-01

Neutral beam injection (NBI) for plasma heating and current drive is necessary for International Thermonuclear Experimental reactor (ITER) tokamak. Due to its various advantages, a radio frequency (RF) driven plasma source type was selected as a reference ion source for the ITER heating NBI. The ITER relevant RF negative ion sources are inductively coupled (IC) devices whose operational working frequency has been chosen to be 1 MHz and are characterized by high RF power density (˜9.4 W cm-3) and low operational pressure (around 0.3 Pa). The RF field is produced by a coil in a cylindrical chamber leading to a plasma generation followed by its expansion inside the chamber. This paper recalls different concepts based on which a methodology is developed to evaluate the efficiency of the RF power transfer to hydrogen plasma. This efficiency is then analyzed as a function of the working frequency and in dependence of other operating source and plasma parameters. The study is applied to a high power IC RF hydrogen ion source which is similar to one simplified driver of the ELISE source (half the size of the ITER NBI source).

Plasma Ion Sources for Atmospheric Pressure Ionization Mass Spectrometry.

NASA Astrophysics Data System (ADS)

Zhao, Jian-Guo

1994-01-01

Atmospheric pressure ionization (API) sources using direct-current (DC) and radio-frequency (RF) plasma have been developed in this thesis work. These ion sources can provide stable discharge currents of ~ 1 mA, 2-3 orders of magnitude larger than that of the corona discharge, a widely used API source. The plasmas can be generated and maintained in 1 atm of various buffer gases by applying -500 to -1000 V (DC plasma) or 1-15 W with a frequency of 165 kHz (RF plasma) on the needle electrode. These ion sources have been used with liquid injection to detect various organic compounds of pharmaceutical, biotechnological and environmental interest. Key features of these ion sources include soft ionization with the protonated molecule as the largest peak, and superb sensitivity with detection limits in the low picogram or femtomole range and a linear dynamic range over ~4 orders of magnitude. The RF plasma has advantages over the DC plasma in its ability to operate in various buffer gases and to produce a more stable plasma. Factors influencing the performance of the ion sources have been studied, including RF power level, liquid flow rate, chamber temperature, solvent composition, and voltage affecting the collision induced dissociation (CID). Ionization of hydrocarbons by the RF plasma API source was also studied. Soft ionization is generally produced. To obtain high sensitivity, the ion source must be very dry and the needle-to-orifice distance must be small. Nitric oxide was used to enhance the sensitivity. The RF plasma source was then used for the analysis of hydrocarbons in auto emissions. Comparisons between the corona discharge and the RF plasma have been made in terms of discharge current, ion residence time, and the ion source model. The RF plasma source provides larger linear dynamic range and higher sensitivity than the corona discharge, due to its much larger discharge current. The RF plasma was also observed to provide longer ion residence times and was not limited by space-charge effect as in the corona source.

Investigation of rf power absorption in the plasma of helicon ion source.

PubMed

Mordyk, S; Alexenko, O; Miroshnichenko, V; Storizhko, V; Stepanov, K; Olshansky, V

2008-02-01

The simulations of the spatial distribution of rf power absorbed in a helicon ion source reveal a correlation between the depth of penetration of rf power into the plasma and the tilt angle of lines of force of the outer magnetic field. The deeper field penetration and greater power absorption were observed at large tilt angles of the field line to the plasma surface. The evaluations as to the possibility of excitation of helicon waves in compact rf ion sources were performed.

RF Phase Stability and Electron Beam Characterization for the PLEIADES Thomson X-Ray Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, W J; Hartemann, F V; Tremaine, A M

2002-10-16

We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. To produce picosecond, high brightness x-ray pulses, picosecond timing, terahertz bandwidth diagnostics, and RF phase control are required. Planned optical, RF, x-ray and electron beam measurements to characterize the dependence of electron beam parameters and synchronization on RF phase stability are presented.

RF-driven ion source with a back-streaming electron dump

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwan, Joe; Ji, Qing

A novel ion source is described having an improved lifetime. The ion source, in one embodiment, is a proton source, including an external RF antenna mounted to an RF window. To prevent backstreaming electrons formed in the beam column from striking the RF window, a back streaming electron dump is provided, which in one embodiment is formed of a cylindrical tube, open at one end to the ion source chamber and capped at its other end by a metal plug. The plug, maintained at the same electrical potential as the source, captures these backstreaming electrons, and thus prevents localized heatingmore » of the window, which due to said heating, might otherwise cause window damage.« less

Filtering peripheral high temperature electrons in a cylindrical rf-driven plasmas by an axisymmetric radial magnetic field

NASA Astrophysics Data System (ADS)

Akahoshi, Hikaru; Takahashi, Kazunori; Ando, Akira

2018-03-01

High temperature electrons generated near a radial wall of a cylindrical source tube in a radiofrequency (rf) inductively-coupled plasma is filtered by an axisymmetric radial magnetic field formed near the source exit by locating annular permanent magnets, where the axial magnetic field strength in the radially central region is fairly uniform inside the source tube and is close to zero near the source exit. The source is operated at 3 mTorr in argon and the rf antenna is powered by a 13.56 MHz and 400 W rf generator. Measurement of electron energy probability functions shows the presence of the peripheral high temperature electrons inside the source, while the temperature of the peripheral electrons downstream of the source is observed to be reduced.

Ways to improve the efficiency and reliability of radio frequency driven negative ion sources for fusion.

PubMed

Kraus, W; Briefi, S; Fantz, U; Gutmann, P; Doerfler, J

2014-02-01

Large RF driven negative hydrogen ion sources are being developed at IPP Garching for the future neutral beam injection system of ITER. The overall power efficiency of these sources is low, because for the RF power supply self-excited generators are utilized and the plasma is generated in small cylindrical sources ("drivers") and expands into the source main volume. At IPP experiments to reduce the primary power and the RF power required for the plasma production are performed in two ways: The oscillator generator of the prototype source has been replaced by a transistorized RF transmitter and two alternative driver concepts, a spiral coil, in which the field is concentrated by ferrites, which omits the losses by plasma expansion and a helicon source are being tested.

The development of data acquisition and processing application system for RF ion source

NASA Astrophysics Data System (ADS)

Zhang, Xiaodan; Wang, Xiaoying; Hu, Chundong; Jiang, Caichao; Xie, Yahong; Zhao, Yuanzhe

2017-07-01

As the key ion source component of nuclear fusion auxiliary heating devices, the radio frequency (RF) ion source is developed and applied gradually to offer a source plasma with the advantages of ease of control and high reliability. In addition, it easily achieves long-pulse steady-state operation. During the process of the development and testing of the RF ion source, a lot of original experimental data will be generated. Therefore, it is necessary to develop a stable and reliable computer data acquisition and processing application system for realizing the functions of data acquisition, storage, access, and real-time monitoring. In this paper, the development of a data acquisition and processing application system for the RF ion source is presented. The hardware platform is based on the PXI system and the software is programmed on the LabVIEW development environment. The key technologies that are used for the implementation of this software programming mainly include the long-pulse data acquisition technology, multi-threading processing technology, transmission control communication protocol, and the Lempel-Ziv-Oberhumer data compression algorithm. Now, this design has been tested and applied on the RF ion source. The test results show that it can work reliably and steadily. With the help of this design, the stable plasma discharge data of the RF ion source are collected, stored, accessed, and monitored in real-time. It is shown that it has a very practical application significance for the RF experiments.

Performance of the LANSCE H^- Source and Low Energy Transport at Higher Peak Current

NASA Astrophysics Data System (ADS)

Pillai, Chandra; Stevens, Ralph; Fitzgerald, Daniel; Garnett, Robert; Ingllas, William; Merrill, Frank; Rybarcyk, Larry; Sander, Oscar

1997-05-01

The Los Alamos Neutron Science Center (LANSCE) 800 MeV linac facility uses a multicusp field, surface ion source to produce H^- beam for delivery to the Proton Storage Ring (PSR) and to the Weapon Neutron Research (WNR) areas. The source typically operates at a duty factor of 9.4% delivering a peak current of about 14 mA into the 750 keV LEBT. Each beam macropulse is chopped to create a sequence of 360 ns pulse, each with a 100 ns ``extraction notch'' for injection into PSR. The average current delivered to the short-pulse spallation target is nominally 70μA. One goal of the present PSR upgrade projects is an increase in the average beam current to 200μA. This will be accomplished by a combination of increased repetition rate (to 30 Hz), upgraded PSR bunchers, and a brighter H^- ion source that will produce higher peak current with lower beam emittance. The present ion source and injector system was studied to investigate the beam qualities of the source and the performance of the low energy transpot. The performance of the ion source at higher currents and the change in beam parameters in the low energy transport compared to those in the standard source conditions will be presented.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butterworth, A., E-mail: andrew.butterworth@cern.ch; Grudiev, A.; Lettry, J.

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 allowsmore » 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.« less

10-fs-level synchronization of photocathode laser with RF-oscillator for ultrafast electron and X-ray sources

PubMed Central

Yang, Heewon; Han, Byungheon; Shin, Junho; Hou, Dong; Chung, Hayun; Baek, In Hyung; Jeong, Young Uk; Kim, Jungwon

2017-01-01

Ultrafast electron-based coherent radiation sources, such as free-electron lasers (FELs), ultrafast electron diffraction (UED) and Thomson-scattering sources, are becoming more important sources in today’s ultrafast science. Photocathode laser is an indispensable common subsystem in these sources that generates ultrafast electron pulses. To fully exploit the potentials of these sources, especially for pump-probe experiments, it is important to achieve high-precision synchronization between the photocathode laser and radio-frequency (RF) sources that manipulate electron pulses. So far, most of precision laser-RF synchronization has been achieved by using specially designed low-noise Er-fibre lasers at telecommunication wavelength. Here we show a modular method that achieves long-term (>1 day) stable 10-fs-level synchronization between a commercial 79.33-MHz Ti:sapphire laser oscillator and an S-band (2.856-GHz) RF oscillator. This is an important first step toward a photocathode laser-based femtosecond RF timing and synchronization system that is suitable for various small- to mid-scale ultrafast X-ray and electron sources. PMID:28067288

10-fs-level synchronization of photocathode laser with RF-oscillator for ultrafast electron and X-ray sources

NASA Astrophysics Data System (ADS)

Yang, Heewon; Han, Byungheon; Shin, Junho; Hou, Dong; Chung, Hayun; Baek, In Hyung; Jeong, Young Uk; Kim, Jungwon

2017-01-01

Ultrafast electron-based coherent radiation sources, such as free-electron lasers (FELs), ultrafast electron diffraction (UED) and Thomson-scattering sources, are becoming more important sources in today’s ultrafast science. Photocathode laser is an indispensable common subsystem in these sources that generates ultrafast electron pulses. To fully exploit the potentials of these sources, especially for pump-probe experiments, it is important to achieve high-precision synchronization between the photocathode laser and radio-frequency (RF) sources that manipulate electron pulses. So far, most of precision laser-RF synchronization has been achieved by using specially designed low-noise Er-fibre lasers at telecommunication wavelength. Here we show a modular method that achieves long-term (>1 day) stable 10-fs-level synchronization between a commercial 79.33-MHz Ti:sapphire laser oscillator and an S-band (2.856-GHz) RF oscillator. This is an important first step toward a photocathode laser-based femtosecond RF timing and synchronization system that is suitable for various small- to mid-scale ultrafast X-ray and electron sources.

Development progresses of radio frequency ion source for neutral beam injector in fusion devices.

PubMed

Chang, D H; Jeong, S H; Kim, T S; Park, M; Lee, K W; In, S R

2014-02-01

A large-area RF (radio frequency)-driven ion source is being developed in Germany for the heating and current drive of an ITER device. Negative hydrogen ion sources are the major components of neutral beam injection systems in future large-scale fusion experiments such as ITER and DEMO. RF ion sources for the production of positive hydrogen (deuterium) ions have been successfully developed for the neutral beam heating systems at IPP (Max-Planck-Institute for Plasma Physics) in Germany. The first long-pulse ion source has been developed successfully with a magnetic bucket plasma generator including a filament heating structure for the first NBI system of the KSTAR tokamak. There is a development plan for an RF ion source at KAERI to extract the positive ions, which can be applied for the KSTAR NBI system and to extract the negative ions for future fusion devices such as the Fusion Neutron Source and Korea-DEMO. The characteristics of RF-driven plasmas and the uniformity of the plasma parameters in the test-RF ion source were investigated initially using an electrostatic probe.

10-fs-level synchronization of photocathode laser with RF-oscillator for ultrafast electron and X-ray sources.

PubMed

Yang, Heewon; Han, Byungheon; Shin, Junho; Hou, Dong; Chung, Hayun; Baek, In Hyung; Jeong, Young Uk; Kim, Jungwon

2017-01-09

Ultrafast electron-based coherent radiation sources, such as free-electron lasers (FELs), ultrafast electron diffraction (UED) and Thomson-scattering sources, are becoming more important sources in today's ultrafast science. Photocathode laser is an indispensable common subsystem in these sources that generates ultrafast electron pulses. To fully exploit the potentials of these sources, especially for pump-probe experiments, it is important to achieve high-precision synchronization between the photocathode laser and radio-frequency (RF) sources that manipulate electron pulses. So far, most of precision laser-RF synchronization has been achieved by using specially designed low-noise Er-fibre lasers at telecommunication wavelength. Here we show a modular method that achieves long-term (>1 day) stable 10-fs-level synchronization between a commercial 79.33-MHz Ti:sapphire laser oscillator and an S-band (2.856-GHz) RF oscillator. This is an important first step toward a photocathode laser-based femtosecond RF timing and synchronization system that is suitable for various small- to mid-scale ultrafast X-ray and electron sources.

The radiofrequency frontier: a review of radiofrequency and combined radiofrequency pulsed-light technology in aesthetic medicine.

PubMed

Sadick, Neil; Sorhaindo, Lian

2005-05-01

Radiofrequency (RF) and combined RF light source technologies have established themselves as safe and effective treatment modalities for several dermatologic procedures, including skin tightening, hair and leg vein removal, acne scarring, skin rejuvenation, and wrinkle reduction. This article reviews the technology, clinical applications, and recent advances of RF and combined RF light/laser source technologies in aesthetic medicine.

Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

NASA Astrophysics Data System (ADS)

Hatayama, A.; Nishioka, S.; Nishida, K.; Mattei, S.; Lettry, J.; Miyamoto, K.; Shibata, T.; Onai, M.; Abe, S.; Fujita, S.; Yamada, S.; Fukano, A.

2018-06-01

The present status of kinetic modeling of particle dynamics in hydrogen negative ion (H‑) source plasmas and their comparisons with experiments are reviewed and discussed with some new results. The main focus is placed on the following topics, which are important for the research and development of H‑ sources for intense and high-quality H‑ ion beams: (i) effects of non-equilibrium features of electron energy distribution function on volume and surface H‑ production, (ii) the origin of the spatial non-uniformity in giant multi-cusp arc-discharge H‑ sources, (iii) capacitive to inductive (E to H) mode transition in radio frequency-inductively coupled plasma H‑ sources and (iv) extraction physics of H‑ ions and beam optics, especially the present understanding of the meniscus formation in strongly electronegative plasmas (so-called ion–ion plasmas) and its effect on beam optics. For these topics, mainly Japanese modeling activities, and their domestic and international collaborations with experimental studies, are introduced with some examples showing how models have been improved and to what extent the modeling studies can presently contribute to improving the source performance. Close collaboration between experimental and modeling activities is indispensable for the validation/improvement of the modeling and its contribution to the source design/development.

Efficient Radio Frequency Inductive Discharges in Near Atmospheric Pressure Using Immittance Conversion Topology

NASA Astrophysics Data System (ADS)

Razzak, M. Abdur; Takamura, Shuichi; Uesugi, Yoshihiko; Ohno, Noriyasu

A radio frequency (rf) inductive discharge in atmospheric pressure range requires high voltage in the initial startup phase and high power during the steady state sustainment phase. It is, therefore, necessary to inject high rf power into the plasma ensuring the maximum use of the power source, especially where the rf power is limited. In order to inject the maximum possible rf power into the plasma with a moderate rf power source of few kilowatts range, we employ the immittance conversion topology by converting a constant voltage source into a constant current source to generate efficient rf discharge by inductively coupled plasma (ICP) technique at a gas pressure with up to one atmosphere in argon. A novel T-LCL immittance circuit is designed for constant-current high-power operation, which is practically very important in the high-frequency range, to provide high effective rf power to the plasma. The immittance conversion system combines the static induction transistor (SIT)-based radio frequency (rf) high-power inverter circuit and the immittance conversion elements including the rf induction coil. The basic properties of the immittance circuit are studied by numerical analysis and verified the results by experimental measurements with the inductive plasma as a load at a relatively high rf power of about 4 kW. The performances of the immittance circuit are also evaluated and compared with that of the conventional series resonance circuit in high-pressure induction plasma generation. The experimental results reveal that the immittance conversion circuit confirms injecting higher effective rf power into the plasma as much as three times than that of the series resonance circuit under the same operating conditions and same dc supply voltage to the inverter, thereby enhancing the plasma heating efficiency to generate efficient rf inductive discharges.

Investigation of ion beam space charge compensation with a 4-grid analyzer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ullmann, C., E-mail: c.ullmann@gsi.de; Adonin, A.; Berezov, R.

2016-02-15

Experiments to investigate the space charge compensation of pulsed high-current heavy ion beams are performed at the GSI ion source text benches with a 4-grid analyzer provided by CEA/Saclay. The technical design of the 4-grid analyzer is revised to verify its functionality for measurements at pulsed high-current heavy ion beams. The experimental investigation of space charge compensation processes is needed to increase the performance and quality of current and future accelerator facilities. Measurements are performed directly downstream a triode extraction system mounted to a multi-cusp ion source at a high-current test bench as well as downstream the post-acceleration system ofmore » the high-current test injector (HOSTI) with ion energies up to 120 keV/u for helium and argon. At HOSTI, a cold or hot reflex discharge ion source is used to change the conditions for the measurements. The measurements were performed with helium, argon, and xenon and are presented. Results from measurements with single aperture extraction systems are shown.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Na; Wu, Yu-Ping; Min, Hao

A radio-frequency (RF) source designed for cold atom experiments is presented. The source uses AD9858, a direct digital synthesizer, to generate the sine wave directly, up to 400 MHz, with sub-Hz resolution. An amplitude control circuit consisting of wideband variable gain amplifier and high speed digital to analog converter is integrated into the source, capable of 70 dB off isolation and 4 ns on-off keying. A field programmable gate array is used to implement a versatile frequency and amplitude co-sweep logic. Owing to modular design, the RF sources have been used on many cold atom experiments to generate various complicatedmore » RF sequences, enriching the operation schemes of cold atoms, which cannot be done by standard RF source instruments.« less

Operation of large RF sources for H-: Lessons learned at ELISE

NASA Astrophysics Data System (ADS)

Fantz, U.; Wünderlich, D.; Heinemann, B.; Kraus, W.; Riedl, R.

2017-08-01

The goal of the ELISE test facility is to demonstrate that large RF-driven negative ion sources (1 × 1 m2 source area with 360 kW installed RF power) can achieve the parameters required for the ITER beam sources in terms of current densities and beam homogeneity at a filling pressure of 0.3 Pa for pulse lengths of up to one hour. With the experience in operation of the test facility, the beam source inspection and maintenance as well as with the results of the achieved source performance so far, conclusions are drawn for commissioning and operation of the ITER beam sources. Addressed are critical technical RF issues, extrapolations to the required RF power, Cs consumption and Cs ovens, the need of adjusting the magnetic filter field strength as well as the temporal dynamic and spatial asymmetry of the co-extracted electron current. It is proposed to relax the low pressure limit to 0.4 Pa and to replace the fixed electron-to-ion ratio by a power density limit for the extraction grid. This would be highly beneficial for controlling the co-extracted electrons.

Outdoor and indoor sources of residential radiofrequency electromagnetic fields, personal cell phone and cordless phone use, and cognitive function in 5-6 years old children.

PubMed

Guxens, Mònica; Vermeulen, Roel; van Eijsden, Manon; Beekhuizen, Johan; Vrijkotte, Tanja G M; van Strien, Rob T; Kromhout, Hans; Huss, Anke

2016-10-01

Little is known about the exposure of young children to radiofrequency electromagnetic fields (RF-EMF) and potentially associated health effects. We assessed the relationship between residential RF-EMF exposure from mobile phone base stations, residential presence of indoor sources, personal cell phone and cordless phone use, and children's cognitive function at 5-6 years of age. Cross-sectional study on children aged 5-6 years from the Amsterdam Born Children and their Development (ABCD) study, the Netherlands (n=2354). Residential RF-EMF exposure from mobile phone base stations was estimated with a 3D geospatial radio wave propagation model. Residential presence of indoor sources (cordless phone base stations and Wi-Fi) and children's cell phone and cordless phone use was reported by the mother. Speed of information processing, inhibitory control, cognitive flexibility, and visuomotor coordination was assessed using the Amsterdam Neuropsychological Tasks. Residential presence of RF-EMF indoor sources was associated with an improved speed of information processing. Higher residential RF-EMF exposure from mobile phone base stations and presence of indoor sources was associated with an improved inhibitory control and cognitive flexibility whereas we observed a reduced inhibitory control and cognitive flexibility with higher personal cordless phone use. Higher residential RF-EMF exposure from mobile phone base stations was associated with a reduced visuomotor coordination whereas we observed an improved visuomotor coordination with residential presence of RF-EMF indoor sources and higher personal cell phone use. We found inconsistent associations between different sources of RF-EMF exposure and cognitive function in children aged 5-6 years. Copyright © 2016 Elsevier Inc. All rights reserved.

RF Conditioning of the Photo-Cathode RF Gun at the Advanced Photon Source - NWA RF Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, T. L.; DiMonte, N.; Nassiri, A.

A new S-band Photo-cathode (PC) gun was recently installed and RF conditioned at the Advanced Photon Source (APS) Injector Test-stand (ITS) at Argonne National Lab (ANL). The APS PC gun is a LCLS type gun fabricated at SLAC [1]. The PC gun was delivered to the APS in October 2013 and installed in the APS ITS in December 2013. At ANL, we developed a new method of fast detection and mitigation of the guns internal arcs during the RF conditioning process to protect the gun from arc damage and to RF condition more efficiently. Here, we report the results ofmore » RF measurements for the PC gun and an Auto-Restart method for high power RF conditioning.« less

High current DC negative ion source for cyclotron

DOE Office of Scientific and Technical Information (OSTI.GOV)

Etoh, H., E-mail: Hrh-Etoh@shi.co.jp; Aoki, Y.; Mitsubori, H.

2016-02-15

A filament driven multi-cusp negative ion source has been developed for proton cyclotrons in medical applications. In Cs-free operation, continuous H{sup −} beam of 10 mA and D{sup −} beam of 3.3 mA were obtained stably at an arc-discharge power of 3 kW and 2.4 kW, respectively. In Cs-seeded operation, H{sup −} beam current reached 22 mA at a lower arc power of 2.6 kW with less co-extracted electron current. The optimum gas flow rate, which gives the highest H{sup −} current, was 15 sccm in the Cs-free operation, while it decreased to 4 sccm in the Cs-seeded operation. Themore » relationship between H{sup −} production and the design/operating parameters has been also investigated by a numerical study with KEIO-MARC code, which gives a reasonable explanation to the experimental results of the H{sup −} current dependence on the arc power.« less

Equivalent circuit of radio frequency-plasma with the transformer model

NASA Astrophysics Data System (ADS)

Nishida, K.; Mochizuki, S.; Ohta, M.; Yasumoto, M.; Lettry, J.; Mattei, S.; Hatayama, A.

2014-02-01

LINAC4 H- source is radio frequency (RF) driven type source. In the RF system, it is required to match the load impedance, which includes H- source, to that of final amplifier. We model RF plasma inside the H- source as circuit elements using transformer model so that characteristics of the load impedance become calculable. It has been shown that the modeling based on the transformer model works well to predict the resistance and inductance of the plasma.

Improved Magnetron Stability and Reduced Noise in Efficient Transmitters for Superconducting Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kazakevich, G.; Johnson, R.; Lebedev, V.

State of the art high-current superconducting accelerators require efficient RF sources with a fast dynamic phase and power control. This allows for compensation of the phase and amplitude deviations of the accelerating voltage in the Superconducting RF (SRF) cavities caused by microphonics, etc. Efficient magnetron transmitters with fast phase and power control are attractive RF sources for this application. They are more cost effective than traditional RF sources such as klystrons, IOTs and solid-state amplifiers used with large scale accelerator projects. However, unlike traditional RF sources, controlled magnetrons operate as forced oscillators. Study of the impact of the controlling signalmore » on magnetron stability, noise and efficiency is therefore important. This paper discusses experiments with 2.45 GHz, 1 kW tubes and verifies our analytical model which is based on the charge drift approximation.« less

Alternative RF coupling configurations for H{sup −} ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Briefi, S.; Fantz, U.; AG Experimentelle Plasmaphysik, Universität Augsburg, 86135 Augsburg

2015-04-08

RF heated sources for negative hydrogen ions both for fusion and accelerators require very high RF powers in order to achieve the required H{sup −} 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 setmore » 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.« less

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.

Overview of High Power Vacuum Dry RF Load Designs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krasnykh, Anatoly

2015-08-27

A specific feature of RF linacs based on the pulsed traveling wave (TW) mode of operation is that only a portion of the RF energy is used for the beam acceleration. The residual RF energy has to be terminated into an RF load. Higher accelerating gradients require higher RF sources and RF loads, which can stably terminate the residual RF power. RF feeders (from the RF source though the accelerating section to the load) are vacuumed to transmit multi-megawatt high power RF. This overview will outline vacuumed RF loads only. A common method to terminate multi-MW RF power is tomore » use circulated water (or other liquid) as an absorbing medium. A solid dielectric interface (a high quality ceramic) is required to separate vacuum and liquid RF absorber mediums. Using such RF load approaches in TW linacs is troubling because there is a fragile ceramic window barrier and a failure could become catastrophic for linac vacuum and RF systems. Traditional loads comprising of a ceramic disk have limited peak and average power handling capability and are therefore not suitable for high gradient TW linacs. This overview will focus on ''vacuum dry'' or ''all-metal'' loads that do not employ any dielectric interface between vacuum and absorber. The first prototype is an original design of RF loads for the Stanford Two-Mile Accelerator.« less

Rf system for the NSLS coherent infrared radiation source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broome, W.; Biscardi, R.; Keane, J.

1995-05-01

The existing NSLS X-ray Lithography Source (XLS Phase I) is being considered for a coherent synchrotron radiation source. The existing 211 MHz warm cavity will be replaced with a 5-cell 2856 MHz superconducting RF cavity, driven by a series of 2 kW klystrons. The RF system will provide a total V{sub RF} of 1.5 MV to produce {sigma}{sub L} = 0.3 mm electron bunches at an energy of 150 MeV. Superconducting technology significantly reduces the required space and power needed to achieve the higher voltage. It is the purpose of this paper to describe the superconducting RF system and cavity,more » power requirements, and cavity design parameters such as input coupling, Quality Factor, and Higher Order Modes.« less

RF-Plasma Source Commissioning in Indian Negative Ion Facility

NASA Astrophysics Data System (ADS)

Singh, M. J.; Bandyopadhyay, M.; Bansal, G.; Gahlaut, A.; Soni, J.; Kumar, Sunil; Pandya, K.; Parmar, K. G.; Sonara, J.; Yadava, Ratnakar; Chakraborty, A. K.; Kraus, W.; Heinemann, B.; Riedl, R.; Obermayer, S.; Martens, C.; Franzen, P.; Fantz, U.

2011-09-01

The Indian program of the RF based negative ion source has started off with the commissioning of ROBIN, the inductively coupled RF based negative ion source facility under establishment at Institute for Plasma research (IPR), India. The facility is being developed under a technology transfer agreement with IPP Garching. It consists of a single RF driver based beam source (BATMAN replica) coupled to a 100 kW, 1 MHz RF generator with a self excited oscillator, through a matching network, for plasma production and ion extraction and acceleration. The delivery of the RF generator and the RF plasma source without the accelerator, has enabled initiation of plasma production experiments. The recent experimental campaign has established the matching circuit parameters that result in plasma production with density in the range of 0.5-1×1018/m3, at operational gas pressures ranging between 0.4-1 Pa. Various configurations of the matching network have been experimented upon to obtain a stable operation of the set up for RF powers ranging between 25-85 kW and pulse lengths ranging between 4-20 s. It has been observed that the range of the parameters of the matching circuit, over which the frequency of the power supply is stable, is narrow and further experiments with increased number of turns in the coil are in the pipeline to see if the range can be widened. In this paper, the description of the experimental system and the commissioning data related to the optimisation of the various parameters of the matching network, to obtain stable plasma of required density, are presented and discussed.

High output lamp with high brightness

DOEpatents

Kirkpatrick, Douglas A.; Bass, Gary K.; Copsey, Jesse F.; Garber, Jr., William E.; Kwong, Vincent H.; Levin, Izrail; MacLennan, Donald A.; Roy, Robert J.; Steiner, Paul E.; Tsai, Peter; Turner, Brian P.

2002-01-01

An ultra bright, low wattage inductively coupled electrodeless aperture lamp is powered by a solid state RF source in the range of several tens to several hundreds of watts at various frequencies in the range of 400 to 900 MHz. Numerous novel lamp circuits and components are disclosed including a wedding ring shaped coil having one axial and one radial lead, a high accuracy capacitor stack, a high thermal conductivity aperture cup and various other aperture bulb configurations, a coaxial capacitor arrangement, and an integrated coil and capacitor assembly. Numerous novel RF circuits are also disclosed including a high power oscillator circuit with reduced complexity resonant pole configuration, parallel RF power FET transistors with soft gate switching, a continuously variable frequency tuning circuit, a six port directional coupler, an impedance switching RF source, and an RF source with controlled frequency-load characteristics. Numerous novel RF control methods are disclosed including controlled adjustment of the operating frequency to find a resonant frequency and reduce reflected RF power, controlled switching of an impedance switched lamp system, active power control and active gate bias control.

Exposure to Radiofrequency Electromagnetic Fields From Wi-Fi in Australian Schools

PubMed Central

Karipidis, Ken; Henderson, Stuart; Wijayasinghe, Don; Tjong, Lydiawati; Tinker, Rick

2017-01-01

Abstract The increasing use of Wi-Fi in schools and other places has given rise to public concern that the radiofrequency (RF) electromagnetic fields from Wi-Fi have the potential to adversely affect children. The current study measured typical and peak RF levels from Wi-Fi and other sources in 23 schools in Australia. All of the RF measurements were much lower than the reference levels recommended by international guidelines for protection against established health effects. The typical and peak RF levels from Wi-Fi in locations occupied by children in the classroom were of the order of 10−4 and 10−2% of the exposure guidelines, respectively. Typical RF levels in the classroom were similar between Wi-Fi and radio but higher than other sources. In the schoolyard typical RF levels were higher for radio, TV and mobile phone base stations compared to Wi-Fi. The results of this study showed that the typical RF exposure of children from Wi-Fi at school is very low and comparable or lower to other sources in the environment. PMID:28074013

Exposure to Radiofrequency Electromagnetic Fields From Wi-Fi in Australian Schools.

PubMed

Karipidis, Ken; Henderson, Stuart; Wijayasinghe, Don; Tjong, Lydiawati; Tinker, Rick

2017-08-01

The increasing use of Wi-Fi in schools and other places has given rise to public concern that the radiofrequency (RF) electromagnetic fields from Wi-Fi have the potential to adversely affect children. The current study measured typical and peak RF levels from Wi-Fi and other sources in 23 schools in Australia. All of the RF measurements were much lower than the reference levels recommended by international guidelines for protection against established health effects. The typical and peak RF levels from Wi-Fi in locations occupied by children in the classroom were of the order of 10-4 and 10-2% of the exposure guidelines, respectively. Typical RF levels in the classroom were similar between Wi-Fi and radio but higher than other sources. In the schoolyard typical RF levels were higher for radio, TV and mobile phone base stations compared to Wi-Fi. The results of this study showed that the typical RF exposure of children from Wi-Fi at school is very low and comparable or lower to other sources in the environment. © The Author 2017. Published by Oxford University Press.

Accoustic Localization of Breakdown in Radio Frequency Accelerating Cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lane, Peter Gwin

Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it wouldmore » be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.« less

Investigation of Helicon discharges as RF coupling concept of negative hydrogen ion sources

NASA Astrophysics Data System (ADS)

Briefi, S.; Fantz, U.

2013-02-01

The ITER reference source for H- and D- requires a high RF input power (up to 90 kW per driver). To reduce the demands on the RF circuit, it is highly desirable to reduce the power consumption while retaining the values of the relevant plasma parameters namely the positive ion density and the atomic hydrogen density. Helicon plasmas are a promising alternative RF coupling concept but they are typically generated in long thin discharge tubes using rare gases and an RF frequency of 13.56 MHz. Hence the applicability to the ITER reference source geometry, frequency and the utilization of hydrogen/deuterium has to be proved. In this paper the strategy of the approach for using Helicon discharges for ITER reference source parameters is introduced and the first promising measurements which were carried out at a small laboratory experiment are presented. With increasing RF power a mode transition to the Helicon regime was observed for argon and argon/hydrogen mixtures. In pure hydrogen/deuterium the mode transition could not yet be achieved as the available RF power is too low. In deuterium a special feature of Helicon discharges, the socalled low field peak, could be observed at a moderate B-field of 3 mT.

Acoustic localization of breakdown in radio frequency accelerating cavities

NASA Astrophysics Data System (ADS)

Lane, Peter

Current designs for muon accelerators require high-gradient radio frequency (RF) cavities to be placed in solenoidal magnetic fields. These fields help contain and efficiently reduce the phase space volume of source muons in order to create a usable muon beam for collider and neutrino experiments. In this context and in general, the use of RF cavities in strong magnetic fields has its challenges. It has been found that placing normal conducting RF cavities in strong magnetic fields reduces the threshold at which RF cavity breakdown occurs. To aid the effort to study RF cavity breakdown in magnetic fields, it would be helpful to have a diagnostic tool which can localize the source of breakdown sparks inside the cavity. These sparks generate thermal shocks to small regions of the inner cavity wall that can be detected and localized using microphones attached to the outer cavity surface. Details on RF cavity sound sources as well as the hardware, software, and algorithms used to localize the source of sound emitted from breakdown thermal shocks are presented. In addition, results from simulations and experiments on three RF cavities, namely the Aluminum Mock Cavity, the High-Pressure Cavity, and the Modular Cavity, are also given. These results demonstrate the validity and effectiveness of the described technique for acoustic localization of breakdown.

Saddle antenna radio frequency ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dudnikov, V., E-mail: vadim@muonsinc.com; Johnson, R.; Murray, S.

Existing RF ion sources for accelerators have specific efficiencies for H{sup +} and H{sup −} ion generation ∼3–5 mA/cm{sup 2} kW, where about 50 kW of RF power is typically needed for 50 mA beam current production. The Saddle Antenna (SA) surface plasma source (SPS) described here was developed to improve H{sup −} ion production efficiency, reliability, and availability. In SA RF ion source, the efficiency of positive ion generation in the plasma has been improved to 200 mA/cm{sup 2} kW. After cesiation, the current of negative ions to the collector was increased from 1 mA to 10 mA withmore » RF power ∼1.5 kW in the plasma (6 mm diameter emission aperture) and up to 30 mA with ∼4 kW RF. Continuous wave (CW) operation of the SA SPS has been tested on the 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. CW operation with negative ion extraction was tested with RF power up to ∼1.2 kW in the plasma with production up to Ic = 7 mA. A stable long time generation of H{sup −} beam without degradation was demonstrated in RF discharge with AlN discharge chamber.« less

Personal radiofrequency electromagnetic field exposure measurements in Swiss adolescents.

PubMed

Roser, Katharina; Schoeni, Anna; Struchen, Benjamin; Zahner, Marco; Eeftens, Marloes; Fröhlich, Jürg; Röösli, Martin

2017-02-01

Adolescents belong to the heaviest users of wireless communication devices, but little is known about their personal exposure to radiofrequency electromagnetic fields (RF-EMF). The aim of this paper is to describe personal RF-EMF exposure of Swiss adolescents and evaluate exposure relevant factors. Furthermore, personal measurements were used to estimate average contributions of various sources to the total absorbed RF-EMF dose of the brain and the whole body. Personal exposure was measured using a portable RF-EMF measurement device (ExpoM-RF) measuring 13 frequency bands ranging from 470 to 3600MHz. The participants carried the device for three consecutive days and kept a time-activity diary. In total, 90 adolescents aged 13 to 17years participated in the study conducted between May 2013 and April 2014. In addition, personal measurement values were combined with dose calculations for the use of wireless communication devices to quantify the contribution of various RF-EMF sources to the daily RF-EMF dose of adolescents. Main contributors to the total personal RF-EMF measurements of 63.2μW/m 2 (0.15V/m) were exposures from mobile phones (67.2%) and from mobile phone base stations (19.8%). WLAN at school and at home had little impact on the personal measurements (WLAN accounted for 3.5% of total personal measurements). According to the dose calculations, exposure from environmental sources (broadcast transmitters, mobile phone base stations, cordless phone base stations, WLAN access points, and mobile phones in the surroundings) contributed on average 6.0% to the brain dose and 9.0% to the whole-body dose. RF-EMF exposure of adolescents is dominated by their own mobile phone use. Environmental sources such as mobile phone base stations play a minor role. Copyright © 2016 Elsevier Ltd. All rights reserved.

Novel multi-source phase-controlled radiofrequency technology for non-ablative and micro-ablative treatment of wrinkles, lax skin and acne scars.

PubMed

Elman, Monica; Harth, Yoram

2011-01-01

The basic properties of lasers and pulsed light sources limit their ability to deliver high energy to the dermis and subcutaneous tissues without excessive damage to the epidermis. Radiofrequency was shown to penetrate deeper than optical light sources independent of skin color. The early RF-based devices used single source bipolar RF, which is safe but limited in use due to the superficial flow of energy between the two bipolar electrodes. Another type of single source RF employs a single electrode (monopolar) in which the RF energy flows from one electrode on the surface of the skin through the entire body to a plate under the body. Although more effective than bipolar, this devices require intense active cooling of the skin and may be associated with considerable pain and other systemic and local safety concerns. Latest generation of RF technology developed by EndyMed Medical Ltd. (Caesarea, Israel) utilizes simultaneously six or more phase controlled RF generators (3DEEP technology). The multiple electrical fields created by the multiple sources "repel" or "attract" each other, leading to the precise 3 dimensional delivery of RF energy to the dermal and sub-dermal targets minimizing the energy flow through the epidermis without the need for active cooling. Confocal microscopy of the skin has shown that 6 treatment sessions of Multisource RF technology improve skin structure features. The skin after treatment had longer and narrower dermal papilla and denser and finer collagen fiber typical to younger skin as compared to pre treatment skin. Ultrasound of the skin showed after 6 treatment sessions reduction of 10 percent in the thickness of the subcutaneous fat layer. Non ablative facial clinical studies showed a significant reduction of wrinkles after treatment further reduced at 3 months follow-up. Body treatment studies showed a circumference reduction of 2.9 cm immediately after 6 treatments, and 2 cm at 12 months after the end of treatment, proving long term collagen remodeling effect. Clinical studies of the multisource fractional RF application have shown significant effects on wrinkles reduction and deep atrophic acne scars after 1-3 treatment sessions.

Novel multi-source phase-controlled radiofrequency technology for non-ablative and micro-ablative treatment of wrinkles, lax skin and acne scars

PubMed Central

Elman, Monica; Harth, Yoram

2011-01-01

The basic properties of lasers and pulsed light sources limit their ability to deliver high energy to the dermis and subcutaneous tissues without excessive damage to the epidermis. Radiofrequency was shown to penetrate deeper than optical light sources independent of skin color. The early RF-based devices used single source bipolar RF, which is safe but limited in use due to the superficial flow of energy between the two bipolar electrodes. Another type of single source RF employs a single electrode (monopolar) in which the RF energy flows from one electrode on the surface of the skin through the entire body to a plate under the body. Although more effective than bipolar, this devices require intense active cooling of the skin and may be associated with considerable pain and other systemic and local safety concerns. Latest generation of RF technology developed by EndyMed Medical Ltd. (Caesarea, Israel) utilizes simultaneously six or more phase controlled RF generators (3DEEP technology). The multiple electrical fields created by the multiple sources “repel” or “attract” each other, leading to the precise 3 dimensional delivery of RF energy to the dermal and sub-dermal targets minimizing the energy flow through the epidermis without the need for active cooling. Confocal microscopy of the skin has shown that 6 treatment sessions of Multisource RF technology improve skin structure features. The skin after treatment had longer and narrower dermal papilla and denser and finer collagen fiber typical to younger skin as compared to pre treatment skin. Ultrasound of the skin showed after 6 treatment sessions reduction of 10 percent in the thickness of the subcutaneous fat layer. Non ablative facial clinical studies showed a significant reduction of wrinkles after treatment further reduced at 3 months follow-up. Body treatment studies showed a circumference reduction of 2.9 cm immediately after 6 treatments, and 2 cm at 12 months after the end of treatment, proving long term collagen remodeling effect. Clinical studies of the multisource fractional RF application have shown significant effects on wrinkles reduction and deep atrophic acne scars after 1–3 treatment sessions. PMID:24155523

Developing field emission electron sources based on ultrananocrystalline diamond for accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baryshev, Sergey V.; Jing, Chunguang; Qiu, Jiaqi

Radiofrequency (RF) electron guns work by establishing an RF electromagnetic field inside a cavity having conducting walls. Electrons from a cathode are generated in the injector and immediately become accelerated by the RF electric field, and exit the gun as a series of electron bunches. Finding simple solutions for electron injection is a long standing problem. While energies of 30-50 MeV are achievable in linear accelerators (linacs), finding an electron source able to survive under MW electric loads and provide an average current of 1-10 mA is important. Meeting these requirements would open various linac applications for industry. The naturalmore » way to simplify and integrate RF injector architectures with the electron source would be to place the source directly into the RF cavity with no need for additional heaters/lasers. Euclid TechLabs in collaboration with Argonne National Lab are prototyping a family of highly effective field emission electron sources based on a nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) platform. Determined metrics suggest that our emitters are emissive enough to meet requirements for magnetized cooling at electron-ion colliders, linac-based radioisotope production and X-ray sterilization, and others.« less

Rf capacitively-coupled electrodeless light source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manos, Dennis M.; Diggs, Jessie; Ametepe, Joseph D.

2000-01-01

An rf capacitively-coupled electrodeless light source is provided. The light source comprises a hollow, elongated chamber and at least one center conductor disposed within the hollow, elongated chamber. A portion of each center conductor extends beyond the hollow, elongated chamber. At least one gas capable of forming an electronically excited molecular state is contained within each center conductor. An electrical coupler is positioned concentric to the hollow, elongated chamber and the electrical coupler surrounds the portion of each center conductor that extends beyond the hollow, elongated chamber. A rf-power supply is positioned in an operable relationship to the electrical couplermore » and an impedance matching network is positioned in an operable relationship to the rf power supply and the electrical coupler.« less

NLC Special Projects

Science.gov Websites

Measurement (with NLC RF group) LCLS and related technologies (LCLS work related to NLC work) Collimation Systems (with Beam Delivery group) Combined Laser System (with NLC sources group) Polarized Positron Sources (with NLC sources group) Crab Cavity Phase Control System Timing and RF distribution System (with

RF Antenna Design for a Helicon Plasma Source

NASA Astrophysics Data System (ADS)

Godden, Katarina; Stassel, Brendan; Warta, Daniel; Yep, Isaac; Hicks, Nathaniel; Munk, Jens

2017-10-01

A helicon plasma source is under development for the new Plasma Science and Engineering Laboratory at the University of Alaska Anchorage. The helicon source is of a type comprising Pyrex and stainless steel cylindrical sections, joined to an ultrahigh vacuum chamber. A radio frequency (RF) helical antenna surrounds the Pyrex chamber, as well as DC solenoidal magnetic field coils. This presentation focuses on the design of the RF helical antenna and RF matching network, such that helicon wave power is coupled to argon plasma with minimal reflected power to the RF amplifier. The amplifier output is selectable between 2-30 MHz, with forward c.w. power up to 1.5 kW. Details and computer simulation of the antenna geometry, materials, and power matching will be presented, as well as the matching network of RF transmission line, tuning capacitors, and cooling system. An initial computational study of power coupling to the plasma will also be described. Supported by U.S. NSF/DOE Partnership in Basic Plasma Science and Engineering Grant PHY-1619615, by the Alaska Space Grant Program, and by UAA Innovate 2017.

Initial experiments with a versatile multi-aperture negative-ion source and related improvements

NASA Astrophysics Data System (ADS)

Cavenago, M.

2016-03-01

A relatively compact ion source, named NIO1 (Negative-Ion Optimization 1), with 9 beam apertures for H- extraction is under commissioning, in collaboration between Consorzio RFX and INFN, to provide a test bench for source optimizations, for innovations, and for simulation code validations in support of Neutral Beam Injectors (NBI) optimization. NIO1 installation includes a 60kV high-voltage deck, power supplies for a 130mA ion nominal current, an X-ray shield, and beam diagnostics. Plasma is heated with a tunable 2MHz radiofrequency (rf) generator. Physical aspects of source operation and rf-plasma coupling are discussed. NIO1 tuning procedures and plasma experiments both with air and with hydrogen as filling gas are described, up to a 1.7kW rf power. Transitions to inductively coupled plasma are reported in the case of air (for a rf power of about 0.5kW and a gas pressure below 2Pa), discussing their robust signature in optical emission, and briefly summarized for hydrogen, where more than 1kW rf power is needed.

Method and source for producing a high concentration of positively charged molecular hydrogen or deuterium ions

DOEpatents

Ehlers, K.W.; Leung, K.N.

1983-07-26

One principal object of the present invention is to provide a novel method and apparatus for generating a high concentration of H/sub 2//sup +/ or D/sub 2//sup +/ ions by using a new and improved multicusp ion source. The basic principle in achieving a high percentage of H/sub 2//sup +/ or D/sub 2//sup +/ ions is to extract them from the source as soon as they are produced. Otherwise they will react with background gas molecules to form tri-atomic ions H/sub 3//sup +/ or D/sub 3//sup +/ or be dissociated by electrons. The former reaction H/sub 2//sup +/ + H/sub 2/ ..-->.. H/sub 3//sup +/ + H can have a very short mean free path length lambda. Assuming a background neutral gas density of approximately 3.3 x 10/sup 13/ cm/sup -3/ and a cross-section sigma of approximately 6 x 10/sup -15/ cm/sup 2/, lambda = (n/sub 0/ sigma)/sup -1/ is estimated to be about 5 cm. Thus the distance traversed by the H/sub 2//sup +/ ion before it arrives at the extractor electrode cannot exceed this value. This in turn sets a limit on the length of the source chamber.

Computational Electromagnetic Analysis in a Human Head Model with EEG Electrodes and Leads Exposed to RF-Field Sources at 915 MHz and 1748 MHz

PubMed Central

Angelone, Leonardo M.; Bit-Babik, Giorgi; Chou, Chung-Kwang

2010-01-01

An electromagnetic analysis of a human head with EEG electrodes and leads exposed to RF-field sources was performed by means of Finite-Difference Time-Domain simulations on a 1-mm3 MRI-based human head model. RF-field source models included a half-wave dipole, a patch antenna, and a realistic CAD-based mobile phone at 915 MHz and 1748 MHz. EEG electrodes/leads models included two configurations of EEG leads, both a standard 10–20 montage with 19 electrodes and a 32-electrode cap, and metallic and high resistive leads. Whole-head and peak 10-g average SAR showed less than 20% changes with and without leads. Peak 1-g and 10-g average SARs were below the ICNIRP and IEEE guideline limits. Conversely, a comprehensive volumetric assessment of changes in the RF field with and without metallic EEG leads showed an increase of two orders of magnitude in single-voxel power absorption in the epidermis and a 40-fold increase in the brain during exposure to the 915 MHz mobile phone. Results varied with the geometry and conductivity of EEG electrodes/leads. This enhancement confirms the validity of the question whether any observed effects in studies involving EEG recordings during RF-field exposure are directly related to the RF fields generated by the source or indirectly to the RF-field-induced currents due to the presence of conductive EEG leads. PMID:20681803

PUBLIC EXPOSURE TO MULTIPLE RF SOURCES IN GHANA.

PubMed

Deatanyah, P; Abavare, E K K; Menyeh, A; Amoako, J K

2018-03-16

This paper describes an effort to respond to the suggestion in World Health Organization (WHO) research agenda to better quantify potential exposure levels from a range of radiofrequency (RF) sources at 200 public access locations in Ghana. Wide-band measurements were performed-with a spectrum analyser and a log-periodic antenna using three-point spatial averaging method. The overall results represented a maximum of 0.19% of the ICNIRP reference levels for public exposure. These results were generally lower than found in some previous but were 58% (2.0 dB) greater, than found in similar work conducted in the USA. Major contributing sources of RF fields were identified to be FM broadcast and mobile base station sites. Three locations with the greatest measured RF fields could represent potential areas for epidemiological studies.

Spatial distribution of the RF power absorbed in a helicon plasma source

NASA Astrophysics Data System (ADS)

Aleksenko, O. V.; Miroshnichenko, V. I.; Mordik, S. N.

2014-08-01

The spatial distributions of the RF power absorbed by plasma electrons in an ion source operating in the helicon mode (ω ci < ω < ω ce < ω pe ) are studied numerically by using a simplified model of an RF plasma source in an external uniform magnetic field. The parameters of the source used in numerical simulations are determined by the necessity of the simultaneous excitation of two types of waves, helicons and Trivelpiece-Gould modes, for which the corresponding transparency diagrams are used. The numerical simulations are carried out for two values of the working gas (helium) pressure and two values of the discharge chamber length under the assumption that symmetric modes are excited. The parameters of the source correspond to those of the injector of the nuclear scanning microprobe operating at the Institute of Applied Physics, National Academy of Sciences of Ukraine. It is assumed that the mechanism of RF power absorption is based on the acceleration of plasma electrons in the field of a Trivelpiece-Gould mode, which is interrupted by pair collisions of plasma electrons with neutral atoms and ions of the working gas. The simulation results show that the total absorbed RF power at a fixed plasma density depends in a resonant manner on the magnetic field. The resonance is found to become smoother with increasing working gas pressure. The distributions of the absorbed RF power in the discharge chamber are presented. The achievable density of the extracted current is estimated using the Bohm criterion.

High Current Density Cathodes for Future Vacuum Electronics Applications

DTIC Science & Technology

2008-05-30

Tube - device for generating high levels of RF power DARPA Defense Advanced Research Agency PBG Photonic band gap W- Band 75-111 GHz dB Decibels GHz...Extended interaction klystron 1. Introduction All RF vacuum electron sources require a high quality electron beam for efficient operation. Research on...with long life. Pres- ently, only thermionic dispenser cathodes are practical for high power RF sources. Typical thermi- onic cathodes consists of a

Instantaneous and efficient surface wave excitation of a low pressure gas or gases

DOEpatents

Levy, Donald J.; Berman, Samuel M.

1988-01-01

A system for instantaneously ionizing and continuously delivering energy in the form of surface waves to a low pressure gas or mixture of low pressure gases, comprising a source of rf energy, a discharge container, (such as a fluorescent lamp discharge tube), an rf shield, and a coupling device responsive to rf energy from the source to couple rf energy directly and efficiently to the gas or mixture of gases to ionize at least a portion of the gas or gases and to provide energy to the gas or gases in the form of surface waves. The majority of the rf power is transferred to the gas or gases near the inner surface of the discharge container to efficiently transfer rf energy as excitation energy for at least one of the gases. The most important use of the invention is to provide more efficient fluorescent and/or ultraviolet lamps.

Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

NASA Astrophysics Data System (ADS)

Brombin, M.; Spolaore, M.; Serianni, G.; Pomaro, N.; Taliercio, C.; Palma, M. Dalla; Pasqualotto, R.; Schiesko, L.

2014-11-01

A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors' holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from Radio Frequency plasma) experiment: tests in BATMAN (BAvarian Test Machine for Negative ions).

PubMed

Brombin, M; Spolaore, M; Serianni, G; Pomaro, N; Taliercio, C; Dalla Palma, M; Pasqualotto, R; Schiesko, L

2014-11-01

A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors' holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

Effect of transverse nonuniformity of the rf field on the efficiency of microwave sources driven by linear electron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nusinovich, G.S.; Sinitsyn, O.V.

This paper contains a simple analytical theory that allows one to evaluate the effect of transverse nonuniformity of the rf field on the interaction efficiency in various microwave sources driven by linear electron beams. The theory is, first, applied to the systems where the beams of cylindrical symmetry interact with rf fields of microwave circuits having Cartesian geometry. Also, various kinds of microwave devices driven by sheet electron beams (orotrons, clinotrons) are considered. The theory can be used for evaluating the efficiency of novel sources of coherent terahertz radiation.

Frequency-tuning radiofrequency plasma source operated in inductively-coupled mode under a low magnetic field

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Nakano, Yudai; Ando, Akira

2017-07-01

A radiofrequency (rf) inductively-coupled plasma source is operated with a frequency-tuning impedance matching system, where the rf frequency is variable in the range of 20-50 MHz and the maximum power is 100 W. The source consists of a 45 mm-diameter pyrex glass tube wound by an rf antenna and a solenoid providing a magnetic field strength in the range of 0-200 Gauss. A reflected rf power for no plasma case is minimized at the frequency of ˜25 MHz, whereas the frequency giving the minimum reflection with the high density plasma is about 28 MHz, where the density jump is observed when minimizing the reflection. A high density argon plasma above 1× {{10}12} cm-3 is successfully obtained in the source for the rf power of 50-100 W, where it is observed that an external magnetic field of a few tens of Gauss yields the highest plasma density in the present configuration. The frequency-tuning plasma source is applied to a compact and high-speed silicon etcher in an Ar-SF6 plasma; then the etching rate of 8~μ m min-1 is obtained for no bias voltage to the silicon wafer, i.e. for the case that a physical ion etching process is eliminated.

Proceedings of the 10th international workshop on ECR ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meyer, F W; Kirkpatrick, M I

This report contains papers on the following topics: Recent Developments and Future Projects on ECR Ion Sources; Operation of the New KVI ECR Ion Source at 10 GHz; Operational Experience and Status of the INS SF-ECR Ion Source; Results of the New ECR4'' 14.5 GHz ECRIS; Preliminary Performance of the AECR; Experimental Study of the Parallel and Perpendicular Particle Losses from an ECRIS Plasma; Plasma Instability in Electron Cyclotron Resonance Heated Ion Sources; The Hyperbolic Energy Analyzer; Status of ECR Source Development; The New 10 GHz CAPRICE Source; First Operation of the Texas A M ECR Ion Source; Recent Developmentsmore » of the RIKEN ECR Ion Sources; The 14 GHz CAPRICE Source; Characteristics and Potential Applications of an ORNL Microwave ECR Multicusp Plasma Ion Source; ECRIPAC: The Production and Acceleration of Multiply Charged Ions Using an ECR Plasma; ECR Source for the HHIRF Tandem Accelerator; Feasibility Studies for an ECR-Generated Plasma Stripper; Production of Ion Beams by using the ECR Plasmas Cathode; A Single Stage ECR Source for Efficient Production of Radioactive Ion Beams; The Single Staged ECR Source at the TRIUMF Isotope Separator TISOL; The Continuous Wave, Optically Pumped H{sup {minus}} Source; The H{sup +} ECR Source for the LAMPF Optically Pumped Polarized Ion Source; Present Status of the Warsaw CUSP ECR Ion Source; An ECR Source for Negative Ion Production; GYRAC-D: A Device for a 200 keV ECR Plasma Production and Accumulation; Status Report of the 14.4 GHZ ECR in Legnaro; Status of JYFL-ECRIS; Report on the Uppsala ECRIS Facility and Its Planned Use for Atomic Physics; A 10 GHz ECR Ion Source for Ion-Electron and Ion-Atom Collision Studies; and Status of the ORNL ECR Source Facility for Multicharged Ion Collision Research.« less

Commissioning and Early Operation for the NSLS-II Booster RF System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marques, C.; Cupolo, J.; Davila, P.

2015-05-03

The National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory (BNL) is a third generation 3GeV, 500mA synchrotron light source. We discuss the booster synchrotron RF system responsible for providing power to accelerate an electron beam from 200MeV to 3GeV. The RF system design and construction are complete and is currently in the operational phase of the NSLS-II project. Preliminary operational data is also discussed.

Development of sub-100 femtosecond timing and synchronization system

NASA Astrophysics Data System (ADS)

Lin, Zhenyang; Du, Yingchao; Yang, Jin; Xu, Yilun; Yan, Lixin; Huang, Wenhui; Tang, Chuanxiang; Huang, Gang; Du, Qiang; Doolittle, Lawrence; Wilcox, Russell; Byrd, John

2018-01-01

The precise timing and synchronization system is an essential part for the ultra-fast electron and X-ray sources based on the photocathode injector where strict synchronization among RF, laser, and beams are required. In this paper, we present an integrated sub-100 femtosecond timing and synchronization system developed and demonstrated recently in Tsinghua University based on the collaboration with Lawrence Berkeley National Lab. The timing and synchronization system includes the fiber-based CW carrier phase reference distribution system for delivering stabilized RF phase reference to multiple receiver clients, the Low Level RF (LLRF) control system to monitor and generate the phase and amplitude controllable pulse RF signal, and the laser-RF synchronization system for high precision synchronization between optical and RF signals. Each subsystem is characterized by its blocking structure and is also expansible. A novel asymmetric calibration sideband signal method was proposed for eliminating the non-linear distortion in the optical synchronization process. According to offline and online tests, the system can deliver a stable signal to each client and suppress the drift and jitter of the RF signal for the accelerator and the laser oscillator to less than 100 fs RMS (˜0.1° in 2856 MHz frequency). Moreover, a demo system with a LLRF client and a laser-RF synchronization client is deployed and operated successfully at the Tsinghua Thomson scattering X-ray source. The beam-based jitter measurement experiments have been conducted to evaluate the overall performance of the system, and the jitter sources are discussed.

Development of sub-100 femtosecond timing and synchronization system.

PubMed

Lin, Zhenyang; Du, Yingchao; Yang, Jin; Xu, Yilun; Yan, Lixin; Huang, Wenhui; Tang, Chuanxiang; Huang, Gang; Du, Qiang; Doolittle, Lawrence; Wilcox, Russell; Byrd, John

2018-01-01

The precise timing and synchronization system is an essential part for the ultra-fast electron and X-ray sources based on the photocathode injector where strict synchronization among RF, laser, and beams are required. In this paper, we present an integrated sub-100 femtosecond timing and synchronization system developed and demonstrated recently in Tsinghua University based on the collaboration with Lawrence Berkeley National Lab. The timing and synchronization system includes the fiber-based CW carrier phase reference distribution system for delivering stabilized RF phase reference to multiple receiver clients, the Low Level RF (LLRF) control system to monitor and generate the phase and amplitude controllable pulse RF signal, and the laser-RF synchronization system for high precision synchronization between optical and RF signals. Each subsystem is characterized by its blocking structure and is also expansible. A novel asymmetric calibration sideband signal method was proposed for eliminating the non-linear distortion in the optical synchronization process. According to offline and online tests, the system can deliver a stable signal to each client and suppress the drift and jitter of the RF signal for the accelerator and the laser oscillator to less than 100 fs RMS (∼0.1° in 2856 MHz frequency). Moreover, a demo system with a LLRF client and a laser-RF synchronization client is deployed and operated successfully at the Tsinghua Thomson scattering X-ray source. The beam-based jitter measurement experiments have been conducted to evaluate the overall performance of the system, and the jitter sources are discussed.

Numerical simulation of electromagnetic fields and impedance of CERN LINAC4 H(-) source taking into account the effect of the plasma.

PubMed

Grudiev, A; Lettry, J; Mattei, S; Paoluzzi, M; Scrivens, R

2014-02-01

Numerical simulation of the CERN LINAC4 H(-) source 2 MHz RF system has been performed taking into account a realistic geometry from 3D Computer Aided Design model using commercial FEM high frequency simulation code. The effect of the plasma has been added to the model by the approximation of a homogenous electrically conducting medium. Electric and magnetic fields, RF power losses, and impedance of the circuit have been calculated for different values of the plasma conductivity. Three different regimes have been found depending on the plasma conductivity: (1) Zero or low plasma conductivity results in RF electric field induced by the RF antenna being mainly capacitive and has axial direction; (2) Intermediate conductivity results in the expulsion of capacitive electric field from plasma and the RF power coupling, which is increasing linearly with the plasma conductivity, is mainly dominated by the inductive azimuthal electric field; (3) High conductivity results in the shielding of both the electric and magnetic fields from plasma due to the skin effect, which reduces RF power coupling to plasma. From these simulations and measurements of the RF power coupling on the CERN source, a value of the plasma conductivity has been derived. It agrees well with an analytical estimate calculated from the measured plasma parameters. In addition, the simulated and measured impedances with and without plasma show very good agreement as well demonstrating validity of the plasma model used in the RF simulations.

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.

Collective Beam Instabilities in the Taiwan Light Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chao, Alex W.

2002-08-12

The storage ring at Taiwan Light Source has experienced a strong collective instability since 1994. Various cures have been attempted to suppress this instability, including the use of damping antenna, tunable rf plungers, different filling patterns, and rf gap voltage modulation. So far these cures have improved the beam intensity, but the operation remains to be limited by the instability. The dominant phenomenon is the longitudinal coupled bunch instability. The major source of longitudinal impedance is from rf cavities of Doris type. The high-order modes of the cavity were numerically analyzed using a 3-D code GdfidL. The correlation of themore » observed phenomenon in user operation with high-order modes of rf cavities will be presented. Results of various attempts to suppress beam instabilities will be summarized. Proposed cures for beam instabilities will be discussed.« less

Using ensemble models to identify and apportion heavy metal pollution sources in agricultural soils on a local scale.

PubMed

Wang, Qi; Xie, Zhiyi; Li, Fangbai

2015-11-01

This study aims to identify and apportion multi-source and multi-phase heavy metal pollution from natural and anthropogenic inputs using ensemble models that include stochastic gradient boosting (SGB) and random forest (RF) in agricultural soils on the local scale. The heavy metal pollution sources were quantitatively assessed, and the results illustrated the suitability of the ensemble models for the assessment of multi-source and multi-phase heavy metal pollution in agricultural soils on the local scale. The results of SGB and RF consistently demonstrated that anthropogenic sources contributed the most to the concentrations of Pb and Cd in agricultural soils in the study region and that SGB performed better than RF. Copyright © 2015 Elsevier Ltd. All rights reserved.

The impact of dual-source parallel radiofrequency transmission with patient-adaptive shimming on the cardiac magnetic resonance in children at 3.0 T.

PubMed

Wang, Haipeng; Qiu, Liyun; Wang, Guangbin; Gao, Fei; Jia, Haipeng; Zhao, Junyu; Chen, Weibo; Wang, Cuiyan; Zhao, Bin

2017-06-01

The cardiac magnetic resonance (CMR) of children at 3.0 T presents a unique set of technical challenges because of their small cardiac anatomical structures, fast heart rates, and the limited ability to keep motionless and hold breathe, which could cause problems associated with field inhomogeneity and degrade the image quality. The aim of our study was to evaluate the effect of dual-source parallel radiofrequency (RF) transmission on the B1 homogeneity and image quality in children with CMR at 3.0 T. The study was approved by the institutional ethics committee and written informed consent was obtained. A total of 30 free-breathing children and 30 breath-hold children performed CMR examinations with dual-source and single-source RF transmission. The B1 homogeneity, contrast ratio (CR) of cine images, and off-resonance artifacts in cine images between dual-source and single-source RF transmission were assessed in free-breathing and breath-hold groups, respectively. In both free-breathing and breath-hold groups, higher mean percentage of flip angle (free-breathing group: 104.2 ± 4.6 vs 95.5 ± 6.3, P < .001; breath-hold group: 101.5 ± 5.1 vs 92.5 ± 6.3, P < .001) and lower coefficient of variation (free-breathing group: 0.06 ± 0.02 vs 0.09 ± 0.03, P < .001; breath-hold group: 0.07 ± 0.03 vs 0.10 ± 0.04, P = .005) were found with dual-source than with single-source RF transmission. Both the CRs in the horizontal long axis (HLA) and short axis of cine images with dual-source RF transmission was improved (P < .05 for all). The scores of off-resonance artifacts in the HLA with dual-source RF transmission were higher in both free-breathing and breath-hold groups (P < .05 for all), with substantial interreader agreement (kappa values from 0.68 to 0.74). Compared with conventional single-source, dual-source parallel RF transmission could significantly improve the B1 homogeneity and image quality for CMR in children at 3.0 T. This technology could be taken into account in CMR for children with cardiac diseases.

Low pressure and high power rf sources for negative hydrogen ions for fusion applications (ITER neutral beam injection).

PubMed

Fantz, U; Franzen, P; Kraus, W; Falter, H D; Berger, M; Christ-Koch, S; Fröschle, M; Gutser, R; Heinemann, B; Martens, C; McNeely, P; Riedl, R; Speth, E; Wünderlich, D

2008-02-01

The international fusion experiment ITER requires for the plasma heating and current drive a neutral beam injection system based on negative hydrogen ion sources at 0.3 Pa. The ion source must deliver a current of 40 A D(-) for up to 1 h with an accelerated current density of 200 Am/(2) and a ratio of coextracted electrons to ions below 1. The extraction area is 0.2 m(2) from an aperture array with an envelope of 1.5 x 0.6 m(2). A high power rf-driven negative ion source has been successfully developed at the Max-Planck Institute for Plasma Physics (IPP) at three test facilities in parallel. Current densities of 330 and 230 Am/(2) have been achieved for hydrogen and deuterium, respectively, at a pressure of 0.3 Pa and an electron/ion ratio below 1 for a small extraction area (0.007 m(2)) and short pulses (<4 s). In the long pulse experiment, equipped with an extraction area of 0.02 m(2), the pulse length has been extended to 3600 s. A large rf source, with the width and half the height of the ITER source but without extraction system, is intended to demonstrate the size scaling and plasma homogeneity of rf ion sources. The source operates routinely now. First results on plasma homogeneity obtained from optical emission spectroscopy and Langmuir probes are very promising. Based on the success of the IPP development program, the high power rf-driven negative ion source has been chosen recently for the ITER beam systems in the ITER design review process.

Commissioning of two RF operation modes for RF negative ion source experimental setup at HUST

NASA Astrophysics Data System (ADS)

Li, D.; Chen, D.; Liu, K.; Zhao, P.; Zuo, C.; Wang, X.; Wang, H.; Zhang, L.

2017-08-01

An RF-driven negative ion source experimental setup, without a cesium oven and an extraction system, has been built at Huazhong University of Science and Technology (HUST). The working gas is hydrogen, and the typical operational gas pressure is 0.3 Pa. The RF generator is capable of delivering up to 20 kW at 0.9 - 1.1 MHz, and has two operation modes, the fixed-frequency mode and auto-tuning mode. In the fixed-frequency mode, it outputs a steady RF forward power (Pf) at a fixed frequency. In the auto-tuning mode, it adjusts the operating frequency to seek and track the minimum standing wave ratio (SWR) during plasma discharge. To achieve fast frequency tuning, the RF signal source adopts a direct digital synthesizer (DDS). To withstand high SWR during the discharge, a tetrode amplifier is chosen as the final stage amplifier. The trend of maximum power reflection coefficient |ρ|2 at plasma ignition is presented at the fixed frequency of 1.02 MHz with the Pf increasing from 5 kW to 20 kW, which shows the maximum |ρ|2 tends to be "steady" under high RF power. The experiments in auto-tuning mode fail due to over-current protection of screen grid. The possible reason is the relatively large equivalent anode impedance caused by the frequency tuning. The corresponding analysis and possible solution are presented.

Gamma source for active interrogation

DOEpatents

Leung, Ka-Ngo; Lou, Tak Pui; Barletta, William A.

2012-10-02

A cylindrical gamma generator includes a coaxial RF-driven plasma ion source and target. A hydrogen plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical gamma generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which has many openings. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired.

Gamma source for active interrogation

DOEpatents

Leung, Ka-Ngo [Hercules, CA; Lou, Tak Pui [Berkeley, CA; Barletta, William A [Oakland, CA

2009-09-29

A cylindrical gamma generator includes a coaxial RF-driven plasma ion source and target. A hydrogen plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical gamma generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which has many openings. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired.

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.

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.

Ultralow-jitter and -amplitude-noise semiconductor-based actively mode-locked laser.

PubMed

Quinlan, Franklyn; Gee, Sangyoun; Ozharar, Sarper; Delfyett, Peter J

2006-10-01

We report a semiconductor-based, low-noise, 10.24 GHz actively mode-locked laser with 4.65 fs of relative timing jitter and a 0.0365% amplitude fluctuation (1 Hz to 100 MHz) of the optical pulse train. The keys to obtaining this result were the laser's high optical power and the low phase noise of the rf source used to mode lock the laser. The low phase noise of the rf source not only improves the absolute and relative timing jitter of the laser, but also prevents coupling of the rf source phase noise to the pulse amplitude fluctuations by the mode-locked laser.

Pre-conditioning procedure suitable for internal-RF-antenna of J-PARC RF-driven H{sup −} ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.

The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H{sup −} ion source has been successfully operated for about 1 yr. By the world brightest level beam, the J-PARC design beam power of 1 MW was successfully demonstrated. Although no internal-RF-antenna failure, except for the once caused by an excess cesium due to a misoperation, occurred in the operation, many antennas failed in pre-conditionings for the first hundred days. The antenna failure rate was drastically decreased by using an antenna with coating thicker than a standard value and the pre-conditioning procedure repeating 15 min 25 kW RF-power operation and impurity-gasmore » evacuation a few times, before the full power (50 kW) operation.« less

Online tuning of impedance matching circuit for long pulse inductively coupled plasma source operation—An alternate approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudhir, Dass; Bandyopadhyay, M., E-mail: mainak@ter-india.org; Chakraborty, A.

2014-01-15

Impedance matching circuit between radio frequency (RF) generator and the plasma load, placed between them, determines the RF power transfer from RF generator to the plasma load. The impedance of plasma load depends on the plasma parameters through skin depth and plasma conductivity or resistivity. Therefore, for long pulse operation of inductively coupled plasmas, particularly for high power (∼100 kW or more) where plasma load condition may vary due to different reasons (e.g., pressure, power, and thermal), online tuning of impedance matching circuit is necessary through feedback. In fusion grade ion source operation, such online methodology through feedback is notmore » present but offline remote tuning by adjusting the matching circuit capacitors and tuning the driving frequency of the RF generator between the ion source operation pulses is envisaged. The present model is an approach for remote impedance tuning methodology for long pulse operation and corresponding online impedance matching algorithm based on RF coil antenna current measurement or coil antenna calorimetric measurement may be useful in this regard.« less

Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brombin, M., E-mail: matteo.brombin@igi.cnr.it; Spolaore, M.; Serianni, G.

2014-11-15

A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors’ holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation.more » No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.« less

Optically controlled switch-mode current-source amplifiers for on-coil implementation in high field parallel transmission

PubMed Central

Gudino, Natalia; Duan, Qi; de Zwart, Jacco A; Murphy-Boesch, Joe; Dodd, Stephen J; Merkle, Hellmut; van Gelderen, Peter; Duyn, Jeff H

2015-01-01

Purpose We tested the feasibility of implementing parallel transmission (pTX) for high field MRI using a radiofrequency (RF) amplifier design to be located on or in the immediate vicinity of a RF transmit coil. Method We designed a current-source switch-mode amplifier based on miniaturized, non-magnetic electronics. Optical RF carrier and envelope signals to control the amplifier were derived, through a custom-built interface, from the RF source accessible in the scanner control. Amplifier performance was tested by benchtop measurements as well as with imaging at 7 T (300 MHz) and 11.7 T (500 MHz). The ability to perform pTX was evaluated by measuring inter-channel coupling and phase adjustment in a 2-channel setup. Results The amplifier delivered in excess of 44 W RF power and caused minimal interference with MRI. The interface derived accurate optical control signals with carrier frequencies ranging from 64 to 750 MHz. Decoupling better than 14 dB was obtained between 2 coil loops separated by only 1 cm. Application to MRI was demonstrated by acquiring artifact-free images at 7 T and 11.7 T. Conclusion An optically controlled miniaturized RF amplifier for on-coil implementation at high field is demonstrated that should facilitate implementation of high-density pTX arrays. PMID:26256671

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorogushin, M.F.

Principle and experimental analysis of RF power feed system, based on 3 db directional couplers, for undesirable modes eliminating, divided power coupling with the RFQ accelerating structure, endotron type RF power source matching, are presented. The structure fine tuning and the system adjustment results and high-speed RF autocontrol system design are considered also.

Up gradation of LHCD system for rf power level up to 2MW for SST1

NASA Astrophysics Data System (ADS)

Sharma, P. K.; Ambulkar, K. K.; Parmar, P. R.; Virani, C. G.; Thakur, A. L.; Kulkarni, S. V.; Lhcd Group

2010-02-01

To operate superconducting steadystate tokamak (SST1) for 1000 seconds, lower hybrid current drive (LHCD) system has been designed at a frequency of 3.7 GHz., which would couple 1.0 MW CW of microwave power to the shaped plasma. The system consists of various rf passive components and transmission line, employing which the rf power from the source is transported to the antenna. During calibration of transmission line, it was observed that the losses in the transmission line is substantial and eventually would lead to less coupled power to the plasma. Further it is anticipated that more LH power would be required for advanced operation of SST1 machine. Thus it is decided to upgrade the existing LHCD system to 2 MW CW power level. The proposed up gradation would demand several infra structural changes and needs to be addressed. Due to lack of space, we have proposed a scheme in which additional two klystrons, along with existing two klystrons would be accommodated in the existing space. The low rf power requirements have also been increased to cater the new needs. Accordingly additional cooling requirements have been proposed to accommodate the two new klystrons. The DAC and auxiliary power supplies have been also designed. The new up graded LHCD system would address several key technological issues. Firstly it would establish the operation of four klystrons at rated power in parallel employing single RHVPS (80kV, 70A). Secondly it would establish the operation of two high power klystrons operation at rated power when their collectors are cooled in series. In this paper we would present the various requirements for up-gradation of LHCD system to 2MW. The main requirements like high power rf source, along with modified support structure, low power rf systems to drive the high power rf source, auxiliary power supplies required for high power rf source, DAC system improvement, cooling improvements, etc. would be discussed.

Radiofrequency antenna for suppression of parasitic discharges in a helicon plasma thruster experiment.

PubMed

Takahashi, Kazunori

2012-08-01

A radiofrequency (rf) antenna for helicon plasma thruster experiments is developed and tested using a permanent magnets helicon plasma source immersed in a vacuum chamber. A magnetic nozzle is provided by permanent magnets arrays and an argon plasma is produced by a 13.56 MHz radiofrequency helicon-wave or inductively-coupled discharge. A parasitic discharge outside the source tube is successfully suppressed by covering the rf antenna with a ceramic ring and a grounded shield; a decrease in the ion saturation current of a Langmuir probe located outside the source tube is observed and the ion saturation current on axis increases simultaneously, compared with the case of a standard uncovered rf antenna. It is also demonstrated that the covered antenna can yield stable operation of the source.

Comparison of Three Plasma Sources for Ambient Desorption/Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

McKay, Kirsty; Salter, Tara L.; Bowfield, Andrew; Walsh, James L.; Gilmore, Ian S.; Bradley, James W.

2014-09-01

Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources.

Comparison of three plasma sources for ambient desorption/ionization mass spectrometry.

PubMed

McKay, Kirsty; Salter, Tara L; Bowfield, Andrew; Walsh, James L; Gilmore, Ian S; Bradley, James W

2014-09-01

Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources.

Physics-electrical hybrid model for real time impedance matching and remote plasma characterization in RF plasma sources.

PubMed

Sudhir, Dass; Bandyopadhyay, M; Chakraborty, A

2016-02-01

Plasma characterization and impedance matching are an integral part of any radio frequency (RF) based plasma source. In long pulse operation, particularly in high power operation where plasma load may vary due to different reasons (e.g. pressure and power), online tuning of impedance matching circuit and remote plasma density estimation are very useful. In some cases, due to remote interfaces, radio activation and, due to maintenance issues, power probes are not allowed to be incorporated in the ion source design for plasma characterization. Therefore, for characterization and impedance matching, more remote schemes are envisaged. Two such schemes by the same authors are suggested in these regards, which are based on air core transformer model of inductive coupled plasma (ICP) [M. Bandyopadhyay et al., Nucl. Fusion 55, 033017 (2015); D. Sudhir et al., Rev. Sci. Instrum. 85, 013510 (2014)]. However, the influence of the RF field interaction with the plasma to determine its impedance, a physics code HELIC [D. Arnush, Phys. Plasmas 7, 3042 (2000)] is coupled with the transformer model. This model can be useful for both types of RF sources, i.e., ICP and helicon sources.

Public Exposure from Indoor Radiofrequency Radiation in the City of Hebron, West Bank-Palestine.

PubMed

Lahham, Adnan; Sharabati, Afefeh; ALMasri, Hussien

2015-08-01

This work presents the results of measured indoor exposure levels to radiofrequency (RF) radiation emitting sources in one of the major cities in the West Bank-the city of Hebron. Investigated RF emitters include FM, TV broadcasting stations, mobile telephony base stations, cordless phones [Digital Enhanced Cordless Telecommunications (DECT)], and wireless local area networks (WLAN). Measurements of power density were conducted in 343 locations representing different site categories in the city. The maximum total power density found at any location was about 2.3 × 10 W m with a corresponding exposure quotient of about 0.01. This value is well below unity, indicating compliance with the guidelines of the International Commission on Non-ionizing Radiation Protection (ICNIRP). The average total exposure from all RF sources was 0.08 × 10 W m. The relative contributions from different sources to the total exposure in terms of exposure quotient were evaluated and found to be 46% from FM radio, 26% from GSM900, 15% from DECT phones, 9% from WLAN, 3% from unknown sources, and 1% from TV broadcasting. RF sources located outdoors contribute about 73% to the population exposure indoors.

Physics-electrical hybrid model for real time impedance matching and remote plasma characterization in RF plasma sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sudhir, Dass, E-mail: dass.sudhir@iter-india.org; Bandyopadhyay, M.; Chakraborty, A.

2016-02-15

Plasma characterization and impedance matching are an integral part of any radio frequency (RF) based plasma source. In long pulse operation, particularly in high power operation where plasma load may vary due to different reasons (e.g. pressure and power), online tuning of impedance matching circuit and remote plasma density estimation are very useful. In some cases, due to remote interfaces, radio activation and, due to maintenance issues, power probes are not allowed to be incorporated in the ion source design for plasma characterization. Therefore, for characterization and impedance matching, more remote schemes are envisaged. Two such schemes by the samemore » authors are suggested in these regards, which are based on air core transformer model of inductive coupled plasma (ICP) [M. Bandyopadhyay et al., Nucl. Fusion 55, 033017 (2015); D. Sudhir et al., Rev. Sci. Instrum. 85, 013510 (2014)]. However, the influence of the RF field interaction with the plasma to determine its impedance, a physics code HELIC [D. Arnush, Phys. Plasmas 7, 3042 (2000)] is coupled with the transformer model. This model can be useful for both types of RF sources, i.e., ICP and helicon sources.« less

Can we estimate plasma density in ICP driver through electrical parameters in RF circuit?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bandyopadhyay, M., E-mail: mainak@iter-india.org; Sudhir, Dass, E-mail: dass.sudhir@iter-india.org; Chakraborty, A., E-mail: arunkc@iter-india.org

2015-04-08

To avoid regular maintenance, invasive plasma diagnostics with probes are not included in the inductively coupled plasma (ICP) based ITER Neutral Beam (NB) source design. Even non-invasive probes like optical emission spectroscopic diagnostics are also not included in the present ITER NB design due to overall system design and interface issues. As a result, negative ion beam current through the extraction system in the ITER NB negative ion source is the only measurement which indicates plasma condition inside the ion source. However, beam current not only depends on the plasma condition near the extraction region but also on the perveancemore » condition of the ion extractor system and negative ion stripping. Nevertheless, inductively coupled plasma production region (RF driver region) is placed at distance (∼ 30cm) from the extraction region. Due to that, some uncertainties are expected to be involved if one tries to link beam current with plasma properties inside the RF driver. Plasma characterization in source RF driver region is utmost necessary to maintain the optimum condition for source operation. In this paper, a method of plasma density estimation is described, based on density dependent plasma load calculation.« less

Surface plasma source with saddle antenna radio frequency plasma generator.

PubMed

Dudnikov, V; Johnson, R P; Murray, S; Pennisi, T; Piller, C; Santana, M; Stockli, M; Welton, R

2012-02-01

A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

RF power absorption by plasma of low pressure low power inductive discharge located in the external magnetic field

NASA Astrophysics Data System (ADS)

Kralkina, E. A.; Rukhadze, A. A.; Nekliudova, P. A.; Pavlov, V. B.; Petrov, A. K.; Vavilin, K. V.

2018-03-01

Present paper is aimed to reveal experimentally and theoretically the influence of magnetic field strength, antenna shape, pressure, operating frequency and geometrical size of plasma sources on the ability of plasma to absorb the RF power characterized by the equivalent plasma resistance for the case of low pressure RF inductive discharge located in the external magnetic field. The distinguishing feature of the present paper is the consideration of the antennas that generate not only current but charge on the external surface of plasma sources. It is shown that in the limited plasma source two linked waves can be excited. In case of antennas generating only azimuthal current the waves can be attributed as helicon and TG waves. In the case of an antenna with the longitudinal current there is a surface charge on the side surface of the plasma source, which gives rise to a significant increase of the longitudinal and radial components of the RF electric field as compared with the case of the azimuthal antenna current.

Characterization of microwave plasma in a multicusp using 2D emission based tomography: Bessel modes and wave absorption

NASA Astrophysics Data System (ADS)

Rathore, Kavita; Bhattacharjee, Sudeep; Munshi, Prabhat

2017-06-01

A tomographic method based on the Fourier transform is used for characterizing a microwave plasma in a multicusp (MC), in order to obtain 2D distribution of plasma emissions, plasma (electron) density (Ne) and temperature (Te). The microwave plasma in the MC is characterized as a function of microwave power, gas pressure, and axial distance. The experimentally obtained 2D emission profiles show that the plasma emissions are generated in a circular ring shape. There are usually two bright rings, one at the plasma core and another near the boundary. The experimental results are validated using a numerical code that solves Maxwell's equations inside a waveguide filled with a plasma in a magnetic field, with collisions included. It is inferred that the dark and bright circular ring patterns are a result of superposition of Bessel modes (TE11 and TE21) of the wave electric field inside the plasma filled MC, which are in reasonable agreement with the plasma emission profiles. The tomographically obtained Ne and Te profiles indicate higher densities in the plasma core (˜1010 cm-3) and enhanced electron temperature in the ECR region (˜13 eV), which are in agreement with earlier results using a Langmuir probe and optical emission spectroscopy (OES) diagnostics.

Effect of source frequency and pulsing on the SiO2 etching characteristics of dual-frequency capacitive coupled plasma

NASA Astrophysics Data System (ADS)

Kim, Hoe Jun; Jeon, Min Hwan; Mishra, Anurag Kumar; Kim, In Jun; Sin, Tae Ho; Yeom, Geun Young

2015-01-01

A SiO2 layer masked with an amorphous carbon layer (ACL) has been etched in an Ar/C4F8 gas mixture with dual frequency capacitively coupled plasmas under variable frequency (13.56-60 MHz)/pulsed rf source power and 2 MHz continuous wave (CW) rf bias power, the effects of the frequency and pulsing of the source rf power on the SiO2 etch characteristics were investigated. By pulsing the rf power, an increased SiO2 etch selectivity was observed with decreasing SiO2 etch rate. However, when the rf power frequency was increased, not only a higher SiO2 etch rate but also higher SiO2 etch selectivity was observed for both CW and pulse modes. A higher CF2/F ratio and lower electron temperature were observed for both a higher source frequency mode and a pulsed plasma mode. Therefore, when the C 1s binding states of the etched SiO2 surfaces were investigated using X-ray photoelectron spectroscopy (XPS), the increase of C-Fx bonding on the SiO2 surface was observed for a higher source frequency operation similar to a pulsed plasma condition indicating the increase of SiO2 etch selectivity over the ACL. The increase of the SiO2 etch rate with increasing etch selectivity for the higher source frequency operation appears to be related to the increase of the total plasma density with increasing CF2/F ratio in the plasma. The SiO2 etch profile was also improved not only by using the pulsed plasma but also by increasing the source frequency.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.

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,more » 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.« less

Ion tracking in photocathode rf guns

NASA Astrophysics Data System (ADS)

Lewellen, John W.

2002-02-01

Projected next-generation linac-based light sources, such as PERL or the TESLA free-electron laser, generally assume, as essential components of their injector complexes, long-pulse photocathode rf electron guns. These guns, due to their design rf pulse durations of many milliseconds to continuous wave, may be more susceptible to ion bombardment damage of their cathodes than conventional rf guns, which typically use rf pulses of microsecond duration. This paper explores this possibility in terms of ion propagation within the gun, and presents a basis for future study of the subject.

Development of new S-band RF window for stable high-power operation in linear accelerator RF system

NASA Astrophysics Data System (ADS)

Joo, Youngdo; Lee, Byung-Joon; Kim, Seung-Hwan; Kong, Hyung-Sup; Hwang, Woonha; Roh, Sungjoo; Ryu, Jiwan

2017-09-01

For stable high-power operation, a new RF window is developed in the S-band linear accelerator (Linac) RF systems of the Pohang Light Source-II (PLS-II) and the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL). The new RF window is designed to mitigate the strength of the electric field at the ceramic disk and also at the waveguide-cavity coupling structure of the conventional RF window. By replacing the pill-box type cavity in the conventional RF window with an overmoded cavity, the electric field component perpendicular to the ceramic disk that caused most of the multipacting breakdowns in the ceramic disk was reduced by an order of magnitude. The reduced electric field at the ceramic disk eliminated the Ti-N coating process on the ceramic surface in the fabrication procedure of the new RF window, preventing the incomplete coating from spoiling the RF transmission and lowering the fabrication cost. The overmoded cavity was coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the waveguide-cavity coupling structure and the possibility of mode competitions in the overmoded cavity. A prototype of the new RF window was fabricated and fully tested with the Klystron peak input power, pulse duration and pulse repetition rate of 75 MW, 4.5 μs and 10 Hz, respectively, at the high-power test stand. The first mass-produced new RF window installed in the PLS-II Linac is running in normal operation mode. No fault is reported to date. Plans are being made to install the new RF window to all S-band accelerator RF modules of the PLS-II and PAL-XFEL Linacs. This new RF window may be applied to the output windows of S-band power sources like Klystron as wells as the waveguide windows of accelerator facilities which operate in S-band.

RF induced energy for partially implanted catheters: a computational study

PubMed Central

Lucano, Elena; Liberti, Micaela; Lloyd, Tom; Apollonio, Francesca; Wedan, Steve; Kainz, Wolfgang; Angelone, Leonardo M.

2018-01-01

Magnetic Resonance Imaging (MRI) is a radiological imaging technique widely used in clinical practice. MRI has been proposed to guide the catheters for interventional procedures, such as cardiac ablation. However, there are risks associated with this procedure, such as RF-induced heating of tissue near the catheters. The aim of this study is to develop a quantitative RF-safety method for patients with partially implanted leads at 64 MHz. RF-induced heating is related to the electric field incident along the catheter, which in turns depends on several variables, including the position of the RF feeding sources and the orientation of the polarization, which are however often unknown. This study evaluates the electric field profile along the lead trajectory using simulations with an anatomical human model landmarked at the heart. The energy absorbed in the volume near the tip of ageneric partially implanted lead was computed for all source positions and field orientation. The results showed that varying source positions and field orientation may result in changes of up to 18% for the E-field magnitude and up to 60% for the 10g-averaged specific absorption rate (SAR) in the volume surrounding the tip of the lead. PMID:28268553

Direct coupling of pulsed radio frequency and pulsed high power in novel pulsed power system for plasma immersion ion implantation.

PubMed

Gong, Chunzhi; Tian, Xiubo; Yang, Shiqin; Fu, Ricky K Y; Chu, Paul K

2008-04-01

A novel power supply system that directly couples pulsed high voltage (HV) pulses and pulsed 13.56 MHz radio frequency (rf) has been developed for plasma processes. In this system, the sample holder is connected to both the rf generator and HV modulator. The coupling circuit in the hybrid system is composed of individual matching units, low pass filters, and voltage clamping units. This ensures the safe operation of the rf system even when the HV is on. The PSPICE software is utilized to optimize the design of circuits. The system can be operated in two modes. The pulsed rf discharge may serve as either the seed plasma source for glow discharge or high-density plasma source for plasma immersion ion implantation (PIII). The pulsed high-voltage glow discharge is induced when a rf pulse with a short duration or a larger time interval between the rf and HV pulses is used. Conventional PIII can also be achieved. Experiments conducted on the new system confirm steady and safe operation.

Optimization of a RF-generated CF4/O2 gas plasma sterilization process.

PubMed

Lassen, Klaus S; Nordby, Bolette; Grün, Reinar

2003-05-15

A sterilization process with the use of RF-generated (13.56 MHz) CF(4)/O(2) gas plasma was optimized in regards to power, flow rate, exposure time, and RF-system type. The dependency of the sporicidal effect on the spore inoculum positioning in the chamber of the RF systems was also investigated. Dried Bacillus stearothermophilus ATCC 7953 endospores were used as test organisms. The treatments were evaluated on the basis of survival curves and corresponding D values. The only parameter found to affect the sterilization process was the power of the RF system. Higher power resulted in higher kill. Finally, when the samples were placed more than 3-8 cm away from a centrally placed electrode in System 2, the sporicidal effect was reduced. The results are discussed and compared to results from the present literature. The RF excitation source is evaluated to be more appropriate for sterilization processes than the MW source. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 239-244, 2003

Improved operation of the nonambipolar electron source.

PubMed

Longmier, Ben; Hershkowitz, Noah

2008-09-01

Significant improvements have been made to the nonambipolar electron source (NES), a radio frequency (rf) plasma-based electron source that does not rely on electron emission at a cathode surface [B. Longmier, S. Baalrud, and N. Hershkowitz, Rev. Sci. Instrum. 77, 113504 (2006)]. A prototype NES has produced 30 A of continuous electron current, using 2 SCCM (SCCM denotes cubic centimeter per minute at STP) Xe, 1300 W rf power at 13.56 MHz, yielding a 180 times gas utilization factor. A helicon mode transition has also been identified during NES operation with an argon propellant, using 15 SCCM Ar, 1000 W rf, and 100 G magnetic field. This NES technology has the ability to replace hollow cathode electron sources and to enable high power electric propulsion missions, eliminating one of the lifetime restrictions that many ion thrusters have previously been faced with.

Compact RF ion source for industrial electrostatic ion accelerator

NASA Astrophysics Data System (ADS)

Kwon, Hyeok-Jung; Park, Sae-Hoon; Kim, Dae-Il; Cho, Yong-Sub

2016-02-01

Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described.

Compact RF ion source for industrial electrostatic ion accelerator.

PubMed

Kwon, Hyeok-Jung; Park, Sae-Hoon; Kim, Dae-Il; Cho, Yong-Sub

2016-02-01

Korea Multi-purpose Accelerator Complex is developing a single-ended electrostatic ion accelerator to irradiate gaseous ions, such as hydrogen and nitrogen, on materials for industrial applications. ELV type high voltage power supply has been selected. Because of the limited space, electrical power, and robust operation, a 200 MHz RF ion source has been developed. In this paper, the accelerator system, test stand of the ion source, and its test results are described.

Cardiac MOLLI T1 mapping at 3.0 T: comparison of patient-adaptive dual-source RF and conventional RF transmission.

PubMed

Rasper, Michael; Nadjiri, Jonathan; Sträter, Alexandra S; Settles, Marcus; Laugwitz, Karl-Ludwig; Rummeny, Ernst J; Huber, Armin M

2017-06-01

To prospectively compare image quality and myocardial T 1 relaxation times of modified Look-Locker inversion recovery (MOLLI) imaging at 3.0 T (T) acquired with patient-adaptive dual-source (DS) and conventional single-source (SS) radiofrequency (RF) transmission. Pre- and post-contrast MOLLI T 1 mapping using SS and DS was acquired in 27 patients. Patient wise and segment wise analysis of T 1 times was performed. The correlation of DS MOLLI measurements with a reference spin echo sequence was analysed in phantom experiments. DS MOLLI imaging reduced T 1 standard deviation in 14 out of 16 myocardial segments (87.5%). Significant reduction of T 1 variance could be obtained in 7 segments (43.8%). DS significantly reduced myocardial T 1 variance in 16 out of 25 patients (64.0%). With conventional RF transmission, dielectric shading artefacts occurred in six patients causing diagnostic uncertainty. No according artefacts were found on DS images. DS image findings were in accordance with conventional T 1 mapping and late gadolinium enhancement (LGE) imaging. Phantom experiments demonstrated good correlation of myocardial T 1 time between DS MOLLI and spin echo imaging. Dual-source RF transmission enhances myocardial T 1 homogeneity in MOLLI imaging at 3.0 T. The reduction of signal inhomogeneities and artefacts due to dielectric shading is likely to enhance diagnostic confidence.

Contributions of projected land use to global radiative forcing ascribed to local sources

NASA Astrophysics Data System (ADS)

Ward, D. S.; Mahowald, N. M.; Kloster, S.

2013-12-01

With global demand for food expected to dramatically increase and put additional pressures on natural lands, there is a need to understand the environmental impacts of land use and land cover change (LULCC). Previous studies have shown that the magnitude and even the sign of the radiative forcing (RF) of biogeophysical effects from LULCC depends on the latitude and forest ecology of the disturbed region. Here we ascribe the contributions to the global RF by land-use related anthropogenic activities to their local sources, organized on a grid of 1.9 degrees latitude by 2.5 degrees longitude. We use RF estimates for the year 2100, using five future LULCC projections, computed from simulations with the National Center for Atmospheric Research Community Land Model and Community Atmosphere Models and additional offline analyses. Our definition of the LULCC RF includes changes to terrestrial carbon storage, methane and nitrous oxide emissions, atmospheric chemistry, aerosol emissions, and surface albedo. We ascribe the RF to gridded locations based on LULCC-related emissions of relevant trace gases and aerosols, including emissions from fires. We find that the largest contributions to the global RF in year 2100 from LULCC originate in the tropics for all future scenarios. In fact, LULCC is the largest tropical source of anthropogenic RF. The LULCC RF in the tropics is dominated by emissions of CO2 from deforestation and methane emissions from livestock and soils. Land surface albedo change is rarely the dominant forcing agent in any of the future LULCC projections, at any location. By combining the five future scenarios we find that deforested area at a specific tropical location can be used to predict the contribution to global RF from LULCC at that location (the relationship does not hold as well in the extratropics). This information could support global efforts like REDD (Reducing Emissions from Deforestation and Forest Degradation), that aim to reduce greenhouse gas emissions from land use, by helping to optimize their effectiveness for climate change mitigation.

Exposure Knowledge and Risk Perception of RF EMF

PubMed Central

Freudenstein, Frederik; Wiedemann, Peter M.; Varsier, Nadège

2015-01-01

The presented study is part of the EU-Project Low EMF Exposure Future Networks (LEXNET), which deals among other things with the issue of whether a reduction of the radiofrequency (RF) electro-magnetic fields (EMF) exposure will result in more acceptance of wireless communication networks in the public sphere. We assume that the effects of any reduction of EMF exposure will depend on the subjective link between exposure perception and risk perception (RP). Therefore we evaluated respondents’ RP of different RF EMF sources and their subjective knowledge about various exposure characteristics with regard to their impact on potential health risks. The results show that participants are more concerned about base stations than about all other RF EMF sources. Concerning the subjective exposure knowledge the results suggest that people have a quite appropriate impact model. The question how RF EMF RP is actually affected by the knowledge about the various exposure characteristics was tested in a linear regression analysis. The regression indicates that these features – except distance – do influence people’s general RF EMF RP. In addition, we analyzed the effect of the quality of exposure knowledge on RF EMF RP of various sources. The results show a tendency that better exposure knowledge leads to higher RP, especially for mobile phones. The study provides empirical support for models of the relationships between exposure perception and RP. It is not the aim to extrapolate these findings to the whole population because the samples are not exactly representative for the general public in the participating countries. PMID:25629026

Electrostatic sensors for SPIDER experiment: Design, manufacture of prototypes, and first tests

NASA Astrophysics Data System (ADS)

Brombin, M.; Spolaore, M.; Serianni, G.; Barzon, A.; Franchin, L.; Pasqualotto, R.; Pomaro, N.; Schiesko, L.; Taliercio, C.; Trevisan, L.

2014-02-01

A system of electrostatic sensors has been designed for the SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) experiment, prototype RF source of the ITER NBI (neutral beam injection). A prototype of the sensor system was manufactured and tested at the BATMAN (BAvarian Test MAchine for Negative ions) facility, where the plasma environment is similar to that of SPIDER. Different aspects concerning the mechanical manufacturing and the signal conditioning are presented, among them the RF compensation adopted to reduce the RF effects which could lead to overestimated values of the electron temperature. The first commissioning tests provided ion saturation current values in the range assumed for the design, so the deduced plasma density estimate is consistent with the expected values.

Electrostatic sensors for SPIDER experiment: design, manufacture of prototypes, and first tests.

PubMed

Brombin, M; Spolaore, M; Serianni, G; Barzon, A; Franchin, L; Pasqualotto, R; Pomaro, N; Schiesko, L; Taliercio, C; Trevisan, L

2014-02-01

A system of electrostatic sensors has been designed for the SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) experiment, prototype RF source of the ITER NBI (neutral beam injection). A prototype of the sensor system was manufactured and tested at the BATMAN (BAvarian Test MAchine for Negative ions) facility, where the plasma environment is similar to that of SPIDER. Different aspects concerning the mechanical manufacturing and the signal conditioning are presented, among them the RF compensation adopted to reduce the RF effects which could lead to overestimated values of the electron temperature. The first commissioning tests provided ion saturation current values in the range assumed for the design, so the deduced plasma density estimate is consistent with the expected values.

Electrostatic sensors for SPIDER experiment: Design, manufacture of prototypes, and first tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brombin, M., E-mail: matteo.brombin@igi.cnr.it; Spolaore, M.; Serianni, G.

2014-02-15

A system of electrostatic sensors has been designed for the SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) experiment, prototype RF source of the ITER NBI (neutral beam injection). A prototype of the sensor system was manufactured and tested at the BATMAN (BAvarian Test MAchine for Negative ions) facility, where the plasma environment is similar to that of SPIDER. Different aspects concerning the mechanical manufacturing and the signal conditioning are presented, among them the RF compensation adopted to reduce the RF effects which could lead to overestimated values of the electron temperature. The first commissioningmore » tests provided ion saturation current values in the range assumed for the design, so the deduced plasma density estimate is consistent with the expected values.« less

Quartz antenna with hollow conductor

DOEpatents

Leung, Ka-Ngo; Benabou, Elie

2002-01-01

A radio frequency (RF) antenna for plasma ion sources is formed of a hollow metal conductor tube disposed within a glass tube. The hollow metal tubular conductor has an internal flow channel so that there will be no coolant leakage if the outer glass tube of the antenna breaks. A portion of the RF antenna is formed into a coil; the antenna is used for inductively coupling RF power to a plasma in an ion source chamber. The antenna is made by first inserting the metal tube inside the glass tube, and then forming the glass/metal composite tube into the desired coil shape.

Negatively Charged Hydrogen Production in a Multicusp Microwave Plasma

NASA Astrophysics Data System (ADS)

Trow, John Robert

1985-06-01

High energy neutral beams are necessary for the continued development of magnetically confined fusion plasma devices. Neutral beams based on positive ions are not efficient at beam energies of 100 keV or above, however negative ion based neutral beam systems are efficient, even at high beam energies. Volume production of H('-) has many advantages over the other methods, chiefly: simplicity of design and operation, and no need for alkalai metals. Since volume production requires a low electron temperature ((TURN)1 eV) but also requires molecular intermediates only formed by more energetic electrons (>20 eV), double plasma devices with a separate hot electron region are desirable. Therefore an experiment was undertaken to examine H('-) production by volume processes in a multicusp microwave discharge, part of the cusp field being enhanced to produce an ECR (electron cyclotron resonance), that would also isolate the hotter plasma formed there. This arrangement is analogous to the "magnetic filters" used in some other negative ion sources. This work describes the experiment set up and the results obtained, which are a survey of the behavior of this type of device. Also included is a discussion of the volume processes associated with H('-) production including numerical estimates, based on the experimental measurements, which indicate H('-) production is by dissociative attachment of cold electrons to vibrationally excited hydrogen molecules, and loss is by mutual neutralization with positive ions. The experimental observations are consistent with this model. These are also the same mechanisms used in the models of Bacal and Hiskes. Since magnetic fields generated by samarium cobalt permanent magnets were an important part of this experiment a set of field calculations was undertaken and is included here as a separate chapter. This device is shown to be a viable scheme of H('-) (or D('-)) produc- tion and is worthy of further development. There are several more. quantities which still need to be measured listed in the conclusion, along with suggested improvements. *This work was supported by the Director, Office of Energy Research, Office of Fusion Energy, Development & Technology Division of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

rf power system for thrust measurements of a helicon plasma source.

PubMed

Kieckhafer, Alexander W; Walker, Mitchell L R

2010-07-01

A rf power system has been developed, which allows the use of rf plasma devices in an electric propulsion test facility without excessive noise pollution in thruster diagnostics. Of particular importance are thrust stand measurements, which were previously impossible due to noise. Three major changes were made to the rf power system: first, the cable connection was changed from a balanced transmission line to an unbalanced coaxial line. Second, the rf power cabinet was placed remotely in order to reduce vibration-induced noise in the thrust stand. Finally, a relationship between transmission line length and rf was developed, which allows good transmission of rf power from the matching network to the helicon antenna. The modified system was tested on a thrust measurement stand and showed that rf power has no statistically significant contribution to the thrust stand measurement.

Simultaneous radiofrequency (RF) heating and magnetic resonance (MR) thermal mapping using an intravascular MR imaging/RF heating system.

PubMed

Qiu, Bensheng; El-Sharkawy, Abdel-Monem; Paliwal, Vaishali; Karmarkar, Parag; Gao, Fabao; Atalar, Ergin; Yang, Xiaoming

2005-07-01

Previous studies have confirmed the possibility of using an intravascular MR imaging guidewire (MRIG) as a heating source to enhance vascular gene transfection/expression. This motivated us to develop a new intravascular system that can perform MR imaging, radiofrequncy (RF) heating, and MR temperature monitoring simultaneously in an MR scanner. To validate this concept, a series of mathematical simulations of RF power loss along a 0.032-inch MRIG and RF energy spatial distribution were performed to determine the optimum RF heating frequency. Then, an RF generator/amplifier and a filter box were built. The possibility for simultaneous RF heating and MR thermal mapping of the system was confirmed in vitro using a phantom, and the obtained thermal mapping profile was compared with the simulated RF power distribution. Subsequently, the feasibility of simultaneous RF heating and temperature monitoring was successfully validated in vivo in the aorta of living rabbits. This MR imaging/RF heating system offers a potential tool for intravascular MR-mediated, RF-enhanced vascular gene therapy.

Review of ion energy and angular distributions in capacitively coupled RF plasma reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawamura, E.; Lieberman, M.A.; Birdsall, C.K.

1995-12-31

The authors present a historical review and discussion of previous works on ion energy and angular distributions (IED and IAD) arriving at the target in the collisionless regime. This regime is of great interest to experimentalists and modelers studying the new generation of high density sources in which the sheath is much thinner than in the conventional RIE systems. The purpose of the review is to asses what has been done so far, and to clarify some issues about sheaths in high density systems. Having determined the important parameters, the authors show some particle-in-cell simulation results of a dually excitedmore » capacitively coupled plasma in which the sheath ions roughly see the scaling as in high density sources. The results show that when {tau}{sub ion}/{tau}{sub rf} < 1, the oscillating voltage and width of the rf sheath significantly affect the IEDs, where {tau}{sub ion} is the ion transit-time and {tau}{sub rf} is rf period.« less

Impact of Lateral Straggle on the Analog/RF Performance of Asymmetric Gate Stack Double Gate MOSFET

NASA Astrophysics Data System (ADS)

Sivaram, Gollamudi Sai; Chakraborty, Shramana; Das, Rahul; Dasgupta, Arpan; Kundu, Atanu; Sarkar, Chandan K.

2016-09-01

This paper presents a systematic comparative study of Analog and RF performances of an underlapped double gate (U-DG) NMOSFET with Gate Stack (GS) for varying straggle lengths. Asymmetric underlap devices (A-U-DG) have been proposed as one of the remedies for reducing Short Channel Effects (SCE's) with the underlap being present towards the source for sub 20 nm devices. However, the Source to Drain (S/D) implant lateral diffusion leads to a variation in the effective underlap length. This paper investigates the impact of variation of straggle length on the Analog and RF parameters of the device. The RF performance is analyzed by considering the intrinsic capacitances (Cgd, Cgs), intrinsic resistances (Rgd, Rgs), transport delay (τm), inductance (Lsd), cutoff frequency (fT), and the maximum frequency of oscillations (fmax). The circuit performance of the devices are also studied. It is seen that the Analog and RF performances of the devices are improved by optimizing the S/D lateral straggle.

Beam dynamics studies of a 30 MeV RF linac for neutron production

NASA Astrophysics Data System (ADS)

Nayak, B.; Krishnagopal, S.; Acharya, S.

2018-02-01

Design of a 30 MeV, 10 Amp RF linac as neutron source has been carried out by means of ASTRA simulation code. Here we discuss details of design simulations for three different cases i.e Thermionic , DC and RF photocathode guns and compare them as injectors to a 30 MeV RF linac for n-ToF production. A detailed study on choice of input parameters of the beam from point of view of transmission efficiency and beam quality at the output have been described. We found that thermionic gun isn't suitable for this application. Both DC and RF photocathode gun can be used. RF photocathode gun would be of better performance.

H- Ion Sources for High Intensity Proton Drivers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Rolland Paul; Dudnikov, Vadim

2015-02-20

Existing RF Surface Plasma Sources (SPS) for accelerators have specific efficiencies for H + and H - ion generation around 3 to 5 mA/cm 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- ion production efficiency, reliability and availability for pulsed operation as used in the ORNL Spallation Neutron Source . At low RF power, the efficiency of positive ion generation in the plasma has been improved to 200 mA/cm 2 per kW of RF power at 13.56more » 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- beam without intensity degradation was demonstrated in the aluminum nitride (AlN) discharge chamber for 32 days at high discharge power in an RF SPS with an external antenna. 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. While this project demonstrated the advantages of the pulsed version of the SA RF SPS as an upgrade to the ORNL Spallation Neutron Source, it led to a possibility for upgrades to CW machines like the many cyclotrons used for commercial applications. Four appendices contain important details of the work carried out under this grant.« less

Status and operation of the Linac4 ion source prototypes

NASA Astrophysics Data System (ADS)

Lettry, J.; Aguglia, D.; Andersson, P.; Bertolo, S.; Butterworth, A.; Coutron, Y.; Dallocchio, A.; Chaudet, E.; Gil-Flores, J.; Guida, R.; Hansen, J.; Hatayama, A.; Koszar, I.; Mahner, E.; Mastrostefano, C.; Mathot, S.; Mattei, S.; Midttun, Ø.; Moyret, P.; Nisbet, D.; Nishida, K.; O'Neil, M.; Ohta, M.; Paoluzzi, M.; Pasquino, C.; Pereira, H.; Rochez, J.; Sanchez Alvarez, J.; Sanchez Arias, J.; Scrivens, R.; Shibata, T.; Steyaert, D.; Thaus, N.; Yamamoto, T.

2014-02-01

CERN's Linac4 45 kV H- ion sources prototypes are installed at a dedicated ion source test stand and in the Linac4 tunnel. The operation of the pulsed hydrogen injection, RF sustained plasma, and pulsed high voltages are described. The first experimental results of two prototypes relying on 2 MHz RF-plasma heating are presented. The plasma is ignited via capacitive coupling, and sustained by inductive coupling. The light emitted from the plasma is collected by viewports pointing to the plasma chamber wall in the middle of the RF solenoid and to the plasma chamber axis. Preliminary measurements of optical emission spectroscopy and photometry of the plasma have been performed. The design of a cesiated ion source is presented. The volume source has produced a 45 keV H- beam of 16-22 mA which has successfully been used for the commissioning of the Low Energy Beam Transport (LEBT), Radio Frequency Quadrupole (RFQ) accelerator, and chopper of Linac4.

Source-to-accelerator quadrupole matching section for a compact linear accelerator

NASA Astrophysics Data System (ADS)

Seidl, P. A.; Persaud, A.; Ghiorso, W.; Ji, Q.; Waldron, W. L.; Lal, A.; Vinayakumar, K. B.; Schenkel, T.

2018-05-01

Recently, we presented a new approach for a compact radio-frequency (RF) accelerator structure and demonstrated the functionality of the individual components: acceleration units and focusing elements. In this paper, we combine these units to form a working accelerator structure: a matching section between the ion source extraction grids and the RF-acceleration unit and electrostatic focusing quadrupoles between successive acceleration units. The matching section consists of six electrostatic quadrupoles (ESQs) fabricated using 3D-printing techniques. The matching section enables us to capture more beam current and to match the beam envelope to conditions for stable transport in an acceleration lattice. We present data from an integrated accelerator consisting of the source, matching section, and an ESQ doublet sandwiched between two RF-acceleration units.

A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements

NASA Astrophysics Data System (ADS)

Hlondo, L. R.; Lalremruata, B.; Punte, L. R. M.; Rebecca, L.; Lalnunthari, J.; Thanga, H. H.

2016-04-01

Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power are studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.

A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hlondo, L. R.; Lalremruata, B.; Punte, L. R. M.

Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power aremore » studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.« less

A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements.

PubMed

Hlondo, L R; Lalremruata, B; Punte, L R M; Rebecca, L; Lalnunthari, J; Thanga, H H

2016-04-01

Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power are studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.

rf power system for thrust measurements of a helicon plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kieckhafer, Alexander W.; Walker, Mitchell L. R.

2010-07-15

A rf power system has been developed, which allows the use of rf plasma devices in an electric propulsion test facility without excessive noise pollution in thruster diagnostics. Of particular importance are thrust stand measurements, which were previously impossible due to noise. Three major changes were made to the rf power system: first, the cable connection was changed from a balanced transmission line to an unbalanced coaxial line. Second, the rf power cabinet was placed remotely in order to reduce vibration-induced noise in the thrust stand. Finally, a relationship between transmission line length and rf was developed, which allows goodmore » transmission of rf power from the matching network to the helicon antenna. The modified system was tested on a thrust measurement stand and showed that rf power has no statistically significant contribution to the thrust stand measurement.« less

Alternative modeling methods for plasma-based Rf ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veitzer, Seth A., E-mail: veitzer@txcorp.com; Kundrapu, Madhusudhan, E-mail: madhusnk@txcorp.com; Stoltz, Peter H., E-mail: phstoltz@txcorp.com

Rf-driven ion sources for accelerators and many industrial applications benefit from detailed numerical modeling and simulation of plasma characteristics. For instance, modeling of the Spallation Neutron Source (SNS) internal antenna H{sup −} source has indicated that a large plasma velocity is induced near bends in the antenna where structural failures are often observed. This could lead to improved designs and ion source performance based on simulation and modeling. However, there are significant separations of time and spatial scales inherent to Rf-driven plasma ion sources, which makes it difficult to model ion sources with explicit, kinetic Particle-In-Cell (PIC) simulation codes. Inmore » particular, if both electron and ion motions are to be explicitly modeled, then the simulation time step must be very small, and total simulation times must be large enough to capture the evolution of the plasma ions, as well as extending over many Rf periods. Additional physics processes such as plasma chemistry and surface effects such as secondary electron emission increase the computational requirements in such a way that even fully parallel explicit PIC models cannot be used. One alternative method is to develop fluid-based codes coupled with electromagnetics in order to model ion sources. Time-domain fluid models can simulate plasma evolution, plasma chemistry, and surface physics models with reasonable computational resources by not explicitly resolving electron motions, which thereby leads to an increase in the time step. This is achieved by solving fluid motions coupled with electromagnetics using reduced-physics models, such as single-temperature magnetohydrodynamics (MHD), extended, gas dynamic, and Hall MHD, and two-fluid MHD models. We show recent results on modeling the internal antenna H{sup −} ion source for the SNS at Oak Ridge National Laboratory using the fluid plasma modeling code USim. We compare demonstrate plasma temperature equilibration in two-temperature MHD models for the SNS source and present simulation results demonstrating plasma evolution over many Rf periods for different plasma temperatures. We perform the calculations in parallel, on unstructured meshes, using finite-volume solvers in order to obtain results in reasonable time.« less

Alternative modeling methods for plasma-based Rf ion sources.

PubMed

Veitzer, Seth A; Kundrapu, Madhusudhan; Stoltz, Peter H; Beckwith, Kristian R C

2016-02-01

Rf-driven ion sources for accelerators and many industrial applications benefit from detailed numerical modeling and simulation of plasma characteristics. For instance, modeling of the Spallation Neutron Source (SNS) internal antenna H(-) source has indicated that a large plasma velocity is induced near bends in the antenna where structural failures are often observed. This could lead to improved designs and ion source performance based on simulation and modeling. However, there are significant separations of time and spatial scales inherent to Rf-driven plasma ion sources, which makes it difficult to model ion sources with explicit, kinetic Particle-In-Cell (PIC) simulation codes. In particular, if both electron and ion motions are to be explicitly modeled, then the simulation time step must be very small, and total simulation times must be large enough to capture the evolution of the plasma ions, as well as extending over many Rf periods. Additional physics processes such as plasma chemistry and surface effects such as secondary electron emission increase the computational requirements in such a way that even fully parallel explicit PIC models cannot be used. One alternative method is to develop fluid-based codes coupled with electromagnetics in order to model ion sources. Time-domain fluid models can simulate plasma evolution, plasma chemistry, and surface physics models with reasonable computational resources by not explicitly resolving electron motions, which thereby leads to an increase in the time step. This is achieved by solving fluid motions coupled with electromagnetics using reduced-physics models, such as single-temperature magnetohydrodynamics (MHD), extended, gas dynamic, and Hall MHD, and two-fluid MHD models. We show recent results on modeling the internal antenna H(-) ion source for the SNS at Oak Ridge National Laboratory using the fluid plasma modeling code USim. We compare demonstrate plasma temperature equilibration in two-temperature MHD models for the SNS source and present simulation results demonstrating plasma evolution over many Rf periods for different plasma temperatures. We perform the calculations in parallel, on unstructured meshes, using finite-volume solvers in order to obtain results in reasonable time.

Digital processing of RF signals from optical frequency combs

NASA Astrophysics Data System (ADS)

Cizek, Martin; Smid, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Cip, Ondřej

2013-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Secondly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique used for assessing the offset and repetition frequencies of the comb, resulting in digital servo-loop stabilization of the fs comb. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset frequency of the fs comb.

Interleaving lattice for the Argonne Advanced Photon Source linac

NASA Astrophysics Data System (ADS)

Shin, S.; Sun, Y.; Dooling, J.; Borland, M.; Zholents, A.

2018-06-01

To realize and test advanced accelerator concepts and hardware, a beam line is being reconfigured in the linac extension area (LEA) of the Argonne Advanced Photon Source (APS) linac. A photocathode rf gun installed at the beginning of the APS linac will provide a low emittance electron beam into the LEA beam line. The thermionic rf gun beam for the APS storage ring and the photocathode rf gun beam for the LEA beam line will be accelerated through the linac in an interleaved fashion. In this paper, the design studies for interleaving lattice realization in the APS linac is described with the initial experiment result.

Spherical neutron generator

DOEpatents

Leung, Ka-Ngo

2006-11-21

A spherical neutron generator is formed with a small spherical target and a spherical shell RF-driven plasma ion source surrounding the target. A deuterium (or deuterium and tritium) ion plasma is produced by RF excitation in the plasma ion source using an RF antenna. The plasma generation region is a spherical shell between an outer chamber and an inner extraction electrode. A spherical neutron generating target is at the center of the chamber and is biased negatively with respect to the extraction electrode which contains many holes. Ions passing through the holes in the extraction electrode are focused onto the target which produces neutrons by D-D or D-T reactions.

Experimental benchmark of the NINJA code for application to the Linac4 H- ion source plasma

NASA Astrophysics Data System (ADS)

Briefi, S.; Mattei, S.; Rauner, D.; Lettry, J.; Tran, M. Q.; Fantz, U.

2017-10-01

For a dedicated performance optimization of negative hydrogen ion sources applied at particle accelerators, a detailed assessment of the plasma processes is required. Due to the compact design of these sources, diagnostic access is typically limited to optical emission spectroscopy yielding only line-of-sight integrated results. In order to allow for a spatially resolved investigation, the electromagnetic particle-in-cell Monte Carlo collision code NINJA has been developed for the Linac4 ion source at CERN. This code considers the RF field generated by the ICP coil as well as the external static magnetic fields and calculates self-consistently the resulting discharge properties. NINJA is benchmarked at the diagnostically well accessible lab experiment CHARLIE (Concept studies for Helicon Assisted RF Low pressure Ion sourcEs) at varying RF power and gas pressure. A good general agreement is observed between experiment and simulation although the simulated electron density trends for varying pressure and power as well as the absolute electron temperature values deviate slightly from the measured ones. This can be explained by the assumption of strong inductive coupling in NINJA, whereas the CHARLIE discharges show the characteristics of loosely coupled plasmas. For the Linac4 plasma, this assumption is valid. Accordingly, both the absolute values of the accessible plasma parameters and their trends for varying RF power agree well in measurement and simulation. At varying RF power, the H- current extracted from the Linac4 source peaks at 40 kW. For volume operation, this is perfectly reflected by assessing the processes in front of the extraction aperture based on the simulation results where the highest H- density is obtained for the same power level. In surface operation, the production of negative hydrogen ions at the converter surface can only be considered by specialized beam formation codes, which require plasma parameters as input. It has been demonstrated that this input can be provided reliably by the NINJA code.

Ion funnel device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ibrahim, Yehia M.; Chen, Tsung-Chi; Harrer, Marques B.

2017-11-21

An ion funnel device is disclosed. A first pair of electrodes is positioned in a first direction. A second pair of electrodes is positioned in a second direction. The device includes an RF voltage source and a DC voltage source. A RF voltage with a superimposed DC voltage gradient is applied to the first pair of electrodes, and a DC voltage gradient is applied to the second pair of electrodes.

Radiofrequency and microwave energy sources in surgical ablation of atrial fibrillation: a comparative analysis.

PubMed

Topkara, Veli K; Williams, Mathew R; Barili, Fabio; Bastos, Renata; Liu, Judy F; Liberman, Elyse A; Russo, Mark J; Oz, Mehmet C; Argenziano, Michael

2006-01-01

Due to its complexity and risk of bleeding, the Maze III procedure has been largely replaced by surgical ablation for atrial fibrillation (AF) using alternative energy sources. Radiofrequency (RF) and microwave (MW) are the most commonly used energy forms. In this study, we sought to compare these energy modalities in terms of clinical outcomes. Two hundred five patients underwent surgical ablation of AF, from October 1999 to May 2004 at our institution via an endocardial approach. Patients were categorized into 2 groups: RF and MW. Baseline characteristics, operative details, and clinical outcomes were compared between the 2 groups. Rhythm success was defined as freedom from AF and atrial flutter as determined by postoperative electrocardiograms. One hundred twenty patients (58.5%) were ablated using RF, whereas 85 (41.5%) were ablated with MW. Most of the patients had persistent AF in both the RF and MW groups (85.7% versus 80.0%, respectively; P = .363). Intraoperative left atrial size was 6.4 +/- 1.7 cm for the RF group and 6.4 +/- 1.7 cm for the MW group (P = .820). Postoperative rhythm success at 6 and 12 months was 72.4% versus 71.4% (P +/- .611) and 75.0% versus 66.7% (P = .909) for the RF and MW groups, respectively. Hospital length of stay was comparable for both groups (15.4 +/- 14.0 versus 13.3 +/- 13.9 days; P = .307). Postoperative survival at 6 months, 1 year, and 3 years was 90.4%, 89.5%, and 86.1% for RF patients compared to 87.9%, 86.5%, and 84.4% for MW patients, respectively (log rank P = .490). RF and MW energy forms yield comparable postoperative rhythm success, hospital length of stay, and postoperative survival. Both sources are rapid, safe, and effective alternatives to "cut and sew" techniques for surgical treatment of AF.

Ultra-High Accelerating Gradients in Radio-Frequency Cryogenic Copper Structures

NASA Astrophysics Data System (ADS)

Cahill, Alexander David

Normal conducting radio-frequency (rf) particle accelerators have many applications, including colliders for high energy physics, high-intensity synchrotron light sources, non-destructive testing for security, and medical radiation therapy. In these applications, the accelerating gradient is an important parameter. Specifically for high energy physics, increasing the accelerating gradient extends the potential energy reach and is viewed as a way to mitigate their considerable cost. Furthermore, a gradient increase will enable for more compact and thus accessible free electron lasers (FELs). The major factor limiting larger accelerating gradients is vacuum rf breakdown. Basic physics of this phenomenon has been extensively studied over the last few decades. During which, the occurrence of rf breakdowns was shown to be probabilistic, and can be characterized by a breakdown rate. The current consensus is that vacuum rf breakdowns are caused by movements of crystal defects induced by periodic mechanical stress. The stress may be caused by pulsed surface heating and large electric fields. A compelling piece of evidence that supports this hypothesis is that accelerating structures constructed from harder materials exhibit larger accelerating gradients for similar breakdown rates. One possible method to increase sustained electric fields in copper cavities is to cool them to temperatures below 77 K, where the rf surface resistance and coefficient of thermal expansion decrease, while the yield strength (which correlates with hardness) and thermal conductivity increase. These changes in material properties at low temperature increases metal hardness and decreases the mechanical stress from exposure to rf electromagnetic fields. To test the validity of the improvement in breakdown rate, experiments were conducted with cryogenic accelerating cavities in the Accelerator Structure Test Area (ASTA) at SLAC National Accelerator Laboratory. A short 11.4 GHz standing wave accelerating structure was conditioned to an accelerating gradient of 250 MV/m at 45 K with 108 rf pulses. At gradients greater than 150 MV/m I observed a degradation in the intrinsic quality factor of the cavity, Q0. I developed a model for the change in Q0 using measured field emission currents and rf signals. I found that the Q 0 degradation is consistent with the rf power being absorbed by strong field emission currents accelerated inside the cavity. I measured rf breakdown rates for 45 K and found 2*10-4/pulse/meter when accounting for any change in Q0. These are the largest accelerating gradients for a structure with similar breakdown rates. The final chapter presents the design of an rf photoinjector electron source that uses the cryogenic normal conducting accelerator technology: the TOPGUN. With this cryogenic rf photoinjector, the beam brightness will increase by over an order of a magnitude when compared to the current photoinjector for the Linac Coherent Light Source (LCLS). When using the TOPGUN as the source for an X-ray Free Electron Laser, the higher brightness would allow for a decrease in the required length of the LCLS undulator by more than a factor of two.

The resonant radio-frequency magnetic probe tuned by coaxial cable.

PubMed

Sun, B; Huo, W G; Ding, Z F

2012-08-01

In this paper, the resonant rf magnetic probe is upgraded by replacing the rotary capacitor in the old version with the series-connected coaxial cable. The numerical calculation and the measurement with the prototype probe show that the rf magnetic probe can achieve resonance at a middle length of the series-connected coaxial cable. The good electrical symmetry of the new rf magnetic probe is ensured by both the identity of series-connected coaxial cables and the new structure of the primary winding. Practical measurements conduced on an rf inductively coupled plasma source demonstrate that performances of the new rf magnetic probe are good.

A large-area RF source for negative hydrogen ions

NASA Astrophysics Data System (ADS)

Frank, P.; Feist, J. H.; Kraus, W.; Speth, E.; Heinemann, B.; Probst, F.; Trainham, R.; Jacquot, C.

1998-08-01

In a collaboration with CEA Cadarache, IPP is presently developing an rf source, in which the production of negative ions (H-/D-) is being investigated. It utilizes PINI-size rf sources with an external antenna and for the first step a small size extraction system with 48 cm2 net extraction area. First results from BATMAN (Ba¯varian T_est Ma¯chine for N_egative Ions) show (without Cs) a linear dependence of the negative ion yield with rf power, without any sign of saturation. At elevated pressure (1.6 Pa) a current density of 4.5 mA/cm2 H- (without Cs) has been found so far. At medium pressure (0.6 Pa) the current density is lower by approx. a factor of 5, but preliminary results with Cesium injection show a relative increase by almost the same factor in this pressure range. Langmuir probe measurements indicate an electron temperature Te>2 eV close to the plasma grid with a moderate magnetic filter (700 Gcm). Attempts to improve the performance by using different magnetic configurations and different wall materials are under way.

Submillimeter-Wave Phasor Beam-Pattern Measurement Based on Two-Stage Heterodyne Mixing With Unitary Harmonic Difference

NASA Astrophysics Data System (ADS)

Hwang, Yuh-Jing; Rao, Ramprasad; Christensen, Rob; Chen, Ming-Tang; Chu, Tah-Hsiung

2007-06-01

A near-field phasor beam measurement system is developed for the characterization of heterodyne receiver optics at submillimeter-wave frequencies. The system synthesizes a pair of submillimeter-wave signals as the RF and local oscillator (LO) sources from common reference sources. The synthesized harmonic numbers of the RF and LO sources are arranged with difference by one, which makes this a new configuration with a unitary harmonic difference. The coherent RF and LO signal are down-converted by the receiver under test, then mixed with the microwave-frequency common reference signal to generate the second-order IF signal around 100 MHz for amplitude and phase comparison. The amplitude and phase fluctuation of the measurement system at 683 GHz is within +-0.2 dB and +-4deg in a 1-h period, respectively. The system dynamic range at 683 and 250 GHz can be as high as 43 and 47 dB, respectively. The system is then used to measure the receiver beam patterns at 683 and 250 GHz with different RF transmitting probe antennas.

Update on developments at SNIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zacks, J., E-mail: jamie.zacks@ccfe.ac.uk; Turner, I.; Day, I.

The Small Negative Ion Facility (SNIF) at CCFE has been undergoing continuous development and enhancement to both improve operational reliability and increase diagnostic capability. SNIF uses a CW 13.56MHz, 5kW RF driven volume source with a 30kV triode accelerator. Improvement and characterisation work includes: Installation of a new “L” type RF matching unit, used to calculate the load on the RF generator. Use of the electron suppressing biased insert as a Langmuir probe under different beam extraction conditions. Measurement of the hydrogen Fulcher molecular spectrum, used to calculate gas temperature in the source. Beam optimisation through parameter scans, using coppermore » target plate and visible cameras, with results compared with AXCEL-INP to provide beam current estimate. Modelling of the beam power density profile on the target plate using ANSYS to estimate beam power and provide another estimate of beam current. This work is described, and has allowed an estimation of the extracted beam current of approximately 6mA (4mA/cm2) at 3.5kW RF power and a source pressure of 0.6Pa.« less

X-Band RF Gun Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlieks, Arnold; Dolgashev, Valery; Tantawi, Sami

In support of the MEGa-ray program at LLNL and the High Gradient research program at SLAC, a new X-band multi-cell RF gun is being developed. This gun, similar to earlier guns developed at SLAC for Compton X-ray source program, will be a standing wave structure made of 5.5 cells operating in the pi mode with copper cathode. This gun was designed following criteria used to build SLAC X-band high gradient accelerating structures. It is anticipated that this gun will operate with surface electric fields on the cathode of 200 MeV/m with low breakdown rate. RF will be coupled into themore » structure through a final cell with symmetric duel feeds and with a shape optimized to minimize quadrupole field components. In addition, geometry changes to the original gun, operated with Compton X-ray source, will include a wider RF mode separation, reduced surface electric and magnetic fields.« less

Commissioning and Early Operation Experience of the NSLS-II Storage Ring RF System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, F.; Rose, J.; Cupolo, J.

2015-05-03

The National Synchrotron Light Source II (NSLS-II) is a 3 GeV electron X-ray user facility commissioned in 2014. The storage ring RF system, essential for replenishing energy loss per turn of the electrons, consists of digital low level RF controllers, 310 kW CW klystron transmitters, CESR-B type superconducting cavities, as well as a supporting cryogenic system. Here we will report on RF commissioning and early operation experience of the system for beam current up to 200mA.

Matching network for RF plasma source

DOEpatents

Pickard, Daniel S.; Leung, Ka-Ngo

2007-11-20

A compact matching network couples an RF power supply to an RF antenna in a plasma generator. The simple and compact impedance matching network matches the plasma load to the impedance of a coaxial transmission line and the output impedance of an RF amplifier at radio frequencies. The matching network is formed of a resonantly tuned circuit formed of a variable capacitor and an inductor in a series resonance configuration, and a ferrite core transformer coupled to the resonantly tuned circuit. This matching network is compact enough to fit in existing compact focused ion beam systems.

Study of RF breakdown and multipacting in accelerator components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pande, Manjiri; Singh, P., E-mail: manjiri@barc.gov.in, E-mail: psingh@barc.gov.in

2014-07-01

Radio frequency (RF) structures that are part of accelerators and energy sources, operate with sinusoidally varying electromagnetic fields under high RF energy. Here, RF breakdown and multipacting take place in RF structures and limit their performance. Electron field emission processes in a RF structure are precursors for breakdown processes. RF breakdown is a major phenomena affecting and causing the irreversible damage to RF structures. Breakdown rate and the damage induced by the breakdowns are its important properties. The damage is related to power absorbed during breakdown, while the breakdown rate is determined by the amplitudes of surface electric and magneticmore » fields, geometry, metal surface preparation and conditioning history. It limits working power and produces irreversible surface damage. The breakdown limit depends on the RF circuit, structure geometry, RF frequency, input RF power, pulse width, materials used, surface processing technique and surface electric and magnetic fields. Multipactor (MP) is a low power, electron multiplication based resonance breakdown phenomenon in vacuum and is often observed in RF structures. A multipactor discharge is undesirable, as it can create a reactive component that detunes the resonant cavities and components, generates noise in communication system and induces gas desorption from the conductor surfaces. In RF structures, certain conditions are required to generate multipacting. (author)« less

RF Negative Ion Source Development at IPP Garching

NASA Astrophysics Data System (ADS)

Kraus, W.; McNeely, P.; Berger, M.; Christ-Koch, S.; Falter, H. D.; Fantz, U.; Franzen, P.; Fröschle, M.; Heinemann, B.; Leyer, S.; Riedl, R.; Speth, E.; Wünderlich, D.

2007-08-01

IPP Garching is heavily involved in the development of an ion source for Neutral Beam Heating of the ITER Tokamak. RF driven ion sources have been successfully developed and are in operation on the ASDEX-Upgrade Tokamak for positive ion based NBH by the NB Heating group at IPP Garching. Building on this experience a RF driven H- ion source has been under development at IPP Garching as an alternative to the ITER reference design ion source. The number of test beds devoted to source development for ITER has increased from one (BATMAN) by the addition of two test beds (MANITU, RADI). This paper contains descriptions of the three test beds. Results on diagnostic development using laser photodetachment and cavity ringdown spectroscopy are given for BATMAN. The latest results for long pulse development on MANITU are presented including the to date longest pulse (600 s). As well, details of source modifications necessitated for pulses in excess of 100 s are given. The newest test bed RADI is still being commissioned and only technical details of the test bed are included in this paper. The final topic of the paper is an investigation into the effects of biasing the plasma grid.

4th Generation ECR Ion Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lyneis, Claude M.; Leitner, D.; Todd, D.S.

2008-12-01

The concepts and technical challenges related to developing a 4th generation ECR ion source with an RF frequency greater than 40 GHz and magnetic confinement fields greater than twice Becr will be explored in this paper. Based on the semi-empirical frequency scaling of ECR plasma density with the square of operating frequency, there should be significant gains in performance over current 3rd generation ECR ion sources, which operate at RF frequencies between 20 and 30 GHz. While the 3rd generation ECR ion sources use NbTi superconducting solenoid and sextupole coils, the new sources will need to use different superconducting materialsmore » such as Nb3Sn to reach the required magnetic confinement, which scales linearly with RF frequency. Additional technical challenges include increased bremsstrahlung production, which may increase faster than the plasma density, bremsstrahlung heating of the cold mass and the availability of high power continuous wave microwave sources at these frequencies. With each generation of ECR ion sources, there are new challenges to be mastered, but the potential for higher performance and reduced cost of the associated accelerator continue to make this a promising avenue for development.« less

Diagnostic study of multiple double layer formation in expanding RF plasma

NASA Astrophysics Data System (ADS)

Chakraborty, Shamik; Paul, Manash Kumar; Roy, Jitendra Nath; Nath, Aparna

2018-03-01

Intensely luminous double layers develop and then expand in size in a visibly glowing RF discharge produced using a plasma source consisting of a semi-transparent cylindrical mesh with a central electrode, in a linear plasma chamber. Although RF discharge is known to be independent of device geometry in the absence of magnetic field, the initiation of RF discharge using such a plasma source results in electron drift and further expansion of the plasma in the vessel. The dynamics of complex plasma structures are studied through electric probe diagnostics in the expanding RF plasma. The measurements made to study the parametric dependence of evolution of double layer structures are analyzed and presented here. The plasma parameter measurements suggest that the complex potential structures initially form with low potential difference between the layers and then gradually expand producing burst oscillations. The present study provides interesting information about the stability of plasma sheath and charge particle dynamics in it that are important to understand the underlying basic sheath physics along with applications in plasma acceleration and propulsion.

Sources of Emittance in RF Photocathode Injectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowell, David

2016-12-11

Advances in electron beam technology have been central to creating the current generation of x-ray free electron lasers and ultra-fast electron microscopes. These once exotic devices have become essential tools for basic research and applied science. One important beam technology for both is the electron source which, for many of these instruments, is the photocathode RF gun. The invention of the photocathode gun and the concepts of emittance compensation and beam matching in the presence of space charge and RF forces have made these high-quality beams possible. Achieving even brighter beams requires a taking a finer resolution view of themore » electron dynamics near the cathode during photoemission and the initial acceleration of the beam. In addition, the high brightness beam is more sensitive to degradation by the optical aberrations of the gun’s RF and magnetic lenses. This paper discusses these topics including the beam properties due to fundamental photoemission physics, space charge effects close to the cathode, and optical distortions introduced by the RF and solenoid fields. Analytic relations for these phenomena are derived and compared with numerical simulations.« less

Development of a plasma generator for a long pulse ion source for neutral beam injectors.

PubMed

Watanabe, K; Dairaku, M; Tobari, H; Kashiwagi, M; Inoue, T; Hanada, M; Jeong, S H; Chang, D H; Kim, T S; Kim, B R; Seo, C S; Jin, J T; Lee, K W; In, S R; Oh, B H; Kim, J; Bae, Y S

2011-06-01

A plasma generator for a long pulse H(+)/D(+) ion source has been developed. The plasma generator was designed to produce 65 A H(+)/D(+) beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and ±7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm(2). © 2011 American Institute of Physics

RF absorption and ion heating in helicon sources.

PubMed

Kline, J L; Scime, E E; Boivin, R F; Keesee, A M; Sun, X; Mikhailenko, V S

2002-05-13

Experimental data are presented that are consistent with the hypothesis that anomalous rf absorption in helicon sources is due to electron scattering arising from parametrically driven ion-acoustic waves downstream from the antenna. Also presented are ion temperature measurements demonstrating anisotropic heating (T( perpendicular)>T(parallel)) at the edge of the discharge. The most likely explanation is ion-Landau damping of electrostatic slow waves at a local lower-hybrid-frequency resonance.

Charge plasma based source/drain engineered Schottky Barrier MOSFET: Ambipolar suppression and improvement of the RF performance

NASA Astrophysics Data System (ADS)

Kale, Sumit; Kondekar, Pravin N.

2018-01-01

This paper reports a novel device structure for charge plasma based Schottky Barrier (SB) MOSFET on ultrathin SOI to suppress the ambipolar leakage current and improvement of the radio frequency (RF) performance. In the proposed device, we employ dual material for the source and drain formation. Therefore, source/drain is divided into two parts as main source/drain and source/drain extension. Erbium silicide (ErSi1.7) is used as main source/drain material and Hafnium metal is used as source/drain extension material. The source extension induces the electron plasma in the ultrathin SOI body resulting reduction of SB width at the source side. Similarly, drain extension also induces the electron plasma at the drain side. This significantly increases the SB width due to increased depletion at the drain end. As a result, the ambipolar leakage current can be suppressed. In addition, drain extension also reduces the parasitic capacitances of the proposed device to improve the RF performance. The optimization of length and work function of metal used in the drain extension is performed to achieve improvement in device performance. Moreover, the proposed device makes fabrication simpler, requires low thermal budget and free from random dopant fluctuations.

Studies and optimization of Pohang Light Source-II superconducting radio frequency system at stable top-up operation with beam current of 400 mA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joo, Youngdo, E-mail: Ydjoo77@postech.ac.kr; Yu, Inha; Park, Insoo

After three years of upgrading work, the Pohang Light Source-II (PLS-II) is now successfully operating. The final quantitative goal of PLS-II is a top-up user-service operation with beam current of 400 mA to be completed by the end of 2014. During the beam store test up to 400 mA in the storage ring (SR), it was observed that the vacuum pressure around the radio frequency (RF) window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. Although available beam current is enhanced by setting a higher RF accelerating voltage, it is bettermore » to keep the RF accelerating voltage as low as possible in the long time top-up operation. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. In our simulation, an equivalent physical modeling was developed using a finite-difference time-domain code. The simulation revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window, which comes with the rapid increase of window vacuum pressure. The RF accelerating voltage of PLS-II RF system was set to 4.95 MV, which was estimated using the maximum available beam current that works as a function of RF voltage, and the top-up operation test with the beam current of 400 mA was successfully carried out.« less

Outdoor radiofrequency radiation levels in the West Bank-Palestine.

PubMed

Lahham, Adnan; Hammash, Alaa

2012-05-01

This work presents the results of exposure levels to radio frequency (RF) emission from different sources in the environment of the West Bank-Palestine. These RF emitters include FM and TV broadcasting stations and mobile phone base stations. Power densities were measured at 65 locations distributed over the West Bank area. These locations include mainly centres of the major cities. Also a 24 h activity level was investigated for a mobile phone base station to determine the maximum activity level for this kind of RF emitters. All measurements were conducted at a height of 1.7 m above ground level using hand held Narda SRM 3000 spectrum analyzer with isotropic antenna capable of collecting RF signals in the frequency band from 75 MHz to 3 GHz. The average value of power density resulted from FM radio broadcasting in all investigated locations was 0.148 μW cm(-2), from TV broadcasting was 0.007 μW cm(-2) and from mobile phone base station was 0.089 μW cm(-2). The maximum total exposure evaluated at any location was 3.86 μW cm(-2). The corresponding exposure quotient calculated for this site was 0.02. This value is well below unity indicating compliance with the International Commission on non-ionising Radiation protection guidelines. Contributions from all relevant RF sources to the total exposure were evaluated and found to be ~62 % from FM radio, 3 % for TV broadcasting and 35 % from mobile phone base stations. The average total exposure from all investigated RF sources was 0.37 μW cm(-2).

RF signal detection by a tunable optoelectronic oscillator based on a PS-FBG.

PubMed

Shao, Yuchen; Han, Xiuyou; Li, Ming; Zhao, Mingshan

2018-03-15

Low-power radio frequency (RF) signal detection is highly desirable for many applications, ranging from wireless communication to radar systems. A tunable optoelectronic oscillator (OEO) based on a phase-shifted fiber Bragg grating for detecting low-power RF signals is proposed and experimentally demonstrated. When the frequency of the input RF signal is matched with the potential oscillation mode of the OEO, it is detected and amplified. The frequency of the RF signal under detection can be estimated simultaneously by scanning the wavelength of the laser source. The RF signals from 1.5 to 5 GHz as low as -91  dBm are detected with a gain of about 10 dB, and the frequency is estimated with an error of ±100  MHz. The performance of the OEO system for detecting an RF signal with different modulation rates is also investigated.

Assessment of general public exposure to LTE and RF sources present in an urban environment.

PubMed

Joseph, Wout; Verloock, Leen; Goeminne, Francis; Vermeeren, Günter; Martens, Luc

2010-10-01

For the first time, in situ electromagnetic field exposure of the general public to fields from long term evolution (LTE) cellular base stations is assessed. Exposure contributions due to different radiofrequency (RF) sources are compared with LTE exposure at 30 locations in Stockholm, Sweden. Total exposures (0.2-2.6 V/m) satisfy the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference levels (from 28 V/m for frequency modulation (FM), up to 61 V/m for LTE) at all locations. LTE exposure levels up to 0.8 V/m were measured, and the average contribution of the LTE signal to the total RF exposure equals 4%.

Free electron lasers for 13nm EUV lithography: RF design strategies to minimise investment and operational costs

NASA Astrophysics Data System (ADS)

Keens, Simon; Rossa, Bernhard; Frei, Marcel

2016-03-01

As the semiconductor industry proceeds to develop ever better sources of extreme ultraviolet (EUV) light for photolithography applications, two distinct technologies have come to prominence: Tin-plasma and free electron laser (FEL) sources. Tin plasma sources have been in development within the industry for many years, and have been widely reported. Meanwhile, FELs represent the most promising alternative to create high power EUV frequencies and, while tin-plasma source development has been ongoing, such lasers have been continuously developed by academic institutions for use in fundamental research programmes in conjunction with universities and national scientific institutions. This paper follows developments in the field of academic FELs, and presents information regarding novel technologies, specifically in the area of RF design strategy, that may be incorporated into future industrial FEL systems for EUV lithography in order to minimize the necessary investment and operational costs. It goes on to try to assess the cost-benefit of an alternate RF design strategy, based upon previous studies.

First experiments with the negative ion source NIO1.

PubMed

Cavenago, M; Serianni, G; De Muri, M; Agostinetti, P; Antoni, V; Baltador, C; Barbisan, M; Baseggio, L; Bigi, M; Cervaro, V; Degli Agostini, F; Fagotti, E; Kulevoy, T; Ippolito, N; Laterza, B; Minarello, A; Maniero, M; Pasqualotto, R; Petrenko, S; Poggi, M; Ravarotto, D; Recchia, M; Sartori, E; Sattin, M; Sonato, P; Taccogna, F; Variale, V; Veltri, P; Zaniol, B; Zanotto, L; Zucchetti, S

2016-02-01

Neutral Beam Injectors (NBIs), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact radio frequency (rf) ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H(-) current of 130 mA, 60 kV acceleration voltage, was installed at Consorzio RFX, including a high voltage deck and an X-ray shield, to provide a test bench for source optimizations for activities in support to the ITER NBI test facility. NIO1 status and plasma experiments both with air and with hydrogen as filling gas are described. Transition from a weak plasma to an inductively coupled plasma is clearly evident for the former gas and may be triggered by rising the rf power (over 0.5 kW) at low pressure (equal or below 2 Pa). Transition in hydrogen plasma requires more rf power (over 1.5 kW).

Self-induced steady-state magnetic field in the negative ion sources with localized rf power deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shivarova, A.; Todorov, D., E-mail: dimitar-tdrv@phys.uni-sofia-bg; Lishev, St.

2016-02-15

The study is in the scope of a recent activity on modeling of SPIDER (Source for Production of Ions of Deuterium Extracted from RF plasma) which is under development regarding the neutral beam injection heating system of ITER. The regime of non-ambipolarity in the source, established before, is completed here by introducing in the model the steady state magnetic field, self-induced in the discharge due to the dc current flowing in it. Strong changes in the discharge structure are reported.

RF to millimeter wave integration and module technologies

NASA Astrophysics Data System (ADS)

Vähä-Heikkilä, T.

2015-04-01

Radio Frequency (RF) consumer applications have boosted silicon integrated circuits (IC) and corresponding technologies. More and more functions are integrated to ICs and their performance is also increasing. However, RF front-end modules with filters and switches as well as antennas still need other way of integration. This paper focuses to RF front-end module and antenna developments as well as to the integration of millimeter wave radios. VTT Technical Research Centre of Finland has developed both Low Temperature Co-fired Ceramics (LTCC) and Integrated Passive Devices (IPD) integration platforms for RF and millimeter wave integrated modules. In addition to in-house technologies, VTT is using module and component technologies from other commercial sources.

Design and Calibration of an RF Actuator for Low-Level RF Systems

NASA Astrophysics Data System (ADS)

Geng, Zheqiao; Hong, Bo

2016-02-01

X-ray free electron laser (FEL) machines like the Linac Coherent Light Source (LCLS) at SLAC require high-quality electron beams to generate X-ray lasers for various experiments. Digital low-level RF (LLRF) systems are widely used to control the high-power RF klystrons to provide a highly stable RF field in accelerator structures for beam acceleration. Feedback and feedforward controllers are implemented in LLRF systems to stabilize or adjust the phase and amplitude of the RF field. To achieve the RF stability and the accuracy of the phase and amplitude adjustment, low-noise and highly linear RF actuators are required. Aiming for the upgrade of the S-band Linac at SLAC, an RF actuator is designed with an I/Qmodulator driven by two digital-to-analog converters (DAC) for the digital LLRF systems. A direct upconversion scheme is selected for RF actuation, and an on-line calibration algorithm is developed to compensate the RF reference leakage and the imbalance errors in the I/Q modulator, which may cause significant phase and amplitude actuation errors. This paper presents the requirements on the RF actuator, the design of the hardware, the calibration algorithm, and the implementation in firmware and software and the test results at LCLS.

Radio-Frequency Down-Conversion via Sampled Analog Optical Links

DTIC Science & Technology

2010-08-09

temporal intensity Popt(ω) includes intensity noise quantities arising from the optical source (e.g. laser intensity noise, amplified spontaneous emission...nm distributed feedback laser RF Down-Conversion via Sampled Links 5 (DFB, EM4, Inc.) the output of which is modulated via a low-biased Mach-Zehnder...Figure 5 (a). For comparison purposes the RF gain of one arm of the balanced link (utilizing a continuous- wave laser source) is measured and

The study of helicon plasma source.

PubMed

Miao, Ting-Ting; Zhao, Hong-Wei; Liu, Zhan-Wen; Shang, Yong; Sun, Liang-Ting; Zhang, Xue-Zhen; Zhao, Huan-Yu

2010-02-01

Helicon plasma source is known as efficient generator of uniform and high density plasma. A helicon plasma source was developed for investigation of plasma neutralization and plasma lens in the Institute of Modern Physics in China. In this paper, the characteristics of helicon plasma have been studied by using Langmuir four-probe and a high argon plasma density up to 3.9x10(13) cm(-3) have been achieved with the Nagoya type III antenna at the conditions of the magnetic intensity of 200 G, working gas pressure of 2.8x10(-3) Pa, and rf power of 1200 W with a frequency of 27.12 MHz. In the experiment, the important phenomena have been found: for a given magnetic induction intensity, the plasma density became greater with the increase in rf power and tended to saturation, and the helicon mode appeared at the rf power between 200 and 400 W.

Method of plasma etching GA-based compound semiconductors

DOEpatents

Qiu, Weibin; Goddard, Lynford L.

2013-01-01

A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent thereto. The chamber contains a Ga-based compound semiconductor sample in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. SiCl.sub.4 and Ar gases are flowed into the chamber. RF power is supplied to the platen at a first power level, and RF power is supplied to the source electrode. A plasma is generated. Then, RF power is supplied to the platen at a second power level lower than the first power level and no greater than about 30 W. Regions of a surface of the sample adjacent to one or more masked portions of the surface are etched at a rate of no more than about 25 nm/min to create a substantially smooth etched surface.

Final Report for "Design calculations for high-space-charge beam-to-RF conversion".

DOE Office of Scientific and Technical Information (OSTI.GOV)

David N Smithe

2008-10-17

Accelerator facility upgrades, new accelerator applications, and future design efforts are leading to novel klystron and IOT device concepts, including multiple beam, high-order mode operation, and new geometry configurations of old concepts. At the same time, a new simulation capability, based upon finite-difference “cut-cell” boundaries, has emerged and is transforming the existing modeling and design capability with unparalleled realism, greater flexibility, and improved accuracy. This same new technology can also be brought to bear on a difficult-to-study aspect of the energy recovery linac (ERL), namely the accurate modeling of the exit beam, and design of the beam dump for optimummore » energy efficiency. We have developed new capability for design calculations and modeling of a broad class of devices which convert bunched beam kinetic energy to RF energy, including RF sources, as for example, klystrons, gyro-klystrons, IOT's, TWT’s, and other devices in which space-charge effects are important. Recent advances in geometry representation now permits very accurate representation of the curved metallic surfaces common to RF sources, resulting in unprecedented simulation accuracy. In the Phase I work, we evaluated and demonstrated the capabilities of the new geometry representation technology as applied to modeling and design of output cavity components of klystron, IOT's, and energy recovery srf cavities. We identified and prioritized which aspects of the design study process to pursue and improve in Phase II. The development and use of the new accurate geometry modeling technology on RF sources for DOE accelerators will help spark a new generational modeling and design capability, free from many of the constraints and inaccuracy associated with the previous generation of “stair-step” geometry modeling tools. This new capability is ultimately expected to impact all fields with high power RF sources, including DOE fusion research, communications, radar and other defense applications.« less

Solid state RF power: The route to 1W per euro cent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heid, Oliver

2013-04-19

In most particle accelerators RF power is a decisive design constraint due to high costs and relative inflexibility of current electron beam based RF sources, i.e. Klystrons, Magnetrons, Tetrodes etc. At VHF/UHF frequencies the transition to solid state devices promises to fundamentally change the situation. Recent progress brings 1 Watt per Euro cent installed cost within reach. We present a Silicon Carbide semiconductor solution utilising the Solid State Direct Drive technology at unprecedented efficiency, power levels and power densities. The proposed solution allows retrofitting of existing RF accelerators and opens the route to novel particle accelerator concepts.

Effect of Electron Seeding on Experimentally Measured Multipactor Discharge Threshold

NASA Astrophysics Data System (ADS)

Noland, Jonathan; Graves, Timothy; Lemon, Colby; Looper, Mark; Farkas, Alex

2012-10-01

Multipactor is a vacuum phenomenon in which electrons, moving in resonance with an externally applied electric field, impact material surfaces. If the number of secondary electrons created per primary electron impact averages more than unity, the resonant interaction can lead to an electron avalanche. Multipactor is a generally undesirable phenomenon, as it can cause local heating, absorb power, or cause detuning of RF circuits. In order to increase the probability of multipactor initiation, test facilities often employ various seeding sources such as radioactive sources (Cesium 137, Strontium 90), electron guns, or photon sources. Even with these sources, the voltage for multipactor initiation is not certain as parameters such as material type, RF pulse length, and device wall thickness can all affect seed electron flux and energy in critical gap regions, and hence the measured voltage threshold. This study investigates the effects of seed electron source type (e.g., photons versus beta particles), material type, gap size, and RF pulse length variation on multipactor threshold. In addition to the experimental work, GEANT4 simulations will be used to estimate the production rate of low energy electrons (< 5 keV) by high energy electrons and photons. A comparison of the experimental fluxes to the typical energetic photon and particle fluxes experienced by spacecraft in various orbits will also be made. Initial results indicate that for a simple, parallel plate device made of aluminum, there is no threshold variation (with seed electrons versus with no seed electrons) under continuous-wave RF exposure.

Efficient RF energy harvesting by using a fractal structured rectenna system

NASA Astrophysics Data System (ADS)

Oh, Sechang; Ramasamy, Mouli; Varadan, Vijay K.

2014-04-01

A rectenna system delivers, collects, and converts RF energy into direct current to power the electronic devices or recharge batteries. It consists of an antenna for receiving RF power, an input filter for processing energy and impedance matching, a rectifier, an output filter, and a load resistor. However, the conventional rectenna systems have drawback in terms of power generation, as the single resonant frequency of an antenna can generate only low power compared to multiple resonant frequencies. A multi band rectenna system is an optimal solution to generate more power. This paper proposes the design of a novel rectenna system, which involves developing a multi band rectenna with a fractal structured antenna to facilitate an increase in energy harvesting from various sources like Wi-Fi, TV signals, mobile networks and other ambient sources, eliminating the limitation of a single band technique. The usage of fractal antennas effects certain prominent advantages in terms of size and multiple resonances. Even though, a fractal antenna incorporates multiple resonances, controlling the resonant frequencies is an important aspect to generate power from the various desired RF sources. Hence, this paper also describes the design parameters of the fractal antenna and the methods to control the multi band frequency.

Impact of underlap and mole-fraction on RF performance of strained-Si/Si1-xGex/strained-Si DG MOSFETs

NASA Astrophysics Data System (ADS)

Dutta, Arka; Koley, Kalyan; Sarkar, Chandan K.

2014-11-01

In this paper, a systematic RF performance analysis of double-gate strained silicon (DGSS) nMOSFETs is presented. The analysis is focused upon impact of Germanium mole-fraction variation on RF performance of underlap engineered DGSS nMOSFET. The RF performance of the device is analysed as a function of intrinsic RF figure of merits (FOMs) including non-quasi static effects (NQS). The RF FOMs are represented by the intrinsic gate to source/drain capacitance (Cgs and Cgd) and resistance (Rgs and Rgd), the transport delay (τm), the intrinsic inductance (Lsd), the cut-off frequency (fT), and the maximum oscillation frequency (fMAX). The results of the study suggested a significant improvement in the device performance, up to 40% increase in Germanium mole fraction (χ).

Biophysics and pathology of catheter energy delivery systems.

PubMed

Nath, S; Haines, D E

1995-01-01

Catheter ablation has rapidly emerged as the treatment of choice for many symptomatic cardiac arrhythmias. The initial experience with catheter ablation used high-energy DC as the energy source. However, over the last several years radiofrequency (RF) catheter ablation has become the dominant mode of energy delivery. Currently, a major limitation of RF ablation is the small lesion size created by this technique that has reduced its success rate in ablation of larger arrhythmogenic substrates such as coronary artery disease-related ventricular tachycardia. Alternate energy sources such as microwave or ultrasound catheter ablation are being developed that have the potential for producing larger lesions than RF ablation. This review will discuss the biophysics and pathophysiology of the various energy modalities used in catheter ablation.

Low-level exposure to radiofrequency electromagnetic fields: health effects and research needs.

PubMed

Repacholi, M H

1998-01-01

The World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the German and Austrian Governments jointly sponsored an international seminar in November of 1996 on the biological effects of low-level radiofrequency (RF) electromagnetic fields. For purposes of this seminar, RF fields having frequencies only in the range of about 10 MHz to 300 GHz were considered. This is one of a series of scientific review seminars held under the International Electromagnetic Field (EMF) Project to identify any health hazards from EMF exposure. The scientific literature was reviewed during the seminar and expert working groups formed to provide a status report on possible health effects from exposure to low-level RF fields and identify gaps in knowledge requiring more research to improve health risk assessments. It was concluded that, although hazards from exposure to high-level (thermal) RF fields were established, no known health hazards were associated with exposure to RF sources emitting fields too low to cause a significant temperature rise in tissue. Biological effects from low-level RF exposure were identified needing replication and further study. These included in vitro studies of cell kinetics and proliferation effects, effects on genes, signal transduction effects and alterations in membrane structure and function, and biophysical and biochemical mechanisms for RF field effects. In vivo studies should focus on the potential for cancer promotion, co-promotion and progression, as well as possible synergistic, genotoxic, immunological, and carcinogenic effects associated with chronic low-level RF exposure. Research is needed to determine whether low-level RF exposure causes DNA damage or influences central nervous system function, melatonin synthesis, permeability of the blood brain barrier (BBB), or reaction to neurotropic drugs. Reported RF-induced changes to eye structure and function should also be investigated. Epidemiological studies should investigate: the use of mobile telephones with hand-held antennae and incidence of various cancers; reports of headache, sleep disturbance, and other subjective effects that may arise from proximity to RF emitters, and laboratory studies should be conducted on people reporting these effects; cohorts with high occupational RF exposure for changes in cancer incidence; adverse pregnancy outcomes in various highly RF exposed occupational groups; and ocular pathologies in mobile telephone users and in highly RF exposed occupational groups. Studies of populations with residential exposure from point sources, such as broadcasting transmitters or mobile telephone base stations have caused widespread health concerns among the public, even though RF exposures are very low. Recent studies that may indicate an increased incidence of cancer in exposed populations should be investigated further.

A microwave imaging-based 3D localization algorithm for an in-body RF source as in wireless capsule endoscopes.

PubMed

Chandra, Rohit; Balasingham, Ilangko

2015-01-01

A microwave imaging-based technique for 3D localization of an in-body RF source is presented. Such a technique can be useful for localization of an RF source as in wireless capsule endoscopes for positioning of any abnormality in the gastrointestinal tract. Microwave imaging is used to determine the dielectric properties (relative permittivity and conductivity) of the tissues that are required for a precise localization. A 2D microwave imaging algorithm is used for determination of the dielectric properties. Calibration method is developed for removing any error due to the used 2D imaging algorithm on the imaging data of a 3D body. The developed method is tested on a simple 3D heterogeneous phantom through finite-difference-time-domain simulations. Additive white Gaussian noise at the signal-to-noise ratio of 30 dB is added to the simulated data to make them more realistic. The developed calibration method improves the imaging and the localization accuracy. Statistics on the localization accuracy are generated by randomly placing the RF source at various positions inside the small intestine of the phantom. The cumulative distribution function of the localization error is plotted. In 90% of the cases, the localization accuracy was found within 1.67 cm, showing the capability of the developed method for 3D localization.

Evaluation of dual-source parallel RF excitation for diffusion-weighted whole-body MR imaging with background body signal suppression at 3.0 T.

PubMed

Mürtz, Petra; Kaschner, Marius; Träber, Frank; Kukuk, Guido M; Büdenbender, Sarah M; Skowasch, Dirk; Gieseke, Jürgen; Schild, Hans H; Willinek, Winfried A

2012-11-01

To evaluate the use of dual-source parallel RF excitation (TX) for diffusion-weighted whole-body MRI with background body signal suppression (DWIBS) at 3.0 T. Forty consecutive patients were examined on a clinical 3.0-T MRI system using a diffusion-weighted (DW) spin-echo echo-planar imaging sequence with a combination of short TI inversion recovery and slice-selective gradient reversal fat suppression. DWIBS of the neck (n=5), thorax (n=8), abdomen (n=6) and pelvis (n=21) was performed both with TX (2:56 min) and with standard single-source RF excitation (4:37 min). The quality of DW images and reconstructed inverted maximum intensity projections was visually judged by two readers (blinded to acquisition technique). Signal homogeneity and fat suppression were scored as "improved", "equal", "worse" or "ambiguous". Moreover, the apparent diffusion coefficient (ADC) values were measured in muscles, urinary bladder, lymph nodes and lesions. By the use of TX, signal homogeneity was "improved" in 25/40 and "equal" in 15/40 cases. Fat suppression was "improved" in 17/40 and "equal" in 23/40 cases. These improvements were statistically significant (p<0.001, Wilcoxon signed-rank test). In five patients, fluid-related dielectric shading was present, which improved remarkably. The ADC values did not significantly differ for the two RF excitation methods (p=0.630 over all data, pairwise Student's t-test). Dual-source parallel RF excitation improved image quality of DWIBS at 3.0 T with respect to signal homogeneity and fat suppression, reduced scan time by approximately one-third, and did not influence the measured ADC values. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

NASA Astrophysics Data System (ADS)

Chaplin, Vernon H.

This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel radius, suggesting that the outer portion of the jet must have been force free, with the current parallel to the magnetic field. The studies of non-equilibrium flows and plasma self-organization being carried out at Caltech are relevant to astrophysical jets and fusion energy research.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdrashitov, G. F.; Belchenko, Yu. I.; Gusev, I. A.

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.

A new RF window designed for high-power operation in an S-band LINAC RF system

NASA Astrophysics Data System (ADS)

Joo, Youngdo; Kim, Seung-Hwan; Hwang, Woonha; Ryu, Jiwan; Roh, Sungjoo

2016-09-01

A new RF window is designed for high-power operation at the Pohang Light Source-II (PLSII) S-band linear accelerator (LINAC) RF system. In order to reduce the strength of the electric field component perpendicular to the ceramic disk, which is commonly known as the main cause of most discharge breakdowns in ceramic disk, we replace the pill-box type cavity in the conventional RF window with an overmoded cavity. The overmoded cavity is coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the iris and the number of possible mode competitions. The finite-difference time-domain (FDTD) simulation, CST MWS, was used in the design process. The simulated maximum electric field component perpendicular to the ceramic for the new RF window is reduced by an order of magnitude compared with taht for the conventional RF window, which holds promise for stable high-power operation.

Development and performance test of a new high power RF window in S-band PLS-II LINAC

NASA Astrophysics Data System (ADS)

Hwang, Woon-Ha; Joo, Young-Do; Kim, Seung-Hwan; Choi, Jae-Young; Noh, Sung-Ju; Ryu, Ji-Wan; Cho, Young-Ki

2017-12-01

A prototype of RF window was developed in collaboration with the Pohang Accelerator Laboratory (PAL) and domestic companies. High power performance tests of the single RF window were conducted at PAL to verify the operational characteristics for its application in the Pohang Light Source-II (PLS-II) linear accelerator (Linac). The tests were performed in the in-situ facility consisting of a modulator, klystron, waveguide network, vacuum system, cooling system, and RF analyzing equipment. The test results with Stanford linear accelerator energy doubler (SLED) have shown no breakdown up to 75 MW peak power with 4.5 μs RF pulse width at a repetition rate of 10 Hz. The test results with the current operation level of PLS-II Linac confirm that the RF window well satisfies the criteria for PLS-II Linac operation.

Magnetoplasmonic RF mixing and nonlinear frequency generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Firby, C. J., E-mail: firby@ualberta.ca; Elezzabi, A. Y.

2016-07-04

We present the design of a magnetoplasmonic Mach-Zehnder interferometer (MZI) modulator facilitating radio-frequency (RF) mixing and nonlinear frequency generation. This is achieved by forming the MZI arms from long-range dielectric-loaded plasmonic waveguides containing bismuth-substituted yttrium iron garnet (Bi:YIG). The magnetization of the Bi:YIG can be driven in the nonlinear regime by RF magnetic fields produced around adjacent transmission lines. Correspondingly, the nonlinear temporal dynamics of the transverse magnetization component are mapped onto the nonreciprocal phase shift in the MZI arms, and onto the output optical intensity signal. We show that this tunable mechanism can generate harmonics, frequency splitting, and frequencymore » down-conversion with a single RF excitation, as well as RF mixing when driven by two RF signals. This magnetoplasmonic component can reduce the number of electrical sources required to generate distinct optical modulation frequencies and is anticipated to satisfy important applications in integrated optics.« less

Modeling of surface-dominated plasmas: from electric thruster to negative ion source.

PubMed

Taccogna, F; Schneider, R; Longo, S; Capitelli, M

2008-02-01

This contribution shows two important applications of the particle-in-cell/monte Carlo technique on ion sources: modeling of the Hall thruster SPT-100 for space propulsion and of the rf negative ion source for ITER neutral beam injection. In the first case translational degrees of freedom are involved, while in the second case inner degrees of freedom (vibrational levels) are excited. Computational results show how in both cases, plasma-wall and gas-wall interactions play a dominant role. These are secondary electron emission from the lateral ceramic wall of SPT-100 and electron capture from caesiated surfaces by positive ions and atoms in the rf negative ion source.

Performance of multi-aperture grid extraction systems for an ITER-relevant RF-driven negative hydrogen ion source

NASA Astrophysics Data System (ADS)

Franzen, P.; Gutser, R.; Fantz, U.; Kraus, W.; Falter, H.; Fröschle, M.; Heinemann, B.; McNeely, P.; Nocentini, R.; Riedl, R.; Stäbler, A.; Wünderlich, D.

2011-07-01

The ITER neutral beam system requires a negative hydrogen ion beam of 48 A with an energy of 0.87 MeV, and a negative deuterium beam of 40 A with an energy of 1 MeV. The beam is extracted from a large ion source of dimension 1.9 × 0.9 m2 by an acceleration system consisting of seven grids with 1280 apertures each. Currently, apertures with a diameter of 14 mm in the first grid are foreseen. In 2007, the IPP RF source was chosen as the ITER reference source due to its reduced maintenance compared with arc-driven sources and the successful development at the BATMAN test facility of being equipped with the small IPP prototype RF source ( {\\sim}\\frac{1}{8} of the area of the ITER NBI source). These results, however, were obtained with an extraction system with 8 mm diameter apertures. This paper reports on the comparison of the source performance at BATMAN of an ITER-relevant extraction system equipped with chamfered apertures with a 14 mm diameter and 8 mm diameter aperture extraction system. The most important result is that there is almost no difference in the achieved current density—being consistent with ion trajectory calculations—and the amount of co-extracted electrons. Furthermore, some aspects of the beam optics of both extraction systems are discussed.

Deuterium results at the negative ion source test facility ELISE

NASA Astrophysics Data System (ADS)

Kraus, W.; Wünderlich, D.; Fantz, U.; Heinemann, B.; Bonomo, F.; Riedl, R.

2018-05-01

The ITER neutral beam system will be equipped with large radio frequency (RF) driven negative ion sources, with a cross section of 0.9 m × 1.9 m, which have to deliver extracted D- ion beams of 57 A at 1 MeV for 1 h. On the extraction from a large ion source experiment test facility, a source of half of this size is being operational since 2013. The goal of this experiment is to demonstrate a high operational reliability and to achieve the extracted current densities and beam properties required for ITER. Technical improvements of the source design and the RF system were necessary to provide reliable operation in steady state with an RF power of up to 300 kW. While in short pulses the required D- current density has almost been reached, the performance in long pulses is determined in particular in Deuterium by inhomogeneous and unstable currents of co-extracted electrons. By application of refined caesium evaporation and distribution procedures, and reduction and symmetrization of the electron currents, considerable progress has been made and up to 190 A/m2 D-, corresponding to 66% of the value required for ITER, have been extracted for 45 min.

Particle model of a cylindrical inductively coupled ion source

NASA Astrophysics Data System (ADS)

Ippolito, N. D.; Taccogna, F.; Minelli, P.; Cavenago, M.; Veltri, P.

2017-08-01

In spite of the wide use of RF sources, a complete understanding of the mechanisms regulating the RF-coupling of the plasma is still lacking so self-consistent simulations of the involved physics are highly desirable. For this reason we are developing a 2.5D fully kinetic Particle-In-Cell Monte-Carlo-Collision (PIC-MCC) model of a cylindrical ICP-RF source, keeping the time step of the simulation small enough to resolve the plasma frequency scale. The grid cell dimension is now about seven times larger than the average Debye length, because of the large computational demand of the code. It will be scaled down in the next phase of the development of the code. The filling gas is Xenon, in order to minimize the time lost by the MCC collision module in the first stage of development of the code. The results presented here are preliminary, with the code already showing a good robustness. The final goal will be the modeling of the NIO1 (Negative Ion Optimization phase 1) source, operating in Padua at Consorzio RFX.

RF power harvesting: a review on designing methodologies and applications

NASA Astrophysics Data System (ADS)

Tran, Le-Giang; Cha, Hyouk-Kyu; Park, Woo-Tae

2017-12-01

Wireless power transmission was conceptualized nearly a century ago. Certain achievements made to date have made power harvesting a reality, capable of providing alternative sources of energy. This review provides a summ ary of radio frequency (RF) power harvesting technologies in order to serve as a guide for the design of RF energy harvesting units. Since energy harvesting circuits are designed to operate with relatively small voltages and currents, they rely on state-of-the-art electrical technology for obtaining high efficiency. Thus, comprehensive analysis and discussions of various designs and their tradeoffs are included. Finally, recent applications of RF power harvesting are outlined.

Integral electrical characteristics and local plasma parameters of a RF ion thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masherov, P. E.; Riaby, V. A., E-mail: riaby2001@yahoo.com; Godyak, V. A.

2016-02-15

Comprehensive diagnostics has been carried out for a RF ion thruster based on inductively coupled plasma (ICP) source with an external flat antenna coil enhanced by ferrite core. The ICP was confined within a cylindrical chamber with low aspect ratio to minimize plasma loss to the chamber wall. Integral diagnostics of the ICP electrical parameters (RF power balance and coil current) allowed for evaluation of the antenna coils, matching networks, and eddy current loss and the true RF power deposited to plasma. Spatially resolved electron energy distribution functions, plasma density, electron temperatures, and plasma potentials were measured with movable Langmuirmore » probes.« less

Four cavity efficiency enhanced magnetically insulated line oscillator

DOEpatents

Lemke, Raymond W.; Clark, Miles C.; Calico, Steve E.

1998-04-21

A four cavity, efficient magnetically insulated line oscillator (C4-E MILO) having seven vanes and six cavities formed within a tube-like structure surrounding a cathode. The C4-E MILO has a primary slow wave structure which is comprised of four vanes and the four cavities located near a microwave exit end of the tube-like structure. The primary slow wave structure is the four cavity (C4) portion of the magnetically insulated line oscillator (MILO). An RF choke is provided which is comprised of three of the vanes and two of the cavities. The RF choke is located near a pulsed power source portion of the tube-like structure surrounding the cathode. The RF choke increases feedback in the primary slow wave structure, prevents microwaves generated in the primary slow wave structure from propagating towards the pulsed power source and modifies downstream electron current so as to enhance microwave power generation. A beam dump/extractor is located at the exit end of the oscillator tube for extracting microwave power from the oscillator, and in conjunction with an RF extractor vane, which comprises the fourth vane of the primary slow wave structure (nearest the exit) having a larger gap radius than the other vanes of the primary SWS, comprises an RF extractor. Uninsulated electron flow is returned downstream towards the exit along an anode/beam dump region located between the beam dump/extractor and the exit where the RF is radiated at said RF extractor vane located near the exit and the uninsulated electron flow is disposed at the beam dump/extractor.

Four cavity efficiency enhanced magnetically insulated line oscillator

DOEpatents

Lemke, R.W.; Clark, M.C.; Calico, S.E.

1998-04-21

A four cavity, efficient magnetically insulated line oscillator (C4-E MILO) having seven vanes and six cavities formed within a tube-like structure surrounding a cathode is disclosed. The C4-E MILO has a primary slow wave structure which is comprised of four vanes and the four cavities located near a microwave exit end of the tube-like structure. The primary slow wave structure is the four cavity portion of the magnetically insulated line oscillator (MILO). An RF choke is provided which is comprised of three of the vanes and two of the cavities. The RF choke is located near a pulsed power source portion of the tube-like structure surrounding the cathode. The RF choke increases feedback in the primary slow wave structure, prevents microwaves generated in the primary slow wave structure from propagating towards the pulsed power source and modifies downstream electron current so as to enhance microwave power generation. A beam dump/extractor is located at the exit end of the oscillator tube for extracting microwave power from the oscillator, and in conjunction with an RF extractor vane, which comprises the fourth vane of the primary slow wave structure (nearest the exit) having a larger gap radius than the other vanes of the primary SWS, comprises an RF extractor. Uninsulated electron flow is returned downstream towards the exit along an anode/beam dump region located between the beam dump/extractor and the exit where the RF is radiated at said RF extractor vane located near the exit and the uninsulated electron flow is disposed at the beam dump/extractor. 34 figs.

Densities of Active species in N2/H2 RF and HF afterglows: application to surface nitriding of TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Ricard, André; Sarrette, Jean-Philippe; Wang, Yunfei; Kim, Yu-Kwon

2017-10-01

N2/0-5% H2 flowing afterglows from Radio Frequency (RF) and High Frequency (HF) sources have been analyzed by optical emission spectroscopy. In similar conditions (pressure 5-6 Torr, flow rate 0.5 slm and power 100 W), it is found in pure N2 a nearly constant N-atom density from the pink to the late afterglow, which is higher in HF than in RF: (1-2) and 0.4 × 1015 cm-3, respectively. With a N2/2% H2 gas mixture, the early afterglows is changed to a late afterglow with about the same N-atom density for both RF and HF cases: (8-9) × 1014 cm-3. Anatase TiO2 nanocrystals and Atomic Layer Deposition-grown films were exposed to the RF afterglows at room temperature. XPS analysis of the samples has shown that the highest N/Ti ratio of 0.24 can be achieved with the pure N2 late afterglow. In the HF pure N2 late afterglow, however, the N/Ti coverage was limited to 0.04 in spite of higher N-atom density. Such differences in the N content between the two RF and HF cases are attributed to the presence of a high O-atom impurity of 2 × 1013 cm-3 in HF as compared to that (8 × 1011 cm-3) in RF. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tiberiu Minea

Thermal modeling for pulsed radiofrequency ablation: analytical study based on hyperbolic heat conduction.

PubMed

López Molina, Juan A; Rivera, María J; Trujillo, Macarena; Berjano, Enrique J

2009-04-01

The objectives of this study were to model the temperature progress of a pulsed radiofrequency (RF) power during RF heating of biological tissue, and to employ the hyperbolic heat transfer equation (HHTE), which takes the thermal wave behavior into account, and compare the results to those obtained using the heat transfer equation based on Fourier theory (FHTE). A theoretical model was built based on an active spherical electrode completely embedded in the biological tissue, after which HHTE and FHTE were analytically solved. We found three typical waveforms for the temperature progress depending on the relations between the dimensionless duration of the RF pulse delta(a) and the expression square root of lambda(rho-1), with lambda as the dimensionless thermal relaxation time of the tissue and rho as the dimensionless position. In the case of a unique RF pulse, the temperature at any location was the result of the overlapping of two different heat sources delayed for a duration delta(a) (each heat source being produced by a RF pulse of limitless duration). The most remarkable feature in the HHTE analytical solution was the presence of temperature peaks traveling through the medium at a finite speed. These peaks not only occurred during the RF power switch-on period but also during switch off. Finally, a physical explanation for these temperature peaks is proposed based on the interaction of forward and reverse thermal waves. All-purpose analytical solutions for FHTE and HHTE were obtained during pulsed RF heating of biological tissues, which could be used for any value of pulsing frequency and duty cycle.

Comparison of RF BPM Receivers for NSLS-II Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinayev,I.; Singh, O.

2009-05-04

The NSLS-II Light Source being built at Brookhaven National Laboratory requires submicron stability of the electron orbit in the storage ring in order to utilize fully very small emittances and electron beam sizes. This sets high stability requirements for beam position monitors and a program has been initiated for the purpose of characterizing RF beam position monitor (BPM) receivers in use at other light sources. Present state-of-the-art performance will be contrasted with more recently available technologies.

Ion Source Development for a Compact Proton Beam Writing System III

DTIC Science & Technology

2013-06-28

to yield ion beam with energies up to 3 keV. The electrical power required to operate multiple components (like RF Valve , Probe and Extraction...they are powered through an isolation transformer. The required gas, to be ionized in the RF ion source, is fed through a coarse needle valve ...connector, the system can be pumped down to 3×10-2 mbar using an oil roughing pump. Nitrogen gas is feed in by adjusting the gas regulating valve

Studies on the Extraction Region of the Type VI RF Driven H- Ion Source

NASA Astrophysics Data System (ADS)

McNeely, P.; Bandyopadhyay, M.; Franzen, P.; Heinemann, B.; Hu, C.; Kraus, W.; Riedl, R.; Speth, E.; Wilhelm, R.

2002-11-01

IPP Garching has spent several years developing a RF driven H- ion source intended to be an alternative to the current ITER (International Thermonuclear Experimental Reactor) reference design ion source. A RF driven source offers a number of advantages to ITER in terms of reduced costs and maintenance requirements. Although the RF driven ion source has shown itself to be competitive with a standard arc filament ion source for positive ions many questions still remain on the physics behind the production of the H- ion beam extracted from the source. With the improvements that have been implemented to the BATMAN (Bavarian Test Machine for Negative Ions) facility over the last two years it is now possible to study both the extracted ion beam and the plasma in the vicinity of the extraction grid in greater detail. This paper will show the effect of changing the extraction and acceleration voltage on both the current and shape of the beam as measured on the calorimeter some 1.5 m downstream from the source. The extraction voltage required to operate in the plasma limit is 3 kV. The perveance optimum for the extraction system was determined to be 2.2 x 10-6 A/V3/2 and occurs at 2.7 kV extraction voltage. The horizontal and vertical beam half widths vary as a function of the extracted ion current and the horizontal half width is generally smaller than the vertical. The effect of reducing the co-extracted electron current via plasma grid biasing on the H- current extractable and the beam profile from the source is shown. It is possible in the case of a silver contaminated plasma to reduce the co-extracted electron current to 20% of the initial value by applying a bias of 12 V. In the case where argon is present in the plasma, biasing is observed to have minimal effect on the beam half width but in a pure hydrogen plasma the beam half width increases as the bias voltage increases. New Langmuir probe studies that have been carried out parallel to the plasma grid (in the vicinity of the peak of the external magnetic filter field) and changes to source parameters as a function of power, and argon addition are reported. The behaviour of the electron density is different when the plasma is argon seeded showing a strong increase with RF power. The plasma potential is decreased by 2 V when argon is added to the plasma. The effect of the presence of unwanted silver sputtered from the Faraday screen by Ar+ ions on both the source performance and the plasma parameters is also presented. The silver dramatically downgraded source performance in terms of current density and produced an early saturation of current with applied RF power. Recently, collaboration was begun with the Technical University of Augsburg to perform spectroscopic measurements on the Type VI ion source. The final results of this analysis are not yet ready but some interesting initial observations on the gas temperature, disassociation degree and impurity ions will be presented.

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.

Negative ion beam development at Cadarache (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simonin, A.; Bucalossi, J.; Desgranges, C.

1996-03-01

Neutral beam injection (NBI) is one of the candidates for plasma heating and current drive in the new generation of large magnetic fusion devices (ITER). In order to produce the required deuterium atom beams with energies of 1 MeV and powers of tens of MW, negative D{sup {minus}} ion beams are required. For this purpose, multiampere D{sup {minus}} beam production and 1 MeV electrostatic acceleration is being studied at Cadarache. The SINGAP experiment, a 1 MeV 0.1 A D{sup {minus}} multisecond beam accelerator facility, has recently started operation. It is equipped with a Pagoda ion source, a multiaperture 60 keVmore » preaccelerator and a 1 MV 120 mA power supply. The particular feature of SINGAP is that the postaccelerator merges the 60 keV beamlets, aiming at accelerating the whole beam to 1 MeV in a single gap. The 1 MV level was obtained in less than 2 weeks, the accumulated voltage on-time of being {approximately}22 min. A second test bed MANTIS, is devoted to the development of multiampere D{sup {minus}} sources. It is capable of driving discharges with current up to 2500 A at arc voltages up to 150 V. A large multicusp source has been tested in pure volume and cesiated operation. With cesium seeding, an accelerated D{sup {minus}} beam current density of up to 5.2 mA/cm{sup 2} (2 A of D{sup {minus}}) was obtained. A modification of the extractor is underway in order to improve this performance. A 3D Monte Carlo code has been developed to simulate the negative ion transport in magnetized plasma sources and optimize magnetic field configuration of the large area D{sup {minus}} sources. {copyright} {ital 1996 American Institute of Physics.}« less

Design of RF energy harvesting platforms for power management unit with start-up circuits

NASA Astrophysics Data System (ADS)

Costanzo, Alessandra; Masotti, Diego

2013-12-01

In this contribution we discuss an unconventional rectifier design dedicated to RF energy harvesting from ultra-low sources, such as ambient RF sources which are typically of the order of few to few tens of μW. In such conditions unsuccessful results may occur if the rectenna is directly connected to its actual load since either the minimum power or the minimum activation voltage may not be simultaneously available. For this reason a double-branch rectifier topology is considered for the power management unit (PMU), instead of traditional single-branch one. The new PMU, interposed between the rectenna and application circuits, allows the system to operate with significantly lower input power with respect to the traditional solution, while preserving efficiency during steady-state power conversion.

Digital processing of signals from femtosecond combs

NASA Astrophysics Data System (ADS)

Čížek, Martin; Šmíd, Radek; Buchta, Zdeněk.; Mikel, Břetislav; Lazar, Josef; Číp, Ondrej

2012-01-01

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique and with fully digital servo-loop stabilization of the fs comb. Secondly, we are using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset and repetition frequencies of the fs comb.

The study of helicon plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao Tingting; Shang Yong; Graduate University of Chinese Academy of Sciences, Beijing 100049

2010-02-15

Helicon plasma source is known as efficient generator of uniform and high density plasma. A helicon plasma source was developed for investigation of plasma neutralization and plasma lens in the Institute of Modern Physics in China. In this paper, the characteristics of helicon plasma have been studied by using Langmuir four-probe and a high argon plasma density up to 3.9x10{sup 13} cm{sup -3} have been achieved with the Nagoya type III antenna at the conditions of the magnetic intensity of 200 G, working gas pressure of 2.8x10{sup -3} Pa, and rf power of 1200 W with a frequency of 27.12more » MHz. In the experiment, the important phenomena have been found: for a given magnetic induction intensity, the plasma density became greater with the increase in rf power and tended to saturation, and the helicon mode appeared at the rf power between 200 and 400 W.« less

Plasma characteristics of direct current enhanced cylindrical inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Yue, HUA; Jian, SONG; Zeyu, HAO; Chunsheng, REN

2018-06-01

Experimental results of a direct current enhanced inductively coupled plasma (DCE-ICP) source which consists of a typical cylindrical ICP source and a plate-to-grid DC electrode are reported. With the use of this new source, the plasma characteristic parameters, namely, electron density, electron temperature and plasma uniformity, are measured by Langmuir floating double probe. It is found that DC discharge enhances the electron density and decreases the electron temperature, dramatically. Moreover, the plasma uniformity is obviously improved with the operation of DC and radio frequency (RF) hybrid discharge. Furthermore, the nonlinear enhancement effect of electron density with DC + RF hybrid discharge is confirmed. The presented observation indicates that the DCE-ICP source provides an effective method to obtain high-density uniform plasma, which is desirable for practical industrial applications.

Power source selection for neutral particle beam systems

NASA Astrophysics Data System (ADS)

Silverman, Sidney W.; Chi, John W. H.; Hill, Gregory

Space based neutral particle beams (NPB) are being considered for use as an SDI weapon as well as a mid-course discriminator. These systems require a radio frequency (RF) power source. Five types of amplifiers were considered for the RF power source: the klystron, the klystrode, the tetrode, the cross field amplifier, and the solid state amplifier. A number of different types of power source systems (nuclear and non-nuclear) were considered for integration with these amplifiers. The most attractive amplifier power system concepts were identified through comparative evaluations that took into account the total masses of integrated amplifier power source systems as well as a number of other factors that consisted of development cost, technology risk, vulnerability, survivability, reliability, and impacts on spacecraft stabilization. These concepts are described and conclusions drawn.

Standing Helicon Wave Induced by a Rapidly Bent Magnetic Field in Plasmas.

PubMed

Takahashi, Kazunori; Takayama, Sho; Komuro, Atsushi; Ando, Akira

2016-04-01

An electron energy probability function and a rf magnetic field are measured in a rf hydrogen helicon source, where axial and transverse static magnetic fields are applied to the source by solenoids and to the diffusion chamber by filter magnets, respectively. It is demonstrated that the helicon wave is reflected by the rapidly bent magnetic field and the resultant standing wave heats the electrons between the source and the magnetic filter, while the electron cooling effect by the magnetic filter is maintained. It is interpreted that the standing wave is generated by the presence of a spatially localized change of a refractive index.

Standing Helicon Wave Induced by a Rapidly Bent Magnetic Field in Plasmas

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Takayama, Sho; Komuro, Atsushi; Ando, Akira

2016-04-01

An electron energy probability function and a rf magnetic field are measured in a rf hydrogen helicon source, where axial and transverse static magnetic fields are applied to the source by solenoids and to the diffusion chamber by filter magnets, respectively. It is demonstrated that the helicon wave is reflected by the rapidly bent magnetic field and the resultant standing wave heats the electrons between the source and the magnetic filter, while the electron cooling effect by the magnetic filter is maintained. It is interpreted that the standing wave is generated by the presence of a spatially localized change of a refractive index.

RF Power Transfer, Energy Harvesting, and Power Management Strategies

NASA Astrophysics Data System (ADS)

Abouzied, Mohamed Ali Mohamed

Energy harvesting is the way to capture green energy. This can be thought of as a recycling process where energy is converted from one form (here, non-electrical) to another (here, electrical). This is done on the large energy scale as well as low energy scale. The former can enable sustainable operation of facilities, while the latter can have a significant impact on the problems of energy constrained portable applications. Different energy sources can be complementary to one another and combining multiple-source is of great importance. In particular, RF energy harvesting is a natural choice for the portable applications. There are many advantages, such as cordless operation and light-weight. Moreover, the needed infra-structure can possibly be incorporated with wearable and portable devices. RF energy harvesting is an enabling key player for Internet of Things technology. The RF energy harvesting systems consist of external antennas, LC matching networks, RF rectifiers for ac to dc conversion, and sometimes power management. Moreover, combining different energy harvesting sources is essential for robustness and sustainability. Wireless power transfer has recently been applied for battery charging of portable devices. This charging process impacts the daily experience of every human who uses electronic applications. Instead of having many types of cumbersome cords and many different standards while the users are responsible to connect periodically to ac outlets, the new approach is to have the transmitters ready in the near region and can transfer power wirelessly to the devices whenever needed. Wireless power transfer consists of a dc to ac conversion transmitter, coupled inductors between transmitter and receiver, and an ac to dc conversion receiver. Alternative far field operation is still tested for health issues. So, the focus in this study is on near field. The goals of this study are to investigate the possibilities of RF energy harvesting from various sources in the far field, dc energy combining, wireless power transfer in the near field, the underlying power management strategies, and the integration on silicon. This integration is the ultimate goal for cheap solutions to enable the technology for broader use. All systems were designed, implemented and tested to demonstrate proof-of concept prototypes.

First results of the ITER-relevant negative ion beam test facility ELISE (invited).

PubMed

Fantz, U; Franzen, P; Heinemann, B; Wünderlich, D

2014-02-01

An important step in the European R&D roadmap towards the neutral beam heating systems of ITER is the new test facility ELISE (Extraction from a Large Ion Source Experiment) for large-scale extraction from a half-size ITER RF source. The test facility was constructed in the last years at Max-Planck-Institut für Plasmaphysik Garching and is now operational. ELISE is gaining early experience of the performance and operation of large RF-driven negative hydrogen ion sources with plasma illumination of a source area of 1 × 0.9 m(2) and an extraction area of 0.1 m(2) using 640 apertures. First results in volume operation, i.e., without caesium seeding, are presented.

Source localization in an ocean waveguide using supervised machine learning.

PubMed

Niu, Haiqiang; Reeves, Emma; Gerstoft, Peter

2017-09-01

Source localization in ocean acoustics is posed as a machine learning problem in which data-driven methods learn source ranges directly from observed acoustic data. The pressure received by a vertical linear array is preprocessed by constructing a normalized sample covariance matrix and used as the input for three machine learning methods: feed-forward neural networks (FNN), support vector machines (SVM), and random forests (RF). The range estimation problem is solved both as a classification problem and as a regression problem by these three machine learning algorithms. The results of range estimation for the Noise09 experiment are compared for FNN, SVM, RF, and conventional matched-field processing and demonstrate the potential of machine learning for underwater source localization.

Design of a cavity ring-down spectroscopy diagnostic for negative ion rf source SPIDER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pasqualotto, R.; Alfier, A.; Lotto, L.

2010-10-15

The rf source test facility SPIDER will test and optimize the source of the 1 MV neutral beam injection systems for ITER. Cavity ring-down spectroscopy (CRDS) will measure the absolute line-of-sight integrated density of negative (H{sup -} and D{sup -}) ions, produced in the extraction region of the source. CRDS takes advantage of the photodetachment process: negative ions are converted to neutral hydrogen atoms by electron stripping through absorption of a photon from a laser. The design of this diagnostic is presented with the corresponding simulation of the expected performance. A prototype operated without plasma has provided CRDS reference signals,more » design validation, and results concerning the signal-to-noise ratio.« less

Final Technical Report - SciDAC Cooperative Agreement: Center for Wave Interactions with Magnetohydrodynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schnack, Dalton D.

Final technical report for research performed by Dr. Thomas G. Jenkins in collaboration with Professor Dalton D. Schnack on SciDAC Cooperative Agreement: Center for Wave Interactions with Magnetohydrodyanics, DE-FC02-06ER54899, for the period of 8/15/06 - 8/14/11. This report centers on the Slow MHD physics campaign work performed by Dr. Jenkins while at UW-Madison and then at Tech-X Corporation. To make progress on the problem of RF induced currents affect magnetic island evolution in toroidal plasmas, a set of research approaches are outlined. Three approaches can be addressed in parallel. These are: (1) Analytically prescribed additional term in Ohm's law tomore » model the effect of localized ECCD current drive; (2) Introduce an additional evolution equation for the Ohm's law source term. Establish a RF source 'box' where information from the RF code couples to the fluid evolution; and (3) Carry out a more rigorous analytic calculation treating the additional RF terms in a closure problem. These approaches rely on the necessity of reinvigorating the computation modeling efforts of resistive and neoclassical tearing modes with present day versions of the numerical tools. For the RF community, the relevant action item is - RF ray tracing codes need to be modified so that general three-dimensional spatial information can be obtained. Further, interface efforts between the two codes require work as well as an assessment as to the numerical stability properties of the procedures to be used.« less

MulRF: a software package for phylogenetic analysis using multi-copy gene trees.

PubMed

Chaudhary, Ruchi; Fernández-Baca, David; Burleigh, John Gordon

2015-02-01

MulRF is a platform-independent software package for phylogenetic analysis using multi-copy gene trees. It seeks the species tree that minimizes the Robinson-Foulds (RF) distance to the input trees using a generalization of the RF distance to multi-labeled trees. The underlying generic tree distance measure and fast running time make MulRF useful for inferring phylogenies from large collections of gene trees, in which multiple evolutionary processes as well as phylogenetic error may contribute to gene tree discord. MulRF implements several features for customizing the species tree search and assessing the results, and it provides a user-friendly graphical user interface (GUI) with tree visualization. The species tree search is implemented in C++ and the GUI in Java Swing. MulRF's executable as well as sample datasets and manual are available at http://genome.cs.iastate.edu/CBL/MulRF/, and the source code is available at https://github.com/ruchiherself/MulRFRepo. ruchic@ufl.edu Supplementary data are available at Bioinformatics online. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Methylation of bacterial release factors RF1 and RF2 is required for normal translation termination in vivo.

PubMed

Mora, Liliana; Heurgué-Hamard, Valérie; de Zamaroczy, Miklos; Kervestin, Stephanie; Buckingham, Richard H

2007-12-07

Bacterial release factors RF1 and RF2 are methylated on the Gln residue of a universally conserved tripeptide motif GGQ, which interacts with the peptidyl transferase center of the large ribosomal subunit, triggering hydrolysis of the ester bond in peptidyl-tRNA and releasing the newly synthesized polypeptide from the ribosome. In vitro experiments have shown that the activity of RF2 is stimulated by Gln methylation. The viability of Escherichia coli K12 strains depends on the integrity of the release factor methyltransferase PrmC, because K12 strains are partially deficient in RF2 activity due to the presence of a Thr residue at position 246 instead of Ala. Here, we study in vivo RF1 and RF2 activity at termination codons in competition with programmed frameshifting and the effect of the Ala-246 --> Thr mutation. PrmC inactivation reduces the specific termination activity of RF1 and RF2(Ala-246) by approximately 3- to 4-fold. The mutation Ala-246 --> Thr in RF2 reduces the termination activity in cells approximately 5-fold. After correction for the decrease in level of RF2 due to the autocontrol of RF2 synthesis, the mutation Ala-246 --> Thr reduced RF2 termination activity by approximately 10-fold at UGA codons and UAA codons. PrmC inactivation had no effect on cell growth in rich media but reduced growth considerably on poor carbon sources. This suggests that the expression of some genes needed for optimal growth under such conditions can become growth limiting as a result of inefficient translation termination.

Injection-locking of terahertz quantum cascade lasers up to 35GHz using RF amplitude modulation.

PubMed

Gellie, Pierre; Barbieri, Stefano; Lampin, Jean-François; Filloux, Pascal; Manquest, Christophe; Sirtori, Carlo; Sagnes, Isabelle; Khanna, Suraj P; Linfield, Edmund H; Davies, A Giles; Beere, Harvey; Ritchie, David

2010-09-27

We demonstrate that the cavity resonance frequency - the round-trip frequency - of Terahertz quantum cascade lasers can be injection-locked by direct modulation of the bias current using an RF source. Metal-metal and single-plasmon waveguide devices with roundtrip frequencies up to 35GHz have been studied, and show locking ranges above 200MHz. Inside this locking range the laser round-trip frequency is phase-locked, with a phase noise determined by the RF-synthesizer. We find a square-root dependence of the locking range with RF-power in agreement with classical injection-locking theory. These results are discussed in the context of mode-locking operation.

Method and apparatus for low-loss signal transmission

NASA Technical Reports Server (NTRS)

Shimabukuro, Fred (Inventor); Yeh, Cavour (Inventor); Fraser, Scott (Inventor); Siegel, Peter (Inventor)

2008-01-01

The present invention relates to the field of radio-frequency (RF) waveguides. More specifically, the present invention pertains to a method and apparatus that provides ultra-low-loss RF waveguide structures targeted between approximately 300 GHz and approximately 30 THz. The RF waveguide includes a hollow core and a flexible honeycomb, periodic-bandgap structure surrounding the hollow core. The flexible honeycomb, periodic-bandgap structure is formed of a plurality of tubes formed of a dielectric material such as of low-loss quartz, polyethylene, or high-resistivity silicon. Using the RF waveguide, a user may attach a terahertz signal source to the waveguide and pass signals through the waveguide, while a terahertz signal receiver receives the signals.

Observation of Repetition-Rate Dependent Emission From an Un-Gated Thermionic Cathode Rf Gun

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edelen, J. P.; Sun, Y.; Harris, J.R.

Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an ungated thermionicmore » cathode RF gun to high average current.« less

Relativistic theory of radiofrequency current drive

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balescu, R.; Metens, T.

1991-05-01

A fully relativistic kinetic theory of rf current drive in a tokamak is developed for both the lower hybrid and the electron cyclotron mechanisms. The problem is treated as a generalization of the classical transport equations, in which the thermodynamic forces are modified by the addition of a rf-source term. In the limit of weak rf amplitude and neglecting toroidal effects (such as particle trapping), explicit analytical expressions are obtained for the rf-generated current, the dissipated power, and the current drive efficiency. These expressions are fully relativistic and are valid over the whole admissible range of frequencies and for allmore » electron temperatures. The relation between efficiency and parallel relativistic transport coefficients is exhibited. The most important relativistic effect is a dramatic broadening of the frequency range over which the rf-generated current is significantly different from zero.« less

Electron bunch energy and phase feed-forward stabilization system for the Mark V RF-linac free-electron laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hadmack, M. R.; Kowalczyk, J. M. D.; Lienert, B. R.

2013-06-15

An amplitude and phase compensation system has been developed and tested at the University of Hawai'i for the optimization of the RF drive system to the Mark V free-electron laser. Temporal uniformity of the RF drive is essential to the generation of an electron beam suitable for optimal free-electron laser performance and the operation of an inverse Compton scattering x-ray source. The design of the RF measurement and compensation system is described in detail and the results of RF phase compensation are presented. Performance of the free-electron laser was evaluated by comparing the measured effects of phase compensation with themore » results of a computer simulation. Finally, preliminary results are presented for the effects of amplitude compensation on the performance of the complete system.« less

Comparative Effect Between Laser and Radiofrequency Heating of RGD-Gold Nanospheres on MCF7 Cell Viability.

PubMed

Sánchez-Hernández, Lidia; Ferro-Flores, Guillermina; Jiménez-Mancilla, Nallely P; Luna-Gutiérrez, Myrna A; Santos-Cuevas, Clara L; Ocampo-García, Blanca E; Azorín-Vega, Erika; Isaac-Olivé, Keila

2015-12-01

Gold nanoparticles conjugated to cyclo-[Arg-Gly-Asp-D-Phe-Lys(Cys)] peptides (AuNP-c[RGDfK(C)]) have been reported as systems with specific cell internalization in breast cancer cells. AuNPs have also been proposed as localized heat sources for cancer treatment using laser irradiation or radiofrequency (RF). The aim of this research was to analyze, based on the Mie theory, the AuNP-c[RGDfK(C)] absorption cross-sections (C(abs)) of low-frequency electromagnetic waves (13.56 MHz, λ = 22 m) and optical frequency waves (laser at λ = 532 nm) and to compare their effect on MCF7 cell viability as thermal conversion sources in AuNPs (20 nm) located inside cells. Cell viability was assessed in MCF7 cells treated with AuNP-c[RGDfK(C)] or water after exposure to the RF field (200 W, 100 V/cm) or laser irradiation (Irradiance 0.65 W/cm2). In both cases (RF and laser) the presence of nanoparticles in cells caused a significant increase in the temperature of the medium (RF: AT = 29.9 ± 1.7 degrees C for AuNP compared to ΔT = 13.0 ± 1.4 degrees C for water; laser: ΔT = 13.5 ± 0.7 degrees C for AuNP compared to 3.3 ± 0.5 degrees C for water). Although RF induced a higher increase in the temperature of the medium with nanoparticles, the largest effect on the cell viability was produced by laser when nanoparticles were located inside the cells (8.7?0.7% for laser compared to 19.4 ± 0.9% for RF). The differences obtained in C(abs) values (laser: 3.7 x 10- (16) m2; RF: 7.9 x 10-(23) m2) and the observed effect on MFC7 cell viability support two mechanisms previously proposed "wave energy absorption by AuNPs" when laser is used as a thermal conversion source, and "attenuation of the wave passing through the AuNP suspension" when RF is applied. The AuNP-c[RGDfK(C)] nanosystem shows suitable properties to improve hyperthermia treatments under laser irradiation due to a larger heat release inside cells.

Measurement Techniques for Transmit Source Clock Jitter for Weak Serial RF Links

NASA Technical Reports Server (NTRS)

Lansdowne, Chatwin A.; Schlesinger, Adam M.

2010-01-01

Techniques for filtering clock jitter measurements are developed, in the context of controlling data modulation jitter on an RF carrier to accommodate low signal-to-noise ratio thresholds of high-performance error correction codes. Measurement artifacts from sampling are considered, and a tutorial on interpretation of direct readings is included.

Lorentz force detuning analysis of the Spallation Neutron Source (SNS) accelerating cavities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, R.R.; Matsumoto, K. Y.; Ciovati, G.

2001-01-01

The Spallation Neutron Source (SNS) project incorporates a superconducting radio-frequency (SRF) accelerator for the final section of the pulsed mode linac. Cavities with geometrical {beta} values of {beta}=0.61 and {beta}=0.81 are utilized in the SRF section, and are constructed out of thin-walled niobium with stiffener rings welded between the cells near the iris. The welded titanium helium vessel and tuner assembly restrains the cavity beam tubes. Cavities with {beta} values less than one have relatively steep and flat side-walls making the cavities susceptible to Lorentz force detuning. In addition, the pulsed RF induces cyclic Lorentz pressures that mechanically excite themore » cavities, producing a dynamic Lorentz force detuning different from a continuous RF system. The amplitude of the dynamic detuning for a given cavity design is a function of the mechanical damping, stiffness of the tuner/helium vessel assembly, RF pulse profile, and the RF pulse rate. This paper presents analysis and testing results to date, and indicates areas where more investigation is required.« less

Advances/applications of MAGIC and SOS

NASA Astrophysics Data System (ADS)

Warren, Gary; Ludeking, Larry; Nguyen, Khanh; Smithe, David; Goplen, Bruce

1993-12-01

MAGIC and SOS have been applied to investigate a variety of accelerator-related devices. Examples include high brightness electron guns, beam-RF interactions in klystrons, cold-test modes in an RFQ and in RF sources, and a high-quality, flexible, electron gun with operating modes appropriate for gyrotrons, peniotrons, and other RF sources. Algorithmic improvements for PIC have been developed and added to MAGIC and SOS to facilitate these modeling efforts. Two new field algorithms allow improved control of computational numerical noise and selective control of harmonic modes in RF cavities. An axial filter in SOS accelerates simulations in cylindrical coordinates. The recent addition of an export/import feature now allows long devices to be modeled in sections. Interfaces have been added to receive electromagnetic field information from the Poisson group of codes and from EGUN and to send beam information to PARMELA for subsequent tracing of bunches through beam optics. Post-processors compute and display beam properties including geometric, normalized, and slice emittances, and phase-space parameters, and video. VMS, UNIX, and DOS versions are supported, with migration underway toward windows environments.

Pulsed beam tests at the SANAEM RFQ beamline

NASA Astrophysics Data System (ADS)

Turemen, G.; Akgun, Y.; Alacakir, A.; Kilic, I.; Yasatekin, B.; Ergenlik, E.; Ogur, S.; Sunar, E.; Yildiz, V.; Ahiska, F.; Cicek, E.; Unel, G.

2017-07-01

A proton beamline consisting of an inductively coupled plasma (ICP) source, two solenoid magnets, two steerer magnets and a radio frequency quadrupole (RFQ) is developed at the Turkish Atomic Energy Authority’s (TAEA) Saraykoy Nuclear Research and Training Center (SNRTC-SANAEM) in Ankara. In Q4 of 2016, the RFQ was installed in the beamline. The high power tests of the RF power supply and the RF transmission line were done successfully. The high power RF conditioning of the RFQ was performed recently. The 13.56 MHz ICP source was tested in two different conditions, CW and pulsed. The characterization of the proton beam was done with ACCTs, Faraday cups and a pepper-pot emittance meter. Beam transverse emittance was measured in between the two solenoids of the LEBT. The measured beam is then reconstructed at the entrance of the RFQ by using computer simulations to determine the optimum solenoid currents for acceptance matching of the beam. This paper will introduce the pulsed beam test results at the SANAEM RFQ beamline. In addition, the high power RF conditioning of the RFQ will be discussed.

Performance of the BATMAN RF source with a large racetrack shaped driver

NASA Astrophysics Data System (ADS)

Kraus, W.; Schiesko, L.; Wimmer, C.; Fantz, U.; Heinemann, B.

2017-08-01

In the negative ion sources in neutral beam injection systems (NBI) of future fusion reactors the plasma is generated in up to eight cylindrical RF sources ("drivers") from which it expands into the main volume. For these large sources, in particular those used in the future DEMO NBI, a high RF efficiency and operational reliability is required. To achieve this it could be favorable to substitute each pair of drivers by one larger one. To investigate this option the cylindrical driver of the BATMAN source at IPP Garching has been replaced by a large source with a racetrack shaped base area and tested using the same extraction system. The main differences are a five times larger source volume and another position of the Cs oven which is mounted onto the driver`s back plate and not onto the expansion volume. The conditioning characteristics and the plasma symmetry in front of the plasma grid were very similar. The extracted H- current densities jex are comparable to that achieved with the small driver at the same power. Because no saturation of jex occurred at 0.6 Pa at high power and the source allows high power operation, a maximum value 45.1 mA/cm2 at 103 kW has been reached. Sputtered Cu from the walls of the expansion volume affected the performance at low pressure, particularly in deuterium. The experiments will be therefore continued with Mo coating of all inner walls.

Non-Equilibrium Plasma MHD Electrical Power Generation at Tokyo Tech

NASA Astrophysics Data System (ADS)

Murakami, T.; Okuno, Y.; Yamasaki, H.

2008-02-01

This paper reviews the recent activities on radio-frequency (rf) electromagnetic-field-assisted magnetohydrodynamic (MHD) power generation experiments at the Tokyo Institute of Technology. An inductively coupled rf field (13.56 MHz) is continuously supplied to the disk-shaped Hall-type MHD generator. The first part of this paper describes a method of obtaining increased power output from a pure Argon plasma MHD power generator by incorporating an rf power source to preionize and heat the plasma. The rf heating enhances ionization of the Argon and raises the temperature of the free electron population above the nominally low 4500 K temperatures obtained without rf heating. This in turn enhances the plasma conductivity making MHD power generation feasible. We demonstrate an enhanced power output when rf heating is on approximately 5 times larger than the input power of the rf generator. The second part of this paper is a demonstration of a physical phenomenon of the rf-stabilization of the ionization instability, that had been conjectured for some time, but had not been seen experimentally. The rf heating suppresses the ionization instability in the plasma behavior and homogenizes the nonuniformity of the plasma structures. The power-generating performance is significantly improved with the aid of the rf power under wide seeding conditions. The increment of the enthalpy extraction ratio of around 2% is significantly greater than the fraction of the net rf power, that is, 0.16%, to the thermal input.

Advanced RF and microwave functions based on an integrated optical frequency comb source.

PubMed

Xu, Xingyuan; Wu, Jiayang; Nguyen, Thach G; Shoeiby, Mehrdad; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

2018-02-05

We demonstrate advanced transversal radio frequency (RF) and microwave functions based on a Kerr optical comb source generated by an integrated micro-ring resonator. We achieve extremely high performance for an optical true time delay aimed at tunable phased array antenna applications, as well as reconfigurable microwave photonic filters. Our results agree well with theory. We show that our true time delay would yield a phased array antenna with features that include high angular resolution and a wide range of beam steering angles, while the microwave photonic filters feature high Q factors, wideband tunability, and highly reconfigurable filtering shapes. These results show that our approach is a competitive solution to implementing reconfigurable, high performance and potentially low cost RF and microwave signal processing functions for applications including radar and communication systems.

Bunch compression efficiency of the femtosecond electron source at Chiang Mai University

NASA Astrophysics Data System (ADS)

Thongbai, C.; Kusoljariyakul, K.; Saisut, J.

2011-07-01

A femtosecond electron source has been developed at the Plasma and Beam Physics Research Facility (PBP), Chiang Mai University (CMU), Thailand. Ultra-short electron bunches can be produced with a bunch compression system consisting of a thermionic cathode RF-gun, an alpha-magnet as a magnetic bunch compressor, and a linear accelerator as a post acceleration section. To obtain effective bunch compression, it is crucial to provide a proper longitudinal phase-space distribution at the gun exit matched to the subsequent beam transport system. Via beam dynamics calculations and experiments, we investigate the bunch compression efficiency for various RF-gun fields. The particle distribution at the RF-gun exit will be tracked numerically through the alpha-magnet and beam transport. Details of the study and results leading to an optimum condition for our system will be presented.

Coupled microwave ECR and radio-frequency plasma source for plasma processing

DOEpatents

Tsai, Chin-Chi; Haselton, Halsey H.

1994-01-01

In a dual plasma device, the first plasma is a microwave discharge having its own means of plasma initiation and control. The microwave discharge operates at electron cyclotron resonance (ECR), and generates a uniform plasma over a large area of about 1000 cm.sup.2 at low pressures below 0.1 mtorr. The ECR microwave plasma initiates the second plasma, a radio frequency (RF) plasma maintained between parallel plates. The ECR microwave plasma acts as a source of charged particles, supplying copious amounts of a desired charged excited species in uniform manner to the RF plasma. The parallel plate portion of the apparatus includes a magnetic filter with static magnetic field structure that aids the formation of ECR zones in the two plasma regions, and also assists in the RF plasma also operating at electron cyclotron resonance.

Coupled microwave ECR and radio-frequency plasma source for plasma processing

DOEpatents

Tsai, C.C.; Haselton, H.H.

1994-03-08

In a dual plasma device, the first plasma is a microwave discharge having its own means of plasma initiation and control. The microwave discharge operates at electron cyclotron resonance (ECR), and generates a uniform plasma over a large area of about 1000 cm[sup 2] at low pressures below 0.1 mtorr. The ECR microwave plasma initiates the second plasma, a radio frequency (RF) plasma maintained between parallel plates. The ECR microwave plasma acts as a source of charged particles, supplying copious amounts of a desired charged excited species in uniform manner to the RF plasma. The parallel plate portion of the apparatus includes a magnetic filter with static magnetic field structure that aids the formation of ECR zones in the two plasma regions, and also assists in the RF plasma also operating at electron cyclotron resonance. 4 figures.

Photo, thermal and chemical degradation of riboflavin

PubMed Central

Kazi, Sadia Hafeez; Ahmed, Sofia; Anwar, Zubair; Ahmad, Iqbal

2014-01-01

Summary Riboflavin (RF), also known as vitamin B2, belongs to the class of water-soluble vitamins and is widely present in a variety of food products. It is sensitive to light and high temperature, and therefore, needs a consideration of these factors for its stability in food products and pharmaceutical preparations. A number of other factors have also been identified that affect the stability of RF. These factors include radiation source, its intensity and wavelength, pH, presence of oxygen, buffer concentration and ionic strength, solvent polarity and viscosity, and use of stabilizers and complexing agents. A detailed review of the literature in this field has been made and all those factors that affect the photo, thermal and chemical degradation of RF have been discussed. RF undergoes degradation through several mechanisms and an understanding of the mode of photo- and thermal degradation of RF may help in the stabilization of the vitamin. A general scheme for the photodegradation of RF is presented. PMID:25246959

Miniature Electron Sources for Tomorrow’s Vacuum THz Devices (MiPRI)

DTIC Science & Technology

2006-07-01

Microwaves, Proceedings of the Fourth Workshop on High Power RF, 22 V. L. Bratman, N. S . Ginzburg, N. F. Kovalev, G. S . Nusinovich, and M. edited by R. M...3Po Kalynov, N. G. Kolganov, V. N. Manuilov, F. S . Rusin, S . V. Samsonov, and A. V. Savilov, in High Energy Density and High Power RF: 7th When this...showed that this will enable the design of future THz sources operating with relatively high efficiency at high power levels. 15. SUBJECT TERMS THz

Characteristics of electromagnetic interference generated during discharge of Mylar samples. [spacecraft-environment interaction simulation

NASA Technical Reports Server (NTRS)

Leung, P. L.

1984-01-01

This paper discusses the measurements of the electromagnetic interference (EMI) generated during discharges of Mylar samples. The two components of EMI, the conducted emission and the radiated emission, are characterized by the replacement current and the radiated RF spectrum respectively. The measured radiated RF spectra reveal important information on the source of the electromagnetic radiation. The possible sources are the replacement current pulse and the discharged generated plasma. The scaling of the amplitudes of the EMI, as a function of the area of the test sample, is also discussed.

Rod-filter-field optimization of the J-PARC RF-driven H{sup −} ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.

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). Although rod-filter-field (RFF) is indispensable and one of the most beam performance dominative parameters for the RF-driven H{sup −} ion source with the internal-antenna, the procedure to optimize it is not established. Inmore » order to optimize the RFF and establish the procedure, the beam performances of the J-PARC source with various types of rod-filter-magnets (RFMs) were measured. By changing RFM’s gap length and gap number inside of the region projecting the antenna inner-diameter along the beam axis, the dependence of the H{sup −} ion beam intensity on the net 2MHz-RF power was optimized. Furthermore, the fine-tuning of RFM’s cross-section (magnetmotive force) was indispensable for easy operation with the temperature (T{sub PE}) of the plasma electrode (PE) lower than 70°C, which minimizes the transverse emittances. The 5% reduction of RFM’s cross-section decreased the time-constant to recover the cesium effects after an slightly excessive cesiation on the PE from several 10 minutes to several minutes for T{sub PE} around 60°C.« less

Semiconductor laser-based optoelectronics oscillators

NASA Astrophysics Data System (ADS)

Yao, X. S.; Maleki, Lute; Wu, Chi; Davis, Lawrence J.; Forouhar, Siamak

1998-08-01

We demonstrate the realization of coupled opto-electronic oscillators (COEO) with different semiconductor lasers, including a ring laser, a Fabry-Perot laser, and a colliding pulse mode-locked laser. Each COEO can simultaneously generate short optical pulses and spectrally pure RF signals. With these devices, we obtained optical pulses as short as 6 picoseconds and RF signals as high in frequency as 18 GHz with a spectral purity comparable with a HP8561B synthesizer. These experiments demonstrate that COEOs are promising compact sources for generating low jitter optical pulses and low phase noise RF/millimeter wave signals.

Gate Drain Underlapped-PNIN-GAA-TFET for Comprehensively Upgraded Analog/RF Performance

NASA Astrophysics Data System (ADS)

Madan, Jaya; Chaujar, Rishu

2017-02-01

This work integrates the merits of gate-drain underlapping (GDU) and N+ source pocket on cylindrical gate all around tunnel FET (GAA-TFET) to form GDU-PNIN-GAA-TFET. It is analysed that the source pocket located at the source-channel junction narrows the tunneling barrier width at the tunneling junction and thereby enhances the ON-state current of GAA-TFET. Further, it is obtained that the GDU resists the extension of carrier density (built-up under the gated region) towards the drain side (under the underlapped length), thereby suppressing the ambipolar current and reducing the parasitic capacitances of GAA-TFET. Consequently, the amalgamated merits of both engineering schemes are obtained in GDU-PNIN-GAA-TFET that thus conquers the greatest challenges faced by TFET. Thus, GDU-PNIN-GAA-TFET results in an up-gradation in the overall performance of GAA-TFET. Moreover, it is realised that the RF figure of merits FOMs such as cut-off frequency (fT) and maximum oscillation frequency (fMAX) are also considerably improved with integration of source pocket on GAA-TFET. Thus, the improved analog and RF performance of GDU-PNIN-GAA-TFET makes it ideal for low power and high-speed applications.

Development of a dual-pulse RF driver for an S-band (= 2856 MHz) RF electron linear accelerator

NASA Astrophysics Data System (ADS)

Cha, Sungsu; Kim, Yujong; Lee, Byeong-No; Lee, Byung Cheol; Cha, Hyungki; Ha, Jang Ho; Park, Hyung Dal; Lee, Seung Hyun; Kim, Hui Su; Buaphad, Pikad

2016-04-01

The radiation equipment research division of Korea Atomic Energy Research Institute has developed a Container Inspection System (CIS) using a Radio Frequency (RF) electron linear accelerator for port security. The primary purpose of the CIS is to detect nuclear materials and explosives, as well country-specific prohibited substances, e.g., smuggled. The CIS consists of a 9/6 MeV dualenergy electron linear accelerator for distinguishing between organic and inorganic materials. The accelerator consists of an electron gun, an RF accelerating structure, an RF driver, a modulator, electromagnets, a cooling system, a X-ray generating target, X-ray collimator, a detector, and a container moving system. The RF driver is an important part of the configuration because it is the RF power source: it supplies the RF power to the accelerating structure. A unique aspect of the RF driver is that it generates dual RF power to generate dual energy (9/6 MeV). The advantage of this RF driver is that it can allow the pulse width to vary and can be used to obtain a wide range of energy output, and pulse repetition rates up to 300 Hz. For this reason, 140 W (5 MW - 9 MeV) and 37 W (3.4 MW - 6 MeV) power outputs are available independently. A high power test for 20 minutes demonstrate that stable dual output powers can be generated. Moreover, the dual power can be applied to the accelerator which has stable accelerator operation. In this paper, the design, fabrication and high power test of the RF driver for the RF electron linear accelerator (linac) are presented.

Penetration and screening of perpendicularly launched electromagnetic waves through bounded supercritical plasma confined in multicusp magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dey, Indranuj; Bhattacharjee, Sudeep

2011-02-15

The question of electromagnetic wave penetration and screening by a bounded supercritical ({omega}{sub p}>{omega} with {omega}{sub p} and {omega} being the electron-plasma and wave frequencies, respectively) plasma confined in a minimum B multicusp field, for waves launched in the k perpendicular B{sub o} mode, is addressed through experiments and numerical simulations. The scale length of radial plasma nonuniformity (|n{sub e}/({partial_derivative}n{sub e}/{partial_derivative}r)|) and magnetostatic field (B{sub o}) inhomogeneity (|B{sub o}/({partial_derivative}B{sub o}/{partial_derivative}r)|) are much smaller than the free space ({lambda}{sub o}) and guided wavelengths ({lambda}{sub g}). Contrary to predictions of plane wave dispersion theory and the Clemow-Mullaly-Allis (CMA) diagram, for a boundedmore » plasma a finite propagation occurs through the central plasma regions where {alpha}{sub p}{sup 2}={omega}{sub p}{sup 2}/{omega}{sup 2}{>=}1 and {beta}{sub c}{sup 2}={omega}{sub ce}{sup 2}/{omega}{sup 2}<<1({approx}10{sup -4}), with {omega}{sub ce} being the electron cyclotron frequency. Wave screening, as predicted by the plane wave model, does not remain valid due to phase mixing and superposition of reflected waves from the conducting boundary, leading to the formation of electromagnetic standing wave modes. The waves are found to satisfy a modified upper hybrid resonance (UHR) relation in the minimum B field and are damped at the local electron cyclotron resonance (ECR) location.« less

Self-starting picosecond optical pulse source using stimulated Brillouin scattering in an optical fiber.

PubMed

Tang, W W; Shu, C

2005-02-21

We demonstrate a regeneratively mode-locked optical pulse source at about 10 GHz using an optoelectronic oscillator constructed with an electro-absorption modulator integrated distributed feedback laser diode. The 10 GHz RF component is derived from the interaction between the pump wave and the backscattered, frequency-downshifted Stokes wave resulted from stimulated Brillouin scattering in an optical fiber. The component serves as a modulation source for the 1556 nm laser diode without the need for any electrical or optical RF filter to perform the frequency extraction. Dispersion-compensated fiber, dispersion-shifted fiber, and standard single-mode fiber have been used respectively to generate optical pulses at variable repetition rates.

RF Coupling into the Fuel Tank of a Large Transport Aircraft from Intentionally Transmitting Peds in the Passenger Cabin

NASA Technical Reports Server (NTRS)

Nguyen, Truong X.; Dudley, Kenneth L.; Scearce, Stephen A.; Ely, Jay J.; Richardson, Robert E.; Hatfield, Michael O.

2000-01-01

An investigation was performed to study the potential for radio frequency (RF) power radiated from Portable Electronic Devices (PEDs) to create an arcing/sparking event within the fuel tank of a large transport aircraft. This paper describes the experimental methods used for measuring RF coupling to the fuel tank and Fuel Quantity Indication System (FQIS) wiring from PED sources located in the passenger cabin. To allow comparison of voltage/current data obtained in a laboratory chamber FQIS installation to an actual aircraft FQIS installation, aircraft fuel tank RF reverberation characteristics were also measured. Results from the measurements, along with a survey of threats from typical intentional transmitting PEDs are presented. The resulting worst-case power coupled onto fuel tank FQIS wiring is derived. The same approach can be applied to measure RF coupling into various other aircraft systems.

RF Noise Generation in High-Pressure Short-Arc DC Xenon Lamps

NASA Astrophysics Data System (ADS)

Minayeva, Olga; Doughty, Douglas

2007-10-01

Continuous direct current xenon arcs will generate RF noise under certain circumstance, which can lead to excessive electro- magnetic interference in systems that use these arcs as light sources. Phenomenological observations are presented for xenon arcs having arc gaps ˜1 mm, cold fill pressures of ˜2.5 MPa, and currents up to 30 amps. Using a loop antenna in the vicinity of an operating lamp, it is observed that as the current to the arc is lowered there is a reproducible threshold at which the RF noise generation begins. This threshold is accompanied by a small abrupt drop in voltage (˜0.2 volts). The RF emission appears in pulses ˜150 nsec wide separated by ˜300 nec - the pulse interval decreases with decreasing current. The properties of the RF emission as a function of arc parameters (such as pressure, arc gap, electrode design) will be discussed and a semi-quantitative model presented.

FERMILAB CRYOMODULE TEST STAND RF INTERLOCK SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petersen, Troy; Diamond, J. S.; McDowell, D.

2016-10-12

An interlock system has been designed for the Fermilab Cryo-module Test Stand (CMTS), a test bed for the cryo- modules to be used in the upcoming Linac Coherent Light Source 2 (LCLS-II) project at SLAC. The interlock system features 8 independent subsystems, one per superconducting RF cavity and solid state amplifier (SSA) pair. Each system monitors several devices to detect fault conditions such as arcing in the waveguides or quenching of the SRF system. Additionally each system can detect fault conditions by monitoring the RF power seen at the cavity coupler through a directional coupler. In the event of amore » fault condition, each system is capable of removing RF signal to the amplifier (via a fast RF switch) as well as turning off the SSA. Additionally, each input signal is available for re- mote viewing and recording via a Fermilab designed digitizer board and MVME 5500 processor.« less

Performance evaluation of a permanent ring magnet based helicon plasma source for negative ion source research

NASA Astrophysics Data System (ADS)

Pandey, Arun; Bandyopadhyay, M.; Sudhir, Dass; Chakraborty, A.

2017-10-01

Helicon wave heated plasmas are much more efficient in terms of ionization per unit power consumed. A permanent magnet based compact helicon wave heated plasma source is developed in the Institute for Plasma Research, after carefully optimizing the geometry, the frequency of the RF power, and the magnetic field conditions. The HELicon Experiment for Negative ion-I source is the single driver helicon plasma source that is being studied for the development of a large sized, multi-driver negative hydrogen ion source. In this paper, the details about the single driver machine and the results from the characterization of the device are presented. A parametric study at different pressures and magnetic field values using a 13.56 MHz RF source has been carried out in argon plasma, as an initial step towards source characterization. A theoretical model is also presented for the particle and power balance in the plasma. The ambipolar diffusion process taking place in a magnetized helicon plasma is also discussed.

Performance evaluation of a permanent ring magnet based helicon plasma source for negative ion source research.

PubMed

Pandey, Arun; Bandyopadhyay, M; Sudhir, Dass; Chakraborty, A

2017-10-01

Helicon wave heated plasmas are much more efficient in terms of ionization per unit power consumed. A permanent magnet based compact helicon wave heated plasma source is developed in the Institute for Plasma Research, after carefully optimizing the geometry, the frequency of the RF power, and the magnetic field conditions. The HELicon Experiment for Negative ion-I source is the single driver helicon plasma source that is being studied for the development of a large sized, multi-driver negative hydrogen ion source. In this paper, the details about the single driver machine and the results from the characterization of the device are presented. A parametric study at different pressures and magnetic field values using a 13.56 MHz RF source has been carried out in argon plasma, as an initial step towards source characterization. A theoretical model is also presented for the particle and power balance in the plasma. The ambipolar diffusion process taking place in a magnetized helicon plasma is also discussed.

Beam property measurement of a 300-kV ion source test stand for a 1-MV electrostatic accelerator

NASA Astrophysics Data System (ADS)

Park, Sae-Hoon; Kim, Dae-Il; Kim, Yu-Seok

2016-09-01

The KOMAC (Korea Multi-purpose Accelerator Complex) has been developing a 300-kV ion source test stand for a 1-MV electrostatic accelerator for industrial purposes. A RF ion source was operated at 200 MHz with its matching circuit. The beam profile and emittance were measured behind an accelerating column to confirm the beam property from the RF ion source. The beam profile was measured at the end of the accelerating tube and at the beam dump by using a beam profile monitor (BPM) and wire scanner. An Allison-type emittance scanner was installed behind the beam profile monitor (BPM) to measure the beam density in phase space. The measurement results for the beam profile and emittance are presented in this paper.

Theoretical investigation of the microwave electron gun

NASA Astrophysics Data System (ADS)

Gao, J.

1990-12-01

In this article the microwave electron gun (rf gun) is investigated theoretically in a general way. After a brief review of the sources of emittance growth in a cavity, the optimization criteria are given and optimized electric field distributions on the axes of the cavities are found, from which cavities for a rf gun can be designed.

Millimeter wave generation by relativistic electron beams and microwave-plasma interaction

NASA Astrophysics Data System (ADS)

Kuo, Spencer

1990-12-01

The design and operation of a compact, high power, millimeter wave source (cusptron) has been completed and proven successful. Extensive theoretical analysis of cusptron beam and rf dynamics has been carried out and published. Theory agrees beautifully with experiment. Microwave Bragg scattering due to been achieved by using expanding plasmas to upshift rf signal frequencies.

OBSERVATION OF REPETITION-RATE DEPENDANT EMISSION FROM AN UN-GATED THERMIONIC CATHODE RF GUN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edelen, J. P.; Sun, Y.; Harris, J. R.

Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an ungated thermionicmore » cathode RF gun to high average current machines.« less

Adapting High Brightness Relativistic Electron Beams for Ultrafast Science

NASA Astrophysics Data System (ADS)

Scoby, Cheyne Matthew

This thesis explores the use of ultrashort bunches generated by a radiofrequency electron photoinjector driven by a femtosecond laser. Rf photoinjector technology has been developed to generate ultra high brightness beams for advanced accelerators and to drive advanced light source applications. The extremely good quality of the beams generated by this source has played a key role in the development of 4th generation light sources such as the Linac Coherent Light Source, thus opening the way to studies of materials science and biological systems with high temporal and spatial resolution. At the Pegasus Photoinjector Lab, we have developed the application of a BNL/SLAC/UCLA 1.6-cell rf photoinjector as a tool for ultrafast science in its own right. It is the aim of this work to explore the generation of ultrashort electron bunches, give descriptions of the novel ultrafast diagnostics developed to be able to characterize the electron bunch and synchronize it with a pump laser, and share some of the scientific results that were obtained with this technology at the UCLA Pegasus laboratory. This dissertation explains the requirements of the drive laser source and describes the principles of rf photoinjector design and operation necessary to produce electron bunches with an rms longitudinal length < 100 femtoseconds containing 107 - 108 electrons per bunch. In this condition, when the laser intensity is sufficiently high, multiphoton photoemission is demonstrated to be more efficient in terms of charge yield than single photon photoemission. When a short laser pulse hits the cathode the resulting beam dynamics are dominated by a strong space charge driven longitudinal expansion which leads to the creation of a nearly ideal uniformly filled ellipsoidal distribution. These beam distributions are characterized by linear space charge forces and hence by high peak brightness and small transverse emittances. This regime of operation of the RF photoinjector is also termed the “blow-out regime.” When the beam charge is maintained low, ultrashort electron bunches can be obtained enabling novel applications such as single shot Femtosecond Relativistic Electron Diffraction (FRED). High precision temporal diagnostic and synchronization techniques are integral to the use of femtosecond electron bunches for ultrafast science. An x-band rf streak camera provides measurements of the longitudinal profiles of sub-ps electron bunches. Spatial encoded electro-optic timestamping is developed to overcome the inherent rf-laser synchronization errors in rf photoinjectors. The ultrafast electron beams generated with the RF photoenjector are employed in pump-probe experiments wherein a target is illuminated with an intense pump laser to induce a transient behavior in the sample. FRED is used to study the melting of gold after heating with an intense femtosecond laser pulse. In a first experiment we study the process by taking different single-shot diffraction patterns at varying delays between the pump an probe beams. In a second experiment a variation of the technique is employed using the rf streak camera to time-stretch the beam after it has diffraction from the sample in order to capture the full melting dynamics in a single shot. Finally, relativistic ultrashort electron bunches are used as a probe of plasma dynamics in electron radiography/shadowgraphy experiments. This technique is used to study photoemission with intense laser pulses and the evolution of electromagnetic fields in a photoinduced dense plasma. This experiment is also performed in two different modes: one where different pictures are acquired at different time delays, and the other where a single streak image is used to obtain visualization of the propagation electromagnetic fields with an unprecedented 35 femtosecond resolution.

A high brightness proton injector for the Tandetron accelerator at Jožef Stefan Institute

NASA Astrophysics Data System (ADS)

Pelicon, Primož; Podaru, Nicolae C.; Vavpetič, Primož; Jeromel, Luka; Ogrinc Potocnik, Nina; Ondračka, Simon; Gottdang, Andreas; Mous, Dirk J. M.

2014-08-01

Jožef Stefan Institute recently commissioned a high brightness H- ion beam injection system for its existing tandem accelerator facility. Custom developed by High Voltage Engineering Europa, the multicusp ion source has been tuned to deliver at the entrance of the Tandetron™ accelerator H- ion beams with a measured brightness of 17.1 A m-2 rad-2 eV-1 at 170 μA, equivalent to an energy normalized beam emittance of 0.767 π mm mrad MeV1/2. Upgrading the accelerator facility with the new injection system provides two main advantages. First, the high brightness of the new ion source enables the reduction of object slit aperture and the reduction of acceptance angle at the nuclear microprobe, resulting in a reduced beam size at selected beam intensity, which significantly improves the probe resolution for micro-PIXE applications. Secondly, the upgrade strongly enhances the accelerator up-time since H and He beams are produced by independent ion sources, introducing a constant availability of 3He beam for fusion-related research with NRA. The ion beam particle losses and ion beam emittance growth imply that the aforementioned beam brightness is reduced by transport through the ion optical system. To obtain quantitative information on the available brightness at the high-energy side of the accelerator, the proton beam brightness is determined in the nuclear microprobe beamline. Based on the experience obtained during the first months of operation for micro-PIXE applications, further necessary steps are indicated to obtain optimal coupling of the new ion source with the accelerator to increase the normalized high-energy proton beam brightness at the JSI microprobe, currently at 14 A m-2 rad-2 eV-1, with the output current at 18% of its available maximum.

COMAR technical information statement: expert reviews on potential health effects of radiofrequency electromagnetic fields and comments on the bioinitiative report.

PubMed

2009-10-01

The Committee on Man and Radiation (COMAR) is a technical committee of the Engineering in Medicine and Biology Society (EMBS) of the Institute of Electrical and Electronics Engineers (IEEE). Its primary area of interest is biological effects of non-ionizing electromagnetic radiation, including radiofrequency (RF) energy. The public interest in possible health effects attributed to RF energy, such as emitted by mobile phones, wireless telephone base stations, TV and radio broadcasting facilities, Wi-Fi systems and many other sources, has been accompanied by commentary in the media that varies considerably in reliability and usefulness for their audience. The focus of this COMAR Technical Information Statement is to identify quality sources of scientific information on potential health risks from exposure to RF energy. This Statement provides readers with references to expert reports and other reliable sources of information about this topic, most of which are available on the Internet. This report summarizes the conclusions from several major reports and comments on the markedly different conclusions in the BioInitiative Report (abbreviated BIR below). Since appearing on the Internet in August 2007, the BIR has received much media attention but, more recently, has been criticized by several health organizations (see Section titled "Views of health agencies about BIR"). COMAR concludes that the weight of scientific evidence in the RF bioeffects literature does not support the safety limits recommended by the BioInitiative group. For this reason, COMAR recommends that public health officials continue to base their policies on RF safety limits recommended by established and sanctioned international organizations such as the Institute of Electrical and Electronics Engineers International Committee on Electromagnetic Safety and the International Commission on Non-Ionizing Radiation Protection, which is formally related to the World Health Organization.

OPAL: prediction of MoRF regions in intrinsically disordered protein sequences.

PubMed

Sharma, Ronesh; Raicar, Gaurav; Tsunoda, Tatsuhiko; Patil, Ashwini; Sharma, Alok

2018-06-01

Intrinsically disordered proteins lack stable 3-dimensional structure and play a crucial role in performing various biological functions. Key to their biological function are the molecular recognition features (MoRFs) located within long disordered regions. Computationally identifying these MoRFs from disordered protein sequences is a challenging task. In this study, we present a new MoRF predictor, OPAL, to identify MoRFs in disordered protein sequences. OPAL utilizes two independent sources of information computed using different component predictors. The scores are processed and combined using common averaging method. The first score is computed using a component MoRF predictor which utilizes composition and sequence similarity of MoRF and non-MoRF regions to detect MoRFs. The second score is calculated using half-sphere exposure (HSE), solvent accessible surface area (ASA) and backbone angle information of the disordered protein sequence, using information from the amino acid properties of flanks surrounding the MoRFs to distinguish MoRF and non-MoRF residues. OPAL is evaluated using test sets that were previously used to evaluate MoRF predictors, MoRFpred, MoRFchibi and MoRFchibi-web. The results demonstrate that OPAL outperforms all the available MoRF predictors and is the most accurate predictor available for MoRF prediction. It is available at http://www.alok-ai-lab.com/tools/opal/. ashwini@hgc.jp or alok.sharma@griffith.edu.au. Supplementary data are available at Bioinformatics online.

Inductive Electron Heating Revisited

NASA Astrophysics Data System (ADS)

Tuszewski, M.

1996-11-01

Inductively Coupled Plasmas (ICPs) have been studied for over a century. Recently, ICPs have been rediscovered by the multi-billion dollar semiconductor industry as an important class of high-density, low-pressure plasma sources suitable for the manufacture of next-generation integrated circuits. Present low-pressure ICP development is among the most active areas of plasma research. However, this development remains largely empirical, a prohibitively expensive approach for upcoming 300-mm diameter wafers. Hence, there is an urgent need for basic ICP plasma physics research, including experimental characterization and predictive numerical modeling. Inductive radio frequency (rf) power absorption is fundamental to the ICP electron heating and the resulting plasma transport but remains poorly understood. For example, recent experimental measurements and supporting fluid calculationsfootnote M. Tuszewski, Phys. Rev. Lett. 77 in press (1996) on a commercial deposition tool prototype show that the induced rf magnetic fields in the source can cause an order of magnitude reduction in plasma conductivity and in electron heating power density. In some cases, the rf fields penetrate through the entire volume of the ICP discharges while existing models that neglect the induced rf magnetic fields predict rf absorption in a thin skin layer near the plasma surface. The rf magnetic fields also cause more subtle changes in the plasma density and in the electron temperature spatial distributions. These data will be presented and the role of basic research in the applied world of semiconductor manufacturing will be discussed. ^*This research was conducted under the auspices of the U.S. DOE, supported by funds provided by the University of California for discretionary research by Los Alamos National Laboratory.

Hybrid simulations of solenoidal radio-frequency inductively coupled hydrogen discharges at low pressures

NASA Astrophysics Data System (ADS)

Yang, Wei; Li, Hong; Gao, Fei; Wang, You-Nian

2016-12-01

In this article, we have described a radio-frequency (RF) inductively coupled H2 plasma using a hybrid computational model, incorporating the Maxwell equations and the linear part of the electron Boltzmann equation into global model equations. This report focuses on the effects of RF frequency, gas pressure, and coil current on the spatial profiles of the induced electric field and plasma absorption power density. The plasma parameters, i.e., plasma density, electron temperature, density of negative ion, electronegativity, densities of neutral species, and dissociation degree of H2, as a function of absorption power, are evaluated at different gas pressures. The simulation results show that the utilization efficiency of the RF source characterized by the coupling efficiency of the RF electric field and power to the plasma can be significantly improved at the low RF frequency, gas pressure, and coil current, due to a low plasma density in these cases. The densities of vibrational states of H2 first rapidly increase with increasing absorption power and then tend to saturate. This is because the rapidly increased dissociation degree of H2 with increasing absorption power somewhat suppresses the increase of the vibrational states of H2, thus inhibiting the increase of the H-. The effects of absorption power on the utilization efficiency of the RF source and the production of the vibrational states of H2 should be considered when setting a value of the coil current. To validate the model simulations, the calculated electron density and temperature are compared with experimental measurements, and a reasonable agreement is achieved.

Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probe.

PubMed

Schmitzer, C; Kronberger, M; Lettry, J; Sanchez-Arias, J; Störi, H

2012-02-01

The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H(-) volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e(-) and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H(-) ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H(-) ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

Plasma characterization of the superconducting proton linear accelerator plasma generator using a 2 MHz compensated Langmuir probea)

NASA Astrophysics Data System (ADS)

Schmitzer, C.; Kronberger, M.; Lettry, J.; Sanchez-Arias, J.; Störi, H.

2012-02-01

The CERN study for a superconducting proton Linac (SPL) investigates the design of a pulsed 5 GeV Linac operating at 50 Hz. As a first step towards a future SPL H- volume ion source, a plasma generator capable of operating at Linac4 or nominal SPL settings has been developed and operated at a dedicated test stand. The hydrogen plasma is heated by an inductively coupled RF discharge e- and ions are confined by a magnetic multipole cusp field similar to the currently commissioned Linac4 H- ion source. Time-resolved measurements of the plasma potential, temperature, and electron energy distribution function obtained by means of a RF compensated Langmuir probe along the axis of the plasma generator are presented. The influence of the main tuning parameters, such as RF power and frequency and the timing scheme is discussed with the aim to correlate them to optimum H- ion beam parameters measured on an ion source test stand. The effects of hydrogen injection settings which allow operation at 50 Hz repetition rate are discussed.

Ultra-low output impedance RF power amplifier for parallel excitation.

PubMed

Chu, Xu; Yang, Xing; Liu, Yunfeng; Sabate, Juan; Zhu, Yudong

2009-04-01

Inductive coupling between coil elements of a transmit array is one of the key challenges faced by parallel RF transmission. An ultra-low output impedance RF power amplifier (PA) concept was introduced to address this challenge. In an example implementation, an output-matching network was designed to transform the drain-source impedance of the metallic oxide semiconductor field effect transistor (MOSFET) into a very low value for suppressing interelement coupling effect, and meanwhile, to match the input impedance of the coil to the optimum load of the MOSFET for maximizing the available output power. Two prototype amplifiers with 500-W output rating were developed accordingly, and were further evaluated with a transmit array in phantom experiments. Compared to the conventional 50-Omega sources, the new approach exhibited considerable effectiveness suppressing the effects of interelement coupling. The experiments further indicated that the isolation performance was comparable to that achieved by optimized overlap decoupling. The new approach, benefiting from a distinctive current-source characteristic, also exhibited a superior robustness against load variation. Feasibility of the new approach in high-field MR was demonstrated on a 3T clinical scanner.

DC and analog/RF performance optimisation of source pocket dual work function TFET

NASA Astrophysics Data System (ADS)

Raad, Bhagwan Ram; Sharma, Dheeraj; Kondekar, Pravin; Nigam, Kaushal; Baronia, Sagar

2017-12-01

We investigate a systematic study of source pocket tunnel field-effect transistor (SP TFET) with dual work function of single gate material by using uniform and Gaussian doping profile in the drain region for ultra-low power high frequency high speed applications. For this, a n+ doped region is created near the source/channel junction to decrease the depletion width results in improvement of ON-state current. However, the dual work function of the double gate is used for enhancement of the device performance in terms of DC and analog/RF parameters. Further, to improve the high frequency performance of the device, Gaussian doping profile is considered in the drain region with different characteristic lengths which decreases the gate to drain capacitance and leads to drastic improvement in analog/RF figures of merit. Furthermore, the optimisation is performed with different concentrations for uniform and Gaussian drain doping profile and for various sectional length of lower work function of the gate electrode. Finally, the effect of temperature variation on the device performance is demonstrated.

Multi-MW K-Band Harmonic Multiplier: RF Source For High-Gradient Accelerator R & D

NASA Astrophysics Data System (ADS)

Solyak, N. A.; Yakovlev, V. P.; Kazakov, S. Yu.; Hirshfield, J. L.

2009-01-01

A preliminary design is presented for a two-cavity harmonic multiplier, intended as a high-power RF source for use in experiments aimed at developing high-gradient structures for a future collider. The harmonic multiplier is to produce power at selected frequencies in K-band (18-26.5 GHz) using as an RF driver an XK-5 S-band klystron (2.856 GHz). The device is to be built with a TE111 rotating mode input cavity and interchangeable output cavities running in the TEn11 rotating mode, with n = 7,8,9 at 19.992, 22.848, and 25.704 GHz. An example for a 7th harmonic multiplier is described, using a 250 kV, 20 A injected laminar electron beam; with 10 MW of S-band drive power, 4.7 MW of 20-GHz output power is predicted. Details are described of the magnetic circuit, cavities, and output coupler.

Dual-mode capability for hardware-in-the-loop

NASA Astrophysics Data System (ADS)

Vamivakas, A. N.; Jackson, Ron L.

2000-07-01

This paper details a Hardware-in-the-Loop Facility (HIL) developed for evaluation and verification of a missile system with dual mode capability. The missile has the capability of tracking and intercepting a target using either an RF antenna or an IR sensor. The testing of a dual mode system presents a significant challenge in the development of the HIL facility. An IR and RF target environment must be presented simultaneously to the missile under test. These targets, simulated by IR and RF sources, must be presented to the missile under test without interference from each other. The location of each source is critical in the development of the HIL facility. The requirements for building a HIL facility with dual mode capability and the methodology for testing the dual mode system are defined within this paper. Methods for the verification and validation of the facility are discussed.

Single element of the matrix source of negative hydrogen ions: Measurements of the extracted currents combined with diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yordanov, D., E-mail: yordanov@phys.uni-sofia.bg; Lishev, St.; Shivarova, A.

2016-02-15

Combining measurements of the extracted currents with probe and laser-photodetachment diagnostics, the study is an extension of recent tests of factors and gas-discharge conditions stimulating the extraction of volume produced negative ions. The experiment is in a single element of a rf source with the design of a matrix of small-radius inductively driven discharges. The results are for the electron and negative-ion densities, for the plasma potential and for the electronegativity in the vicinity of the plasma electrode as well as for the currents of the extracted negative ions and electrons. The plasma-electrode bias and the rf power have beenmore » varied. Necessity of a high bias to the plasma electrode and stable linear increase of the extracted currents with the rf power are the main conclusions.« less

Femtosecond MeV Electron Energy-Loss Spectroscopy

NASA Astrophysics Data System (ADS)

Li, R. K.; Wang, X. J.

2017-11-01

Pump-probe electron energy-loss spectroscopy (EELS) with femtosecond temporal resolution will be a transformative research tool for studying nonequilibrium chemistry and electronic dynamics of matter. In this paper, we propose a concept of femtosecond EELS utilizing mega-electron-volt electron beams from a radio-frequency (rf) photocathode source. The high acceleration gradient and high beam energy of the rf gun are critical to the generation of 10-fs electron beams, which enables an improvement of the temporal resolution by more than 1 order of magnitude beyond the state of the art. In our proposal, the "reference-beam technique" relaxes the energy stability requirement of the rf power source by roughly 2 orders of magnitude. The requirements for the electron-beam quality, photocathode, spectrometer, and detector are also discussed. Supported by particle-tracking simulations, we demonstrate the feasibility of achieving sub-electron-volt energy resolution and approximately 10-fs temporal resolution with existing or near-future hardware performance.

Microwave, irrigated, pulsed, or conventional radiofrequency energy source: which energy source for which catheter ablation?

PubMed

Erdogan, Ali; Grumbrecht, Stephan; Neumann, Thomas; Neuzner, Joerg; Pitschner, Heinz F

2003-01-01

The aim of the study was to compare the diameter of endomyocardial lesions induced with the delivery of microwave, cooled, or pulsed energy versus conventional RF energy. In vitro tests were performed in fresh endomyocardial preparations of pig hearts in a 10-L bath of NaCl 0.9% solution at 37 degrees C and constant 1.5 L/min flow. Ablation 7 Fr catheters with 4-mm tip electrodes were used, except for the delivery of microwave energy. Energy delivery time was set to 60 s/50 W in all experiments. Cooled energy delivery was performed with a closed irrigation catheter. Pulsed energy delivery was performed using a special controller with a duty-cycle of 5 ms. Microwave energy was delivered with a 2.5-GHz generator and 10-mm antenna. Electrode temperature and impedance were measured simultaneously. After ablation, lesion length, width, and depth were measured with microcalipers, and volume calculated by a formula for ellipsoid bodies. Each energy delivery mode was tested in ten experiments. The deepest lesions were created with cooled energy delivery, and the largest volume by microwave energy delivery. Pulsed RF produced significantly deeper lesions than conventional RF energy delivery. Cooled or pulsed RF energy delivery created deeper transmural lesions than conventional RF. To create linear lesions at anatomically complex sites (isthmus), microwave energy seemed superior by rapidly creating deep and long lesions.

A flexible super-capacitive solid-state power supply for miniature implantable medical devices.

PubMed

Meng, Chuizhou; Gall, Oren Z; Irazoqui, Pedro P

2013-12-01

We present a high-energy local power supply based on a flexible and solid-state supercapacitor for miniature wireless implantable medical devices. Wireless radio-frequency (RF) powering recharges the supercapacitor through an antenna with an RF rectifier. A power management circuit for the super-capacitive system includes a boost converter to increase the breakdown voltage required for powering device circuits, and a parallel conventional capacitor as an intermediate power source to deliver current spikes during high current transients (e.g., wireless data transmission). The supercapacitor has an extremely high area capacitance of ~1.3 mF/mm(2), and is in the novel form of a 100 μm-thick thin film with the merit of mechanical flexibility and a tailorable size down to 1 mm(2) to meet various clinical dimension requirements. We experimentally demonstrate that after fully recharging the capacitor with an external RF powering source, the supercapacitor-based local power supply runs a full system for electromyogram (EMG) recording that consumes ~670 μW with wireless-data-transmission functionality for a period of ~1 s in the absence of additional RF powering. Since the quality of wireless powering for implantable devices is sensitive to the position of those devices within the RF electromagnetic field, this high-energy local power supply plays a crucial role in providing continuous and reliable power for medical device operations.

Overview of Chronic Oral Toxicity Values for Chemicals Present in Hydraulic Fracturing Fluids, Flowback, and Produced Waters.

PubMed

Yost, Erin E; Stanek, John; DeWoskin, Robert S; Burgoon, Lyle D

2016-05-03

Concerns have been raised about potential public health effects that may arise if hydraulic fracturing-related chemicals were to impact drinking water resources. This study presents an overview of the chronic oral toxicity values-specifically, chronic oral reference values (RfVs) for noncancer effects, and oral slope factors (OSFs) for cancer-that are available for a list of 1173 chemicals that the United States (U.S.) Environmental Protection Agency (EPA) identified as being associated with hydraulic fracturing, including 1076 chemicals used in hydraulic fracturing fluids and 134 chemicals detected in flowback or produced waters from hydraulically fractured wells. The EPA compiled RfVs and OSFs using six governmental and intergovernmental data sources. Ninety (8%) of the 1076 chemicals reported in hydraulic fracturing fluids and 83 (62%) of the 134 chemicals reported in flowback/produced water had a chronic oral RfV or OSF available from one or more of the six sources. Furthermore, of the 36 chemicals reported in hydraulic fracturing fluids in at least 10% of wells nationwide (identified from EPA's analysis of the FracFocus Chemical Disclosure Registry 1.0), 8 chemicals (22%) had an available chronic oral RfV. The lack of chronic oral RfVs and OSFs for the majority of these chemicals highlights the significant knowledge gap that exists to assess the potential human health hazards associated with hydraulic fracturing.

Ion extraction from a saddle antenna RF surface plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dudnikov, V., E-mail: vadim@muonsinc.com; Johnson, R. P.; Han, B.

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 bymore » 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)« less

Ion extraction from a saddle antenna RF surface plasma source

NASA Astrophysics Data System (ADS)

Dudnikov, V.; Johnson, R. P.; Han, B.; Murray, S.; Pennisi, T.; Piller, C.; Santana, M.; Stockli, M.; Welton, R.; Breitschopf, J.; Dudnikova, G.

2015-04-01

Existing RF Surface Plasma Sources (SPS) for accelerators have specific efficiencies for H+ and H- ion generation around 3 to 5 mA/cm2 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- 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/cm2 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- 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).

Silicon Carbide Mixers Demonstrated to Improve the Interference Immunity of Radio-Based Aircraft Avionics

NASA Technical Reports Server (NTRS)

Neudeck, Philip G.

1998-01-01

Concern over the interference of stray radiofrequency (RF) emissions with key aircraft avionics is evident during takeoff and landing of every commercial flight when the flight attendant requests that all portable electronics be switched off. The operation of key radio-based avionics (such as glide-slope and localizer approach instruments) depends on the ability of front-end RF receivers to detect and amplify desired information signals while rejecting interference from undesired RF sources both inside and outside the aircraft. Incidents where key navigation and approach avionics malfunction because of RF interference clearly represent an increasing threat to flight safety as the radio spectrum becomes more crowded. In an initial feasibility experiment, the U.S. Army Research Laboratory and the NASA Lewis Research Center recently demonstrated the strategic use of silicon carbide (SiC) semiconductor components to significantly reduce the susceptibility of an RF receiver circuit to undesired RF interference. A pair of silicon carbide mixer diodes successfully reduced RF interference (intermodulation distortion) in a prototype receiver circuit by a factor of 10 (20 dB) in comparison to a pair of commercial silicon-based mixer diodes.

Combination of microneedle radiofrequency (RF), fractional RF skin resurfacing and multi-source non-ablative skin tightening for minimal-downtime, full-face skin rejuvenation.

PubMed

Kaplan, Haim; Kaplan, Lilach

2016-12-01

In the recent years, there is a growth in demand for radiofrequency (RF)-based procedures to improve skin texture, laxity and contour. The new generation of systems allow non-invasive and fractional resurfacing treatments on one platform. The aim of this study was to evaluate the safety and efficacy of a new treatment protocol using a multisource RF, combining 3 different modalities in each patient: [1] non-ablative RF skin tightening, [2] fractional skin resurfacing, and [3] microneedling RF for non-ablative coagulation and collagen remodelling. 14 subjects were enrolled in this study using EndyMed PRO ™ platform. Each patient had 8 non-ablative treatments and 4 fractional treatments (fractional skin resurfacing and Intensif). The global aesthetic score was used to evaluate improvement. All patients had improvement in skin appearance. About 43% had excellent or very good improvement above 50%, 18% had good improvement between 25 and 50%, and the rest 39% had a mild improvement of < 25%. Downtime was minimal and no adverse effect was reported. Our data show significant improvement of skin texture, skin laxity and wrinkle reduction achieved using RF treatment platform.

Spectrally pure RF photonic source based on a resonant optical hyper-parametric oscillator

NASA Astrophysics Data System (ADS)

Liang, W.; Eliyahu, D.; Matsko, A. B.; Ilchenko, V. S.; Seidel, D.; Maleki, L.

2014-03-01

We demonstrate a free running 10 GHz microresonator-based RF photonic hyper-parametric oscillator characterized with phase noise better than -60 dBc/Hz at 10 Hz, -90 dBc/Hz at 100 Hz, and -150 dBc/Hz at 10 MHz. The device consumes less than 25 mW of optical power. A correlation between the frequency of the continuous wave laser pumping the nonlinear resonator and the generated RF frequency is confirmed. The performance of the device is compared with the performance of a standard optical fiber based coupled opto-electronic oscillator of OEwaves.

Recent Results With Coupled Opto-Electronic Oscillators

NASA Astrophysics Data System (ADS)

Yao, X. S.; Maleki, L.; Wu, C.; Davis, L.; Forouhar, S.

1998-07-01

We present experimental results of coupled opto-electronic oscillators (COEOs) constructed with a semiconductor optical-amplifier-based ring laser, a semiconductor Fabry-Perot laser, and a semiconductor colliding-pulse mode-locked laser. Each COEO can simultaneously generate short optical pulses and spectrally pure RF signals. With these devices, we obtained optical pulses as short as 6 ps and RF signals as high in frequency as 18 GHz with a spectral purity comparable to an HP 8561B synthesizer. These experiments demonstrate that COEOs are promising compact sources for generating low jitter optical pulses and low phase noise RF/millimeter wave signals.

Recent results with the coupled opto-electronic oscillator

NASA Astrophysics Data System (ADS)

Yao, X. S.; Maleki, Lute; Wu, Chi; Davis, Lawrence J.; Forouhar, Siamak

1998-11-01

We present experimental results of coupled opto-electronic oscillators (COEO) constructed with a semiconductor optical amplifier based ring laser, a semiconductor Fabry-Perot laser, and a semiconductor colliding pulse mode-locked laser. Each COEO can simultaneously generate short optical pulses and spectrally pure RF signals. With these devices, we obtained optical pulses as short as 6 picoseconds and RF signals as high in frequency as 18 GHz with a spectral purity comparable with a HP8561B synthesizer. These experiments demonstrate that COEOs are promising compact sources for generating low jitter optical pulses and low phase noise RF/millimeter wave signals.

Coil extensions improve line shapes by removing field distortions

NASA Astrophysics Data System (ADS)

Conradi, Mark S.; Altobelli, Stephen A.; McDowell, Andrew F.

2018-06-01

The static magnetic susceptibility of the rf coil can substantially distort the field B0 and be a dominant source of line broadening. A scaling argument shows that this may be a particular problem in microcoil NMR. We propose coil extensions to reduce the distortion. The actual rf coil is extended to a much longer overall length by abutted coil segments that do not carry rf current. The result is a long and nearly uniform sheath of copper wire, in terms of the static susceptibility. The line shape improvement is demonstrated at 43.9 MHz and in simulation calculations.

Characteristics of a RF-Driven Ion Source for a Neutron Generator Used for Associated Particle Imaging

NASA Astrophysics Data System (ADS)

Wu, Ying; Hurley, John P.; Ji, Qing; Kwan, Joe; Leung, Ka-Ngo

2009-03-01

We present recent work on a prototype compact neutron generator for associated particle imaging (API). API uses alpha particles that are produced simultaneously with neutrons in the deuterium-tritium (2D(3T,n)4α) fusion reaction to determine the direction of the neutrons upon exiting the reaction. This method determines the spatial position of each neutron interaction and requires the neutrons to be generated from a small spot in order to achieve high spatial resolution. The ion source for API is designed to produce a focused ion beam with a beam spot diameter of 1-mm or less on the target. We use an axial type neutron generator with a predicted neutron yield of 108 n/s for a 50 μA D/T ion beam current accelerated to 80 kV. The generator utilizes an RF planar spiral antenna at 13.56 MHz to create a highly efficient inductively coupled plasma at the ion source. Experimental results show that beams with an atomic ion fraction of over 80% can be obtained while utilizing only 100 watts of RF power in the ion source. A single acceleration gap with a secondary electron suppression electrode is used in the tube. Experimental results from ion source testing, such as the current density, atomic ion fraction, electron temperature, and electron density will be discussed.

Overview of ion source characterization diagnostics in INTF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bandyopadhyay, M., E-mail: mainak@iter-india.org; Sudhir, Dass; Bhuyan, M.

2016-02-15

INdian Test Facility (INTF) is envisaged to characterize ITER diagnostic neutral beam system and to establish the functionality of its eight inductively coupled RF plasma driver based negative hydrogen ion source and its beamline components. The beam quality mainly depends on the ion source performance and therefore, its diagnostics plays an important role for its safe and optimized operation. A number of diagnostics are planned in INTF to characterize the ion source performance. Negative ions and its cesium contents in the source will be monitored by optical emission spectroscopy (OES) and cavity ring down spectroscopy. Plasma near the extraction regionmore » will be studied using standard electrostatic probes. The beam divergence and negative ion stripping losses are planned to be measured using Doppler shift spectroscopy. During initial phase of ion beam characterization, carbon fiber composite based infrared imaging diagnostics will be used. Safe operation of the beam will be ensured by using standard thermocouples and electrical voltage-current measurement sensors. A novel concept, based on plasma density dependent plasma impedance measurement using RF electrical impedance matching parameters to characterize the RF driver plasma, will be tested in INTF and will be validated with OES data. The paper will discuss about the overview of the complete INTF diagnostics including its present status of procurement, experimentation, interface with mechanical systems in INTF, and integration with INTF data acquisition and control systems.« less

Overview of ion source characterization diagnostics in INTF

NASA Astrophysics Data System (ADS)

Bandyopadhyay, M.; Sudhir, Dass; Bhuyan, M.; Soni, J.; Tyagi, H.; Joshi, J.; Yadav, A.; Rotti, C.; Parmar, Deepak; Patel, H.; Pillai, S.; Chakraborty, A.

2016-02-01

INdian Test Facility (INTF) is envisaged to characterize ITER diagnostic neutral beam system and to establish the functionality of its eight inductively coupled RF plasma driver based negative hydrogen ion source and its beamline components. The beam quality mainly depends on the ion source performance and therefore, its diagnostics plays an important role for its safe and optimized operation. A number of diagnostics are planned in INTF to characterize the ion source performance. Negative ions and its cesium contents in the source will be monitored by optical emission spectroscopy (OES) and cavity ring down spectroscopy. Plasma near the extraction region will be studied using standard electrostatic probes. The beam divergence and negative ion stripping losses are planned to be measured using Doppler shift spectroscopy. During initial phase of ion beam characterization, carbon fiber composite based infrared imaging diagnostics will be used. Safe operation of the beam will be ensured by using standard thermocouples and electrical voltage-current measurement sensors. A novel concept, based on plasma density dependent plasma impedance measurement using RF electrical impedance matching parameters to characterize the RF driver plasma, will be tested in INTF and will be validated with OES data. The paper will discuss about the overview of the complete INTF diagnostics including its present status of procurement, experimentation, interface with mechanical systems in INTF, and integration with INTF data acquisition and control systems.

An adaptable multiple power source for mass spectrometry and other scientific instruments.

PubMed

Lin, T-Y; Anderson, G A; Norheim, R V; Prost, S A; LaMarche, B L; Leach, F E; Auberry, K J; Smith, R D; Koppenaal, D W; Robinson, E W; Paša-Tolić, L

2015-09-01

An Adaptable Multiple Power Source (AMPS) system has been designed and constructed. The AMPS system can provide up to 16 direct current (DC) (±400 V; 5 mA), 4 radio frequency (RF) (two 500 VPP sinusoidal signals each, 0.5-5 MHz) channels, 2 high voltage sources (±6 kV), and one ∼40 W, 250 °C temperature-regulated heater. The system is controlled by a microcontroller, capable of communicating with its front panel or a computer. It can assign not only pre-saved fixed DC and RF signals but also profiled DC voltages. The AMPS system is capable of driving many mass spectrometry components and ancillary devices and can be adapted to other instrumentation/engineering projects.

Development of a compact permanent magnet helicon plasma source for ion beam bioengineering.

PubMed

Kerdtongmee, P; Srinoum, D; Nisoa, M

2011-10-01

A compact helicon plasma source was developed as a millimeter-sized ion source for ion beam bioengineering. By employing a stacked arrangement of annular-shaped permanent magnets, a uniform axial magnetic flux density up to 2.8 kG was obtained. A cost effective 118 MHz RF generator was built for adjusting forward output power from 0 to 40 W. The load impedance and matching network were then analyzed. A single loop antenna and circuit matching elements were placed on a compact printed circuit board for 50 Ω impedance matching. A plasma density up to 1.1 × 10(12) cm(-3) in the 10 mm diameter tube under the magnetic flux density was achieved with 35 W applied RF power.

Development of a compact permanent magnet helicon plasma source for ion beam bioengineering

NASA Astrophysics Data System (ADS)

Kerdtongmee, P.; Srinoum, D.; Nisoa, M.

2011-10-01

A compact helicon plasma source was developed as a millimeter-sized ion source for ion beam bioengineering. By employing a stacked arrangement of annular-shaped permanent magnets, a uniform axial magnetic flux density up to 2.8 kG was obtained. A cost effective 118 MHz RF generator was built for adjusting forward output power from 0 to 40 W. The load impedance and matching network were then analyzed. A single loop antenna and circuit matching elements were placed on a compact printed circuit board for 50 Ω impedance matching. A plasma density up to 1.1 × 1012 cm-3 in the 10 mm diameter tube under the magnetic flux density was achieved with 35 W applied RF power.

Increased collection efficiency of LIFI high intensity electrodeless light source

NASA Astrophysics Data System (ADS)

Hafidi, Abdeslam; DeVincentis, Marc; Duelli, Markus; Gilliard, Richard

2008-02-01

Recently, RF driven electrodeless high intensity light sources have been implemented successfully in the projection display systems for HDTV and videowall applications. This paper presents advances made in the RF waveguide and electric field concentrator structures with the purpose of reducing effective arc size and increasing light collection. In addition, new optical designs are described that further improve system efficiency. The results of this work demonstrate that projection system light throughput is increased relative to previous implementations and performance is optimized for home theater and other front projector applications that maintain multi-year lifetime without re-lamping, complete spectral range, fast start times and high levels of dynamic contrast due to dimming flexibility in the light source system.

rf streak camera based ultrafast relativistic electron diffraction.

PubMed

Musumeci, P; Moody, J T; Scoby, C M; Gutierrez, M S; Tran, T

2009-01-01

We theoretically and experimentally investigate the possibility of using a rf streak camera to time resolve in a single shot structural changes at the sub-100 fs time scale via relativistic electron diffraction. We experimentally tested this novel concept at the UCLA Pegasus rf photoinjector. Time-resolved diffraction patterns from thin Al foil are recorded. Averaging over 50 shots is required in order to get statistics sufficient to uncover a variation in time of the diffraction patterns. In the absence of an external pump laser, this is explained as due to the energy chirp on the beam out of the electron gun. With further improvements to the electron source, rf streak camera based ultrafast electron diffraction has the potential to yield truly single shot measurements of ultrafast processes.

Multiphysics Analysis of Frequency Detuning in Superconducting RF Cavities for Proton Particle Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awida, M. H.; Gonin, I.; Passarelli, D.

2016-01-22

Multiphysics analyses for superconducting cavities are essential in the course of cavity design to meet stringent requirements on cavity frequency detuning. Superconducting RF cavities are the core accelerating elements in modern particle accelerators whether it is proton or electron machine, as they offer extremely high quality factors thus reducing the RF losses per cavity. However, the superior quality factor comes with the challenge of controlling the resonance frequency of the cavity within few tens of hertz bandwidth. In this paper, we investigate how the multiphysics analysis plays a major role in proactively minimizing sources of frequency detuning, specifically; microphonics andmore » Lorentz Force Detuning (LFD) in the stage of RF design of the cavity and mechanical design of the niobium shell and the helium vessel.« less

A Polarized Electron RF Photoinjector Using the Plane-Wave-Transformer (PWT) Design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clendenin, James E

Polarized electron beams are now in routine use in particle accelerators for nuclear and high energy physics experiments. These beams are presently produced by dc-biased photoelectron sources combined with rf chopping and bunching systems with inherently high transverse emittances. Low emittances can be produced with an rf gun, but the vacuum environment has until now been considered too harsh to support a negative electron affinity GaAs photocathode. We propose to significantly improve the vacuum conditions by adapting a PWT rf photoinjector to achieve reasonable cathode emission rates and lifetimes. This adaptation can also be combined with special optics that willmore » result in a flat beam with a normalized rms emittance in the narrow dimension that may be as low as 10{sup -8} m.« less

Variable frequency matching to a radiofrequency source immersed in vacuum

NASA Astrophysics Data System (ADS)

Charles, C.; Boswell, R. W.; Bish, A.

2013-09-01

A low-weight (0.12 kg) low-volume fixed ceramic capacitor impedance matching system is developed for frequency agile tuning of a radiofrequency (rf) Helicon plasma thruster. Three fixed groups of capacitors are directly mounted onto a two loop rf antenna with the thruster immersed in a vacuum chamber. Optimum plasma tuning at the resonance frequency is demonstrated via measurements of the load impedance, power transfer efficiency and plasma density versus driving frequency in the 12.882-14.238 MHz range. The resonance frequency with the plasma on is higher than the resonance frequency in vacuum. The minimum rf power necessary for ignition decreases when the ignition frequency is shifted downwards from the resonance frequency. This development has direct applications in space qualification and space use of rf plasma thrusters.

Efficient 30-W, 140-MHz rf amplifier for CW CO2 waveguide laser excitation

NASA Technical Reports Server (NTRS)

Hochuli, U. E.; Haldemann, P. R.

1988-01-01

Details of a 30-W, 140-MHz rf amplifier for CW CO2 waveguide laser excitation are presented. The amplifier delivers 30 W into a 50-Ohm load while requiring only 40 W of dc power from a 28-V supply and 100 mW of rf drive power for an overall efficiency of 75 percent. A coupling-starting network design theory is given that provides the initiation over voltage for the discharge plasma from an rf power source of limited output voltage capability. The network then matches the drive circuit to the new input impedance of the operating discharge without any adjustments. This design theory applies to the whole class of networks whose losses can be approximated by a loss conductance in parallel with the gas discharge.

Design of a high particle flux hydrogen helicon plasma source for used in plasma materials interaction studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goulding, R. H.; Chen, G.; Meitner, S.

2009-11-26

Existing linear plasma materials interaction (PMI) facilities all use plasma sources with internal electrodes. An rf-based helicon source is of interest because high plasma densities can be generated with no internal electrodes, allowing true steady state operation with minimal impurity generation. Work has begun at Oak Ridge National Laboratory (ORNL) to develop a large (15 cm) diameter helicon source producing hydrogen plasmas with parameters suitable for use in a linear PMI device: n{sub e}{>=}10{sup 19} m{sup -3}, T{sub e} = 4-10 eV, particle flux {gamma}{sub p}>10{sup 23}m{sup -3} s{sup -1}, and magnetic field strength |B| up to 1 T inmore » the source region. The device, whose design is based on a previous hydrogen helicon source operated at ORNL[1], will operate at rf frequencies in the range 10-26 MHz, and power levels up to {approx}100 kW. Limitations in cooling will prevent operation for pulses longer than several seconds, but a major goal will be the measurement of power deposition on device structures so that a later steady state version can be designed. The device design, the diagnostics to be used, and results of rf modeling of the device will be discussed. These include calculations of plasma loading, resulting currents and voltages in antenna structures and the matching network, power deposition profiles, and the effect of high |B| operation on power absorption.« less

Battery-powered pulsed high density inductively coupled plasma source for pre-ionization in laboratory astrophysics experiments.

PubMed

Chaplin, Vernon H; Bellan, Paul M

2015-07-01

An electrically floating radiofrequency (RF) pre-ionization plasma source has been developed to enable neutral gas breakdown at lower pressures and to access new experimental regimes in the Caltech laboratory astrophysics experiments. The source uses a customized 13.56 MHz class D RF power amplifier that is powered by AA batteries, allowing it to safely float at 3-6 kV with the electrodes of the high voltage pulsed power experiments. The amplifier, which is capable of 3 kW output power in pulsed (<1 ms) operation, couples electrical energy to the plasma through an antenna external to the 1.1 cm radius discharge tube. By comparing the predictions of a global equilibrium discharge model with the measured scalings of plasma density with RF power input and axial magnetic field strength, we demonstrate that inductive coupling (rather than capacitive coupling or wave damping) is the dominant energy transfer mechanism. Peak ion densities exceeding 5 × 10(19) m(-3) in argon gas at 30 mTorr have been achieved with and without a background field. Installation of the pre-ionization source on a magnetohydrodynamically driven jet experiment reduced the breakdown time and jitter and allowed for the creation of hotter, faster argon plasma jets than was previously possible.

Performance characterization of a permanent-magnet helicon plasma thruster

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Charles, Christine; Boswell, Rod

2012-10-01

Helicon plasma thrusters operated at a few kWs of rf power is an active area of an international research. Recent experiments have clarified part of the thrust-generation mechanisms. Thrust components which have been identified include an electron pressure inside the source region and a Lorentz force due to an electron diamagnetic drift current and a radial component of the applied magnetic field. The use of permanent magnets (PMs) instead of solenoids is one of the solutions for improving the thruster efficiency because it does not require electricity for the magnetic nozzle formation. Here the thrust imparted from a permanent-magnet helicon plasma thruster is directly measured using a pendulum thrust balance. The source consists of permanent magnet (PM) arrays, a double turn rf loop antenna powered by a 13.56 MHz rf generator and a glass source tube. The PM arrays provide a magnetic nozzle near the open exit of the source and two configurations, which have maximum field strengths of about 100 and 270 G, are tested. A thrust of 15 mN, specific impulse of 2000 sec and a thrust efficiency of 8 percent are presently obtained for 2 kW of input power, 24 sccm flow rate of argon and the stronger magnetic field configuration.

Theoretical and experimental studies of a planar inductive coupled rf plasma source as the driver in simulator facility (ISTAPHM) of interactions of waves with the edge plasma on tokamaks

NASA Astrophysics Data System (ADS)

Ghanei, V.; Nasrabadi, M. N.; Chin, O.-H.; Jayapalan, K. K.

2017-11-01

This research aims to design and build a planar inductive coupled RF plasma source device which is the driver of the simulator project (ISTAPHM) of the interactions between ICRF Antenna and Plasma on tokamak by using the AMPICP model. For this purpose, a theoretical derivation of the distribution of the RF magnetic field in the plasma-filled reactor chamber is presented. An experimental investigation of the field distributions is described and Langmuir measurements are developed numerically. A comparison of theory and experiment provides an evaluation of plasma parameters in the planar ICP reactor. The objective of this study is to characterize the plasma produced by the source alone. We present the results of the first analysis of the plasma characteristics (plasma density, electron temperature, electron-ion collision frequency, particle fluxes and their velocities, stochastic frequency, skin depth and electron energy distribution functions) as function of the operating parameters (injected power, neutral pressure and magnetic field) as measured with fixed and movable Langmuir probes. The plasma is currently produced only by the planar ICP. The exact goal of these experiments is that the produced plasma by external source can exist as a plasma representative of the edge of tokamaks.

Experimental pathways to understand and avoid high-Z impurity contamination from ICRF heating in tokamaks

NASA Astrophysics Data System (ADS)

Reinke, Matthew

2016-10-01

Recent results from Alcator C-Mod and JET demonstrate progress in understanding and mitigating core high-Z impurity contamination linked to ICRF heating in tokamaks with high-Z PFCs. Theory has identified two likely mechanisms: impurity sources due to sputtering enhanced by RF-rectified sheaths and greater cross-field SOL transport due to ExB convective cells. New experiments on Alcator C-Mod and JET demonstrate convective cell transport is likely a sub-dominant effect, despite directly observing ExB flows from rectified RF fields on C-Mod. Trace N2 introduced in the far SOL on field lines connected to and well away from an active ICRF antenna result in similar levels of core nitrogen, indicating local RF-driven transport is weak. This suggests the core high-Z density, nZ,core, is determined by sheath-induced sputtering and RF-independent SOL transport, allowing further reductions through antenna design. ICRF heating on C-Mod uses a unique, field aligned (FAA) and a pair of conventional, toroidally aligned (TAA) antennas. The FAA is designed to reduce rectified voltages relative to the TAA, and the impact of sheath-induced sputtering is explored by observing nZ,core while varying the TAA/FAA heating mix. A reduction of approximately 50% in core high-Z content is seen in L-modes when using the FAA and high-Z sources at the antenna limiter are effectively eliminated, indicating the remaining RF-driven source is away from the limiter. A drop in nZ,core may also be realized by locating the RF antenna on the inboard side where SOL transport aids impurity screening. New C-Mod experiments demonstrate up to a factor of 5 reduction in core nitrogen when N2 is injected on the high-field side as compared to low-field side impurity fueling. Varying the magnetic topology helps to elucidate the SOL transport physics responsible, laying a physics basis for inboard RF antenna placement. This work is supported by U.S. DOE Award DE-FC02-99ER54512, using Alcator C-Mod and carried out within the framework of the EUROfusion Consortium and has received funding from Euratom under Grant Agreement No 633053.

An analog RF gap voltage regulation system for the Advanced Photon Source storage ring.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Horan, D.

1999-04-13

An analog rf gap voltage regulation system has been designed and built at Argonne National Laboratory to maintain constant total storage ring rf gap voltage, independent of beam loading and cavity tuning effects. The design uses feedback control of the klystron mod-anode voltage to vary the amount of rf power fed to the storage ring cavities. The system consists of two independent feedback loops, each regulating the combined rf gap voltages of eight storage ring cavities by varying the output power of either one or two rf stations, depending on the mode of operation. It provides full operator control andmore » permissive logic to permit feedback control of the rf system output power only if proper conditions are met. The feedback system uses envelope-detected cavity field probe outputs as the feedback signal. Two different methods of combining the individual field probe signals were used to generate a relative DC level representing one-half of the total storage ring rf voltage, an envelope-detected vector sum of the field probe rf signals, and the DC sum of individual field probe envelope detector outputs. The merits of both methods are discussed. The klystron high-voltage power supply (HVPS) units are fitted with an analog interface for external control of the mod-anode voltage level, using a four-quadrant analog multiplier to modulate the HVPS mod-anode voltage regulator set-point in response to feedback system commands.« less

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.

Low-pressure RF remote plasma cleaning of carbon-contaminated B4C-coated optics

NASA Astrophysics Data System (ADS)

Moreno Fernández, H.; Thomasset, M.; Sauthier, G.; Rogler, D.; Dietsch, R.; Barrett, R.; Carlino, V.; Pellegrin, E.

2017-05-01

Boron carbide (B4C) - due to its exceptional mechanical properties - is one of the few existing materials that can withstand the extremely high brilliance of the photon beam from free electron lasers (FELs) and is thus of considerable interest for optical applications in this field. However, as in the case of many other optics operated at modern accelerator-, plasma-, or laser-based light source facilities, B4C-coated optics are subject to ubiquitous carbon contaminations. These contaminations - that are presumably produced via cracking of CHx and CO2 molecules by photoelectrons emitted from the optical components - represent a serious issue for the operation of the pertinent high performance beamlines due to a severe reduction of photon flux and beam coherence, not necessarily restricted to the photon energy range of the carbon K-edge. Thus, a variety of B4C cleaning technologies have been developed at different laboratories with varying success [1]. Here, we present a study regarding the low-pressure RF plasma cleaning of a series of carbon-contaminated B4C test samples via an inductively coupled O2/Ar and Ar/H2 remote RF plasma produced using the IBSS GV10x plasma source following previous studies using the same RF plasma source [2, 3]. Results regarding the chemistry, morphology as well as other aspects of the B4C optical coatings and surfaces before and after the plasma cleaning process are reported.

Pantechnik new superconducting ion source: PantechniK Indian Superconducting Ion Source.

PubMed

Gaubert, G; Bieth, C; Bougy, W; Brionne, N; Donzel, X; Leroy, R; Sineau, A; Vallerand, C; Villari, A C C; Thuillier, T

2012-02-01

The new ECR ion source PantechniK Indian Superconducting Ion Source (PKISIS) was recently commissioned at Pantechnik. Three superconducting coils generate the axial magnetic field configuration, while the radial magnetic field is done with the multi-layer permanent magnets. Special care was devoted to the design of the hexapolar structure, allowing a maximum magnetic field of 1.32 T at the wall of the 82 mm diameter plasma chamber. The three superconducting coils using low temperature superconducting wires are cooled by a single double stage cryo-cooler (4.2 K). Cryogen-free technology is used, providing reliability and easy maintenance at low cost. The maximum installed RF power (18.0 GHz) is of 2 kW. Metallic beams can be produced with an oven (T(max) = 1400 °C) installed with an angle of 5° with respect to the source axis or a sputtering system, mounted on the axis of the source. The beam extraction system is constituted of three electrodes in accel-decel configuration. The new source of Pantechnik is conceived for reaching optimum performances at 18 GHz RF frequencies. PKISIS magnetic fields are 2.1 T axial B(inj) and 1.32 T radial field in the wall, variable B(min) with an independent coil and a large and opened extraction region. Moreover, PKISIS integrates modern design concepts, like RF direct injection (2 kW availability), dc-bias moving disk, out-of-axis oven and axial sputtering facility for metal beams. Finally, PKISIS is also conceived in order to operate in a high-voltage platform with minor power consumption.

Environmental Radiofrequency Electromagnetic Fields Exposure at Home, Mobile and Cordless Phone Use, and Sleep Problems in 7-Year-Old Children

PubMed Central

Huss, Anke; van Eijsden, Manon; Guxens, Monica; Beekhuizen, Johan; van Strien, Rob; Kromhout, Hans; Vrijkotte, Tania; Vermeulen, Roel

2015-01-01

Background We evaluated if exposure to RF-EMF was associated with reported quality of sleep in 2,361 children, aged 7 years. Methods This study was embedded in the Amsterdam Born Children and their Development (ABCD) birth cohort study. When children were about five years old, school and residential exposure to RF-EMF from base stations was assessed with a geospatial model (NISMap) and from indoor sources (cordless phone/WiFi) using parental self-reports. Parents also reported their children’s use of mobile or cordless phones. When children were seven years old, we evaluated sleep quality as measured with the Child Sleep Habits Questionnaire (CSHQ) filled in by parents. Of eight CSHQ subscales, we evaluated sleep onset delay, sleep duration, night wakenings, parasomnias and daytime sleepiness with logistic or negative binomial regression models, adjusting for child’s age and sex and indicators of socio-economic position of the parents. We evaluated the remaining three subscales (bedtime resistance, sleep anxiety, sleep disordered breathing) as unrelated outcomes (negative control) because these were a priori hypothesised not to be associated with RF-EMF. Results Sleep onset delay, night wakenings, parasomnias and daytime sleepiness were not associated with residential exposure to RF-EMF from base stations. Sleep duration scores were associated with RF-EMF levels from base stations. Higher use mobile phones was associated with less favourable sleep duration, night wakenings and parasomnias, and also with bedtime resistance. Cordless phone use was not related to any of the sleeping scores. Conclusion Given the different results across the evaluated RF-EMF exposure sources and the observed association between mobile phone use and the negative control sleep scale, our study does not support the hypothesis that it is the exposure to RF-EMF that is detrimental to sleep quality in 7-year old children, but potentially other factors that are related to mobile phone usage. PMID:26509676

Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choe, Kyumin; Jung, Bongki; Chung, Kyoung-Jae, E-mail: jkjlsh1@snu.ac.kr

2014-02-15

Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm{sup 3}), four helicon plasma injectors with annular permanent magnetsmore » and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented.« less

Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus

NASA Astrophysics Data System (ADS)

Choe, Kyumin; Jung, Bongki; Chung, Kyoung-Jae; Hwang, Y. S.

2014-02-01

Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm3), four helicon plasma injectors with annular permanent magnets and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented.

Development of a radio frequency ion source with multi-helicon plasma injectors for neutral beam injection system of Versatile Experiment Spherical Torus.

PubMed

Choe, Kyumin; Jung, Bongki; Chung, Kyoung-Jae; Hwang, Y S

2014-02-01

Despite of high plasma density, helicon plasma has not yet been applied to a large area ion source such as a driver for neutral beam injection (NBI) system due to intrinsically poor plasma uniformity in the discharge region. In this study, a radio-frequency (RF) ion source with multi-helicon plasma injectors for high plasma density with good uniformity has been designed and constructed for the NBI system of Versatile Experiment Spherical Torus at Seoul National University. The ion source consists of a rectangular plasma expansion chamber (120 × 120 × 120 mm(3)), four helicon plasma injectors with annular permanent magnets and RF power system. Main feature of the source is downstream plasma confinement in the cusp magnetic field configuration which is generated by arranging polarities of permanent magnets in the helicon plasma injectors. In this paper, detailed design of the multi-helicon plasma injector and plasma characteristics of the ion source are presented.

RF Conditioning and Testing of Fundamental Power Couplers for SNS Superconducting Cavity Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

M. Stirbet; G.K. Davis; M. A. Drury

The Spallation Neutron Source (SNS) makes use of 33 medium beta (0.61) and 48 high beta (0.81) superconducting cavities. Each cavity is equipped with a fundamental power coupler, which should withstand the full klystron power of 550 kW in full reflection for the duration of an RF pulse of 1.3 msec at 60 Hz repetition rate. Before assembly to a superconducting cavity, the vacuum components of the coupler are submitted to acceptance procedures consisting of preliminary quality assessments, cleaning and clean room assembly, vacuum leak checks and baking under vacuum, followed by conditioning and RF high power testing. Similar acceptancemore » procedures (except clean room assembly and baking) were applied for the airside components of the coupler. All 81 fundamental power couplers for SNS superconducting cavity production have been RF power tested at JLAB Newport News and, beginning in April 2004 at SNS Oak Ridge. This paper gives details of coupler processing and RF high power-assessed performances.« less

Bridging the Gap between RF and Optical Patch Antenna Analysis via the Cavity Model.

PubMed

Unal, G S; Aksun, M I

2015-11-02

Although optical antennas with a variety of shapes and for a variety of applications have been proposed and studied, they are still in their infancy compared to their radio frequency (rf) counterparts. Optical antennas have mainly utilized the geometrical attributes of rf antennas rather than the analysis tools that have been the source of intuition for antenna engineers in rf. This study intends to narrow the gap of experience and intuition in the design of optical patch antennas by introducing an easy-to-understand and easy-to-implement analysis tool in rf, namely, the cavity model, into the optical regime. The importance of this approach is not only its simplicity in understanding and implementation but also its applicability to a broad class of patch antennas and, more importantly, its ability to provide the intuition needed to predict the outcome without going through the trial-and-error simulations with no or little intuitive guidance by the user.

High stability buffered phase comparator

NASA Technical Reports Server (NTRS)

Adams, W. A.; Reinhardt, V. S. (Inventor)

1984-01-01

A low noise RF signal phase comparator comprised of two high stability driver buffer amplifiers driving a double balanced mixer which operate to generate a beat frequency between the two RF input signals coupled to the amplifiers from the RF sources is described. The beat frequency output from the mixer is applied to a low noise zero crossing detector which is the phase difference between the two RF inputs. Temperature stability is provided by mounting the amplifiers and mixer on a common circuit board with the active circuit elements located on one side of a circuit board and the passive circuit elements located on the opposite side. A common heat sink is located adjacent the circuit board. The active circuit elements are embedded into the bores of the heat sink which slows the effect of ambient temperature changes and reduces the temperature gradients between the active circuit elements, thus improving the cancellation of temperature effects. The two amplifiers include individual voltage regulators, which increases RF isolation.

Use of simple x-ray measurement in the performance analysis of cryogenic RF accelerator cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. Dotson; M. Drury; R. May

X-ray emission by radiofrequency (RF) resonant cavities has long been known to accelerator health physicists as a potentially serious source of radiation exposure. The authors points out the danger of klystrons and microwave cavities by stating that the radiation source term is erratic and may be unpredictable depending on microscopic surface conditions which change with time. He also states the x-ray output is a rapidly increasing function of RF input power. At Jefferson Lab, the RF cavities used to accelerate the electron beam employ superconducting technology. X-rays are emitted at high cavity gradients, and measurements of cavity x-rays are valuablemore » for health physics purposes and provide a useful diagnostic tool for assessing cavity performance. The quality factor (Q) for superconducting RF resonant cavities used at Jefferson Lab, is typically 5 x 10{sup 9} for the nominal design gradient of 5 MVm{sup {minus}1}. This large value for Q follows from the small resistive loss in superconducting technology. The operating frequency is 1,497 MHz. In the absence of beam, the input power for a cavity is typically 750 W and the corresponding dissipated power is 2.6 W. At 5 MWm{sup {minus}1}, the input power is 3 kW fully beam loaded. At higher gradients, performance degradation tends to occur due to the onset of electron field emission from defects in the cavity.« less

Design and implementation of a RF powering circuit for RFID tags or other batteryless embedded devices.

PubMed

Liu, Dongsheng; Wang, Rencai; Yao, Ke; Zou, Xuecheng; Guo, Liang

2014-08-13

A RF powering circuit used in radio-frequency identification (RFID) tags and other batteryless embedded devices is presented in this paper. The RF powering circuit harvests energy from electromagnetic waves and converts the RF energy to a stable voltage source. Analysis of a NMOS gate-cross connected bridge rectifier is conducted to demonstrate relationship between device sizes and power conversion efficiency (PCE) of the rectifier. A rectifier with 38.54% PCE under normal working conditions is designed. Moreover, a stable voltage regulator with a temperature and voltage optimizing strategy including adoption of a combination resistor is developed, which is able to accommodate a large input range of 4 V to 12 V and be immune to temperature variations. Latch-up prevention and noise isolation methods in layout design are also presented. Designed with the HJTC 0.25 μm process, this regulator achieves 0.04 mV/°C temperature rejection ratio (TRR) and 2.5 mV/V voltage rejection ratio (VRR). The RF powering circuit is also fabricated in the HJTC 0.25 μm process. The area of the RF powering circuit is 0.23 × 0.24 mm². The RF powering circuit is successfully integrated with ISO/IEC 15693-compatible and ISO/IEC 14443-compatible RFID tag chips.

Design and Implementation of a RF Powering Circuit for RFID Tags or Other Batteryless Embedded Devices

PubMed Central

Liu, Dongsheng; Wang, Rencai; Yao, Ke; Zou, Xuecheng; Guo, Liang

2014-01-01

A RF powering circuit used in radio-frequency identification (RFID) tags and other batteryless embedded devices is presented in this paper. The RF powering circuit harvests energy from electromagnetic waves and converts the RF energy to a stable voltage source. Analysis of a NMOS gate-cross connected bridge rectifier is conducted to demonstrate relationship between device sizes and power conversion efficiency (PCE) of the rectifier. A rectifier with 38.54% PCE under normal working conditions is designed. Moreover, a stable voltage regulator with a temperature and voltage optimizing strategy including adoption of a combination resistor is developed, which is able to accommodate a large input range of 4 V to 12 V and be immune to temperature variations. Latch-up prevention and noise isolation methods in layout design are also presented. Designed with the HJTC 0.25 μm process, this regulator achieves 0.04 mV/°C temperature rejection ratio (TRR) and 2.5 mV/V voltage rejection ratio (VRR). The RF powering circuit is also fabricated in the HJTC 0.25 μm process. The area of the RF powering circuit is 0.23 × 0.24 mm2. The RF powering circuit is successfully integrated with ISO/IEC 15693-compatible and ISO/IEC 14443-compatible RFID tag chips. PMID:25123466

Progress on the Design of the Storage Ring Vacuum System for the Advanced Photon Source Upgrade Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stillwell, B.; Billett, B.; Brajuskovic, B.

2017-06-20

Recent work on the design of the storage ring vacuum system for the Advanced Photon Source Upgrade project (APS-U) includes: revising the vacuum system design to accommodate a new lattice with reverse bend magnets, modifying the designs of vacuum chambers in the FODO sections for more intense incident synchrotron radiation power, modifying the design of rf-shielding bellows liners for better performance and reliability, modifying photon absorber designs to make better use of available space, and integrated planning of components needed in the injection, extraction and rf cavity straight sections. An overview of progress in these areas is presented.

A circuit model for nonlinear simulation of radio-frequency filters using bulk acoustic wave resonators.

PubMed

Ueda, Masanori; Iwaki, Masafumi; Nishihara, Tokihiro; Satoh, Yoshio; Hashimoto, Ken-ya

2008-04-01

This paper describes a circuit model for the analysis of nonlinearity in the filters based on radiofrequency (RF) bulk acoustic wave (BAW) resonators. The nonlinear output is expressed by a current source connected parallel to the linear resonator. Amplitude of the nonlinear current source is programmed proportional to the product of linear currents flowing in the resonator. Thus, the nonlinear analysis is performed by the common linear analysis, even for complex device structures. The analysis is applied to a ladder-type RF BAW filter, and frequency dependence of the nonlinear output is discussed. Furthermore, this analysis is verified through comparison with experiments.

Investigation of radiofrequency plasma sources for space travel

NASA Astrophysics Data System (ADS)

Charles, C.; Boswell, R. W.; Takahashi, K.

2012-12-01

Optimization of radiofrequency (RF) plasma sources for the development of space thrusters differs from other applications such as plasma processing of materials since power efficiency, propellant usage, particle acceleration or heating become driving parameters. The development of two RF (13.56 MHz) plasma sources, the high-pressure (˜1 Torr) capacitively coupled ‘pocket rocket’ plasma micro-thruster and the low-pressure (˜1 mTorr) inductively coupled helicon double layer thruster (HDLT), is discussed within the context of mature and emerging electric propulsion devices. The density gradient in low-pressure expanding RF plasmas creates an electric field that accelerates positive ions out of the plasma. Generally, the total potential drop is similar to that of a wall sheath allowing the plasma electrons to neutralize the ion beam. A high-pressure expansion with no applied magnetic field can result in large dissociation rates and/or a collimated beam of ions of small area and a flowing heated neutral beam (‘pocket rocket’). A low-pressure expansion dominated by a magnetic field can result in the formation of electric double layers which produce a very directed neutralized beam of ions of large area (HDLT).

Design, construction and measurements of an alpha magnet as a solution for compact bunch compressor for the electron beam from Thermionic RF Gun

NASA Astrophysics Data System (ADS)

Rajabi, A.; Jazini, J.; Fathi, M.; Sharifian, M.; Shokri, B.

2018-03-01

The beam produced by a thermionic RF gun has wide energy spread that makes it unsuitable for direct usage in photon sources. Here in the present work, we optimize the extracted beam from a thermionic RF gun by a compact economical bunch compressor. A compact magnetic bunch compressor (Alpha magnet) is designed and constructed. A comparison between simulation results and experimental measurements shows acceptable conformity. The beam dynamics simulation results show a reduction of the energy spread as well as a compression of length less than 1 ps with 2.3 mm-mrad emittance.

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.

Measurements and modeling of radio frequency field structures in a helicon plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, C. A.; Chen, Guangye; Arefiev, A. V.

2011-01-01

Measurements of the radio frequency (rf) field structure, plasma density, and electron temperature are presented for a 1 kW argon helicon plasma source. The measured profiles change considerably when the equilibrium magnetic field is reversed. The measured rf fields are identified as fields of radially localized helicon waves, which propagate in the axial direction. The rf field structure is compared to the results of two-dimensional cold plasma full-wave simulations for the measured density profiles. Electron collision frequency is adjusted in the simulations to match the simulated and measured field profiles. The resulting frequency is anomalously high, which is attributed tomore » the excitation of an ion-acoustic instability. The calculated power deposition is insensitive to the collision frequency and accounts for most of the power supplied by the rf-generator.« less

Method and apparatus for varying accelerator beam output energy

DOEpatents

Young, Lloyd M.

1998-01-01

A coupled cavity accelerator (CCA) accelerates a charged particle beam with rf energy from a rf source. An input accelerating cavity receives the charged particle beam and an output accelerating cavity outputs the charged particle beam at an increased energy. Intermediate accelerating cavities connect the input and the output accelerating cavities to accelerate the charged particle beam. A plurality of tunable coupling cavities are arranged so that each one of the tunable coupling cavities respectively connect an adjacent pair of the input, output, and intermediate accelerating cavities to transfer the rf energy along the accelerating cavities. An output tunable coupling cavity can be detuned to variably change the phase of the rf energy reflected from the output coupling cavity so that regions of the accelerator can be selectively turned off when one of the intermediate tunable coupling cavities is also detuned.

Exact cancellation of emittance growth due to coupled transverse dynamics in solenoids and rf couplers

NASA Astrophysics Data System (ADS)

Dowell, David H.; Zhou, Feng; Schmerge, John

2018-01-01

Weak, rotated magnetic and radio frequency quadrupole fields in electron guns and injectors can couple the beam's horizontal with vertical motion, introduce correlations between otherwise orthogonal transverse momenta, and reduce the beam brightness. This paper discusses two important sources of coupled transverse dynamics common to most electron injectors. The first is quadrupole focusing followed by beam rotation in a solenoid, and the second coupling comes from a skewed high-power rf coupler or cavity port which has a rotated rf quadrupole field. It is shown that a dc quadrupole field can correct for both types of couplings and exactly cancel their emittance growths. The degree of cancellation of the rf skew quadrupole emittance is limited by the electron bunch length. Analytic expressions are derived and compared with emittance simulations and measurements.

Standing helicon induced by a rapidly bent magnetic field in plasmas

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Takayama, Sho; Komuro, Atsushi; Ando, Akira; Plasma physics Team

2016-09-01

An electron energy probability function and an rf magnetic field are measured in an rf hydrogen helicon source, where axial and transverse static magnetic fields are applied to the source by solenoids and to the diffusion chamber by filter magnets, respectively. It is demonstrated that the helicon wave is reflected by the rapidly bent magnetic field and the resultant standing wave heats the electrons between the source and the magnetic filter, while the electron cooling effect by the magnetic filter is maintained. It is interpreted that the standing wave is generated by the presence of spatially localized change of a refractive index. The application to the hydrogen negative ion source used for the neutral beam injection system for fusion plasma heating is discussed. This work is partially supported by grant-in-aid for scientific research (16H04084 and 26247096) from the Japan Society for the Promotion of Science.

Status of the RF-driven H{sup −} ion source for J-PARC linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oguri, H., E-mail: oguri.hidetomo@jaea.go.jp; Ohkoshi, K.; Ikegami, K.

2016-02-15

For the upgrade of the Japan Proton Accelerator Research Complex linac beam current, a cesiated RF-driven negative hydrogen ion source was installed during the 2014 summer shutdown period, with subsequent operations commencing on September 29, 2014. The ion source has been successfully operating with a beam current and duty factor of 33 mA and 1.25% (500 μs and 25 Hz), respectively. The result of recent beam operation has demonstrated that the ion source is capable of continuous operation for approximately 1100 h. The spark rate at the beam extractor was observed to be at a frequency of less than oncemore » a day, which is an acceptable level for user operation. Although an antenna failure occurred during operation on October 26, 2014, no subsequent serious issues have occurred since then.« less

Numerical study of the inductive plasma coupling to ramp up the plasma density for the Linac4 H- ion source

NASA Astrophysics Data System (ADS)

Ohta, M.; Mattei, S.; Yasumoto, M.; Hatayama, A.; Lettry, J.

2014-02-01

In the Linac4 H- ion source, the plasma is generated by an RF antenna operated at 2 MHz. In order to investigate the conditions necessary for ramping up the plasma density of the Linac4 H- ion source in the low plasma density, a numerical study has been performed for a wide range of parameter space of RF coil current and initial pressure from H2 gas injection. We have employed an Electromagnetic Particle in Cell model, in which the collision processes have been calculated by a Monte Carlo method. The results have shown that the range of initial gas pressure from 2 to 3 Pa is suitable for ramping up plasma density via inductive coupling.

Laser-free RF-gun as a combined source of THz and ps-sub-ps X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agustsson, R.; Boucher, S.; Finn, O.

A coherent, mm-sub-mm-wave source driven by a RF electron gun is proposed for wide research applications as well as auxiliary inspection and screening, safe imaging, cancer diagnostics, surface defectoscopy, and enhanced time-domain spectroscopy. It allows generation of high peak and average THz-sub-THz radiation power provided by beam pre-bunching and chirping in the RF gun followed by microbunching in magnetic compressor, and resonant Cherenkov radiation of an essentially flat beam in a robust, ~inch-long, planar, mm-sub-mm gap structure. The proof-of-principle has been successfully demonstrated in Phase I on a 5 MeV beam of L-band thermionic injector of Idaho Accelerator Center. Themore » system can also deliver an intense, ps-sub-ps bursts of low-to-moderate dose of relativistic electrons and X-ray radiation produced by the same beam required for pulsed radiolysis as well as to enhance screening efficiency, throughput and safety.« less

Laser-free RF-gun as a combined source of THz and ps-sub-ps X-rays

DOE PAGES

Agustsson, R.; Boucher, S.; Finn, O.; ...

2015-01-01

A coherent, mm-sub-mm-wave source driven by a RF electron gun is proposed for wide research applications as well as auxiliary inspection and screening, safe imaging, cancer diagnostics, surface defectoscopy, and enhanced time-domain spectroscopy. It allows generation of high peak and average THz-sub-THz radiation power provided by beam pre-bunching and chirping in the RF gun followed by microbunching in magnetic compressor, and resonant Cherenkov radiation of an essentially flat beam in a robust, ~inch-long, planar, mm-sub-mm gap structure. The proof-of-principle has been successfully demonstrated in Phase I on a 5 MeV beam of L-band thermionic injector of Idaho Accelerator Center. Themore » system can also deliver an intense, ps-sub-ps bursts of low-to-moderate dose of relativistic electrons and X-ray radiation produced by the same beam required for pulsed radiolysis as well as to enhance screening efficiency, throughput and safety.« less

Current transmission and nonlinear effects in un-gated thermionic cathode RF guns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edelen, J. P.; Harris, J. R.

Un-gated thermionic cathode RF guns are well known as a robust source of electrons for many accelerator applications. These sources are in principle scalable to high currents without degradation of the transverse emittance due to control grids but they are also known for being limited by back-bombardment. While back-bombardment presents a significant limitation, there is still a lack of general understanding on how emission over the whole RF period will affect the nature of the beams produced from these guns. In order to improve our understanding of how these guns can be used in general we develop analytical models thatmore » predict the transmission efficiency as a function of the design parameters, study how bunch compression and emission enhancement caused by Schottky barrier lowering affect the output current profile in the gun, and study the onset of space-charge limited effects and the resultant virtual cathode formation leading to a modulation in the output current distribution.« less

Stepped frequency ground penetrating radar

DOEpatents

Vadnais, Kenneth G.; Bashforth, Michael B.; Lewallen, Tricia S.; Nammath, Sharyn R.

1994-01-01

A stepped frequency ground penetrating radar system is described comprising an RF signal generating section capable of producing stepped frequency signals in spaced and equal increments of time and frequency over a preselected bandwidth which serves as a common RF signal source for both a transmit portion and a receive portion of the system. In the transmit portion of the system the signal is processed into in-phase and quadrature signals which are then amplified and then transmitted toward a target. The reflected signals from the target are then received by a receive antenna and mixed with a reference signal from the common RF signal source in a mixer whose output is then fed through a low pass filter. The DC output, after amplification and demodulation, is digitized and converted into a frequency domain signal by a Fast Fourier Transform. A plot of the frequency domain signals from all of the stepped frequencies broadcast toward and received from the target yields information concerning the range (distance) and cross section (size) of the target.

Coupling of RF antennas to large volume helicon plasma

NASA Astrophysics Data System (ADS)

Chang, Lei; Hu, Xinyue; Gao, Lei; Chen, Wei; Wu, Xianming; Sun, Xinfeng; Hu, Ning; Huang, Chongxiang

2018-04-01

Large volume helicon plasma sources are of particular interest for large scale semiconductor processing, high power plasma propulsion and recently plasma-material interaction under fusion conditions. This work is devoted to studying the coupling of four typical RF antennas to helicon plasma with infinite length and diameter of 0.5 m, and exploring its frequency dependence in the range of 13.56-70 MHz for coupling optimization. It is found that loop antenna is more efficient than half helix, Boswell and Nagoya III antennas for power absorption; radially parabolic density profile overwhelms Gaussian density profile in terms of antenna coupling for low-density plasma, but the superiority reverses for high-density plasma. Increasing the driving frequency results in power absorption more near plasma edge, but the overall power absorption increases with frequency. Perpendicular stream plots of wave magnetic field, wave electric field and perturbed current are also presented. This work can serve as an important reference for the experimental design of large volume helicon plasma source with high RF power.

1995 second modulator-klystron workshop: A modulator-klystron workshop for future linear colliders

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-03-01

This second workshop examined the present state of modulator design and attempted an extrapolation for future electron-positron linear colliders. These colliders are currently viewed as multikilometer-long accelerators consisting of a thousand or more RF sources with 500 to 1,000, or more, pulsed power systems. The workshop opened with two introductory talks that presented the current approaches to designing these linear colliders, the anticipated RF sources, and the design constraints for pulse power. The cost of main AC power is a major economic consideration for a future collider, consequently the workshop investigated efficient modulator designs. Techniques that effectively apply the artmore » of power conversion, from the AC mains to the RF output, and specifically, designs that generate output pulses with very fast rise times as compared to the flattop. There were six sessions that involved one or more presentations based on problems specific to the design and production of thousands of modulator-klystron stations, followed by discussion and debate on the material.« less

Comparison of three rf plasma impedance monitors on a high phase angle planar inductively coupled plasma source

NASA Astrophysics Data System (ADS)

Uchiyama, H.; Watanabe, M.; Shaw, D. M.; Bahia, J. E.; Collins, G. J.

1999-10-01

Accurate measurement of plasma source impedance is important for verification of plasma circuit models, as well as for plasma process characterization and endpoint detection. Most impedance measurement techniques depend in some manner on the cosine of the phase angle to determine the impedance of the plasma load. Inductively coupled plasmas are generally highly inductive, with the phase angle between the applied rf voltage and the rf current in the range of 88 to near 90 degrees. A small measurement error in this phase angle range results in a large error in the calculated cosine of the angle, introducing large impedance measurement variations. In this work, we have compared the measured impedance of a planar inductively coupled plasma using three commercial plasma impedance monitors (ENI V/I probe, Advanced Energy RFZ60 and Advanced Energy Z-Scan). The plasma impedance is independently verified using a specially designed match network and a calibrated load, representing the plasma, to provide a measurement standard.

Femtosecond MeV Electron Energy-Loss Spectroscopy

DOE PAGES

Li, R. K.; Wang, X. J.

2017-11-09

Pump-probe electron energy-loss spectroscopy (EELS) with femtosecond temporal resolution will be a transformative research tool for studying nonequilibrium chemistry and electronic dynamics of matter. Here in this article, we propose a concept of femtosecond EELS utilizing mega-electron-volt electron beams from a radio-frequency (rf) photocathode source. The high acceleration gradient and high beam energy of the rf gun are critical to the generation of 10-fs electron beams, which enables an improvement of the temporal resolution by more than 1 order of magnitude beyond the state of the art. In our proposal, the “referencebeam technique” relaxes the energy stability requirement of themore » rf power source by roughly 2 orders of magnitude. The requirements for the electron-beam quality, photocathode, spectrometer, and detector are also discussed. Supported by particle-tracking simulations, we demonstrate the feasibility of achieving subelectron- volt energy resolution and approximately 10-fs temporal resolution with existing or near-future hardware performance.« less

Femtosecond MeV Electron Energy-Loss Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, R. K.; Wang, X. J.

Pump-probe electron energy-loss spectroscopy (EELS) with femtosecond temporal resolution will be a transformative research tool for studying nonequilibrium chemistry and electronic dynamics of matter. Here in this article, we propose a concept of femtosecond EELS utilizing mega-electron-volt electron beams from a radio-frequency (rf) photocathode source. The high acceleration gradient and high beam energy of the rf gun are critical to the generation of 10-fs electron beams, which enables an improvement of the temporal resolution by more than 1 order of magnitude beyond the state of the art. In our proposal, the “referencebeam technique” relaxes the energy stability requirement of themore » rf power source by roughly 2 orders of magnitude. The requirements for the electron-beam quality, photocathode, spectrometer, and detector are also discussed. Supported by particle-tracking simulations, we demonstrate the feasibility of achieving subelectron- volt energy resolution and approximately 10-fs temporal resolution with existing or near-future hardware performance.« less

APS Storage Ring Monopulse RF BPM Upgrade

NASA Astrophysics Data System (ADS)

Lill, R.; Pietryla, A.; Norum, E.; Lenkszus, F.

2004-11-01

The Advanced Photon Source (APS) is a third-generation synchrotron light source in its ninth year of operation. The storage ring monopulse radio frequency (rf) beam position monitor (BPM) was designed to measure single-turn and multi-turn beam positions for operations and machine physics studies. Many of the components used in the original design are obsolete and costly to replace. In this paper we present a proposal to upgrade the monopulse rf BPMs in which the existing system hardware is repartitioned and the aging data acquisition system is replaced. By replacing only the data acquisition system, we will demonstrate a cost-effective approach to improved beam stability, reliability, and enhanced postmortem capabilities. An eight-channel ADC/digitizer VXI board with sampling rate of up to 105 MHz (per channel) and 14-bit resolution coupled with a field-programmable gate array and embedded central processing will provide the flexibility to revitalize this system for another decade of operation. We will discuss the upgrade system specifications, design, and prototype test results.

RF H-minus ion source development in China spallation neutron source

NASA Astrophysics Data System (ADS)

Chen, W.; Ouyang, H.; Xiao, Y.; Liu, S.; Lü, Y.; Cao, X.; Huang, T.; Xue, K.

2017-08-01

China Spallation Neutron Source (CSNS) phase-I project currently uses a Penning surface plasma H- ion source, which has a life time of several weeks with occasional sparks between high voltage electrodes. To extend the life time of the ion source and prepare for the CSNS phase-II, we are trying to develop a RF negative hydrogen ion source with external antenna. The configuration of the source is similar to the DESY external antenna ion source and SNS ion source. However several changes are made to improve the stability and the life time. Firstly, Si3N4 ceramic with high thermal shock resistance, and high thermal conductivity is used for plasma chamber, which can endure an average power of 2000W. Secondly, the water-cooled antenna is brazed on the chamber to improve the energy efficiency. Thirdly, cesium is injected directly to the plasma chamber if necessary, to simplify the design of the converter and the extraction. Area of stainless steel exposed to plasma is minimized to reduce the sputtering and degassing. Instead Mo, Ta, and Pt coated materials are used to face the plasma, which makes the self-cleaning of the source possible.

Beam Dynamics Simulation of Photocathode RF Electron Gun at the PBP-CMU Linac Laboratory

NASA Astrophysics Data System (ADS)

Buakor, K.; Rimjaem, S.

2017-09-01

Photocathode radio-frequency (RF) electron guns are widely used at many particle accelerator laboratories due to high quality of produced electron beams. By using a short-pulse laser to induce the photoemission process, the electrons are emitted with low energy spread. Moreover, the photocathode RF guns are not suffered from the electron back bombardment effect, which can cause the limited electron current and accelerated energy. In this research, we aim to develop the photocathode RF gun for the linac-based THz radiation source. Its design is based on the existing gun at the PBP-CMU Linac Laboratory. The gun consists of a one and a half cell S-band standing-wave RF cavities with a maximum electric field of about 60 MV/m at the centre of the full cell. We study the beam dynamics of electrons traveling through the electromagnetic field inside the RF gun by using the particle tracking program ASTRA. The laser properties i.e. transverse size and injecting phase are optimized to obtain low transverse emittance. In addition, the solenoid magnet is applied for beam focusing and emittance compensation. The proper solenoid magnetic field is then investigated to find the optimum value for proper emittance conservation condition.

Studies of RF sheaths and diagnostics on IShTAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crombé, K., E-mail: Kristel.Crombe@UGent.be; LPP-ERM/KMS, Royal Military Academy, Brussels; Devaux, S.

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 tomore » 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.« less

Preliminary results from the Small Negative Ion Facility (SNIF) at CCFE

NASA Astrophysics Data System (ADS)

Zacks, J.; McAdams, R.; Booth, J.; Flinders, K.; Holmes, A. J. T.; Simmonds, M.; Stevens, B.; Stevenson, P.; Surrey, E.; Warder, S.; Whitehead, A.; Young, D.

2013-02-01

At Culham Centre for Fusion Energy, a new beam extraction test facility has been built with the purpose of studying and enhancing negative ion beam production and transport. The multipole hydrogen ion source is based on a RF generated plasma using a continuous 5kW power supply operating at the industrial standard frequency of 13.56MHz. The cylindrical source has a diameter of 30cm and a depth of 20cm, with a flat spiral antenna driving the source through a quartz window. The magnet configuration is arranged to produce a dipole filter field across the ion source close to the plasma grid. The plasma load is matched to the RF generator using a Pi matching network. The accelerator uses a single extraction aperture of 14mm diameter, with a biased insert for electron suppression. The accelerator is a triode design with a beam energy of up to 30kV. The beamline consists of a turbomolecular pumped vacuum tank with an instrumented beam dump and ports for additional diagnostics. The ITER Neutral Beam source operates with the enhancement of caesium, which, when scaled up to a reactor, will be heavily consumed. The small size of SNIF allows for fast turn around of modifications and alternative materials to caesium can be tested. A full description of the facility and planned diagnostics is given. Initial results are presented, including measurements and calculations of the plasma load on the RF generator, and beam extraction measurements.

Spectrally resolved, broadband frequency response characterization of photodetectors using continuous-wave supercontinuum sources

NASA Astrophysics Data System (ADS)

Choudhury, Vishal; Prakash, Roopa; Nagarjun, K. P.; Supradeepa, V. R.

2018-02-01

A simple and powerful method using continuous wave supercontinuum lasers is demonstrated to perform spectrally resolved, broadband frequency response characterization of photodetectors in the NIR Band. In contrast to existing techniques, this method allows for a simple system to achieve the goal, requiring just a standard continuous wave(CW) high-power fiber laser source and an RF spectrum analyzer. From our recent work, we summarize methods to easily convert any high-power fiber laser into a CW supercontinuum. These sources in the time domain exhibit interesting properties all the way down to the femtosecond time scale. This enables measurement of broadband frequency response of photodetectors while the wide optical spectrum of the supercontinuum can be spectrally filtered to obtain this information in a spectrally resolved fashion. The method involves looking at the RF spectrum of the output of a photodetector under test when incident with the supercontinuum. By using prior knowledge of the RF spectrum of the source, the frequency response can be calculated. We utilize two techniques for calibration of the source spectrum, one using a prior measurement and the other relying on a fitted model. Here, we characterize multiple photodetectors from 150MHz bandwidth to >20GHz bandwidth at multiple bands in the NIR region. We utilize a supercontinuum source spanning over 700nm bandwidth from 1300nm to 2000nm. For spectrally resolved measurement, we utilize multiple wavelength bands such as around 1400nm and 1600nm. Interesting behavior was observed in the frequency response of the photodetectors when comparing broadband spectral excitation versus narrower band excitation.

Analytical and numerical study of New field emitter processing for superconducting cavities

NASA Astrophysics Data System (ADS)

Volkov, Vladimir; Petrov, Victor

2018-02-01

In this article a scientific prove for a new technology to maximize the accelerating gradient in superconducting cavities by processing on higher order mode frequencies is presented. As dominant energy source the heating of field emitters by an induced rf current (rf-heating) is considered. The field emitter structure is assumed to be a chain of conductive particles, which are formed by attractive forces.

High Current Density Scandate Cathodes for Future Vacuum Electronics Applications

DTIC Science & Technology

2008-05-30

of Technology HFSS Ansoft Corporation’s High Frequency Structure Simulator TWT Traveling Wave Tube - device for generating high levels of RF power ...cathodes are practical for high power RF sources. Typical thermi- onic cathodes consists of a tungsten matrix impregnated with a mixture of barium oxide...electron beam with the largest possible diameter, consistent with high gain, bandwidth, and efficiency at W- Band . The research concentrated on photonic

FID navigator-based MR thermometry method to monitor small temperature changes in the brain of ventilated animals.

PubMed

Boulant, Nicolas; Bottlaender, Michel; Uhrig, Lynn; Giacomini, Eric; Luong, Michel; Amadon, Alexis; Massire, Aurélien; Larrat, Benoît; Vignaud, Alexandre

2015-01-01

An MR thermometry method is proposed for measuring in vivo small temperature changes engendered by external RF heat sources. The method relies on reproducible and stable respiration and therefore currently applies to ventilated animals whose breathing is carefully controlled. It first consists in characterizing the stability of the main magnetic field as well as the variations induced by breathing during a first monitoring stage. Second, RF heating is applied while the phase and thus temperature evolutions are continuously measured, the corrections due to breathing and field drift being made thanks to the data accumulated during the first period. The RF heat source is finally stopped and the temperature rise likewise is continuously monitored during a third and last stage to observe the animal cooling down and to validate the assumptions made for correcting for the main field variation and the physiological noise. Experiments were performed with a clinical 7 T scanner on an anesthetized baboon and with a dedicated RF heating setup. Analysis of the data reveals a precision around 0.1°C, which allows us to reliably measure sub-degree temperature rises in the muscle and in the brain of the animal. Copyright © 2014 John Wiley & Sons, Ltd.

Research and Development for an Alternative RF Source Using Magnetrons in CEBAF

NASA Astrophysics Data System (ADS)

Jacobs, Andrew

2016-09-01

At Jefferson Lab, klystrons are currently used as a radiofrequency (RF) power source for the 1497 MHz Continuous Electron Beam Accelerator Facility (CEBAF) Continuous Wave (CW) system. A drop-in replacement for the klystrons in the form of a system of magnetrons is being developed. The klystron DC-RF efficiency at CEBAF is 35-51% while the estimated magnetron efficiency is 80-90%. Thus, the introduction of magnetrons to CEBAF will have enormous benefits in terms of electrical power saving. The primary focus of this project was to characterize a magnetron's frequency pushing and pulling curves at 2.45 GHz with stub tuner and anode current adjustments so that a Low Level RF controller for a new 1.497 GHz magnetron can be built. A Virtual Instrument was created in LabVIEW, and data was taken. The resulting data allowed for the creation of many constant lines of frequency and output power. Additionally, the results provided a characterization of magnetron oven temperature drift over the operation time and the relationship between anode current and frequency. Using these results, the control model of different variables and their feedback or feedforward that affect the frequency pushing and pulling of the magnetron is better developed. Department of Energy, Science Undergraduate Laboratory Internships, and Jefferson Lab.

Method of making radio frequency ion source antenna

DOEpatents

Ehlers, Kenneth W.; Leung, Ka-Ngo

1988-01-01

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

RF Wave Simulation Using the MFEM Open Source FEM Package

NASA Astrophysics Data System (ADS)

Stillerman, J.; Shiraiwa, S.; Bonoli, P. T.; Wright, J. C.; Green, D. L.; Kolev, T.

2016-10-01

A new plasma wave simulation environment based on the finite element method is presented. MFEM, a scalable open-source FEM library, is used as the basis for this capability. MFEM allows for assembling an FEM matrix of arbitrarily high order in a parallel computing environment. A 3D frequency domain RF physics layer was implemented using a python wrapper for MFEM and a cold collisional plasma model was ported. This physics layer allows for defining the plasma RF wave simulation model without user knowledge of the FEM weak-form formulation. A graphical user interface is built on πScope, a python-based scientific workbench, such that a user can build a model definition file interactively. Benchmark cases have been ported to this new environment, with results being consistent with those obtained using COMSOL multiphysics, GENRAY, and TORIC/TORLH spectral solvers. This work is a first step in bringing to bear the sophisticated computational tool suite that MFEM provides (e.g., adaptive mesh refinement, solver suite, element types) to the linear plasma-wave interaction problem, and within more complicated integrated workflows, such as coupling with core spectral solver, or incorporating additional physics such as an RF sheath potential model or kinetic effects. USDoE Awards DE-FC02-99ER54512, DE-FC02-01ER54648.

Method of making radio frequency ion source antenna and such antenna

DOEpatents

Ehlers, K.W.; Leung, K.N.

1985-05-22

In the method, the radio frequency (rf) antenna is made by providing a clean coil made of copper tubing or other metal conductor, which is coated with a tacky organic binder, and then with a powdered glass frit, as by sprinkling the frit uniformly over the binder. The coil is then heated internally in an inert gas atmosphere, preferably by passing an electrical heating current along the coil. Initially, the coil is internally heated to about 200/sup 0/C to boil off the water from the binder, and then to about 750 to 850/sup 0/C to melt the glass frit, while also burning off the organic binder. The melted frit forms a molten glass coating on the metal coil, which is then cooled to solidify the glass, so that the metal coil is covered with a thin continuous homogeneous impervious glass coating of substantially uniform thickness. The glass coating affords complete electrical insulation and complete dielectric protection for the metal coil of the rf antenna, to withstand voltage breakdown and to prevent sputtering, while also doubling the plasma generating efficiency of the rf antenna, when energized with RF power in the vacuum chamber of an ion source for a particle accelerator or the like. The glass frit preferably contains approximately 45% lead oxide.

Agile Blocker and Clock Jitter Tolerant Low-Power Frequency Selective Receiver with Energy Harvesting Capability.

PubMed

Hasan, Abul; Helaoui, Mohamed; Ghannouchi, Fadhel M

2017-08-29

In this article, a novel tunable, blocker and clock jitter tolerant, low power, quadrature phase shift frequency selective (QPS-FS) receiver with energy harvesting capability is proposed. The receiver's design embraces and integrates (i) the baseband to radio frequency (RF) impedance translation concept to improve selectivity over that of conventional homodyne receiver topologies and (ii) broadband quadrature phase shift circuitry in the RF path to remove an active multi-phase clock generation circuit in passive mixer (PM) receivers. The use of a single local oscillator clock signal with a passive clock division network improves the receiver's robustness against clock jitter and reduces the source clock frequency by a factor of N, compared to PM receivers using N switches (N≥4). As a consequence, the frequency coverage of the QPS-FS receiver is improved by a factor of N, given a clock source of maximum frequency; and, the power consumption of the whole receiver system can eventually be reduced. The tunable QPS-FS receiver separates the wanted RF band signal from the unwanted blockers/interferers. The desired RF signal is frequency down-converted to baseband, while the undesired blocker/interferer signals are reflected by the receiver, collected and could be energy recycled using an auxiliary energy harvesting device.

Modeling of neutrals in the Linac4 H- ion source plasma: Hydrogen atom production density profile and Hα intensity by collisional radiative model

NASA Astrophysics Data System (ADS)

Yamamoto, T.; Shibata, T.; Ohta, M.; Yasumoto, M.; Nishida, K.; Hatayama, A.; Mattei, S.; Lettry, J.; Sawada, K.; Fantz, U.

2014-02-01

To control the H0 atom production profile in the H- ion sources is one of the important issues for the efficient and uniform surface H- production. The purpose of this study is to construct a collisional radiative (CR) model to calculate the effective production rate of H0 atoms from H2 molecules in the model geometry of the radio-frequency (RF) H- ion source for Linac4 accelerator. In order to validate the CR model by comparison with the experimental results from the optical emission spectroscopy, it is also necessary for the model to calculate Balmer photon emission rate in the source. As a basic test of the model, the time evolutions of H0 production and the Balmer Hα photon emission rate are calculated for given electron energy distribution functions in the Linac4 RF H- ion source. Reasonable test results are obtained and basis for the detailed comparisons with experimental results have been established.

Development of an RF-EMF Exposure Surrogate for Epidemiologic Research.

PubMed

Roser, Katharina; Schoeni, Anna; Bürgi, Alfred; Röösli, Martin

2015-05-22

Exposure assessment is a crucial part in studying potential effects of RF-EMF. Using data from the HERMES study on adolescents, we developed an integrative exposure surrogate combining near-field and far-field RF-EMF exposure in a single brain and whole-body exposure measure. Contributions from far-field sources were modelled by propagation modelling and multivariable regression modelling using personal measurements. Contributions from near-field sources were assessed from both, questionnaires and mobile phone operator records. Mean cumulative brain and whole-body doses were 1559.7 mJ/kg and 339.9 mJ/kg per day, respectively. 98.4% of the brain dose originated from near-field sources, mainly from GSM mobile phone calls (93.1%) and from DECT phone calls (4.8%). Main contributors to the whole-body dose were GSM mobile phone calls (69.0%), use of computer, laptop and tablet connected to WLAN (12.2%) and data traffic on the mobile phone via WLAN (6.5%). The exposure from mobile phone base stations contributed 1.8% to the whole-body dose, while uplink exposure from other people's mobile phones contributed 3.6%. In conclusion, the proposed approach is considered useful to combine near-field and far-field exposure to an integrative exposure surrogate for exposure assessment in epidemiologic studies. However, substantial uncertainties remain about exposure contributions from various near-field and far-field sources.

Development of an RF-EMF Exposure Surrogate for Epidemiologic Research

PubMed Central

Roser, Katharina; Schoeni, Anna; Bürgi, Alfred; Röösli, Martin

2015-01-01

Exposure assessment is a crucial part in studying potential effects of RF-EMF. Using data from the HERMES study on adolescents, we developed an integrative exposure surrogate combining near-field and far-field RF-EMF exposure in a single brain and whole-body exposure measure. Contributions from far-field sources were modelled by propagation modelling and multivariable regression modelling using personal measurements. Contributions from near-field sources were assessed from both, questionnaires and mobile phone operator records. Mean cumulative brain and whole-body doses were 1559.7 mJ/kg and 339.9 mJ/kg per day, respectively. 98.4% of the brain dose originated from near-field sources, mainly from GSM mobile phone calls (93.1%) and from DECT phone calls (4.8%). Main contributors to the whole-body dose were GSM mobile phone calls (69.0%), use of computer, laptop and tablet connected to WLAN (12.2%) and data traffic on the mobile phone via WLAN (6.5%). The exposure from mobile phone base stations contributed 1.8% to the whole-body dose, while uplink exposure from other people’s mobile phones contributed 3.6%. In conclusion, the proposed approach is considered useful to combine near-field and far-field exposure to an integrative exposure surrogate for exposure assessment in epidemiologic studies. However, substantial uncertainties remain about exposure contributions from various near-field and far-field sources. PMID:26006132

Investigation of plasma parameters at BATMAN for variation of the Cs evaporation asymmetry and comparing two driver geometries

NASA Astrophysics Data System (ADS)

Wimmer, C.; Fantz, U.; Aza, E.; Jovović, J.; Kraus, W.; Mimo, A.; Schiesko, L.

2017-08-01

The Neutral Beam Injection (NBI) system for fusion devices like ITER and, beyond ITER, DEMO requires large scale sources for negative hydrogen ions. BATMAN (Bavarian Test Machine for Negative ions) is a test facility attached with the prototype source for the ITER NBI (1/8 source size of the ITER source), dedicated to physical investigations due to its flexible access for diagnostics and exchange of source components. The required amount of negative ions is produced by surface conversion of hydrogen atoms or ions on caesiated surfaces. Several diagnostic tools (Optical Emission Spectroscopy, Cavity Ring-Down Spectroscopy for H-, Langmuir probes, Tunable Diode Laser Absorption Spectroscopy for Cs) allow the determination of plasma parameters in the ion source. Plasma parameters for two modifications of the standard prototype source have been investigated: Firstly, a second Cs oven has been installed in the bottom part of the back plate in addition to the regularly used oven in the top part of the back plate. Evaporation from the top oven only can lead to a vertically asymmetric Cs distribution in front of the plasma grid. Using both ovens, a symmetric Cs distribution can be reached - however, in most cases no significant change of the extracted ion current has been determined for varying Cs symmetry if the source is well-conditioned. Secondly, BATMAN has been equipped with a much larger, racetrack-shaped RF driver (area of 32×58 cm2) instead of the cylindrical RF driver (diameter of 24.5 cm). The main idea is that one racetrack driver could substitute two cylindrical drivers in larger sources with increased reliability and power efficiency. For the same applied RF power, the electron density is lower in the racetrack driver due to its five times higher volume. The fraction of hydrogen atoms to molecules, however, is at a similar level or even slightly higher, which is a promising result for application in larger sources.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogacz, Alex

We summarize the current state of a concept for muon acceleration aimed at a future Neutrino Factory and extendable to Higgs Factory. The main thrust of these studies was to reduce the overall cost while maintaining performance by exploring the interplay between the complexity of the cooling systems and the acceptance of the accelerator complex. To ensure adequate survival for the short-lived muons, acceleration must occur at high average gradient. The need for large transverse and longitudinal acceptances drives the design of the acceleration system to an initially low RF frequency, e.g., 325 MHz, which is then increased to 650more » MHz as the transverse size shrinks with increasing energy. High-gradient normal conducting RF cavities at these frequencies require extremely high peak-power RF sources. Hence superconducting RF (SRF) cavities are chosen. We consider an SRF-efficient design based on a multi-pass (4.5) ?dogbone? RLA, extendable to multi-pass FFAG-like arcs.« less

Exact cancellation of emittance growth due to coupled transverse dynamics in solenoids and rf couplers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowell, David H.; Zhou, Feng; Schmerge, John

Weak, rotated magnetic and radio frequency quadrupole fields in electron guns and injectors can couple the beam’s horizontal with vertical motion, introduce correlations between otherwise orthogonal transverse momenta, and reduce the beam brightness. This paper discusses two important sources of coupled transverse dynamics common to most electron injectors. The first is quadrupole focusing followed by beam rotation in a solenoid, and the second coupling comes from a skewed high-power rf coupler or cavity port which has a rotated rf quadrupole field. It is shown that a dc quadrupole field can correct for both types of couplings and exactly cancel theirmore » emittance growths. The degree of cancellation of the rf skew quadrupole emittance is limited by the electron bunch length. Analytic expressions are derived and compared with emittance simulations and measurements.« less

Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata

DOE Office of Scientific and Technical Information (OSTI.GOV)

Som, Sumit; Seth, Sudeshna; Mandal, Aditya

2013-02-15

Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and {+-}0.2{sup 0}, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ('Dee' voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTemore » X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.« less

Exact cancellation of emittance growth due to coupled transverse dynamics in solenoids and rf couplers

DOE PAGES

Dowell, David H.; Zhou, Feng; Schmerge, John

2018-01-17

Weak, rotated magnetic and radio frequency quadrupole fields in electron guns and injectors can couple the beam’s horizontal with vertical motion, introduce correlations between otherwise orthogonal transverse momenta, and reduce the beam brightness. This paper discusses two important sources of coupled transverse dynamics common to most electron injectors. The first is quadrupole focusing followed by beam rotation in a solenoid, and the second coupling comes from a skewed high-power rf coupler or cavity port which has a rotated rf quadrupole field. It is shown that a dc quadrupole field can correct for both types of couplings and exactly cancel theirmore » emittance growths. The degree of cancellation of the rf skew quadrupole emittance is limited by the electron bunch length. Analytic expressions are derived and compared with emittance simulations and measurements.« less

Compression of high-density 0.16 pC electron bunches through high field gradients for ultrafast single shot electron diffraction: The Compact RF Gun

PubMed Central

Daoud, Hazem; Floettmann, Klaus; Dwayne Miller, R. J.

2017-01-01

We present an RF gun design for single shot ultrafast electron diffraction experiments that can produce sub-100 fs high-charge electron bunches in the 130 keV energy range. Our simulations show that our proposed half-cell RF cavity is capable of producing 137 keV, 27 fs rms (60 fs FWHM), 106 electron bunches with an rms spot size of 276 μm and a transverse coherence length of 2.0 nm. The required operation power is 9.2 kW, significantly lower than conventional rf cavity designs and a key design feature. This electron source further relies on high electric field gradients at the cathode to simultaneously accelerate and compress the electron bunch to open up new space-time resolution domains for atomically resolved dynamics. PMID:28428973

Langmuir probe measurements in the intense RF field of a helicon discharge

NASA Astrophysics Data System (ADS)

Chen, Francis F.

2012-10-01

Helicon discharges have extensively been studied for over 25 years both because of their intriguing physics and because of their utility in producing high plasma densities for industrial applications. Almost all measurements so far have been made away from the antenna region in the plasma ejected into a chamber where there may be a strong magnetic field (B-field) but where the radiofrequency (RF) field is much weaker than under the antenna. Inside the source region, the RF field distorts the current-voltage (I-V) characteristic of the probe unless it is specially designed with strong RF compensation. For this purpose, a thin probe was designed and used to show the effect of inadequate compensation on electron temperature (Te) measurements. The subtraction of ion current from the I-V curve is essential; and, surprisingly, Langmuir's orbital motion limited theory for ion current can be used well beyond its intended regime.

Design of 6 MeV X-band electron linac for dual-head gantry radiotherapy system

NASA Astrophysics Data System (ADS)

Shin, Seung-wook; Lee, Seung-Hyun; Lee, Jong-Chul; Kim, Huisu; Ha, Donghyup; Ghergherehchi, Mitra; Chai, Jongseo; Lee, Byung-no; Chae, Moonsik

2017-12-01

A compact 6 MeV electron linac is being developed at Sungkyunkwan University, in collaboration with the Korea atomic energy research institute (KAERI). The linac will be used as an X-ray source for a dual-head gantry radiotherapy system. X-band technology has been employed to satisfy the size requirement of the dual-head gantry radiotherapy machine. Among the several options available, we selected a pi/2-mode, standing-wave, side-coupled cavity. This choice of radiofrequency (RF) cavity design is intended to enhance the shunt impedance of each cavity in the linac. An optimum structure of the RF cavity with a high-performance design was determined by applying a genetic algorithm during the optimization procedure. This paper describes the detailed design process for a single normal RF cavity and the entire structure, including the RF power coupler and coupling cavity, as well as the beam dynamics results.

A novel photonic oscillator

NASA Technical Reports Server (NTRS)

Yao, X. S.; Maleki, L.

1995-01-01

We report a novel oscillator for photonic RF systems. This oscillator is capable of generating high-frequency signals up to 70 GHz in both electrical and optical domains and is a special voltage-controlled oscillator with an optical output port. It can be used to make a phase-locked loop (PLL) and perform all functions that a PLL is capable of for photonic systems. It can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and PLL. It can also be self-phase locked and self-injection locked to generate a high-stability photonic RF reference. Its applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb-frequecy and square-wave generation, carrier recovery, and clock recovery. We anticipate that such photonic voltage-controlled oscillators (VCOs) will be as important to photonic RF systems as electrical VCOs are to electrical RF systems.

Beam Test of a Dielectric Loaded High Pressure RF Cavity for Use in Muon Cooling Channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freemire, Ben; Bowring, Daniel; Kochemirovskiy, Alexey

2016-06-01

Bright muon sources require six dimensional cooling to achieve acceptable luminosities. Ionization cooling is the only known method able to do so within the muon lifetime. One proposed cooling channel, the Helical Cooling Channel, utilizes gas filled radio frequency cavities to both mitigate RF breakdown in the presence of strong, external magnetic fields, and provide the cooling medium. Engineering constraints on the diameter of the magnets within which these cavities operate dictate the radius of the cavities be decreased at their nominal operating frequency. To accomplish this, one may load the cavities with a larger dielectric material. A 99.5% aluminamore » ring was inserted in a high pressure RF test cell and subjected to an intense proton beam at the MuCool Test Area at Fermilab. The results of the performance of this dielectric loaded high pressure RF cavity will be presented.« less

Electron Heating Mode Transitions in Nitrogen (13.56 and 40.68) MHz RF-CCPs

NASA Astrophysics Data System (ADS)

Erozbek Gungor, Ummugul; Bilikmen, Sinan Kadri; Akbar, Demiral

2015-09-01

Capacitively coupled radio frequency plasmas (RF-CCPs) are commonly used in plasma material processing. Parametrical structure of the plasma determines the demands of processing applications. For example; high density plasmas in gamma mode are mostly preferred for etching applications while stabile plasmas in gamma mode are usually used in sputtering applications. For this reason, characterization of the plasma is very essential before surface modification of the materials. In this work, analysis of electron heating mode transition in high frequency (40.68 MHz) RF-CCP was deeply investigated. The plasma was generated in a home-made (500 × 400 mm2) stainless steel cylindrical reactor in which two identical (200 mm in diameter) electrodes were placed with 40 mm interval. In addition, L-type automatic matching network system was connected to the 40.68 MHz RF generator to get high accuracy. Moreover, the pure (99.995 %) nitrogen was used as an activation gas on account of having an appreciable impression in plasma processing applications. Furthermore, diagnostic measurements of the plasma were done by using the Impedans Langmuir single and double probe systems. It was found that two transition points; α- γ (pressure dependent) and γ- α (RF power dependent) were observed in both medium and high RF-CCPs. As a result, the α- γ pressure transition increased, whereas the γ- α power transition remained constant by changing the RF frequency sources.

RF Sheath-Enhanced Plasma Surface Interaction Studies using Beryllium Optical Emission Spectroscopy in JET ITER-Like Wall

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarici, G.; Klepper, C Christopher; Colas, L.

A dedicated study on JET-ILW, deploying two types of ICRH antennas and spectroscopic observation spots at two outboard, beryllium limiters, has provided insight on long-range (up to 6m) RFenhanced plasma-surface interactions (RF-PSI) due to near-antenna electric fields. To aid in the interpretation of optical emission measurements of these effects, the antenna near-fields are computed using the TOPICA code, specifically run for the ITER-like antenna (ILA); similar modelling already existed for the standard JET antennas (A2). In the experiment, both antennas were operated in current drive mode, as RF-PSI tends to be higher in this phasing and at similar power (∼0.5more » MW). When sweeping the edge magnetic field pitch angle, peaked RF-PSI effects, in the form of 2-4 fold increase in the local Be source,are consistently measured with the observation spots magnetically connect to regions of TOPICAL-calculated high near-fields, particularly at the near-antenna limiters. It is also found that similar RF-PSI effects are produced by the two types of antenna on similarly distant limiters. Although this mapping of calculated near-fields to enhanced RF-PSI gives only qualitative interpretion of the data, the present dataset is expected to provide a sound experimental basis for emerging RF sheath simulation model validation.« less

Coupling extended magnetohydrodynamic fluid codes with radiofrequency ray tracing codes for fusion modeling

NASA Astrophysics Data System (ADS)

Jenkins, Thomas G.; Held, Eric D.

2015-09-01

Neoclassical tearing modes are macroscopic (L ∼ 1 m) instabilities in magnetic fusion experiments; if unchecked, these modes degrade plasma performance and may catastrophically destroy plasma confinement by inducing a disruption. Fortunately, the use of properly tuned and directed radiofrequency waves (λ ∼ 1 mm) can eliminate these modes. Numerical modeling of this difficult multiscale problem requires the integration of separate mathematical models for each length and time scale (Jenkins and Kruger, 2012 [21]); the extended MHD model captures macroscopic plasma evolution while the RF model tracks the flow and deposition of injected RF power through the evolving plasma profiles. The scale separation enables use of the eikonal (ray-tracing) approximation to model the RF wave propagation. In this work we demonstrate a technique, based on methods of computational geometry, for mapping the ensuing RF data (associated with discrete ray trajectories) onto the finite-element/pseudospectral grid that is used to model the extended MHD physics. In the new representation, the RF data can then be used to construct source terms in the equations of the extended MHD model, enabling quantitative modeling of RF-induced tearing mode stabilization. Though our specific implementation uses the NIMROD extended MHD (Sovinec et al., 2004 [22]) and GENRAY RF (Smirnov et al., 1994 [23]) codes, the approach presented can be applied more generally to any code coupling requiring the mapping of ray tracing data onto Eulerian grids.

Results of Research on Overcoming Pulse Shortening of GW Class HPM Sources

DTIC Science & Technology

1997-05-29

The RPM sources basic research program of the Air Force has a major emphasis on the pulse shortening problem. This includes collaborative work in...universities and the Phillips Laboratory . We have demonstrated two fundamentally different RPM sources which radiate rf power in excess of 1 GW and are

Results from the RF BPM Upgrade Prototype at the Advanced Photon Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pietryla, Anthony; Lill, Robert; Norum, Eric

2006-11-20

The Advanced Photon Source (APS), a third-generation synchrotron light source, has been in operation for 10 years. The monopulse radio frequency (RF) beam position monitor (BPM) is one of three BPM types now employed in the storage ring at the APS. It is a broadband (10 MHz) system designed to measure single-turn and multi-turn beam positions, but it suffers from an aging data acquisition system. The replacement BPM system retains the existing monopulse receivers and replaces the data acquisition system with high-speed analog-to-digital converters (ADCs) and a field programmable gate array (FPGA) that performs the signal processing. A prototype systemmore » was constructed and is currently being evaluated. This paper presents the results obtained from laboratory and field tests of the prototype system.« less

Results from the RF BPM upgrade prototype at the Advanced Photon Source.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pietryla, A.; Lill, R.; Norum, E.

2006-01-01

The Advanced Photon Source (APS), a third-generation synchrotron light source, has been in operation for 10 years. The monopulse radio frequency (RF) beam position monitor (BPM) is one of three BPM types now employed in the storage ring at the APS. It is a broadband (10 MHz) system designed to measure single-turn and multi-turn beam positions, but it suffers from an aging data acquisition system. The replacement BPM system retains the existing monopulse receivers and replaces the data acquisition system with high-speed analog-to-digital converters (ADCs) and a field programmable gate array (FPGA) that performs the signal processing. A prototype systemmore » was constructed and is currently being evaluated. This paper presents the results obtained from laboratory and field tests of the prototype system.« less

Discontinuous model with semi analytical sheath interface for radio frequency plasma

NASA Astrophysics Data System (ADS)

Miyashita, Masaru

2016-09-01

Sumitomo Heavy Industries, Ltd. provide many products utilizing plasma. In this study, we focus on the Radio Frequency (RF) plasma source by interior antenna. The plasma source is expected to be high density and low metal contamination. However, the sputtering the antenna cover by high energy ion from sheath voltage still have been problematic. We have developed the new model which can calculate sheath voltage wave form in the RF plasma source for realistic calculation time. This model is discontinuous that electronic fluid equation in plasma connect to usual passion equation in antenna cover and chamber with semi analytical sheath interface. We estimate the sputtering distribution based on calculated sheath voltage waveform by this model, sputtering yield and ion energy distribution function (IEDF) model. The estimated sputtering distribution reproduce the tendency of experimental results.

Plasma driven neutron/gamma generator

DOEpatents

Leung, Ka-Ngo; Antolak, Arlyn

2015-03-03

An apparatus for the generation of neutron/gamma rays is described including a chamber which defines an ion source, said apparatus including an RF antenna positioned outside of or within the chamber. Positioned within the chamber is a target material. One or more sets of confining magnets are also provided to create a cross B magnetic field directly above the target. To generate neutrons/gamma rays, the appropriate source gas is first introduced into the chamber, the RF antenna energized and a plasma formed. A series of high voltage pulses are then applied to the target. A plasma sheath, which serves as an accelerating gap, is formed upon application of the high voltage pulse to the target. Depending upon the selected combination of source gas and target material, either neutrons or gamma rays are generated, which may be used for cargo inspection, and the like.

Laboratory Observation of a Plasma-Flow-State Transition from Diverging to Stretching a Magnetic Nozzle.

PubMed

Takahashi, Kazunori; Ando, Akira

2017-06-02

An axial magnetic field induced by a plasma flow in a divergent magnetic nozzle is measured when injecting the plasma flow from a radio frequency (rf) plasma source located upstream of the nozzle. The source is operated with a pulsed rf power of 5 kW, and the high density plasma flow is sustained only for the initial ∼100  μsec of the discharge. The measurement shows a decrease in the axial magnetic field near the source exit, whereas an increase in the field is detected at the downstream side of the magnetic nozzle. These results demonstrate a spatial transition of the plasma-flow state from diverging to stretching the magnetic nozzle, where the importance of both the Alfvén and ion Mach numbers is shown.

Fine-tuning to minimize emittances of J-PARC RF-driven H{sup −} ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ueno, A., E-mail: akira.ueno@j-parc.jp; Ohkoshi, K.; Ikegami, K.

2016-02-15

The Japan Proton Accelerator Research Complex (J-PARC) cesiated RF-driven H{sup −} ion source has been successfully operated for about one year. By the world’s brightest level beam, the J-PARC design beam power of 1 MW was successfully demonstrated. In order to minimize the transverse emittances, the rod-filter-field (RFF) was optimized by changing the triple-gap-lengths of each of pairing five piece rod-filter-magnets. The larger emittance degradation seems to be caused by impurity-gases than the RFF. The smaller beam-hole-diameter of the extraction electrode caused the more than expected improvements on not only the emittances but also the peak beam intensity.

Beam Measurement of 11.424 GHz X-Band Linac for Compton Scattering X-ray Source

NASA Astrophysics Data System (ADS)

Natsui, Takuya; Mori, Azusa; Masuda, Hirotoshi; Uesaka, Mitsuru; Sakamoto, Fumito

2010-11-01

An inverse Compton scattering X-ray source for medical applications, consisting of an X-band (11.424 GHz) linac and Q-switched Nd:YAG laser, is currently being developed at the University of Tokyo. This system uses an X-band 3.5-cell thermionic cathode RF gun for electron beam generation. We can obtain a multi-bunch electron beam with this gun. The beam is accelerated to 30 MeV by a traveling-wave accelerating tube. So far, we have verified stable beam generation (around 2.3 MeV) by using the newly designed RF gun and we have succeeded in beam transportation to a beam dump.

Digital approach to stabilizing optical frequency combs and beat notes of CW lasers

NASA Astrophysics Data System (ADS)

Čížek, Martin; Číp, Ondřej; Å míd, Radek; Hrabina, Jan; Mikel, Břetislav; Lazar, Josef

2013-10-01

In cases when it is necessary to lock optical frequencies generated by an optical frequency comb to a precise radio frequency (RF) standard (GPS-disciplined oscillator, H-maser, etc.) the usual practice is to implement phase and frequency-locked loops. Such system takes the signal generated by the RF standard (usually 10 MHz or 100 MHz) as a reference and stabilizes the repetition and offset frequencies of the comb contained in the RF output of the f-2f interferometer. These control loops are usually built around analog electronic circuits processing the output signals from photo detectors. This results in transferring the stability of the standard from RF to optical frequency domain. The presented work describes a different approach based on digital signal processing and software-defined radio algorithms used for processing the f-2f and beat-note signals. Several applications of digital phase and frequency locks to a RF standard are demonstrated: the repetition (frep) and offset frequency (fceo) of the comb, and the frequency of the beat note between a CW laser source and a single component of the optical frequency comb spectrum.

Comparative study of ITO and TiN fabricated by low-temperature RF biased sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, Daniel K., E-mail: daniel.simon@namlab.com; Schenk, Tony; Dirnstorfer, Ingo

2016-03-15

Radio frequency (RF) biasing induced by a second plasma source at the substrate is applied to low-temperature sputtering processes for indium tin oxide (ITO) and titanium nitride (TiN) thin films. Investigations on crystal structure and surface morphology show that RF-biased substrate plasma processes result in a changed growth regime with different grain sizes and orientations than those produced by processes without a substrate bias. The influence of the RF bias is shown comparatively for reactive RF-sputtered ITO and reactive direct-current-sputtered TiN. The ITO layers exhibit an improved electrical resistivity of 0.5 mΩ cm and an optical absorption coefficient of 0.5 × 10{sup 4 }cm{supmore » −1} without substrate heating. Room-temperature sputtered TiN layers are deposited that possess a resistivity (0.1 mΩ cm) of 3 orders of magnitude lower than, and a density (5.4 g/cm{sup 3}) up to 45% greater than, those obtained from layers grown using the standard process without a substrate plasma.« less

RF Simulation of the 187 MHz CW Photo-RF Gun Cavity at LBNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Tong-Ming

2008-12-01

A 187 MHz normal conducting Photo-RF gun cavity is designed for the next generation light sources. The cavity is capable of operating in CW mode. As high as 750 kV gap voltage can be achieved with a 20 MV/m acceleration gradient. The original cavity optimization is conducted using Superfish code (2D) by Staples. 104 vacuum pumping slots are added and evenly spaced over the cavity equator in order to achieve better than 10 -10-Tor of vacuum. Two loop couplers will be used to feed RF power into the cavity. 3D simulations are necessary to study effects from the vacuum pumpingmore » slots, couplers and possible multipactoring. The cavity geometry is optimized to minimize the power density and avoid multipactoring at operating field level. The vacuum slot dimensions are carefully chosen in consideration of both the vacuum conduction, local power density enhancement and the power attenuation at the getter pumps. This technical note gives a summary of 3D RF simulation results, multipactoring simulations (2D) and preliminary electromagnetic-thermal analysis using ANSYS code.« less

Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields.

PubMed

Freudenstein, Frederik; Wiedemann, Peter M; Brown, Tim W C

2015-01-01

The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF) exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one's own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed.

Evidence-based rules from family practice to inform family practice; the learning healthcare system case study on urinary tract infections.

PubMed

Soler, Jean K; Corrigan, Derek; Kazienko, Przemyslaw; Kajdanowicz, Tomasz; Danger, Roxana; Kulisiewicz, Marcin; Delaney, Brendan

2015-05-16

Analysis of encounter data relevant to the diagnostic process sourced from routine electronic medical record (EMR) databases represents a classic example of the concept of a learning healthcare system (LHS). By collecting International Classification of Primary Care (ICPC) coded EMR data as part of the Transition Project from Dutch and Maltese databases (using the EMR TransHIS), data mining algorithms can empirically quantify the relationships of all presenting reasons for encounter (RfEs) and recorded diagnostic outcomes. We have specifically looked at new episodes of care (EoC) for two urinary system infections: simple urinary tract infection (UTI, ICPC code: U71) and pyelonephritis (ICPC code: U70). Participating family doctors (FDs) recorded details of all their patient contacts in an EoC structure using the ICPC, including RfEs presented by the patient, and the FDs' diagnostic labels. The relationships between RfEs and episode titles were studied using probabilistic and data mining methods as part of the TRANSFoRm project. The Dutch data indicated that the presence of RfE's "Cystitis/Urinary Tract Infection", "Dysuria", "Fear of UTI", "Urinary frequency/urgency", "Haematuria", "Urine symptom/complaint, other" are all strong, reliable, predictors for the diagnosis "Cystitis/Urinary Tract Infection" . The Maltese data indicated that the presence of RfE's "Dysuria", "Urinary frequency/urgency", "Haematuria" are all strong, reliable, predictors for the diagnosis "Cystitis/Urinary Tract Infection". The Dutch data indicated that the presence of RfE's "Flank/axilla symptom/complaint", "Dysuria", "Fever", "Cystitis/Urinary Tract Infection", "Abdominal pain/cramps general" are all strong, reliable, predictors for the diagnosis "Pyelonephritis" . The Maltese data set did not present any clinically and statistically significant predictors for pyelonephritis. We describe clinically and statistically significant diagnostic associations observed between UTIs and pyelonephritis presenting as a new problem in family practice, and all associated RfEs, and demonstrate that the significant diagnostic cues obtained are consistent with the literature. We conclude that it is possible to generate clinically meaningful diagnostic evidence from electronic sources of patient data.

Power supply system for negative ion source at IPR

NASA Astrophysics Data System (ADS)

Gahlaut, Agrajit; Sonara, Jashwant; Parmar, K. G.; Soni, Jignesh; Bandyopadhyay, M.; Singh, Mahendrajit; Bansal, Gourab; Pandya, Kaushal; Chakraborty, Arun

2010-02-01

The first step in the Indian program on negative ion beams is the setting up of Negative ion Experimental Assembly - RF based, where 100 kW of RF power shall be coupled to a plasma source producing plasma of density ~5 × 1012 cm-3, from which ~ 10 A of negative ion beam shall be produced and accelerated to 35 kV, through an electrostatic ion accelerator. The experimental system is modelled similar to the RF based negative ion source, BATMAN presently operating at IPP, Garching, Germany. The mechanical system for Negative Ion Source Assembly is close to the IPP source, remaining systems are designed and procured principally from indigenous sources, keeping the IPP configuration as a base line. High voltage (HV) and low voltage (LV) power supplies are two key constituents of the experimental setup. The HV power supplies for extraction and acceleration are rated for high voltage (~15 to 35kV), and high current (~ 15 to 35A). Other attributes are, fast rate of voltage rise (< 5ms), good regulation (< ±1%), low ripple (< ±2%), isolation (~50kV), low energy content (< 10J) and fast cut-off (< 100μs). The low voltage (LV) supplies required for biasing and providing heating power to the Cesium oven and the plasma grids; have attributes of low ripple, high stability, fast and precise regulation, programmability and remote operation. These power supplies are also equipped with over-voltage, over-current and current limit (CC Mode) protections. Fault diagnostics, to distinguish abnormal rise in currents (breakdown faults) with over-currents is enabled using fast response breakdown and over-current protection scheme. To restrict the fault energy deposited on the ion source, specially designed snubbers are implemented in each (extraction and acceleration) high voltage path to swap the surge energy. Moreover, the monitoring status and control signals from these power supplies are required to be electrically (~ 50kV) isolated from the system. The paper shall present the design basis, topology selection, manufacturing, testing, commissioning, integration and control strategy of these HVPS. A complete power interconnection scheme, which includes all protective devices and measuring devices, low & high voltage power supplies, monitoring and control signals etc. shall also be discussed. The paper also discusses the protocols involved in grounding and shielding, particularly in operating the system in RF environment.

Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities

PubMed Central

Aslam, Saleem; Hasan, Najam Ul; Jang, Ju Wook; Lee, Kyung-Geun

2016-01-01

This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH) on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP)-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU) activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones. PMID:27918424

Thermal Analysis of AlGaN/GaN High-Electron-Mobility Transistor and Its RF Power Efficiency Optimization with Source-Bridged Field-Plate Structure.

PubMed

Kwak, Hyeon-Tak; Chang, Seung-Bo; Jung, Hyun-Gu; Kim, Hyun-Seok

2018-09-01

In this study, we consider the relationship between the temperature in a two-dimensional electron gas (2-DEG) channel layer and the RF characteristics of an AlGaN/GaN high-electron-mobility transistor by changing the geometrical structure of the field-plate. The final goal is to achieve a high power efficiency by decreasing the channel layer temperature. First, simulations were performed to compare and contrast the experimental data of a conventional T-gate head structure. Then, a source-bridged field-plate (SBFP) structure was used to obtain the lower junction temperature in the 2-DEG channel layer. The peak electric field intensity was reduced, and a decrease in channel temperature resulted in an increase in electron mobility. Furthermore, the gate-to-source capacitance was increased by the SBFP structure. However, under the large current flow condition, the SBFP structure had a lower maximum temperature than the basic T-gate head structure, which improved the device electron mobility. Eventually, an optimum position of the SBFP was used, which led to higher frequency responses and improved the breakdown voltages. Hence, the optimized SBFP structure can be a promising candidate for high-power RF devices.

Eight channel transmit array volume coil using on-coil radiofrequency current sources

PubMed Central

Kurpad, Krishna N.; Boskamp, Eddy B.

2014-01-01

Background At imaging frequencies associated with high-field MRI, the combined effects of increased load-coil interaction and shortened wavelength results in degradation of circular polarization and B1 field homogeneity in the imaging volume. Radio frequency (RF) shimming is known to mitigate the problem of B1 field inhomogeneity. Transmit arrays with well decoupled transmitting elements enable accurate B1 field pattern control using simple, non-iterative algorithms. Methods An eight channel transmit array was constructed. Each channel consisted of a transmitting element driven by a dedicated on-coil RF current source. The coil current distributions of characteristic transverse electromagnetic (TEM) coil resonant modes were non-iteratively set up on each transmitting element and 3T MRI images of a mineral oil phantom were obtained. Results B1 field patterns of several linear and quadrature TEM coil resonant modes that typically occur at different resonant frequencies were replicated at 128 MHz without having to retune the transmit array. The generated B1 field patterns agreed well with simulation in most cases. Conclusions Independent control of current amplitude and phase on each transmitting element was demonstrated. The transmit array with on-coil RF current sources enables B1 field shimming in a simple and predictable manner. PMID:24834418

Optimized Energy Harvesting, Cluster-Head Selection and Channel Allocation for IoTs in Smart Cities.

PubMed

Aslam, Saleem; Hasan, Najam Ul; Jang, Ju Wook; Lee, Kyung-Geun

2016-12-02

This paper highlights three critical aspects of the internet of things (IoTs), namely (1) energy efficiency, (2) energy balancing and (3) quality of service (QoS) and presents three novel schemes for addressing these aspects. For energy efficiency, a novel radio frequency (RF) energy-harvesting scheme is presented in which each IoT device is associated with the best possible RF source in order to maximize the overall energy that the IoT devices harvest. For energy balancing, the IoT devices in close proximity are clustered together and then an IoT device with the highest residual energy is selected as a cluster head (CH) on a rotational basis. Once the CH is selected, it assigns channels to the IoT devices to report their data using a novel integer linear program (ILP)-based channel allocation scheme by satisfying their desired QoS. To evaluate the presented schemes, exhaustive simulations are carried out by varying different parameters, including the number of IoT devices, the number of harvesting sources, the distance between RF sources and IoT devices and the primary user (PU) activity of different channels. The simulation results demonstrate that our proposed schemes perform better than the existing ones.

Neutral particle dynamics in a high-power RF source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Todorov, D., E-mail: dimitar-tdrv@phys.uni-sofia.bg; Paunska, Ts.; Shivarova, A.

2015-04-08

Previous studies on the spatial discharge structure in the SPIDER source of negative hydrogen/deuterium ions carried out at low applied power are extended towards description of the discharge maintenance under the conditions of the actual rf power deposition of 100 kW planned for a single driver of the source. In addition to the expected higher electron density, the results show strong increase of the electron temperature and of the temperatures of the neutral species (hydrogen atoms and molecules). In the discussions, not only the spatial distribution of the plasma parameters but also that of the fluxes in the discharge (particlemore » and energy fluxes) is involved. The obtained results come in confirmation of basic concepts for low-pressure discharge maintenance: (i) mutually related electron density and temperature as a display of the generalized Schottky condition, (ii) discharge behavior governed by the fluxes, i.e. strong nonlocality in the discharge, and (iii) a non-ambipolarity in the discharge regime, which originates from shifted maxima of the electron density and temperature and shows evidence in a vortex electron flux and in a dc current in a rf discharge, the latter resulting from a shift in the positions of the maxima of the electron density and plasma potential.« less

Disturbance Driven Rainfall in O`ahu, Hawai`i (1990-2010)

NASA Astrophysics Data System (ADS)

Longman, R. J.; Elison Timm, O.; Giambelluca, T. W.; Kaiser, L.; Newman, A. J.; Arnold, J.; Clark, M. P.

2017-12-01

Trade wind orographic rainfall is the most prevalent synoptic weather pattern in Hawai`i and provides a year-round source of moisture to the windward areas across the Island chain. Significant contributions to total and extreme precipitation have also been linked to one of four atmospheric disturbance situations that include: cold fronts, Kona storms, upper-tropospheric disturbances (upper level lows), and tropical systems. The primary objective of this research is to determine how these disturbance types contribute to total wet-season rainfall (RF) on the Island of O`ahu, Hawai`i and to identify any significant changes in the frequency of occurrence and or the intensity of these events. Atmospheric fronts that occurred in the Hawai`i region (17-26°N, 150-165°W) were extracted from a global dataset and combined with a Kona low and upper level low dataset to create a daily categorical weather classification time series (1990-2010). Mean rainfall was extracted from gridded daily O`ahu RF maps. Results show that the difference between a wet and dry year is predominantly explained by the RF contributions from disturbance events (r2 = 0.57, p < 0.01), in particularly, the contributions coming from Kona low and cold fronts that cross the Island. During the wettest season on record, disturbances accounted for 48% of the total RF, while during the driest season they accounted for only 6% of the total RF. The event-based RF analysis also compared the RF intensity in the absence of disturbance events with the average RF intensity on days when atmospheric fronts are present but do not cross the island. The results show that non-crossing fronts reduce the average RF intensity. A possible explanation is that these events are too far away to produce RF, but close enough to disrupt normal trade wind flow, thus limiting orographic RF on the island. This new event-based RF analysis has important implications for the projection of regional climate change in Hawai`i. Our results suggest that if storm tracks were to shift poleward, O`ahu wet season RF would be reduced. The most obvious effect is that fronts crossing the Island would likely occur less frequently reducing the number of days per year with heavy cold front rainfall. In addition, non-crossing fronts could occur more often and hence reducing the orographic RF.

Compact electrostatic beam optics for multi-element focused ion beams: simulation and experiments.

PubMed

Mathew, Jose V; Bhattacharjee, Sudeep

2011-01-01

Electrostatic beam optics for a multi-element focused ion beam (MEFIB) system comprising of a microwave multicusp plasma (ion) source is designed with the help of two widely known and commercially available beam simulation codes: AXCEL-INP and SIMION. The input parameters to the simulations are obtained from experiments carried out in the system. A single and a double Einzel lens system (ELS) with and without beam limiting apertures (S) have been investigated. For a 1 mm beam at the plasma electrode aperture, the rms emittance of the focused ion beam is found to reduce from ∼0.9 mm mrad for single ELS to ∼0.5 mm mrad for a double ELS, when S of 0.5 mm aperture size is employed. The emittance can be further improved to ∼0.1 mm mrad by maintaining S at ground potential, leading to reduction in beam spot size (∼10 μm). The double ELS design is optimized for different electrode geometrical parameters with tolerances of ±1 mm in electrode thickness, electrode aperture, inter electrode distance, and ±1° in electrode angle, providing a robust design. Experimental results obtained with the double ELS for the focused beam current and spot size, agree reasonably well with the simulations.

Spatial and temporal variability of personal environmental exposure to radio frequency electromagnetic fields in children in Europe.

PubMed

Birks, Laura Ellen; Struchen, Benjamin; Eeftens, Marloes; van Wel, Luuk; Huss, Anke; Gajšek, Peter; Kheifets, Leeka; Gallastegi, Mara; Dalmau-Bueno, Albert; Estarlich, Marisa; Fernandez, Mariana F; Meder, Inger Kristine; Ferrero, Amparo; Jiménez-Zabala, Ana; Torrent, Maties; Vrijkotte, Tanja G M; Cardis, Elisabeth; Olsen, Jørn; Valič, Blaž; Vermeulen, Roel; Vrijheid, Martine; Röösli, Martin; Guxens, Mònica

2018-08-01

Exposure to radiofrequency electromagnetic fields (RF-EMF) has rapidly increased and little is known about exposure levels in children. This study describes personal RF-EMF environmental exposure levels from handheld devices and fixed site transmitters in European children, the determinants of this, and the day-to-day and year-to-year repeatability of these exposure levels. Personal environmental RF-EMF exposure (μW/m 2 , power flux density) was measured in 529 children (ages 8-18 years) in Denmark, the Netherlands, Slovenia, Switzerland, and Spain using personal portable exposure meters for a period of up to three days between 2014 and 2016, and repeated in a subsample of 28 children one year later. The meters captured 16 frequency bands every 4 s and incorporated a GPS. Activity diaries and questionnaires were used to collect children's location, use of handheld devices, and presence of indoor RF-EMF sources. Six general frequency bands were defined: total, digital enhanced cordless telecommunications (DECT), television and radio antennas (broadcast), mobile phones (uplink), mobile phone base stations (downlink), and Wireless Fidelity (WiFi). We used adjusted mixed effects models with region random effects to estimate associations of handheld device use habits and indoor RF-EMF sources with personal RF-EMF exposure. Day-to-day and year-to-year repeatability of personal RF-EMF exposure were calculated through intraclass correlations (ICC). Median total personal RF-EMF exposure was 75.5 μW/m 2 . Downlink was the largest contributor to total exposure (median: 27.2 μW/m 2 ) followed by broadcast (9.9 μW/m 2 ). Exposure from uplink (4.7 μW/m 2 ) was lower. WiFi and DECT contributed very little to exposure levels. Exposure was higher during day (94.2 μW/m 2 ) than night (23.0 μW/m 2 ), and slightly higher during weekends than weekdays, although varying across regions. Median exposures were highest while children were outside (157.0 μW/m 2 ) or traveling (171.3 μW/m 2 ), and much lower at home (33.0 μW/m 2 ) or in school (35.1 μW/m 2 ). Children living in urban environments had higher exposure than children in rural environments. Older children and users of mobile phones had higher uplink exposure but not total exposure, compared to younger children and those that did not use mobile phones. Day-to-day repeatability was moderate to high for most of the general frequency bands (ICCs between 0.43 and 0.85), as well as for total, broadcast, and downlink for the year-to-year repeatability (ICCs between 0.49 and 0.80) in a small subsample. The largest contributors to total personal environmental RF-EMF exposure were downlink and broadcast, and these exposures showed high repeatability. Urbanicity was the most important determinant of total exposure and mobile phone use was the most important determinant of uplink exposure. It is important to continue evaluating RF-EMF exposure in children as device use habits, exposure levels, and main contributing sources may change. Copyright © 2018 Elsevier Ltd. All rights reserved.

Identifying possible non-thermal effects of radio frequency energy on inactivating food microorganisms.

PubMed

Kou, Xiaoxi; Li, Rui; Hou, Lixia; Zhang, Lihui; Wang, Shaojin

2018-03-23

Radio frequency (RF) heating has been successfully used for inactivating microorganisms in agricultural and food products. Athermal (non-thermal) effects of RF energy on microorganisms have been frequently proposed in the literature, resulting in difficulties for developing effective thermal treatment protocols. The purpose of this study was to identify if the athermal inactivation of microorganisms existed during RF treatments. Escherichia coli and Staphylococcus aureus in apple juice and mashed potato were exposed to both RF and conventional thermal energies to compare their inactivation populations. A thermal death time (TDT) heating block system was used as conventional thermal energy source to simulate the same heating treatment conditions, involving heating temperature, heating rate and uniformity, of a RF treatment at a frequency of 27.12 MHz. Results showed that a similar and uniform temperature distribution in tested samples was achieved in both heating systems, so that the central sample temperature could be used as representative one for evaluating thermal inactivation of microorganisms. The survival patterns of two target microorganisms in two food samples were similar both for RF and heating block treatments since their absolute difference of survival populations was <1 log CFU/ml. The statistical analysis indicated no significant difference (P > 0.05) in inactivating bacteria between the RF and the heating block treatments at each set of temperatures. The solid temperature and microbial inactivation data demonstrated that only thermal effect of RF energy at 27.12 MHz was observed on inactivating microorganisms in foods. Copyright © 2018 Elsevier B.V. All rights reserved.

Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1 MHz

NASA Astrophysics Data System (ADS)

Rauner, D.; Mattei, S.; Briefi, S.; Fantz, U.; Hatayama, A.; Lettry, J.; Nishida, K.; Tran, M. Q.

2017-08-01

The power requirements of RF heated sources for negative hydrogen ions in fusion are substantial, which poses strong demands on the generators and components of the RF circuit. Consequently, an increase of the RF coupling efficiency would be highly beneficial. Fundamental investigations of the RF efficiency in inductively coupled hydrogen and deuterium discharges in cylindrical symmetry are conducted at the lab experiment CHARLIE. The experiment is equipped with several diagnostics including optical emission spectroscopy and a movable floating double probe to monitor the plasma parameters. The presented investigations are performed in hydrogen at a varying pressure between 0.3 and 10 Pa, utilizing a conventional helical ICP coil driven at a frequency of 1 MHz and a fixed power of 520 W for plasma generation. The coupling efficiency is strongly affected by the variation in pressure, reaching up to 85 % between 1 and 3 Pa while dropping down to only 50 % at 0.3 Pa, which is the relevant operating pressure for negative hydrogen ion sources for fusion. Due to the lower power coupling, also the measured electron density at 0.3 Pa is only 5 . 1016 m-3, while it reaches up to 2.5 . 1017 m-3 with increasing coupling efficiency. In order to gain information on the spatially resolved aspects of RF coupling and plasma heating which are not diagnostically accessible, first simulations of the discharge by an electromagnetic Particle-In-Cell Monte Carlo collision method have been conducted and are compared to the measurement data. At 1 Pa, the simulated data corresponds well to the results of both axially resolved probe measurements and radially resolved emission profiles obtained via OES. Thereby, information regarding the radial distribution of the electron density and mean energy is provided, revealing a radial distribution of the electron density which is well described by a Bessel profile.

Photocathodes for RF photoinjectors

NASA Astrophysics Data System (ADS)

Michelato, P.

1997-02-01

Over the past ten years photocathodes have been extensively used as high-brightness electron sources in RF guns. In this paper, I present a general review of the alkali-based high quantum efficiency (QE) photoemitters (e.g. Cs 3Sb, K 2CsSb and Cs 2Te), together with a comparative analysis of the different preparation procedures and the results obtained, both in the preparation chambers and in RF guns. The need to increase the photocathode reliability has provided the impetus to get an R&D activity to go over the alchemy of photocathode preparation procedure. In this paper, I will discuss the results so far obtained in different laboratories, both by using traditional investigation strategy (e.g. QE and RF behavior) and by means of surface science techniques as Auger Electron Spectroscopy (AES) and X-ray Photoelectron Spectroscopy (XPS). Alkali antimonides have been used at first in the RF gun due to the high QE response to the green light of the Nd:YLF second-harmonic radiation. Measurements have confirmed the high reactivity of the alkali antimonide photocathodes to the residual gases: this fact makes their use in RF guns not practical, mainly for short lifetimes. Further investigations have shown that the choice of the substratum preparation procedure and chemical composition plays a fundamental role in the photocathode performance, both from the point of view of the QE and the operative lifetime and ruggedness to gas exposition. Cesium telluride (Cs 2Te) prepared on a molybdenum substratum seems to be, nowadays, the best compromise, in terms of preparation procedure reliability and ruggedness, that now the characteristics and drawbacks of this material are well understood (e.g. the need of an UV laser source). Future possible developments will be discussed. In particular, the measurement and the control of the thermal emittance and the time response could be an important task.

Generation of multiple analog pulses with different duty cycles within VME control system for ICRH Aditya system

NASA Astrophysics Data System (ADS)

Joshi, Ramesh; Singh, Manoj; Jadav, H. M.; Misra, Kishor; Kulkarni, S. V.; ICRH-RF Group

2010-02-01

Ion Cyclotron Resonance Heating (ICRH) is a promising heating method for a fusion device due to its localized power deposition profile, a direct ion heating at high density, and established technology for high RF power generation and transmission at low cost. Multiple analog pulse with different duty cycle in master of digital pulse for Data acquisition and Control system for steady state RF ICRH System(RF ICRH DAC) to be used for operating of RF Generator in Aditya to produce pre ionization and second analog pulse will produce heating. The control system software is based upon single digital pulse operation for RF source. It is planned to integrate multiple analog pulses with different duty cycle in master of digital pulse for Data acquisition and Control system for RF ICRH System(RF ICRH DAC) to be used for operating of RF Generator in Aditya tokamak. The task of RF ICRH DAC is to control and acquisition of all ICRH system operation with all control loop and acquisition for post analysis of data with java based tool. For pre ionization startup as well as heating experiments using multiple RF Power of different powers and duration. The experiment based upon the idea of using single RF generator to energize antenna inside the tokamak to radiate power twise, out of which first analog pulse will produce pre ionization and second analog pulse will produce heating. The whole system is based on standard client server technology using tcp/ip protocol. DAC Software is based on linux operating system for highly reliable, secure and stable system operation in failsafe manner. Client system is based on tcl/tk like toolkit for user interface with c/c++ like environment which is reliable programming languages widely used on stand alone system operation with server as vxWorks real time operating system like environment. The paper is focused on the Data acquisition and monitoring system software on Aditya RF ICRH System with analog pulses in slave mode with digital pulse in master mode for control acquisition and monitoring and interlocking.

SNP-markers in Allium species to facilitate introgression breeding in onion.

PubMed

Scholten, Olga E; van Kaauwen, Martijn P W; Shahin, Arwa; Hendrickx, Patrick M; Keizer, L C Paul; Burger, Karin; van Heusden, Adriaan W; van der Linden, C Gerard; Vosman, Ben

2016-08-31

Within onion, Allium cepa L., the availability of disease resistance is limited. The identification of sources of resistance in related species, such as Allium roylei and Allium fistulosum, was a first step towards the improvement of onion cultivars by breeding. SNP markers linked to resistance and polymorphic between these related species and onion cultivars are a valuable tool to efficiently introgress disease resistance genes. In this paper we describe the identification and validation of SNP markers valuable for onion breeding. Transcriptome sequencing resulted in 192 million RNA seq reads from the interspecific F1 hybrid between A. roylei and A. fistulosum (RF) and nine onion cultivars. After assembly, reliable SNPs were discovered in about 36 % of the contigs. For genotyping of the interspecific three-way cross population, derived from a cross between an onion cultivar and the RF (CCxRF), 1100 SNPs that are polymorphic in RF and monomorphic in the onion cultivars (RF SNPs) were selected for the development of KASP assays. A molecular linkage map based on 667 RF-SNP markers was constructed for CCxRF. In addition, KASP assays were developed for 1600 onion-SNPs (SNPs polymorphic among onion cultivars). A second linkage map was constructed for an F2 of onion x A. roylei (F2(CxR)) that consisted of 182 onion-SNPs and 119 RF-SNPs, and 76 previously mapped markers. Markers co-segregating in both the F2(CxR) and the CCxRF population were used to assign the linkage groups of RF to onion chromosomes. To validate usefulness of these SNP markers, QTL mapping was applied in the CCxRF population that segregates for resistance to Botrytis squamosa and resulted in a QTL for resistance on chromosome 6 of A. roylei. Our research has more than doubled the publicly available marker sequences of expressed onion genes and two onion-related species. It resulted in a detailed genetic map for the interspecific CCxRF population. This is the first paper that reports the detection of a QTL for resistance to B. squamosa in A. roylei.

X-band RF gun and linac for medical Compton scattering X-ray source

NASA Astrophysics Data System (ADS)

Dobashi, Katsuhito; Uesaka, Mitsuru; Fukasawa, Atsushi; Sakamoto, Fumito; Ebina, Futaro; Ogino, Haruyuki; Urakawa, Junji; Higo, Toshiyasu; Akemoto, Mitsuo; Hayano, Hitoshi; Nakagawa, Keiichi

2004-12-01

Compton scattering hard X-ray source for 10-80 keV are under construction using the X-band (11.424 GHz) electron linear accelerator and YAG laser at Nuclear Engineering Research laboratory, University of Tokyo. This work is a part of the national project on the development of advanced compact medical accelerators in Japan. National Institute for Radiological Science is the host institute and U.Tokyo and KEK are working for the X-ray source. Main advantage is to produce tunable monochromatic hard (10-80 keV) X-rays with the intensities of 108-1010 photons/s (at several stages) and the table-top size. Second important aspect is to reduce noise radiation at a beam dump by adopting the deceleration of electrons after the Compton scattering. This realizes one beamline of a 3rd generation SR source at small facilities without heavy shielding. The final goal is that the linac and laser are installed on the moving gantry. We have designed the X-band (11.424 GHz) traveling-wave-type linac for the purpose. Numerical consideration by CAIN code and luminosity calculation are performed to estimate the X-ray yield. X-band thermionic-cathode RF-gun and RDS(Round Detuned Structure)-type X-band accelerating structure are applied to generate 50 MeV electron beam with 20 pC microbunches (104) for 1 microsecond RF macro-pulse. The X-ray yield by the electron beam and Q-switch Nd:YAG laser of 2 J/10 ns is 107 photons/RF-pulse (108 photons/sec at 10 pps). We design to adopt a technique of laser circulation to increase the X-ray yield up to 109 photons/pulse (1010 photons/s). 50 MW X-band klystron and compact modulator have been constructed and now under tuning. The construction of the whole system has started. X-ray generation and medical application will be performed in the early next year.

American Indian Access to Department of Defense Facilities: Source Documents and Bibliography (Legacy Resource Management Program)

DTIC Science & Technology

1993-09-01

who under the terms of the Archeological and Historic Preservation Act must respond within 48 hours of notification. The DCA may render an immediate...1965 The Surviving Chumash. UCLA Archaeological Survey Annual Reports 65:277-302. Grant, Campbell 1973a Chuirash: Introduction. In R.F. Heizer , ed...Coastal Chumash. In R.F. Heizer , et., California. Volume 8, Handbook of North American"Indians, William C. Sturtevant, General Editor. Washington

A Systematic Review of Serum Biomarkers Anti-Cyclic Citrullinated Peptide and Rheumatoid Factor as Tests for Rheumatoid Arthritis

PubMed Central

Taylor, Peter; Gartemann, Juliane; Hsieh, Jeanie; Creeden, James

2011-01-01

This systematic review assesses the current status of anti-cyclic citrullinated peptide (anti-CCP) and rheumatoid factor (RF) tests in the diagnosis and prognosis of rheumatoid arthritis (RA). We reviewed publications on tests and biomarkers for early diagnosis of RA from English-language MEDLINE-indexed journals and non-MEDLINE-indexed sources. 85 publications were identified and reviewed, including 68 studies from MEDLINE and 17 non-MEDLINE sources. Anti-CCP2 assays provide improved sensitivity over anti-CCP assays and RF, but anti-CCP2 and RF assays in combination demonstrate a positive predictive value (PPV) nearing 100%, greater than the PPV of either of the tests alone. The combination also appears to be able to distinguish between patients whose disease course is expected to be more severe and both tests are incorporated in the 2010 ACR Rheumatoid Arthritis Classification Criteria. While the clinical value of anti-CCP tests has been established, differences in cut-off values, sensitivities and specificities exist between first-, second- and third-generation tests and harmonization efforts are under way. Anti-CCP and RF are clinically valuable biomarkers for the diagnosis and prognosis of RA patients. The combination of the two biomarkers in conjunction with other clinical measures is an important tool for the diagnosis and management of RA patients. PMID:21915375

Calibration of a speckle-based compressive sensing receiver

NASA Astrophysics Data System (ADS)

Sefler, George A.; Shaw, T. Justin; Stapleton, Andrew D.; Valley, George C.

2017-02-01

Optical speckle in a multimode waveguide has been proposed to perform the function of a compressive sensing (CS) measurement matrix (MM) in a receiver for GHz-band radio frequency (RF) signals. Unlike other devices used for the CS MM, e.g. the digital micromirror device (DMD) used in the single pixel camera, the elements of the speckle MM are not known before use and must be measured and calibrated. In our system, the RF signal is modulated on a repetitively pulsed chirped wavelength laser source, generated from mode-locked laser pulses that have been dispersed in time or from an electrically addressed distributed Bragg reflector laser. Next, the optical beam with RF propagates through a multimode fiber or waveguide, which applies different weights in wavelength (or equivalently time) and space and performs the function of the CS MM. The output of the guide is directed to or imaged on a bank of photodiodes with integration time set to the pulse length of the chirp waveform. The output of each photodiode is digitized by an analog-to-digital converter (ADC), and the data from these ADCs are used to form the CS measurement vector. Accurate recovery of the RF signal from CS measurements depends critically on knowledge of the weights in the MM. Here we present results using a stable wavelength laser source to probe the guide.

Noise reduction efforts for the ALS infrared beamlines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scarvie, Tom; Andresen, Nord; Baptiste, Ken

2003-08-10

The quality of infrared microscopy and spectroscopy data collected at synchrotron based sources is strongly dependent on signal-to-noise. We have successfully identified and suppressed several noise sources affecting Beamlines 1.4.2, 1.4.3, and 1.4.4 at the Advanced Light Source (ALS), resulting in a significant increase in the quality of FTIR spectra obtained. In this paper, we present our methods of noise source analysis, the negative effect of noise on the infrared beam quality, and the techniques used to reduce the noise. These include reducing the phase noise in the storage ring radio-frequency (RF) system, installing an active mirror feedback system, analyzingmore » and changing physical mounts to better isolate portions of the beamline optics from low-frequency environmental noise, and modifying the input signals to the main ALS RF system. We also discuss the relationship between electron beam energy oscillations at a point of dispersion and infrared beamline noise.« less

Noise Reduction Efforts for the ALS Infrared Beamlines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scarvie, Tom; Andresen, Nord; Baptiste, Ken

2004-05-12

The quality of infrared microscopy and spectroscopy data collected at synchrotron based sources is strongly dependent on signal-to-noise. We have successfully identified and suppressed several noise sources affecting Beamlines 1.4.2, 1.4.3, and 1.4.4 at the Advanced Light Source (ALS), resulting in a significant increase in the quality of FTIR spectra obtained. In this paper, we present our methods of noise source analysis, the negative effect of noise on the infrared beam quality, and the techniques used to reduce the noise. These include reducing the phase noise in the storage ring radio-frequency (RF) system, installing an active mirror feedback system, analyzingmore » and changing physical mounts to better isolate portions of the beamline optics from low-frequency environmental noise, and modifying the input signals to the main ALS RF system. We also discuss the relationship between electron beam energy oscillations at a point of dispersion and infrared beamline noise.« less

Low level impurities in imported wheat are a likely source of feral transgenic oilseed rape (Brassica napus L.) in Switzerland.

PubMed

Schulze, Juerg; Brodmann, Peter; Oehen, Bernadette; Bagutti, Claudia

2015-11-01

In Switzerland, the cultivation of genetically modified (GM) oilseed rape (Brassica napus L.) and the use of its seeds for food and feed are not permitted. Nevertheless, the GM oilseed rape events GT73, MS8×RF3, MS8 and RF3 have recently been found in the Rhine port of Basel, Switzerland. The sources of GM oilseed rape seeds have been unknown. The main agricultural good being imported at the Rhine port of Basel is wheat and from 2010 to 2013, 19% of all Swiss wheat imports originated from Canada. As over 90% of all oilseed rape grown in Canada is GM, we hypothesised that imports of Canadian wheat may contain low level impurities of GM oilseed rape. Therefore, waste fraction samples gathered during the mechanical cleaning of Canadian wheat from two Swiss grain mills were analysed by separating oilseed rape seeds from waste fraction samples and testing DNA of pooled seeds for the presence of transgenes by real-time PCR. Furthermore, oilseed rape seeds from each grain mill were sown in a germination experiment, and seedling DNA was tested for the presence of transgenes by real-time PCR. GT73, MS8×RF3, MS8 and RF3 oilseed rape was detected among seed samples and seedlings of both grain mills. Based on this data, we projected a mean proportion of 0.005% of oilseed rape in wheat imported from Canada. Besides Canadian wheat, the Rhine port of Basel does not import any other significant amounts of agricultural products from GM oilseed rape producing countries. We therefore conclude that Canadian wheat is the major source of unintended introduction of GM oilseed rape seeds into Switzerland.

Sensitivity enhancement of fluorescence detection in CE by coupling and conducting excitation light with tapered optical fiber.

PubMed

Yang, Xiupei; Huo, Feng; Yuan, Hongyan; Zhang, Bo; Xiao, Dan; Choi, Martin M F

2011-01-01

This paper reports the enhancement of sensitivity of detection for in-column fiber optic-induced fluorescence detection system in CE by tapered optical fiber (TOF). Two types of optical fiber, TOF and conventional cylindrical optical fiber (COF), were employed to construct the CE (TOF-CE and COF-CE) and were compared for sensitivity to riboflavin (RF). The fluorescence intensities from a RF sample with excitation light sources and fibers at various coupling angles were investigated. The fluorescence signal from TOF-CE was ca. ten times that of COF-CE. In addition, the detection performance of four excitation light source-fiber configurations including Laser-TOF, Laser-COF, LED-TOF, and LED-COF were compared. The LODs for RF were 0.21, 0.82, 0.80, and 7.5 nM, respectively, for the four excitation light source-fiber configurations. The results demonstrate that the sensitivity obtained by LED-TOF is close to that of Laser-COF. Both Laser-TOF and LED-TOF can greatly improve the sensitivity of detection in CE. TOF has the major attribute of collecting and focusing the excitation light intensity. Thus, the sensitivity obtained by LED-TOF without focusing lens is just same as that of LED-COF with a focusing lens. This demonstrates that the CE system can be further simplified by eliminating the focusing lens for excitation light. LED-TOF-CE and LED-COF-CE system were applied to the separation and determination of RF in real sample (green tea), respectively. The tapered fiber optic-induced fluorescence detection system in CE is an ideal tool for trace analysis. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The injection of microorganisms into an atmospheric pressure rf-driven microplasma

NASA Astrophysics Data System (ADS)

Maguire, P. D.; Mahony, C. M. O.; Diver, D.; Mariotti, D.; Bennet, E.; Potts, H.; McDowell, D. A.

2013-09-01

The introduction of living organisms, such as bacteria, into atmospheric pressure microplasmas offers a unique means to study certain physical mechanisms in individual microorganisms and also help understand the impact of macroscopic entities and liquid droplets on plasma characteristics. We present the characterization of an RF-APD operating at 13.56 MHz and containing microorganisms in liquid droplets emitted from a nebulizer, with the spray entrained in a gas flow by a gas shroud and passed into the plasma source. We report successful microorganism injection and transmission through the plasma with stable plasma operation of at least one hour. Diagnostics include RF electrical characterization, optical emission spectrometry and electrostatic deflection to investigate microorganism charging. A close-coupled Impedans Octiv VI probe indicates source efficiencies of 10 to 15%. The introduction of the droplets/microorganisms results in increased plasma conductivity and reduced capacitance, due to their impact on electron density and temperature. An electrical model will be presented based on diagnostic data and deflection studies with input from simulations of charged aerosol diffusion and evaporation. Engineering and Physical Sciences Research Council EP/K006088, EP/K006142.

Upgrade of the BATMAN test facility for H- source development

NASA Astrophysics Data System (ADS)

Heinemann, B.; Fröschle, M.; Falter, H.-D.; Fantz, U.; Franzen, P.; Kraus, W.; Nocentini, R.; Riedl, R.; Ruf, B.

2015-04-01

The development of a radio frequency (RF) driven source for negative hydrogen ions for the neutral beam heating devices of fusion experiments has been successfully carried out at IPP since 1996 on the test facility BATMAN. The required ITER parameters have been achieved with the prototype source consisting of a cylindrical driver on the back side of a racetrack like expansion chamber. The extraction system, called "Large Area Grid" (LAG) was derived from a positive ion accelerator from ASDEX Upgrade (AUG) using its aperture size (ø 8 mm) and pattern but replacing the first two electrodes and masking down the extraction area to 70 cm2. BATMAN is a well diagnosed and highly flexible test facility which will be kept operational in parallel to the half size ITER source test facility ELISE for further developments to improve the RF efficiency and the beam properties. It is therefore planned to upgrade BATMAN with a new ITER-like grid system (ILG) representing almost one ITER beamlet group, namely 5 × 14 apertures (ø 14 mm). Additionally to the standard three grid extraction system a repeller electrode upstream of the grounded grid can optionally be installed which is positively charged against it by 2 kV. This is designated to affect the onset of the space charge compensation downstream of the grounded grid and to reduce the backstreaming of positive ions from the drift space backwards into the ion source. For magnetic filter field studies a plasma grid current up to 3 kA will be available as well as permanent magnets embedded into a diagnostic flange or in an external magnet frame. Furthermore different source vessels and source configurations are under discussion for BATMAN, e.g. using the AUG type racetrack RF source as driver instead of the circular one or modifying the expansion chamber for a more flexible position of the external magnet frame.

Status of the RF BPM upgrade at the Advanced Photon Source.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pietryla, A.; Bui, H.; Decker, G.

2008-01-01

The Advanced Photon Source (APS),a third-generation synchrotron light source, has been in operation for eleven years. The monopulse radio frequency (rf) beam position monitor (BPM) is one of three BPM types now employed in the storage ring at the APS. It is a broadband (10 MHz) system designed to measure single-turn and multi-turn beam positions, but it suffers from an aging data acquisition system. The replacement BPM system retains the existing monopulse receivers and replaces the data acquisition system with high-speed analog-to-digital converters (ADCs) and a field-programmable gate array (FPGA) that performs the signal processing. A first-article system has beenmore » constructed and is currently being evaluated. This paper presents the results of testing of the first-article system as well as the progress made in other areas of this upgrade effort.« less

Electron Energy Distribution function in a weakly magnetized expanding helicon plasma discharge

NASA Astrophysics Data System (ADS)

Sirse, Nishant; Harvey, Cleo; Gaman, Cezar; Ellingboe, Bert

2016-09-01

Helicon wave heating is well known to produce high-density plasma source for application in plasma thrusters, plasma processing and many more. Our previous study (B Ellingboe et al. APS Gaseous Electronics Conference 2015, abstract #KW2.005) has shown observation of helicon wave in a weakly magnetized inductively coupled plasma source excited by m =0 antenna at 13.56 MHz. In this paper, we investigated the Electron Energy Distribution Function (EEDF) in the same setup by using an RF compensated Langmuir probe. The ac signal superimposition technique (second harmonic technique) is used to determine EEDF. The EEDF is measured for 5-100 mTorr gas pressure, 100 W - 1.5 kW rf power and at different locations in the source chamber, boundary and diffusion chamber. This paper will discuss the change in the shape of EEDF for various heating mode transitions.

Effects of rf power on chemical composition and surface roughness of glow discharge polymer films

NASA Astrophysics Data System (ADS)

Zhang, Ling; He, Xiaoshan; Chen, Guo; Wang, Tao; Tang, Yongjian; He, Zhibing

2016-03-01

The glow discharge polymer (GDP) films for laser fusion targets were successfully fabricated by plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The films were deposited using trans-2-butene (T2B) mixed with hydrogen as gas sources. The composition and state of plasma were diagnosed by quadrupole mass spectrometer (QMS) and Langmuir probe during the deposition process. The composition, surface morphology and roughness were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and white-light interferometer (WLI), respectively. Based on these observation and analyses, the growth mechanism of defects in GDP films were studied. The results show that, at low rf power, there is a larger probability for secondary polymerization and formation of multi-carbon C-H species in the plasma. In this case, the surface of GDP film turns to be cauliflower-like. With the increase of rf power, the degree of ionization is high, the relative concentration of smaller-mass hydrocarbon species increases, while the relative concentration of larger-mass hydrocarbon species decreases. At higher rf power, the energy of smaller-mass species are high and the etching effects are strong correspondingly. The GDP film's surface roughness shows a trend of decrease firstly and then increase with the increasing rf power. At rf power of 30 W, the surface root-mean-square roughness (Rq) drops to the lowest value of 12.8 nm, and no ;void; defect was observed.

RF priming of a long pulse relativistic magnetron

NASA Astrophysics Data System (ADS)

White, William Michael

Rapid startup, increased pulsewidth and mode locking of magnetrons have been demonstrated experimentally on a relativistic magnetron by radio frequency (RF) priming. Experiments utilize a -300 kV, 2-8 kA, 300-500 ns electron beam to drive a Titan 6-vane relativistic magnetron (˜100 MW output power). The RF priming source is a 100 kW pulsed magnetron operating at 1.27-1.32 GHz. Tuning stubs were utilized in the Titan structure to adjust the operating frequency of the relativistic magnetron pi-mode upward by 30%. The tuning was guided by simulation in the MAGIC 3D code and experimental cold tests including a mapping of the azimuthal electric field inside the relativistic magnetron structure. The most successful tuning geometry was that of a standard anode resonant structure, but RF priming experiments were performed on a rising-sun structure as well. The Time Frequency Analysis (TFA) program was used to directly observe the effects of RF priming on the relativistic magnetron. RF priming was successful in decreasing mode competition by suppressing the generation of the 2pi/3-mode power by 41%. RF priming experiments were also successful in increasing microwave pulsewidth by 12% and decreasing microwave output delay by 22%. These improvements were observed while operating in a priming regime not satisfying Adler's Relation. Overall, the improvements made to the performance of the relativistic magnetron were modest because of the low priming power available (50-250 kW).

Free electron laser using Rf coupled accelerating and decelerating structures

DOEpatents

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

1984-01-01

A free electron laser and free electron laser amplifier using beam transport devices for guiding an electron beam to a wiggler of a free electron laser and returning the electron beam to decelerating cavities disposed adjacent to the accelerating cavities of the free electron laser. Rf energy is generated from the energy depleted electron beam after it emerges from the wiggler by means of the decelerating cavities which are closely coupled to the accelerating cavities, or by means of a second bore within a single set of cavities. Rf energy generated from the decelerated electron beam is used to supplement energy provided by an external source, such as a klystron, to thereby enhance overall efficiency of the system.

Simulations of Field-Emission Electron Beams from CNT Cathodes in RF Photoinjectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihalcea, Daniel; Faillace, Luigi; Panuganti, Harsha

2015-06-01

Average field emission currents of up to 700 mA were produced by Carbon Nano Tube (CNT) cathodes in a 1.3 GHz RF gun at Fermilab High Brightness Electron Source Lab. (HBESL). The CNT cathodes were manufactured at Xintek and tested under DC conditions at RadiaBeam. The electron beam intensity as well as the other beam properties are directly related to the time-dependent electric field at the cathode and the geometry of the RF gun. This report focuses on simulations of the electron beam generated through field-emission and the results are compared with experimental measurements. These simulations were performed with themore » time-dependent Particle In Cell (PIC) code WARP.« less

Electromagnetic fields and the public: EMF standards and estimation of risk

NASA Astrophysics Data System (ADS)

Grigoriev, Yury

2010-04-01

Mobile communications are a relatively new and additional source of electromagnetic exposure for the population. Standard daily mobile-phone use is known to increase RF-EMF (radiofrequency electromagnetic field) exposure to the brains of users of all ages, whilst mobile-phone base stations, and base station units for cordless phones, can regularly increase the exposures of large numbers of the population to RF-EMF radiation in everyday life. The need to determine appropriate standards stipulating the maximum acceptable short-term and long-term RF-EMF levels encountered by the public, and set such levels as general guidelines, is of great importance in order to help preserve the general public's health and that of the next generation of humanity.

Photoacoustic image reconstruction from ultrasound post-beamformed B-mode image

NASA Astrophysics Data System (ADS)

Zhang, Haichong K.; Guo, Xiaoyu; Kang, Hyun Jae; Boctor, Emad M.

2016-03-01

A requirement to reconstruct photoacoustic (PA) image is to have a synchronized channel data acquisition with laser firing. Unfortunately, most clinical ultrasound (US) systems don't offer an interface to obtain synchronized channel data. To broaden the impact of clinical PA imaging, we propose a PA image reconstruction algorithm utilizing US B-mode image, which is readily available from clinical scanners. US B-mode image involves a series of signal processing including beamforming, followed by envelope detection, and end with log compression. Yet, it will be defocused when PA signals are input due to incorrect delay function. Our approach is to reverse the order of image processing steps and recover the original US post-beamformed radio-frequency (RF) data, in which a synthetic aperture based PA rebeamforming algorithm can be further applied. Taking B-mode image as the input, we firstly recovered US postbeamformed RF data by applying log decompression and convoluting an acoustic impulse response to combine carrier frequency information. Then, the US post-beamformed RF data is utilized as pre-beamformed RF data for the adaptive PA beamforming algorithm, and the new delay function is applied by taking into account that the focus depth in US beamforming is at the half depth of the PA case. The feasibility of the proposed method was validated through simulation, and was experimentally demonstrated using an acoustic point source. The point source was successfully beamformed from a US B-mode image, and the full with at the half maximum of the point improved 3.97 times. Comparing this result to the ground-truth reconstruction using channel data, the FWHM was slightly degraded with 1.28 times caused by information loss during envelope detection and convolution of the RF information.

Impact of input data uncertainty on environmental exposure assessment models: A case study for electromagnetic field modelling from mobile phone base stations.

PubMed

Beekhuizen, Johan; Heuvelink, Gerard B M; Huss, Anke; Bürgi, Alfred; Kromhout, Hans; Vermeulen, Roel

2014-11-01

With the increased availability of spatial data and computing power, spatial prediction approaches have become a standard tool for exposure assessment in environmental epidemiology. However, such models are largely dependent on accurate input data. Uncertainties in the input data can therefore have a large effect on model predictions, but are rarely quantified. With Monte Carlo simulation we assessed the effect of input uncertainty on the prediction of radio-frequency electromagnetic fields (RF-EMF) from mobile phone base stations at 252 receptor sites in Amsterdam, The Netherlands. The impact on ranking and classification was determined by computing the Spearman correlations and weighted Cohen's Kappas (based on tertiles of the RF-EMF exposure distribution) between modelled values and RF-EMF measurements performed at the receptor sites. The uncertainty in modelled RF-EMF levels was large with a median coefficient of variation of 1.5. Uncertainty in receptor site height, building damping and building height contributed most to model output uncertainty. For exposure ranking and classification, the heights of buildings and receptor sites were the most important sources of uncertainty, followed by building damping, antenna- and site location. Uncertainty in antenna power, tilt, height and direction had a smaller impact on model performance. We quantified the effect of input data uncertainty on the prediction accuracy of an RF-EMF environmental exposure model, thereby identifying the most important sources of uncertainty and estimating the total uncertainty stemming from potential errors in the input data. This approach can be used to optimize the model and better interpret model output. Copyright © 2014 Elsevier Inc. All rights reserved.

Radiofrequency-electromagnetic field exposures in kindergarten children.

PubMed

Bhatt, Chhavi Raj; Redmayne, Mary; Billah, Baki; Abramson, Michael J; Benke, Geza

2017-09-01

The aim of this study was to assess environmental and personal radiofrequency-electromagnetic field (RF-EMF) exposures in kindergarten children. Ten children and 20 kindergartens in Melbourne, Australia participated in personal and environmental exposure measurements, respectively. Order statistics of RF-EMF exposures were computed for 16 frequency bands between 88 MHz and 5.8 GHz. Of the 16 bands, the three highest sources of environmental RF-EMF exposures were: Global System for Mobile Communications (GSM) 900 MHz downlink (82 mV/m); Universal Mobile Telecommunications System (UMTS) 2100MHz downlink (51 mV/m); and GSM 900 MHz uplink (45 mV/m). Similarly, the three highest personal exposure sources were: GSM 900 MHz downlink (50 mV/m); UMTS 2100 MHz downlink, GSM 900 MHz uplink and GSM 1800 MHz downlink (20 mV/m); and Frequency Modulation radio, Wi-Fi 2.4 GHz and Digital Video Broadcasting-Terrestrial (10 mV/m). The median environmental exposures were: 179 mV/m (total all bands), 123 mV/m (total mobile phone base station downlinks), 46 mV/m (total mobile phone base station uplinks), and 16 mV/m (Wi-Fi 2.4 GHz). Similarly, the median personal exposures were: 81 mV/m (total all bands), 62 mV/m (total mobile phone base station downlinks), 21 mV/m (total mobile phone base station uplinks), and 9 mV/m (Wi-Fi 2.4 GHz). The measurements showed that environmental RF-EMF exposure levels exceeded the personal RF-EMF exposure levels at kindergartens.

Low cost high efficiency GaAs monolithic RF module for SARSAT distress beacons

NASA Technical Reports Server (NTRS)

Petersen, W. C.; Siu, D. P.; Cook, H. F.

1991-01-01

Low cost high performance (5 Watts output) 406 MHz beacons are urgently needed to realize the maximum utilization of the Search and Rescue Satellite-Aided Tracking (SARSAT) system spearheaded in the U.S. by NASA. Although current technology can produce beacons meeting the output power requirement, power consumption is high due to the low efficiency of available transmitters. Field performance is currently unsatisfactory due to the lack of safe and reliable high density batteries capable of operation at -40 C. Low cost production is also a crucial but elusive requirement for the ultimate wide scale utilization of this system. Microwave Monolithics Incorporated (MMInc.) has proposed to make both the technical and cost goals for the SARSAT beacon attainable by developing a monolithic GaAs chip set for the RF module. This chip set consists of a high efficiency power amplifier and a bi-phase modulator. In addition to implementing the RF module in Monolithic Microwave Integrated Circuit (MMIC) form to minimize ultimate production costs, the power amplifier has a power-added efficiency nearly twice that attained with current commercial technology. A distress beacon built using this RF module chip set will be significantly smaller in size and lighter in weight due to a smaller battery requirement, since the 406 MHz signal source and the digital controller have far lower power consumption compared to the 5 watt power amplifier. All the program tasks have been successfully completed. The GaAs MMIC RF module chip set has been designed to be compatible with the present 406 MHz signal source and digital controller. A complete high performance low cost SARSAT beacon can be realized with only additional minor iteration and systems integration.

Analog and RF performance of a multigate FinFET at nano scale

NASA Astrophysics Data System (ADS)

Kumar, Abhishek

2016-12-01

In this paper, analog and RF performance of the Fin field effect transistor (FET) at Nano scale is observed through 3D simulation. FinFET devices like rectangular gate all around (RE-GAA) FinFET, cylindrical gate all around (CY-GAA) FinFET and triple gate (TG) FinFET are observed. The figure of merit (FOMs) such as input-output characteristics, trans-conductance (gm), output-conductance (gd), intrinsic gain (gm/gd), gate capacitance (gate to source and total gate capacitance), unity gain cut-off frequency (ft), trans-conductance generation factor (TGF), gain frequency product (GFP), gain bandwidth product (GBP) and gain transconductance frequency product (GTFP) are observed. The analog performance of a FinFETs are observed by realising source follower circuit with NMOS transistor as a current source. The source follower circuit gain is observed. It has been observed that maximum capacitance is observed in case gate all around condition. Rectangular gate all around has the highest transconductance. In the source follower circuit, the gain curve (Vout/Vin) is sharper for TG-FinFET.

Electron Beam Production and Characterization for the PLEIADES Thomson X-ray Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, W J; Hartemann, F V; Tremaine, A M

2002-10-14

We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 {pi}mm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 10{sup 20} photons/s/mm{sup 2}/mrad{sup 2}/0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and controlmore » methods are discussed.« less

Noise and interference study for satellite lightning sensor

NASA Technical Reports Server (NTRS)

Herman, J. R.

1981-01-01

The use of radio frequency techniques for the detection and monitoring of terrestrial thunderstorms from space are discussed. Three major points are assessed: (1) lightning and noise source characteristics; (2) propagation effects imposed by the atmosphere and ionosphere; and (3) the electromagnetic environment in near space within which lightning RF signatures must be detected. A composite frequency spectrum of the peak of amplitude from lightning flashes is developed. Propagation effects (ionospheric cutoff, refraction, absorption, dispersion and scintillation) are considered to modify the lightning spectrum to the geosynchronous case. It is suggested that in comparing the modified spectrum with interfering noise source spectra RF lightning pulses on frequencies up to a few GHz are detectable above the natural noise environment in near space.

Design of a high-bunch-charge 112-MHz superconducting RF photoemission electron source

NASA Astrophysics Data System (ADS)

Xin, T.; Brutus, J. C.; Belomestnykh, Sergey A.; Ben-Zvi, I.; Boulware, C. H.; Grimm, T. L.; Hayes, T.; Litvinenko, Vladimir N.; Mernick, K.; Narayan, G.; Orfin, P.; Pinayev, I.; Rao, T.; Severino, F.; Skaritka, J.; Smith, K.; Than, R.; Tuozzolo, J.; Wang, E.; Xiao, B.; Xie, H.; Zaltsman, A.

2016-09-01

High-bunch-charge photoemission electron-sources operating in a continuous wave (CW) mode are required for many advanced applications of particle accelerators, such as electron coolers for hadron beams, electron-ion colliders, and free-electron lasers. Superconducting RF (SRF) has several advantages over other electron-gun technologies in CW mode as it offers higher acceleration rate and potentially can generate higher bunch charges and average beam currents. A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory to produce high-brightness and high-bunch-charge bunches for the coherent electron cooling proof-of-principle experiment. The gun utilizes a quarter-wave resonator geometry for assuring beam dynamics and uses high quantum efficiency multi-alkali photocathodes for generating electrons.

Energy Recovery Linacs for Light Source Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

George Neil

2011-04-01

Energy Recovery Linacs are being considered for applications in present and future light sources. ERLs take advantage of the continuous operation of superconducting rf cavities to accelerate high average current beams with low losses. The electrons can be directed through bends, undulators, and wigglers for high brightness x ray production. They are then decelerated to low energy, recovering power so as to minimize the required rf drive and electrical draw. When this approach is coupled with advanced continuous wave injectors, very high power, ultra-short electron pulse trains of very high brightness can be achieved. This paper will review the statusmore » of worldwide programs and discuss the technology challenges to provide such beams for photon production.« less

1985 Particle Accelerator Conference: Accelerator Engineering and Technology, 11th, Vancouver, Canada, May 13-16, 1985, Proceedings

NASA Astrophysics Data System (ADS)

Strathdee, A.

1985-10-01

The topics discussed are related to high-energy accelerators and colliders, particle sources and electrostatic accelerators, controls, instrumentation and feedback, beam dynamics, low- and intermediate-energy circular accelerators and rings, RF and other acceleration systems, beam injection, extraction and transport, operations and safety, linear accelerators, applications of accelerators, radiation sources, superconducting supercolliders, new acceleration techniques, superconducting components, cryogenics, and vacuum. Accelerator and storage ring control systems are considered along with linear and nonlinear orbit theory, transverse and longitudinal instabilities and cures, beam cooling, injection and extraction orbit theory, high current dynamics, general beam dynamics, and medical and radioisotope applications. Attention is given to superconducting RF structures, magnet technology, superconducting magnets, and physics opportunities with relativistic heavy ion accelerators.

Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

NASA Astrophysics Data System (ADS)

Hussain, S.; Qazi, H. I. A.; Badar, M. A.

2014-03-01

An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the α and γ modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in γ mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

Glass antenna for RF-ion source operation

DOEpatents

Leung, Ka Ngo; Lee, Yung-Hee Yvette; Perkins, Luke T.

2000-01-01

An antenna comprises a plurality of small diameter conductive wires disposed in a dielectric tube. The number and dimensions of the conductive wires is selected to improve the RF resistance of the antenna while also facilitating a reduction in thermal gradients that may create thermal stresses on the dielectric tube. The antenna may be mounted in a vacuum system using a low-stress antenna assembly that cushions and protects the dielectric tube from shock and mechanical vibration while also permitting convenient electrical and coolant connections to the antenna.

Lorentz Force Detuning Analysis of the SNS Accelerating Cavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

R. Mitchell; K. Matsumoto; G. Ciovati

2001-09-01

The Spallation Neutron Source (SNS) project incorporates a superconducting radio-frequency (SRF) accelerator for the final section of the pulsed mode linac Cavities with geometrical {beta} values of {beta} = 0.61 and {beta} = 0.81 are utilized in the SRF section, and are constructed out of thin-walled niobium with stiffener rings welded between the cells near the iris. The welded titanium helium vessel and tuner assembly restrains the cavity beam tubes Cavities with {beta} values less than one have relatively steep and flat side-walls making the cavities susceptible to Ised RF induces cyclic Lorentz pressures that mechanically excite the cavities, producingmore » a dynamic Lorentz force detuning different from a continuous RF system. The amplitude of the dynamic detuning for a given cavity design is a function of the mechanical damping, stiffness of the tuner/helium vessel assembly, RF pulse profile, and the RF pulse rate. This paper presents analysis and testing results to date, and indicates areas where more investigation is required.« less

Cathode Priming vs. RF Priming for Relativistic Magnetrons

NASA Astrophysics Data System (ADS)

White, W. M.; Spencer, T. A.; Price, D.

2005-10-01

Magnetron start-oscillation time, pulsewidth and pi-mode locking are experimentally compared for RF priming versus cathode priming on the Michigan-Titan relativistic magnetron (-300 kV, 2-10 kA, 300-500 ns). Cathode priming [1, 2] is an innovative technique first demonstrated experimentally at UM. In this technique, the cathode is fabricated with N/2 emitting strips or N/2-separate cathodes (for an N-cavity magnetron), which generate the desired number of spokes for pi-mode. Cathode priming yields 13% faster startup with more reproducible pi-mode oscillation. Radio Frequency (RF) priming is investigated as the baseline priming technique for magnetrons. The external priming source is a 100kW, 3μs pulsewidth magnetron on loan from AFRL. RF priming reduced startup delay by 15% and increased pulsewidth by 9%. [1] M.C. Jones, V.B. Neculaes, R.M. Gilgenbach, W.M. White, M.R. Lopez, Y.Y. Lau, T.A. Spencer, and D. Price, Rev. Sci. Inst., 75, 2976 (2004) [2] M.C. Jones, Doctoral Dissertation, University of Michigan, 2005

Design and Development of Amplitude and phase measurement of RF signal with Digital I-Q Demodulator

NASA Astrophysics Data System (ADS)

Soni, Dipal; Rajnish, Kumar; Verma, Sriprakash; Patel, Hriday; Trivedi, Rajesh; Mukherjee, Aparajita

2017-04-01

ITER-India, working as a nodal agency from India for ITER project [1], is responsible to deliver one of the packages, called Ion Cyclotron Heating & Current Drive (ICH&CD) - Radio Frequency Power Sources (RFPS). RFPS is having two cascaded amplifier chains (10 kW, 130 kW & 1.5 MW) combined to get 2.5 MW RF power output. Directional couplers are inserted at the output of each stage to extract forward power and reflected power as samples for measurement of amplitude and phase. Using passive mixer, forward power and reflected power are down converted to 1MHz Intermediate frequency (IF). This IF signal is used as an input to the Digital IQ Demodulator (DIQDM). DIQDM is realized using National Instruments make PXI hardware & LabVIEW software tool. In this paper, Amplitude and Phase measurement of RF signal with DIQDM technique is described. Also test results with dummy signals and signal generated from low power RF systems is discussed here.

Attributes for MRB_E2RF1 Catchments in Selected Major River Basins: Population Density, 2000

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This data set represents the average population density, in number of people per square kilometer multiplied by 10 for the year 2000, compiled for every MRB_E2RF1 catchment of selected Major River Basins (MRBs, Crawford and others, 2006). The source data set is the 2000 Population Density by Block Group for the Conterminous United States (Hitt, 2003). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) RF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

The 30-GHz monolithic receive module

NASA Technical Reports Server (NTRS)

Sokolov, V.; Geddes, J.; Bauhahn, P.

1983-01-01

Key requirements for a 30 GHz GaAs monolithic receive module for spaceborne communication antenna feed array applications include an overall receive module noise figure of 5 dB, a 30 dB RF to IF gain with six levels of intermediate gain control, a five-bit phase shifter, and a maximum power consumption of 250 mW. The RF designs for each of the four submodules (low noise amplifier, some gain control, phase shifter, and RF to IF sub-module) are presented. Except for the phase shifter, high frequency, low noise FETs with sub-half micron gate lengths are employed in the submodules. For the gain control, a two stage dual gate FET amplifier is used. The phase shifter is of the passive switched line type and consists of 5-bits. It uses relatively large gate width FETs (with zero drain to source bias) as the switching elements. A 20 GHz local oscillator buffer amplifier, a FET compatible balanced mixer, and a 5-8 GHz IF amplifier constitute the RF/IF sub-module. Phase shifter fabrication using ion implantation and a self-aligned gate technique is described. Preliminary RF results obtained on such phase shifters are included.

Analysis of RF emissions from laser induced breakdown of atmospheric air and metals

NASA Astrophysics Data System (ADS)

Paturi, Prem Kiran; Lakshmi, Vinoth Kumar; Elle, Manikanta; Chelikani, Leela

2013-10-01

The low frequency (RF, microwave) emissions from laser produced plasma (LPP) are of great interest because of their variety of applications. The RF waves emitted by the nanosecond LPP of atmospheric air and metal (Al, Cu) targets were detected using antennas over frequency ranges (30 MHz-18 GHz) and were monitored using a spectrum analyzer (3 Hz-50 GHz). With different target materials, the dominant emission lines were observed to fall in different specific frequency ranges within the detection limit. The emissions from Cu were in the higher frequency range (100-200 MHz) than that of Al (30-100 MHz) may be due to the higher electron density of Cu, which contributes to the LPP conductivity. From the LPP of atmospheric air, the RF output was found to be increasing with the input laser energy up to certain value, beyond which almost no emission was observed. This effect is attributed to the modification in the net induced dipole moment due to the multiple plasma sources in the LPP at higher input laser energies. The detected radiation was observed to be dependent on laser and antenna polarization. Further studies may lead to an efficient technique for material identification from the RF characteristic peaks.

Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields

PubMed Central

Wiedemann, Peter M.; Brown, Tim W. C.

2015-01-01

The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF) exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one's own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed. PMID:26229540

The status of normal conducting RF (NCRF) guns, a summary of the ERL2005 workshop

NASA Astrophysics Data System (ADS)

Dowell, David H.; Lewellen, John W.; Nguyen, Dinh; Rimmer, Robert

2006-02-01

The 32nd Advanced ICFA Beam Dynamics Workshop on Energy Recovering Linacs (ERL2005) was held at Jefferson Laboratory, March 20-23, 2005. A wide range of ERL-related topics were presented and discussed in several working groups with Working Group 1 concentrating upon the physics and technology issues for DC, superconducting RF (SRF) and normal conducting RF (NCRF) guns. This paper summarizes the NCRF gun talks and reviews the status of NCRF gun technology. It begins with the presentations made on the subject of low-frequency, high-duty factor guns most appropriate for ERLs. One such gun at 433 MHz was demonstrated at 25%DF in 1992, while the CW and much improved version is currently being constructed at 700 MHz for LANL. In addition, the idea of combining the NCRF gun with a SRF linac booster was presented and is described in this paper. There was also a talk on high-field guns typically used for SASE-free electron lasers. In particular, the DESY coaxial RF feed design provides rotationally symmetric RF fields and greater flexibility in the placement of the focusing magnetic field. While in the LCLS approach, the symmetric fields are obtained with a dual RF feed and racetrack cell shape. Although these guns cannot be operated at high-duty factor, they do produce the best quality beams. With these limitations in mind, a section with material not presented at the workshop has been included in the paper. This work describes a re-entrant approach which may allow NCRF guns to operate with simultaneously increased RF fields and duty factors. And finally, a novel proposal describing a high-duty factor, two-frequency RF gun using a field emission source instead of a laser driven photocathode was also presented.

Recent Development of IMP ECR Ion Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, H.W.; Zhang, Z.M.; Sun, L.T.

2005-03-15

Great efforts have been made to develop highly charged ECR ion sources for application of heavy ion accelerator and atomic physics research at IMP in the past few years. The latest development of ECR ion sources at IMP is briefly reviewed. Intense beams with high and intermediate charge states have been produced from IMP LECR3 by optimization of the ion source conditions including rf frequency extended up to 18GHz. 1.1 emA of Ar8+ and 325 e{mu} A of Ar11+ were produced. Dependence of beam emittance on those key parameters of ECR ion source, beam extraction and space charge compensation weremore » experimentally studied at LECR3. Furthermore, an advanced superconducting ECR ion source named SECRAL is being constructed. SECRAL is designed to operate at rf frequency 18-28GHz with axial mirror magnetic fields 3.6-4.0 Tesla at injection, 2.2 Tesla at extraction and sextupole field 2.0 Tesla at the wall. The superconducting magnet with sextupole and three solenoids was tested in a test-cryostat and 95% of designed fields were reached. Construction status and planed schedule of SECRAL are presented.« less

THz and Sub-THz Capabilities of a Table-Top Radiation Source Driven by an RF Thermionic Electron Gun

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, Alexei V.; Agustsson, R.; Boucher, S.

Design features and experimental results are presented for a sub-mm wave source [1] based on APS RF thermionic electron gun. The setup includes compact alpha-magnet, quadrupoles, sub-mm-wave radiators, and THz optics. The sub-THz radiator is a planar, oversized structure with gratings. Source upgrade for generation frequencies above 1 THz is discussed. The THz radiator will use a short-period undulator having 1 T field amplitude, ~20 cm length, and integrated with a low-loss oversized waveguide. Both radiators are integrated with a miniature horn antenna and a small ~90°-degree in-vacuum bending magnet. The electron beamline is designed to operate different modes includingmore » conversion to a flat beam interacting efficiently with the radiator. The source can be used for cancer diagnostics, surface defectoscopy, and non-destructive testing. Sub-THz experiment demonstrated a good potential of a robust, table-top system for generation of a narrow bandwidth THz radiation. This setup can be considered as a prototype of a compact, laser-free, flexible source capable of generation of long trains of Sub-THz and THz pulses with repetition rates not available with laser-driven sources.« less

Automating RPM Creation from a Source Code Repository

DTIC Science & Technology

2012-02-01

apps/usr --with- libpq=/apps/ postgres make rm -rf $RPM_BUILD_ROOT umask 0077 mkdir -p $RPM_BUILD_ROOT/usr/local/bin mkdir -p $RPM_BUILD_ROOT...from a source code repository. %pre %prep %setup %build ./autogen.sh ; ./configure --with-db=/apps/db --with-libpq=/apps/ postgres make

[Dietetic factors associated with prostate cancer: protective effects of Mediterranean diet].

PubMed

Ferrís-Tortajada, J; Berbel-Tornero, O; García-Castell, J; Ortega-García, J A; López-Andreu, J A

2012-04-01

To review diet risk factors (RF) implied, more or less evidence-based, in the etiopathology of prostate carcinoma (PC), especially those that characterize the traditional Mediterranean diet (MD). Literature review of PC related diet RF in MedLine, CancerLit, Science Citation Index y Embase. Search profiles were "Dietetic Factors/Nutritional Factors/Mediterranean Diet/Primary Prevention", and "Prostate Cancer". Diet RF are associated with 35% of cancer mortality and 10-12% of PC mortality. The main diet RF, implied in the development of PC but with a protective effect, which are considered characteristic of MD are: high daily ingestion of vegetarian products (cereals, legumes, dried and fresh fruits, tubers, vegetables..); olive oil as main lipid source; low intake of animal saturated fat, processed red meat, milk and dairy products; regular consumption of small fish; and low alcohol intake (wine with meals). The MD contains many phytoactive compounds (lycopene, lupeol, quercetin, genistein, carnosol, resveratrol, catechins, vitamins..) with PC protective effects. Diet RF have a role on prostatic carcinogenesis. Further epidemiologic studies with better designs are needed to clarify PC related diet RF. PC risk is reduced in persons on MD compared with those on Western diet. The preventive effect of MD is due to the great number and quality of phytochemicals with antioxidant and antinflammatory properties that contains. Copyright © 2011 AEU. Published by Elsevier Espana. All rights reserved.

Deciphering the Routes of invasion of Drosophila suzukii by Means of ABC Random Forest.

PubMed

Fraimout, Antoine; Debat, Vincent; Fellous, Simon; Hufbauer, Ruth A; Foucaud, Julien; Pudlo, Pierre; Marin, Jean-Michel; Price, Donald K; Cattel, Julien; Chen, Xiao; Deprá, Marindia; François Duyck, Pierre; Guedot, Christelle; Kenis, Marc; Kimura, Masahito T; Loeb, Gregory; Loiseau, Anne; Martinez-Sañudo, Isabel; Pascual, Marta; Polihronakis Richmond, Maxi; Shearer, Peter; Singh, Nadia; Tamura, Koichiro; Xuéreb, Anne; Zhang, Jinping; Estoup, Arnaud

2017-04-01

Deciphering invasion routes from molecular data is crucial to understanding biological invasions, including identifying bottlenecks in population size and admixture among distinct populations. Here, we unravel the invasion routes of the invasive pest Drosophila suzukii using a multi-locus microsatellite dataset (25 loci on 23 worldwide sampling locations). To do this, we use approximate Bayesian computation (ABC), which has improved the reconstruction of invasion routes, but can be computationally expensive. We use our study to illustrate the use of a new, more efficient, ABC method, ABC random forest (ABC-RF) and compare it to a standard ABC method (ABC-LDA). We find that Japan emerges as the most probable source of the earliest recorded invasion into Hawaii. Southeast China and Hawaii together are the most probable sources of populations in western North America, which then in turn served as sources for those in eastern North America. European populations are genetically more homogeneous than North American populations, and their most probable source is northeast China, with evidence of limited gene flow from the eastern US as well. All introduced populations passed through bottlenecks, and analyses reveal five distinct admixture events. These findings can inform hypotheses concerning how this species evolved between different and independent source and invasive populations. Methodological comparisons indicate that ABC-RF and ABC-LDA show concordant results if ABC-LDA is based on a large number of simulated datasets but that ABC-RF out-performs ABC-LDA when using a comparable and more manageable number of simulated datasets, especially when analyzing complex introduction scenarios. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

A novel injection-locked amplitude-modulated magnetron at 1497 MHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neubauer, Michael; Wang, Haipeng

2015-12-15

Thomas Jefferson National Accelerator Facility (JLab) uses low efficiency klystrons in the CEBAF machine. In the older portion they operate at 30% efficiency with a tube mean time between failure (MTBF) of five to six years. A highly efficient source (>55-60%) must provide a high degree of backwards compatibility, both in size and voltage requirements, to replace the klystron presently used at JLab, while providing energy savings. Muons, Inc. is developing a highly reliable, highly efficient RF source based upon a novel injection-locked amplitude modulated (AM) magnetron with a lower total cost of ownership, >80% efficiency, and MTBF of sixmore » to seven years. The design of the RF source is based upon a single injection-locked magnetron system at 8 kW capable of operating up to 13 kW, using the magnetron magnetic field to achieve the AM required for backwards compatibility to compensate for microphonics and beam loads. A novel injection-locked 1497 MHz 8 kW AM magnetron with a trim magnetic coil was designed and its operation numerically simulated during the Phase I project. The low-level RF system to control the trim field and magnetron anode voltage was designed and modeled for operation at the modulation frequencies of the microphonics. A plan for constructing a prototype magnetron and control system was developed.« less

Duty factor variation possibility from 1% to 100% with PKU microwave driven Cs-free volume H{sup −} sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, S. X., E-mail: sxpeng@pku.edu.cn; Zhang, T.; Ren, H. T.

Microwave driven cesium-free volume H{sup −} sources, that have the ability to deliver tens of mA H{sup −} at 35 keV both in CW and 10% duty factor (100 Hz/1 ms), were developed at Peking University (PKU) [S. X. Peng et al., in Proceeding of IPAC 2015, WEPWA027, Richmond, Virginia, USA, 3–8 May 2015]. Recently, special efforts were paid on the investigation of duty factor variation possibility from 1% to 100% with them. Most of the experiments were carried out with a pulsed length (τ) of 1 ms and different intervals of 99 ms, 49 ms, 39 ms, 29 ms,more » 19 ms, 9 ms, 4 ms, 2 ms, 1 ms, 0.5 ms, and 0 ms, respectively. Other experiments were focused on CW operation and fixed duty factor of 1%. Experimental results prove that PKU H{sup −} sources can deliver tens of mA H{sup −} at duty factor from 1% to 100%. The RF power efficiency increases steadily with the increasing of duty factor from 1% to CW at a fixed pulsed length. Under a given duty factor and pulsed length, RF power efficiency keeps constant and the H{sup −} current increases with RF power linearly. Details will be presented in the paper.« less

Peak Source Power Associated with Positive Narrow Bipolar Lightning Pulses

NASA Astrophysics Data System (ADS)

Bandara, S. A.; Marshall, T. C.; Karunarathne, S.; Karunarathne, N. D.; Siedlecki, R. D., II; Stolzenburg, M.

2017-12-01

During the summer of 2016, we deployed a lightning sensor array in and around Oxford Mississippi, USA. The array system comprised seven lightning sensing stations in a network approximately covering an area of 30 km × 30 km. Each station is equipped with four sensors: Fast antenna (10 ms decay time), Slow antenna (1.0 s decay time)), field derivative sensor (dE/dt) and Log-RF antenna (bandwidth 187-192 MHz). We have observed 319 Positive NBPs and herein we report on comparisons of the NBP properties measured from the Fast antenna data with the Log-RF antenna data. These properties include 10-90% rise time, full width at half maximum, zero cross time, and range-normalized amplitude at 100 km. NBPs were categorized according to the fine structure of the electric field wave shapes into Types A-D, as in Karunarathne et al. [2015]. The source powers of NBPs in each category were determined using single station Log-RF data. Furthermore, we also categorized the NBPs in three other groups: initial event of an IC flash, isolated, and not-isolated (according to their spatiotemporal relationship with other lightning activity). We compared the source powers within each category. Karunarathne, S., T. C. Marshall, M. Stolzenburg, and N. Karunarathna (2015), Observations of positive narrow bipolar pulses, J. Geophys. Res. Atmos., 120, doi:10.1002/2015JD023150.

Theoretical study of a dual harmonic system and its application to the CSNS/RCS

NASA Astrophysics Data System (ADS)

Yuan, Yao-Shuo; Wang, Na; Xu, Shou-Yan; Yuan, Yue; Wang, Sheng

2015-12-01

Dual harmonic systems have been widely used in high intensity proton synchrotrons to suppress the space charge effect, as well as reduce the beam loss. To investigate the longitudinal beam dynamics in a dual rf system, the potential well, the sub-buckets in the bunch and the multi-solutions of the phase equation are studied theoretically in this paper. Based on these theoretical studies, optimization of bunching factor and rf voltage waveform are made for the dual harmonic rf system in the upgrade phase of the China Spallation Neutron Source Rapid Cycling Synchrotron (CSNS/RCS). In the optimization process, the simulation with space charge effect is done using a newly developed code, C-SCSIM. Supported by National Natural Science Foundation of China (11175193)

Characterizing and Optimizing Photocathode Laser Distributions for Ultra-low Emittance Electron Beam Operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, F.; Bohler, D.; Ding, Y.

2015-12-07

Photocathode RF gun has been widely used for generation of high-brightness electron beams for many different applications. We found that the drive laser distributions in such RF guns play important roles in minimizing the electron beam emittance. Characterizing the laser distributions with measurable parameters and optimizing beam emittance versus the laser distribution parameters in both spatial and temporal directions are highly desired for high-brightness electron beam operation. In this paper, we report systematic measurements and simulations of emittance dependence on the measurable parameters represented for spatial and temporal laser distributions at the photocathode RF gun systems of Linac Coherent Lightmore » Source. The tolerable parameter ranges for photocathode drive laser distributions in both directions are presented for ultra-low emittance beam operations.« less

Cylindrical neutron generator

DOEpatents

Leung, Ka-Ngo [Hercules, CA

2008-04-22

A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

Cylindrical neutron generator

DOEpatents

Leung, Ka-Ngo

2005-06-14

A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

Cylindrical neutron generator

DOEpatents

Leung, Ka-Ngo [Hercules, CA

2009-12-29

A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

Study of dual radio frequency capacitively coupled plasma: an analytical treatment matched to an experiment

NASA Astrophysics Data System (ADS)

Saikia, P.; Bhuyan, H.; Escalona, M.; Favre, M.; Wyndham, E.; Maze, J.; Schulze, J.

2018-01-01

The behavior of a dual frequency capacitively coupled plasma (2f CCP) driven by 2.26 and 13.56 MHz radio frequency (rf) source is investigated using an approach that integrates a theoretical model and experimental data. The basis of the theoretical analysis is a time dependent dual frequency analytical sheath model that casts the relation between the instantaneous sheath potential and plasma parameters. The parameters used in the model are obtained by operating the 2f CCP experiment (2.26 MHz + 13.56 MHz) in argon at a working pressure of 50 mTorr. Experimentally measured plasma parameters such as the electron density, electron temperature, as well as the rf current density ratios are the inputs of the theoretical model. Subsequently, a convenient analytical solution for the output sheath potential and sheath thickness was derived. A comparison of the present numerical results is done with the results obtained in another 2f CCP experiment conducted by Semmler et al (2007 Plasma Sources Sci. Technol. 16 839). A good quantitative correspondence is obtained. The numerical solution shows the variation of sheath potential with the low and high frequency (HF) rf powers. In the low pressure plasma, the sheath potential is a qualitative measure of DC self-bias which in turn determines the ion energy. Thus, using this analytical model, the measured values of the DC self-bias as a function of low and HF rf powers are explained in detail.

Epidemiology of Health Effects of Radiofrequency Exposure

PubMed Central

Ahlbom, Anders; Green, Adele; Kheifets, Leeka; Savitz, David; Swerdlow, Anthony

2004-01-01

We have undertaken a comprehensive review of epidemiologic studies about the effects of radiofrequency fields (RFs) on human health in order to summarize the current state of knowledge, explain the methodologic issues that are involved, and aid in the planning of future studies. There have been a large number of occupational studies over several decades, particularly on cancer, cardiovascular disease, adverse reproductive outcome, and cataract, in relation to RF exposure. More recently, there have been studies of residential exposure, mainly from radio and television transmitters, and especially focusing on leukemia. There have also been studies of mobile telephone users, particularly on brain tumors and less often on other cancers and on symptoms. Results of these studies to date give no consistent or convincing evidence of a causal relation between RF exposure and any adverse health effect. On the other hand, the studies have too many deficiencies to rule out an association. A key concern across all studies is the quality of assessment of RF exposure. Despite the ubiquity of new technologies using RFs, little is known about population exposure from RF sources and even less about the relative importance of different sources. Other cautions are that mobile phone studies to date have been able to address only relatively short lag periods, that almost no data are available on the consequences of childhood exposure, and that published data largely concentrate on a small number of outcomes, especially brain tumor and leukemia. PMID:15579422

Precursor and Neutral Loss Scans in an RF Scanning Linear Quadrupole Ion Trap

NASA Astrophysics Data System (ADS)

Snyder, Dalton T.; Szalwinski, Lucas J.; Schrader, Robert L.; Pirro, Valentina; Hilger, Ryan; Cooks, R. Graham

2018-03-01

Methodology for performing precursor and neutral loss scans in an RF scanning linear quadrupole ion trap is described and compared to the unconventional ac frequency scan technique. In the RF scanning variant, precursor ions are mass selectively excited by a fixed frequency resonance excitation signal at low Mathieu q while the RF amplitude is ramped linearly to pass ions through the point of excitation such that the excited ion's m/z varies linearly with time. Ironically, a nonlinear ac frequency scan is still required for ejection of the product ions since their frequencies vary nonlinearly with the linearly varying RF amplitude. In the case of the precursor scan, the ejection frequency must be scanned so that it is fixed on a product ion m/z throughout the RF scan, whereas in the neutral loss scan, it must be scanned to maintain a constant mass offset from the excited precursor ions. Both simultaneous and sequential permutation scans are possible; only the former are demonstrated here. The scans described are performed on a variety of samples using different ionization sources: protonated amphetamine ions generated by nanoelectrospray ionization (nESI), explosives ionized by low-temperature plasma (LTP), and chemical warfare agent simulants sampled from a surface and analyzed with swab touch spray (TS). We lastly conclude that the ac frequency scan variant of these MS/MS scans is preferred due to electronic simplicity. In an accompanying manuscript, we thus describe the implementation of orthogonal double resonance precursor and neutral loss scans on the Mini 12 using constant RF voltage. [Figure not available: see fulltext.

A numerical investigation on the effect of RF coil feed variability on global and local electromagnetic field exposure in human body models at 64 MHz.

PubMed

Lucano, Elena; Liberti, Micaela; Lloyd, Tom; Apollonio, Francesca; Wedan, Steve; Kainz, Wolfgang; Angelone, Leonardo M

2018-02-01

This study aims to investigate how the positions of the feeding sources of the transmit radiofrequency (RF) coil, field orientation direction with respect to the patient, and patient dimensions affect the global and local electromagnetic exposure in human body models. Three RF coil models were implemented, namely a specific two-source (S2) feed and two multisource feed configurations: generic 32-source (G32) and hybrid 16-source (H16). Thirty-two feeding conditions were studied for the S2, whereas two were studied for the G32 and H16. The study was performed using five human body models. Additionally, for two of the body models, the case of a partially implanted lead was evaluated. The results showed an overall variation due to coil feeding conditions of the whole-body specific absorption rate (SAR) of less than 20%, but deviations up to 98% of the magnitude of the electric field tangential to a possible lead path. For the analysis with the partially implanted lead, a variation of local SAR at the tip of the lead of up to 60% was observed with respect to feed position and field orientation direction. The results of this study suggest that specific information about feed position and field orientation direction must be considered for an accurate evaluation of patient exposure. Magn Reson Med 79:1135-1144, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Three-Dimensional Passive-Source Reverse-Time Migration of Converted Waves: The Method

NASA Astrophysics Data System (ADS)

Li, Jiahang; Shen, Yang; Zhang, Wei

2018-02-01

At seismic discontinuities in the crust and mantle, part of the compressional wave energy converts to shear wave, and vice versa. These converted waves have been widely used in receiver function (RF) studies to image discontinuity structures in the Earth. While generally successful, the conventional RF method has its limitations and is suited mostly to flat or gently dipping structures. Among the efforts to overcome the limitations of the conventional RF method is the development of the wave-theory-based, passive-source reverse-time migration (PS-RTM) for imaging complex seismic discontinuities and scatters. To date, PS-RTM has been implemented only in 2D in the Cartesian coordinate for local problems and thus has limited applicability. In this paper, we introduce a 3D PS-RTM approach in the spherical coordinate, which is better suited for regional and global problems. New computational procedures are developed to reduce artifacts and enhance migrated images, including back-propagating the main arrival and the coda containing the converted waves separately, using a modified Helmholtz decomposition operator to separate the P and S modes in the back-propagated wavefields, and applying an imaging condition that maintains a consistent polarity for a given velocity contrast. Our new approach allows us to use migration velocity models with realistic velocity discontinuities, improving accuracy of the migrated images. We present several synthetic experiments to demonstrate the method, using regional and teleseismic sources. The results show that both regional and teleseismic sources can illuminate complex structures and this method is well suited for imaging dipping interfaces and sharp lateral changes in discontinuity structures.

Some Notes on Sparks and Ignition of Fuels

NASA Technical Reports Server (NTRS)

Fisher, Franklin A.

2000-01-01

This report compliments a concurrent analysis of the electromagnetic field threat to the fuel system of a transport aircraft. The accompanying effort assessed currents, voltages and power levels that may be induced upon fuel tank wiring from radio transmitters (inside and outside the aircraft). In addition to this, it was also essential to determine how much voltage, current, or power is required to create a fuel-vapor ignition hazard. The widely accepted minimum guideline for aircraft fuel-vapor ignition is the application of a 0.2 millijoule energy level. However, when considering radio frequency (RF) sources, this guideline is seriously inadequate. This report endeavors to bridge the gap between a traditional understanding of electrical breakdown, heating and combustion; and supplement the knowledge with available information regarding aircraft fuel-vapor ignition by RF sources

Definition and test of the electromagnetic immunity of UAS for first responders

NASA Astrophysics Data System (ADS)

Adami, C.; Chmel, S.; Jöster, M.; Pusch, T.; Suhrke, M.

2015-11-01

Recent technological developments considerably lowered the barrier for unmanned aerial systems (UAS) to be employed in a variety of usage scenarios, comprising live video transmission from otherwise inaccessible vantage points. As an example, in the French-German ANCHORS project several UAS guided by swarm intelligence provide aerial views and environmental data of a disaster site while deploying an ad-hoc communication network for first responders. Since being able to operate in harsh environmental conditions is a key feature, the immunity of the UAS against radio frequency (RF) exposure has been studied. Conventional Electromagnetic Compatibility (EMC) applied to commercial and industrial electronics is not sufficient since UAS are airborne and can as such move beyond the bounds within which RF exposure is usually limited by regulatory measures. Therefore, the EMC requirements have been complemented by a set of specific RF test frequencies and parameters where strong sources are expected to interfere in the example project test case of an inland port environment. While no essential malfunctions could be observed up to field strengths of 30 V m-1, a sophisticated, more exhaustive approach for testing against potential sources of interference in key scenarios of UAS usage should be derived from our present findings.

RF model of the distribution system as a communication channel, phase 2. Volume 4: Sofware source program and illustrations ASCII database listings

NASA Technical Reports Server (NTRS)

Rustay, R. C.; Gajjar, J. T.; Rankin, R. W.; Wentz, R. C.; Wooding, R.

1982-01-01

Listings of source programs and some illustrative examples of various ASCII data base files are presented. The listings are grouped into the following categories: main programs, subroutine programs, illustrative ASCII data base files. Within each category files are listed alphabetically.

Infrasound Observations from Lightning

NASA Astrophysics Data System (ADS)

Arechiga, R. O.; Johnson, J. B.; Edens, H. E.; Thomas, R. J.; Jones, K. R.

2008-12-01

To provide additional insight into the nature of lightning, we have investigated its infrasound manifestations. An array of three stations in a triangular configuration, with three sensors each, was deployed during the Summer of 2008 (July 24 to July 28) in the Magdalena mountains of New Mexico, to monitor infrasound (below 20 Hz) sources due to lightning. Hyperbolic formulations of time of arrival (TOA) measurements and interferometric techniques were used to locate lightning sources occurring over and outside the network. A comparative analysis of simultaneous Lightning Mapping Array (LMA) data and infrasound measurements operating in the same area was made. The LMA locates the sources of impulsive RF radiation produced by lightning flashes in three spatial dimensions and time, operating in the 60 - 66 MHz television band. The comparison showed strong evidence that lightning does produce infrasound. This work is a continuation of the study of the frequency spectrum of thunder conducted by Holmes et al., who reported measurements of infrasound frequencies. The integration of infrasound measurements with RF source localization by the LMA shows great potential for improved understanding of lightning processes.

Development Status of Ion Source at J-PARC Linac Test Stand

NASA Astrophysics Data System (ADS)

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

The Japan Proton Accelerator Research Complex (J-PARC) linac power upgrade program is now in progress in parallel with user operation. To realize a nominal performance of 1 MW at 3 GeV Rapid Cycling Synchrotron and 0.75 MW at the Main Ring synchrotron, we need to upgrade the peak beam current (50 mA) of the linac. For the upgrade program, we are testing a new front-end system, which comprises a cesiated RF-driven H- ion source and a new radio -frequency quadrupole linac (RFQ). The H- ion source was developed to satisfy the J-PARC upgrade requirements of an H- ion-beam current of 60 mA and a lifetime of more than 50 days. On February 6, 2014, the first 50 mA H- beams were accelerated by the RFQ during a beam test. To demonstrate the performance of the ion source before its installation in the summer of 2014, we tested the long-term stability through continuous beam operation, which included estimating the lifetime of the RF antenna and evaluating the cesium consumption.

An Adaptable Multiple Power Source for Mass Spectrometry and other Scientific Instruments

DOE PAGES

Lin, Tzu-Yung; Anderson, Gordon A.; Norheim, Randolph V.; ...

2015-09-18

Power supplies are commonly used in the operation of many types of scientific equipment, including mass spectrometers and ancillary instrumentation. A generic modern mass spectrometer comprises an ionization source, such as electrospray ionization (ESI), ion transfer devices such as ion funnels and multipole ion guides, and ion signal detection apparatus. Very often such platforms include, or are interfaced with ancillary elements in order to manipulate samples before or after ionization. In order to operate such scientific instruments, numerous direct current (DC) channels and radio frequency (RF) signals are required, along with other controls such as temperature regulation. In particular, DCmore » voltages in the range of ±400 V, along with MHz range RF signals with peak-to-peak amplitudes in the hundreds of volts range are commonly used to transfer ionized samples under vacuum. Additionally, an ESI source requires a high voltage (HV) DC source capable of producing several thousand volts and heaters capable of generating temperatures up to 300°C. All of these signals must be properly synchronized and managed in order to carry out ion trapping, accumulation and detection.« less

Ion sources for electric propulsion

NASA Technical Reports Server (NTRS)

Stuhlinger, E.

1971-01-01

Ion systems, which accelerate ions of Cs, Hg, or colloid particles by electrostatic fields, are furthest advanced and ready for application. Four kinds of ion sources have been developed: The contact ionization source for Cs as propellants, the electron bombardment source for Cs or Hg, the RF ionization source for Hg, and the hollow needle spray nozzle for colloidal glycerol particles. In each case, the ion beam must be neutralized by injection of electrons shortly behind the exit orifice to avoid adverse space charge effects.

Instrumentation for localized superconducting cavity diagnostics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conway, Z. A.; Ge, M.; Iwashita, Y.

2017-01-12

Superconducting accelerator cavities are now routinely operated at levels approaching the theoretical limit of niobium. To achieve these operating levels more information than is available from the RF excitation signal is required to characterize and determine fixes for the sources of performance limitations. This information is obtained using diagnostic techniques which complement the analysis of the RF signal. In this paper we describe the operation and select results from three of these diagnostic techniques: the use of large scale thermometer arrays, second sound wave defect location and high precision cavity imaging with the Kyoto camera.

Review of the High Performance Antiproton Trap (HiPAT) Experiment at the Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Pearson, J. B.; Sims, Herb; Martin, James; Chakrabarti, Suman; Lewis, Raymond; Fant, Wallace

2003-01-01

The significant energy density of matter-antimatter annihilation is attractive to the designers of future space propulsion systems, with the potential to offer a highly compact source of power. Many propulsion concepts exist that could take advantage of matter-antimatter reactions, and current antiproton production rates are sufficient to support basic proof-of-principle evaluation of technology associated with antimatter- derived propulsion. One enabling technology for such experiments is portable storage of low energy antiprotons, allowing antiprotons to be trapped, stored, and transported for use at an experimental facility. To address this need, the Marshall Space Flight Center's Propulsion Research Center is developing a storage system referred to as the High Performance Antiproton Trap (HiPAT) with a design goal of containing 10(exp 12) particles for up to 18 days. The HiPAT makes use of an electromagnetic system (Penning- Malmberg design) consisting of a 4 Telsa superconductor, high voltage electrode structure, radio frequency (RF) network, and ultra high vacuum system. To evaluate the system normal matter sources (both electron guns and ion sources) are used to generate charged particles. The electron beams ionize gas within the trapping region producing ions in situ, whereas the ion sources produce the particles external to the trapping region and required dynamic capture. A wide range of experiments has been performed examining factors such as ion storage lifetimes, effect of RF energy on storage lifetime, and ability to routinely perform dynamic ion capture. Current efforts have been focused on improving the FW rotating wall system to permit longer storage times and non-destructive diagnostics of stored ions. Typical particle detection is performed by extracting trapped ions from HiPAT and destructively colliding them with a micro-channel plate detector (providing number and energy information). This improved RF system has been used to detect various plasma modes for both electron and ion plasmas in the two traps at MSFC, including axial, cyclotron, and diocotron modes. New diagnostics are also being added to HiPAT to measure the axial density distribution of the trapped cloud to match measured RF plasma modes to plasma conditions.

The Physics and Applications of High Brightness Electron Beams

NASA Astrophysics Data System (ADS)

Palumbo, Luigi; Rosenzweig, J.; Serafini, Luca

2007-09-01

Plenary sessions. RF deflector based sub-Ps beam diagnostics: application to FEL and advanced accelerators / D. Alesini. Production of fermtosecond pulses and micron beam spots for high brightness electron beam applications / S.G. Anderson ... [et al.]. Wakefields of sub-picosecond electron bunches / K.L.F. Bane. Diamond secondary emitter / I. Ben-Zvi ... [et al.]. Parametric optimization for an X-ray free electron laser with a laser wiggler / R. Bonifacio, N. Piovella and M.M. Cola. Needle cathodes for high-brightness beams / C.H. Boulware ... [et al.]. Non linear evolution of short pulses in FEL cascaded undulators and the FEL harmonic cascade / L. Giannessi and P. Musumeci. High brightness laser induced multi-meV electron/proton sources / D. Giulietti ... [et al.]. Emittance limitation of a conditioned beam in a strong focusing FEL undulator / Z. Huang, G. Stupakov and S. Reiche. Scaled models: space-charge dominated electron storage rings / R.A. Kishek ... [et al.]. High brightness beam applications: energy recovered linacs / G.A. Krafft. Maximizing brightness in photoinjectors / C. Limborg-Deprey and H. Tomizawa. Ultracold electron sources / O.J. Luiten ... [et al.]. Scaling laws of structure-based optical accelerators / A. Mizrahi, V. Karagodsky and L. Schächter. High brightness beams-applications to free-electron lasers / S. Reiche. Conception of photo-injectors for the CTF3 experiment / R. Roux. Superconducting RF photoinjectors: an overview / J. Sekutowicz. Status and perspectives of photo injector developments for high brightness beams / F. Stephan. Results from the UCLA/FNLP underdense plasma lens experiment / M.C. Thompson ... [et al.]. Medical application of multi-beam compton scattering monochromatic tunable hard X-ray source / M. Uesaka ... [et al.]. Design of a 2 kA, 30 fs RF-photoinjector for waterbag compression / S.B. Van Der Geer, O.J. Luiten and M.J. De Loos. Proposal for a high-brightness pulsed electron source / M. Zolotorev ... [et al.]. -- Working Group 1. Summary of working group 1 on electron sources / M. Ferrario and G. Gatti. Design and RF measurements of an X-band accelerating structure for the SPARC project / D. Alesini ... [et al.]. Mitigation of RF gun breakdown by removal of tuning rods in high field regions / A.M. Cook... [et al.]. Measurements of quantum efficiency of Mg films produced by pulsed laser ablation deposition for application to bright electron sources / G. Gatti ... [et al.]. The S-band 1.6 cell RF gun correlated energy spread dependence on Pi and 0 mode relative amplitude / F. Schmerge ... [et al.]. RF gun photo-emission model for metal cathodes including time dependent emission / J.F. Schmerge ... [et al.]. Superconducting photocathodes / J. Smedley ... [et al.]. -- Working Group 2. Summary of Working Group 2: diagnostics and beam manipulation / G. Travish. Observation of coherent edge radiation emitted by a 100 Femtosecond compressed electron beam / G. Andonian, M, Dunning, E. Hemsing, J. B. Rosenzweig ... [et al.]. PARMELA simulations for PITZ: first machine studies and interpretation of measurements / M. Boscolo ... [et al.]. The LCLS single-shot relative bunch length monitor system / M.P. Dunning ... [et al.]. Beam shaping and permanent magnet quadrupole focusing with applications to the plasma wakefield accelerator / R.J. England ... [et al.]. Commissioning of the SPARC movable emittance meter and its first operation at PITZ / D. Filippetto... [et al.]. Experimental testing of dynamically optimized photoelectron beams / J.B. Rosenzweig ... [et al.]. Synchronization between the laser and electron beam in a photocathode RF gun / A. Sakumi ... [et al.]. Method of bunch radiation photochronography with 10 Femtosecond and less resolution / A. Tron and I. Merinov -- Working Group 3. New challenges in theory and modeling-summary for working group 3. L. Giannessi. Resonant modes in a 1.6 cells RF gun / M. Ferrario and C. Ronsivalle. Emittance degradation due to wake fields in a high brightness photoinjector / M. Ferrario, V. Fusco, M. Migliorati and L. Palumbo. Simulations of coherent synchroton radiation effects in electron machines / M. Migliorati, A, Schiavi and G. Dattoli. QFEL: A numerical code for multi-dimensional simulation of free electron lasers in the quantum regime / A. Schiavi ... [et al.]. First simulations results on laser pulse jitter and microbunching instability at Saprxino / M. Boscolo ... [et al.]. -- Working Group 4. Working group 4 summary: applications of high brightness beams to advanced accelerators and light sources / M. Uesaka and A. Rossi. Study of transverse effects in the production of X-rays with free-electron laser based on an optical ondulator / A. Bacci ... [et al.]. Channeling projects at LNF: from crystal undulators to capillary waveguides / S.B. Dabagov ... [et al.]. Mono-Energetic electron generation and plasma diagnosis experiments in a laser plasma cathode / K. Kinoshita ... [et al.]. A high-density electron beam and quad-scan measurements at Pleiades Thompson X-ray source / J.K. Lim ... [et al.]. Laser pulse circulation system for compact monochromatic tunable hard X-ray source / H. Ogino ... [et al.]. Limits on production of narrow band photons from inverse compton scattering / J. Rosenzweig and O. Williams. Preliminary results from the UCLA/SLAC ultra-high gradient Cerenkov wakefield accelerator experiment / M.C. Thompson ... [et al.]. Status of the polarized nonlinear inverse compton scattering experiment at UCLA / O. Williams... [et al.]. Coupling laser power into a slab-symmetric accelerator structure / R.B. Yoder and J.B. Rosenzweig.

Correlating ion energies and CF{sub 2} surface production during fluorocarbon plasma processing of silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Ina T.; Zhou Jie; Fisher, Ellen R.

2006-07-01

Ion energy distribution (IED) measurements are reported for ions in the plasma molecular beam source of the imaging of radicals interacting with surfaces (IRIS) apparatus. The IEDs and relative intensities of nascent ions in C{sub 3}F{sub 8} and C{sub 4}F{sub 8} plasma molecular beams were measured using a Hiden PSM003 mass spectrometer mounted on the IRIS main chamber. The IEDs are complex and multimodal, with mean ion energies ranging from 29 to 92 eV. Integrated IEDs provided relative ion intensities as a function of applied rf power and source pressure. Generally, higher applied rf powers and lower source pressures resultedmore » in increased ion intensities and mean ion energies. Most significantly, a comparison to CF{sub 2} surface interaction measurements previously made in our laboratories reveals that mean ion energies are directly and linearly correlated to CF{sub 2} surface production in these systems.« less

Physicsdesign point for a 1MW fusion neutron source

NASA Astrophysics Data System (ADS)

Woodruff, Simon; Melnik, Paul; Sieck, Paul; Stuber, James; Romero-Talamas, Carlos; O'Bryan, John; Miller, Ronald

2016-10-01

We are developing a design point for a spheromak experiment heated by adiabatic compression for use as a compact neutron source. We utilize the CORSICA and NIMROD MHD codes as well as analytic modeling to assess a concept with target parameters R0 =0.5m, Rf =0.17m, T0 =1keV, Tf =8keV, n0 =2e20m-3 and nf = 5e21m-3, with radial convergence of C =R0/Rf =3. We present results from CORSICA showing the placement of coils and passive structure to ensure stability during compression. We specify target parameters for the compression in terms of plasma beta, formation efficiency and energy confinement. We present results simulations of magnetic compression using the NIMROD code to examine the role of rotation on the stability and confinement of the spheromak as it is compressed. Supported by DARPA Grant N66001-14-1-4044 and IAEA CRP on Compact Fusion Neutron Sources.

A Response to Odland et al.'s Misleading, Alarmist Estimates of Risk for Overpathologizing when Interpreting the MMPI-2-RF.

PubMed

Tarescavage, Anthony M; Ben-Porath, Yossef S

2015-01-01

In a recently published article in this journal, Odland, Lammy, Perle, Martin, and Grote report Monte Carlo-simulated normative base rates of scale elevations on the Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF). Their primary conclusion--reflected in the title of their article--is that MMPI-2-RF interpretation is associated with "high risk of pathologizing healthy adults" when the 40 substantive scales of the test are simultaneously interpreted. In this paper, we describe how their conclusion follows from several faulty premises, three of which were already debunked in an earlier article and remain false despite counterarguments proposed by Odland and colleagues. We also address these authors' misinterpretation of their analyses and, furthermore, their premise that MMPI-2-RF interpretive guidelines are flawed because they "currently do not account for a basic statistical principle: Type I (or alpha) error inflation" (p. 1). This premise is irrelevant to psychological test interpretation and misaligned with neuropsychological testing literature cited in support of it. Consistent with suggestions by some of the authors they cite, we reiterate MMPI-2-RF interpretive guidelines designed to mitigate the impact of measurement error (not alpha error) by way of a scientific assessment approach that relies on integration of information derived from multiple sources.

Random Forests for Global and Regional Crop Yield Predictions.

PubMed

Jeong, Jig Han; Resop, Jonathan P; Mueller, Nathaniel D; Fleisher, David H; Yun, Kyungdahm; Butler, Ethan E; Timlin, Dennis J; Shim, Kyo-Moon; Gerber, James S; Reddy, Vangimalla R; Kim, Soo-Hyung

2016-01-01

Accurate predictions of crop yield are critical for developing effective agricultural and food policies at the regional and global scales. We evaluated a machine-learning method, Random Forests (RF), for its ability to predict crop yield responses to climate and biophysical variables at global and regional scales in wheat, maize, and potato in comparison with multiple linear regressions (MLR) serving as a benchmark. We used crop yield data from various sources and regions for model training and testing: 1) gridded global wheat grain yield, 2) maize grain yield from US counties over thirty years, and 3) potato tuber and maize silage yield from the northeastern seaboard region. RF was found highly capable of predicting crop yields and outperformed MLR benchmarks in all performance statistics that were compared. For example, the root mean square errors (RMSE) ranged between 6 and 14% of the average observed yield with RF models in all test cases whereas these values ranged from 14% to 49% for MLR models. Our results show that RF is an effective and versatile machine-learning method for crop yield predictions at regional and global scales for its high accuracy and precision, ease of use, and utility in data analysis. RF may result in a loss of accuracy when predicting the extreme ends or responses beyond the boundaries of the training data.

Attributes for MRB_E2RF1 Catchments in Selected Major River Basins of the Conterminous United States: Contact Time, 2002

USGS Publications Warehouse

Wieczorek, Michael; LaMotte, Andrew E.

2010-01-01

This tabular data set represents the average contact time, in units of days, compiled for every MRB_E2RF1 catchment of Major River Basins (MRBs, Crawford and others, 2006). Contact time, as described in Vitvar and others (2002), is defined as the baseflow residence time in the subsurface. The source data set was the U.S. Geological Survey's (USGS) 1-kilometer grid for the conterminous United States (D.M. Wolock, U.S. Geological Survey, written commun., 2008). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) RF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

RF wave simulation for cold edge plasmas using the MFEM library

NASA Astrophysics Data System (ADS)

Shiraiwa, S.; Wright, J. C.; Bonoli, P. T.; Kolev, T.; Stowell, M.

2017-10-01

A newly developed generic electro-magnetic (EM) simulation tool for modeling RF wave propagation in SOL plasmas is presented. The primary motivation of this development is to extend the domain partitioning approach for incorporating arbitrarily shaped SOL plasmas and antenna to the TORIC core ICRF solver, which was previously demonstrated in the 2D geometry [S. Shiraiwa, et. al., "HISTORIC: extending core ICRF wave simulation to include realistic SOL plasmas", Nucl. Fusion in press], to larger and more complicated simulations by including a 3D realistic antenna and integrating RF rectified sheath potential model. Such an extension requires a scalable high fidelity 3D edge plasma wave simulation. We used the MFEM [http://mfem.org], open source scalable C++ finite element method library, and developed a Python wrapper for MFEM (PyMFEM), and then a radio frequency (RF) wave physics module in Python. This approach allows for building a physics layer rapidly, while separating the physics implementation being apart from the numerical FEM implementation. An interactive modeling interface was built on pScope [S Shiraiwa, et. al. Fusion Eng. Des. 112, 835] to work with an RF simulation model in a complicated geometry.