A protection system for the JET ITER-like wall based on imaging diagnosticsa)

NASA Astrophysics Data System (ADS)

Arnoux, G.; Devaux, S.; Alves, D.; Balboa, I.; Balorin, C.; Balshaw, N.; Beldishevski, M.; Carvalho, P.; Clever, M.; Cramp, S.; de Pablos, J.-L.; de la Cal, E.; Falie, D.; Garcia-Sanchez, P.; Felton, R.; Gervaise, V.; Goodyear, A.; Horton, A.; Jachmich, S.; Huber, A.; Jouve, M.; Kinna, D.; Kruezi, U.; Manzanares, A.; Martin, V.; McCullen, P.; Moncada, V.; Obrejan, K.; Patel, K.; Lomas, P. J.; Neto, A.; Rimini, F.; Ruset, C.; Schweer, B.; Sergienko, G.; Sieglin, B.; Soleto, A.; Stamp, M.; Stephen, A.; Thomas, P. D.; Valcárcel, D. F.; Williams, J.; Wilson, J.; Zastrow, K.-D.; JET-EFDA Contributors

2012-10-01

The new JET ITER-like wall (made of beryllium and tungsten) is more fragile than the former carbon fiber composite wall and requires active protection to prevent excessive heat loads on the plasma facing components (PFC). Analog CCD cameras operating in the near infrared wavelength are used to measure surface temperature of the PFCs. Region of interest (ROI) analysis is performed in real time and the maximum temperature measured in each ROI is sent to the vessel thermal map. The protection of the ITER-like wall system started in October 2011 and has already successfully led to a safe landing of the plasma when hot spots were observed on the Be main chamber PFCs. Divertor protection is more of a challenge due to dust deposits that often generate false hot spots. In this contribution we describe the camera, data capture and real time processing systems. We discuss the calibration strategy for the temperature measurements with cross validation with thermal IR cameras and bi-color pyrometers. Most importantly, we demonstrate that a protection system based on CCD cameras can work and show examples of hot spot detections that stop the plasma pulse. The limits of such a design and the associated constraints on the operations are also presented.

Integrated modeling of temperature and rotation profiles in JET ITER-like wall discharges

NASA Astrophysics Data System (ADS)

Rafiq, T.; Kritz, A. H.; Kim, Hyun-Tae; Schuster, E.; Weiland, J.

2017-10-01

Simulations of 78 JET ITER-like wall D-D discharges and 2 D-T reference discharges are carried out using the TRANSP predictive integrated modeling code. The time evolved temperature and rotation profiles are computed utilizing the Multi-Mode anomalous transport model. The discharges involve a broad range of conditions including scans over gyroradius, collisionality, and values of q95. The D-T reference discharges are selected in anticipation of the D-T experimental campaign planned at JET in 2019. The simulated temperature and rotation profiles are compared with the corresponding experimental profiles in the radial range from the magnetic axis to the ρ = 0.9 flux surface. The comparison is quantified by calculating the RMS deviations and Offsets. Overall, good agreement is found between the profiles produced in the simulations and the experimental data. It is planned that the simulations obtained using the Multi-Mode model will be compared with the simulations using the TGLF model. Research supported in part by the US, DoE, Office of Sciences.

Plasma core power exhaust in ELMy H-Mode in JET with ITER-Like Wall

NASA Astrophysics Data System (ADS)

Guillemaut, C.; Metzger, C.; Appel, L.; Drewelow, P.; Horvath, L.; Matthews, G. F.; Szepesi, G.; Solano, E. R.; contributors, JET

2018-07-01

The mitigation of target heat load in future steady state fusion devices will require dissipation of a significant amount of power through radiation. Plasma operations relying on ELMy H-modes could be problematic since ELMs may transport substantial amounts of power to the target without significant dissipation. Therefore, estimation of the average ELM power exhaust from the plasma core is crucial to evaluate the potential limitation on the power dissipation in ELMy H-mode regime. A series of more than 50 Type-I ELMy H-mode discharges in JET with ITER-Like Wall (JET-ILW) with a wide range of conditions has been used here to compare the average ELM power to the average input power. The effect of input power, ELM frequency, plasma current, confinement and radiation on ELM power exhaust has been studied and reported in this paper. Good agreement has been found here with previous studies made in carbon machines. This work suggests that it should not be possible to dissipate more than 70%–80% of the input power in Type-I ELMy H-modes in JET-ILW which is consistent with the maximum radiative fraction found experimentally.

Gyrokinetic Simulations of JET Carbon and ITER-Like Wall Pedestals

NASA Astrophysics Data System (ADS)

Hatch, David; Kotschenreuther, Mike; Mahajan, Swadesh; Liu, Xing; Blackmon, Austin; Giroud, Carine; Hillesheim, Jon; Maggi, Costanza; Saarelma, Samuli; JET Contributors Team

2017-10-01

Gyrokinetic simulations using the GENE code are presented, which target a fundamental understanding of JET pedestal transport and, in particular, its modification after installation of an ITER like wall (ILW). A representative pre-ILW (carbon wall) discharge is analyzed as a base case. In this discharge, magnetic diagnostics observe washboard modes, which preferentially affect the temperature pedestal and have frequencies (accounting for Doppler shift) consistent with microtearing modes and inconsistent with kinetic ballooning modes. A similar ILW discharge is examined, which recovers a similar value of H98, albeit at reduced pedestal temperature. This discharge is distinguished by a much higher value of eta, which produces strong ITG and ETG driven instabilities in gyrokinetic simulations. Experimental observations provide several targets for comparisons with simulation data, including the toroidal mode number and frequency of magnetic fluctuations, heat fluxes, and inter-ELM profile evolution. Strategies for optimizing pedestal performance will also be discussed. This work was supported by U.S. DOE Contract No. DE-FG02-04ER54742 and by EUROfusion under Grant No. 633053.

Overview of fuel inventory in JET with the ITER-like wall

NASA Astrophysics Data System (ADS)

Widdowson, A.; Coad, J. P.; Alves, E.; Baron-Wiechec, A.; Barradas, N. P.; Brezinsek, S.; Catarino, N.; Corregidor, V.; Heinola, K.; Koivuranta, S.; Krat, S.; Lahtinen, A.; Likonen, J.; Matthews, G. F.; Mayer, M.; Petersson, P.; Rubel, M.; Contributors, JET

2017-08-01

Post mortem analyses of JET ITER-Like-Wall tiles and passive diagnostics have been completed after each of the first two campaigns (ILW-1 and ILW-2). They show that the global fuel inventory is still dominated by co-deposition; hence plasma parameters and sputtering processes affecting material migration influence the distribution of retained fuel. In particular, differences between results from the two campaigns may be attributed to a greater proportion of pulses run with strike points in the divertor corners, and having about 300 discharges in hydrogen at the end of ILW-2. Recessed and remote areas can contribute to fuel retention due to the larger areas involved, e.g. recessed main chamber walls, gaps in castellated Be main chamber tiles and material migration to remote divertor areas. The fuel retention and material migration due to the bulk W Tile 5 during ILW-1 are presented. Overall these tiles account for only a small percentage of the global accountancy for ILW-1.

First Operation with the JET ITER-Like Wall

NASA Astrophysics Data System (ADS)

Neu, Rudolf

2012-10-01

To consolidate ITER design choices and prepare for its operation, JET has implemented ITER's plasma facing materials, namely Be at the main wall and W in the divertor. In addition, protection systems, diagnostics and the vertical stability control were upgraded and the heating capability of the neutral beams was increased to over 30 MW. First results confirm the expected benefits and the limitations of all metal plasma facing components (PFCs), but also yield understanding of operational issues directly relating to ITER. H-retention is lower by at least a factor of 10 in all operational scenarios compared to that with C PFCs. The lower C content (˜ factor 10) have led to much lower radiation during the plasma burn-through phase eliminating breakdown failures. Similarly, the intrinsic radiation observed during disruptions is very low, leading to high power loads and to a slow current quench. Massive gas injection using a D2/Ar mixture restores levels of radiation and vessel forces similar to those of mitigated disruptions with the C wall. Dedicated L-H transition experiments indicate a reduced power threshold by 30%, a distinct minimum density and pronounced shape dependence. The L-mode density limit was found up to 30% higher than for C allowing stable detached divertor operation over a larger density range. Stable H-modes as well as the hybrid scenario could be only re-established when using gas puff levels of a few 10^21e/s. On average the confinement is lower with the new PFCs, but nevertheless, H factors around 1 (H-Mode) and 1.2 (at βN˜3, Hybrids) have been achieved with W concentrations well below the maximum acceptable level (<10-5).

The near infrared imaging system for the real-time protection of the JET ITER-like wall

NASA Astrophysics Data System (ADS)

Huber, A.; Kinna, D.; Huber, V.; Arnoux, G.; Balboa, I.; Balorin, C.; Carman, P.; Carvalho, P.; Collins, S.; Conway, N.; McCullen, P.; Jachmich, S.; Jouve, M.; Linsmeier, Ch; Lomanowski, B.; Lomas, P. J.; Lowry, C. G.; Maggi, C. F.; Matthews, G. F.; May-Smith, T.; Meigs, A.; Mertens, Ph; Nunes, I.; Price, M.; Puglia, P.; Riccardo, V.; Rimini, F. G.; Sergienko, G.; Tsalas, M.; Zastrow, K.-D.; contributors, JET

2017-12-01

This paper describes the design, implementation and operation of the near infrared (NIR) imaging diagnostic system of the JET ITER-like wall (JET-ILW) plasma experiment and its integration into the existing JET protection architecture. The imaging system comprises four wide-angle views, four tangential divertor views, and two top views of the divertor covering 66% of the first wall and up to 43% of the divertor. The operation temperature ranges which must be observed by the NIR protection cameras are, for the materials used on JET: Be 700 °C-1400 °C W coating 700 °C-1370 °C W bulk 700 °C-1400 °C. The Real-Time Protection system operates routinely since 2011 and successfully demonstrated its capability to avoid the overheating of the main chamber beryllium wall as well as of the divertor W and W-coated carbon fibre composite (CFC) tiles. During this period, less than 0.5% of the terminated discharges were aborted by a malfunction of the system. About 2%-3% of the discharges were terminated due to the detection of actual hot spots.

Overview of experimental preparation for the ITER-Like Wall at JET

NASA Astrophysics Data System (ADS)

Jet Efda Contributors Brezinsek, S.; Fundamenski, W.; Eich, T.; Coad, J. P.; Giroud, C.; Huber, A.; Jachmich, S.; Joffrin, E.; Krieger, K.; McCormick, K.; Lehnen, M.; Loarer, T.; de La Luna, E.; Maddison, G.; Matthews, G. F.; Mertens, Ph.; Nunes, I.; Philipps, V.; Riccardo, V.; Rubel, M.; Stamp, M. F.; Tsalas, M.

2011-08-01

Experiments in JET with carbon-based plasma-facing components have been carried out in preparation of the ITER-Like Wall with beryllium main chamber and full tungsten divertor. The preparatory work was twofold: (i) development of techniques, which ensure safe operation with the new wall and (ii) provision of reference plasmas, which allow a comparison of operation with carbon and metallic wall. (i) Compatibility with the W divertor with respect to energy loads could be achieved in N2 seeded plasmas at high densities and low temperatures, finally approaching partial detachment, with only moderate confinement reduction of 10%. Strike-point sweeping increases the operational space further by re-distributing the load over several components. (ii) Be and C migration to the divertor has been documented with spectroscopy and QMBs under different plasma conditions providing a database which will allow a comparison of the material transport to remote areas with metallic walls. Fuel retention rates of 1.0-2.0 × 1021 D s-1 were obtained as references in accompanied gas balance studies.

Overview of LH experiments in JET with an ITER-like wall

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

Kirov, K. K.; Baranov, Yu.; Brix, M.

2014-02-12

An overview of the recent results of Lower Hybrid (LH) experiments at JET with the ITER-like wall (ILW) is presented. Topics relevant to LH wave coupling are addressed as well as issues related to ILW and LH system protections. LH wave coupling was studied in conditions determined by ILW recycling and operational constraints. It was concluded that LH wave coupling was not significantly affected and the pre-ILW performance could be recovered after optimising the launcher position and local gas puffing. SOL density measurements were performed using a Li-beam diagnostic. Dependencies on the D2 injection rate from the dedicated gas valve,more » the LH power and the LH launcher position were analysed. SOL density modifications due to LH were modelled by the EDGE2D code assuming SOL heating by collisional dissipation of the LH wave and/or possible ExB drifts in the SOL. The simulations matched reasonably well the measured SOL profiles. Observations of arcs and hotspots with visible and IR cameras viewing the LH launcher are presented.« less

The influence of an ITER-like wall on disruptions at JET

NASA Astrophysics Data System (ADS)

de Vries, Peter

2013-10-01

Disruptions are a key issue for tokamaks such as ITER because the fast release of the high thermal and magnetic energies will result in large forces and heat loads. Hence, finding methods to avoid them or mitigate their impact is vital. The recent replacement of carbon tiles with a metallic ITER-like wall (ILW) has greatly increased the significance of disruptions for JET operations. This paper summarizes how the metallic wall influenced the disruption physics itself and its influence on the causes of disruptions. Tolerable heat loads on the ILW are reduced compared to the carbon wall because of the potential for melting. This is exacerbated by the fact that with the ILW, significantly less energy is radiated during the disruption and thus more energy is conducted to the wall. The lower radiation and thus higher temperatures also slow down the current decay, yielding larger vessel forces. Mitigation by massive gas injection had to be applied routinely in order to safely operate JET with the new wall. The start of operations with the ILW showed a marked rise in the average disruption rate from 3.4% to 10%, although in the last 2 weeks, H-mode operations with only 3.3% disruptions was achieved. The increased disruption rate can be attributed to the influence of the new wall on plasma operation and control, requiring adjustments of the established carbon-wall scenarios. A detailed survey of disruption causes will be presented, showing the improvements made to avoid various disruption classes, but also indicating those disruption types responsible for the enhanced disruption rate. The latter can be mainly attributed to disruptions due to too high core radiation but also due to density control issues and error field locked modes. Detailed technical and physics understanding of disruption causes is essential for devising optimum strategies to avoid or mitigate these events. This research was funded partly by the European Communities under the contract of Association

Studies of the pedestal structure and inter-ELM pedestal evolution in JET with the ITER-like wall

NASA Astrophysics Data System (ADS)

Maggi, C. F.; Frassinetti, L.; Horvath, L.; Lunniss, A.; Saarelma, S.; Wilson, H.; Flanagan, J.; Leyland, M.; Lupelli, I.; Pamela, S.; Urano, H.; Garzotti, L.; Lerche, E.; Nunes, I.; Rimini, F.; Contributors, JET

2017-11-01

The pedestal structure of type I ELMy H-modes has been analysed for JET with the ITER-like Wall (JET-ILW). The electron pressure pedestal width is independent of ρ * and increases proportionally to  √β pol,PED. Additional broadening of the width is observed, at constant β pol, PED, with increasing ν * and/or neutral gas injection and the contribution of atomic physics effects in setting the pedestal width cannot as yet be ruled out. Neutral penetration alone does not determine the shape of the edge density profile in JET-ILW. The ratio of electron density to electron temperature scale lengths in the edge transport barrier region, η e, is of order 2-3 within experimental uncertainties. Existing understanding, represented in the stationary linear peeling-ballooning mode stability and the EPED pedestal structure models, is extended to the dynamic evolution between ELM crashes in JET-ILW, in order to test the assumptions underlying these two models. The inter-ELM temporal evolution of the pedestal structure in JET-ILW is not unique, but depends on discharge conditions, such as heating power and gas injection levels. The strong reduction in p e,PED with increasing D 2 gas injection at high power is primarily due to clamping of \

Upgrade of the infrared camera diagnostics for the JET ITER-like wall divertor.

PubMed

Balboa, I; Arnoux, G; Eich, T; Sieglin, B; Devaux, S; Zeidner, W; Morlock, C; Kruezi, U; Sergienko, G; Kinna, D; Thomas, P D; Rack, M

2012-10-01

For the new ITER-like wall at JET, two new infrared diagnostics (KL9B, KL3B) have been installed. These diagnostics can operate between 3.5 and 5 μm and up to sampling frequencies of ∼20 kHz. KL9B and KL3B image the horizontal and vertical tiles of the divertor. The divertor tiles are tungsten coated carbon fiber composite except the central tile which is bulk tungsten and consists of lamella segments. The thermal emission between lamellae affects the surface temperature measurement and therefore KL9A has been upgraded to achieve a higher spatial resolution (by a factor of 2). A technical description of KL9A, KL9B, and KL3B and cross correlation with a near infrared camera and a two-color pyrometer is presented.

Development of a mirror-based endoscope for divertor spectroscopy on JET with the new ITER-like wall (invited).

PubMed

Huber, A; Brezinsek, S; Mertens, Ph; Schweer, B; Sergienko, G; Terra, A; Arnoux, G; Balshaw, N; Clever, M; Edlingdon, T; Egner, S; Farthing, J; Hartl, M; Horton, L; Kampf, D; Klammer, J; Lambertz, H T; Matthews, G F; Morlock, C; Murari, A; Reindl, M; Riccardo, V; Samm, U; Sanders, S; Stamp, M; Williams, J; Zastrow, K D; Zauner, C

2012-10-01

A new endoscope with optimised divertor view has been developed in order to survey and monitor the emission of specific impurities such as tungsten and the remaining carbon as well as beryllium in the tungsten divertor of JET after the implementation of the ITER-like wall in 2011. The endoscope is a prototype for testing an ITER relevant design concept based on reflective optics only. It may be subject to high neutron fluxes as expected in ITER. The operating wavelength range, from 390 nm to 2500 nm, allows the measurements of the emission of all expected impurities (W I, Be II, C I, C II, C III) with high optical transmittance (≥ 30% in the designed wavelength range) as well as high spatial resolution that is ≤ 2 mm at the object plane and ≤ 3 mm for the full depth of field (± 0.7 m). The new optical design includes options for in situ calibration of the endoscope transmittance during the experimental campaign, which allows the continuous tracing of possible transmittance degradation with time due to impurity deposition and erosion by fast neutral particles. In parallel to the new optical design, a new type of possibly ITER relevant shutter system based on pneumatic techniques has been developed and integrated into the endoscope head. The endoscope is equipped with four digital CCD cameras, each combined with two filter wheels for narrow band interference and neutral density filters. Additionally, two protection cameras in the λ > 0.95 μm range have been integrated in the optical design for the real time wall protection during the plasma operation of JET.

Development of a mirror-based endoscope for divertor spectroscopy on JET with the new ITER-like wall (invited)

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

Huber, A.; Brezinsek, S.; Mertens, Ph.

2012-10-15

A new endoscope with optimised divertor view has been developed in order to survey and monitor the emission of specific impurities such as tungsten and the remaining carbon as well as beryllium in the tungsten divertor of JET after the implementation of the ITER-like wall in 2011. The endoscope is a prototype for testing an ITER relevant design concept based on reflective optics only. It may be subject to high neutron fluxes as expected in ITER. The operating wavelength range, from 390 nm to 2500 nm, allows the measurements of the emission of all expected impurities (W I, Be II,more » C I, C II, C III) with high optical transmittance ({>=}30% in the designed wavelength range) as well as high spatial resolution that is {<=}2 mm at the object plane and {<=}3 mm for the full depth of field ({+-}0.7 m). The new optical design includes options for in situ calibration of the endoscope transmittance during the experimental campaign, which allows the continuous tracing of possible transmittance degradation with time due to impurity deposition and erosion by fast neutral particles. In parallel to the new optical design, a new type of possibly ITER relevant shutter system based on pneumatic techniques has been developed and integrated into the endoscope head. The endoscope is equipped with four digital CCD cameras, each combined with two filter wheels for narrow band interference and neutral density filters. Additionally, two protection cameras in the {lambda} > 0.95 {mu}m range have been integrated in the optical design for the real time wall protection during the plasma operation of JET.« less

JPL-IDEAS - ITERATIVE DESIGN OF ANTENNA STRUCTURES

NASA Technical Reports Server (NTRS)

Levy, R.

1994-01-01

The Iterative DEsign of Antenna Structures (IDEAS) program is a finite element analysis and design optimization program with special features for the analysis and design of microwave antennas and associated sub-structures. As the principal structure analysis and design tool for the Jet Propulsion Laboratory's Ground Antenna and Facilities Engineering section of NASA's Deep Space Network, IDEAS combines flexibility with easy use. The relatively small bending stiffness of the components of large, steerable reflector antennas allows IDEAS to use pinjointed (three translational degrees of freedom per joint) models for modeling the gross behavior of these antennas when subjected to static and dynamic loading. This facilitates the formulation of the redesign algorithm which has only one design variable per structural element. Input data deck preparation has been simplified by the use of NAMELIST inputs to promote clarity of data input for problem defining parameters, user selection of execution and design options and output requests, and by the use of many attractive and familiar features of the NASTRAN program (in many cases, NASTRAN and IDEAS formatted bulk data cards are interchangeable). Features such as simulation of a full symmetric structure based on analyses of only half the structure make IDEAS a handy and efficient analysis tool, with many features unavailable in any other finite element analysis program. IDEAS can choose design variables such as areas of rods and thicknesses of plates to minimize total structure weight, constrain the structure weight to a specified value while maximizing a natural frequency or minimizing compliance measures, and can use a stress ratio algorithm to size each structural member so that it is at maximum or minimum stress level for at least one of the applied loads. Calculations of total structure weight can be broken down according to material. Center of gravity weight balance, static first and second moments about the center of

Performance assessment of the antenna setup for the ITER plasma position reflectometry in-vessel systems.

PubMed

Varela, P; Belo, J H; Quental, P B

2016-11-01

The design of the in-vessel antennas for the ITER plasma position reflectometry diagnostic is very challenging due to the need to cope both with the space restrictions inside the vacuum vessel and with the high mechanical and thermal loads during ITER operation. Here, we present the work carried out to assess and optimise the design of the antenna. We show that the blanket modules surrounding the antenna strongly modify its characteristics and need to be considered from the early phases of the design. We also show that it is possible to optimise the antenna performance, within the design restrictions.

Tungsten and beryllium armour development for the JET ITER-like wall project

NASA Astrophysics Data System (ADS)

Maier, H.; Hirai, T.; Rubel, M.; Neu, R.; Mertens, Ph.; Greuner, H.; Hopf, Ch.; Matthews, G. F.; Neubauer, O.; Piazza, G.; Gauthier, E.; Likonen, J.; Mitteau, R.; Maddaluno, G.; Riccardi, B.; Philipps, V.; Ruset, C.; Lungu, C. P.; Uytdenhouwen, I.; EFDA contributors, JET

2007-03-01

For the ITER-like wall project at JET the present main chamber CFC tiles will be exchanged with Be tiles and in parallel a fully tungsten-clad divertor will be prepared. Therefore three R&D programmes were initiated: Be coatings on Inconel as well as Be erosion markers were developed for the first wall of the main chamber. High heat flux screening and cyclic loading tests carried out on the Be coatings on Inconel showed excellent performance, above the required power and energy density. For the divertor a conceptual design for a bulk W horizontal target plate was investigated, with the emphasis on minimizing electromagnetic forces. The design consisted of stacks of W lamellae of 6 mm width that were insulated in the toroidal direction. High heat flux tests of a test module were performed with an electron beam at an absorbed power density up to 9 MW m-2 for more than 150 pulses and finally with increasing power loads leading to surface temperatures in excess of 3000 °C. No macroscopic failure occurred during the test while SEM showed the development of micro-cracks on the loaded surface. For all other divertor parts R&D was performed to provide the technology to coat the 2-directional CFC material used at JET with thin tungsten coatings. The W-coated CFC tiles were subjected to heat loads with power densities ranging up to 23.5 MW m-2 and exposed to cyclic heat loading for 200 pulses at 10.5 MW m-2. All coatings developed cracks perpendicular to the CFC fibres due to the stronger contraction of the coating upon cool-down after the heat pulses.

Front-end antenna system design for the ITER low-field-side reflectometer system using GENRAY ray tracing.

PubMed

Wang, G; Doyle, E J; Peebles, W A

2016-11-01

A monostatic antenna array arrangement has been designed for the microwave front-end of the ITER low-field-side reflectometer (LFSR) system. This paper presents details of the antenna coupling coefficient analyses performed using GENRAY, a 3-D ray tracing code, to evaluate the plasma height accommodation capability of such an antenna array design. Utilizing modeled data for the plasma equilibrium and profiles for the ITER baseline and half-field scenarios, a design study was performed for measurement locations varying from the plasma edge to inside the top of the pedestal. A front-end antenna configuration is recommended for the ITER LFSR system based on the results of this coupling analysis.

Erosion and deposition in the JET divertor during the second ITER-like wall campaign

NASA Astrophysics Data System (ADS)

Mayer, M.; Krat, S.; Baron-Wiechec, A.; Gasparyan, Yu; Heinola, K.; Koivuranta, S.; Likonen, J.; Ruset, C.; de Saint-Aubin, G.; Widdowson, A.; Contributors, JET

2017-12-01

Erosion of plasma-facing materials and successive transport and redeposition of eroded material are crucial processes determining the lifetime of plasma-facing components and the trapped tritium inventory in redeposited material layers. Erosion and deposition in the JET divertor were studied during the second JET ITER-like wall campaign ILW-2 in 2013-2014 by using a poloidal row of specially prepared divertor marker tiles including the tungsten bulk tile 5. The marker tiles were analyzed using elastic backscattering with 3-4.5 MeV incident protons and nuclear reaction analysis using 0.8-4.5 MeV 3He ions before and after the campaign. The erosion/deposition pattern observed during ILW-2 is qualitatively comparable to the first campaign ILW-1 in 2011-2012: deposits consist mainly of beryllium with 5-20 at.% of carbon and oxygen and small amounts of Ni and W. The highest deposition with deposited layer thicknesses up to 30 μm per campaign is still observed on the upper and horizontal parts of the inner divertor. Outer divertor tiles 5, 6, 7 and 8 are net W erosion areas. The observed D inventory is roughly comparable to the inventory observed during ILW-1. The results obtained during ILW-2 therefore confirm the positive results observed in ILW-1 with respect to reduced material deposition and hydrogen isotopes retention in the divertor.

Iterated Stretching of Viscoelastic Jets

NASA Technical Reports Server (NTRS)

Chang, Hsueh-Chia; Demekhin, Evgeny A.; Kalaidin, Evgeny

1999-01-01

We examine, with asymptotic analysis and numerical simulation, the iterated stretching dynamics of FENE and Oldroyd-B jets of initial radius r(sub 0), shear viscosity nu, Weissenberg number We, retardation number S, and capillary number Ca. The usual Rayleigh instability stretches the local uniaxial extensional flow region near a minimum in jet radius into a primary filament of radius [Ca(1 - S)/ We](sup 1/2)r(sub 0) between two beads. The strain-rate within the filament remains constant while its radius (elastic stress) decreases (increases) exponentially in time with a long elastic relaxation time 3We(r(sup 2, sub 0)/nu). Instabilities convected from the bead relieve the tension at the necks during this slow elastic drainage and trigger a filament recoil. Secondary filaments then form at the necks from the resulting stretching. This iterated stretching is predicted to occur successively to generate high-generation filaments of radius r(sub n), (r(sub n)/r(sub 0)) = square root of 2[r(sub n-1)/r(sub 0)](sup 3/2) until finite-extensibility effects set in.

Pedestal evolution physics in low triangularity JET tokamak discharges with ITER-like wall

NASA Astrophysics Data System (ADS)

Bowman, C.; Dickinson, D.; Horvath, L.; Lunniss, A. E.; Wilson, H. R.; Cziegler, I.; Frassinetti, L.; Gibson, K.; Kirk, A.; Lipschultz, B.; Maggi, C. F.; Roach, C. M.; Saarelma, S.; Snyder, P. B.; Thornton, A.; Wynn, A.; Contributors, JET

2018-01-01

The pressure gradient of the high confinement pedestal region at the edge of tokamak plasmas rapidly collapses during plasma eruptions called edge localised modes (ELMs), and then re-builds over a longer time scale before the next ELM. The physics that controls the evolution of the JET pedestal between ELMs is analysed for 1.4 MA, 1.7 T, low triangularity, δ  =  0.2, discharges with the ITER-like wall, finding that the pressure gradient typically tracks the ideal magneto-hydrodynamic ballooning limit, consistent with a role for the kinetic ballooning mode. Furthermore, the pedestal width is often influenced by the region of plasma that has second stability access to the ballooning mode, which can explain its sometimes complex evolution between ELMs. A local gyrokinetic analysis of a second stable flux surface reveals stability to kinetic ballooning modes; global effects are expected to provide a destabilising mechanism and need to be retained in such second stable situations. As well as an electron-scale electron temperature gradient mode, ion scale instabilities associated with this flux surface include an electro-magnetic trapped electron branch and two electrostatic branches propagating in the ion direction, one with high radial wavenumber. In these second stability situations, the ELM is triggered by a peeling-ballooning mode; otherwise the pedestal is somewhat below the peeling-ballooning mode marginal stability boundary at ELM onset. In this latter situation, there is evidence that higher frequency ELMs are paced by an oscillation in the plasma, causing a crash in the pedestal before the peeling-ballooning boundary is reached. A model is proposed in which the oscillation is associated with hot plasma filaments that are pushed out towards the plasma edge by a ballooning mode, draining their free energy into the cooler plasma there, and then relaxing back to repeat the process. The results suggest that avoiding the oscillation and maximising the region

ICRH antenna S-matrix measurements and plasma coupling characterisation at JET

NASA Astrophysics Data System (ADS)

Monakhov, I.; Jacquet, P.; Blackman, T.; Bobkov, V.; Dumortier, P.; Helou, W.; Lerche, E.; Kirov, K.; Milanesio, D.; Maggiora, R.; Noble, C.; Contributors, JET

2018-04-01

The paper is dedicated to the characterisation of multi-strap ICRH antenna coupling to plasma. Relevance of traditional concept of coupling resistance to antennas with mutually coupled straps is revised and the importance of antenna port excitation consistency for application of the concept is highlighted. A method of antenna S-matrix measurement in presence of plasma is discussed allowing deeper insight into the problem of antenna-plasma coupling. The method is based entirely on the RF plant hardware and control facilities available at JET and it involves application of variable phasing between the antenna straps during the RF plant operations at  >100 kW. Unlike traditional techniques relying on low-power (~10 mW) network analysers, the applied antenna voltage amplitudes are relevant to practical conditions of ICRH operations; crucially, they are high enough to minimise possible effects of antenna loading non-linearity due to the RF sheath effects and other phenomena which could affect low-power measurements. The method has been successfully applied at JET to conventional 4-port ICRH antennas energised at frequencies of 33 MHz, 42 MHz and 51 MHz during L-mode plasma discharges while different gas injection modules (GIMs) were used to maintain comparable plasma densities during the pulses. The S-matrix assessment and its subsequent processing yielding ‘global’ antenna coupling resistances in conditions of equalised port maximum voltages allowed consistent description of antenna coupling to plasma at different strap phasing, operational frequencies and applied GIMs. Comprehensive experimental characterisation of mutually coupled antenna straps in presence of plasma also provided a unique opportunity for in-depth verification of TOPICA computer simulations.

Plasma-surface interaction in the Be/W environment: Conclusions drawn from the JET-ILW for ITER

NASA Astrophysics Data System (ADS)

Brezinsek, S.; JET-EFDA contributors

2015-08-01

The JET ITER-Like Wall experiment (JET-ILW) provides an ideal test bed to investigate plasma-surface interaction (PSI) and plasma operation with the ITER plasma-facing material selection employing beryllium in the main chamber and tungsten in the divertor. The main PSI processes: material erosion and migration, (b) fuel recycling and retention, (c) impurity concentration and radiation have be1en studied and compared between JET-C and JET-ILW. The current physics understanding of these key processes in the JET-ILW revealed that both interpretation of previously obtained carbon results (JET-C) and predictions to ITER need to be revisited. The impact of the first-wall material on the plasma was underestimated. Main observations are: (a) low primary erosion source in H-mode plasmas and reduction of the material migration from the main chamber to the divertor (factor 7) as well as within the divertor from plasma-facing to remote areas (factor 30 - 50). The energetic threshold for beryllium sputtering minimises the primary erosion source and inhibits multi-step re-erosion in the divertor. The physical sputtering yield of tungsten is low as 10-5 and determined by beryllium ions. (b) Reduction of the long-term fuel retention (factor 10 - 20) in JET-ILW with respect to JET-C. The remaining retention is caused by implantation and co-deposition with beryllium and residual impurities. Outgassing has gained importance and impacts on the recycling properties of beryllium and tungsten. (c) The low effective plasma charge (Zeff = 1.2) and low radiation capability of beryllium reveal the bare deuterium plasma physics. Moderate nitrogen seeding, reaching Zeff = 1.6 , restores in particular the confinement and the L-H threshold behaviour. ITER-compatible divertor conditions with stable semi-detachment were obtained owing to a higher density limit with ILW. Overall JET demonstrated successful plasma operation in the Be/W material combination and confirms its advantageous PSI behaviour

Real-time control of divertor detachment in H-mode with impurity seeding using Langmuir probe feedback in JET-ITER-like wall

NASA Astrophysics Data System (ADS)

Guillemaut, C.; Lennholm, M.; Harrison, J.; Carvalho, I.; Valcarcel, D.; Felton, R.; Griph, S.; Hogben, C.; Lucock, R.; Matthews, G. F.; Perez Von Thun, C.; Pitts, R. A.; Wiesen, S.; contributors, JET

2017-04-01

Burning plasmas with 500 MW of fusion power on ITER will rely on partially detached divertor operation to keep target heat loads at manageable levels. Such divertor regimes will be maintained by a real-time control system using the seeding of radiative impurities like nitrogen (N), neon or argon as actuator and one or more diagnostic signals as sensors. Recently, real-time control of divertor detachment has been successfully achieved in Type I ELMy H-mode JET-ITER-like wall discharges by using saturation current (I sat) measurements from divertor Langmuir probes as feedback signals to control the level of N seeding. The degree of divertor detachment is calculated in real-time by comparing the outer target peak I sat measurements to the peak I sat value at the roll-over in order to control the opening of the N injection valve. Real-time control of detachment has been achieved in both fixed and swept strike point experiments. The system has been progressively improved and can now automatically drive the divertor conditions from attached through high recycling and roll-over down to a user-defined level of detachment. Such a demonstration is a successful proof of principle in the context of future operation on ITER which will be extensively equipped with divertor target probes.

Analyses of microstructure, composition and retention of hydrogen isotopes in divertor tiles of JET with the ITER-like wall

NASA Astrophysics Data System (ADS)

Masuzaki, S.; Tokitani, M.; Otsuka, T.; Oya, Y.; Hatano, Y.; Miyamoto, M.; Sakamoto, R.; Ashikawa, N.; Sakurada, S.; Uemura, Y.; Azuma, K.; Yumizuru, K.; Oyaizu, M.; Suzuki, T.; Kurotaki, H.; Hamaguchi, D.; Isobe, K.; Asakura, N.; Widdowson, A.; Heinola, K.; Jachmich, S.; Rubel, M.; contributors, JET

2017-12-01

Results of the comprehensive surface analyses of divertor tiles and dusts retrieved from JET after the first ITER-like wall campaign (2011-2012) are presented. The samples cored from the divertor tiles were analyzed. Numerous nano-size bubble-like structures were observed in the deposition layer on the apron of the inner divertor tile, and a beryllium dust with the same structures were found in the matter collected from the inner divertor after the campaign. This suggests that the nano-size bubble-like structures can make the deposition layer to become brittle and may lead to cracking followed by dust generation. X-ray photoelectron spectroscopy analyses of chemical states of species in the deposition layers identified the formation of beryllium-tungsten intermetallic compounds on an inner vertical tile. Different tritium retention profiles along the divertor tiles were observed at the top surfaces and at deeper regions of the tiles by using the imaging plate technique.

Experimental validation of an analytical kinetic model for edge-localized modes in JET-ITER-like wall

NASA Astrophysics Data System (ADS)

Guillemaut, C.; Metzger, C.; Moulton, D.; Heinola, K.; O’Mullane, M.; Balboa, I.; Boom, J.; Matthews, G. F.; Silburn, S.; Solano, E. R.; contributors, JET

2018-06-01

The design and operation of future fusion devices relying on H-mode plasmas requires reliable modelling of edge-localized modes (ELMs) for precise prediction of divertor target conditions. An extensive experimental validation of simple analytical predictions of the time evolution of target plasma loads during ELMs has been carried out here in more than 70 JET-ITER-like wall H-mode experiments with a wide range of conditions. Comparisons of these analytical predictions with diagnostic measurements of target ion flux density, power density, impact energy and electron temperature during ELMs are presented in this paper and show excellent agreement. The analytical predictions tested here are made with the ‘free-streaming’ kinetic model (FSM) which describes ELMs as a quasi-neutral plasma bunch expanding along the magnetic field lines into the Scrape-Off Layer without collisions. Consequences of the FSM on energy reflection and deposition on divertor targets during ELMs are also discussed.

X-ray crystal spectrometer upgrade for ITER-like wall experiments at JETa)

NASA Astrophysics Data System (ADS)

Shumack, A. E.; Rzadkiewicz, J.; Chernyshova, M.; Jakubowska, K.; Scholz, M.; Byszuk, A.; Cieszewski, R.; Czarski, T.; Dominik, W.; Karpinski, L.; Kasprowicz, G.; Pozniak, K.; Wojenski, A.; Zabolotny, W.; Conway, N. J.; Dalley, S.; Figueiredo, J.; Nakano, T.; Tyrrell, S.; Zastrow, K.-D.; Zoita, V.

2014-11-01

The high resolution X-Ray crystal spectrometer at the JET tokamak has been upgraded with the main goal of measuring the tungsten impurity concentration. This is important for understanding impurity accumulation in the plasma after installation of the JET ITER-like wall (main chamber: Be, divertor: W). This contribution provides details of the upgraded spectrometer with a focus on the aspects important for spectral analysis and plasma parameter calculation. In particular, we describe the determination of the spectrometer sensitivity: important for impurity concentration determination.

Long-term evolution of the impurity composition and impurity events with the ITER-like wall at JET

NASA Astrophysics Data System (ADS)

Coenen, J. W.; Sertoli, M.; Brezinsek, S.; Coffey, I.; Dux, R.; Giroud, C.; Groth, M.; Huber, A.; Ivanova, D.; Krieger, K.; Lawson, K.; Marsen, S.; Meigs, A.; Neu, R.; Puetterich, T.; van Rooij, G. J.; Stamp, M. F.; Contributors, JET-EFDA

2013-07-01

This paper covers aspects of long-term evolution of intrinsic impurities in the JET tokamak with respect to the newly installed ITER-like wall (ILW). At first the changes related to the change over from the JET-C to the JET-ILW with beryllium (Be) as the main wall material and tungsten (W) in the divertor are discussed. The evolution of impurity fluxes in the newly installed W divertor with respect to studying material migration is described. In addition, a statistical analysis of transient impurity events causing significant plasma contamination and radiation losses is shown. The main findings comprise a drop in carbon content (×20) (see also Brezinsek et al (2013 J. Nucl. Mater. 438 S303)), low oxygen content (×10) due to the Be first wall (Douai et al 2013 J. Nucl. Mater. 438 S1172-6) as well as the evolution of the material mix in the divertor. Initially, a short period of repetitive ohmic plasmas was carried out to study material migration (Krieger et al 2013 J. Nucl. Mater. 438 S262). After the initial 1600 plasma seconds the material surface composition is, however, still evolving. With operational time, the levels of recycled C are increasing slightly by 20% while the Be levels in the deposition-dominated inner divertor are dropping, hinting at changes in the surface layer material mix made of Be, C and W. A steady number of transient impurity events, consisting of W and constituents of inconel, is observed despite the increase in variation in machine operation and changes in magnetic configuration as well as the auxiliary power increase.

Interaction of ICRF Fields with the Plasma Boundary in AUG and JET and Guidelines for Antenna Optimization

NASA Astrophysics Data System (ADS)

Bobkov, V.; Bilato, R.; Braun, F.; Colas, L.; Dux, R.; Van Eester, D.; Giannone, L.; Goniche, M.; Herrmann, A.; Jacquet, P.; Kallenbach, A.; Krivska, A.; Lerche, E.; Mayoral, M.-L.; Milanesio, D.; Monakhov, I.; Müller, H. W.; Neu, R.; Noterdaeme, J.-M.; Pütterich, Th.; Rohde, V.

2009-11-01

W sputtering during ICRF on ASDEX Upgrade (AUG) and temperature rise on JET A2 antenna septa are considered in connection with plasma conditions at the antenna plasma facing components and E‖ near-fields. Large antenna-plasma clearance, high gas puff and low light impurity content are favorable to reduce W sputtering in AUG. The spatial distribution of spectroscopically measured effective W sputtering yields clearly points to the existence of strong E‖ fields at the antenna box ("feeder fields") which dominate over the fields in front of the antenna straps. The picture of E‖ fields, obtained by HFSS code, corroborates the dominant role of E‖ at the antenna box on the formation of sheath-driving RF voltages for AUG. Large antenna-plasma clearance and low gas puff are favorable to reduce septum temperature of JET A2 antennas. Assuming a linear relation between the septum temperature and the sheath driving RF voltage calculated by HFSS, the changes of the temperature with dipole phasing (00ππ, 0ππ0 or 0π0π) are well described by the related changes of the RF voltages. Similarly to the AUG antenna, the strongest E‖ are found at the limiters of the JET A2 antenna for all used dipole phasings and at the septum for the phasings different from 0π0π. A simple general rule can be used to minimize E‖ at the antenna: image currents can be allowed only at the surfaces which do not intersect magnetic field lines at large angles of incidence. Possible antenna modifications generally rely either on a reduction of the image currents, on their short-circuiting by introducing additional conducting surfaces or on imposing the E‖ = 0 boundary condition. On the example of AUG antenna, possible options to minimize the sheath driving voltages are presented.

Optimization of Antenna Current Feeding for the Alfvén Eigenmodes Active Diagnostic System of JET

NASA Astrophysics Data System (ADS)

Albarracin Manrique, Marcos A.; Ruchko, L.; Pires, C. J. A.; Galvão, R. M. O.; Elfimov, A. G.

2018-04-01

The possibility of exploring proper phasing of the feeding currents in the existing antenna of the Alfvén Eigenmodes Active Diagnostic system of JET, to excite pure toroidal spectra of Toroidal Alfvén Eigenmodes, is numerically investigated. Special attention is given to the actual perturbed fields excited in the plasma, which are calculated self-consistently using the antenna version of the CASTOR code. It is found that due to the close spacing of the JET antenna modules and quasi degeneracy of modes with medium to high values of the toroidal mode number n, although a proper choice of the phasing of the feeding currents of the antenna modules indeed leads to an increase of the perturbed fields of the selected mode, modes with nearby values of n are also excited with large amplitudes, so that a scheme to proper select the detected modes remains necessary. A scheme using different antenna position distribution is proposed to achieve successful optimization.

Innovative diagnostics for ITER physics addressed in JET

NASA Astrophysics Data System (ADS)

Murari, A.; Edlington, T.; Alfier, A.; Alonso, A.; Andrew, Y.; Arnoux, G.; Beurskens, M.; Coad, P.; Crombe, C.; Gauthier, E.; Giroud, C.; Hidalgo, C.; Hong, S.; Kempenaars, M.; Kiptily, V.; Loarer, T.; Meigs, A.; Pasqualotto, R.; Tala, T.; Contributors, JET-EFDA

2008-12-01

In recent years, JET diagnostic capability has been significantly improved to widen the range of physical phenomena that can be studied and thus contribute to the understanding of some ITER relevant issues. The most significant results reported in this paper refer to the plasma wall interactions, the interplay between core and edge physics and fast particles. A synergy between new infrared cameras, visible cameras and spectroscopy diagnostics has allowed investigating a series of new aspects of the plasma wall interactions. The power loads on the plasma facing components of JET main chambers have been assessed at steady state and during transient events like ELMs and disruptions. Evidence of filaments in the edge region of the plasma has been collected with a new fast visible camera and high resolution Thomson scattering. The physics of detached plasmas and some new aspects of dust formation have also been devoted particular attention. The influence of the edge plasma on the core has been investigated with upgraded active spectroscopy, providing new information on momentum transport and the effects of impurity injection on ELMs and ITBs and their interdependence. Given the fact that JET is the only machine with a plasma volume big enough to confine the alphas, a coherent programme of diagnostic developments for the energetic particles has been undertaken. With upgraded γ-ray spectroscopy and a new scintillator probe, it is now possible to study both the redistribution and the losses of the fast particles in various plasma conditions.

Long-term fuel retention and release in JET ITER-Like Wall at ITER-relevant baking temperatures

NASA Astrophysics Data System (ADS)

Heinola, K.; Likonen, J.; Ahlgren, T.; Brezinsek, S.; De Temmerman, G.; Jepu, I.; Matthews, G. F.; Pitts, R. A.; Widdowson, A.; Contributors, JET

2017-08-01

The fuel outgassing efficiency from plasma-facing components exposed in JET-ILW has been studied at ITER-relevant baking temperatures. Samples retrieved from the W divertor and Be main chamber were annealed at 350 and 240 °C, respectively. Annealing was performed with thermal desoprtion spectrometry (TDS) for 0, 5 and 15 h to study the deuterium removal effectiveness at the nominal baking temperatures. The remained fraction was determined by emptying the samples fully of deuterium by heating W and Be samples up to 1000 and 775 °C,respectively. Results showed the deposits in the divertor having an increasing effect to the remaining retention at temperatures above baking. Highest remaining fractions 54 and 87 % were observed with deposit thicknesses of 10 and 40 μm, respectively. Substantially high fractions were obtained in the main chamber samples from the deposit-free erosion zone of the limiter midplane, in which the dominant fuel retention mechanism is via implantation: 15 h annealing resulted in retained deuterium higher than 90 % . TDS results from the divertor were simulated with TMAP7 calculations. The spectra were modelled with three deuterium activation energies resulting in good agreement with the experiments.

Carbon charge exchange analysis in the ITER-like wall environment.

PubMed

Menmuir, S; Giroud, C; Biewer, T M; Coffey, I H; Delabie, E; Hawkes, N C; Sertoli, M

2014-11-01

Charge exchange spectroscopy has long been a key diagnostic tool for fusion plasmas and is well developed in devices with Carbon Plasma-Facing Components. Operation with the ITER-like wall at JET has resulted in changes to the spectrum in the region of the Carbon charge exchange line at 529.06 nm and demonstrates the need to revise the core charge exchange analysis for this line. An investigation has been made of this spectral region in different plasma conditions and the revised description of the spectral lines to be included in the analysis is presented.

Fractal Based Triple Band High Gain Monopole Antenna

NASA Astrophysics Data System (ADS)

Pandey, Shashi Kant; Pandey, Ganga Prasad; Sarun, P. M.

2017-10-01

A novel triple-band microstrip fed planar monopole antenna is proposed and investigated. A fractal antenna is created by iterating a narrow pulse (NP) generator model at upper side of modified ground plane, which has a rhombic patch, for enhancing the bandwidth and gain. Three iterations are carried out to study the effects of fractal geometry on the antenna performance. The proposed antenna can operate over three frequency ranges viz, 3.34-4.8 GHz, 5.5-10.6 GHz and 13-14.96 GHz suitable for WLAN 5.2/5.8 GHz, WiMAX 3.5/5.5 GHz and X band applications respectively. Simulated and measured results are in good agreements with each others. Results show that antenna provides wide/ultra wide bandwidths, monopole like radiation patterns and very high antenna gains over the operating frequency bands.

Experience on divertor fuel retention after two ITER-Like Wall campaigns

NASA Astrophysics Data System (ADS)

Heinola, K.; Widdowson, A.; Likonen, J.; Ahlgren, T.; Alves, E.; Ayres, C. F.; Baron-Wiechec, A.; Barradas, N.; Brezinsek, S.; Catarino, N.; Coad, P.; Guillemaut, C.; Jepu, I.; Krat, S.; Lahtinen, A.; Matthews, G. F.; Mayer, M.; Contributors, JET

2017-12-01

The JET ITER-Like Wall experiment, with its all-metal plasma-facing components, provides a unique environment for plasma and plasma-wall interaction studies. These studies are of great importance in understanding the underlying phenomena taking place during the operation of a future fusion reactor. Present work summarizes and reports the plasma fuel retention in the divertor resulting from the two first experimental campaigns with the ITER-Like Wall. The deposition pattern in the divertor after the second campaign shows same trend as was observed after the first campaign: highest deposition of 10-15 μm was found on the top part of the inner divertor. Due to the change in plasma magnetic configurations from the first to the second campaign, and the resulted strike point locations, an increase of deposition was observed on the base of the divertor. The deuterium retention was found to be affected by the hydrogen plasma experiments done at the end of second experimental campaign.

Overview of the JET results in support to ITER

NASA Astrophysics Data System (ADS)

Litaudon, X.; Abduallev, S.; Abhangi, M.; Abreu, P.; Afzal, M.; Aggarwal, K. M.; Ahlgren, T.; Ahn, J. H.; Aho-Mantila, L.; Aiba, N.; Airila, M.; Albanese, R.; Aldred, V.; Alegre, D.; Alessi, E.; Aleynikov, P.; Alfier, A.; Alkseev, A.; Allinson, M.; Alper, B.; Alves, E.; Ambrosino, G.; Ambrosino, R.; Amicucci, L.; Amosov, V.; Andersson Sundén, E.; Angelone, M.; Anghel, M.; Angioni, C.; Appel, L.; Appelbee, C.; Arena, P.; Ariola, M.; Arnichand, H.; Arshad, S.; Ash, A.; Ashikawa, N.; Aslanyan, V.; Asunta, O.; Auriemma, F.; Austin, Y.; Avotina, L.; Axton, M. D.; Ayres, C.; Bacharis, M.; Baciero, A.; Baião, D.; Bailey, S.; Baker, A.; Balboa, I.; Balden, M.; Balshaw, N.; Bament, R.; Banks, J. W.; Baranov, Y. F.; Barnard, M. A.; Barnes, D.; Barnes, M.; Barnsley, R.; Baron Wiechec, A.; Barrera Orte, L.; Baruzzo, M.; Basiuk, V.; Bassan, M.; Bastow, R.; Batista, A.; Batistoni, P.; Baughan, R.; Bauvir, B.; Baylor, L.; Bazylev, B.; Beal, J.; Beaumont, P. S.; Beckers, M.; Beckett, B.; Becoulet, A.; Bekris, N.; Beldishevski, M.; Bell, K.; Belli, F.; Bellinger, M.; Belonohy, É.; Ben Ayed, N.; Benterman, N. A.; Bergsåker, H.; Bernardo, J.; Bernert, M.; Berry, M.; Bertalot, L.; Besliu, C.; Beurskens, M.; Bieg, B.; Bielecki, J.; Biewer, T.; Bigi, M.; Bílková, P.; Binda, F.; Bisoffi, A.; Bizarro, J. P. S.; Björkas, C.; Blackburn, J.; Blackman, K.; Blackman, T. R.; Blanchard, P.; Blatchford, P.; Bobkov, V.; Boboc, A.; Bodnár, G.; Bogar, O.; Bolshakova, I.; Bolzonella, T.; Bonanomi, N.; Bonelli, F.; Boom, J.; Booth, J.; Borba, D.; Borodin, D.; Borodkina, I.; Botrugno, A.; Bottereau, C.; Boulting, P.; Bourdelle, C.; Bowden, M.; Bower, C.; Bowman, C.; Boyce, T.; Boyd, C.; Boyer, H. J.; Bradshaw, J. M. A.; Braic, V.; Bravanec, R.; Breizman, B.; Bremond, S.; Brennan, P. D.; Breton, S.; Brett, A.; Brezinsek, S.; Bright, M. D. J.; Brix, M.; Broeckx, W.; Brombin, M.; Brosławski, A.; Brown, D. P. D.; Brown, M.; Bruno, E.; Bucalossi, J.; Buch, J.; Buchanan, J.; Buckley, M. A.; Budny, R.; Bufferand, H.; Bulman, M.; Bulmer, N.; Bunting, P.; Buratti, P.; Burckhart, A.; Buscarino, A.; Busse, A.; Butler, N. K.; Bykov, I.; Byrne, J.; Cahyna, P.; Calabrò, G.; Calvo, I.; Camenen, Y.; Camp, P.; Campling, D. C.; Cane, J.; Cannas, B.; Capel, A. J.; Card, P. J.; Cardinali, A.; Carman, P.; Carr, M.; Carralero, D.; Carraro, L.; Carvalho, B. B.; Carvalho, I.; Carvalho, P.; Casson, F. J.; Castaldo, C.; Catarino, N.; Caumont, J.; Causa, F.; Cavazzana, R.; Cave-Ayland, K.; Cavinato, M.; Cecconello, M.; Ceccuzzi, S.; Cecil, E.; Cenedese, A.; Cesario, R.; Challis, C. D.; Chandler, M.; Chandra, D.; Chang, C. S.; Chankin, A.; Chapman, I. T.; Chapman, S. C.; Chernyshova, M.; Chitarin, G.; Ciraolo, G.; Ciric, D.; Citrin, J.; Clairet, F.; Clark, E.; Clark, M.; Clarkson, R.; Clatworthy, D.; Clements, C.; Cleverly, M.; Coad, J. P.; Coates, P. A.; Cobalt, A.; Coccorese, V.; Cocilovo, V.; Coda, S.; Coelho, R.; Coenen, J. W.; Coffey, I.; Colas, L.; Collins, S.; Conka, D.; Conroy, S.; Conway, N.; Coombs, D.; Cooper, D.; Cooper, S. R.; Corradino, C.; Corre, Y.; Corrigan, G.; Cortes, S.; Coster, D.; Couchman, A. S.; Cox, M. P.; Craciunescu, T.; Cramp, S.; Craven, R.; Crisanti, F.; Croci, G.; Croft, D.; Crombé, K.; Crowe, R.; Cruz, N.; Cseh, G.; Cufar, A.; Cullen, A.; Curuia, M.; Czarnecka, A.; Dabirikhah, H.; Dalgliesh, P.; Dalley, S.; Dankowski, J.; Darrow, D.; Davies, O.; Davis, W.; Day, C.; Day, I. E.; De Bock, M.; de Castro, A.; de la Cal, E.; de la Luna, E.; De Masi, G.; de Pablos, J. L.; De Temmerman, G.; De Tommasi, G.; de Vries, P.; Deakin, K.; Deane, J.; Degli Agostini, F.; Dejarnac, R.; Delabie, E.; den Harder, N.; Dendy, R. O.; Denis, J.; Denner, P.; Devaux, S.; Devynck, P.; Di Maio, F.; Di Siena, A.; Di Troia, C.; Dinca, P.; D'Inca, R.; Ding, B.; Dittmar, T.; Doerk, H.; Doerner, R. P.; Donné, T.; Dorling, S. E.; Dormido-Canto, S.; Doswon, S.; Douai, D.; Doyle, P. T.; Drenik, A.; Drewelow, P.; Drews, P.; Duckworth, Ph.; Dumont, R.; Dumortier, P.; Dunai, D.; Dunne, M.; Ďuran, I.; Durodié, F.; Dutta, P.; Duval, B. P.; Dux, R.; Dylst, K.; Dzysiuk, N.; Edappala, P. V.; Edmond, J.; Edwards, A. M.; Edwards, J.; Eich, Th.; Ekedahl, A.; El-Jorf, R.; Elsmore, C. G.; Enachescu, M.; Ericsson, G.; Eriksson, F.; Eriksson, J.; Eriksson, L. G.; Esposito, B.; Esquembri, S.; Esser, H. G.; Esteve, D.; Evans, B.; Evans, G. E.; Evison, G.; Ewart, G. D.; Fagan, D.; Faitsch, M.; Falie, D.; Fanni, A.; Fasoli, A.; Faustin, J. M.; Fawlk, N.; Fazendeiro, L.; Fedorczak, N.; Felton, R. C.; Fenton, K.; Fernades, A.; Fernandes, H.; Ferreira, J.; Fessey, J. A.; Février, O.; Ficker, O.; Field, A.; Fietz, S.; Figueiredo, A.; Figueiredo, J.; Fil, A.; Finburg, P.; Firdaouss, M.; Fischer, U.; Fittill, L.; Fitzgerald, M.; Flammini, D.; Flanagan, J.; Fleming, C.; Flinders, K.; Fonnesu, N.; Fontdecaba, J. M.; Formisano, A.; Forsythe, L.; Fortuna, L.; Fortuna-Zalesna, E.; Fortune, M.; Foster, S.; Franke, T.; Franklin, T.; Frasca, M.; Frassinetti, L.; Freisinger, M.; Fresa, R.; Frigione, D.; Fuchs, V.; Fuller, D.; Futatani, S.; Fyvie, J.; Gál, K.; Galassi, D.; Gałązka, K.; Galdon-Quiroga, J.; Gallagher, J.; Gallart, D.; Galvão, R.; Gao, X.; Gao, Y.; Garcia, J.; Garcia-Carrasco, A.; García-Muñoz, M.; Gardarein, J.-L.; Garzotti, L.; Gaudio, P.; Gauthier, E.; Gear, D. F.; Gee, S. J.; Geiger, B.; Gelfusa, M.; Gerasimov, S.; Gervasini, G.; Gethins, M.; Ghani, Z.; Ghate, M.; Gherendi, M.; Giacalone, J. C.; Giacomelli, L.; Gibson, C. S.; Giegerich, T.; Gil, C.; Gil, L.; Gilligan, S.; Gin, D.; Giovannozzi, E.; Girardo, J. B.; Giroud, C.; Giruzzi, G.; Glöggler, S.; Godwin, J.; Goff, J.; Gohil, P.; Goloborod'ko, V.; Gomes, R.; Gonçalves, B.; Goniche, M.; Goodliffe, M.; Goodyear, A.; Gorini, G.; Gosk, M.; Goulding, R.; Goussarov, A.; Gowland, R.; Graham, B.; Graham, M. E.; Graves, J. P.; Grazier, N.; Grazier, P.; Green, N. R.; Greuner, H.; Grierson, B.; Griph, F. S.; Grisolia, C.; Grist, D.; Groth, M.; Grove, R.; Grundy, C. N.; Grzonka, J.; Guard, D.; Guérard, C.; Guillemaut, C.; Guirlet, R.; Gurl, C.; Utoh, H. H.; Hackett, L. J.; Hacquin, S.; Hagar, A.; Hager, R.; Hakola, A.; Halitovs, M.; Hall, S. J.; Hallworth Cook, S. P.; Hamlyn-Harris, C.; Hammond, K.; Harrington, C.; Harrison, J.; Harting, D.; Hasenbeck, F.; Hatano, Y.; Hatch, D. R.; Haupt, T. D. V.; Hawes, J.; Hawkes, N. C.; Hawkins, J.; Hawkins, P.; Haydon, P. W.; Hayter, N.; Hazel, S.; Heesterman, P. J. L.; Heinola, K.; Hellesen, C.; Hellsten, T.; Helou, W.; Hemming, O. N.; Hender, T. C.; Henderson, M.; Henderson, S. S.; Henriques, R.; Hepple, D.; Hermon, G.; Hertout, P.; Hidalgo, C.; Highcock, E. G.; Hill, M.; Hillairet, J.; Hillesheim, J.; Hillis, D.; Hizanidis, K.; Hjalmarsson, A.; Hobirk, J.; Hodille, E.; Hogben, C. H. A.; Hogeweij, G. M. D.; Hollingsworth, A.; Hollis, S.; Homfray, D. A.; Horáček, J.; Hornung, G.; Horton, A. R.; Horton, L. D.; Horvath, L.; Hotchin, S. P.; Hough, M. R.; Howarth, P. J.; Hubbard, A.; Huber, A.; Huber, V.; Huddleston, T. M.; Hughes, M.; Huijsmans, G. T. A.; Hunter, C. L.; Huynh, P.; Hynes, A. M.; Iglesias, D.; Imazawa, N.; Imbeaux, F.; Imríšek, M.; Incelli, M.; Innocente, P.; Irishkin, M.; Ivanova-Stanik, I.; Jachmich, S.; Jacobsen, A. S.; Jacquet, P.; Jansons, J.; Jardin, A.; Järvinen, A.; Jaulmes, F.; Jednoróg, S.; Jenkins, I.; Jeong, C.; Jepu, I.; Joffrin, E.; Johnson, R.; Johnson, T.; Johnston, Jane; Joita, L.; Jones, G.; Jones, T. T. C.; Hoshino, K. K.; Kallenbach, A.; Kamiya, K.; Kaniewski, J.; Kantor, A.; Kappatou, A.; Karhunen, J.; Karkinsky, D.; Karnowska, I.; Kaufman, M.; Kaveney, G.; Kazakov, Y.; Kazantzidis, V.; Keeling, D. L.; Keenan, T.; Keep, J.; Kempenaars, M.; Kennedy, C.; Kenny, D.; Kent, J.; Kent, O. N.; Khilkevich, E.; Kim, H. T.; Kim, H. S.; Kinch, A.; king, C.; King, D.; King, R. F.; Kinna, D. J.; Kiptily, V.; Kirk, A.; Kirov, K.; Kirschner, A.; Kizane, G.; Klepper, C.; Klix, A.; Knight, P.; Knipe, S. J.; Knott, S.; Kobuchi, T.; Köchl, F.; Kocsis, G.; Kodeli, I.; Kogan, L.; Kogut, D.; Koivuranta, S.; Kominis, Y.; Köppen, M.; Kos, B.; Koskela, T.; Koslowski, H. R.; Koubiti, M.; Kovari, M.; Kowalska-Strzęciwilk, E.; Krasilnikov, A.; Krasilnikov, V.; Krawczyk, N.; Kresina, M.; Krieger, K.; Krivska, A.; Kruezi, U.; Książek, I.; Kukushkin, A.; Kundu, A.; Kurki-Suonio, T.; Kwak, S.; Kwiatkowski, R.; Kwon, O. J.; Laguardia, L.; Lahtinen, A.; Laing, A.; Lam, N.; Lambertz, H. T.; Lane, C.; Lang, P. T.; Lanthaler, S.; Lapins, J.; Lasa, A.; Last, J. R.; Łaszyńska, E.; Lawless, R.; Lawson, A.; Lawson, K. D.; Lazaros, A.; Lazzaro, E.; Leddy, J.; Lee, S.; Lefebvre, X.; Leggate, H. J.; Lehmann, J.; Lehnen, M.; Leichtle, D.; Leichuer, P.; Leipold, F.; Lengar, I.; Lennholm, M.; Lerche, E.; Lescinskis, A.; Lesnoj, S.; Letellier, E.; Leyland, M.; Leysen, W.; Li, L.; Liang, Y.; Likonen, J.; Linke, J.; Linsmeier, Ch.; Lipschultz, B.; Liu, G.; Liu, Y.; Lo Schiavo, V. P.; Loarer, T.; Loarte, A.; Lobel, R. C.; Lomanowski, B.; Lomas, P. J.; Lönnroth, J.; López, J. M.; López-Razola, J.; Lorenzini, R.; Losada, U.; Lovell, J. J.; Loving, A. B.; Lowry, C.; Luce, T.; Lucock, R. M. A.; Lukin, A.; Luna, C.; Lungaroni, M.; Lungu, C. P.; Lungu, M.; Lunniss, A.; Lupelli, I.; Lyssoivan, A.; Macdonald, N.; Macheta, P.; Maczewa, K.; Magesh, B.; Maget, P.; Maggi, C.; Maier, H.; Mailloux, J.; Makkonen, T.; Makwana, R.; Malaquias, A.; Malizia, A.; Manas, P.; Manning, A.; Manso, M. E.; Mantica, P.; Mantsinen, M.; Manzanares, A.; Maquet, Ph.; Marandet, Y.; Marcenko, N.; Marchetto, C.; Marchuk, O.; Marinelli, M.; Marinucci, M.; Markovič, T.; Marocco, D.; Marot, L.; Marren, C. A.; Marshal, R.; Martin, A.; Martin, Y.; Martín de Aguilera, A.; Martínez, F. J.; Martín-Solís, J. R.; Martynova, Y.; Maruyama, S.; Masiello, A.; Maslov, M.; Matejcik, S.; Mattei, M.; Matthews, G. F.; Maviglia, F.; Mayer, M.; Mayoral, M. L.; May-Smith, T.; Mazon, D.; Mazzotta, C.; McAdams, R.; McCarthy, P. J.; McClements, K. G.; McCormack, O.; McCullen, P. A.; McDonald, D.; McIntosh, S.; McKean, R.; McKehon, J.; Meadows, R. C.; Meakins, A.; Medina, F.; Medland, M.; Medley, S.; Meigh, S.; Meigs, A. G.; Meisl, G.; Meitner, S.; Meneses, L.; Menmuir, S.; Mergia, K.; Merrigan, I. R.; Mertens, Ph.; Meshchaninov, S.; Messiaen, A.; Meyer, H.; Mianowski, S.; Michling, R.; Middleton-Gear, D.; Miettunen, J.; Militello, F.; Militello-Asp, E.; Miloshevsky, G.; Mink, F.; Minucci, S.; Miyoshi, Y.; Mlynář, J.; Molina, D.; Monakhov, I.; Moneti, M.; Mooney, R.; Moradi, S.; Mordijck, S.; Moreira, L.; Moreno, R.; Moro, F.; Morris, A. W.; Morris, J.; Moser, L.; Mosher, S.; Moulton, D.; Murari, A.; Muraro, A.; Murphy, S.; Asakura, N. N.; Na, Y. S.; Nabais, F.; Naish, R.; Nakano, T.; Nardon, E.; Naulin, V.; Nave, M. F. F.; Nedzelski, I.; Nemtsev, G.; Nespoli, F.; Neto, A.; Neu, R.; Neverov, V. S.; Newman, M.; Nicholls, K. J.; Nicolas, T.; Nielsen, A. H.; Nielsen, P.; Nilsson, E.; Nishijima, D.; Noble, C.; Nocente, M.; Nodwell, D.; Nordlund, K.; Nordman, H.; Nouailletas, R.; Nunes, I.; Oberkofler, M.; Odupitan, T.; Ogawa, M. T.; O'Gorman, T.; Okabayashi, M.; Olney, R.; Omolayo, O.; O'Mullane, M.; Ongena, J.; Orsitto, F.; Orszagh, J.; Oswuigwe, B. I.; Otin, R.; Owen, A.; Paccagnella, R.; Pace, N.; Pacella, D.; Packer, L. W.; Page, A.; Pajuste, E.; Palazzo, S.; Pamela, S.; Panja, S.; Papp, P.; Paprok, R.; Parail, V.; Park, M.; Parra Diaz, F.; Parsons, M.; Pasqualotto, R.; Patel, A.; Pathak, S.; Paton, D.; Patten, H.; Pau, A.; Pawelec, E.; Soldan, C. Paz; Peackoc, A.; Pearson, I. J.; Pehkonen, S.-P.; Peluso, E.; Penot, C.; Pereira, A.; Pereira, R.; Pereira Puglia, P. P.; Perez von Thun, C.; Peruzzo, S.; Peschanyi, S.; Peterka, M.; Petersson, P.; Petravich, G.; Petre, A.; Petrella, N.; Petržilka, V.; Peysson, Y.; Pfefferlé, D.; Philipps, V.; Pillon, M.; Pintsuk, G.; Piovesan, P.; Pires dos Reis, A.; Piron, L.; Pironti, A.; Pisano, F.; Pitts, R.; Pizzo, F.; Plyusnin, V.; Pomaro, N.; Pompilian, O. G.; Pool, P. J.; Popovichev, S.; Porfiri, M. T.; Porosnicu, C.; Porton, M.; Possnert, G.; Potzel, S.; Powell, T.; Pozzi, J.; Prajapati, V.; Prakash, R.; Prestopino, G.; Price, D.; Price, M.; Price, R.; Prior, P.; Proudfoot, R.; Pucella, G.; Puglia, P.; Puiatti, M. E.; Pulley, D.; Purahoo, K.; Pütterich, Th.; Rachlew, E.; Rack, M.; Ragona, R.; Rainford, M. S. J.; Rakha, A.; Ramogida, G.; Ranjan, S.; Rapson, C. J.; Rasmussen, J. J.; Rathod, K.; Rattá, G.; Ratynskaia, S.; Ravera, G.; Rayner, C.; Rebai, M.; Reece, D.; Reed, A.; Réfy, D.; Regan, B.; Regaña, J.; Reich, M.; Reid, N.; Reimold, F.; Reinhart, M.; Reinke, M.; Reiser, D.; Rendell, D.; Reux, C.; Reyes Cortes, S. D. A.; Reynolds, S.; Riccardo, V.; Richardson, N.; Riddle, K.; Rigamonti, D.; Rimini, F. G.; Risner, J.; Riva, M.; Roach, C.; Robins, R. J.; Robinson, S. A.; Robinson, T.; Robson, D. W.; Roccella, R.; Rodionov, R.; Rodrigues, P.; Rodriguez, J.; Rohde, V.; Romanelli, F.; Romanelli, M.; Romanelli, S.; Romazanov, J.; Rowe, S.; Rubel, M.; Rubinacci, G.; Rubino, G.; Ruchko, L.; Ruiz, M.; Ruset, C.; Rzadkiewicz, J.; Saarelma, S.; Sabot, R.; Safi, E.; Sagar, P.; Saibene, G.; Saint-Laurent, F.; Salewski, M.; Salmi, A.; Salmon, R.; Salzedas, F.; Samaddar, D.; Samm, U.; Sandiford, D.; Santa, P.; Santala, M. I. K.; Santos, B.; Santucci, A.; Sartori, F.; Sartori, R.; Sauter, O.; Scannell, R.; Schlummer, T.; Schmid, K.; Schmidt, V.; Schmuck, S.; Schneider, M.; Schöpf, K.; Schwörer, D.; Scott, S. D.; Sergienko, G.; Sertoli, M.; Shabbir, A.; Sharapov, S. E.; Shaw, A.; Shaw, R.; Sheikh, H.; Shepherd, A.; Shevelev, A.; Shumack, A.; Sias, G.; Sibbald, M.; Sieglin, B.; Silburn, S.; Silva, A.; Silva, C.; Simmons, P. A.; Simpson, J.; Simpson-Hutchinson, J.; Sinha, A.; Sipilä, S. K.; Sips, A. C. C.; Sirén, P.; Sirinelli, A.; Sjöstrand, H.; Skiba, M.; Skilton, R.; Slabkowska, K.; Slade, B.; Smith, N.; Smith, P. G.; Smith, R.; Smith, T. J.; Smithies, M.; Snoj, L.; Soare, S.; Solano, E. R.; Somers, A.; Sommariva, C.; Sonato, P.; Sopplesa, A.; Sousa, J.; Sozzi, C.; Spagnolo, S.; Spelzini, T.; Spineanu, F.; Stables, G.; Stamatelatos, I.; Stamp, M. F.; Staniec, P.; Stankūnas, G.; Stan-Sion, C.; Stead, M. J.; Stefanikova, E.; Stepanov, I.; Stephen, A. V.; Stephen, M.; Stevens, A.; Stevens, B. D.; Strachan, J.; Strand, P.; Strauss, H. R.; Ström, P.; Stubbs, G.; Studholme, W.; Subba, F.; Summers, H. P.; Svensson, J.; Świderski, Ł.; Szabolics, T.; Szawlowski, M.; Szepesi, G.; Suzuki, T. T.; Tál, B.; Tala, T.; Talbot, A. R.; Talebzadeh, S.; Taliercio, C.; Tamain, P.; Tame, C.; Tang, W.; Tardocchi, M.; Taroni, L.; Taylor, D.; Taylor, K. A.; Tegnered, D.; Telesca, G.; Teplova, N.; Terranova, D.; Testa, D.; Tholerus, E.; Thomas, J.; Thomas, J. D.; Thomas, P.; Thompson, A.; Thompson, C.-A.; Thompson, V. K.; Thorne, L.; Thornton, A.; Thrysøe, A. S.; Tigwell, P. A.; Tipton, N.; Tiseanu, I.; Tojo, H.; Tokitani, M.; Tolias, P.; Tomeš, M.; Tonner, P.; Towndrow, M.; Trimble, P.; Tripsky, M.; Tsalas, M.; Tsavalas, P.; Tskhakaya jun, D.; Turner, I.; Turner, M. M.; Turnyanskiy, M.; Tvalashvili, G.; Tyrrell, S. G. J.; Uccello, A.; Ul-Abidin, Z.; Uljanovs, J.; Ulyatt, D.; Urano, H.; Uytdenhouwen, I.; Vadgama, A. P.; Valcarcel, D.; Valentinuzzi, M.; Valisa, M.; Vallejos Olivares, P.; Valovic, M.; Van De Mortel, M.; Van Eester, D.; Van Renterghem, W.; van Rooij, G. J.; Varje, J.; Varoutis, S.; Vartanian, S.; Vasava, K.; Vasilopoulou, T.; Vega, J.; Verdoolaege, G.; Verhoeven, R.; Verona, C.; Verona Rinati, G.; Veshchev, E.; Vianello, N.; Vicente, J.; Viezzer, E.; Villari, S.; Villone, F.; Vincenzi, P.; Vinyar, I.; Viola, B.; Vitins, A.; Vizvary, Z.; Vlad, M.; Voitsekhovitch, I.; Vondráček, P.; Vora, N.; Vu, T.; Pires de Sa, W. W.; Wakeling, B.; Waldon, C. W. F.; Walkden, N.; Walker, M.; Walker, R.; Walsh, M.; Wang, E.; Wang, N.; Warder, S.; Warren, R. J.; Waterhouse, J.; Watkins, N. W.; Watts, C.; Wauters, T.; Weckmann, A.; Weiland, J.; Weisen, H.; Weiszflog, M.; Wellstood, C.; West, A. T.; Wheatley, M. R.; Whetham, S.; Whitehead, A. M.; Whitehead, B. D.; Widdowson, A. M.; Wiesen, S.; Wilkinson, J.; Williams, J.; Williams, M.; Wilson, A. R.; Wilson, D. J.; Wilson, H. R.; Wilson, J.; Wischmeier, M.; Withenshaw, G.; Withycombe, A.; Witts, D. M.; Wood, D.; Wood, R.; Woodley, C.; Wray, S.; Wright, J.; Wright, J. C.; Wu, J.; Wukitch, S.; Wynn, A.; Xu, T.; Yadikin, D.; Yanling, W.; Yao, L.; Yavorskij, V.; Yoo, M. G.; Young, C.; Young, D.; Young, I. D.; Young, R.; Zacks, J.; Zagorski, R.; Zaitsev, F. S.; Zanino, R.; Zarins, A.; Zastrow, K. D.; Zerbini, M.; Zhang, W.; Zhou, Y.; Zilli, E.; Zoita, V.; Zoletnik, S.; Zychor, I.; JET Contributors

2017-10-01

The 2014-2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L-H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H  =  1 at β N ~ 1.8 and n/n GW ~ 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D-T campaign and 14 MeV neutron calibration strategy are reviewed.

Overview of the JET results in support to ITER

DOE PAGES

Litaudon, X.; Abduallev, S.; Abhangi, M.; ...

2017-06-15

Here, the 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L–H power threshold in Deuterium and Hydrogen are given, stressing themore » importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H = 1 at β N ~ 1.8 and n/n GW ~ 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D–T campaign and 14 MeV neutron calibration strategy are reviewed.« less

Overview of the JET results in support to ITER

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

Litaudon, X.; Abduallev, S.; Abhangi, M.

Here, the 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L–H power threshold in Deuterium and Hydrogen are given, stressing themore » importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H = 1 at β N ~ 1.8 and n/n GW ~ 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D–T campaign and 14 MeV neutron calibration strategy are reviewed.« less

Comparison of JET AVDE disruption data with M3D simulations and implications for ITER

DOE PAGES

Strauss, H.; Joffrin, E.; Riccardo, V.; ...

2017-10-02

Nonlinear 3D MHD asymmetric vertical displacement disruption simulations have been performed using JET equilibrium reconstruction initial data. There were several experimentally measured quantities compared with the simulation. These include vertical displacement, halo current, toroidal current asymmetry, and toroidal rotation. The experimental data and the simulations are in reasonable agreement. Also compared was the correlation of the toroidal current asymmetry and the vertical displacement asymmetry. The Noll relation between asymmetric wall force and vertical current moment is verified in the simulations. Also verified is the toroidal flux asymmetry. Though, JET is a good predictor of ITER disruption behavior, JET and ITERmore » can be in different parameter regimes, and extrapolating from JET data can overestimate the ITER wall force.« less

Comparison of JET AVDE disruption data with M3D simulations and implications for ITER

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

Strauss, H.; Joffrin, E.; Riccardo, V.

Nonlinear 3D MHD asymmetric vertical displacement disruption simulations have been performed using JET equilibrium reconstruction initial data. There were several experimentally measured quantities compared with the simulation. These include vertical displacement, halo current, toroidal current asymmetry, and toroidal rotation. The experimental data and the simulations are in reasonable agreement. Also compared was the correlation of the toroidal current asymmetry and the vertical displacement asymmetry. The Noll relation between asymmetric wall force and vertical current moment is verified in the simulations. Also verified is the toroidal flux asymmetry. Though, JET is a good predictor of ITER disruption behavior, JET and ITERmore » can be in different parameter regimes, and extrapolating from JET data can overestimate the ITER wall force.« less

First tritium operation of ITER-prototype VUV spectroscopy on JET

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

Coffey, I.H.; Barnsley, R.

Results from tritium operation of the VUV survey spectrometer on the JET tokamak are presented. The instrument, located outside the biological shield and offset from a direct plasma 1-o-s for maximum radiation protection, was operational during the trace tritium campaign (TTE) at JET. No discernible increase in detector background noise levels were detected for total neutron rates of up to 1x10{sup 17}/s, demonstrating the shielding effectiveness of the configuration. Some tritium retention in the detector microchannel plate was measurable, but has not hampered subsequent operations. As a reference the unshielded detector of a close-coupled XUV instrument was operated during TTEmore » (the spectrometer itself was valved off from the JET vessel). This was exposed to neutron fluxes of {approx}10{sup 9}/cm{sup 2} s, in excess of those predicted for the corresponding instrument on ITER (10{sup 7}-10{sup 8}/cm{sup 2} s). A corresponding increase in the background level equivalent to {approx}5% of the detector dynamic range was measured. This demonstration of the shielding effectiveness of the SPRED configuration during DT operations, coupled with the tolerable noise levels measured in the SOXMOS detector, give confidence in the planned implementation of such instruments in ITER.« less

Comparative analysis of core heat transport of JET high density H-mode plasmas in carbon wall and ITER-like wall

NASA Astrophysics Data System (ADS)

Kim, Hyun-Tae; Romanelli, M.; Voitsekhovitch, I.; Koskela, T.; Conboy, J.; Giroud, C.; Maddison, G.; Joffrin, E.; contributors, JET

2015-06-01

A consistent deterioration of global confinement in H-mode experiments has been observed in JET [1] following the replacement of all carbon plasma facing components (PFCs) with an all metal (‘ITER-like’) wall (ILW). This has been correlated to the observed degradation of the pedestal confinement, as lower electron temperature (Te) values are routinely measured at the top of the edge barrier region. A comparative investigation of core heat transport in JET-ILW and JET-CW (carbon wall) discharges has been performed, to assess whether core confinement has also been affected by the wall change. The results presented here have been obtained by analysing a set of discharges consisting of high density JET-ILW H-mode plasmas and comparing them against their counterpart discharges in JET-CW having similar global operational parameters. The set contains 10 baseline ({βN}=1.5∼ 2 ) discharge-pairs with 2.7 T toroidal magnetic field, 2.5 MA plasma current, and 14 to 17 MW of neutral beam injection (NBI) heating. Based on a Te profile analysis using high resolution Thomson scattering (HRTS) data, the Te profile peaking (i.e. core Te (ρ = 0.3) / edge Te (ρ = 0.7)) is found to be similar, and weakly dependent on edge Te, for both JET-ILW and JET-CW discharges. When ILW discharges are seeded with N2, core and edge Te both increase to maintain a similar peaking factor. The change in core confinement is addressed with interpretative TRANSP simulations. It is found that JET-ILW H-mode plasmas have higher NBI power deposition to electrons and lower NBI power deposition to ions as compared to the JET-CW counterparts. This is an effect of the lower electron temperature at the top of the pedestal. As a result, the core electron energy confinement time is reduced in JET-ILW discharges, but the core ion energy confinement time is not decreased. Overall, the core energy confinement is found to be the same in the JET-ILW discharges compared to the JET-CW counterparts.

Prospects for steady-state scenarios on JET

NASA Astrophysics Data System (ADS)

Litaudon, X.; Bizarro, J. P. S.; Challis, C. D.; Crisanti, F.; DeVries, P. C.; Lomas, P.; Rimini, F. G.; Tala, T. J. J.; Akers, R.; Andrew, Y.; Arnoux, G.; Artaud, J. F.; Baranov, Yu F.; Beurskens, M.; Brix, M.; Cesario, R.; DeLa Luna, E.; Fundamenski, W.; Giroud, C.; Hawkes, N. C.; Huber, A.; Joffrin, E.; Pitts, R. A.; Rachlew, E.; Reyes-Cortes, S. D. A.; Sharapov, S. E.; Zastrow, K. D.; Zimmermann, O.; JET EFDA contributors, the

2007-09-01

In the 2006 experimental campaign, progress has been made on JET to operate non-inductive scenarios at higher applied powers (31 MW) and density (nl ~ 4 × 1019 m-3), with ITER-relevant safety factor (q95 ~ 5) and plasma shaping, taking advantage of the new divertor capabilities. The extrapolation of the performance using transport modelling benchmarked on the experimental database indicates that the foreseen power upgrade (~45 MW) will allow the development of non-inductive scenarios where the bootstrap current is maximized together with the fusion yield and not, as in present-day experiments, at its expense. The tools for the long-term JET programme are the new ITER-like ICRH antenna (~15 MW), an upgrade of the NB power (35 MW/20 s or 17.5 MW/40 s), a new ITER-like first wall, a new pellet injector for edge localized mode control together with improved diagnostic and control capability. Operation with the new wall will set new constraints on non-inductive scenarios that are already addressed experimentally and in the modelling. The fusion performance and driven current that could be reached at high density and power have been estimated using either 0D or 1-1/2D validated transport models. In the high power case (45 MW), the calculations indicate the potential for the operational space of the non-inductive regime to be extended in terms of current (~2.5 MA) and density (nl > 5 × 1019 m-3), with high βN (βN > 3.0) and a fraction of the bootstrap current within 60-70% at high toroidal field (~3.5 T).

High-performance finite-difference time-domain simulations of C-Mod and ITER RF antennas

NASA Astrophysics Data System (ADS)

Jenkins, Thomas G.; Smithe, David N.

2015-12-01

Finite-difference time-domain methods have, in recent years, developed powerful capabilities for modeling realistic ICRF behavior in fusion plasmas [1, 2, 3, 4]. When coupled with the power of modern high-performance computing platforms, such techniques allow the behavior of antenna near and far fields, and the flow of RF power, to be studied in realistic experimental scenarios at previously inaccessible levels of resolution. In this talk, we present results and 3D animations from high-performance FDTD simulations on the Titan Cray XK7 supercomputer, modeling both Alcator C-Mod's field-aligned ICRF antenna and the ITER antenna module. Much of this work focuses on scans over edge density, and tailored edge density profiles, to study dispersion and the physics of slow wave excitation in the immediate vicinity of the antenna hardware and SOL. An understanding of the role of the lower-hybrid resonance in low-density scenarios is emerging, and possible implications of this for the NSTX launcher and power balance are also discussed. In addition, we discuss ongoing work centered on using these simulations to estimate sputtering and impurity production, as driven by the self-consistent sheath potentials at antenna surfaces.

High-performance finite-difference time-domain simulations of C-Mod and ITER RF antennas

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

Jenkins, Thomas G., E-mail: tgjenkins@txcorp.com; Smithe, David N., E-mail: smithe@txcorp.com

Finite-difference time-domain methods have, in recent years, developed powerful capabilities for modeling realistic ICRF behavior in fusion plasmas [1, 2, 3, 4]. When coupled with the power of modern high-performance computing platforms, such techniques allow the behavior of antenna near and far fields, and the flow of RF power, to be studied in realistic experimental scenarios at previously inaccessible levels of resolution. In this talk, we present results and 3D animations from high-performance FDTD simulations on the Titan Cray XK7 supercomputer, modeling both Alcator C-Mod’s field-aligned ICRF antenna and the ITER antenna module. Much of this work focuses on scansmore » over edge density, and tailored edge density profiles, to study dispersion and the physics of slow wave excitation in the immediate vicinity of the antenna hardware and SOL. An understanding of the role of the lower-hybrid resonance in low-density scenarios is emerging, and possible implications of this for the NSTX launcher and power balance are also discussed. In addition, we discuss ongoing work centered on using these simulations to estimate sputtering and impurity production, as driven by the self-consistent sheath potentials at antenna surfaces.« less

Modeling the excitation of global Alfven modes by an external antenna in the Joint European Torus (JET)

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

Huysmans, G.T.A.; Kerner, W.; Borba, D.

1995-05-01

The active excitation of global Alfven modes using the saddle coils in the Joint European Torus (JET) [{ital Plasma} {ital Physics} {ital and} {ital Controlled} {ital Nuclear} {ital Fusion} {ital Research} 1984, Proceedings of the 10th International Conference, London (International Atomic Energy Agency, Vienna, 1985), Vol. 1, p. 11] as the external antenna, will provide information on the damping of global modes without the need to drive the modes unstable. For the modeling of the Alfven mode excitation, the toroidal resistive magnetohydrodynamics (MHD) code CASTOR (Complex Alfven Spectrum in TORoidal geometry) [18{ital th} {ital EPS} {ital Conference} {ital On} {italmore » Controlled} {ital Fusion} {ital and} {ital Plasma} {ital Physics}, Berlin, 1991, edited by P. Bachmann and D. C. Robinson (The European Physical Society, Petit-Lancy, 1991), Vol. 15, Part IV, p. 89] has been extended to calculate the response to an external antenna. The excitation of a high-performance, high beta JET discharge is studied numerically. In particular, the influence of a finite pressure is investigated. Weakly damped low-{ital n} global modes do exist in the gaps in the continuous spectrum at high beta. A pressure-driven global mode is found due to the interaction of Alfven and slow modes. Its frequency scales solely with the plasma temperature, not like a pure Alfven mode with a density and magnetic field.« less

Development of steady-state scenarios compatible with ITER-like wall conditions

NASA Astrophysics Data System (ADS)

Litaudon, X.; Arnoux, G.; Beurskens, M.; Brezinsek, S.; Challis, C. D.; Crisanti, F.; DeVries, P. C.; Giroud, C.; Pitts, R. A.; Rimini, F. G.; Andrew, Y.; Ariola, M.; Baranov, Yu F.; Brix, M.; Buratti, P.; Cesario, R.; Corre, Y.; DeLa Luna, E.; Fundamenski, W.; Giovannozzi, E.; Gryaznevich, M. P.; Hawkes, N. C.; Hobirk, J.; Huber, A.; Jachmich, S.; Joffrin, E.; Koslowski, H. R.; Liang, Y.; Loarer, Th; Lomas, P.; Luce, T.; Mailloux, J.; Matthews, G. F.; Mazon, D.; McCormick, K.; Moreau, D.; Pericoli, V.; Philipps, V.; Rachlew, E.; Reyes-Cortes, S. D. A.; Saibene, G.; Sharapov, S. E.; Voitsekovitch, I.; Zabeo, L.; Zimmermann, O.; Zastrow, K. D.; JET-EFDA Contributors, the

2007-12-01

A key issue for steady-state tokamak operation is to determine the edge conditions that are compatible both with good core confinement and with the power handling and plasma exhaust capabilities of the plasma facing components (PFCs) and divertor systems. A quantitative response to this open question will provide a robust scientific basis for reliable extrapolation of present regimes to an ITER compatible steady-state scenario. In this context, the JET programme addressing steady-state operation is focused on the development of non-inductive, high confinement plasmas with the constraints imposed by the PFCs. A new beryllium main chamber wall and tungsten divertor together with an upgrade of the heating/fuelling capability are currently in preparation at JET. Operation at higher power with this ITER-like wall will impose new constraints on non-inductive scenarios. Recent experiments have focused on the preparation for this new phase of JET operation. In this paper, progress in the development of advanced tokamak (AT) scenarios at JET is reviewed keeping this long-term objective in mind. The approach has consisted of addressing various critical issues separately during the 2006-2007 campaigns with a view to full scenario integration when the JET upgrades are complete. Regimes with internal transport barriers (ITBs) have been developed at q95 ~ 5 and high triangularity, δ (relevant to the ITER steady-state demonstration) by applying more than 30 MW of additional heating power reaching βN ~ 2 at Bo ~ 3.1 T. Operating at higher δ has allowed the edge pedestal and core densities to be increased pushing the ion temperature closer to that of the electrons. Although not yet fully integrated into a performance enhancing ITB scenario, Neon seeding has been successfully explored to increase the radiated power fraction (up to 60%), providing significant reduction of target tile power fluxes (and hence temperatures) and mitigation of edge localized mode (ELM) activity. At

ELM mitigation studies in JET and implications for ITER

NASA Astrophysics Data System (ADS)

de La Luna, Elena

2009-11-01

Type I edge localized modes (ELMs) remain a serious concern for ITER because of the high transient heat and particle flux that can lead to rapid erosion of the divertor plates. This has stimulated worldwide research on exploration of different methods to avoid or at least mitigate the ELM energy loss while maintaining adequate confinement. ITER will require reliable ELM control over a wide range of operating conditions, including changes in the edge safety factor, therefore a suite of different techniques is highly desirable. In JET several techniques have been demonstrated for control the frequency and size of type I ELMs, including resonant perturbations of the edge magnetic field (RMP), ELM magnetic triggering by fast vertical movement of the plasma column (``vertical kicks'') and ELM pacing using pellet injection. In this paper we present results from recent dedicated experiments in JET focusing on integrating the different ELM mitigation methods into similar plasma scenarios. Plasma parameter scans provide comparison of the performance of the different techniques in terms of both the reduction in ELM size and on the impact of each control method on plasma confinement. The compatibility of different ELM mitigation schemes has also been investigated. The plasma response to RMP and vertical kicks during the ELM mitigation phase shares common features: the reduction in ELM size (up to a factor of 3) is accompanied by a reduction in pedestal pressure (mainly due to a loss of density) with only minor (< 10%) reduction of the stored energy. Interestingly, it has been found that the combined application of RMP and kicks leads to a reduction of the threshold perturbation level (vertical displacement in the case of the kicks) necessary for the ELM mitigation to occur. The implication of these results for ITER will be discussed.

Determination of tungsten and molybdenum concentrations from an x-ray range spectrum in JET with the ITER-like wall configuration

NASA Astrophysics Data System (ADS)

Nakano, T.; Shumack, A. E.; Maggi, C. F.; Reinke, M.; Lawson, K. D.; Coffey, I.; Pütterich, T.; Brezinsek, S.; Lipschultz, B.; Matthews, G. F.; Chernyshova, M.; Jakubowska, K.; Scholz, M.; Rzadkiewicz, J.; Czarski, T.; Dominik, W.; Kasprowicz, G.; Pozniak, K.; Zabolotny, W.; Zastrow, K.-D.; Conway, N. J.; contributors, JET

2015-07-01

The {{W}45+} and {{W}46+} 3p-4d inner shell excitation lines in addition to M{{o}32+} 2p-3s lines have been identified from the spectrum taken by an upgraded high-resolution x-ray spectrometer. It is found from analysis of the absolute intensities of the {{W}46+} and M{{o}32+} lines that W and Mo concentrations are in the range of ˜ {{10}-5} and ˜ {{10}-6}, respectively, with a ratio of ˜5% in JET with the ITER-like wall configuration for ELMy H-mode plasmas with a plasma current of 2.0-2.5 MA, a toroidal magnetic field of 2.7 T and a neutral beam injection power of 14-18 MW. For the purpose of checking self-consistency, it is confirmed that the W concentration determined from the {{W}45+} line is in agreement with that from the {{W}46+} line within 20% and that the plasma effective charge determined from the continuum of the first order reflection spectrum is also in agreement with that from the second order within 50%. Further, the determined plasma effective charge is in agreement with that determined from a visible spectroscopy, confirming that the sensitivity of the x-ray spectrometer is valid and that the W and the Mo concentrations are also likely to be valid.

Operations of the External Conjugate-T Matching System for the A2 ICRH Antennas at JET

NASA Astrophysics Data System (ADS)

Monakhov, I.; Graham, M.; Blackman, T.; Mayoral, M.-L.; Nightingale, M.; Sheikh, H.; Whitehurst, A.

2009-11-01

The External Conjugate-T (ECT) matching system was successfully commissioned on two A2 ICRH antennas at JET in 2009. The system allows trip-free injection of RF power into ELMy H-mode plasmas in the 32-52 MHz band without antenna phasing restrictions. The ECT demonstrates robust and predictable performance and high load-tolerance during routine operations, injecting up to 4 MW average power into H-mode plasma with Type-I ELMs. The total power coupled to ELMy plasma by all the A2 antennas using the ECT and 3dB systems has been increased to 7 MW. Antenna arcing during ELMs has been identified as a new challenge to high-power ICRH operations in H-mode plasma. The implemented Advanced Wave Amplitude Comparison System (AWACS) has proven to be an efficient protection tool for the ECT scheme.

Operations of the External Conjugate-T Matching System for the A2 ICRH Antennas at JET

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

Monakhov, I.; Graham, M.; Blackman, T.

2009-11-26

The External Conjugate-T (ECT) matching system was successfully commissioned on two A2 ICRH antennas at JET in 2009. The system allows trip-free injection of RF power into ELMy H-mode plasmas in the 32-52 MHz band without antenna phasing restrictions. The ECT demonstrates robust and predictable performance and high load-tolerance during routine operations, injecting up to 4 MW average power into H-mode plasma with Type-I ELMs. The total power coupled to ELMy plasma by all the A2 antennas using the ECT and 3dB systems has been increased to 7 MW. Antenna arcing during ELMs has been identified as a new challengemore » to high-power ICRH operations in H-mode plasma. The implemented Advanced Wave Amplitude Comparison System (AWACS) has proven to be an efficient protection tool for the ECT scheme.« less

Analysis of LH Launcher Arrays (Like the ITER One) Using the TOPLHA Code

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

Maggiora, R.; Milanesio, D.; Vecchi, G.

2009-11-26

TOPLHA (Torino Polytechnic Lower Hybrid Antenna) code is an innovative tool for the 3D/1D simulation of Lower Hybrid (LH) antennas, i.e. accounting for realistic 3D waveguides geometry and for accurate 1D plasma models, and without restrictions on waveguide shape, including curvature. This tool provides a detailed performances prediction of any LH launcher, by computing the antenna scattering parameters, the current distribution, electric field maps and power spectra for any user-specified waveguide excitation. In addition, a fully parallelized and multi-cavity version of TOPLHA permits the analysis of large and complex waveguide arrays in a reasonable simulation time. A detailed analysis ofmore » the performances of the proposed ITER LH antenna geometry has been carried out, underlining the strong dependence of the antenna input parameters with respect to plasma conditions. A preliminary optimization of the antenna dimensions has also been accomplished. Electric current distribution on conductors, electric field distribution at the interface with plasma, and power spectra have been calculated as well. The analysis shows the strong capabilities of the TOPLHA code as a predictive tool and its usefulness to LH launcher arrays detailed design.« less

EDITORIAL: The interaction of radio-frequency fields with fusion plasmas: the JET experience The interaction of radio-frequency fields with fusion plasmas: the JET experience

NASA Astrophysics Data System (ADS)

Ongena, Jef

2012-07-01

The JET Task Force Heating is proud to present this special issue. It is the result of hard and dedicated work by everybody participating in the Task Force over the last four years and gives an overview of the experimental and theoretical results obtained in the period 2008-2010 with radio frequency heating of JET fusion plasmas. Topics studied and reported in this issue are: investigations into the operation of lower hybrid heating accompanied by new modeling results; new experimental results and insights into the physics of various ion cyclotron range of frequencies (ICRF) heating scenarios; progress in studies of intrinsic and ion cyclotron wave-induced plasma rotation and flows; a summary of the developments over the last years in designing an ion cyclotron radiofrequency heating (ICRH) system that can cope with the presence of fast load variations in the edge, as e.g. caused by pellets or edge localized modes (ELMs) during H-Mode operation; an overview of the results obtained with the ITER-like antenna operating in H-Mode with a packed array of straps and power densities close to those of the projected ITER ICRH antenna; and, finally, a summary of the results obtained in applying ion cyclotron waves for wall conditioning of the tokamak. This issue would not have been possible without the strong motivation and efforts (sometimes truly heroic) of all colleagues of the JET Task Force Heating. A sincere word of thanks, therefore, to all authors and co-authors involved in the experiments, analysis and compilation of the papers. It was a special privilege to work with all of them during the past very intense years. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the operations team of JET and the colleagues of the Close Support Unit in Culham. Thanks also to the editors, Editorial Board and referees of Plasma Physics and Controlled Fusion, together with the publishing staff of IOPP, who have not only

Effect of nitrogen seeding on the energy losses and on the time scales of the electron temperature and density collapse of type-I ELMs in JET with the ITER-like wall

NASA Astrophysics Data System (ADS)

Frassinetti, L.; Dodt, D.; Beurskens, M. N. A.; Sirinelli, A.; Boom, J. E.; Eich, T.; Flanagan, J.; Giroud, C.; Jachmich, M. S.; Kempenaars, M.; Lomas, P.; Maddison, G.; Maggi, C.; Neu, R.; Nunes, I.; Perez von Thun, C.; Sieglin, B.; Stamp, M.; Contributors, JET-EFDA

2015-02-01

The baseline type-I ELMy H-mode scenario has been re-established in JET with the new tungsten MKII-HD divertor and beryllium on the main wall (hereafter called the ITER-like wall, JET-ILW). The first JET-ILW results show that the confinement is degraded by 20-30% in the baseline scenarios compared to the previous carbon wall JET (JET-C) plasmas. The degradation is mainly driven by the reduction in the pedestal temperature. Stored energies and pedestal temperature comparable to the JET-C have been obtained to date in JET-ILW baseline plasmas only in the high triangularity shape using N2 seeding. This work compares the energy losses during ELMs and the corresponding time scales of the temperature and density collapse in JET-ILW baseline plasmas with and without N2 seeding with similar JET-C baseline plasmas. ELMs in the JET-ILW differ from those with the carbon wall both in terms of time scales and energy losses. The ELM time scale, defined as the time to reach the minimum pedestal temperature soon after the ELM collapse, is ˜2 ms in the JET-ILW and lower than 1 ms in the JET-C. The energy losses are in the range ΔWELM/Wped ≈ 7-12% in the JET-ILW and ΔWELM/Wped ≈ 10-20% in JET-C, and fit relatively well with earlier multi-machine empirical scalings of ΔWELM/Wped with collisionality. The time scale of the ELM collapse seems to be related to the pedestal collisionality. Most of the non-seeded JET-ILW ELMs are followed by a further energy drop characterized by a slower time scale ˜8-10 ms (hereafter called slow transport events), that can lead to losses in the range ΔWslow/Wped ≈ 15-22%, slightly larger than the losses in JET-C. The N2 seeding in JET-ILW significantly affects the ELMs. The JET-ILW plasmas with N2 seeding are characterized by ELM energy losses and time scales similar to the JET-C and by the absence of the slow transport events.

JET ICRH plant statistics from 2008-2012

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

Wooldridge, E.; Monakhov, I.; Blackman, T.

2014-02-12

JET ICRH plant faults from 2008 - 2012 have been catalogued and a new assessment of the reliability of the plant by sub-system is given. Data from pulses where ICRH was used, excluding the ITER-Like Antenna (ILA) and its generators, has been collated. This is compared to fault data in order to investigate any correlation between faults and operations. The number of faults is shown to have decreased between 2011-2012 in comparison to 2008-2009 as the time between faults is shown to have increased. Future electronic fault logging requirements to enable easier analysis are discussed. Due to the changing configurationmore » of the ICRH plant; the introduction of ELM tolerant systems, generator upgrade, changes to the settings of the VSWR protection et cetera, a method to expand the fault database to include more historical data [1] in a consistent way are discussed.« less

Preliminary consideration of CFETR ITER-like case diagnostic system.

PubMed

Li, G S; Yang, Y; Wang, Y M; Ming, T F; Han, X; Liu, S C; Wang, E H; Liu, Y K; Yang, W J; Li, G Q; Hu, Q S; Gao, X

2016-11-01

Chinese Fusion Engineering Test Reactor (CFETR) is a new superconducting tokamak device being designed in China, which aims at bridging the gap between ITER and DEMO, where DEMO is a tokamak demonstration fusion reactor. Two diagnostic cases, ITER-like case and towards DEMO case, have been considered for CFETR early and later operating phases, respectively. In this paper, some preliminary consideration of ITER-like case will be presented. Based on ITER diagnostic system, three versions of increased complexity and coverage of the ITER-like case diagnostic system have been developed with different goals and functions. Version A aims only machine protection and basic control. Both of version B and version C are mainly for machine protection, basic and advanced control, but version C has an increased level of redundancy necessary for improved measurements capability. The performance of these versions and needed R&D work are outlined.

Preliminary consideration of CFETR ITER-like case diagnostic system

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

Li, G. S.; Liu, Y. K.; Gao, X.

2016-11-15

Chinese Fusion Engineering Test Reactor (CFETR) is a new superconducting tokamak device being designed in China, which aims at bridging the gap between ITER and DEMO, where DEMO is a tokamak demonstration fusion reactor. Two diagnostic cases, ITER-like case and towards DEMO case, have been considered for CFETR early and later operating phases, respectively. In this paper, some preliminary consideration of ITER-like case will be presented. Based on ITER diagnostic system, three versions of increased complexity and coverage of the ITER-like case diagnostic system have been developed with different goals and functions. Version A aims only machine protection and basicmore » control. Both of version B and version C are mainly for machine protection, basic and advanced control, but version C has an increased level of redundancy necessary for improved measurements capability. The performance of these versions and needed R&D work are outlined.« less

W transport and accumulation control in the termination phase of JET H-mode discharges and implications for ITER

NASA Astrophysics Data System (ADS)

Köchl, F.; Loarte, A.; de la Luna, E.; Parail, V.; Corrigan, G.; Harting, D.; Nunes, I.; Reux, C.; Rimini, F. G.; Polevoi, A.; Romanelli, M.; Contributors, JET

2018-07-01

Tokamak operation with W PFCs is associated with specific challenges for impurity control, which may be particularly demanding in the transition from stationary H-mode to L-mode. To address W control issues in this phase, dedicated experiments have been performed at JET including the variation of the decrease of the power and current, gas fuelling and central ion cyclotron heating (ICRH), and applying active ELM control by vertical kicks. The experimental results obtained demonstrate the key role of maintaining ELM control to control the W concentration in the exit phase of H-modes with slow (ITER-like) ramp-down of the neutral beam injection power in JET. For these experiments, integrated fully predictive core+edge+SOL transport modelling studies applying discrete models for the description of transients such as sawteeth and ELMs have been performed for the first time with the JINTRAC suite of codes for the entire transition from stationary H-mode until the time when the plasma would return to L-mode focusing on the W transport behaviour. Simulations have shown that the existing models can appropriately reproduce the plasma profile evolution in the core, edge and SOL as well as W accumulation trends in the termination phase of JET H-mode discharges as function of the applied ICRH and ELM control schemes, substantiating the ambivalent effect of ELMs on W sputtering on one side and on edge transport affecting core W accumulation on the other side. The sensitivity with respect to NB particle and momentum sources has also been analysed and their impact on neoclassical W transport has been found to be crucial to reproduce the observed W accumulation characteristics in JET discharges. In this paper the results of the JET experiments, the comparison with JINTRAC modelling and the adequacy of the models to reproduce the experimental results are described and conclusions are drawn regarding the applicability of these models for the extrapolation of the applied W

Overview of the JET results

NASA Astrophysics Data System (ADS)

Romanelli, F.; JET Contributors,

2015-10-01

Since the installation of an ITER-like wall, the JET programme has focused on the consolidation of ITER design choices and the preparation for ITER operation, with a specific emphasis given to the bulk tungsten melt experiment, which has been crucial for the final decision on the material choice for the day-one tungsten divertor in ITER. Integrated scenarios have been progressed with the re-establishment of long-pulse, high-confinement H-modes by optimizing the magnetic configuration and the use of ICRH to avoid tungsten impurity accumulation. Stationary discharges with detached divertor conditions and small edge localized modes have been demonstrated by nitrogen seeding. The differences in confinement and pedestal behaviour before and after the ITER-like wall installation have been better characterized towards the development of high fusion yield scenarios in DT. Post-mortem analyses of the plasma-facing components have confirmed the previously reported low fuel retention obtained by gas balance and shown that the pattern of deposition within the divertor has changed significantly with respect to the JET carbon wall campaigns due to the absence of thermally activated chemical erosion of beryllium in contrast to carbon. Transport to remote areas is almost absent and two orders of magnitude less material is found in the divertor.

ON A CORONAL BLOWOUT JET: THE FIRST OBSERVATION OF A SIMULTANEOUSLY PRODUCED BUBBLE-LIKE CME AND A JET-LIKE CME IN A SOLAR EVENT

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

Shen Yuandeng; Liu Yu; Su Jiangtao

2012-02-01

The coronal blowout jet is a peculiar category among various jet phenomena, in which the sheared base arch, often carrying a small filament, experiences a miniature version of blowout eruption that produces large-scale coronal mass ejection (CME). In this paper, we report such a coronal blowout jet with high-resolution multi-wavelength and multi-angle observations taken from Solar Dynamics Observatory, Solar Terrestrial Relations Observatory, and Big Bear Solar Observatory. For the first time, we find that simultaneous bubble-like and jet-like CMEs were dynamically related to the blowout jet that showed cool and hot components next to each other. Our observational results indicatemore » that (1) the cool component resulted from the eruption of the filament contained within the jet's base arch, and it further caused the bubble-like CME; (2) the jet-like CME was associated with the hot component, which was the outward moving heated plasma generated by the reconnection of the base arch and its ambient open field lines. On the other hand, bifurcation of the jet's cool component was also observed, which resulted from the uncoupling of the erupting filament's two legs that were highly twisted at the very beginning. Based on these results, we propose a model to interpret the coronal blowout jet, in which the external reconnection not only produces the jet-like CME, but also leads to the rising of the filament. Subsequently, internal reconnection starts underneath the rising filament and thereby causes the bubble-like CME.« less

JET disruption studies in support of ITER

NASA Astrophysics Data System (ADS)

Riccardo, V.; Arnoux, G.; Cahyna, P.; Hender, T. C.; Huber, A.; Jachmich, S.; Kiptily, V.; Koslowski, R.; Krlin, L.; Lehnen, M.; Loarte, A.; Nardon, E.; Paprok, R.; Tskhakaya (Sr, D.; contributors, JET-EFDA

2010-12-01

Plasma disruptions affect plasma-facing and structural components of tokamaks due to electromechanical forces, thermal loads and generation of high energy runaway electrons (REs). Asymmetries in poloidal halo and toroidal plasma current can now be routinely measured in four positions 90° apart. Their assessment is used to validate the design of the ITER vessel support system and its in-vessel components. The challenge of disruption thermal loads comes from both the short duration over which a large energy has to be lost and the potential for asymmetries. The focus of this paper will be on localized heat loads. Resonant magnetic perturbations failed to reduce the generation of REs in JET. An explanation of the limitations applying to these attempts is offered together with a minimum guideline. The REs generated by a moderate, but fast, Ar injection in limiter plasmas show evidence of milder and more efficient losses due to the high Ar background density.

Satellite Antenna Systems

NASA Technical Reports Server (NTRS)

1997-01-01

Through the Technology Affiliates Program at the Jet Propulsion Laboratory, the ACTS antenna system was transferred from experimental testing status to commercial development with KVH Industries, Inc. The ACTS design enables mobile satellite antennas to remain pointed at the satellite, regardless of the motion or vibration on which it is mounted. KVH's first product based on the ACTS design is a land-mobile satellite antenna system that will enable direct broadcast satellite television aboard moving trucks, recreational vehicles, trains, and buses. Future products could include use in broadcasting, emergency medical and military vehicles.

Large space antenna communications systems: Integrated Langley Research Center/Jet Propulsion Laboratory technology development activities. 1: Introduction

NASA Technical Reports Server (NTRS)

Campbell, T. G.

1983-01-01

The Jet Propulsion Laboratory and the Langley Research Center have been developing technology related to large space antennas (LSA) during the past several years. The need for a communication system research program became apparent during the recent studies for the Land Mobile Satellite System. This study indicated the need for additional research in (1) electromagnetic analysis methods, (2) design and development of multiple beam feed systems, and (3) the measurement methods for LSA reflectors.

Estimates of RF-induced erosion at antenna-connected beryllium plasma-facing components in JET

DOE PAGES

Klepper, C. C.; Borodin, D.; Groth, M.; ...

2016-01-18

Radio-frequency (RF)-enhanced surface erosion of beryllium (Be) plasma-facing components is explored, for the first time, using the ERO code. We applied the code in order to measure the RF-enhanced edge Be line emission at JET Be outboard limiters, in the presence of high-power, ion cyclotronresonance heating (ICRH) in L-mode discharges. In this first modelling study, the RF sheath effect from an ICRH antenna on a magnetically connected, limiter region is simulated by adding a constant potential to the local sheath, in an attempt to match measured increases in local Be I and Be II emission of factors of 2 3.more » It was found that such increases are readily simulated with added potentials in the range of 100 200 V, which is compatible with expected values for potentials arising from rectification of sheath voltage oscillations from ICRH antennas in the scrape-off layer plasma. We also estimated absolute erosion values within the uncertainties in local plasma conditions.« less

UHF coplanar-slot antenna for aircraft-to-satellite data communications

NASA Technical Reports Server (NTRS)

Myhre, R. W.

1979-01-01

A lightweight low drag coplanar slot antenna was developed for use on commercial jet aircraft that will provide upper hemisphere coverage in the UHF band at frequencies of 402 and 468 MHz is described. The antenna is designed to transmit meteorological data from wide body jet aircraft to ground users via synchronous meteorological data relay satellites. The low profile antenna (23.5 cm wide by 38.1 cm long slot by 1.9 cm high) is a conformal antenna utilizing the coplanar approach with the advantages of broad frequency bandwidth and improved electrical integrity over wide range of temperature. The antenna is circular polarized, has anon axis gain of near +2.5 dB, and a HPBW greater than 90 deg. Areas discussed include antenna design, radiation characteristics, flight testing, and system performance.

Refractive and relativistic effects on ITER low field side reflectometer design.

PubMed

Wang, G; Rhodes, T L; Peebles, W A; Harvey, R W; Budny, R V

2010-10-01

The ITER low field side reflectometer faces some unique design challenges, among which are included the effect of relativistic electron temperatures and refraction of probing waves. This paper utilizes GENRAY, a 3D ray tracing code, to investigate these effects. Using a simulated ITER operating scenario, characteristics of the reflected millimeter waves after return to the launch plane are quantified as a function of a range of design parameters, including antenna height, antenna diameter, and antenna radial position. Results for edge/SOL measurement with both O- and X-mode polarizations using proposed antennas are reported.

Neutron spectroscopy as a fuel ion ratio diagnostic: lessons from JET and prospects for ITER.

PubMed

Ericsson, G; Conroy, S; Gatu Johnson, M; Andersson Sundén, E; Cecconello, M; Eriksson, J; Hellesen, C; Sangaroon, S; Weiszflog, M

2010-10-01

The determination of the fuel ion ratio n(t)/n(d) in ITER is required at a precision of 20%, time resolution of 100 ms, spatial resolution of a/10, and over a range of 0.01ITER to assess the possibility to use neutron emission spectroscopy (NES) for such measurements. We show that NES meets the requirements for ion temperatures T(i)>6 keV and for n(T)/n(D)<0.6. A crucial issue is the signal-to-background situation in the measurement of the weak 2.5 MeV emission from DD reactions in the presence of a background of scattered 14 MeV DT neutrons. Important experimental input and corroboration for this assessment are presented from the time-of-flight neutron spectrometer at JET where the presence of a strong component of backscattered neutrons is observed. Neutron emission components on ITER due to beam-thermal and tritium-tritium reactions can further enhance the prospects for NES.

Recent Developments in the External Conjugate-T Matching Project at JET

NASA Astrophysics Data System (ADS)

Monakhov, I.; Walden, A.

2007-09-01

The External Conjugate-T (ECT) matching system is planned for installation on two A2 ICRH antenna arrays at JET in 2007. This will enhance the operational capabilities of the RF plant during ELMy plasma scenarios and create new opportunities for ITER-relevant matching studies. The main features of the project are discussed in the paper focusing on the specific challenges of the ECT automatic matching and arc detection in optimized ELM-tolerant configurations. A `co/counter-clockwise' automatic control mode selection and an Advanced Wave Amplitude Comparison System (AWACS) complementing the existing VSWR monitoring are proposed as simple and viable solutions to the identified problems.

Recent Developments in the External Conjugate-T Matching Project at JET

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

Monakhov, I.; Walden, A.

2007-09-28

The External Conjugate-T (ECT) matching system is planned for installation on two A2 ICRH antenna arrays at JET in 2007. This will enhance the operational capabilities of the RF plant during ELMy plasma scenarios and create new opportunities for ITER-relevant matching studies. The main features of the project are discussed in the paper focusing on the specific challenges of the ECT automatic matching and arc detection in optimized ELM-tolerant configurations. A 'co/counter-clockwise' automatic control mode selection and an Advanced Wave Amplitude Comparison System (AWACS) complementing the existing VSWR monitoring are proposed as simple and viable solutions to the identified problems.

Kinetics of carbide formation in the molybdenum-tungsten coatings used in the ITER-like Wall

NASA Astrophysics Data System (ADS)

Maier, H.; Rasinski, M.; von Toussaint, U.; Greuner, H.; Böswirth, B.; Balden, M.; Elgeti, S.; Ruset, C.; Matthews, G. F.

2016-02-01

The kinetics of tungsten carbide formation was investigated for tungsten coatings on carbon fibre composite with a molybdenum interlayer as they are used in the ITER-like Wall in JET. The coatings were produced by combined magnetron sputtering and ion implantation. The investigation was performed by preparing focused ion beam cross sections from samples after heat treatment in argon atmosphere. Baking of the samples was done at temperatures of 1100 °C, 1200 °C, and 1350 °C for hold times between 30 min and 20 h. It was found that the data can be well described by a diffusional random walk with a thermally activated diffusion process. The activation energy was determined to be (3.34 ± 0.11) eV. Predictions for the isothermal lifetime of this coating system were computed from this information.

In-vessel calibration of the imaging diagnostics for the real-time protection of the JET ITER-like wall.

PubMed

Huber, V; Huber, A; Kinna, D; Balboa, I; Collins, S; Conway, N; Drewelow, P; Maggi, C F; Matthews, G F; Meigs, A G; Mertens, Ph; Price, M; Sergienko, G; Silburn, S; Wynn, A; Zastrow, K-D

2016-11-01

The in situ absolute calibration of the JET real-time protection imaging system has been performed for the first time by means of radiometric light source placed inside the JET vessel and operated by remote handling. High accuracy of the calibration is confirmed by cross-validation of the near infrared (NIR) cameras against each other, with thermal IR cameras, and with the beryllium evaporator, which lead to successful protection of the JET first wall during the last campaign. The operation temperature ranges of NIR protection cameras for the materials used on JET are Be 650-1600 °C, W coating 600-1320 °C, and W 650-1500 °C.

In-vessel calibration of the imaging diagnostics for the real-time protection of the JET ITER-like wall

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

Huber, V., E-mail: V.Huber@fz-juelich.de; Huber, A.; Mertens, Ph.

The in situ absolute calibration of the JET real-time protection imaging system has been performed for the first time by means of radiometric light source placed inside the JET vessel and operated by remote handling. High accuracy of the calibration is confirmed by cross-validation of the near infrared (NIR) cameras against each other, with thermal IR cameras, and with the beryllium evaporator, which lead to successful protection of the JET first wall during the last campaign. The operation temperature ranges of NIR protection cameras for the materials used on JET are Be 650-1600 °C, W coating 600-1320 °C, and W 650-1500 °C.

First Production of C60 Nanoparticle Plasma Jet for Study of Disruption Mitigation for ITER

NASA Astrophysics Data System (ADS)

Bogatu, I. N.; Thompson, J. R.; Galkin, S. A.; Kim, J. S.; Brockington, S.; Case, A.; Messer, S. J.; Witherspoon, F. D.

2012-10-01

Unique fast response and large mass-velocity delivery of nanoparticle plasma jets (NPPJs) provide a novel application for ITER disruption mitigation, runaway electrons diagnostics and deep fueling. NPPJs carry a much larger mass than usual gases. An electromagnetic plasma gun provides a very high injection velocity (many km/s). NPPJ has much higher ram pressure than any standard gas injection method and penetrates the tokamak confining magnetic field. Assimilation is enhanced due to the NP large surface-to-volume ratio. Radially expanding NPPJs help achieving toroidal uniformity of radiation power. FAR-TECH's NPPJ system was successfully tested: a coaxial plasma gun prototype (˜35 cm length, 96 kJ energy) using a solid state TiH2/C60 pulsed power cartridge injector produced a hyper-velocity (>4 km/s), high-density (>10^23 m-3), C60 plasma jet in ˜0.5 ms, with ˜1-2 ms overall response-delivery time. We present the TiH2/C60 cartridge injector output characterization (˜180 mg of sublimated C60 gas) and first production results of a high momentum C60 plasma jet (˜0.6 g.km/s).

A New Newton-Like Iterative Method for Roots of Analytic Functions

ERIC Educational Resources Information Center

Otolorin, Olayiwola

2005-01-01

A new Newton-like iterative formula for the solution of non-linear equations is proposed. To derive the formula, the convergence criteria of the one-parameter iteration formula, and also the quasilinearization in the derivation of Newton's formula are reviewed. The result is a new formula which eliminates the limitations of other methods. There is…

Impurity re-distribution in the corner regions of the JET divertor

NASA Astrophysics Data System (ADS)

Widdowson, A.; Coad, J. P.; Alves, E.; Baron-Wiechec, A.; Barradas, N. P.; Catarino, N.; Corregidor, V.; Heinola, K.; Krat, S.; Likonen, J.; Matthews, G. F.; Mayer, M.; Petersson, P.; Rubel, M.; Contributors, JET

2017-12-01

The International Thermonuclear Experimental Reactor (ITER) will use a mixture of deuterium (D) and tritium (T) as the fuel to generate power. Since T is both radioactive and expensive the Joint European Torus (JET) has been at the forefront of research to discover how much T is used and where it may be retained within the main reaction chamber. Until the year 2010 the JET plasma facing components were constructed of carbon fibre composites. During the JET carbon (C) phases impurities accumulated at the corners of the divertor located towards the bottom of the chamber in regions shadowed from the plasma where they are very difficult to reach and remove. This build-up of C and the associated H-isotope (including T) retention were of particular concern for future fusion reactors therefore, in 2010 JET changed the wall protection to (mainly) Be and the divertor to tungsten (W)—the JET ITER-like wall (ILW)—the choice of materials for ITER. This paper reveals that with the JET ILW impurities are still accumulating in the shadowed regions, with Be being the majority element, though the overall quantities are very much reduced from those in the C phases. Material will be transported into the shadowed regions principally when the plasma strike points are on the corner tiles, but particles typically have about a 75% probability of reflection from line-of sight surfaces, and multiple reflection/scattering results in deposition over all surfaces.

Non-Gimbaled Antenna Pointing

NASA Technical Reports Server (NTRS)

Vigil, Jeannine S.

1997-01-01

The small satellite community has been interested in accessing fixed ground stations for means of space-to-ground transmissions, although a problem arises from the limited global coverage. There is a growing interest for using the Space Network (SN) or Tracking and Data Relay Satellites (TDRS) as the primary support for communications because of the coverage it provides. This thesis will address the potential for satellite access of the Space Network with a non-gimbaled antenna configuration and low-power, coded transmission. The non-gimbaled antenna and the TDRS satellites, TDRS-East, TDRS-West, and TDRS-Zone of Exclusion, were configured in an orbital analysis software package called Satellite Tool Kit to emulate the three-dimensional position of the satellites. The access potential, which is the average number of contacts per day and the average time per contact, were obtained through simulations run over a 30-day period to gain all the possible orientations. The orbital altitude was varied from 600 km through 1200 km with the results being a function of orbital inclination angles varying from 20 deg through 100 deg and pointing half-angles of I0 deg through 40 deg. To compare the validity of the simulations, Jet Propulsion Laboratory granted the use of the TOPEX satellite. The TOPEX satellite was configured to emulate a spin-stabilized antenna with its communications antenna stowed in the zenith-pointing direction. This mimicked the antenna pointing spin-stabilized satellite in the simulations. To make valid comparisons, the TOPEX orbital parameters were entered into Satellite Tool Kit and simulated over five test times provided by Jet Propulsion Laboratory.

Development of the ITER ICH Transmission Line and Matching System

NASA Astrophysics Data System (ADS)

Rasmussen, D. A.; Goulding, R. H.; Pesavento, P. V.; Peters, B.; Swain, D. W.; Fredd, E. H.; Hosea, J.; Greenough, N.

2011-10-01

The ITER Ion Cyclotron Heating (ICH) System is designed to couple 20 MW of heating power for ion and electron heating. Prototype components for the ITER Ion Cyclotron Heating (ICH) transmission line and matching system are being designed and tested. The ICH transmission lines are pressurized 300 mm diameter coaxial lines with water-cooled aluminum outer conductor and gas-cooled and water-cooled copper inner conductor. Each ICH transmission line is designed to handle 40-55 MHz power at up to 6 MW/line. A total of 8 lines split to 16 antenna inputs on two ICH antennas. Industrial suppliers have designed coaxial transmission line and matching components and prototypes will be manufactured. The prototype components will be qualified on a test stand operating at the full power and pulse length needed for ITER. The matching system must accommodated dynamic changes in the plasma loading due to ELMS and the L to H-mode transition. Passive ELM tolerance will be performed using hybrid couplers and loads, which can absorb the transient reflected power. The system is also designed to compensate for the mutual inductances of the antenna current straps to limit the peak voltages on the antenna array elements.

Extending helium partial pressure measurement technology to JET DTE2 and ITER.

PubMed

Klepper, C C; Biewer, T M; Kruezi, U; Vartanian, S; Douai, D; Hillis, D L; Marcus, C

2016-11-01

The detection limit for helium (He) partial pressure monitoring via the Penning discharge optical emission diagnostic, mainly used for tokamak divertor effluent gas analysis, is shown here to be possible for He concentrations down to 0.1% in predominantly deuterium effluents. This result from a dedicated laboratory study means that the technique can now be extended to intrinsically (non-injected) He produced as fusion reaction ash in deuterium-tritium experiments. The paper also examines threshold ionization mass spectroscopy as a potential backup to the optical technique, but finds that further development is needed to attain with plasma pulse-relevant response times. Both these studies are presented in the context of continuing development of plasma pulse-resolving, residual gas analysis for the upcoming JET deuterium-tritium campaign (DTE2) and for ITER.

Physics and technology in the ion-cyclotron range of frequency on Tore Supra and TITAN test facility: implication for ITER

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

Litaudon, X; Bernard, J. M.; Colas, L.

2013-01-01

To support the design of an ITER ion-cyclotron range of frequency heating (ICRH) system and to mitigate risks of operation in ITER, CEA has initiated an ambitious Research & Development program accompanied by experiments on Tore Supra or test-bed facility together with a significant modelling effort. The paper summarizes the recent results in the following areas: Comprehensive characterization (experiments and modelling) of a new Faraday screen concept tested on the Tore Supra antenna. A new model is developed for calculating the ICRH sheath rectification at the antenna vicinity. The model is applied to calculate the local heat flux on Toremore » Supra and ITER ICRH antennas. Full-wave modelling of ITER ICRH heating and current drive scenarios with the EVE code. With 20 MW of power, a current of 400 kA could be driven on axis in the DT scenario. Comparison between DT and DT(3He) scenario is given for heating and current drive efficiencies. First operation of CW test-bed facility, TITAN, designed for ITER ICRH components testing and could host up to a quarter of an ITER antenna. R&D of high permittivity materials to improve load of test facilities to better simulate ITER plasma antenna loading conditions.« less

New developments in the diagnostics for the fusion products on JET in preparation for ITER (invited).

PubMed

Murari, A; Angelone, M; Bonheure, G; Cecil, E; Craciunescu, T; Darrow, D; Edlington, T; Ericsson, G; Gatu-Johnson, M; Gorini, G; Hellesen, C; Kiptily, V; Mlynar, J; Perez von Thun, C; Pillon, M; Popovichev, S; Syme, B; Tardocchi, M; Zoita, V L

2010-10-01

Notwithstanding the advances of the past decades, significant developments are still needed to satisfactorily diagnose “burning plasmas.” D–T plasmas indeed require a series of additional measurements for the optimization and control of the configuration: the 14 MeV neutrons, the isotopic composition of the main plasma, the helium ash, and the redistribution and losses of the alpha particles. Moreover a burning plasma environment is in general much more hostile for diagnostics than purely deuterium plasmas. Therefore, in addition to the development and refinement of new measuring techniques, technological advances are also indispensable for the proper characterization of the next generation of devices. On JET an integrated program of diagnostic developments, for JET future and in preparation for ITER, has been pursued and many new results are now available. In the field of neutron detection, the neutron spectra are now routinely measured in the energy range of 1–18 MeV by a time of flight spectrometer and they have allowed studying the effects of rf heating on the fast ions. A new analysis method for the interpretation of the neutron cameras measurements has been refined and applied to the data of the last trace tritium campaign (TTE). With regard to technological upgrades, chemical vapor deposition diamond detectors have been qualified both as neutron counters and as neutron spectrometers, with a potential energy resolution of about one percent. The in situ calibration of the neutron diagnostics, in preparation for the operation with the ITER-like wall, is also promoting important technological developments. With regard to the fast particles, for the first time the temperature of the fast particle tails has been obtained with a new high purity Germanium detector measuring the gamma emission spectrum from the plasma. The effects of toroidal Alfven eigenmodes modes and various MHD instabilities on the confinement of the fast particles have been determined

New developments in the diagnostics for the fusion products on JET in preparation for ITER (invited)

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

Murari, A.; Angelone, M.; Pillon, M.

Notwithstanding the advances of the past decades, significant developments are still needed to satisfactorily diagnose ''burning plasmas.'' D-T plasmas indeed require a series of additional measurements for the optimization and control of the configuration: the 14 MeV neutrons, the isotopic composition of the main plasma, the helium ash, and the redistribution and losses of the alpha particles. Moreover a burning plasma environment is in general much more hostile for diagnostics than purely deuterium plasmas. Therefore, in addition to the development and refinement of new measuring techniques, technological advances are also indispensable for the proper characterization of the next generation ofmore » devices. On JET an integrated program of diagnostic developments, for JET future and in preparation for ITER, has been pursued and many new results are now available. In the field of neutron detection, the neutron spectra are now routinely measured in the energy range of 1-18 MeV by a time of flight spectrometer and they have allowed studying the effects of rf heating on the fast ions.A new analysis method for the interpretation of the neutron cameras measurements has been refined and applied to the data of the last trace tritium campaign (TTE). With regard to technological upgrades, chemical vapor deposition diamond detectors have been qualified both as neutron counters and as neutron spectrometers, with a potential energy resolution of about one percent. The in situ calibration of the neutron diagnostics, in preparation for the operation with the ITER-like wall, is also promoting important technological developments. With regard to the fast particles, for the first time the temperature of the fast particle tails has been obtained with a new high purity Germanium detector measuring the gamma emission spectrum from the plasma. The effects of toroidal Alfven eigenmodes modes and various MHD instabilities on the confinement of the fast particles have been determined

A gyrokinetic perspective on the JET-ILW pedestal

NASA Astrophysics Data System (ADS)

Hatch, D. R.; Kotschenreuther, M.; Mahajan, S.; Valanju, P.; Liu, X.

2017-03-01

JET has been unable to recover historical confinement levels when operating with an ITER-like wall (ILW) due largely to the inaccessibility of high pedestal temperatures. Finding a path to overcome this challenge is of utmost importance for both a prospective JET DT campaign and for future ITER operation. Gyrokinetic simulations (using the Gene code) quantitatively capture experimental transport levels for a representative experimental discharge and qualitatively recover the major experimental trends. Microtearing turbulence is a major transport mechanisms for the low-temperature pedestals characteristic of unseeded JET-ILW discharges. At higher temperatures and/or lower {ρ\\ast} , we identify electrostatic ITG transport of a type that is strongly shear-suppressed on smaller machines. Consistent with observations, this transport mechanism is strongly reduced by the presence of a low-Z impurity (e.g. carbon or nitrogen at the level of {{Z}\\text{eff}}∼ 2 ), recovering the accessibility of high pedestal temperatures. Notably, simulations based on dimensionless {ρ\\ast} scans recover historical scaling behavior except in the unique JET-ILW parameter regime where ITG turbulence becomes important. Our simulations also elucidate the observed degradation of confinement caused by gas puffing, emphasizing the important role of the density pedestal structure. This study maps out important regions of parameter space, providing insights that may point to optimal physical regimes that can enable the recovery of high pedestal temperatures on JET.

Overview of the JET results with the ITER-like wall

NASA Astrophysics Data System (ADS)

Romanelli, F.; EFDA Contributors, JET

2013-10-01

Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Zeff (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H98,y2 close to 1 and βN ˜ 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.

Post-stenotic plug-like jet with a vortex ring demonstrated by 4D flow MRI.

PubMed

Kim, Guk Bae; Ha, Hojin; Kweon, Jihoon; Lee, Sang Joon; Kim, Young-Hak; Yang, Dong Hyun; Kim, Namkug

2016-05-01

To investigate the details of the flow structure of a plug-like jet that had a vortex ring in pulsatile stenotic phantoms using 4D flow MRI. Pulsatile Newtonian flows in two stenotic phantoms with 50% and 75% reductions in area were scanned by 4D flow MRI. Blood analog working fluid was circulated via the stenotic phantom using a pulsatile pump at a constant pulsating frequency of 1Hz. The velocity and vorticity fields of the plug-like jet with a vortex ring were quantitatively analyzed in the spatial and temporal domains. Pulsatile stenotic flow showed a plug-like jet at the specific stenotic degree of 50% in our pulsatile waveform design. This plug-like jet was found at the decelerating period in the post-stenotic region of 26.4mm (1.2 D). It revealed a vortex ring structure with vorticity strength in the range of ±100s(-1). We observed a plug-like jet with a vortex ring in pulsatile stenotic flow by in vitro visualization using 4D flow MRI. In this plug-like jet, the local fastest flow region occurred at the post-systole phase in the post-stenotic region, which was distinguishable from a typical stenotic jet flow at systole phase. Copyright © 2015 Elsevier Inc. All rights reserved.

Pulsating jet-like structures in magnetized plasma

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

Goncharov, V. P.; Pavlov, V. I.

The formation of pulsating jet-like structures has been studied in the scope of the nonhydrostatic model of a magnetized plasma with horizontally nonuniform density. We discuss two mechanisms which are capable of stopping the gravitational spreading appearing to grace the Rayleigh-Taylor instability and to lead to the formation of stationary or oscillating localized structures. One of them is caused by the Coriolis effect in the rotating frames, and another is connected with the Lorentz effect for magnetized fluids. Magnetized jets/drops with a positive buoyancy must oscillate in transversal size and can manifest themselves as “radio pulsars.” The estimates of theirmore » frequencies are made for conditions typical for the neutron star's ocean.« less

Response Sensitivity of Typical Aircraft Jet Engine Fan Blade-Like Structures to Bird Impacts.

DTIC Science & Technology

1982-05-01

AIRCRAFT ENGINE BU--ETC F/G 21/5 RESPONSE SENSITIVITY OF TYPICAL AIRCRAFT JET ENGINE FAN BLADE -L...SENSITIVITY OF TYPICAL AIRCRAFT JET ENGINE FAN BLADE -LIKE STRUCTURES TO BIRD IMPACTS David P. Bauer Robert S. Bertke University of Dayton Research...COVERED RESPONSE SENSITIVITY OF TYPICAL AIRCRAFT FINAL REPORT JET ENGINE FAN BLADE -LIKE STRUCTURES Oct. 1977 to Jan. 1979 TO BIRD IMPACTS s.

Modern Design of Resonant Edge-Slot Array Antennas

NASA Technical Reports Server (NTRS)

Gosselin, R. B.

2006-01-01

Resonant edge-slot (slotted-waveguide) array antennas can now be designed very accurately following a modern computational approach like that followed for some other microwave components. This modern approach makes it possible to design superior antennas at lower cost than was previously possible. Heretofore, the physical and engineering knowledge of resonant edge-slot array antennas had remained immature since they were introduced during World War II. This is because despite their mechanical simplicity, high reliability, and potential for operation with high efficiency, the electromagnetic behavior of resonant edge-slot antennas is very complex. Because engineering design formulas and curves for such antennas are not available in the open literature, designers have been forced to implement iterative processes of fabricating and testing multiple prototypes to derive design databases, each unique for a specific combination of operating frequency and set of waveguide tube dimensions. The expensive, time-consuming nature of these processes has inhibited the use of resonant edge-slot antennas. The present modern approach reduces costs by making it unnecessary to build and test multiple prototypes. As an additional benefit, this approach affords a capability to design an array of slots having different dimensions to taper the antenna illumination to reduce the amplitudes of unwanted side lobes. The heart of the modern approach is the use of the latest commercially available microwave-design software, which implements finite-element models of electromagnetic fields in and around waveguides, antenna elements, and similar components. Instead of building and testing prototypes, one builds a database and constructs design curves from the results of computational simulations for sets of design parameters. The figure shows a resonant edge-slot antenna designed following this approach. Intended for use as part of a radiometer operating at a frequency of 10.7 GHz, this antenna

A two-dimensional, iterative solution for the jet flap

NASA Technical Reports Server (NTRS)

Herold, A. C.

1973-01-01

A solution is presented for the jet-flapped wing in two dimensions. The main flow is assumed to be inviscid and incompressible. The flow inside the jet is considered irrotational and the upper and lower boundaries between the jet and free stream are assumed to behave as vortex sheets which allow no mixing. The solution is found to be in satisfactory agreement with two dimensional experimental results and other theoretical work for intermediate values of momentum coefficient, but the regions of agreement vary with jet exit angle. At small values of momentum coefficient, the trajectory for the jet, as computed by this method, has more penetration than that of other available data, while at high values of moment coefficient this solution results in less penetration of the jet into the main flow.

Search for vector-like quark production in the lepton+jets and dilepton+jets final states using 5.4 fb -1 of Run II data

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

Caughron, Seth

2011-01-01

The Standard Model of particle physics provides an excellent description of particle interactions at energies up to ~1 TeV, but it is expected to fail above that scale. Multiple models developed to describe phenomena above the TeV scale predict the existence of very massive, vector-like quarks. A search for single electroweak production of such particles in pmore » $$\\bar{p}$$ collisions at a center-of-mass energy of 1.96 TeV is performed in the W+jets and Z+jets channels. The data were collected by the DØ detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4 fb -1. Events consistent with a heavy object decaying to a vector boson and a jet are selected. We observe no significant excess in comparison to the background prediction and set 95% confidence level upper limits on production cross sections for vector-like quarks decaying to W+jet and Z+jet. Assuming a vector-like quark -- standard model quark coupling parameter $$\\tilde{κ}$$ qQ of unity, we exclude vector-like quarks with mass below 693 GeV for decays to W+jet and mass below 449 GeV for decays to Z+jet. These represent the most sensitive limits to date.« less

Progress in the Design and Development of the ITER Low-Field Side Reflectometer (LFSR) System

NASA Astrophysics Data System (ADS)

Doyle, E. J.; Wang, G.; Peebles, W. A.; US LFSR Team

2015-11-01

The US has formed a team, comprised of personnel from PPPL, ORNL, GA and UCLA, to develop the LFSR system for ITER. The LFSR system will contribute to the measurement of a number of plasma parameters on ITER, including edge plasma electron density profiles, monitor Edge Localized Modes (ELMs) and L-H transitions, and provide physics measurements relating to high frequency instabilities, plasma flows, and other density transients. An overview of the status of design activities and component testing for the system will be presented. Since the 2011 conceptual design review, the number of microwave transmission lines (TLs) and antennas has been reduced from twelve (12) to seven (7) due to space constraint in the ITER Tokamak Port Plug. This change has required a reconfiguration and recalculation of the performance of the front-end antenna design, which now includes use of monostatic transmission lines and antennas. Work supported by US ITER/PPPL Subcontracts S013252-C and S012340, and PO 4500051400 from GA to UCLA.

Analysis of the phase control of the ITER ICRH antenna array. Influence on the load resilience and radiated power spectrum

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

Messiaen, A., E-mail: a.messiaen@fz-juelich.de; Ongena, J.; Vervier, M.

2015-12-10

The paper analyses how the phasing of the ITER ICRH 24 strap array evolves from the power sources up to the strap currents of the antenna. The study of the phasing control and coherence through the feeding circuits with prematching and automatic matching and decoupling network is made by modeling starting from the TOPICA matrix of the antenna array for a low coupling plasma profile and for current drive phasing (worst case for mutual coupling effects). The main results of the analysis are: (i) the strap current amplitude is well controlled by the antinode V{sub max} amplitude of the feedingmore » lines, (ii) the best toroidal phasing control is done by the adjustment of the mean phase of V{sub max} of each poloidal straps column, (iii) with well adjusted system the largest strap current phasing error is ±20°, (iv) the effect on load resilience remains well below the maximum affordable VSWR of the generators, (v) the effect on the radiated power spectrum versus k{sub //} computed by means of the coupling code ANTITER II remains small for the considered cases.« less

Environmental projects. Volume 6: Environmental assessment. New 34-meter antenna at Venus site

NASA Technical Reports Server (NTRS)

Kushner, L.

1988-01-01

The Jet Propulsion Lab has proposed replacing the 26-meter antenna at the Venus Station of the Goldstone Deep Space Communications Complex with a new 34-meter antenna. An environmental impact assessment of this proposed change is presented. It is concluded that the proposed antenna and its operation would not result in significant adverse impacts to the physical or human environment. It will, however, be necessary to manage electromagnetic transmissions from the antenna in such a manner as to ensure safe operation.

Tungsten dust impact on ITER-like plasma edge

DOE PAGES

Smirnov, R. D.; Krasheninnikov, S. I.; Pigarov, A. Yu.; ...

2015-01-12

The impact of tungsten dust originating from divertor plates on the performance of edge plasma in ITER-like discharge is evaluated using computer modeling with the coupled dust-plasma transport code DUSTT-UEDGE. Different dust injection parameters, including dust size and mass injection rates, are surveyed. It is found that tungsten dust injection with rates as low as a few mg/s can lead to dangerously high tungsten impurity concentrations in the plasma core. Dust injections with rates of a few tens of mg/s are shown to have a significant effect on edge plasma parameters and dynamics in ITER scale tokamaks. The large impactmore » of certain phenomena, such as dust shielding by an ablation cloud and the thermal force on tungsten ions, on dust/impurity transport in edge plasma and consequently on core tungsten contamination level is demonstrated. Lastly, it is also found that high-Z impurities provided by dust can induce macroscopic self-sustained plasma oscillations in plasma edge leading to large temporal variations of edge plasma parameters and heat load to divertor target plates.« less

Mitigation of Parallel RF Potentials by an Appropriate Antenna Design Using TOPICA

NASA Astrophysics Data System (ADS)

Maggiora, R.; Milanesio, D.

2011-12-01

A substantial effort has been devoted in recent years to the optimization of the ITER Ion Cyclotron (IC) launcher [1], above all with the aim of maximizing the coupling performances of the antenna; good improvements have been documented by using TOPICA code [2], a predictive tool for the design and optimization of RF launchers in front of a plasma region. Despite the progresses in the mentioned topic, this is not the only issue related to the design of IC antennas: a second crucial aspect is the impurities production, which is driven by the parallel RF potentials generated by the antenna itself and by the surrounding structures. The goal of this work is to analyze a set of innovative solutions that could be implemented in the next generation of IC antennas in order to mitigate the parallel RF potentials without reducing the power delivered to plasma. To achieve this challenging task, the TOPICA code has been adopted, taking advantage of recently introduced features. In particular, the code permits to compute the electric field distribution everywhere inside the antenna enclosure and in the plasma column, allowing to determine not only the magnitude and shape of the fields in front of the antenna, but also to evaluate their radial decay. Provided the electric field map, it is then possible to determine the parallel RF potentials and, even more important, to directly verify the impact of geometrical modifications of the front elements of the antenna on the RF potentials themselves. Furthermore, the capability to simulate the full 3D antenna with a high geometrical accuracy (as the one provided by commercial codes) and to account for an accurate plasma model indicates in TOPICA code a perfect candidate for this specific task. To lower the parallel RF potentials, two complementary approaches are outlined in the paper: the first one acts on the reduction of the electric field values, the second works on the minimization of the geometrical asymmetries. Pros and cons of

Study of array plasma antenna parameters

NASA Astrophysics Data System (ADS)

Kumar, Rajneesh; Kumar, Prince

2018-04-01

This paper is aimed to investigate the array plasma antenna parameters to help the optimization of an array plasma antenna. Single plasma antenna is transformed into array plasma antenna by changing the operating parameters. The re-configurability arises in the form of striations, due to transverse bifurcation of plasma column by changing the operating parameters. Each striation can be treated as an antenna element and system performs like an array plasma antenna. In order to achieve the goal of this paper, three different configurations of array plasma antenna (namely Array 1, Array 2 and Array 3) are simulated. The observations are made on variation in antenna parameters like resonance frequency, radiation pattern, directivity and gain with variation in length and number of antenna elements for each array plasma antenna. Moreover experiments are also performed and results are compared with simulation. Further array plasma antenna parameters are also compared with monopole plasma antenna parameters. The study of present paper invoke the array plasma antenna can be applied for steering and controlling the strength of Wi-Fi signals as per requirement.

Phase Retrieval for Radio Telescope and Antenna Control

NASA Technical Reports Server (NTRS)

Dean, Bruce

2011-01-01

Phase-retrieval is a general term used in optics to describe the estimation of optical imperfections or "aberrations." The purpose of this innovation is to develop the application of phase retrieval to radio telescope and antenna control in the millimeter wave band. Earlier techniques do not approximate the incoherent subtraction process as a coherent propagation. This approximation reduces the noise in the data and allows a straightforward application of conventional phase retrieval techniques for radio telescope and antenna control. The application of iterative-transform phase retrieval to radio telescope and antenna control is made by approximating the incoherent subtraction process as a coherent propagation. Thus, for systems utilizing both positive and negative polarity feeds, this approximation allows both surface and alignment errors to be assessed without the use of additional hardware or laser metrology. Knowledge of the antenna surface profile allows errors to be corrected at a given surface temperature and observing angle. In addition to imperfections of the antenna surface figure, the misalignment of multiple antennas operating in unison can reduce or degrade the signal-to-noise ratio of the received or broadcast signals. This technique also has application to the alignment of antenna array configurations.

Method for Fabricating and Packaging an M.Times.N Phased-Array Antenna

NASA Technical Reports Server (NTRS)

Xu, Xiaochuan (Inventor); Chen, Yihong (Inventor); Chen, Ray T. (Inventor); Subbaraman, Harish (Inventor)

2017-01-01

A method for fabricating an M.times.N, P-bit phased-array antenna on a flexible substrate is disclosed. The method comprising ink jet printing and hardening alignment marks, antenna elements, transmission lines, switches, an RF coupler, and multilayer interconnections onto the flexible substrate. The substrate of the M.times.N, P-bit phased-array antenna may comprise an integrated control circuit of printed electronic components such as, photovoltaic cells, batteries, resistors, capacitors, etc. Other embodiments are described and claimed.

The Role of Combined ICRF and NBI Heating in JET Hybrid Plasmas in Quest for High D-T Fusion Yield

NASA Astrophysics Data System (ADS)

Mantsinen, Mervi; Challis, Clive; Frigione, Domenico; Graves, Jonathan; Hobirk, Joerg; Belonohy, Eva; Czarnecka, Agata; Eriksson, Jacob; Gallart, Dani; Goniche, Marc; Hellesen, Carl; Jacquet, Philippe; Joffrin, Emmanuel; King, Damian; Krawczyk, Natalia; Lennholm, Morten; Lerche, Ernesto; Pawelec, Ewa; Sips, George; Solano, Emilia R.; Tsalas, Maximos; Valisa, Marco

2017-10-01

Combined ICRF and NBI heating played a key role in achieving the world-record fusion yield in the first deuterium-tritium campaign at the JET tokamak in 1997. The current plans for JET include new experiments with deuterium-tritium (D-T) plasmas with more ITER-like conditions given the recently installed ITER-like wall (ILW). In the 2015-2016 campaigns, significant efforts have been devoted to the development of high-performance plasma scenarios compatible with ILW in preparation of the forthcoming D-T campaign. Good progress was made in both the inductive (baseline) and the hybrid scenario: a new record JET ILW fusion yield with a significantly extended duration of the high-performance phase was achieved. This paper reports on the progress with the hybrid scenario which is a candidate for ITER longpulse operation (˜1000 s) thanks to its improved normalized confinement, reduced plasma current and higher plasma beta with respect to the ITER reference baseline scenario. The combined NBI+ICRF power in the hybrid scenario was increased to 33 MW and the record fusion yield, averaged over 100 ms, to 2.9x1016 neutrons/s from the 2014 ILW fusion record of 2.3x1016 neutrons/s. Impurity control with ICRF waves was one of the key means for extending the duration of the high-performance phase. The main results are reviewed covering both key core and edge plasma issues.

Tritium analysis of divertor tiles used in JET ITER-like wall campaigns by means of β-ray induced x-ray spectrometry

NASA Astrophysics Data System (ADS)

Hatano, Y.; Yumizuru, K.; Koivuranta, S.; Likonen, J.; Hara, M.; Matsuyama, M.; Masuzaki, S.; Tokitani, M.; Asakura, N.; Isobe, K.; Hayashi, T.; Baron-Wiechec, A.; Widdowson, A.; contributors, JET

2017-12-01

Energy spectra of β-ray induced x-rays from divertor tiles used in ITER-like wall campaigns of the Joint European Torus were measured to examine tritium (T) penetration into tungsten (W) layers. The penetration depth of T evaluated from the intensity ratio of W(Lα) x-rays to W(Mα) x-rays showed clear correlation with poloidal position; the penetration depth at the upper divertor region reached several micrometers, while that at the lower divertor region was less than 500 nm. The deep penetration at the upper part was ascribed to the implantation of high energy T produced by DD fusion reactions. The poloidal distribution of total x-ray intensity indicated higher T retention in the inboard side than the outboard side of the divertor region.

Optical Links and RF Distribution for Antenna Arrays

NASA Technical Reports Server (NTRS)

Huang, Shouhua; Calhoun, Malcolm; Tjoelker, Robert

2006-01-01

An array of three antennas has recently been developed at the NASA Jet Propulsion Laboratory capable of detecting signals at X and Ka band. The array requires a common frequency reference and high precision phase alignment to correlate received signals. Frequency and timing references are presently provided from a remotely located hydrogen maser and clock through a combination of commercially and custom developed optical links. The selected laser, photodetector, and fiber components have been tested under anticipated thermal and simulated antenna rotation conditions. The resulting stability limitations due to thermal perturbations or induced stress on the optical fiber have been characterized. Distribution of the X band local oscillator includes a loop back and precision phase monitor to enable correlation of signals received from each antenna.

The Galileo high gain antenna deployment anomaly

NASA Technical Reports Server (NTRS)

Johnson, Michael R.

1994-01-01

On April 11, 1991, the Galileo spacecraft executed a sequence that would open the spacecraft's High Gain Antenna. The Antenna's launch restraint had been released just after deployment sequence, the antenna, which opens like an umbrella, never reached the fully deployed position. The analyses and tests that followed allowed a conclusive determination of the likely failure mechanisms and pointed to some strategies to use for recovery of the high gain antenna.

The sound of oscillating air jets: Physics, modeling and simulation in flute-like instruments

NASA Astrophysics Data System (ADS)

de La Cuadra, Patricio

Flute-like instruments share a common mechanism that consists of blowing across one open end of a resonator to produce an air jet that is directed towards a sharp edge. Analysis of its operation involves various research fields including fluid dynamics, aero-acoustics, and physics. An effort has been made in this study to extend this description from instruments with fixed geometry like recorders and organ pipes to flutes played by the lips. An analysis of the jet's response to a periodic excitation is the focus of this study, as are the parameters under the player's control in forming the jet. The jet is excited with a controlled excitation consisting of two loudspeakers in opposite phase. A Schlieren system is used to visualize the jet, and image detection algorithms are developed to extract quantitative information from the images. In order to study the behavior of jets observed in different flute-like instruments, several geometries of the excitation and jet shapes are studied. The obtained data is used to propose analytical models that correctly fit the observed measurements and can be used for simulations. The control exerted by the performer on the instrument is of crucial importance in the quality of the sound produced for a number of flute-like instruments. The case of the transverse flute is experimentally studied. An ensemble of control parameters are measured and visualized in order to describe some aspects of the subtle control attained by an experienced flautist. Contrasting data from a novice flautist are compared. As a result, typical values for several non-dimensional parameters that characterize the normal operation of the instrument have been measured, and data to feed simulations has been collected. The information obtained through experimentation is combined with research developed over the last decades to put together a time-domain simulation. The model proposed is one-dimensional and driven by a single physical input. All the variables in the

Structural optimization and recent large ground antenna installations

NASA Technical Reports Server (NTRS)

Levy, Roy

1989-01-01

Within the past several years, the Jet Propulsion Laboratory has designed and built major ground antenna structures in Spain, Australia, and California. One of the antennas at each location is a 70 meter-diameter structure that is a retrofit of the existing 64 meter antenna. The 64 meter existing antennas were first stripped back to a 34 meter interior and then completely new construction with deeper trusses was added to extend the interior to 70 meters. The 70 meter project included the rare opportunity to collect field data to compare with predictions of the finite-element analytical models. The new quadripod design was tested for its lower mode natural frequencies and the main reflector was measured by theodolite to determine deflections of subsets of the backup-structure deformations under load. The emphasis here is to examine measurement results and possibly provide some appreciation of the relationship of predictions made from the design model to actual measurements.

First operation with the JET International Thermonuclear Experimental Reactor-like walla)

NASA Astrophysics Data System (ADS)

Neu, R.; Arnoux, G.; Beurskens, M.; Bobkov, V.; Brezinsek, S.; Bucalossi, J.; Calabro, G.; Challis, C.; Coenen, J. W.; de la Luna, E.; de Vries, P. C.; Dux, R.; Frassinetti, L.; Giroud, C.; Groth, M.; Hobirk, J.; Joffrin, E.; Lang, P.; Lehnen, M.; Lerche, E.; Loarer, T.; Lomas, P.; Maddison, G.; Maggi, C.; Matthews, G.; Marsen, S.; Mayoral, M.-L.; Meigs, A.; Mertens, Ph.; Nunes, I.; Philipps, V.; Pütterich, T.; Rimini, F.; Sertoli, M.; Sieglin, B.; Sips, A. C. C.; van Eester, D.; van Rooij, G.; JET-EFDA Contributors

2013-05-01

To consolidate International Thermonuclear Experimental Reactor (ITER) design choices and prepare for its operation, Joint European Torus (JET) has implemented ITER's plasma facing materials, namely, Be for the main wall and W in the divertor. In addition, protection systems, diagnostics, and the vertical stability control were upgraded and the heating capability of the neutral beams was increased to over 30 MW. First results confirm the expected benefits and the limitations of all metal plasma facing components (PFCs) but also yield understanding of operational issues directly relating to ITER. H-retention is lower by at least a factor of 10 in all operational scenarios compared to that with C PFCs. The lower C content (≈ factor 10) has led to much lower radiation during the plasma burn-through phase eliminating breakdown failures. Similarly, the intrinsic radiation observed during disruptions is very low, leading to high power loads and to a slow current quench. Massive gas injection using a D2/Ar mixture restores levels of radiation and vessel forces similar to those of mitigated disruptions with the C wall. Dedicated L-H transition experiments indicate a 30% power threshold reduction, a distinct minimum density, and a pronounced shape dependence. The L-mode density limit was found to be up to 30% higher than for C allowing stable detached divertor operation over a larger density range. Stable H-modes as well as the hybrid scenario could be re-established only when using gas puff levels of a few 1021 es-1. On average, the confinement is lower with the new PFCs, but nevertheless, H factors up to 1 (H-Mode) and 1.3 (at βN≈3, hybrids) have been achieved with W concentrations well below the maximum acceptable level.

Optimization studies of the ITER low field side reflectometer.

PubMed

Diem, S J; Wilgen, J B; Bigelow, T S; Hanson, G R; Harvey, R W; Smirnov, A P

2010-10-01

Microwave reflectometry will be used on ITER to measure the electron density profile, density fluctuations due to MHD/turbulence, edge localized mode (ELM) density transients, and as an L-H transition monitor. The ITER low field side reflectometer system will measure both core and edge quantities using multiple antenna arrays spanning frequency ranges of 15-155 GHz for the O-mode system and 55-220 GHz for the X-mode system. Optimization studies using the GENRAY ray-tracing code have been done for edge and core measurements. The reflectometer launchers will utilize the HE11 mode launched from circular corrugated waveguide. The launched beams are assumed to be Gaussian with a beam waist diameter of 0.643 times the waveguide diameter. Optimum launcher size and placement are investigated by computing the antenna coupling between launchers, assuming the launched and received beams have a Gaussian beam pattern.

ITER-relevant calibration technique for soft x-ray spectrometer.

PubMed

Rzadkiewicz, J; Książek, I; Zastrow, K-D; Coffey, I H; Jakubowska, K; Lawson, K D

2010-10-01

The ITER-oriented JET research program brings new requirements for the low-Z impurity monitoring, in particular for the Be—the future main wall component of JET and ITER. Monitoring based on Bragg spectroscopy requires an absolute sensitivity calibration, which is challenging for large tokamaks. This paper describes both “component-by-component” and “continua” calibration methods used for the Be IV channel (75.9 Å) of the Bragg rotor spectrometer deployed on JET. The calibration techniques presented here rely on multiorder reflectivity calculations and measurements of continuum radiation emitted from helium plasmas. These offer excellent conditions for the absolute photon flux calibration due to their low level of impurities. It was found that the component-by-component method gives results that are four times higher than those obtained by means of the continua method. A better understanding of this discrepancy requires further investigations.

Automatic location of disruption times in JET

NASA Astrophysics Data System (ADS)

Moreno, R.; Vega, J.; Murari, A.

2014-11-01

The loss of stability and confinement in tokamak plasmas can induce critical events known as disruptions. Disruptions produce strong electromagnetic forces and thermal loads which can damage fundamental components of the devices. Determining the disruption time is extremely important for various disruption studies: theoretical models, physics-driven models, or disruption predictors. In JET, during the experimental campaigns with the JET-C (Carbon Fiber Composite) wall, a common criterion to determine the disruption time consisted of locating the time of the thermal quench. However, with the metallic ITER-like wall (JET-ILW), this criterion is usually not valid. Several thermal quenches may occur previous to the current quench but the temperature recovers. Therefore, a new criterion has to be defined. A possibility is to use the start of the current quench as disruption time. This work describes the implementation of an automatic data processing method to estimate the disruption time according to this new definition. This automatic determination allows both reducing human efforts to locate the disruption times and standardizing the estimates (with the benefit of being less vulnerable to human errors).

A subtraction scheme for computing QCD jet cross sections at NNLO: integrating the iterated singly-unresolved subtraction terms

NASA Astrophysics Data System (ADS)

Bolzoni, Paolo; Somogyi, Gábor; Trócsányi, Zoltán

2011-01-01

We perform the integration of all iterated singly-unresolved subtraction terms, as defined in ref. [1], over the two-particle factorized phase space. We also sum over the unresolved parton flavours. The final result can be written as a convolution (in colour space) of the Born cross section and an insertion operator. We spell out the insertion operator in terms of 24 basic integrals that are defined explicitly. We compute the coefficients of the Laurent expansion of these integrals in two different ways, with the method of Mellin-Barnes representations and sector decomposition. Finally, we present the Laurent-expansion of the full insertion operator for the specific examples of electron-positron annihilation into two and three jets.

Qualification of tungsten coatings on plasma-facing components for JET

NASA Astrophysics Data System (ADS)

Maier, H.; Neu, R.; Greuner, H.; Böswirth, B.; Balden, M.; Lindig, S.; Matthews, G. F.; Rasinski, M.; Wienhold, P.; Wiltner, A.

2009-12-01

This contribution summarizes the work that has been performed to establish the industrial production of tungsten coatings on carbon fibre composite (CFC) for application within the ITER-like Wall Project at JET. This comprises the investigation of vacuum plasma-sprayed coatings, physical vapour deposited tungsten/rhenium multilayers, as well as coatings deposited by combined magnetron-sputtering and ion implantation. A variety of analysis tools were applied to investigate failures and oxide and carbide formation in these systems.

Antenna Efficiency and the Genius of the IEEE Standard for Antenna Terms [Education Column

NASA Astrophysics Data System (ADS)

Warnick, Karl F.

2012-08-01

At a 2007 Square Kilometre Array Design Studies (SKADS) workshop in Dwingeloo, Wim van Cappellen of the Nether lands Institute for Radio Astronomy (ASTRON) gave a presentation on figures of merit, in which he memorably compared antenna terms to apples. What seems like a simple, homogeneous fruit comes in all colors and varieties. Similarly, a survey of antenna literature and textbooks shows that authors use a wide variety of antenna figures of merit, often not in compliance with the relevant IEEE Standard Definitions of Terms for Antennas [1]. Since this standard is now in the process of revision by the Antennas and Propagation Society Antenna Standards Committee, it seems worth while to consider the standard, and clarify some common misunderstandings and inconsistent usages.

Demonstration of an X-Band Multilayer Yagi-Like Microstrip Patch Antenna With High Directivity and Large Bandwidth

NASA Technical Reports Server (NTRS)

Nessel, James A.; Zaman, Afroz; Lee, Richard Q.; Lambert, Kevin

2005-01-01

The feasibility of obtaining large bandwidth and high directivity from a multilayer Yagi-like microstrip patch antenna at 10 GHz is investigated. A measured 10-dB bandwidth of approximately 20 percent and directivity of approximately 11 dBi is demonstrated through the implementation of a vertically-stacked structure with three parasitic directors, above the driven patch, and a single reflector underneath the driven patch. Simulated and measured results are compared and show fairly close agreement. This antenna offers the advantages of large bandwidth, high directivity, and symmetrical broadside patterns, and could be applicable to satellite as well as terrestrial communications.

Experiments and Simulations of ITER-like Plasmas in Alcator C-Mod

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

.R. Wilson, C.E. Kessel, S. Wolfe, I.H. Hutchinson, P. Bonoli, C. Fiore, A.E. Hubbard, J. Hughes, Y. Lin, Y. Ma, D. Mikkelsen, M. Reinke, S. Scott, A.C.C. Sips, S. Wukitch and the C-Mod Team

Alcator C-Mod is performing ITER-like experiments to benchmark and verify projections to 15 MA ELMy H-mode Inductive ITER discharges. The main focus has been on the transient ramp phases. The plasma current in C-Mod is 1.3 MA and toroidal field is 5.4 T. Both Ohmic and ion cyclotron (ICRF) heated discharges are examined. Plasma current rampup experiments have demonstrated that (ICRF and LH) heating in the rise phase can save voltseconds (V-s), as was predicted for ITER by simulations, but showed that the ICRF had no effect on the current profile versus Ohmic discharges. Rampdown experiments show an overcurrent inmore » the Ohmic coil (OH) at the H to L transition, which can be mitigated by remaining in H-mode into the rampdown. Experiments have shown that when the EDA H-mode is preserved well into the rampdown phase, the density and temperature pedestal heights decrease during the plasma current rampdown. Simulations of the full C-Mod discharges have been done with the Tokamak Simulation Code (TSC) and the Coppi-Tang energy transport model is used with modified settings to provide the best fit to the experimental electron temperature profile. Other transport models have been examined also. __________________________________________________« less

Density Convection near Radiating ICRF Antennas and its Effect on the Coupling of Lower Hybrid Waves

NASA Astrophysics Data System (ADS)

Ekedahl, A.; Colas, L.; Mayoral, M.-L.; Beaumont, B.; Bibet, Ph.; Brémond, S.; Kazarian, F.; Mailloux, J.; Noterdaeme, J.-M.; Efda-Jet Contributors

2003-12-01

Combined operation of Lower Hybrid (LH) and Ion Cyclotron Resonance Frequency (ICRF) waves can result in a degradation of the LH wave coupling, as observed both in the Tore Supra and JET tokamaks. The reflection coefficient on the part of the LH launcher magnetically connected to the powered ICRF antenna increases, suggesting a local decrease in the electron density in the connecting flux tubes. This has been confirmed by Langmuir probe measurements on the LH launchers in the latest Tore Supra experiments. Moreover, recent experiments in JET indicate that the LH coupling degradation depends on the ICRF power and its launched k//-spectrum. The 2D density distribution around the Tore Supra ICRF antennas has been modelled with the CELLS-code, balancing parallel losses with diffusive transport and sheath induced E×B convection, obtained from RF field mapping using the ICANT-code. The calculations are in qualitative agreement with the experimental observations, i.e. density depletion is obtained, localised mainly in the antenna shadow, and dependent on ICRF power and antenna spectrum.

Metamaterial-based "sabre" antenna

NASA Astrophysics Data System (ADS)

Hafdallah Ouslimani, Habiba; Yuan, Tangjie; Kanane, Houcine; Priou, Alain; Collignon, Gérard; Lacotte, Guillaume

2014-05-01

The "sabre" antenna is an array of two monopole elements, vertically polarized with omnidirectional radiation patterns, and placed on either side of a composite material on the tail of an airplane. As an in-phase reflector plane, the antenna uses a compact dual-layer high-impedance surface (DL-HIS) with offset mushroom-like Sivenpiper square shape unit cells. This topology allows one to control both operational frequency and bandgap width, while reducing the total height of the antenna to under λ0/36. The designed antenna structure has a wide bandwidth higher than 24% around 1.4 GHz. The measurements and numerical simulations agree very well.

Magnetic antenna excitation of whistler modes. IV. Receiving antennas and reciprocity

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

Stenzel, R. L., E-mail: stenzel@physics.ucla.edu; Urrutia, J. M.

Antenna radiation patterns are an important property of antennas. Reciprocity holds in free space and the radiation patterns for exciting and receiving antennas are the same. In anisotropic plasmas, radiation patterns are complicated by the fact that group and phase velocities differ and certain wave properties like helicity depend on the direction of wave propagation with respect to the background magnetic field B{sub 0}. Interference and wave focusing effects are different than in free space. Reciprocity does not necessarily hold in a magnetized plasma. The present work considers the properties of various magnetic antennas used for receiving whistler modes. Itmore » is based on experimental data from exciting low frequency whistler modes in a large uniform laboratory plasma. By superposition of linear waves from different antennas, the radiation patterns of antenna arrays are derived. Plane waves are generated and used to determine receiving radiation patterns of different receiving antennas. Antenna arrays have radiation patterns with narrow lobes, whose angular position can be varied by physical rotation or electronic phase shifting. Reciprocity applies to broadside antenna arrays but not to end fire arrays which can have asymmetric lobes with respect to B{sub 0}. The effect of a relative motion between an antenna and the plasma has been modeled by the propagation of a short wave packet moving along a linear antenna array. An antenna moving across B{sub 0} has a radiation pattern characterized by an oscillatory “whistler wing.” A receiving antenna in motion can detect any plane wave within the group velocity resonance cone. The radiation pattern also depends on loop size relative to the wavelength. Motional effects prevent reciprocity. The concept of the radiation pattern loses its significance for wave packets since the received signal does not only depend on the antenna but also on the properties of the wave packet. The present results are of

Progress in Development of C60 Nanoparticle Plasma Jet for Diagnostic of Runaway Electron Beam-Plasma Interaction and Disruption Mitigation Study for ITER

NASA Astrophysics Data System (ADS)

Bogatu, I. N.; Thompson, J. R.; Galkin, S. A.; Kim, J. S.

2013-10-01

We produced a C60 nanoparticle plasma jet (NPPJ) with uniquely fast response-to-delivery time (~ 1 - 2 ms) and unprecedentedly high momentum (~ 0 . 6 g .km/s). The C60 NPPJ was obtained by using a solid state TiH2/C60 pulsed power cartridge producing ~180 mg of C60 molecular gas by sublimation and by electromagnetic acceleration of the C60 plasma in a coaxial gun (~35 cm length, 96 kJ energy) with the output of a high-density (>1023 m-3) hyper-velocity (>4 km/s) plasma jet. The ~ 75 mg C60/C plasma jet has the potential to rapidly and deeply deliver enough mass to significantly increase electron density (to ne ~ 2 . 4 ×1021 m-3, i.e. ~ 60 times larger than typical DIII-D pre-disruption value, ne 0 ~ 4 ×1019 m-3), and to modify the 'critical electric field' and the runaway electrons (REs) collisional drag during different phases of REs dynamics. The C60 NPPJ, as a novel injection technique, allows RE beam-plasma interaction diagnostic by quantitative spectroscopy of C ions visible/UV line intensity. The system is scalable to ~ 1 - 2 g C60/C plasma jet output and technology is adaptable to ITER acceptable materials (BN and Be) for disruption mitigation. Work supported by US DOE DE-FG02-08ER85196 grant.

Neutron streaming studies along JET shielding penetrations

NASA Astrophysics Data System (ADS)

Stamatelatos, Ion E.; Vasilopoulou, Theodora; Batistoni, Paola; Obryk, Barbara; Popovichev, Sergey; Naish, Jonathan

2017-09-01

Neutronic benchmark experiments are carried out at JET aiming to assess the neutronic codes and data used in ITER analysis. Among other activities, experiments are performed in order to validate neutron streaming simulations along long penetrations in the JET shielding configuration. In this work, neutron streaming calculations along the JET personnel entrance maze are presented. Simulations were performed using the MCNP code for Deuterium-Deuterium and Deuterium- Tritium plasma sources. The results of the simulations were compared against experimental data obtained using thermoluminescence detectors and activation foils.

The AGHS at JET and preparations for a future DT campaign

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

Smith, R.; JET-EFDA, Culham Science Centre, Abingdon

2015-03-15

The Active Gas Handling System (AGHS) at JET is a unique facility enabling JET to perform reactor like, DT operations. As a future DT experimental campaign (DTE2) is scheduled for 2017 this paper provides a brief overview of the AGHS and a summary of ongoing work supporting the currently JET experimental campaign. In order to improve tritium accountancy a solid state based detector for tritium is being developed. Another important upgrade concerns tritium injection, 4 existing GIMs (Tritium Gas Introduction Module) will inject a mix of D and T rather than T{sub 2} in the divertor region rather than inmore » the torus mid plane enabling a far better control and variability of the introduction of tritium into the plasma. An overview of the scale of DTE2 is included as well as an example of some of the upgrades currently being undertaken to fully exploit the learning opportunities for ITER and DEMO DTE2 provides. (authors)« less

Mobile SATCOM Antenna Developments and Experimental Results of Land- and Aeronautical -Mobile Field Trials

NASA Technical Reports Server (NTRS)

Densmore, A. C.; Huang, J.

1996-01-01

This paper discusses several mobile satcom antenna systems that the Jet Propulsion Laboratory (JPL) has developed and demonstrated during the last ten years for land -and aeronautical mobile digital audio/data/video satellite communication.

Observations of diffusion-limited aggregation-like patterns by atmospheric plasma jet

NASA Astrophysics Data System (ADS)

Chiu, Ching-Yang; Chu, Hong-Yu

2017-11-01

We report on the observations of diffusion-limited aggregation-like patterns during the thin film removal process by an atmospheric plasma jet. The fractal patterns are found to have various structures like dense branching and tree-like patterns. The determination of surface morphology reveals that the footprints of discharge bursts are not as random as expected. We propose a diffusion-limited aggregation model with a few extra requirements by analogy with the experimental results, and thereby present the beauty of nature. We show that the model simulates not only the shapes of the patterns similar to the experimental observations, but also the growing sequences of fluctuating, oscillatory, and zigzag traces.

Reduction of asymmetric wall force in ITER disruptions with fast current quench

NASA Astrophysics Data System (ADS)

Strauss, H.

2018-02-01

One of the problems caused by disruptions in tokamaks is the asymmetric electromechanical force produced in conducting structures surrounding the plasma. The asymmetric wall force in ITER asymmetric vertical displacement event (AVDE) disruptions is calculated in nonlinear 3D MHD simulations. It is found that the wall force can vary by almost an order of magnitude, depending on the ratio of the current quench time to the resistive wall magnetic penetration time. In ITER, this ratio is relatively low, resulting in a low asymmetric wall force. In JET, this ratio is relatively high, resulting in a high asymmetric wall force. Previous extrapolations based on JET measurements have greatly overestimated the ITER wall force. It is shown that there are two limiting regimes of AVDEs, and it is explained why the asymmetric wall force is different in the two limits.

Improvements to the ICRH antenna time-domain 3D plasma simulation model

NASA Astrophysics Data System (ADS)

Smithe, David N.; Jenkins, Thomas G.; King, J. R.

2015-12-01

We present a summary of ongoing improvements to the 3D time-domain plasma modeling software that has been used to look at ICRH antennas on Alcator C-Mod, NSTX, and ITER [1]. Our past investigations have shown that in low density cases where the slow wave is propagating, strong amplitude lower hybrid resonant fields can occur. Such a scenario could result in significant parasitic power loss in the SOL. The primary resonance broadening in this case is likely collisions with neutral gas, and thus we are upgrading the model to include realistic neutral gas in the SOL, in order to provide a better understanding of energy balance in these situations. Related to this, we are adding a temporal variation capability to the local plasma density in front of the antenna in order to investigate whether the near fields of the antenna could modify the local density sufficiently to initiate a low density situation. We will start with a simple scalar ponderomotive potential density expulsion model [2] for the density evolution, but are also looking to eventually couple to a more complex fluid treatment that would include tensor pressures and convective physics and sources of neutrals and ionization. We also review continued benchmarking efforts, and ongoing and planned improvements to the computational algorithms, resulting from experience gained during our recent supercomputing runs on the Titan supercomputer, including GPU operations.

OVERVIEW OF NEUTRON MEASUREMENTS IN JET FUSION DEVICE.

PubMed

Batistoni, P; Villari, R; Obryk, B; Packer, L W; Stamatelatos, I E; Popovichev, S; Colangeli, A; Colling, B; Fonnesu, N; Loreti, S; Klix, A; Klosowski, M; Malik, K; Naish, J; Pillon, M; Vasilopoulou, T; De Felice, P; Pimpinella, M; Quintieri, L

2017-10-05

The design and operation of ITER experimental fusion reactor requires the development of neutron measurement techniques and numerical tools to derive the fusion power and the radiation field in the device and in the surrounding areas. Nuclear analyses provide essential input to the conceptual design, optimisation, engineering and safety case in ITER and power plant studies. The required radiation transport calculations are extremely challenging because of the large physical extent of the reactor plant, the complexity of the geometry, and the combination of deep penetration and streaming paths. This article reports the experimental activities which are carried-out at JET to validate the neutronics measurements methods and numerical tools used in ITER and power plant design. A new deuterium-tritium campaign is proposed in 2019 at JET: the unique 14 MeV neutron yields produced will be exploited as much as possible to validate measurement techniques, codes, procedures and data currently used in ITER design thus reducing the related uncertainties and the associated risks in the machine operation. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Beam ion acceleration by ICRH in JET discharges

NASA Astrophysics Data System (ADS)

Budny, R. V.; Gorelenkova, M.; Bertelli, N.; JET Collaboration

2015-11-01

The ion Monte-Carlo orbit integrator NUBEAM, used in TRANSP has been enhanced to include an ``RF-kick'' operator to simulate the interaction of RF fields and fast ions. The RF quasi-linear operator (localized in space) uses a second R-Z orbit integrator. We apply this to analysis of recent JET discharges using ICRH with the ITER-like first wall. An example of results for a high performance Hybrid discharge for which standard TRANSP analysis simulated the DD neutron emission rate below measurements, re-analysis using the RF-kick operator results in increased beam parallel and perpendicular energy densities (~=40% and 15% respectively), and increased beam-thermal neutron emission (~= 35%), making the total rate closer to the measurement. Checks of the numerics, comparisons with measurements, and ITER implications will be presented. Supported in part by the US DoE contract DE-AC02-09CH11466 and by EUROfusion No 633053.

The Joint European Torus (JET)

NASA Astrophysics Data System (ADS)

Rebut, Paul-Henri

2017-02-01

This paper addresses the history of JET, the Tokamak that reached the highest performances and the experiment that so far came closest to the eventual goal of a fusion reactor. The reader must be warned, however, that this document is not a comprehensive study of controlled thermonuclear fusion or even of JET. The next step on this road, the ITER project, is an experimental reactor. Actually, several prototypes will be required before a commercial reactor can be built. The fusion history is far from been finalised. JET is still in operation some 32 years after the first plasma and still has to provide answers to many questions before ITER takes the lead on research. Some physical interpretations of the observed phenomena, although coherent, are still under discussion. This paper also recalls some basic physics concepts necessary to the understanding of confinement: a knowledgeable reader can ignore these background sections. This fascinating story, comprising successes and failures, is imbedded in the complexities of twentieth and the early twenty-first centuries at a time when world globalization is evolving and the future seems loaded with questions. The views here expressed on plasma confinement are solely those of the author. This is especially the case for magnetic turbulence, for which other scientists may have different views.

Modelling of transitions between L- and H-mode in JET high plasma current plasmas and application to ITER scenarios including tungsten behaviour

NASA Astrophysics Data System (ADS)

Koechl, F.; Loarte, A.; Parail, V.; Belo, P.; Brix, M.; Corrigan, G.; Harting, D.; Koskela, T.; Kukushkin, A. S.; Polevoi, A. R.; Romanelli, M.; Saibene, G.; Sartori, R.; Eich, T.; Contributors, JET

2017-08-01

The dynamics for the transition from L-mode to a stationary high Q DT H-mode regime in ITER is expected to be qualitatively different to present experiments. Differences may be caused by a low fuelling efficiency of recycling neutrals, that influence the post transition plasma density evolution on the one hand. On the other hand, the effect of the plasma density evolution itself both on the alpha heating power and the edge power flow required to sustain the H-mode confinement itself needs to be considered. This paper presents results of modelling studies of the transition to stationary high Q DT H-mode regime in ITER with the JINTRAC suite of codes, which include optimisation of the plasma density evolution to ensure a robust achievement of high Q DT regimes in ITER on the one hand and the avoidance of tungsten accumulation in this transient phase on the other hand. As a first step, the JINTRAC integrated models have been validated in fully predictive simulations (excluding core momentum transport which is prescribed) against core, pedestal and divertor plasma measurements in JET C-wall experiments for the transition from L-mode to stationary H-mode in partially ITER relevant conditions (highest achievable current and power, H 98,y ~ 1.0, low collisionality, comparable evolution in P net/P L-H, but different ρ *, T i/T e, Mach number and plasma composition compared to ITER expectations). The selection of transport models (core: NCLASS  +  Bohm/gyroBohm in L-mode/GLF23 in H-mode) was determined by a trade-off between model complexity and efficiency. Good agreement between code predictions and measured plasma parameters is obtained if anomalous heat and particle transport in the edge transport barrier are assumed to be reduced at different rates with increasing edge power flow normalised to the H-mode threshold; in particular the increase in edge plasma density is dominated by this edge transport reduction as the calculated neutral influx across the

Iterative Most-Likely Point Registration (IMLP): A Robust Algorithm for Computing Optimal Shape Alignment

PubMed Central

Billings, Seth D.; Boctor, Emad M.; Taylor, Russell H.

2015-01-01

We present a probabilistic registration algorithm that robustly solves the problem of rigid-body alignment between two shapes with high accuracy, by aptly modeling measurement noise in each shape, whether isotropic or anisotropic. For point-cloud shapes, the probabilistic framework additionally enables modeling locally-linear surface regions in the vicinity of each point to further improve registration accuracy. The proposed Iterative Most-Likely Point (IMLP) algorithm is formed as a variant of the popular Iterative Closest Point (ICP) algorithm, which iterates between point-correspondence and point-registration steps. IMLP’s probabilistic framework is used to incorporate a generalized noise model into both the correspondence and the registration phases of the algorithm, hence its name as a most-likely point method rather than a closest-point method. To efficiently compute the most-likely correspondences, we devise a novel search strategy based on a principal direction (PD)-tree search. We also propose a new approach to solve the generalized total-least-squares (GTLS) sub-problem of the registration phase, wherein the point correspondences are registered under a generalized noise model. Our GTLS approach has improved accuracy, efficiency, and stability compared to prior methods presented for this problem and offers a straightforward implementation using standard least squares. We evaluate the performance of IMLP relative to a large number of prior algorithms including ICP, a robust variant on ICP, Generalized ICP (GICP), and Coherent Point Drift (CPD), as well as drawing close comparison with the prior anisotropic registration methods of GTLS-ICP and A-ICP. The performance of IMLP is shown to be superior with respect to these algorithms over a wide range of noise conditions, outliers, and misalignments using both mesh and point-cloud representations of various shapes. PMID:25748700

Time-domain simulation of flute-like instruments: comparison of jet-drive and discrete-vortex models.

PubMed

Auvray, Roman; Ernoult, Augustin; Fabre, Benoît; Lagrée, Pierre-Yves

2014-07-01

This paper presents two models of sound production in flute-like instruments that allow time-domain simulations. The models are based on different descriptions of the jet flow within the window of the instrument. The jet-drive model depicts the jet by its transverse perturbation that interacts with the labium to produce sound. The discrete-vortex model depicts the jet as two independent shear layers along which vortices are convected and interact with the acoustic field within the window. The limit of validity between both models is usually discussed according to the aspect ratio of the jet W/h, with W the window length and h the flue channel height. The present simulations, compared with experimental data gathered on a recorder, allow to extend the aspect ratio criterion to the notion of dynamic aspect ratio defined as λ/h where λ is the hydrodynamic wavelength that now accounts for geometrical properties, such as W/h, as well as for dynamic properties, such as the Strouhal number. The two models are found to be applicable over neighboring values of geometry and blowing pressure.

Modification of jet-like correlations in Pb-Au collisions at 158A GeV/c

NASA Astrophysics Data System (ADS)

Ceres Collaboration; Adamová, D.; Agakichiev, G.; Antończyk, D.; Appelshäuser, H.; Belaga, V.; Bielčíková, J.; Braun-Munzinger, P.; Busch, O.; Cherlin, A.; Damjanović, S.; Dietel, T.; Dietrich, L.; Drees, A.; Dubitzky, W.; Esumi, S. I.; Filimonov, K.; Fomenko, K.; Fraenkel, Z.; Garabatos, C.; Glässel, P.; Holeczek, J.; Kalisky, M.; Kniege, S.; Kushpil, V.; Maas, A.; Marín, A.; Milošević, J.; Milov, A.; Miśkowiec, D.; Panebrattsev, Yu.; Petchenova, O.; Petráček, V.; Pfeiffer, A.; Płoskoń, M.; Rak, J.; Ravinovich, I.; Rehak, P.; Sako, H.; Schmitz, W.; Schuchmann, S.; Sedykh, S.; Shimansky, S.; Stachel, J.; Šumbera, M.; Tilsner, H.; Tserruya, I.; Wessels, J. P.; Wienold, T.; Wurm, J. P.; Xie, W.; Yurevich, S.; Yurevich, V.

2009-07-01

Results of a two-particle correlation analysis of high-p charged particles in Pb-Au collisions at 158A GeV/c are presented. The data have been recorded by the CERES experiment at the CERN-SPS. The correlations are studied as function of transverse momentum, particle charge and collision centrality. We observe a jet-like structure in the vicinity of a high-p trigger particle and a broad back-to-back distribution. The yields of associated particles per trigger show a strong dependence on the trigger/associate charge combination. A comparison to PYTHIA confirms the jet-like pattern at the near-side but suggests a strong modification at the away-side, implying significant energy transfer of the hard-scattered parton to the medium.

Unidirectional Magneto-Electric Dipole Antenna for Base Station: A Review

NASA Astrophysics Data System (ADS)

Idayachandran, Govindanarayanan; Nakkeeran, Rangaswamy

2018-04-01

Unidirectional base station antenna design using Magneto-Electric Dipole (MED) has created enormous interest among the researchers due to its excellent radiation characteristics like low back radiation, symmetrical radiation at E-plane and H-plane compared to conventional patch antenna. Generally, dual polarized antennas are used to increase channel capacity and reliability of the communication systems. In order to serve the evolving mobile communication standards like long term evolution LTE and beyond, unidirectional dual polarized MED antenna are required to have broad impedance bandwidth, broad half power beamwidth, high port isolation, low cross polarization level, high front to back ratio and high gain. In this paper, the critical electrical requirements of the base station antenna and frequently used frequency bands for modern mobile communication have been presented. It is followed by brief review on broadband patch antenna and discussion on complementary antenna concepts. Finally, the performance of linearly polarized and dual polarized magneto-electric dipole antennas along with their feeding techniques are discussed and summarized. Also, design and modeling of developed MED antenna is presented.

Auxiliary principle technique and iterative algorithm for a perturbed system of generalized multi-valued mixed quasi-equilibrium-like problems.

PubMed

Rahaman, Mijanur; Pang, Chin-Tzong; Ishtyak, Mohd; Ahmad, Rais

2017-01-01

In this article, we introduce a perturbed system of generalized mixed quasi-equilibrium-like problems involving multi-valued mappings in Hilbert spaces. To calculate the approximate solutions of the perturbed system of generalized multi-valued mixed quasi-equilibrium-like problems, firstly we develop a perturbed system of auxiliary generalized multi-valued mixed quasi-equilibrium-like problems, and then by using the celebrated Fan-KKM technique, we establish the existence and uniqueness of solutions of the perturbed system of auxiliary generalized multi-valued mixed quasi-equilibrium-like problems. By deploying an auxiliary principle technique and an existence result, we formulate an iterative algorithm for solving the perturbed system of generalized multi-valued mixed quasi-equilibrium-like problems. Lastly, we study the strong convergence analysis of the proposed iterative sequences under monotonicity and some mild conditions. These results are new and generalize some known results in this field.

Commercial applications of the ACTS mobile terminal millimeter-wave antennas

NASA Technical Reports Server (NTRS)

Densmore, Arthur C.; Crist, Rick A.; Jamnejad, Vahraz; Tulintseff, Ann N.

1991-01-01

NASA's Jet Propulsion Laboratory is currently developing the Advanced Communications Technology Satellite (ACTS) Mobile Terminal (AMT), which will provide voice, data, and video communications to and from a vehicle (van, truck, or car) via NASA's geostationary ACTS satellite using the K- and K(sub a)-band frequency bands. The AMT is already planned to demonstrate a variety of communications from within the mobile vehicular environment, and within this paper a summary of foreseen commercial application opportunities is given. A critical component of the AMT is its antenna system, which must establish and maintain the basic RF link with the satellite. Two versions of the antenna are under development, each incorporating different technologies and offering different commercial applications.

Radio antennas

NASA Astrophysics Data System (ADS)

Gibson, S. W.

This book is concerned with providing an explanation of the function of an antenna without delving too deeply into the mathematics or theory. The characteristics of an antenna are examined, taking into account aspects of antenna radiation, wave motion on the antenna, resistance in the antenna, impedance, the resonant antenna, the effect of the ground, polarization, radiation patterns, coupling effects between antenna elements, and receiving vs. transmitting. Aspects of propagation are considered along with the types of antennas, transmission lines, matching devices, questions of antenna design, antennas for the lower frequency bands, antennas for more than one band, limited space antennas, VHF antennas, and antennas for 20, 15, and 10 meters. Attention is given to devices for measuring antenna parameters, approaches for evaluating the antenna, questions of safety, and legal aspects.

Broadband standard dipole antenna for antenna calibration

NASA Astrophysics Data System (ADS)

Koike, Kunimasa; Sugiura, Akira; Morikawa, Takao

1995-06-01

Antenna calibration of EMI antennas is mostly performed by the standard antenna method at an open-field test site using a specially designed dipole antenna as a reference. In order to develop broadband standard antennas, the antenna factors of shortened dipples are theoretically investigated. First, the effects of the dipole length are analyzed using the induced emf method. Then, baluns and loads are examined to determine their influence on the antenna factors. It is found that transformer-type baluns are very effective for improving the height dependence of the antenna factors. Resistive loads are also useful for flattening the frequency dependence. Based on these studies, a specification is developed for a broadband standard antenna operating in the 30 to 150 MHz frequency range.

Phased Antenna Array for Global Navigation Satellite System Signals

NASA Technical Reports Server (NTRS)

Turbiner, Dmitry (Inventor)

2015-01-01

Systems and methods for phased array antennas are described. Supports for phased array antennas can be constructed by 3D printing. The array elements and combiner network can be constructed by conducting wire. Different parameters of the antenna, like the gain and directivity, can be controlled by selection of the appropriate design, and by electrical steering. Phased array antennas may be used for radio occultation measurements.

Antenna array geometry optimization for a passive coherent localisation system

NASA Astrophysics Data System (ADS)

Knott, Peter; Kuschel, Heiner; O'Hagan, Daniel

2012-11-01

Passive Coherent Localisation (PCL), also known as Passive Radar, making use of RF sources of opportunity such as Radio or TV Broadcasting Stations, Cellular Phone Network Base Stations, etc. is an advancing technology for covert operation because no active radar transmitter is required. It is also an attractive addition to existing active radar stations because it has the potential to discover low-flying and low-observable targets. The CORA (Covert Radar) experimental passive radar system currently developed at Fraunhofer-FHR features a multi-channel digital radar receiver and a circular antenna array with separate elements for the VHF- and the UHF-range and is used to exploit alternatively Digital Audio (DAB) or Video Broadcasting (DVB-T) signals. For an extension of the system, a wideband antenna array is being designed for which a new discone antenna element has been developed covering the full DVB-T frequency range. The present paper describes the outline of the system and the numerical modelling and optimisation methods applied to solve the complex task of antenna array design: Electromagnetic full wave analysis is required for the parametric design of the antenna elements while combinatorial optimization methods are applied to find the best array positions and excitation coefficients for a regular omni-directional antenna performance. The different steps are combined in an iterative loop until the optimum array layout is found. Simulation and experimental results for the current system will be shown.

Fibrillar Chromospheric Spicule-Like Counterparts to an EUV and Soft X-Ray Blowout Coronal Jet

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Harra, Louise K.; Moore, Ronald L.

2010-01-01

We observe an erupting jet feature in a solar polar coronal hole, using data from Hinode/SOT, EIS, and XRT, with supplemental data from STEREO/EUVI. From EUV and soft X-ray (SXR) images we identify the erupting feature as a blowout coronal jet: in SXRs it is a jet with bright base, and in EUV it appears as an eruption of relatively cool (approximately 50,000 K) material of horizontal size scale approximately 30" originating from the base of the SXR jet. In SOT Ca II H images the most pronounced analog is a pair of thin (approximately 1") ejections, at the locations of either of the two legs of the erupting EUV jet. These Ca II features eventually rise beyond 45", leaving the SOT field of view, and have an appearance similar to standard spicules except that they are much taller. They have velocities similar to that of "type II" spicules, approximately 100 kilometers per second, and they appear to have spicule-like substructures splitting off from them with horizontal velocity approximately 50 kilometers per second, similar to the velocities of splitting spicules measured by Sterling et al. (2010). Motions of splitting features and of other substructures suggest that the macroscopic EUV jet is spinning or unwinding as it is ejected. This and earlier work suggests that a sub-population of Ca II type II spicules are the Ca II manifestation of portions of larger-scale erupting magnetic jets. A different sub-population of type II spicules could be blowout jets occurring on a much smaller horizontal size scale than the event we observe here.

Radiation pattern of a borehole radar antenna

USGS Publications Warehouse

Ellefsen, K.J.; Wright, D.L.

2002-01-01

To understand better how a borehole antenna radiates radar waves into a formation, this phenomenon is simulated numerically using the finite-difference, time-domain method. The simulations are of two different antenna models that include features like a driving point fed by a coaxial cable, resistive loading of the antenna, and a water-filled borehole. For each model, traces are calculated in the far-field region, and then, from these traces, radiation patterns are calculated. The radiation patterns show that the amplitude of the radar wave is strongly affected by its frequency, its propagation direction, and the resistive loading of the antenna.

New Techniques For The Improvement Of The ICRH System ELM Tolerance On JET

NASA Astrophysics Data System (ADS)

Monakhov, I.; Blackman, T.; Walden, A.; Nightingale, M.; Whitehurst, A.; Durodie, F.; Jet Efda Contributors

2003-12-01

Two complementary improvements to the ELM tolerance of the existing A2 antennas on JET are being assessed. The use of external conjugate-T matching of straps of adjacent antenna arrays could reduce the VSWR levels at RF amplifier output during fast load perturbations. The scheme under consideration uses coaxial line-stretchers (trombones) for tuning the conjugate-T to low resistive impedance (3-6 Ohm) with subsequent stub/trombone circuit impedance transformation to 30 Ohms. Another technique is to modify the RF plant protection system logic to reduce the high VSWR trip duration to an absolute minimum corresponding to a typical ELM response (˜1-2ms) without compromising the plant safety. Both projects are presently being tested and could increase the average power delivered by RF plant into ELMy plasmas at JET.

Omnidirectional, circularly polarized, cylindrical microstrip antenna

NASA Technical Reports Server (NTRS)

Stanton, Philip H. (Inventor)

1985-01-01

A microstrip cylindrical antenna comprised of two concentric subelements on a ground cylinder, a vertically polarized (E-field parallel to the axis of the antenna cylinder) subelement on the inside and a horizontally polarized (E-field perpendicular to the axis) subelement on the outside. The vertical subelement is a wraparound microstrip radiator. A Y-shaped microstrip patch configuration is used for the horizontally polarized radiator that is wrapped 1.5 times to provide radiating edges on opposite sides of the cylindrical antenna for improved azimuthal pattern uniformity. When these subelements are so fed that their far fields are equal in amplitude and phased 90.degree. from each other, a circularly polarized EM wave results. By stacking a plurality of like antenna elements on the ground cylinder, a linear phased array antenna is provided that can be beam steered to the desired elevation angle.

Optical antenna gain. I - Transmitting antennas

NASA Technical Reports Server (NTRS)

Klein, B. J.; Degnan, J. J.

1974-01-01

The gain of centrally obscured optical transmitting antennas is analyzed in detail. The calculations, resulting in near- and far-field antenna gain patterns, assume a circular antenna illuminated by a laser operating in the TEM-00 mode. A simple polynomial equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn that display the losses in antenna gain due to pointing errors and the cone angle of the beam in the far field as a function of antenna aperture size and its central obscuration. The results are presented in a series of graphs that allow the rapid and accurate evaluation of the antenna gain which may then be substituted into the conventional range equation.

Evaluation of detectable angle of mid-infrared slot antennas

NASA Astrophysics Data System (ADS)

Obara, R.; Horikawa, J.; Shimakage, H.; Kawakami, A.

2017-07-01

For evaluations of a mid-infrared (MIR) detectors with antenna, we constructed an angular dependence measurement system of the antenna properties. The fabricated MIR detector consisted of twin slot antennas and a bolometer. The area of the slot antennas was designed to be 2.6 × 0.2 μm2 as to resonate at 61 THz, and they were located parallel and separated 1.6 μm each other. The bolometer was fabricated using by a 7.0-nm thick NbN thin film, and located at the center of the twin antennas. We measured polarization angle dependence and directivity, and showed that the MIR antennas have polarization dependence and directivity like radiofrequency antennas.

X-Antenna: A graphical interface for antenna analysis codes

NASA Technical Reports Server (NTRS)

Goldstein, B. L.; Newman, E. H.; Shamansky, H. T.

1995-01-01

This report serves as the user's manual for the X-Antenna code. X-Antenna is intended to simplify the analysis of antennas by giving the user graphical interfaces in which to enter all relevant antenna and analysis code data. Essentially, X-Antenna creates a Motif interface to the user's antenna analysis codes. A command-file allows new antennas and codes to be added to the application. The menu system and graphical interface screens are created dynamically to conform to the data in the command-file. Antenna data can be saved and retrieved from disk. X-Antenna checks all antenna and code values to ensure they are of the correct type, writes an output file, and runs the appropriate antenna analysis code. Volumetric pattern data may be viewed in 3D space with an external viewer run directly from the application. Currently, X-Antenna includes analysis codes for thin wire antennas (dipoles, loops, and helices), rectangular microstrip antennas, and thin slot antennas.

Modelling of combined ICRF and NBI heating in JET hybrid plasmas

NASA Astrophysics Data System (ADS)

Gallart, Dani; Mantsinen, Mervi; Challis, Clive; Frigione, Domenico; Graves, Jonathan; Hobirk, Joerg; Belonohy, Eva; Czarnecka, Agata; Eriksson, Jacob; Goniche, Marc; Hellesen, Carl; Jacquet, Philippe; Joffrin, Emmanuel; Krawczyk, Natalia; King, Damian; Lennholm, Morten; Lerche, Ernesto; Pawelec, Ewa; Sips, George; Solano, Emilia; Tsalas, Maximos; Valisa, Marco

2017-10-01

During the 2015-2016 JET campaigns many efforts have been devoted to the exploration of high performance plasma scenarios envisaged for ITER operation. In this paper we model the combined ICRF+NBI heating in selected key hybrid discharges using PION. The antenna frequency was tuned to match the cyclotron frequency of minority hydrogen (H) at the center of the tokamak coinciding with the second harmonic cyclotron resonance of deuterium. The modelling takes into account the synergy between ICRF and NBI heating through the second harmonic cyclotron resonance of deuterium beam ions which allows us to assess its impact on the neutron rate RNT. We evaluate the influence of H concentration which was varied in different discharges in order to test their role in the heating performance. According to our modelling, the ICRF enhancement of RNT increases by decreasing the H concentration which increases the ICRF power absorbed by deuterons. We find that in the recent hybrid discharges this ICRF enhancement was in the range of 10-25%. Finally, we extrapolate the results to D-T and find that the best performing hybrid discharges correspond to an equivalent fusion power of ˜7.0 MW in D-T.

Effect of the relative shift between the electron density and temperature pedestal position on the pedestal stability in JET-ILW and comparison with JET-C

NASA Astrophysics Data System (ADS)

Stefanikova, E.; Frassinetti, L.; Saarelma, S.; Loarte, A.; Nunes, I.; Garzotti, L.; Lomas, P.; Rimini, F.; Drewelow, P.; Kruezi, U.; Lomanowski, B.; de la Luna, E.; Meneses, L.; Peterka, M.; Viola, B.; Giroud, C.; Maggi, C.; contributors, JET

2018-05-01

The electron temperature and density pedestals tend to vary in their relative radial positions, as observed in DIII-D (Beurskens et al 2011 Phys. Plasmas 18 056120) and ASDEX Upgrade (Dunne et al 2017 Plasma Phys. Control. Fusion 59 14017). This so-called relative shift has an impact on the pedestal magnetohydrodynamic (MHD) stability and hence on the pedestal height (Osborne et al 2015 Nucl. Fusion 55 063018). The present work studies the effect of the relative shift on pedestal stability of JET ITER-like wall (JET-ILW) baseline low triangularity (δ) unseeded plasmas, and similar JET-C discharges. As shown in this paper, the increase of the pedestal relative shift is correlated with the reduction of the normalized pressure gradient, therefore playing a strong role in pedestal stability. Furthermore, JET-ILW tends to have a larger relative shift compared to JET carbon wall (JET-C), suggesting a possible role of the plasma facing materials in affecting the density profile location. Experimental results are then compared with stability analysis performed in terms of the peeling-ballooning model and with pedestal predictive model EUROPED (Saarelma et al 2017 Plasma Phys. Control. Fusion). Stability analysis is consistent with the experimental findings, showing an improvement of the pedestal stability, when the relative shift is reduced. This has been ascribed mainly to the increase of the edge bootstrap current, and to minor effects related to the increase of the pedestal pressure gradient and narrowing of the pedestal pressure width. Pedestal predictive model EUROPED shows a qualitative agreement with experiment, especially for low values of the relative shift.

ELM-induced transient tungsten melting in the JET divertor

NASA Astrophysics Data System (ADS)

Coenen, J. W.; Arnoux, G.; Bazylev, B.; Matthews, G. F.; Autricque, A.; Balboa, I.; Clever, M.; Dejarnac, R.; Coffey, I.; Corre, Y.; Devaux, S.; Frassinetti, L.; Gauthier, E.; Horacek, J.; Jachmich, S.; Komm, M.; Knaup, M.; Krieger, K.; Marsen, S.; Meigs, A.; Mertens, Ph.; Pitts, R. A.; Puetterich, T.; Rack, M.; Stamp, M.; Sergienko, G.; Tamain, P.; Thompson, V.; Contributors, JET-EFDA

2015-02-01

The original goals of the JET ITER-like wall included the study of the impact of an all W divertor on plasma operation (Coenen et al 2013 Nucl. Fusion 53 073043) and fuel retention (Brezinsek et al 2013 Nucl. Fusion 53 083023). ITER has recently decided to install a full-tungsten (W) divertor from the start of operations. One of the key inputs required in support of this decision was the study of the possibility of W melting and melt splashing during transients. Damage of this type can lead to modifications of surface topology which could lead to higher disruption frequency or compromise subsequent plasma operation. Although every effort will be made to avoid leading edges, ITER plasma stored energies are sufficient that transients can drive shallow melting on the top surfaces of components. JET is able to produce ELMs large enough to allow access to transient melting in a regime of relevance to ITER. Transient W melt experiments were performed in JET using a dedicated divertor module and a sequence of IP = 3.0 MA/BT = 2.9 T H-mode pulses with an input power of PIN = 23 MW, a stored energy of ˜6 MJ and regular type I ELMs at ΔWELM = 0.3 MJ and fELM ˜ 30 Hz. By moving the outer strike point onto a dedicated leading edge in the W divertor the base temperature was raised within ˜1 s to a level allowing transient, ELM-driven melting during the subsequent 0.5 s. Such ELMs (δW ˜ 300 kJ per ELM) are comparable to mitigated ELMs expected in ITER (Pitts et al 2011 J. Nucl. Mater. 415 (Suppl.) S957-64). Although significant material losses in terms of ejections into the plasma were not observed, there is indirect evidence that some small droplets (˜80 µm) were released. Almost 1 mm (˜6 mm3) of W was moved by ˜150 ELMs within 7 subsequent discharges. The impact on the main plasma parameters was minor and no disruptions occurred. The W-melt gradually moved along the leading edge towards the high-field side, driven by j × B forces. The evaporation rate determined

Comparative Study of Antenna Elements for TDRSS Enhanced Multiple Access System

NASA Technical Reports Server (NTRS)

Kory, Carol L.; Lambert, Kevin; Acosta, Roberto; Nessel, James

2006-01-01

We compare three antennas, which are candidates for the TDRSS-Continuation enhanced MA array antenna elements. Measured and simulated data show very good agreement for all antenna elements. All of the antennas meet the specifications with the exception of the SBA isolation. However, improvements can likely be made with further design efforts.

Fuzzy jets

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

Mackey, Lester; Nachman, Benjamin; Schwartzman, Ariel

Collimated streams of particles produced in high energy physics experiments are organized using clustering algorithms to form jets . To construct jets, the experimental collaborations based at the Large Hadron Collider (LHC) primarily use agglomerative hierarchical clustering schemes known as sequential recombination. We propose a new class of algorithms for clustering jets that use infrared and collinear safe mixture models. These new algorithms, known as fuzzy jets , are clustered using maximum likelihood techniques and can dynamically determine various properties of jets like their size. We show that the fuzzy jet size adds additional information to conventional jet tagging variablesmore » in boosted topologies. Furthermore, we study the impact of pileup and show that with some slight modifications to the algorithm, fuzzy jets can be stable up to high pileup interaction multiplicities.« less

Fuzzy jets

DOE PAGES

Mackey, Lester; Nachman, Benjamin; Schwartzman, Ariel; ...

2016-06-01

Collimated streams of particles produced in high energy physics experiments are organized using clustering algorithms to form jets . To construct jets, the experimental collaborations based at the Large Hadron Collider (LHC) primarily use agglomerative hierarchical clustering schemes known as sequential recombination. We propose a new class of algorithms for clustering jets that use infrared and collinear safe mixture models. These new algorithms, known as fuzzy jets , are clustered using maximum likelihood techniques and can dynamically determine various properties of jets like their size. We show that the fuzzy jet size adds additional information to conventional jet tagging variablesmore » in boosted topologies. Furthermore, we study the impact of pileup and show that with some slight modifications to the algorithm, fuzzy jets can be stable up to high pileup interaction multiplicities.« less

Conceptual study of an ICRH traveling-wave antenna system for low-coupling conditions as expected in DEMO

NASA Astrophysics Data System (ADS)

Ragona, R.; Messiaen, A.

2016-07-01

For the central heating of a fusion reactor ion cyclotron radio frequency heating (ICRH) is the first choice method as it is able to couple RF power to the ions without density limit. The drawback of this heating method is the problem of excitation of the magneto-sonic wave through the plasma boundary layer from the antenna located along the wall, without exceeding its voltage standoff. The amount of coupling depends on the antenna excitation and the surface admittance at the antenna output due to the plasma profile. The paper deals with the optimization of the antenna excitation by the use of sections of traveling-wave antennas (TWAs) distributed all along the reactor wall between the blanket modules. They are mounted and fed in resonant ring system(s). First, the physics of the coupling of a strap array is studied by simple models and the coupling code ANTITER II. Then, after the study of the basic properties of a TWA section, its feeding problem is solved by hybrids driving them in resonant ring circuit(s). The complete modeling is obtained from the matrices of the TWA sections connected to one of the feeding hybrid(s). The solution is iterated with the coupling code to determine the loading for a reference low-coupling ITER plasma profile. The resulting wave pattern up to the plasma bulk is derived. The proposed system is totally load resilient and allows us to obtain a very selective exciting wave spectrum. A discussion of some practical implementation problems is added.

Deployable reflector antenna performance optimization using automated surface correction and array-feed compensation

NASA Technical Reports Server (NTRS)

Schroeder, Lyle C.; Bailey, M. C.; Mitchell, John L.

1992-01-01

Methods for increasing the electromagnetic (EM) performance of reflectors with rough surfaces were tested and evaluated. First, one quadrant of the 15-meter hoop-column antenna was retrofitted with computer-driven and controlled motors to allow automated adjustment of the reflector surface. The surface errors, measured with metric photogrammetry, were used in a previously verified computer code to calculate control motor adjustments. With this system, a rough antenna surface (rms of approximately 0.180 inch) was corrected in two iterations to approximately the structural surface smoothness limit of 0.060 inch rms. The antenna pattern and gain improved significantly as a result of these surface adjustments. The EM performance was evaluated with a computer program for distorted reflector antennas which had been previously verified with experimental data. Next, the effects of the surface distortions were compensated for in computer simulations by superimposing excitation from an array feed to maximize antenna performance relative to an undistorted reflector. Results showed that a 61-element array could produce EM performance improvements equal to surface adjustments. When both mechanical surface adjustment and feed compensation techniques were applied, the equivalent operating frequency increased from approximately 6 to 18 GHz.

Aligning a Receiving Antenna Array to Reduce Interference

NASA Technical Reports Server (NTRS)

Jongeling, Andre P.; Rogstad, David H.

2009-01-01

A digital signal-processing algorithm has been devised as a means of aligning (as defined below) the outputs of multiple receiving radio antennas in a large array for the purpose of receiving a desired weak signal transmitted by a single distant source in the presence of an interfering signal that (1) originates at another source lying within the antenna beam and (2) occupies a frequency band significantly wider than that of the desired signal. In the original intended application of the algorithm, the desired weak signal is a spacecraft telemetry signal, the antennas are spacecraft-tracking antennas in NASA s Deep Space Network, and the source of the wide-band interfering signal is typically a radio galaxy or a planet that lies along or near the line of sight to the spacecraft. The algorithm could also afford the ability to discriminate between desired narrow-band and nearby undesired wide-band sources in related applications that include satellite and terrestrial radio communications and radio astronomy. The development of the present algorithm involved modification of a prior algorithm called SUMPLE and a predecessor called SIMPLE. SUMPLE was described in Algorithm for Aligning an Array of Receiving Radio Antennas (NPO-40574), NASA Tech Briefs Vol. 30, No. 4 (April 2006), page 54. To recapitulate: As used here, aligning signifies adjusting the delays and phases of the outputs from the various antennas so that their relatively weak replicas of the desired signal can be added coherently to increase the signal-to-noise ratio (SNR) for improved reception, as though one had a single larger antenna. Prior to the development of SUMPLE, it was common practice to effect alignment by means of a process that involves correlation of signals in pairs. SIMPLE is an example of an algorithm that effects such a process. SUMPLE also involves correlations, but the correlations are not performed in pairs. Instead, in a partly iterative process, each signal is appropriately weighted

The 113 GHz ECRH system for JET

NASA Astrophysics Data System (ADS)

Verhoeven, A. G. A.; Bongers, W. A.; Elzendoorn, B. S. Q.; Graswinckel, M.; Hellingman, P.; Kamp, J. J.; Kooijman, W.; Kruijt, O. G.; Maagdenberg, J.; Ronden, D.; Stakenborg, J.; Sterk, A. B.; Tichler, J.; Alberti, S.; Goodman, T.; Henderson, M.; Hoekzema, J. A.; Oosterbeek, J. W.; Fernandez, A.; Likin, K.; Bruschi, A.; Cirant, S.; Novak, S.; Piosczyk, B.; Thumm, M.; Bindslev, H.; Kaye, A.; Fleming, C.; Zohm, H.

2003-02-01

An ECRH (Electron Cyclotron Resonance Heating) system has been designed for JET in the framework of the JET Enhanced-Performance project (JET-EP) under the European Fusion Development Agreement (EFDA). Due to financial constraints it has recently been decided not to implement this project. Nevertheless, the design work conducted from April 2000 to January 2002 shows a number of features that can be relevant in preparation of future ECRH systems, e.g., for ITER. The ECRH system was foreseen to comprise 6 gyrotrons, 1 MW each, in order to deliver 5 MW into the plasma [1]. The main aim was to enable the control of neo-classical tearing modes (NTM). The paper will concentrate on: • The power-supply and modulation system, including series IGBT switches, to enable independent control of each gyrotron and an all-solid-state body power supply to stabilise the gyrotron output power and to enable fast modulations up to 10 kHz. • A plug-in launcher, that is steerable in both toroidal and poloidal angle, and able to handle 8 separate mm-wave beams. Four steerable launching mirrors were foreseen to handle two mm-wave beams each. Water cooling of all the mirrors was a particularly ITER relevant feature.

First ERO2.0 modeling of Be erosion and non-local transport in JET ITER-like wall

NASA Astrophysics Data System (ADS)

Romazanov, J.; Borodin, D.; Kirschner, A.; Brezinsek, S.; Silburn, S.; Huber, A.; Huber, V.; Bufferand, H.; Firdaouss, M.; Brömmel, D.; Steinbusch, B.; Gibbon, P.; Lasa, A.; Borodkina, I.; Eksaeva, A.; Linsmeier, Ch; Contributors, JET

2017-12-01

ERO is a Monte-Carlo code for modeling plasma-wall interaction and 3D plasma impurity transport for applications in fusion research. The code has undergone a significant upgrade (ERO2.0) which allows increasing the simulation volume in order to cover the entire plasma edge of a fusion device, allowing a more self-consistent treatment of impurity transport and comparison with a larger number and variety of experimental diagnostics. In this contribution, the physics-relevant technical innovations of the new code version are described and discussed. The new capabilities of the code are demonstrated by modeling of beryllium (Be) erosion of the main wall during JET limiter discharges. Results for erosion patterns along the limiter surfaces and global Be transport including incident particle distributions are presented. A novel synthetic diagnostic, which mimics experimental wide-angle 2D camera images, is presented and used for validating various aspects of the code, including erosion, magnetic shadowing, non-local impurity transport, and light emission simulation.

Study and optimization of lower hybrid wave coupling in advanced scenario plasmas in JET

NASA Astrophysics Data System (ADS)

Pericoli Ridolfini, V.; Ekedahl, A.; Erents, S. K.; Mailloux, J.; Podda, S.; Sarazin, Y.; Tuccillo, A. A.; Workprogramme contributors, EFDA-JET

2004-02-01

Active current drive with lower hybrid (LH) waves in the advanced scenario plasmas at JET-EFDA was successful after a systematic study of the coupling problems that derive from the H-mode features of the edge plasma, namely very low density and ELM activity. The LH coupling has been improved compared to the past, by making the edge plasma in front of the LH launcher denser and more uniform. Injecting deuterated methane (CD4) from a nearby gas pipe increases the density in front of the LH launcher at least by a factor of 1.5, above the cut-off value for the LH frequency. A better matching of the plasma shape to that of the LH antenna makes the plasma ahead of the LH launcher more regular along the poloidal angle. These two techniques together have permitted a balanced supply of the three LH grills, with an average reflection below 4%, as in the previous L-mode operation. CD4 does not affect the performances nor does it contaminate the main plasma up to the maximum flow rate so far used, \\Phi_{CD_4}>10^{22}el\\,s^{-1} and now it is routinely applied in JET (up to 4 MW have been injected for longer than 8 s) with very encouraging results for LHCD. Even though CD4 is not suitable for ITER for tritium retention, the possibility of controlling locally and safely the scrape-off plasma density has been demonstrated.

Antenna Deployment for a Pathfinder Lunar Radio Observatory

NASA Astrophysics Data System (ADS)

MacDowall, Robert J.; Minetto, F. A.; Lazio, T. W.; Jones, D. L.; Kasper, J. C.; Burns, J. O.; Stewart, K. P.; Weiler, K. W.

2012-05-01

A first step in the development of a large radio observatory on the moon for cosmological or other astrophysical and planetary goals is to deploy a few antennas as a pathfinder mission. In this presentation, we describe a mechanism being developed to deploy such antennas from a small craft, such as a Google Lunar X-prize lander. The antenna concept is to deposit antennas and leads on a polyimide film, such as Kapton, and to unroll the film on the lunar surface. The deployment technique utilized is to launch an anchor which pulls a double line from a reel at the spacecraft. Subsequently, the anchor is set by catching on the surface or collecting sufficient regolith. A motor then pulls in one end of the line, pulling the film off of its roller onto the lunar surface. Detection of a low frequency cutoff of the galactic radio background or of solar radio bursts by such a system would determine the maximum lunar ionospheric density at the time of measurement. The current design and testing, including videos of the deployment, will be presented. These activities are funded in part by the NASA Lunar Science Institute as an activity of the Lunar University Network for Astrophysical Research (LUNAR) consortium. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Antenna Deployment for a Pathfinder Lunar Radio Observatory

NASA Technical Reports Server (NTRS)

MacDowall, Robert J.; Minetto, F. A.; Lazio, T. W.; Jones, D. L.; Kasper, J. C.; Burns, J. O.; Stewart, K. P.; Weiler, K. W.

2012-01-01

A first step in the development of a large radio observatory on the moon for cosmological or other astrophysical and planetary goals is to deploy a few antennas as a pathfinder mission. In this presentation, we describe a mechanism being developed to deploy such antennas from a small craft, such as a Google Lunar X-prize lander. The antenna concept is to deposit antennas and leads on a polyimide film, such as Kapton, and to unroll the film on the lunar surface. The deployment technique utilized is to launch an anchor which pulls a double line from a reel at the spacecraft. Subsequently, the anchor is set by catching on the surface or collecting sufficient regolith. A motor then pulls in one end of the line, pulling the film off of its roller onto the lunar surface. Detection of a low frequency cutoff of the galactic radio background or of solar radio bursts by such a system would determine the maximum lunar ionospheric density at the time of measurement. The current design and testing, including videos of the deployment, will be presented. These activities are funded in part by the NASA Lunar Science Institute as an activity of the Lunar University Network for Astrophysical Research (LUNAR) consortium. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

The NASA/JPL 64-meter-diameter antenna at Goldstone, California: Project report, technical staff, tracking and data acquisition organization

NASA Technical Reports Server (NTRS)

1974-01-01

The significant management and technical aspects of the JPL Project to develop and implement a 64-meter-diameter antenna at the Goldstone Deep Space Communications Complex in California, which was the first of the Advanced Antenna Systems of the National Aeronautics and Space Administration/Jet Propulsion Laboratory Deep Space Network are described. The original need foreseen for a large-diameter antenna to accomplish communication and tracking support of NASA's solar system exploration program is reviewed, and the translation of those needs into the technical specification of an appropriate ground station antenna is described. The antenna project is delineated by phases to show the key technical and managerial skills and the technical facility resources involved. There is a brief engineering description of the antenna and its closely related facilities. Some difficult and interesting engineering problems, then at the state-of-the-art level, which were met in the accomplishment of the Project, are described. The key performance characteristics of the antenna, in relation to the original specifications and the methods of their determination, are stated.

Algorithm for Aligning an Array of Receiving Radio Antennas

NASA Technical Reports Server (NTRS)

Rogstad, David

2006-01-01

A digital-signal-processing algorithm (somewhat arbitrarily) called SUMPLE has been devised as a means of aligning the outputs of multiple receiving radio antennas in a large array for the purpose of receiving a weak signal transmitted by a single distant source. As used here, aligning signifies adjusting the delays and phases of the outputs from the various antennas so that their relatively weak replicas of the desired signal can be added coherently to increase the signal-to-noise ratio (SNR) for improved reception, as though one had a single larger antenna. The method was devised to enhance spacecraft-tracking and telemetry operations in NASA's Deep Space Network (DSN); the method could also be useful in such other applications as both satellite and terrestrial radio communications and radio astronomy. Heretofore, most commonly, alignment has been effected by a process that involves correlation of signals in pairs. This approach necessitates the use of a large amount of hardware most notably, the N(N - 1)/2 correlators needed to process signals from all possible pairs of N antennas. Moreover, because the incoming signals typically have low SNRs, the delay and phase adjustments are poorly determined from the pairwise correlations. SUMPLE also involves correlations, but the correlations are not performed in pairs. Instead, in a partly iterative process, each signal is appropriately weighted and then correlated with a composite signal equal to the sum of the other signals (see Figure 1). One benefit of this approach is that only N correlators are needed; in an array of N much greater than 1 antennas, this results in a significant reduction of the amount of hardware. Another benefit is that once the array achieves coherence, the correlation SNR is N - 1 times that of a pair of antennas.

Stability of iterative procedures with errors for approximating common fixed points of a couple of q-contractive-like mappings in Banach spaces

NASA Astrophysics Data System (ADS)

Zeng, Lu-Chuan; Yao, Jen-Chih

2006-09-01

Recently, Agarwal, Cho, Li and Huang [R.P. Agarwal, Y.J. Cho, J. Li, N.J. Huang, Stability of iterative procedures with errors approximating common fixed points for a couple of quasi-contractive mappings in q-uniformly smooth Banach spaces, J. Math. Anal. Appl. 272 (2002) 435-447] introduced the new iterative procedures with errors for approximating the common fixed point of a couple of quasi-contractive mappings and showed the stability of these iterative procedures with errors in Banach spaces. In this paper, we introduce a new concept of a couple of q-contractive-like mappings (q>1) in a Banach space and apply these iterative procedures with errors for approximating the common fixed point of the couple of q-contractive-like mappings. The results established in this paper improve, extend and unify the corresponding ones of Agarwal, Cho, Li and Huang [R.P. Agarwal, Y.J. Cho, J. Li, N.J. Huang, Stability of iterative procedures with errors approximating common fixed points for a couple of quasi-contractive mappings in q-uniformly smooth Banach spaces, J. Math. Anal. Appl. 272 (2002) 435-447], Chidume [C.E. Chidume, Approximation of fixed points of quasi-contractive mappings in Lp spaces, Indian J. Pure Appl. Math. 22 (1991) 273-386], Chidume and Osilike [C.E. Chidume, M.O. Osilike, Fixed points iterations for quasi-contractive maps in uniformly smooth Banach spaces, Bull. Korean Math. Soc. 30 (1993) 201-212], Liu [Q.H. Liu, On Naimpally and Singh's open questions, J. Math. Anal. Appl. 124 (1987) 157-164; Q.H. Liu, A convergence theorem of the sequence of Ishikawa iterates for quasi-contractive mappings, J. Math. Anal. Appl. 146 (1990) 301-305], Osilike [M.O. Osilike, A stable iteration procedure for quasi-contractive maps, Indian J. Pure Appl. Math. 27 (1996) 25-34; M.O. Osilike, Stability of the Ishikawa iteration method for quasi-contractive maps, Indian J. Pure Appl. Math. 28 (1997) 1251-1265] and many others in the literature.

Nonlinear Structural Analysis Methodology and Dynamics Scaling of Inflatable Parabolic Reflector Antenna Concepts

NASA Technical Reports Server (NTRS)

Sreekantamurthy, Tham; Gaspar, James L.; Mann, Troy; Behun, Vaughn; Pearson, James C., Jr.; Scarborough, Stephen

2007-01-01

Ultra-light weight and ultra-thin membrane inflatable antenna concepts are fast evolving to become the state-of-the-art antenna concepts for deep-space applications. NASA Langley Research Center has been involved in the structural dynamics research on antenna structures. One of the goals of the research is to develop structural analysis methodology for prediction of the static and dynamic response characteristics of the inflatable antenna concepts. This research is focused on the computational studies to use nonlinear large deformation finite element analysis to characterize the ultra-thin membrane responses of the antennas. Recently, structural analyses have been performed on a few parabolic reflector antennas of varying size and shape, which are referred in the paper as 0.3 meters subscale, 2 meters half-scale, and 4 meters full-scale antenna. The various aspects studied included nonlinear analysis methodology and solution techniques, ways to speed convergence in iterative methods, the sensitivities of responses with respect to structural loads, such as inflation pressure, gravity, and pretension loads in the ground and in-space conditions, and the ultra-thin membrane wrinkling characteristics. Several such intrinsic aspects studied have provided valuable insight into evaluation of structural characteristics of such antennas. While analyzing these structural characteristics, a quick study was also made to assess the applicability of dynamics scaling of the half-scale antenna. This paper presents the details of the nonlinear structural analysis results, and discusses the insight gained from the studies on the various intrinsic aspects of the analysis methodology. The predicted reflector surface characteristics of the three inflatable ultra-thin membrane parabolic reflector antenna concepts are presented as easily observable displacement fringe patterns with associated maximum values, and normal mode shapes and associated frequencies. Wrinkling patterns are

Porous textile antenna designs for improved wearability

NASA Astrophysics Data System (ADS)

Shahariar, Hasan; Soewardiman, Henry; Muchler, Clifford A.; Adams, Jacob J.; Jur, Jesse S.

2018-04-01

Textile antennas are an integral part of the next generation personalized wearable electronics system. However, the durability of textile antennas are rarely discussed in the literature. Typical textile antennas are prone to damage during normal wearable user scenarios, washing, and heat cycling over time. Fabricating a durable, washable, flexible, and breathable (like textile materials) antenna is challenging due to the incompatibility of the mechanical properties of conductive materials and soft textile materials. This paper describes a scalable screen printing process on an engineered nonwoven substrate to fabricate microstrip patch antennas with enhanced durability. This work used an Evolon® nonwoven substrate with low surface roughness (˜Ra = 18 μm) and high surface area (˜2.05 mm2 mm-2 of fabric area) compared to traditional textile materials, which allows the ink to penetrate evenly in the fiber bulk with its strong capillary wicking force and enhances print resolution. The composite layer of ink and fiber is conductive and enables the antennas to maintain high mechanical flexibility without varying its RF (Radio Frequency) properties. Additionally, the antennas are packaged by laminating porous polyurethane web to make the device durable and washable. The fully packaged antennas maintain the structural flexibility and RF functionality after 15 cycles of washing and drying. To improve the air permeability and enhance flexibility the antenna is also modified by incorporating holes in the both patch and ground layer of the antenna. The antennas were analyzed before and after submerging in water to observe the effect of wetting and drying with respect to frequency response. The porous antenna with holes recovered 3x times faster than the one without holes (solid) from fully wet state (saturated with water) to the dry state, demonstrating its potential use as a moisture sensor system.

Antennae

NASA Technical Reports Server (NTRS)

1999-01-01

Atlas Image mosaic, covering 7' x 7' on the sky of the interacting galaxies NGC 4038 and NGC 4039, better known as the Antennae, or Ring Tail galaxies. The two galaxies are engaged in a tug-of-war as they collide. The mutual gravitation between them is working to distort each spiral galaxy's appearance as the two merge. The interaction is evidently impetus for an intense burst of new star formation, as can be seen from the many infrared-bright knots and bright galactic nuclei. Compare the 2MASS view of this system with that obtained by the Hubble Space Telescope in the optical. Many of the same features are seen, although 2MASS is able to peer through much of the dust seen in the galaxies' disks. The galaxy light looks smoother. Also, in the near-infrared the bright knots of star formation are likely highlighted by the light of massive red supergiant stars. The much more extended 'tidal tails,' which give the Antennae their name, are quite faint in the 2MASS image mosaic.

Research on Radiation Characteristic of Plasma Antenna through FDTD Method

PubMed Central

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic. PMID:25114961

Research on radiation characteristic of plasma antenna through FDTD method.

PubMed

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic.

TENTATIVE EVIDENCE FOR RELATIVISTIC ELECTRONS GENERATED BY THE JET OF THE YOUNG SUN-LIKE STAR DG Tau

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

Ainsworth, Rachael E.; Ray, Tom P.; Taylor, Andrew M.

2014-09-01

Synchrotron emission has recently been detected in the jet of a massive protostar, providing further evidence that certain jet formation characteristics for young stars are similar to those found for highly relativistic jets from active galactic nuclei. We present data at 325 and 610 MHz taken with the Giant Metrewave Radio Telescope of the young, low-mass star DG Tau, an analog of the Sun soon after its birth. This is the first investigation of a low-mass young stellar object at such low frequencies. We detect emission with a synchrotron spectral index in the proximity of the DG Tau jet and interpretmore » this emission as a prominent bow shock associated with this outflow. This result provides tentative evidence for the acceleration of particles to relativistic energies due to the shock impact of this otherwise very low-power jet against the ambient medium. We calculate the equipartition magnetic field strength B {sub min} ≈ 0.11 mG and particle energy E {sub min} ≈ 4 × 10{sup 40} erg, which are the minimum requirements to account for the synchrotron emission of the DG Tau bow shock. These results suggest the possibility of low energy cosmic rays being generated by young Sun-like stars.« less

Research at ITER towards DEMO: Specific reactor diagnostic studies to be carried out on ITER

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

Krasilnikov, A. V.; Kaschuck, Y. A.; Vershkov, V. A.

2014-08-21

In ITER diagnostics will operate in the very hard radiation environment of fusion reactor. Extensive technology studies are carried out during development of the ITER diagnostics and procedures of their calibration and remote handling. Results of these studies and practical application of the developed diagnostics on ITER will provide the direct input to DEMO diagnostic development. The list of DEMO measurement requirements and diagnostics will be determined during ITER experiments on the bases of ITER plasma physics results and success of particular diagnostic application in reactor-like ITER plasma. Majority of ITER diagnostic already passed the conceptual design phase and representmore » the state of the art in fusion plasma diagnostic development. The number of related to DEMO results of ITER diagnostic studies such as design and prototype manufacture of: neutron and γ–ray diagnostics, neutral particle analyzers, optical spectroscopy including first mirror protection and cleaning technics, reflectometry, refractometry, tritium retention measurements etc. are discussed.« less

Research at ITER towards DEMO: Specific reactor diagnostic studies to be carried out on ITER

NASA Astrophysics Data System (ADS)

Krasilnikov, A. V.; Kaschuck, Y. A.; Vershkov, V. A.; Petrov, A. A.; Petrov, V. G.; Tugarinov, S. N.

2014-08-01

In ITER diagnostics will operate in the very hard radiation environment of fusion reactor. Extensive technology studies are carried out during development of the ITER diagnostics and procedures of their calibration and remote handling. Results of these studies and practical application of the developed diagnostics on ITER will provide the direct input to DEMO diagnostic development. The list of DEMO measurement requirements and diagnostics will be determined during ITER experiments on the bases of ITER plasma physics results and success of particular diagnostic application in reactor-like ITER plasma. Majority of ITER diagnostic already passed the conceptual design phase and represent the state of the art in fusion plasma diagnostic development. The number of related to DEMO results of ITER diagnostic studies such as design and prototype manufacture of: neutron and γ-ray diagnostics, neutral particle analyzers, optical spectroscopy including first mirror protection and cleaning technics, reflectometry, refractometry, tritium retention measurements etc. are discussed.

Design and Development of Aerogel-Based Antennas for Aerospace Applications: A Final Report to the NARI Seedling

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Miranda, Felix A.

2014-01-01

As highly porous solids possessing low density and low dielectric permittivity combined with good mechanical properties, polyimide (PI) aerogels offer great promise as an enabling technology for lightweight aircraft antenna systems. While they have been aggressively explored for thermal insulation, barely any effort has been made to leverage these materials for antennas or other applications that take advantage of their aforementioned attributes. In Phase I of the NARI Seedling Project, we fabricated PI aerogels with properties tailored to enable new antenna concepts with performance characteristics (wide bandwidth and high gain) and material properties (low density, environmental stability, and robustness) superior to the state of practice (SOP). We characterized electromagnetic properties, including permittivity, reflectivity, and propagation losses for the aerogels. Simple, prototype planar printed circuit patch antennas from down-selected aerogel formulations were fabricated by molding the aerogels to net shapes and by gold-metalizing the pattern onto the templates via electron beam evaporation in a clean room environment. These aerogel based antennas were benchmarked against current antenna SOP, and exhibited both broader bandwidth and comparable or higher gain performance at appreciably lower mass. Phase II focused on the success of the Phase I results pushing the PI aerogel based antenna technology further by exploring alternative antenna design (i.e., slot coupled antennas) and by examining other techniques for fabricating the antennas including ink jet printing with the goal of optimizing antenna performance and simplifying production. We also examined new aerogel formulations with better moisture and solvent resistance to survive processing conditions. In addition, we investigated more complex antenna designs including passive phased arrays such as 2x4 and 4x8 element arrays to assess the scalability of the aerogel antenna concept. Furthermore, we

The design of an ECRH system for JET-EP

NASA Astrophysics Data System (ADS)

Verhoeven, A. G. A.; Bongers, W. A.; Elzendoorn, B. S. Q.; Graswinckel, M.; Hellingman, P.; Kooijman, W.; Kruijt, O. G.; Maagdenberg, J.; Ronden, D.; Stakenborg, J.; Sterk, A. B.; Tichler, J.; Alberti, S.; Goodman, T.; Henderson, M.; Hoekzema, J. A.; Oosterbeek, J. W.; Fernandez, A.; Likin, K.; Bruschi, A.; Cirant, S.; Novak, S.; Piosczyk, B.; Thumm, M.; Bindslev, H.; Kaye, A.; Fleming, C.; Zohm, H.

2003-11-01

An electron cyclotron resonance heating (ECRH) system has been designed for JET in the framework of the JET enhanced performance project (JET-EP) under the European fusion development agreement. Due to financial constraints it has been decided not to implement this project. Nevertheless, the design work conducted from April 2000 to January 2002 shows a number of features that can be relevant in preparation of future ECRH systems, e.g. for ITER. The ECRH system was foreseen to comprise six gyrotrons, 1 MW each, in order to deliver 5 MW into the plasma (Verhoeven A.G.A. et al 2001 The ECRH system for JET 26th Int. Conf. on Infrared and Millimeter Waves (Toulouse, 10 14 September 2001) p 83; Verhoeven A.G.A. et al 2003 The 113 GHz ECRH system for JET Proc. 12th Joint Workshop on ECE and ECRH (13 16 May 2002) ed G. Giruzzi (Aix-en-Provence: World Scientific) pp 511 16). The main aim was to enable the control of neo-classical tearing modes. The paper will concentrate on: the power-supply and modulation system, including series IGBT switches, to enable independent control of each gyrotron and an all-solid-state body power supply to stabilize the gyrotron output power and to enable fast modulations up to 10 kHz and a plug-in launcher that is steerable in both toroidal and poloidal angles and able to handle eight separate mm-wave beams. Four steerable launching mirrors were foreseen to handle two mm-wave beams each. Water cooling of all the mirrors was a particularly ITER-relevant feature.

Adaptive iterative learning control of a class of nonlinear time-delay systems with unknown backlash-like hysteresis input and control direction.

PubMed

Wei, Jianming; Zhang, Youan; Sun, Meimei; Geng, Baoliang

2017-09-01

This paper presents an adaptive iterative learning control scheme for a class of nonlinear systems with unknown time-varying delays and control direction preceded by unknown nonlinear backlash-like hysteresis. Boundary layer function is introduced to construct an auxiliary error variable, which relaxes the identical initial condition assumption of iterative learning control. For the controller design, integral Lyapunov function candidate is used, which avoids the possible singularity problem by introducing hyperbolic tangent funciton. After compensating for uncertainties with time-varying delays by combining appropriate Lyapunov-Krasovskii function with Young's inequality, an adaptive iterative learning control scheme is designed through neural approximation technique and Nussbaum function method. On the basis of the hyperbolic tangent function's characteristics, the system output is proved to converge to a small neighborhood of the desired trajectory by constructing Lyapunov-like composite energy function (CEF) in two cases, while keeping all the closed-loop signals bounded. Finally, a simulation example is presented to verify the effectiveness of the proposed approach. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

One antenna, two antennae, big antennae, small: total antennae length, not bilateral symmetry, predicts odor-tracking performance in the American cockroach Periplaneta americana.

PubMed

Lockey, Jacob K; Willis, Mark A

2015-07-01

Determining the location of a particular stimulus is often crucial to an animal's survival. One way to determine the local distribution of an odor is to make simultaneous comparisons across multiple sensors. If the sensors detect differences in the distribution of an odor in space, the animal can then steer toward the source. American cockroaches, Periplaneta americana, have 4 cm long antennae and are thought to track odor plumes using a spatial sampling strategy, comparing the amount of odor detected between these bilateral sensors. However, it is not uncommon for cockroaches to lose parts of their antennae and still track a wind-borne odor to its source. We examined whether bilateral odor input is necessary to locate an odor source in a wind-driven environment and how the loss of increasing lengths of the antennae affects odor tracking. The tracking performances of individuals with two bilaterally symmetrical antennae of decreasing length were compared with antennal length-matched individuals with one antenna. Cockroaches with one antenna were generally able to track an odor plume to its source. In fact, the performances of unilaterally antennectomized individuals were statistically identical to those of their bilaterally symmetrical counterparts when the combined length of both antennae equaled the length of the single antenna of the antennectomized individuals. This suggests that the total length of available antennae influences odor tracking performance more than any specific piece of antenna, and that they may be doing something more complex than a simple bilateral comparison between their antennae. The possibility of an antenna-topic map is discussed. © 2015. Published by The Company of Biologists Ltd.

User Antennas

NASA Technical Reports Server (NTRS)

Jamnejad, Vahraz; Cramer, Paul

1990-01-01

The following subject areas are covered: (1) impact of frequency change of user and spacecraft antenna gain and size; (2) basic personal terminal antennas (impact of 20/30 GHz frequency separation; parametric studies - gain, size, weight; gain and figure of merit (G/T); design data for selected antenna concepts; critical technologies and development goals; and recommendations); and (3) user antenna radiation safety concerns.

Stretchable and reversibly deformable radio frequency antennas based on silver nanowires.

PubMed

Song, Lingnan; Myers, Amanda C; Adams, Jacob J; Zhu, Yong

2014-03-26

We demonstrate a class of microstrip patch antennas that are stretchable, mechanically tunable, and reversibly deformable. The radiating element of the antenna consists of highly conductive and stretchable material with screen-printed silver nanowires embedded in the surface layer of an elastomeric substrate. A 3-GHz microstrip patch antenna and a 6-GHz 2-element patch array are fabricated. Radiating properties of the antennas are characterized under tensile strain and agree well with the simulation results. The antenna is reconfigurable because the resonant frequency is a function of the applied tensile strain. The antenna is thus well suited for applications like wireless strain sensing. The material and fabrication technique reported here could be extended to achieve other types of stretchable antennas with more complex patterns and multilayer structures.

Reconfigurable antenna pattern verification

NASA Technical Reports Server (NTRS)

Drexler, Jerome P. (Inventor); Becker, Robert C. (Inventor); Meyers, David W. (Inventor); Muldoon, Kelly P. (Inventor)

2013-01-01

A method of verifying programmable antenna configurations is disclosed. The method comprises selecting a desired antenna configuration from a plurality of antenna configuration patterns, with the selected antenna configuration forming at least one reconfigurable antenna from reconfigurable antenna array elements. The method validates the formation of the selected antenna configuration to determine antenna performance of the at least one reconfigurable antenna.

Synthesis of multiple shaped beam antenna patterns

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Coffey, E. L.

1973-01-01

Results are presented of research into the problem of finding an excitation of a given antenna such that the desired radiation pattern is approximated to within acceptable limits. This is to be done in such a fashion that boundary conditions involving hardware limitations may be inserted into the problem. The intended application is synthesis of multiple shaped beam antennas. Since this is perhaps the most difficult synthesis problem an antenna engineer is likely to encounter, the approach taken was to include as a by-product capability for synthesizing simpler patterns. The synthesis technique has been almost totally computerized. The class of antennas which may be synthesized with the computer program are those which may be represented as planar (continuous or discrete) current distributions. The technique is not limited in this sense and could indeed by extended to include, for example, the synthesis of conformal arrays or current distributions on the surface of reflectors. The antenna types which the program is set up to synthesize are: line source, rectangular aperture, circular aperture, linear array, rectangular array, and arbitrary planar array.

Equipment: Antenna systems

NASA Astrophysics Data System (ADS)

Petrie, L. E.

1983-05-01

Some antenna fundamentals as well as definitions of the principal terms used in antenna engineering are described. Methods are presented for determining the desired antenna radiation patterns for an HF communication circuit or service area. Sources for obtaining or computing radiation pattern information are outlined. Comparisons are presented between the measured and computed radiation patterns. The effect of the properties of the ground on the antenna gain and pattern are illustrated for several types of antennas. Numerous examples are given of the radiation patterns for typical antennas used on short, intermediate and long distance circuits or both mobile and fixed service operations. The application of adaptive antenna arrays and active antennas in modern HF communication systems are briefly reviewed.

Equipment: Antenna systems

NASA Astrophysics Data System (ADS)

Petrie, L. E.

1986-03-01

Some antenna fundamentals as well as definitions of the principal terms used in antenna engineering are described. Methods are presented for determining the desired antenna radiation patterns for HF communication circuit or service area. Sources for obtaining or computing radiation pattern information are outlined. Comparisons are presented between the measured and computed radiation patterns. The effect of the properties of the ground on the antenna gain and the pattern are illustrated for several types of antennas. Numerous examples are given of the radiation patterns for typical antennas used on short, intermediate and long distance circuits for both mobile and fixed service operations. The application of adaptive antenna arrays and active antennas in modern HF communication systems are briefly reviewed.

Metallic mirrors for plasma diagnosis in current and future reactors: tests for ITER and DEMO

NASA Astrophysics Data System (ADS)

Rubel, M.; Moon, Soonwoo; Petersson, P.; Garcia-Carrasco, A.; Hallén, A.; Krawczynska, A.; Fortuna-Zaleśna, E.; Gilbert, M.; Płociński, T.; Widdowson, A.; Contributors, JET

2017-12-01

Optical spectroscopy and imaging diagnostics in next-step fusion devices will rely on metallic mirrors. The performance of mirrors is studied in present-day tokamaks and in laboratory systems. This work deals with comprehensive tests of mirrors: (a) exposed in JET with the ITER-like wall (JET-ILW); (b) irradiated by hydrogen, helium and heavy ions to simulate transmutation effects and damage which may be induced by neutrons under reactor conditions. The emphasis has been on surface modification: deposited layers on JET mirrors from the divertor and on near-surface damage in ion-irradiated targets. Analyses performed with ion beams, microscopy and spectro-photometry techniques have revealed: (i) the formation of multiple co-deposited layers; (ii) flaking-off of the layers already in the tokamak, despite the small thickness (130-200 nm) of the granular deposits; (iii) deposition of dust particles (0.2-5 μm, 300-400 mm-2) composed mainly of tungsten and nickel; (iv) that the stepwise irradiation of up to 30 dpa by heavy ions (Mo, Zr or Nb) caused only small changes in the optical performance, in some cases even improving reflectivity due to the removal of the surface oxide layer; (v) significant reflectivity degradation related to bubble formation caused by the irradiation with He and H ions.

Design, performance, and grounding aspects of the International Thermonuclear Experimental Reactor ion cyclotron range of frequencies antenna

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

Durodié, F., E-mail: frederic.durodie@rma.ac.be; Dumortier, P.; Vrancken, M.

2014-06-15

ITER's Ion Cyclotron Range of Frequencies (ICRF) system [Lamalle et al., Fusion Eng. Des. 88, 517–520 (2013)] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf of ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER's Vacuum Vessel (VV) ports. Each launcher is an array of 4 toroidal by 6 poloidal RF current straps specified to couple up to 20 MW in total to the plasma in the frequency range of 40 to 55 MHz but limited to a maximum system voltage of 45 kV andmore » limits on RF electric fields depending on their location and direction with respect to, respectively, the torus vacuum and the toroidal magnetic field. A crucial aspect of coupling ICRF power to plasmas is the knowledge of the plasma density profiles in the Scrape-Off Layer (SOL) and the location of the RF current straps with respect to the SOL. The launcher layout and details were optimized and its performance estimated for a worst case SOL provided by the IO. The paper summarizes the estimated performance obtained within the operational parameter space specified by IO. Aspects of the RF grounding of the whole antenna PP to the VV port and the effect of the voids between the PP and the Blanket Shielding Modules (BSM) surrounding the antenna front are discussed. These blanket modules, whose dimensions are of the order of the ICRF wavelengths, together with the clearance gaps between them will constitute a corrugated structure which will interact with the electromagnetic waves launched by ICRF antennas. The conditions in which the grooves constituted by the clearance gaps between the blanket modules can become resonant are studied. Simple analytical models and numerical simulations show that mushroom type structures (with larger gaps at the back than at the front) can bring down the resonance frequencies, which could lead to large voltages in the gaps between the blanket modules and

Screen printed UHF antennas on flexible substrates

NASA Astrophysics Data System (ADS)

Janeczek, Kamil; Młożniak, Anna; Kozioł, Grażyna; Araźna, Aneta; Jakubowska, Małgorzata; Bajurko, Paweł

2010-09-01

Printed electronics belongs to the most important developing electronics technologies. It provides new possibilities to produce low cost and large area devices. In its range several applications can be distinguished like printed batteries, OLED, biosensors, photovoltaic cells or RFID tags. In the presented investigation, antennas working in UHF frequency range were elaborated. It can be applied in the future for flexible RFID tags. To produce these antennas polymer paste with silver flakes was used. It was deposited on two flexible substrates (foil and photo paper) with screen printing techniques. After printing process surface profile, electrical and microwave parameters of performed antennas were measured using digital multimeter and network analyzer, relatively. Furthermore, a thickness of printed layers was measured.

Light impurity transport in JET ILW L-mode plasmas

NASA Astrophysics Data System (ADS)

Bonanomi, N.; Mantica, P.; Giroud, C.; Angioni, C.; Manas, P.; Menmuir, S.; Contributors, JET

2018-03-01

A series of experimental observations of light impurity profiles was carried out in JET (Joint European Torus) ITER-like wall (ILW) L-mode plasmas in order to investigate their transport mechanisms. These discharges feature the presence of 3He, Be, C, N, Ne, whose profiles measured by active Charge Exchange diagnostics are compared with quasi-linear and non-linear gyro-kinetic simulations. The peaking of 3He density follows the electron density peaking, Be and Ne are also peaked, while the density profiles of C and N are flat in the mid plasma region. Gyro-kinetic simulations predict peaked density profiles for all the light impurities studied and at all the radial positions considered, and fail predicting the flat or hollow profiles observed for C and N at mid radius in our cases.

Self-Similarity of Plasmon Edge Modes on Koch Fractal Antennas.

PubMed

Bellido, Edson P; Bernasconi, Gabriel D; Rossouw, David; Butet, Jérémy; Martin, Olivier J F; Botton, Gianluigi A

2017-11-28

We investigate the plasmonic behavior of Koch snowflake fractal geometries and their possible application as broadband optical antennas. Lithographically defined planar silver Koch fractal antennas were fabricated and characterized with high spatial and spectral resolution using electron energy loss spectroscopy. The experimental data are supported by numerical calculations carried out with a surface integral equation method. Multiple surface plasmon edge modes supported by the fractal structures have been imaged and analyzed. Furthermore, by isolating and reproducing self-similar features in long silver strip antennas, the edge modes present in the Koch snowflake fractals are identified. We demonstrate that the fractal response can be obtained by the sum of basic self-similar segments called characteristic edge units. Interestingly, the plasmon edge modes follow a fractal-scaling rule that depends on these self-similar segments formed in the structure after a fractal iteration. As the size of a fractal structure is reduced, coupling of the modes in the characteristic edge units becomes relevant, and the symmetry of the fractal affects the formation of hybrid modes. This analysis can be utilized not only to understand the edge modes in other planar structures but also in the design and fabrication of fractal structures for nanophotonic applications.

Integrated modeling of plasma ramp-up in DIII-D ITER-like and high bootstrap current scenario discharges

NASA Astrophysics Data System (ADS)

Wu, M. Q.; Pan, C. K.; Chan, V. S.; Li, G. Q.; Garofalo, A. M.; Jian, X.; Liu, L.; Ren, Q. L.; Chen, J. L.; Gao, X.; Gong, X. Z.; Ding, S. Y.; Qian, J. P.; Cfetr Physics Team

2018-04-01

Time-dependent integrated modeling of DIII-D ITER-like and high bootstrap current plasma ramp-up discharges has been performed with the equilibrium code EFIT, and the transport codes TGYRO and ONETWO. Electron and ion temperature profiles are simulated by TGYRO with the TGLF (SAT0 or VX model) turbulent and NEO neoclassical transport models. The VX model is a new empirical extension of the TGLF turbulent model [Jian et al., Nucl. Fusion 58, 016011 (2018)], which captures the physics of multi-scale interaction between low-k and high-k turbulence from nonlinear gyro-kinetic simulation. This model is demonstrated to accurately model low Ip discharges from the EAST tokamak. Time evolution of the plasma current density profile is simulated by ONETWO with the experimental current ramp-up rate. The general trend of the predicted evolution of the current density profile is consistent with that obtained from the equilibrium reconstruction with Motional Stark effect constraints. The predicted evolution of βN , li , and βP also agrees well with the experiments. For the ITER-like cases, the predicted electron and ion temperature profiles using TGLF_Sat0 agree closely with the experimental measured profiles, and are demonstrably better than other proposed transport models. For the high bootstrap current case, the predicted electron and ion temperature profiles perform better in the VX model. It is found that the SAT0 model works well at high IP (>0.76 MA) while the VX model covers a wider range of plasma current ( IP > 0.6 MA). The results reported in this paper suggest that the developed integrated modeling could be a candidate for ITER and CFETR ramp-up engineering design modeling.

Mutual Elements and Substrate Effect Analysis on Patch Antenna Arrays

NASA Astrophysics Data System (ADS)

Wallace, Matthew J.

There have been many different technology advancements with the invention of solid state electronics, leading to the digital era which has changed the way users employ electronic circuits. Antennas are no different; however, they are still analog devices. With the advancements in technology, antennas are being fabricated on much higher frequencies and with greater bandwidths, all while trying to keep size and weight to a minimum. Centimeter and millimeter wave technologies have evolved for many different radio frequency (RF) applications. Microstrip patch antennas have been developed, as wire and tubular antenna elements are difficult to fabricate with the tolerances required at micro-wavelengths. Microstrip patch antennas are continuously being improved. These types of antennas are great for embedded or conformal applications where size and weight are of the essence and the ease of manufacturing elements to tight tolerances is important. One of the greatest benefits of patch antennas is the ease in creating an array. Many simulation programs have been created to assist in the design of patch antennas and arrays. However, there are still discrepancies between simulated results and actual measurements. This research will focus on these differences. It begins with a literature research of patch antenna design, followed by an assessment of simulation programs used for patch antenna design. The resulting antenna design was realized by the fabrication of an antenna from the Genesys software. Laboratory measurements of the real-world antenna are then compared to the theoretical antenna characteristics. This process is used to illustrate deficiencies in the software models and likely improvements that need to be made.

A (likely) X-ray jet from NGC6217 observed by XMM-Newton

NASA Astrophysics Data System (ADS)

Falocco, Serena; Larsson, Josefin; Nandi, Sumana

2017-12-01

NGC6217 is a nearby spiral galaxy with a starburst region near its centre. Evidence for a low-luminosity Active Galactic Nucleus (AGN) in its core has also been found in optical spectra. Intriguingly, X-ray observations by ROSAT revealed three knots aligned with the galaxy centre, resembling a jet structure. This paper presents a study of XMM-Newton observations made to assess the hypothesis of a jet emitted from the centre of NGC6217. The XMM data confirm the knots found with ROSAT and our spectral analysis shows that they have similar spectral properties with a hard photon index Γ ∼ 1.7. The core of NGC6217 is well fitted by a model with an AGN and a starburst component, where the AGN contributes at most 46 per cent of the total flux. The candidate jet has an apparent length ∼15 kpc and a luminosity of ∼5 × 1038 erg s- 1. It stands out by being hosted by a spiral galaxy, since jets are more widely associated with ellipticals. To explain the jet launching mechanism we consider the hypothesis of an advection dominated accretion flow with a low accretion rate. The candidate jet emitted from NGC6217 is intriguing since it represents a challenge to the current knowledge of the connection between AGN, jets and host galaxies.

Circular Microstrip Antenna with Fractal Slots for Multiband Applications

NASA Astrophysics Data System (ADS)

Singh, Sivia Jagtar; Singh, Gurpreet; Bharti, Gurpreet

2017-10-01

In this paper, a multiband, fractal, slotted, Circular Microstrip Patch Antenna for GSM, WiMAX, C and X bands (satellite communication applications) is presented. A cantor set theory is used to make fractal slots for obtaining the desired multiband. The projected antenna is simulated using Ansys HFSS v13.0 software. Simulation test of this antenna has been carried out for a frequency range of 1 GHz-10 GHz and a peak gain of 9.19 dB at a resonance frequency of 1.9 GHz is obtained. The antenna also resonates at 3.7 GHz, 6.06 GHz and 7.9 GHz with gains of 3.04 dB, 5.19 dB and 5.39 dB respectively. Parameters like voltage standing wave ratio, return loss, and gain are used to compare the results of the projected antenna with conventional CMPA's of same dimensions with full and defective grounds. The projected antenna is fabricated on a glass epoxy material and is tested using Vector Network Analyzer. The performance parameters of the antenna are found to in good agreement with each both using simulated and measured data.

ITER L-mode confinement database

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

Kaye, S.M.

This paper describes the content of an L-mode database that has been compiled with data from Alcator C-Mod, ASDEX, DIII, DIII-D, FTU, JET, JFT-2M, JT-60, PBX-M, PDX, T-10, TEXTOR, TFTR, and Tore-Supra. The database consists of a total of 2938 entries, 1881 of which are in the L-phase while 922 are ohmically heated only (OH). Each entry contains up to 95 descriptive parameters, including global and kinetic information, machine conditioning, and configuration. The paper presents a description of the database and the variables contained therein, and it also presents global and thermal scalings along with predictions for ITER.

OBSERVATIONS OF A SERIES OF FLARES AND ASSOCIATED JET-LIKE ERUPTIONS DRIVEN BY THE EMERGENCE OF TWISTED MAGNETIC FIELDS

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

Lim, Eun-Kyung; Yurchyshyn, Vasyl; Kim, Sujin

We studied temporal changes of morphological and magnetic properties of a succession of four confined flares followed by an eruptive flare using the high-resolution New Solar Telescope (NST) operating at the Big Bear Solar Observatory (BBSO) and Helioseismic and Magnetic Imager (HMI) magnetograms and Atmospheric Image Assembly (AIA) EUV images provided by the Solar Dynamics Observatory (SDO). From the NST/Hα and the SDO/AIA 304 Å observations we found that each flare developed a jet structure that evolved in a manner similar to evolution of the blowout jet: (1) an inverted-Y-shaped jet appeared and drifted away from its initial position; (2) jets formed amore » curtain-like structure that consisted of many fine threads accompanied by subsequent brightenings near the footpoints of the fine threads; and finally, (3) the jet showed a twisted structure visible near the flare maximum. Analysis of the HMI data showed that both the negative magnetic flux and the magnetic helicity have been gradually increasing in the positive-polarity region, indicating the continuous injection of magnetic twist before and during the series of flares. Based on these results, we suggest that the continuous emergence of twisted magnetic flux played an important role in producing successive flares and developing a series of blowout jets.« less

Assessment of the measurement performance of the in-vessel system of gap 6 of the ITER plasma position reflectometer using a finite-difference time-domain Maxwell full-wave code.

PubMed

da Silva, F; Heuraux, S; Ricardo, E; Quental, P; Ferreira, J

2016-11-01

We conducted a first assessment of the measurement performance of the in-vessel components at gap 6 of the ITER plasma position reflectometry with the aid of a synthetic Ordinary Mode (O-mode) broadband frequency-modulated continuous-wave reflectometer implemented with REFMUL, a 2D finite-difference time-domain full-wave Maxwell code. These simulations take into account the system location within the vacuum vessel as well as its access to the plasma. The plasma case considered is a baseline scenario from Fusion for Energy. We concluded that for the analyzed scenario, (i) the plasma curvature and non-equatorial position of the antenna have neglectable impact on the measurements; (ii) the cavity-like space surrounding the antenna can cause deflection and splitting of the probing beam; and (iii) multi-reflections on the blanket wall cause a substantial error preventing the system from operating within the required error margin.

No-go theorem for iterations of unknown quantum gates

NASA Astrophysics Data System (ADS)

Soleimanifar, Mehdi; Karimipour, Vahid

2016-01-01

We propose a no-go theorem by proving the impossibility of constructing a deterministic quantum circuit that iterates a unitary oracle by calling it only once. Different schemes are provided to bypass this result and to approximately realize the iteration. The optimal scheme is also studied. An interesting observation is that for a large number of iterations, a trivial strategy like using the identity channel has the optimal performance, and preprocessing, postprocessing, or using resources like entanglement does not help at all. Intriguingly, the number of iterations, when being large enough, does not affect the performance of the proposed schemes.

Antenna data storage concept for phased array radio astronomical instruments

NASA Astrophysics Data System (ADS)

Gunst, André W.; Kruithof, Gert H.

2018-04-01

Low frequency Radio Astronomy instruments like LOFAR and SKA-LOW use arrays of dipole antennas for the collection of radio signals from the sky. Due to the large number of antennas involved, the total data rate produced by all the antennas is enormous. Storage of the antenna data is both economically and technologically infeasible using the current state of the art storage technology. Therefore, real-time processing of the antenna voltage data using beam forming and correlation is applied to achieve a data reduction throughout the signal chain. However, most science could equally well be performed using an archive of raw antenna voltage data coming straight from the A/D converters instead of capturing and processing the antenna data in real time over and over again. Trends on storage and computing technology make such an approach feasible on a time scale of approximately 10 years. The benefits of such a system approach are more science output and a higher flexibility with respect to the science operations. In this paper we present a radically new system concept for a radio telescope based on storage of raw antenna data. LOFAR is used as an example for such a future instrument.

Automated Antenna Design with Evolutionary Algorithms

NASA Technical Reports Server (NTRS)

Hornby, Gregory S.; Globus, Al; Linden, Derek S.; Lohn, Jason D.

2006-01-01

constrain the evolutionary design to a monopole wire antenna. The results of the runs produced requirements-compliant antennas that were subsequently fabricated and tested. The evolved antenna has a number of advantages with regard to power consumption, fabrication time and complexity, and performance. Lower power requirements result from achieving high gain across a wider range of elevation angles, thus allowing a broader range of angles over which maximum data throughput can be achieved. Since the evolved antenna does not require a phasing circuit, less design and fabrication work is required. In terms of overall work, the evolved antenna required approximately three person-months to design and fabricate whereas the conventional antenna required about five. Furthermore, when the mission was modified and new orbital parameters selected, a redesign of the antenna to new requirements was required. The evolutionary system was rapidly modified and a new antenna evolved in a few weeks. The evolved antenna was shown to be compliant to the ST5 mission requirements. It has an unusual organic looking structure, one that expert antenna designers would not likely produce. This antenna has been tested, baselined and is scheduled to fly this year. In addition to the ST5 antenna, our laboratory has evolved an S-band phased array antenna element design that meets the requirements for NASA's TDRS-C communications satellite scheduled for launch early next decade. A combination of fairly broad bandwidth, high efficiency and circular polarization at high gain made for another challenging design problem. We chose to constrain the evolutionary design to a crossed-element Yagi antenna. The specification called for two types of elements, one for receive only and one for transmit/receive. We were able to evolve a single element design that meets both specifications thereby simplifying the antenna and reducing testing and integration costs. The highest performance antenna found using a getic

Studying AGN Jets At Extreme Angular Resolution

NASA Astrophysics Data System (ADS)

Bruni, Gabriele

2016-10-01

RadioAstron is a 10m antenna orbiting on the Russian Speckt-R spacecraft, launched in 2011. Performing radio interferometry with a global array of ground telescopes, it is providing record angular resolution. The Key Science Project on AGN polarization is exploiting it to study in great detail the configuration of magnetic fields in AGN jets, and understand their formation and collimation. To date, the project has already achieved the highest angular resolution image ever obtained in Astronomy, and detected brightness temperatures exceeding the ones predicted by theory of AGN.

Physics and Engineering Design of the ITER Electron Cyclotron Emission Diagnostic

NASA Astrophysics Data System (ADS)

Rowan, W. L.; Austin, M. E.; Houshmandyar, S.; Phillips, P. E.; Beno, J. H.; Ouroua, A.; Weeks, D. A.; Hubbard, A. E.; Stillerman, J. A.; Feder, R. E.; Khodak, A.; Taylor, G.; Pandya, H. K.; Danani, S.; Kumar, R.

2015-11-01

Electron temperature (Te) measurements and consequent electron thermal transport inferences will be critical to the non-active phases of ITER operation and will take on added importance during the alpha heating phase. Here, we describe our design for the diagnostic that will measure spatial and temporal profiles of Te using electron cyclotron emission (ECE). Other measurement capability includes high frequency instabilities (e.g. ELMs, NTMs, and TAEs). Since results from TFTR and JET suggest that Thomson Scattering and ECE differ at high Te due to driven non-Maxwellian distributions, non-thermal features of the ITER electron distribution must be documented. The ITER environment presents other challenges including space limitations, vacuum requirements, and very high-neutron-fluence. Plasma control in ITER will require real-time Te. The diagnosic design that evolved from these sometimes-conflicting needs and requirements will be described component by component with special emphasis on the integration to form a single effective diagnostic system. Supported by PPPL/US-DA via subcontract S013464-C to UT Austin.

Jet Fuel Thermal Stability Investigations using Ellipsometry

NASA Technical Reports Server (NTRS)

Nash, Leigh; Klettlinger, Jennifer; Vasu, Subith

2017-01-01

Ellipsometry is an optical technique used to measure the thickness of thin films. This technique was used to measure the thickness of deposits created by heated jet fuel, specifically Sasol IPK on stainless steel tubes. A new amorphous model was used to iteratively determine the film thickness. This method was found to be repeatable, and the thickness of deposit increased with increasing temperature and increasing concentration of naphthalene.

Large space antenna communications systems: Integrated Langley Research Center/Jet Propulsion Laboratory development activities. 2: Langley Research Center activities

NASA Technical Reports Server (NTRS)

Cambell, T. G.; Bailey, M. C.; Cockrell, C. R.; Beck, F. B.

1983-01-01

The electromagnetic analysis activities at the Langley Research Center are resulting in efficient and accurate analytical methods for predicting both far- and near-field radiation characteristics of large offset multiple-beam multiple-aperture mesh reflector antennas. The utilization of aperture integration augmented with Geometrical Theory of Diffraction in analyzing the large reflector antenna system is emphasized.

Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Mod

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

Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.

Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlyingmore » physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%–30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are

MMS observations of guide field reconnection at the interface between colliding reconnection jets inside flux rope-like structures at the magnetopause

NASA Astrophysics Data System (ADS)

Oieroset, M.; Phan, T.; Haggerty, C. C.; Shay, M.; Eastwood, J. P.; Gershman, D. J.; Drake, J. F.; Fujimoto, M.; Ergun, R.; Mozer, F.; Oka, M.; Torbert, R. B.; Burch, J. L.; Wang, S.; Chen, L. J.; Swisdak, M.; Pollock, C. J.; Dorelli, J.; Fuselier, S. A.; Lavraud, B.; Kacem, I.; Giles, B. L.; Moore, T. E.; Saito, Y.; Avanov, L. A.; Paterson, W. R.; Strangeway, R. J.; Schwartz, S. J.; Khotyaintsev, Y. V.; Lindqvist, P. A.; Malakit, K.

2017-12-01

The formation and evolution of magnetic flux ropes is of critical importance for a number of collisionless plasma phenomena. At the dayside magnetopause flux rope-like structures can form between two X-lines. The two X-lines produce converging plasma jets. At the interface between the colliding jets a compressed current sheet can form, which in turn can undergo reconnection. We present MMS observations of the exhaust and diffusion region of such reconnection.

Damping Rate Measurements of Medium n Alfv'en Eigenmodes in JET

NASA Astrophysics Data System (ADS)

Klein, Alexander; Testa, Duccio; Snipes, Joseph; Fasoli, Ambrogio; Carfantan, Hervé

2007-11-01

Alfv'en Eigenmodes (AE's) with mode numbers 5 < n < 20 are expected to be unstable in burning tokamaks and may lead to loss of fast particle confinement. The active MHD spectroscopy program at JET has already provided a wealth of information about low n (n <= 2) AE's in the past decade, but a recently installed array of four antennas is capable of driving higher mode numbered (n < 100, 30 < f < 350 kHz) perturbations. In the latest JET campaign, the damping rates for several types of AE's were measured parasitically in a wide range of tokamak scenarios. We review the active MHD diagnostic and present the first measurements of medium-n AE stability on JET, then describe future plans for the active MHD spectroscopy project. The data analysis involves a novel method for resolving multiple AE's that exist at identical frequencies, which uses techniques based on the SparSpec code.

Waveform Optimization for Target Estimation by Cognitive Radar with Multiple Antennas.

PubMed

Yao, Yu; Zhao, Junhui; Wu, Lenan

2018-05-29

A new scheme based on Kalman filtering to optimize the waveforms of an adaptive multi-antenna radar system for target impulse response (TIR) estimation is presented. This work aims to improve the performance of TIR estimation by making use of the temporal correlation between successive received signals, and minimize the mean square error (MSE) of TIR estimation. The waveform design approach is based upon constant learning from the target feature at the receiver. Under the multiple antennas scenario, a dynamic feedback loop control system is established to real-time monitor the change in the target features extracted form received signals. The transmitter adapts its transmitted waveform to suit the time-invariant environment. Finally, the simulation results show that, as compared with the waveform design method based on the MAP criterion, the proposed waveform design algorithm is able to improve the performance of TIR estimation for extended targets with multiple iterations, and has a relatively lower level of complexity.

Shock-capturing parabolized Navier-Stokes model /SCIPVIS/ for the analysis of turbulent underexpanded jets

NASA Technical Reports Server (NTRS)

Dash, S. M.; Wolf, D. E.

1983-01-01

A new computational model, SCIPVIS, has been developed to predict the multiple-cell wave/shock structure in under or over-expanded turbulent jets. SCIPVIS solves the parabolized Navier-Stokes jet mixing equations utilizing a shock-capturing approach in supersonic regions of the jet and a pressure-split approach in subsonic regions. Turbulence processes are represented by the solution of compressibility corrected two-equation turbulence models. The formation of Mach discs in the jet and the interactive turbulent mixing process occurring behind the disc are handled in a detailed fashion. SCIPVIS presently analyzes jets exhausting into a quiescent or supersonic external stream for which a single-pass spatial marching solution can be obtained. The iterative coupling of SCIPVIS with a potential flow solver for the analysis of subsonic/transonic external streams is under development.

Antenna theory: Analysis and design

NASA Astrophysics Data System (ADS)

Balanis, C. A.

The book's main objective is to introduce the fundamental principles of antenna theory and to apply them to the analysis, design, and measurements of antennas. In a description of antennas, the radiation mechanism is discussed along with the current distribution on a thin wire. Fundamental parameters of antennas are examined, taking into account the radiation pattern, radiation power density, radiation intensity, directivity, numerical techniques, gain, antenna efficiency, half-power beamwidth, beam efficiency, bandwidth, polarization, input impedance, and antenna temperature. Attention is given to radiation integrals and auxiliary potential functions, linear wire antennas, loop antennas, linear and circular arrays, self- and mutual impedances of linear elements and arrays, broadband dipoles and matching techniques, traveling wave and broadband antennas, frequency independent antennas and antenna miniaturization, the geometrical theory of diffraction, horns, reflectors and lens antennas, antenna synthesis and continuous sources, and antenna measurements.

Fundamental Fractal Antenna Design Process

NASA Astrophysics Data System (ADS)

Zhu, L. P.; Kim, T. C.; Kakas, G. D.

2017-12-01

Antenna designers are always looking to come up with new ideas to push the envelope for new antennas, using a smaller volume while striving for higher bandwidth, wider bandwidth, and antenna gain. One proposed method of increasing bandwidth or shrinking antenna size is via the use of fractal geometry, which gives rise to fractal antennas. Fractals are those fun shapes that if one zooms in or zoom out, the structure is always the same. Design a new type of antenna based on fractal antenna design by utilize the Design of Experiment (DOE) will be shown in fractal antenna design process. Investigate conformal fractal antenna design for patterns, dimensions, and size, of the antenna but maintaining or improving the antenna performance. Research shows an antenna designer how to create basic requirements of the fractal antenna through a step by step process, and provides how to optimize the antenna design with the model prediction, lab measurement, and actual results from the compact range measurement on the antenna patterns.

View north of the antenna array, note the communications antenna ...

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

View north of the antenna array, note the communications antenna in the middleground - Over-the-Horizon Backscatter Radar Network, Christmas Valley Radar Site Transmit Sector Four Antenna Array, On unnamed road west of Lost Forest Road, Christmas Valley, Lake County, OR

View of antenna tunnel end. Right to Antenna Silo #1, ...

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

View of antenna tunnel end. Right to Antenna Silo #1, left to Antenna Silo #2 - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

Jet-Like Structures and Wake in Mg I (518 nm) Images of 1999 Leonid Storm Meteors

NASA Technical Reports Server (NTRS)

Taylor, M. J.; Murray, I. S.; Jenniskens, P.

2000-01-01

Small meteoric fragments are ejected at significant transverse velocities from some (up to approx. 8%) fast Leonid meteors. We reach this conclusion using low light intensified image measurements obtained during the 1999 Leonid Multi-Instrument Aircraft Campaign. High spatial resolution, narrow band image measurements of the Mg I emission at 518 nm have been used to clearly identify jet-like features in the meteor head that are the same as first observed in white light. We postulate that these unusual structures are caused by tiny meteoroid fragments (containing metallic grains) being rapidly ejected away from the core meteoroid as the constituent glue evaporates. Marked curvature observed in the jet-like filaments suggest that the parent meteoroids are spinning and as the whirling fragments are knocked away by the impinging air molecules, or by grain-grain collisions in the fragment ensemble, they ablate quickly generating an extended area of structured luminosity up to about 1-2 km from the meteoroid center. Fragments with smaller transverse velocity components are thought to be responsible for the associated beading evident in the wake of these unusual Leonid meteors.

L-Band Orthogonal-Mode Crossed-Slot Antenna and VHF Crossed-Loop Antenna

DOT National Transportation Integrated Search

1972-01-01

A low-gain, circularly polarized, L-ban antenna; a low-gain, lineraly polarized, L-band antenna; and a low-gain, lineraly polarized, L-ban antenna; and a low-gain, circularly polarized, upper hemisphere, VHF satellite communications antenna intended ...

Resolving boosted jets with XCone

DOE PAGES

Thaler, Jesse; Wilkason, Thomas F.

2015-12-01

We show how the recently proposed XCone jet algorithm smoothly interpolates between resolved and boosted kinematics. When using standard jet algorithms to reconstruct the decays of hadronic resonances like top quarks and Higgs bosons, one typically needs separate analysis strategies to handle the resolved regime of well-separated jets and the boosted regime of fat jets with substructure. XCone, by contrast, is an exclusive cone jet algorithm that always returns a fixed number of jets, so jet regions remain resolved even when (sub)jets are overlapping in the boosted regime. In this paper, we perform three LHC case studies $-$ dijet resonances,more » Higgs decays to bottom quarks, and all-hadronic top pairs$-$ that demonstrate the physics applications of XCone over a wide kinematic range.« less

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.

Jet-like features near the Nucleus of Chiron

NASA Technical Reports Server (NTRS)

Elliot, J. L.; Olkin, C. B.; Dunham, E. W.; Ford, C. H.; Gilmore, D. K.; Kurtz, D.; Lazzaro, D.; Rank, D. M.; Temi, P.; Bandyopadhyay, R. M.;

SMI adaptive antenna arrays for weak interfering signals

NASA Technical Reports Server (NTRS)

Gupta, I. J.

1987-01-01

The performance of adaptive antenna arrays is studied when a sample matrix inversion (SMI) algorithm is used to control array weights. It is shown that conventional SMI adaptive antennas, like other adaptive antennas, are unable to suppress weak interfering signals (below thermal noise) encountered in broadcasting satellite communication systems. To overcome this problem, the SMI algorithm is modified. In the modified algorithm, the covariance matrix is modified such that the effect of thermal noise on the weights of the adaptive array is reduced. Thus, the weights are dictated by relatively weak coherent signals. It is shown that the modified algorithm provides the desired interference protection. The use of defocused feeds as auxiliary elements of an SMI adaptive array is also discussed.

Antenna Controller Replacement Software

NASA Technical Reports Server (NTRS)

Chao, Roger Y.; Morgan, Scott C.; Strain, Martha M.; Rockwell, Stephen T.; Shimizu, Kenneth J.; Tehrani, Barzia J.; Kwok, Jaclyn H.; Tuazon-Wong, Michelle; Valtier, Henry; Nalbandi, Reza;

Fuel inventory and deposition in castellated structures in JET-ILW

NASA Astrophysics Data System (ADS)

Rubel, M.; Petersson, P.; Zhou, Y.; Coad, J. P.; Lungu, C.; Jepu, I.; Porosnicu, C.; Matveev, D.; Kirschner, A.; Brezinsek, S.; Widdowson, A.; Alves, E.; Contributors, JET

2017-06-01

Since 2011 the JET tokamak has been operated with a metal ITER-like wall (JET-ILW) including castellated beryllium limiters and lamellae-type bulk tungsten tiles in the divertor. This has allowed for a large scale test of castellated plasma-facing components (PFC). Procedures for sectioning the limiters into single blocks of castellation have been developed. This facilitated morphology studies of morphology of surfaces inside the grooves for limiters after experimental campaigns 2011-2012 and 2013-2014. The deposition in the 0.4-0.5 mm wide grooves of the castellation is ‘shallow’. It reaches 1-2 mm into the 12 mm deep gap. Deuterium concentrations are small (mostly below 1  ×  1018 cm-2). The estimated total amount of deuterium in all the castellated limiters does not exceed the inventory of the plasma-facing surfaces (PFS) of the limiters. There are only traces of Ni, Cr and Fe deposited in the castellation gaps. The same applies to the carbon content. Also low deposition of D, Be and C has been measured on the sides of the bulk tungsten lamellae pieces. Modelling clearly reflects: (a) a sharp decrease in the measured deposition profiles and(b) an increase in deposition with the gap width. Both experimental and modelling data give a strong indication and information to ITER that narrow gaps in the castellated PFC are essential. X-ray diffraction on PFS has clearly shown two distinct composition patterns: Be with an admixture of Be-W intermetallic compounds (e.g. Be22W) in the deposition zone, whilst only pure Be has been detected in the erosion zone. The lack of compound formation in the erosion zone indicates that no distinct changes in the thermo-mechanical properties of the Be PFC might be expected.

Spacecraft Antennas

NASA Technical Reports Server (NTRS)

Jamnejad, Vahraz; Manshadi, Farzin; Rahmat-Samii, Yahya; Cramer, Paul

1990-01-01

Some of the various categories of issues that must be considered in the selection and design of spacecraft antennas for a Personal Access Satellite System (PASS) are addressed, and parametric studies for some of the antenna concepts to help the system designer in making the most appropriate antenna choice with regards to weight, size, and complexity, etc. are provided. The question of appropriate polarization for the spacecraft as well as for the User Terminal Antenna required particular attention and was studied in some depth. Circular polarization seems to be the favored outcome of this study. Another problem that has generally been a complicating factor in designing the multiple beam reflector antennas, is the type of feeds (single vs. multiple element and overlapping vs. non-overlapping clusters) needed for generating the beams. This choice is dependent on certain system design factors, such as the required frequency reuse, acceptable interbeam isolation, antenna efficiency, number of beams scanned, and beam-forming network (BFN) complexity. This issue is partially addressed, but is not completely resolved. Indications are that it may be possible to use relatively simple non-overlapping clusters of only a few elements, unless a large frequency reuse and very stringent isolation levels are required.

Antenna Allocation in MIMO Radar with Widely Separated Antennas for Multi-Target Detection

PubMed Central

Gao, Hao; Wang, Jian; Jiang, Chunxiao; Zhang, Xudong

2014-01-01

In this paper, we explore a new resource called multi-target diversity to optimize the performance of multiple input multiple output (MIMO) radar with widely separated antennas for detecting multiple targets. In particular, we allocate antennas of the MIMO radar to probe different targets simultaneously in a flexible manner based on the performance metric of relative entropy. Two antenna allocation schemes are proposed. In the first scheme, each antenna is allocated to illuminate a proper target over the entire illumination time, so that the detection performance of each target is guaranteed. The problem is formulated as a minimum makespan scheduling problem in the combinatorial optimization framework. Antenna allocation is implemented through a branch-and-bound algorithm and an enhanced factor 2 algorithm. In the second scheme, called antenna-time allocation, each antenna is allocated to illuminate different targets with different illumination time. Both antenna allocation and time allocation are optimized based on illumination probabilities. Over a large range of transmitted power, target fluctuations and target numbers, both of the proposed antenna allocation schemes outperform the scheme without antenna allocation. Moreover, the antenna-time allocation scheme achieves a more robust detection performance than branch-and-bound algorithm and the enhanced factor 2 algorithm when the target number changes. PMID:25350505

Antenna allocation in MIMO radar with widely separated antennas for multi-target detection.

PubMed

Gao, Hao; Wang, Jian; Jiang, Chunxiao; Zhang, Xudong

2014-10-27

In this paper, we explore a new resource called multi-target diversity to optimize the performance of multiple input multiple output (MIMO) radar with widely separated antennas for detecting multiple targets. In particular, we allocate antennas of the MIMO radar to probe different targets simultaneously in a flexible manner based on the performance metric of relative entropy. Two antenna allocation schemes are proposed. In the first scheme, each antenna is allocated to illuminate a proper target over the entire illumination time, so that the detection performance of each target is guaranteed. The problem is formulated as a minimum makespan scheduling problem in the combinatorial optimization framework. Antenna allocation is implemented through a branch-and-bound algorithm and an enhanced factor 2 algorithm. In the second scheme, called antenna-time allocation, each antenna is allocated to illuminate different targets with different illumination time. Both antenna allocation and time allocation are optimized based on illumination probabilities. Over a large range of transmitted power, target fluctuations and target numbers, both of the proposed antenna allocation schemes outperform the scheme without antenna allocation. Moreover, the antenna-time allocation scheme achieves a more robust detection performance than branch-and-bound algorithm and the enhanced factor 2 algorithm when the target number changes.

MSU Antenna Pattern Data

NASA Technical Reports Server (NTRS)

Mo, Tsan; Kleespies, Thomas J.; Green, J. Philip

2000-01-01

The Microwave Sounding Unit (MSU) antenna pattern data for nine MSU Flight Models (FMs) have been successfully rescued from 22-year old 7-track and 9-track magnetic tapes and cartridges. These antenna pattern data were unpacked into user-friendly ASCII format, and are potentially useful for making antenna pattern corrections to MSU antenna temperatures in retrieving the true brightness temperatures. We also properly interpreted the contents of the data and show how to convert the measured antenna signal amplitude in volts into relative antenna power in dB with proper normalization. It is found that the data are of high quality with a 60-dB drop in the co-polarized antenna patterns from the central peak value to its side-lobe regions at scan angles beyond 30 deg. The unpacked antenna pattern data produced in this study provide a useful database for data users to correct the antenna side-lobe contribution to MSU measurements. All of the data are available to the scientific community on a single CD-ROM.

A High Power Helicon Antenna Design for DIII-D

DOE PAGES

Nagy, A.; deGrassie, J.; Moeller, C.; ...

2017-08-02

A new antenna design for driving current in high beta tokamaks using electromagnetic waves, called Helicons, will be experimentally tested for the first time at power approaching 1 megawatt (MW) in the DIII-D Tokamak. This method is expected to be more efficient than current drive using electron cyclotron waves or neutral beam injection, and may be well suited to reactor-like configurations. A low power (100 watt (W)) 476 megahertz (MHz) “comb-line” antenna, consisting of 12 inductively coupled electrostatically shielded, modular resonators, was tested in DIII-D and showed strong coupling to the plasma without disturbing its characteristics or introducing metal impurities.more » The high power antenna consists of 30 modules affixed to back-plates and mounted on the outer wall of the vacuum vessel above the mid-plane. The antenna design follows a similar low power antenna design modified to minimize RF loss. Heat removal is provided by water cooling and a novel heat conducting path using pyrolytic graphite sheet. The CuCrZr antenna modules are designed to handle high eddy current forces. The modules use molybdenum Faraday shields that have the plasma side coated with boron carbide to enhance thermal resistance and minimize high Z impurities. A RF strip-line feed routes the RF power from coaxial vacuum feed-throughs to the antenna. Multipactor analysis of the antenna, strip line, and feedthrough will be performed. A 1.2 MW, 476 MHz klystron system, provided by the Stanford Linear Accelerator (SLAC) will provide RF power to the new antenna. Lastly, a description of the design of the high power antenna, the RF strip-line feeds, and the vessel installation will be presented.« less

A High Power Helicon Antenna Design for DIII-D

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

Nagy, A.; deGrassie, J.; Moeller, C.

A new antenna design for driving current in high beta tokamaks using electromagnetic waves, called Helicons, will be experimentally tested for the first time at power approaching 1 megawatt (MW) in the DIII-D Tokamak. This method is expected to be more efficient than current drive using electron cyclotron waves or neutral beam injection, and may be well suited to reactor-like configurations. A low power (100 watt (W)) 476 megahertz (MHz) “comb-line” antenna, consisting of 12 inductively coupled electrostatically shielded, modular resonators, was tested in DIII-D and showed strong coupling to the plasma without disturbing its characteristics or introducing metal impurities.more » The high power antenna consists of 30 modules affixed to back-plates and mounted on the outer wall of the vacuum vessel above the mid-plane. The antenna design follows a similar low power antenna design modified to minimize RF loss. Heat removal is provided by water cooling and a novel heat conducting path using pyrolytic graphite sheet. The CuCrZr antenna modules are designed to handle high eddy current forces. The modules use molybdenum Faraday shields that have the plasma side coated with boron carbide to enhance thermal resistance and minimize high Z impurities. A RF strip-line feed routes the RF power from coaxial vacuum feed-throughs to the antenna. Multipactor analysis of the antenna, strip line, and feedthrough will be performed. A 1.2 MW, 476 MHz klystron system, provided by the Stanford Linear Accelerator (SLAC) will provide RF power to the new antenna. Lastly, a description of the design of the high power antenna, the RF strip-line feeds, and the vessel installation will be presented.« less

Optimization of wearable microwave antenna with simplified electromagnetic model of the human body

NASA Astrophysics Data System (ADS)

Januszkiewicz, Łukasz; Barba, Paolo Di; Hausman, Sławomir

2017-12-01

In this paper the problem of optimization design of a microwave wearable antenna is investigated. Reference is made to a specific antenna design that is a wideband Vee antenna the geometry of which is characterized by 6 parameters. These parameters were automatically adjusted with an evolution strategy based algorithm EStra to obtain the impedance matching of the antenna located in the proximity of the human body. The antenna was designed to operate in the ISM (industrial, scientific, medical) band which covers the frequency range of 2.4 GHz up to 2.5 GHz. The optimization procedure used the finite-difference time-domain method based full-wave simulator with a simplified human body model. In the optimization procedure small movements of antenna towards or away of the human body that are likely to happen during real use were considered. The stability of the antenna parameters irrespective of the movements of the user's body is an important factor in wearable antenna design. The optimization procedure allowed obtaining good impedance matching for a given range of antenna distances with respect to the human body.

Edge transport and mode structure of a QCM-like fluctuation driven by the Shoelace antenna

NASA Astrophysics Data System (ADS)

Golfinopoulos, T.; LaBombard, B.; Brunner, D.; Terry, J. L.; Baek, S. G.; Ennever, P.; Edlund, E.; Han, W.; Burke, W. M.; Wolfe, S. M.; Irby, J. H.; Hughes, J. W.; Fitzgerald, E. W.; Granetz, R. S.; Greenwald, M. J.; Leccacorvi, R.; Marmar, E. S.; Pierson, S. Z.; Porkolab, M.; Vieira, R. F.; Wukitch, S. J.; The Alcator C-Mod Team

2018-05-01

The Shoelace antenna was built to drive edge fluctuations in the Alcator C-Mod tokamak, matching the wavenumber (k\\perp≈1.5 cm‑1) and frequency (30≲ f ≲ 200 kHz) of the quasi-coherent mode (QCM), which is responsible for regulating transport across the plasma boundary in the steady-state, ELM-free Enhanced D α (EDA) H-mode. Initial experiments in 2012 demonstrated that the antenna drove a resonant response in the edge plasma in steady-state EDA and transient, non-ELMy H-modes, but transport measurements were unavailable. In 2016, the Shoelace antenna was relocated to enable direct measurements of driven transport by a reciprocating Mirror Langmuir Probe, while also making available gas puff imaging and reflectometer data to provide additional radial localization of the driven fluctuation. This new data suggests a  ∼4 mm-wide mode layer centered on or just outside the separatrix. Fluctuations coherent with the antenna produced a radial electron flux with {Γ_e}/{n_e}∼4 m s‑1 in EDA H-mode, smaller than but comparable to the QCM level. But in transient ELM-free H-mode, {Γ_e}/{n_e} was an order of magnitude smaller, and driven fluctuations reduced by a factor of ≳ 3. The driven mode is quantitatively similar to the intrinsic QCM across measured spectral quantities, except that it is more coherent and weaker. This work informs the prospect of achieving control of edge transport by direct coupling to edge modes, as well as the use of such active coupling for diagnostic purposes.

Deployable antenna

NASA Technical Reports Server (NTRS)

Fink, Patrick W. (Inventor); Dobbins, Justin A. (Inventor); Lin, Greg Y. (Inventor); Chu, Andrew W. (Inventor); Scully, Robert C. (Inventor)

2006-01-01

A deployable antenna and method for using wherein the deployable antenna comprises a collapsible membrane having at least one radiating element for transmitting electromagnetic waves, receiving electromagnetic waves, or both.

Radiation pattern synthesis of planar antennas using the iterative sampling method

NASA Technical Reports Server (NTRS)

Stutzman, W. L.; Coffey, E. L.

1975-01-01

A synthesis method is presented for determining an excitation of an arbitrary (but fixed) planar source configuration. The desired radiation pattern is specified over all or part of the visible region. It may have multiple and/or shaped main beams with low sidelobes. The iterative sampling method is used to find an excitation of the source which yields a radiation pattern that approximates the desired pattern to within a specified tolerance. In this paper the method is used to calculate excitations for line sources, linear arrays (equally and unequally spaced), rectangular apertures, rectangular arrays (arbitrary spacing grid), and circular apertures. Examples using these sources to form patterns with shaped main beams, multiple main beams, shaped sidelobe levels, and combinations thereof are given.

A liquid metal-based structurally embedded vascular antenna: II. Multiobjective and parameterized design exploration

NASA Astrophysics Data System (ADS)

Hartl, D. J.; Frank, G. J.; Malak, R. J.; Baur, J. W.

2017-02-01

Research on the structurally embedded vascular antenna concept leverages past efforts on liquid metal (LM) reconfigurable electronics, microvascular composites, and structurally integrated and reconfigurable antennas. Such a concept has potential for reducing system weight or volume while simultaneously allowing in situ adjustment of resonant frequencies and/or changes in antenna directivity. This work considers a microvascular pattern embedded in a laminated composite and filled with LM. The conductive liquid provides radio frequency (RF) functionality while also allowing self-cooling. Models describing RF propagation and heat transfer, in addition to the structural effects of both the inclusion of channels and changes in temperature, were described in part 1 of this two-part work. In this part 2, the engineering models developed and demonstrated in part 1 toward the initial exploration of design trends are implemented into multiple optimization frameworks for more detailed design studies, one of which being novel and particularly applicable to this class of problem. The computational expense associated with the coupled multiphysical analysis of the structurally embedded LM transmitting antenna motivates the consideration of surrogate-based optimization methods. Both static and adaptive approaches are explored; it is shown that iteratively correcting the surrogate leads to more accurate optimized design predictions. The expected strong dependence of antenna performance on thermal environment motivates the consideration of a novel ‘parameterized’ optimization approach that simultaneously calculates whole families of optimal designs based on changes in design or operational variables generally beyond the control of the designer. The change in Pareto-optimal response with evolution in operating conditions is clearly demonstrated.

Removal of millimeter-scale rolled edges using bevel-cut-like tool influence function in magnetorheological jet polishing.

PubMed

Yang, Hao; Cheng, Haobo; Feng, Yunpeng; Jing, Xiaoli

2018-05-01

Subaperture polishing techniques usually produce rolled edges due to edge effect. The rolled edges, especially those in millimeter scale on small components, are difficult to eliminate using conventional polishing methods. Magnetorheological jet polishing (MJP) offers the possibility of the removal of these structures, owing to its small tool influence function (TIF) size. Hence, we investigate the removal characters of inclined MJP jetting models by means of computational fluid dynamics (CFD) simulations and polishing experiments. A discrete phase model (DPM) is introduced in the simulation to get the influence of abrasive particle concentration on the removal mechanism. Therefore, a more accurate model for MJP removal mechanisms is built. With several critical problems solved, a small bevel-cut-like TIF (B-TIF), which has fine acentric and unimodal characteristics, is obtained through inclined jetting. The B-TIF proves to have little edge effect and is applied in surface polishing of thin rolled edges. Finally, the RMS of the experimental section profile converges from 10.5 nm to 1.4 nm, and the rolled edges are successfully suppressed. Consequently, it is validated that the B-TIF has remarkable ability in the removal of millimeter-scale rolled edges.

Description of Jet Breakup

NASA Technical Reports Server (NTRS)

Papageorgiou, Demetrios T.

1996-01-01

In this article we review recent results on the breakup of cylindrical jets of a Newtonian fluid. Capillary forces provide the main driving mechanism and our interest is in the description of the flow as the jet pinches to form drops. The approach is to describe such topological singularities by constructing local (in time and space) similarity solutions from the governing equations. This is described for breakup according to the Euler, Stokes or Navier-Stokes equations. It is found that slender jet theories can be applied when viscosity is present, but for inviscid jets the local shape of the jet at breakup is most likely of a non-slender geometry. Systems of one-dimensional models of the governing equations are solved numerically in order to illustrate these differences.

Theory of an airfoil equipped with a jet flap under low-speed flight conditions

NASA Technical Reports Server (NTRS)

Addessio, F. L.; Skifstad, J. G.

1975-01-01

A theory is developed, for the inviscid, incompressible flow past a thin airfoil equipped with a thin, part-span jet flap, by treating the induced flowfields of the jet and the wing separately and by obtaining the fully coupled solution in an iterative manner. Spanwise variation of the jet vortex strength is assumed to be elliptical in the analysis. Since the method considers the vorticity associated with the jet to be positioned on the computed locus of the jet, the downwash aft of the wing is evaluated as well as forces and moments on the wing. A lifting-surface theory is incorporated for the aerodynamics of the wing. Computational results are presented for a rectangular wing at momentum coefficients above 2.0 and compared with existing linear theories and experimental data. Good agreement is found for small angles of attack, jet-deflection angles, and jet-momentum coefficients where the linear theories and experimental data are applicable. Downwash data at a point in the vicinity of a control surface, the load distribution on the airfoil, and the jet, and the jet location are also presented for representative flight conditons.

A novel antenna for ultra-wide-band applications

NASA Technical Reports Server (NTRS)

Lai, Albert K. Y.; Sinopoli, Albert L.; Burnside, Walter D.

1992-01-01

An ultrawideband antenna based on a slotline feed structure, a bowtie horn, and a rolled edge termination was developed, analyzed, and measured. Empirical data showed that its beamwidths and bandwidth are dependent on its physical dimensions which are easily controllable by an antenna designer. Measured patterns of models with various radiation properties are shown to substantiate these design rules. A flat plateau-like main beam, low voltage standing-wave ratio (VSWR), the ability to produce both wide (60 deg) and narrow (30 deg) half-power beamwidths, low sidelobes and backlobe (40-50 dB down), low cross-polarized levels (20-25 dB down), and independent control of E- and H-plane beamwidths over an ultrawide bandwidth, say 2-18 GHz, are some of the strong points of this antenna type.

Development of the low-field side reflectometer for ITER

NASA Astrophysics Data System (ADS)

Muscatello, Christopher; Anderson, James; Gattuso, Anthony; Doyle, Edward; Peebles, William; Seraydarian, Raymond; Wang, Guiding; Kramer, Gerrit; Zolfaghari, Ali; Atomics Team, General; University of California Los Angeles Team; Princeton Plasma Physics Laboratory Team

2017-10-01

The Low-Field Side Reflectometer (LFSR) for ITER will provide real-time edge density profiles every 10 ms for feedback control and every 24 μs for physics evaluation. The spatial resolution will be better than 5 mm over 30 - 165 GHz, probing the scrape-off layer to the top of the pedestal in H-mode plasmas. An antenna configuration has been selected for measurements covering anticipated plasma elevations. Laboratory validation of diagnostic performance is underway using a LFSR transmission line (TL) mockup. The 40-meter TL includes circular corrugated waveguide, length calibration feature, Gaussian telescope, vacuum windows, containment membranes, and expansion joint. Transceiver modules coupled to the input of the TL provide frequency-modulated (FM) data for evaluation of performance as a monostatic reflectometer. Results from the mockup tests are presented and show that, with some further optimization, the LFSR will meet or exceed the measurement requirements for ITER. An update of the LFSR instrumentation design status is also presented with preliminary test results. Work supported by PPPL under subcontract S013252-A.

Radio crickets: chirping jets from black hole binaries entering their gravitational wave inspiral

NASA Astrophysics Data System (ADS)

Kulkarni, Girish; Loeb, Abraham

2016-03-01

We study a novel electromagnetic signature of supermassive black hole (BH) binaries whose inspiral starts being dominated by gravitational wave (GW) emission. Recent simulations suggest that the binary's member BHs can continue to accrete gas from the circumbinary accretion disc in this phase of the binary's evolution, all the way until coalescence. If one of the binary members produces a radio jet as a result of accretion, the jet precesses along a biconical surface due to the binary's orbital motion. When the binary enters the GW phase of its evolution, the opening angle widens, the jet exhibits milliarcsecond-scale wiggles, and the conical surface of jet precession is twisted due to apparent superluminal motion. The rapidly increasing orbital velocity of the binary gives the jet an appearance of a `chirp'. This helical chirping morphology of the jet can be used to infer the binary parameters. For binaries with mass 107-1010 M⊙ at redshifts z < 0.5, monitoring these features in current and archival data will place a lower limit on sources that could be detected by Evolved Laser Interferometer Space Antenna and Pulsar Timing Arrays. In the future, microarcsecond interferometry with the Square Kilometre Array will increase the potential usefulness of this technique.

STS-59 payload SIR-C/X-SAR antenna view

NASA Image and Video Library

1993-10-30

S93-48551 (October 1993) --- The Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) antenna, developed by the Jet Propulsion Laboratory (JPL) as part of NASA's Mission to Planet Earth (MTPE), will fly aboard the Space Shuttle Endeavour. The radar antenna uses microwave energy which gives it the ability to collect data over virtually any region at any time, regardless of weather or sunlight conditions. The radar waves can penetrate clouds, and under certain conditions the radar can also see through vegetation, ice and dry sand. In many cases, spaceborne radar is the only way scientists can explore large-scale and inaccessible regions of the Earth's surface. SIR-C/X-SAR uses three microwave wavelengths: L-Band (24 cm), C-Band (6 cm) and X-Ban (3 cm). The multi-frequency data will be used by the international scientific community to monitor global environmental processes with a focus on climate change. The MTPE spaceborne data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity.

A lifting surface computer code with jet-in-crossflow interference effects. Volume 1: Theoretical description

NASA Technical Reports Server (NTRS)

Furlong, K. L.; Fearn, R. L.

1983-01-01

A method is proposed to combine a numerical description of a jet in a crossflow with a lifting surface panel code to calculate the jet/aerodynamic-surface interference effects on a V/STOL aircraft. An iterative technique is suggested that starts with a model for the properties of a jet/flat plate configuration and modifies these properties based on the flow field calculated for the configuration of interest. The method would estimate the pressures, forces, and moments on an aircraft out of ground effect. A first-order approximation to the method suggested is developed and applied to two simple configurations. The first-order approximation is a noniterative precedure which does not allow for interactions between multiple jets in a crossflow and also does not account for the influence of lifting surfaces on the jet properties. The jet/flat plate model utilized in the examples presented is restricted to a uniform round jet injected perpendicularly into a uniform crossflow for a range of jet-to-crossflow velocity ratios from three to ten.

European Technological Effort in Preparation of ITER Construction

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

Andreani, Roberto

2005-04-15

Europe has started since the '80s with the preparatory work done on NET, the Next European Torus, the successor of JET, to prepare for the construction of the next generation experiment on the road to the fusion reactor. In 2000 the European Fusion Development Agreement (EFDA) has been signed by sixteen countries, including Switzerland, not a member of the Union. Now the signatory countries have increased to twenty-five. A vigorous programme of design and R and D in support of ITER construction has been conducted by EFDA through the coordinated effort of the national institutes and laboratories supported financially, inmore » the framework of the VI European Framework Research Programme (2002-2006), by contracts of association with EURATOM. In the last three years, with the expenditure of 160 M[Euro], the accent has been particularly put on the preparation of the industrial manufacturing activities of components and systems for ITER. Prototypes and manufacturing methods have been developed in all the main critical areas of machine construction with the objective of providing sound and effective solutions: vacuum vessel, toroidal field coils, poloidal field coils, remote handling equipment, plasma facing components and divertor components, electrical power supplies, generators and power supplies for the Heating and Current Drive Systems and other minor subsystems.Europe feels to be ready to host the ITER site and to provide adequate support and guidance for the success of construction to our partners in the ITER collaboration, wherever needed.« less

System overview on electromagnetic compensation for reflector antenna surface distortion

NASA Technical Reports Server (NTRS)

Acosta, R. J.; Zaman, A. J.; Terry, J. D.

1993-01-01

The system requirements and hardware implementation for electromagnetic compensation of antenna performance degradations due to thermal effects was investigated. Future commercial space communication antenna systems will utilize the 20/30 GHz frequency spectrum and support very narrow multiple beams (0.3 deg) over wide angle field of view (15-20 beamwidth). On the ground, portable and inexpensive very small aperture terminals (VSAT) for transmitting and receiving video, facsimile and data will be employed. These types of communication system puts a very stringent requirement on spacecraft antenna beam pointing stability (less than .01 deg), high gain (greater than 50 dB) and very lowside lobes (less than -25 dB). Thermal analysis performed on the advanced communication technology satellite (ACTS) has shown that the reflector surfaces, the mechanical supporting structures and metallic surfaces on the spacecraft body will distort due thermal effects from a varying solar flux. The antenna performance characteristics (e.g., pointing stability, gain, side lobe, etc.) will degrade due to thermal distortion in the reflector surface and supporting structures. Specifically, antenna RF radiation analysis has shown that pointing error is the most sensitive antenna performance parameter to thermal distortions. Other antenna parameters like peak gain, cross polarization level (beam isolation), and side lobe level will also degrade with thermal distortions. In order to restore pointing stability and in general antenna performance several compensation methods were proposed. In general these compensation methods can be classified as being either of mechanical or electromagnetic type. This paper will address only the later one. In this approach an adaptive phased array antenna feed is used to compensate for the antenna performance degradation. Extensive work has been devoted to demonstrate the feasibility of adaptive feed compensation on space communication antenna systems. This

Mitigating Multipath Bias Using a Dual-Polarization Antenna: Theoretical Performance, Algorithm Design, and Simulation

PubMed Central

Xie, Lin; Cui, Xiaowei; Zhao, Sihao; Lu, Mingquan

2017-01-01

It is well known that multipath effect remains a dominant error source that affects the positioning accuracy of Global Navigation Satellite System (GNSS) receivers. Significant efforts have been made by researchers and receiver manufacturers to mitigate multipath error in the past decades. Recently, a multipath mitigation technique using dual-polarization antennas has become a research hotspot for it provides another degree of freedom to distinguish the line-of-sight (LOS) signal from the LOS and multipath composite signal without extensively increasing the complexity of the receiver. Numbers of multipath mitigation techniques using dual-polarization antennas have been proposed and all of them report performance improvement over the single-polarization methods. However, due to the unpredictability of multipath, multipath mitigation techniques based on dual-polarization are not always effective while few studies discuss the condition under which the multipath mitigation using a dual-polarization antenna can outperform that using a single-polarization antenna, which is a fundamental question for dual-polarization multipath mitigation (DPMM) and the design of multipath mitigation algorithms. In this paper we analyze the characteristics of the signal received by a dual-polarization antenna and use the maximum likelihood estimation (MLE) to assess the theoretical performance of DPMM in different received signal cases. Based on the assessment we answer this fundamental question and find the dual-polarization antenna’s capability in mitigating short delay multipath—the most challenging one among all types of multipath for the majority of the multipath mitigation techniques. Considering these effective conditions, we propose a dual-polarization sequential iterative maximum likelihood estimation (DP-SIMLE) algorithm for DPMM. The simulation results verify our theory and show superior performance of the proposed DP-SIMLE algorithm over the traditional one using only an

Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

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

Pease, Leonard F.; Bamberger, Judith A.; Minette, Michael J.

This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from jets characteristic of pulse jet mixers (PJMs) has been analyzed, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell break through? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g.,more » six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored.« less

A folded waveguide ICRF antenna for PBX-M and TFTR

NASA Astrophysics Data System (ADS)

Bigelow, T. S.; Carter, M. D.; Fogelman, C. H.; Yugo, J. J.; Baity, F. W.; Bell, G. L.; Gardner, W. L.; Goulding, R. H.; Hoffman, D. J.; Ryan, P. M.; Swain, D. W.; Taylor, D. J.; Wilson, R.; Bernabei, S.; Kugel, H.; Ono, M.

1996-02-01

The folded waveguide (FWG) antenna is an advanced ICRF launcher under development at ORNL that offers many significant advantages over current-strap type antennas. These features are particularly beneficial for reactor-relevant applications such as ITER and TPX. Previous tests of a development folded waveguide with a low density plasma load have shown a factor of 5 increase in power capability over loop antennas into similar plasma conditions. The performance and reliability of a FWG with an actual tokamak plasma load must now be verified for further acceptance of this concept. A 58 MHz, 4 MW folded waveguide is being designed and built for the PBX-M and TFTR tokamaks at Princeton Plasma Physics Laboratory. This design has a square cross-section that can be installed as either a fast wave (FW) or ion-Bernstein wave (IBW) launcher by 90° rotation. Two new features of the design are: a shorter quarter-wavelength resonator configuration and a rear-feed input power coupling loop. Loading calculations with a standard shorting plate indicate that a launched power level of 4 MW is possible on either machine. Mechanical and disruption force analysis indicates that bolted construction will withstand the disruption loads. An experimental program is planned to characterize the plasma loading, heating effectiveness, power capability, impurity generation and other factors for both FW and IBW cases. High power tests of the new configuration are being performed with a development FWG unit on RFTF at ORNL.

GPS antenna designs

NASA Technical Reports Server (NTRS)

Laube, Samuel J. P.

1987-01-01

Application of the current GPS NAVSTAR system to civilian service requires that a right hand, circularly polarized, -160 dBW spread spectrum signal be received from an orbiting satellite, where the antenna environment is also moving. This presents a design challenge when inexpensive antennas are desired. The intent of this survey is to provide information on the antennas mentioned and to construct and test prototypes to determine whether the choice made by the industry, the quadrifilar helix, is the best. The helix antenna is currently the low cost standard for GPS. Prototype versions were constructed using 12 gauge wire and subminiature coaxial hardline. The constructed antennas were tested using a signal generator and a reference turnstile. A spectrum analyzer was used to measure the level of the received signal.

Dual Mode Slotted Monopole Antenna

DTIC Science & Technology

2017-01-05

of 15 DUAL MODE SLOTTED MONOPOLE ANTENNA STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured and used by...to a dual mode antenna having one mode as a slotted cylinder antenna and another mode as a monopole antenna . (2) Description of the Prior Art...0004] Slotted cylinder antennas are popular antennas for use in line of sight communications systems, especially where the carrier frequency exceeds

SUMMARY REPORT-FY2006 ITER WORK ACCOMPLISHED

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

Martovetsky, N N

2006-04-11

Six parties (EU, Japan, Russia, US, Korea, China) will build ITER. The US proposed to deliver at least 4 out of 7 modules of the Central Solenoid. Phillip Michael (MIT) and I were tasked by DoE to assist ITER in development of the ITER CS and other magnet systems. We work to help Magnets and Structure division headed by Neil Mitchell. During this visit I worked on the selected items of the CS design and carried out other small tasks, like PF temperature margin assessment.

Cellular Reflectarray Antenna

NASA Technical Reports Server (NTRS)

Romanofsky, Robert R.

2010-01-01

The cellular reflectarray antenna is intended to replace conventional parabolic reflectors that must be physically aligned with a particular satellite in geostationary orbit. These arrays are designed for specified geographical locations, defined by latitude and longitude, each called a "cell." A particular cell occupies nominally 1,500 square miles (3,885 sq. km), but this varies according to latitude and longitude. The cellular reflectarray antenna designed for a particular cell is simply positioned to align with magnetic North, and the antenna surface is level (parallel to the ground). A given cellular reflectarray antenna will not operate in any other cell.

Development of a Jet Noise Prediction Method for Installed Jet Configurations

NASA Technical Reports Server (NTRS)

Hunter, Craig A.; Thomas, Russell H.

2003-01-01

This paper describes development of the Jet3D noise prediction method and its application to heated jets with complex three-dimensional flow fields and installation effects. Noise predictions were made for four separate flow bypass ratio five nozzle configurations tested in the NASA Langley Jet Noise Laboratory. These configurations consist of a round core and fan nozzle with and without pylon, and an eight chevron core nozzle and round fan nozzle with and without pylon. Predicted SPL data were in good agreement with experimental noise measurements up to 121 inlet angle, beyond which Jet3D under predicted low frequency levels. This is due to inherent limitations in the formulation of Lighthill's Acoustic Analogy used in Jet3D, and will be corrected in ongoing development. Jet3D did an excellent job predicting full scale EPNL for nonchevron configurations, and captured the effect of the pylon, correctly predicting a reduction in EPNL. EPNL predictions for chevron configurations were not in good agreement with measured data, likely due to the lower mixing and longer potential cores in the CFD simulations of these cases.

High-temperature superconductor antenna investigations

NASA Technical Reports Server (NTRS)

Karasack, Vincent G.

1990-01-01

The use of superconductors to increase antenna radiation efficiency and gain is examined. Although the gain of all normal-metal antennas can be increased through the use of superconductors, some structures have greater potential for practical improvement than others. Some structures suffer a great degradation in bandwidth when replaced with superconductors, while for others the improvement in efficiency is trivial due to the minimal contribution of the conductor loss mechanism to the total losses, or the already high efficiency of the structure. The following antennas and related structures are discussed: electrically small antennas, impedance matching of antennas, microstrip antennas, microwave and millimeter-wave antenna arrays, and superdirective arrays. The greatest potential practical improvements occur for large microwave and millimeter-wave arrays and the impedance matching of antennas.

Antenna radiation patterns in the whistler wave regime measured in a large laboratory plasma

NASA Technical Reports Server (NTRS)

Stenzel, R. L.

1976-01-01

Antenna radiation patterns of balanced electric dipoles and shielded magnetic loop antennas are obtained by measuring the relative wave amplitude with a small receiver antenna scanned around the exciter in a large uniform collisionless magnetized laboratory plasma in the whistler wave regime. The boundary effects are assumed to be negligible even for many farfield patterns. Characteristic differences are observed between electrically short and long antennas, the former exhibiting resonance cones and the latter showing dipole-like antenna patterns along the magnetic field. Resonance cones due to small electric dipoles and magnetic loops are observed in both the near zone and the far zone. A self-focusing process is revealed which produces a pencil-shaped field-aligned radiation pattern.

Time dependent 14 MeV neutrons measurement using a polycrystalline chemical vapor deposited diamond detector at the JET tokamak

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

Angelone, M.; Pillon, M.; Bertalot, L.

A polycrystalline chemical vapor deposited (CVD) diamond detector was installed on a JET tokamak in order to monitor the time dependent 14 MeV neutron emission produced by D-T plasma pulses during the Trace Tritium Experiment (TTE) performed in October 2003. This was the first tentative ever attempted to use a CVD diamond detector as neutron monitor in a tokamak environment. Despite its small active volume, the detector was able to detect the 14 MeV neutron emission (>1.0x10{sup 15} n/shot) with good reliability and stability during the experimental campaign that lasted five weeks. The comparison with standard silicon detectors presently usedmore » at JET as 14 MeV neutron monitors is reported, showing excellent correlation between the measurements. The results prove that CVD diamond detectors can be reliably used in a tokamak environment and therefore confirm the potential of this technology for next step machines like ITER.« less

Determination of antenna factors using a three-antenna method at open-field test site

NASA Astrophysics Data System (ADS)

Masuzawa, Hiroshi; Tejima, Teruo; Harima, Katsushige; Morikawa, Takao

1992-09-01

Recently NIST has used the three-antenna method for calibration of the antenna factor of an antenna used for EMI measurements. This method does not require the specially designed standard antennas which are necessary in the standard field method or the standard antenna method, and can be used at an open-field test site. This paper theoretically and experimentally examines the measurement errors of this method and evaluates the precision of the antenna-factor calibration. It is found that the main source of the error is the non-ideal propagation characteristics of the test site, which should therefore be measured before the calibration. The precision of the antenna-factor calibration at the test site used in these experiments, is estimated to be 0.5 dB.

Fast Acting Eddy Current Driven Valve for Massive Gas Injection on ITER

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

Lyttle, Mark S; Baylor, Larry R; Carmichael, Justin R

2015-01-01

Tokamak plasma disruptions present a significant challenge to ITER as they can result in intense heat flux, large forces from halo and eddy currents, and potential first-wall damage from the generation of multi-MeV runaway electrons. Massive gas injection (MGI) of high Z material using fast acting valves is being explored on existing tokamaks and is planned for ITER as a method to evenly distribute the thermal load of the plasma to prevent melting, control the rate of the current decay to minimize mechanical loads, and to suppress the generation of runaway electrons. A fast acting valve and accompanying power supplymore » have been designed and first test articles produced to meet the requirements for a disruption mitigation system on ITER. The test valve incorporates a flyer plate actuator similar to designs deployed on TEXTOR, ASDEX upgrade, and JET [1 3] of a size useful for ITER with special considerations to mitigate the high mechanical forces developed during actuation due to high background magnetic fields. The valve includes a tip design and all-metal valve stem sealing for compatibility with tritium and high neutron and gamma fluxes.« less

An iterative truncation method for unbounded electromagnetic problems using varying order finite elements

NASA Astrophysics Data System (ADS)

Paul, Prakash

2009-12-01

, different shaped metallic and dielectric obstacles (spheres, ogives, cube, flat plate, multi-layer slab etc.) are used for the scattering problems. For the radiation problems, waveguide excited antennas (horn antenna, waveguide with flange, microstrip patch antenna) are used. Using the AEC the peak reduction in computation time during the iteration is typically a factor of 2, compared to the IABC using the same element orders throughout. In some cases, it can be as high as a factor of 4.

Flow cytometer jet monitor system

DOEpatents

Van den Engh, Ger

1997-01-01

A direct jet monitor illuminates the jet of a flow cytometer in a monitor wavelength band which is substantially separate from the substance wavelength band. When a laser is used to cause fluorescence of the substance, it may be appropriate to use an infrared source to illuminate the jet and thus optically monitor the conditions within the jet through a CCD camera or the like. This optical monitoring may be provided to some type of controller or feedback system which automatically changes either the horizontal location of the jet, the point at which droplet separation occurs, or some other condition within the jet in order to maintain optimum conditions. The direct jet monitor may be operated simultaneously with the substance property sensing and analysis system so that continuous monitoring may be achieved without interfering with the substance data gathering and may be configured so as to allow the front of the analysis or free fall area to be unobstructed during processing.

Mode Matching for Optical Antennas

NASA Astrophysics Data System (ADS)

Feichtner, Thorsten; Christiansen, Silke; Hecht, Bert

2017-11-01

The emission rate of a point dipole can be strongly increased in the presence of a well-designed optical antenna. Yet, optical antenna design is largely based on radio-frequency rules, ignoring, e.g., Ohmic losses and non-negligible field penetration in metals at optical frequencies. Here, we combine reciprocity and Poynting's theorem to derive a set of optical-frequency antenna design rules for benchmarking and optimizing the performance of optical antennas driven by single quantum emitters. Based on these findings a novel plasmonic cavity antenna design is presented exhibiting a considerably improved performance compared to a reference two-wire antenna. Our work will be useful for the design of high-performance optical antennas and nanoresonators for diverse applications ranging from quantum optics to antenna-enhanced single-emitter spectroscopy and sensing.

Antenna cab interior showing equipment rack and fiberglass antenna panels, ...

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

Antenna cab interior showing equipment rack and fiberglass antenna panels, looking west. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

Antenna cab interior showing equipment rack and fiberglass antenna panels, ...

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

Antenna cab interior showing equipment rack and fiberglass antenna panels, looking southeast. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

Nonlinear Dynamics in Viscoelastic Jets

NASA Astrophysics Data System (ADS)

Majmudar, Trushant; Varagnat, Matthieu; McKinley, Gareth

2008-11-01

Instabilities in free surface continuous jets of non-Newtonian fluids, although relevant for many industrial processes, remain poorly understood in terms of fundamental fluid dynamics. Inviscid, and viscous Newtonian jets have been studied in considerable detail, both theoretically and experimentally. Instability in viscous jets leads to regular periodic coiling of the jet, which exhibits a non-trivial frequency dependence with the height of the fall. Here we present a systematic study of the effect of viscoelasticity on the dynamics of continuous jets of worm-like micellar surfactant solutions of varying viscosities and elasticities. We observe complex nonlinear spatio-temporal dynamics of the jet, and uncover a transition from periodic to quasi-periodic to a multi-frequency, broad-spectrum dynamics. Beyond this regime, the jet dynamics smoothly crosses over to exhibit the ``leaping shampoo'' or the Kaye effect. We examine different dynamical regimes in terms of scaling variables, which depend on the geometry (dimensionless height), kinematics (dimensionless flow rate), and the fluid properties (elasto-gravity number) and present a regime map of the dynamics of the jet in terms of these dimensionless variables.

Nonlinear Dynamics in Viscoelastic Jets

NASA Astrophysics Data System (ADS)

Majmudar, Trushant; Varagnat, Matthieu; McKinley, Gareth

2009-03-01

Instabilities in free surface continuous jets of non-Newtonian fluids, although relevant for many industrial processes, remain poorly understood in terms of fundamental fluid dynamics. Inviscid, and viscous Newtonian jets have been studied in considerable detail, both theoretically and experimentally. Instability in viscous jets leads to regular periodic coiling of the jet, which exhibits a non-trivial frequency dependence with the height of the fall. Here we present a systematic study of the effect of viscoelasticity on the dynamics of continuous jets of worm-like micellar surfactant solutions of varying viscosities and elasticities. We observe complex nonlinear spatio-temporal dynamics of the jet, and uncover a transition from periodic to quasi-periodic to a multi-frequency, broad-spectrum dynamics. Beyond this regime, the jet dynamics smoothly crosses over to exhibit the ``leaping shampoo'' or the Kaye effect. We examine different dynamical regimes in terms of scaling variables, which depend on the geometry (dimensionless height), kinematics (dimensionless flow rate), and the fluid properties (elasto-gravity number) and present a regime map of the dynamics of the jet in terms of these dimensionless variables.

Computational Modeling And Analysis Of Synthetic Jets

NASA Technical Reports Server (NTRS)

Mittal, Rajat; Cattafesta, Lou

2005-01-01

In the last report we focused on the study of 3D synthetic jets of moderate jet aspect-ratio. Jets in quiescent and cross-flow cases were investigated. Since most of the synthetic jets in practical applications are found to be of large aspect ratio, the focus was shifted to studying synthetic jets of large aspect ratio. In the current year, further progress has been made by studying jets of aspect ratio 8 and infinity. Some other aspects of the jet, like the vorticity flux is looked into apart from analyzing the vortex dynamics, velocity profiles and the other dynamical characteristics of the jet which allows us to extract some insight into the effect of these modifications on the jet performance. Also, efforts were made to qualitatively validate the simulated results with the NASA Langley test cases at higher jet Reynolds number for the quiescent jet case.

Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak.

PubMed

Xu, J C; Wang, L; Xu, G S; Luo, G N; Yao, D M; Li, Q; Cao, L; Chen, L; Zhang, W; Liu, S C; Wang, H Q; Jia, M N; Feng, W; Deng, G Z; Hu, L Q; Wan, B N; Li, J; Sun, Y W; Guo, H Y

2016-08-01

In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triple probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.

Upgrade of Langmuir probe diagnostic in ITER-like tungsten mono-block divertor on experimental advanced superconducting tokamak

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

Xu, J. C.; Jia, M. N.; Feng, W.

2016-08-15

In order to withstand rapid increase in particle and power impact onto the divertor and demonstrate the feasibility of the ITER design under long pulse operation, the upper divertor of the EAST tokamak has been upgraded to actively water-cooled, ITER-like tungsten mono-block structure since the 2014 campaign, which is the first attempt for ITER on the tokamak devices. Therefore, a new divertor Langmuir probe diagnostic system (DivLP) was designed and successfully upgraded on the tungsten divertor to obtain the plasma parameters in the divertor region such as electron temperature, electron density, particle and heat fluxes. More specifically, two identical triplemore » probe arrays have been installed at two ports of different toroidal positions (112.5-deg separated toroidally), which can provide fundamental data to study the toroidal asymmetry of divertor power deposition and related 3-dimension (3D) physics, as induced by resonant magnetic perturbations, lower hybrid wave, and so on. The shape of graphite tip and fixed structure of the probe are designed according to the structure of the upper tungsten divertor. The ceramic support, small graphite tip, and proper connector installed make it possible to be successfully installed in the very narrow interval between the cassette body and tungsten mono-block, i.e., 13.5 mm. It was demonstrated during the 2014 and 2015 commissioning campaigns that the newly upgraded divertor Langmuir probe diagnostic system is successful. Representative experimental data are given and discussed for the DivLP measurements, then proving its availability and reliability.« less

Antenna cab interior showing waveguide from external parabolic antenna (later ...

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

Antenna cab interior showing waveguide from external parabolic antenna (later addition), looking north. - Western Union Telegraph Company, Jennerstown Relay, Laurel Summit Road off U.S. 30, Laughlintown, Westmoreland County, PA

Comsat Antenna

NASA Technical Reports Server (NTRS)

1978-01-01

The antenna shown is the new, multiple-beam, Unattended Earth Terminal, located at COMSAT Laboratories in Clarksburg, Maryland. Seemingly simple, it is actually a complex structure capable of maintaining contact with several satellites simultaneously (conventional Earth station antennas communicate with only one satellite at a time). In developing the antenna, COMSAT Laboratories used NASTRAN, NASA's structural analysis computer program, together with BANDIT, a companion program. The computer programs were used to model several structural configurations and determine the most suitable, The speed and accuracy of the computerized design analysis afforded appreciable savings in time and money.

A PIC-MCC code RFdinity1d for simulation of discharge initiation by ICRF antenna

NASA Astrophysics Data System (ADS)

Tripský, M.; Wauters, T.; Lyssoivan, A.; Bobkov, V.; Schneider, P. A.; Stepanov, I.; Douai, D.; Van Eester, D.; Noterdaeme, J.-M.; Van Schoor, M.; ASDEX Upgrade Team; EUROfusion MST1 Team

2017-12-01

Discharges produced and sustained by ion cyclotron range of frequency (ICRF) waves in absence of plasma current will be used on ITER for (ion cyclotron-) wall conditioning (ICWC, Te = 3{-}5 eV, ne < 1018 m-3 ). In this paper, we present the 1D particle-in-cell Monte Carlo collision (PIC-MCC) RFdinity1d for the study the breakdown phase of ICRF discharges, and its dependency on the RF discharge parameters (i) antenna input power P i , (ii) RF frequency f, (iii) shape of the electric field and (iv) the neutral gas pressure pH_2 . The code traces the motion of both electrons and ions in a narrow bundle of magnetic field lines close to the antenna straps. The charged particles are accelerated in the parallel direction with respect to the magnetic field B T by two electric fields: (i) the vacuum RF field of the ICRF antenna E_z^RF and (ii) the electrostatic field E_zP determined by the solution of Poisson’s equation. The electron density evolution in simulations follows exponential increase, {\\dot{n_e} ∼ ν_ion t } . The ionization rate varies with increasing electron density as different mechanisms become important. The charged particles are affected solely by the antenna RF field E_z^RF at low electron density ({ne < 1011} m-3 , {≤ft \\vert E_z^RF \\right \\vert \\gg ≤ft \\vert E_zP \\right \\vert } ). At higher densities, when the electrostatic field E_zP is comparable to the antenna RF field E_z^RF , the ionization frequency reaches the maximum. Plasma oscillations propagating toroidally away from the antenna are observed. The simulated energy distributions of ions and electrons at {ne ∼ 1015} m-3 correspond a power-law Kappa energy distribution. This energy distribution was also observed in NPA measurements at ASDEX Upgrade in ICWC experiments.

Multimachine data–based prediction of high-frequency sensor signal noise for resistive wall mode control in ITER

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

Liu, Yueqiang; Sabbagh, S. A.; Chapman, I. T.

The high-frequency noise measured by magnetic sensors, at levels above the typical frequency of resistive wall modes, is analyzed across a range of present tokamak devices including DIII-D, JET, MAST, ASDEX Upgrade, JT-60U, and NSTX. A high-pass filter enables identification of the noise component with Gaussian-like statistics that shares certain common characteristics in all devices considered. A conservative prediction is made for ITER plasma operation of the high-frequency noise component of the sensor signals, to be used for resistive wall mode feedback stabilization, based on the multimachine database. The predicted root-mean-square n = 1 (n is the toroidal mode number)more » noise level is 10 4 to 10 5 G/s for the voltage signal, and 0.1 to 1 G for the perturbed magnetic field signal. The lower cutoff frequency of the Gaussian pickup noise scales linearly with the sampling frequency, with a scaling coefficient of about 0.1. As a result, these basic noise characteristics should be useful for the modeling-based design of the feedback control system for the resistive wall mode in ITER.« less

Multimachine data–based prediction of high-frequency sensor signal noise for resistive wall mode control in ITER

DOE PAGES

Liu, Yueqiang; Sabbagh, S. A.; Chapman, I. T.; ...

2017-03-27

The high-frequency noise measured by magnetic sensors, at levels above the typical frequency of resistive wall modes, is analyzed across a range of present tokamak devices including DIII-D, JET, MAST, ASDEX Upgrade, JT-60U, and NSTX. A high-pass filter enables identification of the noise component with Gaussian-like statistics that shares certain common characteristics in all devices considered. A conservative prediction is made for ITER plasma operation of the high-frequency noise component of the sensor signals, to be used for resistive wall mode feedback stabilization, based on the multimachine database. The predicted root-mean-square n = 1 (n is the toroidal mode number)more » noise level is 10 4 to 10 5 G/s for the voltage signal, and 0.1 to 1 G for the perturbed magnetic field signal. The lower cutoff frequency of the Gaussian pickup noise scales linearly with the sampling frequency, with a scaling coefficient of about 0.1. As a result, these basic noise characteristics should be useful for the modeling-based design of the feedback control system for the resistive wall mode in ITER.« less

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic.

PubMed

Rowan, W L; Houshmandyar, S; Phillips, P E; Austin, M E; Beno, J H; Hubbard, A E; Khodak, A; Ouroua, A; Taylor, G

2016-11-01

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct view of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic

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

Rowan, W. L., E-mail: w.l.rowan@austin.utexas.edu; Houshmandyar, S.; Phillips, P. E.

2016-11-15

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct viewmore » of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Blackbody radiation sources are provided for in situ calibration.« less

Jets in Polar Coronal Holes

NASA Astrophysics Data System (ADS)

Scullion, E.; Popescu, M. D.; Banerjee, D.; Doyle, J. G.; Erdélyi, R.

2009-10-01

Here, we explore the nature of small-scale jet-like structures and their possible relation to explosive events and other known transient features, like spicules and macrospicules, using high-resolution spectroscopy obtained with the Solar and Heliospheric Observatory/Solar Ultraviolet Measurements of Emitted Radiation instrument. We present a highly resolved spectroscopic analysis and line parameter study of time-series data for jets occurring on-disk and off-limb in both a northern and a southern coronal hole. The analysis reveals many small-scale transients which rapidly propagate between the mid-transition region (N IV 765 Å line formation: 140,000 K) and the lower corona (Ne VIII 770 Å line formation: 630,000 K). In one example, a strong jet-like event is associated with a cool feature not present in the Ne VIII 770 Å line radiance or Doppler velocity maps. Another similar event is observed, but with a hot component, which could be perceived as a blinker. Our data reveal fast, repetitive plasma outflows with blueshift velocities of ≈145 km s-1 in the lower solar atmosphere. The data suggest a strong role for smaller jets (spicules), as a precursor to macrospicule formation, which may have a common origin with explosive events.

Multibeam antenna study, phase 1

NASA Technical Reports Server (NTRS)

Bellamy, J. L.

1972-01-01

A multibeam antenna concept was developed for providing spot beam coverage of the contiguous 48 states. The selection of a suitable antenna concept for the multibeam application and an experimental evaluation of the antenna concept selected are described. The final analysis indicates that the preferred concept is a dual-antenna, circular artificial dielectric lens. A description of the analytical methods is provided, as well as a discussion of the absolute requirements placed on the antenna concepts. Finally, a comparative analysis of reflector antenna off-axis beam performance is presented.

Transcatheter Antenna For Microwave Treatment

NASA Technical Reports Server (NTRS)

Arndt, G. Dickey (Inventor); Carl, James R. (Inventor); Raffoul, George W. (Inventor); Karasack, Vincent G. (Inventor); Pacifico, Antonio (Inventor); Pieper, Carl F. (Inventor)

2000-01-01

Method and apparatus are provided for propagating microwave energy into heart tissues to produce a desired temperature profile therein at tissue depths sufficient for thermally ablating arrhythmogenic cardiac tissue to treat ventricular tachycardia and other arrhythmias while preventing excessive heating of surrounding tissues, organs, and blood. A wide bandwidth double-disk antenna is effective for this purpose over a bandwidth of about six gigahertz. A computer simulation provides initial screening capabilities for an antenna such as antenna, frequency, power level, and power application duration. The simulation also allows optimization of techniques for specific patients or conditions. In operation, microwave energy between about 1 Gigahertz and 12 Gigahertz is applied to monopole microwave radiation having a surface wave limiter. A test setup provides physical testing of microwave radiators to determine the temperature profile created in actual heart tissue or ersatz heart tissue. Saline solution pumped over the heart tissue with a peristaltic pump simulates blood flow. Optical temperature sensors disposed at various tissue depths within the heart tissue detect the temperature profile without creating any electromagnetic interference. The method may he used to produce a desired temperature profile in other body tissues reachable by catheter such as tumors and the like.

A True Metasurface Antenna.

PubMed

El Badawe, Mohamed; Almoneef, Thamer S; Ramahi, Omar M

2016-01-13

We present a true metasurface antenna based on electrically-small resonators. The resonators are placed on a flat surface and connected to one feed point using corporate feed. Unlike conventional array antennas where the distance between adjacent antennas is half wavelength to reduce mutual coupling between adjacent antennas, here the distance between the radiating elements is electrically very small to affect good impedance matching of each resonator to its feed. A metasurface antenna measuring 1.2λ × 1.2λ and designed to operate at 3 GHz achieved a gain of 12 dBi. A prototype was fabricated and tested showing good agreement between numerical simulations and experimental results. Through numerical simulation, we show that the metasurface antenna has the ability to provide beam steering by phasing all the resonators appropriately.

Study of the choice of the decoupling layout for the ITER ICRH system

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

Vervier, M., E-mail: michel.vervier@rma.ac.be; Messiaen, A.; Ongena, J.

10 decouplers are used to neutralize the mutual coupling effects and to control the current amplitude of the 24 straps array of the ITER ICRH antenna in the case of current drive phasing. In the case of heating phasing only 4 decouplers are active and the array current control needs to act on the ratio between the power delivered by the 4 generators. This ratio is very sensitive to the precise adjustment of the antenna array phasing. The maximum total radiated power capability is then limited when the power of one generator reaches its maximum value. With the addition ofmore » four switches all 10 installed decouplers are made active and can act on all mutual coupling effects with equal source power from the 4 generators. With four more switches the current drive phasing could work with a reduced poloidal phasing resulting in a 35% increase of its coupling to the plasma.« less

An antenna pointing mechanism for large reflector antennas

NASA Technical Reports Server (NTRS)

Heimerdinger, H.

1981-01-01

An antenna pointing mechanism for large reflector antennas on direct broadcasting communication satellites was built and tested. After listing the requirements and constraints for this equipment the model is described, and performance figures are given. Futhermore, results of the qualification level tests, including functional, vibrational, thermovacuum, and accelerated life tests are reported. These tests were completed successfully.

Astigmatism in reflector antennas.

NASA Technical Reports Server (NTRS)

Cogdell, J. R.; Davis, J. H.

1973-01-01

Astigmatic phase error in large parabolic reflector antennas is discussed. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is described. Theoretical analysis is conducted to determine the nature of this error in such antennas.

Miniaturization of Microwave Ablation Antennas

NASA Astrophysics Data System (ADS)

Luyen, Hung

Microwave ablation (MWA) is a promising minimally invasive technique for the treatment of various types of cancers as well as non-oncological diseases. In MWA, an interstitial antenna is typically used to deliver microwave energy to the diseased tissue and heat it up to lethal temperature levels that induce cell death. The desired characteristics of the interstitial antenna include a narrow diameter to minimize invasiveness of the treatment, a low input reflection coefficient at the operating frequency, and a localized heating zone. Most interstitial MWA antennas are fed by coaxial cables and designed for operation at either 915 MHz or 2.45 GHz. Coax-fed MWA antennas are commonly equipped with coaxial baluns to achieve localized heating. However, the conventional implementation of coaxial baluns increases the overall diameters of the antennas and therefore make them more invasive. It is highly desirable to develop less invasive antennas with shorter active lengths and smaller diameters for MWA applications. In this work, we demonstrate the feasibility of using higher frequency microwaves for tissue ablation and present several techniques for decreasing diameters of MWA antennas. First, we investigated MWA at higher frequencies by conducting numerical and experimental studies to compare ablation performance at 10 GHz and 1.9 GHz. Simulation and ex vivo ablation experiment results demonstrate comparable ablation zone dimensions achieved at these two frequencies. Operating at higher frequencies enables interstitial antennas with shorter active lengths. This can be combined with smaller-diameter antenna designs to create less invasive applicators or allow integration of multiple radiating elements on a single applicator to have better control and customization of the heating patterns. Additionally, we present three different coax-fed antenna designs and a non-coaxial-based balanced antenna that have smaller-diameter configurations than conventional coax-fed balun

Experimental studies of shock-induced particle jetting

NASA Astrophysics Data System (ADS)

Xue, Kun; Du, Kaiyuan; Shi, Xiaoliang

2018-05-01

The dispersion of particle rings or shells by a radially divergent shock front trailed by the pressurized gases takes the form of hierarchical particle jetting. Through a semi-two-dimensional configuration, we characterize the evolution of the jetting pattern using the boundary tracking technique. In contrast to the refined filamentary jetting spread induced by the dispersal of soft and ductile flour particles, the hard and brittle quartz sand particles are dispersed into a finger-like branched pattern with much fewer jets. The interplay between the primary and secondary jets suffices to reverse the flour jetting pattern, which by contrast is negligible in the quartz sand jetting. The distinct jetting patterns displayed by the flour and quartz sand particles are related with the distinguishable networks of force chains invoked in two particles which dictate the nucleation of jets.

'Invisible' antenna takes up less space

NASA Astrophysics Data System (ADS)

Shelley, M.; Bond, K.

1986-06-01

A compensated microstrip patch design is described that also uses grounded coplanar waveguide to permit a second, independent antenna to be mounted on any type of existing primary radar antenna aboard an aircraft without affecting its radiation. Successful integration of the IFF (identification friend or foe) antenna, which works at D-band, and the primary radar antenna is possible because of the diversity in frequency between the two antennas. Construction of a microstrip radiating element, electromagnetically invisible to the primary antenna, requires orthogonal grating elements and use of the primary antenna as the ground plane. Coplanar mounting of a stripline array with the primary antenna reduces the manufacturing costs and increases the functional performance of the IFF antenna.

Reinstated JET ICRF ILA: Overview and Results

NASA Astrophysics Data System (ADS)

Dumortier, Pierre; Durodié, Frédéric; Blackman, Trevor; Helou, Walid; Jacquet, Philippe; Lerche, Ernesto; Monakhov, Igor; Noble, Craig; Bobkov, Volodymyr; Goulding, Richard; Kaufman, Michael; Van Eester, Dirk

2017-10-01

The works undertaken to reinstate the JET ICRF ILA are reviewed. The vacuum matching capacitors were replaced, an extensive calibration of all the measurements in the RF circuit was carried out, new simulation tools were created and new control algorithms were implemented for the - toroidal and poloidal - phase control of the array as well as for the matching of the second stage. A review of the contribution of the reinstated ILA to the JET programme during the last campaigns is given showing namely that the new controls allowed extending the range of the operation to lower (29MHz) and higher (51MHz) frequencies than previously achieved and allowed more flexible and reliable operation. Operation with coupled power levels up to 2.8MW and voltages up to 40kV was achieved. ILA results on plasma are discussed and emphasis is given to the features of interest for ITER.

Notch Antennas

NASA Technical Reports Server (NTRS)

Lee, Richard Q.

2004-01-01

Notch antennas, also known as the tapered slot antenna (TSA), have been the topics of research for decades. TSA has demonstrated multi-octave bandwidth, moderate gain (7 to 10 dB), and symmetric E- and H- plane beam patterns and can be used for many different applications. This chapter summarizes the research activities on notch antennas over the past decade with emphasis on their most recent advances and applications. This chapter begins with some discussions on the designs of single TSA; then follows with detailed discussions of issues associated with TSA designs and performance characteristics. To conclude the chapter, some recent developments in TSA arrays and their applications are highlighted.

One- and two-dimensional antenna arrays for microwave wireless power transfer (MWPT) systems and dual-antenna transceivers

NASA Astrophysics Data System (ADS)

Lin, Yo-Sheng; Hu, Chun-Hao; Chang, Chi-Ho; Tsao, Ping-Chang

2018-06-01

In this work, we demonstrate novel one-dimensional (1D) and two-dimensional (2D) antenna arrays for both microwave wireless power transfer (MWPT) systems and dual-antenna transceivers. The antenna array can be used as the MWPT receiving antenna of an integrated MWPT and Bluetooth (BLE) communication module (MWPT-BLE module) for smart CNC (computer numerical control) spindle incorporated with the cloud computing system SkyMars. The 2D antenna array has n rows of 1 × m 1D array, and each array is composed of multiple (m) differential feeding antenna elements. Each differential feeding antenna element is a differential feeding structure with a microstrip antenna stripe. The stripe length is shorter than one wavelength to minimise the antenna area and to prevent being excited to a high-order mode. That is, the differential feeding antenna element can suppress the even mode. The mutual coupling between the antenna elements can be suppressed, and the isolation between the receiver and the transmitter can be enhanced. An inclination angle of the main beam aligns with the broadside, and the main beam is further concentrated and shrunk at the elevation direction. Moreover, if more differential feeding antenna elements are used, antenna gain and isolation can be further enhanced. The excellent performance of the proposed antenna arrays indicates that they are suitable for both MWPT systems and dual-antenna transceivers.

A New Blind Pointing Model Improves Large Reflector Antennas Precision Pointing at Ka-Band (32 GHz)

NASA Technical Reports Server (NTRS)

Rochblatt, David J.

2009-01-01

The National Aeronautics and Space Administration (NASA), Jet Propulsion Laboratory (JPL)-Deep Space Network (DSN) subnet of 34-m Beam Waveguide (BWG) Antennas was recently upgraded with Ka-Band (32-GHz) frequency feeds for space research and communication. For normal telemetry tracking a Ka-Band monopulse system is used, which typically yields 1.6-mdeg mean radial error (MRE) pointing accuracy on the 34-m diameter antennas. However, for the monopulse to be able to acquire and lock, for special radio science applications where monopulse cannot be used, or as a back-up for the monopulse, high-precision open-loop blind pointing is required. This paper describes a new 4th order pointing model and calibration technique, which was developed and applied to the DSN 34-m BWG antennas yielding 1.8 to 3.0-mdeg MRE pointing accuracy and amplitude stability of 0.2 dB, at Ka-Band, and successfully used for the CASSINI spacecraft occultation experiment at Saturn and Titan. In addition, the new 4th order pointing model was used during a telemetry experiment at Ka-Band (32 GHz) utilizing the Mars Reconnaissance Orbiter (MRO) spacecraft while at a distance of 0.225 astronomical units (AU) from Earth and communicating with a DSN 34-m BWG antenna at a record high rate of 6-megabits per second (Mb/s).

Design and development of a unit element microstrip antenna for aircraft collision avoidance system

NASA Astrophysics Data System (ADS)

De, Debajit; Sahu, Prasanna Kumar

2017-10-01

Aircraft/traffic alert and collision avoidance system (ACAS/TCAS) is an airborne system which is designed to provide the service as a last defense equipment for avoiding mid-air collisions between the aircraft. In the existing system, four monopole stub-elements are used as ACAS directional antenna and one blade type element is used as ACAS omnidirectional antenna. The existing ACAS antenna has some drawbacks such as low gain, large beamwidth, frequency and beam tuning/scanning issues etc. Antenna issues like unwanted signals reception may create difficulties to identify the possible threats. In this paper, the focus is on the design and development of a unit element microstrip antenna which can be used for ACAS application and to overcome the possible limitations associated with the existing techniques. Two proposed antenna models are presented here, which are single feed and dual feed microstrip dual patch slotted antenna. These are designed and simulated in CST Microwave Studio tool. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. A good reflection coefficient, Voltage Standing Wave Ratio (VSWR), narrow beamwidth, perfect directional radiation pattern, high gain and directivity make this proposed antenna a good candidate for this application.

ATCRBS Antenna Modification Kit

DOT National Transportation Integrated Search

1976-06-01

The report describes the design, fabrication and test results of an improved ATCRBS (Air Traffic Control Radar Beacon System) array antenna for mounting on the reflector of an ASR radar antenna. The antenna consists of a 4-foot high by 26-foot wide a...

Simulations of Solar Jets

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-02-01

chromosphere, and erupting plasma is released outward into the solar corona.A second comparison of simulated observations based on the authors model (left panels) to actual EUV observations of jets (right panels). [Szente et al. 2017]Global InfluencesAfter demonstrating that their models could successfully lead to jet production and propagation, Szente and collaborators compared their results to actual observations of solar jets. The authors constructed simulated EUV and X-ray observations of their modeled events, and they verified that the behavior and structures in these simulated observations were very similar to real observations of coronal jet events from telescopes like SDO/AIA and Hinode.With this confirmed, the authors then used their models to determine how the jets influence the global solar corona and the solar wind. They found that the large-scale corona is significantly affected by the plasma waves from the jet, which travel across 40 in latitude and out to 24 solar radii. In spite of this, the simulated jets contributed only a few percent to the steady-state solar-wind energy outflow.These simulations represent an important step in realistic modeling of the quiet Sun. Because the models make specific predictions about temperature and density gradients within the corona, we can look forward to testing them with upcoming missions like Solar Probe Plus, which should be able to explore the Sun all the way down to ninesolar radii.CitationJ. Szente et al 2017 ApJ 834 123. doi:10.3847/1538-4357/834/2/123

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1213 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antennas. 95.1213 Section 95.1213... SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1213 Antennas. No antenna for a MedRadio transmitter shall be configured for permanent outdoor use. In addition, any MedRadio antenna used outdoors...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1213 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antennas. 95.1213 Section 95.1213... SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1213 Antennas. No antenna for a MedRadio transmitter shall be configured for permanent outdoor use. In addition, any MedRadio antenna used outdoors...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

47 CFR 95.1013 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antennas. 95.1013 Section 95.1013... SERVICES Low Power Radio Service (LPRS) General Provisions § 95.1013 Antennas. (a) The maximum allowable... this chapter, at the band edges. (b) AMTS stations must employ directional antennas. (c) Antennas used...

Carbon Nanotube Thin-Film Antennas.

PubMed

Puchades, Ivan; Rossi, Jamie E; Cress, Cory D; Naglich, Eric; Landi, Brian J

2016-08-17

Multiwalled carbon nanotube (MWCNT) and single-walled carbon nanotube (SWCNT) dipole antennas have been successfully designed, fabricated, and tested. Antennas of varying lengths were fabricated using flexible bulk MWCNT sheet material and evaluated to confirm the validity of a full-wave antenna design equation. The ∼20× improvement in electrical conductivity provided by chemically doped SWCNT thin films over MWCNT sheets presents an opportunity for the fabrication of thin-film antennas, leading to potentially simplified system integration and optical transparency. The resonance characteristics of a fabricated chlorosulfonic acid-doped SWCNT thin-film antenna demonstrate the feasibility of the technology and indicate that when the sheet resistance of the thin film is >40 ohm/sq no power is absorbed by the antenna and that a sheet resistance of <10 ohm/sq is needed to achieve a 10 dB return loss in the unbalanced antenna. The dependence of the return loss performance on the SWCNT sheet resistance is consistent with unbalanced metal, metal oxide, and other CNT-based thin-film antennas, and it provides a framework for which other thin-film antennas can be designed.

Experimental Study of RF Sheath Formation on a Fast Wave Antenna and Limiter in the LAPD

NASA Astrophysics Data System (ADS)

Martin, Michael; Gekelman, Walter; Pribyl, Patrick; van Compernolle, Bart; Carter, Troy

2015-11-01

Ion cyclotron resonance heating (ICRH) will be an essential component of heating power in ITER. During ICRH, radio frequency (RF) sheaths may form both at the exciting antenna and further away, e.g. in the divertor region, and may cause wall material sputtering and decreased RF power coupling to the plasma. It is important to do detailed laboratory experiments that fully diagnose the sheaths and wave fields. This is not possible in fusion devices. A new RF system has recently been constructed for performing such studies in the LAPD plasma column (ne ~1012 -1013cm-3 , Te ~ 1 - 10 eV ,B0 ~ 400 - 2000 G , diameter ~ 60cm , length ~ 18 m) . The RF system is capable of pulsing at the 1 Hz rep. rate of the LAPD plasma and operating between 2-6 MHz (1st - 9th harmonic of fci in H) with a power output of 200 kW. First results of this system driving a single-strap fast wave antenna will be presented. Emissive and Langmuir probe measurements in the vicinity of both the antenna and a remote limiter and wave coupling measured by magnetic pickup loops will be presented.

NASA Hubble Sees Sparring Antennae Galaxies

NASA Image and Video Library

2013-11-15

The NASA/ESA Hubble Space Telescope has snapped the best ever image of the Antennae Galaxies. Hubble has released images of these stunning galaxies twice before, once using observations from its Wide Field and Planetary Camera 2 (WFPC2) in 1997, and again in 2006 from the Advanced Camera for Surveys (ACS). Each of Hubble’s images of the Antennae Galaxies has been better than the last, due to upgrades made during the famous servicing missions, the last of which took place in 2009. The galaxies — also known as NGC 4038 and NGC 4039 — are locked in a deadly embrace. Once normal, sedate spiral galaxies like the Milky Way, the pair have spent the past few hundred million years sparring with one another. This clash is so violent that stars have been ripped from their host galaxies to form a streaming arc between the two. In wide-field images of the pair the reason for their name becomes clear — far-flung stars and streamers of gas stretch out into space, creating long tidal tails reminiscent of antennae. This new image of the Antennae Galaxies shows obvious signs of chaos. Clouds of gas are seen in bright pink and red, surrounding the bright flashes of blue star-forming regions — some of which are partially obscured by dark patches of dust. The rate of star formation is so high that the Antennae Galaxies are said to be in a state of starburst, a period in which all of the gas within the galaxies is being used to form stars. This cannot last forever and neither can the separate galaxies; eventually the nuclei will coalesce, and the galaxies will begin their retirement together as one large elliptical galaxy. This image uses visible and near-infrared observations from Hubble’s Wide Field Camera 3 (WFC3), along with some of the previously-released observations from Hubble’s Advanced Camera for Surveys (ACS). Credit: NASA/European Space Agency NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors

View of Antenna #1 (foreground), and Antenna #2 surface doors. ...

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

View of Antenna #1 (foreground), and Antenna #2 surface doors. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

Implantable multilayer microstrip antenna for retinal prosthesis: antenna testing.

PubMed

Permana, Hans; Fang, Qiang; Rowe, Wayne S T

2012-01-01

Retinal prosthesis has come to a more mature stage and become a very strategic answer to Retinitis Pigmentosa (RP) and Age-related Macular Degeneration (AMD) diseases. In a retinal prosthesis system, wireless link holds a great importance for the continuity of the system. In this paper, an implantable multilayer microstrip antenna was proposed for the retinal prosthesis system. Simulations were performed in High Frequency Structure Simulator (HFSS) with the surrounding material of air and Vitreous Humor fluid. The fabricated antenna was measured for characteristic validation in free space. The results showed that the real antenna possessed similar return loss and radiation pattern, while there was discrepancy with the gain values.

Ion source with external RF antenna

DOEpatents

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

2005-12-13

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

E-Textile Antennas for Space Environments

NASA Technical Reports Server (NTRS)

Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.

2007-01-01

The ability to integrate antennas and other radio frequency (RF) devices into wearable systems is increasingly important as wireless voice, video, and data sources become ubiquitous. Consumer applications including mobile computing, communications, and entertainment, as well as military and space applications for integration of biotelemetry, detailed tracking information and status of handheld tools, devices and on-body inventories are driving forces for research into wearable antennas and other e-textile devices. Operational conditions for military and space applications of wireless systems are often such that antennas are a limiting factor in wireless performance. The changing antenna platform, i.e. the dynamic wearer, can detune and alter the radiation characteristics of e-textile antennas, making antenna element selection and design challenging. Antenna designs and systems that offer moderate bandwidth, perform well with flexure, and are electronically reconfigurable are ideally suited to wearable applications. Several antennas, shown in Figure 1, have been created using a NASA-developed process for e-textiles that show promise in being integrated into a robust wireless system for space-based applications. Preliminary characterization of the antennas with flexure indicates that antenna performance can be maintained, and that a combination of antenna design and placement are useful in creating robust designs. Additionally, through utilization of modern smart antenna techniques, even greater flexibility can be achieved since antenna performance can be adjusted in real-time to compensate for the antenna s changing environment.

Analytical study of STOL Aircraft in ground effect. Part 1: Nonplanar, nonlinear wing/jet lifting surface method

NASA Technical Reports Server (NTRS)

Shollenberger, C. A.; Smyth, D. N.

1978-01-01

A nonlinear, nonplanar three dimensional jet flap analysis, applicable to the ground effect problem, is presented. Lifting surface methodology is developed for a wing with arbitrary planform operating in an inviscid and incompressible fluid. The classical, infintely thin jet flap model is employed to simulate power induced effects. An iterative solution procedure is applied within the analysis to successively approximate the jet shape until a converged solution is obtained which closely satisfies jet and wing boundary conditions. Solution characteristics of the method are discussed and example results are presented for unpowered, basic powered and complex powered configurations. Comparisons between predictions of the present method and experimental measurements indicate that the improvement of the jet with the ground plane is important in the analyses of powered lift systems operating in ground proximity. Further development of the method is suggested in the areas of improved solution convergence, more realistic modeling of jet impingement and calculation efficiency enhancements.

Producing Satisfactory Solutions to Scheduling Problems: An Iterative Constraint Relaxation Approach

NASA Technical Reports Server (NTRS)

Chien, S.; Gratch, J.

1994-01-01

One drawback to using constraint-propagation in planning and scheduling systems is that when a problem has an unsatisfiable set of constraints such algorithms typically only show that no solution exists. While, technically correct, in practical situations, it is desirable in these cases to produce a satisficing solution that satisfies the most important constraints (typically defined in terms of maximizing a utility function). This paper describes an iterative constraint relaxation approach in which the scheduler uses heuristics to progressively relax problem constraints until the problem becomes satisfiable. We present empirical results of applying these techniques to the problem of scheduling spacecraft communications for JPL/NASA antenna resources.

DIRECTIONAL ANTENNA

DOEpatents

Bittner, B.J.

1958-05-20

A high-frequency directional antenna of the 360 d scaring type is described. The antenna has for its desirable features the reduction in both size and complexity of the mechanism for rotating the antenna through its scanning movement. These advantages result from the rotation of only the driven element, the reflector remaining stationary. The particular antenna structure comprises a refiector formed by a plurality of metallic slats arranged in the configuration of an annular cage having the shape of a zone of revolution. The slats are parallel to each other and are disposed at an angle of 45 d to the axis of the cage. A directional radiator is disposed inside the cage at an angle of 45 d to the axis of the cage in the same direction as the reflecting slats which it faces. As the radiator is rotated, the electromagnetic wave is reflected from the slats facing the radiator and thereafter passes through the cage on the opposite side, since these slats are not parallel with the E vector of the wave.

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

47 CFR 80.866 - Spare antenna.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Spare antenna. 80.866 Section 80.866... Spare antenna. A spare transmitting antenna completely assembled for immediate erection must be provided. If the installed transmitting antenna is suspended between supports, this spare antenna must be a...

Transient induced tungsten melting at the Joint European Torus (JET)

NASA Astrophysics Data System (ADS)

Coenen, J. W.; Matthews, G. F.; Krieger, K.; Iglesias, D.; Bunting, P.; Corre, Y.; Silburn, S.; Balboa, I.; Bazylev, B.; Conway, N.; Coffey, I.; Dejarnac, R.; Gauthier, E.; Gaspar, J.; Jachmich, S.; Jepu, I.; Makepeace, C.; Scannell, R.; Stamp, M.; Petersson, P.; Pitts, R. A.; Wiesen, S.; Widdowson, A.; Heinola, K.; Baron-Wiechec, A.; Contributors, JET

2017-12-01

Melting is one of the major risks associated with tungsten (W) plasma-facing components (PFCs) in tokamaks like JET or ITER. These components are designed such that leading edges and hence excessive plasma heat loads deposited at near normal incidence are avoided. Due to the high stored energies in ITER discharges, shallow surface melting can occur under insufficiently mitigated plasma disruption and so-called edge localised modes—power load transients. A dedicated program was carried out at the JET to study the physics and consequences of W transient melting. Following initial exposures in 2013 (ILW-1) of a W-lamella with leading edge, new experiments have been performed on a sloped surface (15{}\\circ slope) during the 2015/2016 (ILW-3) campaign. This new experiment allows significantly improved infrared thermography measurements and thus resolved important issue of power loading in the context of the previous leading edge exposures. The new lamella was monitored by local diagnostics: spectroscopy, thermography and high-resolution photography in between discharges. No impact on the main plasma was observed despite a strong increase of the local W source consistent with evaporation. In contrast to the earlier exposure, no droplet emission was observed from the sloped surface. Topological modifications resulting from the melting are clearly visible between discharges on the photographic images. Melt damage can be clearly linked to the infrared measurements: the emissivity drops in zones where melting occurs. In comparison with the previous leading edge experiment, no runaway melt motion is observed, consistent with the hypothesis that the escape of thermionic electrons emitted from the melt zone is largely suppressed in this geometry, where the magnetic field intersects the surface at lower angles than in the case of perpendicular impact on a leading edge. Utilising both exposures allows us to further test the model of the forces driving melt motion that

Corkscrew Structures and Precessing Jets

NASA Astrophysics Data System (ADS)

Sahai, Raghvendra

2005-07-01

Collimated jets are one of the most intriguing, yet poorly understood phenomena in astrophysics. Jets have been found in a wide variety of object classes which include AGNs, YSOs, massive X-ray binaries {e.g. SS433}, black hole X-ray transients, symbiotic stars, supersoft X-ray sources, and finally, planetary and preplanetary nebulae {PNs & PPNs}. In the case of PNs and PPNs, we have propsoed that wobbling collimated jets are the universal mechanism which can shape the wide variety of bipolar and multipolar morphologies seen in these objects. Most of our knowledge of post-AGB jets is indirectly inferred from their effects on the circumstellar envelopes of the progenitor AGB stars and, for that reason, these jets remain very poorly understood. Thus the mechanism that powers and collimates these jet-like post-AGB outflows remains as one of the most important, unsolved issues in post-AGB evolution. We propose an archival study of two bipolar PPNs, motivated by two recent discoveries which indicate that precessing jets are likely to be operational in them, and that the properties of the jets and the bipolar lobes produced by them, may be directly measured. One of these is IRAS16342-3814 {IRAS1634}, previously imaged with WPFC2, in which new Adaptive Optics {AO} observations at near-IR wavelengths show a remarkable corkscrew-shaped structure, the tell-tale signature of a precessing jet. Inspection of WFPC2 images of another PPN, OH231.8+4.2 in which we have recently discovered a A-type companion to the central mass-losing star, shows a sinuous nebulosity in a broad-band continuum image, resembling a corkscrew structure. We will use the latter to constrain the phsyical properties of the jet {precession period, opening angle, jet beam diameter, temporal history} in OH231.8. Using the multi-wavelength data on both sources, we will build models of the density distribution of the lobes and their interiors. In the case of IRAS1634, these models will be used to investigate the

Wide sector coverage antennas

NASA Astrophysics Data System (ADS)

Yaw, D. F.

1984-09-01

The general design and performance characteristics of transmit and receive antennas that are currently used in electronic warfare systems are reviewed. Among transmit antennas, three-to-one bandwidth, asymmetric-beam, and circularly polarized horns are discussed, as are extremely broadband monopoles and spiral antennas. In a discussion of receive antennas, attention is given to flat and conical spirals, including cavity-backed flat spirals operating over the 2.5-18 GHz range; log periodic dipoles; and biconical horns. Finally, the design configurations and performance of interferometer direction-finding systems are briefly discussed.

Dichotomy of Solar Coronal Jets: Standard Jets and Blowout Jets

NASA Technical Reports Server (NTRS)

Moore, R. L.; Cirtain, J. W.; Sterling, A. C.; Falconer, D. A.

2010-01-01

By examining many X-ray jets in Hinode/XRT coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H alpha macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major CMEs. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jets that were also caught in He II 304 Angstrom snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T 10(exp 4) - 10(exp 5) K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.

View of Antenna #1 (foreground), and Antenna #2 surface doors. ...

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

View of Antenna #1 (foreground), and Antenna #2 surface doors. Orientation Target #2 in background. Image looking northeast - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

View of Antenna #2 (foreground), and Antenna #1 surface doors. ...

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

View of Antenna #2 (foreground), and Antenna #1 surface doors. Orientation Target #1 in background. Image looking northwest - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

Physics design of the in-vessel collection optics for the ITER electron cyclotron emission diagnostic

DOE PAGES

Rowan, W. L.; Houshmandyar, S.; Phillips, P. E.; ...

2016-09-07

Measurement of the electron cyclotron emission (ECE) is one of the primary diagnostics for electron temperature in ITER. In-vessel, in-vacuum, and quasi-optical antennas capture sufficient ECE to achieve large signal to noise with microsecond temporal resolution and high spatial resolution while maintaining polarization fidelity. Two similar systems are required. One views the plasma radially. The other is an oblique view. Both views can be used to measure the electron temperature, while the oblique is also sensitive to non-thermal distortion in the bulk electron distribution. The in-vacuum optics for both systems are subject to degradation as they have a direct viewmore » of the ITER plasma and will not be accessible for cleaning or replacement for extended periods. Here, blackbody radiation sources are provided for in situ calibration.« less

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

47 CFR 73.69 - Antenna monitors.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antenna monitors. 73.69 Section 73.69... Broadcast Stations § 73.69 Antenna monitors. (a) Each station using a directional antenna must have in operation at the transmitter site an FCC authorized antenna monitor. (b) In the event that the antenna...

Compact self-grounded Bow-Tie antenna design for an UWB phased-array hyperthermia applicator.

PubMed

Takook, Pegah; Persson, Mikael; Gellermann, Johanna; Trefná, Hana Dobšíček

2017-01-08

Using UWB hyperthermia systems has the potential to improve the heat delivery to deep seated tumours. In this paper, we present a novel self-grounded Bow-Tie antenna design which is to serve as the basis element in a phased-array applicator. The UWB operation in the frequency range of 0.43-1 GHz is achieved by immersing the antenna in a water bolus. The radiation characteristics are improved by appropriate shaping the water bolus and by inclusion of dielectric layers on the top of the radiating arms of the antenna. In order to find the most appropriate design, we use a combination of performance indicators representing the most important attributes of the antenna. These are the UWB impedance matching, the transmission capability and the effective field size. The antenna was constructed and experimentally validated on muscle-like phantom. The measured reflection and transmission coefficients as well as radiation characteristics are in excellent agreement with the simulated results. MR image acquisitions with antenna located inside MR bore indicate a negligible distortion of the images by the antenna itself, which indicates MR compatibility.

From antenna to antenna: lateral shift of olfactory memory recall by honeybees.

PubMed

Rogers, Lesley J; Vallortigara, Giorgio

2008-06-04

Honeybees, Apis mellifera, readily learn to associate odours with sugar rewards and we show here that recall of the olfactory memory, as demonstrated by the bee extending its proboscis when presented with the trained odour, involves first the right and then the left antenna. At 1-2 hour after training using both antennae, recall is possible mainly when the bee uses its right antenna but by 6 hours after training a lateral shift has occurred and the memory can now be recalled mainly when the left antenna is in use. Long-term memory one day after training is also accessed mainly via the left antenna. This time-dependent shift from right to left antenna is also seen as side biases in responding to odour presented to the bee's left or right side. Hence, not only are the cellular events of memory formation similar in bees and vertebrate species but also the lateralized networks involved may be similar. These findings therefore seem to call for remarkable parallel evolution and suggest that the proper functioning of memory formation in a bilateral animal, either vertebrate or invertebrate, requires lateralization of processing.

Experimental Study of Convective Cells and RF Sheaths Excited by a Fast Wave Antenna in the LAPD

NASA Astrophysics Data System (ADS)

Martin, Michael; Gekelman, Walter; Pribyl, Patrick; van Compernolle, Bart; Carter, Troy; van Eester, Dirk; Crombé, Kristel

2016-10-01

Ion cyclotron resonance heating (ICRH) will be essential for ITER where it is planned to couple 20 MW to the plasma. During ICRH, radio frequency (RF) sheaths may form on the antenna or farther away, and convective cells are suspected to form adjacent to ICRH antennas, negatively affecting both machine and plasma performance. The LAPD (ne 10 12 - 13cm-3 , Te 1-10 eV, B0 0.4 to 2 kG, diameter 60 cm, length 17m) is an ideal device for performing detailed experiments to fully diagnose these phenomena. A 200 kW RF system capable of pulsing at the 1 Hz. rep. rate of the LAPD and operating from 2 to 2.5 MHz has been constructed to perform such studies. B0 can be adjusted so that this encompasses the 1st to 7th harmonic of fci in H plasmas. Emissive, Mach, Langmuir, and B-field probes measured plasma potential, bulk plasma flows, wave patterns, ne, and Te in 2D planes at various axial locations from the antenna. Plasma potential enhancements of up to 90 V along magnetic field lines connected to the antenna and induced ExB flows consistent in structure with convective cells were observed. Details of these observations along with power scaling of RF sheath voltage and convective cell flows will be presented.

Characteristics and generation of secondary jets and secondary gigantic jets

NASA Astrophysics Data System (ADS)

Lee, Li-Jou; Huang, Sung-Ming; Chou, Jung-Kung; Kuo, Cheng-Ling; Chen, Alfred B.; Su, Han-Tzong; Hsu, Rue-Rou; Frey, Harald U.; Takahashi, Yukihiro; Lee, Lou-Chuang

2012-06-01

Secondary transient luminous events (TLEs) recorded by the ISUAL-FORMOSAT2 mission can either be secondary jets or secondary gigantic jets (GJs), depending on their terminal altitudes. The secondary jets emerge from the cloud top beneath the preceding sprites and extend upward to the base of the sprites at ˜50 km. The secondary jets likely are negative electric discharges with vertically straight luminous columns, morphologically resembling the trailing jet of the type-I GJs. The number of luminous columns in a secondary jet seems to be affected by the size of the effective capacitor plate formed near the base of the preceding sprites and the charge distribution left behind by the sprite-inducing positive cloud-to-ground discharges. The secondary GJs originate from the cloud top under the shielding area of the preceding sprites, and develop upward to reach the lower ionosphere at ˜90 km. The observed morphology of the secondary GJs can either be the curvy shifted secondary GJs extending outside the region occupied by the preceding sprites or the straight pop-through secondary GJs developing through the center of the preceding circular sprites. A key factor in determining the terminal height of the secondary TLEs appears to be the local ionosphere boundary height that established by the preceding sprites. The abundance and the distribution of the negative charge in the thundercloud following the sprite-inducing positive cloud-to-ground discharges may play important role in the generation of the secondary TLEs.

Status on Iterative Transform Phase Retrieval Applied to the GBT Data

NASA Technical Reports Server (NTRS)

Dean, Bruce; Aronstein, David; Smith, Scott; Shiri, Ron; Hollis, Jan M.; Lyons, Richard; Prestage, Richard; Hunter, Todd; Ghigo, Frank; Nikolic, Bojan

2007-01-01

This slide presentation reviews the use of iterative transform phase retrieval in the analysis of the Green Bank Radio Telescope (GBT) Data. It reviews the NASA projects that have used phase retrieval, and the testbed for the algorithm to be used for the James Webb Space Telescope. It shows the comparison of phase retrieval with an interferometer, and reviews the two approaches used for phase retrieval, iterative transform (ITA) or parametric (non-linear least squares model fitting). The concept of ITA Phase Retrieval is reviewed, and the application to Radio Antennas is reviewed. The presentation also examines the National Radio Astronomy Observatory (NRAO) data from the GBT, and the Fourier model that NRAO uses to analyze the data. The challenge for ITA phase retrieval is reviewed, and the coherent approximation for incoherent data is shown. The validity of the approximation is good for a large tilt. There is a review of the proof of concept of the Phase Review simulation using the input wavefront, and the initial sampling parameters estimate from the focused GBT data.

ITER L-Mode Confinement Database

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

S.M. Kaye and the ITER Confinement Database Working Group

This paper describes the content of an L-mode database that has been compiled with data from Alcator C-Mod, ASDEX, DIII, DIII-D, FTU, JET, JFT-2M, JT-60, PBX-M, PDX, T-10, TEXTOR, TFTR, and Tore-Supra. The database consists of a total of 2938 entries, 1881 of which are in the L-phase while 922 are ohmically heated (OH) only. Each entry contains up to 95 descriptive parameters, including global and kinetic information, machine conditioning, and configuration. The paper presents a description of the database and the variables contained therein, and it also presents global and thermal scalings along with predictions for ITER. The L-modemore » thermal confinement time scaling was determined from a subset of 1312 entries for which the thermal confinement time scaling was provided.« less

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

47 CFR 80.863 - Antenna system.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Antenna system. 80.863 Section 80.863... Antenna system. (a) An antenna system must be installed which is as nondirectional and as efficient as is... construction of the required antenna must insure operation in time of emergency. (b) If the required antenna is...

Antenna Technologies for NASA Applications

NASA Technical Reports Server (NTRS)

Miranda, Felix

2007-01-01

This presentation addresses the efforts being performed at GRC to develop antenna technology in support of NASA s Exploration Vision. In particular, the presentation discusses the communications architecture asset-specific data services, as well as wide area coverage, high gain, low mass deployable antennas. Phased array antennas as well as electrically small, lightweight, low power, multifunctional antennas will be also discussed.

Antenna Technologies for NASA Applications

NASA Technical Reports Server (NTRS)

Miranda, Felix A.

2006-01-01

This presentation addresses the efforts being performed at GRC to develop antenna technology in support of NASA s Exploration Vision. In particular, the presentation discusses the communications architecture asset-specific data services, as well as wide area coverage, high gain, low mass deployable antennas. Phased array antennas as well as electrically small, lightweight, low power, multifunctional antennas will be also discussed.

Autonomous omnidirectional spacecraft antenna system

NASA Technical Reports Server (NTRS)

Taylor, T. H.

1983-01-01

The development of a low gain Electronically Switchable Spherical Array Antenna is discussed. This antenna provides roughly 7 dBic gain for receive/transmit operation between user satellites and the Tracking and Data Relay Satellite System. When used as a pair, the antenna provides spherical coverage. The antenna was tested in its primary operating modes: directed beam, retrodirective, and Omnidirectional.

Time-resolved deposition in the remote region of the JET-ILW divertor: measurements and modelling

NASA Astrophysics Data System (ADS)

Catarino, N.; Widdowson, A.; Baron-Wiechec, A.; Coad, J. P.; Heinola, K.; Rubel, M.; Alves, E.; Contributors, JET

2017-12-01

One crucial requirement for the development of fusion power is to know where, and how much, impurities collect in the machine, and how much of the fuelling isotope tritium will be trapped therein. The most relevant information on this issue comes from the operation of the Joint European Tokamak (JET), which is the world’s largest operating tokamak and has the same interior plasma-facing materials as the next step machine, ITER. Much of the information gained so far has been from post-mortem analysis of samples collected after whole campaigns involving varied types of operation. This paper describes time-resolved measurements of the deposition rate using rotating collectors (RC) placed in remote areas of the JET divertor during the 2013-2014 campaign with the ITER-like Wall (ILW). These techniques allow the effects of different types of operation to be distinguished. Rotating collectors made of silicon discs housed behind an aperture are exposed to the plasma. Each time the magnetic field coils are ramped up for a discharge the disc rotates, providing a linear relationship between the exposed region and the discharge number. Post-mortem ion beam analyses provide information on the deposit composition as a function of the discharge number. The results show that the Be deposition average for the RC in the corners of the inner and outer divertor are 4.9 × 1016 cm-2 and 1.8 × 1017 cm-2, respectively, accumulated over an average of ˜25 pulses. Data from the rotating collector below Tile 5 in the central region of divertor indicate a Be deposition rate of 9.3 × 1015 cm-2, per ˜25 pulses.

Jet Velocity Profile Effects on Spray Characteristics of Impinging Jets at High Reynolds and Weber Numbers

NASA Astrophysics Data System (ADS)

Rodrigues, Neil S.; Kulkarni, Varun; Sojka, Paul E.

2014-11-01

While like-on-like doublet impinging jet atomization has been extensively studied in the literature, there is poor agreement between experimentally observed spray characteristics and theoretical predictions (Ryan et al. 1995, Anderson et al. 2006). Recent works (Bremond and Villermaux 2006, Choo and Kang 2007) have introduced a non-uniform jet velocity profile, which lead to a deviation from the standard assumptions for the sheet velocity and the sheet thickness parameter. These works have assumed a parabolic profile to serve as another limit to the traditional uniform jet velocity profile assumption. Incorporating a non-uniform jet velocity profile results in the sheet velocity and the sheet thickness parameter depending on the sheet azimuthal angle. In this work, the 1/7th power-law turbulent velocity profile is assumed to provide a closer match to the flow behavior of jets at high Reynolds and Weber numbers, which correspond to the impact wave regime. Predictions for the maximum wavelength, sheet breakup length, ligament diameter, and drop diameter are compared with experimental observations. The results demonstrate better agreement between experimentally measured values and predictions, compared to previous models. U.S. Army Research Office under the Multi-University Research Initiative Grant Number W911NF-08-1-0171.

Non-iterative geometric approach for inverse kinematics of redundant lead-module in a radiosurgical snake-like robot.

PubMed

Omisore, Olatunji Mumini; Han, Shipeng; Ren, Lingxue; Zhang, Nannan; Ivanov, Kamen; Elazab, Ahmed; Wang, Lei

2017-08-01

Snake-like robot is an emerging form of serial-link manipulator with the morphologic design of biological snakes. The redundant robot can be used to assist medical experts in accessing internal organs with minimal or no invasion. Several snake-like robotic designs have been proposed for minimal invasive surgery, however, the few that were developed are yet to be fully explored for clinical procedures. This is due to lack of capability for full-fledged spatial navigation. In rare cases where such snake-like designs are spatially flexible, there exists no inverse kinematics (IK) solution with both precise control and fast response. In this study, we proposed a non-iterative geometric method for solving IK of lead-module of a snake-like robot designed for therapy or ablation of abdominal tumors. The proposed method is aimed at providing accurate and fast IK solution for given target points in the robot's workspace. n-1 virtual points (VPs) were geometrically computed and set as coordinates of intermediary joints in an n-link module. Suitable joint angles that can place the end-effector at given target points were then computed by vectorizing coordinates of the VPs, in addition to coordinates of the base point, target point, and tip of the first link in its default pose. The proposed method is applied to solve IK of two-link and redundant four-link modules. Both two-link and four-link modules were simulated with Robotics Toolbox in Matlab 8.3 (R2014a). Implementation result shows that the proposed method can solve IK of the spatially flexible robot with minimal error values. Furthermore, analyses of results from both modules show that the geometric method can reach 99.21 and 88.61% of points in their workspaces, respectively, with an error threshold of 1 mm. The proposed method is non-iterative and has a maximum execution time of 0.009 s. This paper focuses on solving IK problem of a spatially flexible robot which is part of a developmental project for abdominal

A model for straight and helical solar jets: II. Parametric study of the plasma beta.

PubMed

Pariat, E; Dalmasse, K; DeVore, C R; Antiochos, S K; Karpen, J T

2016-12-01

Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g., in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma β on the generation and properties of solar-like jets. The parametric study validates our model of jets for plasma β ranging from 10 -3 to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various β ≤ 1. This study introduces the new original result that the plasma β modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Our results allow us to understand the energisation, triggering, and driving processes of jet-like events. Our model allows us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.

A Model for Straight and Helical Solar Jets: II. Parametric Study of the Plasma Beta

NASA Technical Reports Server (NTRS)

Pariat, E.; Dalmasse, K.; DeVore, C. R.; Antiochos, S. K.; Karpen, J. T.

2016-01-01

Context. Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Aims. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g. in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. Methods. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma beta on the generation and properties of solar-like jets. Results. The parametric study validates our model of jets for plasma beta ranging from 10(sup 3) to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various beta less than or equal to 1. We show that the plasma beta modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Conclusions. Our results allow us to understand the energisation, triggering, and driving processes of jet-like events. Our model allows us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.

Design of broadband single polarized antenna

NASA Astrophysics Data System (ADS)

Shin, Phoo Kho; Aziz, Mohamad Zoinol Abidin Abd.; Ahmad, Badrul Hisham; Ramli, Mohamad Hafize Bin; Fauzi, Noor Azamiah Md; Malek, Mohd Fareq Abd

2015-05-01

In practical wireless communication application, bandwidth enhancement becomes one of the major design considerations. At the same time, circular polarized (CP) antenna received much attention for the applications of modern wireless communication system when compared to linear polarized (LP) antenna. This is because CP antenna can reduce the multipath effect. Hence, broadband antenna with operating frequency at 2.4GHz for WLAN application is proposed. The proposed antenna is done by using L-probe amendment with rectangular patch. The rectangular patch and copper ground plane is separated with 10mm air gap. This approach is used to enhance the bandwidth and the gain of the proposed antenna. The bandwidth of the designed antenna is more than 200MHz which meet broadband application. The return loss for the antenna is below -10dB to achieved 90% matching efficiency. The position of L-probe feed is altered in order to obtained different polarizations. The broadband antenna had been designed and simulated by using Computer Simulation Technology (CST) software. In this paper, the comparison for single polarized antenna with the design of non-inverted patch and inverted patch is discussed. The characteristics of the S-parameter, axial ratio, gain, surface current for each designed antenna are analyzed.

DICHOTOMY OF SOLAR CORONAL JETS: STANDARD JETS AND BLOWOUT JETS

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

Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.

2010-09-01

By examining many X-ray jets in Hinode/X-Ray Telescope coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H{alpha} macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major coronal mass ejections. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jetsmore » that were also caught in He II 304 A snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T {approx} 10{sup 4} - 10{sup 5} K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.« less

Improved Gain Microstrip Patch Antenna

DTIC Science & Technology

2015-08-06

08-2015 Publication Improved Gain Microstrip Patch Antenna David A. Tonn Naval Under Warfare Center Division, Newport 1176 Howell St., Code 00L...GAIN MICROSTRIP PATCH ANTENNA STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured and used by or for the...patch antenna having increased gain, and an apparatus for increasing the gain and bandwidth of an existing microstrip patch antenna . (2) Description

Development and qualification of a bulk tungsten divertor row for JET

NASA Astrophysics Data System (ADS)

Mertens, Ph.; Altmann, H.; Hirai, T.; Philipps, V.; Pintsuk, G.; Rapp, J.; Riccardo, V.; Schweer, B.; Uytdenhouwen, I.; Samm, U.

2009-06-01

A bulk tungsten divertor row has been developed in the frame of the ITER-like Wall project at JET. It consists of 96 tiles grouped in 48 modules around the torus. The outer strike point is located on those tiles for most of the ITER-relevant, high triangularity plasmas. High power loads (locally up to 10-20 MW/m 2) and erosion rates are expected, even a risk of melting, especially with the transients or ELM loads. These are demanding conditions for an inertially cooled design as prescribed. A lamella design has been selected for the tungsten, arranged to control the eddy and halo current flows. The lamellae must also withstand high temperature gradients (2200 to 220 °C over 40 mm height), without overheating the supporting carrier (600-700 °C maximum). As a consequence of the tungsten emissivity, the radiative cooling drops appreciably in comparison with the current CFC tiles, calling for interleaved plasma scenarios in terms of performance. The compromise between shadowing and power handling is discussed, as well as the consequences for operation. Prototypes have been exposed in TEXTOR and in an electron beam facility (JUDITH-2) to the nominal power density of 7 MW/m 2 for 10 s and, in addition, to higher loads leading to surface temperatures above 2000 °C.

Radar cross-section reduction based on an iterative fast Fourier transform optimized metasurface

NASA Astrophysics Data System (ADS)

Song, Yi-Chuan; Ding, Jun; Guo, Chen-Jiang; Ren, Yu-Hui; Zhang, Jia-Kai

2016-07-01

A novel polarization insensitive metasurface with over 25 dB monostatic radar cross-section (RCS) reduction is introduced. The proposed metasurface is comprised of carefully arranged unit cells with spatially varied dimension, which enables approximate uniform diffusion of incoming electromagnetic (EM) energy and reduces the threat from bistatic radar system. An iterative fast Fourier transform (FFT) method for conventional antenna array pattern synthesis is innovatively applied to find the best unit cell geometry parameter arrangement. Finally, a metasurface sample is fabricated and tested to validate RCS reduction behavior predicted by full wave simulation software Ansys HFSSTM and marvelous agreement is observed.

Thermal analysis of the in-vessel components of the ITER plasma-position reflectometry.

PubMed

Quental, P B; Policarpo, H; Luís, R; Varela, P

2016-11-01

The ITER plasma position reflectometry system measures the edge electron density profile of the plasma, providing real-time supplementary contribution to the magnetic measurements of the plasma-wall distance. Some of the system components will be in direct sight of the plasma and therefore subject to plasma and stray radiation, which may cause excessive temperatures and stresses. In this work, thermal finite element analysis of the antenna and adjacent waveguides is conducted with ANSYS V17 (ANSYS® Academic Research, Release 17.0, 2016). Results allow the identification of critical temperature points, and solutions are proposed to improve the thermal behavior of the system.

Thermal analysis of the in-vessel components of the ITER plasma-position reflectometry

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

Quental, P. B., E-mail: pquental@ipfn.tecnico.ulisboa.pt; Policarpo, H.; Luís, R.

The ITER plasma position reflectometry system measures the edge electron density profile of the plasma, providing real-time supplementary contribution to the magnetic measurements of the plasma-wall distance. Some of the system components will be in direct sight of the plasma and therefore subject to plasma and stray radiation, which may cause excessive temperatures and stresses. In this work, thermal finite element analysis of the antenna and adjacent waveguides is conducted with ANSYS V17 (ANSYS® Academic Research, Release 17.0, 2016). Results allow the identification of critical temperature points, and solutions are proposed to improve the thermal behavior of the system.

47 CFR 25.158 - Consideration of GSO-like satellite applications.

Code of Federal Regulations, 2010 CFR

2010-10-01

... directional antennas. Examples of GSO-like satellite systems are those which use earth stations with antennas... contiguous bandwidth in both the uplink and downlink band. Each licensee's bandwidth selection shall not... selection. (e) Services offered pursuant to a GSO-like license in a frequency band granted before the...

Multi-mode horn antenna simulation

NASA Technical Reports Server (NTRS)

Dod, L. R.; Wolf, J. D.

1980-01-01

Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions. The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR). This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes. A computer program for the radiation field expressions using the summation of waveguide radiation modes is described. The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given. Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown. The multimode horn antenna provides a low noise feed suitable for radiometric applications.

Antenna Calibration and Measurement Equipment

NASA Technical Reports Server (NTRS)

Rochblatt, David J.; Cortes, Manuel Vazquez

2012-01-01

A document describes the Antenna Calibration & Measurement Equipment (ACME) system that will provide the Deep Space Network (DSN) with instrumentation enabling a trained RF engineer at each complex to perform antenna calibration measurements and to generate antenna calibration data. This data includes continuous-scan auto-bore-based data acquisition with all-sky data gathering in support of 4th order pointing model generation requirements. Other data includes antenna subreflector focus, system noise temperature and tipping curves, antenna efficiency, reports system linearity, and instrument calibration. The ACME system design is based on the on-the-fly (OTF) mapping technique and architecture. ACME has contributed to the improved RF performance of the DSN by approximately a factor of two. It improved the pointing performances of the DSN antennas and productivity of its personnel and calibration engineers.

Spiral microstrip antenna with resistance

NASA Technical Reports Server (NTRS)

Shively, David G. (Inventor)

1994-01-01

The present invention relates to microstrip antennas, and more particularly to wide bandwidth spiral antennas with resistive loading. A spiral microstrip antenna having resistor element embedded in each of the spiral arms is provided. The antenna is constructed using a conductive back plane as a base. The back plane supports a dielectric slab having a thickness between one-sixteenth and one-quarter of an inch. A square spiral, having either two or four arms, is attached to the dielectric slab. Each arm of the spiral has resistor elements thereby dissipating an excess energy not already emitted through radiation. The entire configuration provides a thin, flat, high gain, wide bandwidth antenna which requires no underlying cavity. The configuration allows the antenna to be mounted conformably on an aircraft surface.

Characteristics of microstrip muscle-loaded single-arm Archimedean spiral antennas as investigated by FDTD numerical computations.

PubMed

Jacobsen, Svein; Rolfsnes, Hans Olav; Stauffer, Paul R

2005-02-01

The radiation characteristics and mode of operation of single-arm, groundplane backed, Archimedean spiral antennas are investigated by means of conformal finite difference time domain numerical analysis. It is shown that this antenna type may be categorized as a well-matched, broadband, circularly polarized traveling wave structure that can be fed directly by nonbalanced coaxial networks. The study further concentrates on relevant design and description features parameterized in terms of measures like radiation efficiency, sensing depth, directivity, and axial ratio of complementary polarizations. We document that an antenna of only 30-mm transverse size produces circularly polarized waves in a two-octave frequency span (2-8 GHz) with acceptable radiation efficiency (76%-94%) when loaded by muscle-like tissue.

Improving microwave antenna gain and bandwidth with phase compensation metasurface

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

Chen, Ke; Yang, Zhongjie; Feng, Yijun, E-mail: yjfeng@nju.edu.cn

Metasurface, as a planar version of artificial metamaterial, provide an effective way to manipulate electromagnetic wave propagation. Here, we present a transparent metasurface for compensating the out-of-phase radiation from a microstrip patch antenna to improve its radiation gain and bandwidth. Based on the equivalence principle of Huygens’ surface, we propose metasurface composed of both inductive and capacitive resonant elements which could produce high transmission with variable phase characteristics. Such metasurface mounted on a patch antenna can transform the spherical-like phase profile generated from the patch into an in-phase planar one. A prototype antenna has been fabricated and validated the squeezedmore » radiation pattern with suppressed sidelobes as well as enhanced impedance bandwidth due to strong near-field coupling. As operating at around 5.7 GHz, the proposed antenna may have potential application in wireless communication systems especially for point-to-point data transmission. It is believed that the design methodology could also be scaled to other frequency bands such as millimeter or terahertz wave.« less

Jet in jet in M87

NASA Astrophysics Data System (ADS)

Sob'yanin, Denis Nikolaevich

2017-11-01

New high-resolution Very Long Baseline Interferometer observations of the prominent jet in the M87 radio galaxy show a persistent triple-ridge structure of the transverse 15-GHz profile with a previously unobserved ultra-narrow central ridge. This radio structure can reflect the intrinsic structure of the jet, so that the jet as a whole consists of two embedded coaxial jets. A relativistic magnetohydrodynamic model is considered in which an inner jet is placed inside a hollow outer jet and the electromagnetic fields, pressures and other physical quantities are found. The entire jet is connected to the central engine that plays the role of a unipolar inductor generating voltage between the jets and providing opposite electric currents, and the charge neutrality and current closure together with the electromagnetic fields between the jets can contribute to the jet stabilization. The constant voltage is responsible for the similar widening laws observed for the inner and outer jets. This jet-in-jet structure can indicate simultaneous operation of two different jet-launching mechanisms, one relating to the central supermassive black hole and the other to the surrounding accretion disc. An inferred magnetic field of 80 G at the base is sufficient to provide the observed jet luminosity.

Broadband Cylindrical Antenna and Method

DTIC Science & Technology

2016-07-27

1 of 12 BROADBAND CYLINDRICAL ANTENNA AND METHOD STATEMENT OF GOVERNMENT INTEREST [0001] The invention described herein may be manufactured and...directed to a cylindrical antenna having a broader bandwidth and a method for making such an antenna . (2) Description of the Prior Art [0004...Slotted cylinder antennas have been proposed in submarine applications before. For example, in U.S. Patent No. 6,127,983, Rivera and Josypenko disclose

A Simple Tool for the Design and Analysis of Multiple-Reflector Antennas in a Multi-Disciplinary Environment

NASA Technical Reports Server (NTRS)

Katz, Daniel S.; Cwik, Tom; Fu, Chuigang; Imbriale, William A.; Jamnejad, Vahraz; Springer, Paul L.; Borgioli, Andrea

2000-01-01

The process of designing and analyzing a multiple-reflector system has traditionally been time-intensive, requiring large amounts of both computational and human time. At many frequencies, a discrete approximation of the radiation integral may be used to model the system. The code which implements this physical optics (PO) algorithm was developed at the Jet Propulsion Laboratory. It analyzes systems of antennas in pairs, and for each pair, the analysis can be computationally time-consuming. Additionally, the antennas must be described using a local coordinate system for each antenna, which makes it difficult to integrate the design into a multi-disciplinary framework in which there is traditionally one global coordinate system, even before considering deforming the antenna as prescribed by external structural and/or thermal factors. Finally, setting up the code to correctly analyze all the antenna pairs in the system can take a fair amount of time, and introduces possible human error. The use of parallel computing to reduce the computational time required for the analysis of a given pair of antennas has been previously discussed. This paper focuses on the other problems mentioned above. It will present a methodology and examples of use of an automated tool that performs the analysis of a complete multiple-reflector system in an integrated multi-disciplinary environment (including CAD modeling, and structural and thermal analysis) at the click of a button. This tool, named MOD Tool (Millimeter-wave Optics Design Tool), has been designed and implemented as a distributed tool, with a client that runs almost identically on Unix, Mac, and Windows platforms, and a server that runs primarily on a Unix workstation and can interact with parallel supercomputers with simple instruction from the user interacting with the client.

Shape of initial portion of boundary of supersonic axisymmetric free jets at large jet pressure ratios

NASA Technical Reports Server (NTRS)

Love, Eugene S; Lee, Louise P

1958-01-01

Calculations have been made of the initial portion of the boundary of axisymmetric free jets exhausting at large pressure ratios from a conically divergent nozzle having a jet exit Mach number of 2.5 and a semidivergence angle of 15 degrees. The results of the calculations indicate the size and shape of the jet to be expected at large pressure ratios, the effects of ratio of specific heats, and the large initial inclinations of the boundary that are likely to be encountered by hypersonic vehicles at high altitude.

Measurements of AAFE RADSCAT antenna characteristics

NASA Technical Reports Server (NTRS)

Cross, A. E.; Jones, W. L., Jr.; Jones, A. L.

1977-01-01

Antenna characteristics (active and passive) for a modified AAFE-RADSCAT parabolic dish antenna are documented for a variety of antenna configurations. The modified antenna was a replacement for the original unit which was damaged in January 1975. Pattern measurements made at Langley Research Center and Johnson Space Center are presented, with an analysis of the results. Antenna loss measurements are also presented and summarized.

Improved Object Detection Using a Robotic Sensing Antenna with Vibration Damping Control

PubMed Central

Feliu-Batlle, Vicente; Feliu-Talegon, Daniel; Castillo-Berrio, Claudia Fernanda

2017-01-01

Some insects or mammals use antennae or whiskers to detect by the sense of touch obstacles or recognize objects in environments in which other senses like vision cannot work. Artificial flexible antennae can be used in robotics to mimic this sense of touch in these recognition tasks. We have designed and built a two-degree of freedom (2DOF) flexible antenna sensor device to perform robot navigation tasks. This device is composed of a flexible beam, two servomotors that drive the beam and a load cell sensor that detects the contact of the beam with an object. It is found that the efficiency of such a device strongly depends on the speed and accuracy achieved by the antenna positioning system. These issues are severely impaired by the vibrations that appear in the antenna during its movement. However, these antennae are usually moved without taking care of these undesired vibrations. This article proposes a new closed-loop control schema that cancels vibrations and improves the free movements of the antenna. Moreover, algorithms to estimate the 3D beam position and the instant and point of contact with an object are proposed. Experiments are reported that illustrate the efficiency of these proposed algorithms and the improvements achieved in object detection tasks using a control system that cancels beam vibrations. PMID:28406449

Improved Object Detection Using a Robotic Sensing Antenna with Vibration Damping Control.

PubMed

Feliu-Batlle, Vicente; Feliu-Talegon, Daniel; Castillo-Berrio, Claudia Fernanda

2017-04-13

Some insects or mammals use antennae or whiskers to detect by the sense of touch obstacles or recognize objects in environments in which other senses like vision cannot work. Artificial flexible antennae can be used in robotics to mimic this sense of touch in these recognition tasks. We have designed and built a two-degree of freedom (2DOF) flexible antenna sensor device to perform robot navigation tasks. This device is composed of a flexible beam, two servomotors that drive the beam and a load cell sensor that detects the contact of the beam with an object. It is found that the efficiency of such a device strongly depends on the speed and accuracy achieved by the antenna positioning system. These issues are severely impaired by the vibrations that appear in the antenna during its movement. However, these antennae are usually moved without taking care of these undesired vibrations. This article proposes a new closed-loop control schema that cancels vibrations and improves the free movements of the antenna. Moreover, algorithms to estimate the 3D beam position and the instant and point of contact with an object are proposed. Experiments are reported that illustrate the efficiency of these proposed algorithms and the improvements achieved in object detection tasks using a control system that cancels beam vibrations.

47 CFR 25.158 - Consideration of GSO-like satellite applications.

Code of Federal Regulations, 2012 CFR

2012-10-01

...-like satellite system” is defined as a GSO satellite designed to communicate with earth stations with directional antennas. Examples of GSO-like satellite systems are those which use earth stations with antennas... of this letter to the other participants in the processing round pursuant to § 1.47 of this chapter...

47 CFR 25.158 - Consideration of GSO-like satellite applications.

Code of Federal Regulations, 2011 CFR

2011-10-01

...-like satellite system” is defined as a GSO satellite designed to communicate with earth stations with directional antennas. Examples of GSO-like satellite systems are those which use earth stations with antennas... of this letter to the other participants in the processing round pursuant to § 1.47 of this chapter...

47 CFR 25.158 - Consideration of GSO-like satellite applications.

Code of Federal Regulations, 2013 CFR

2013-10-01

...-like satellite system” is defined as a GSO satellite designed to communicate with earth stations with directional antennas. Examples of GSO-like satellite systems are those which use earth stations with antennas... of this letter to the other participants in the processing round pursuant to § 1.47 of this chapter...

47 CFR 25.158 - Consideration of GSO-like satellite applications.

Code of Federal Regulations, 2014 CFR

2014-10-01

...-like satellite system” is defined as a GSO satellite designed to communicate with earth stations with directional antennas. Examples of GSO-like satellite systems are those which use earth stations with antennas... of this letter to the other participants in the processing round pursuant to § 1.47 of this chapter...

Optical antenna enhanced spontaneous emission

PubMed Central

Eggleston, Michael S.; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C.

2015-01-01

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼200 THz optical frequency show a spontaneous emission intensity enhancement of 35× corresponding to a spontaneous emission rate speedup ∼115×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼2,500× spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d2. Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, Io = qω|xo|/d, feeding the antenna-enhanced spontaneous emission, where q|xo| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency. PMID:25624503

Optical antenna enhanced spontaneous emission

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

Eggleston, Michael S.; Messer, Kevin; Zhang, Liming

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ~200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ~115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ~2,500 × spontaneous emission speedup at d ~10 nm, proportional to 1/d 2. Unfortunately, at dmore » < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Additionally, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.« less

Optical antenna enhanced spontaneous emission.

PubMed

Eggleston, Michael S; Messer, Kevin; Zhang, Liming; Yablonovitch, Eli; Wu, Ming C

2015-02-10

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ∼ 200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ∼ 115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ∼ 2,500 × spontaneous emission speedup at d ∼ 10 nm, proportional to 1/d(2). Unfortunately, at d < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Moreover, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.

Optical antenna enhanced spontaneous emission

DOE PAGES

Eggleston, Michael S.; Messer, Kevin; Zhang, Liming; ...

2015-01-26

Atoms and molecules are too small to act as efficient antennas for their own emission wavelengths. By providing an external optical antenna, the balance can be shifted; spontaneous emission could become faster than stimulated emission, which is handicapped by practically achievable pump intensities. In our experiments, InGaAsP nanorods emitting at ~200 THz optical frequency show a spontaneous emission intensity enhancement of 35 × corresponding to a spontaneous emission rate speedup ~115 ×, for antenna gap spacing, d = 40 nm. Classical antenna theory predicts ~2,500 × spontaneous emission speedup at d ~10 nm, proportional to 1/d 2. Unfortunately, at dmore » < 10 nm, antenna efficiency drops below 50%, owing to optical spreading resistance, exacerbated by the anomalous skin effect (electron surface collisions). Quantum dipole oscillations in the emitter excited state produce an optical ac equivalent circuit current, I(o) = qω|x(o)|/d, feeding the antenna-enhanced spontaneous emission, where q|x(o)| is the dipole matrix element. Despite the quantum-mechanical origin of the drive current, antenna theory makes no reference to the Purcell effect nor to local density of states models. Additionally, plasmonic effects are minor at 200 THz, producing only a small shift of antenna resonance frequency.« less

Advanced Antenna Measurement Processing

DTIC Science & Technology

2014-06-18

reflector antenna where the reflector functions as a passive scatterer. Here we proposed to demonstrate this separation scheme using experimentally derived...orders in the multiple reflections between these antennas . The nature of these composite patterns is not known a priori so one cannot know the accuracy...SECURITY CLASSIFICATION OF: This research project is focused on the advancement of methods of post measurement processing of antenna pattern

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.

Fine metal dust particles on the wall probes from JET-ILW

NASA Astrophysics Data System (ADS)

Fortuna-Zaleśna, E.; Grzonka, J.; Moon, Sunwoo; Rubel, M.; Petersson, P.; Widdowson, A.; Contributors, JET

2017-12-01

Collection and ex situ studies of dust generated in controlled fusion devices during plasma operation are regularly carried out after experimental campaigns. Herewith results of the dust survey performed in JET after the second phase of operation with the metal ITER-like wall (2013-2014) are presented. For the first-time-ever particles deposited on silicon plates acting as dust collectors installed in the inner and outer divertor have been examined. The emphasis is on analysing metal particles (Be and W) with the aim to determine their composition, size and surface topography. The most important is the identification of beryllium dust in the form of droplets (both splashes and spherical particles), flakes of co-deposits and small fragments of Be tiles. Tungsten and nickel rich (from Inconel) particles are also identified. Nitrogen from plasma edge cooling has been detected in all types of particles. They are categorized and the origin of various constituents is discussed.

Beam-Steerable Flat-Panel Reflector Antenna

NASA Technical Reports Server (NTRS)

Lee, Choon Sae; Lee, Chanam; Miranda, Felix A.

2005-01-01

Many space applications require a high-gain antenna that can be easily deployable in space. Currently, the most common high-gain antenna for space-born applications is an umbrella-type reflector antenna that can be folded while being lifted to the Earth orbit. There have been a number of issues to be resolved for this type of antenna. The reflecting surface of a fine wire mesh has to be light in weight and flexible while opening up once in orbit. Also the mesh must be a good conductor at the operating frequency. In this paper, we propose a different type of high-gain antenna for easy space deployment. The proposed antenna is similar to reflector antennas except the curved main reflector is replaced by a flat reconfigurable surface for easy packing and deployment in space. Moreover it is possible to steer the beam without moving the entire antenna system.

An antenna-pointing mechanism for the ETS-6 K-band Single Access (KSA) antenna

NASA Technical Reports Server (NTRS)

Takada, Noboru; Amano, Takahiro; Ohhashi, Toshiro; Wachi, Shigeo

1991-01-01

Both the design philosophy for the Antenna Pointing Mechanism (APM) to be used for the K-band Single Access (KSA) antenna system and experimental results of the APM Engineering Model (EM) tests are described. The KSA antenna system will be flown on the Engineering Test Satellite 6 (ETS-6).

Unfurlable satellite antennas - A review

NASA Technical Reports Server (NTRS)

Roederer, Antoine G.; Rahmat-Samii, Yahia

1989-01-01

A review of unfurlable satellite antennas is presented. Typical application requirements for future space missions are first outlined. Then, U.S. and European mesh and inflatable antenna concepts are described. Precision deployables using rigid panels or petals are not included in the survey. RF modeling and performance analysis of gored or faceted mesh reflector antennas are then reviewed. Finally, both on-ground and in-orbit RF test techniques for large unfurlable antennas are discussed.

Overview of image processing tools to extract physical information from JET videos

NASA Astrophysics Data System (ADS)

Craciunescu, T.; Murari, A.; Gelfusa, M.; Tiseanu, I.; Zoita, V.; EFDA Contributors, JET

2014-11-01

automatic detection of MARFE (multifaceted asymmetric radiation from the edge) occurrences, which precede disruptions in density limit discharges. An original spot detection method has been developed for large surveys of videos in JET, and for the assessment of the long term trends in their evolution. The analysis of JET IR videos, recorded during JET operation with the ITER-like wall, allows the retrieval of data and hence correlation of the evolution of spots properties with macroscopic events, in particular series of intentional disruptions.

Broad band antennas and feed methods

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

Benzel, David M.; Twogood, Richard E.

Two or more Vivaldi antennas, consisting of two plates each, each with the antenna's natural impedance of approximately 100 ohms, are placed in parallel to achieve a 50 ohm impedance in the case of two antennas or other impedances (100/n ohms) for more than two antennas. A single Vivaldi antenna plate (half Vivaldi antenna) over a ground plane can also be used to achieve a 50 ohm impedance, or two or more single plates over a ground plane to achieve other impedances. Unbalanced 50 ohm transmission lines, e.g. coaxial cables, can be used to directly feed, the dual Vivaldi (fourmore » plate) antenna in a center fed angled center departure, or more desirably, a center fed offset departure configuration.« less

Broadband Pillbox Antennas.

DTIC Science & Technology

1984-09-21

Identify by block number) - FIELD GROUP SUB-GROUP Double layer pillbox antennas Triple layer pillbox antenna The possibility of designing very broadband... Design .................... 1 Broadband Feed De gn ........................................... 2 Ex mental Simulation of Double Layer Pillbox...5 REFERENCES ................................................... 6 APPENDIX - COAXIAL TO WAVEGUIDE JUNCTION DESIGN

Volumetric pattern analysis of fuselage-mounted airborne antennas. Ph.D. Thesis; [prediction analysis techniques for antenna radiation patterns of microwave antennas on commercial aircraft

NASA Technical Reports Server (NTRS)

Yu, C. L.

1976-01-01

A volumetric pattern analysis of fuselage-mounted airborne antennas at high frequencies was investigated. The primary goal of the investigation was to develop a numerical solution for predicting radiation patterns of airborne antennas in an accurate and efficient manner. An analytical study of airborne antenna pattern problems is presented in which the antenna is mounted on the fuselage near the top or bottom. Since this is a study of general-type commercial aircraft, the aircraft was modeled in its most basic form. The fuselage was assumed to be an infinitely long perfectly conducting elliptic cylinder in its cross-section and a composite elliptic cylinder in its elevation profile. The wing, cockpit, stabilizers (horizontal and vertical) and landing gear are modeled by "N" sided bent or flat plates which can be arbitrarily attached to the fuselage. The volumetric solution developed utilizes two elliptic cylinders, namely, the roll plane and elevation plane models to approximate the principal surface profile (longitudinal and transverse) at the antenna location. With the belt concept and the aid of appropriate coordinate system transformations the solution can be used to predict the volumetric patterns of airborne antennas in an accurate and efficient manner. Applications of this solution to various airborne antenna problems show good agreement with scale model measurements. Extensive data are presented for a microwave landing antenna system.

Two-wavelength LIDAR Thomson scattering for ITER core plasma

NASA Astrophysics Data System (ADS)

Nielsen, P.; Gowers, C.; Salzmann, H.

2017-07-01

Our proposal for a LIDAR Thomson scattering system to measure Te and ne profiles in the ITER core plasma, is based on experience with the LIDAR system on JET, which is still operational after 30 years. The design uses currently available technology and complies with the measurement requirements given by ITER. In addition, it offers the following advantages over the conventional imaging approach currently being adopted by ITER: 1) No gas fill of the vessel required for absolute calibration. 2) Easier alignment. 3) Measurements over almost the complete plasma diameter. 4) Two mirrors only as front optics. For a given laser wavelength the dynamic range of the Te measurements is mainly limited by the collection optics' transmission roll-off in the blue and the range of spectral sensitivity of the required fast photomultipliers. With the originally proposed Ti:Sapphire laser, measurements of the envisaged maximum temperature of 40 keV are marginally possible. Here we present encouraging simulation results on the use of other laser systems and on the use of two lasers with different wavelength. Alternating two wavelengths was proposed already in 1997 as a method for calibrating the transmission of the collection system. In the present analysis, the two laser pulses are injected simultaneously. We find that the use of Nd:YAG lasers operated at fundamental and second harmonic, respectively, yields excellent results and preserves the spectral recalibration feature.

The principles of radio engineering and antennas. II Antennas (2nd revised and enlarged edition)

NASA Astrophysics Data System (ADS)

Belotserkovskii, G. B.

This book represents the second part of a textbook for technical schools. The characteristics and parameters of antennas are considered along with transmission lines, the theory of single dipoles and radiator systems, and the technological realization of elements and units of the antenna-feeder system, taking into account filters and multiport networks for microwave communications applications, and ferrite circulators and isolators. The first edition of this textbook was published in 1969. For the current edition, the material in the first edition has been revised, and new material has been introduced. Much attention is given to microwave antennas, including, in particular, arrays with electrical scanning characteristics. Other topics discussed are related to the general principles of antennas, the matching of the impedance of transmission lines, the elements of transmission lines, aperture-type antennas for microwaves, and the functional characteristics of antennas for ultrashort waves.

Coiling, Entrainment, and Hydrodynamic Coupling of Decelerated Fluid Jets

NASA Astrophysics Data System (ADS)

Dombrowski, Christopher; Lewellyn, Braddon; Pesci, Adriana I.; Restrepo, Juan M.; Kessler, John O.; Goldstein, Raymond E.

2005-10-01

From algal suspensions to magma upwellings, one finds jets which exhibit complex symmetry-breaking instabilities as they are decelerated by their surroundings. We consider here a model system—a saline jet descending through a salinity gradient—which produces dynamics unlike those of standard momentum jets or plumes. The jet coils like a corkscrew within a conduit of viscously entrained fluid, whose upward recirculation braids the jet, and nearly confines transverse mixing to the narrow conduit. We show that the underlying jet structure and certain scaling relations follow from similarity solutions to the fluid equations and the physics of Kelvin-Helmholtz instabilities.

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

47 CFR 73.753 - Antenna systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna systems. 73.753 Section 73.753... International Broadcast Stations § 73.753 Antenna systems. All international broadcasting stations shall operate with directional antennas. Such antennas shall be designed and operated so that the radiated power in...

Ionospheric effects to antenna impedance

NASA Technical Reports Server (NTRS)

Bethke, K. H.

1986-01-01

The reciprocity between high power satellite antennas and the surrounding plasma are examined. The relevant plasma states for antenna impedance calculations are presented and plasma models, and hydrodynamic and kinetic theory, are discussed. A theory from which a variation in antenna impedance with regard to the radiated power can be calculated for a frequency range well above the plasma resonance frequency is give. The theory can include photo and secondary emission effects in antenna impedance calculations.

Antenna structure with distributed strip

DOEpatents

Rodenbeck, Christopher T.

2008-10-21

An antenna comprises electrical conductors arranged to form a radiating element including a folded line configuration and a distributed strip configuration, where the radiating element is in proximity to a ground conductor. The folded line and the distributed strip can be electrically interconnected and substantially coplanar. The ground conductor can be spaced from, and coplanar to, the radiating element, or can alternatively lie in a plane set at an angle to the radiating element. Embodiments of the antenna include conductor patterns formed on a printed wiring board, having a ground plane, spacedly adjacent to and coplanar with the radiating element. Other embodiments of the antenna comprise a ground plane and radiating element on opposed sides of a printed wiring board. Other embodiments of the antenna comprise conductors that can be arranged as free standing "foils". Other embodiments include antennas that are encapsulated into a package containing the antenna.

Antenna structure with distributed strip

DOEpatents

Rodenbeck, Christopher T [Albuquerque, NM

2008-03-18

An antenna comprises electrical conductors arranged to form a radiating element including a folded line configuration and a distributed strip configuration, where the radiating element is in proximity to a ground conductor. The folded line and the distributed strip can be electrically interconnected and substantially coplanar. The ground conductor can be spaced from, and coplanar to, the radiating element, or can alternatively lie in a plane set at an angle to the radiating element. Embodiments of the antenna include conductor patterns formed on a printed wiring board, having a ground plane, spacedly adjacent to and coplanar with the radiating element. Other embodiments of the antenna comprise a ground plane and radiating element on opposed sides of a printed wiring board. Other embodiments of the antenna comprise conductors that can be arranged as free standing "foils". Other embodiments include antennas that are encapsulated into a package containing the antenna.

A Mars Riometer: Antenna Considerations

NASA Technical Reports Server (NTRS)

Fry, Craig D.

2001-01-01

This is the final report on NASA Grant NAG5-9706. This project explored riometer (relative ionospheric opacity meter) antenna designs that would be practical for a Mars surface or balloon mission. The riometer is an important radio science instrument for terrestrial aeronomy investigations. The riometer measures absorption of cosmic radio waves by the overhead ionosphere. Studies have shown the instrument should work well on Mars, which has an appreciable daytime ionosphere. There has been concern that the required radio receiver antenna (with possibly a 10 meter scale size) would be too large or too difficult to deploy on Mars. This study addresses those concerns and presents several antenna designs and deployment options. It is found that a Mars balloon would provide an excellent platform for the riometer antenna. The antenna can be incorporated into the envelope design, allowing self-deployment of the antenna as the balloon inflates.

An experimental investigation of gas jets in confined swirling air flow

NASA Technical Reports Server (NTRS)

Mongia, H.; Ahmed, S. A.; Mongia, H. C.

1984-01-01

The fluid dynamics of jets in confined swirling flows which is of importance to designers of turbine combustors and solid fuel ramjets used to power missiles fired from cannons were examined. The fluid dynamics of gas jets of different densities in confined swirling flows were investigated. Mean velocity and turbulence measurements are made with a one color, one component laser velocimeter operating in the forward scatter mode. It is shown that jets in confined flow with large area ratio are highly dissipative which results in both air and helium/air jet centerline velocity decays. For air jets, the jet like behavior in the tube center disappears at about 20 diameters downstream of the jet exit. This phenomenon is independent of the initial jet velocity. The turbulence field at this point also decays to that of the background swirling flow. A jet like behavior in the tube center is noticed even at 40 diameters for the helium/air jets. The subsequent flow and turbulence field depend highly on the initial jet velocity. The jets are fully turbulent, and the cause of this difference in behavior is attributed to the combined action swirl and density difference. This observation can have significant impact on the design of turbine combustors and solid fuel ramjets subject to spin.

Analysis and Modeling of a Two-Phase Jet Pump of a Thermal Management System for Aerospace Applications

NASA Technical Reports Server (NTRS)

Sherif, S.A.; Hunt, P. L.; Holladay, J. B.; Lear, W. E.; Steadham, J. M.

1998-01-01

Jet pumps are devices capable of pumping fluids to a higher pressure by inducing the motion of a secondary fluid employing a high speed primary fluid. The main components of a jet pump are a primary nozzle, secondary fluid injectors, a mixing chamber, a throat, and a diffuser. The work described in this paper models the flow of a two-phase primary fluid inducing a secondary liquid (saturated or subcooled) injected into the jet pump mixing chamber. The model is capable of accounting for phase transformations due to compression, expansion, and mixing. The model is also capable of incorporating the effects of the temperature and pressure dependency in the analysis. The approach adopted utilizes an isentropic constant pressure mixing in the mixing chamber and at times employs iterative techniques to determine the flow conditions in the different parts of the jet pump.

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

47 CFR 73.510 - Antenna systems.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antenna systems. 73.510 Section 73.510... Noncommercial Educational FM Broadcast Stations § 73.510 Antenna systems. (a) All noncommercial educational... § 73.316 concerning antenna systems contained in subpart B of this part. (b) Directional antenna. No...

Technique for Radiometer and Antenna Array Calibration with Two Antenna Noise Diodes

NASA Technical Reports Server (NTRS)

Srinivasan, Karthik; Limaye, Ashutosh; Laymon, Charles; Meyer, Paul

2011-01-01

This paper presents a new technique to calibrate a microwave radiometer and phased array antenna system. This calibration technique uses a radiated noise source in addition to an injected noise sources for calibration. The plane of reference for this calibration technique is the face of the antenna and therefore can effectively calibration the gain fluctuations in the active phased array antennas. This paper gives the mathematical formulation for the technique and discusses the improvements brought by the method over the existing calibration techniques.

EDITORIAL: Special section on recent progress on radio frequency heating and current drive studies in the JET tokamak Special section on recent progress on radio frequency heating and current drive studies in the JET tokamak

NASA Astrophysics Data System (ADS)

Ongena, Jef; Mailloux, Joelle; Mayoral, Marie-Line

2009-04-01

This special cluster of papers summarizes the work accomplished during the last three years in the framework of the Task Force Heating at JET, whose mission it is to study the optimisation of heating systems for plasma heating and current drive, launching and deposition questions and the physics of plasma rotation. Good progress and new physics insights have been obtained with the three heating systems available at JET: lower hybrid (LH), ion cyclotron resonance heating (ICRH) and neutral beam injection (NBI). Topics covered in the present issue are the use of edge gas puffing to improve the coupling of LH waves at large distances between the plasma separatrix and the LH launcher. Closely linked with this topic are detailed studies of the changes in LH coupling due to modifications in the scrape-off layer during gas puffing and simultaneous application of ICRH. We revisit the fundamental ICRH heating of D plasmas, include new physics results made possible by recently installed new diagnostic capabilities on JET and point out caveats for ITER when NBI is simultaneously applied. Other topics are the study of the anomalous behaviour of fast ions from NBI, and a study of toroidal rotation induced by ICRH, both again with possible implications for ITER. In finalizing this cluster of articles, thanks are due to all colleagues involved in preparing and executing the JET programme under EFDA in recent years. We want to thank the EFDA leadership for the special privilege of appointing us as Leaders or Deputies of Task Force Heating, a wonderful and hardworking group of colleagues. Thanks also to all other European and non-European scientists who contributed to the JET scientific programme, the Operations team of JET and the colleagues of the Close Support Unit (CSU). Thanks are also due to the Editors, Editorial Board and referees of Plasma Physics and Controlled Fusion together with the publishing staff of IOP Publishing who have supported and contributed substantially to

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 5 2010-10-01 2010-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 5 2014-10-01 2014-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 5 2011-10-01 2011-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 5 2012-10-01 2012-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 73.816 - Antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Antennas. 73.816 Section 73.816... Low Power FM Broadcast Stations (LPFM) § 73.816 Antennas. (a) Permittees and licensees may employ nondirectional antennas with horizontal only polarization, vertical only polarization, circular polarization or...

47 CFR 101.517 - Antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 5 2013-10-01 2013-10-01 false Antennas. 101.517 Section 101.517... SERVICES 24 GHz Service and Digital Electronic Message Service § 101.517 Antennas. (a) Transmitting antennas may be omnidirectional or directional, consistent with coverage and interference requirements. (b...

Tungsten impurity transport experiments in Alcator C-Mod to address high priority research and development for ITER

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

Loarte, A.; Polevoi, A. R.; Hosokawa, M.

2015-05-15

Experiments in Alcator C-Mod tokamak plasmas in the Enhanced D-alpha H-mode regime with ITER-like mid-radius plasma density peaking and Ion Cyclotron Resonant heating, in which tungsten is introduced by the laser blow-off technique, have demonstrated that accumulation of tungsten in the central region of the plasma does not take place in these conditions. The measurements obtained are consistent with anomalous transport dominating tungsten transport except in the central region of the plasma where tungsten transport is neoclassical, as previously observed in other devices with dominant neutral beam injection heating, such as JET and ASDEX Upgrade. In contrast to such results,more » however, the measured scale lengths for plasma temperature and density in the central region of these Alcator C-Mod plasmas, with density profiles relatively flat in the core region due to the lack of core fuelling, are favourable to prevent inter and intra sawtooth tungsten accumulation in this region under dominance of neoclassical transport. Simulations of ITER H-mode plasmas, including both anomalous (modelled by the Gyro-Landau-Fluid code GLF23) and neoclassical transport for main ions and tungsten and with density profiles of similar peaking to those obtained in Alcator C-Mod show that accumulation of tungsten in the central plasma region is also unlikely to occur in stationary ITER H-mode plasmas due to the low fuelling source by the neutral beam injection (injection energy ∼ 1 MeV), which is in good agreement with findings in the Alcator C-Mod experiments.« less

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 1 2014-10-01 2014-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 1 2012-10-01 2012-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 4 2011-10-01 2011-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 4 2013-10-01 2013-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 4 2014-10-01 2014-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 4 2012-10-01 2012-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

47 CFR 15.203 - Antenna requirement.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Antenna requirement. 15.203 Section 15.203... Antenna requirement. An intentional radiator shall be designed to ensure that no antenna other than that furnished by the responsible party shall be used with the device. The use of a permanently attached antenna...

47 CFR 73.1680 - Emergency antennas.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 4 2010-10-01 2010-10-01 false Emergency antennas. 73.1680 Section 73.1680... Rules Applicable to All Broadcast Stations § 73.1680 Emergency antennas. (a) An emergency antenna is one that is erected for temporary use after the authorized main and auxiliary antennas are damaged and...

Novel type of red-shifted chlorophyll a antenna complex from Chromera velia: II. Biochemistry and spectroscopy.

PubMed

Bína, David; Gardian, Zdenko; Herbstová, Miroslava; Kotabová, Eva; Koník, Peter; Litvín, Radek; Prášil, Ondřej; Tichý, Josef; Vácha, František

2014-06-01

A novel chlorophyll a containing pigment-protein complex expressed by cells of Chromera velia adapted to growth under red/far-red illumination [1]. Purification of the complex was achieved by means of anion-exchange chromatography and gel-filtration. The antenna is shown to be an aggregate of ~20kDa proteins of the light-harvesting complex (LHC) family, unstable in the isolated form. The complex possesses an absorption maximum at 705nm at room temperature in addition to the main chlorophyll a maximum at 677nm producing the major emission band at 714nm at room temperature. The far-red absorption is shown to be the property of the isolated aggregate in the intact form and lost upon dissociation. The purified complex was further characterized by circular dichroism spectroscopy and fluorescence spectroscopy. This work thus identified the third different class of antenna complex in C. velia after the recently described FCP-like and LHCr-like antennas. Possible candidates for red antennas are identified in other taxonomic groups, such as eustigmatophytes and the relevance of the present results to other known examples of red-shifted antenna from other organisms is discussed. This work appears to be the first successful isolation of a chlorophyll a-based far-red antenna complex absorbing above 700nm unrelated to LHCI. Copyright © 2014 Elsevier B.V. All rights reserved.

Reconnection-Driven Coronal-Hole Jets with Gravity and Solar Wind

NASA Technical Reports Server (NTRS)

Karpen, J. T.; Devore, C. R.; Antiochos, S. K.; Pariat, E.

2017-01-01

Coronal-hole jets occur ubiquitously in the Sun's coronal holes, at EUV and X-ray bright points associated with intrusions of minority magnetic polarity. The embedded-bipole model for these jets posits that they are driven by explosive, fast reconnection between the stressed closed field of the embedded bipole and the open field of the surrounding coronal hole. Previous numerical studies in Cartesian geometry, assuming uniform ambient magnetic field and plasma while neglecting gravity and solar wind, demonstrated that the model is robust and can produce jet-like events in simple configurations. We have extended these investigations by including spherical geometry,gravity, and solar wind in a nonuniform, coronal hole-like ambient atmosphere. Our simulations confirm that the jet is initiated by the onset of a kink-like instability of the internal closed field, which induces a burst of reconnection between the closed and external open field, launching a helical jet. Our new results demonstrate that the jet propagation is sustained through the outer corona, in the form of a traveling nonlinear Alfven wave front trailed by slower-moving plasma density enhancements that are compressed and accelerated by the wave. This finding agrees well with observations of white-light coronal-hole jets, and can explain microstreams and torsional Alfven waves detected in situ in the solar wind. We also use our numerical results to deduce scaling relationships between properties of the coronal source region and the characteristics of the resulting jet, which can be tested against observations.

Self-Powered Wireless Affinity-Based Biosensor Based on Integration of Paper-Based Microfluidics and Self-Assembled RFID Antennas.

PubMed

Yuan, Mingquan; Alocilja, Evangelyn C; Chakrabartty, Shantanu

2016-08-01

This paper presents a wireless, self-powered, affinity-based biosensor based on the integration of paper-based microfluidics with our previously reported method for self-assembling radio-frequency (RF) antennas. At the core of the proposed approach is a silver-enhancement technique that grows portions of a RF antenna in regions where target antigens hybridize with target specific affinity probes. The hybridization regions are defined by a network of nitrocellulose based microfluidic channels which implement a self-powered approach to sample the reagent and control its flow and mixing. The integration substrate for the biosensor has been constructed using polyethylene and the patterning of the antenna on the substrate has been achieved using a low-cost ink-jet printing technique. The substrate has been integrated with passive radio-frequency identification (RFID) tags to demonstrate that the resulting sensor-tag can be used for continuous monitoring in a food supply-chain where direct measurement of analytes is typically considered to be impractical. We validate the proof-of-concept operation of the proposed sensor-tag using IgG as a model analyte and using a 915 MHz Ultra-high-frequency (UHF) RFID tagging technology.

Simulations of Gamma-Ray Burst Jets in a Stratified External Medium: Dynamics, Afterglow Light Curves, Jet Breaks, and Radio Calorimetry

NASA Astrophysics Data System (ADS)

De Colle, Fabio; Ramirez-Ruiz, Enrico; Granot, Jonathan; Lopez-Camara, Diego

2012-05-01

The dynamics of gamma-ray burst (GRB) jets during the afterglow phase is most reliably and accurately modeled using hydrodynamic simulations. All published simulations so far, however, have considered only a uniform external medium, while a stratified external medium is expected around long duration GRB progenitors. Here, we present simulations of the dynamics of GRB jets and the resulting afterglow emission for both uniform and stratified external media with ρextvpropr -k for k = 0, 1, 2. The simulations are performed in two dimensions using the special relativistic version of the Mezcal code. Common to all calculations is the initiation of the GRB jet as a conical wedge of half-opening angle θ0 = 0.2 whose radial profile is taken from the self-similar Blandford-McKee solution. The dynamics for stratified external media (k = 1, 2) are broadly similar to those derived for expansion into a uniform external medium (k = 0). The jet half-opening angle is observed to start increasing logarithmically with time (or radius) once the Lorentz factor Γ drops below θ-1 0. For larger k values, however, the lateral expansion is faster at early times (when Γ > θ-1 0) and slower at late times with the jet expansion becoming Newtonian and slowly approaching spherical symmetry over progressively longer timescales. We find that, contrary to analytic expectations, there is a reasonably sharp jet break in the light curve for k = 2 (a wind-like external medium), although the shape of the break is affected more by the viewing angle (for θobs <= θ0) than by the slope of the external density profile (for 0 <= k <= 2). Steeper density profiles (i.e., increasing k values) are found to produce more gradual jet breaks while larger viewing angles cause smoother and later appearing jet breaks. The counterjet becomes visible as it becomes sub-relativistic, and for k = 0 this results in a clear bump-like feature in the light curve. However, for larger k values the jet decelerates more

JPL Large Advanced Antenna Station Array Study

NASA Technical Reports Server (NTRS)

1978-01-01

In accordance with study requirements, two antennas are described: a 30 meter standard antenna and a 34 meter modified antenna, along with a candidate array configuration for each. Modified antenna trade analyses are summarized, risks analyzed, costs presented, and a final antenna array configuration recommendation made.

Negative ion source with external RF antenna

DOEpatents

Leung, Ka-Ngo; Hahto, Sami K.; Hahto, Sari T.

2007-02-13

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